Reactive oxygen species are considered to play a role in the development of type 2 diabetes mellitus (T2DM) and its complications. 8-Oxoguanine, which is one of the major oxidation base lesions produced by reactive oxygen species, may cause G:C to T:A transversion mutations because it can mispair with adenine. hMTH1 (human mutT homolog 1), hOGG1 (human 8-oxoguanine glycosylase 1) and MUTYH (human mutY homolog) genes constitute the 8-oxoG repair pathway. In this study, we screened for the polymorphism variants Val83Met (c.247G>A, rs4866) in hMTH1; c.-53G>C (rs56387615), c.-23A>G (rs1801129) and c.-18G>T (rs1801126) in the 5'-UTR of hOGG1; and AluYb8 insertion in MUTYH (AluYb8MUTYH, rs10527342) and investigated their synergistic effect on the risk of T2DM in the Chinese population. The genotypes were determined by electrophoresis, a high-resolution melting technique and sequencing of PCR products. Our results showed that the c.247G>A variant in the hMTH1 gene increased the risk of T2DM in >55 years of age groups (OR=1.579; 95%CI: 1.029-2.421). The set of c.-53G>C, c.-23A>G and c.-18G>T variants detected in the 5'-UTR of the hOGG1 gene and the AluYb8 insertion in the MUTYH gene were each associated with an increased risk of T2DM (OR=1.507, 95%CI: 1.122-2.024; OR=1.229, 95%CI: 1.030-1.466, respectively). Combined analysis of the variations among the three genes suggested that the c.247G>A variant in hMTH1 combined with AluYb8MUTYH variant had a synergistic effect on increasing the risk of T2DM (OR=1.635; 95%CI: 1.147-2.330). This synergy was also observed between the variants in the 5'-UTR of the hOGG1 and the AluYb8MUTYH variant (OR=1.804; 95%CI: 1.254-2.595). Our results suggest, for the first time, the combined effects of AluYb8MUTYH with either hMTH1 c.247G>A or variants in the 5'-UTR of the hOGG1 on the risk of T2DM.
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