Identification of specific angiotensin-converting enzyme variants and haplotypes that confer risk and protection against type 2 diabetic nephropathy

Background Cross-sectional and family studies identified angiotensin-converting enzyme (ACE) gene as a risk factor for diabetic nephropathy (DN). The contribution of ACE gene variants to DN development and progression is controversial and varies among different ethnic/racial groups. Methods We investigated the association of three ACE gene variants with DN, rs1799752 insertion/deletion (I/D), rs1800764T/C and rs12449782A/G in 917 Tunisian type 2 diabetic (T2DM) patients: 515 with (DN) and 402 without (DWN) nephropathy. ACE genotyping was done by PCR-based assays; haplotype estimation was performed using H-Plus software (chi(2)-test based). Results Genotype frequency distributions of the three studied variants were in Hardy-Weinberg equilibrium. Minor allele frequency of rs1800764 was higher in DN patients than DWN patients or healthy controls, and minor allele frequency of rs1799752 was higher in DN than DWN patients. Higher frequency of rs1799752 and rs1800764 homozygous mutant genotypes was seen in DN compared to DWN patients. Of the three variants, only rs1799752 deletion/deletion (D/D) genotype was associated with a significant increase in albumin to creatinine ratios levels, and D/D carriers had elevated low-density lipoprotein, total cholesterol and urea. Three locus haplotype [rs1799752(I/D)/rs1800764(T/C)/rs12449782(A/G)] analysis revealed that the frequency of DCG haplotype was higher, while that of ITG and ICA haplotypes were lower among unselected type 2 diabetic patients. Taking ITA haplotype as reference, multivariate regression analysis confirmed the negative (ITG), and positive (DCG, DTG, DCA and DTA) association of specific ACE haplotypes with DN, after adjusting for potential nephropathy-linked covariates. Conclusions Our results support the involvement of specific ACE variants in DN pathogenesis and demonstrate the presence of DN-specific haplotypes at the ACE locus. Copyright (C) 2009 John Wiley & Sons, Ltd.