DPP4 and diabetes mellitus: Various pharmacotherapeutic groups have been used for the treatment of diabetes mellitus: biguanides, insulin secretagogues, thiazolidinediones, alpha-glucosidase inhibitors, DPP-4 inhibitors, GLP-1 receptor agonists, SGLT2 inhibitors, insulins, combined medicinal products (DPP4 inhibitors plus metformin ((sitagliptin; vildagliptin)/metformin), SGLT2 inhibitors plus metformin ((dapagliflozin; empagliflozin)/metformin)).