ACE gene polymorphism and renal responsiveness to ACE inhibitors in IgA nephropathy patients

Role of angiotensin converting enzyme and angiotensinogen gene polymorphisms in angiotensin converting enzyme inhibitor-mediated antiproteinuric action in type 2 diabetic nephropathy patients

AIM

To investigate the role of genetic variants of angiotensin converting enzyme (ACE) and angiotensinogen (AGT) genes in the antiproteinuric efficacy of ACE inhibitor therapy in diabetic nephropathy (DN) patients.

METHODS

In the present study, 270 type 2 diabetes mellitus patients with nephropathy were enrolled and treated with ACE inhibitor (ramipril) and followed at 6 mo for renal function and albumin excretion by estimating serum creatinine, end stage renal disease, and albumin/creatinine ratio (ACR) in urine. Genotyping of ACE I/D and AGT M235T polymorphisms were performed by using primer specific polymerase chain reaction (PCR) and PCR-RFLP techniques, respectively.

RESULTS

Forty-eight percent of DN patients (responders) benefited with respect to proteinuria from ACE inhibitor therapy at 6 mo follow-up. A significant reduction in ACR was observed after 6 mo treatment with ACE inhibitor irrespective of whether DN patients were micro-albuminuric (≥ 30 and < 300 mg/g creatinine) or macro-albuminuric (≥ 300 mg/g creatinine) at the time of enrollment. However, macro-albuminuric patients (55%) showed better response to therapy. A reduction in urinary ACR was found independent of genotypes of ACE I/D and AGT M235T polymorphisms although macro-albuminuric patients having TT genotype showed statistically insignificant increased response (72%).

CONCLUSION

ACE inhibitor therapy reduced urinary ACR by ≥ 30% in 50% of DN patients and the response is independent of ACE I/D and AGT M235T polymorphisms.

High dose Losartan and ACE gene polymorphism in IgA nephritis

Background/aims Several studies have reported varying results of the influence of ACE gene on ACEI/ARB therapy. The efficacy of high dose ARB and its influence on ACE gene have not been explored. This is a 6 year randomised trial in IgA nephritis comparing high dose ARB (Losartan 200 mg/day) with normal dose ARB (Losartan 100 mg/day), normal dose ACEI (20 mg/day) and low dose ACEI (10 mg/day). Results Patients on high dose ARB had significantly lower proteinuria, 1.0 +/- 0.8 gm/day compared to 1.7 +/- 1.0 g/day in the other groups (P = 0.0005). The loss in eGFR was 0.7 ml min(-1)year(-1) for high dose ARB compared to 3.2-3.5 ml min(-1)year(-1) for the other three groups (P = 0.0005). There were more patients on high dose ARB with improvement in eGFR compared to other three groups (P < 0.001). Comparing patients with the three ACE genotypes DD, ID and II, all three groups responded well to therapy with decrease in proteinuria (P < 0.002). Only those on low dose ACEI (10 mg/day) with the I allele had increased in ESRF (P = 0.037). Conclusion High dose ARB is more efficacious in reducing proteinuria and preserving renal function when compared with normal dose ARB and ACEI, and also obviates the genomic influence of ACE gene polymorphism on renal survival.

Angiotensin converting enzyme insertion/deletion polymorphism and renoprotection in diabetic and nondiabetic nephropathies

Despite the huge amount of studies looking for candidate genes, the ACE gene remains the unique, well-characterized locus clearly associated with pathogenesis and progression of chronic kidney disease, and with response to treatment with drugs that directly interfere with the renin angiotensin system (RAS), such as angiotensin converting enzyme (ACE) inhibitors and angiotensin II receptor antagonists (ARA). The II genotype is protective against development and progression of type I and type II nephropathy and is associated with a slower progression of nondiabetic proteinuric kidney disease. ACE inhibitors are particularly effective at the stage of normoalbuminuria or microalbuminuria in both type I and type II diabetics with the II genotype, whereas the DD genotype is associated with a better response to ARA therapy in overt nephropathy of type II diabetes and to ACE inhibitors in male patients with nondiabetic proteinuric nephropathies. The role of other RAS or non-RAS polymorphisms and their possible interactions with different ACE I/D genotypes are less clearly defined. Thus, evaluating the ACE I/D polymorphism is a reliable tool to identify patients at risk and those who may benefit the most of renoprotective therapy with ACE inhibitors or ARA. This may guide pharmacologic therapy in individual patients and help design clinical trials in progressive nephropathies. Moreover, it might help optimize prevention and intervention strategies at population levels, in particular, in countries where resources are extremely limited and 1 million patients continue to die every year of cardiovascular or renal disease.

Angiotensin-Converting Enzyme Inhibitor versus Angiotensin 2 Receptor Antagonist Therapy and the Influence of Angiotensin-Converting Enzyme Gene Polymorphism in IgA Nephritis

Introduction: In this study of 109 patients with IgA nephritis (IgAN), we compared the long term effects on patients treated with angiotensin converting enzyme inhibitor (ACEI) or angiotensin receptor antagonist (ATRA) alone with respect to renal outcome in terms of ESRF from 1995 to 2006. The renal outcome is also correlated with the ACE gene ID polymorphism to study its influence on response to ACEI/ATRA therapy. Materials and Methods: Seventy-seven patients were on treatment with ACEI/ATRA (22 on ACEI alone, 47 on ATRA alone and 8 on both). The other 32 patients were on no treatment (control group). Results: Compared to controls, treated patients had lower serum creatinine (P<0.001), lower proteinuria (P<0.001) and fewer number progressing to ESRF (P<0.001). For those with the II and ID genotype there were significantly fewer patients with ESRF in the treatment group. With the DD genotype, treatment did not change the poor renal outcome with regard to ESRF. Patients on ACEI therapy had a higher incidence of ESRF compared to those on ATRA (P<0.001). For the control group, the projected number of years-to-ESRF was 10 years. For those on ACEI therapy it was 11 years, and for those on ATRA therapy it was 24 years. Among patients with the II genotype, those treated with ATRA had significantly less incidence of ESRF compared to those treated with ACEI (P<0.001). Conclusion: ATRA therapy was found to be effective in retarding disease progression to ESRF in IgAN compared to ACEI therapy. Genotyping showed better response to ATRA therapy only for those with the II genotype. Key words: End-stage renal failure, Genotyping, Reciprocal creatinine plots

Multiple Polymorphisms in the renin- angiotensin-aldosterone system (ACE, CYP11B2, AGTR1) and their contribution to hypertension in African Americans and Latinos in the multiethnic cohort

OBJECTIVE

When compared with other U.S. populations, African Americans have excess hypertension. Genetic variants in elements of the renin-angiotensin-aldosterone system (RAAS), namely the angiotensin-converting enzyme (ACE), aldosterone synthase (CYP11B2), and angiotensin II type 1 receptor (AGTR1) genes, have been associated with risk of hypertension in some populations.

METHODS

We genotyped the D/I polymorphism in the ACE gene, the C(-344)T polymorphism in the CYP11B2 gene, and the C(-535)T polymorphism in the AGTR1 gene among African American and Latino members of the Multiethnic Cohort Study (MEC) to determine their association with hypertension.

RESULTS

We observed no significant increase in the risk of hypertension for either African Americans or Latinos homozygous or heterozygous for the D allele of the ACE gene. Among African Americans we observed carriers of the (-344)T allele of CYP11B2 to be at increased risk of hypertension (versus CC genotype: TC genotype, OR = 1.66 [95% CI: 1.01-2.72]; TT genotype, OR = 1.74 [95% CI: 1.07-2.82]). There was also an increase in risk of hypertension associated with the AGTR1 T allele for African Americans (versus CC genotype: TC genotype, OR = 2.62 [95% CI: 1.46-4.72]; TT genotype, OR = 2.67 [95% CI: 1.51-4.74]). The associations observed with CYP11B2 and AGTR1 genotypes were not observed among Latinos.

CONCLUSION

These data suggest that the (-535)T allele of AGTR1 and (-344)T allele of CYP11B2 may increase hypertension risk among African Americans but not among Latinos. Characterization of the linkage disequilibrium and haplotype patterns in the RAAS pathway genes will be crucial to understanding differences in hypertension susceptibility in these ethnic populations.