DPP4 and diabetes mellitus: Dipeptidyl peptidase-4 (DPP-4) inhibitors are a class of new oral antidiabetics for the treatment of type 2 diabetes mellitus (T2DM), which can not only regulate the metabolism of glucose and lipids in vivo, but also improve endothelial function and reduce the pro-oxidation and pro-inflammatory states of injured cells [23].