DPP4 and type 2 diabetes mellitus: The current treatment of T2DM disease patients is based on drugs such as metformin, sulfonylureas, dipeptidyl peptidase-4 (DPP-4) inhibitors, sodium–glucose cotransporter 2 (SGLT2) inhibitors, glucagon-like peptide-1 (GLP-1) receptor agonists, and thiazolidinediones, which work to lower blood sugar levels by increasing the sensitivity of the body to insulin but are associated with side effects.