INS and type 2 diabetes mellitus: In this study, we aimed to investigate the distributive characteristics of SLC22A1 rs594709 and SLC47A1 rs2289669 between T2DM patients and healthy subjects and the influences of SLC22A1 rs594709 and SLC47A1 rs2289669 polymorphisms on metformin's therapeutic efficacy in glucose lowering, serum lipids, and insulin sensitivity.