Glucagon-like peptide-1 receptor agonist liraglutide inhibits endothelin-1 in endothelial cell by repressing nuclear factor-kappa B activation.

PURPOSE

The increase in endothelin-1 (ET-1) and the decrease in endothelial nitric oxide synthase (eNOS) both induce vasoconstriction and lead to molecular changes associated with diabetes mellitus and atherosclerosis. Glucagon-like peptide-1 (GLP-1) activation stimulates insulin secretion and may prevent atherosclerosis by increasing eNOS synthesis. However, there is paucity of information on the effect of GLP-1 activation on ET-1 expression. This study was conducted to address this issue.

METHODS AND RESULTS

Human umbilical vein endothelial cells (HUVECs) were incubated with different concentrations of liraglutide, a GLP-1 agonist, and the expression of ET-1 and eNOS and activity of NF-κB were measured. Liraglutide, in a concentration-dependent manner, was observed to promote eNOS expression and to inhibit ET-1 expression both at mRNA and protein levels. Liraglutide also inhibited NF-κB phosphorylation and its translocation from cytoplasm to the nucleus. To ascertain the role of NF-κB activation in the altered expression of ET-1 and eNOS, we treated HUVECs with phorbol 12-myristate 13-acetate (PMA). PMA activated NF-κB and reversed the effects of liraglutide on eNOS and ET-1 expression. The effects of PMA on eNOS and ET-1 expression were reproduced in experiments wherein cells were treated with TNF-α. Further, we measured the generation of IL-6, apowerful pro-inflammatory molecule released by endothelial cells, as a measure of cellular function. PMA increased IL-6 generation, and this effect was blocked by liraglutide.

CONCLUSIONS

Our observations suggest liraglutide suppresses ET-1 expression by inhibiting the phosphorylation of NF-κB. This mechanism may underlie the potential anti-atherosclerotic effects of GLP-1 agonists. Of note, these effects of liraglutide were seen in an in vitro setting wherein cellular glucose concentrations were elevated.