DPP4 and type 2 diabetes mellitus: In contrast to type 1 diabetes, which is treated only with insulin, drugs with different mechanisms have been developed for T2DM treatment, including biguanides (BG), sulfonylureas (SU), meglitinides (MG), thiazolidinediones (TZD), alpha-glucosidase inhibitors (AGI), dipeptidyl peptidase-4 inhibitors (DPP-4 inhibitors), glucagon-like peptide-1 (GLP-1) agonists, sodium glucose co-transporter-2 inhibitors (SGLT-2), etc. [24].