Posted in HTN on April 21, 2015| Leave a Comment »
New BP guidelines reduce antihypertensive therapy eligibility by 6 million … – Healio
Reporter: Aviva Lev-Ari, PhD, RN
SAN DIEGO — The number of patients in the US who would be eligible for antihypertensive therapy decreases by 6.1 million under the guidelines written by the panel convened for the Eighth Joint National Committee, according to data presented at the…
Source: www.healio.com
See on Scoop.it – Cardiotoxicity
Posted in BioIT: BioInformatics, NGS, Clinical & Translational, Pharmaceutical R&D Informatics, Clinical Genomics, Cancer Informatics, Biological Networks, Biological Networks, Gene Regulation and Evolution, Biomarkers & Medical Diagnostics, Chemical Genetics, Computational Biology/Systems and Bioinformatics, Congenital Heart Disease, Frontiers in Cardiology and Cardiovascular Disorders, Gene Regulation, Gene Regulation and Evolution, Genomic Testing: Methodology for Diagnosis, HTN, Origins of Cardiovascular Disease, Personalized and Precision Medicine & Genomic Research on April 16, 2015| Leave a Comment »
Reporter: Aviva Lev-Ari, PhD, RN
NHLBI-led Team Untangles Gene Networks Involved in Blood Pressure Regulation
Apr 16, 2015
NEW YORK (GenomeWeb) – Using network approaches, researchers from the US National Heart, Lung, and Blood Institute and their colleagues combined genome-wide association and mRNA expression data to home in on sets of co-expressed genes that appear to influence blood pressure regulation.
As they reported in Molecular Systems Biology today, the NHLBI-led team drew on data from more than 3,600 people participating in the Framingham Heart Study to identify four potentially causal gene modules and key driver genes contained within them.
“Our work was able to pinpoint several gene networks closely linked to the regulation of blood pressure,” first author Tianxiao Huan from NHLBI said in a statement.
In addition, Huan and her colleagues traced the function of one key driver gene — SH2B3 — to response to angiotensin II infusion in a mouse model, indicating that this approach may help identify new treatment targets.
For this study, Huan and her colleagues examined the gene expression profiles of 3,679 Framingham Heart Study participants of European descent who were not taking an antihypertensive drug. They correlated gene expression changes they observed in this cohort with systolic blood pressure, diastolic blood pressure, and hypertension and, after accounting for age, BMI, gender, and other factors, came up with 83 associated genes.
At the same time, the researchers constructed gene co-expression networks from that gene expression data to develop gene co-expression network modules that they then also correlated to blood pressure phenotypes. Of these 27 gene co-expression network modules, seven were significantly associated with either systolic or diastolic blood pressure, the researchers said.
While that set of 83 blood pressure-related genes wasn’t significantly enriched for any gene ontology terms, the seven gene co-expression network modules were linked to a variety of functions, including chromatin modification, immune cell-mediated cytotoxicity, inflammatory response, and more. This suggested to the researchers that genes involved in a range of biological processes are tightly co-regulated with respect to blood pressure.
Using a SNP set enrichment analysis approach, the researchers found that four of the gene co-expression network modules appeared to be potentially causal and that more than a dozen genes in those modules appeared to contribute to their association with blood pressure regulation.
For instance, one SNP, dubbed rs3184504, had been linked with blood pressure through a genome-wide association study, and it is linked with the expression of four genes in the set of genetically inferred causal blood pressure genes.
Using blood Bayesian networks and protein-protein interaction networks other groups had developed, Huan and her colleagues further zoomed in on key driver genes by testing whether the surrounding region of each gene in those four gene co-expression network modules was enriched for other potentially causal blood pressure genes.
These top key driver genes, they noted, were involved in subnetworks that appeared to regulate blood pressure-related genes.
For example, a missense SNP in an exon of SH2B3 has been associated with blood pressure and hypertension in a GWAS and is linked to expression changes in 10 other genes the researchers identified. These genes, Huan and her colleagues said, were enriched for activity in the intracellular signaling cascade, T-cell activation, and T-cell differentiation. This SH2B3-subnework was also enriched for genes known to be linked to blood pressure.
Previous work had linked SH2B3 to blood pressure regulation, Huan and her colleagues said, but how it had its effect wasn’t clear.
Mice lacking the SH2B3 gene, they noted, had normal baseline blood pressure, though it became elevated in response to a low dose of angiotensin II, an effect not seen in wild-type mice.
In addition, RNA sequencing of the whole-blood transcriptomes from wild-type and Sh2b3-/- mice indicated that more than 2,240 genes were differentially expressed between the two, especially ones involved in immune and inflammatory response. These genes significantly overlapped with the SH2B3 genetic subnetwork, and those overlapping genes were enriched for ones involved in the intracellular signaling cascade and T-cell activation, the researchers reported.
“Moving forward, it should be possible to study additional key driver genes in this way, which should help in our efforts to identify novel targets for the prevention and treatment of hypertension,” Huan added.
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Posted in Atherogenic Processes & Pathology, Cardiovascular Research, Curation, Disease Biology, Disease Biology, Small Molecules in Development of Therapeutic Drugs, Frontiers in Cardiology and Cardiovascular Disorders, Human Immune System in Health and in Disease, Innovations, Lipid metabolism, Lipids, Microbiologial genetics, Molecular Genetics & Pharmaceutical, Origins of Cardiovascular Disease, Patents, Pharmaceutical Analytics, Pharmaceutical Discovery, Pharmacotherapy of Cardiovascular Disease, Population Health Management, Genetics & Pharmaceutical, Pre-Clinical Animal Model Development, Proteomics, tagged anti-atheromatous vaccine, Antioxidant, atheromatous plaque, atheroslerosis, LDL APOB100, lipid peroxidation, ox-LDL, oxidative stress on March 17, 2015| Leave a Comment »
Writer and Curator: Larry, MD, FCAP
Introduction
Research investigators at Wayne State University in collaboration with La Jolla Institute for Allergy and Immunology (LJAI) are developing a T-cell peptide-based vaccine for cardiovascular disease, specifically, to reduce immune-based inflammatory plaques in arteries. The scientists published their findings in the December 2013 issue of Frontiers in Immunology, titled “Atheroprotective vaccination with MCH-II restricted peptides from Apo B-100.” These experiments show proof of concept for the development of an autoantigen-specific vaccine for reducing the amount of atherosclerotic plaques in mice.
The published work was done in the laboratory of Klaus Ley, M.D., a prominent vascular biolist of LIAI based on the discovery by Harley Tse, Ph.D., Professor of immunology and microbiology at Wayne Stae University School of Medicine, and Wayne State’s Cardiovascular Research Institute with Michael Shae, Ph.D., adjunct assistant professor of immunology and microbiology.Shaw and Tse are the first to demonstrate that two T-cell epitopes of the autoantigen apoB100 are deeply involved in the development of the disease. The discovery is reported in J Immunol Clin Res Apr-Jun, 2014; 2: “Identification of two immunogenic T cell epitopes of ApoB100 and their Autoimmune Implications.”
Atheroprotective Vaccination with MHC-II Restricted Peptides from ApoB-100.
Tse K, Gonen A, Sidney J, Ouyang H, Witztum JL, Sette A, Tse H, Ley K
Front Immunol. 2013 Dec 27; 4:493.
http://dx.doi.org:/10.3389/fimmu.2013.00493 eCollection 2013.
BACKGROUND: Subsets of CD4(+) T-cells have been proposed to serve differential roles in the development of atherosclerosis. Some T-cell types are atherogenic (T-helper type 1), while others are thought to be protective (regulatory T-cells). Lineage commitment toward one type of helper T-cell versus another is strongly influenced by the inflammatory context in which antigens are recognized. Immunization of atherosclerosis-prone mice with low-density lipoprotein (LDL) or its oxidized derivative (ox-LDL) is known to be atheroprotective. However, the antigen specificity of the T-cells induced by vaccination and the mechanism of protection are not known.
METHODS: Identification of two peptide fragments (ApoB3501-3516 and ApoB978-993) from murine ApoB-100 was facilitated using I-Ab prediction models, and their binding to I-Ab determined. Utilizing a vaccination scheme based on complete and incomplete Freund’s adjuvant (CFA and IFA) [1 × CFA + 4 × IFA], we immunized Apoe(-/-)mice with ApoB3501-3516 or ApoB978-993 emulsified in CFA once and subsequently boosted in IFA four times over 15 weeks. Spleens, lymph nodes, and aortas were harvested and evaluated by flow cytometry and real time RT-PCR. Total atherosclerotic plaque burden was determined by aortic pinning and by aortic root histology.
RESULTS: Mice immunized with ApoB3501-3516 or ApoB978-993 demonstrated 40% reduction in overall plaque burden when compared to adjuvant-only control mice. Aortic root frozen sections from ApoB3501-3516 immunized mice showed a >60% reduction in aortic sinus plaque development. Aortas from both ApoB3501-3516 and ApoB978-993 immunized mice contained significantly more mRNA for IL-10. Both antigen-specific IgG1 and IgG2c titers were elevated in ApoB3501-3516 or ApoB978-993 immunized mice, suggesting helper T-cell immune activity after immunization.
CONCLUSION: Our data show that MHC Class II restricted ApoB-100 peptides can be atheroprotective, potentially through a mechanism involving elevated IL-10.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3873602/bin/fimmu-04-00493-g001.jpg
Atherosclerosis is decreased in ApoB3501–3516 and ApoB978–993-treated mice compared to controls. (A) Vaccination schedule: 8-week-old female Apoe−/− mice were immunized once with either PBS or peptide in CFA, then boosted four more times with PBS or peptide in IFA. WD was maintained for 13 weeks. Mice were sacrificed and organs harvested at 23 weeks of age. (B,C) Results of aortic pinning analysis after Sudan IV staining are shown with representative photographs. N = 12–15 in each group, *p < 0.05 when compared to 1× CFA + 4× IFA group. (D) Representative aortic root staining sections after ORO staining, counter-stained with hematoxylin. (E) Plaque area from aortic roots stained from each group. Lesion sizes from 30 to 40 μm distal to start of the aortic valve were averaged per group. N = 5 in each group, *p < 0.05 when compared to 1× CFA + 1× IFA control group.
Inhibition of T cell response to native low density lipoprotein reduces atherosclerosis
Andreas Hermansson, DFJ Ketelhuth, D Strodthoff, M Wurm, E. Hansson, et al.
J. Exp. Med. Mar 2015; 207(5): 1081-1093
http://www.jem.org/cgi/doi/10.1084/jem.20092243
Atherosclerosis is a chronic inflammatory disease in which lipoproteins accumulate, eliciting an inflammatory response in the arterial wall. Adaptive immune responses that engage clonally expanded T cell populations contribute to this process, as do innate immune responses that are mounted by macrophages and other cells. Several studies have suggested that components of low-density lipoprotein (LDL) particles trigger vascular inflammation (Tabas et al., 2007; Hartvigsen et al., 2009).
As a consequence of oxidation, the double bonds of fatty acid residues in phospholipids, cholesteryl esters, and triglycerides are cleaved, thus generating reactive aldehydes and truncated lipids (Esterbauer et al., 1990). Among the latter, modified phospholipids, such as lysophosphatidylcholine and oxidized 1-palmitoyl-2-arachidonyl-sn-glycero-3-phosphocholine (ox-PAPC), induce endothelial cells, macrophages, and B1-type B cells to initiate innate immune responses, effecting adhesion molecule expression, chemokine production, and secretion of natural antibodies containing germline IgM sequences (Leitinger et al., 1997; Binder et al., 2004; Gharavi et al., 2007).
Immune responses to oxidized low-density lipoprotein (oxLDL) are proposed to be important in atherosclerosis. To identify the mechanisms of recognition that govern T cell responses to LDL particles, we generated T cell hybridomas from human ApoB100 transgenic (huB100tg) mice that were immunized with human oxLDL. Surprisingly, none of the hybridomas responded to oxidized LDL, only to native LDL and the purified LDL apolipoprotein ApoB100.
However, sera from immunized mice contained IgG antibodies to oxLDL, suggesting that T cell responses to native ApoB100 help B cells making antibodies to oxLDL. ApoB100 responding CD4+ T cell hybridomas were MHC class II–restricted and expressed a single T cell receptor (TCR) variable (V) chain, TRBV31, with different V chains. Immunization of huB100tgxLdlr/ mice with a TRBV31-derived peptide induced anti-TRBV31 antibodies that blocked T cell recognition of ApoB100. This treatment significantly reduced atherosclerosis by 65%, with a concomitant reduction of macrophage infiltration and MHC class II expression in lesions. In conclusion, CD4+ T cells recognize epitopes on native ApoB100 protein, this response is associated with a limited set of clonotypic TCRs, and blocking TCR-dependent antigen recognition by these T cells protects against atherosclerosis.
Impact of multiple antigenic epitopes from ApoB100, hHSP60 and Chlamydophila pneumoniae on atherosclerotic lesion development in Apobtm2SgyLdlrtm1HerJ mice
Xinjie Lu, Min Xia, V Endresz, I Faludi, A Szabo, et al.
Atherosclerosis Nov 2012; 225(1): 56–68
http://www.sciencedirect.com.scopeesprx.elsevier.com/science/article/pii/S0021915012004935
http://dx.doi.org:/10.1016/j.atherosclerosis.2012.07.021
Highlights
► We produced 5 constructs using dendroaspin as a scaffold for immunization study. ► All constructs have the effect on lesion reduction. ► Modulation in atherosclerosis-related autoimmunity appears by Tregs.
Atherosclerosis is increasingly recognized as a complex chronic inflammatory disease of the arterial walls [1], [2] and [3], as evidenced by the presence of inflammatory cells, activated immune cells and cytokines in lesions, all of which indicate involvement of the immune system. Atherosclerotic plaques are known to contain macrophage-derived foam cells in which macrophages interact with T-cells to produce a wide array of cytokines that can exert both pro- and anti-inflammatory effects.
Antibodies against aldehyde-modified ApoB100, a major constituent of low-density lipoprotein, reduce atherosclerosis in mice expressing human ApoB100, suggesting an immunogenic role of ApoB100. Antibodies against epitopes of the human heat shock protein 60 (hHSP60) molecule (hHSP60153–163: AELKKQSKPVT and hHSP60303-312: PGFGDNRKNQ) are present in atherosclerotic patients and share considerable homology with human cytomegalovirus (HCMV)-derived protein (immediate early protein UL122) and Porphyromonas gingivalis microbial HSP60. Sequence homology between microbial HSP60 and hHSP60 has been suggested to result in immunological cross-reactivity, which may play a role in atherogenesis. Titers of Cpn antibodies are not always positively associated with the Cpn organism in atheroma; however, these antibodies might exert cross-reactivity to non-Cpn antigens.
Immunization of mice with a single construct containing multiple epitopes derived from ApoB100, hHSP60 and Cpn was more effective in reducing early atherosclerotic lesions through the induction of a specific Treg-cell response than was the construct containing either mono- or bi-epitopes. This approach offers attractive opportunities for the design of protein-based, multivalent vaccines against atherosclerosis.
Immunization with a combination of ApoB and HSP60 epitopes significantly reduces early atherosclerotic lesion in Apobtm2SgyLdlrtm1Her/J mice
Xinjie Lu, Daxin Chen, Valeria Endreszb, Min Xia, Ildiko Faludi, et. al.
Atherosclerosis 212 (2010) 472–480
http://dx.doi.org:/10.1016/j.atherosclerosis.2010.06.007
Objective: HSP60 is emerging as an immune-dominant target of autoantibodies in atherosclerosis and recent studies have revealed oxLDL as a key antigen in the development of atherosclerosis. In this study, we assay whether immunizing Apobtm2SgyLdlrtm1Her/J mice with a combination of ApoB and human HSP60 peptides has an additive effect on athero-protection compared to ApoB or HSP60 peptides applied alone by following atherosclerotic lesion development. Methods and results: In this study, 2 weeks after the first immunization, Apobtm2SgyLdlrtm1Her/J mice were placed on a high-fat diet for 8 weeks followed by 2 weeks on a normal diet allowing the mice to adapt to the environment before sacrifice. High levels of ApoB and HSP60 antibodies were detectable in week 2 and week 12 following the first immunization with KLH-conjugated ApoB and HSP60 peptides either individually or in combination. Histological analyses demonstrated that mice immunized with both, ApoB and HSP60 peptides, showed the most significant reduction in atherosclerotic lesions (41.3%; p < 0.001) compared to a reduction of 14.7% (p < 0.05) and 21.1% (p < 0.01) in mice immunized with ApoB or HSP60 peptides, respectively; control mice were immunized with either PBS or adjuvant alone. These results
were further supported by significant differences in the cellular and humoral immune responses between test animals. Conclusions: Immunization with a combination of ApoB and HSP60 peptide antigens significantly reduced early atherosclerotic lesions in the Apobtm2SgyLdlrtm1Her/J mouse model of atherosclerosis. This approach offers promise as a novel strategy for developing anti-atherosclerotic agents.
Chlamydophila (Chlamydia) pneumoniae infection promotes vascular smooth muscle cell adhesion and migration through IQ domain GTPase-activating protein 1
Lijun Zhang, Xiankui Li, Lijun Zhang, Beibei Wang, Tengteng Zhang, Jing Ye
Microb Pathogen 2012; 53(5–6): 207–213
http://dx.doi.org:/10.1016/j.micpath.2012.07.005
Highlights
► C. pneumoniae infection increases the adhesion of vascular smooth muscle cells. ► C. pneumoniae infection promotes the migration of vascular smooth muscle cells. ► IQGAP1 expression was increased in the infected vascular smooth muscle cells. ► Depletion of IQGAP1 inhibits the infection-induced cell adhesion and migration.
The mechanisms for Chlamydophila (Chlamydia) pneumoniae (C. pneumoniae) infection-induced atherosclerosis are still unclear. Cell adhesion has important roles in vascular smooth muscle cell (VSMC) migration required in the development of atherosclerosis. However, it is still unknown whether IQ domain GTPase-activating protein 1 (IQGAP1) plays pivotal roles in C. pneumoniae infection-induced the adhesion and migration of rat primary VSMCs. Accordingly, in this study, we demonstrated that rat primary VSMC adhesion (P < 0.001) and migration (P < 0.01) measured by cell adhesion assay and Transwell assay, respectively, were significantly enhanced after C. pneumoniae infection. Reverse transcription-polymerase chain reaction analysis revealed that the mRNA expression levels of IQGAP1 in the infected rat primary VSMCs were found to increase gradually to reach a peak and then decrease gradually to a level similar to the control. We further showed that the increases in rat primary VSMC adhesion to Matrigel (P < 0.001) and migration (P < 0.01) caused by C. pneumoniae infection were markedly inhibited after IQGAP1 knockdown by a pool of four short hairpin RNAs. Taken together, our results suggest that C. pneumoniae infection may promote the adhesion and migration of VSMCs possibly by upregulating the IQGAP1 expression.
Rosiglitazone negatively regulates c-Jun N-terminal kinase and toll-like receptor 4 proinflammatory signalling during initiation of experimental aortic aneurysms
Grisha Pirianov, Evelyn Torsney, Franklyn Howe, Gillian W. Cockerill
Atherosclerosis 2012; 225(1): 69–75
http://dx.doi.org:/10.1016/j.atherosclerosis.2012.07.034
Highlights
► Rosiglitazone has a marked effect on both aneurysm rupture and development. ► Rosiglitazone modulates inflammation by blocking TLR4/JNK signalling. ► Specific antagonists of JNK and TLR4 may be therapeutic for aneurysms.
Development and rupture of aortic aneurysms (AA) is a complex process involving inflammation, cell death, tissue and matrix remodelling. The thiazolidinediones (TZDs) including Rosiglitazone (RGZ) are a family of drugs which act as agonists of the nuclear peroxisome proliferator-activated receptors and have a broad spectrum of effects on a number of biological processes in the cardiovascular system. In our previous study we have demonstrated that RGZ has a marked effect on both aneurysm rupture and development, however, the precise mechanism of this is unknown.
Methods and results In the present study, we examined possible targets of RGZ action in the early stages of Angiotensin II-induced AA in apolipoprotein E-deficient mice. For this purpose we employed immunoblotting, ELISA and antibody array approaches. We found that RGZ significantly inhibited c-Jun N-terminal kinase (JNK) phosphorylation and down-regulated toll-like receptor 4 (TLR4) expression at the site of lesion formation in response to Angiotensin II infusion in the initiation stage (6–72 h) of experimental AA development. Importantly, this effect was also associated with a decrease of CD4 antigen and reduction in production of TLR4/JNK-dependant proinflammatory chemokines MCP-1 and MIP-1α. Conclusion These data suggest that RGZ can modulate inflammatory processes by blocking TLR4/JNK signalling in initiation stages of AA development.
Atheroprotective immunization with malondialdehyde-modified LDL is hapten specific and dependent on advanced MDA adducts: implications for development of an atheroprotective vaccine.
Gonen A, Hansen LF, Turner WW, Montano EN, Que X,…, Hartvigsen K.
J Lipid Res. 2014 Oct;55(10):2137-55.
http://dx.doi.org:/10.1194/jlr.M053256. Epub 2014 Aug 20.
Immunization with homologous malondialdehyde (MDA)-modified LDL (MDA-LDL) leads to atheroprotection in experimental models supporting the concept that a vaccine to oxidation-specific epitopes (OSEs) of oxidized LDL could limit atherogenesis. However, modification of human LDL with OSE to use as an immunogen would be impractical for generalized use. Furthermore, when MDA is used to modify LDL, a wide variety of related MDA adducts are formed, both simple and more complex. To define the relevant epitopes that would reproduce the atheroprotective effects of immunization with MDA-LDL, we sought to determine the responsible immunodominant and atheroprotective adducts. We now demonstrate that fluorescent adducts of MDA involving the condensation of two or more MDA molecules with lysine to form malondialdehyde-acetaldehyde (MAA)-type adducts generate immunodominant epitopes that lead to atheroprotective responses. We further demonstrate that a T helper (Th) 2-biased hapten-specific humoral and cellular response is sufficient, and thus, MAA-modified homologous albumin is an equally effective immunogen. We further show that such Th2-biased humoral responses per se are not atheroprotective if they do not target relevant antigens. These data demonstrate the feasibility of development of a small-molecule immunogen that could stimulate MAA-specific immune responses, which could be used to develop a vaccine approach to retard or prevent atherogenesis.
Low density lipoprotein oxidation and atherogenesis: from experimental models to clinical studies.
Napoli C
G Ital Cardiol. 1997 Dec; 27(12):1302-14.
Oxidative modifications of low-density lipoproteins (LDL) (“oxidation hypothesis”) appears to be the pathophysiologic mechanism implicated in early atherogenesis. Oxidized LDL (ox-LDL) may also induce several pro-atherogenic mechanisms, such as the regulation of vascular tone, by interfering with nitric oxide, the stimulation of cytokines and chemotactic factors (MCP-1, M-CSF, VCAM-1, etc.) and transcription factors (AP1 and NFk beta). These phenomena complicate the spectrum of direct and indirect actions of ox-LDL. The immunogenicity of ox-LDL was used to generate monoclonal antibodies against many epitopes of ox-LDL, such as malondialdehyde-lysine (MDA-2) or 4-hydroxynonenal-lysine (NA59). These antibodies showed the occurrence of ox-LDL in vivo. Another issue is the role of the humoral and cellular immune system in atherogenesis, in particular whether the immune response to ox-LDL enhances or reduces early atherogenesis. Moreover, the induction of autoantibodies against ox-LDL and the recognition by “natural” antibodies, and the use of the antigens to screen human sera may serve as a marker of atherosclerosis. In this review, we have stressed the importance of methodologic approach in the assessment of LDL-oxidation and the fact that lipoprotein (a) may also undergo oxidative modifications. Several clinical conditions are associated with increased rate of LDL-oxidation. Recently, we have observed the presence of LDL oxidation-specific epitopes in human fetal aortas. Antioxidants studies in primary prevention of atherosclerosis have produced contradictory results. This may be explained in part by the selection of patients who had advanced lesions and were often smokers. New trails suggest that antioxidants be administered early in children. Lastly, antioxidant studies in the secondary prevention of coronary heart disease (CHAOS, WACS, and HOPE) show clear evidence of the benefits of antioxidants in reducing new cardiovascular events.
Summary:
Atheroprotective Vaccine
Tech ID: 19640 / UC Case 2006-250-0
http://www.ucop.edu//ncd/12343.html
Atherosclerosis is a chronic inflammatory disease and immunological mechanisms are of central importance. It is known that oxidized LDL and its oxidized moieties were a major class of immunodominant epitopes within the atherosclerotic plaque. Oxidation of LDL leads to the generation of a variety of oxidized lipids and oxidized lipid-apo-B adducts.
Technology Description
UC San Deigo researchers proposed that an immunization strategy could be used to inhibit the progression of atherosclerosis by showing that immunization of rabbits and/or mice (and ultimately humans) with MDA-LDL could inhibit atherosclerosis. To develop a safe vaccine for human use would require the identification of the specific immunogenic oxidation-specific epitope(s) that provides the atheroprotective immunity. Until now, the mechanism of the protection, that is, the immunodominant epitope(s) has not yet been determined.
UC San Diego researchers have been able to identify a small group of MDA-derived adducts which are immunodominant and atheroprotective in mice following immunization. The invention described here has the potential to provide an antigen to formulate a wholly synthetic vaccine to inhibit the development of atherosclerosis in man. Furthermore, in vivo levels of the adducts, and the autoantibodies recognizing them, may be used as diagnostic tools in patients with cardiovascular and other inflammatory diseases.
State Of Development
Mice have been immunized with the adducts resulting in atheroprotection. Techniques are currently being developed for a totally synthetic immunogen suitable for human clinical studies. Assays are also being developed.
Intellectual Property Info
A patent application has been filed on this technology.
Posted in Cell Biology, Signaling & Cell Circuits, Child and Adolescent Psychiatry, Cognition, Curation, Disease Biology, Epigenetics and Cardiovascular Risks, Gastroenterology, HTN, Indigent Nutrition, Innovations in Neurophysiology & Neuropsychology, Lipids, Liver & Digestive Diseases Research, Neurological Diseases, Nitric Oxide in Health and Disease, Nutrition and Phytochemistry, Nutrition Disorders, Origins of Cardiovascular Disease, Population Health Management, Population Health Management, Nutrition and Phytochemistry, Prescription Drugs Costs, Uninsured and Underinsured, tagged adults, anxiety, behavioral treatments, geriatrics, pediatrics, psychosomatic illness, Stress on March 4, 2015| Leave a Comment »
Writer and Curator: Larry H Bernstein, MD, FCAP
Introduction
This article follows immediately after two on diet and obesity and diet and exercise. The hypothalamus has been discussed in some detail, although There is more that needs to be said about glutamate receptors, which is a topic in itself. However, this material fits in place quite well. There is a considerable amount of obesity, and exercise is limited by time and commitment. The shrinking middle class and the working poor, and the unemployed poor as well, have a struggle to make ends meet, and with the divorce rates that we are seeing, it is stressful for a single mother to carry on a complete life as mother and caregiver, and it is not unusual to see one or both couples in a household, regardless of sex, to hold two jobs. Students enter colleges for higher education and leave with significant debts. Graduates with advanced degrees may have to compete with a crowd of qualified applicants for an academic position, or even for a job in technology. In addition, there is an increase in stress related disorders in the pre-school, elementary and middle school population. We no longer have to read the front pages to learn that a violent act has been carried out somewhere, in some neighborhood in our great nation that has experienced a great civil war, two world wars, the Mc Carthy hearings, the Cold War, and Vietnam, and the Iraq War, all of which was accompanied by migrations, immigration, and outsourcing of jobs. The following is another look at how we are adjusting.
Effectiveness of a meditation-based stress management program as an adjunct to pharmacotherapy in patients with anxiety disorder
Sang Hyuk Lee, Seung Chan Ahn, Yu Jin Lee, Tae Kyu Choi, et al.
J Psychosomatic Research 62 (2007) 189–195
http://dx.doi.org:/10.1016/j.jpsychores.2006.09.009
Objective: The objective of this study was to examine the effectiveness of a meditation-based stress management program in patients with anxiety disorder.
Methods: Patients with anxiety disorder were randomly assigned to an 8-week clinical trial of either a meditation-based stress management program or an anxiety disorder education program. The Hamilton Anxiety Rating Scale (HAM-A), the Hamilton Depression Rating Scale (HAM-D), the State–Trait Anxiety Inventory (STAI), the Beck Depression Inventory, and the Symptom Checklist- 90 — Revised (SCL-90-R) were used to measure outcome at 0, 2, 4, and 8 weeks of the program. Results: Compared to the education group, the meditation-based stress management group showed significant improvement in scores on all anxiety scales (HAM-A, P=.001; STAI state, P=.001; STAI trait, P=.001; anxiety subscale of SCL-90-R,P=.001) and in the SCL-90-R hostility subscale (P=.01). Findings on depression measures were inconsistent, with no significant improvement shown by subjects in the meditation-based stress management group compared to those in the education group. The meditation-based stress management group did not show significant improvement in somatization, obsessive–compulsive symptoms, and interpersonal sensitivity scores, or in the SCL-90-R phobic anxiety subscale compared to the education group. Conclusions: A meditation-based stress management program can be effective in relieving anxiety symptoms in patients with anxiety disorder. However, well-designed, randomized, and controlled trials are needed to scientifically prove the worth of this intervention prior to treatment.
Evidence and Potential Mechanisms for Mindfulness Practices and Energy Psychology for Obesity and Binge-Eating Disorder
Renee Sojcher, Susan Gould Fogerite, and Adam Perlman
Explore 2012; 8(5):271-276
http://dx.doi.org/10.1016/j.explore.2012.06.003
Obesity is a growing epidemic. Chronic stress produces endocrine and immune factors that are contributors to obesity’s etiology. These biochemical alsocan affect appetite and eating behaviors that can lead to binge-eating disorder. The inadequacies of standard care and the problem of patient noncompliance have inspired a search for alternative treatments. Proposals in the literature have called for combination therapies involving behavioral or new biological therapies. This manuscript suggests that mindbody interventions would be ideal for such combinations. Two mind body modalities, energy psychology and mindfulness meditation, are reviewed for their potential in treating weight loss, stress, and behavior modification related to binge-eating disorder.
Whereas mindfulness meditation and practices show more compelling evidence, energy psychology, in the infancy stages of elucidation, exhibits initially promising outcomes but requires further evidence-based trials. “Diets Don’t Work” has been a mantra repeated over and over in the media. In fact, in a 2006 study in which investigators compared several popular diets comprising either high carbohydrates, high protein, or high fat, they found a rapid regression of compliance after six months, to the extent that it did not matter which diet had initially been more effective. In another study, authors examined a combination of diet and exercise compared with diet alone and observed that 50% of their subjects in both groups regained the weight that they lost after one year, despite their having lost more weight with the combination therapy. Despite the failure of diet alone in most studies, strategies incorporating both diet and exercise can be effective: a Cochrane review on exercise for overweight or obesity concluded that exercise had a positive effect on body weight and cardiovascular risk factors and that this effect was enhanced by a combination of exercise with dietary interventions.
The authors of a more recent study found that the benefits of exercise in inducing weight loss may come through psychological pathways rather than through actual energy expenditure. These factors include self-regulation and self-efficacy, which may mediate the relationship between exercise and weight change. Psychological interventions, particularly behavioral therapy and CBT, have been shown to be effective, especially when combined with diet and exercise. However, these interventions are costly and require extensive clinical contact for long durations to achieve efficacy. The authors of a recent randomized controlled trial (RCT) with a three-year follow-up period looked at a new form of CBT that addresses patients’ overeating and low level of activity, as well as factors that impede weight maintenance, and found that this form of therapy did not result in improved weight maintenance. These authors concluded that CBT is not sufficiently effective in helping patients maintain their weight loss in the long term. Although 20% of people will not change their eating behaviors under stress, most do; approximately 40% will increase and 40% will decrease their eating.
The emotional eaters, who tend to increase food intake, are more likely to crave high-fat/sweet and rewarding comfort foods. The basis for this behavior is becoming understood to entail brain pathways that involve learning and memory of reward and pleasure. Habit formation and decreased cognitive control are also involved. These habits form the basis of BED. Binge eating occurs when a person eats larger amounts of food than normal in a short amount of time. It therefore involves a loss of control and is often precipitated by a range of negative emotions, such as anxiety, depression, anger, and loneliness. Overweight subjects may or may not be characterized as binge eaters.
The stress response, also known as the “fight or flight response,” involves the interaction of the autonomic nervous system, which includes the sympathetic and the parasympathetic nervous systems, the hypothalamic pituitary adrenal axis and endocrine secretion. Together, these systems comprise neuro-endocrine pathways that collaborate to maintain the body’s regulation of homeostasis. This mechanism is very effective when stress is acute, but in the case of chronic stress, the effect can be injurious to one’s physiological state. Over time, chronic exposure to stress hormones contributes to“ allostatic load.” The stress hormones released by the body, mostly cortisol, can alter the body’s fuel metabolism, especially by adipose tissue, leading to an increase in upper-body obesity. Furthermore, hormones such as leptin, ghrelin, and neuropeptide Y can affect appetite and cause changes in fat mass storage. This results in the linking of stress and obesity.
Given the limited success of conventional approaches and the new information about the psychological and physiological mechanisms underlying obesity, we propose that a specific sub-group of mind-body therapies, including energy psychology and mindfulness-based approaches, could add an important new dimension to the integrative treatment of eating disorders. Energy psychology refers to a family of therapies that are used for treating physical disorders and psychological symptoms, which includes Thought Field Therapy, Emotional Freedom Techniques (EFT), Eye Movement Desensitization and Reprocessing, and Tapas Acupressure Technique (TAT). These therapies incorporate concepts originating from non-Western healing and spiritual systems, including acupuncture, acupressure, yoga, meditation, and qigong, and they combine physical activity with mental activation on the basis of the premise that the body is composed of electrical signals or energy fields. Energy psychology has been quite controversial among psychotherapists and has been the subject of much heated debate in the literature. Nonetheless, the clinical application of these practices is growing and is beginning to be investigated for efficacy. Mindfulness-Based Eating Awareness Training (ie,MB-EAT) involves the cultivation of mindfulness, mindful eating, emotional balance, and self-acceptance.
A pilot trial of a six-week group curriculum for providing mindfulness training to obese individuals, called Mindful Eating and Living (ie,MEAL), showed significant increases in measures of mindfulness and cognitive restraint around eating and significant decreases in weight, eating disinhibition, bingeeating, depression, perceived stress, physical symptoms, negative affect ,and C-reactive protein. In a recent systematic review of eight studies, authors examined a variety of mindfulness techniques in treating eating disorders, including anorexia, bulimia, and BED. Because trial quality varied and sample sizes were small, the researchers concluded that mindfulness may be effective in treating eating disorders but that further research was needed. The authors noted, however, that all of the articles that met the study’s criterion reported positive outcomes for the mindfulness intervention. Two additional studies recently addressed the treatment of obesity with a combination of mindfulness strategies and ACT. Lillis et al. conducted a RCT on 87 subjects who had all completed at least a six-month weight loss program. Using a wait list control against treatment of the experimental group through a one-day workshop, the authors found that, compared with the control group, the experimental group showed greater improvements in obesity-related stigma, quality of life, psychological distress, and reduction of body mass in a three-month follow-up. Alberts et al. conducted an RCT on 19 participants in a 10-week dietary group treatment that examined the effect of mindfulness plus ACT on food cravings. Experimental subjects underwent an additional seven-week, manual-based mindfulness/acceptance training. The control group received information on healthy food choices. The experimental group showed significantly lower food cravings, a lower preoccupation with food in four subscales, less loss of control, and better positive outcome expectancy, as compared with the control group. There was no significant effect observed for emotional craving. The authors of both of these studies conclude that mindfulness strategies combined with acceptance are effective in reducing the behaviors that lead many obese patients to overeat. With regards to stress, mindfulness can reduce psychological factors that have been shown to contribute to obesity.
In a recent well conducted systematic review, Mars and Abbey examined 22 studies with conditions ranging from participants with Axis I disorders, various diagnosed medical disorders, and healthy subjects. Axis I disorders include a range of psychopathologies such as childhood developmental and adjustment abnormalities, adult anxiety, and mood, sleep, and sexual disorders. Subjects with BED are known to have greater comorbidity forAxis I disorders. The authors report that five studies examining Axis I disorders showed statistically significant results for an eight-week, two hours per week MBCT program in reducing psychological stress, recurring bouts of depression, and pain. They conclude that, despite some methodological difficulties in the trials, mindfulness therapy may have a positive impact on reducing stress and depression. Despite increasing public awareness of obesity’s detrimental effects on health, the conventional approaches to managing this condition have not been effective. The recommended standard care for overweight and obesity, namely diet and exercise, are for the most part ineffective in the long term. Behavioral therapy and CBT may have some effect but are costly and difficult to implement. Issues with bariatric surgery and pharmacological therapies attributable to cost and the potential for harm, as well as lack of long-term efficacy, have limited their utility.
The effectiveness of a stress coping program based on mindfulness meditation on the stress, anxiety, and depression experienced by nursing students in Korea
Yune Sik Kang, So Young Choi, Eunjung Ryu
Nurse Education Today 29 (2009) 538–543
http://dx.doi.org:/10.1016/j.nedt.2008.12.003
This study examined the effectiveness of a stress coping program based on mindfulness meditation on the stress, anxiety, and depression experienced by nursing students in Korea. A nonequivalent, control group, pre-posttest design was used. A convenience sample of 41 nursing students were randomly assigned to experimental (n=21) and control groups (n=20). Stress was measured with the PWI-SF(5-point) developed by Chang. Anxiety was measured with Spieberger’s state anxiety y inventory. Depression was measured with the Beck depression inventory. The experimental group attended 90-min sessions for eight weeks. No intervention was administered to the control group. Nine participants were excluded from the analysis because they did not complete the study due to personal circumstances, resulting in16 participants in each group for the final analysis. Results for the two groups showed
(1) a significant difference in stress scores (F=6.145,p=0.020),
(2) a significant difference in anxiety scores (F=6.985,p=0.013), and
(3) no significant difference in depression scores (t=1.986,p=0.056).
A stress coping program based on mindfulness meditation was an effective intervention for nursing students to decrease their stress and anxiety, and could be used to manage stress in student nurses. In the future, long-term studies should be pursued to standardize and detail the program, with particular emphasis on studies to confirm the effects of the program in patients with diseases, such as cancer.
Meditation and Anxiety Reduction: A Literature Review
M. M. Delmonte Clin
Psychol Rev 1985; 5: 91-102
Meditation is increasingly being practiced as a therapeutic technique. The effects of practice on psychometrically assessed anxiety levels has been extensively researched. Prospective meditators tend to report above average anxiety. In general, high anxiety levels predict a subsequent low frequency of practice. However, the evidence suggests that those who practice regularly tend to show significant decreases in anxiety. Meditation does not appear to be more effective than comparative interventions in reducing anxiety. There is evidence to suggest that hypnotizability and expectancy may both play a role in reported anxiety decrease. Certain individuals with a capacity to engage in autonomous self-absorbed relaxation, may benefit most from meditation.
Meta-analysis on the effectiveness of mindfulness-based stress reduction therapy on mental health of adults with a chronic disease: What should the reader not make of it?
Ernst Bohlmeijer, Rilana Prenger, ErikTaal
Letters to the Editor/J Psychosom Res 69 (2010) 613–615
http://dx.doi.org:/10.1016/j.jpsychores.2010.09.005
In a letter to the editor, Nyklíček et al. discuss the study of Bohlmeijer et al. [1]on the meta-analysis on the effectiveness of mindfulness-based stress reduction (MBSR) therapy on mental health of adults with a chronic disease. They claim that the effects of MBSR are underestimated in this meta-analysis due to the inclusion of a study using an active education support group as control group and to the omission of some subscales for which larger effect sizes have been found. We do not agree that the study using an active education support group as a control group should not have been included in the meta-analysis. It is a common procedure to include studies with various types of control groups, e.g., waiting-list, placebo, minimal interventions, or evidence-based treatment. Normally, subgroup analyses can be conducted, contrasting studies that use differen ttypes of control groups. As seven studies used a waiting-list control condition and only one study used an education support group, this subgroup comparison was not useful. However, when we conducted a meta-analysis of the seven RCTs using a waiting-list control group an overall effect size of 0.30 instead of 0.26 was found. In addition, it is often found in meta-analyses that the largest effect sizes are reported in studies that use waiting-list control groups, e.g. ,Refs.[2,3]. The fact that almost all studies included in our meta-analysis in fact used waiting-list control groups makes it unlikely that the effects of MBSR were underestimated. As to the second claim by Nyklíček e tal.that some outcomes were selectively omitted from the meta-analysis, we can state that the subscales of the POMS were included in the meta-analysis.The program that was used in our study, Comprehensive Meta-Analysis, combined the scales that measure the same outcome, e.g., anxiety in one study. So the larger effects sizes for the subscales of the POMS were included in the meta-analysis. Lastly, Nyklíčeketal. State that ‘decentering’ is not an exclusive process of MBCT but is a central feature of MBSR as well. MBCT was specifically developed for people with recurrent depression and on the basis of a thorough analysis of the role of specific cognitions in people with recurrent depression. In ouropinion, this may explain the large effect sizes that have been found in randomized controlled trials, e.g., [4]. In general, other studies have shown that integrating MBSR in behavioral therapy is a very promising strategy for enhancing the efficacy of treatments of psychological distress[5,6]. However, more studies with different target groups are needed to answer the question as to which mindfulness-based intervention is most effective for which target group in which setting. Overall, in response to the letter to the editor by Nyklíček et al. we cannot corroborate their claim that the effects of MBSR were underestimated and have to stand with our conclusion that, on the basis of current RCTs, MBSR has small leffects on depression and anxiety in people with chronic medical diseases.
[1] BohlmeijerET, PrengerR, TaalE, CuijpersP.
The effects of mindfulness-based stress reduction therapy on the mental health of adults with a chronic medical disease: A meta-analysis.
JPsychosom Res 2010; 68:539–44.
[2]Powers MB, Zum Vörde Sive Vörding MB, Emmelkamp PMG.
Acceptance and commitment therapy: A meta-analytic review.
Psychoth Psychosom 2009; 78:73–80.
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Writer and Curator: Larry H. Bernstein, MD, FCAP
Introduction
We are all familiar with the conundrum of diet and cholesterol. As previously described, cholesterol is made by the liver. It is the backbone for the synthesis of sex hormones, corticosteroids, bile, and vitamin D. It is also under regulatory control, and that is not fully worked out, but it has health consequences. The liver is a synthetic organ that is involved with glycolysis, gluconeogenesis, cholesterol synthesis, and unlike the heart and skeletal muscles – which are energy transducers – the liver is anabolic, largely dependent on NADPH. The mitochondria, which are associated with aerobic metabolism, respiration, are also rich in the liver. The other part of this story is the utilization of lipids synthesized by the liver in the vascular endothelium. The vascular endothelium takes up and utilizes/transforms cholesterol, which is involved in the degenerative development of pathogenic plaque. Plaque is associated with vascular rigidity, rupture and hemorrhage, essential in myocardial inmfarction. What about steroid hormones? There is some evidence that sex hormone differences may be a factor in coronary vascular disease and cardiac dysfunction. The evidence that exercise is beneficial is well established, but acute coronary events can occur during exercise. WE need food, and food is at the center of the discussion – diet and cholesterol. The utilization of food varies regionally, and is dependent on habitat. But it is also strongly influence by culture. We explore this further in what follows.
A high fat, high cholesterol diet leads to changes in metabolite patterns in pigs – A metabolomic study
Jianghao Sun, Maria Monagas, Saebyeol Jang, Aleksey Molokin, et al.
Food Chemistry 173 (2015) 171–178
http://dx.doi.org/10.1016/j.foodchem.2014.09.161
Non-targeted metabolite profiling can identify biological markers of dietary exposure that lead to a better understanding of interactions between diet and health. In this study, pigs were used as an animal model to discover changes in metabolic profiles between regular basal and high fat/high cholesterol diets. Extracts of plasma, fecal and urine samples from pigs fed high fat or basal regular diets for 11 weeks were analysed using ultra-high performance liquid chromatography with high-resolution mass spectrometry (UHPLC–HRMS) and chemometric analysis. Cloud plots from XCMS online were used for class separation of the most discriminatory metabolites. The major metabolites contributing to the discrimination were identified as bile acids (BAs), lipid metabolites, fatty acids, amino acids and phosphatidic acid (PAs), phosphatidylglycerol (PGs), glycerophospholipids (PI), phosphatidylcholines (PCs) and tripeptides. These results suggest the developed approach can be used to identify biomarkers associated with specific feeding diets and possible metabolic disorders related to diet.
Nutritional metabolomics is a rapidly developing sub-branch of metabolomics, used to profile small-molecules to support integration of diet and nutrition in complex bio-systems research. Recently, the concept of ‘‘food metabolome’’ was introduced and defined as all metabolites derived from food products. Chemical components in foods are absorbed either directly or after digestion, undergo extensive metabolic modification in the gastrointestinal tract and liver and then appear in the urine and feces as final metabolic products. It is well known that diet has a close relationship with the long-term health and well-being of individuals. Hence, investigation of the ‘‘food metabolome’’ in biological samples, after feeding specific diets, has the potential to give objective information about the short- and long-term dietary intake of individuals, and to identify potential biomarkers of certain dietary patterns. Previous studies have identified potential biomarkers after consumption of specific fruits, vegetables, cocoa, and juices. More metabolites were revealed by using metabolomic approaches compared with the detection of pre-defined chemicals found in those foods.
Eating a high-fat and high cholesterol diet is strongly associated with conditions of obesity, diabetes and metabolic syndrome, that are increasingly recognized as worldwide health concerns. For example, a high fat diet is a major risk factor for childhood obesity, cardiovascular diseases and hyperlipidemia. Little is known on the extent to which changes in nutrient content of the human diet elicit changes in metabolic profiles. There are several reports of metabolomic profiling studies on plasma, serum, urine and liver from high fat-diet induced obese mice, rats and humans. Several potential biomarkers of obesity and related diseases, including lysophosphatidylcholines (lysoPCs), fatty acids and branched-amino acids (BCAAs) have been reported.
To model the metabolite response to diet in humans, pigs were fed a high fat diet for 11 weeks and the metabolite profiles in plasma, urine and feces were analyzed. Non-targeted ultra high performance liquid chromatography tandem with high resolution mass spectrometry (UHPLC–MS) was utilized for metabolomics profiling. Bile acids (BAs), lipid metabolites, fatty acids, amino acids and phosphatidic acid (PAs), phosphatidylglycerol (PGs), glycerophospholipids (PI), phosphatidylcholines (PCs), tripeptides and isoflavone conjugates were found to be the final dietary metabolites that differentiated pigs fed a high-fat and high cholesterol diet versus a basal diet. The results of this study illustrate the capacity of this metabolomic profiling approach to identify new metabolites and to recognize different metabolic patterns associated with diet.
Body weight, cholesterol and triglycerides were measured for all the pigs studied. There was no significant body weight gain between pigs fed diet A and diet B after 11 weeks of treatment. The serum cholesterol and triglyceride levels were significantly higher in pigs fed with diet B compared with the control group at the end of experiment.
Plasma, urine and fecal samples were analyzed in both positive and negative ionization mode. To obtain reliable and high-quality metabolomic data, a pooled sample was used as a quality control (QC) sample to monitor the run. The QC sample (a composite of equal volume from 10 real samples) was processed as real samples and placed in the sample queue to monitor the stability of the system. All the samples were submitted in random for analysis. The quantitative variation of the ion features across the QC samples was less than 15%. The ion features from each possible metabolite were annotated by XCMS online to confirm the possible fragment ions, isotopic ions and possible adduct ions. The reproducibility of the chromatography was determined by the retention time variation profiles that were generated by XCMS. The retention time deviation was less than 0.3 min for plasma samples, less than 0.3 min for fecal samples, and less than 0.2 min for urine samples, respectively. On the basis of these results of data quality assessment, the differences between the test samples from different pigs proved more likely to reflect varied metabolite profiles rather than analytical variation. The multivariate analysis results from the QC sample showed the deviation of the analytical system was acceptable.
Good separation can be observed between pigs on the two diets, which is also reflected in the goodness of prediction (Q2), of 0.64 using data from the positive ionization mode. For negative ionization mode data, better separation appears with a Q2of 0.73.
Cloud plot is a new multidimensional data visualization method for global metabolomic data (Patti et al., 2013). Data characteristics, such as the p-value, fold change, retention time, mass-to-charge ratio and signal intensity of features, can be presented simultaneously using the cloud plot. In this study, the cloud plot was used to illustrate the ion features causing the group separation. In Fig. 2 and 82 features with p < 0.05 and fold change >2, including visualisation of the p-value, the directional fold change, the retention time and the mass to charge ratio of features, are shown. Also, the total ion chromato-grams for each sample were shown. The upper panel in (2A) shows the chromatograms of plasma samples from pigs fed the high fat diet, while the lower panel shows the chromatograms of samples from pigs fed the regular diet. Features whose intensity is increased are shown in green, whereas features whose intensity is decreased are shown in pink (2A). The size of each bubble corresponds to the log fold change of the feature: the larger the bubble, the larger the fold changes. The statistical significance of the fold change, as calculated by a Welch t-test with unequal variances, is represented by the intensity of the feature’s color where features with low p-values are brighter compared to features with high p-values. The Y coordinate for each feature corresponds to the mass-to-charge ratio of the compound, as determined by mass spectrometry. Each feature is also color coded, such as features that are shown with a black outline have database hits in METLIN, whereas features shown without a black outline do not have any database hits.
From the cloud plot (Fig. 2A), 82 discriminating ion features from positive data and 48 discriminating ions features from negative data were considered as of great importance for class separation. After filtering out the fragment ions, isotope annotations, and adduct ions, thirty-one metabolites were tentatively assigned using a Metlin library search (Table S4).
Among the assigned metabolites detected, five of the highest abundant metabolites were identified as bile acid and bile acid conjugates (Fig. 2B). This series of compounds shared the following characteristics; the unconjugated bile acids showed [M-H]– ion as base peak in the negative mode.
The characteristic consistent with bile acid hyodeoxycholic acid (HDCA) was confirmed with a reference standard. For the conjugated bile acids (usually with glycine and taurine), the [M-H]– and [M+H]+ are always observed as the base peaks. For example, the ion feature m/z 448.3065 at 21.18 min was identified as chenodeoxycholic acid glycine conjugate. The neutral loss of 62 amu (H2O + CO2) was considered as a characteristic fragmentation pathway for bile acid glycine conjugates. This above mentioned characteristic can easily identify a series of bile acids compounds. The five metabolite ions detected in plasma were significantly different between pigs fed the high fat diet (Fig. 2B, red bars) and regular diet (Fig. 2B, blue bars) for 11 weeks, and were identified as chenodeoxycholic acid glycine conjugate, tauroursodeoxycholic acid, hyodeoxycholic acid, deoxycholic acid glycine conjugate and glycocholic acid; chenodeoxycholic acid glycine and hyodeoxycholic acid.
Figures 1-4 , not shown.
Fig 1. The PCA score plot of plasma (A) (+)ESI data with all the ion features; (B) (+)ESI data with selected ion features; (C) (-)ESI data with all ion features; (D) (-)ESI data with selected ion features. Samples were taken from pigs fed diet A (BS, blue) and diet B (HF, red). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
Fig 2. Cloud plot showing 82 discriminatory ion features (negative ion data) in plasma, and (B) box-plot of data set of the five most abundant bile acids identified in plasma (negative ion data) samples.
Fig. 3. PCA score plot of fecal samples from pigs fed diet A (BS, blue) and diet B (HF, red) (A) week 0, (B) week 2, (C) week 4 (D) week 6, (E) week 11 for distal samples (F) week 11 for proximal colon samples. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
Fig. 4. PCA and PLS-DA score plot of urine samples from (+)ESI-data (A and C) and (-)ESI-data (B and D) taken at the end of the study (week 11) from pigs fed diet A (BS, blue) and diet B (HF, red). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
Plasma, fecal and urine metabolites from pigs fed either a high fat or regular diet were investigated using a UHPLC–HRMS based metabolomic approach. Their metabolic profiles were compared by multivariate statistical analysis.
Diet is logically believed to have a close relationship with metabolic profiles. Feeding a high fat and high cholesterol diet to pigs for 11 weeks resulted in
an increase in bile acids and their derivatives in plasma, fecal and urine samples, though at this stage, there was no significant weight gain observed.
In a previous study, a significantly higher level of muricholic acid, but not cholic acid, was found in pigs fed a high fat diet. The gut microbiota of these pigs were altered by diet and considered to regulate bile acid metabolism by reducing the levels of tauro-beta-muricholic acid. In our study, the unconjugated bile acids, hyodeoxycholic acid and deoxycholic acid were found to be significantly higher in the fecal samples of pigs fed a high-fat diet.
Chenodeoxycholic acid glycine was 8.6 times higher in pigs fed a high fat and high cholesterol diet compared to those fed a regular diet. These results confirm that feeding a high fat and high cholesterol diet leads to a changing metabolomic pattern over time, represented by excretion of certain bile acids in the feces. We also found that several metabolites associated with lipid metabolism were increased in the feces of pigs fed the high-fat diet. Feeding the high fat diet to pigs for 11 weeks did not induce any overt expression of disease, except for significantly higher levels of circulating cholesterol and triglycerides in the blood. It is likely, however, that longer periods of feeding would increase expression of metabolic syndrome disorders and features of cardiovascular disease in pigs, as have been previously demonstrated. Products of lipid metabolism that changed early in the dietary treatment could be useful as biomarkers. This may be important because the composition of the fats in the diet, used in this study, was complex and from multiple sources including lard, soybean oil and coconut oil.
In summary, a number of metabolite differences were detected in the plasma, urine and feces of pigs fed a high fat and high cholesterol diet versus a regular diet that significantly increased over time. PCA showed a clear separation of metabolites in all biological samples tested from pigs fed the different diets. This methodology could be used to associate metabolic profiles with early markers of disease expression or the responsiveness of metabolic profiles to alterations in the diet. The ability to identify metabolites from bio-fluids, feces, and tissues that change with alterations in the diet has the potential to identify new biomarkers and to better understand mechanisms related to diet and health.
Amino acid, mineral, and polyphenolic profiles of black vinegar, and its lipid lowering and antioxidant effects in vivo
Chung-Hsi Chou, Cheng-Wei Liu, Deng-Jye Yang, Yi-Hsieng S Wuf, Yi-Chen Chen
Food Chemistry 168 (2015) 63–69
http://dx.doi.org/10.1016/j.foodchem.2014.07.035
Black vinegar (BV) contains abundant essential and hydrophobic amino acids, and polyphenolic contents, especially catechin and chlorogenic acid via chemical analyses. K and Mg are the major minerals in BV, and Ca, Fe, Mn, and Se are also measured. After a 9-week experiment, high-fat/cholesterol-diet (HFCD) fed hamsters had higher (p < 0.05) weight gains, relative visceral-fat sizes, serum/liver lipids, and serum cardiac indices than low-fat/cholesterol diet (LFCD) fed ones, but BV supplementation decreased (p < 0.05) them which may resulted from the higher (p < 0.05) fecal TAG and TC contents. Serum ALT value, and hepatic thiobarbituric acid reactive substances (TBARS), and hepatic TNF-α and IL-1β contents in HFCD-fed hamsters were reduced (p < 0.05) by supplementing BV due to increased (p < 0.05) hepatic glutathione (GSH) and trolox equivalent antioxidant capacity (TEAC) levels, and catalase (CAT) and glutathione peroxidase (GPx) activities. Taken together, the component profiles of BV contributed the lipid lowering and antioxidant effects on HFCD fed hamsters.
World Health Organization (WHO) reported that more than 1.4 billion adults were overweight (WHO, 2013). As we know, imbalanced fat or excess energy intake is one of the most important environmental factors resulted in not only increased serum/liver lipids but also oxidative stress, further leading cardiovascular disorders and inflammatory responses. Food scientists strive to improve serum lipid profile and increase serum antioxidant capacity via medical foods or functional supplementation.
Vinegar is not only used as an acidic seasoning but also is shown to have some beneficial effects, such as digestive, appetite stimulation, antioxidant, exhaustion recovering effects, lipid lowering effects, and regulations of blood pressure. Polyphenols exist in several food categories, such as vegetable, fruits, tea, wine, juice, and vinegar that have effects against lipid peroxidation, hypertension, hyperlipidemia, inflammation, DNA damage, and. Black vinegar (BV) (Kurosu) is produced from unpolished rice with rice germ and bran through a stationary surface fermentation and contains higher amounts of amino acids and organic acids than other vinegars. Black vinegar is also characterised as a health food rather than only an acidic seasoning because it was reported to own a DPPH radical scavenging ability and decrease the adipocyte size in rat models. Moreover, the extract of BV shows the highest radical scavenging activity in a DPPH radical system than rice, grain, apple, and wine vinegars. The extract suppresses increased lipid peroxidation in mouse skin treated with 12-o-tetradecanoylphorbol-13-acetate.
This study focused on the nutritional compositions in BV, and the in-vivo lipid lowering and antioxidant effects. First, the amino acid, mineral, and polyphenolic profile of BV were identified. Hypolipidemic hamsters induced by a high-fat/cholesterol diet (HFCD) were orally administered with different doses of BV. Serum lipid profile and liver damage indices liver and fecal lipid contents, as well as hepatic antioxidant capacities [thiobarbituric acid reactive substances (TBARS), glutathione (GSH), trolox equivalent antioxidant capacity (TEAC), and activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx)] and hepatic cytokine levels were assayed to demonstrated physiological functions of BV.
Higher serum AST, ALT, and free fatty acids, as well as hepatic cholesterol, triacylglycerol, MDA, hydroperoxide, and cytokine (IL-1β and TNF-α) levels were easily observed in a high-fat-consumption rodent. Several reports indicated some amino acids antioxidant activities in vitro and in vivo. Acidic amino acids, such as Asp and Glu and hydrophobic amino acids, such as Ile, Leu, and Val display high antioxidant properties. Recently, an in vivo study indicated that a pepsin hydrolyzation significantly enhanced Asp, Glu, Leu, and Val contents in chicken livers; meanwhile, chicken-liver hydrolysates showed an antioxidant capacity in brain and liver of D-galactose treated mice. In addition, it was also reported that Mg and Se play important roles in SOD and GPx activities, respectively. Uzun and Kalender (2013) used chlorpyrifos, an organophosphorus insecticide, to induce hepatotoxic and hematologic changes in rats, but they observed that catechin can attenuate the chlorpyrifos-induced hepatotoxicity by increasing GPx and glutathione-S-transferase activities and decreasing MDA contents. Meanwhile, chlorogenic acid elevated SOD, CAT, and GPx activities with concomitantly decreased lipid peroxidation of liver and kidney in streptozotocin-nicotinamide induced type-2 diabetic rats. Hence, it is reasonable to assume that increased antioxidant capacities and decreased damage in livers of HFCD fed hamsters supplemented with BV should be highly related to the components, i.e. amino acid profile, mineral profile, and polyphenol contents, as well as the lowered liver lipid accumulations.
In analyses of amino acids, minerals and polyphenols, BV contained abundant essential amino acids and hydrophobic amino acids. Mg, K, Ca, Fe, Mn, and Se were measured in BV where K and Mg were major. Gallic acid, catechin, chlorogenic acid, p-hydroxybezoic acid, p-cumeric acid, ferulic acid, and sinapic acid were also identified in BV where catechin and chlorogenic acid were the majorities. Meanwhile, the lipid-lowering and antioxidant effects of BV were also investigated via a hamster model. BV supplementation apparently decreased weight gain (g and %), relative size of visceral fat, serum/liver TC levels, serum cardiac index, and hepatic TBARS values and damage indices (serum ALT and hepatic TNF-α and IL-1β) but increased fecal lipid contents and hepatic antioxidant capacities (GSH level, TEAC level, CAT activity, and GPx activity) in HFCD fed hamsters. To sum up, those benefits could be attributed to a synergetic effect of compounds in BV.
Analysis of pecan nut (Carya illinoinensis) unsaponifiable fraction – Effect of ripening stage on phytosterols and phytostanols composition
Intidhar Bouali, Hajer Trabelsi, Wahid Herchi, Lucy Martine, et al.
Food Chemistry 164 (2014) 309–316
http://dx.doi.org/10.1016/j.foodchem.2014.05.029
Changes in 4-desmethylsterol, 4-monomethylsterol, 4,4-dimethylsterol and phytostanol composition were quantitatively and qualitatively investigated during the ripening of three varieties of Tunisian grown pecan nuts. These components have many health benefits, especially in lowering LDL-cholesterol and preventing heart disease. The phytosterol composition of whole pecan kernel was quantified by Gas Chromatography–Flame Ionization Detection (GC–FID) and identified by Gas Chromatography–Mass Spectrometry (GC–MS). Fifteen phytosterols and one phytostanol were quantified. The greatest amount of phytosterols (2852.5 mg/100 g of oil) was detected in Mahan variety at 20 weeks after the flowering date (WAFD). Moore had the highest level of phytostanols (7.3 mg/100 g of oil) at 20 WAFD. Phytosterol and phytostanol contents showed a steep decrease during pecan nut development. Results from the quantitative characterization of pecan nut oils revealed that β-sitosterol, D5-avenasterol, and campesterol were the most abundant phytosterol compounds at all ripening stages.
Association between HMW adiponectin, HMW-total adiponectin ratio and early-onset coronary artery disease in Chinese population
Ying Wang, Aihua Zheng, Yunsheng Yan, Fei Song, et al.
Atherosclerosis 235 (2014) 392-397
http://dx.doi.org/10.1016/j.atherosclerosis.2014.05.910
Objective: Adiponectin is an adipose-secreting protein that shows atheroprotective property and has inverse relation with coronary artery disease (CAD). High-molecular weight (HMW) adiponectin is reported as the active form of adiponectin. In the present study, we aimed to investigate the association between total adiponectin, HMW adiponectin, HMW-total adiponectin ratio and the severity of coronary atherosclerosis, and to compare their evaluative power for the risk of CAD. Methods: Serum levels of total and HMW adiponectin were measured in 382 early-onset CAD (EOCAD) patients and 305 matched controls undergoing coronary angiography by enzyme-linked immunosorbent assay (ELISA). Gensini score was used to evaluate the severity of coronary atherosclerosis. Results: CAD onset age was positively correlated with HMW adiponectin (r = 0.383, P < 0.001) and HMW-total adiponectin ratio (r = 0.429, P < 0.001) in EOCAD patients. Total and HMW adiponectin and HMW-total adiponectin ratio were all inversely correlated with Gensini score (r=0.417, r=0.637, r=0.578, respectively; all P < 0.001). Multivariate binary logistic regression analysis demonstrated that HMW adiponectin and HMW-total adiponectin ratio were both inversely correlated with the risk of CAD (P < 0.05). ROC analysis indicated that areas under the ROC curves of HMW adiponectin and HMW-total adiponectin ratio were larger than that of total adiponectin (P < 0.05). Conclusions: Adiponectin is cardioprotective against coronary atherosclerosis onset in EOCAD patients. HMW adiponectin and HMW-total adiponectin ratio show stronger negative associations with the severity of coronary atherosclerosis than total adiponectin does. HMW adiponectin and HMW-total adiponectin ratio are effective biomarkers for the risk of CAD in Chinese population.
Gender and age were well matched between patients and controls. EOCAD patients were tended to have a history of diabetes or hypertension, more current smoking, and more use of lipid lowering drugs. Levels of total cholesterol, LDL-c, FPG, HbA1c and triglycerides were significantly higher in the patients than in controls, while HDL-cholesterol, total adiponectin, HMW adiponectin, and HMW-total adiponectin ratio were significantly lower in the patients. EOCAD patients developed different degrees of coronary atherosclerosis, and had significantly higher levels of high-sensitivity CRP and larger circumferences of waist and hip than controls.
Spearman correlation coefficients between selected cardiovascular risk factors, Gensini score and adiponectin were significant. Total and HMW adiponectin and HMW-total adiponectin ratio were all inversely correlated with Gensini score, BMI and pack years of cigarette smoking. Total and HMW adiponectin were negatively associated with triglycerides and circumference of waist and hip. LDL-cholesterol and high-sensitivity CRP were inversely correlated with HMW adiponectin and HMW-total adiponectin ratio, while HDL-cholesterol and age were positively correlated with them. FPG was only inversely associated with HMW-total adiponectin ratio.
All participants were divided into four groups according to their Gensini score, group A (control, n = 305), group B (<20, n = 154), group C (20-40, n = 121) and group D (>40, n = 105). With the increasing of Gensini score, a stepwise downward trend was observed in levels of total and HMW adiponectin and HMW-total adiponectin ratio (P < 0.001). Specifically, total adiponectin of four groups were 1.58 (0.61-4.36) mg/ml, 1.21 (0.70-2.83) mg/ml, 1.00 (0.73-1.88) mg/ml, and 0.76 (0.37-1.19) mg/ml, respectively. Except group A with B and group B with C, the differences of pairwise comparisons among all the other groups were statistically significant (all P < 0.05). HMW adiponectin of four groups were 0.91 (0.39-3.26) mg/ml, 0.55 (0.32-1.49) mg/ml, 0.46 (0.21-0.876) mg/ml, and 0.23 (0.14-0.39) mg/ml, respectively. The differences of pairwise comparisons among all the other groups were statistically significant (all P < 0.05) except group B with C. HMW-total adiponectin ratio of four groups were 0.58 (0.31-0.81), 0.47 (0.26-0.69), 0.41 (0.24-0.57), and 0.36 (0.21-0.42), respectively. The differences of pairwise comparisons among all the other groups were statistically significant (all P < 0.05) except group B with C. In the model of multivariate binary logistic regression analysis, after adjustment for conventional cardiovascular risk factors, HMW adiponectin (OR = 0.234, P < 0.011) and HMW-total adiponectin ratio (OR = 0.138, P < 0.005) remained inversely correlated with the risk of CAD, while no significant association was observed between total adiponectin and CAD
Areas under the ROC curves were compared pairwise to identify the diagnostic power for CAD among total adiponectin, HMW adiponectin, and HMW-total adiponectin ratio. HMW adiponectin and HMW-total adiponectin ratio showed greater capability for identifying CAD than total adiponectin did (0.797 vs. 0.674, 0.806 vs. 0.674; respectively, all P < 0.05); however, no significant difference was observed between HMW and HMW-total ratio (P > 0.05).
Associations between total adiponectin, HMW adiponectin, HMW-total adiponectin ratio and the severity of coronary atherosclerosis in EOCAD patients (evaluated by Gensini score). *P < 0.05; **P < 0.001; ***P < 0.005 by Mann-Whitney U test.
Compares diagnostic power
Fig. Compares diagnostic power among total adiponectin, HMW adiponectin and HMW-total adiponectin ratio for CAD by ROC curves. Diagnostic power for CAD was based on discriminating patients with or without coronary atherosclerosis. The area under the curve for HMW-total adiponectin ratio (dotted black line) was larger than that for total adiponectin (fine black line) (0.806 [95%CI 0.708-0.903] vs. 0.674 [95%CI 0.552-0.797], P < 0.05) and HMW adiponectin (bold black line) (0.806 [95%CI 0.708-0.903] vs. 0.797 [95%CI 0.706-0.888], no statistically difference). Sensitivity, specificity and optimal cut off value for them were total adiponectin (57.38%, 75.86%, 1.11 mg/ml), HMW (55.74%, 93.1%, 0.49 mg/ml) and H/T (78.69%, 75.86%, 0.52), respectively.
There are two strengths in our study. One is the precise Gensini scoring system to carefully evaluate stenosis of coronary artery or branches > 0% diameter as coronary lesion, another is the specific study subjects of EOCAD in a Chinese Han population that is particularly genetically determined and not influenced by racial/ethnic disparities. The limitations of our study lie in the interference of medications such as the effect of lipid lowering drugs on the levels of adiponectin, and cardiovascular risk factors. Smoking is a conventional cardiovascular risk factor, whose interaction with HMW adiponectin level is rarely investigated, but it has been revealed to be associated with HMW adiponectin level in men according to the study from Kawamoto R et al. We did not adjust the result for the pack/year variable in the multivariate logistic regression analysis for the limitation of small sample size of male subjects in our study. The relatively small study sample also restrained our conclusion generalizable to all populations. Future researches in larger study samples and different populations are in need to validate our findings, and to explore the association of smoking with adiponectin in male subgroup analysis, and to investigate the potential mechanisms by which adiponectin affects the progression of coronary atherosclerosis.
In summary, the present study has demonstrated that adiponectin is protective against coronary atherosclerosis onset in EOCAD patients. HMW adiponectin and HMW-total adiponectin ratio show stronger negative associations with the severity of coronary atherosclerosis than total adiponectin does. HMW adiponectin and HMW-total adiponectin ratio are more effective biomarkers for the risk of CAD than total adiponectin.
Berberis aristata combined with Silybum marianum on lipid profile in patients not tolerating statins at high doses
Giuseppe Derosa, Davide Romano, Angela D’Angelo, Pamela Maffioli
Atherosclerosis 239 (2015) 87-92
http://dx.doi.org/10.1016/j.atherosclerosis.2014.12.043
Aim: To evaluate the effects of Berberis aristata combined with Silybum marianum in dyslipidemic patients intolerant to statins at high doses.
Methods: 137 euglycemic, dyslipidemic subjects, with previous adverse events to statins at high doses, were enrolled. Statins were stopped for 1 month (run-in), then they were re-introduced at the half of the previously taken dose. At randomization, patients tolerating the half dose of statin, were assigned to
add placebo or B. aristata/S. marianum 588/105 mg, 1 tablet during the lunch and 1 tablet during the dinner, for six months. We evaluated lipid profile and safety parameters variation at randomization, and after 3, and 6 months.
Results: B. aristata/S. marianum reduced fasting plasma glucose (-9 mg/dl), insulin (-0.7 mU/ml), and HOMA-index (-0.35) levels compared to baseline and also to placebo. Lipid profile did not significantly change after 6 months since the reduction of statin dosage and the introduction of B. aristata/S. marianum, while it worsened in the placebo group both compared to placebo and with active treatment (+23.4 mg/dl for total cholesterol, +19.6 mg/dl for LDL-cholesterol, +23.1 mg/dl for triglycerides with placebo compared to B. aristata/S. marianum). We did not record any variations of safety parameters
in either group. Conclusions: B. aristata/S. marianum can be considered as addition to statins in patients not tolerating high dose of these drugs.
Statins, also known as 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors, are effective medications for reducing the risk of death and future cardiovascular disease. In the latest years, however, statin intolerance (including adverse effects related to quality of life, leading to decisions to decrease or stop the use of an otherwise-beneficial drug) has come to the forefront of clinical concern, whereas the safety of statins has come to be regarded as largely favorable. Statin intolerance is defined as any adverse symptoms, signs, or laboratory abnormalities attributed by the patient or physician to the statin and in most cases perceived by the patient to interfere unacceptably with activities of daily living, leading to a decision to stop or reduce statin therapy. The physician might also decide to stop or reduce statin therapy on the basis of clinical/laboratory assessment [abnormal liver function tests, creatine phosphokinase values (CPK)] suggesting undue risk. Adverse events are more common at higher doses of statins, and often contribute to patients low adherence to treatment. For this reason, researchers are testing alternative strategies for lipid treatment when statin intolerance is recognized. One strategy to reduce the risk of statin-induced adverse events includes using a low-dose of statin combined with nonstatin drugs in order to achieve the goals of therapy. Nonstatin drugs include nutraceuticals; in the latest years relatively large number of dietary supplements and nutraceuticals have been studied for their supposed or demonstrated ability to reduce cholesterolemia in humans, in particular Berberis Aristata, has been studied in randomized clinical trials and proved to be effective in improving lipid profile. In particular, B. aristata acts up-regulating LDL-receptor (LDL-R) expression independent of sterol regulatory element binding proteins, but dependent on extracellular signal-regulated kinases (ERK) and c-Jun N-terminal kinase (JNK) activation leading to total cholesterol (TC) and LDL-C reduction of about 30 and 25%, respectively. Hwever, B. aristata is a problem in terms of oral bioavailability, affected by a P-glycoprotein (P-gp) mediated gut extrusion process. P-gp seems to reduce by about 90% the amount of B. aristata able to cross the enterocytes, but the use of a potential P-gp inhibitor could ameliorate its oral poor bioavailability improving its effectiveness. Among the potential Pgp inhibitors, silymarin from S. marianum, an herbal drug used as liver protectant, could be considered a good candidate due to its high safety profile.
Analyzing the results of our study, it can appear, at a first glance, that B. aristata/S. marianum has a neutral effect of lipid profile that did not change during the study after the addition of the nutraceutical combination. This lack of effect, however, is only apparent, because, when we analyzed what happens in placebo group, we observed a worsening of lipid profile after statin dose reduction. In other words, the addition of B. aristata/S. marianum neutralized the worsening of lipid profile observed with placebo after statins dose reduction. These results are in line with what was reported by Kong et al., who evaluated the effects of a combination of berberine and simvastatin in sixty-three outpatients diagnosed with hypercholesterolemia. As compared with monotherapies, the combination showed an improved lipid lowering effect with 31.8% reduction of serum LDL-C, and similar efficacies were observed in the reduction of TC as well as Tg in patients. Considering the results of this study, B. aristata/S. marianum can be considered as addition to statins in patients not tolerating high dose of these drugs.
CETP inhibitors downregulate hepatic LDL receptor and PCSK9 expression in vitro and in vivo through a SREBP2 dependent mechanism
Bin Dong, Amar Bahadur Singh, Chin Fung, Kelvin Kan, Jingwen Liu
Atherosclerosis 235 (2014) 449-462
http://dx.doi.org/10.1016/j.atherosclerosis.2014.05.931
Background: CETP inhibitors block the transfer of cholesteryl ester from HDL-C to VLDL-C and LDL-C, thereby raising HDL-C and lowering LDL-C. In this study, we explored the effect of CETP inhibitors on hepatic LDL receptor (LDLR) and PCSK9 expression and further elucidated the underlying regulatory mechanism. Results: We first examined the effect of anacetrapib (ANA) and dalcetrapib (DAL) on LDLR and PCSK9 expression in hepatic cells in vitro. ANA exhibited a dose-dependent inhibition on both LDLR and PCSK9 expression in CETP-positive HepG2 cells and human primary hepatocytes as well as CETP-negative mouse primary hepatocytes (MPH). Moreover, the induction of LDLR protein expression by rosuvastatin in MPH was blunted by cotreatment with ANA. In both HepG2 and MPH ANA treatment reduced the amount of mature form of SREBP2 (SREBP2-M). In vivo, oral administration of ANA to dyslipidemic C57BL/6J mice at a daily dose of 50 mg/kg for 1 week elevated serum total cholesterol by approximately 24.5% (p < 0.05%) and VLDL-C by 70% (p < 0.05%) with concomitant reductions of serum PCSK9 and liver LDLR/SREBP2-M protein. Finally, we examined the in vitro effect of two other strong CETP inhibitors evacetrapib and torcetrapib on LDLR/PCSK9 expression and observed a similar inhibitory effect as ANA in a concentration range of 1-10 µM. Conclusion: Our study revealed an unexpected off-target effect of CETP inhibitors that reduce the mature form of SREBP2, leading to attenuated transcription of hepatic LDLR and PCSK9. This negative regulation of SREBP pathway by ANA manifested in mice where CETP activity was absent and affected serum cholesterol metabolism.
Effect of Eclipta prostrata on lipid metabolism in hyperlipidemic animals
Yun Zhao, Lu Peng, Wei Lu, Yiqing Wang, Xuefeng Huang, et al.
Experimental Gerontology 62 (2015) 37–44
http://dx.doi.org/10.1016/j.exger.2014.12.017
Eclipta prostrata (Linn.) Linn. is a traditional Chinese medicine and has previously been reported to have hypolipidemic effects. However, its mechanism of action is not well understood. This study was conducted to identify the active fraction of Eclipta, its toxicity, its effect on hyperlipidemia, and its mechanism of action. The ethanol extract (EP) of Eclipta and fractions EPF1–EPF4, obtained by eluting with different concentrations of ethanol from a HPD-450 macroporous resin column chromatography of the EP, were screened in hyperlipidemic mice for lipid lowering activity, and EPF3 was the most active fraction. The LD50 of EPF3 was undetectable because no mice died with administration of EPF3 at 10.4 g/kg. Then, 48 male hamsters were used and randomly assigned to normal chow diet, high-fat diet, high-fat diet with Xuezhikang (positive control) or EPF3 (75, 150 and 250 mg/kg) groups. We evaluated the effects of EPF3 on body weight gain, liver weight gain, serum lipid concentration, antioxidant enzyme activity, and the expression of genes involved in lipid metabolism in hyperlipidemic hamsters. The results showed that EPF3 significantly decreased body-weight gain and liver-weight gain and reduced the serum lipid levels in hyperlipidemic hamsters. EPF3 also increased the activities of antioxidant enzymes; upregulated the mRNA expression of peroxisome proliferator-activated receptor α (PPARα), low density lipoprotein receptor (LDLR), lecithin-cholesterol transferase (LCAT) and scavenger receptor class B type Ι receptor (SR-BI); and down-regulated the mRNA expression of 3-hydroxy-3-methyl-glutaryl-CoA reductase (HMGR) in the liver. These results indicate that EPF3 ameliorates hyperlipidemia, in part, by reducing oxidative stress and modulating the transcription of genes involved in lipid metabolism.
Although Eclipta has long been used as a food additive, no studies or reports have clearly shown any liver or kidney toxicity from its use. Therefore, E. prostrata is safe and beneficial for preventing hyperlipidemia in experimental animals and can be used as an alternative medicine for the regulation of dyslipidemia.
Effect of high fiber products on blood lipids and lipoproteins in hamsters
HE Martinez-Floresa, Y Kil Chang, F Martinez-Bustosc, V Sgarbieri
Nutrition Research 24 (2004) 85–93
http://dx.doi.org:/10.1016/S0271-5317(03)00206-9
Serum and liver lipidemic responses in hamsters fed diets containing 2% cholesterol and different dietary fiber sources were studied. The following diets were made from: a) the control diet made from extruded cassava starch (CSH) contained 9.3% cellulose, b) cassava starch extruded with 9.7% resistant starch (CS-RS), c) cassava starch extruded with 9.9% oat fiber (CS-OF), d) the reference diet contained 9.5% cellulose, and no cholesterol was added. Total cholesterol, LDLVLDL-cholesterol and triglycerides were significantly lower (P < 0.05) in serum of hamsters fed on the CS-RS (17.87%, 62.92% and 9.17%, respectively) and CS-OF (15.12%, 67.41% and 18.35%, respectively) diets, as compared to hamster fed with the CSH diet. Similar results were found in the livers of hamsters fed on the CS-RS and CS-OF diets, as compared to hamsters fed with the CSH diet. The diets containing these fibers could be used as active ingredients in human diets to improve the human health.
A new piece in the puzzling effect of n-3 fatty acids on atherosclerosis?
Wilfried Le Goff
Atherosclerosis 235 (2014) 358-362
http://dx.doi.org/10.1016/j.atherosclerosis.2014.03.038
Omega-3 fatty acids (ω-3) FA are reported to be protective against cardiovascular disease (CVD), notably through their beneficial action on atherosclerosis development. In this context dietary intake of long chain marine eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) is recommended and randomised trials largely support that EPA and DHA intake is associated with a reduction of CVD. However, mechanisms governing the atheroprotective action of ω-3 FA are still unclear and numerous studies using mouse models conducted so far do not allow to reach a precise view of the cellular and molecular effects of ω-3 FA on atherosclerosis. In the current issue of Atherosclerosis, Chang et al. provide important new information on the anti-atherogenic properties of ω-3 FA by analyzing the incremental replacement of saturated FA by pure fish oil as a source of EPA and DHA in Ldlr -/- mice fed a high fat/high cholesterol diet.
Cardiovascular disease (CVD) is the leading causes of death in the world and is frequently associated with atherosclerosis, a pathology characterized by the accumulation of lipids, mainly cholesterol in the arterial wall. Among major risk factors for CVD, circulating levels of lipids and more especially those originating from diets are closely linked to development of atherosclerosis. In this context, not only cholesterol, but also dietary fatty acids (FA) may appear particularly deleterious in regards to atherosclerosis and associated CVD. However, although saturated fats are proatherogenic, omega-3 fatty acids (ω-3 FA), and more especially long-chain marine eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), exert atheroprotective properties through several potential underlying mechanisms. Therefore, the intake of EPA and DHA is recommended around the world and randomised trials with ω-3 FA confirmed that EPA and DHA intake reduced risk for CVD events. However benefits of ω-3 FA intake were challenged by recent clinical trials that failed to replicate protective effects of EPA + DHA on CVD, raising the controversy on the healthy side of marine ω-3 FA.
Animal models are commonly employed in order to decipher mechanisms by which ω-3 FA exert their beneficial actions regarding lipid metabolism and atherosclerosis. Since the last past 20 years, mouse models, and more especially genetically modified mouse models, became the reference model to evaluate the effects of dietary fatty acids, especially ω-3 FA, on atherosclerosis development [7-20]. However, the use of different mouse models of atherosclerosis (Apoe-/-, Ldlr-/-, double Apoe-/- x Ldlr-/- , Ldlr-/- x hApoB mice), as well as diet composition (chow, high cholesterol, high fat, high cholesterol/high fat), source of ω-3 FA supplementation (fish oil, perilla seed oil, flaxseed, pure ALA, EPA or DHA), duration of the diet (from 4 to 32 weeks), size of atherosclerotic lesions in control animals (from 51 to 700.103 mm2) in
those studies led to heterogeneous results and therefore to a partial understanding of the effects of ω-3 FA on atherosclerosis.
Contrary to what observed in Apoe-/- mice, dietary supplementation of Ldlr-/- mice with ω-3 FA led to a reproducible reduction of aortic atherosclerosis, although to various degrees, confirming that Ldlr-/- mice constitute the most appropriate model for studying the atheroprotective effects of ω-3 FA. When evaluated, the decrease of atherosclerosis upon ω-3 FA-rich diet was accompanied by a reduction in the macrophage content as well as inflammation in aortic lesions highlighting the major impact of ω-3 FA on monocyte recruitment and subsequent macrophage accumulation in the arterial wall. However, although supplementation with ω-3 FA allows an efficacious lowering of plasma lipid levels in humans, studies in mouse models suggest that the antiatherogenic action of ω-3 FA is independent of any effects on plasma cholesterol or triglyceride levels. However, that must be asserted with caution as lipid metabolism is quite different in mouse in comparison to humans, highlighting the need to study in the future the effects of ω-3 FA on atherosclerosis in a mouse model exhibiting a more “humanized” lipid metabolism as achieved in hApoB/CETP mice.
In a previous issue of Atherosclerosis, Chang et al. reevaluate the impact of fish oil ω-3 FA on atherosclerosis development by operating an incremental replacement of saturated fats (SAT) by ω-3 FA (pure fish oil, EPA- and DHA-rich) in Ldlr-/- mice fed a high-fat (21%, w/w)/high-cholesterol (0.2%, w/w) diet for a 12-week period. This experimental approach is quite pertinent as dietary fat intake in developed countries, as in United States, derived mostly from saturated FA and is poor in ω-3 FA. Then, using this strategy the authors were able to evaluate the potential beneficial effects of a supplementation with fish oil ω-3 FA in a dietary context for which ω-3 FA intake is relevant.
Here, Chang et al. demonstrated that the progressive increase of dietary intake of fish oil ω-3 FA (EPA and DHA) abrogated the deleterious effects of a SAT diet, thereby suggesting that a dietary ω-3 FA intake on a SAT background is potentially efficient to decrease CVD in humans. Indeed, replacement of SAT by fish oil ω-3 FA markedly reduced plasma cholesterol and triglycerides levels and abolished diet-induced atherosclerosis mediated by SAT in Ldlr-/-mice. To note that in the present study, Ldlr-/- mice only developed small atherosclerosic lesions (~100.103 mm2) after 12 weeks of diet with SAT.
As previously reported, decreased atherosclerotic lesions were accompanied by a reduced content of aortic macrophages and inflammation. Based on their previous works, the authors proposed that the reduction of atherosclerosis upon ω-3 FA resulted from an impairment of cholesterol uptake by arterial macrophages consecutive to the decrease of Lipoprotein Lipase (LPL) expression in those cells. Indeed, beyond its lipolysis action on triglycerides, LPL was reported to promote lipid accumulation, in particular in macrophages, by binding to lipoproteins and cell surface proteoglycans and then acting as a bridging molecule that facilitates cellular lipid uptake. Coherent with this mechanism, macrophage LPL expression was reported to promote foam cell formation and atherosclerosis. In the present study, replacement of SAT by ω-3 FA both decreased expression and altered distribution of arterial LPL. Such a mechanism for ω-3 FA (EPA and DHA) was proposed by this group in earlier studies to favor reduction of arterial LDL-cholesterol. It is noteworthy that lipid rafts alter distribution of LPL at the cell surface and subsequently the LPL dependent accumulation of lipids in macrophages and foam cell formation. As incorporation of ω-3 FA, such as DHA, into cell membrane phospholipids disrupts lipid rafts organization, it cannot be exclude that reduction of lipid accumulation in arterial macrophages upon addition of ω-3 FA results in part from an impairment of the localization and of the anchoring function of LPL at the cell surface of macrophages. Indeed Chang et al. observed that progressive replacement of SAT by ω-3 FA affected aortic FA composition leading to a pronounced increase of arterial EPA and DHA, then suggesting that content of ω-3 FA in macrophage membrane may be equally altered. However, the implication of LPL in the atheroprotective effects of ω-3 FA need to be validated using an appropriate mouse model for which LPL expression may be controlled.
Among the various mechanisms by which ω-3 FA exert anti-inflammatory properties, EPA and DHA repressed inflammation by shutting down NF-kB activation in macrophages. Since expression of TLR-4 and NF-kB target genes, IL-6 and TNFα, in aorta from mice fed diets containing ω-3 FA were decreased when compared to SAT, those results strongly support the contention that ω-3 FA repress inflammation by inhibiting the TLR4/NF-kB signaling cascade likely through the macrophage ω-3 FA receptor GPR120.
Although further studies are needed to explore the complete spectrum of actions of ω-3 FA on atherosclerosis development and CVD, this study provides important information that supports that ω-3 FA intake is a pertinent strategy to reduce risk of CVD.
Effects of dietary hull-less barley β-glucan on the cholesterol metabolism of hypercholesterolemic hamsters
Li-Tao Tong, Kui Zhong, Liya Liu, Xianrong Zhou, Ju Qiu, Sumei Zhou
Food Chemistry 169 (2015) 344–349
http://dx.doi.org/10.1016/j.foodchem.2014.07.157
The aim of the present study is to investigate the hypocholesterolemic effects of dietary hull-less barley β-glucan (HBG) on cholesterol metabolism in hamsters which were fed a hypercholesterolemic diet. The hamsters were divided into 3 groups and fed experimental diets, containing 5‰ HBG or 5‰ oat β-glucan (OG), for 30 days. The HBG, as well as OG, lowered the concentration of plasma LDL-cholesterol significantly. The excretion of total lipids and cholesterol in feces were increased in HBG and OG groups compared with the control group. The activity of 3-hydroxy-3-methyl glutaryl-coenzyme A (HMG-CoA) reductase in liver was reduced significantly in the HBG group compared with the control and OG groups. The activity of cholesterol 7-α hydroxylase (CYP7A1) in the liver, in the HBG and OG groups, was significantly increased compared with the control group. The concentrations of acetate, propionate and total short chain fatty acids (SCFAs) were not significantly different between the HBG and control groups. These results indicate that dietary HBG reduces the concentration of plasma LDL cholesterol by promoting the excretion of fecal lipids, and regulating the activities of HMG-CoA reductase and CYP7A1 in hypercholesterolemic hamsters.
Effects of dietary wheat bran arabinoxylans on cholesterolmetabolism of hypercholesterolemic hamsters
Li-Tao Tong, Kui Zhong, Liya Liu, Ju Qiu, Lina Guo, et al.
Carbohydrate Polymers 112 (2014) 1–5
http://dx.doi.org/10.1016/j.carbpol.2014.05.061
The aim of the present study is to investigate the effects of dietary wheat bran arabinoxylans (AXs) on cholesterol metabolism in hypercholesterolemic hamsters. The hamsters were divided into 3 groups and fed the experimental diets containing AXs or oat β-glucan at a dose of 5 g/kg for 30 days. As the results,the AXs lowered plasma total cholesterol and LDL-cholesterol concentrations, and increased excretions of total lipids, cholesterol and bile acids, as well as oat β-glucan. The AXs reduced the activity of 3-hydroxy-3-methyl glutaryl-coenzyme A (HMG-CoA) reductase, and increased the activity of cholesterol 7-α hydroxylase (CYP7A1) in liver. Moreover, the AXs increased propionate and the total short-chain fatty acids (SCFAs) concentrations. These results indicated that dietary AXs reduced the plasma total cholesterol and LDL-cholesterol concentrations by promoting the excretion of fecal lipids, regulating the activities of HMG-CoA reductase and CYP7A1, and increasing colonic SCFAs in hamsters.
High-fructose feeding promotes accelerated degradation of hepatic LDL receptor and hypercholesterolemia in hamsters via elevated circulating PCSK9 levels
Bin Dong, Amar Bahadur Singh, Salman Azhar, Nabil G. Seidah, Jingwen Liu
Atherosclerosis 239 (2015) 364-374
http://dx.doi.org/10.1016/j.atherosclerosis.2015.01.013
Background: High fructose diet (HFD) induces dyslipidemia and insulin resistance in experimental animals and humans with incomplete mechanistic understanding. By utilizing mice and hamsters as in vivo models, we investigated whether high fructose consumption affects serum PCSK9 and liver LDL receptor (LDLR) protein levels. Results: Feeding mice with an HFD increased serum cholesterol and reduced serum PCSK9 levels as compared with the mice fed a normal chow diet (NCD). In contrast to the inverse relationship in mice, serum PCSK9 and cholesterol levels were co-elevated in HFD-fed hamsters. Liver tissue analysis revealed that PCSK9 mRNA and protein levels were both reduced in mice and hamsters by HFD feeding, however, liver LDLR protein levels were markedly reduced by HFD in hamsters but not in mice. We further showed that circulating PCSK9 clearance rates were significantly lower in hamsters fed an HFD as compared with the hamsters fed NCD, providing additional evidence for the reduced hepatic LDLR function by HFD consumption. The majority of PCSK9 in hamster serum was detected as a 53 kDa N-terminus cleaved protein. By conducting in vitro studies, we demonstrate that this 53 kDa truncated hamster PCSK9 is functionally active in promoting hepatic LDLR degradation. Conclusion: Our studies for the first time demonstrate that high fructose consumption increases serum PCSK9 concentrations and reduces liver LDLR protein levels in hyper-lipidemic hamsters. The positive correlation between circulating cholesterol and PCSK9 and the reduction of liver LDLR protein in HFD-fed hamsters suggest that hamster is a better animal model than mouse to study the modulation of PCSK9/LDLR pathway by atherogenic diets.
High-oleic canola oil consumption enriches LDL particle cholesteryl oleate content and reduces LDL proteoglycan binding in humans
Peter J.H. Jones, Dylan S. MacKay, Vijitha K. Senanayake, Shuaihua Pu, et al.
Atherosclerosis 238 (2015) 231-238
http://dx.doi.org/10.1016/j.atherosclerosis.2014.12.010
Oleic acid consumption is considered cardio-protective according to studies conducted examining effects of the Mediterranean diet. However, animal models have shown that oleic acid consumption increases LDL particle cholesteryl oleate content which is associated with increased LDL-proteoglycan binding and atherosclerosis. The objective was to examine effects of varying oleic, linoleic and docosahexaenoic acid consumption on human LDL-proteoglycan binding in a non-random subset of the Canola Oil Multi-center Intervention Trial (COMIT) participants. COMIT employed a randomized, double-blind, five-period, crossover trial design. Three of the treatment oil diets: 1) a blend of corn/safflower oil (25:75); 2) high oleic canola oil; and 3) DHA-enriched high oleic canola oil were selected for analysis of LDL-proteoglycan binding in 50 participants exhibiting good compliance. LDL particles were isolated from frozen plasma by gel filtration chromatography and LDL cholesteryl esters quantified by mass-spectrometry. LDL-proteoglycan binding was assessed using surface plasmon resonance. LDL particle cholesterol ester fatty acid composition was sensitive to the treatment fatty acid compositions, with the main fatty acids in the treatments increasing in the LDL cholesterol esters. The corn/safflower oil and high-oleic canola oil diets lowered LDL-proteoglycan binding relative to their baseline values (p < 0.0005 and p < 0.0012, respectively). At endpoint, high-oleic canola oil feeding resulted in lower LDL-proteoglycan binding than corn/safflower oil (p < 0.0243) and DHA-enriched high oleic canola oil (p < 0.0249), although high-oleic canola oil had the lowest binding at baseline (p < 0.0344). Our findings suggest that high-oleic canola oil consumption in humans increases cholesteryl oleate percentage in LDL, but in a manner not associated with a rise in LDL-proteoglycan binding.
Posted in Anemia in CVD Patients, Biological Networks, Biomarkers & Medical Diagnostics, Ca2+ triggered activation, Calcium Signaling, Calmodulin Kinase and Contraction, Cardiomyopathy, Cardiovascular Pharmacogenomics, Curation, Diagnostics and Lab Tests, Disease Biology, Gene Regulation, HTN, Innovations, tagged Angiotensin II receptor antagonist, Cardiovascular Biology, endothelins, Heart Failure, hyoertension, mesangium, Pulmonary hypertension on February 27, 2015| Leave a Comment »
Writer and Curator: Larry H. Bernstein, MD, FCAP
Introduction
The basic functioning of the heart, and the kidney have been covered in depth elsewhere, and pulmonary function less, except in this series. The relationship between them on the basis of endocrine, signaling, and metabolic balance is the focus in this piece.
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Sodium homeostasis
Icariin attenuates angiotensin II‑induced hypertrophy and apoptosis in H9c2 cardiomyocytes by inhibiting reactive oxygen species‑dependent JNK and p38 pathways
H Zhou, Y Yuan, Y Liu, Wei Deng, Jing Zong, Zhou‑Yan Bian, Jia Dai and Qi‑Zhu Tang
Exper and Therapeutic Med 7: 1116-1122, 2014
http://dx.doi.org:/10.3892/etm.2014.1598
Icariin, the major active component isolated from plants of the Epimedium family, has been reported to have potential protective effects on the cardiovascular system. However, it is not known whether icariin has a direct effect on angiotensin II (Ang II)‑induced cardiomyocyte enlargement and apoptosis. In the present study, embryonic rat heart‑derived H9c2 cells were stimulated by Ang II, with or without icariin administration. Icariin treatment was found to attenuate the Ang II‑induced increase in mRNA expression levels of hypertrophic markers, including atrial natriuretic peptide and B‑type natriuretic peptide, in a concentration‑dependent manner. The cell surface area of Ang II‑treated H9c2 cells also decreased with icariin administration. Furthermore, icariin repressed Ang II‑induced cell apoptosis and protein expression levels of Bax and cleaved‑caspase 3, while the expression of Bcl‑2 was increased by icariin. In addition, 2′,7’‑dichlorofluorescein diacetate incubation revealed that icariin inhibited the production of intracellular reactive oxygen species (ROS), which were stimulated by Ang II. Phosphorylation of c‑Jun N‑terminal kinase (JNK) and p38 in Ang II‑treated H9c2 cells was blocked by icariin. Therefore, the results of the present study indicated that icariin protected H9c2 cardiomyocytes from Ang II‑induced hypertrophy and apoptosis by inhibiting the ROS‑dependent JNK and p38 pathways.
Short-term add-on therapy with angiotensin receptor blocker for end-stage inotrope-dependent heart failure patients: B-type natriuretic peptide reduction in a randomized clinical trial
Marcelo E. Ochiai, ECO Brancalhao, RSN Puig, KRN Vieira, et al.
Clinics. 2014; 69(5):308-313
http://dx.doi.org:/10.6061/clinics/2014(05)02
OBJECTIVE: We aimed to evaluate angiotensin receptor blocker add-on therapy in patients with low cardiac output during decompensated heart failure. METHODS: We selected patients with decompensated heart failure, low cardiac output, dobutamine dependence, and an ejection fraction ,0.45 who were receiving an angiotensin-converting enzyme inhibitor. The patients were randomized to losartan or placebo and underwent invasive hemodynamic and B-type natriuretic peptide measurements at baseline and on the seventh day after intervention. ClinicalTrials.gov: NCT01857999. RESULTS: We studied 10 patients in the losartan group and 11 patients in the placebo group. The patient characteristics were as follows: age 52.7 years, ejection fraction 21.3%, dobutamine infusion 8.5 mcg/kg.min, indexed systemic vascular resistance 1918.0 dynes.sec/cm5.m2, cardiac index 2.8 L/min.m2, and B-type natriuretic peptide 1,403 pg/mL. After 7 days of intervention, there was a 37.4% reduction in the B-type natriuretic peptide levels in the losartan group compared with an 11.9% increase in the placebo group (mean difference, – 49.1%; 95% confidence interval: -88.1 to -9.8%, p = 0.018). No significant difference was observed in the hemodynamic measurements. CONCLUSION: Short-term add-on therapy with losartan reduced B-type natriuretic peptide levels in patients hospitalized for decompensated severe heart failure and low cardiac output with inotrope dependence.
Development of a Novel Heart Failure Risk Tool: The Barcelona Bio-Heart Failure Risk Calculator (BCN Bio-HF Calculator)
Josep Lupon, Marta de Antonio, Joan Vila, Judith Penafiel, et al.
PLoS ONE 9(1): e85466. http://dx.doi.org:/10.1371/journal.pone.0085466
Background: A combination of clinical and routine laboratory data with biomarkers reflecting different pathophysiological pathways may help to refine risk stratification in heart failure (HF). A novel calculator (BCN Bio-HF calculator) incorporating N-terminal pro B-type natriuretic peptide (NT-proBNP, a marker of myocardial stretch), high-sensitivity cardiac troponin T (hs-cTnT, a marker of myocyte injury), and high-sensitivity soluble ST2 (ST2), (reflective of myocardial fibrosis and remodeling) was developed. Methods: Model performance was evaluated using discrimination, calibration, and reclassi-fication tools for 1-, 2-, and 3-year mortality. Ten-fold cross-validation with 1000 bootstrapping was used. Results: The BCN Bio-HF calculator was derived from 864 consecutive outpatients (72% men) with mean age 68.2612 years (73%/27% New York Heart Association (NYHA) class I-II/III-IV, LVEF 36%, ischemic etiology 52.2%) and followed for a median of 3.4 years (305 deaths). After an initial evaluation of 23 variables, eight independent models were developed. The variables included in these models were age, sex, NYHA functional class, left ventricular ejection fraction, serum sodium, estimated glomerular filtration rate, hemoglobin, loop diuretic dose, β-blocker, Angiotensin converting enzyme inhibitor/Angiotensin-2 receptor blocker and statin treatments, and hs-cTnT, ST2, and NT-proBNP levels. The calculator may run with the availability of none, one, two, or the three biomarkers. The calculated risk of death was significantly changed by additive biomarker data. The average C-statistic in cross-validation analysis was 0.79. Conclusions: A new HF risk-calculator that incorporates available biomarkers reflecting different pathophysiological pathways better allowed individual prediction of death at 1, 2, and 3 years.
TNF and angiotensin type 1 receptors interact in the brain control of blood pressure in heart failure
Tymoteusz Zera, Marcin Ufnal, Ewa Szczepanska-Sadowska
Cytokine 71 (2015) 272–277
http://dx.doi.org/10.1016/j.cyto.2014.10.019
Accumulating evidence suggests that the brain renin-angiotensin system and proinflammatory cytokines, such as TNF-α, play a key role in the neuro-hormonal activation in chronic heart failure (HF). In this study we tested the involvement of TNF-α and angiotensin type 1 receptors (AT1Rs) in the central control of the cardiovascular system in HF rats. Methods: we carried out the study on male Sprague–Dawley rats subjected to the left coronary artery ligation (HF rats) or to sham surgery (sham-operated rats). The rats were pretreated for four weeks with intracerebroventricular (ICV) infusion of either saline (0.25 µl/h) or TNF-α inhibitor etanercept (0.25 µg/0.25 µl/h). At the end of the pretreatment period, we measured mean arterial blood pressure (MABP) and heart rate (HR) at baseline and during 60 min of ICV administration of either saline (5 µl/h) or AT1Rs antagonist losartan (10 µg/5 µl/h). After the experiments, we measured the left ventricle end-diastolic pressure (LVEDP) and the size of myocardial scar. Results: MABP and HR of sham-operated and HF rats were not affected by pretreatments with etanercept or saline alone. In sham-operated rats the ICV infusion of losartan did not affect MABP either in saline or in etanercept pretreated rats. In contrast, in HF rats the ICV infusion of losartan significantly decreased MABP in rats pretreated with saline, but not in those pretreated with etanercept. LVEDP was significantly elevated in HF rats but not in sham-operated ones. Surface of the infarct scar exceeded 30% of the left ventricle in HF groups, whereas sham-operated rats did not manifest evidence of cardiac scarring. Conclusions: our study provides evidence that in rats with post-infarction heart failure the regulation of blood pressure by AT1Rs depends on centrally acting endogenous TNF-α.
Statins in heart failure—With preserved and reduced ejection fraction. An update
Dimitris Tousoulis , E Oikonomou, G Siasos, C Stefanadis
Pharmacology & Therapeutics 141 (2014) 79–91
http://dx.doi.org/10.1016/j.pharmthera.2013.09.001
HMG-CoA reductase inhibitors or statins beyond their lipid lowering properties and mevalonate inhibition exert also their actions through a multiplicity of mechanisms. In heart failure (HF) the inhibition of isoprenoid intermediates and small GTPases, which control cellular function such as cell shape, secretion and proliferation, is of clinical significance. Statins share also the peroxisome proliferator-activated receptor pathway and inactivate extracellular-signal-regulated kinase phosphorylation suppressing inflammatory cascade. By down-regulating Rho/Rho kinase signaling pathways, statins increase the stability of eNOS mRNA and induce activation of eNOS through phosphatidylinositol 3-kinase/Akt/eNOS pathway restoring endothelial function. Statins change also myocardial action potential plateau by modulation of Kv1.5 and Kv4.3 channel activity and inhibit sympathetic nerve activity suppressing arrhythmogenesis. Less documented evidence proposes also that statins have antihypertrophic effects – through p21ras/mitogen activated protein kinase pathway – which modulate synthesis of matrix metalloproteinases and procollagen 1 expression affecting interstitial fibrosis and diastolic dysfunction. Clinical studies have partly confirmed the experimental findings and despite current guidelines new evidence supports the notion that statins can be beneficial in some cases of HF. In subjects with diastolic HF, moderately impaired systolic function, low B-type natriuretic peptide levels, exacerbated inflammatory response and mild interstitial fibrosis evidence supports that statins can favorably affect the outcome. Under the lights of this evidence in this review article we discuss the current knowledge on the mechanisms of statins’ actions and we link current experimental and clinical data to further understand the possible impact of statins’ treatment on HF syndrome.
Since 1980 when the first 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor or statin was introduced in clinical practice, statins have been extensively used in the treatment of patients with dyslipidemia as well as of those with coronary artery disease (CAD). Importantly, large scale trials and metanalysis have documented their significant benefits in terms of primary and secondary CAD prevention which out-weigh any potential side effects. Statins’ benefits extend, according to recent studies, even in patients with normal or low cholesterol levels and beyond their lipid lowering effects, indicating their multiple protective mechanisms.
Heart failure (HF) is a complex syndrome with different definitions and its diagnosis is based on a combination of symptoms, clinical signs and imaging or laboratory data. different categorization schemes have been used dividing HF in acute or chronic, in systolic or diastolic, and in ischemic or dilated simply reflecting the complexity of the syndrome and the multiplicity of the pathophysiologic mechanisms implicated in the disease development and progression. In addition to the diverse pathophysiology of HF the syndrome is also characterized by high morbidity and mortality. Recent treatment advantages such as angiotensin converting enzyme inhibitors and beta blockers have not yet proven their clinical benefit in subjects with diastolic HF.
As the most common cause of HF is CAD and statins have proven their benefits in a wide spectrum of diseases directly or indirectly associated with atherosclerotic cardiovascular disease, HMG-CoA reductase inhibitors have been tested in subjects with HF. Interestingly, non-randomized, observational and retrospective early studies in subjects with HF of ischemic and non-ischemic etiology have suggested that statins are associated with improved outcomes. Thereafter, two large scale randomized control trials failed to demonstrate any benefits in mortality of HF patients treated with rosuvastatin and subsequently current HF guidelines do not include recommendations for statin use except from when they are indicated for comorbidities, such as established CAD.
Statins inhibit HMG-CoA reductase. This enzyme catalyzes the conversion of 3-hydroxy-3-methylglutaryl-coenzyme A to L-mevalonic acid, which is the rate-limiting step in the cholesterol synthesis pathway. Inhibition of the mevalonate pathway and of cholesterol synthesis triggers an increase in LDL receptor activity by stimulating production of mRNA for LDL receptor in liver. The induction of LDL receptors is responsible for the observed increase in plasma clearance of LDL cholesterol. CAD is the cause of approximately two-thirds of cases of systolic HF. The beneficial effects of statins-induced LDL reduction are well established in patients with atherosclerosis and CAD. Nevertheless, the results from statin treatment, even in ischemic HF cases, are not straightforward and several mechanisms have been proposed for this paradox.
multiplicity of HMG CoA reductase inhibitors mechanisms and their effects
The figure demonstrates the multiplicity of HMG CoA reductase inhibitors mechanisms and their effects. ↓: decrease; ↑ increase; FPP: farnesyl pyrophosphate: GGPP: geranylgeranyl pyrophosphate; Ras, Rac, Rho; small GTPases; eNOS: endothelial nitric oxide synthase; ATP: adenosine triphosphate; PI-3 kinase: phosphatidylinositol 3-kinase; AMPK: AMP activated protein kinase; GTP: Guanosine triphosphate; NADPH: Nicotinamide adenine dinucleotide phosphate; ERK: extracellular-signal-regulated kinase; Shadow box represents adverse mechanism and actions of HGM CoA reductase inhibitors.
The anti-inflammatory effects of HMG CoA reductase inhibitors in atherosclerosis have been early recognized. Statins also have a potent anti-inflammatory effect in HF models. Importantly, there is a link between inflammation and HF pathogenesis and is now widely accepted that pro-inflammatory cytokines cause systolic dysfunction, myocardial hypertrophy, activate a fetal gene program in cardiac myocytes, disturb extracellular matrix structure, cause cardiac cachexia etc. In addition, data from the Vesnarinone trial (VEST) in 384 patients with HF demonstrate a decline in survival with increasing TNFα levels confirming the notion that circulating cytokines are associated with adverse prognosis of HF patients.
The proposed, by the aforementioned mechanisms, anti-inflammatory effects of statins have been confirmed experimentally. Indeed, in a rat HF model with preserved ejection fraction (EF), treatment with rosuvastatin resulted in a significant additional improvement in HF and cardiac remodeling, partly due to decreased myocardial inflammation. In rats after acute myocardial infarction simvastatin treatment for 4 weeks beneficially modified the levels of TNFα, interleukin (IL)-1, 6 and 10 in the infarct regions. Importantly, in 446 patients with systolic HF, followed up for a period of 24 months, statins’ treatment was associated with a decrease in serum levels of C-reactive protein (CRP), IL-6 and tumor necrosis factor-alpha receptor II. Recently, in a randomized study of 22 subjects with ischemic HF short term atorvastatin treatment achieved a significant decrease in serum levels of intracellular adhesion molecule-1.
Taken together we can conclude that HMG CoA reductase inhibitors can modify inflammatory status by modulation of PRAP and ERK pathways by down regulating Toll like receptor 4 mRNA expressions and LDL oxidation and by reducing soluble lipoprotein-associated phospholipase A2 mass and activity. Importantly, the theoretical anti-inflammatory properties were confirmed in experimental and clinical HF models.
Endothelial dysfunction contributes to the pathogenesis of HF and can enhance adverse left ventricle (LV) remodeling and increase afterload in subjects with HF. Interestingly, statins have been constantly associated with improved endothelial function in subjects with a variety of cardiovascular diseases. Endothelium derived nitric oxide (NO) is an important determinant of endothelial function and HMG-CoA reductase inhibitors can up regulate endothelial NO synthase (eNOS) by different mechanisms.
Statins induce down regulation of Rho/Rho kinase signaling pathways, increasing the stability of eNOS mRNA and its expression . In addition, in human endothelial cells the Rho-kinase inhibitor, hydroxyfasudil leads to the activation of the phosphatidylinositol 3-kinase/Akt/eNOS pathway. Statins also induce activation of eNOS through the rapid activation of the serine–threonine protein kinase Akt. The beneficial effects of Akt activation are not limited to eNOS phoshorylation but extend to the promotion of new blood vessels growth. HMG CoA reductase inhibitors can further affect endothelial function through their effect on caveolin-1. Caveolin-1 binds to eNOS inhibiting NO production. Incubation of endothelial cells with atorvastatin promotes NO production by decreasing caveolin-1 expression, regardless of the level of extracellular LDL-cholesterol. These effects were reversed with mevalonate highlighting the therapeutic potential of inhibiting cholesterol synthesis in peripheral cells to correct NO-dependent endothelial dysfunction associated with hypercholesterolemia and possibly other diseases.
Although the experimentally confirmed benefits of HMG CoA reductase inhibitors in diastolic dysfunction and left ventricle stiffness, few data exist concerning the underlying mechanisms. As diastolic dysfunction precedes myocardial hypertrophy the anti-hypertrophic pathways mentioned in the previous section (inhibition of RhoA/Ras/ERK, PRAPγ pathways, inhibition of a large G(h) protein-coupled pathway etc.), may also contribute to the restoration of diastolic function. Moreover, in angiotensin II induced diastolic dysfunction in hypertensive mice, pravastatin not only improved diastolic function but also down-regulated collagen I, transforming growth factor-beta, matrix metalloproteinases (MMPs)-2 and -3, atrial natriuretic factor, IL-6 TNFα, Rho kinase 1 gene expression, and upregulated eNOS gene expression. These findings suggest the potential involvement of Rho kinase 1 in the beneficial effects of pravastatin in diastolic HF. Taken together data suggest that HMG CoA reductase inhibitors might be beneficial in patients with diastolic HF, a hypothesis that remains to be confirmed by clinical studies. Nevertheless, mechanistic studies have not fully explored the pathways affecting diastolic function and most data until now are indirect. Therefore efforts should be focus on the underline mechanisms affecting collagen synthesis, MMPs activity extracellular matrix synthesis and overall diastolic function in HF subjects under statin treatment.
Statins through inhibition of small GTPases can modulate MMPs activity in several cell types such as endothelial cells and human macrophages. In rat and human cardiac fibroblasts, stimulated with either transforming growth factor β1 or angiotensin II, atorvastatin reduced collagen synthesis and α1-procollagen mRNA as well as gene expression of the profibrotic peptide connective tissue growth factor 4. This antifibrotic action may contribute to the anti-remodelling effect of statins. In mouse cardiac fibroblasts treated with angiotensin II, the combination of pravastatin and pioglitazone blocked angiotensin II p38 MAPK and p44/42 MAPK activation and procollagen expression-1.
Several studies have documented the impact of statin treatment on arrhythmia potential. The arrhythmic protective effects of statins can be attributed not only to anti-inflammatory properties but also to changes in myocardial action potential plateau by modulation of Kv1.5 and Kv4.3 channel activity. Atorvastatin and simvastatin block Kv1.5 and Kv4.3 channels shifting the inactivation curve to more negative potentials following a complex mechanism that does not imply the binding of the drug to the channel pore. Moreover, in hypertrophied neonatal rat ventricular myocytes simvastatin alleviated the reduction of Kv4.3 expression, I(to) currents in subepicardial myocardium from the hypertrophied left ventricle. Furthermore, pravastatin in an animal model attenuated reperfusion induced lethal ventricular arrhythmias by inhibition of calcium overload.
Taking together experimental and cellular evidence supporting an effect of statin treatment in myocardial contractility is spare and for the time being we cannot definitively conclude on the clinical impact of HMG CoA reductase inhibitors in myocardial systolic performance.
Half of the cases of HF are attributed to diastolic dysfunction and the prognosis of HF with preserved EF is as ominous as the prognosis of HF with systolic dysfunction. Unfortunately, no treatment has yet been shown, convincingly, to reduce morbidity and mortality in patients with HF and preserved EF, while this group of patients is usually excluded from large prospective randomized trials and accordingly few data exist for the role of statins in this heterogeneous population.
As there is substantially lack of evidence concerning the effects of HMG CoA reductase inhibitors in subjects with HF and preserved EF the first indirect hypothesis was extrapolated from observational prospective studies in subjects with ischemic heart disease and no evidence of congestive HF. Indeed, in a cohort of 430 consecutive patients with ischemic heart disease and a mean EF of 57% Okura et al. observed that subjects under HMG CoA reductase inhibitors treatment had decreased E/E′ ratio—corresponding to a better diastolic function—and a significantly higher survival rate (Okura et al., 2007). According to the authors those beneficially effects can be attributed to improved endothelial function and vasodilatory response to reactive hyperemia, attenuation of myocardial hypertrophy, and interstitial fibrosis.
Despite the positive results from mechanistic and experimental studies clinical studies have failed to confirm a definitive role of HMG CoA reductase inhibitors in HF. Nevertheless, by extrapolating experimental and mechanistic data in clinical settings we further understand how HMG-CoA reductase inhibitors can beneficially affect subgroups of HF subjects such as those with preserved EF, low B-type natriuretic peptide levels, exacerbated inflammatory response and limited interstitial fibrosis. Nevertheless, as a definitive mechanism is lacking, there is uncertainty about the decisive mode of action and further mechanistic studies are needed to reveal how HMG-CoA reductase inhibitors act in HF substrate.
Pro- A-Type Natriuretic Peptide, Proadrenomedullin, and N-Terminal Pro-B-Type Natriuretic Peptide Used in a Multimarker Strategy in Primary Health Care in Risk Assessment of Patients with Symptoms of Heart Failure
Urban Alehagen, Ulf Dahlstr€Om, Jens F. Rehfeld, And Jens P. Goetze
J Cardiac Fail 2013; 19(1):31-39. http://dx.doi.org/10.1016/j.cardfail.2012.11.002
Use of new biomarkers in the handling of heart failure patients has been advocated in the literature, but most often in hospital-based populations. Therefore, we wanted to evaluate whether plasma measurement of N-terminal pro-B-type natriuretic peptide (NT-proBNP), midregional pro-A-type atriuretic peptide (MR-proANP), and midregional proadrenomedullin (MR-proADM), individually or combined, gives prognostic information regarding cardiovascular and all-cause mortality that could motivate use in elderly patients presenting with symptoms suggestive of heart failure in primary health care. Methods and Results: The study included 470 elderly patients (mean age 73 years) with symptoms of heart failure in primary health care. All participants underwent clinical examination, 2-dimenstional echocardiography, and plasma measurement of the 3 propeptides and were followed for 13 years. All mortality was registered during the follow-up period. The 4th quartiles of the biomarkers were applied as cutoff values. NT-proBNP exhibited the strongest prognostic information with 4-fold increased risk for cardiovascular mortality within 5 years. For all-cause mortality MR-proADM exhibited almost 2-fold and NTproBNP 3-fold increased risk within 5 years. In the 5e13-year perspective, NT-proBNP and MR-proANP showed significant and independent cardiovascular prognostic information. NT-proBNP and MR-proADM showed significant prognostic information regarding all-cause mortality during the same time. In those with ejection fraction (EF) !40%, MR-proADM exhibited almost 5-fold increased risk of cardiovascular mortality with 5 years, whereas in those with EF O50% NT-proBNP exhibited 3-fold increased risk if analyzed as the only biomarker in the model. If instead the biomarkers were all below the cutoff value, the patients had a highly reduced mortality risk, which also could influence the handling of patients. Conclusions: The 3 biomarkers could be integrated in a multimarker strategy for use in primary health care.
Novel Biomarkers in Heart Failure with Preserved Ejection Fraction
Kevin S. Shah, Alan S. Maisel
Heart Failure Clin 10 (2014) 471–479
http://dx.doi.org/10.1016/j.hfc.2014.04.005
KEY POINTS
Heart failure (HF) is a global epidemic, defined as an abnormality of cardiac function leading to the inability to deliver oxygen at a rate adequate to meet the requirements of tissues. It is truly a clinical syndrome of symptoms and signs resulting from this cardiac abnormality. Over the past decade, further characterization into 2 entities has occurred: HF with preserved ejection fraction (HFPEF) and HF with reduced ejection fraction (HFREF). HFPEF, previously termed diastolic HF, encompasses the syndrome of HF with a preserved ejection fraction. Cutoffs for this ejection fraction typically are from 45% to 50%. The prevalence of HF is upward of 1% to 2% of the adult population, with an increased prevalence found in elderly and female patients. Multiple studies have shown that the prevalence of HFPEF is actually comparable with the number of patients with HFREF. As expected, most deaths from HFPEF are cardiovascular, comprising 51% to 70% of mortality.
The pathophysiology of HFPEF is controversial and remains poorly understood. Originally, HFPEF was thought to be a primary manifestation of diastolic dysfunction of the left ventricle. However, patients with HFREF are known to also commonly have impaired ventricular relaxation. The primary mechanism of left ventricular (LV) dysfunction is based on structural remodeling and endothelial dysfunction, lending itself to LV stiffness, and increased left atrial pressure. This pressure change is what drives pulmonary venous congestion and subsequent symptomatology. The ventricular stiffness commonly seen in HFPEF is attributed to multiple mechanisms, including fibrosis, excessive collagen deposition, cardiomyocyte stiffness, and slow LV relaxation.
The natriuretic peptides (NPs) are the cornerstone biomarker in congestive HF (CHF). Many of the details of the role of NPs are covered in an article – Florea VG, Anand IS. Biomarkers. Heart Fail Clin 2012;8(2):207–24. The Breathing Not Properly trial originally helped establish the role of B-type natriuretic peptide (BNP) in the diagnosis of CHF. BNP and the N-terminal prohormone BNP (NT-proBNP) have been shown in numerous trials to be an excellent tool for ruling out CHF as a cause of acute dyspnea. Aside from a strong negative predictive value, NPs correlate with HF severity, prognostication, outpatient CHF management, and screening. When attempting to use NPs specifically to distinguish between HFPEF and HFREF, results have shown that NPs do not have a particular cutoff, but are typically elevated in HFPEF in comparison with patients without HF. These levels of NPs in HFPEF are typically lower than levels in patients with HFREF.
Although the role of novel renal biomarkers has not been fully explored specifically in HFPEF, they likely have an impactful role in the assessment and management of acute kidney injury (AKI) and the cardiorenal syndrome. Two biomarkers are briefly discussed here: neutrophil gelatinase-associated lipocalin (NGAL) and cystatin C. NGAL is a 25-kDa protein in the lipocalin family of proteins with a role in inflammation and immune modulation.
The future of biomarkers and their utility in HF is very promising, starting with the potential for using biomarkers as end points in trials. Biomarkers serve as surrogates for various pathophysiologic mechanisms, and there are potential benefits in using them as trial end points. Advantages include the ability to obtain quick and early data, as well as possibly better understand the nature of the disease. However, the counterargument against using biomarkers as trial end points includes whether treatment effects on a biomarker reliably predict effects on a clinically meaningful end point.
Reduced cGMP signaling activates NF-κB in hypertrophied hearts of mice lacking natriuretic peptide receptor-A
Elangovan Vellaichamy, Naveen K. Sommana, Kailash N. Pandey
Biochemical and Biophysical Research Communications 327 (2005) 106–111
http://dx.doi.org:/10.1016/j.bbrc.2004.11.153
Mice lacking natriuretic peptide receptor-A (NPRA) develop progressive cardiac hypertrophy and congestive heart failure. However, the mechanisms responsible for cardiac hypertrophic growth in the absence of NPRA signaling are not yet known. We sought to determine the activation of nuclear factor-κB (NF-κB) in Npr1 (coding for NPRA) gene-knockout (Npr1-/-) mice exhibiting cardiac hypertrophy and fibrosis. NF-κB binding activity was 4-fold greater in the nuclear extract of Npr1-/-mutant mice hearts as compared with wild-type (Npr1+/+) mice hearts. In parallel, inhibitory κB kinase-b activity and IκB-α protein phosphorylation were also increased 3- and 4-fold, respectively, in hypertrophied hearts of mutant mice. cGMP levels were significantly reduced 5-fold in plasma and 10-fold in ventricular tissues of mutant mice hearts relative to wild-type controls. The present findings provide direct evidence that ablation of NPRA/cGMP signaling activates NF-κB binding activity associated with hypertrophic growth of mutant mice hearts.
Regulation of guanylyl cyclase/natriuretic peptide receptor-A gene expression
Renu Garg, Kailash N. Pandey
Peptides 26 (2005) 1009–1023
http://dx.doi.org:/10.1016/j.peptides.2004.09.022
Natriuretic peptide receptor-A (NPRA) is the biological receptor of the peptide hormones atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP). The level and activity of this receptor determines the biological effects of ANP and BNP in different tissues mainly directed towards the maintenance of salt and water homeostasis. The core transcriptional machinery of the TATA-less Npr1 gene, which encodes NPRA, consists of three SP1 binding sites and the inverted CCAAT box. This promoter region of Npr1 gene has been shown to contain several putative binding sites for the known transcription factors, but the functional significance of most of these regulatory sequences is yet to be elucidated. The present review discusses the current knowledge of the functional significance of the promoter region of Npr1 gene and its transcriptional regulation by a number of factors including different hormones, growth factors, changes in extracellular osmolarity, and certain physiological and patho-physiological conditions.
Atrial natriuretic peptide (ANP), a member of natriuretic peptide family is a polypeptide consisting of 28 amino acids and was discovered as a potent vasodilator and diuretic hormone produced in granules of the atrium. The natriuretic peptide family consists of the peptide hormones ANP, brain natriuretic peptide (BNP) and C-type natriuretic peptide (CNP), each of which is derived from a separate gene. ANP and BNP are cardiac derived peptides, which are secreted and up-regulated in myocardium in response to different patho-physiological stimuli, while CNP is an endothelium-derived mediator that plays an important paracrine role in the vasculature. All of these natriuretic peptides elicit a number of vascular, renal, and endocrine effects mainly directed towards the maintenance of blood pressure and extracellular fluid volume by binding to their specific cell surface receptors. ANP exerts its effects at a number of sites including the kidney, where it produces natriuretic and diuretic responses; the adrenal gland, where it inhibits aldosterone synthesis and secretion; vascular smooth muscle cells, where it produces vasorelaxation; the endothelial cells, where it may regulate vascular permeability; gonadal cells, where it affects synthesis of androgen and estradiol. Each of these target sites of ANP activity has been shown to possess specific high affinity receptors for ANP. To date, three different subtypes of natriuretic peptide receptors have been characterized, purified, and cloned, i.e. natriuretic peptide receptors A, B, and C also designated as NPRA, NPRB, and NPRC, respectively. ANP and BNP specifically bind to NPRA, which contains guanylyl cyclase catalytic activity and produces intracellular secondary messenger cGMP in response to hormone binding.
NPRA is considered the biological receptor of ANP and BNP because most of the physiological effects of these hormones are triggered by generation of cGMP or its cell permeable analogs. Recent studies with mice lacking the Npr1 gene, demonstrated that genetic disruption of NPRA increases the blood pressure and causes hypertension in these animals. On the other hand, the effect of ANP was found to be increased linearly in Npr1 gene-duplicated mice
in a manner consistent with gene copy number. All this clearly indicates that the level of NPRA expression determines the extent of the biological effects of ANP and BNP. But the intervention strategies aimed at controlling NPRA expression are limited by the paucity of studies in this area. The cDNA and gene encoding NPRA designated as Npr1 has been cloned and characterized in mouse, rat, bull frog, euryhaline eel, and medaka fish. The primary structure of this gene is essentially same in all the different species and contains 22 exons interrupted by 21 introns. The Npr1 gene sequence has been found to be interspersed with a number of repetitive elements including (SINES), (MER2), and tandem repeat elements in all the different species.
Although the Npr1 gene transcriptional regulation is only poorly understood, the activity and expression of NPRA assessed primarily through ANP stimulated cGMP accumulation are found to be regulated by a number of factors including auto-regulation by natriuretic peptides themselves, other hormones such as endothelin, glucocorticoids, and angiotensin II (ANG II), growth factors, changes in extracellular ion composition, and certain physiological and patho-physiological conditions.
The core molecular machinery of the TATA-less Npr1 gene consisting of SP1 binding sites and the inverted CCAAT box has been authenticated to be indeed functional in rat promoter element. It has been shown that the molecular machinery that regulates the basal expression of Npr1 gene consists of three SP1 binding sites in conjunction with an inverted CCAAT box present in the proximal promoter region. Mutation in any of these SP1 binding sites which
are located within 350 bp upstream of transcription start site in rat Npr1 promoter inhibited SP1 and SP3 binding and decreased the promoter activity by 50–75%, while simultaneous mutation of all the three led to a >90% reduction in promoter activity. The proximal SP1 binding site was much more effective than the distal sites in inducing the expression implying that the proximity to the core transcriptional machinery contributes to the magnitude of the observed effect. The over-expression of either SP1 or SP3 resulted in the induction of the wild type Npr1 promoter, confirming that these transcription factors serve as positive regulators of the Npr1 gene expression.
A number of natriuretic peptides such as ANP, BNP, CNP, and urodilatin (i.e. ANP95–126) can down-regulate ligand dependent NPRA activity after as little as 2 h prior exposure to the ligand, which remains suppressed until 48 h of exposure in cultured cells. The early reduction of NPRA activity is independent of changes in Npr1 gene expression as the pretreatment of cultured cells with actinomycin D (an inhibitor of transcription) for 1 h failed to block the response to ANP implying that ligand acts, at least early on, through a post transcriptional mechanism in reducing NPRA activity. The sustained reduction of NPRA activity, on the other hand, has been shown in fact due to reduction in NPRA mRNA levels (∼50%) by treatment with 100nM ANP for 48 h. This reduction could also be affected by treatment of cultured cells with 8-Br-cGMP with similar kinetic response and was amplified by phosphodiesterase inhibitors, but was not shared by NPRC-selective ligand cANF, suggesting that the down regulation of Npr1 gene expression is mediated by elevations of intracellular cGMP involving either NPRA or NPRB. .. The cGMP regulatory region was pinpointed to position−1372 to−1354 bp from the transcription start site of Npr1 by gel shift assays and footprinting analysis, which indicated its interaction with transcriptional factor(s). Further cross-competition experiments with mutated oligonucleotides led to the definition of a consensus sequence (−1372 bp AaAtRKaNTTCaAcAKTY −1354 bp) for the novel cGMP-RE, which is conserved in the human (75% identity) and mouse (95% identity) Npr1 promoters. The combination of these transcriptional and post-transcriptional ligand-dependent regulatory mechanisms provides the cells with greater flexibility in both initiating and maintaining the suppression of NPRA activity.
The peptide hormone Ang II is an important component of renin-angiotensin system (RAS) and exerts its biological effects such as blood pressure regulation, vasoconstriction, and cell proliferation in many tissues including the kidney, adrenal glands, brain, and vasculature. The two vasoactive peptide hormones, Ang II (vasoconstrictive) and ANP (vasodilatory), interact and mutually antagonize the biological effects of each other at various levels. ANP has been shown to inhibit Ang II-induced contraction of isolated glomeruli and cultured mesangial cells, as well as Ang II-stimulated activation of protein kinase C and mitogen activated protein kinase in vascular smooth muscle cells in a cGMP-dependent manner. Inversely, Ang II has been shown to down-regulate guanylyl cyclase activity of the biological receptor of ANP, NPRA, by activating protein kinase C and/or by stimulating protein tyrosine phosphatase activity, thereby inhibiting the ANP stimulated cGMP accumulation. Ang II also reduces the ANP dependent cGMP levels by stimulating cGMP hydrolysis, apparently
via a calcium dependent cGMP phosphodiesterase.
Endothelin is a vasoconstrictor peptide that was originally isolated from porcine endothelial cells. It is produced as three isoforms (ET1-3) that bind to two receptor subtypes (ETA and ETB). ET is produced in the kidney and subject to regulation by a number of local and systemic factors including immune cytokines and extracellular tonicity. Since, endothelin is avidly expressed in the nephron segment, where NPRA is up-regulated by osmotic stimulus, it was investigated whether endothelin plays a role in the control of basal or osmotically regulated Npr1 gene expression in these cells. The endogenous endothelin and not the exogeneously administered endothelin inhibit the basal but not osmotically stimulated expression of Npr1. The type A (BQ610) and type B (IRL 1038) endothelin receptor antagonists increased the level of NPRA mRNA by two to three-fold, whereas co-administration of exogenous endothelin resulted in partial reversal of this stimulatory effect of receptor antagonists. The increase in extracellular tonicity reduces the endothelin mRNA accumulation (∼15% of control levels) in inner medullary collecting duct cells but this reduction is not found to be linked to the stimulation of NPRA activity/expression in response to osmotic stress.
Glucocorticoids influence the cardiovascular system and induce a rapid increase in blood pressure. Glucocorticoids are known to regulate
transcription in many systems, possibly by interacting with glucocorticoid responsive elements and associated chromatin proteins. These have been shown to affect the atrial endocrine system by regulating both the synthesis and secretion of ANP in vitro and in vivo. Thus, it seems plausible that glucocorticoid may also interact with the atrial endocrine system by modulating ANP receptor levels. The stimulation of vascular smooth muscle cells from rat mesenteric artery with dexa-methasone (a highly specific synthetic glucocorticoid agonist) caused an increase in NPRA mRNA levels in a time dependent manner which reached a plateau after 48 h of glucocorticoid administration. This mRNA increase was mimicked by cortisol and inhibited by glucocorticoid receptor antagonists RU38486. Also cGMP generated by NPRA in dexamethasone treated cells was higher than in control cells and this production was mimicked by cortisol and blocked by RU 38486. These results suggest that glucocorticoids exert a positive effect on NPRA transcription in rat mesenteric arteries.
Previous studies have shown that guanylyl cyclase activity of NPRA is either activated, or inhibited by an increase in extracellular tonicity. Though none of these studies were definitive in terms of elucidating the mechanisms involved, they suggested that the activation predominates with longer exposure (∼24 h), while the inhibition with short-term exposure (minutes) to the osmotic stimulus. More recently, the mechanism(s) underlying the activation of NPRA expression by osmotic stimulus has been investigated. The NaCl (75 mM) or sucrose (150 mM), but not osmotically inert solute, urea (150 mM) increased NPRA activity, gene expression, and promoter activity after as early as 4 h reaching a maximum at 24 h in inner medullary collecting duct cells. The osmotic stimulus also activated extracellular signal regulated kinase (ERK), c-Jun-NH2-terminal kinase (JNK), and p38 mitogen activated protein kinase- (p38 MAPK-β). The inhibition of p38 MAPK-βwith SB20580 completely blocked the osmotic stimulation of receptor activity and expression, and caused a dose-dependent reduction in promoter activity, whereas inhibition of ERK with PD98059 had no effect.
The expression of NPRB, the biological receptor of CNP, has been shown to be regulated by a number of factors including natriuretic peptide ligands, intracellular cAMP levels, water deprivation, TGF-1, dexamethasone treatment, as well as renal sodium status, as its mRNA levels were upregulated in the renal cortex of sodium depleted animals. NPRB expression has also been found to be regulated by alternative splicing. Three isoforms of NPRB have been identified of which NPRB1 is the full length form and responds maximally to CNP, NPRB2 isoform contains a 25 amino acid deletion in protein kinase homology domain and NPRB3 contains a partial extracellular ligand binding domain and fails to bind the ligand. The relative expression levels of the three isoforms vary across different tissues. Since, the smaller splice variants of NPRB act as dominant negative isoforms by blocking formation of active NPRB1 homodimers, these isoforms might play important role in the tissue specific regulation of receptor, NPRB.
The NPRC expression has also been found to be down-regulated by its ligands and their secondary messenger, cGMP, hormones, growth factors, dietary salt supplementation, β-adrenergic blocker, and physiological as well as patho-physiological conditions. On the other hand, NPRC expression gets augmented by TGF-β1, 1,25-dihydroxy VitaminD3 and during conditions like chronic heart failure.
Hypertension is the leading cause of human deaths in today’s world. The natriuretic peptide system plays a well defined role in the regulation of blood pressure and fluid volume. The cellular and physiological effects of natriuretic peptides (ANP, BNP, and CNP) are mediated by their specific receptors NPRA, NPRB, and NPRC. The transcriptional regulation of these receptors has been studied since their identification, but still remains poorly understood. Better understanding and the elucidation of different molecular mechanisms responsible for the regulation of NPRA expression would provide us the framework to develop the therapeutic strategies to manipulate the expression levels of this receptor and to control the biological actions of ANP and BNP during different patho-physiological conditions.
Inhibition of Heat Shock Protein 90 (Hsp90) in Proliferating Endothelial Cells Uncouples Endothelial Nitric Oxide Synthase Activity
Jingsong Ou, Zhijun Ou, AW Ackerman, KT Oldham, & KA Pritchard, Jr.
Free Radical Biol Med 2003; 34(2):269–276
PII S0891-5849(02)01299-6
Dual increases in nitric oxide (•NO) and superoxide anion (O2•-) production are one of the hallmarks of endothelial cell proliferation. Increased expression of endothelial nitric oxide synthase (eNOS) has been shown to play an important role in maintaining high levels of •NO generation to offset the increase in O2•- that occurs during proliferation. Although recent reports indicate that heat shock protein 90 (hsp90) associates with eNOS to increase •NO generation, the role of hsp90 association with eNOS during endothelial cell proliferation remains unknown. In this report, we examine the effects of endothelial cell proliferation on eNOS expression, hsp90 association with eNOS, and the mechanisms governing eNOS generation of •NO and O2•-. Western analysis revealed that endothelial cells not only increased eNOS expression during proliferation but also hsp90 interactions with the enzyme. Pretreatment of cultures with radicicol (RAD, 20 µM), a specific inhibitor that does not redox cycle, decreased A23187-stimulated •NO production and increased Lω-nitroargininemethylester (L-NAME)-inhibitable O2•-generation. In contrast, A23187 stimulation of controls in the presence of L-NAME increased O2•- generation, confirming that during proliferation eNOS generates •NO. Our findings demonstrate that hsp90 plays an important role in maintaining •NO generation during proliferation. Inhibition of hsp90 in vascular endothelium provides a convenient mechanism for uncoupling eNOS activity to inhibit •NO production. This study provides new understanding of the mechanisms by which ansamycin antibiotics inhibit endothelial cell proliferation. Such information may be useful in the development and design of new antineoplastic agents in the future.
Natriuretic Peptides, Ejection Fraction, and Prognosis – Parsing the Phenotypes of Heart Failure
James L. Januzzi, JR
J Amer Coll Cardiol 2013; 61(14): 1507-9
http://dx.doi.org/10.1016/j.jacc.2013.01.039
Since the first pivotal studies introduced the natriuretic peptides as biomarkers for the diagnosis of heart failure (HF), use of both B-type natriuretic peptide (BNP) and its N-terminal equivalent (NT-proBNP) has grown not only for this indication, but also for establishing HF prognosis as well. Indeed, a vast array of studies has established the natriuretic peptides as the biomarker gold standard to prognosticate risk for a wide array of relevant complications in HF (ranging from ventricular arrhythmias to pump failure). In these studies, the prognostic information provided by BNP and NT-proBNP in HF was independent of a number of relevant covariates, including left ventricular ejection fraction (LVEF).
It has been known for quite a while that patients with heart failure and preserved ejection fraction (HFpEF) typically have lower natriuretic peptide values than do those with heart failure and reduced ejection fraction (HFrEF). A conundrum is thus present: whereas both BNP and NTproBNP tend to be lower in HFpEF, when these peptides are elevated in this setting, they remain prognostic; this intriguing circumstance has been relatively poorly studied. It is in this setting that van Veldhuisen et al. examined the impact of LVEF on the prognostic merits of BNP in the COACH (Coordinating Study Evaluating Outcomes of Advising and Counseling in Heart Failure) study in the present issue of the Journal. The investigators found—as expected—that BNP levels were lower in HFpEF, but for a given BNP concentration, prognosis of those with HFpEF in COACH was just as poor as those with HFrEF at matched BNP values. Stated differently, a high BNP in a patient with HFpEF imparted similar prognostic information as it would in someone with HFrEF. Actually, whereas LVEF was not obviously prognostically impactful, when considered across the range of ventricular function, an elevated BNP concentration in the most normal range of LVEF seemed to be associated with a higher risk than at the lower ranges of pump function. Although it is previously established that BNP or NT-proBNP are prognostic independently of LVEF, the well-executed analysis by van Veldhuisen et al. (van Veldhuisen DJ, Linssen GCM, Jaarsma T, et al. B-type natriuretic peptide and prognosis in heart failure patients with preserved and reduced ejection fraction. J Am Coll Cardiol 2013;61:1498–506.) allows for a more in-depth examination of this phenomenon and raises some important questions.
Phenotypic Definition of the Patient With Heart Failure
Phenotypic Definition of the Patient With Heart Failure
Natriuretic Peptides in Heart Failure with Preserved Ejection Fraction
Mark Richards, James L. Januzzi Jr, Richard W. Troughton
Heart Failure Clin 10 (2014) 453–470
http://dx.doi.org/10.1016/j.hfc.2014.04.006
KEY POINTS
The bioactivity of atrial NP (ANP) and B-type NP (BNP) encompasses short-term and longterm hemodynamic, renal, neurohormonal, and trophic effects. The relationship between cardiac hemodynamic load, plasma concentrations of ANP and BNP, and the cardioprotective profile of NP bioactivity have led to investigation of both biomarker and therapeutic potential of
NPs in HF.
| PlasmaBNPandNT-proBNP thresholds (100pg/mL and 300 pg/mL, respectively) used in the diagnosis of undifferentiated ADHF retain good diagnosticperformance for acute HFPEF |
| Plasma NPs are related to multiple echo indicators of cardiac structure and function in both HFREF and HFPEF. |
| Box 1Causes of increased plasma cardiac natriuretic peptides
Cardiac Heart failure, acute and chronic Acute coronary syndromes Atrial fibrillation Valvular heart disease Cardiomyopathies Myocarditis Cardioversion Left ventricular hypertrophy Noncardiac Age Female sex Renal impairment Pulmonary embolism Pneumonia (severe) Obstructive sleep apnea Critical illness Bacterial sepsis Severe burns Cancer chemotherapy Toxic and metabolic insults |
| BNP and NT-proBNP fall below ADHF thresholds in stable HFREF in approximately 50% and 20% of cases, respectively. Levels in stable HFPEF are even lower, approximately half those in HFREF. |
| Whereas BNPs have 90% sensitivity for asymptomatic LVEF of less than 40% in the community (a precursor state for HFREF), they offer no clear guide to the presence of early community based HFPEF. |
| Guidelines recommend BNP and NT-proBNP as adjuncts to the diagnosis of acute and chronic HF and for risk stratification. Refinements for application to HFPEF are needed. |
| The prognostic power of NPs is similar in HFREF and HFPEF. Defined levels of BNP and NT-proBNP correlate with similar short-term and long-term risks of important clinical adverse outcomes in both HFREF and HFPEF. |
Diagnostic algorithm for suspected heart failure presenting either acutely or nonacutely
Diagnostic algorithm for suspected heart failure presenting either acutely or nonacutely. a In the acute setting, mid-regional pro–atrial natriuretic peptide may also be used (cutoff point 120 pmol/L; ie, <120 pmol/L 5 heart failure unlikely). b Other causes of elevated natriuretic peptide levels in the acute setting are an acute coronary syndrome, atrial or ventricular arrhythmias, pulmonary embolism, and severe chronic obstructive pulmonary disease with elevated right heart pressures, renal failure, and sepsis. Other causes of an elevated natriuretic level in the nonacute setting are old age (>75 years), atrial arrhythmias, left ventricular hypertrophy, chronic obstructive pulmonary disease, and chronic kidney disease. c Exclusion cutoff points for natriuretic peptides are chosen to minimize the false-negative rate while reducing unnecessary referrals for echocardiography. d Treatment may reduce natriuretic peptide concentration, and natriuretic peptide concentrations may not be markedly elevated in patients with heart failure with preserved ejection fraction. BNP, B-type natriuretic peptide; ECG, electrocardiogram; NT-proBNP, N-terminal prohormone of B-type natriuretic peptide. (From McMurray JJ, Adamopoulos S, Anker SD, et al. The task force for the diagnosis and treatment of acute and chronic heart failure 2012 of the European Society of Cardiology. ESC guidelines for the diagnosis and treatment of acute and chronic heart failure 2012. Eur Heart J 2012;33:1787–847; with permission.)
Natriuretic Peptide Receptor-A Negatively Regulates Mitogen-Activated Protein Kinase and Proliferation of Mesangial Cells: Role of cGMP-Dependent Protein Kinase
Kailash N. Pandey, Houng T. Nguyen, Ming Li, and John W. Boyle
Biochem Biophys Res Commun 271, 374–379 (2000)
http://dx.doi.org:/10.1006/bbrc.2000.2627
peptide (ANP) and its guanylyl cyclase/natriuretic peptide receptor-A (NPRA) on mitogen-activated protein kinase/extracellular signal-regulated kinase 2 (MAPK/ERK2) activity in rat mesangial cells overexpressing NPRA. Agonist hormones such as platelet-derived growth factor (PDGF), fibroblast growth factor (FGF), angiotensin II (ANG II), and endothelin-1 (ET-1) stimulated 2.5- to 3.5-fold immunoreactive MAPK/ERK2 activity in these cells. ANP inhibited agonist-stimulated activity of MAPK/ERK2 by 65–75% in cells overexpressing NPRA, whereas in vector transfected cells, its inhibitory effect was only 18–20%. NPRA antagonist A71915 and KT5823, a specific inhibitor of cGMP-dependent protein kinase (PKG) completely reversed the inhibitory effect of ANP on MAPK/ERK2 activity. ANP also inhibited the PDGF stimulated [3H]thymidine uptake by almost 70% in cells overexpressing NPRA, as compared with only 20–25% inhibition in vector-transfected cells. These
results demonstrate that ANP/NPRA system negatively regulates MAPK/ERK2 activity and proliferation of mesangial cells in a PKG-dependent manner.
Regulation of lipoprotein lipase by Angptl4
Wieneke Dijk and Sander Kersten
Trends in Endocrin and Metab, Mar2014; 25(3):146-155
http://dx.doi.org/10.1016/j.tem.2013.12.005
Triglyceride (TG)-rich chylomicrons and very low density lipoproteins (VLDL) distribute fatty acids (FA) to various tissues by interacting with the enzyme lipoprotein lipase (LPL). The protein angiopoietin-like 4 (Angptl4) is under sensitive transcriptional control by FA and the FA-activated peroxisome proliferator activated receptors (PPARs), and its tissue expression largely overlaps with that of LPL. Growing evidence indicates that Angptl4 mediates the physiological fluctuations in LPL activity, including the decrease in
adipose tissue LPL activity during fasting. This review focuses on the major ambiguities concerning the mechanism of LPL inhibition by Angptl4, as well as on the physiological role of Angptl4 in lipid metabolism, highlighting its function in a variety of tissues, and uses this information to make suggestions for further research.
Box 1. LPL and TG metabolism
LPL belongs to a family of lipases that also includes hepatic lipase, pancreatic lipase, and endothelial lipase. Because LPL is essential in the lipolytic processing of chylomicrons and VLDL, LPL is primarily expressed in tissues that either require large amounts of FA as fuel or are responsible for TG storage, which include heart, skeletal muscle, and adipose tissue. Upon production by the underlying parenchymal cells, LPL is released into the subendothelial space and is transported to the luminal side of the capillary endothelium by the GPI-anchored protein GPIHBP1, which after transport continues to anchor LPL to the capillary endothelium. The essential role for LPL in the clearance of plasma TG is well-demonstrated by the severe hypertriglyceridemia of patients carrying homozygous mutations in the LPL gene. Generalized deletion of LPL in mice results in severe hypertriglycer-idemia, resulting in the premature death of pups within 24 h after birth. Analogous to the deletion of LPL, the mislocalization of LPL to the subendothelial spaces due the absence or misfolding of GPIHBP1 also results in severe chylomicronemia and hypertriglyceridemia. The LPL enzyme is catalytically active as a non-covalent head-to-tail dimer with a catalytic N-terminal domain and a non-catalytic C terminal domain. Folding of LPL into its dimer conformation occurs in the endoplasmic reticulum, chaperoned by lipase maturation factor 1, calreticulin, and calnexin. In its active 3D conformation, the catalytic site of LPL is postulated to be covered by a lid, which can be opened by the binding of chylomicrons and VLDL to the C terminus. The active LPL dimers rapidly exchange subunits, indicating that a dynamic equilibrium exists between LPL dimers and dimerization-competent monomers. Dimerization-competent monomers have, however, not yet been isolated, and it is unclear whether this monomer is catalytically active. The enzymatic activity of LPL is lost when the LPL dimer is converted into inactive, folded monomers. This conversion to inactive monomers is mainly regulated via post-translational mechanisms and is dependent on nutritional state. Enzymatic activity of inactive monomers can be regained in vitro by the addition of calcium, indicating that inactivation of LPL is a reversible process.
One of the key questions is whether (patho)physiological variations in LPL activity are mediated via regulation of Angptl4 cleavage and/or oligomerization, and which factors are involved in modulating Angptl4 in vivo. Recent biochemical evidence suggests that FA may be able to promote dissociation of oligomers, which, by destabilizing the protein, would impair its ability to inhibit LPL. Destabilization of Angptl4 by FA is, however, seemingly at odds with the marked stimulatory effect of FA on Angptl4 production observed in vitro and in vivo.
The currently accepted molecular model for the inhibition of LPL by Angptl4 is that Angptl4 stimulates the conversion of catalytically active LPL dimers into inactive monomers – following in vitro studies showing that coincubation of LPL and Angptl4 increases the abundance of LPL monomers. Subsequent studies revealed that the proportion of LPL dimers is reduced in post-heparin plasma of mice that overexpress Angptl4 in favor of LPL monomers, providing in vivo support for the dimer-to monomer conversion. The elucidation of the purported biochemical mechanism has strengthened the status of Angptl4 as a LPL inhibitor, but several questions related to the in vivo mechanism remain unanswered. Whereas the original in vitro experiments favored the hypothesis that Angptl4 enzymatically and irreversibly catalyzes the LPL dimer-to-monomer conversion, an in vivo study of Angptl4 transgenic mice suggested that Angptl4 is physically bound to LPL monomers, thereby driving the LPL dimer–monomer equilibrium towards inactive monomers. The latter study also revealed that the relative decrease in post-heparin plasma LPL activity upon Angptl4 overexpression is much more pronounced than the relative decrease in heparin-releasable LPL dimers, pointing to an additional or alternative mechanism. In support, a recently published study suggests that Angptl4, instead of acting as a catalyst, functions as a conventional, non-competitive inhibitor that binds to LPL to prevent the hydrolysis of substrate LPL and Angptl4 are regulated by changes in nutritional state in a tissue-specific manner, reflecting the different functions of these tissues and the corresponding variations in physiological requirements for lipids. Below, we discuss current knowledge on the regulation of Angptl4 and LPL in response to various physiological stimuli and address the importance of Angptl4 in lipid uptake. An overview of the role of Angptl4 in physiological regulation of lipid metabolism is presented in Figure 2.
model for mechanisms of lipoprotein lipase (LPL) inhibition by Angptl4.
Figure 1. Hypothetical model for mechanisms of lipoprotein lipase (LPL) inhibition by Angptl4. Angiopoietin-like 4 (Angptl4) and LPL are expressed in the parenchymal cells of muscle, heart, and adipose tissue. Following secretion of LPL and Angptl4 into the subendothelial space, transport of LPL to the capillary lumen is mediated by two mechanisms. The principal transport mechanism (1) relies on GPIHBP1 [glycosylphosphatidylinositol (GPI)-anchored high density lipoprotein-binding protein] picking up LPL from the subendothelial space and transporting it to the capillary lumen. This action by GPIHBP1 is opposed by Angptl4, which is bound to extracellular matrix (ECM) proteins and which retains and inhibits LPL. In the presence of GPIHBP1, high expression levels of Angptl4 are needed to overcome the competition with GPIHBP1. Angptl4 secreted into the capillary lumen, primarily as N-terminal truncation fragment generated by cleavage by proprotein convertases (PCs), inhibits LPL activity on the endothelium by promoting the irreversible conversion of LPL dimers into inactive monomers and/or via a reversible mechanism that requires binding of Angptl4 to LPL. The second transport mechanism involves a so far unidentified carrier and can be disrupted by Angptl4. In the absence of GPIHBP1, Angptl4 fully retains LPL in the subendothelial space (a). The additional loss of Angptl4 liberates LPL and allows it to be transported to the endothelial surface via the unidentified carrier (b). This model suggests that Angptl4 and LPL start interacting before arrival in the capillary lumen, either in the parenchymal cells or in the subendothelial space. Abbreviation: HSPG, heparan sulfate proteoglycan.
Regulation and role of angiopoietin-like 4 (Angptl4)
Figure 2. Regulation and role of angiopoietin-like 4 (Angptl4) in lipid metabolism. Angptl4 is expressed in parenchymal cells of white adipose tissue (WAT), liver, intestine, heart and muscle, as well as in macrophages, where it is subject to cell- and tissue-specific regulation. Angptl4 is a sensitive target of peroxisome proliferator-activated receptor (PPAR) transcription factors in several tissues. In WAT the expression of Angptl4 is induced during fasting and by the transcription factors PPARg, glucocorticoid receptor (GR), and hypoxia inducible factor 1a (HIF1a). In WAT Angptl4 stimulates lipolysis of stored triglycerides (TG) and inhibits lipoprotein lipase (LPL) activity. Expression of Angptl4 in liver is stimulated by PPARa, PPARd, and GR. Because the liver does not express LPL, Angptl4 is mainly released into the blood, affecting LPL activity in peripheral tissues. Angptl4 may also impact upon hepatic lipase activity in liver. Expression of Angptl4 in heart and skeletal muscle is potently induced by fatty acids (FA) via PPARd activation. Angptl4 inhibits LPL activities in cardiac and likely skeletal muscle. FA also stimulate Angptl4 expression in macrophages via PPARd, leading to local inhibition of LPL activity. We hypothesize that macrophage LPL enables uptake of remnant particles containing lipid antigens, which are subsequently presented to natural killer T cells. In the intestine, FA stimulate Angptl4 expression via one of the PPARs. Angptl4 produced by enterocytes may be released towards the lumen and inhibit pancreatic lipase activity. Angptl4 produced by enteroendocrine cells is released towards the blood and may inhibit LPL in distant tissues.
Box 2. Outstanding questions
In the past decade, angiopoietin-like proteins have been demonstrated to regulate plasma TG levels powerfully in mice and humans. The elucidation of these proteins as inhibitors of LPL activity has led to a paradigm shift in how clearance of circulating TG and thereby tissue uptake of FA are regulated. Most of our understanding of angiopoietin-like proteins has resulted from detailed study of Angptl4.
A major portion of the physiological variation in LPL activity in various tissues can be attributed to regulation of Angptl4 production. We predict that Angptl4 will turn out to be equally important for governing LPL activity in muscle during exercise, in brown adipose tissue during cold, and in several tissues during fasting.
Besides the increasing recognition of the pivotal role of Angptl4 in lipid metabolism as an inhibitor of LPL, major insight has been gained into the molecular mechanism of action of Angptl4. Key questions remain, however, especially related to the interaction between LPL, GPIHBP1, and Angptl4 on the endothelium and in the subendothelial space. Several points of interest have been highlighted throughout the text; these include the elucidation of the molecular structure for LPL and Angptl4 by X-ray crystallography and the clarification of in vivo Angptl4 cleavage and oligomerization.
Native Low-Density Lipoprotein Induces Endothelial Nitric Oxide Synthase Dysfunction: Role of Heat Shock Protein 90 And Caveolin-1
Kirkwood A. Pritchard, Jr., Allan W. Ackerman, Jingsong Ou, et al.
Free Radical Biol & Med 2002; 33(1):52–62 PII S0891-5849(02)00851-1
Although native LDL (n-LDL) is well recognized for inducing endothelial cell (EC) dysfunction, the mechanisms remain unclear. One hypothesis is n-LDL increases caveolin-1 (Cav-1), which decreases nitric oxide (•NO) production by binding endothelial nitric oxide synthase (eNOS) in an inactive state. Another is n-LDL increases superoxide anion (O2•-), which inactivates •NO. To test these hypotheses, EC were incubated with n-LDL and then analyzed for •NO, O2•-, phospho-eNOS (S1179), eNOS, Cav-1, calmodulin (CaM), and heat shock protein 90 (hsp90). n-LDL increased NOx by more than 4-fold while having little effect on A23187-stimulated nitrite production. In contrast, n-LDL decreased cGMP under basal and A23187-stimulated conditions and increased O2•-by a mechanism that could be inhibited by L-nitroargininemethylester (L-NAME) and BAPTA/AM. n-LDL increased phospho-eNOS by 149%, eNOS by [1]34%, and Cav-1 by 28%, and decreased the association of hsp90 with eNOS by 49%. n-LDL did not appear to alter eNOS distribution between membrane fractions (-85%) and cytosol (-15%). Only 3–6% of eNOS in membrane fractions was associated with Cav-1. These data support the hypothesis that n-LDL increases O2•-, which scavenges •NO, and suggest that n-LDL uncouples eNOS activity by decreasing the association of hsp90 as an initial step in signaling eNOS to generate O2•-.
In conclusion, n-LDL decreases the association of hsp90 with eNOS, increases phospho-eNOS levels, and increases eNOS-dependent O2•-generation. These findings suggest that activation of eNOS without adequate levels of hsp90 may signal eNOS to switch from •NO to O2•-generation. Such changes in eNOS radical product generation may play an important role in impairing endothelial and vascular function.
New insights into IGF-1 signaling in the heart
Rodrigo Troncoso, C Ibarra, JM Vicencio, E Jaimovich, and S Lavandero
Trends in Endocrin and Metab, Mar 2014; 25(3):128-131
http://dx.doi.org/10.1016/j.tem.2013.12.002
Insulin-like growth factor 1 (IGF-1) signaling regulates contractility, metabolism, hypertrophy, autophagy, senescence, and apoptosis in the heart. IGF-1 deficiency is associated with an increased risk of cardiovascular disease, whereas cardiac activation of IGF-1 receptor (IGF-1R) protects from the detrimental effects of a high-fat diet and myocardial infarction. IGF-1R activates multiple pathways through its intrinsic tyrosine kinase activity and through coupling to heterotrimeric G protein. These pathways involve classic second messengers, phosphorylation cascades, lipid signaling, Ca2+ transients, and gene expression. In addition, IGF-1R triggers signaling in different subcellular locations including the plasma membrane, perinuclear T tubules, and also in internalized vesicles. In this review, we provide a fresh and updated view of the complex IGF-1 scenario in the heart, including a critical focus on therapeutic strategies.
The hormone insulin-like growth factor 1 (IGF-1) is a small peptide of 7.6 kDa, which is composed of 70 amino acids and shares 50% homology with insulin. IGF-1 plays key roles in regulating proliferation, differentiation, metabolism, and cell survival. It is mainly synthesized and secreted by the liver in response to hypothalamic growth hormone (GH); its plasma concentration is finely regulated (Box 1). However, other tissues also produce IGF-1, which acts locally as an autocrine and paracrine hormone. IGF-1 exhibits pleiotropic effects in many organs and is also involved in the development of several pathologies.
| Box 1. IGF-1 synthesis and biodisponibilityInsulin-like growth factor 1 (IGF-1) is a 70 amino acid peptide
hormone with endocrine, paracrine, and autocrine effects. It shares >60% structure homology with IGF-2 and 50% with pro-insulin. IGF- 1 is mainly synthesized in the liver in response to hypothalamic growth hormone (GH). In the peripheral circulation it exerts negative feedback on the somatotrophic axis suppressing pituitary GH release. IGF-1 can also be generated in almost all tissues, but liver synthesis accounts for nearly 75% of circulating IGF-1 levels. As a hormone with a wide range of physiological roles, IGF-1 circulating levels must be strictly controlled. Around 98% of circulating IGF-1 is bound to insulin-like growth factor binding protein (IGFBP). Six forms of high affinity IGFBP have been described, with IGFBP3 binding approximately 90% of circulating IGF-1. Also, IGFBP1–6 and their fragments have significant intrinsic biological activity independent of IGF-1 interaction. |
Canonical and noncanonical IGF-1 signaling pathways Activation of IGF-1R requires the sequential phosphorylation of three conserved tyrosine residues within the activation loop of the catalytic domain. From these phosphorylated motifs, tyrosine 950 contained in an NPXY motif provides a docking site for the recruitment of adaptor proteins, such as insulin receptor substrate-1 (IRS-1) and Shc, as an obligatory step to initiate signaling cascades. Two canonical pathways are activated by IGF-1R in cardiomyocytes – the phosphatidylinositol-3 kinase (PI3K)/Akt pathway and the extracellular signal-regulated kinase (ERK) pathway. Both pathways have been extensively studied, and their involvement in the pro-hypertrophic and pro-survival actions in cardiomyocytes is well established. Interestingly, a noncanonical signaling mechanism for IGF-1R in cardiomyocytes has been described in several recent studies. These studies show that some of the effects of IGF-1 are inhibited by the heterotrimeric Gi protein blocker Pertussis toxin (PTX) in several cell lines, suggesting that IGF-1R is a dual-activity receptor that triggers tyrosine-kinase-dependent responses as well as Gi-protein-dependent pathways. This duality has been reported in cultured neonatal cardiomyocytes; IGF-1R can activate ERK and Akt but also phospholipase C (PLC), which increases inositol 1,4,5 triphosphate (InsP3; IP3) leading to nuclear Ca2+ signals.
The cardiac effects of IGF-1 are mediated by activation of the plasma membrane IGF-1R, which belongs to the receptor tyrosine kinase (RTK) family. IGF-1R comprises a α2β2 heterotetrameric complex of approximately 400 kDa. Structurally, IGF-1R has two extracellular a-subunits that contain the ligand-binding sites. Each α-subunit couples to one of two membrane-spanning β-subunits, which contain an intracellular domain with intrinsic tyrosine kinase activity. Both subunits of IGF-1R are the product of one single gene, which is synthesized as a 180 kDa precursor. The immature IGF-1R full peptide is further glycosylated, dimerized, and proteolytically processed for assembly of the mature receptor isoforms a and b. In neonatal and adult rat cardiomyocytes, the IGF-1R precursor peptide and the processed α and β receptor subunits have been detected. Binding of IGF-1 to its receptor initiates a complex signaling cascade in cardiomyocytes.
Figure 1. not shown. Canonical and noncanonical signaling pathways activated by insulin-like growth factor 1 (IGF-1) in cardiomyocytes. Binding of IGF-1 to plasma membrane IGF-1 receptor (IGF-1R) leads to receptor autophosphorylation in the intracellular β-subunits. Docking of Grβ2 to the phosphorylated IGF-1Rβ subunits leads to extracellular signal-regulated kinase (ERK) phosphorylation through the Ras/Raf/Mitogen-activated protein kinase (MEK) axis. Phosphorylated ERK can translocate to the nucleus to control gene expression. Phosphorylated β-subunits also provide docking sites for insulin receptor substrate-1 (IRS-1), which mediates phosphatidylinositol-3 kinase (PI3K) activation and Akt phosphorylation. Downstream targets of activated Akt are mechanistic target of rapamycin (mTOR), which suppresses autophagy and promotes protein synthesis by activating S6K and eukaryotic translation initiation factor 4E binding protein 1 (4EBP1). Akt also phosphorylates and inactivates Bad, thus inhibiting apoptosis. IGF-1R activation also promotes its interaction with a Pertussis-toxin-sensitive heterotrimeric Gi protein, which mediates the activation of phospholipase C (PLC) and hydrolysis of plasma membrane phosphatidylinositol 4,5 biphosphate (PIP2) to form inositol 1,4,5 triphosphate (InsP3; IP3) which activates InsP3 receptors located at the endoplasmin reticulum (ER)/nuclear envelope Ca2+ store, producing nucleoplasmic and cytoplasmic Ca2+ increases. The former is involved in the regulation of specific target genes and the latter promotes mitochondrial Ca2+ uptake, which increases mitochondrial respiration and metabolism, further preventing apoptosis and regulating autophagy. Canonical signaling pathways include the ERK and Akt axes, and are shown in red, whereas the noncanonical G protein pathway is shown in blue. Both pathways interact as Ca2+ contributes to ERK activation and additionally both Akt and ERK can compensate each other’s activation. Abbreviations: MEK, Mitogen-activated protein kinase; mTOR, mechanistic target of rapamycin; 4EBP1, eukaryotic translation initiation factor 4E binding protein 1; PIP2, phosphatidylinositol 4,5 biphosphate.
Figure 2. not shown. Classical versus proposed models of nuclear Ca2+ signaling in cardiomyocytes. The insulin-like growth factor 1 receptor (IGF-1R) can specifically regulate nuclear Ca2+ signaling independently of the role of Ca2+ on excitation–contraction coupling. On the classic model, inositol 1,4,5 triphosphate (InsP3; IP3) produced after IGF-1R activation travels from the peripheral plasma membrane to the nucleus, where it activates InsP3 receptors. In this model InsP3 bypasses its receptors present on the sarcoplasmic reticulum, which would lead to cytosolic Ca2+ signals. The novel model that we propose is based on recent findings, where the IGF-1R signaling complex is present in T-tubule invaginations toward the nucleus. In these compartments, IGF-1R activation leads to locally restricted InsP3 production that allows nuclear Ca2+ signals to regulate gene expression of genes associated with the development of cardiomyocyte hypertrophy. Abbreviations: RyR, ryanodine receptor; ECC, excitation–contraction coupling; PLC, phospholipase C; DHPR, dihydropyridine receptor.
The beneficial roles of IGF-1 in the cardiovascular system largely explain the interest in the development of new IGF-1-based treatments for cardiovascular disease. So far the FDA has approved two drugs for the treatment of IGF-1 deficiency: mecasermin (Increlex1), a human recombinant IGF-1 analog; and mecasermin rinfabate (IPLEX1), a binary protein complex of human recombinant IGF-1 and human recombinant IGBP-3. The safety of a chronic systemic IGF-1 therapy is open to question because it could promote severe adverse effects, such as an increased risk of cancer. To avoid these problems, several researchers have selectively overexpressed IGF-1 and IGF-1R in the heart.
| Box 2. Outstanding questionsInsulin-like growth factor 1 (IGF-1) is an old friend of the heart. Despite the well-known protective effects of IGF-1 on cardiac function and the antiapoptotic effects of this peptide, novel evidence opens new questions to this longstanding relationship.
· How do the multiple signaling pathways triggered by IGF-1 receptor (IGF-1R) interact with each other? · What lies further than extracellular signal-regulated kinase (ERK)/Akt/Ca2+ activation toward heart function? · Do these signaling pathways regulate cardiac fibroblast or endothelial cell function? · Which are the specific downstream signaling pathways of the different pools of IGF-1R and their role in regulating cardiomyocyte survival, hypertrophy, metabolism, proliferation? · What drives IGF-1R to such specific subcellular compartments? · What is the relevance of the hybrid IGF-1R/insulin receptors on cardiovascular disease? · Does a crosstalk exist between insulin receptor and IGF-1R in the heart under physiological and pathological conditions? · Is one pathway more beneficial than the other? · Will stem cell therapy of cardiac progenitors be able to provide concrete treatment opportunities? · Is IGF-1 a key regulator of this outcome? |
Abundant evidence supports the key physiological roles of IGF-1 in the heart. In cardiomyocytes, IGF-1 activates multiple downstream signaling pathways for controlling cell death, metabolism, autophagy, differentiation, transcription, and protein synthesis (Figure 1). Of great interest are the findings that the entire IGF-1R complex is strategically located in perinuclear sarcolemmal invaginations that locally control nuclear Ca2+ signaling and transcriptional upregulation (Figure 2). This novel evidence changesmthe classical paradigm of IGF-1 signaling and adds a new level of complexity that may be relevant for other signaling receptors in the heart: interorganelle communication between plasma membrane invaginations and the nucleus.
The strategic localization of IGF-1R in these structures and the association with heterotrimeric G proteins may explain the differences in the phenotypic response induced by IGF-1 and others agonists, like endothelin-1 and angiotensin II, that also signal through intracellular Ca2+. By activating a noncanonical, selective mechanism of nuclear Ca2+ release, IGF-1 can regulate the expression of a specific set of cardiac genes via the generation of a particular signal-encoding pattern, leading to adaptive cardiac hypertrophy, antiapoptotic effects, and metabolic adaptation.
Pulmonary Hypertension in Heart Failure with Preserved Ejection Fraction – any Pathophysiological Role of Mitral Regurgitation
Marco Guazzi
http://dx.doi.org:/10.1016/j.jacc.2009.04.088
read with interest the study by Lam et al. (1) as an important contribution to the pathophysiological and clinical impact of pulmonary hypertension (PH) in hypertensive patients with heart failure and preserved left ventricular ejection fraction (HFpEF). Recent guidelines on arterial PH recognize HFpEF as a growing cause of left-sided PH, but a definitive appreciation of its true prevalence and prognostic relevance is lacking. The present study provides some new important information on this subject.
It is noteworthy that HFpEF was associated, in a high rate of cases (83%), with a typical hemodynamic pattern of precapillary PH, and a strong correlation was found between pulmonary artery systolic pressure and pulmonary capillary wedge pressure. Most important, pulmonary artery systolic pressure, rather than other echocardiography-derived measures of diastolic dysfunction, was the only significant multivariate predictor of mortality, a finding that was confirmed even when combined comorbid diseases potentially contributing to PH development, such as chronic obstructive pulmonary disease, were taken into account.
In patients with systolic heart failure, a major determinant of PH development is mitral regurgitation. Whether mitral regurgitation could be a putative factor in the pathogenesis of PH in HFpEF patients remains an open and intriguing question.
Accordingly, it would be of interest if the authors could provide some details on how many HFpEF patients exhibited mitral regurgitation, especially in comparison with control hypertensive patients without HFpEF.
Lam CSP, Roger VL, Rodeheffer RJ, Borlaug BA, Enders FT, Redfield MM. Pulmonary hypertension in heart failure with preserved ejection fraction: a community-based study. J Am Coll Cardiol 2009; 53:1119–23.
Midregion Prohormone Adrenomedullin and Prognosis in Patients Presenting with Acute Dyspnea Results from the BACH (Biomarkers in Acute Heart Failure) Trial
Alan Maisel, MD, Christian Mueller, Richard M. Nowak,W. Frank Peacock, et al.
J Am Coll Cardiol 2011; 58(10):1057–67
http://dx.doi.org:/10.1016/j.jacc.2011.06.006
Objectives The aim of this study was to determine the prognostic utility of midregion proadrenomedullin (MR-proADM) in all patients, cardiac and noncardiac, presenting with acute shortness of breath.
Background The recently published BACH (Biomarkers in Acute Heart Failure) study demonstrated that MR-proADM had superior accuracy for predicting 90-day mortality compared with B-type natriuretic peptide (area under the curve: 0.674 vs. 0.606, respectively, p < 0.001) in acute heart failure.
Methods The BACH trial was a prospective, 15-center, international study of 1,641 patients presenting to the emergency department with dyspnea. Using this dataset, the prognostic accuracy of MR-proADM was evaluated in all patients enrolled for predicting 90-day mortality with respect to other biomarkers, the added value in addition to clinical variables, as well as the added value of additional measurements during hospital admission.
Results Compared with B-type natriuretic peptide or troponin, MR-proADM was superior for predicting 90-day all-cause mortality in patients presenting with acute dyspnea (c index = 0.755, p < 0.0001). Furthermore, MR-proADM added significantly to all clinical variables (all adjusted hazard ratios: HR=3.28), and it was also superior to all other biomarkers. MRproADM added significantly to the best clinical model (bootstrap-corrected c index increase: 0.775 to 0.807; adjusted standardized hazard ratio: 2.59; 95% confidence interval: 1.91 to 3.50; p < 0.0001). Within the model, MR-proADM was the biggest contributor to the predictive performance, with a net reclassification improvement of 8.9%. Serial evaluation of MR-proADM performed in patients admitted provided a significant added value compared with a model with admission values only (p< 0.0005). More than one-third of patients originally at high risk could be identified by the biomarker evaluation at discharge as low-risk patients. Conclusions MR-proADM identifies patients with high 90-day mortality and adds prognostic value to natriuretic peptides in patients presenting with acute shortness of breath. Serial measurement of this biomarker may also prove useful for monitoring, although further studies will be required. (Biomarkers in Acute Heart Failure [BACH]; NCT00537628)
Invasive Hemodynamic Characterization of Heart Failure with Preserved Ejection Fraction
Mads J. Andersen, Barry A. Borlaug
Heart Failure Clin 10 (2014) 435–444
http://dx.doi.org/10.1016/j.hfc.2014.03.001
KEY POINTS
The circulatory system serves to deliver substrates to the body via the bloodstream while removing the byproducts of cellular metabolism. Hemodynamics broadly refers to the study of the forces involved in the circulation of blood, which are governed by to the physical properties of the heart and vasculature and their dynamic regulation by the autonomic nervous system.
Afterload represents the forces opposing ventricular ejection and can be quantified by systolic left ventricular (LV) wall stress and aortic input impedance or its individual components (resistance, compliance, characteristic impedance). Wall stress is inconvenient because it depends on heart size and geometry, whereas impedance is cumbersome because it is a frequency-domain parameter that cannot be easily coupled with time-domain measures of ventricular function. Effective arterial elastance (Ea), defined by the ratio of LV end-systolic pressure (ESP) to stroke volume, provides a robust measure of total arterial load. Ea is not a directly measured parameter but, instead, a net or lumped stiffness of the vasculature that incorporates both mean and oscillatory components of afterload (Fig. 1). Preload reflects the degree of myofiber stretch before the onset of contraction, which, in turn, dictates the force and velocity of contraction according to the Frank-Starling principle. In everyday practice, preload is often conceptualized as equivalent to LV filling pressures. However, in fact, preload is most accurately reflected by the LV volume at end-diastole volume (EDV). Filling pressures are related to EDV by the LV diastolic chamber stiffness, which differs in healthy volunteers and subjects with HFpEF.
Fig. 1. Not shown. Ventricular-arterial coupling in the pressure-volume plane. Pressure volume loop at steady state is shown in dark black. The area subtended by the loop (shaded) represents the stroke work. Stroke volume is the difference between end-diastolic volume (EDV) and end-systolic volume (ESV). Ea is defined by the negative slope connecting the ESP and ESV coordinates with EDV and pressure = 0. With acute preload reduction (dotted line loops) there is progressive reduction in EDV, ESV, and ESP. The linear slope of the endsystolic pressure volume relationship (ESPVR) is LV end-systolic elastance (Ees). The curvilinear slope of the end diastolic pressure–volume relationship (EDVPR) is derived by fitting pressure volume coordinates measured during diastasis to the equation shown. The exponential power or stiffness constant (b) obtained is a measure of LV diastolic stiffness. (Adapted from Borlaug BA, Kass DA. Invasive hemodynamic assessment in heart failure. Heart Fail Clin 2009;5(2):217–28; with permission.)
Fig. 3. Not shown. Left ventricular diastolic reserve in HFpEF. In the normal healthy adult, the rate of LV pressure decay during isovolumic contraction (t) is rapid and increases markedly during exercise in association with a reduction in LVmin, allowing for suction of blood into the LV, with no increase in left atrial pressure or LV end-diastolic pressure (LVEDP) despite an increase in LV end-diastolic volume and marked shortening of the cycle length. In HFpEF, relaxation is prolonged at baseline (increased t) with inadequate hastening (shortening of t) during exercise, contributing to an inability to reduce LVmin and, consequently, a complete lack of suction effects. LV filling then completely depends on left atrial hypertension, which develops in tandem with marked elevation in LVEDP. (Data from Borlaug BA, Jaber WA, Ommen SR, et al. Diastolic relaxation and compliance reserve during dynamic exercise in heart failure with preserved ejection fraction. Heart 2011;97(12):964–9.)
Fig. 4. Preload and filling pressures in HFpEF. (A) Cumulative distribution plot shows that acute changes in stroke volume with nitroprusside infusion are lower in HFpEF (black) compared with HFrEF (red). Because afterload (Ea) is lowered, any acute reduction in SV must be related to reduction in preload volume (EDV) and nearly 40% of HFpEF patients experienced stroke volume reduction with nitroprusside, despite high filling pressures (PCWP 20–25 mm Hg), indicating increased reliance on high pressures to achieve adequate EDV. *p<0.0001 compared with HFrEF. (B) LVEDP in a healthy adult (blue) and in a HFpEF patient with increased LV diastolic stiffness (green). At the same preload (EDV), pressure is more than twofold higher in HFpEF. In contrast, at the same LV diastolic pressure (15 mm Hg), LV volume is much lower in HFpEF, indicating decreased LV diastolic capacitance. V15, volume at end-diastolic pressure = 15 mm Hg; LVEDP. (Adapted from Schwartzenberg S, Redfield MM, From AM, et al. Effects of vasodilation in heart failure with preserved or reduced ejection fraction implications of distinct pathophysiologies on response to therapy. J Am Coll Cardiol 2012;59(5):442–51; with permission.)
Updated Clinical Classification of Pulmonary Hypertension
Gérald Simonneau, Ivan M. Robbins, Maurice Beghetti, et al.
J Am Coll of Cardiol 2009; 54(1), Suppl S
http://dx.doi.org:/10.1016/j.jacc.2009.04.012
The aim of a clinical classification of pulmonary hypertension (PH) is to group together different manifestations of disease sharing similarities in pathophysiologic mechanisms, clinical presentation, and therapeutic approaches. In 2003, during the 3rd World Symposium on Pulmonary Hypertension, the clinical classification of PH initially adopted in 1998 during the 2nd World Symposium was slightly modified. During the 4th World Symposium held in 2008, it was decided to maintain the general architecture and philosophy of the previous clinical classifications. The modifications adopted during this meeting principally concern Group 1, pulmonary arterial hypertension (PAH). This subgroup includes patients with PAH with a family history or patients with idiopathic PAH with germline mutations (e.g., bone morphogenetic protein receptor-2, activin receptor-like kinase type 1, and endoglin). In the new classification, schistosomiasis and chronic hemolytic anemia appear as separate entities in the subgroup of PAH associated with identified diseases. Finally, it was decided to place pulmonary venoocclusive disease and pulmonary capillary hemangiomatosis in a separate group, distinct from but very close to Group 1 (now called Group 1=). Thus, Group 1 of PAH is now more homogeneous. (J Am Coll Cardiol 2009; 54: S43–54)
Updated Evidence-Based Treatment Algorithm in Pulmonary Arterial Hypertension
Robyn J. Barst, J. Simon R. Gibbs, Hossein A. Ghofrani, et al.
J Am Coll Cardiol 2009; 54(1), Suppl S,
Uncontrolled and controlled clinical trials with different compounds and procedures are reviewed to define the risk benefit profiles for therapeutic options in pulmonary arterial hypertension (PAH). A grading system for the level of evidence of treatments based on the controlled clinical trials performed with each compound is used to propose an evidence-based treatment algorithm. The algorithm includes drugs approved by regulatory agencies for the treatment of PAH and/or drugs available for other indications. The different treatments have been evaluated mainly in idiopathic PAH, heritable PAH, and in PAH associated with the scleroderma spectrum of diseases or with anorexigen use. Extrapolation of these recommendations to other PAH subgroups should be done with caution. Oral anticoagulation is proposed for most patients; diuretic treatment and supplemental oxygen are indicated in cases of fluid retention and hypoxemia, respectively. High doses of calcium-channel blockers are indicated only in the minority of patients who respond to acute vasoreactivity testing. Nonresponders to acute vasoreactivity testing or responders who remain in World Health Organization (WHO) functional class III, should be considered candidates for treatment with either an oral phosphodiesterase-5 inhibitor or an oral endothelin-receptor antagonist. Continuous intravenous administration of epoprostenol remains the treatment of choice in WHO functional class IV patients. Combination therapy is recommended for patients treated with PAH monotherapy who remain in WHO functional class III. Atrial septostomy and lung transplantation are indicated for refractory patients or where medical treatment is unavailable. (J Am Coll Cardiol 2009;54:S78–84)
Inhibition and down-regulation of gene transcription and guanylyl cyclase activity of NPRA by angiotensin II involving protein kinase C
Kiran K. Arise, Kailash N. Pandey
Biochem and Biophys Res Commun 349 (2006) 131–135
http://dx.doi.org:/10.1016/j.bbrc.2006.08.003
The objective of this study was to investigate the role of protein kinase C (PKC) in the angiotensin II (Ang II)-dependent repression of Npr1 (coding for natriuretic peptide receptor-A, NPRA) gene transcription. Mouse mesangial cells (MMCs) were transfected with Npr1 gene promoter-luciferase construct and treated with Ang II and PKC agonist or antagonist. The results showed that the treatment of MMCs with 10 nM Ang II produced a 60% reduction in the promoter activity of Npr1 gene. MMCs treated with 10 nM Ang II exhibited 55% reduction in NPRA mRNA levels, and subsequent stimulation with 100 nM ANP resulted in 50% reduction in guanylyl cyclase (GC) activity. Furthermore, the treatment of MMCs with Ang II in the presence of PKC agonist phorbol ester (100 nM) produced an almost 75% reduction in NPRA mRNA and 70% reduction in the intracellular accumulation of cGMP levels. PKC antagonist staurosporine completely reversed the effect of Ang II and phorbol ester. This is the first report to demonstrate that ANG II-dependent transcriptional repression of Npr1 gene promoter activity and down-regulation of GC activity of translated protein, NPRA is regulated by PKC pathways.
Transcriptional regulation of guanylyl cyclase/natriuretic peptide receptor-A gene
Prerna Kumar, Kiran K. Arise, Kailash N. Pandey
peptides 27 (2006) 1762–1769
http://dx.doi.org:/10.1016/j.peptides.2006.01.004
Activation of natriuretic peptide receptor-A (NPRA) produces the second messenger cGMP, which plays a pivotal role in maintaining blood pressure and cardiovascular homeostasis. In the present study, we have examined the role of trans-acting factor Ets-1 in transcriptional regulation of Npr1 gene (coding for NPRA).Using deletional analysis of the Npr1 promoter, we have defined a 400 base pair (bp) region as the core promoter, which contains consensus binding sites for transcription factors including: Ets-1, Lyf-1, and GATA-1/2. Over-expression of Ets-1 in mouse mesangial cells (MMCs) enhanced Npr1 gene transcription by 12-fold. However, overexpression of GATA-1 or Lyf-1 repressed Npr1 basal promoter activity by 50% and 80%, respectively. The constructs having a mutant Ets-1 binding site or lacking this site failed to respond to Ets-1 activation of Npr1 gene transcription. Collectively, the present results demonstrate that Ets-1 greatly stimulates Npr1 gene promoter activity, implicating its critical role in the regulation and function of NPRA at the molecular level.
Several agents that are known to upregulate Ets-1 transcription, include RA, TNF-alpha, VEGF, and TPA. Ets-1 is upregulated at exposure to agonists such as serum in vitro and is expressed in injured vasculature. MAPK-mediated phosphorylation positively regulates the transcriptional activation functions of Ets-1 by recruiting CBP/p300. Not much is known about Ets-1 expression or regulation in mesangial cells. A temporal increase of mesangial cell Ets-1 expression has been reported which correlates with mesangial cell activation
in mesangioproliferative glomerulonephritis suggesting involvement of PDGF-B. There might be a possibility that during glomerulonephritis increased Ets-1 expression upregulates Npr1 gene as a protective mechanism. Npr1 gene has been shown to negatively regulate mitogen-activated protein kinase and proliferation of mesangial cells.
In conclusion, our results demonstrate that the precise control of Npr1 gene transcriptional activity is achieved through a synergy of activators and repressors in which Ets-1 plays an integral role as a transcriptional activator. Comparatively, Lyf-1 and GATA-1 act as repressors, inhibiting and regulating the transcriptional activity of Npr1 gene promoter. The present findings suggest that Ets-1 plays a critical role in enhancing Npr1 gene transcription and may have an important influence in hypertension and cardiovascular homeostasis at the molecular level.
Krüppel-like transcription factor 11 (KLF11) overexpression inhibits cardiac hypertrophy and fibrosis in mice
Yue Zheng, Ye Kong, Feng Li
Biochem and Biophys Res Commun 443 (2014) 683–688
http://dx.doi.org/10.1016/j.bbrc.2013.12.024
The Krüppel-like factors (KLFs) belong to a subclass of Cys2/His2 zinc-finger DNA-binding proteins. The KLF family member KLF11 is originally identified as a transforming growth factor b (TGF-b)-inducible gene and is one of the most studied in this family. KLF11 is expressed ubiquitously and participates in diabetes and regulates hepatic lipid metabolism. However, the role of KLF11 in cardiovascular system is largely unknown. Here in this study, we reported that KLF11 expression is down-regulated in failing human hearts and hypertrophic murine hearts. To evaluate the roles of KLF11 in cardiac hypertrophy, we generated cardiac-specific KLF11 transgenic mice. KLF11 transgenic mice do not show any difference from their littermates at baseline. However, cardiac-specific KLF11 overexpression protects mice from TAC-induced cardiac hypertrophy, with reduced radios of heart weight (HW)/body weight (BW), lung weight/BW and HW/tibia length, decreased left ventricular wall thickness and increased fractional shortening. We also observe lower expression of hypertrophic fetal genes in TAC-challenged KLF11 transgenic mice compared with WT mice. In addition, KLF11 reduces cardiac fibrosis in mice underwent hypertrophy. The expression of fibrosis markers are also down-regulated when KLF11 is overexpressed in TAC-challenged mice. Taken together, our findings identify a novel anti-hypertrophic and anti-fibrotic role of KLF11, and KLF11 activator may serve as candidate drug for heart failure patients.
Posted in Atrial Fibrilation (a-Fib), Cardiac Pacing and Arrhythmias, Cardiac and Cardiovascular Surgical Procedures, Electrophysiology, Frontiers in Cardiology and Cardiovascular Disorders, HTN, Origins of Cardiovascular Disease on February 19, 2015| Leave a Comment »
Reporter: Aviva Lev-Ari, PhD, RN
Significance
Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a disease that is selective to the right side of the heart and results in heart failure and sudden death. Genetic defects in desmosome components account for approximately 50% of human ARVC cases; in the other 50% of patients, however, the causes remain unknown. We show that inhibitor of apoptosis-stimulating protein of p53 (iASPP) is an important regulator of desmosomes. It interacts with desmoplakin and desmin in cardiomyocytes and regulates desmosome integrity and intermediate filaments. iASPP-deficient mice display pathological features of ARVC and die of sudden death. In human ARVC patients, cardiomyocytes exhibit reduced levels of iASPP at the cell junctions, suggesting that iASPP may be critical in ARVC pathogenesis.
Abstract
Desmosomes are anchoring junctions that exist in cells that endure physical stress such as cardiac myocytes. The importance of desmosomes in maintaining the homeostasis of the myocardium is underscored by frequent mutations of desmosome components found in human patients and animal models. Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a phenotype caused by mutations in desmosomal components in ∼50% of patients, however, the causes in the remaining 50% of patients still remain unknown. A deficiency of inhibitor of apoptosis-stimulating protein of p53 (iASPP), an evolutionarily conserved inhibitor of p53, caused by spontaneous mutation recently has been associated with a lethal autosomal recessive cardiomyopathy in Poll Hereford calves and Wa3 mice. However, the molecular mechanisms that mediate this putative function of iASPP are completely unknown. Here, we show that iASPP is expressed at intercalated discs in human and mouse postmitotic cardiomyocytes. iASPP interacts with desmoplakin and desmin in cardiomyocytes to maintain the integrity of desmosomes and intermediate filament networks in vitro and in vivo. iASPP deficiency specifically induces right ventricular dilatation in mouse embryos at embryonic day 16.5. iASPP-deficient mice with exon 8 deletion (Ppp1r13lΔ8/Δ8) die of sudden cardiac death, displaying features of ARVC. Intercalated discs in cardiomyocytes from four of six human ARVC cases show reduced or loss of iASPP. ARVC-derived desmoplakin mutants DSP-1-V30M and DSP-1-S299R exhibit weaker binding to iASPP. These data demonstrate that by interacting with desmoplakin and desmin, iASPP is an important regulator of desmosomal function both in vitro and in vivo. This newly identified property of iASPP may provide new molecular insight into the pathogenesis of ARVC.
A team led by Oxford University researchers was looking at how a protein, iASPP, might be involved in the growth of tumours. However, serendipitously they found that mice lacking this gene died prematurely of sudden cardiac death. More detailed investigations showed that these mice had an irregular conductance in the right side of the heart, a condition known as arrhythmogenic right ventricular cardiomyopathy (ARVC).
The researchers discovered that iASPP had a previously unknown role in controlling desmosomes – one of the main structures that ‘glue’ individual heart muscle cells (cardiomyocytes) together. The genetic defect was shown to weaken desmosome function at the junctions of heart muscle cells: this affected the structural integrity of the heart, making mice lacking iASPP prone to ARVC.
Further studies of heart tissue from human patients who had died from ARVC showed that some of them have similar defects in desmosomes as in the mice suggesting that the faulty iASPP gene could also be responsible for ARVC deaths in humans. This finding also explains why a previously reported cattle herd with spontaneous iASPP gene deletion died of sudden cardiac death.
A team led by Oxford University researchers was looking at how a protein, iASPP, might be involved in the growth of tumours. However, serendipitously they found that mice lacking this gene died prematurely of sudden cardiac death. More detailed investigations showed that these mice had an irregular conductance in the right side of the heart, a condition known as arrhythmogenic right ventricular cardiomyopathy (ARVC).
Posted in Ca2+ triggered activation, Calcium Signaling, Calmodulin Kinase and Contraction, Cardiovascular Research, Curation, Cytoskeleton, Diabetes Mellitus, Disease Biology, Electrophysiology, Frontiers in Cardiology and Cardiovascular Disorders, HTN, Innovations in Neurophysiology & Neuropsychology, Metabolism, Small Molecules in Development of Therapeutic Drugs, tagged cardiopulmonary physiology, HCN channels, Heart rate, Hypertension, Physical exercise, regulation of heart rhythm, sinoatrial node, treadmill test on February 15, 2015| Leave a Comment »
Writer and Curator: Larry H Bernstein, MD, FCAP
The heart is a four-chambered 350 gm semi-oval muscular organ composed of syncytial myocardium, innervated by the vagus nerve with a sino-atrial (SA) and a atrial ventricular (AV) node. The blood circulates through it by way of the pulmonary artery and aorta, carrying blood away from the ventricles, to the lungs and the systemic circulation, respectively, and two veins, the vena cava and pulmonary, carrying blood to the atria from the systemic circulation and lungs, respectively. The coronary arterial supply is the left anterior and left circumflex artery, and posteriorly, the right coronary artery, supplied by the aorta. Much of the pathology has been referred to in the introduction, except for the molecular pathology of atherosclerosis, which has been well covered in this journal. The chambers are divided centrally by the interventricular septum, which is not completely closed in the blue-baby syndrome, which was repaired surgically by Helen Taussig and Richard Bing. The piece that follows is primarily directed to the sympathetic innervation of the heart, variation in heart rate, and exercise or reaction to external threats.
What are the common observable events that stimulate or relax the heart:
Some things that can cause a disruption of balance in integrated circulation, neural innervation, innate immune and hormonal response are:
The basis for the physiological distress has long been the primary basis for acupuncture, holistic and transcendental medicine, and stress management.
I shall here examine the experimental work that supports such an approach – in principle.
Seattle Heart Watch: Initial Clinical, Circulatory and Electrocardiographic Responses to Maximal Exercise
Robert A Bruce, G0 Gey, Jr., Mn Cooper, Ld Fisher, Dr Peterson
Amer J Cardiol 1974; 33(4): 459-469.
A network of 15 maximal exercise testing facilities in four teaching hospitals, 10 private offices and clinics and an industrial medical department was organized in July 1971 to study prospectively the antecedents of myocardial infarction and sudden cardiac death. Within 18 months 2,332 men were tested: 1,275 healthy “normal” subjects, 97 with prior myocardial infarction, 306 with angina pectoris, 193 with hypertension and 461 with various mutually exclusive combinations of these diagnoses; among these clinical groups were five patients who had had a prior episode of ventricular fibrillation.
Historical, physical and laboratory data were recorded on self-teaching printed forms, with normal, borderline and abnormal responses arranged in three columns. Classification with respect to “unlikely,” “questionable” or “likely” risk of future cardiac events was assessed from the highest tally of items in these columns.
Analysis showed computer-averaged S-T segment responses were more consistent and reliable predictors than visual interpretations. Cardiac manifestations in healthy men varled with age and risk assessment, and in patients with cardiovascular disease varied with diagnosis and natural history of disease. Many significant differences provided insights into mechanisms of impaired cardiac function in relation to type of clinical disease. Testing was responsible for one post-exertional cardiac arrest. Recovery was effected promptly by defibrillation; there was no mortality.
Normal and Abnormal Heart Rate Responses to Exercise
Of the many factors ultimately important in determining the cardiac output, the heart rate is certainly the easiest to measure. By analysis of the heart rate response to exercise in a variety of disease states we felt that the interrelationships of inotropic state, stroke volume, autonomic dysfunction, and myocardial disease could be clarified. This paper reviews the normal and abnormal heart rate responses to exercise.
The normal heart rate is determined by the frequency of depolarization of specialized cells within the sino-atrial node (S-A node). The S-A node, the vestigal sinus venosus, lies in the posterior portion of the heart near the demarcation between the right atrium and the superior vena cava. In about 80% of humans it receives its primary source of blood from a branch of the right coronary artery. Unlike other myocardial cells, the specialized cells of the S-A node have a slow sodium channel and a low resting potential which give these cells their special property. The slowly rising diastolic depolarization (stage four) leads to a rhythmic slow rising action potential.
The autonomic nervous system plays a key role in the regulation of heart rate (Fig 1). The sympathetic nervous system input to the heart originates in a nucleus in the medulla oblongata. Stimulation of this area with implanted electrodes results in increased heart rate and systemic vascular resistance due to increased sympathetic output. Axons from these nuclei descend to the sympathetic trunk via the intermediolateral columns of the spinal cord. From their synapses in cervical ganglia, postganglionic fibers directly innervate the atrial and ventricular musculature, the S-A node, and the A-V node. The effector neurotransmitter is norepinephrine and the receptors are of the beta adrenergic type. There is evidence from competitive binding studies that the postganglionic fibers are predominantly associated with type I beta receptors. The parasympathetic influence to the S-A node and the myocardium originates from nuclei very near the origin of the sympathetic nerves. From the motor nuclei of the vagus and the nucleus solitarius come fibers that form part of the vagus nerve. These fibers terminate at ganglia in the wall of the heart. The postganglionic cholinergic fibers end mostly near the S-A node and the A-V node; there is little evidence for the distribution of parasympathetic nerves to the ventricular myocardium although cholinergic muscarinic receptors have been characterized. In normal conditions there exists a well balanced autonomic tone influencing the S-A node.
There is a complex interrelation among many systems to determine the autonomic tone at the S-A node (Fig 2). [Arterial mechanoreceptors of the carotid sinus and aortic arch respond to changes in arterial pressure and result in appropriate adjustment in the sympathetic and vagal outflow to the heart and resistance and capacitance vessels. (Reprinted with permission from Shepherd JT, Van Houlte PM: The Human Cardiovascular System, Facts and Concepts. New York, Raven Press, 1979).]
There are cortical inputs to the medullary centers; for example, fear results in tachycardia by this pathway. Visceral afferent inputs increase parasympathetic tone resulting in bradycardia. Several reflexes are present for homeostasis. For example, the baroreflex is important in sensing changes in blood pressure and increasing or decreasing the heart rate via autonomic influences at the S-A node to maintain appropriate cardiac output.
Arterial mechanoreceptors of the carotid sinus and aortic arch respond to changes in arterial pressure and result in appropriate adjustment in the sympathetic and vagal outflow to the heart and resistance and capacitance vessels. (Reprinted with permission from Shepherd JT, Van Houlte PM: The Human Cardiovascular System, Facts and Concepts. New York, Raven Press, 1979).
Although the importance of autonomic influence is well accepted in the usual cardioacceleration to exercise, the role of the recovery or deceleration of heart rate following exercise may not be influenced by autonomic input. Six men were studied after peak treadmill exercise. To assess the contribution of autonomic factors in heart rate recovery, the men were given atropine, propranolol, or both agents. It was found that exponential cardio-deceleration occurred under each experimental condition. They concluded that heart rate recovery after exercise is regulated by changes in venous return mediated through atrial stretch receptors of pacemaker tissue. This study implies that deceleration depends primarily on factors intrinsic to the intact circulation that are independent of autonomic control.
The control of heart rate is complex; autonomic tone, central and peripheral reflexes, hormonal influences, and factors intrinsic to the heart are all important. Although easily measured, the heart rate reflects an integrated physiologic response.
The physiologic response to exercise depends on the type of exercise performed; the two major types are isometric and isotonic. Creating muscle tension with no movement against resistance is a pure form of isometric exercise; this results in increased muscle mass and strength. Isotonic exercise is the repetitive, rhythmic movement of large muscle masses against little resistance, known also as dynamic or aerobic exercise. Although most activities involve degrees of both, running is predominantly dynamic, and weight lifting is predominantly isometric.
Bezucha and colleagues investigated the cardiovascular responses to isometric (static) exercise (leg extension) and compared these to those observed during static-dynamic exercise (one arm cranking) and dynamic exercise (leg cycling) in normal men. Heart rate responses to these three tasks were markedly different with static exercise (holding a 30% of maximum voluntary contraction for 3 minutes) resulting in a mean heart rate of 110 + 6 compared with 164 + 4 beats/min in bicycle exercise at 80% of Vo max. Cardiac outputs were raised in all three activities in a proportional manner: 6.8 + 0.7 for static, 10.8 f 0.7 for arm cranking, and 31.9 + 1.0 L/min for bicycling. Stroke volume did not significantly change in the static or combined static-dynamic exercises. The increases in cardiac output were primarily the result of increases in heart rate. This study demonstrates the predominant pressor response and modest cardio-acceleration of isometric exercise.
Longhurst and coworkers, examined the response to acute and chronic exercise in two groups of athletes who typify the two major types of exercise: long distance runners (dynamic) and weight lifters (isometric). The runners responded to isometric exercise with lower double products than the weight lifters. The end-diastolic volume index (evaluated by echocardiography) in the runners was greater than control subjects both at rest and with exercise. In contrast, the weight lifters’ responses were similar to weight matched controls. Not only is the type of exercise an important determinant of acute physiologic response, but chronic static exercise results in physiologic responses that are no different from the responses of sedentary men.
Dynamic exercise, also called isotonic or aerobic, involves the rapid movement of large muscle masses that results in the need for the body to respond with increased ventilation to increase oxygen consumption. Such exercise is called aerobic since it must be performed by using oxygen. The heart must increase its output and performs flow work rather than pressure work. The response to dynamic muscular exercise consists of a complex series of cardiovascular adjustments designed to:
(1) see that active muscles receive a blood supply appropriate to their metabolic needs;
(2) dissipate the heat generated by active muscles; and,
(3) maintain the blood supply to the brain and the heart.
The regulation of the circulation during exercise involves the four following adaptations?
The relationship of pressure, flow, and resistance in rigid tubes is defined by Poiseuille’s law. This law states that resistance is proportional to pressure divided by flow. Peripheral resistance increases in the tissues that do not function in the performance of the ongoing exercise and decreases in active muscle. The result is a decrease in systemic vascular resistance. While pressure only increases mildly, flow can increase by as much as five times during dynamic exercise. Since flow increases much more than pressure, the result is a decrease in systemic resistance. Another mechanical adaptation occurs when the increasing venous return dilates the left ventricle and cardiac function is enhanced via the Frank-Starling mechanism.
There is a highly predictable relationship between total body oxygen consumption and both the cardiovascular and respiratory responses to exercise (Fig 4). [ (A) The linear relationship between heart rate and oxygen uptake. The data was collected from 86 adult male and female subjects. (B) The linear relationship between cardiac output and oxygen uptake. C The data was collected from 23 adult male and female subjects. (C) The linear relationship between minute ventilation and oxygen uptake. ] The data was collected from 225 subjects. (Reprinted with permission.) Both parameters increase linearly with increasing oxygen consumption until maximal oxygen consumption is approached.
In summary, the type of exercise is an important determinant of both acute and chronic cardiovascular responses. Isometric exercise can be viewed as a pressure load and dynamic exercise as a volume load to the left ventricle. The acute physiological adjustments to dynamic exercise include peripheral vasodilation in exercising muscle, neural mediated increases in sympathetic tone to the heart and the periphery, the release of catecholamines from the adrenal medulla, and changes in venous return due to mechanical and humoral factors. A linear relationship exists between the consumption of oxygen and cardiac output and minute ventilation such that the work performed is highly correlated with the amount of blood pumped and the oxygen consumed.
An increase in heart rate is a major factor contributing to the exercise-induced increased cardiac output. Bowditch demonstrated that the time interval between beats is a determinant of the force of myocardial contraction. This has been called the frequency-force relationship (Fig 5). [The frequency force relationship is demonstrated by a sudden increase in beat frequency in papillary muscle fixed for isometric contraction. A slow increase in isometric tension results from the change in rate implying in increased contractile state. Each vertical line represents an isometric contraction. (Reprinted with permission of W.B. Saunders.)] The increased tension that accompanies an increased heart rate is the result of increased contractility. Although the mechanism of this phenomenon is not known, it may have to do with calcium availability to contractile elements. Thus an increase in heart rate results in an increase in the force of contraction.
Variations in and Significance of Systolic Pressure During Maximal Exercise (Treadmill) Testing: Relation to Severity of Coronary Artery Disease and Cardiac Mortality
John B. Irving, Robert A. Bruce,, Timothy A. Derouen
Amer J Cardiol 1977; 39: 841-848.
Variations in clinical noninvasive systolic pressure at the point of symptom-limited exercise on a treadmill were examined in six groups of subjects: 5,459 men and 749 women classified into three categories each. Among the men, 2,532 were asymptomatic healthy, 592 were hypertensive and 1,586 had clinical manifestations of coronary heart disease (that is, typical angina pectoris, prior myocardial Infarction or sudden cardiac arrest with resuscitation). Among the women, 244, 158 and 347 were in the corresponding clinical categories. None had had cardiac surgery; all had follow-up status ascertained by periodic mail questionnaires.
Reported deaths were reviewed and classified by three cardiologists; 140 deaths were attributed to coronary heart disease, 118 of them in the men classified as having coronary heart disease. The majority of maximal systolic blood pressure readings were reported to the nearest centimeter rather than millimeter of pressure. Retesting of 156 persons from 1 to 32 months later showed that pressure values agreed within 10 percent in two thirds, the overall mean difference was only 8.6 mm Hg and the correlation at maximal exercise was superior to that of the resting observations just before exercise. Hypertensive patients had a significantly greater body weight than normotensive persons. Among men, the lowest maximal systolic pressure was observed in the group with coronary heart disease; among women, the lowest mean pressure was found in the healthy group. Patients with coronary heart disease were slightly older, and only the women showed a significant correlation in maximal pressure with age. Only 5 percent of the variation in maximal systolic pressure in the patients with coronary heart disease was due to a shortened duration of exercise. Maximal systolic pressures correlated fairly well (r = 0.46 to 0.68 for the various groups) with resting systolic pressure, and this relation was independent of the diagnosis of cardiovascular disease in both men and women. Relations between pressure and the number of stenotic coronary arteries and Impaired ejection fraction at rest were examined in 22 men without and 162 men with coronary artery disease. Lower maximal systolic pressures were often associated with two or three vessel disease or reduced ejection fraction, or both.
The prognostic value of maximal systolic pressure for subsequent death due to coronary heart disease was examined in the men with coronary heart disease. The annual rate of sudden cardiac death decreased from 97.9 per 1,000 men to 25.3 and 6.6 per 1,000 men as the range of maximal systolic pressure increased from less than 140 to 140 to 199 and to 200 mm Hg or more, respectively. Cardiomegaly, Q waves in the resting electrocardiogram and persistent postexertional S-T depression were more common in men with the lowest systolic pressure at maximal exercise.
Circulatory Adjustments to Dynamic Exercise and Effect of Physical Training in Normal Subjects and in Patients With Coronary Artery Disease
Jan Praetorius Clausen
Prog Cardiov Dis 1976; XVIII(6): 459-496
The present paper focuses upon the importance of peripheral circulatory alterations during adjustments to exercise and training. Although training results in central circulatory adaptations and may also improve left ventricular function, the prime importance of such adaptations as regards the circulatory and metabolic response to training will be questioned. The thesis that increased maximal exercise capacity can at least in part be attributed to local alterations in the trained muscles will be presented and analyzed. While it is accepted that maximal oxygen uptake is limited by the blood oxygen transport capacity, it will be postulated that the primary event normally responsible for an enhanced oxygen supply after training is an increased ability to reduce resistance to blood flow in exercising muscles rather than improved performance of the central pump.
adjustment to exercise is limited to factors pertinent to physical training of patients with CAD. More detailed accounts of the normal response to exercise can be found in recent books or reviews.
In connection with patients with CAD, only one type of muscular work is of interest; namely, rhythmic or dynamic exercise, in which a considerable part of the skeletal muscle mass is active. This applies to naturally occurring physical activity. Only these types of activity will be referred to and only at work intensities that can be continued for 3-5 min or more.
Dynamic muscular exercise is characterized by a high metabolic rate in the muscle cells with the skeletal muscle functioning in a manner similar to the myocardium, with regularly alternating contraction and relaxation phases. The mechanical energy expended is grossly proportional to the force and the frequency of contraction, and it is derived from the breakdown of adenosine triphosphate (ATP) and creatine phosphate (CP). Only a limited number of a muscle’s fibers, and thus, of its maximal contractile power, can be used in dynamic work continuing for several minutes. During maximal exercise on a bicycle ergometer with a pedaling frequency of 60 rpm, about 15%-2% of the maximal isometric strength of the quadriceps muscle is mobilized. This is thought related to the fact that skeletal muscle, in contrast to myocardium, is composed of several types of fibers with different enzymatic characteristics.29 Some fibers are similar to cardiac muscle being rich in oxidative intramitochondrial enzymes connected to the citric acid cycle, the fatty acid cycle, and the respiratory chain. These are the classical “red” muscle fibers. At the other end of a continuous spectrum is the typical “white” muscle fiber, with a high content of enzymes necessary for anaerobic glycolysis, but containing few mitochondria. Due to their great capability for aerobic metabolism, red fibers sustain rhythmic contractions for long periods of time, whereas the anaerobic white fibers require longer restitution phases even after short periods of activity.
Oxygen extraction per milliliter of blood perfusing the muscle may increase three- to fourfold, and the enhanced muscle blood flow (MBF) is responsible for the remainder of the augmented oxygen uptake. In human muscle, maximal MBF is in the order of 70-100 ml X 100 g-r X min--1 against a resting value of 2-5 ml X 100 g-r X min--1. The increase in MBF is locally controlled by release of vasodilator metabolites and thereby closely geared to the metabolic demands. Muscle blood flow per unit weight of muscle is closely related to the relative work load; i.e., percentage of maximal work load. The metabolites responsible for the exercise-induced vasodilation and hyperemia in muscle are not yet conclusively identified. The finding that both MBF and ATP-CP depletion are related to the relative work load supports the speculation that split products from high energy phosphates may be involved.
During strenuous exercise, VO2 can attain individually varying maximal values, typically ranging from 2.0 to 6.0 1 02/min. The maximal oxygen consumption (VO2 max) is a highly reproducible measure of a given subject’s capability to perform this type of exercise, and it constitutes a useful physiologic reference standard. The conditions required to obtain VO2 max, and its physiologic implications have recently been reviewed in detail by Rowe and by Hermansen. The VO2 max for a given type of work is normally achieved at a work intensity that can be sustained for at least 3 min, but will cause complete exhaustion within 5-10 min. At this intensity of exercise, the cardiovascular functional capacity with respect to increase in cardiac output (Q), widening of systemic arteriovenous oxygen difference (AVDO2), and elevation of heart rate (HR) will be challenged maximally for the given type of exercise. However, the relative contribution of Q and AVDO2.
The above description of the normal central and peripheral circulatory adjustment to exercise can be recapitulated as follows:
During dynamic exercise, Q increases in direct proportion to the augmentation of 30,. The increase in Q is directed to exercising skeletal muscles, to the myocardium and-if exercise is continued for more than approximately 5 min-also to the skin. Blood flow to most “nonexercising” tissues (SBF, RBF,
and noncontracting muscles) is reduced due to a general sympathetic vasoconstriction. At submaximal levels, muscle blood flow per unit tissue,
the degree of peripheral vasoconstriction, the acceleration of HR, and in consequence, the increase in myocardial blood flow and oxygen consumption are all functions of the relative V02 ; i.e., the actual VO2 expressed as a percentage of the highest achievable V02 for the given type of exercise.
Most patients with CAD who have been included in exercise and training studies have had healed myocardial infarction and/or stable angina pectoris and have been between 35 and 65 years of age. Both the aging process and myocardial lesions contribute to the modification of the circulatory response to exercise in this group, as compared to healthy young people. In advanced age-especially after 60 years-the circulation tends to become hypokinetic; i.e., Q/VO2 is reduced. The decline of Q in l/min is almost the same during submaximal exercise as at rest, and thus the increase in Q with VO2 is essentially the same in older as in younger subjects. Stroke volume is lower at a given VO2 , while arterial blood pressures are higher; Q, HR, and VO2 max decline with aging.
Although patients with angina pectoris often exhibit a more profound impairment of left ventricular function and of working capacity than patients with CAD without angina, there seems not to be any specific differences in their central or peripheral circulatory response to exercise. Accordingly, the abnormalities in hemodynamic adaptations in a patient with angina pectoris are present also at workloads that do not provoke angina pectoris.
From the point of view of an exercise physiologist, the patient with angina pectoris is peculiar in that his capacity for dynamic work is not limited by his total body VO2 max, but by VO2 max in myocardial regions supplied by narrowed coronary arteries. If pain is prevented by prophylactic administration of nitroglycerin, a patient with angina pectoris can exercise longer at a given work load or achieve higher workloads and thus obtain a higher VO2 max.
The circulatory adjustment to exercise in patients with CAD typically differs from that of normal subjects in that the maximal values for Q (and thus for VO2), for HR, and for blood pressures are lower. During submaximal exercise, the relation between Q and VO2 tends to be reduced. Moreover, most of the patients with CAD exhibit signs of left ventricular failure during exercise, including a decrease in SV at higher workloads, reduced myocardial contractility, and increased LVEDp. Nonetheless, the peripheral circulatory regulation in patients with CAD corresponds in principle to that seen in healthy subjects of the same age.
Training changes the different local flows during exercise in such a way that, within the framework of an unchanged or reduced Q, its regional distribution at a given submaximal work load deviates less from that seen at rest: the perfusion of nonworking tissues is relatively greater and the flow to active muscles less elevated. However, this is only valid for exercise performed with trained muscles.
Although the precise mechanism mediating exercise hyperemia is unknown, it seems acceptable that enhanced content of oxidative enzymes enables a reduction in MBF at a given submaximal VO2 . After training, due to the increased capacity for oxidative phosphorylation, ATP and CP in active muscles stabilize at a higher steady state level. At the same time glycolysis occurs at a slower rate, pH is relatively increased, and the concentration of multiple intermediate metabolic products may be lower. In consequence, the intra- and intercellular biochemical milieu-concentrations of electrolytes and osmolality included-is less disturbed as compared to the conditions at rest. Whatever substance or combinations of chemical alterations cause the vasodilation, their extent of change is probably reduced at a given respiratory rate in trained muscle tissue, and the vasodilation is thus diminished.
Training improves exercise tolerance in most patients with angina pectoris. The main part of this effect can be related to the training-induced reduction in HR and SBP that decreases myocardial O2 requirements at a given total body O2 uptake. However, at the same time, higher values for the product of HR and SBP are tolerated before pain is provoked after training, suggesting that training has additional economizing effects on myocardial function or directly improves myocardial O2 supply. As judged from the results obtained in exercise tests, training and nitroglycerin seem almost equally potent in alleviating or preventing angina pectoris on exertion. Beta receptor blockade may be somewhat less efficient, whereas aorto-coronary bypass surgery, when practicable, may be the most efficient treatment of exertional angina available today.
Physical training is efficient in improving exercise capacity in about two thirds of all patients with angina pectoris. Patients with angina pectoris provoked only by exercise will often respond favorably to training, even if their exercise capacity is low. In contrast, patients who suffer from angina at rest, especially nocturnal attacks, may be less likely to increase their exercise tolerance by training. Accordingly, Hellerstein reports that in patients with more severe coronary arteriosclerosis as assessed from coronary arteriograms and left ventricular function, physical fitness fails to improve from training.
Unfortunately, it appears that the patients who cannot be expected to respond favorably to training are also less likely to improve from other modes of treatment. According to Balcon, only younger patients with normal left ventricular function are prone to achieve substantial improvement in physical working capacity by vein graft surgery. Furthermore, the mortality from the operation is higher in patients with abnormal ventricular function. Thus, the appearance of an apparently efficient surgical intervention has not simplified the selection of treatment.
Characteristics of the Ventilatory Exercise Stimulus
F.M. Bennett and W.E. Fordyce
Respiration Physiology 1985; 59, 55-63
Simple mathematical models were used to quantitatively examine a number of hypotheses concerning the nature of the exercise stimulus. The modelling demonstrated the following for an exercise intensity of 5 times the resting metabolic rate.
(1) During the steady state, a deviation in the coupling between VE and metabolic rate by + 25 % of the value necessary for isocapnia, results in a deviation of Paco2 of + 2 torr from isocapnia.
(2) In the transient phase, a mismatch between VE and Q (and thus CO2 flow) of 50% results in a change of Paco2 of only 1 torr.
(3)When resting Paco2 is changed by 10 torr and it is assumed that the coupling between VE and Paco2 does not change, Paco2 deviates from isocapnia by less than 2 torr.
It is concluded that –
(1) to experimentally test hypotheses of the exercise stimulus requires resolution of small changes in Paco2;
(2) good regulation of Paco2 does not necessarily imply precise coupling between VE and Vco2;
(3) the ventilatory exercise stimulus need not be a precise function of metabolic rate;
(4) in the steady state, the normal CO2 controller will be very effective in minimizing changes in Paco2 due to a mismatch between ventilation and metabolic rate.
Cardiorespiratory and Metabolic Responses to Positive, Negative and
Minimum-Load Dynamic Leg Exercise
Carl Magnus Hesser, Dag Linnarsson And Hilding Bjurstedt
Respiration Physiology 1977; 30, 5 I-67
Cardiorespiratory and metabolic responses to steady-state dynamic leg exercise were studied in seven male subjects who performed positive and negative work on a modified Krogh cycle ergometer at loads of 0. 16,33,49.98, and 147 W with a pedaling rate of60 rpm.
In positive work, O2 uptake increased with the ergometric load in a parabolic fashion. Net O2 uptake averaged 220 ml*min– 1 at 0 W (loadless pedaling), and was 75 ml* min– 1 lower at the point of physiological minimum load which occurred in negative work at approximately 9 W. The O2 cost of loadless pedaling is for one-third attributed to the work of overcoming elastic and viscous resistance, the remaining part being due mainly to the work of antagonistic muscle contraction in the moving legs. Although at a given Vo2 work rate was much higher in negative than in positive work, corresponding values for VE were similar, suggesting that the mechanical tension in working muscles is of little or no importance in the control of ventilation in steady-state exercise.
Heart rate increased linearly with Vo2 in both positive and negative work, with a steeper slope in negative work. Evidence is presented that none of the current definitions of muscular efficiency yields the true efficiency of muscular contraction in cycle ergometry, net efficiency calculation resulting in too low estimates, and work and delta efficiency calculations in overestimated values in the low-intensity work range, and in underestimated values in the high-intensity range.
The effect of exercise on left ventricular ejection time in patients with hypertension or angina pectoris
James R. Bowlby
Amer Heart J 1979; 97(3): 348-350
Using the method and regression equation of Lewis and associates, the present study confirms their findings in normal men up to the age of 65 years. Despite the significantly higher myocardial oxygen consumption, as measured by the double product, the hypertensive patients responded in a similar fashion. The patients with angina pectoris, however, showed a significantly prolonged post-exercise ejection time.
Cardiac Effects of Prolonged and Intense Exercise Training in Patients With Coronary Artery Disease
Ali A. Ehsani, Wade H. Martin Iii, Gregory W. Heath, Edward F. Coyle
Amer J Cardiol 1982; 50: 246-254
The effects of intense and prolonged exercise training on the heart were studied with echocardiography in eight men with coronary artery disease with a mean age (standard error of the mean) of 52 + 3 years. Training consisted of endurance exercise 3 times/week at 50 to 60 percent of the measured maximal oxygen uptake for 3 months followed by exercise 4 to 5 days/week at 70 to 60 percent of maximal oxygen uptake for 9 months. Maximal oxygen uptake capacity increased by 42 percent (26 + 1 versus 37 + 2 ml/kg per min; p <0.001). Heart rate at rest and submaximal heart rate and systolic blood pressure at a given work rate were significantly lower after training. Systolic blood pressure at the time of maximal exercise increased (145 + 9 before versus 166 + 6 mm Hg after training; probability [p] <0.01). Left ventricular end-diastolic diameter was increased after 12 months of training (from 47 + 1 to 51 + 1 mm; p <0.01. Left ventricular fractional shortening and mean velocity of circumferential shortening decreased progressively in response to graded iisometric handgrip exercise before training but not after training. At comparable levels of blood pressure during static exercise, mean velocity of circumferential shortening was significantly higher after training (0.76 + 0.04 versus 0.96 + 0.07 diameter/set, p <0.01). No improvement in echocardio-graphic or exercise variables was observed over a 12 month period in another group of five patients who did not exercise. Thus the data suggest that prolonged and vigorous exercise training in selected patients with coronary artery disease can elicit cardiac adaptations.
Physical activity and resting pulse rate in older adults: Findings from a randomized controlled trial
Bríain O’Hartaigh, Marco Pahor, Thomas W. Buford, John A. Dodson, et al.
Am Heart J 2014;168:597-604
Background Elevated resting pulse rate (RPR) is a well-recognized risk factor for adverse outcomes. Epidemiological evidence supports the beneficial effects of regular exercise for lowering RPR, but studies are mainly confined to persons younger than 65 years. We set out to evaluate the utility of a physical activity (PA) intervention for slowing RPR among older adults.
Methods A total of 424 seniors (ages 70-89 years) were randomized to a moderate intensity PA intervention or an education-based “successful aging” health program. Resting pulse rate was assessed at baseline, 6 months, and 12 months. Longitudinal differences in RPR were evaluated between treatment groups using generalized estimating equation models, reporting unstandardized β coefficients with robust SEs.
Results Increased frequency and duration of aerobic training were observed for the PA group at 6 and 12 months as compared with the successful aging group (P = 0.001). In both groups, RPR remained unchanged over the course of the 12-month study period (P = .67). No significant improvement was observed (β [SE] = 0.58 [0.88]; P = .51) for RPR when treatment groups were compared using the generalized estimating equation method. Comparable results were found after omitting participants with a pacemaker, cardiac arrhythmia, or who were receiving β-blockers.
Conclusions Twelve months of moderate intensity aerobic training did not improve RPR among older adults. Additional studies are needed to determine whether PA of longer duration and/or greater intensity can slow RPR in older persons.
Autonomic regulation and maze-learning performance in older and younger dults
Karen J. Mathewson, J Dywan, PJ Snyder, WJ Tays, SJ Segalowitz
Biological Psychology 88 (2011) 20– 27
http://dx.doi.org:/10.1016/j.biopsycho.2011.06.003
There is growing evidence that centrally modulated autonomic regulation can influence performance on complex cognitive tasks but the specificity of these influences and the effects of age-related decline in these systems have not been determined. We recorded pre-task levels of respiratory sinus arrhythmia (RSA; an index of phasic vagal cardiac control) and rate pressure produce (RPP; an index of cardiac workload) to determine their relationship to performance on a cumulative maze learning task. Maze performance has been shown to reflect executive error monitoring capacity and non-executive visuomotor processing speed. Error monitoring was predicted by RSA in both older and younger adults but by RPP only in the older group. Non-executive processes were unrelated to either measure. These data suggest that vagal regulation is more closely associated with executive than nonexecutive aspects of maze performance and that, in later life, pre-task levels of cardiac workload also influence executive control.
Sympathovagal Imbalance Contributes to Prehypertension Status and Cardiovascular Risks Attributed by Insulin Resistance, Inflammation, Dyslipidemia and Oxidative Stress in First Degree Relatives of Type 2 Diabetics
Gopal Krushna Pal, C Adithan, P Hariharan Ananthanarayanan, Pravati Pal, et al.
PLoS OME 2013; 8(11), e78072 http://dx.doi.org:/10.1371/journal.pone.0078072
Background: Though cardiovascular (CV) risks are reported in first-degree relatives (FDR) of type 2 diabetics, the pathophysiological mechanisms contributing to these risks are not known. We investigated the association of sympathovagal imbalance (SVI) with CV risks in these subjects.
Subjects and Methods: Body mass index (BMI), basal heart rate (BHR), blood pressure (BP), rate-pressure product (RPP), spectral indices of heart rate variability (HRV), autonomic function tests, insulin resistance (HOMA-IR), lipid profile, inflammatory markers, oxidative stress (OS) marker, rennin, thyroid profile and serum electrolytes were measured and analyzed in subjects of study group (FDR of type 2 diabetics, n = 72) and control group (subjects with no family history of diabetes, n = 104).
Results: BMI, BP, BHR, HOMA-IR, lipid profile, inflammatory and OS markers, renin, LF-HF (ratio of low-frequency to high frequency power of HRV, a sensitive marker of SVI) were significantly increased (p,0.0001) in study group compared to the control group. SVI in study group was due to concomitant sympathetic activation and vagal inhibition. There was significant correlation and independent contribution of markers of insulin resistance, dyslipidemia, inflammation and OS to LF-HF ratio. Multiple-regression analysis demonstrated an independent contribution of LF-HF ratio to prehypertension status (standardized beta 0.415, p,0.001) and bivariate logistic-regression showed significant prediction (OR 2.40, CI 1.128–5.326, p = 0.002) of LF-HF ratio of HRV to increased RPP, the marker of CV risk, in study group.
Conclusion: SVI in FDR of type 2 diabetics occurs due to sympathetic activation and vagal withdrawal. The SVI contributes to prehypertension status and CV risks caused by insulin resistance, dyslipidemia, inflammation and oxidative stress in FDR of type 2 diabetics.
Exercise prescription for patients with type 2 diabetes and pre-diabetes: A position statement from Exercise and Sport Science Australia
Matthew D. Hordern, DW Dunstan, JB Prins, MK Baker, et al.
Journal of Science and Medicine in Sport 15 (2012) 25–31
http://dx.doi.org:/10.1016/j.jsams.2011.04.005
Type 2 diabetes mellitus (T2DM) and pre-diabetic conditions such as impaired fasting glucose (IFG) and/or impaired glucose tolerance (IGT) are rapidly increasing in prevalence. There is compelling evidence that T2DM is more likely to develop in individuals who are insufficiently active. Exercise training, often in combination with other lifestyle strategies, has beneficial effects on preventing the onset of T2DM and improving glycaemic control in those with pre-diabetes. In addition, exercise training improves cardiovascular risk profile, body composition and cardiorespiratory fitness, all strongly related to better health outcomes. Based on the evidence, it is recommended that patients with T2DM or pre-diabetes accumulate a minimum of 210 min per week of moderate-intensity exercise or 125 min per week of vigorous intensity exercise with no more than two consecutive days without training. Vigorous intensity exercise is more time efficient and may also result in greater benefits in appropriate individuals with consideration of complications and contraindications. It is further recommended that two or more resistance training sessions per week (2–4 sets of 8–10 repetitions) should be included in the total 210 or 125 min of moderate or vigorous exercise, respectively. It is also recommended that, due to the high prevalence and incidence of comorbid conditions in patients with T2DM, exercise training programs should be written and delivered by individuals with appropriate qualifications and experience to recognise and accommodate comorbidities and complications.
Estimation of the Ejection Fraction in Patients with Myocardial Infarction Obtained from the Combined Index of Systolic and Diastolic Left Ventricular Function: A New Method
Jorge A. Lax, Alejandra M. Bermann, Tomás F. Cianciulli, Luis A. Morita, et al.
J Am Soc Echocardiogr 2000;13:116-23.
The index of myocardial performance combining systolic and diastolic time intervals (Index) is a useful method, already explained in past studies, that offers new values that have not been widely known among clinical cardiologists. The aim of this study is to obtain from this Index a measurement of the ejection fraction (EF), which is a very well-known value.
The study involved 97 patients with myocardial infarction, 55 of whom were studied retrospectively (group A, aged 46-62 years, 50 men) to obtain and test the formula EF = 60 – (34 × Index). The second group (group B, aged 47-63 years, 40 men) included 42 patients who were evaluated prospectively. The EF obtained was compared with that reached through the use of radionuclide angiography (EF-RNA).
The Index was obtained through the use of the formula (a – b)/b, where a is the interval between cessation and onset of the mitral inflow, and b is the ejection time. In group A the EF obtained by the Index (EF-Index) was 37.5% ± .8%, and the EF-RNA was 37.7% ± 11% (r = 0.76). In group B the EF-Index was 41.6% ± 7%, and the EF-RNA was 41.2% ± 10% (r = 0.75).
Conclusion: Through the new formula described here it is possible to obtain a reliable measurement of the EF in patients with myocardial infarction, a well known and extremely useful value, especially for those patients with poor acoustic windows.
HCN channels: new roles in sinoatrial node function
Christian Wahl-Schott, Stefanie Fenske and Martin Biel
Current Opinion in Pharmacology 2014, 15:83–90
http://dx.doi.org/10.1016/j.coph.2013.12.005
Hyperpolarization-activated cyclic nucleotide gated (HCN) channels pass a cationic current (Ih/If) that crucially contributes to the slow diastolic depolarization (SDD) of sinoatrial pacemaker cells and, hence, is a key determinant of cardiac automaticity and the generation of the heart beat. There is growing evidence, that HCN channel functions in the sinoatrial node (SAN) are not restricted to impulse formation but are also required for impulse propagation. In addition, HCN channels are involved in coordination and maintenance of sinoatrial network activity and, hence, are crucial for stabilizing cardiac rhythmicity. In the present review we will outline these new concepts.
In this review we will focus on HCN channel functions in the sinoatrial node beyond the established concepts described above. We will outline recent advances involving the characterization of the HCN1-deficient mouse line (HCN1-/- mouse) which have provided evidence that HCN channels are required for impulse propagation and the precision of the heart beat [19**]. Furthermore, we show how these properties can be generalized across the other HCN channel subtypes in the sinoatrial node.
19** Fenske S, Krause SC, Hassan SI, Becirovic E, Auer F, Bernard R, Kupatt C, Lange P, Ziegler T, Wotjak CT et al.: Sick sinus syndrome in HCN1-deficient Mice. Circulation 2013. Epub 2013 Nov 11.
First demonstration of a functional relevance of HCN1 channels in the murine sinoatrial node. The authors demonstrate that mice lacking the pacemaker channel HCN1 display congenital sinoatrial node dysfunction characterized by bradycardia, sinus dysrhythmia, prolonged sinoatrial node recovery time, increased sinoatrial conduction time and recurrent sinus pauses. As a consequence of sinoatrial node dysfunction HCN1-deficient mice display a severely reduced cardiac output.
Recent studies indicate that the role of cardiac HCN channels extends well beyond generation of pacemaker potentials. In addition to being merely ‘pacemaker channels’, HCN channels are important for sinoatrial impulse propagation, cardiac excitability and for the precision of the heartbeat. Furthermore, cardiac HCN channels are involved in the repolarization process of heart ventricles [56**,57]. It will be important to consider the full spectrum of these diverse cardiac functions when exploring agents acting on HCN channels for a specific clinical purpose such as reduction of heart rate.
56.** Fenske S, Mader R, Scharr A, Paparizos C, Cao-Ehlker X, et al.: HCN3 contributes to the ventricular action potential waveform in the murine heart. Circ Res 2011, 109:1015-1023.
First study demonstrating a functional role of HCN3 channels in the heart. Using HCN3-deficient mouse line the authors show that HCN3 together with other members of the HCN channel family confers a depolarizing background current that regulates ventricular resting potential and counteracts the action of hyperpolarizing potassium currents in late repolarization.
57. Fenske S, Krause S, Biel M, Wahl-Schott C: The role of HCN channels in ventricular repolarization. Trends Cardiovasc Med 2011, 21:216-220.
Roles of HCN1 channels for sinoatrial impulse conduction (source-sink relation) The primary impulse initiating the heart beat is generated in the leading pacemaker cell(s) of the sinoatrial node. Once the leading pacemaker cell(s) reaches the threshold for L-type Ca2+ channels an action potential is generated. Since pacemaker cells are interconnected via gap junctions, the impulse is conducted through the sinoatrial network and to the atrium. During impulse propagation the source cell (the cell which first reached AP threshold and is firing the action potential) charges the neighboring cell (sink), in which the membrane potential is below threshold (Figure 1) [24*]. Impulse propagation depends on the source-sink relation [24*, 25–29]. HCN1 deletion increases the sinoatrial conduction time suggesting the existence of a source sink mismatch in the HCN1-deficient mouse [19**].
Role of HCN1 channels for impulse formation and impulse conduction in the sinoatrial node. Schematic pacemaker potential in sinoatrial node cells of wild type (a) and HCN1-/- mice.
(b) HCN channels contribute to the slow diastolic depolarization. In the absence of HCN1 the slope of SDD isdecreased and the time to threshold for an action potential increased. HCN channels decrease the maximal diastolic potential (MDP). In the absence of HCN1 the MDP is increased. This results in an increased distance and time to threshold for an action potential and a decrease in impulse propagation. [SDD: slow diastolic depolarization; MDD: maximal diastolic depolarization; Vthr: threshold potential for the generation of an action potential.]
(c) Direction of intracellular and extracellular current flow during propagation of an action potential from depolarized (source) to resting cells (sink).
(d)Source sink relationship in propagation. Charge from excited cells (source) flows into unexcited cell (sink) and provides the charge to depolarize them to activation threshold. Arrows and dotted lines indicate changes observed in HCN1-/- mice of parameter indicated leading to source sink mismatch and prolonged sinoatrial conduction. Modified from [24*].
24.* Spector P: Principles of cardiac electric propagation and their implications for re-entrant arrhythmias. Circ Arrhythm Electrophysiol 2013, 6:655-661.
The authors provide an excellent review of the principles of impulse propagation in relation to arrhythmia.
HCN1 channels increase the temporal and spatial precision of impulse formation in sinoatrial node
HCN1 channels increase the temporal and spatial precision of impulse formation in sinoatrial node.
(a) Schematic of the sinoatrial node. Atrial cells invaginate into the central sinoatrial node. Putative localization of HCN1 channels at contact interface between strands of atrial myocytes which extend into the central SAN and sinoatrial node pacemaker cells. Green: autonomous innervation. HCN1 channels dampen network noise generated by neighboring pacemaker cells in the sinoatrial network, by invading hyperpolarization of atrial cells and by autonomous regulation. SAN: sinoatrial node, RA: right atrium, CT: crista terminalis.
(b) Model of sinoatrial node function (for detail see text). Note that individual cells display different phases and slightly different periods.
Pharmacological inhibition of cardiac HCN channels
HCN channels have emerged as interesting targets for the development of drugs that lower the heart rate. Ivabradine is the first and currently the only clinically approved compound that specifically targets HCN channels. The therapeutic indication of ivabradine is the symptomatic treatment of chronic stable angina pectoris in patients with coronary artery disease with a normal sinus rhythm (for details see [48], the international trial on the treatment of angina with ivabradine vs. atenolol (INITIATIVE) trial (n = 939) [49] and the antianginal efficacy and safety of the association of the Ih/If current inhibitor ivabradine with a beta-blocker (ASSOCIATE) study (n = 889) [50]).
The Role of HCN Channels in Ventricular Repolarization
Stefanie Fenske, Stefanie Krause, Martin Biel, and Christian Wahl-Schott
Trends Cardiovasc Med 2011; 21:216-220
PII S1050-1738(12)00143-0
Hyperpolarization-activated cyclic nucleotide gated (HCN) channels pass a cationic current (Ih/If) that crucially contributes to the slow diastolic depolarization (SDD) of sinoatrial pacemaker cells and, hence, is a key determinant of cardiac automaticity and the generation of the heartbeat. However, there is growing evidence that HCN channels are not restricted to the spontaneously active cells of the sinoatrial node and the conduction system but are also present in ventricular cardiomyocytes that produce an action potential lacking SDD. This observation raises the question of the principal function(s) of HCN channels in working myocardium. Our recent analysis of an HCN3-deficient (HCN3–/–) mouse line has shed new light on this central question.
We propose that HCN channels contribute to the ventricular action potential waveform, specifically during late repolarization. In this review, we outline this new concept.
In the late 1970s, the hyperpolarization activated current (Ih/If) was discovered and characterized in sinoatrial node cells (Brown and Difrancesco 1980). This current displays several unique biophysical properties: activation upon hyperpolarization and deactivation by depolarization, with a small but substantial degree of activation at resting potentials typically observed in sinoatrial node pacemaker cells (–60 to –50 mV) and ventricular cells (–85 to –75 mV); shift of the activation curve to more positive potentials by cAMP; block by millimolar concentrations of external Cs+; and permeability for Na+ and K+ions with a reversal potential near –35 mV.
Neurophysiology of HCN channels: From cellular functions to multiple regulations
Chao He, Fang Chen, Bo Li, Zhian Hu
Progress in Neurobiology 112 (2014) 1–23
http://dx.doi.org/10.1016/j.pneurobio.2013.10.001
Hyperpolarization-activated cyclic nucleotide-gated (HCN) cation channels are encoded by HCN1-4 gene family and have four subtypes. These channels are activated upon hyperpolarization of membrane potential and conduct an inward, excitatory current Ih in the nervous system. Ih acts as pacemaker current to initiate rhythmic firing, dampen dendritic excitability and regulate presynaptic neurotransmitter release. This review summarizes recent insights into the cellular functions of Ih and associated behavior such as learning and memory, sleep and arousal. HCN channels are excellent targets of various cellular signals to finely regulate neuronal responses to external stimuli. Numerous mechanisms, including transcriptional control, trafficking, as well as channel assembly and modification, underlie HCN channel regulation. In the next section, we discuss how the intracellular signals, especially recent findings concerning protein kinases and interacting proteins such as cGKII, Ca2+/CaMKII and TRIP8b, regulate function and expression of HCN channels, and subsequently provide an overview of the effects of neurotransmitters on HCN channels and their corresponding intracellular mechanisms. We also discuss the dysregulation of HCN channels in pathological conditions. Finally, insight into future directions in this exciting area of ion channel research is provided.
The hyperpolarization-activated current, Ih, was first observed in sino-atrial node tissue in 1976 and later was identified in rod photoreceptors and hippocampal pyramidal neurons (Noma and Irisawa, 1976). Due to its unique properties, particularly the activation upon hyperpolarization of the membrane potential, Ih has been also termed If (f for funny) or Iq (q for queer). The hyperpolarization-activated cyclic nucleotide-gated (HCN) cation ion channels underlying Ih were discovered in the late 1990s and subsequently, the genes encoding these channels were identified, which enable the expression of HCN channels in heterologous systems.
HCN channels belong to the superfamily of voltage-gated pore loop channels with four pore-forming subunits (HCN1-4) encoded by the HCN1-4 gene family in mammals (Robinson and Siegelbaum, 2003). Each subunit has six transmembrane helices (S1–S6), with the positively charged voltage sensor (S4) and the pore region carrying the GYG motif between S5 and S6, which forms the ion selectivity filter (Macri et al., 2012). Following S6 is the 80-residue C-linker comprising six a-helices (A0–F0) and the cyclic nucleotide binding domain (CNBD). The CNBD consists of three a-helices (A–C) and a b-roll between the A- and B-helices (Fig. 1) (Biel et al., 2009; Wahl-Schott and Biel, 2009; Wicks et al., 2011). Together, the C-linker and CBND can be referred to as the ‘‘cAMP-sensing domain’’ (CSD) because they are of functional importance for the cAMP-induced positive shift of the voltage-dependent activation of HCN channels. The crystal structure of CSD has been elucidated at an atomic resolution, but a high-resolution structure of the transmembrane core remains unsolved.
Structure of HCN channels
Structure of HCN channels. Left: one subunit is composed of six transmembrane segments (S1–S6), with the positive charged voltage sensor (S4) and the pore region carrying the GYG motif between S5 and S6. The C-terminal of HCN channels is composed of the C-linker and the cyclic nucleotide-binding domain (CNBD) which mediates their responses to cAMP. The C-linker consists of six a-helices: A0 to F0 . The CNBD follows the C-linker domain and consists of a-helices A–C with a b-roll between the A- and B-helices. Right: the four subunits assemble in homomeric or heteromeric tetramer configurations in vivo.
Regulatory mechanisms of Ih function by the small molecules, protein kinases and interacting proteins.
Regulatory mechanisms of Ih function by the small molecules, protein kinases and interacting proteins. Black arrows indicate known sites of HCN channels interaction with small molecules, protein kinases and interacting proteins. Broken lines indicate the speculated interaction sites. Filamin A interacts with HCN1 via a region of 22 amino acids located downstream from the CNBD. Tamalin and Mint2 bind to the CNBD-downstream sequence of HCN2. The binding of the PDZ domain of S-SCAM occurs at the cyclic nucleotide-binding domain (CNBD) and the CNBD downstream sequence of the carboxy-terminal tail. CNBD, cyclic nucleotide binding domain; SNL, C-terminal tripeptide of HCN1, HCN2 and HCN4.
modulation of HCN channels by neurotransmitters and associated intracellular signal pathways
The modulation of HCN channels by neurotransmitters and associated intracellular signal pathways. Glutamate (Glu) activates N-methyl-D-aspartate receptors (NMDARs) and a-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) which results in the Ca2+ influx and subsequently activates calcium calmodulin kinase (CaMKII). CaMKII increases channels surface expression through the interacting protein TRIP8b (1a-4) or reduces the HCN1 gene transcription via Neuronal Restrictive Silencing Factor (NRSF) in pathological conditions. Glu, norepinephrine (NE, in rats), 5-hydroxytryptamine (5-HT) and triphosphate (ATP) bind to specific G-coupled receptors and modulate the activity of HCN channels via the PLC-PKC or p38-MAPK signaling pathways. Activation of PKC suppresses the activation of HCN channels, whereas p38-MAPK causes a positive shift of HCN channels voltage-dependent activation. Adenosine, NE (in monkey), 5-HT, dopamine (DA) and Ach (acetylcholine) bind to Gs- or Gi coupled receptors. Gs or Gi oppositely control the activity of adenylate cyclase (AC), which catalyzes the ATP to cAMP. cAMP could shift the HCN channels voltage-dependent activation to positive direction and accelerate the kinetics of channels activation. Nitric oxide (NO) interacts with soluble guanylyl cyclase (GC) and thus increases the intracellular concentration of cGMP, which induces a positive shift of HCN channels voltage-dependent activation. Sharp and blunted arrows represent the positive and negative regulation, respectively. Broken lines indicate the speculated signal pathway.
Ultimately, the study of the HCN channels will provide an overall picture underlying the real-time in vivo regulation of the function and expression of HCN channels to fulfill complex functions in different contexts.
Oxygen uptake kinetics during high-intensity arm and leg exercise
Katrien Koppo, Jacques Bouckaert, Andrew M. Jones
Respiratory Physiology & Neurobiology 133 (2002) 241-250
PII: S1569 – 9048 ( 02 ) 00184 – 2
The purpose of the present study was to examine the oxygen uptake kinetics during heavy arm exercise using appropriate modelling techniques, and to compare the responses to those observed during heavy leg exercise at the same relative intensity. We hypothesized that any differences in the response might be related to differences in muscle fiber composition that are known to exist between the upper and lower body musculature. To test this, ten subjects completed several bouts of constant-load cycling and arm cranking exercise at 90% of the mode specific ˙VO2 peak. There was no difference in plasma [lactate] at the end of arm and leg exercise. The time constant of the fast component response was significantly longer in arm exercise compared to leg exercise (mean + S.D., 489 +12 vs. 219 + 5 sec; P < 0.01), while the fast component gain was significantly greater in arm exercise (12.19 + 1.0 vs. 9.29 + 0.5 ml min-1 W-1; P < 0.01). The ˙VO2 slow component emerged later in arm exercise (1269 + 27 vs. 959 + 20 sec; P < 0.01) and, in relative terms, increased more per unit time (5.5 vs. 4.4% min-1; P < 0.01). These differences between arm crank and leg cycle exercise are consistent with a greater and/or earlier recruitment of type II muscle fibers during arm crank exercise.
Probability and magnitude of response to cardiac resynchronization therapy according to QRS duration and gender in nonischemic cardiomyopathy and LBBB
Niraj Varma, Mahesh Manne, Dat Nguyen, …, Patrick Tchou
Heart Rhythm 2014; 11: 1139–1147
http://dx.doi.org/10.1016/j.hrthm.2014.04.001
BACKGROUND QRS morphology and QRS duration (QRSd) determine cardiac resynchronization therapy (CRT) candidate selection but criteria require refinement.
OBJECTIVE To assess CRT effect according to QRSd, treated by dichotomization vs a continuous function, and modulation by gender.
METHODS Patients selected were those with New York Heart Association classIII/IV heart failure and with left bundle branch block and nonischemic cardiomyopathy (totest “pure” CRT effect) with pre-and post- implant echocardiographic evaluations. Positive response was defined as increased left ventricular ejection fraction (LVEF) post-CRT.
RESULTS In 212 patients (LVEF 19% + 7.1%; QRSd 160 + 23 ms; 105 (49.5%) women), CRT increased LVEF to 30% + 15% (P < .001) during a median follow-up of 2 years. Positive response occurred in 150 of 212 (71%) patients. Genders did not differ for QRSd, pharmacotherapy, and comorbidities, but response to CRT among women was greater: incidence 84% (88of105) in women vs 58% (62of107) in men (P < .001); increase in LVEF 15%+ 14% vs 7.2% + 13%, respectively (P < .001). Overall, the response rate was 58% when QRSd <150 ms and 76% when QRSd > 150 ms (P <.009). This probability differed between genders: 86% in women vs 36% in men (P < .001) when QRSd <150 ms and 83% vs 69%, respectively, when QRSd >150 ms (P < .05). Thus, female response rates remained high whether QRSd was < 150 ms >150 ms (86% vs 83%; P = .77) but differed in men (36% vs 69%; P < .001). With QRSd as a continuum, the CRT-response relationship was nonlinear and significantly different between genders. Female superiority at shorter QRSd inverted with prolongation > 180 ms.
CONCLUSION The QRSd-CRT response relationship in patients with heart failure and with left bundle branch block and non-ischemic cardiomyopathy is better described by a sex-specific continuous function and not by dichotomization by 150ms, which excludes a large proportion of women with potentially favorable outcome.
Comparison of eterminants Myocardial Oxygen Consumption During Arm and Leg Exercise in Normal Persons
Gary J. Balady, et al. Am J Cardiol 1985; 57: 1385-87.
The effects of arm exercise on myocardiai oxygen consumption are not well understood; they may differ from the effects of leg exercise. Previous studies have shown that the ischemic threshold is higher in patients performing arm exercise and leg exercise at the same heart rate-blood pressure product. The contribution of other determinants of myocardiai oxygen consumption-left ventricular (LV) peak meridional systolic wail stress and contractility-to these observed differences were studied.
Thirty healthy subjects exercised to the same peak rate-pressure product during dynamic upper- and lower-extremity exercise. Peak workload was lower
during arm exercise (100 + 16 W) leg exercise (170 + 21 W, p < 0.001). LV wail stress did not differ during either form of exercise (197 + 44 vs 204 + 33 dynes/cm2 X 103, arm vs leg, respectively). This was also true of contractility as assessed by the velocity of circumferential fiber shortening (2.6 + 0.6 vs 2.5 + 0.4 circ/s, arm vs leg, respectively) and the preejection period/LV ejection time ratio (0.33 + 0.11 vs 0.31 + 0.07, arm vs leg, respectively). Normal subjects exercising to a similar rate-pressure product showed the same levels at LV wail stress and contractility for arm and leg exercise despite the lower rkioad performed with arm exercise.
Anti-hypertensive effect of radiofrequency renal denervation in spontaneously hypertensive rats
Takeshi Machino, N Murakoshi, A Sato, …, T Hoshi, T Kimura, K Aonuma
Life Sciences 110 (2014) 86–92 http://dx.doi.org/10.1016/j.lfs.2014.06.015
Aims: We aimed to investigate the anti-hypertensive effect of radiofrequency (RF) renal denervation (RDN) in an animal model of hypertension. Materials and methods: RF energy was delivered to bilateral renal arteries through a 2 Fr catheter with opening abdomen in 8 spontaneously hypertensive rats (SHRs) and 8 Wistar–Kyoto rats (WKYs). Sham operation was performed in other 8 SHRs and 8 WKYs. Blood pressure (BP), heart rate (HR), and urinary norepinephrine excretion were followed up for 3 months. Plasma and renal tissue concentrations of norepinephrine and plasma renin activity were measured 3 months after the procedure. The RDN was confirmed by a decrease in renal tissue norepinephrine.
Key findings: RF-RDN restrained a spontaneous rise in systolic BP (46 ± 12% increase from 158 ± 8 to 230 ± 14 mmHg vs. 21 ± 18% increase from 165 ± 9 to 197 ± 20 mmHg, p= 0.01) and diastolic BP (55 ± 27% increase from 117 ± 9 to 179 ± 23 mmHg vs. 28 ± 13% increase from 120 ± 7 to 154 ± 13 mm Hg, p= 0.04) in SHRs; however, WKYs were not affected. Although there were no changes in HR and systemic norepinephrine, the renal tissue norepinephrine was decreased by RF-RDN in both SHR (302±41 vs. 159±44 ng/g kidney, p b 0.01) and WKY (203 ± 33 vs. 145 ± 26 ng/g kidney, p= 0.01). Plasma renin activity was reduced by the RF-RDN only in SHR (35.3 ± 9.5 vs. 21.4 ± 8.6 ng/mL/h, p < 0.01).
Significance: RF-RDN demonstrated an anti-hypertensive effect with a reduction of renal tissue norepinephrine and plasma renin activity in SHR.
Effectiveness of Renal Denervation Therapy for Resistant Hypertension: A Systematic Review and Meta-Analysis
Mark I. Davis, KB Filion, D Zhang, MJ Eisenberg, …, EL Schiffrin, D Joyal
J Am Coll Cardiol 2013; 62(3): 231-241.
http://dx.doi.org/10.1016/j.jacc.2013.04.010
Objectives This study sought to determine the current effectiveness and safety of sympathetic renal denervation (RDN) for resistant hypertension. Background RDN is a novel approach that has been evaluated in multiple small studies.
Methods We performed a systematic review and meta-analysis of published studies evaluating the effect of RDN in patients with resistant hypertension. Studies were stratified according to controlled versus uncontrolled design and analyzed using random-effects meta-analysis models. Results We identified 2 randomized controlled trials, 1 observational study with a control group, and 9 observational studies without a control group. In controlled studies, there was a reduction in mean systolic and diastolic blood pressure (BP) at 6 months of –28.9 mm Hg (95% confidence interval [CI]: –37.2 to –20.6 mm Hg) and –11.0 mm Hg (95% CI: –16.4 to –5.7 mm Hg), respectively, compared with medically treated patients (for both, p < 0.0001). In uncontrolled studies, there was a reduction in mean systolic and diastolic BP at 6 months of –25.0 mm Hg (95% CI: –29.9 to –20.1 mm Hg) and –10.0 mm Hg (95% CI: –12.5 to –7.5 mm Hg), respectively, compared with pre-RDN values (for both, p < 0.00001). There was no difference in the effect of RDN according to the 5 catheters employed. Reported procedural complications included 1 renal artery dissection and 4 femoral pseudoaneurysms.
Conclusions RDN resulted in a substantial reduction in mean BP at 6 months in patients with resistant hypertension. The decrease in BP was similar irrespective of study design and type of catheter employed. Large randomized controlled trials with long-term follow-up are needed to confirm the sustained efficacy and safety of RDN.
Effects of renal denervation on the development of post-myocardial infarction heart failure and cardiac autonomic nervous system in rats
Jialu Hu, Yan Yan, Qina Zhou, Meng Ji, Conway Niu, Yuemei Hou, Junbo Ge
Intl J Cardiol 172 (2014) e414–e416 http://dx.doi.org/10.1016/j.ijcard.2013.12.254
Prior studies indicated that radiofrequency renal denervation (RD) had beneficial effects on post-myocardial infarction (MI) heart failure (HF) in rats. In this study we aimed to assess its effects on cardiac autonomic nervous system (CANS) which might be one of the most important mechanisms of RD’s therapeutic effect on post-MI HF and determine the best timing for RD.
One hundred Wistar rats were randomly assigned into five experimental groups: MI group (n = 20), RD group (n = 20), MI-1d + RD group (RD performed one day post-MI, n = 20), MI-4w + RD group (RD performed four weeks post-MI, n = 20), and N group (control group, n = 20).MI was produced through ligation of the anterior descending artery. RD was performed through stripping of the renal nerves. The experimental design and implementation were conducted in accordance with animal welfare guidelines.
Eight weeks post-MI, significant improvements were observed in both MI-1d + RD and MI-4w + RD groups compared to the MI group, that include
(1) improved left ventricular (LV) function and hemodynamics with increased water and sodium excretion;
(2) decreased plasma and renal tissue norepinephrine levels while tissue norepinephrine content increased in myocardium;
(3) increased β1-receptor in myocardium and improved heart rate variability; (4) decreased plasma renin, angiotensin II, aldosterone, BNP and endothelin levels.
More therapeutic effects were found in the MI-1d + RD group than the MI-4w + RD group.
Firstly, our study showed that RD attenuated the remodeling of CANS and modulated its activities. RD leads to preservation of β1 receptors content along with the β1 mRNA expression in noninfarcted cardiac tissue in this HF model (Fig. 1). This correlated with an improvement in heart function and cardiac remodeling. HRV is a sensitive marker for the CANS. RD led to a slower HR and higher SDNN in both intervention groups.
Secondly, we found that RD blocked both peripheral and central RAAS and sympathetic nervous system (SNS) at the same time. And this may answer the question how RD exerted effect on CANS. In our study RD restores renin, angiotensin II, and aldosterone to near normal levels. This not only explains the increase in sodium and water excretion, but also confirms that RD blocks renal RAAS via blockage of the efferent renal sympathetic nerves which is consistent with our previous study.
Thirdly, early RD, performed one day post-MI, resulted in greater excretion of urinary sodium, lower circulating BNP and ET-1 levels compared to late interventions (four weeks post-MI). This suggests that RD performed in the acute phase of MI may not only reverse cardiac remodeling but also has a preventive effect against the development of HF, as what was observed with β-blockers. RD alleviated cardiac preload and afterload by increasing water and sodium retention, blocking cardiac sympathetic activation and decreasing a variety of vasomotor factors which may lead to alleviated acute and chronic ischemia of the heart.
RD improves hemodynamics, decreases neuro-hormonal activations, modulates cardiac autonomic activities, and attenuates LV remodeling in HF. Early intervention appears to have greater beneficial effects on cardiac functional recovery and reverse remodeling after myocardial injury. Circulating neuro-hormones may be effective indicators to evaluate the therapeutic effect of RD on HF. Our data suggested that RD is a safe, non-pharmaceutical treatment of HF after cardiac injury, with unique benefits in stabilizing cardiac autonomic activity and remodeling post-MI.
The cardiac pacemaker current
Mirko Baruscotti, Andrea Barbuti, Annalisa Bucchi
Journal of Molecular and Cellular Cardiology 48 (2010) 55–64
http://dx.doi.org:/10.1016/j.yjmcc.2009.06.019
In mammals cardiac rate is determined by the duration of the diastolic depolarization of sinoatrial node (SAN) cells which is mainly determined by the pacemaker If current. f-channels are encoded by four members of the hyperpolarization-activated cyclic nucleotide-gated gene (HCN1–4) family. HCN4 is the most abundant isoform in the SAN, and its relevance to pacemaking has been further supported by the discovery of four loss-of-function mutations in patients with mild or severe forms of cardiac rate disturbances. Due to its selective contribution to pacemaking, the If current is also the pharmacological target of a selective heart rate-reducing agent (ivabradine) currently used in the clinical practice. Albeit to a minor extent, the If current is also present in other spontaneously active myocytes of the cardiac conduction system (atrioventricular node and Purkinje fibres). In working atrial and ventricular myocytes f-channels are expressed at a very low level and do not play any physiological role; however in certain pathological conditions over-expression of HCN proteins may represent an arrhythmogenic mechanism. In this review some of the most recent findings on f/HCN channels contribution to pacemaking are described.
Cardiac pacemaking originates in the sinoatrial node (SAN) as a consequence of spontaneous firing of rhythmic action potentials generated by specialized myocytes. Although the electrical behavior of a typical SAN cell differs in several aspects from that of a working myocyte, the functional hallmark can be precisely identified in the events that take place during the diastolic interval. During this phase atrial and ventricular myocytes rest in a standby-like condition at a stable voltage (∼−80 mV); a quite different situation characterizes SAN cells, where the cell potential slowly creeps up from the
maximum diastolic potential of about −60 mV to the threshold for the ignition of a new action potential. Since this time interval sets the pace of the heart, this phase is named “pacemaker depolarization”. Given the large spectrum of heart rates observed in mammals the duration of this phase can vary substantially, however the voltage range encompassed is extremely constant and roughly extends from −60 to−40 mV . To sustain this phase several ionic currents and pumps enter in action at variable times and voltages, and this complexity allows for a highly flexible system since the chronotropic fine tuning operated by neuro-hormonal regulators can target different effectors.
In this review we will focus on the If current which is responsiblefor initiating the diastolic depolarization of SAN cells. Due to its fundamental role and its unusual characteristics of being activated in hyperpolarization, this current was named “pacemaker current” or “funny” (If) current. The unique property of a reverse voltage dependence, together with the inward nature of the current at diastolic potentials, makes this current apt to initiate and support the diastolic depolarization. In addition, the direct modulation of the current operated by the second messenger cAMP, represents one of the main pathways by which the autonomic nervous system controls cardiac chronotropism. Two recent clinical findings further confirm the role of f-channels in setting the cardiac rate: one is the evidence of a causative link between the presence of loss-of-function mutations found in these channels and the arrhythmic state of individuals carrying the mutations, and the other is the specific heart rate reduction observed in patients treated with ivabradine, a drug that at therapeutic doses selectively reduces the If current (see specific sections in this review).
Although originally discovered in the heart, the If current is also abundantly present in a large fraction of neuronal elements, where it contributes to rhythmic firing, synaptic integration, and dendritic integration.
Molecular and functional properties of SAN myocytes
Molecular and functional properties of SAN myocytes. (A) Spontaneous action potentials (left) and If current traces (right) recorded from typical rabbit SANmyocytes; currents were elicited by hyperpolarizing voltage steps in the range−45 to −75 mV. (B) Immunofluorescence analysis of rabbit SAN tissue slice labelled with anti-connexin 43 (Cx43, red) and anti-HCN4 (green) antibodies. HCN4 is strongly expressed in the central region of the SAN, while the opposite staining is observed for Cx43; crista terminalis (CT), interatrial septum (IS). (C) HCN4 labelling of single myocytes isolated from CT, SAN and IS (top), and representative current traces recorded at−125mV frommyocytes isolated from the same regions (bottom). Both If current density and HCN4 labelling are more abundant in the central nodal area. (Panels B and C from [61] with permission).
[61] Brioschi C, Micheloni S, Tellez JO, Pisoni G, Longhi R, Moroni P, et al. Distribution of the pacemaker HCN4 channel mRNA and protein in the rabbit sinoatrial node. J Mol Cell Cardiol 2009;47:221–7.
The search of new therapeutic tools consisting of gene- and/or cell-based intervention aimed to restore compromised cardiac functions has prompted researchers to exploit the use of HCN channels to alter cellular electrical activity in order to generate, in normally quiescent substrates, stable rhythmic activity similar to that of native pacemaker myocytes. The specific features of pacemaker channels and in particular the fact that they are activated only at diastolic potentials and do not contribute to other phases of the action potentials, make them particularly suitable for such purpose. Early in vitro studies demonstrated that virus-mediated over-expression of HCN2 channels induced a significant increase in the rate of spontaneously beating neonatal ventricular myocytes by causing an If-mediated increase of the diastolic depolarization slope. This approach was later confirmed in vivo by showing that direct injection of the HCN2-adenovirus in the left atrium or into the ventricular conduction system of dogs, was able to induce ectopic regular spontaneous activity after AV block. Similarly, adenovirus-mediated over-expression of HCN1 or HCN4 was sufficient to induce a regular rhythm in quiescent cardiomyocyte. Alternative cell-based strategies, aimed to avoid the use of viruses, have been developed by engineering cells in order to express high levels of HCN channels. Engineered human mesenchymal stem cells (hMSCs) expressing either HCN2 or HCN4 have been shown in vitro to properly connect to neonatal cardiomyocytes and to increase their intrinsic spontaneous rhythm. HCN2-expressing hMSCs have also been successfully transplanted in canine left ventricular wall where they were able to induce stable ectopic beats.
Currently, ivabradine is marketed for treatment of chronic stable angina in patients with normal sinus rhythm who have a contraindication or intolerance to β-blockers; clinical studies of patients with chronic stable angina have shown that ivabradine acts as a pure heart rate-reducing agent and has anti-ischemic and anti-anginal properties equivalent to β-blockers and Ca2+ channel blockers and presents a good safety and tolerability profile even during long-term treatment. Mild visual symptoms (phosphenes) were occasionally reported, but were generally well tolerated. Additional information comes from results from a recent large clinical trial (BEAUTIFUL) which indicate that ivabradine treatment of patients with stable coronary artery disease (CAD) and heart rate ≥70 bpm can reduce the incidence of some CAD outcomes such as hospitalization for myocardial infarction and coronary revascularization.
The beat goes on: Cardiac pacemaking in extreme conditions
Christopher M.Wilson, Georgina K. Cox, Anthony P. Farrell
Comparative Biochemistry and Physiology, Part A xxx (2014) xxx–xxx
http://dx.doi.org/10.1016/j.cbpa.2014.08.014
In order for an animal to survive, the heart beat must go on in all environmental conditions, or at least restart its beat. This review is about maintaining a rhythmic heartbeat under the extreme conditions of anoxia (or very severe hypoxia) and high temperatures. It starts by considering the primitive versions of the protein channels that are responsible for initiating the heartbeat, HCN channels, divulging recent findings from the ancestral craniate, the Pacific hagfish (Eptatretus stoutii). It then explores how a heartbeat can maintain a rhythm, albeit slower, for hours without any oxygen, and sometimes without autonomic innervation. It closes with a discussion of recent work on fishes, where the cardiac rhythm can become arrhythmic when a fish experiences extreme heat.
Sympathetic renal denervation: Hypertension beyond SYMPLICITY
Israel M. Barbash, Ron Waksman
Cardiovascular Revascularization Medicine 14 (2013) 229–235
http://dx.doi.org/10.1016/j.carrev.2013.02.004
Despite a wide range of drug treatment for hypertension, resistant hypertension rates remain high. The Symplicity™ Renal Denervation System (Medtronic, Santa Rosa, CA), which creates renal nerve denervation, has shown initial success in lowering blood pressure among patients with resistant hypertension. Given the enormous market for this treatment approach, an estimated two dozen other companies are pursuing technologies with alternative approaches. Despite this fact, very little has been published on preclinical and clinical experience with these new devices. The current review summarizes the most prominent technologies in the pipeline and provides insight into the mechanism of action, preclinical, and clinical experience with these new devices
A large body of evidence has established the central role of the kidneys in hypertension, both as an affector and effector of the central sympathetic system [9]. Renal efferent sympathetic activity initiates processes towards fluid retention, such as the release of renin and increased tubular sodium reabsorption. Moreover, afferent sympathetic activity increases central sympathetic drive, which plays a major role in sustaining hypertension. In fact, historic studies of surgical sympathectomy in patients with resistant hypertension or malignant hypertension uncontrolled by pharmacotherapy were shown to be effective in reducing blood pressure, albeit with severe side effects. Thus, with the introduction of more effective medications, this procedure was abandoned. Renal sympathetic nerves run alongside the renal artery adventitia to enter the hilus of the kidney. Thereafter, they divide into smaller nerve bundles following the anatomic course of the renal blood vessels, penetrating the cortical and juxtamedullary areas inside the kidneys. Based on these anatomic features, it was postulated that creating local nerve injury along the renal arteries may achieve effective denervation.
A key issue in accomplishing effective RDN is to target the sympathetic nerve bundles lying in the adventitia of the renal arteries. Because the vast majority of devices currently under development are percutaneous, RDN is performed from within the vessel lumen. Thus, one of the most important features of such a device is the ability to minimize the damage to the renal artery wall.
Ultrasound energy consists of high-frequency sound waves emitted by a transducer within the catheter. This high energy can pass through surrounding fluids and can generate frictional heating in tissues resulting in a temperature increase that is sufficient to cause injury to the surrounding tissue, specifically the renal nerves. Based on these principles, several systems were developed and are currently being evaluated. ReCor Medical’s (Ronkonkoma, NY) PARADISE™ Percutaneous Renal Denervation System is based on delivery of high ultrasonic energy to induce nerve tissue injury. The PARADISE system is composed of two components: a 6 F-compatible balloon catheter with a cylindrical ultrasound transducer that emits ultrasound energy circumferentially (Fig. 2A)[ Ultrasound based renal denervation systems: (A) Percutaneous Renal Denervation System (PARADISE™); (B) TIVUS system] and a portable generator which controls automated balloon inflation and deflation, and energy delivery. Energy is delivered in 3 different locations along the artery with 50 s inflation and delivery of ultrasound energy at each site. This device received CE mark in February 2012. For RDN, the PARADISE balloon catheter is positioned inside the renal artery and the generator automatically inflates the balloon, delivers the ultrasonic energy, and deflates the balloon. Endothelial thermal damage is prevented by cooled fluid in the balloon.
Radiofrequency based renal denervation systems: (A) Symplicity Renal Denervation System; (B) EnligHTN Renal Denervation System; (C) V2 bipolar balloon catheter; (D) OneShot Balloon catheter
Sample Entropy and Traditional Measures of Heart Rate Dynamics Reveal Different Modes of Cardiovascular Control During Low Intensity Exercise
Matthias Weippert, Martin Behrens, Annika Rieger and Kristin Behrens
Entropy 2014, 16, 5698-5711; http://dx.doi.org:/10.3390/e16115698
Biological time series like the normal heartbeat-to-heartbeat fluctuation demonstrate complex dynamics. Based on their potential to give additional information beyond traditional heart rate variability (HRV) indices, nonlinear parameters have been applied for investigating short and long term effects of exercise on heart rate (HR) control. However, despite their diagnosticity and their clinical significance, the physiological background of their behavior is not very well established. It is assumed that complexity and regularity measures are fundamentally different from traditional HRV indices and show no correlation to these measures. However, many researchers found at least modest correlations for some nonlinear measures and traditional HRV indices under different conditions. It has also been shown that complexity of short-term HRV is under control of the autonomic nervous system. Currently, there are only few studies available that compared the cardiovascular response pattern to different exercise modes at similar HR. Lindquist et al. found a stronger increase of systolic (SBP) and diastolic arterial blood pressure (DBP) during isometric handgrip compared to cycling at comparable HR of 90 bpm.
Nonlinear parameters of heart rate variability (HRV) have proven their prognostic value in clinical settings, but their physiological background is not very well established. We assessed the effects of low intensity isometric (ISO) and dynamic (DYN) exercise of the lower limbs on heart rate matched intensity on traditional and entropy measures of HRV. Due to changes of afferent feedback under DYN and ISO a distinct autonomic response, mirrored by HRV measures, was hypothesized. Five-minute inter-beat interval measurements of 43 healthy males (26.0 ± 3.1 years) were performed during rest, DYN and ISO in a randomized order. Blood pressures and rate pressure product were higher during ISO vs. DYN (p < 0.001). HRV indicators SDNN as well as low and high frequency power were significantly higher during ISO (p < 0.001 for all measures). Compared to DYN, sample entropy (SampEn) was lower during ISO (p < 0.001). Concluding, contraction mode itself is a significant modulator of the autonomic cardiovascular response to exercise. Compared to DYN, ISO evokes a stronger blood pressure response and an enhanced interplay between both autonomic branches. Non-linear HRV measures indicate a more regular behavior under ISO. Results support the view of the reciprocal antagonism being only one of many modes of autonomic heart rate control. Under different conditions; the identical “end product” heart rate might be achieved by other modes such as sympathovagal co-activation as well.
ANOVA revealed a significant effect of experimental condition on all cardiovascular measures and autonomic indices. Average HR raised moderately from 65 ± 9 bpm at baseline to 85 ± 9 bpm during both types of exercise. HR during the first exercise perfectly matched HR of the subsequent exercise; average difference was only 0.3 ± 1.5 bpm (range: −2.6 to 4.3 bpm). Accordingly, HR and average R-R interval did not differ between DYN and ISO. The traditional vagal modulation HRV measure RMSSD was also not affected by the exercise mode, whereas SDNN was. Natural log-transformed HRV spectral indices HFP and LFP, the normalized powers LF n. u. and HF n. u. as well SampEn (Figure 1) were significantly different between DYN and ISO. Interestingly, SampEn did not differ between REST and DYN. There was no difference of the LF/HF ratio between REST and ISO, whereas comparison of REST vs. DYN showed a statistical trend (p = 0.077). Further, there was a small effect of condition on the HF peak frequency (F(2; 84) = 4.959, p < 0.01, η² = 0.106). While HF peak significantly shifted from 0.22 ± 0.07 Hz during REST to 0.26 ± 0.09 Hz during DYN (p < 0.05), no difference was found between REST and ISO (0.23 ± 0. 07 Hz). Post-hoc pair wise comparison between DYN and ISO showed a statistical trend for the HF peak shift (p = 0.063). SBP and RPP were moderately, DBP and MAP largely affected by the type of exercise. In comparison to DYN, myocardial oxygen consumption, reflected by RPP, was about 5% higher under ISO. Correlation analysis revealed only modest associations between traditional HRV indices and entropy measures during the different experimental conditions. Consistent correlation coefficients across all conditions were found for SampEn and R-R length only.
Mean ± SD of sample entropy during REST, ISO, and DYN; N = 43.
*** = significantly different from rest on a p-level < 0.001;
§§§ = significantly different from the respective exercise condition on a p-level < 0.001.
Role of neurotensin and opioid receptors in the cardiorespiratory effects of [Ile9]PK20, a novel antinociceptive chimeric peptide
Katarzyna Kaczynska, M Szereda-Przestaszewska, P Kleczkowska, AW Lipkowski European Journal of Pharmaceutical Sciences 63 (2014) 8–13 http://dx.doi.org/10.1016/j.ejps.2014.06.018
Ile9PK20 is a novel hybrid of opioid–neurotensin peptides synthesized from the C-terminal hexapeptide of neurotensin and endomorphin-2 pharmacophore. This chimeric compound shows potent central and peripheral antinociceptive activity in experimental animals, however nothing is known about its influence on the respiratory and cardiovascular parameters.
The present study was designed to determine the cardiorespiratory effects exerted by an intravenous injection (i.v.) of [Ile9]PK20. Share of the vagal afferentation and the contribution of NTS1 neurotensin and opioid receptors were tested.
Intravenous injection of the hybrid at a dose of 100 lg/kg in the intact, anaesthetized rats provoked an increase in tidal volume preceded by a prompt short-lived decrease. Immediately after the end of injection brief acceleration of the respiratory rhythm appeared, and was ensued by the slowing down of breathing. Changes in respiration were concomitant with a bi-phasic response of the blood pressure: an immediate increase was followed by a sustained hypotension. Midcervical vagotomy eliminated the increase in tidal volume and respiratory rate responses. Antagonist of opioid receptors – naloxone hydrochloride eliminated only [Ile9]PK20-evoked decline in tidal volume response. Blockade of NTS1 receptors with an intravenous dose of SR 142,948, lessened the remaining cardiorespiratory effects. This study depicts that [Ile9]PK20 acting through neurotensin NTS1 receptors augments the tidal component of the breathing pattern and activates respiratory timing response through the vagal pathway. Blood pressure effects occur outside vagal afferentation and might result from activation of the central and peripheral vascular NTS1 receptors. In summary the respiratory effects of the hybrid appeared not to be profound, but they were accompanied with unfavorable prolonged hypotension.
Integrative regulation of human brain blood flow
Christopher K.Willie, Yu-Chieh Tzeng, Joseph A. Fisher and Philip N. Ainslie
J Physiol 2014; 592(5): pp 841–859
http://dx.doi.org:/10.1113/jphysiol.2013.268953
Herein, we review mechanisms regulating cerebral blood flow (CBF), with specific focus on humans. We revisit important concepts from the older literature and describe the interaction of various mechanisms of cerebrovascular control. We amalgamate this broad scope of information into a brief review, rather than detailing any one mechanism or area of research. The relationship between regulatory mechanisms is emphasized, but the following three broad categories of control are explicated:
With respect to these control mechanisms, we provide evidence against several canonized paradigms of CBF control. Specifically, we corroborate the following four key theses:
(1) that cerebral autoregulation does not maintain constant perfusion through a mean arterial pressure range of 60–150 mmHg;
(2) that there is important stimulatory synergism and regulatory interdependence of arterial blood gases and blood pressure on CBF regulation;
(3) that cerebral autoregulation and cerebrovascular sensitivity to changes in arterial blood gases are not modulated solely at the pial arterioles; and
(4) that neurogenic control of the cerebral vasculature is an important player in autoregulatory function and, crucially, acts to buffer surges in perfusion pressure.
Finally, we summarize the state of our knowledge with respect to these areas, outline important gaps in the literature and suggest avenues for future research.
Integrative physiological and computational approaches to understand autonomic control of cerebral autoregulation
Can Ozan Tan and J. Andrew Taylor
Exp Physiol 99.1 (2014) pp 3–15 http://dx.doi.org:/10.1113/expphysiol.2013.072355
New Findings
This review focuses on the autonomic control of the cerebral vasculature in health and disease from an integrative physiological and computational perspective.
This review highlights recent studies exploring autonomic effectors of cerebral autoregulation as well as recent advances in experimental and analytical approaches to understand cerebral autoregulation.
The brain requires steady delivery of oxygen and glucose, without which neurodegeneration occurs within minutes. Thus, the ability of the cerebral vasculature to maintain relatively steady blood flow in the face of changing systemic pressure, i.e. cerebral autoregulation, is critical to neurophysiological health. Although the study of autoregulation dates to the early 20th century, only the recent availability of cerebral blood flow measures with high temporal resolution has allowed rapid, beat-by-beat measurements to explore the characteristics and mechanisms of autoregulation. These explorations have been further enhanced by the ability to apply sophisticated computational approaches that exploit the large amounts of data that can be acquired. These advances have led to unique insights. For example, recent studies have revealed characteristic time scales wherein cerebral autoregulation is most active, as well as specific regions wherein autonomic mechanisms are prepotent. However, given that effective cerebral autoregulation against pressure fluctuations results in relatively unchanging flow despite changing pressure, estimating the pressure–flow relationship can be limited by the error inherent in computational models of autoregulatory function. This review focuses on the autonomic neural control of the cerebral vasculature in health and disease from an integrative physiological perspective. It also provides a critical overview of the current analytical approaches to understand cerebral autoregulation.
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Writer and Curator: Larry H. Bernstein, MD, FCAP
Novel serum protein biomarker panel revealed by mass spectrometry and its prognostic value in breast cancer
Liping Chung, K Moore, L Phillips, FM Boyle, DJ Marsh and RC Baxter
Breast Cancer Research 2014, 16:R63
http://breast-cancer-research.com/content/16/3/R63
Introduction: Serum profiling using proteomic techniques has great potential to detect biomarkers that might improve diagnosis and predict outcome for breast cancer patients (BC). This study used surface-enhanced laser desorption/ionization time-of-flight (SELDI-TOF) mass spectrometry (MS) to identify differentially expressed proteins in sera from BC and healthy volunteers (HV), with the
goal of developing a new prognostic biomarker panel.
Methods: Training set serum samples from 99 BC and 51 HV subjects were applied to four adsorptive chip surfaces (anion-exchange, cation-exchange, hydrophobic, and metal affinity) and analyzed by time-of-flight MS. For validation, 100 independent BC serum samples and 70 HV samples were analyzed similarly. Cluster analysis of protein spectra was performed to identify protein patterns related to BC and HV groups. Univariate and multivariate statistical analyses were used to develop a protein panel to distinguish breast cancer sera from healthy sera, and its prognostic potential was evaluated.
Results: From 51 protein peaks that were significantly up- or downregulated in BC patients by univariate analysis, binary logistic regression yielded five protein peaks that together classified BC and HV with a receiver operating characteristic (ROC) area-under-the-curve value of 0.961. Validation on an independent patient cohort confirmed the five-protein parameter (ROC value 0.939). The five-protein parameter showed positive association with large tumor size (P = 0.018) and lymph node involvement (P = 0.016). By matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) MS, immunoprecipitation and western blotting the proteins were identified as a fragment of apolipoprotein H (ApoH), ApoCI, complement C3a, transthyretin, and ApoAI. Kaplan-Meier analysis on 181 subjects after median follow-up of >5 years demonstrated that the panel significantly predicted disease-free survival (P = 0.005), its efficacy apparently greater in women with estrogen receptor (ER)-negative tumors (n = 50, P = 0.003) compared to ER-positive (n = 131, P = 0.161), although the influence of ER status needs to be confirmed after longer follow-up.
Conclusions: Protein mass profiling by MS has revealed five serum proteins which, in combination, can distinguish between serum from women with breast cancer and healthy control subjects with high sensitivity and specificity. The five-protein panel significantly predicts recurrence-free survival in women with ER-negative tumors and may have value in the management of these patients.
Variants of uncertain significance in BRCA: a harbinger of ethical and policy issues to come?
Jae Yeon Cheon, Jessica Mozersky and Robert Cook-Deegan
Genome Medicine 2014, 6:121
http://genomemedicine.com/content/6/12/121
After two decades of genetic testing and research, the BRCA1 and BRCA2 genes are two of the most well-characterized genes in the human genome. As a result, variants of uncertain significance (VUS; also called variants of unknown significance) are reported less frequently than for genes that have been less thoroughly studied. However, VUS continue to be uncovered, even for BRCA1/2. The increasing use of multi-gene panels and whole-genome and whole-exome sequencing will lead to higher rates of VUS detection because more genes are being tested, and most genomic loci have been far less intensively characterized than BRCA1/2. In this article, we draw attention to ethical and policy-related issues that will emerge. Experience garnered from BRCA1/2 testing is a useful introduction to the challenges of detecting VUS in other genetic testing contexts, while features unique to BRCA1/2 suggest key differences between the BRCA experience and the current challenges of multi-gene panels in clinical care. We propose lines of research and policy development, emphasizing the importance of pooling data into a centralized open-access database for the storage of gene variants to improve VUS interpretation. In addition, establishing ethical norms and regulated practices for sharing and curating data, analytical algorithms, interpretive frameworks and patient re-contact are important policy areas.
The Significance of Normal Pretreatment Levels of CA125 (<35 U/mL) in Epithelial Ovarian Carcinoma
Joseph Menczer, Erez Ben-Shem, Abraham Golan, and Tally Levy
Rambam Maimonides Med J 2015;6 (1):e0005. http://dx.doi.org:/10.5041/RMMJ.10180
Objective: To assess the association between normal CA125 levels at diagnosis of epithelial ovarian carcinoma (EOC) with prognostic factors and with outcome.
Methods: The study group consisted of histologically confirmed EOC patients with normal pretreatment CA125 levels, and the controls consisted of EOC patients with elevated (≥35 U/mL) pretreatment CA125 levels, diagnosed and treated between 1995 and 2112. Study and control group patients fulfilled the following criteria: 1) their pretreatment CA125 levels were assessed; 2) they had full standard primary treatment, i.e. cytoreductive surgery and cisplatin-based chemotherapy; and 3) they were followed every 2–4 months during the first two years and every 4–6 months thereafter.
Results: Of 114 EOC patients who fulfilled the inclusion criteria, 22 (19.3%) had normal pretreatment CA125 levels. The control group consisted of the remaining 92 patients with ≥35 U/mL serum CA125 levels pretreatment. The proportion of patients with early-stage and low-grade disease, with optimal cytoreduction, and with platin-sensitive tumors was significantly higher in the study group than in the control group. The progression-free survival (PFS) and overall survival (OS) were significantly higher in the study group than in the control group on univariate analysis but not on multivariate analysis.
Higher gene expression variability in the more aggressive subtype of chronic lymphocytic leukemia
Simone Ecker, Vera Pancaldi, Daniel Rico and Alfonso Valencia
Genome Medicine (2015) 7:8 http://dx.doi.org:/10.1186/s13073-014-0125-z
Background: Chronic lymphocytic leukemia (CLL) presents two subtypes which have drastically different clinical outcomes, IgVH mutated (M-CLL) and IgVH unmutated (U-CLL). So far, these two subtypes are not associated to clear differences in gene expression profiles. Interestingly, recent results have highlighted important roles for heterogeneity, both at the genetic and at the epigenetic level in CLL progression.
Methods: We analyzed gene expression data of two large cohorts of CLL patients and quantified expression variability across individuals to investigate differences between the two subtypes using different measures and statistical tests. Functional significance was explored by pathway enrichment and network analyses. Furthermore, we implemented a random forest approach based on expression variability to classify patients into disease subtypes.
Results: We found that U-CLL, the more aggressive type of the disease, shows significantly increased variability of gene expression across patients and that, overall, genes that show higher variability in the aggressive subtype are related to cell cycle, development and inter-cellular communication. These functions indicate a potential relation between gene expression variability and the faster progression of this CLL subtype. Finally, a classifier based on gene expression variability was able to correctly predict the disease subtype of CLL patients.
Conclusions: There are strong relations between gene expression variability and disease subtype linking significantly increased expression variability to phenotypes such as aggressiveness and resistance to therapy in CLL.
The Emerging Roles of Thyroglobulin
Yuqian Luo, Yuko Ishido, Naoki Hiroi, Norihisa Ishii, and Koichi Suzuki
Advances in Endocrinology 2014, Article ID 189194, 7 pages http://dx.doi.org/10.1155/2014/189194
Thyroglobulin (Tg), the most important and abundant protein in thyroid follicles, is well known for its essential role in thyroid hormone synthesis. In addition to its conventional role as the precursor of thyroid hormones, we have uncovered a novel function of Tg as an endogenous regulator of follicular function over the past decade. The newly discovered negative feedback effect of Tg on follicular function observed in the rat and human thyroid provides an alternative explanation for the observation of follicle heterogeneity. Given the essential role of the regulatory effects of Tg, we consider that dysregulation of normal Tg function is associated with multiple human thyroid diseases including autoimmune thyroid disease and thyroid cancer. Additionally, extrathyroid Tg may serve a regulatory function in other organs. Further exploration of Tg action, especially at the molecular level, is needed to obtain a better understanding of both the physiological and pathological roles of Tg.
The GUIDE-IT trial will help doctors find a new standard of care for heart failure.
Heart failure affects more than 25 million people worldwide, including 5.8 million in the United States and 6.9 million in Europe. About one to two percent of adults in developed countries have been diagnosed with heart failure; this increases to more than 10 percent in people over age 70. Moreover, heart failure accounts for more than 17 percent of Medicare spending and about 5 percent of total US healthcare spending. The cost to society in the US is about 30 billion dollars a year—and rising.
For people hospitalized due to heart failure, the outlook isn’t encouraging. Following discharge, one in four patients is likely to be back in the hospital in less than a month. With every acute heart failure event that requires readmission, the chances of dying from the disease increase.
Heart failure occurs when the heart is unable to fill with or pump sufficient blood to meet the needs of the body. Some heart failure symptoms—shortness of breath, fatigue and fluid buildup—which are present in other health problems. Heart failure may develop from coronary artery disease, high blood pressure, cardiomyopathy, heart valve disease, arrhythmias, viral or bacterial infections, and congenital heart defects. As a consequence, these patients often have additional diseases (comorbidities) and managing heart failure can be extremely challenging.
There have been no new drugs for heart failure in more than a decade. The last breakthrough was cardiac resynchronization therapy, a device and not a drug. The goals of therapy are to treat heart failure’s underlying causes, reduce symptoms, improve the patient’s quality of life and keep the disease from getting worse.
More than a pump
The heart isn’t just a muscle pumping blood through the body. It is also an endocrine gland that secretes peptides and hormones. When the heart is failing, its stressed cells release larger amounts of substances known as natriuretic peptides, including N-terminal prohormone brain natriuretic peptide, or NT-proBNP.
Roche’s NT-proBNP test measures the levels of this peptide and helps doctors to determine whether patients are suffering from heart failure and to assess their prognosis. Most recently, NT-proBNP has also been shown to help physicians guide and adjust the patient’s drug therapy. The objective of the pivotal GUIDE-IT trial is to demonstrate the efficacy and safety of NT-proBNP guided heart failure therapy.
Sponsored by the National Institutes of Health (NIH), the GUIDE-IT trial will help doctors answer important questions about NT-proBNP’s impact on medical care. About 1100 patients are enrolled in this robustly powered, randomized controlled trial comparing NT-proBNP guided therapy on top of standard care versus standard care alone in high-risk heart failure patients. Its primary endpoint is time to cardiovascular death or first heart failure hospitalization.
With the NT-proBNP biomarker, doctors can create personalized treatment plans for patients to substantially reduce mortality and morbidity. It can be viewed as a companion diagnostic that works with all the drugs recommended by the major guidelines.
Finding new answers
GUIDE-IT will last five years and involve approximately 45 trial sites in the United States. The first group of patients will be enrolled by the end of 2012.
“We need to take a more strategic approach if we are going to meet the AHA/ASA’s 2020 goal of reducing heart failure hospitalizations by 20 percent,” Dr. O’Connor, Chief of the Division of Cardiovascular Medicine at Duke Heart Center in Durham, North Carolina, said at a media briefing held in October at Roche Diagnostics International in Rotkreuz, Switzerland.
The relative and combined ability of: high-sensitivity cardiac troponin T, and N-terminal pro-B-type natriuretic Peptide – to predict cardiovascular events and death in patients with type 2 diabetes.
Hillis GS; Welsh P; Chalmers J; Perkovic V; Chow CK; Li Q; Jun M; Neal B; et al.
http://reference.medscape.com/medline/abstract/24089534?src=wnl_ref_prac_diab
OBJECTIVE Current methods of risk stratification in patients with type 2 diabetes are suboptimal. The current study assesses the ability of N-terminal pro-B-type natriuretic peptide (NT-proBNP) and high-sensitivity cardiac troponin T (hs-cTnT) to improve the prediction of cardiovascular events and death in patients with type 2 diabetes.
RESEARCH DESIGN AND METHODS A nested case-cohort study was performed in 3,862 patients who participated in the Action in Diabetes and Vascular Disease: Preterax and Diamicron Modified Release Controlled Evaluation (ADVANCE) trial. RESULTS Seven hundred nine (18%) patients experienced a major cardiovascular event (composite of cardiovascular death, nonfatal myocardial infarction, or nonfatal stroke) and 706 (18%) died during a median of 5 years of follow-up. In Cox regression models, adjusting for all established risk predictors, the hazard ratio for cardiovascular events for NT-proBNP was 1.95 per 1 SD increase (95% CI 1.72, 2.20) and the hazard ratio for hs-cTnT was 1.50 per 1 SD increase (95% CI 1.36, 1.65). The hazard ratios for death were 1.97 (95% CI 1.73, 2.24) and 1.52 (95% CI 1.37, 1.67), respectively. The addition of either marker improved 5-year risk classification for cardiovascular events (net reclassification index in continuous model, 39% for NT-proBNP and 46% for hs-cTnT). Likewise, both markers greatly improved the accuracy with which the 5-year risk of death was predicted. The combination of both markers provided optimal risk discrimination.
CONCLUSIONS NT-proBNP and hs-cTnT appear to greatly improve the accuracy with which the risk of cardiovascular events or death can be estimated in patients with type 2 diabetes.
Genetics and Heart Failure: A Concise Guide for the Clinician
Cécile Skrzynia, Jonathan S. Berg, Monte S. Willis and Brian C. Jensen
Current Cardiology Reviews, 2013; 9.
Abstract: The pathogenesis of heart failure involves a complex interaction between genetic and environmental factors. Genetic factors may influence the susceptibility to the underlying etiology of heart failure, the rapidity of disease progression, or the response to pharmacologic therapy. The genetic contribution to heart failure is relatively minor in most multifactorial cases, but more direct and profound in the case of familial dilated cardiomyopathy. Early studies of genetic risk for heart failure focused on polymorphisms in genes integral to the adrenergic and renin-angiotensin-aldosterone system. Some of these variants were found to increase the risk of developing heart failure, and others appeared to affect the therapeutic response to neurohormonal antagonists. Regardless, each variant individually confers a relatively modest increase in risk and likely requires complex interaction with other variants and the environment for heart failure to develop. Dilated cardiomyopathy frequently leads to heart failure, and a genetic etiology increasingly has been recognized in cases previously considered to be “idiopathic”. Up to 50% of dilated cardiomyopathy cases without other cause likely are due to a heritable genetic mutation. Such mutations typically are found in genes encoding sarcomeric proteins and are inherited in an autosomal dominant fashion. In recent years, rapid advances in sequencing technology have improved our ability to diagnose familial dilated cardiomyopathy and those diagnostic tests are available widely. Optimal care for the expanding population of patients with heritable heart failure involves counselors and physicians with specialized training in genetics, but numerous online genetics resources are available to practicing clinicians.
Cardiac Troponin Testing Is Overused after the Rule-In or Rule-Out of Myocardial Infarction
Olaia Rodriguez Fraga, Y Sandoval, SA Love, ZJ McKinney, MAM Murakami, SW Smith, FS Apple
Clinical Chemistry 2015; 61:2 http://dx.doi.org:/10.1373/clinchem.2014.232694
No good studies have systematically evaluated appropriate clinical utilization of cardiac troponin testing in the clinical setting of the rule-in and rule-out of myocardial infarction (MI). Our collective 100-plus years of clinical and laboratory experience suggested that provider test ordering and use of cardiac troponin has been excessive after a diagnosis of MI or no MI has been determined. There is no evidence that supports continuation of cardiac troponin testing after a diagnosis is made.
Number of cTnI results demonstrating excessive orders by diagnosis
Time and Frequency Domain Analysis of Heart Rate Variability and their orrelations in Diabetes Mellitus
T. Ahamed Seyd, V. I. Thajudin Ahamed, Jeevamma Jacob, Paul Joseph K
Intl J Biolog and Life Sciences 2008; 4(1)
Diabetes mellitus (DM) is frequently characterized by autonomic nervous dysfunction. Analysis of heart rate variability (HRV) has become a popular noninvasive tool for assessing the activities of autonomic nervous system (ANS). In this paper, changes in ANS
activity are quantified by means of frequency and time domain analysis of R-R interval variability. Electrocardiograms (ECG) of 16 patients suffering from DM and of 16 healthy volunteers were recorded. Frequency domain analysis of extracted normal to normal interval (NN interval) data indicates significant difference in very low frequency (VLF) power, low frequency (LF) power and high frequency (HF) power, between the DM patients and control group. Time domain measures, standard deviation of NN interval (SDNN), root mean square of successive NN interval differences (RMSSD), successive NN intervals differing more than 50 ms (NN50 Count), percentage value of NN50 count (pNN50), HRV triangular index and triangular interpolation of NN intervals (TINN) also show significant difference between the DM patients and control group.
Power Spectral Density of the RR interval of a 55 year old healthy volunteer
Power Spectral Density of the RR interval of a 55 year old healthy volunteer
Power Spectral Density of the RR interval of a 62 year old woman suffering
Power Spectral Density of the RR interval of a 62 year old woman suffering
from diabetes for the last 15 years
HRV analysis has gained much importance in recent years, as a technique employed to explore the activity of ANS, and as an important early marker for identifying different pathological conditions. DM is a disease in which the cardiac autonomic activity is progressively compromised. Our investigation indicates that different time domain and frequency domain measures of HRV would be able to provide valuable information regarding the autonomic dysfunction to DM.
Time domain and frequency domain analysis of the RR interval variability of diabetic and normal subjects shows that there is significant difference in these measures for DM patients with respect to normal subjects. Variation of the HRV parameters indicates changes in ANS activity of DM patients. This can provide valid information regarding autonomic neuropathy in people with diabetes. It may be noted that these methods can detect changes before clinical signs appear. So we can expect that these measures enable early detection and treatment/subsequent management of patients and thus can avoid acute and chronic complications.
Multiparametric diagnostics of cardiomyopathies by microRNA signatures
Christine S. Siegismund & Maria Rohde & Uwe Kühl & Dirk Lassner
Microchim Acta 2014 http://dx.doi.org:/10.1007/s00604-014-1249-y
The diagnosis of cardiomyopathies by endomyocardial biopsy analysis is the gold standard for confirmation of causative reasons but is failing if a sample does not contain the area of interest due to focal pathology. Biopsies are revealing an extract of the current situation of the heart muscle only, and the need for global organ-specific or systemic markers is obvious in order to minimize sampling errors. Global markers like specific gene expression signatures in myocardial tissue may therefore reflect the focal situation or condition of the whole myocardium. Besides gene expression profiles, microRNAs (miRNAs) represent a new group of stable biomarkers that are detectable both in tissue and body fluids. Such miRNAs may serve as cardiological biomarkers to characterize inflammatory processes, to confirm viral infections, and to differentiate various forms of infection.
The predictive power of single miRNAs for diagnosis of complex diseases may be further increased if several distinctly deregulated candidates are combined to form a specific miRNA signature. Diagnostic systems that generate disease related miRNA profiles are based on microarrays, bead-based oligo sorbent assays, or on assays based on real-time polymerase chain reactions and placed on microfluidic cards or nanowell plates. Multiparametric diagnostic systems that can measure differentially expressed miRNAs may become the diagnostic tool of the future due to their predictive value with respect to clinical course, therapeutic decisions, and therapy monitoring. We discuss here specific merits, limitations and the potential of currently available analytical platforms for diagnostics of heart muscle diseases based on miRNA profiling.
Predictive value of plasma galectin-3 levels in heart failure with reduced and preserved ejection fraction
Rudolf A. de Boer, DJA Lok, T Jaarsma, P van der Meer, AA Voors, et al.
Annals Med, 2011; 43: 60–68 http://dx.doi.org:/10.3109/07853890.2010.538080
We studied the prognostic value of base-line galectin-3 in a large HF cohort, with preserved and reduced left ventricular ejection fraction (LVEF), and compared this to other biomarkers.
Methods. We studied 592 HF patients who had been hospitalized for HF and were followed for 18 months. The primary end-point was a composite of all-cause mortality and HF hospitalization.
Results. A doubling of galectin-3 levels was associated with a hazard ratio (HR) of 1.97 (1.62–2.42) for the primary outcome (P= 0.001). After correction for age, gender, BNP, eGFR, and diabetes the HR was 1.38 (1.07–1.78; P= 0.015). Galectin-3 levels were correlated with higher IL -6 and CRP levels (P= 0.002). Changes of galectin-3 levels after 6 months did not add prognostic information to the base-line value (n= 291); however, combining plasma galectin-3 and BNP levels increased prognostic value over either biomarker alone (ROC analysis, P = 0.05). The predictive value of galectin-3 was stronger in patients with preserved LVEF (n= 114) compared to patients with reduced LVEF (P= 0.001).
Conclusions. Galectin-3 is an independent marker for outcome in HF and appears to be particularly useful in HF patients with preserved LVEF.
Criteria for the use of omics-based predictors in clinical trials
Lisa M. McShane, MM Cavenagh, TG Lively, DA Eberhard, et al.
Nature 17 Oct 2013; 502: 317-320. http://dx.doi.org:/10.1038/nature12564
The US National Cancer Institute (NCI), in collaboration with scientists representing multiple areas of expertise relevant to ‘omics’-based test development, has developed a checklist of criteria that can be used to determine the readiness of omics-based tests for guiding patient care in clinical trials. The checklist criteria cover issues relating to specimens, assays, mathematical modelling, clinical trial design, and ethical, legal and regulatory aspects. Funding bodies and journals are encouraged to consider the checklist, which they may find useful for assessing study quality and evidence strength. The checklist will be used to evaluate proposals for NCI-sponsored clinical
trials in which omics tests will be used to guide therapy.
M-Atrial Natriuretic Peptide and Nitroglycerin in a Canine Model of Experimental Acute Hypertensive Heart Failure: Differential Actions of 2 cGMP Activating Therapeutics.
Paul M McKie, Alessandro Cataliotti, Tomoko Ichiki, S Jeson Sangaralingham, Horng H Chen, John C Burnett
J Am Heart Assoc 01/2014; 3(1):e000206. http://dx.doi.org:/10.1161/JAHA.113.000206
Systemic hypertension is a common characteristic in acute heart failure (HF). This increasingly recognized phenotype is commonly associated with renal dysfunction and there is an unmet need for renal enhancing therapies. In a canine model of HF and acute vasoconstrictive hypertension we characterized and compared the cardiorenal actions of M-atrial natriuretic peptide (M-ANP), a novel particulate guanylyl cyclase (pGC) activator, and nitroglycerin, a soluble guanylyl cyclase (sGC) activator.
HF was induced by rapid RV pacing (180 beats per minute) for 10 days. On day 11, hypertension was induced by continuous angiotensin II infusion. We characterized the cardiorenal and humoral actions prior to, during, and following intravenous M-ANP (n=7), nitroglycerin (n=7), and vehicle (n=7) infusion. Mean arterial pressure (MAP) was reduced by M-ANP (139±4 to 118±3 mm Hg, P<0.05) and nitroglycerin (137±3 to 116±4 mm Hg, P<0.05); similar findings were recorded for pulmonary wedge pressure (PCWP) with M-ANP (12±2 to 6±2 mm Hg, P<0.05) and nitroglycerin (12±1 to 6±1 mm Hg, P<0.05). M-ANP enhanced renal function with significant increases (P<0.05) in glomerular filtration rate (38±4 to 53±5 mL/min), renal blood flow (132±18 to 236±23 mL/min), and natriuresis (11±4 to 689±37 mEq/min) and also inhibited aldosterone activation (32±3 to 23±2 ng/dL, P<0.05), whereas nitroglycerin had no significant (P>0.05) effects on these renal parameters or aldosterone activation.
Our results advance the differential cardiorenal actions of pGC (M-ANP) and sGC (nitroglycerin) mediated cGMP activation. These distinct renal and aldosterone modulating actions make M-ANP an attractive therapeutic for HF with concomitant hypertension, where renal protection is a key therapeutic goal.
Genome-Wide Association Study of a Heart Failure Related Metabolomic Profile Among African Americans in the Atherosclerosis Risk in Communities (ARIC) Study
Bing Yu, Y Zheng, D Alexander, TA Manolio, A Alonso, JA Nettleton, & E Boerwinkle
Genet Epidemiol 2013; 00:1–6, http://dx.doi.org:/10.1002/gepi.21752
Both the prevalence and incidence of heart failure (HF) are increasing, especially among African Americans, but no large-scale, genome-wide association study (GWAS) of HF-related metabolites has been reported. We sought to identify novel genetic variants that are associated with metabolites previously reported to relate to HF incidence. GWASs of three metabolites identified previously as risk factors for incident HF (pyroglutamine, dihydroxy docosatrienoic acid, and X-11787, being either hydroxy-leucine or hydroxy-isoleucine) were performed in 1,260 African Americans free of HF at the baseline examination of the Atherosclerosis Risk in Communities (ARIC) study. A significant association on chromosome 5q33 (rs10463316, MAF = 0.358, P-value = 1.92 × 10−10) was identified for pyroglutamine. One region on chromosome 2p13 contained a nonsynonymous substitution in N-acetyltransferase 8 (NAT8) was associated with X-11787 (rs13538, MAF = 0.481, P-value = 1.71 × 10−23). The smallest P-value for dihydroxy docosatrienoic acid was rs4006531 on chromosome 8q24 (MAF = 0.400, P-value = 6.98 × 10−7). None of the above SNPs were individually associated with incident HF, but a genetic risk score (GRS) created by summing the most significant risk alleles from each metabolite detected 11% greater risk of HF per allele. In summary, we identified three loci associated with previously reported HF-related metabolites. Further use of metabolomics technology will facilitate replication of these findings in independent samples.
Global Left Atrial Strain Correlates with CHADS2 Risk Score in Patients with Atrial Fibrillation
SK Saha, PL Anderson, G Caracciolo, A Kiotsekoglou, S Wilansky, S Govind, et al.
J Am Soc Echocardiogr 2011; 24(5): 506-512.
http://dx.doi.org:/10.1016/j.echo.2011.02.012
Background: The aim of this cross-sectional study was to explore the association between echocardiographic parameters and CHADS2 score in patients with nonvalvular atrial fibrillation (AF).
Methods: Seventy-seven subjects (36 patients with AF, 41 control subjects) underwent standard twodimensional, Doppler, and speckle-tracking echocardiography to compute regional and global left atrial (LA) strain.
Results: Global longitudinal LA strain was reduced in patients with AF compared with controls (P < .001) and was a predictor of high risk for thromboembolism (CHADS2 score $ 2; odds ratio, 0.86; P = .02). LA strain indexes showed good interobserver and intraobserver variability. In sequential Cox models, the prediction of hospitalization and/or death was improved by addition of global LA strain and indexed LA volume to CHADS2 score (P = .003).
Conclusions: LA strain is a reproducible marker of dynamic LA function and a predictor of stroke risk and cardiovascular outcomes in patients with AF.
Gene Expression and Genetic Variation in Human Atria
Honghuang Lin, EV Dolmatova, MP Morley, KL Lunetta, et al.
Heart Rhythm, HRTHM5533. PII: S1547-5271(13)01226-5
http://dx.doi.org/10.1016/j.hrthm.2013.10.051
Background— The human left and right atria have different susceptibilities to develop atrial fibrillation (AF). However, the molecular events related to structural and functional changes that enhance AF susceptibility are still poorly understood.
Objective— To characterize gene expression and genetic variation in human atria.
Methods— We studied the gene expression profiles and genetic variations in 53 left atrial and 52 right atrial tissue samples collected from the Myocardial Applied Genomics Network (MAGNet) repository. The tissues were collected from heart failure patients undergoing transplantation and from unused organ donor hearts with normal ventricular function. Gene expression was profiled using the Affymetrix GeneChip Human Genome U133A Array. Genetic variation was profiled using the Affymetrix Genome-Wide Human SNP Array 6.0.
Results— We found that 109 genes were differentially expressed between left and right atrial tissues. A total of 187 and 259 significant cis-associations between transcript levels and genetic variants were identified in left and right atrial tissues, respectively. We also found that a SNP at a known AF locus, rs3740293, was associated with the expression of MYOZ1 in both left and right atrial tissues. Conclusion— We found a distinct transcriptional profile between the right and left atrium, and extensive cis-associations between atrial transcripts and common genetic variants. Our results implicate MYOZ1 as the causative gene at the chromosome 10q22 locus for AF.
Atrial Natriuretic Peptide Single Nucleotide Polymorphisms in Patients with Nonfamilial Structural Atrial Fibrillation
Pietro Francia, A Ricotta, A Frattari, R Stanzione, A Modestino, et al.
Clinical Medicine Insights: Cardiology 2013:7 153–159
http://dx.doi.org:/10.4137/CMC.S12239
Background: Atrial natriuretic peptide (ANP) has antihypertrophic and antifibrotic properties that are relevant to AF substrates. The −G664C and rs5065 ANP single nucleotide polymorphisms (SNP) have been described in association with clinical phenotypes, including hypertension and left ventricular hypertrophy. A recent study assessed the association of early AF and rs5065 SNPs in low-risk subjects. In a Caucasian population with moderate-to-high cardiovascular risk profile and structural AF, we conducted a case-control study to assess whether the ANP −G664C and rs5065 SNP associate with nonfamilial structural AF.
Methods: 168 patients with nonfamilial structural AF and 168 age- and sex-matched controls were recruited. The rs5065 and −G664C ANP SNPs were genotyped.
Results: The study population had a moderate-to-high cardiovascular risk profile with 86% having hypertension, 23% diabetes, 26% previous myocardial infarction, and 23% left ventricular systolic dysfunction. Patients with AF had greater left atrial diameter (44 ± 7
vs. 39 ± 5 mm; P , 0.001) and higher plasma NTproANP levels (6240 ± 5317 vs. 3649 ± 2946 pmol/mL; P , 0.01). Odds ratios (ORs)
for rs5065 and −G664C gene variants were 1.1 (95% confidence interval [CI], 0.7–1.8; P = 0.71) and 1.2 (95% CI, 0.3–3.2; P = 0.79), respectively, indicating no association with AF. There were no differences in baseline clinical characteristics among carriers and noncarriers of the −664C and rs5065 minor allele variants.
Conclusions: We report lack of association between the rs5065 and −G664C ANP gene SNPs and AF in a Caucasian population of patients with structural AF. Further studies will clarify whether these or other ANP gene variants affect the risk of different subphenotypes of AF driven by distinct pathophysiological mechanisms.
N-terminal proBNP and mortality in hospitalized patients with heart failure and preserved vs. reduced systolic function: data from the prospective Copenhagen Hospital Heart Failure Study (CHHF)
Kirk, M. Bay, J. Parnerc, K. Krogsgaard, T.M. Herzog, S. Boesgaard, et al.
Eur Journal Heart Failure 6 (2004) 335–341
http://dx.doi.org:/10.1016/j.ejheart.2004.01.002
Preserved systolic function among heart failure patients is a common finding, a fact that has only recently been fully appreciated. The aim of the present study was to examine the value of NT-proBNP to predict mortality in relation to established risk factors among consecutively hospitalised heart failure patients and secondly to characterise patients in relation to preserved and reduced systolic function. Material: At the time of admission 2230 consecutively hospitalised patients had their cardiac status evaluated through determinations of NT-proBNP, echocardiography, clinical examination and medical history. Follow-up was performed 1 year later in all patients. Results: 161 patients fulfilled strict diagnostic criteria for heart failure (HF). In this subgroup of patients 1-year mortality was approximately 30% and significantly higher as compared to the remaining non-heart failure population (approx. 16%). Using univariate analysis left ventricular ejection fraction (LVEF), New York Heart Association classification (NYHA) and plasma levels of NT-proBNP all predicted mortality independently. However, regardless of systolic function, age and NYHA class, risk-stratification was provided by measurements of NT-proBNP. Having measured plasma levels of NT-proBNP, LVEF did not provide any additional prognostic information on mortality among heart failure patients (multivariate analysis).
Conclusion: The results show that independent of LVEF, measurements of NT-proBNP add additional prognostic information. It is concluded that NT-proBNP is a strong predictor of 1-year mortality in consecutively hospitalised patients with heart failure with preserved as well as reduced systolic function.
N-terminal pro-B-type natriuretic peptide and the prediction of primary cardiovascular events: results from 15-year follow-up of WOSCOPS
Paul Welsh, Orla Doolin, Peter Willeit, Chris Packard, Peter Macfarlane, et al.
Eur Heart Journal 2014. http://eurheartj.oxfordjournals.org/
Aims: To test whether N-terminal pro-B-type natriuretic peptide (NT-proBNP) was independently associated with, and improved the prediction of, cardiovascular disease (CVD) in a primary prevention cohort.
Methods and results: In the West of Scotland Coronary Prevention Study (WOSCOPS), a cohort of middle-aged men with hypercholesterolemia at a moderate risk of CVD, we related the baseline NT-proBNP (geometric mean 28 pg/mL) in 4801 men to the risk of CVD over 15 years during which 1690 experienced CVD events. Taking into account the competing risk of non-CVD death, NT-proBNP was associated with an increased risk of all CVD [HR: 1.17 (95% CI: 1.11–1.23) per standard deviation increase in log NT-proBNP] after adjustment for classical and clinical cardiovascular risk factors plus C-reactive protein. N-terminal pro-B-type natriuretic peptide was more strongly related to the risk of fatal [HR: 1.34 (95% CI: 1.19–1.52)] than non-fatal CVD [HR: 1.17 (95% CI: 1.10–1.24)] (P ¼ 0.022). The addition of NT-proBNP to traditional risk factors improved the C-index (+0.013; P , 0.001). The continuous net reclassification index improved with the addition of NT-proBNP by 19.8% (95% CI: 13.6–25.9%) compared with 9.8% (95% CI: 4.2–15.6%) with the addition of C-reactive protein. N-terminal pro-B-type natriuretic peptide correctly reclassified 14.7% of events, whereas C-reactive protein correctly reclassified 3.4% of events. Results were similar in the 4128 men without evidence of angina, nitrate prescription, minor ECG abnormalities, or prior cerebrovascular disease.
Conclusion: N-terminal pro-B-type natriuretic peptide predicts CVD events in men without clinical evidence of CHD, angina, or history of stroke, and appears related more strongly to the risk for fatal events. N-terminal pro-B-type natriuretic peptide also provides moderate risk discrimination, in excess of that provided by the measurement of C-reactive protein.
Effect of B-type natriuretic peptide-guided treatment of chronic heart failure on total mortality and hospitalization: an individual patient meta-analysis
Richard W. Troughton, Christopher M. Frampton, Hans-Peter Brunner-La Rocca,
Matthias Pfisterer, Luc W.M. Eurlings, Hans Erntell, Hans Persson, et al.
Eur Heart J 2014; 35: 1559–1567 http://dx.doi.org:/10.1093/eurheartj/ehu090
Aims Natriuretic peptide-guided (NP-guided) treatment of heart failure has been tested against standard clinically guided care in multiple studies, but findings have been limited by study size. We sought to perform an individual patient data metaanalysis to evaluate the effect of NP-guided treatment of heart failure on all-cause mortality.
Methods and results
Eligible randomized clinical trials were identified from searches of Medline andEMBASEdatabases and the Cochrane Clinical
Trials Register. The primary pre-specified outcome, all-cause mortality was tested using a Cox proportional hazards regression model that included study of origin, age (< 75 or ≥75 years), and left ventricular ejection fraction (LVEF, ≤45 or .45%) as covariates. Secondary endpoints included heart failure or cardiovascular hospitalization. Of 11 eligible studies, 9 provided individual patient data and 2 aggregate data. For the primary endpoint individual data from 2000 patients were included, 994 randomized to clinically guided care and 1006 to NP-guided care. All-cause mortality was significantly reduced by NP-guided treatment [hazard ratio = 0.62 (0.45–0.86);
P = 0.004] with no heterogeneity between studies or interaction with LVEF. The survival benefit from NP-guided therapy was seen in younger ( <75 years) patients [0.62 (0.45–0.85); P = 0.004] but not older (≥75 years) patients [0.98 (0.75–1.27); P = 0.96]. Hospitalization due to heart failure [0.80 (0.67–0.94); P = 0.009] or cardiovascular disease [0.82 (0.67–0.99); P = 0.048]was significantly lower in NP-guided patients with no heterogeneity between studies and no interaction with age or LVEF.
Conclusion: Natriuretic peptide-guided treatment of heart failure reduces all-cause mortality in patients aged < 75 years and overall reduces heart failure and cardiovascular hospitalization.
Diagnostic and prognostic evaluation of left ventricular systolic heart failure by plasma N-terminal pro-brain natriuretic peptide concentrations in a large sample of the general population
B A Groenning, I Raymond, P R Hildebrandt, J C Nilsson, M Baumann, F Pedersen
Heart 2004;90:297–303. http://dx.doi.org:/10.1136/hrt.2003.026021
Objective: To evaluate N-terminal pro-brain natriuretic peptide (NT-proBNP) as a diagnostic and prognostic marker for systolic heart failure in the general population.
Design: Study participants, randomly selected to be representative of the background population, filled in a heart failure questionnaire and underwent pulse and blood pressure measurements, electrocardiography, echocardiography, and blood sampling and were followed up for a median (range) period of 805 (6021171) days.
Setting: Participants were recruited from four randomly selected general practitioners and were examined in a Copenhagen university hospital.
Patients: 382 women and 290 men in four age groups (50259 (n = 174); 60269 (n = 204); 70279 (n = 174); > 80 years (n = 120)).
Main outcome measures: Value of NT-proBNP in evaluating patients with symptoms of heart failure and impaired left ventricular (LV) systolic function; prognostic value of NT-proBNP for mortality and hospital admissions.
Results: In 38 (5.6%) participants LV ejection fraction (LVEF) was (40%. NT-proBNP identified patients with symptoms of heart failure and LVEF (40% with a sensitivity of 0.92, a specificity of 0.86, positive and negative predictive values of 0.11 and 1.00, and area under the curve of 0.94. NT-proBNP was the strongest independent predictor of mortality (hazard ratio (HR) = 5.70, p = 0.0001), hospital admissions for heart failure (HR = 13.83, p = 0.0001), and other cardiac admissions (HR = 3.69, p = 0.0001). Mortality (26 v 6, p = 0.0003), heart failure admissions (18 v 2, p = 0.0002), and admissions for other cardiac causes (44 v 13, p = 0.0001) were significantly higher in patients with NTproBNP above the study median (32.5 pmol/l). Conclusions: Measurement of NT-proBNP may be useful as a screening tool for systolic heart failure in the general population.
Copeptin—Marker of Acute Myocardial Infarction
Martin Möckel & Julia Searle
Curr Atheroscler Rep 2014; 16:421 http://dx.doi.org:/10.1007/s11883-014-0421-5
The concentration of copeptin, the C-terminal part of pro-arginine vasopressin, has been shown to increase early after acute and severe events. Owing to complementary pathophysiology and kinetics, the unspecific marker copeptin, in combination with highly cardio-specific troponin, has been evaluated as an early-rule-out strategy for acute myocardial infarction in patients presenting with signs and symptoms of acute coronary syndrome. Overall, most studies have reported a negative predictive value between 97 and 100 % for the diagnosis of acute myocardial infarction in low- to intermediate-risk patients with suspected acute coronary syndrome. Additionally, a recent multicenter, randomized process study, where patients who tested negative for copeptin and troponin were discharged from the emergency department, showed that the safety of the new process was comparable to that of the current standard process. Further interventional trials and data from registries are needed to ensure the effectiveness and patient benefit of the new strategy.
The role of copeptin as a diagnostic and prognostic biomarker for risk stratification in the emergency department
Christian H Nickel1, Roland Bingisser and Nils G Morgenthaler
BMC Medicine 2012, 10:7 http://www.biomedcentral.com/1741-7015/10/7
The hypothalamic-pituitary-adrenal axis is activated in response to stress. One of the activated hypothalamic hormones is arginine vasopressin, a hormone involved in hemodynamics and osmoregulation. Copeptin, the C-terminal part of the arginine vasopressin precursor peptide, is a sensitive and stable surrogate marker for arginine vasopressin release. Measurement of copeptin levels has been shown to be useful in a variety of clinical scenarios, particularly as a prognostic marker in patients with acute diseases such as lower respiratory tract infection, heart disease and stroke. The measurement of copeptin levels may provide crucial information for risk stratification in a variety of clinical situations. As such, the emergency department appears to be the ideal setting for its potential use. This review summarizes the recent progress towards determining the prognostic and diagnostic value of copeptin in the emergency department.
Variability of the Transferrin Receptor 2 Gene in AMD
Daniel Wysokinski, Janusz Blasiak, Mariola Dorecka, Marta Kowalska, et al.
Disease Markers 2014, Article ID 507356, 8 pages http://dx.doi.org/10.1155/2014/507356
Oxidative stress is a major factor in the pathogenesis of age-related macular degeneration (AMD). Iron may catalyze the Fenton reaction resulting in overproduction of reactive oxygen species. Transferrin receptor 2 plays a critical role in iron homeostasis and variability in its gene may influence oxidative stress and AMD occurrence. To verify this hypothesis we assessed the association between polymorphisms of the TFR2 gene and AMD. A total of 493AMDpatients and 171matched controls were genotyped for the two polymorphisms of the TFR2 gene: c.1892C>T (rs2075674) and c.−258+123T>C (rs4434553). We also assessed the modulation of some AMD risk factors by these polymorphisms.The CC and TT genotypes of the c.1892C>T were associated with AMD occurrence but the latter only in obese patients. The other polymorphism was not associated with AMD occurrence, but the CC genotype was correlated with an increasing AMD frequency in subjects with BMI < 26. The TT genotype and the T allele of this polymorphism decreased AMD occurrence in subjects above 72 years, whereas the TC genotype and the C allele increased occurrence of AMD in this group.The c.1892C>T and c.−258+123T>C polymorphisms of the TRF2 gene may be associated with AMD occurrence, either directly or by modulation of risk factors.
Urinary N-Acetyl-beta-D-glucosaminidase as an Early Marker for Acute Kidney Injury in Full-Term Newborns with Neonatal Hyperbilirubinemia
Bangning Cheng, Y Jin, G Liu, Z Chen, H Dai, and M Liu
Disease Markers 2014, Article ID 315843, 6 pages http://dx.doi.org/10.1155/2014/315843
Purpose. To investigate renal function estimated by markers in full-term newborns with hyperbilirubinemia.
Methods. A total of 332 full-term newborns with hyperbilirubinemia and 60 healthy full-term newborns were enrolled. Total serum bilirubin, serum creatinine (Cr), serum blood urea nitrogen (BUN), serum cystatin C (Cys-C), urinary beta-2-microglobulin (𝛽2MG) index, and urinary N-acetyl-beta-D-glucosaminidase (NAG) index were measured before and after treatment. All newborns were divided into three groups according to total serum bilirubin levels: group 1 (221-256), group 2 (256-342), and group 3 (>342). Results. The control group and group 1 did not differ significantly in regard to serum Cr, serum BUN, serum Cys-C, urinary 𝛽2MG index, and urinary NAG index. Urinary NAG index in group 2 was significantly higher than that in control group (𝑃 < 0.001). Between control group and group 3, serum Cys-C, urinary 𝛽2MG index, and urinary NAG index differed significantly. The significant positive correlation between total serum bilirubin and urinary NAG index was found in newborns when total serum bilirubin level was more than 272 𝜇mol/L.
Conclusions. High unconjugated bilirubin could result in acute kidney injury in full-term newborns. Urinary NAG might be the suitable marker for predicting acute kidney injury in full-term newborns with hyperbilirubinemia.
Urinary C-peptide creatinine ratio detects absolute insulin deficiency in Type 2 diabetes.
S V Hope, A G Jones, E Goodchild, M Shepherd, R E J Besser, B Shields, T McDonald, B A Knight, A Hattersley
Department of Geriatrics, Royal Devon and Exeter NHS Foundation Trust; NIHR Exeter Clinical Research Facility, University of Exeter.
Diabetic Medicine (impact factor: 2.9). 05/2013; http://dx.doi.org:/10.1111/dme.12222
Source: PubMed
ABSTRACT AIMS: To determine the prevalence and clinical characteristics of absolute insulin deficiency in long-standing Type 2 diabetes, using a strategy based on home urinary C-peptide creatinine ratio measurement.
METHODS: We assessed the urinary C-peptide creatinine ratios, from urine samples taken at home 2 h after the largest meal of the day, in 191 insulin-treated subjects with Type 2 diabetes (diagnosis age ≥45 years, no insulin in the first year). If the initial urinary C-peptide creatinine ratio was ≤0.2 nmol/mmol (representing absolute insulin deficiency), the assessment was repeated. A standardized mixed-meal tolerance test with 90-min stimulated serum C-peptide measurement was performed in nine subjects with a urinary C-peptide creatinine ratio ≤ 0.2 nmol/mmol (and in nine controls with a urinary C-peptide creatinine ratio >0.2 nmol/mmol) to confirm absolute insulin deficiency.
RESULTS: A total of 2.7% of participants had absolute insulin deficiency confirmed by a mixed-meal tolerance test. They were identified initially using urinary C-peptide creatinine ratio: 11/191 subjects (5.8%) had two consistent urinary C-peptide creatinine ratios ≤ 0.2 nmol/mmol; 9/11 subjects completed a mixed-meal tolerance test and had a median stimulated serum C-peptide of 0.18nmol/l. Five out of nine subjects had stimulated serum C-peptide <0.2 nmol/l and 9/9 subjects with urinary C-peptide creatinine ratio >0.2 had endogenous insulin secretion confirmed by the mixed-meal tolerance test. Compared with subjects with a urinary C-peptide creatinine ratio >0.2 nmol/mmol, those with confirmed absolute insulin deficiency had a shorter time to insulin treatment (median 2.5 vs. 6 years, P=0.005) and lower BMI (25.1 vs. 29.1kg/m(2) , P=0.04). Two out of five patients were glutamic acid decarboxylase autoantibody-positive.
CONCLUSIONS: Absolute insulin deficiency may occur in long-standing Type 2 diabetes, and cannot be reliably predicted by clinical features or autoantibodies. Its recognition should help guide treatment, education and management. The urinary C-peptide creatinine ratio is a practical non-invasive method to aid detection of absolute insulin deficiency, with a urinary C-peptide creatinine ratio > 0.2 nmol/mmol being a reliable indicator of retained endogenous insulin secretion.
Unlocking Biomarkers’ Full Potential
David Daniels, Ph.D. genengnews Feb 1, 2013 (Vol. 33, No. 3)
http://www.genengnews.com/gen-articles/unlocking-biomarkers-full-potential/4700/
Biomarker research and development has evolved over the past years from looking for a single marker (e.g., PSA) linked to a disease state to looking for a panel of markers that can capture the heterogeneity inherent in both the disease and the impacted patient population.
That is one of the key messages to be delivered at GTC’s “Biomarkers Summit” next month. Across the board, resources are being focused on the delivery of more precise, quantifiable biomarkers with predictive value in therapeutic decisions and for the prognosis of illness.
“Our focus on biomarker development is the recognition that the new products need to provide cost savings for the already strapped healthcare systems rather than just be cost effective,” shares Paul Billings, M.D., Ph.D., CMO at Life Technologies.
“We have built a new medical sciences group to address the needs of the multiple delivery systems in the world—from the sophisticated medical clinics in the developed world to the nurse-run shanty clinic in the third world. Providing tools for equitable access to quality diagnosis, on assay platforms that can provide care for all patients, is our goal.”
Life Tech’s medical sciences division has been built by acquisition of Pinpoint Genomics, Navigenics, and Compendia, and collaborations with partners such as Ingenuity Systems and CollabRx. The division is focused on taking the tools that have been used in the life science laboratories and providing molecular diagnostic data to the clinic. The intent is to deliver data in a valuable format that can be used by the molecular pathologist or the treating physician.
The division is developing the Pervenio™ Lung RS assay, a 14-gene expression profile that serves as a risk stratifier that uses a weighted algorithm for the expressed biomarkers within the tumor biopsy, a first-of-its-kind prognostic test for lung cancer, the firm reports.
Initially, tests will be offered as a service through Life Tech’s CLIA laboratory. Then, from the performance lessons learned, Life Tech’s will develop a simpler assay platform, with FDA approval, that can be dispersed globally without reduction of the essential content in the biomarker panel. The focus is on the workflow—screening for known mutations using established easy-to-use assay platforms, like RT-PCR. Should the screen not produce useful results, clinicians can search for new mutations via discovery platforms like next-gen sequencing (NGS).
http://www.genengnews.com/Media/images/Article/thumb_Sequenom_LungCartaPanel1722631391.jpg
Sequenom’s LungCarta panel of 214 somatic mutations in 26 tumor suppressors and oncogenes covers highly mutated pathways in lung adenocarcinomas.
At Sequenom, the company provides both the tools (DNA mass spectrometry and reagents) for confirmatory biomarker development as well as serving on the front lines as a diagnostic service provider (CLIA lab). The beauty of DNA mass spec is that it can process multiplexed PCR samples (10–60 loci) in a method that is quantitative when used for profiling tumor biopsies that are either archival or fresh tissue.
Given a tumor sample with multiple somatic mutations, the instrument enables the determination of the homogeneity of the cells, in which case the mutations will have the same allele frequency. Accuracy, as measured by coefficient of variance, is less than 2%. Despite this level of sensitivity, the mass spec can only be used as a confirmatory tool looking for known mutations. Discovery is best done using DNA sequencing. DNA mass spec can also be used to study methylation in tumor samples.
“In the not-too-distant future, we will be looking for mutations in plasma samples rather than biopsies,” predicts Charles Cantor, Ph.D., CSO at Sequenom.
“The key is to look noninvasively for mutations within plasma samples such that we can potentially catch the disease state earlier, rather than after tumor formation. Regardless of the tumor type, this approach will enable us to monitor therapeutic response and metastatic potential noninvasively. DNA mass spec is an ultrasensitive detection product that can detect somatic mutations at levels of 1 per 1,000. This level of sensitivity is critical for the future of plasma screening. NGS technology is not that sensitive.”
Sequenom’s CLIA lab is using automated DNA mass spec to provide three different test protocols: (1) carrier screening for cystic fibrosis looking at more than 100 different mutations, (2) adult macular degeneration progression using an SNP test with 13 loci, and (3) a noninvasive test for Rh compatibility between a mother and her unborn fetus.
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Scientists are using Illumina’s HiSeq system to discover molecular biomarkers that may provide opportunities for early detection of a range of diseases.
Sequenom has also set up an NGS facility within a CLIA lab in San Diego using Illumina’s HiSEQ platform. The NGS platform has been set up for noninvasive aneuploidy detection of maternal plasma (10 cc sample) looking at chromosomes 13, 18, and 21. The lab says it has analyzed more than 40,000 samples this year and is planning to increase that volume up to 100,000 samples per year. Most of these samples come from the U.S., but given the development of a new blood collection tube that allows for 72-hour ambient shipping, the lab is looking to increase the number of samples from outside the U.S.
Drug Development
During drug development, biomarkers function as pharmacodynamic markers to help assess the mechanism of action of a drug candidate, to define the downstream biological pathway, and to determine whether the drug is engaging the target with the anticipated biological effect. Later, biomarkers help determine whether a drug is effective using the tested regime (route of delivery, dosage level, and length of exposure time).
Following early development, the second stage is to use biomarkers to help segment patients for clinical trials. Part of the consideration here is how heterogeneous the disease is; are there homogeneous subsets of patients that will respond differentially to the drug based on different mechanisms of the disease?
“Biomarker research is focused on on- target effects,” says Nick Dracopoli, Ph.D., vp, head of oncology biomarkers at Janssen Research and Development, a J&J company.
“We look at indications and at patients with those indications that are most likely to respond to the drug candidates we’re developing. For oncology biomarkers, germ-line effects are weaker indicators than somatic changes in the tumor. As a consequence, SNP-based, genome-wide association studies are not very useful. It is better to focus on molecular changes within the tumor and define gene expression profiles and epigenetic modifications that correlate with the tumor phenotype. We are increasingly tracking patient immune response, particularly as more immuno-oncology products are moving into the drug development pipeline.”
The number of biomarkers being developed varies from project to project. But it is very clear that to be successful in the clinic, the biomarkers and the assays need to be of low complexity. Of the 10 to 12 companion diagnostics that have been approved by the FDA to date, all measure the status of the drug target (on-target markers). For example, EGFR measures the level of receptor expression; Braf and Kras markers measure the presence of the mutation and translocation in the ALK gene measures gene knockout.
It is important to realize that molecular profiles for first-in-class drugs are not optimal because they are based on only a few patients. Consequently they have weak predictive value overall.
“Aside from that rule of thumb, if you have a greater than 50% response rate for your drug, it is unlikely that you need a biomarker to predict response. Biomarker utility is best for drugs that would have a difficult road to approval, where it is critical to enrich for the subpopulation of responders. For example, Pfizer’s crizontinib was approved for non-small-cell lung patients but is only effective for 5% of all patients. If Pfizer was unable to demonstrate the relationship between activation of the ALK gene and disease, this inhibitor would not have been approved,” says Dr. Dracopoli.
“Drugs that are more broadly active can come to market without a companion diagnostic test. There is always a balance between the predictive values of the biomarker test and the response rates to treatment. That is, we should not treat if the chance of response is only 3–5%, rather than if it were 50% where the patient would want to take the chance if the drug were safe.”
An important take-home message is that mutations are not unique to an indication. So if you find a driver mutation in indications for which the drug has not been approved, you could discover new indications for the drug.
“At the end of the day, this is what cancer is—heterogeneous,” says Dr. Dracopoli. “We’d all love to treat one cancer with one drug and at one dose, but the story is more complex. The future of oncology is around understanding the molecular heterogeneity or underlying molecular pathology of the disease and the diversity of it, and then treat each patient accordingly.”
Clinical Considerations
“Given the complexity of biology,” says Achim Plum, Ph.D., principal consultant, Siemens, “whether is it cancer, metabolic disease, or any other disease state, we have been forced to move away from the idea that a single biomarker can capture the entire ‘story’ or mechanistic view of any disease. Hence newly developed biomarkers will be made up of a panel of markers that serve as a profile. In addition, with the sheer volume of DNA and protein analytics data, the clinic will need to employ software tools and algorithms to help the decision making.”
The task of getting broad profiling technologies that are analytical into a clinical setting and making them routine is difficult but not insurmontable. This will take a collaborative effort, something that Siemens among others are looking to develop. The key is to avoid technology hype and to establish good reliable software to process the data for decision making. “Data is not knowledge, and knowledge is not automatically decision making.”
As an academic, Daniel Chan, Ph.D., has a view of the whole value chain for biomarkers from discovery to development to use in the clinic. Dr. Chan holds the titles of professor in pathology, oncology, radiology, and urology, and is the director of the clinical chemistry division lab at Johns Hopkins Hospital.
Given his perspective from discovery to clinical use, Dr. Chan indicated that from the clinical point of view, “we need more markers.” He oversees the discovery of new biomarkers in his research lab, their validation in his translational research lab, and finally their utility in practice in his clinical chemistry lab. He is a strong advocate for collaboration of biomarker development from discovery to verification and validation to incorporation within the clinical practice.
Beyond the use of biomarkers for patient stratification and correlation between marker and therapeutic choice, as is the focus of the biopharma industry, for the clinic the use of biomarkers is for prevention and early detection. The earlier the detection, the better the outcome. That is, provide the “cure” before you need to initiate treatment.
To be successful in the future of biomarkers, we need to look beyond the biopharma focus and expand the horizon for early detection and monitor therapy later, says Dr. Chan. He describes a roadmap of developing bridges (to bridge the knowledge gaps), gates (decision gates for go/no go decisions as to whether a development path is viable), and partnerships (to collaborate with different points of view) for efficient new biomarker development.
According to Dr. Chan, we must define the intended use of the biomarker, which identifies the specific application and sets up the clinical study and study population to meet the clinical needs. We need to define specific assays to monitor biomarkers that will work within a clinical setting, not a research lab setting that uses disease models (tissue culture cells or small animals) and not real patient samples.
“The days when single markers are sufficient (PSA for prostate cancer or troponin for cardiovascular disease) are behind us. We need to develop a panel of markers or a profile pattern to address patient population heterogeneity and disease complexity that will guide our decision-making process,” remarks Dr. Chan. “Molecular biomarkers are giving way to protein biomarkers,” he adds.
Prevention and early detection will require the use of whole-body scans, so the sampling technology and analytical tools to be developed are critical to realize this goal. Assay ease of use, automation, and analytical performance that is suitable for the clinical lab are fundamental.
“An important future goal for biomarkers,” says Dr. Billings, “is to sample circulating tumor cells or circulating DNA in blood or plasma samples as a noninvasive measure of patient status. A decline in tumor biomarkers during chemotherapy, for example, could reflect the efficacy of the therapy. In contrast, an increase in tumor biomarkers, in a patient who had previously undergone surgery and therapy, might indicate disease recurrence, and is likely to do so before a tumor mass is detectable by imaging methods.”
STAT4 Gene Polymorphisms Are Associated with Susceptibility and ANA Status in Primary Biliary Cirrhosis
Satoru Joshita, T Umemura, M Nakamura, Y Katsuyama, S Shibata, et al.
Disease Markers 2014, Article ID 727393, 8 pages http://dx.doi.org/10.1155/2014/727393
Recent genome-wide association studies suggest that genetic factors contribute to primary biliary cirrhosis (PBC) susceptibility. Although several reports have demonstrated that the interleukin (IL) 12 signaling pathway is involved in PBC pathogenesis, its precise genetic factors have not been fully clarified. Here, we performed an association analysis between IL12A, IL12RB, and signal transducer and activator of transcription 4 (STAT4) genetic variations and susceptibility to PBC. Single nucleotide polymorphisms (SNPs) were genotyped in 395 PBC patients and 458 healthy subjects of Japanese ethnicity and evaluated for associations with PBC susceptibility, anti-nuclear antibody (ANA) status, and anti-mitochondrial antibody (AMA) status. We detected significant associations with PBC susceptibility for several STAT4 SNPs (rs10168266; p = 9.4 × 10−3, rs11889341; p = 1.2 × 10−3, rs7574865; p = 4.0 × 10−4, rs8179673; p = 2.0 × 10−4, and rs10181656; p = 4.2 × 10−5). Three risk alleles (rs7574865; p = 0.040, rs8179673; p = 0.032, and rs10181656; p = 0.031) were associated with ANA status, but not with AMA positivity. Our findings confirm that STAT4 is involved in PBC susceptibility and may play a role in ANA status in the Japanese population.
Serum Omentin-1 as a Disease Activity Marker for Crohn’s Disease
Yan Lu, Li Zhou, L Liu, Yan Feng, Li Lu, X Ren, X Dong, & W Sang
Disease Markers 2014, Article ID 162517, 5 pages http://dx.doi.org/10.1155/2014/162517
Background and Aim. It remains challenging to determine the inflammatory activity in Crohn’s disease (CD) for lack of specific laboratory markers. Recent studies suggest that serum omentin-1 is associated with inflammatory response. We aimed to assess the potential of serum omentin-1 as a marker of disease activity in CD patients.
Methods. Serum omentin-1 concentrations were determined by enzyme-linked immunosorbent assay (ELISA) in patients with CD (n = 240), functional gastrointestinal disorders (FGDs, n = 120), and healthy controls (HC, n = 60) and evaluated for correlation with disease activity. Expression of omentin-1 in colonic tissues from patients with CD was also analyzed by real-time PCR and Western blotting. Serum omentin-1 levels as an activity index were evaluated using a receiver operating characteristic (ROC) curve.
Results. Serum omentin-1 concentrations were significantly decreased in active CD patients compared with patients in remission, FGDs, and HC (all p < 0.001). Expression of omentin-1 was decreased at mRNA and protein levels in inflamed colonic tissues in active CD than that in noninflamed colonic tissues. Serum omentin-1 levels were negatively correlated with disease activity in CD, better than C-reactive protein (CRP).
Conclusion. Our results indicate that serum and colonic omentin-1 expressions are decreased in active CD patients. The correlation of serum omentin-1 with disease activity in CD is superior to that of CRP. Serum omentin-1 is a potential marker for CD disease activity.
Serum Levels of Resistin, Adiponectin, and Apelin in Gastroesophageal Cancer Patients
Dorota Diakowska, K Markocka-Mdczka, P Szelachowski, and K Grabowski
Disease Markers 2014, Article ID 619649, 8 pages http://dx.doi.org/10.1155/2014/619649
The aim of the study was the investigation of relationship between cachexia syndrome and serum resistin, adiponectin, and apelin in patients with gastroesophageal cancer (GEC).
Material and Methods. Adipocytokines concentrations were measured in sera of 85 GEC patients and 60 healthy controls. They were also evaluated in tumor tissue and appropriate normal mucosa of 38 operated cancer patients.
Results. Resistin and apelin concentrations were significantly higher in GEC patients than in the controls. The highest resistin levels were found in cachectic patients and in patients with distant metastasis. Serum adiponectin significantly decreased in GEC patients with regional and distant metastasis. Serum apelin was significantly higher in cachectic patients than in the controls. Apelin was positively correlated with hsCRP level. Resistin and apelin levels increased significantly in tumor tissues. Weak positive correlations between adipocytokines levels in serum and in tumor tissue were observed.
Conclusions. Resistin is associated with cachexia and metastasis processes of GEC. Reduction of serum adiponectin reflects adipose tissue wasting in relation to GEC progression. Correlation of apelin with hsCRP can reflect a presumable role of apelin in systemic inflammatory response in esophageal and gastric cancer.
Serum Level of HER-2 Extracellular Domain in Iranian Patients with Breast Cancer: A Follow-up Study
Mehrnoosh Doroudchi, Abdolrasoul Talei, Helmout Modjtahedi, et al.
IJI 2005; 2(4): 191-200
Background: A soluble form of HER-2/neu extracellular domain (sHER-2) is reported to be released in the sera of metastatic breast cancer patients.
Objective: To measure the level of sHER-2 in sera of 115 breast cancer patients. Methods: Serial samples of 27 patients with metastasis, 18 non-metastatic patients, 15 patients in stage 0/I and 14 patients with accompanying benign breast disease were also included in this study.
Results: No significant difference was observed between sHER-2 level in the pre-operative sera of breast cancer patients and that of healthy individuals. Only 8 out of 27 patients whom later developed metastasis showed elevated levels of sHER-2 in their first serum sample. However, a trend of increase in the level of sHER-2 was observed in 14 (51.8%) of 27 metastatic sera before clinical diagnosis of the metastasis. A significant association between sHER-2 positive status and vascular invasion of the tumor was observed (P = 0.02). In addition, significant correlation of sHER-2 level with CEA (highest r = 0.74) and CA 15.3 (highest r = 0.74) tumor marker levels in the serial sera were observed. The mean time from sHER-2 positivity to tumor metastasis was calculated to be 98 days (range = 29-174). Conclusion: Our results indicate that a relatively high percentage of Iranian patients with breast cancer show an elevated level of sHER-2 in their sera before clinical diagnosis of the tumor metastasis. Therefore, measuring the level of this oncoprotein, not only helps physicians in monitoring the patients during HERCEPTIN therapy, but also can be helpful in choosing more aggressive treatments at the early satges of tumor metastasis.
B-type natriuretic peptide is a biomarker for pulmonary hypertension in preterm infants with bronchopulmonary dysplasia
Alain Cuna, Jegen Kandasamy, Naomi Fineberg, Brian Sims
Research and Reports in Neonatology 2013:3 33–36
http://dx.doi.org/10.2147/RRN.S42236
Background: B-type natriuretic peptide (BNP) is a cardiac biomarker useful in screening for pulmonary hypertension (PH) in adults. It is possible that BNP may also be useful in detecting PH among preterm infants with bronchopulmonary dysplasia (BPD).
Objective: To determine the utility of BNP for identification of PH among preterm infants with BPD.
Methods: We retrospectively identified preterm infants with BPD who underwent screening echocardiography for suspected PH and had serum BNP levels measured within 10 days before or after echocardiography. Eligible infants were classified based on echocardiographic diagnosis of either PH or no PH. Median and interquartile ranges (IQR) of BNP values were compared, and area under the curve (AUC) of receiver operator characteristic (ROC) analysis was used to determine the optimum threshold value for detection of PH.
Results: Twenty-five preterm infants with BPD (mean gestational age 26.5 ± 1.7 weeks, mean birth weight 747 ± 248 g) were identified. The median difference in days between echocardiography and BNP measurement was 1 day (IQR 0–3, range 0–10 days). Based on echocardiography, 16 were diagnosed with PH and nine without PH. No significant difference in terms of gestational age, birth weight, sex, race, or respiratory support was found between the two groups. Median (IQR) BNP values of those with PH were higher than those without PH (413 [212–1178] pg/mL versus 55 [21–84] pg/mL, P , 0.001). AUC of ROC analysis showed that a BNP value of 117 pg/mL had 93.8% sensitivity and 100% specificity for detecting PH.
Conclusion: BNP estimation may be useful for screening of PH in infants with BPD.
2012pharmaceutical
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