GSTP1 and type 2 diabetes mellitus: This is the first study investigating the association between the combined effect of GSTM1, GSTT1, and GSTP1 genotypes in a population consisting of a control group and T2DM patients with and without DSPN in Romania and to our knowledge the first study of its kind to investigate the effect of these combined genotypes on the occurrence of DSPN in T2DM.