DPP4 and type 2 diabetes mellitus: Since native GLP-1 is immediately inactivated by the ubiquitous serine protease dipeptidyl peptidase enzyme (DPP)-4, degradation-resistant analogs of GLP-1 (exendin-4, liraglutide, semaglutide, dulaglutide, albiglutide or lixisesnatide) have been developed and approved for use as second or third-line therapy in the treatment of T2D [9].