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Posts Tagged ‘Kidney’


Renal (Kidney) Cancer: Connections in Metabolism at Krebs cycle  and Histone Modulation

Curator: Demet Sag, PhD, CRA, GCP

Through Histone Modulation

Renal cell carcinoma accounts for only 3% of total human malignancies but it is still the most common type of urological cancer with a high prevalence in elderly men (>60 years of age).

ICD10 C64
ICD9-CM 189.0
ICD-O M8312/3
OMIM 144700 605074
DiseasesDB 11245
MedlinePlus 000516
eMedicine med/2002

Most kidney cancers are renal cell carcinomas (RCC). RCC lacks early warning signs and 70 % of patients with RCC develop metastases. Among them, 50 % of patients having skeletal metastases developed a dismal survival of less than 10 % at 5 years.

There are three main histopathological entities:

  1. Clear cell RCC (ccRCC), dominant in histology (65%)
  2. Papillary (15-20%) and
  3. Chromophobe RCC (5%).

There are very rare forms of RCC shown in collecting duct, mucinous tubular, spindle cell, renal medullary, and MiTF-TFE translocation carcinomas.

Subtypes of clear cell and papillary RCC, and a new subtype, clear cell papillary http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3399969/bin/nihms380694f6.jpg

Different subtypes of clear cell RCC can be defined by HIF patterns as well as by transcriptomic expression as defined by ccA and ccB subtypes. Papillary RCC also demonstrates distinct histological subtypes. A recently described variant denoted as clear cell papillary RCC is VHL wildtype (VHL WT), while other clear cell tumors are characterized by VHL mutation, loss, or inactivation (VHL MT).

KEY POINTS

  • Renal cell cancer is a disease in which malignant (cancer) cells form in tubules of the kidney.
  • Smoking and misuse of certain pain medicines can affect the risk of renal cell cancer.
  • Signs of renal cell cancer include
  • Blood in your urine, which may appear pink, red or cola colored
  • A lump in the abdomen.
  • Back pain just below the ribs that doesn’t go away
  • Weight loss
  • Fatigue
  • Intermittent fever

 

Factors that can increase the risk of kidney cancer include:

  • Older age.
  • High blood pressure (hypertension).
  • Treatment for kidney failure.(long-term dialysis to treat chronic kidney failure)
  • Certain inherited syndromes.
  • von Hippel-Lindau disease

Tests that examine the abdomen and kidneys are used to detect (find) and diagnose renal cell cancer.

The following tests and procedures may be used:

There are 3 treatment approaches for Renal Cancer:

Stages of Renal Cancer:

Stage I Tumour of a diameter of 7 cm (approx. 23⁄4 inches) or smaller, and limited to the kidney. No lymph node involvement or metastases to distant organs.
Stage II Tumour larger than 7.0 cm but still limited to the kidney. No lymph node involvement or metastases to distant organs.
Stage III
any of the following
Tumor of any size with involvement of a nearby lymph node but no metastases to distant organs. Tumour of this stage may be with or without spread to fatty tissue around the kidney, with or without spread into the large veins leading from the kidney to the heart.
Tumour with spread to fatty tissue around the kidney and/or spread into the large veins leading from the kidney to the heart, but without spread to any lymph nodes or other organs.
Stage IV
any of the following
Tumour that has spread directly through the fatty tissue and the fascia ligament-like tissue that surrounds the kidney.
Involvement of more than one lymph node near the kidney
Involvement of any lymph node not near the kidney
Distant metastases, such as in the lungs, bone, or brain.
Grade Level Nuclear Characteristics
Grade I Nuclei appear round and uniform, 10 μm; nucleoli are inconspicuous or absent.
Grade II Nuclei have an irregular appearance with signs of lobe formation, 15 μm; nucleoli are evident.
Grade III Nuclei appear very irregular, 20 μm; nucleoli are large and prominent.
Grade IV Nuclei appear bizarre and multilobated, 20 μm or more; nucleoli are prominent

 

GENETICS:

90% or more of kidney cancers are believed to be of epithelial cell origin, and are referred to as renal cell carcinoma (RCC), which are further subdivided based on histology into clear-cell RCC (75%), papillary RCC (15%),

chromophobe tumor (5%), and oncocytoma (5%).

Nephrectomy continues to be the cornerstone of treatment for localized renal cell carcinoma (RCC). Research is still underway to developed targeted agents against the vascular endothelial growth factor (VEGF) molecule and related pathways as well as inhibitors of the mammalian target of rapamycin (mTOR),

clear cell RCC (ccRCC) doesn’t respond well to radiation chemotherapy due to high radiation resistancy.  The hallmark genetic features of solid tumors such as KRAS or TP53 mutations are also absent. However, there is a well-designed association presented between ccRCC and mutations in the VHL gene

Hereditary RCC, accounts for around 4% of cases, has been a relatively dominant area of RCC genetics.

Causative genes have been identified in several familial cancer syndromes that predispose to RCC including

  • VHLmutations in von Hippel-Lindau disease that predispose to ccRCC and VHL is somatically mutated in up to 80% of ccRCC
  • METmutations in familial papillary renal cancer,
  • dominantly activating kinase domainMET mutation reported in 4–10% of sporadic papillary RCC[2].
  • FH (fumarate hydratase) mutations in hereditary leiomyomatosis and renal cell cancer that predispose to papillary RCC
  • FLCN(folliculin) mutations in Birt-Hogg-Dubé syndrome that predispose to primarily chromophobe RCC.

In addition, there are germline mutations:

  • in theTSC1/2 genes predispose to tuberous sclerosis complex where approximately 3% of cases develop ccRCC,
  • in the SDHB(succinate dehydrogenase type B) in patients with paraganglioma syndrome shows elevated risk to develop multiple types of RCC.

GWAS in almost 6000 RCC cases demonstrated that loci on 2p21 and 11q13.3 play a role in RCC. Although EPAS1 gene encoding a transcription factor operative in hypoxia-regulated responses in  2p21 , 11q13.3 has no known coding genes.

There has been, however, comparatively less progress in the elaboration of the somatic genetics of sporadic RCC.

Absent mutations in sporadic RCC:

  • somaticFH mutations
  • somatic mutations ofTSC12 and SDHB

Present mutations in sporadic ccRCC (chromophobe RCC) are

  • TSC1mutations occur in 5% of ccRCCs and
  • somatic mutations inFLCN  rare
  • may predict for extraordinary sensitivity to mTORC1 inhibitors clinically.

The COSMIC database reports somatic point mutations in TP53 in 10% of cases, KRAS/HRAS/NRAS combined ≤1%, CDKN2A 10%, PTEN 3%, RB1 3%, STK11/LKB1 ≤1%, PIK3Ca ≤1%, EGFR1% and BRAF ≤1% in all histological samples. Further information can be found at (http://www.sanger.ac.uk/ genetics/CGP/cosmic/) for the  RCC somatic genetics.

HIF- and hypoxia-mediated epigenetic regulation work together due to histone modification because HIF activate several chromatin demethylases, including JMJD1A (KDM3A), JMJD2B (KDM4B), JMJD2C (KDM4C) and JARID1B (KDM5B), all of which are directly targeted by HIF.

Overview of Histone 3 modifications implicated in RCC genetics http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3399969/bin/nihms380694f1.jpg

A number of histone modifying genes are mutated in renal cell carcinoma. These include the H3K36 trimethylase SETD2, the H3K27 demethylase UTX/KDM6A, the H3K4 demethylase JARID1C/KDM5C and the SWI/SNF complex compenent PBRM1, shown in this cartoon to represent their relative activities on Histone H3.

Hyper-methylation is observed on RASSF1 highly (50% f RCC) yet less on VHL and CDKN2A, yet there is a methylation and silencing observed on TIMP3 and secreted frizzled-related protein 2.

RCC is ONE OF THE “CILIOPATHIES” among Polycystic Kidney Disease (PKD), Tuberous Sclerosis Complex (TSC) and VHL Syndrome. The main display of cysts is dysfunctional primary cilia.

Mol Cancer Res. Author manuscript; available in PMC 2013 Jan 1.

Mol Cancer Res. 2012 Jul; 10(7): 859–880. Published online 2012 May 25. doi:  10.1158/1541-7786.MCR-12-0117

pVHL mutants are categorized as Class A, B and C depending on the affected step in pVHL protein quality control http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3399969/bin/nihms380694f2.jpg

VHL proteostasis involves the chaperone mediated translocation of nascent VHL peptide from the ribosome to the TRiC/CCT chaperonin, where folding occurs in an ATP dependent process. The VBC complex is formed while VHL is bound to TRiC, and the mature complex is then released. Three different classes of mutation exist: Class A mutations prevent binding of VHL to TRiC, and abrogate folding into a mature complex. Class B mutations prevent association of Elongins C and B to VHL. Class C mutations inhibit interaction between VHL and HIF1 a.

# 193300. VON HIPPEL-LINDAU SYNDROME; VHL ICD+, Links
VON HIPPEL-LINDAU SYNDROME, MODIFIERS OF, INCLUDED
Cytogenetic locations: 3p25.3 , 11q13.3
Matching terms: lindau, disease, von, hippellindau, hippel
  • Birt-Hogg-Dube syndrome,
# 135150. BIRT-HOGG-DUBE SYNDROME; BHD ICD+, Links
Cytogenetic location: 17p11.2 
Matching terms: birthoggdube, syndrome, birt, hogg, dube
  • tuberous sclerosis
# 191100. TUBEROUS SCLEROSIS 1; TSC1 ICD+, Links
Cytogenetic location: 9q34.13 
Matching terms: tuber, sclerosi, tuberous
  • familial papillary renal cell carcinoma.
# 144700. RENAL CELL CARCINOMA, NONPAPILLARY; RCC ICD+, Links
NONPAPILLARY RENAL CARCINOMA 1 LOCUS, INCLUDED
Cytogenetic locations: 3p25.3 3p25.3 3q21.1 8q24.13 12q24.31 17p11.2 17q12 
Matching terms: renal, familial, papillary, carcinoma, cell

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4358399/bin/467fig3.jpg

Model for the control of the fate of nephron progenitor cells. Eya1 lies genetically upstream of Six2. Six2 labels the nephron progenitor cells, which can either maintain a progenitor state and self-renew or differentiate via the Wnt4-mediated MET. Wnt4 expression is under the direct control of Wt1. β-Catenin is involved in both progenitor cell fates through activation of different transcriptional programs. Active nuclear phosphorylated Yap/Taz shifts the progenitor balance toward the self-renewal fate. Eya1 and Six2 interact directly with Mycn, leading to dephosphorylation of Mycn pT58, stabilization of the protein, increased proliferation, and potentially a shift of the nephron progenitor toward self-renewal. Genes activated in Wilms’ tumors are depicted in green, and inactivated genes are in blue. Deregulation of Yap/Taz in Wilms’ tumors results in phosphorylated Yap not being retained in the cytoplasm as it should, but it translocates to the nucleus and thus shifts the progenitor cell balance toward self-renewal. This model is likely a simplification, as it presumes that all Wilms’ tumors, regardless of causative mutation, are caused by the same mechanism.

Epigenetic aberrations associated with Wilms’ tumor

Chinese Case Study: PMCID: PMC4471788

They u8ndertook this study based on association of low circulating adiponectin concentrations with a higher risk of several cancers, including renal cell carcinoma. Thus they demonstrated that by case–control study that ADIPOQ rs182052 is significantly associated with ccRCC risk.

They investigated the frequency of three single nucleotide polymorphisms (SNPs), rs182052G>A, rs266729C>G, rs3774262G>A, in the adiponectin gene (ADIPOQ).  1004 registered patients with clear cell renal cell carcinoma (ccRCC) compared with 1108 healthy subjects (= 1108).

The first table presents the characteristics of 1004 patients with clear cell renal cell carcinoma and 1108 cancer-free controls from a Chinese Han population. The Second and third table shows the SNP results.

Table 1: The characteristics of the examined population.

Variable Cases, n (%) Controls, n (%) P-value
1004 (100) 1108 (100)
Age, years
 ≤44 195 (19.4) 230 (20.8) 0.559
 45–64 580 (57.8) 644 (58.1)
 ≥65 229 (22.8) 234 (21.1)
Sex
 Male 711 (70.8) 815 (73.6) 0.160
 Female 293 (29.2) 293 (26.4)
BMI, kg/m2
 <25 480 (47.8) 589 (53.2) 0.014
 ≥25 524 (52.2) 519 (46.8)
Smoking status
 Never 455 (45.3) 529 (47.7) 0.265
 Ever/current 549 (54.7) 579 (52.3)
Hypertension
 No 639 (63.6) 780 (70.4) 0.001
 Yes 365 (36.4) 328 (29.6)
Fuhrman grade
 I 40 (4.0)
 II 380 (37.8)
 III 347 (34.6)
 IV 175 (17.4)
 Missing 62 (6.2)
Stage at diagnosis
 I 738 (73.5)
 II 71 (7.1)
 III 19 (1.9)
 IV 176 (17.5)

Pearson’s χ2-test.

Table 2:

Association between ADIPOQ single nucleotide polymorphisms (SNP) and clear cell renal cell carcinoma risk

SNP HWE Cases, n(%) Controls, n(%) Crude OR (95% CI) P-value Adjusted OR (95% CI) P-value
rs182052
 GG 0.636 249 (24.8) 315 (28.4) 1.00 1.00
 AG 485 (48.3) 544 (49.1) 1.13 (0.92–1.39) 0.253 1.11 (0.90–1.37) 0.331
 AA 270 (26.9) 249 (22.5) 1.37 (1.08–1.75) 0.010 1.36 (1.07–1.74) 0.013
 AG/AA versusGG 1.20 (0.99–1.46) 0.060 1.19 (0.98–1.45) 0.086
 AA versusGG/AG 1.28 (1.04–1.57) 0.019 1.27 (1.04–1.56) 0.019
rs266729
 CC 0.143 502 (50.0) 572 (51.6) 1.00 1.00
 CG 398 (39.6) 434 (39.2) 1.05 (0.88–1.25) 0.635 1.05 (0.87–1.26) 0.633
 GG 104 (10.4) 102 (9.2) 1.16 (0.86–1.57) 0.324 1.17 (0.86–1.58) 0.307
 CG/GG versusCC 1.07 (0.91–1.29) 0.456 1.07 (0.90–1.27) 0.445
 GG versus CC/CG 1.19 (0.83–1.59) 0.377 1.15 (0.86–1.54) 0.353
rs3774262
 GG 0.106 482 (48.0) 523 (47.2) 1.00 1.00
 AG 420 (41.8) 459 (41.4) 0.99 (0.83–1.20) 0.938 0.99 (0.82–1.19) 0.905
 AA 102 (10.2) 126 (11.4) 0.88 (0.66–1.17) 0.381 0.90 (0.67–1.20) 0.463
 AG/AA versusGG 0.98 (0.80–1.16) 0.711 0.97 (0.82–1.15) 0.722
 AA versusGG/AG 0.88 (0.67–1.18) 0.372 0.90 (0.68–1.19) 0.465

Bold values indicate significance.

Adjusted for age, sex, BMI, smoking status, and hypertension. CI, confidence interval; OR, odds ratio; HWE, Hardy–Weinberg equilibrium.

Table 3:

Association between ADIPOQ single nucleotide polymorphisms (SNP) and clear cell renal cell carcinoma risk

SNP HWE Cases, n(%) Controls, n(%) Crude OR (95% CI) P-value Adjusted OR (95% CI) P-value
rs182052
 GG 0.636 249 (24.8) 315 (28.4) 1.00 1.00
 AG 485 (48.3) 544 (49.1) 1.13 (0.92–1.39) 0.253 1.11 (0.90–1.37) 0.331
 AA 270 (26.9) 249 (22.5) 1.37 (1.08–1.75) 0.010 1.36 (1.07–1.74) 0.013
 AG/AA versusGG 1.20 (0.99–1.46) 0.060 1.19 (0.98–1.45) 0.086
 AA versusGG/AG 1.28 (1.04–1.57) 0.019 1.27 (1.04–1.56) 0.019
rs266729
 CC 0.143 502 (50.0) 572 (51.6) 1.00 1.00
 CG 398 (39.6) 434 (39.2) 1.05 (0.88–1.25) 0.635 1.05 (0.87–1.26) 0.633
 GG 104 (10.4) 102 (9.2) 1.16 (0.86–1.57) 0.324 1.17 (0.86–1.58) 0.307
 CG/GG versusCC 1.07 (0.91–1.29) 0.456 1.07 (0.90–1.27) 0.445
 GG versus CC/CG 1.19 (0.83–1.59) 0.377 1.15 (0.86–1.54) 0.353
rs3774262
 GG 0.106 482 (48.0) 523 (47.2) 1.00 1.00
 AG 420 (41.8) 459 (41.4) 0.99 (0.83–1.20) 0.938 0.99 (0.82–1.19) 0.905
 AA 102 (10.2) 126 (11.4) 0.88 (0.66–1.17) 0.381 0.90 (0.67–1.20) 0.463
 AG/AA versusGG 0.98 (0.80–1.16) 0.711 0.97 (0.82–1.15) 0.722
 AA versusGG/AG 0.88 (0.67–1.18) 0.372 0.90 (0.68–1.19) 0.465

Bold values indicate significance.

Adjusted for age, sex, BMI, smoking status, and hypertension. CI, confidence interval; OR, odds ratio; HWE, Hardy–Weinberg equilibrium.

Molecular Genetics Level for Physiology (Function):

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4503866/bin/10585_2015_9731_Fig6_HTML.jpg

a The protein–protein interaction for the identified 8 proteins in STRING (10 necessary proteins/genes were added into the network so as to find the potential strong connection among them. The red dotted lines circled three main pathways. b The ingenuity pathway analysis (IPA) for all these 18 genes showing that oxidative phosphorylation, mitochondria dysfunction and granzyme A are the significantly activated pathways (fold change over 1.5, P < 0.05). c The possible mechanism related mitochondria functions: unspecific condition like inflammation, carcinogens, radiation (ionizing or ultraviolet), intermittent hypoxia, viral infections which is carcinogenesis in our study that damages a cell’s oxidative phosphorylation. Any of these conditions can damage the structure and function of mitochondria thus activating a respiratory chain changes (Complex I, II, III, IV) and also cytochrome c release. When the mitochondrial dysfunction persists, it produces genome instability (mtDNA mutation), and further lead to malignant transformation (metastasis) via increased ROS and apoptotic resistance. (Color figure online)

RENAL CELL CARCINOMA AND METABOLISM goes hand to hand in genes encoding enzymes of the Krebs cycle suppress tumor formation in kidney cells. This includes Succinate dehydrogenase (SDH), Fumarate hydratase (FH).  As a result of accumulation of succinate or fumarate causes the inhibition of a family of 2-oxoglutarate-dependent dioxygeneases.

The FH and SDH genes function as two-hit tumor suppressor genes.

SDH has a complex of 4 different polypeptides (SDHA-D) function in electron transfer, catalyzes the conversion of succinate to fumarate. Furthermore, heterozygous germline mutations in SDHsubunits predispose to pheochromocytoma/paraganglioma. FH function to convert fumarate to malate.  When its mutations presented as heterozygous germline, it predisposes hereditary leiomyomatosis and renal cell cancer (HLRCC). Among them about 20–50% of HLRCC families are typically papillary-type 2 (pRCC-2) and overwhelmingly aggressive.RCC is increasingly being recognized as a metabolic disease, and key lesions in nutrient sensing and processing have been detected.

Regulation of Prolyl Hydroxylases and Keap1 by Krebs cycle http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3399969/bin/nihms380694f4.jpg

Regulation of Prolyl Hydroxylases by Tricarboxylic Acid (TCA) Cycle Intermediates. Prolyl hydroxylases use TCA cycle intermediates to help catalyze the oxygen, iron and ascorbate dependent- addition of a hydroxyl side chain to a Pro402 and Pro564 of HIF alpha subunits, leading to VHL binding and degradation. Defects in either fumarate hydratase or succinate dehydrogenase will drive up levels of fumarate and succinate, which competitively bind prolyl hydroxylases, and prevent HIF prolyl hydroxylation. This results in higher intracellular HIF levels.

Regulation of mTORC1 http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3399969/bin/nihms380694f5.jpg

HIF regulation and mTOR pathway connections. Hypoxia blocks HIF expression in a TSC1/2 and REDD dependent pathway [155]. HIF1α appears to be both TORC1 and TORC2 dependent, whereas HIF2α is only TORC2 dependent [275]. Signaling via TORC2 appears to upregulate HIF2α in an AKT dependent manner [69].

TREATMENT:

Based on the types of renal cancers the treatment method may vary but the general scheme is:

 

Drugs Approved for Kidney (Renal Cell) Cancer

Food and Drug Administration (FDA) approved drugs for kidney (renal cell) cancer. Some of the drug names link to NCI’s Cancer Drug Information summaries.

T cell regulation in RCC http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3399969/bin/nihms380694f7.jpg

Immune regulation of renal tumor cells. A: When an antigen presenting cell (APC) engages a T-cell via a cognate T-cell receptor (TCR) and CD28, T-cell cell activation occurs. B: Early and late T-cell inhibitory signals are mediated via CTLA-4 and PD-1 receptors, and this occurs via engagement of the APC via B7 and PD-L1, respectively. C: Inhibitory antibodies against CTLA-4 and PD-1 can overcome T-cell downregulation and once again allow cytokine production.

Phase III Trials of Targeted Therapy in Metastatic Renal Cell Carcinoma

Trial Number
of
patients
Clinical setting RR (%) PFS (months) OS (months)
VEGF-Targeted Therapy
*AVOREN

Bevacizumab +
IFNa
vs.IFNa[270]

649 First-line 31 vs. 12 10.2 vs. 5.5
(p<0.001)
23.3 vs. 21.3
(p=0.129)
*CALBG 90206

Bevacizumab +
IFNa
vs.IFNa[271]

732 First-line 25.5 vs. 13 8.4 vs. 4.9
(p<0.001)
18.3 vs. 17.4
(p=0.069)
Sunitinib vs.
IFNa[248]
750 First-line 47 vs. 12 11 vs. 5
(p=0.0001)
26.4 vs. 21.8
(p=0.051)
*TARGET

Sorafenib vs.
Placebo[272]

903 Second-line

(post-cytokine)

10 vs. 2 5.5 vs. 2.8
(p<0.01)
17.8vs.15.2
(p=0.88)
Pazopanib vs.
placebo[273]
435 First line/second line

(post-cytokine)

30 vs. 3 9.2 vs. 4.2
(p<0.0001)
22.9 vs. 20.5
(p=0.224)
*AXIS

Axitinib vs.
sorafenib [269]

723 Second line

(post-sunitinib, cytokine,
bevacizumab or
temsirolimus)

19 vs. 9
(p=0.0001)
6.7 vs. 4.7
(p<0.0001)
Not reported
mTOR-Targeted Therapy
*ARCC
Temsirolimus
vs. Tem + IFNa
vs. IFNa[249]
624 First line, ≥ 3 poor risk
featuresa
9 vs. 5 3.8 vs. 1.9 for
IFNa
monotherapy
(p=0.0001)
10.9 vs. 7.3 for
IFNa(p=0.008)
*RECORD-1
Everolimus vs.
placebo [274]
410 Second line
(post sunitinib and/or
sorafenib)
2 vs. 0 4.9 vs. 1.9

(p<0.0001)

14.8 vs. 14.5

RCC renal cell carcinoma, RR response rate, OS overall survival, PFS progression free survival, VEGFvascular endothelial growth factor, IFNa interferon alphamTOR mammalian target of rapamycin. AVORENAVastin fOr RENal cell cancer, CALBG Cancer and Leukemia Group B. TARGET Treatment Approaches in Renal Cancer Global Evaluation Trial. AXIS Axitinib in Second Line. ARCC Advanced Renal-Cell Carcinoma. RECORD-1 REnal Cell cancer treatment withOral RAD001 given Daily.

aIncluding serum lactate dehydrogenase level of more than 1.5 times the upper limit of the normal range, a hemoglobin level below the lower limit of the normal range; a corrected serum calcium level of more than 10 mg per deciliter (2.5 mmol per liter), a time from initial diagnosis of renal-cell carcinoma to randomization of less than 1 year, a Karnofsky performance score of 60 or 70, or metastases in multiple organs.

PMC full text: Open Access J Urol. Author manuscript; available in PMC 2013 Jul 8.

Open Access J Urol. 2010 Aug; 2010(2): 125–141. doi:  10.2147/RRU.S7242

Table: RCC-Associated Antigens (RCCAA) Recognized by T Cells.

Antigen Antigen
Category
Frequency of
Expression
Among RCC
Tumors (%)
CD8+ T cell
recognition:
Patients with
HLA Class I
Allele(s)
CD4+ T cell
recognition:
Patients with
HLA Class II
Allele(s)
References found in Open Access J Urol. Author manuscript; available in PMC 2013 Jul 8.
Survivina ML 100 Multiple Multiple 114
OFA-iLR OF 100 A2 NR 115116
IGFBP3ab ML 97 NR Multiple 117118
EphA2a ML > 90 A2 DR4 1744119
RU2AS Antisense
transcript
> 90 B7 NR 120
G250
(CA-IX) ab
RCC 90 A2, A24 Multiple 4751
EGFRab ML 85 A2 NR 121122
HIFPH3a ML 85 A24 NR 123
c-Meta ML > 80 A2 NR 124
WT-1a ML 80 A2, A24 NR 125128
MUC1ab ML 76 A2 DR3 46129130
5T4 ML 75 A2, Cw7 DR4 54131133
iCE aORF 75 B7 NR 134
MMP7a ML 75 A3 Multiple 117135136
Cyclin D1a ML 75 A2 Multiple 117137138
HAGE b CT 75 A2 DR4 139
hTERT ab ML > 70 Mutliple Multiple 140142
FGF-5 Protein splice variant > 60 A3 NR 143
mutVHLab ML > 60 NR NR 144
MAGE-A3 b CT 60 Multiple Multiple 145
SART-3 ML 57 Mulitple NR 146149
SART-2 ML 56 A24 NR 150
PRAME b CT 40 Multiple NR 151154
p53ab Mutant/WT
ML
32 Mutliple Multiple 155156
MAGE-A9b CT >30 A2 NR 157
MAGE-A6b CT 30 Mutliple DR4 18158
MAGE-D4b CT 30 A25 NR 159
Her2/neua ML 1030 Multiple Multiple 45160164
SART-1a ML 25 Multiple NR 165167
RAGE-1 CT (ORF2/5) 21 Mutliple Multiple 151157168169
TRP-1/ gp75 ML 11 A31 DR4 151170172

A summary is provided for RCCAA that have been defined at the molecular level. RCCAA are characterized with regard to their antigen category, their prevalence of (over)expression among total RCC specimens evaluated, whether RCCAA expression is modulated by hypoxia or tumor DNA methylation status, and which HLA class I and class II alleles have been reported to serve as presenting molecules for T cell recognition of peptides derived from a given RCCAA.

Abbreviations: CT = Cancer-Testis Antigens; ML = Multi-lineage Antigens; NR = Not Reported; OF = Oncofetal Antigen; aORF = altered open reading frame; ORF = open reading frame; RCC = Renal cell carcinoma; WT = Wild-Type;

aHypoxia-Induced;

bHypomethylation-Induced.

PMC full text: Open Access J Urol. Author manuscript; available in PMC 2013 Jul 8.

Open Access J Urol. 2010 Aug; 2010(2): 125–141. doi:  10.2147/RRU.S7242

Expected Impact on Teff versus Suppressor Cells
Co-Therapeutic Agent Teff
priming
Teff
function
Teff
survival
Teff
(TME)
Treg/
MDSC
References found in Open Access J Urol. Author manuscript; available in PMC 2013 Jul 8.
Cytokines
IL-2 +/− ↑ (Treg) 173175
IL-7 ↑ (Treg) 176178
IL-12 – (Treg), ↓ (MDSC) 179181
IL-15 ↑ (Treg)* 182183
IL-18 ↓ (Treg) 184186
IL-21 ? +/− (Treg) 187190
IFN-α +/− (Treg) 175191194
IFN-γ -? ? ↑ ↑ (Treg); ↑ ?(MDSC) 195197
GM-CSF ? ↑ (Treg); ↑(MDSC) 198202
Coinhibitory Antagonist
CTLA-4 ? ↓ (Treg) 203204
PD1/PD1L ↓ (Treg) 205207
Costimulatory Agonist
CD40/CD40L ↑ (Treg); ↑(MDSC) 208211
GITR/GITRL ↓ (Treg); ↓ (MDSC) 212213
OX40/OX86 ↑↓ (Treg); ↓ (MDSC) 214219
4-1BB/4-1BBL ↑ (Treg) 220224
TLR Agonists
Imiquimod (TLR7) ? 225227
Resiquimod (TLR8) ? ? 228229
CpG (TLR9) ↓ (Treg) 230232
Anti-Angiogenic
VEGF-Trap ? ? 233
Sunitinib ? ↓ (Treg/MDSC) 98100234
Sorafenib ? ↓ (MDSC) 235
Bevacizumab ? ? ↓ (MDSC) 236237
Gefitinib (IRESSA) ? ? ? ? ? 238239
Cetuximab ? ? ? ? 240
mTOR Inhibitors
Temsirolimus/Everolimus ? ↓ (Treg) 241
Treg/MDSC Inhibitors
Iplimumab (CTLA-4) ? ↓ (Treg) 242243
ONTAK (CD25) +/− +/− ? ? ↓ (Treg) 244
Anti-TGFβ/TGFβR ↓ (Treg) 245247
Anti-IL10/IL10R +/− ↓ (Treg) 248249
Anti-IL35/IL35R ↑? ↑? ↑? ↑? ↓ (Treg) 250
1-methyl trytophan ? ? ↓ (MDSC) 251
ATRA ? ? ↑ (Treg), ↓ (MDSC) 9093

Agents that are currently or soon-to-be in clinical trials are summarized with regard to their anticipated impact(s) on Type-1 anti-tumor T cell (Te) activation, function, survival and recruitment into the TME. Additional anticipated effects of drugs on suppressor cells (Treg and MDSC) are also summarized. Key: ↑, agent is expected to increase parameter; ↓, agent is expected to inhibit parameter; +/−, minimal increase or decrease is expected in parameter as a consequence of treatment with agent; ?, unknown effect of agent on parameter.

Abbreviations: ATRA, all-trans retinoic acid; CTLA-4, cytotoxic T Lymphocyte antigen 4; GITR(L), glucocorticoid-induced TNF receptor (ligand); GM-CSF, granulocyte-macrophage colony stimulating factor; IFN, interferon; IL, interleukin; MDSC, myeloid-derived suppressor cell; PD1/PD1L, programmed cell death 1 (ligand); TGF-β(R), tumor necrosis factor-β(receptor); TLR, Toll-like receptor; TME, tumor microenvironment; Treg, regulatory T cell; VEGF, vascular endothelial growth factor.

Alternative and Complementary Therapies for Cancer:

  • Art therapy
  • Dance or movement therapy
  • Exercise
  • Meditation
  • Music therapy
  • Relaxation exercises

Mol Cancer Res. 2012 Jul; 10(7): 859–880. Published online 2012 May 25. doi:  10.1158/1541-7786.MCR-12-0117 PMCID: PMC3399969 NIHMSID: NIHMS380694

State-of-the-science: An update on renal cell carcinoma

Eric Jonasch,1 Andrew Futreal,1 Ian Davis,2 Sean Bailey,2 William Y. Kim,2 James Brugarolas,3 Amato Giaccia,4 Ghada Kurban,5 Armin Pause,6 Judith Frydman,4 Amado Zurita,1 Brian I. Rini,7 Pam Sharma,8Michael Atkins,9 Cheryl Walker,8,* and W. Kimryn Rathmell2,*

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Wolchok JD, Kluger H, Callahan MK, Postow MA, Rizvi NA, Lesokhin AM, Segal NH, Ariyan CE, Gordon RA, Reed K, Burke MM, Caldwell A, Kronenberg SA, Agunwamba BU, Zhang X, Lowy I, Inzunza HD, Feely W, Horak CE, Hong Q, et al. Nivolumab plus ipilimumab in advanced melanoma.N Engl J Med 369(2):122-133, 2013.

Yang JC, Hughes M, Kammula U, Royal R, Sherry RM, Topalian SL, Suri KB, Levy C, Allen T, Mavroukakis S, Lowy I, White DE, Rosenberg SA. Ipilimumab (anti-CTLA4 antibody) causes regression of metastatic renal cell cancer associated with enteritis and hypophysitis. J Immunother30(8):825-830, 2007.

Zou W, Chen L. Inhibitory B7-family molecules in the tumour microenvironment. Nat Rev Immunol8(6):467-477, 2008.

[Discovery Medicine; ISSN: 1539-6509; Discov Med 18(101):341-350, December 2014.Copyright © Discovery Medicine. All rights reserved.]

 

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Risks for Patients’ and Physician’s Health in the Cath Lab

Reporter and Curator: Aviva Lev-Ari, PhD, RN

On Thursday, June 27th, 2013, Bayer HealthCare, Nuance® Healthcare, and The Mount Sinai Hospital held a live webinar outlining how one of America’s leading Radiology Departments is pioneering the next generation of imaging informatics. If you were unable to watch it live, or would like to view it again, it is now available online here.
The Mount Sinai Hospital in New York has taken Contrast Dose Management and IT interoperability to a new level with two industry-leading forces – Bayer’s Certegra® Informatics Platform and Nuance’s PowerScribe® 360 | Reporting.
The FREE 60-minute webinar includes:
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Experiences with Informatics including Point of Care Documentation, Injection Protocol Management for Patient-Based Dosing, Interfacing with IT Systems, and Analytics
Live Q&A panel: The Mount Sinai Hospital, Bayer and Nuance

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Risks for Physician’s Health in the Cath Lab

EuroIntervention. 2012 Jan;7(9):1081-6. doi: 10.4244/EIJV7I9A172.

Brain tumours among interventional cardiologists: a cause for alarm? Report of four new cases from two cities and a review of the literature.

Source

Interventional Cardiology, Rambam Medical Center, Bruce Rappaport Faculty of Medicine, the Technion, Israel Institute of Technology, Haifa, Israel. aroguin@technion.ac.il

Abstract

AIMS:

Interventional cardiologists who work in cardiac catheterisation laboratories are exposed to low doses of ionising radiation that could pose a health hazard. DNA damage is considered to be the main initiating event by which radiation damage to cells results in development of cancer.

METHODS AND RESULTS:

We report on four interventional cardiologists, all with brain malignancies in the left hemisphere. In a literature search, we found five additional cases and thus present data on six interventional cardiologist and three interventional radiologists who were diagnosed with brain tumours. All worked for prolonged periods with exposure to ionising radiation in the catheterisation laboratory.

CONCLUSIONS:

In interventional cardiologists and radiologists, the left side of the head is known to be more exposed to radiation than the right. A connection to occupational radiation exposure is biologically plausible, but risk assessment is difficult due to the small population of interventional cardiologists and the low incidence of these tumours. This may be a chance occurrence, but the cause may also be radiation exposure. Scientific study further delineating occupational risks is essential. Since interventional cardiologists have the highest radiation exposure among health professionals, major awareness of radiation safety and training in radiological protection are essential and imperative, and should be used in every procedure.

Risks for Patients’ Health in the Cath Lab

Contrast-Induced Nephropathy

  • Author: Renu Bansal, MD; Chief Editor: Vecihi Batuman, MD, FACP, FASN

SOURCE

http://emedicine.medscape.com/article/246751-medication#showall

Contrast-induced nephropathy (CIN) is defined as the impairment of renal function and is measured as either a 25% increase in serum creatinine (SCr) from baseline or 0.5 mg/dL (44 µmol/L) increase in absolute value, within 48-72 hours of intravenous contrast administration. (See Etiology.)

For renal insufficiency (RI) to be attributable to contrast administration, it should be acute, usually within 2-3 days, although it has been suggested that RI up to 7 days post–contrast administration be considered CIN; it should also not be attributable to any other identifiable cause of renal failure. A temporal link is thus implied.[1] Following contrast exposure, SCr levels peak between 2 and 5 days and usually return to normal in 14 days. (See Clinical and Workup.)

Complications

CIN is one of the leading causes of hospital-acquired acute renal failure. It is associated with a significantly higher risk of in-hospital and 1-year mortality, even in patients who do not need dialysis.

Nonrenal complications include procedural cardiac complications (eg, Q-wave MI, coronary artery bypass graft [CABG], hypotension, shock), vascular complications (eg, femoral bleeding, hematoma, pseudoaneurysm, stroke), and systemic complications (eg, acute respiratory distress syndrome [ARDS], pulmonary embolism).

There is a complicated relationship between CIN, comorbidity, and mortality. Most patients who develop CIN do not die from renal failure. Death, if it does occur, is more commonly from either a preexisting nonrenal complication or a procedural complication.

Concerns

Many physicians who refer patients for contrast procedures and some who perform the procedure themselves are not fully informed about the risk of CIN. A survey found that less than half of referring physicians were aware of potential risk factors, including diabetes mellitus. (See Differentials.)

CIN suffers from a lack of consensus regarding its definition and treatment. Studies differ in regard to the marker used for renal function (SCr vs eGFR), the day of initial measurement and remeasurement of the marker, and the percentage increase used to define CIN. This makes it difficult to compare studies, especially in terms of the efficacy of various treatment modalities. (See Treatment and Medication.)[2]

The reported incidence of CIN might be an underestimation. SCr levels normally rise by day 3 of contrast administration. Most patients do not remain hospitalized for so long and there is no specific protocol to order outpatient SCr levels 3-5 days after the procedure.

Other renal function markers

The use of SCr as a marker of renal function has its limitations. Indicators such as the estimated glomerular filtration rate (eGFR) and cystatin C are increasingly considered to be more reliable and accurate reflectors of existing renal function.[3, 4]

The eGFR can be calculated using the Modification of Diet in Renal Disease (MDRD) formula or the Cockroft-Gault formula. The Cockroft-Gault formula calculates eGFR using age, sex, and body weight, which are factors that, independent of GFR, influence SCr. The MDRD equation also includes blood urea nitrogen (BUN) and serum albumin.

The eGFR works best at low creatinine values. SCr and GFR share a curvilinear relationship. At lower SCr values, doubling SCr is associated with a corresponding 50% decrease in GFR. However, in elderly patients with chronic kidney disease(CKD) who have high SCr values at baseline, a 25% rise in SCr is actually indicative of a relatively modest reduction in GFR. Nonetheless, even a 25% increase in SCr in this situation has been shown to have great impact, especially in terms of inhospital and 1-year mortality.[5]

Serum cystatin C is a serum protein that is secreted by nucleated cells. It is freely filtered by the glomerulus and has been found to be an accurate marker of GFR. Compared with SCr, cystatin C changes much earlier after contrast administration and is not subject to confounding factors, such age, sex, and muscle mass, that influence SCr values independent of the underlying GFR. Cystatin C is increasingly being used as a marker of renal function in cardiac surgical patients.

Patient education

Patients with risk factors for CIN should be educated about the necessity of follow-up care with their physicians with a postprocedure SCr estimation, especially if the initial procedure was done on an outpatient basis.

Etiology

Contrast media (CM) act on distinct anatomic sites within the kidney and exert adverse effects via multiple mechanisms. They cause a direct cytotoxic effect on the renal proximal tubular cells, enhance cellular damage by reactive oxygen species, and increase resistance to renal blood flow. They also exacerbate renal vasoconstriction, particularly in the deeper portions of the outer medulla. This is especially important in patients with CKD, because their preexisting abnormal vascular pathobiology is made worse by the effects of CM.[6, 7]

Renal (particularly medullary) microcirculation depends on a complex interplay of neural, hormonal, paracrine and autocrine influences. Of note are the vasodilator nitric oxide (NO) and the vasoconstrictors vasopressin, adenosine (when it acts via the high affinity A1 receptors), angiotensin II, and endothelins. Prostaglandins cause a redistribution of blood flow to the juxtamedullary cortex and, therefore, are protective.

NO, in particular, seems to be very important, with antiplatelet, vasodilatory, insulin sensitizing, anti-inflammatory, and antioxidant properties. It has been suggested that plasma levels of asymmetrical dimethylarginine (ADMA), which is an endogenous inhibitor of all NO synthase isoforms, can be used as a marker of CIN, especially in patients with unfavorable outcomes.

CM-mediated vasoconstriction is the result of a direct action of CM on vascular smooth muscle and from metabolites such as adenosine and endothelin. Additionally, the osmotic property of CM, especially in the tubular lumen, decreases water reabsorption, leading to a buildup of interstitial pressure. This, along with the increased salt and water load to the distal tubules, reduces GFR and causes local compression of the vasa recta. All of this contributes to worsening medullary hypoxemia and renal vasoconstriction in patients who are already volume depleted.

Finally, CM also increase resistance to blood flow by increasing blood viscosity and by decreasing red cell deformability. This intravascular sludging generates local ischemia and causes activation of reactive oxygen species that result in tubular damage at a cellular level.

Comparison of contrast-agent nephropathy potential

The ability of different classes of CM to cause CIN is influenced by their osmolality, ionicity (the ability of the contrast media to dissociate in water), and molecular structure. Each of these characteristics, in turn, influences their behavior in body fluid and their potential to cause adverse effects. (See Table 1, below.)[8]

Agents are classified as high, low, or iso-osmolar, depending on their osmolality in relation to blood. Low-osmolarity contrast media (LOCM) is actually a misnomer, since these agents have osmolalities of 600-900 mOsm/kg and so are 2-3 times more hyperosmolar than blood. High-osmolarity contrast media (HOCM) are 5-7 times more hyperosmolar than blood, with osmolalities greater than 1500 mOsm/kg.

Molecular structure of CM refers to the number of benzene rings. Most CM that were developed in the 1990s are dimers with 2 benzene rings. Dimeric CM, while nonionic and with low osmolarity, have high viscosity, which may influence renal tubular blood flow.

The ratio of iodine to dissolved particles describes an important relationship between opacification and osmotoxicity of the contrast agent. The higher ratios are more desirable. High-osmolar agents have a ratio of 1.5, low-osmolar agents have a ratio of 3, and iso-osmolar agents have the highest ratio, 6.

While the safety of LOCM over HOCM in terms of CIN seems intuitive, clinical evidence of it came from a meta-analysis by Barrett and Carlisle.[9] They showed the benefit of using LOCM over HOCM mostly in high-risk patients. The Iohexol Cooperative Study was a large, prospective, randomized, double-blinded, multicenter trial that compared the risk of developing CIN in patients receiving the low-osmolarity agent iohexol versus the high-osmolarity agent diatrizoate. While the HOCM group was 3.3 times more likely to develop CIN compared with the LOCM group, this was seen only in patients with preexisting CKD (baseline SCr greater than or equal to 1.5 mg/dL). In addition to CKD; diabetes mellitus, male sex, and contrast volume were found to be independent risk factors.

Even within the LOCM category, the risk is not the same for all agents. High-risk patients receiving iohexol have a higher likelihood of developing CIN than do patients receiving another agent (ie, iopamidol) in the same class.

When LOCM were compared with iso-osmolar contrast media (IOCM), the Nephrotoxicity in High-Risk Patients Study of Iso-Osmolar and Low-Osmolar Non-Ionic Contrast Media (NEPHRIC study), arguably the most definitive study in this category to date, found that the odds of developing CIN in high-risk patients were almost 9 times greater for the study’s iohexol group than for the investigation’s iodixanol group (iso-osmolar contrast agent). The incidence of CIN was 3% in the iodixanol group versus 26% in the iohexol group.[10] These results, though promising, were not duplicated in some subsequent studies.

When iodixanol was used, the Rapid Protocol for the Prevention of Contrast-Induced Renal Dysfunction (RAPPID) trial found a 21% incidence of CIN,[11] and the Contrast Media and Nephrotoxicity Following Coronary Revascularization by Angioplasty (CONTRAST) trial found a 33% incidence of CIN.[12] Finally, the Renal Toxicity Evaluation and Comparison Between Visipaque (Iodixanol) and Hexabrix (Ioxaglate) in Patients With Renal Insufficiency Undergoing Coronary Angiography (RECOVER) trial compared the iso-osmolar contrast medium iodixanol to the low-osmolarity agent ioxaglate and found a significantly lower incidence of CIN with iodixanol than with ioxaglate (7.9% vs 17%, respectively).[13]

Thus, although the data are by no means uniform, they seem to suggest that the iso-osmolar contrast agent iodixanol may be associated with smaller increases in SCr and lower rates of CIN when compared with low-osmolar agents, especially in patients with CKD and in those with CKD and diabetes mellitus.[14]

Risk factors

Risk factors for CIN can be divided into patient-related, procedure-related, and contrast-related factors (although the risk factors for CIN are still being identified and remain poorly understood). Patient-related risk factors are as follows:

  • Age
  • CKD
  • Diabetes mellitus
  • Hypertension
  • Metabolic syndrome
  • Anemia
  • Multiple myeloma
  • Hypoalbuminemia
  • Renal transplant
  • Hypovolemia and decreased effective circulating volumes – As evidenced by congestive heart failure (CHF), an ejection fraction (EF) of less than 40%, hypotension, and intra-aortic balloon counterpulsation (IABP) use

Procedure-related risk factors are as follows:

  • Urgent versus elective
  • Arterial versus venous
  • Diagnostic versus therapeutic

Contrast-related risk factors are as follows:

  • Volume of contrast
  • Contrast characteristics, including osmolarity, ionicity, molecular structure, and viscosity

The single most important patient-related risk factor is preexisting CKD, even more so than diabetes mellitus.[15] Patients with CKD in the setting of diabetes mellitus have a 4-fold increase in the risk of CIN compared with patients without diabetes mellitus or preexisting CKD.

Table: Physiochemical Properties of Contrast Media

Although the data is by no means uniform, they seem to suggest that the iso-osmolar contrast agent iodixanol may be associated with smaller increases in SCr and lower rates of CIN when compared with low-osmolar agents, especially in patients with CKD and in those with CKD and diabetes mellitus.[14] Guidelines from the American Heart Association (AHA)/American College of Cardiology (ACC) for the management of acute coronary syndromes patients with CKD recommend the use of IOCM (Class I, level of Evidence).

Table 1. Physiochemical Properties of Contrast Media[16] (Open Table in a new window)

Class of Contrast Agent Type of Contrast Agent Iodine Dose(mg/mL) Iodine/Particle Ratio Viscosity(cPs at 37°C) Osmolality(mOsm/kg H2 O) Molecular Weight (Da)
High-osmolar monomers(ionic) Diatrizoate (Renografin)Ioxithalamate (Telebrix) 370350 1.51.5 2.32.5 18702130 636643
Low-osmolar dimers(ionic) Ioxaglate (Hexabrix) 320 3 7.5 600 1270
Low-osmolar monomers(nonionic) Iohexol (Omnipaque)Iopamidol (Isovue)Iomeprol (Iomeron)

Ioversol (Optiray)

Iopromide (Ultravist)

Iopentol (Imagopaque)

350370400

350

370

350

333

3

3

3

10.49.412.6

9

10

12

780790620

790

770

810

821777778

807

791

835

Iso-osmolar dimers(nonionic) Iodixanol (Visipaque)Iotrolan (Isovist) 320320 66 11.88.5 290290 15501620

Epidemiology

Occurrence in the United States

CIN is the third leading cause of hospital-acquired renal failure. Decreased renal perfusion and surgery (or in some studies, nephrotoxic medications) are the number one and number two causes, respectively.

An analysis of 15 prospective and retrospective studies from 1976-1996 report an incidence of CIN of 3.1-31%. The number varies depending on the definition used for CIN; the contrast agent characteristics, including the type, amount, duration, and route of administration; preexisting risk factors; and length of follow-up (including the day of measurement of postcontrast serum creatinine).

In patients without risk factors, the incidence may be as low as 2%. With the introduction of risk factors, like diabetes, the number rises to 9%, with incidences being as high as 90% in diabetics with CKD. Therefore, the number and the type of preexisting risk factors directly influence the incidence of renal insufficiency. It is also procedure dependant, with 14.5% overall in patients undergoing coronary interventions compared to 1.6-2.3% for diagnostic intervention, as reported in literature.[17]

Race- and age-related demographics

While African Americans with diabetic nephropathy have a faster acceleration of end-stage renal disease (ESRD), independent of other variables, race has not been found to be a risk factor for CIN.

The incidence of CIN in patients older than age 60 years has been variously reported as 8-16%. It has also been shown that in patients with acute MI who have undergone coronary intervention, an age of 75 years or older is an independent risk factor for CIN.

Prognosis

CIN is normally a transient process, with renal functions reverting to normal within 7-14 days of contrast administration. Less than one-third patients develop some degree of residual renal impairment.

Dialysis is required in less than 1% of patients, with a slightly higher incidence in patients with underlying renal impairment (3.1%) and in those undergoing primary PCI for myocardial infarction (MI) (3%). However, in patients with diabetes and severe renal failure, the rate of dialysis can be as high as 12%.

Of the patients who need dialysis, 18% end up on permanent dialysis therapy. However, many of these patients will have had advanced renal insufficiency and concomitant diabetic nephropathy and will have been destined for dialysis regardless of the episode of CIN.

A growing body of knowledge indicates that acute kidney injury after contrast medium can be a harbinger of CKD or ESRD. In one observational study, the population studied appeared representative of the general population undergoing angiography and the rate of acute kidney ingury was consonant with other studies. The finding that persistent kidney damage can occur after contrast-induced acute kidney injury highlights the potential for acceleration of the progression of kidney injury in individuals with pre-existing CKD.[18]

Mortality

Patients who require dialysis have a considerably worse mortality rate, with reported rates of 35.7% inhospital mortality (compared with 7.1% in the nondialysis group) and a 2-year survival rate of only 19%.

CIN by itself may be an independent mortality risk factor. Following invasive cardiology procedures, patients with normal baseline renal function who develop CIN have reduced survival compared with patients with baseline chronic CKD who do not develop CIN.

Gadolinium-based agents

Gadolinium-based CM (used for magnetic resonance imaging [MRI]), when compared with iodine-based CM, have a similar, if not worse, adverse effect profile in patients with moderate CKD and eGFR of less than 30 mL/min. Their use has been implicated in the development of nephrogenic systemic fibrosis, a chronic debilitating condition with no cure.

A review of 3 series and 4 case reports suggested that the risk of renal insufficiency with gadolinium is similar to that of iodinated radiocontrast dye. The reported incidence varies from 4% in stage 3 CKD to 20% in stage 4 CKD. It may even be worse, as suggested by some investigators. A prospective study of 57 patients found that acute renal failure was seen in 28% of patients in the gadolinium group, compared with 6.5% of patients in the iodine group, despite prophylactic saline and N-acetylcysteine (NAC).

The risk factor profile is similar to that for iodinated CM; increased incidence of acute renal failure is seen in older patients and in those with lower baseline creatinine clearance, diabetic nephropathy, anemia, and hypoalbuminemia.

Risk stratification scoring systems

CIN is the result of a complex interplay of many of the above risk factors. The presence of 2 or more risk factors is additive, and the likelihood of CIN rises sharply as the number of risk factors increases. Researchers have tried to objectively quantify and predict the contribution of each risk factor to the ultimate outcome of CIN.

Risk stratification scoring systems have been devised to calculate an individual patient’s risk of developing CIN. This has mostly been done in patients undergoing percutaneous coronary intervention (PCI), especially those with preexisting risk factors. Mehran et al developed the following scoring system based on points awarded to each of 7 multivariate predictors[19] :

  • Hypotension = 5 points
  • IABP use = 5 points
  • CHF = 5 points
  • SCr of greater than 1.5 mg/dL = 4 points
  • Age greater than 75 years = 4 points
  • Anemia = 3 points
  • Diabetes mellitus = 3 points
  • Contrast volume = 1 point for each 100 cc used

Based on the total calculated score, patients were divided into low-risk (score of less than or equal to 5), moderate-risk (score of 6-10), high-risk (score of 11-15), and very–high-risk (score of greater than or equal to 16) categories. The rate of CIN and the requirement for dialysis were 7.5 and 0.04%, 14 and 0.12%, 26.1 and 1.09%, and 57.3 and 12.6%, respectively, for each of the 4 groups.

Bartholomew et al worked to create another scoring system and took into consideration 8 variables, including creatinine clearance of less than 60 mL/min, IABP use, urgent coronary procedure, diabetes mellitus, CHF, hypertension, peripheral vascular disease (PVD), and volume of contrast used.[20]

History and Physical Examination

History

Patients usually present with a history of contrast administration 24-48 hours prior to presentation, having undergone a diagnostic or therapeutic procedure (eg, PCI). The renal failure is usually nonoliguric.

Physical examination

A physical examination is useful for ruling out other causes of acute nephropathy, such as cholesterol emboli (eg, blue toe, livedo reticularis) or drug-induced interstitial nephritis (eg, rash). Patients may have evidence of volume depletion or may be in decompensated CHF.

Diagnostic Considerations

Conditions to consider in the differential diagnosis of CIN include the following:

  • Atheroembolic renal failure – More than 1 week after contrast, blue toes, livedo reticularis, transient eosinophilia, prolonged course, and lower recovery
  • Acute renal failure (includes prerenal and postrenal azotemia) – There may also be associated dehydration from aggressive diuresis, exacerbated by preexisting fluid depletion; the acute renal failure is usually oliguric, and recovery is anticipated in 2-3 weeks
  • Acute interstitial nephritis (triad of fever, skin rash, and eosinophilia) – Also eosinophiluria; the nephritis is usually from drugs such as penicillin, cephalosporins, and nonsteroidal anti-inflammatory drugs (NSAIDs)
  • Acute tubular necrosis – Ischemia from prerenal causes; endogenous toxins, such as hemoglobin, myoglobin, and light chains; exogenous toxins, such as antibiotics, chemotherapeutic agents, organic solvents, and heavy metals

Approach Considerations

SCr concentration usually begins to increase within 24 hours after contrast agent administration, peaks between days 3 and 5, and returns to baseline in 7-10 days. Serum cystatin C (which has been suggested as a surrogate marker of renal function in lieu of SCr) is increased in patients with CIN.

Nonspecific formed elements can appear in the urine, including renal tubular epithelial cells, pigmented granular casts, urate crystals, and debris. However, these urine findings do not correlate with severity.

Urine osmolality tends to be less than 350 mOsm/kg. The fractional excretion of sodium (FENa) may vary widely. In the minority of patients with oliguric CIN, the FENa is low in the early stages, despite no clinical evidence of volume depletion.

Histology

CM cause direct toxic effects on renal tubular epithelial cells, characterized by cell vacuolization, interstitial inflammation, and cellular necrosis. In a study, these characteristic changes, called osmotic nephrosis, were observed in 22.3% of patients undergoing renal biopsy, within 10 days of contrast exposure.[21]

Approach Considerations

Hydration therapy is the cornerstone of CIN prevention. Renal perfusion is decreased for up to 20 hours following contrast administration. Intravascular volume expansion maintains renal blood flow, preserves nitric oxide production, prevents medullary hypoxemia, and enhances contrast elimination.

However, a number of other CIN therapies have been investigated, including the use of statins, bicarbonate, N-acetylcysteine (NAC), ascorbic acid, the adenosine antagonists theophylline and aminophylline, vasodilators, forced diuresis, and renal replacement therapy. Patients with CIN should be managed in consultation with a nephrologist.

Hydration Therapy

The first study revealing the benefit of hydration in CIN prevention came from Solomon et al.[22] They also found forced diuresis to be inferior to hydration with 0.45% saline. Fluids with different compositions and tonicity have since been studied, including bicarbonate and mannitol.

Normal saline has been found to be superior to half-normal saline in terms of its enhanced ability in intravascular volume expansion. It also causes increased delivery of sodium to the distal nephron, prevents rennin-angiotensin activation, and thus maintains increased renal blood flow. In terms of route of administration, oral fluids, while beneficial, are not as effective as intravenous hydration.[23, 24]

The CIN Consensus Working Panel found that adequate intravenous volume expansion with isotonic crystalloids (1-1.5 mL/kg/h), 3-12 hours before the procedure and continued for 6-24 hours afterward, decreases the incidence of CIN in patients at risk. The panel studied 6 clinical trials with different protocols for volume expansion. The studies differed in the type of fluid used for hydration (isotonic vs half-normal saline), route, duration, timing, and amount of fluid used.[25]

For hospitalized patients, volume expansion should begin 6 hours prior to the procedure and be continued for 6-24 hours postprocedure. For outpatients, administration of fluids can be initiated 3 hours before and continued for 12 hours after the procedure. Postprocedure volume expansion is more important than preprocedure hydration. It has been suggested that a urine output of 150 mL/h should guide the rate of intravenous fluid replacement, although the CIN Consensus Working Panel did not find it useful to recommend a target urine output.

CHF poses a particular challenge. Patients with compensated CHF should still be given volume, albeit at lower rates. Uncompensated CHF patients should undergo hemodynamic monitoring, if possible, and diuretics should be continued. In emergency situations, one’s clinical judgment should be used, and, in the absence of any baseline renal function, adequate postprocedure hydration should be carried out.

What is interesting, however, is that, while hydration remains the cornerstone for CIN prevention, a randomized, controlled trial comparing a strategy of volume expansion with no volume expansion has not been performed to date.

Statins

Statins are widely used in coronary artery disease (CAD) for their pleiotropic effects (favorable effects on endothelin and thrombus formation, plaque stabilization, and anti-inflammatory properties), and it was believed that, given the vascular nature of CIN, they might have similar renoprotective effects. The data for statin use, however, are retrospective and anecdotal; they are taken mostly from patients already on statins who underwent PCI.[26]

A significantly lower incidence of CIN was found in patients treated with statins preoperatively (CIN incidence of 4.37% in the statin group vs 5.93% in the nonstatin group). However, prospective trials looking at statin use in patients undergoing noncardiac procedures are needed to better qualify this initial promise.

Bicarbonate Therapy

Bicarbonate therapy alkalinizes the renal tubular fluid and, thus, prevents free radical injury. Hydrogen peroxide and an oxygen ion (from superoxide) react to form a hydroxide ion, all agents of free radical injury. This reaction, called the Harber-Weiss reaction, is activated in an acidic environment. Bicarbonate, by alkalinizing the environment, slows down the reaction. It also scavenges reactive oxygen species (ROS) from NO, such as peroxynitrite.

Bicarbonate protocols most often include infusion of sodium bicarbonate at the rate of 3 mL/kg/hour an hour before the procedure, continued at 1 mL/kg/hour for 6 hours after. Some investigators have used 1 mL/kg/hour for 24 hours, starting 12 hours before the procedure. The exact duration, however, remains a matter of debate. Hydration with sodium bicarbonate has been found by some researchers to be more protective than normal saline alone.

Treatment controversy

A 2008 retrospective cohort study at the Mayo Clinic assessed the risk of CIN associated with the use of sodium bicarbonate, NAC, and the combination of sodium bicarbonate with NAC and found that, compared with no treatment, sodium bicarbonate used alone was associated with an increased risk of CIN. NAC alone or in combination with sodium bicarbonate did not significantly affect the incidence of CIN. The results were obtained after adjusting for confounding factors, including total volume of hydration, medications, baseline creatinine, and contrast iodine load.[27] Given the above new information, it is recommended that the use of sodium bicarbonate to prevent CIN should be further evaluated.

N-acetylcysteine

NAC is acetylated L-cysteine, an amino acid. Its sulfhydryl groups make it an excellent antioxidant and scavenger of free oxygen radicals. It also enhances the vasodilatory properties of nitric oxide. Twelve meta-analyses covering 29 randomized, controlled trials have been published on the effect of NAC therapy in CIN. They all suffer from significant heterogeneity. The standard oral NAC regimen consists of 600 mg twice daily for 24 hours before and on the day of the procedure. Higher doses of 1 g, 1200 mg, and 1500 mg twice daily have also been studied, with no significant dose-related or route-related (oral vs intravenous) difference. NAC has very low oral bioavailability; substantial interpatient variability and inconsistency between the available oral products obscure the picture further.[3, 24, 28]

Treatment controversy

The latest controversy relating to NAC therapy questioned the parameter on which its effectiveness was based. It was suggested that the beneficial effect of NAC in CIN is related to its SCr-lowering ability rather than to improved GFR. It was believed that NAC directly reduces SCr by increasing SCr’s excretion (tubular secretion), decreasing its production (augments activity of creatine kinase), or interfering with its laboratory measurement, enzymatic or nonenzymatic (Jaffe method).

This was supported by a study that demonstrated a significant decrease in SCr after 4 doses of 600 mg of oral NAC in healthy volunteers with normal kidney function and no exposure to radiocontrast media.[29] This would bring doubt into the results of at least 13 randomized, controlled trials that showed NAC to be protective in CIN, with SCr used as the endpoint. However, Haase et al compared the effect of NAC on SCr by simultaneously studying its effect on cystatin C and found that NAC did not artifactually lower SCr when measured by the Jaffe method.[30]

The CIN Working Panel concluded that the existing data on NAC therapy in CIN is sufficiently varied to preclude a definite recommendation.[25] In the practice of medicine, though, it remains part of the standard of care and is routinely administered because of its low cost, lack of adverse effects, and potential beneficial effect, as demonstrated by the relative risk reduction of CIN, ranging from 0.37-0.73, as reported in several meta-analyses.

Renal Replacement Therapy

Less than 1% of patients with CIN ultimately go on to require dialysis, the number being slightly higher in patients with underlying renal impairment (3.1%) and in those undergoing primary PCI for MI (3%). However, in patients with diabetes and severe renal failure, the rate of dialysis can be as high as 12%. Patients who get dialyzed do considerably worse, with inhospital mortality rates of 35.7% (compared with 7.1% in the nondialysis group) and a 2-year survival rate of only 19%.

CM have molecular weights that range between 650 and 1600 mOsm/kg. They have low lipophilicity, low plasma protein binding, and minimal biotransformation. They quickly equilibrate across capillary membranes and have volumes of distribution equivalent to that of the extracellular fluid volume. In patients with normal renal function, CM are excreted with the first glomerular passage and the decrease in their plasma concentration follows a 2-part exponential function, a distribution phase and an elimination phase. However, in patients with renal impairment, the renal clearance values are reduced. For example, 50% of the low-osmolarity contrast agent iomeprol is eliminated within 2 hours in healthy subjects, compared with 16-84 hours in patients with severe renal impairment.

In patients already on dialysis, the commonly sited issues with contrast administration include volume load and direct toxicity of contrast to the remaining nonfunctional nephrons and nonrenal tissues. Thus, the perceived need for emergent dialysis and contrast removal.

Rodby attempted to address these concerns, calculating that the administration of 100 mL of hyperosmolar contrast would move 265 mL of water from the intracellular to the extracellular compartment, resulting in an increase in extracellular volume by 365 mL. The increase in intravascular space would therefore be only a third, or 120 mL. Fluid shifts with LOCM are even less. He also found that extrarenal toxicity of CM was cited in mostly single case reports, and no objective evidence could be identified in 3 prospective studies.[31]

The risk of acute damage from contrast is therefore greatest in patients with CKD. This can be explained by the increase in single nephron GFR and, thus, the filtered load of contrast per nephron. This is akin to a double hit to the remaining nephrons; increased contrast load and prolonged tubular exposure. While this may not seem to be a concern in patients with ESRD who are already on dialysis, residual renal function, in fact, plays a big role in their outcome, more so in patients on peritoneal dialysis. Its preservation is therefore important.[31]

CM can be effectively and efficiently removed by hemodialysis (HD). Factors that influence CM removal include blood flow, membrane surface area, molecular size, transmembrane pressure, and dialysis time. High-flux dialysis membranes with blood flows of between 120-200 mL/min can remove almost 50% of iodinated CM within an hour and 80% in 4 hours. Even in patients with CKD, in whom contrast excretion is delayed, it was found that 70-80% of contrast can be removed by a 4-hour HD treatment. In view of the limited benefit of therapies such as hydration, bicarbonate and NAC, dialysis may seem like the definitive answer.

However, an excellent meta-analysis by Cruz et al—8 trials (6 randomized and 2 nonrandomized, controlled studies) were included in the analysis, with a pooled sample size of 412 patients—indicated that periprocedural extracorporeal blood purification (ECBP) does not significantly reduce the incidence of CIN in comparison with standard medical therapy. ECBP in the study consisted of HD (6 trials), continuous venovenous hemofiltration (1 trial), and continuous venovenous hemodiafiltration (1 trial).[32]

Cruz et al found that the incidence of CIN in the standard medical therapy group was 35.2%, compared with 27.8% in the ECBP group. Renal death (combined endpoint of death or dialysis dependence) was 12.5% in the standard medical therapy group, compared with 7.9% in the ECBP group.

An important consideration is the role of ECBP therapy in patients with severe renal impairment (ie, stage 5 CKD) not yet on maintenance dialysis. A study by Lee et al indicated that in patients with chronic renal failure who are undergoing coronary angiography, prophylactic HD can improve renal outcome. The study included 82 patients with stage 5 CKD who were not on dialysis and who were referred for coronary angiography.[33] The patients were randomly assigned to either undergo prophylactic HD (initiated within 81 ± 32 min) or to receive intravenous normal saline (control group).

The baseline creatinine of the dialysis group was 13.2 mL/min/1.73 m2, comparable to that of the control group (12.6 mL/min/1.73 m2). The investigators’ primary endpoint was change in creatinine clearance in the 2 groups on day 4, which was found to be statistically significant (0.4 ± 0.9 mL/min/1.73 m2 in the dialysis group vs 2.2 ± 2.8 mL/min/1.73 m2 in the control group).

Lee et al found that 35% of the control group required temporary renal replacement therapy, compared with 2% of the dialysis group. In addition, long-term, postdischarge dialysis was required in 13% of the control patients but in none of the dialysis patients. Among those patients who did not require chronic dialysis, an increase in SCr at discharge of over 1 mg/dL from baseline was found in 13 patients in the control group and in 2 patients in the dialysis group.

The study, though hopeful, does raise some concerns. While the change in creatinine clearance on day 4 from baseline was statistically significant, the day 4 creatinine clearance itself was not significantly different between the 2 groups. Also, the results were not expressed as CIN incidence. This patient population is very fragile and is already on the verge of dialysis. How much time off dialysis a single HD session was able to buy these patients was not discussed. The duration of follow-up was also not clear.

Marenzi et al found better outcomes in patients who received venovenous hemofiltration both pre- and post-CM administration than in patients who received post-CM hemofiltration or no hemofiltration at all. These outcomes included a lower likelihood of CIN, no need for HD, and no 1-year mortality, in the pre-/post-CM group.[34]

The biggest confounder in studies of continuous renal replacement therapy (CRRT) is that the outcome measure (SCr) is affected by the treatment itself. While the advantage of CRRT is the lack of delay in its institution, contrast clearance rates would be 1 L/h (16.6 mL/min provided a maximal sieving coefficient for contrast across the hemofiltration membrane of 1), substantially less than standard HD.

Furthermore, continuous venovenous hemofiltration is expensive, highly invasive, and requires trained personnel; the procedure itself needs to be performed in the intensive care unit (ICU). In the face of equivocal benefit of a highly invasive and expensive procedure, the role of continuous venovenous hemofiltration has yet to be accepted as a prophylactic treatment for avoiding CIN.

Dialysis immediately after contrast administration has been suggested for patients already on long-term HD and for those at very high risk of CIN. Three studies looked at its necessity and found that LOCM can be given safely to patients with ESRD who are being maintained on HD without the added expense or inconvenience of emergent postprocedural HD.

The only condition in which HD might be argued to have a beneficial role is in patients on peritoneal dialysis who rely on their residual renal function. In this setting, HD performed soon after CM administration may provide enhanced removal and therefore protect residual renal function. It should be noted, however, that these patients on peritoneal dialysis would therefore need an additional HD procedure with concomitant vascular access, as the clearance with peritoneal dialysis would be far too slow to offer any protection.

In a study to determine if renal replacement therapy in concert with contrast administration helps, Frank et al found that although the overall clearance of contrast was significantly increased by dialysis, the peak plasma concentration of iomeprol 15 minutes after contrast administration was not significantly changed by simultaneous dialysis. In their report, the investigators prospectively studied 17 patients with chronic renal insufficiency (SCr >3 mg/dL), dialysis independent, who were then randomized to receive high-flux HD over 6 hours simultaneously with contrast administration, and[35]

In the study, Frank et al also found that to be clinically effective, simultaneous dialysis should reduce the risk of developing ESRD by 50%. If type 1 and type 2 errors are set at 0.01, the result could be accepted only if none of the 48 sequential patients with simultaneous dialysis required dialysis during the 8 weeks after contrast exposure. To reject the hypothesis, 239 sequential patients with simultaneous dialysis would have to be included. Therefore, most CIN studies, are seriously underpowered.

Studies of HD for CIN vary with respect to the definition of CIN used, the patient population, the type and volume of CM, how long after CM administration HD is started, and, finally, the dialysis treatment modality itself. While existing studies do not show HD to be superior to hydration alone for CIN prevention, if HD is used in conjunction with hydration and CIN protective therapy, such as NAC and bicarbonate, it might prove to be efficacious in some high-risk patients. However, most studies have had only an 8-week follow-up period. While the initiation of long-term dialysis was 5-15%, the progression to uremia over a long-term follow-up period is still unanswered.[16]

Other Therapies

Ascorbic acid, which has antioxidant properties, was studied for its ability to counter the effect of free radicals and reactive oxygen species. One study found that oral ascorbic acid administered in a 3-g dose preprocedure and two 2-g doses postprocedure was associated with a 62% risk reduction in CIN incidence.[36]

Theophylline and aminophylline are adenosine antagonists that counteract the intrarenal vasoconstrictor and tubuloglomerular feedback effects of adenosine. They have been found to have a statistically significant effect in preventing CIN in high-risk patients. However, their use is limited by their narrow therapeutic window and adverse effects profile.

Vasodilators, such as calcium channel blockers, dopamine/fenoldopam, atrial natriuretic peptide, and L-arginine, all with different mechanisms of action, have a favorable effect on renal hemodynamics. However, their use for CIN prevention has not been borne out by most controlled trials, and they are not routinely recommended at this point.

Forced diuresis with furosemide and mannitol was studied in the hope that this procedure would dilute CM within the tubular lumen and enhance their excretion. Furosemide and mannitol in fact worsen CIN by causing dehydration in patients who may already have intravascular volume depletion. Their use at this time is discouraged.

Deterrence and Prevention

The best therapy for CIN is prevention. Physicians need to be increasingly aware that CIN is a common and potentially serious complication. Patients at risk should be identified early, especially those with CKD (ie, eGFR < 60 mL/min/1.73 m2). A detailed history inquiring for risk factors, especially diabetes mellitus, should be ascertained.

In patients with risk factors for CIN, the possibility of alternative imaging studies that do not need contrast should be explored. MRI with gadolinium is no longer considered a safe alternative to contrast because of the risk of nephrogenic systemic fibrosis, an irreversible, debilitating condition seen mostly in patients with an eGFR of less than 30 mL/min/1.73 m2.

In patients with a moderate to severe risk of CIN, creatinine clearance rates or eGFR should be estimated by either the MDRD formula or the Cockroft-Gault formula and then measured again 24-48 hours after contrast administration.

In the emergency setting, where the benefit of very early imaging studies outweighs that of waiting, the imaging procedure can be carried out without an initial estimation of SCr or eGFR.

Intra-arterial administration of iodinated CM poses a greater risk for CIN than does the intravenous approach. For patients at an increased risk for CIN receiving intra-arterial contrast, nonionic iso-osmolar agents (iodixanol) are associated with the lowest risk of CIN.

The amount of contrast used during the procedure should be limited to as little as possible and kept under 100 mL. Most investigators have found this to be the cut-off value below which no patient needed dialysis. The risk of CIN increases by 12% for each 100 mL of contrast used beyond the first 100 mL. Most angiographic diagnostic studies usually require 100 mL of contrast, compared with 200-250 mL for angioplasty. The maximum amount of contrast that can be used safely should be individualized, taking into account the preexisting renal function.

Various formulas for calculating the maximal safe CM dose have been suggested. Two most often cited are those suggested by Cigarroa et al and the European Society of Urogenital Radiology (ESUR).[37, 38] Cigarroa et al, in a retrospective study of 115 patients undergoing cardiac catheterization and angiography, using the HOCM diatrizoate, suggested that the dose of CM should not exceed 5 mL/kg of body weight (maximum 300 mL divided by SCr [mg/dL]). The ESUR, in turn, has published maximal LOCM volumes for various SCr cut-off values.

While the formulas from Cigarroa and the ESUR take into account the SCr, it has been suggested that the eGFR (a more accurate predictor of renal function) and the iodine dose of CM should be reflected in any estimates or predictions of safe CM dosages. There exists, however, no unimpeachably safe CM dose algorithm for CIN prevention.

The length of time between 2 contrast procedures should be at least 48-72 hours. Rapid repetition of contrast administration has been found to be a univariate risk factor for CIN.

Potentially nephrotoxic drugs (eg, NSAIDs, aminoglycosides, amphotericin B, cyclosporin, tacrolimus) should be withdrawn at least 24 hours prior, in patients at risk (eGFR < 60 mL/min).

Metformin, though not nephrotoxic, should be used prudently, because if renal failure does occur, there is risk of concomitant lactic acidosis. Therefore, metformin should be stopped at the time of the procedure and resumed 48 hours later if renal function remains normal.

Angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs) cause a 10-15% rise in SCr by reducing intraglomerular pressure. While they should not be started at this time, whether they should be discontinued remains a matter of debate. Much of the literature in this area is unclear and controversial.

Minimizing contrast administration

The amount of contrast used during the procedure should be limited to as little as possible and kept under 100 mL. Most investigators have found this to be the cut-off value below which no patient needed dialysis. The risk of CIN increases by 12% for each 100 mL of contrast used beyond the first 100 mL. Most angiographic diagnostic studies usually require 100 mL of contrast, compared with 200-250 mL for angioplasty. The maximum amount of contrast that can be used safely should be individualized, taking into account the preexisting renal function.

Various formulas for calculating the maximal safe CM dose have been suggested. Two most often cited are those suggested by Cigarroa et al and the European Society of Urogenital Radiology (ESUR).[37, 38] Cigarroa et al, in a retrospective study of 115 patients undergoing cardiac catheterization and angiography, using the HOCM diatrizoate, suggested that the dose of CM should not exceed 5 mL/kg of body weight (maximum 300 mL divided by SCr [mg/dL]). The ESUR, in turn, has published maximal LOCM volumes for various SCr cut-off values.

While the formulas from Cigarroa and the ESUR take into account the SCr, it has been suggested that the eGFR (a more accurate predictor of renal function) and the iodine dose of CM should be reflected in any estimates or predictions of safe CM dosages. There exists, however, no unimpeachably safe CM dose algorithm for CIN prevention.

RAAS blockade

A prospective, 50-month Mayo study found renin-angiotensin-aldosterone system (RAAS) blockade, particularly in older patients with CHD, exacerbates CIN (43% incidence of dialysis and 29% progression to ESRD).[39] The marker used for renal function was eGFR, as calculated by the MDRD formula. The study recommended that RAAS blockade be withheld 48 hours prior to contrast exposure.

RAAS blockage, however, can improve renal perfusion and decrease proximal tubular reabsorption, including CM absorption by the tubular cells. This effect can be documented with the increase in the fractional excretion of urea seen with low-dose RAAS therapy in patients with CHF and moderate CKD (the majority of the CIN-susceptible population).[40] In this group, reduction in intraglomerular pressure and filtration fraction from RAAS therapy might decrease tubular CM concentration and therefore lessen its adverse effects.

Medication Summary

NAC is acetylated L-cysteine, an amino acid. As previously mentioned, its sulfhydryl groups make it an excellent antioxidant and scavenger of free oxygen radicals. It also enhances the vasodilatory properties of nitric oxide. Twelve meta-analyses covering 29 randomized, controlled trials have been published on the effect of NAC therapy in CIN. They all suffer from significant heterogeneity. The standard oral NAC regimen consists of 600 mg twice daily for 24 hours before and on the day of the procedure. Higher doses of 1 g, 1200 mg, and 1500 mg twice daily have also been studied, with no significant dose-related or route-related (oral vs intravenous) difference. NAC has very low oral bioavailability; substantial interpatient variability and inconsistency between the available oral products obscure the picture further.[24, 28]

Antidote, Acetaminophen

Class Summary

Used for prevention of contrast toxicity.

N-acetylcysteine (Acetadote)

Used for prevention of contrast toxicity in susceptible individuals such as those with diabetes mellitus. May provide substrate for conjugation with toxic metabolites.

Antilipemic Agents

Class Summary

These agents are used for their favorable effects on endothelin and thrombus formation, plaque stabilization and anti-inflammatory properties by improving lipid profile.

Simvastatin (Zocor)

Indicated for hyperlipoproteinemia (Type III). Inhibit 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA reductase), which in turn inhibit cholesterol synthesis, and increases cholesterol metabolism. Increase HDL cholesterol and decrease LDL-C, total-C, apolipoprotein B, VLDL cholesterol, and plasma triglycerides.

Atorvastatin (Lipitor)

The most efficacious of the statins at high doses. Inhibits 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA reductase), which in turn inhibits cholesterol synthesis and increases cholesterol metabolism. Reports have shown as much as a 60% reduction in LDL-C. The Atorvastatin versus Revascularization Treatment study (AVERT) compared 80 mg atorvastatin daily to standard therapy and angioplasty in patients with CHD. While events at 18 mo were the same between both groups, the length of time until the first CHD event occurred was longer with aggressive LDL-C lowering. The half-life of atorvastatin and its active metabolites is longer than that of all the other statins (ie, approximately 48 h compared to 3-4 h).

May modestly elevate HDL-C levels. Clinically, reduced levels of circulating total cholesterol, LDL-C, and serum TGs are observed.

Before initiating therapy, patients should be placed on a cholesterol-lowering diet for 3-6 mo; the diet should be continued indefinitely.

Lovastatin (Mevacor, Altoprev)

Adjunct to dietary therapy in reducing serum cholesterol. Immediate-release (Mevacor) and extended-release (Altocor) are available.

Fluvastatin (Lescol, Lescol XL)

Synthetically prepared HMG-CoA reductase inhibitor with some similarities to lovastatin, simvastatin, and pravastatin. However, structurally distinct and has different biopharmaceutical profile (eg, no active metabolites, extensive protein binding, minimal CSF penetration).

Used as an adjunct to dietary therapy in decreasing cholesterol levels.

Pravastatin (Pravachol)

Effective in reducing circulating lipid levels and improving the clinical and anatomic course of atherosclerosis.

Rosuvastatin (Crestor)

HMG-CoA reductase inhibitor that in turn decreases cholesterol synthesis and increases cholesterol metabolism. Reduces total-C, LDL-C, and TG levels and increases HDL-C level. Used adjunctively with diet and exercise to treat hypercholesterolemia.

SOURCE

Managing Your Risks: Patient and Physician Health in the Cath Lab

flouro image

In this post we’ll explore the issue of radiation exposure, occupational risks in the catheterization lab, and how that can impact your care.

I. Patient Risks in the Cath Lab

Fluoroscopy is a type of medical imaging used during percutaneous coronary interventions that displays a continuous x-ray image. Blood flow and artery blockages are not able to be seen using x-ray only imaging. Physicians inject a contrast solution into the arteries so that when an x-ray beam is passed through the tissue, the physician can get a real-time image of the coronary arteries. On average, angioplasty procedures will last about an hour, this means the patient is exposed to ionizing radiation from the fluoroscopy for a significant amount of time. Lengthy procedures lead to greater exposure to the radiation of fluoroscopy.

Radiation has a cumulative effect and leads to increased risk for many conditions, most notably, cancer.  In healthcare where radiation is required for treatment, there is a prevailing philosophy called ALARA, which stands for as low as (is) reasonably achievable.   Wherever possible, physicians should be looking for ways to limit exposure to radiation to limit the cumulative effects of radiation on patients. Along with the risks posed by radiation, patients in the cath lab also face potentially high doses of the contrast medium which can cause a condition known as contrast induced nephropathy. The contrast solution that is so valuable to imaging can be toxic to the kidneys, and when the body is unable to process the contrast, it leads to CIN in which the kidneys shut down.  While most patients who develop CIN typically recover within 1- 2 weeks, it can cause serious renal (kidney) complications in patients with certain risk factors including diabetes, prior kidney transplant, chronic kidney disease, and hypertensive disorders. Therefore, physicians need to keep a constant watch on the contrast volume used during procedures to minimize the risk of CIN.

II. Occupational Hazards in the Cath Lab

It is well documented that Interventional Cardiologists face serious dangers of long-term radiation exposure in the cath lab. Risks to clinicians include: skin damage to hands and exposed tissue, injury to the lens of the eye/ cataracts, and in some cases the development of brain tumors and other cancers. In a 2012 study, researchers found an increased incidence of left hemisphere brain tumors in a study group of interventional cardiologists that may be attributed to the prolonged exposure to ionizing radiation to the left side of the head during interventional procedures.

Via LifeScience PLUS

Physicians in the Cardiac Cath Lab (Via LifeScience PLUS)

Lead aprons are the standard convention used in Cath labs across the US to reduce radiation exposure to physicians and staff; however these protective barriers can weigh between 15-20 pounds and place up to 300 pounds per square inch of pressure on vertebral disks. In one study more than 400 interventionalists were surveyed and 71% of the study population reported some type of orthopedic disease. According to Dr. Tom Ports, Director of Interventional Cardiology at University of San Francisco, the leading cause of early retirement for interventional cardiologists is spinal injury!

Attention to the danger of radiation exposure and other risks in the cath lab for both patients and staff is on the rise. As more focus is being brought upon safety practices in the cath lab, improved procedural measures are being put in place to protect physicians and staff, and improve the quality of care for patients.

http://blog.corindus.com/?p=124

REFERENCES

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Reporter and Curator: Dr. Sudipta Saha, Ph.D.

The metabolite pool of cells and tissues represents the end result of metabolism determined by genetic, environmental and nutritional factors. The metabolic profile of biological systems is closely related to the individual phenotype and reflects the biological endpoint of a multitude of pathways and their interaction with any confounding stimuli. Cancer cells exhibit activation of specific metabolic pathways to compensate for their extremely high energy demands. Indeed increased glucose uptake and lactate production and decreased respiration are key phenomena of tumour cell metabolism. In particular, the generation of an acidic microenvironment through increased lactate production, even under aerobic conditions, may confer extracellular matrix degeneration and exert toxic effects on surrounding cell populations, while being harmless for the cancer cell itself. Thus, the metabolic adaptations may indeed be critical for the development of accelerated proliferation and the invasive growth of tumour cell populations. The molecular mechanisms underlying the metabolic hallmarks of cancer are still poorly understood, although genetic, epigenetic and environmental factors driving cancer development and progression will interact to determine the metabolic phenotype of tumour cells. Recent studies suggest that metabolic changes play a pivotal role in the biology of renal cell carcinoma – a tumour entity that is largely resistant to conventional chemo- and radiotherapy. The metabolic profile of renal tumours may thus serve as a reliable biomarker of malignant transformation and biological behaviour.

Recent advances in metabolic profiling technologies by providing quantitative measures of metabolite profiles from gas chromatography time-of-flight mass spectrometry (GC-TOF-MS) based technology present the opportunity to apply this technique in human specimens. Global metabolic profiling has emerged as a promising approach to characterize the metabolite pool within a cell, tissue or bodily fluid under certain conditions, such as health or disease status. Metabolic profiling is applied to monitor the health to disease continuum and has the potential of increasing our understanding of the mechanisms of disease. Thus the characterization of the metabolic features in tumours is expected to provide a better understanding of the mechanisms of malignant transformation and progression and may lead to the identification of metabolic biomarkers for cancer detection and prognostication. However, comparative profiling of low molecular weight compounds, such as sugars, lipids and amino acids, in cancer as compared to the corresponding normal tissue is a rather unexplored area. The objective of this study was to characterize the key metabolic features of renal cell carcinoma using GC-TOF-MS and mutual information as well as decision tree-based data analysis.

Hypoxia is key in tumour cell behaviour. Hypoxia, via hypoxia inducible factor, plays a key role in the metabolic changes in the kidney cancer cell and influences different pathways. Pathways that use tyrosine kinases and mammalian target of rapamycin are well studied. Hypoxia-related effects on vascular epithelial growth factors and angiogenesis will influence the metabolic status of the cell significantly. This is the basis of inhibitor-type drugs or antibody blocking agents and the effect on the clinical course of renal cell carcinoma patients. Detailed information about metabolic changes is crucial to understanding these mechanisms more clearly. Treating renal cell carcinoma patients is not like treating one disease. Renal cell carcinoma has different morphologic entities with distinct differences in cytogenetic background. These differences should be reflected in the different approaches of diagnostic and therapeutic strategies. This consideration will help to increase the efficacy of novel agents and decrease unnecessary side-effects. Metabolomics explains the importance of explaining genetic changes and the functional outcome of the tumour cells. In addition, epidemiologic differences in incidence and prevalence in different parts of the world may help provide insight into the etiology of kidney cancer. Factors that may influence renal cancer likelihood (eg, obesity, antihypertensive therapy) may have an explanation in metabolomics.

Source References:

http://www.europeanurology.com/article/S0302-2838(12)01352-8/fulltext

http://www.ncbi.nlm.nih.gov/pubmed/19845817

http://www.ncbi.nlm.nih.gov/pubmed/18072195

http://www.ncbi.nlm.nih.gov/pubmed/17123452

http://www.ncbi.nlm.nih.gov/pubmed/20464042

http://www.ncbi.nlm.nih.gov/pubmed/21930086

https://www.google.com.tw/url?sa=t&rct=j&q=&esrc=s&source=web&cd=8&cad=rja&ved=0CGwQFjAH&url=http%3A%2F%2Fjournals.sfu.ca%2Fcuaj%2Findex.php%2Fjournal%2Farticle%2Fdownload%2F665%2F466&ei=-ub8UbD0JcfolAXeyYGYBw&usg=AFQjCNFIzdti065pBEGKlEDkBDCPA4IwUw&sig2=scgq8qT9ffKa65MxAvpuNg&bvm=bv.50165853,d.dGI

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The Cardiorenal Syndrome in Heart Failure: Cardiac? Renal? syndrome?

Writer and Curator: Larry H. Bernstein, MD, FCAP

and

Curator: Aviva Lev-Ari, PhD, RN 

Triposkiadis F, Starling RC, Boudoulas H, Giamouzis G, Butler J.
Heart Fail Rev. 2012 May;17(3):355-66. http://dx.doi.org/10.1007/s10741-011-9291-x Review

There has been increasing interest on the so-called cardiorenal syndrome (CRS), defined as

  • a complex pathophysiological disorder of the heart and kidneys where by acute or chronic dysfunction in one organ may induce acute or chronic dysfunction in the other.

In this review, we contend that there is lack of evidence warranting the adoption of a specific clinical construct such as the CRS within the heart failure (HF) syndrome by demonstrating that:

(a) the approaches and tools regarding the definition of kidney involvement in HF are suboptimal;
(b) development of renal failure in HF is often confounded by age, hypertension, and diabetes;
(c) worsening of renal function (WRF) in HF may be largely independent of alterations in cardiac function;
(d) the bidirectional association between HF and renal failure is not unique and represents one of the several such associations encountered in HF; and
(e) inflammation is a common denominator for HF and associated noncardiac morbidities.

Based on these arguments, we believe that

  • dissecting one of the multiple bidirectional associations in HF and
  • constructing the so-called cardiorenal syndrome is not justified pathophysiologically.

Fully understanding of all morbid associations and not only the cardiorenal, that is of great significance for the clinician who is caring for the patient with HF.

Ultrafiltration in Heart Failure with Cardiorenal Syndrome

N Engl J Med 2013; 368:1157-1160 http://dx.doi.org/10.1056/NEJMc1300456

Bart et al. (Dec. 13 issue)1 report the results of the Cardiorenal Rescue Study in Acute Decompensated Heart Failure (CARRESS-HF). They state that ultrafiltration was inferior to a strategy of stepped pharmacologic therapy with respect to the

It is unclear at first sight why renal function should be different at 96 hours only when serum creatinine concentrations are used as a marker of renal function,

  • but not when the level of cystatin C or the glomerular filtration rate are used.

How can this discrepancy be explained?

According to the study Ultrafiltration in Decompensated Heart Failure with Cardiorenal Syndrome

Bart BA., Goldsmith SR., Lee KL, Givertz MM, et al.
N Engl J Med 2012; 367:2296-2304 http://dx.doi.org/10.1056/NEJMoa1210357

Ultrafiltration is an alternative strategy to diuretic therapy for the treatment of patients with acute decompensated heart failure.

Little is known about the efficacy and safety of ultrafiltration in patients with acute decompensated heart failure

  • complicated by persistent congestion and worsened renal function.

Ultrafiltration was inferior to pharmacologic therapy with respect to the bivariate end point of

  1. the change in the serum creatinine level and body weight 96 hours after enrollment (P=0.003),
  2. owing primarily to an increase in the creatinine level in the ultrafiltration group.
  • At 96 hours, the mean change in the creatinine level was −0.04±0.53 mg per deciliter (−3.5±46.9 μmol per liter) in the pharmacologic-therapy group,
  • as compared with +0.23±0.70 mg per deciliter (20.3±61.9 μmol per liter) in the ultrafiltration group (P=0.003).

A higher percentage of patients in the ultrafiltration group than in the pharmacologic-therapy group had a serious adverse event (72% vs. 57%, P=0.03).
In a randomized trial involving patients hospitalized for acute decompensated heart failure,

  1. worsened renal function, and
  2. persistent congestion,

the use of a stepped pharmacologic-therapy algorithm was superior to a strategy of ultrafiltration for

  • the preservation of renal function at 96 hours,
  • with a similar amount of weight loss with the two approaches. 

Other related articles published on this Open Access Online Scientific Journal 

Acute and Chronic Myocardial Infarction: Quantification of Myocardial Perfusion Viability – FDG-PET/MRI vs. MRI or PET alone (Justin Pearlman, (Aviva Lev-Ari)
https://pharmaceuticalintelligence.com/2013/05/22/acute-and-chronic-myocardial-infarction-quantification-of-myocardial-viability-fdg-petmri-vs-mri-or-pet-alone/

Accurate Identification and Treatment of Emergent Cardiac Events (larryhbern)
https://pharmaceuticalintelligence.com/2013/03/15/accurate-identification-and-treatment-of-emergent-cardiac-events/

Nitric Oxide and it’s Impact on Cardiothoracic Surgery (tildabarliya)
https://pharmaceuticalintelligence.com/2012/12/15/nitric-oxide-and-its-impact-on-cardiothoracic-surgery/

CABG or PCI: Patients with Diabetes – CABG Rein Supreme (Aviva Lev-Ari)
https://pharmaceuticalintelligence.com/2012/11/05/cabg-or-pci-patients-with-diabetes-cabg-rein-supreme/

Endothelin Receptors in Cardiovascular Diseases: The Role of eNOS Stimulation (Aviva Lev-Ari)
https://pharmaceuticalintelligence.com/2012/10/04/endothelin-receptors-in-cardiovascular-diseases-the-role-of-enos-stimulation/

Critical Care | Abstract | Cardiac ischemia in patients with septic … (Aviva Lev-Ari)
https://pharmaceuticalintelligence.com/2013/06/26/critical-care-abstract-cardiac-ischemia-in-patients-with-septic/

Dealing with the Use of the High Sensitivity Troponin (hs cTn) Assays (larryhbern)
https://pharmaceuticalintelligence.com/2013/05/18/dealing-with-the-use-of-the-hs-ctn-assays/

Acute Chest Pain/ER Admission: Three Emerging Alternatives to Angiography and PCI – Corus CAD, hs cTn, CCTA (Aviva Lev-ARi)
https://pharmaceuticalintelligence.com/2013/03/10/acute-chest-painer-admission-three-emerging-alternatives-to-angiography-and-pci/

Assessing Cardiovascular Disease with Biomarkers (larryhbern)
https://pharmaceuticalintelligence.com/2012/12/25/assessing-cardiovascular-disease-with-biomarkers/

Heart Failure Treatment Improves, But Death Rate Remains High : NPR (Aviva Lev-Ari)
https://pharmaceuticalintelligence.com/2013/05/29/heart-failure-treatment-improves-but-death-rate-remains-high-npr/

Economic Toll of Heart Failure in the US: Forecasting the Impact of Heart Failure in the United States – A Policy Statement From the American Heart Association (Aviva Lev-Ari)
https://pharmaceuticalintelligence.com/2013/04/25/economic-toll-of-heart-failure-in-the-us-forecasting-the-impact-of-heart-failure-in-the-united-states-a-policy-statement-from-the-american-heart-association/

Stenosis, ischemia and heart failure (Aviva Lev-Ari)
https://pharmaceuticalintelligence.com/2013/05/16/stenosis-ischemia-and-heart-failure/

Congestive Heart Failure & Personalized Medicine: Two-gene Test predicts response to Beta Blocker Bucindolol (Aviva Lev-Ari)
https://pharmaceuticalintelligence.com/2012/10/17/chronic-heart-failure-personalized-medicine-two-gene-test-predicts-response-to-beta-blocker-bucindolol/

Heart Remodeling by Design – Implantable Synchronized Cardiac Assist Device: Abiomed’s Symphony (Aviva lev-Ari)
https://pharmaceuticalintelligence.com/2012/07/23/heart-remodeling-by-design-implantable-synchronized-cardiac-assist-device-abiomeds-symphony/

Long-Term Mortality in Treated Hypertensive Patients: Serum Uric Acid Level, Longitudinal Blood Pressure and Renal Function

Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/05/20/long-term-mortality-in-treated-hypertensive-patients-serum-uric-acid-level-longitudinal-blood-pressure-and-renal-function/

Renal Sympathetic Denervation: Updates on the State of Medicine

Aviva Lev-Ari, PhD,RN

https://pharmaceuticalintelligence.com/2012/12/31/renal-sympathetic-denervation-updates-on-the-state-of-medicine/

Chapter 8: Nitric Oxide and Kidney Dysfunction

https://pharmaceuticalintelligence.com/biomed-e-books/perspectives-on-nitric-oxide-in-disease-mechanisms-v2/

8.1 Part I: The Amazing Structure and Adaptive Functioning of the Kidneys: Nitric Oxide

Larry H. Bernstein, MD, FCAP

8.2 Part II: Nitric Oxide and iNOS have Key Roles in Kidney Diseases

Larry H. Bernstein, MD, FCAP

8.3 Part III: The Molecular Biology of Renal Disorders: Nitric Oxide

Larry H. Bernstein, MD, FCAP

8.4 Part IV: New Insights on Nitric Oxide Donors

Larry H. Bernstein, MD, FCAP

8.5 The Essential Role of Nitric Oxide and Therapeutic Nitric Oxide Donor Targets in Renal Pharmacotherapy

What is Acute Heart Failure?

What is Acute Heart Failure? (Photo credit: Novartis AG)

English: Physiology of Nephron

English: Physiology of Nephron (Photo credit: Wikipedia)

Forrester-classification for classification of...

Forrester-classification for classification of Congestive heart failure ; Forrester-Klassifikation zur Einteilung einer akuten Herzinsuffizienz (Photo credit: Wikipedia)

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Subtitle: The Balance of Nitric Oxide, Peroxinitrite, and NO donors in Maintenance of Renal Function

Curator and Author: Larry H. Bernstein, MD, FCAP

The Nitric Oxide and Renal is presented in FOUR parts:

Part I: The Amazing Structure and Adaptive Functioning of the Kidneys: Nitric Oxide

Part II: Nitric Oxide and iNOS have Key Roles in Kidney Diseases

Part III: The Molecular Biology of Renal Disorders: Nitric Oxide

Part IV: New Insights on Nitric Oxide donors 

Conclusion to this series is presented in

The Essential Role of Nitric Oxide and Therapeutic NO Donor Targets in Renal Pharmacotherapy

Evolution of kidney function

The Emergence of  a Mammalian Kidney as Subterranian Life Crawls from Sea to Land
In fish the nerves that activate breathing take a short journey from an ancient part of the brain, the brain stem, to the throat and gills. For the ancient tadpole, the nerve controlling a reflex related to hiccup in man served a useful purpose, allowing the entrance to the lung to remain open when breathing air but closing it off when gulping water – which would then be directed only to the gills. For humans and other mammals it provides a bit of evidence of our common ancestry. DNA evidence has pinned iguanas and chameleons as the closest relatives to snakes.

In utero, we develop three separate kidneys in succession, absorbing the first two before we wind up with the embryonic kidney that will become our adult kidney. The first two of these reprise embryonic kidneys of ancestral forms, and in the proper evolutionary order. The pronephric kidney does not function in human and other mammalian embryos. It disappears and gives rise to the Mesonephric kidney. This kidney filters wastes from the blood and excretes them to the outside of the body via a pair of tubes called the mesonephric ducts (also “Wolffian ducts”). The mesonephric kidney goes on to develop into the adult kidney of fish and amphibians. This kidney does function for a few weeks in the human embryo, but then disappears as our final kidney forms, which is the Metanephric kidney.

The Metanephric kidney begins developing about five weeks into gestation, and consists of an organ that filters wastes from the blood and excretes them to the outside through a pair ureters. In the embryo, the wastes are excreted directly into the amniotic fluid. The metanephric kidney is the final adult kidney of reptiles, birds, and mammals. The first two kidneys resemble, in order, those of primitive aquatic vertebrates (lampreys and hagfish) and aquatic or semiaquatic vertebrates (fish and amphibians): an evolutionary order. The explanation, then, is that we go through developmental stages that show organs resembling those of our ancestors.

Take a step back and we see that fresh water fish have glomerular filtration. Cardiac contraction provides the pressure to force the water, small molecules, and ions into the glomerulus as nephric filtrate. The essential ingredients are then reclaimed by the tubules, returning to the blood in the capillaries surrounding the tubules. The amphibian kidney also functions chiefly as a device for excreting excess water. But the problem is to conserve water, not eliminate it. The frog adjusts to the varying water content of its surroundings by adjusting the rate of filtration at the glomerulus. When blood flow through the glomerulus is restricted, a renal portal system is present to carry away materials reabsorbed through the tubules. Bird kidneys function like those of reptiles (from which they are descended). Uric acid is also their chief nitrogenous waste.

All mammals share our use of urea as their chief nitrogenous waste. Urea requires much more water to be excreted than does uric acid. Thus, mammals produce large amounts of nephric filtrate but are able to reabsorb most of this in the tubules. Even so, humans lose several hundred ml each day in flushing urea out of the body. In his hypothesis of the evolution of renal function Homer Smith proposed that the formation of glomerular nephron and body armor had been adequate for the appearance of primitive vertebrates in fresh water and that the adaptation of homoisotherms to terrestrial life was accompanied by the appearance of the loop of Henle.

In the current paper, the increase in the arterial blood supply and glomerular filtration rate and the sharp elevation of the proximal reabsorption are viewed as important mechanisms in the evolution of the kidney. The presence of glomeruli in myxines and of nephron loops in lampreys suggests that fresh water animals used the preformed glomerular apparatus of early vertebrates, while mechanisms of urinary concentration was associated with the subdivision of the kidney into the renal cortex and medulla. The principles of evolution of renal functions can be observed at several levels of organizations in the kidney.
Natochin YV. Evolutionary aspects of renal function. Kidney International 1996; 49: 1539–1542; doi:10.1038/ki.1996.220.
Smith HW: From Fish to Philosopher. Boston, Little, Brown, 1953.

The Kidney: Anatomy and Physiology

The kidney lies in the lower abdomen capped by the adrenal glands. It has an outer cortex and an inner medulla. The basic unit is the nephron, which filters blood at the glomerulus, and not only filters urine eliminating mainly urea, also uric acid, and other nitrogenous waste, but also reabsorbs Na+ in exchange for H+/(reciprocal K+) through the carbonic anhydrase of the epithelium. In addition, it serves as a endocrine organ and receptor through the renin-angiotensin/aldosterone system, sensitivity to water loss controlled by distal acting antidiuretic hormone, and is sensitive to the natriuretic peptides of the heart. The kidney is an elegant structure with a high concentration of glomeruli in the cortex, and in the medulla one finds a U-shaped tube that is critical in functioning of a countercurrent multiplier system with a descending limb, Loop of Henley, and ascending limb.

The glomerulus is a dense ball of capillaries (glomerular capillaries) that branches from the afferent arteriole that enters the nephron. Because blood in the glomerular capillaries is under high pressure, substances in the blood that are small enough to pass through the pores (fenestrae, or endothelial fenestrations) in the capillary walls are forced out and into the encircling glomerular capsule. The glomerular capsule is a cup-shaped body that encircles the glomerular capillaries and collects the material (filtrate) that is forced out of the glomerular capillaries. The filtrate collects in the interior of the glomerular capsule, the capsular space, which is an area bounded by an inner visceral layer (that faces the glomerular capillaries) and an outer parietal layer.

The glomerular filtrate passes into the proximal convoluted tubule (PCT),  a winding tube in the renal cortex.  The PCT is mitochondria roch and has a high-energy yield.  The large surface area of these cells support their functions of reabsorption and secretion. The filtrate passes down the descending tubule and reaches the Loop of Henle. The  loop is shaped like a hairpin and consists of a descending limb that drops into the renal medulla and an ascending limb that rises back into the renal cortex.  The distal convoluted tubule (DCT) coils within the renal cortex and empties into the collecting duct.   In the final portions of the DCT and the collecting duct, there are cells that respond to the hormones aldosterone and antidiuretic hormone (ADH), and there are cells that secrete H+ in an effort to maintain proper pH.

The juxtaglomerular apparatus (JGA) is an area of the nephron where the afferent arteriole and the initial portion of the distal convoluted tubule are in close contact. Here, specialized smooth muscle cells of the afferent arteriole, called granular juxtaglomerular (JG) cells, act as mechanoreceptors that monitor blood pressure in the afferent arteriole. In the adjacent distal convoluted tubule, specialized cells, called macula densa, act as chemoreceptors that monitor the concentration of Na+ and Cl in the urine inside the tubule. Together, these cells help regulate blood pressure and the production of urine in the nephron.

The operation of the human nephron consists of three processes:

  • Glomerular filtration
  • Tubular reabsorption
  • Tubular secretion

The net filtration pressure (NFP) determines the quantity of filtrate that is forced into the glomerular capsule. The NFP, estimated at about 10 mm Hg, is the sum of pressures that promote filtration less the sum of those that oppose filtration. The following contribute to the NFP:

  • The glomerular hydrostatic pressure (blood pressure in the glomerulus) promotes filtration.
  • The glomerular osmotic pressure  is created as a result of the movement of water and solutes out of the glomerular capillaries. The increase in the concentration of solutes in the glomerular capillaries draws into the glomerular capillaries.
  • The capsular hydrostatic pressure inhibits filtration. This pressure develops as water collects in the glomerular capsule.

As the filtrate flows through the glomerulus into the descending limb, glucose is reabsorbed  to a threshhold maximum, and H+ is converted by the carbonic anhydrase  to water and CO2, except with serious acidemia, in which K+ is reabsorbed with H+ loss to the filtrate, resulting in a hyperkalemia. In the descending limb Na+ is absorbed into the interstitium, and the hypertonic interstitium draws water back for circulation, regulated by the action of ADH on the epithelium of the ascending limb. The result in terms of basic urinary clearance, the volume of urine loss is moderated by the amount needed for circulation (10 units of whole blood) without dehydration, and an amount sufficient for metabolite loss (including drug metabolites). The urine flows into the kidney pelvis and flow down the ureters.

The reabsorption of most substances from the tubule to the interstitial fluids requires a membrane-bound transport protein that carries these substances across the tubule cell membrane by active transport. When all of the available transport proteins are being used, the rate of reabsorption reaches a transport maximum (Tm), and substances that cannot be transported are lost in the urine.

The blood reaches the glomerulus by way of the afferent arteriole and leaves by way of the efferent arteriole. In a book by the Harvard Pathologist Shields Warren on diabetes he made a distinction between hypertension and diabetes in that efferent arteriolar sclerosis is present in both, but diabetes is uniquely identified by afferent arteriolar sclerosis. In diabetes you also have a typical glomerulosclerosis, which might be related to the same hyalinization found in the pancreatic islets – a secondary amyloidosis.

The renal artery for each kidney enters the renal hilus and successively branches into segmental arteries and then into interlobar arteries, which pass between the renal pyramids toward the renal cortex. The interlobar arteries then branch into the arcuate arteries, which curve as they pass along the junction of the renal medulla and cortex. Branches of the arcuate arteries, called interlobular arteries, penetrate the renal cortex, where they again branch into afferent arterioles, which enter the filtering mechanisms, or glomeruli, of the nephrons.

Summary

The criticality of renal function is traced to the emergence of animal forms from the sea to land, and its evolutionary change is recapitulated in the embryo.  We have already described the key role that nitric oxide and the NO synthases play in reduction of oxidative stress, and we have seen that a balance has to be struck between pro- and anti-oxidative as well as inflammatory elements for avoidance of diseases, specifically involving the circulation, but effectively not limited to any organ system. In addition, we have noted the importance of oxidative stress and modifications in mitochondrial function in oncogenesis related to a reliance on aerobic glycolysis to support both energy and synthetic activities in growth and proliferation of the “cancer” cell, that becomes more like a cancer “prototype” than its forebears.  In this discussion we pay attention to kidney function, and what follows is the adaptive role of NO and NO donors. This is an extension of a series of posts on NO and NO related disorders.

Frontal section through the kidney

Frontal section through the kidney (Photo credit: Wikipedia)

Structures of the kidney: Renal pyramid Interl...

Structures of the kidney: Renal pyramid Interlobar artery Renal artery Renal vein Renal hylum Renal pelvis Ureter Minor calyx Renal capsule Inferior extremity Superior extremity Interlobar vein Nephron Renal sinus Major calyx Renal papilla Renal column (no distinction for red/blue (oxygenated or not) blood, arteriole is between capilaries and larger vessels) (Photo credit: Wikipedia)

Distribution of blood vessels in cortex of kid...

Distribution of blood vessels in cortex of kidney. (Although the figure labels the efferent vessel as a vein, it is actually an arteriole.) (Photo credit: Wikipedia)

English: Nephron, Diagram of the urine formati...

English: Nephron, Diagram of the urine formation. The number inside tubular urine concentration in mOsm/l – when ADH acts  (Photo credit: Wikipedia)

Anatomy of the Kidneys. CliffsNotes. www.cliffsnotes.com/…/Anatomy-of-the-Kidneys

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The Molecular Biology of Renal Disorders: Nitric Oxide – Part III

Subtitle: Nitric Oxide, Peroxinitrite, and NO donors in Renal Function Loss 

Curator and Author: Larry H. Bernstein, MD, FCAP

Four Parts present this topic:

Part I: The Amazing Structure and Adaptive Functioning of the Kidneys: Nitric Oxide

Part II: Nitric Oxide and iNOS have Key Roles in Kidney Diseases

Part III: The Molecular Biology of Renal Disorders: Nitric Oxide

Part IV: New Insights on Nitric Oxide donors 

Conclusion to this series is presented in

The Essential Role of Nitric Oxide and Therapeutic NO Donor Targets in Renal Pharmacotherapy

Part III.  The Molecular Biology of Renal Disorders

Renal function affecting urine formation, electrolyte balance, nitrogen excretion, and vascular tone becomes acutely and/or chronically dysfunctional in metabolic, systemic inflammatory and immunological diseases of man. We have already described the key role that nitric oxide and the NO synthases play in reduction of oxidative stress, and we have seen that a balance has to be struck between pro- and anti-oxidative as well as inflammatory elements for avoidance of diseases, specifically involving the circulation. Similar stresses are important in the circulation, in liver disease, in pulmonary function, and in neurodegenerative disease.  In this discussion we continue to look at kidney function, NO and NO donors. This is an extension of a series of posts on NO and NO related disorders.

Part IIIa. Acute renal failure

Acute renal failure (ARF), characterized by sudden loss of the ability of the kidneys to

  1. excrete wastes,
  2. concentrate urine,
  3. conserve electrolytes, and
  4. maintain fluid balance,

is a frequent clinical problem, particularly in the intensive care unit, where it is associated with a mortality of between 50% and 80%.

This clinical entity was described as an acute loss of kidney function that occurred in severely injured crush victims because of histological evidence for patchy necrosis of renal tubules at autopsy. In the clinical setting, the terms ATN and acute renal failure (ARF) are frequently used interchangeably. However, ARF does not include increases in blood urea due to reversible renal vasoconstriction (prerenal azotemia) or urinary tract obstruction (postrenal azotemia). Acute hemodialysis was first used clinically during the Korean War in 1950 to treat military casualties, and this led to a decrease in mortality of the ARF clinical syndrome from about 90% to about 50%.

In the half century that has since passed, much has been learned about the pathogenesis of ischemic and nephrotoxic ARF in experimental models, but there has been very little improvement in mortality. This may be explained by changing demographics: the age of patients with ARF continues to rise, and comorbid diseases are increasingly common in this population. Both factors may obscure any increased survival related to improved critical care.

Examining the incidence of ARF in several military conflicts does, however, provide some optimism. The incidence of ARF in seriously injured casualties decreased between World War II and the Korean War, and again between that war and the Vietnam War, despite the lack of any obvious difference in the severity of the injuries. What was different was the rapidity of the fluid resuscitation of the patients. Fluid resuscitation on the battlefield with the rapid evacuation of the casualties to hospitals by helicopter began during the Korean War and was optimized further during the Vietnam War. For seriously injured casualties the incidence of ischemic ARF was one in 200 in the Korean War and one in 600 in the Vietnam War. This historical sequence of events suggests that early intervention could prevent the occurrence of ARF, at least in military casualties.

In experimental studies it has been shown that progression from an azotemic state associated with

  • renal vasoconstriction and
  • intact tubular function (prerenal azotemia)

to established ARF with tubular dysfunction occurs if the renal ischemia is prolonged. Moreover, early intervention with fluid resuscitation was shown to prevent the progression from prerenal azotemia to established ARF.

Diagnostic evaluation of ARF

One important question, therefore, is how to assure that an early diagnosis of acute renal vasoconstriction can be made prior to the occurrence of tubular dysfunction, thus providing the potential to prevent progression to established ARF. In this regard, past diagnostics relied on observation of the patient response to a fluid challenge:

  • decreasing levels of blood urea nitrogen (BUN) indicated the presence of reversible vasoconstriction, while
  • uncontrolled accumulation of nitrogenous waste products, i.e., BUN and serum creatinine, indicated established ARF.

This approach, however, frequently led to massive fluid overload in the ARF patient with resultant pulmonary congestion, hypoxia, and premature need for mechanical ventilatory support and/or hemodialysis. On this background the focus turned to an evaluation of urine sediment and urine chemistries to differentiate between renal vasoconstriction with intact tubular function and established ARF. It was well established that if tubular function was intact, renal vaso-constriction was associated with enhanced tubular sodium reabsorption. Specifically, the fraction of filtered sodium that is rapidly reabsorbed by normal tubules of the vasoconstricted kidney is greater than 99%. Thus, when nitrogenous wastes, such as creatinine and urea, accumulate in the blood due to a fall in glomerular filtration rate (GFR) secondary to renal vasoconstriction with intact tubular function,

the fractional excretion of filtered sodium (FENa = [(urine sodium × plasma creatinine) / (plasma sodium × urine creatinine)]) is less than 1%.

An exception to this physiological response of the normal kidney to vasoconstriction is when the patient is receiving a diuretic, including mannitol, or has glucosuria, which decreases tubular sodium reabsorption and increases FENa. It has recently been shown in the presence of diuretics that a rate of fractional excretion of urea (FEurea) of less than 35 indicates intact tubular function, thus favoring renal vasoconstriction rather than established ARF as a cause of the azotemia.

Mechanisms of ARF

 

Based on the foregoing comments, this discussion of mechanisms of ARF will not include nitrogenous-waste accumulation due to renal vasoconstriction with intact tubular function (prerenal azotemia) or urinary tract obstruction (postrenal azotemia). The mechanisms of ARF involve both vascular and tubular factors.

An ischemic insult to the kidney will in general be the cause of the ARF. While a decrease in renal blood flow with diminished oxygen and substrate delivery to the tubule cells is an important ischemic factor, it must be remembered that a relative increase in oxygen demand by the tubule is also a factor in renal ischemia.

Approximately 30–70% of these shed epithelial tubule cells in the urine are viable and can be grown in culture. Recent studies using cellular and molecular techniques have provided information relating to the structural abnormalities of injured renal tubules that occur both in vitro and in vivo.

In vitro studies using chemical anoxia have revealed abnormalities in the proximal tubule cytoskeleton that are associated with translocation of Na+/K+-ATPase from the basolateral to the apical membrane. A comparison of cadaveric transplanted kidneys with delayed versus prompt graft function has also provided important results regarding the role of Na+/K+-ATPase in ischemic renal injury.  This study demonstrated that, compared with kidneys with prompt graft function, those with delayed graft function had a significantly greater cytoplasmic concentration of Na+/K+-ATPase and actin-binding proteins — spectrin (also known as fodrin) and ankyrin — that had translocated from the basolateral membrane to the cytoplasm. Such a translocation of Na+/K+-ATPase from the basolateral membrane to the cytoplasm could explain the decrease in tubular sodium reabsorption that occurs with ARF.

The mechanisms whereby the critical residence of Na+/K+-ATPase in the basolateral membrane, which facilitates vectorial sodium transport, is uncoupled by hypoxia or ischemia have been an important focus of research. The actin-binding proteins, spectrin and ankyrin, serve as substrates for the calcium-activated cysteine protease calpain. In this regard, in vitro studies in proximal tubules have shown a rapid rise in cytosolic calcium concentration during acute hypoxia, which antedates the evidence of tubular injury as assessed by lactic dehydrogenase (LDH) release.  There is further evidence to support the importance of the translocation of Na+/K+-ATPase from the basolateral membrane to the cytoplasm during renal ischemia/reperfusion.

Specifically, calpain-mediated breakdown products of the actin-binding protein spectrin have been shown to occur with renal ischemia. Calpain activity was also demonstrated to be increased during hypoxia in isolated proximal tubules. Measurement of LDH release following calpain inhibition has demonstrated attenuation of hypoxic damage to proximal tubules. There was no evidence in proximal tubules during hypoxia of an increase in cathepsin, another cysteine protease. Further studies demonstrated a calcium-independent pathway for calpain activation during hypoxia. Calpastatin, an endogenous cellular inhibitor of calpain activation, was shown to be diminished during hypoxia in association with the rise in another cysteine protease, caspase. This effect of diminished calpastatin activity could be reversed by caspase inhibition. Proteolytic pathways that may be involved in calpain-mediated proximal tubule cell injury during hypoxia are illustrated. Calcium activation of phospholipase A has also been shown to contribute to renal tubular injury during ischemia.

Location of renal medulla

Location of renal medulla (Photo credit: Wikipedia)

Diagram of renal corpuscle structure

Diagram of renal corpuscle structure (Photo credit: Wikipedia)

English: Reactions leading to generation of Ni...

English: Reactions leading to generation of Nitric Oxide and Reactive Nitrogen Species. Novo and Parola Fibrogenesis & Tissue Repair 2008 1:5 doi:10.1186/1755-1536-1-5 (Photo credit: Wikipedia)

The reaction mechanism of Nitric oxide synthase

The reaction mechanism of Nitric oxide synthase (Photo credit: Wikipedia)

Tubular obstruction in ischemic ARF.

 

The existence of proteolytic pathways involving cysteine proteases, namely calpain and caspases, may therefore explain the decrease in proximal tubule sodium reabsorption and increased FENa secondary to proteolytic uncoupling of Na+/K+-ATPase from its basolateral membrane anchoring proteins. This tubular perturbation alone, however, does not explain the fall in GFR that leads to nitrogenous-waste retention and thus the rise in BUN and serum creatinine.

Decreased proximal tubule sodium reabsorption may lead to a decreased GFR during ARF. First of all, brush border membranes and cellular debris could provide the substrate for intraluminal obstruction in the highly resistant portion of distal nephrons. In fact, microdissection of individual nephrons of kidneys from patients with ARF demonstrated obstructing casts in distal tubules and collecting ducts. This observation could explain the dilated proximal tubules that are observed upon renal biopsy of ARF kidneys. The intraluminal casts in ARF kidneys stain prominently for Tamm-Horsfall protein (THP), which is produced in the thick ascending limb.

Importantly, THP is secreted into tubular fluid as a monomer but subsequently may become a polymer that forms a gel-like material in the presence of increased luminal Na+ concentration, as occurs in the distal nephron during clinical ARF with the decrease in tubular sodium reabsorption. Thus, the THP polymeric gel in the distal nephron provides an intraluminal environment for distal cast formation involving

  • viable,
  • apoptotic, and
  • necrotic cells.

The loss of the tubular epithelial cell barrier and/or the tight junctions between viable cells during acute renal ischemia could lead to a leak of glomerular filtrate back into the circulation. If this occurs and normally non-reabsorbable substances, such as inulin, leak back into the circulation, then a falsely low GFR will be measured as inulin clearance. It should be noted, however, that the degree of extensive tubular damage observed in experimental studies demonstrating tubular fluid backleak is rarely observed with clinical ARF in humans. Moreover, dextran sieving studies in patients with ARF demonstrated that, at best, only a 10% decrease in GFR could be explained by backleak of filtrate. Cadaveric transplanted kidneys with delayed graft function, however, may have severe tubular necrosis, and thus backleak of glomerular filtration may be more important in this setting.

Inflammation and NO

There is now substantial evidence for the involvement of inflammation in the pathogenesis of the decreased GFR associated with acute renal ischemic injury. In this regard, there is experimental evidence that iNOS may contribute to tubular injury during ARF. Hypoxia in isolated proximal tubules has been shown to increase NO release, and Western blot analysis in ischemic kidney homogenates has demonstrated increased iNOS protein expression. An antisense oligonucleotide was shown to block the upregulation of iNOS and afford functional protection against acute renal ischemia. Moreover, when isolated proximal tubules from iNOS, eNOS, and neuronal NO synthase (nNOS) knockout mice were exposed to hypoxia, only the tubules from the iNOS knockout mice were protected against hypoxia, as assessed by LDH release. The iNOS knockout mice were also shown to have lower mortality during ischemia/reperfusion than wild-type mice. There is also evidence that the scavenging of NO by oxygen radicals produces peroxynitrite that causes tubule damage during ischemia.

  • While iNOS may contribute to ischemic injury of renal tubules, there is evidence that the vascular effect of eNOS in the glomerular afferent arteriole is protective against ischemic injury.
  • In this regard, eNOS knockout mice have been shown to be more sensitive to endotoxin-related injury than normal mice.
  • Moreover, the protective role of vascular eNOS may be more important than the deleterious effect of iNOS at the tubule level during renal ischemia.

The basis for this tentative conclusion is the observation that treatment of mice with the nonspecific NO synthase (NOS) inhibitor L-NAME, which blocks both iNOS and eNOS, worsens renal ischemic injury.

It has also been demonstrated that NO may downregulate eNOS and is a potent inducer of heme oxygenase-1, which has been shown to be cytoprotective against renal injury. The MAPK pathway also appears to be involved in renal oxidant injury. Activation of extracellular signal–regulated kinase (ERK) or inhibition of JNK has been shown to ameliorate oxidant injury–induced necrosis in mouse renal proximal tubule cells in vitro. Upregulation of ERK may also be important in the effect of preconditioning whereby early ischemia affords protection against a subsequent ischemia/reperfusion insult. Alterations in cell cycling have also been shown to be involved in renal ischemic injury. Upregulation of p21, which inhibits cell cycling, appears to allow cellular repair and regeneration, whereas homozygous p21 knockout mice demonstrate enhanced cell necrosis in response to an ischemic insult.

Downregulated Upregulated
eNOS heme-oxygenase-1
ERK JNK
  p21

Prolonged duration of the ARF clinical course and the need for dialysis are major factors projecting a poor prognosis. Patients with ARF who require dialysis have a 50–70% mortality rate. Infection and cardiopulmonary complications are the major causes of death in patients with ARF. Excessive fluid administration in patients with established ARF may lead to

  • pulmonary congestion,
  • hypoxia,
  • the need for ventilatory support,
  • pneumonia, and
  • multiorgan dysfunction syndrome (80–90% mortality).

Until means to reverse the diminished host defense mechanisms in azotemic patients with clinical ARF are available, every effort should be made to avoid invasive procedures such as the placement of bladder catheters, intravenous lines, and mechanical ventilation. Over and above such supportive care, it may be that combination therapy will be necessary to prevent or attenuate the course of ARF. Such combination therapy must involve agents with potential beneficial effects on vascular tone, tubular obstruction, and inflammation.

Schrier RW, Wang W, Poole B, and Mitra A. Acute renal failure: definitions, diagnosis, pathogenesis, and therapy. The Journal of Clinical Investigation 2004; 114(1):5-14.

http://www.jci.org

Part IIIb.  Additional Related References on NO, oxidative stress and Kidney

Shelgikar PJ, Deshpande KH, Sardeshmukh AS, Katkam RV, Suryakarl AN. Role of oxidants and antioxidants in ARF patients undergoing hemodialysis. Indian J Nephrol 2005;15: 73-76.

Lee JW. Renal Dysfunction in Patients with Chronic Liver Disease. Electrolytes Blood Press 7:42-50, 2009ㆍdoi: 10.5049/EBP.2009.7.2.42.

Saadat H, et al.  Endothelial Nitric Oxide Function and Tubular Injury in Premature Infants. Int J App Sci and Technol 2012; 7(6): 77-81. www.ijastnet.com.

 

Amaresan MS. Cardiovascular disease in chronic kidney disease. Indian J Nephrol 2005;15: 1-7.

Traditional risk factors for CVD in CKD

  • Hypertension
  • Older Age
  • Diabetes Mellitus
  • Male gender
  •  White Race
  • Physical inactivity
  • High LDL
  • Low HDL
  • Smoking
  • Menopause
  • LVH

CKD Related CV Risk Factors

 

Blood Pressure ADMA (Asymmetric Dimethyl Arginine
Na+ Retention Hypervolemia
Insulin Resistance Anemia
Adiponectin Proteinuria & Hypoalbuminemia
Inflammation 5 Lipoxygenase
Homocysteinemia Genetic factors
ROS Lp (a)   
NO synthesis Iron over load
Ca++ x P++ Vit. C or E

 

 

S Vikrant, SC Tiwari. Essential Hypertension – Pathogenesis and Pathophysiology. J Indian Acad Clinical Medicine 2001; 2(3):141-161.

Pathogenesis of salt dependent hypertension. The hypothesis proposes that early hypertension is episodic and is mediated by a hyperactive sympathetic nervous system or activated renin-angiotensin system.

Cell membrane alterations

Hypotheses linking abnormal ionic fluxes to increased peripheral resistance through increase in cell sodium, calcium, or pH.

The hypertension that is more common in obese people may arise in large part from the insulin resistance and resultant hyperinsulinaemia that results from the increased mass of fat.

However, rather unexpectedly, insulin resistance may also be involved in hypertension in non-obese people.

The explanation for insulin resistance found in as many as half of nonobese hypertensive is not obvious and may involve one or more aspects of insulin’s action

Proposed mechanisms by which insulin resistance and/or hyperinsulinemia may lead to increased blood pressure.

  • Enhanced renal sodium and water reabsorption.
  • Increased blood pressure sensitivity to dietary salt intake
  • Augmentation of the pressure and aldosterone responses to AII
  • Changes in transmembrane electrolyte transport
  1. Increased intracellular sodium
  2. Decreased Na+/K+ – ATPase activity
  3. Increased intracellular Ca2+ pump activity
  4. Increased intracellular Ca2+ accumulation
  5. Stimulation of growth factors

Summary:  This portion of the discussion concerns mainly acute renal failure, but also expands upon the development of longer term renal tubular disease.  The last consideration is the link between essential hypertension, obesity and insulin resistance, and impaired renal water retention, sodium retention, decreased Na+/K+ – ATPase activity.  The issue of early intervention with fluid resuscitation is tempered by the risk of pulmonary edema as a significant complication.  A review of the literature indicates that both eNOS and iNOS have counter-effects in the genesis of ARF and CRF.  The protective role of vascular eNOS may be more important than the deleterious effect of iNOS at the tubule level during renal ischemia.

 

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Overview of New Strategy for Treatment of T2DM: SGLT2 Inhibiting Oral Antidiabetic Agents

 

Author and Curator: Aviral Vatsa, PhD, MBBS

Type 2 diabetes mellitus (T2DM) is a chronic disease, which is affecting widespread populations in epidemic proportions across the globe 1. It is characterised by hyperglycemia, which if not controlled adequately, eventually leads to microvascular and metabolic complications (Fig 1). Traditionally, T2DM management includes alteration in lifestyle, oral hypoglycemic agents and/or insulin. The present pharmacological approaches predominantly target glucose metabolism by compensating for reduction in insulin secretion and/or insulin action. However, these approaches are often limited by inadequate glucose control and the the possibility of severe adverse effects such as hypoglycemia, weight gain, nausea, and sometimes lactic acidosis 2–4 (Fig 1). Hence the search for new drugs with different mechanism of action and with little side affects is key in providing better glycemic control in T2DM patients and hence offering better prognosis with reduced morbidity and mortality.

Figure 1 (credit: aviral vatsa): Short overview of Type 2 diabetes mellitus (T2DM): complications, present therapeutic approaches and their limitations.

Along with pancreas, our kidneys play a vital role in regulating glucose levels in the plasma. Under physiological conditions, kidneys absorb 99% of the plasma glucose filtered through the renal glomeruli tubules. Majority i.e. 80-90% of this renal glucose resorbtion is mediated via the sodium glucose co-transporter 2 (SGLT2) 5,6. SGLT2 is a high-capacity low-affinity transporter that is mainly located in the proximal segment S1 of the proximal convoluted tubule 6. Inhibition of SGLT2 activity can thus induce glucosuria which inturn can lower blood glucose levels without targeting insulin resistance and insulin secretion pathways of glucose modulation (Fig 2).

Figure 2 (credit: aviral vatsa): Schematic overview of regulation of plasma glucose by sodium glucose co-transporter (SGLT).

Thus inhibition of SGLT2 provides a novel way to modulate blood glucose levels and consequently limit long term complications of hyperglycemia 7,8. Moreover, SGLT2 inhibitors will selectively target the renal glucose transportation and spare the counter regulatory hormones involved in glucose metabolism because SGLT2 is almost exclusively located in the kidneys. This novel way of glucose modulation will likely avoid severe side affects, e.g. hypoglycemia and weight gain, that are seen with present antidiabetic pharmacological agents.

Agents currently under development

Table below gives an overview of the SGLT2 inhibotors in development.

(Credit: Chao et al 2010)

 

In summary, increasing urinary glucose excretion represents a new approach to addressing the challenge of hyperglycaemia. SGLT2 inhibitors may have indications both in the prevention and treatment of T2DM, and perhaps T1DM, with a possible application in obesity. Further studies in large numbers of human subjects are necessary to delineate efficacy, safety and how to most effectively use these agents in the treatment of diabetes.

Bibliography

  1. Diabetes Atlas. International Diabetes Federation, (2009) at <www.diabetesatlas.org>
  2. Intensive blood-glucose control with sulphonylureas or insulin compared with conventional treatment and risk of complications in patients with type 2 diabetes (UKPDS 33). UK Prospective Diabetes Study (UKPDS) Group. Lancet 352, 837–853 (1998).
  3. Buse, J. B. et al. Effects of exenatide (exendin-4) on glycemic control over 30 weeks in sulfonylurea-treated patients with type 2 diabetes. Diabetes Care 27, 2628–2635 (2004).
  4. Inzucchi, S. E. Oral antihyperglycemic therapy for type 2 diabetes: scientific review. JAMA 287, 360–372 (2002).
  5. Brown, G. K. Glucose transporters: Structure, function and consequences of deficiency. Journal of Inherited Metabolic Disease 23, 237–246 (2000).
  6. Wright, E. M. Renal Na+-glucose cotransporters. Am J Physiol Renal Physiol 280, F10–F18 (2001).
  7. Chao, E. C. & Henry, R. R. SGLT2 inhibition — a novel strategy for diabetes treatment. Nature Reviews Drug Discovery 9, 551–559 (2010).
  8. Ferrannini, E. & Solini, A. SGLT2 inhibition in diabetes mellitus: rationale and clinical prospects. Nature Reviews Endocrinology 8, 495–502 (2012).

 

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