PREP and type 2 diabetes mellitus: Dipeptidyl peptidase IV (DPP-IV) (EC 3.4.14.5), a serine exopeptidase belonging to the prolyl oligopeptidase family, is considered an interesting therapeutic target for the management of type 2 diabetes (T2D), because it plays a key role in glucose metabolism by the N-terminal truncation and inactivation of the incretins glucagon-like peptide 1 (GLP-1) and gastrointestinal insulinotropic peptide (GIP) that together are responsible for up to 70% of post-prandial insulin secretion [15].