Metformin and dipeptidyl peptidase IV (DPP4) inhibitors, such as vildagliptin, sitagliptin, and alogliptin, which are well-known anti-diabetes drugs for type 2 diabetes mellitus (T2DM), had no effect on body weight or blood glucose in the T1DM animal models [18,19,20,21]. The gene discussed is DPP4; the disease is type 1 diabetes mellitus.