GSTM1 and type 2 diabetes mellitus: In overall populations, combinations of GSTM1, GSTT1 and GSTP1 polymorphisms was considerably associated with T2DM risk (model 1: OR = 1.47, 95% CI = 1.10–1.96, model 9: OR = 2.71, 95% CI = 1.56–4.72, model 10: OR = 2.69, 95% CI = 1.74–4.17, Table 7).