Gender specific association of aldosterone synthase gene polymorphism with renal survival in patients with IgA nephropathy

Diabetes and Renin-Angiotensin-Aldosterone System: Pathophysiology and Genetics

Diabetes mellitus (DM) is a metabolic disorder and characterized by hyperglycemia. Being a concern of both the developed and developing world, diabetes is a global health burden and is a major cause of mortality world-wide. The most common is the type 2 diabetes mellitus (T2DM), which is mainly caused by resistance to insulin. Long-term complications of diabetes cause microvascular related problems (eg. nephropathy, neuropathy and retinopathy) along with macrovascular complications (eg. cardiovascular diseases, ischemic heart disease, peripheral vascular disease). Renin-angiotensin-aldosterone system (RAAS) regulates homeostasis of body fluid that in turn, maintains blood pressure. Thus, RAAS plays pivotal role in the pathogenesis of long-term DM complications like cardiovascular diseases and chronic kidney diseases. T2DM is a polygenic disease, and the roles of RAAS components in insulin signaling pathway and insulin resistance have been well documented. Hyperglycemia has been found to be associated with the increased plasma renin activity, arterial pressure and renal vascular resistance. Several studies have reported involvement of single variants within particular genes in initiation and development of T2D using different approaches. This chapter aims to investigate and discuss potential genetic polymorphisms underlying T2D identified through candidate gene studies, genetic linkage studies, genome wide association studies.

Gene-gene interactions in renin-angiotensin-aldosterone system contributes to end-stage renal disease susceptibility in a Han Chinese population

Objective. In this study, we investigated whether RAAS gene single nucleotide polymorphisms (SNPs) and their interactions were associated with end-stage renal stage (ESRD). Methodology and Results. This was a case-control study for 647 ESRD cases and 644 controls. AGT (M235T (rs699) and T174M (rs4762)), AGTR1 (A1166C (rs5186) and C573T (rs5182)), ACE (I/D (rs1799752) and G2350A (rs4343)), and CYP11B2 C-344T (rs1799998) were genotyped and compared between cases and controls to identify SNPs associated with ESRD susceptibility. Multifactor dimensionality reduction (MDR) was used to identify gene-gene interactions. Several RAAS genes were associated with ESRD: AGT M235T, ACE I/D, ACE G2350A, and CYP11B2 C-344T. By MDR analysis, a three-locus model (ACE ID/ACE G2350A/CYP11B2 C-344T) of gene-gene interaction was the best for predicting ESRD risk, and its maximum testing accuracy was 56.08% and maximum cross-validation consistency was 9/10. ESRD risk was higher with the simultaneous occurrence of ACE I/D DD-ACE G2350A AA. AGT, ACE, and CYP11B2 gene polymorphisms are associated with ESRD. Conclusions. The gene-gene interaction effects of ACE I/D, ACE G2350A, and CYP11B2 C-344T polymorphisms are more important than individual factors for ESRD development among Han Chinese.

Association of aldosterone synthase (CYP11B2) gene -344T/C polymorphism with the risk of primary chronic glomerulonephritis in the Polish population

INTRODUCTION

We evaluate whether angiotensinogen AGT M235T (rs699), angiotensin-converting enzyme ACE (I/D) (rs4646994) and aldosterone synthase CYP11B2 -344C/T (rs1799998) polymorphisms can be genetic risk factors of chronic glomerulonephritis (GN) in the Polish population.

MATERIALS AND METHODS

The study was conducted in 140 patients with primary chronic GN: mesangial proliferative GN (MesPGN) (n = 49), IgA nephropathy (IgAN) (n = 31), membranous nephropathy (MN) (n = 27), focal segmental glomerulosclerosis (FSGS) (n = 25), membranoproliferative GN (MPGN) (n = 4), and minimal change disease (MCD) (n = 4), and controls (n = 187). Genotypes were determined by HRM curve analysis for AGT M235T, by PCR and agarose gel separation for ACE (I/D), and by PCR-RFLP for CYP11B2 -344C/T.

RESULTS

We found a significant association of the CYP11B2 -344C/T polymorphism in the recessive model with all subtypes of GN (OR = 1.925 (95% CI = 1.152-3.219, p = 0.0118, p(corr) = 0.0354)). We also observed that the CYP11B2 -344C/T polymorphism in the recessive model may also be an independent significant risk factor of IgAN (OR = 2.743 (95% CI = 1.219-6.172, p = 0.0122, p(corr) = 0.0366)), FSGS (OR = 2.895 (95% CI = 1.200-6.985, p = 0.0145, p(corr) = 0.0435)), and all proliferative GNs (MesPGN, IgAN, MPGN) (OR = 2.171 (95% CI = 1.211-3.894, p = 0.0084, p(corr) = 0.0252)).

CONCLUSION

Our results suggest that the CYP11B2 -344C/T polymorphism might be an independent risk factor of IgAN, FSGS and all proliferative chronic GNs.

Associations of the -344 T>C and the 3097 G>A polymorphisms of CYP11B2 gene with hypertension, type 2 diabetes, and metabolic syndrome in a French population

BACKGROUND

Aldosterone can affect both blood pressure (BP) and glucose metabolism. We assessed the association of two polymorphisms -344 T>C and the 3097 G>A in the aldosterone synthase gene (CYP11B2) with prevalent and incident hypertension (HT), type 2 diabetes (T2D), and the metabolic syndrome (MetS).

METHODS

We studied the 5,212 participants to D.E.S.I.R. (Data from Epidemiologic Study on the Insulin Resistance syndrome), a cohort from French general population. Genotyping was done by a TaqMan assay. Analysis of covariance, multivariate logistic regression (adjusted for age, MetS components) and haplotype analysis were performed.

RESULTS

The prevalences and 9-year incidences were 16.7 and 36.1% for HT, 2.6 and 6.2% for T2D, and 19.3 and 25.1% for the MetS. Risk for incident HT was reduced with the AA genotype of 3097 G>A, adjusted odds ratios (OR): 0.67; p = 0.04. The prevalence of HT was lower in women carrying the C allele of -344 T>C, OR 0.75; p = 0.03 for the TC genotype and 0.69; p = 0.03 for the CC genotype. In men, incident T2D was associated with both polymorphisms, adjusted OR for -344 T>C: 1.63; p = 0.04 for TC genotype and 2.12; p = 0.008 for CC genotype; for the 3097 G>A: the AA genotype was associated with a lower risk, OR 0.23; p = 0.02. In men, incident MetS was associated with 3097 G>A, OR: 0.57; p = 0.02 for AA genotype. Significant associations between haplotype combinations and the prevalence or incidence of the three diseases were also found.

CONCLUSION

The -344 T>C and 3097 G>A polymorphisms in the CYP11B2 are associated with T2D, hypertension and the MetS in European subjects with gender variations.

A systemic review of the relationship between aldosterone synthase - 344 C/T polymorphism and hypertension in Han

Many studies reported the association between aldosterone synthase gene CYP11B2 polymorphism and essential hypertension in Chinese. So far, no meta- analysis was conducted between the etiology of essential hypertension and CYP11B2 -344 C/T polymorphism in Han Chinese, the majority (93% of the total population) in China. Recruited literature was based on searching the Cochrane Library, MEDLINE, EMBASE, the Chinese Biomedicine Database (CBM), CNKI, VIP, and reference lists of articles without language restrictions. Nine studies with case-control involving 4259 unselected essential hypertension patients and 3213 controls were included in the analysis. From the nine homogeneous studies with gender, age, and ethnicity matched controls, we found no significant association between the etiology of essential hypertension and the -344 C/T variant in Han Chinese with random effect models (for homozygous CC: odds ratio (OR), 1.04, 95% confidence interval (CI), 0.791.37, P = 0.79; for allele C: OR, 1.04, 95% CI, 0.921.18, P = 0.56). No significant association was observed between CYP11B2 -344 C/T polymorphism and hypertension susceptibility in both sexes. Current large sample analysis did not support the association between the etiology of essential hypertension and CYP11B2 - 344 C/T polymorphism in Han Chinese.

Toll-like receptor 9 affects severity of IgA nephropathy

Environmental pathogens are suspected to aggravate renal injury in IgA nephropathy (IgAN), but neither underlying mechanisms nor specific exogenous antigens have been identified. In this study, a genome-wide scan of ddY mice, which spontaneously develop IgAN, was performed, and myeloid differentiation factor 88 (MyD88) was identified as a candidate gene for progression of renal injury (chi(2) = 21.103, P = 0.00017). For evaluation of the potential influence of environmental pathogens on progression of renal injury, ddY mice were housed in either conventional or specific pathogen-free conditions. Expression of genes encoding toll-like receptors (TLR) and the signaling molecule MyD88 were quantified by real-time reverse transcription-PCR in splenocytes. Although the housing conditions did not affect the prevalence of IgAN, the severity of renal injuries was higher in the conventionally housed group. Mice that had IgAN and were housed in conventional conditions had higher levels of TLR9 and MyD88 transcripts than mice that had IgAN and were housed in specific pathogen-free conditions. Furthermore, nasal challenge with CpG-oligodeoxynucleotides, which are ligands for TLR9, aggravated renal injury, led to strong Th1 polarization, and increased serum and mesangial IgA. For investigation of whether these results may be generalizable to humans, single-nucleotide polymorphisms in the TLR9 and MyD88 genes were analyzed in two cohorts of patients with IgAN; an association was observed between TLR9 polymorphisms and disease progression. In summary, these findings suggest that activation of the TLR9/MyD88 pathway by common antigens may affect the severity of IgAN.

Haplotypic analyses of the aldosterone synthase gene CYP11B2 associated with stage-2 hypertension in northern Han Chinese

The objective of this study was to investigate the association of polymorphisms in the aldosterone synthase gene CYP11B2 (-344T/C, Lys173/Arg, and an intronic conversion [IC]) with stage-2 hypertension in northern Han Chinese. A total of 503 hypertensives and their age-, gender-, and area-matched controls were included in this study. The female hypertensives had significantly higher frequencies of the -344T, 173Lys, and IC-conversion alleles (p = 0.002, 0.002, and 0.014, respectively). The estimated frequency of haplotype composed of the -344T, 173Lys, and IC-conversion alleles (haplotype 4) was significantly higher in the female hypertensives compared with their controls (p = 0.007). Using a multivariate score test, we found that haplotype 4 remained associated with female hypertension after the adjustment for covariates (p = 0.003), while the haplotype 3 of T-Arg-WT showed a protective effect both in the males and in the females (p = 0.03 and 0.006, respectively). The odds ratio for haplotype phase of 4-4 was 2.60 (95% CI, 1.21-5.58) and for 3-3, 0.20 (95% CI, 0.03-0.77). These results indicate that the Lys173 and the IC-conversion allele of the CYP11B2 gene confer an increased risk for stage-2 hypertension in northern Han Chinese women.