Synthesis and Bioactivity Evaluation of Dipeptidyl Peptidase IV Resistant Glucagon-like Peptide-1 Analogues

Glucagon-like peptide -1 (GLP-1) is an incretin hormone displaying glucose-dependent stimulation of insulin secretion and trophic effects on the pancreatic β-cells. However, GLP-1 is rapidly degraded to GLP-1(9-36) by dipeptidyl peptidase-IV (DPP-IV), which removes the N-terminal dipeptide His7-Ala8. The rapid inactivation of GLP-1 in the blood circulation limits its clinical application. Hence, we replaced the enzymatic hydrolyzation position Ala8 with other natural amino acids. The GLP-1 analogues were synthesized rapidly and efficiently under microwave irradiation, using Fmoc/tBu orthogonal protection strategy. Studies on blood-glucose-lowering effect of GLP-1 analogues in vivo were undertaken using 10-week-old male Kunming mice. The metabolic stability was tested by incubation with dipeptidyl peptidase-IV (DPP-IV). Generally, Xaa8-GLP-1 analogues exhibit resistance to DPP-IV degradation in vitro and stronger hypoglycemic effect than GLP-1. This may help to understand the structure-activity relationship of GLP-1 analogues.