Glucagon-like peptide-1 activates endothelial nitric oxide synthase in human umbilical vein endothelial cells

Aim: To investigate the effects of glucagon-like peptide-1 (GLP-1) on endothelial NO synthase (eNOS) in human umbilical vein endothelial cells (HUVECs), and elucidate whether GLP-1 receptor (GLP-1R) and GLP-1(9-36) are involved in these effects. Methods: HUVECs were used. The activity of eNOS was measured with NOS assay kit. Phosphorylated and total eNOS proteins were detected using Western blot analysis. The level of eNOS mRNA was quantified with real-time RT-PCR. Results: Incubation of HUVECs with GLP-1 (50-5000 pmol/L) for 30 min significantly increased the activity of eNOS. Incubation of HUVECs with GLP-1 (500-5000 pmol/L) for 5 or 10 min increased eNOS phosphorylated at ser-1177. Incubation with GLP-1 (5000 pmol/L) for 48 h elevated the level of eNOS protein, did not affect the level of eNOS mRNA. GLP-1R agonists exenatide and GLP-1(9-36) at the concentration of 5000 pmol/L increased the activity, phosphorylation and protein level of eNOS. GLP-1R antagonist exendin(9-39) or DPP-4 inhibitor sitagliptin, which abolished GLP-1(9-36) formation, at the concentration of 5000 pmol/L partially blocked the effects of GLP-1 on eNOS. Conclusion: GLP-1 upregulated the activity and protein expression of eNOS in HUVECs through the GLP-1R-dependent and GLP-1(9-36)-related pathways. GLP-1 may prevent or delay the formation of atherosclerosis in diabetes mellitus by improving the function of eNOS.