SLC22A1 and type 2 diabetes mellitus: In this study, we studied the correlation between SLC22A1, SLC22A2, SLC47A1, and SLC47A2 variants and the risk of T2DM in Han Chinese from Chaoshan, China; and explored the effect of genotype on FPG, HbA1c, FINS, HOMA-IR, and HOMA-IS in T2DM patients receiving metformin treatment.