GCG and type 2 diabetes mellitus: Currently, T2DM can be managed with biguanides, sulfonylureas, meglitinide derivatives, alpha-glucosidase inhibitors, thiazolidinediones, selective sodium-glucose transporter-2 (SGLT2) inhibitors, insulins, amylinomimetics, bile acid sequestrants, dopamine agonists, and incretin-based therapies, which include glucagon-like peptide1 (GLP-1) agonists and DPP-4 inhibitors, of which sitagliptin was the first to be discovered and marketed [29, 30].