DPP4 and type 2 diabetes mellitus: Novel therapeutic druggable targets for the management of T2DM have been emerging, namely carbohydrate-hydrolyzing enzymes α-amylase and α-glucosidase, fructose-1,6-bisphosphatase (FBPase), protein tyrosine phosphatase 1B (PTP-1B), dipeptidyl peptidase-4 (DPP-4) and glycogen phosphorylase (GP).