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Michael Rudnicki, who has done pioneering work in muscle stem cell biology and muscle regeneration, and whose work has been featured several times on this blog, has struck again. Rudnicki, who serves as director of the Regenerative Medicine Program at The Ottawa Hospital and a professor at the University of Ottawa and holds the prestigious Canada Research Chair in Molecular Genetics, teamed up with workers from the Sprott Centre for Stem Cell Research and the Sinclair Centre for Regenerative Medicine to investigate the role of muscle-specific stem cells in patients who suffer from Duchenne muscular dystrophy. This new earth-shaking study, which was published in the journal Nature Medicine (November 16, 2015), has changed the way we think about muscular dystrophy and will almost certainly force people to rethink the treatments and cures for this dreadful disease.
According to this new study, Duchenne muscular dystrophy directly affects muscle stem cells, and is, largely a disease of muscle stem cells.
Rudicki said: “For nearly 20 years, we’ve thought that the muscle weakness observed in patients with Duchenne muscular dystrophy is primarily due to problems in their muscle fibers, but our research shows that it is also due to intrinsic defects in the function of their muscle stem cells. This completely changes our understanding of Duchenne muscular dystrophy and could eventually lead to far more effective treatments.”
Muscular dystrophy comes in several different forms, but the predominant sign of muscular dystrophy is progressive muscle weakness. Altogether, muscular dystrophy refers to a group of more than 30 genetic diseases, all of which cause progressive weakness and degeneration of skeletal muscles used during voluntary movement. Approximately half of all who suffer from muscular dystrophy have Duchenne muscular dystrophy (DMD). Because muscular dystrophy results from mutations in the dystrophin gene, which is on the X chromosome, the vast majority of muscular dystrophy patients are male. Girls can be carriers of muscular dystrophy and can be mildly affected.
Interestingly, somewhere around one-third of boys who suffer from DMD have no family history of the disease. Because the dystrophin gene is so large, spontaneous mutations in it are probably relatively common.
The signs and symptoms typically appear between the ages of 2 and 3, and may include frequent falls, difficulty getting up from a lying or sitting position, trouble running and jumping, a strange, shuffling way of walking or having a tendency to walk on their toes, calf muscles that are abnormally large, muscle pain and stiffness, and some learning disabilities.
Muscular dystrophy affects all ethnic groups and occurs globally. It affects around 1 in every 3,500 to 6,000 male births each year in the United States. DMD affects approximately one in 3,600 boys.
Because DMD results from mutations in the dystrophin gene, the vast majority of muscular dystrophy research was based on a simple model in which the Dystrophin protein played a structural role in the structural integrity of muscle fibers. Abnormal versions of the Dystrophin protein caused the muscle fibers to become damaged and die as a result of contraction. Dystrophin anchors the cytoskeleton of the muscle fibers, which are essential for muscle contraction, to the muscle cell membrane, and then to the extracellular matrix outside the cell that serves as a foundation upon which the muscle cells are built.
However in this current study, Rudnicki and his team discovered that muscle stem cells also express the dystrophin protein. This is a revelation because Dystrophin was thought to be protein that ONLY appeared in mature muscle. However, in this study, it became exceedingly clear that in the absence of Dystrophin, muscle stem cells generated ten-fold fewer muscle precursor cells, and, consequently, far fewer functional muscle fibers. Dystrophin is also a component of a signal transduction pathway that allows muscle stem cells to properly ascertain if they need to replace dead or dying muscle. Muscle stem cells repair the muscle in response to injury or exercise by dividing to generate precursor cells that differentiate into muscle fibers.
Even though Rudnicki used mice as a model system in these experiments, the Dystrophin protein is highly conserved in most vertebrate animals. Therefore, it is highly likely that these results will also apply to human muscle stem cells.
Gene therapy experiments and trials are in progress and even show some promise, but Rudnicki’s work tells us that gene therapy approaches must target muscle stem cells as well as muscle fibers if they are to work properly.
“We’re already looking at approaches to correct this problem in muscle stem cells,” said Dr. Rudnicki.
This paper has received high praise from the likes of Ronald Worton, who was one of the co-discovers of the dystrophin gene with Louis Kunkel in 1987.
Early pathogenesis of Duchenne muscular dystrophy modelled in patient-derived human induced pluripotent stem cells
Duchenne muscular dystrophy (DMD) is a progressive and fatal muscle degenerating disease caused by a dystrophin deficiency. Effective suppression of the primary pathology observed in DMD is critical for treatment. Patient-derived human induced pluripotent stem cells (hiPSCs) are a promising tool for drug discovery. Here, we report an in vitro evaluation system for a DMD therapy using hiPSCs that recapitulate the primary pathology and can be used for DMD drug screening. Skeletal myotubes generated from hiPSCs are intact, which allows them to be used to model the initial pathology of DMD in vitro. Induced control and DMD myotubes were morphologically and physiologically comparable. However, electric stimulation of these myotubes for in vitro contraction caused pronounced calcium ion (Ca2+) influx only in DMD myocytes. Restoration of dystrophin by the exon-skipping technique suppressed this Ca2+ overflow and reduced the secretion of creatine kinase (CK) in DMD myotubes. These results suggest that the early pathogenesis of DMD can be effectively modelled in skeletal myotubes induced from patient-derived iPSCs, thereby enabling the development and evaluation of novel drugs.
Duchenne muscular dystrophy (DMD) is characterised by progressive muscle atrophy and weakness that eventually leads to ambulatory and respiratory deficiency from early childhood1. It is an X-linked recessive inherited disease with a relatively high frequency of 1 in 3500 males1,2.DMD, which is responsible for DMD, encodes 79 exons and produces dystrophin, which is one of the largest known cytoskeletal structural proteins3. Most DMD patients have various types of deletions or mutations in DMD that create premature terminations, resulting in a loss of protein expression4. Several promising approaches could be used to treat this devastating disease, such as mutation-specific drug exon-skipping5,6, cell therapy7, and gene therapy1,2.
Myoblasts from patients are the most common cell sources for assessing the disease phenotypes of DMD11,12. …Previous reports have shown that muscle cell differentiation from DMD patient myoblasts is delayed and that these cells have poor proliferation capacity compared to those of healthy individuals11,12. Our study revealed that control and DMD myoblasts obtained by activating tetracycline-dependent MyoD transfected into iPS cells (iPStet-MyoD cells) have comparable growth and differentiation potential and can produce a large number of intact and homogeneous myotubes repeatedly.
The pathogenesis of DMD is initiated and progresses with muscle contraction. The degree of muscle cell damage at the early stage of DMD can be evaluated by measuring the leakage of creatine kinase (CK) into the extracellular space15. Excess calcium ion (Ca2+) influx into skeletal muscle cells, together with increased susceptibility to plasma membrane injury, is regarded as the initial trigger of muscle damage in DMD19,20,21,22,23,24. Targeting these early pathogenic events is considered essential for developing therapeutics for DMD.
In this study, we established a novel evaluation system to analyse the cellular basis of early DMD pathogenesis by comparing DMD myotubes with the same clone but with truncated dystrophin-expressing DMD myotubes, using the exon-skipping technique. We demonstrated through in vitro contraction that excessive Ca2+ influx is one of the earliest events to occur in intact dystrophin-deficient muscle leading to extracellular leakage of CK in DMD myotubes.
Generation of tetracycline-inducible MyoD-transfected DMD patient-derived iPSCs (iPStet-MyoD cells)
Figure 1: Generation and characterization of control and DMD patient-derived Tet-MyoD-transfected hiPS cells. Full size image
Morphologically and physiologically comparable intact myotubes differentiated from control and DMD-derived hiPSCs
Figure 2: Morphologically and physiologically comparable skeletal muscle cells differentiated from Control-iPStet-MyoD and DMD-iPStet-MyoD. Full size image
Exon-skipping with AO88 restored expression of Dystrophin in DMD myotubes differentiated from DMD-iPStet-MyoD cells
Figure 3: Restoration of dystrophin protein expression by AO88. Full size image
Restored dystrophin expression attenuates Ca2+ overflow in DMD-Myocytes
Figure 4: Restored expression of dystrophin diminishes Ca2+ influx in DMD muscle in response to electric stimulation. Full size image
Ca2+ influx provokes skeletal muscle cellular damage in DMD muscle
Figure 5: Ca2+ influx induces prominent skeletal muscle cellular damage in DMD-Myocytes. Full size image
Skeletal muscle differentiation in myoblasts from DMD patients is generally delayed compared to that in healthy individuals11,36,37. Our differentiation system successfully induced the formation of myotubes from DMD patients, and the myotubes displayed analogous morphology and maturity compared with control myotubes (Fig. 2a–c). Comparing myotubes generated from patient-derived iPS cells with those derived from the same DMD clones but expressing dystrophin by application of the exon-skipping technique enabled us to demonstrate the primary cellular phenotypes in skeletal muscle solely resulting from the loss of the dystrophin protein (Fig. 4b). Our results demonstrate that truncated but functional dystrophin protein expression improved the cellular phenotype of DMD myotubes.
In DMD, the lack of dystrophin induces an excess influx of Ca2+ , leading to pathological dystrophic changes22. We consistently observed excess Ca2+ influx in DMD-Myocytes compared to Control-Myocytes (Supplementary Figure S3a and S3b) in response to electric stimulation. TRP channels, which are mechanical stimuli-activated Ca2+ channels40that are expressed in skeletal muscle cells41, can account for this pathogenic Ca2+ influx…
In conclusion, our study revealed that the absence of dystrophin protein induces skeletal muscle damage by allowing excess Ca2+ influx in DMD myotubes. Our experimental system recapitulated the early phase of DMD pathology as demonstrated by visualisation and quantification of Ca2+ influx using intact myotubes differentiated from hiPS cells. This evaluation system significantly expands prospective applications with regard to assessing the effectiveness of exon-skipping drugs and also enables the discovery of drugs that regulate the initial events in DMD.
Duchenne muscular dystrophy affects stem cells, University of Ottawa study finds
New treatments could one day be available for the most common form of muscular dystrophy after a study suggests the debilitating genetic disease affects the stem cells that produce healthy muscle fibres.
The findings are based on research from the University of Ottawa and The Ottawa Hospital, published Monday in the journal Nature Medicine.
For nearly two decades, doctors had thought the muscular weakness that is the hallmark of the disease was due to problems with human muscle fibers, said Dr. Michael Rudnicki, the study’s senior author.
The new research shows the specific protein characterized by its absence in Duchenne muscular dystrophy normally exists in stem cells.
Dystrophin protein found in stem cells
“The prevailing notion was that the protein that’s missing in Duchenne muscular dystrophy — a protein called dystrophin — was not involved at all in the function of the stem cells.”
When the genetic mutations caused by Duchenne muscular dystrophy inhibit the production of dystrophin in stem cells, those stem cells produce significantly fewer precursor cells — and thus fewer properly functioning muscle fibres. Further, stem cells need dystrophin to sense their environment to figure out if they need to divide to produce more stem cells or perform muscle repair work.
July 25, 2011|By Thomas H. Maugh II, Los Angeles Times
A genetic technique that allows the body to work around a crucial mutation that causes Duchenne muscular dystrophy increased the mass and function of muscles in a small group of patients with the devastating disease, paving the way for larger clinical trials of the drug. The study in a handful of boys age 5 to 15 showed that patients receiving the highest level of the drug, called AVI-4658 or eteplirsen, had a significant increase in production of a missing protein and increases in muscle fibers. The study demonstrated that the drug is safe in the short term. Results were reported Sunday in the journal Lancet.
Duchenne muscular dystrophy affects about one in every 3,500 males worldwide. It is caused by any one of several different mutations that affect production of a protein called dystrophin, which is important for the production and maintenance of muscle fibers. Affected patients become unable to walk and must use a wheelchair by age 8 to 12. Deterioration continues through their teens and 20s, and the condition typically proves fatal as muscle failure impairs their ability to breathe.
This study is designed to assess the efficacy, safety, tolerability, and pharmacokinetics (PK) of AVI-4658 (eteplirsen) in both 50.0 mg/kg and 30.0 mg/kg doses administered over 24 weeks in subjects diagnosed with Duchenne muscular dystrophy (DMD).
A Randomized, Double-Blind, Placebo-Controlled, Multiple Dose Efficacy, Safety, Tolerability and Pharmacokinetics Study of AVI-4658(Eteplirsen),in the Treatment of Ambulant Subjects With Duchenne Muscular Dystrophy
Dystrophin is expressed in differentiated myofibers, in which it is required for sarcolemmal integrity, and loss-of-function mutations in the gene that encodes it result in Duchenne muscular dystrophy (DMD), a disease characterized by progressive and severe skeletal muscle degeneration. Here we found that dystrophin is also highly expressed in activated muscle stem cells (also known as satellite cells), in which it associates with the serine-threonine kinase Mark2 (also known as Par1b), an important regulator of cell polarity. In the absence of dystrophin, expression of Mark2 protein is downregulated, resulting in the inability to localize the cell polarity regulator Pard3 to the opposite side of the cell. Consequently, the number of asymmetric divisions is strikingly reduced in dystrophin-deficient satellite cells, which also display a loss of polarity, abnormal division patterns (including centrosome amplification), impaired mitotic spindle orientation and prolonged cell divisions. Altogether, these intrinsic defects strongly reduce the generation of myogenic progenitors that are needed for proper muscle regeneration. Therefore, we conclude that dystrophin has an essential role in the regulation of satellite cell polarity and asymmetric division. Our findings indicate that muscle wasting in DMD not only is caused by myofiber fragility, but also is exacerbated by impaired regeneration owing to intrinsic satellite cell dysfunction.
This article is the THIRD in a four-article Series covering the topic of the Roles of the Mitochondria in Cardiovascular Diseases. They include the following;
Mitochondria and Cardiovascular Disease: A Tribute to Richard Bing, Larry H Bernstein, MD, FACP
Mitochondrial Metabolism in Impaired Cardiac Function
Mitochondrial Dysfunction and the Heart
Chronically elevated plasma free fatty acid levels in heart failure are associated with
decreased metabolic efficiency and cellular insulin resistance.
The mitochondrial theory of aging (MTA) and the free-radical theory of aging (FRTA) are closely related.
They were in fact proposed by the same researcher about 20 years apart. MTA adds
the mitochondria and its production of free radicals
into the concept that free-radicals damage DNA over time.
Tissue hypoxia, resulting from low cardiac output with or independent of endothelial impairment,
increases oxidative stress and leads to apoptosis and mitochondrial DNA damage.
This dysfunctional state causes loss of mitochondrial mass. Therapies aimed at protecting mitochondrial function
have shown promise in patients and animal models with heart failure that will be the subject of Chapter III.
Myocardial function in hypertension
Genetic variation in vitamin D-dependent signaling
is associated with congestive heart failure in human subjects with hypertension.
Functional polymorphisms were selected from five candidate genes:
CYP27B1,
CYP24A1,
VDR,
REN and
ACE.
Using the Marshfield Clinic Personalized Medicine Research Project,
205 subjects with hypertension and congestive heart failure,
206 subjects with hypertension alone and
206 controls (frequency matched by age and gender) were genotyped.
In the context of hypertension, a SNP in CYP27B1 was associated with congestive heart failure
(odds ratio: 2.14 for subjects homozygous for the C allele; 95% CI: 1.05–4.39).
Genetic variation in vitamin D biosynthesis is associated with increased risk of heart failure.
While initially unregulated, a gradual decline was observed over time (from day 45 to 90), in
hypoxic-inducible factor 1 and
stromal-derived factor 1 mRNA expression .
On serial assessment, endothelial progenitor cell migration was progressively impaired in response to chemo-attractant gradients of:
vascular endothelial growth factor (10-200 ng/mL)
and stromal cell-derived factor-1 (10-100 ng/mL) .
Decreased circulating levels and migratory dysfunction of bone marrow derived endothelial progenitor cells
were documented in a reproducible clinically relevant model of myocardial ischemia.
Nitric Oxide (NO) in Myocardial Ischemia and Infarct
Nitric oxide (NO) is a free radical with an unpaired electron; it is an important physiologic messenger,
produced by nitric oxide synthases, which catalyze the reaction l-arginine to citrulline and NO.
The constitutive isoforms exists in neuronal and endothelial cells and is calcium dependent. Calcium binds to calmodulin and
the calcium calmodulin complex activates the constitutive NO synthase that releases NO,
relaxing smooth muscle cells through activation of guanylate cyclase and the production cGMP.
Therefore, the NO produced has a negative inotropic effect on the heart and is instrumental in the autoregulation of the coronary circulation.
The inducible form of NO synthase (iNOS), mostly produced in macrophages, is activated by cytokines and endotoxin. It eliminates intracellular pathogens,
damaging cells by inhibiting
ATP production
oxidative phosphorylation
DNA synthesis.
In infection, lipopolysaccharide released from bacterial walls, stimulates production of iNOS. The large amount of NO produced
causes extensive vasodilation and hypotension.
We sought to assess whether oxidation products of
nitric oxide (NO), nitrite (NO2−) and nitrate (NO3−), referred to as NOx,
are released by the heart of patients after acute myocardial infarction (AMI) and
whether NOx can be determined in peripheral blood of these patients.
Previously we reported that in experimental myocardial infarction (rabbits) NOx is released mainly by inflammatory cells
(macrophages) in the myocardium 3 days after onset of ischemia.
NOx is formed in heart muscle from NO; It originates through the activity of the inducible form of nitric oxide synthase (iNOS).
Eight patients with acute anterior MI and an equal number of controls were studied. Coronary venous blood was obtained by
coronary sinus catheterization; NOx concentrations in coronary sinus, in arterial and peripheral venous plasma were measured.
Left ventricular end-diastolic pressure was determined. Measurements were carried out 24, 48 and 72 h after onset of symptoms.
The type and location of coronary arterial lesions were determined by coronary angiography. Plasma NO3− was reduced to NO2−
by nitrate reductase before determination of NO2− concentration by chemiluminescence.
The results provided evidence that in patients with acute anterior MI, the myocardial production of nitrite and nitrate (NOx) was increased,
as well as the coronary arterial–venous difference.
Increased NOx production by the infarcted heart accounted for the increase of NOx concentration in arterial and the peripheral venous plasma.
The peak elevation of NOx occurred on days 2 and 3 after onset of the symptoms, suggesting that NOx production was at least in part the result of
production of NO by inflammatory cells (macrophages) in the heart.
The appearance of oxidative products of NO (NO2− and NO3−) in peripheral blood of patients with acute MI is
the result of their increased release from infarcted heart during the inflammatory phase of myocardial ischemia.
Further studies are needed to define the clinical value of these observations.
EUK-8, a superoxide dismutase and catalase mimetic improved survival and contractile parameters in a mutant mouse model
of pressure overload-induced oxidative stress and heart failure and in wild-type mice subjected to pressure overload.
In addition, mitochondria show
functional impairment and
morphological disorganization
in the left ventricle of Hypertrophic Cardiomyopathy (HCM) patients without baseline systolic dysfunction.
These mitochondrial changes were associated with impaired myocardial contractile and relaxation reserves.
A strategy to protect the heart against oxidative stress could lie with
the modulation of mitochondrial electron transport itself.
Mild mitochondrial uncoupling may offer a potential cardioprotective effect by decreasing ROS production
preventing electron accumulation at complex III and
the Fe–S centres of complex I, and may therefore
mtDNA, Autophagy, and Heart Failure
Mitochondria are evolutionary endosymbionts derived from bacteria and contain DNA similar to bacterial DNA.
Mitochondria damaged by external haemodynamic stress are degraded by the autophagy/lysosome system in cardiomyocytes.
Mitochondrial DNA (mtDNA) that escapes from autophagy cell-autonomously leads to Toll-like receptor (TLR) 9-mediated
inflammatory responses in cardiomyocytes and
is capable of inducing myocarditis and dilated cardiomyopathy.
Cardiac-specific deletion of lysosomal deoxyribonuclease (DNase) II showed no cardiac phenotypes under baseline conditions,
but increased mortality and caused severe myocarditis and dilated cardiomyopathy 10 days after treatment with pressure overload.
Early in the pathogenesis, DNase II-deficient hearts showed
infiltration of inflammatory cells
increased messenger RNA expression of inflammatory cytokines
accumulation of mitochondrial DNA deposits in autolysosomes in the myocardium.
Administration of inhibitory oligodeoxynucleotides against TLR9, which is known to be activated by bacterial DNA6, or ablation of Tlr9
attenuated the development of cardiomyopathy in DNase II-deficient mice.
Furthermore, Tlr9 ablation
improved pressure overload-induced cardiac dysfunction and
inflammation even in mice with wild-type Dnase2a alleles.
These data provide new perspectives on the mechanism of genesis of chronic inflammation in failing hearts.
T Oka, S Hikoso, O Yamaguchi, M Taneike, T Takeda, T Tamai, et al. Mitochondrial DNA that escapes from autophagy causes inflammation and heart failure.
Clinical Trials Results for Endothelin System: Pathophysiological role in Chronic Heart Failure, Acute Coronary Syndromes and MI – Marker of Disease Severity or Genetic Determination? Aviva Lev-Ari, PhD, RN 10/19/2012
Inhibition of ET-1, ETA and ETA-ETB, Induction of NO production, stimulation of eNOS and Treatment Regime with PPAR-gamma agonists (TZD): cEPCs Endogenous Augmentation for Cardiovascular Risk Reduction – A Bibliography, Aviva Lev-Ari, PhD, RN 10/4/2012
Genomics & Genetics of Cardiovascular Disease Diagnoses: A Literature Survey of AHA’s Circulation Cardiovascular Genetics, 3/2010 – 3/2013, L H Bernstein, MD, FACP and Aviva Lev-Ari,PhD, RN 3/7/2013
Cardiovascular Disease (CVD) and the Role of agent alternatives in endothelial Nitric Oxide Synthase (eNOS) Activation and Nitric Oxide Production, Aviva Lev-Ari, PhD, RN 7/19/2012
Hypertriglyceridemia concurrent Hyperlipidemia: Vertical Density Gradient Ultracentrifugation a Better Test to Prevent Undertreatment of High-Risk Cardiac Patients, Aviva Lev-Ari, PhD, RN 4/4/2013
Fight against Atherosclerotic Cardiovascular Disease: A Biologics not a Small Molecule – Recombinant Human lecithin-cholesterol acyltransferase (rhLCAT) attracted AstraZeneca to acquire AlphaCore, Aviva Lev-Ari, PhD, RN 4/3/2013
High-Density Lipoprotein (HDL): An Independent Predictor of Endothelial Function & Atherosclerosis, A Modulator, An Agonist, A Biomarker for Cardiovascular Risk, Aviva Lev-Ari, PhD, RN 3/31/2013
Peroxisome proliferator-activated receptor (PPAR-gamma) Receptors Activation: PPARγ transrepression for Angiogenesis in Cardiovascular Disease and PPARγ transactivation for Treatment of Diabetes, Aviva Lev-Ari, PhD, RN 11/13/2012
This article is the FOURTH in a four-article Series covering the topic of the Roles of the Mitochondria in Cardiovascular Diseases. They include the following;
Mitochondria and Cardiovascular Disease: A Tribute to Richard Bing, Larry H Bernstein, MD, FACP
Alpha lipoic acid is known to be a mitochondrial antioxidant that preserves or improves mitochondrial function.
lipoic acid can prevent arterial calcification, and
arterial calcification may be related to mitochondrial dysfunction
methods are under study to increase lipoic acid synthase production, the enzyme responsible for making lipoic acid in the body.
Co-Enzyme Q10
It is well known that statin drugs taken for high cholesterol severely reduce CoQ10 levels, and causes other negative cardiovascular side effects.
A study on CAD patients has shown that over 8 weeks of supplementing with 300mg of CoQ10 reversed
mitochondrial dysfunction (as measured by a reduced lactate:pyruvate ratio) and
improved endothelial function (as measured by increased flow-mediated dilation)
Other Mitochondrial Antioxidants
Other natural compounds that have been shown to have antioxidant effects in the mitochondria include
resveratrol, found in wine and grapes,
curcumin from turmeric and
EGCG, found abundantly in green tea extract.
But no studies have been conducted for these compounds in CVD.
Metabolic syndrome and serum carotenoids: findings of a cross-sectional study
in Queensland, Australia
Metabolic syndrome and serum carotenoids.
T Coyne, TI Ibiebele, PD Baade, CS McClintock and JE Shaw.
Viertel Center for Research in Cancer Control, Cancer Council Queensland, and School of Public Health,
Queensland University of Technology and University of Queensland, Brisbane, Australia
Several components of the metabolic syndrome are known to be oxidative stress-related conditions
diabetes and
cardiovascular disease,
Carotenoids are compounds derived primarily from plants and several have been shown to be potent antioxidant nutrients.
Both diabetes and cardiovascular disease are known to be oxidative stress-related conditions such that
antioxidant nutrients may play a protective role in these conditions.
Several cross–sectional surveys have found lower levels of serum carotenoids among those with impaired glucose metabolism or type 2 diabetes.
Carotenoids are compounds derived primarily from plants, several of which are known to be potent antioxidants.
Epidemiological evidence indicates that some serum carotenoids may play a protective role against the development of chronic diseases such as
atherosclerosis,
stroke,
hypertension,
certain cancers,
inflammatory diseases and
diabetic retinopathy.
The primary carotenoids found in human serum are
α-carotene
β-carotene
β-cryptoxanthin
lutein/zeaxanthin
lycopene.
The aim of this study was to examine the associations between metabolic syndrome status and major serum carotenoids in adult Australians.
Data on the presence of the metabolic syndrome, based on International Diabetes Federation 2005 criteria, were collected from 1523 adults
aged 25 years and over in six randomly selected urban centers in Queensland, Australia, using a cross sectional study design.
The following were determined:
Weight
height
BMI
waist circumference
blood pressure
fasting and 2-34 hour blood glucose
lipids
five serum carotenoids.
Criteria used to assess the number of metabolic syndrome components present in a 171 participant using the
2005 International Diabetes Federation definition are as follows:
Components = 0 -none of the metabolic syndrome components (i.e. abdominal obesity, raised triglyceride,
reduced HDL-cholesterol, raised blood pressure, and impaired fasting plasma glucose) are present;
Components = any 1 one of the five metabolic syndrome components is present ;
Components = 2 – any two of the five components are present;
Components = 3 any three of the components are present;
Components = 4 – any four of the components are present;
Components = 5 = all five metabolic syndrome components are present.
This study investigated the relationships between these five primary serum carotenoids and the metabolic syndrome
in a cross-sectional population-based study in Queensland, Australia. Distributions of serum carotenoids were skewed
and therefore natural logarithmically transformed to better approximate the normal distribution for regression analyses.
Association between log transformed serum carotenoids as dependent variables and metabolic syndrome status were
assessed using multiple linear regression analysis. Results are reported as back transformed geometric means.
Analysis was performed for each serum carotenoid separately, and the sum of the five carotenoids,
adjusting for the following potential confounders:
age
sex
education
BMI
smoking
alcohol intake
physical activity
vitamin use.
Mean serum alpha-carotene, beta-carotene and the sum of the five carotenoid concentrations were significantly lower (p<0.05)
in persons with the metabolic syndrome (after adjusting for age,sex, education, BMI status, alcohol intake, smoking, physical activity
status and vitamin/mineral use) than persons without the syndrome. Alpha, beta and total carotenoids also decreased significantly
(p<0.05) with increased number of components of the metabolic syndrome, after adjusting for these confounders. These differences
were significant among former smokers and non-smokers, but not in current smokers. Low concentrations of serum
alpha-carotene,
beta carotene and
the sum of five carotenoids
appear to be associated with metabolic syndrome status.
The overall prevalence of the syndrome was 24% and was significantly higher among males than females. As would be expected, significant
differences in prevalence of the syndrome were seen with
body mass index
waist circumference
systolic and diastolic blood pressure
blood lipids.
Significant differences were also evident by
age group, smoking status, educational status and income.
Income was marginally inversely associated. The prevalence increased with age, and was lower in those with post graduate education.
No significant differences were seen by alcohol intake, physical activity levels, vitamin usage, or fruit intake. There was actually an
inverse relationship between vegetable intake (not fruit) and serum carotenoids.
Those who consumed 4 serves or more of vegetable were less likely to have the metabolic syndrome
compared to those who consumed 1 serve or less of vegetables.
The mean concentrations of serum alpha-carotene, beta-carotene and the sum of the five carotenoids were significantly lower for participants
with the metabolic syndrome present compared with those without the syndrome, after adjusting for potential confounding variables.
Concentrations of alpha-carotene, beta-carotene and the sum of the five carotenoids decreased significantlyas
the number of components of the metabolic syndrome increased after adjusting for potential confounding variables.
Similarly there was an inverse association between quartiles of
individual and total serum carotenoids and metabolic syndrome status and each of its components.
This study was designed to investigate the association between several serum carotenoids and the metabolic syndrome.
The data from the present population study suggest that several serum carotenoids are inversely related to the metabolic syndrome.
The study showed significantly lower concentrations present among those with the metabolic syndrome of
α-carotene,
β-carotene and
the sum of the five carotenoids
compared to those without.We also found decreasing concentrations of all the carotenoids tested as
the number of the metabolic syndrome components increased.
This was significant for
α-carotene,
β-carotene,
β-cryptoxanthin
total carotenoids.
(not lycopenes)
These findings are consistent with data reported from the third National Health and Nutrition Examination Survey (NHANES III).
In the NHANES III study, significantly lower concentrations of all the carotenoids, except lycopene, were found among persons
with the metabolic syndrome compared with those without, after adjusting for confounding factors similar to those in our study.
Carnitine: A novel health factor-An overview.
CD Dayanand, N Krishnamurthy, S Ashakiran, KN Shashidhar
Int J Pharm Biomed Res 2011; 2(2): 79-89. ISSN No: 0976-0350
Carnitine comprises L-carnitine, acetyl –L-carnitine and Propionyl –L-carnitine. Carnitine is
obtained in greater amount from animal dietary sources than from plant sources.
The endogenous synthesis of carnitine takes place in animal tissues like
liver
kidney
brain
using precursor amino acids lysine and methionine by a pathway
dependent on iron, vitamin C, niacin, pyridoxine .
This is the basis of vegans generally depending on carnitine in larger proportion
through in vivo synthesis than omnivorous subjects.
The concentration of tri-methyl lysine residues and the tissue specificity of butyro-betaine dehydrogenase
plays a significant role in regulating the carnitine biosynthesis.
Carnitine transport from the site of synthesis to target tissue occurs via blood.
The measurement of plasma carnitine concentration represents –
the balance between the rate of synthesis and rate of excretion
through specific transporter proteins.
The cellular functional role of carnitine depends on the uptake into cells through
carnitine transport proteins and
transport into mitochondrial matrix.
The function of carnitine is to traverse Long-chain Fatty Acids across inner mitochondrial membrane
for β-oxidation, thereby, generating ATP.
Carnitine deficiency results in muscle disorders. The deficiency states are primary and secondar.
The primary is of systemic or myopathic, characterized by a defect of high affinity organic cation transporter protein (CTP)
present on the plasma membrane of liver and kidney and
also due to dysfunction of carnitine reabsorbtion through
similar transport proteins in renal tubules.
Secondary carnitine deficiency is associated with
mitochondrial disorders and also
defective β-oxidation such as CPT-II and acyl CoA dehydrogenase.
In recent times, carnitine has been extensively studied in various research activities to explore the therapeutic benefit.
Thus, carnitine justifies as a novel health factor.
PLC improved the insulin-resistant state and reversed the increased total cholesterol
but not the increase in free fatty acid, triglyceride and HDL/LDL ratio induced by high-fat diet.
Vehicle-HF exhibited a reduced
cardiac output/body weight ratio,
endothelial dysfunction and
tissue decrease of NO production,
all of them being improved by PLC treatment.
The decrease of hepatic mitochondrial activity by high-fat diet was reversed by PLC.
Oral administration of PLC improves the insulin-resistant state developed by obese animals and
decreases the cardiovascular risk associated with the metabolically impaired mitochondrial function.
Omega-3 Fatty Acid and cardioprotection
The Benefits of Flaxseed
By Elaine Magee, MPH, RD WebMD Expert Column
Some call it one of the most powerful plant foods on the planet. There’s some evidence it may help reduce your risk of
heart disease, cancer, stroke, and diabetes.
That’s quite a tall order for a tiny seed that’s been around for centuries.
Flaxseed was cultivated in Babylon as early as 3000 BC. In the 8th century, King Charlemagne believed so strongly in the
health benefits of flaxseed that he passed laws requiring his subjects to consume it. Now, thirteen centuries later, some
experts say we have preliminary research to back up what Charlemagne suspected.
Fibroblast growth factor 21 (FGF21) is a distinctive member of the FGF family with potent beneficial effects on
lipid
body weight
glucose metabolism
A monoclonal antibody, mimAb1, binds to βKlotho with high affinity and specifically
activates signaling from the βKlotho/FGFR1c (FGF receptor 1c) receptor complex.
Injection of mimAb1 into obese cynomolgus monkeys led to FGF21-like metabolic effects:
decreases in body weight,
plasma insulin,
triglycerides, and
glucose during tolerance testing.
Mice with adipose-selective FGFR1 knockout were refractory to FGF21-induced improvements
in glucose metabolism and body weight.
mimAb1 depends on βKlotho to activate FGFR1c, but
it is not expected to induce side effects caused by activating FGFR1c alone.
The results in obese monkeys (with mimAb1) and in FGFR1 knockout mice (with FGF21) demonstrated
the essential role of FGFR1c in FGF21 function and
suggest fat as a critical target tissue for the cytokine and antibody.
This antibody activates FGF21-like signaling through cell surface receptors, and provided
preclinical validation for an innovative therapeutic approach to diabetes and obesity.
Influencing Factors on Cardiac Structure and Function Beyond Glycemic Control
in Patients With Type 2 Diabetes Mellitus (T2DM)
R Ichikawa, M Daimon, T Miyazaki, T Kawata, et al. Cardiovasc Diabetol. 2013;12(38)
We studied 148 asymptomatic patients with T2DM without overt heart disease.
Early (E) and late (A) diastolic mitral flow velocity and early diastolic mitral annular velocity (e’)
were measured for assessing left ventricular (LV) diastolic function.
In addition
insulin resistance,
non-esterified fatty acid,
high-sensitive CRP,
estimated glomerular filtration rate,
waist/hip ratio,
abdominal visceral adipose tissue (VAT),
subcutaneous adipose tissue (SAT)
In T2DM (compared to controls),
E/A and e’ were significantly lower, and
E/e’, left atrial volume and LV mass were significantly greater
VAT and age were independent determinants of
left atrial volume (β =0.203, p=0.011),
E/A (β =−0.208, p=0.002), e’ (β =−0.354, p<0.001) and
E/e’ (β=0.220, p=0.003).
Independent determinants of LV mass were
systolic blood pressure,
waist-hip ratio (β=0.173, p=0.024)
VAT/SAT ratio (β=0.162, p=0.049)
Excessive visceral fat accompanied by adipocyte dysfunction may play a greater role than
glycemic control in the development of diastolic dysfunction and LV hypertrophy in T2DM
Proposed mechanisms through which overexpression of the
mitochondrial transcription factor A (TFAM) gene prevents
mitochondrial DNA (mtDNA) damage,
oxidative stress, and
myocardial remodelling and failure.
In wild-type mice, mitochondrial transcription factor A
directly interacts with mitochondrial DNA to form nucleoids.
Stress such as ischaemia causes mitochondrial DNA damage, which
increases the production of reactive oxygen species (ROS)
leading to a catastrophic cycle of mitochondrial electron transport impairment,
further reactive oxygen species generation, and mitochondrial dysfunction.
TFAM overexpression may protect mitochondrial DNA from damage by
directly binding and stabilizing mitochondrial DNA and
increasing the steady-state levels of mitochondrial DNA
ameliorating mitochondrial dysfunction and thus the development and progression of heart failure.
Conclusion
Heart failure is a multifactorial syndrome that is characterized by
abnormal energetics and substrate metabolism in heart and skeletal muscle.
Although existing therapies have been beneficial, there is a clear need for new approaches to treatment.
Pharmacological targeting of the cellular stresses underlying mitochondrial dysfunction, such as
elevated fatty acid levels,
tissue hypoxia and oxidative stress and
metabolic modulation of heart and skeletal muscle mitochondria,
appears to offer a promising therapeutic strategy for tackling heart failure.
Murray AJ, Anderson RE, Watson GC, et al. Uncoupling proteins in human heart. Lancet 2004; 364:1786.
Delarue J, Magnan C. Free fatty acids and insulin resistance. Curr Opin ClinNutr Metab Care 2007; 10:142
Lee L, Campbell R, Scheuermann-Freestone M, et al. Metabolic modulation with perhexiline in chronic heart failure: a randomized, controlled trialof short-term use of a novel treatment. Circulation 2005; 112:3280
Tsutsui H, Kinugawa S, Matsushima S. Mitochondrial oxidative stress and dysfunction in myocardial remodelling. Cardiovasc Res. 2009;81(3):449-56. http://dxdoi.org/10.1093/cvr/cvn280.
A research team from Massachusetts and Maryland used array-based transcriptome profiling to explore the genetic basis of a progressive neuromuscular condition called facioscapulohumeral muscular dystrophy, or FSHD. By testing bicep and deltoid muscle biopsy samples from dozens of individuals with FSHD and almost as many unaffected relatives of those subjects, the team tracked down hundreds of genes showing expression shifts in those with FSHD. Of those, 29 genes were differentially expressed in both bicep and deltoid muscle samples, the researchers report. And, they found expression levels at 15 genes could distinguish between bicep samples from those with or without the disease around 90 percent of the time in follow-up experiments. The accuracy was closer to 80 percent when classifying deltoid tissue based on expression of these genes. Those involved in the study say such a ‘molecular signature’ of FSHD could help in understanding the disease and in testing new treatments for it.
bThe Senator Paul D. Wellstone Muscular Dystrophy Cooperative Research Center and
cBoston Biomedical Research Institute, Watertown, MA 02472;
dHugo W. Moser Research Institute at Kennedy Krieger Institute, Baltimore, MD 21205; Departments of
eNeurology and
gNeuroscience, The Johns Hopkins School of Medicine, Baltimore, MD 21205; and
fThe Manton Center for Orphan Disease Research, Boston Children’s Hospital, Boston, MA 02115
Contributed by Louis M. Kunkel, June 4, 2012 (sent for review May 24, 2012)
Abstract
Facioscapulohumeral muscular dystrophy (FSHD) is a progressive neuromuscular disorder caused by contractions of repetitive elements within the macrosatellite D4Z4 on chromosome 4q35. The pathophysiology of FSHD is unknown and, as a result, there is currently no effective treatment available for this disease. To better understand the pathophysiology of FSHD and develop mRNA-based biomarkers of affected muscles, we compared global analysis of gene expression in two distinct muscles obtained from a large number of FSHD subjects and their unaffected first-degree relatives. Gene expression in two muscle types was analyzed using GeneChip Gene 1.0 ST arrays: biceps, which typically shows an early and severe disease involvement; and deltoid, which is relatively uninvolved. For both muscle types, the expression differences were mild: using relaxed cutoffs for differential expression (fold change ≥1.2; nominal P value <0.01), we identified 191 and 110 genes differentially expressed between affected and control samples of biceps and deltoid muscle tissues, respectively, with 29 genes in common. Controlling for a false-discovery rate of <0.25 reduced the number of differentially expressed genes in biceps to 188 and in deltoid to 7. Expression levels of 15 genes altered in this study were used as a “molecular signature” in a validation study of an additional 26 subjects and predicted them as FSHD or control with 90% accuracy based on biceps and 80% accuracy based on deltoids.
Author contributions: F.R., O.D.K., C.P.E., L.M.K., and K.R.W. designed research; F.R., O.D.K., D.G.L., and G.M.B. performed research; D.G.L., G.M.B., and K.R.W. contributed new reagents/analytic tools; F.R., O.D.K., C.P.E., L.M.K., and K.R.W. analyzed data; and F.R., O.D.K., L.M.K., and K.R.W. wrote the paper.
The authors declare no conflict of interest.
Data deposition: The data reported in this paper have been deposited in the Gene Expression Omnibus (GEO) database, www.ncbi.nlm.nih.gov/geo(accession no. GSE36398).
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