Advances of N-terminal modifications of GLP-1 and their applications for the treatment of type 2 diabetes

Glucagon-like peptide-1 (GLP-1) is an endogenous insulinotropic hormone with excellent blood glucose-lowering activity, however, it is rapidly inactivated in the plasma mainly by dipeptidyl peptidase IV (DPP-IV). To overcome this problem, various N-terminal modifications of GLP-1 have been performed to prolong the in vivo biological activity,by improving the DPP-IV resistance while retaining receptor affinity and receptor activation. These studies have included modifications of His⁷, Ala⁸ or Glu⁹ at the N-terminus of GLP-1 and some other modifications. Among them, Ala⁸ substitutions with glycine (Gly⁸) and α-aminoisobutyric acid (Aib⁸) have been clinically applied in the development of diabetic therapy, such as Exenatide, Semaglutide, Albiglutide and Taspoglutide. In this review, we introduce N-terminal modifications of GLP-1 that have been reported, and discuss their potential and challenges for the treatment of type 2 diabetes.