DPP4 and diabetes mellitus: Currently, therapeutic agents for DM include metformin, sulfonylureas, thiazolidinediones, glinides, glucagon-like peptide-1 (GLP-1) receptor agonists, sodium-glucose cotransporter 2 (SGLT2) inhibitors, dipeptidyl peptidase-4 (DPP-4) inhibitors, α-glucosidase inhibitors, and exogenous insulin [8,9].