Genetic polymorphisms in extracellular superoxide dismutase Leu53Leu, Arg213Gly, and Ala40Thr and susceptibility to type 2 diabetes mellitus.

The most common type of endocrine disease is type 2 diabetes mellitus (T2DM); genetic factors contribute to the development to T2DM. In this study, we investigated the role of the Leu53Leu, Arg213Gly, and Ala40Thr polymorphisms in extracellular superoxide dismutase (EC-SOD) gene in the development of T2DM in a Chinese population. DNA was extracted from peripheral blood samples obtained from 256 T2DM patients and 324 control subjects recruited from our hospital between January 2013 and March 2015. DNA was genotyped by polymerase chain reaction-restriction fragment length polymorphism. The obtained data was then statistically analyzed. The chi-square test revealed a statistically significant difference in the genotype frequencies of EC-SOD Ala40Thr (χ = 13.26, P = 0.001) between the patients and controls. Unconditional regression analysis indicated that the GA and AA genotypes of EC-SOD Ala40Thr were associated with an increased risk of T2DM compared to the GG genotype {adjusted odds ratio (OR) [95% confidence interval (CI)] = 1.46 (1.01-2.11) and 2.67 (1.48-4.85), respectively}. In the dominant model, the GA+AA genotype of EC-SOD Ala40Thr was correlated with a higher risk of T2DM, in comparison with the GG genotype (OR = 1.64, 95%CI = 1.16-2.33). In the recessive model, AA of EC-SOD Ala40Thr showed a 2.19-fold higher risk of developing T2DM than the GG+GA genotype. In conclusion, people with the Ala40Thr polymorphism in EC-SOD are at a higher risk of developing T2DM; therefore, this may be utilized as a biomarker for early screening of T2DM in a Chinese population.