DPP4 and type 2 diabetes mellitus: Conventional T2D treatments involve dietary recommendations and treatment with biguanides, α-glucosidase inhibitors, glucagon-like peptide 1 receptor (GLP-1R) agonists, dipeptidyl peptidase 4 (DPP-4) inhibitors, sodium/glucose cotransporter 2 (SGLT2) inhibitors, insulin secretagogues (sulfonylureas or non-sulfonylureas), thiazolidinediones, and exogenous insulin.