GLP-1-dependent and independent effects and molecular mechanisms of a dipeptidyl peptidase 4 inhibitor in vascular endothelial cells

The potential atheroprotective effects of glucagon-like peptide-1 (GLP-1), long-acting GLP-1 analogues and inhibitors of the enzyme dipeptidyl peptidase 4 (DPP-4) are currently the subject of intense research. Recent evidence suggests the effects of DPP-IV inhibitors, may, in-part, be mediated by GLP-1 independent molecular mechanisms. In this report we demonstrate that treatment of human vascular endothelial cells with the DPP-IV inhibitor sitagliptin inhibited tumour necrosis factor alpha (TNFα) induction of plasminogen activator inhibitor type-1 (PAI-1), intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) mRNA and protein expression and that this effect was observed to be both GLP-1-dependent and independent. Importantly we identify a molecular mechanism involving sitagliptin-mediated attenuation of TNFα-mediated induction of NFκB and orphan nuclear receptor NUR77 mRNA expression, also able to be reproduced, in part, independent of GLP-1. Taken together these observations may serve to provide a molecular explanation, involving transcriptional regulation of gene expression, for recent in vivo studies suggesting DPP-IV inhibitors may have novel, GLP-1 independent, effects in acting to attenuate endothelial cell dysfunction and atherogenesis.