Role of the Endothelin-1 Gene Locus for Renal Impairment in the General Nondiabetic Population

Endothelin-1 RS5370 gene polymorphism in primary nephrotic syndrome: A case-control study

INTRODUCTION

Primary nephrotic syndrome (NS) is a common glomerular disease in children. We assessed the genotypes and frequency of the rs5370 allelic variant of the EDN1 gene in children with primary NS.

PATIENTS AND METHODS

We conducted a case-control study in Mansoura University Children's Hospital, Egypt between December 2015 and January 2018. We recruited 50 patients with steroid-sensitive NS (SSNS) and 50 patients with steroid-resistant NS (SRNS) in addition to 100 healthy controls. The patients underwent clinical evaluations and tests including measurement of serum albumin, cholesterol, creatinine and urea levels and a 24-h urinary protein test. We used polymerase chain reaction methods to assess the genotypes of rs5370 variants of the EDN1 gene (GG, GT and TT) and alleles (T and G) in the groups under study.

RESULTS

The most frequent genotype of the EDN1 gene at the locus of interest in the control group was the GT genotype (88%; P=.001) while the GG genotype was more frequent in the NS group compared to the control group (P=.02). We did not find statistically significant differences between the NS and control groups in regard to the EDN1 rs5370 alleles (P=.69). The GG genotype was more frequent in the SSNS group compared to the SRNS and control groups (P=.03). When we compared allele frequencies between the control, SSNS and SRNS groups, we did not find significant differences (P=.89). The GT genotype was associated with normal blood pressure in children with NS (P=.007), while the GG genotype was associated with hypertension (P<.001). We did not find statistically significant differences in renal histopathology or serum cholesterol levels based on the genotype.

CONCLUSIONS

The GG genotype at the rs5370 locus of the EDN1 gene may be associated with an increased risk of primary NS and a better response to steroid therapy.

[Endothelin-1 rs5370 gene polymorphism in primary nephrotic syndrome: A case-control study]

INTRODUCTION

Primary nephrotic syndrome (NS) is a common glomerular disease in children. We assessed the genotypes and frequency of the rs5370 allelic variant of the EDN1 gene in children with primary NS.

PATIENTS AND METHODS

We conducted a case-control study in Mansoura University Children's Hospital, Egypt, between December 2015 and January 2018. We recruited 50 patients with steroid-sensitive NS (SSNS) and 50 patients with steroid-resistant NS (SRNS) in addition to 100 healthy controls. The patients underwent clinical evaluations and tests including measurement of serum albumin, cholesterol, creatinine and urea levels and a 24-hour urinary protein test. We used polymerase chain reaction methods to assess the genotypes of rs5370 variants of the EDN1 gene (GG, GT and TT) and alleles (T and G) in the groups under study.

RESULTS

The most frequent genotype of the EDN1 gene at the locus of interest in the control group was the GT genotype (88%; P=.001) while the GG genotype was more frequent in the NS group compared to the control group (P=.02). We did not find statistically significant differences between the NS and control groups in regard to the EDN1 rs5370 alleles (P=.69). The GG genotype was more frequent in the SSNS group compared to the SRNS and control groups (P=.03). When we compared allele frequencies between the control, SSNS and SRNS groups, we did not find significant differences (P=.89). The GT genotype was associated with normal blood pressure in children with NS (P=.007), while the GG genotype was associated with hypertension (P<.001). We did not find statistically significant differences in renal histopathology or serum cholesterol levels based on the genotype.

CONCLUSIONS

The GG genotype at the rs5370 locus of the EDN1 gene may be associated with an increased risk of primary NS and a better response to steroid therapy.

Association of Endothelin-1 rs5370 G>T gene polymorphism with the risk of nephrotic syndrome in children

Background:

Primary nephrotic syndrome (NS) is a common kidney disease in children. Objectives: The present study was aimed to investigate whether rs5370 G>T (lys198Asn) genetic variant of endothelin-1 (ET-1) is involved in the susceptibility to NS.

Patients and Methods:

This case-control study was performed on 138 patients with NS and 150 healthy children. Genomic DNA was extracted from whole blood using salting out method. Polymorphism of the ET-1 rs5370 G>T (lys198Asn) polymorphism detected by T-ARMS-PCR as well as PCR-RFLP method.

Results:

The results showed that the genotype and allelic frequencies of the ET-1 rs5370 G>T variant were not significantly different between cases and controls. Furthermore, subgroup analysis showed that rs5370 G>T variant was not associated with gender of patients. In NS patients the genotype was not associated with cholesterol, triglyceride, total protein and albumin levels.

Conclusions:

In conclusion, our findings indicate that ET-1 rs5370 G>T is not associated with NS. Further studies with larger sample sizes and different ethnicities are required to validate our findings.

Genetic Polymorphisms in Endothelin-1 as Predictors for Long-Term Survival and the Cardiac Index in Patients Undergoing On-Pump Cardiac Surgery

Genetic variants within the endothelin-1 gene (EDN1) have been associated with several cardiovascular diseases and may act as genetic prognostic markers. Here, we explored the overall relevance of EDN1 polymorphisms for long-term survival in patients undergoing on-pump cardiac surgery. A prospectively collected cohort of 455 Caucasian patients who underwent cardiac surgery with cardiopulmonary bypass was followed up for 5 years. The obtained genotypes and inferred haplotypes were analyzed for their associations with the five-year mortality rate (primary endpoint). The EDN1 T-1370G and K198N genotype distributions did not deviate from Hardy–Weinberg equilibrium and the major allele frequencies were 83% and 77%, respectively. The cardiovascular risk factors were equally distributed in terms of the different genotypes and haplotypes associated with the two polymorphisms. The five-year mortality rate did not differ among the different EDN1 T-1370G and K198N genotypes and haplotypes. Haplotype analysis revealed that carriers of the G-T (compound EDN1 T-1370G G/K198N T) haplotype had a higher cardiac index than did non-carriers (p = 0.0008); however, this difference did not reach significance after adjusting for multiple testing. The results indicate that common variations in EDN1 do not act as prognostic markers for long-term survival in patients undergoing on-pump cardiac surgery.

Endothelin-1 gene polymorphisms and diabetic kidney disease in patients with type 2 diabetes mellitus

BACKGROUND AND AIMS

Diabetic kidney disease (DKD) is the leading cause of end stage renal disease worldwide and is associated with increased cardiovascular mortality. The endothelin system has been implicated in the pathogenesis of arterial hypertension and renal dysfunction. In the present study, the association of DKD with polymorphisms in ET-1 (EDN1) and ETRA (EDNRA) genes was analyzed in patients with type 2 diabetes mellitus (T2DM).

METHODS

A case-control study was conducted in 548 white T2DM patients. Patients with proteinuria or on dialysis were considered cases and patients with normoalbuminuria were considered controls. Two polymorphisms in the EDN1 gene (rs1800541 and rs57072783) and five in EDNRA gene (rs6842241; rs4835083; rs4639051; rs5333 and rs5343) were genotyped and haplotype analyses were performed.

RESULTS

The presence of rs57072783 T allele (TT/TG vs. GG) or rs1800541 G allele (GG/GT vs. TT) protected against DKD (OR = 0.69, 95 % CI 0.48-0.99, P = 0.049; and OR = 0.60, 95 % CI 0.41-0.88, P = 0.009, respectively). However in multivariate analyses, only the rs1800541 G allele remained independently associated with DKD (P = 0.046).

CONCLUSIONS

The present study shows that ET-1 could be involved in the pathogenesis of DKD in patients with T2DM.

Genetic association studies: discovery of the genetic basis of renal disease

Genetic association studies are a means to investigate the causal role of genes in diseases in order to unravel pathways involved in the etiology of disease. There are two types of genetic association studies: hypothesis-driven studies, i.e. candidate gene studies, targeting genes with a known or presumed role in pathways or diseases of interest, and non-hypothesis-driven studies, i.e. genome-wide association studies, aiming for the discovery of new genetic associations. This educational article is an introduction to genetic association studies for nephrologists and researchers in the domain of kidney disease.

Endothelial nitric oxide synthase gene variation associated with chronic kidney disease after liver transplant

OBJECTIVE

To identify single nucleotide polymorphisms (SNPs) associated with risk of developing chronic kidney disease (CKD), a prevalent comorbidity, after liver transplant (LT).

PATIENTS AND METHODS

This study consists of a cohort of adult (> or =18 years) primary-LT recipients who had normal renal function before LT and who survived 1 year or more after LT at a high-volume US LT program between January 1, 1990, and December 31, 2000. Patients with adequate renal function (estimated glomerular filtration rate, > or =40 mL/min per 1.73 m(2) during follow-up; n=308) and patients with incident CKD (estimated glomerular filtration rate, <40 mL/min per 1.73 m(2) after LT; n=92) were identified. To investigate the association of 6 candidate genes with post-LT CKD, we selected SNPs that have been associated with renal function in the literature. Hazard ratios were estimated using Cox regression, adjusted for potential confounding variables.

RESULTS

The variant allele (298Asp) of the Glu298Asp SNP in the endothelial nitric oxide synthase gene (NOS3) was significantly associated with CKD after LT (P=.05; adjusted for multiple comparisons). The 5-year incidence of CKD was 70% among patients homozygous for the NOS3 variant allele (298Asp) compared with 42% among those not homozygous for the NOS3 variant allele. Specifically, homozygosity for the NOS3 variant allele conferred a 2.5-fold increased risk of developing CKD after LT (P=.005, adjusted for confounding variables).

CONCLUSION

Homozygosity for the variant allele of NOS3 (298Asp) is associated with CKD after LT and may be useful for identifying recipients at higher risk of post-LT CKD.

Lack of association between endothelin-1 gene variants and myocardial infarction

AIM

Endothelin-1 (ET-1) promotes vasoconstriction and cell proliferation, and has been implicated in hypertension and coronary artery disease. Our aim was to analyse the role of the ET-1 gene (EDN1) in the risk for atherosclerosis/myocardial infarction (MI) in a population with smoking as the prevalent risk factor.

METHODS

The study included 316 patients with early onset MI (<55 years old). All were male with at least one diseased coronary vessel. Denaturing high performance liquid chromatography (DHPLC), single-strand conformation analysis (SSCA), and direct sequencing were used to search for DNA variants in the five EDN1 exons and the promoter region. To determine the association of EDN1 polymorphisms with MI, we genotyped the patients and controls (n=350) and compared the allele and genotype frequencies between groups.

RESULTS

We found six common nucleotide changes: -1394 (T/G) and -974 C/A (promoter), +120 ins/del A (exon 1, 5' UTR), 568 A/G (exon 3, E106E), 844 G/T (exon 5, K198N), and 1617 T/C (exon 5, 3' UTR). No rare EDN1-variants specific to the MIpatients were found. None of the EDN1 polymorphisms were significantly associated with early-onset MI in our population. The two promoter polymorphisms were in linkage disequilibrium with K198N, but no haplotype was associated with MI risk.

CONCLUSIONS

In our population, the EDN1 variation did not contribute to early-onset MI.

Microarray analysis of multiple candidate genes and associated plasma proteins for nephropathy secondary to type 2 diabetes among Chinese individuals

AIMS/HYPOTHESIS

Evolving research suggests that common and rare alleles jointly constitute the genetic landscape of complex disease. We studied the association between 43 pathway-related candidate genes with 'intermediate phenotype' (i.e. corresponding plasma protein) and diabetic nephropathy in a customised microarray of 1,536 SNPs.

METHODS

In this case-control study of type 2 diabetic Chinese individuals with and without diabetic nephropathy, cases (n = 545) were defined on the basis of a spot urinary albumin/creatinine ratio (ACR) > 113 mg/mmol; the value for controls (n = 503) was ACR < 3.3 mg/mmol. Genotyping was performed using Illumina GoldenGate assay.

RESULTS

No single nucleotide polymorphism (SNP) remained significant in single locus analysis after correction for multiple testing. Therefore, we explored the best approximately 1% SNPs. Of these 13 SNPs, four clustered to a 5' end NADPH oxidase homologue 4 (NOX4) haplotype (GGCC frequency = 0.776) with estimated OR for diabetic nephropathy of 2.05 (95% CI 1.04-4.06) (heterozygous) and 2.48 (1.27-4.83) (homozygous) (p = 0.0055). The haplotype was correlated with plasma Cu/Zn superoxide dismutase (SOD) concentration, suggesting increased oxidative burden. Endothelin-1 SNP (rs1476046G>A, frequency = 0.252) was correlated with plasma C-terminal pro-endothelin-1 concentrations with an estimated OR for diabetic nephropathy of (heterozygous) 1.26 (0.96-1.66) and (homozygous) 1.87 (1.13-3.12) (p = 0.0072). Nitric oxide synthase 1 (NOS1) 5' haplotype (TGTC frequency = 0.38) also revealed a suggestive association with diabetic nephropathy: heterozygous 1.26 (0.95-1.67), homozygous 1.57 (1.04-2.35) (p = 0.0073). A rare NADPH oxidase homologue 1 (NOX1)-coding non-synonymous SNP (Arg315His, frequency = 0.006) was found exclusively among cases.

CONCLUSIONS/INTERPRETATION

Our preliminary observations suggest that common haplotypes from NOX4 and endothelin-1 SNP correlated with plasma Cu/Zn SOD and C-terminal pro-endothelin-1 concentrations, respectively, and might have conferred diabetic nephropathy susceptibility. Common NOS1 and rare NOX1 variants also revealed a suggestive association with diabetic nephropathy. Future studies to validate our observation are needed.

Impact of endothelin-1 Lys198Asn polymorphism on coronary artery disease and endorgan damage in hypertensives

OBJECTIVE

Endothelin is the most potent endogenous vasoconstrictor and is involved in several vascular disorders such as arterial hypertension. Its intense interaction with other vasoactive hormone systems revealed the consideration about the endothelin gene as an interesting candidate for influencing the development of essential hypertension and hypertensive endorgan damage. The purpose of this study was to investigate the role of endothelin-1 Lys198Asn polymorphism in patients with severe arterial hypertension as well as associated endorgan damages.

METHODS

In 400 hypertensive patients and 150 normotensive controls we examined the endothelin-1 Lys198Asn polymorphism by DNA sequencing and patients were divided according to their genotype (GG, GT, and TT). Moreover, the frequency of endothelin-1 Lys198Asn polymorphism was investigated with respect to the prevalence of several actual or historical endorgan damages (renal disorder, coronary artery disease, vascular events, vascular damage, and congestive heart failure) in hypertensive patients.

RESULTS

Genotype distribution for endothelin-1 Lys198Asn polymorphism was 57.3% (GG), 41.3% (GT), and 1.43% (TT) in normotensive individuals; and in hypertensive individuals was 54.75% (GG), 43% (GT) and 2.25% (TT). Genotype distribution was unaffected in patients with severe hypertension, renal disorder, vascular events, vascular damage, and congestive heart failure. We, however, found a significant difference in hypertensive individuals with coronary artery disease and TT genotype (P=0.004).

CONCLUSION

Homozygous TT carrier contributes to a higher prevalence of coronary artery disease, especially for three-vessel disease in hypertensive individuals. Thus, the polymorphism at position 198 could serve as a possibility to differentiate high-risk subgroups in the heterogeneous population of hypertensive patients.

Heredity of Endothelin Secretion

Background— Endothelial dysfunction predisposes to vascular injury in association with hypertension. Endothelin (ET-1) is a potent vasoactive peptide that is synthesized and released by the vascular endothelium and is a marker of endothelial function. Chromogranin A (CHGA) regulates the storage and release of catecholamines and may have direct actions on the microvasculature. CHGA , a candidate gene for intermediate phenotypes that contribute to hypertension, shows a pattern of single nucleotide polymorphism variations that alter the expression and function of this gene both in vivo and in vitro.

Methods and Results— In a study of twins (n=238 pairs), plasma ET-1 was 58±5% ( P <0.0001) heritable. Plasma ET-1 was both correlated and associated with chromogranin fragment levels, and the 2 were influenced by shared genetic determination (pleiotropy [ρ G ]; for the CHGA precursor, ρ G =0.318±0.105; P =0.0032). We therefore hypothesized that variation in the CHGA gene may influence ET-1 secretion. Carriers of the CHGA promoter −988G, −462A, and −89A minor alleles showed significantly higher mean plasma ET-1 than their major allele homozygote counterparts ( P =0.02, P =0.006, P =0.03, respectively). Analysis of a linkage disequilibrium block that spans these 3 single nucleotide polymorphisms showed a significant association between the GATACA haplotype and plasma ET-1 ( P =0.0075). In cultured human umbilical vein endothelial cells, CHGA caused dose-dependent secretion of ET-1 over a brief (<1 hour) time course at relatively low concentrations of CHGA (10 to 100 nmol/L) with a threshold concentration (10 nmol/L) in the range found circulating in humans in vivo.

Conclusions— These results suggest that common, heritable variation in expression of the human CHGA gene influences endothelial ET-1 secretion in vivo, explained by a CHGA stimulus/ET-1 secretion coupling in endothelial cells in vitro. The findings document a previously unsuspected interaction between the sympathochromaffin system and the endothelium and suggest novel genetic and cell biological approaches to the prediction, diagnosis, and mechanism of endothelial dysfunction in human disease.

Genetic risk factors for diabetic nephropathy on chromosomes 6p and 7q identified by the set-association approach

AIMS/HYPOTHESIS

In the present study we investigated potential associations of a set of 45 single nucleotide polymorphisms (SNP) in 20 candidate genes on eight chromosomes with diabetic nephropathy (DN) in type 2 diabetes mellitus. We aimed to compare two methodological approaches suitable for analysing susceptibility to complex traits: single- and multi-locus analyses.

MATERIALS AND METHODS

The study comprised a total of 647 subjects in one of three groups: diabetes with or without DN, or no diabetes. Genotypes were detected by PCR-based methodology (PCR only, PCR plus RFLP, or allele-specific PCR). Haplotypes were inferred in silico. Set association (tested using SUMSTAT software) was used for multilocus analysis.

RESULTS

After correction for multiple comparisons, only one SNP, in the gene encoding the receptor of advanced glycation end products, AGER 2184A/G (gene symbol formerly known as RAGE) showed a significant association with DN (p = 0.0006) in single-locus analysis. In multi-locus analysis, six SNPs exhibited a significant association with DN: four SNPs on chromosome 6p (AGER 2184A/G, LTA 252A/G, EDN1 8002G/A and AGER -429T/C) and two SNPs on chromosome 7q (NOS3 774C/T and NOS3 E298D), omnibus p = 0.033. Haplotype analysis revealed significant differences between DN and control groups in haplotype frequencies on chromosome 6 (p = 0.0002); however, there were no significant difference in the frequencies of the NOS3 haplotypes on chromosome 7. Logistic regression analysis identified SNPs AGER 2184A/G and NOS3 774C/T, together with diabetes duration and HbA1c, as significant predictors of DN. Testing for interactions between SNPs on chromosomes 6 and 7 did not provide significant evidence for epistatic interaction.

CONCLUSIONS/INTERPRETATION

Using the set-association approach we identified significant associations of several SNPs on chromosomes 6 and 7 with DN. The single- and multi-locus analyses represent complementary methods.

Screening of the endothelin1 gene (EDN1) in a cohort of patients with essential left ventricular hypertrophy

Our objective was to analyse the role of endothelin1 gene (EDN1) variation in essential left ventricular hypertrophy (LVH). We searched for EDN1 variants in 145 Spanish patients with an essential form of LVH (not secondary to hypertension, aortic stenosis, or any other disease that could explain the hypertrophy). The five EDN1 coding exons and 1.5 kilobases of the promoter region were analysed through single strand conformation analysis and direct sequencing. We found four nucleotide changes: -1224 C/A (promoter), -131 ins/del A (exon 1, 5'-non-translated sequence), A/G in codon 106 (exon 3, silent), and G/T in codon 198 (exon 5, lys198asn). To determine the association between these polymorphisms and cardiac hypertrophy, we compared the genotype frequencies from these 145 patients with 250 healthy controls. We found a higher frequency of patients homozygous for 198 lys (198 KK) (65% vs. 52%; p = 0.01; OR = 1.76) and for -1224 AA (73% vs. 66%; p = 0.19). Homozygotes for -1224 A + 198 K (AA+KK) were significantly more frequent in patients (62% vs. 45%; p = 0.0007; OR = 2.10; 95% CI = 1.35-3.25). The expression of the -1224 C/A and exon 5 K198N variants was analysed with cells in culture. These in vitro studies showed that these variations did not differ in their expression levels. In conclusion, our work has shown that EDN1 variation, and in particular homozygosity for the -1224A/198K haplotype, is associated with the risk of developing cardiac hypertrophy. However, these EDN1 variants do not affect in vitro gene expression.

Systematic Analysis of Sequence Variability of the Endothelin-1 Gene: A Prerequisite for Association Studies

We analyzed allele frequencies and pairwise linkage disequilibria of 13 variants in the EDN1 gene of 298 young males, the majority of German ancestry. Our analysis comprises all common variants in the five exons and flanking intronic regions, as well as known polymorphisms in the promoter sequence. In addition to previously analyzed polymorphisms, our haplotype reconstruction included five recently described variants and was done by using three different algorithms to allow inference of result stability. More than 30 haplotypes were predicted. All haplotypes with frequencies > or = 1% were inferred by all three methods and can be described by seven haplotype tagging single-nucleotide polymorphisms (htSNPs), reducing the genotyping load to 65%. Three of these haplotypes with frequencies of about 11%, 9%, and 4% had been mistaken for one haplotype in the previous analysis, which included only six polymorphisms, some of them not being htSNPs. Systematic analysis of sequence variability and comprehensive haplotype analysis of the EDN1 gene determined a substantial part of its genetic variability for further association studies and helped to reduce the genotyping load for common phenotypes.

Influence of endothelin-1 gene polymorphisms on the progression of autosomal dominant polycystic kidney disease

BACKGROUND/AIM

A significant phenotypical variability is observed in autosomal dominant polycystic kidney disease (ADPKD). The variability cannot be fully explained by the genetic heterogeneity of the disease. Endothelin-1 (ET-1) has been suggested to be a major promoting factor in renal diseases. The role of the ET-1 gene locus (EDN1) in the renal function in the general nondiabetic population was evaluated. We examined the influence of three single-nucleotide polymorphisms of the ET-1 gene (EDN1)--K198N, 3A/4A, and T-1370G--on the progression of ADPKD towards end-stage renal disease (ESRD).

METHODS

Two hundred and five ADPKD patients (113 males and 92 females) who had reached ESRD were analyzed. The patients were divided into three groups: (1) 48 patients (23 males and 25 females) with ESRD later than 63 years of age (slow progressors), (2) 74 patients (41 males and 33 females) with ESRD before 45 years of age (rapid progressors), and (3) 83 patients (49 males and 34 females) with ESRD between 45 and 63 years old. DNA samples from collected blood were genotyped for three single-nucleotide polymorphisms of EDN1: K198N, 3A/4A, and T-1370G. Haplotype analysis was also done in 200 healthy individuals. We compared the frequencies of the different genotypes between the groups of slow and rapid progressors and the ages at the time of ESRD regarding the EDN1 genotypes.

RESULTS

The EDN1 genotype distribution showed no differences among the groups of slow progressors, rapid progressors, the ADPKD group with ESRD between 45 and 63 years old, and the control group. Comparing the ages of ESRD of all patients, we did not find significant differences with regard to the different genotypes. Furthermore, we compared the combinations of the different haplotypes and the ages at the time of ESRD. We found no differences in ages at the time of ESRD in patients with different haplotypes in the endothelin promoter (T-1370G) in combination with 3A/4A or K198N polymorphisms. Comparing the ages at the time of ESRD in patients with different 3A/4A and K198N haplotypes, we found a significantly lower age at the time of ESRD (47.1 +/- 8.7 years) in the carriers of the 4A allele in combination with the 198N allele (4A/4A, 3A/4A + 198KN,NN) than in the carriers of the 4A allele homozygous for the K198 allele (52.9 +/- 10.9 years; 4A/4A, 3A/4A + 198KK; t test: p < 0.01) and in the carriers of the 198N allele homozygous for the 3A allele (53 +/- 11.2 years; 3A/3A + 198KN,NN; t test: p < 0.05).

CONCLUSIONS

We excluded an effect of K198N, 3A/4A, and T-1370G polymorphisms of EDN1 on the progression of ADPKD. However, a deleterious effect of the combination of 4A and 198N alleles of EDN1 was observed in APKDK individuals.

Genetic variation in the endothelin system: do polymorphisms affect the therapeutic strategies?

Endothelin-1 (ET-1) exerts multiple biological effects, including vasoconstriction and the stimulation of cell proliferation in tissues both within and outside of the cardiovascular system. ET-1 is synthesized by ET-converting enzymes (ECE), chymases (CMAs), and non-ECE metalloproteases through a process regulated in an autocrine fashion in vascular and nonvascular cells. ET-1 acts through the activation of G(i)protein-coupled receptors. ET(A) receptors mediate vasoconstriction and cell proliferation, whereas ET(B) receptors are important for aldosterone secretion, endothelial cell (EC) migration, the release of nitric oxide (NO) and prostacyclin, the clearance of ET-1, and the inhibition of ECE-1. ET is activated in scleroderma, hypertension, atherosclerosis, restenosis, heart failure, idiopathic cardiomyopathy, and renal failure. Tissue concentrations more reliably reflect the activation of the ET system because of the predominantly abluminal secretion of the peptide. Experimental studies and clinical trials have demonstrated that ET-1 plays a major role in normal cardiovascular homeostasis and in the functional and structural changes observed in arterial and pulmonary hypertension, glomerulosclerosis, atherosclerosis, and heart failure. Accordingly, ET antagonists are promising new agents in the treatment of cardiovascular diseases. Single nucleotide polymorphisms (SNPs) of the genes of preproET-1, ECE-1, CMA, ET(A) and ET(B) receptors have been identified and can be important for their functional regulation. However, for most of them the association with disease conditions and the evidence for a functional role remain controversial. Thus, even though ET antagonists are being used for the treatment of pulmonary hypertension, there is no convincing evidence for a role of SNPs in affecting the therapeutic strategies.

ET-1 Lys198Asn and ETA Receptor H323H Polymorphisms in Heart Failure

BACKGROUND

The endothelin (ET) system plays a central role in the control of myocardial function and its pathophysiology. The aim of the present study was to explore whether genetic variations of ET-1 (G/T substitution that predicts an Lys/Asn change at codon 198) and its receptor ET(A) (T/C in exon 6, H323H) could predispose carriers to heart failure (HF).

METHODS

Genotyping at these two loci was done in 122 patients with HF [echocardiographic left ventricular ejection fraction (LVEF) < or =40%] and 216 age-matched subjects without HF. Causes of HF included ischemic (n = 96) and idiopathic cardiomyopathies (n = 26).

RESULTS

The ET-1 Lys198Asn was significantly associated with the occurrence of HF (p = 0.005). The risk of HF was independently increased among Asn/Asn in comparison to Lys carriers (OR = 3.2, p = 0.03). Moreover, homozygous carriers of both ET-1 and ET(A) variants showed a marked increase in the risk of HF (adjusted OR = 8.6, p = 0.005), displayed significantly lower LVEF (p = 0.002) and higher left ventricular end-diastolic (p = 0.03) and end-systolic diameters (p = 0.04; for Asn/Asn and TT vs. Lys and C carriers of the ET-1 and ET(A )polymorphisms, respectively). Furthermore, the extent of coronary artery disease (r = -0.62, p < 0.0001) and the Asn/Asn and TT double genotype (r = -0.30, p = 0.0001) were the only significant and independent predictors of LVEF by multivariate analysis.

CONCLUSIONS

The ET-1 Lys198Asn and ET(A) receptor H323H polymorphisms seem to act synergistically to increase the risk of HF.

Progression of renal disease: new insights into risk factors and pathomechanisms

PURPOSE OF REVIEW

Progression of renal failure, irrespective of the primary cause, is characterized by modification of renal structure, which culminates in terminal renal insufficiency. Interfering with progression continues to be a major challenge and is at the forefront of renal research. This review focuses on recent progress in the understanding of the mechanisms of progression and efforts to interfere with this process.

RECENT FINDINGS

In addition to the long-known risk factors (hypertension and inadequate activation of the renin-angiotensin system), several novel risk factors and pathomechanisms, such as obesity, hyperglycemia, smoking, and several hormones, have recently been identified and investigated. Furthermore, the specific and blood pressure-independent pathogenetic roles of the sympathetic nervous system and the endothelin system in progression have been further clarified. Finally, novel animal models and techniques for studying specific aspects of progression have been developed and introduced.

SUMMARY

Recently, considerable progress has been made concerning novel risk factors, understanding the underlying pathomechanisms, and interfering with the course of progression of renal diseases. Such improved insights will undoubtedly lead to new strategies in the future.