GSTM1 and type 2 diabetes mellitus: An increased risk of T2DM was yielded on the combined effects of both GSTM1 and GSTP1 (model 4: OR = 1.84, 95% CI = 1.13–3.00, model 6: OR = 1.37, 95% CI = 1.03–1.82, Table 5) in overall analysis.