Polymorphic variations in manganese superoxide dismutase (MnSOD) and endothelial nitric oxide synthase (eNOS) genes contribute to the development of type 2 diabetes mellitus in the Chinese Han population

Impaired antioxidant defense increases the oxidative stress and contributes to the development of type 2 diabetes mellitus (T2DM). MnSOD and eNOS are important antioxidant enzymes. This aim of this study was to verify the association of MnSOD and eNOS tagSNPs with T2DM in a Chinese Han population. Four tagSNPs of MnSOD and eight tagSNPs of eNOS were detected using TaqMan technology in 1272 healthy controls and 1234 T2DM patients. All study participants were unrelated members of the Han ethnic group in China. In this study, the frequency of the rs4880 MnSOD single nucleotide polymorphisms (SNP) genotype differed significantly between T2DM patients and controls [allele: P = 0.03, genotype: P = 0.04, odd's ratio (OR) = 1.26; 95% confidence interval (CI) = 1.07-1.49]. The A-T haplotype and G-T haplotype remained significant in T2DM after Bonferroni correction (P = 1.58 x 10(-6) and 8.00 x 10(-4), respectively) with a global p-value of 7.25 x 10(-8). The rs1799983 and rs891512 SNPs of eNOS differed significantly between T2DM patients and controls [rs1799983: corrected allele: P = 2.10 x 10(-3), corrected genotype: P = 6.30 x 10(-3), OR = 1.43 (95%CI = 1.18-1.73); rs891512, corrected allele: P = 3.50 x 10(-3), corrected genotype: P = 9.10 x 10(-3), OR = 1.70 (95%CI = 1.26-2.30)]. Following Bonferroni correction, none of the haplotypes of eNOS were significant in T2DM. These results indicate that common variants in MnSOD and eNOS increased the risk of T2DM in the Chinese Han population.