Abstract 16057: Endothelial Dysfunction is Associated With Abnormal Insulin-Mediated eNOS Regulation and NFκB Activation in Endothelial Cells From Diabetic Patients
Disruption of endothelial function contributes to cardiovascular risk in patients with diabetes. Experimental studies suggest that impaired endothelial insulin signaling leads to reduced nitric oxide bioavailability and promotes atherosclerosis. Activation of the pro-inflammatory transcription factor, nuclear factor κB (NFκB), may mediate endothelial insulin resistance. We sought to establish whether similar mechanisms operate in the endothelium in human diabetes. Using quantitative immunofluorescence, we examined protein expression in freshly isolated venous endothelial cells obtained by j-wire biopsy from patients with diabetes (n=25) and age-matched controls (n=21). Unexpectedly, we observed markedly higher basal eNOS phosphorylation in diabetes (P<0.01) without a difference in total eNOS expression. In healthy controls, administration of insulin to endothelial cells produced a 30±9% increase in eNOS phosphorylation. In contrast, insulin-induced eNOS activation was absent in patients with diabetes (Figure). We found evidence of higher NFκB activity in the diabetic endothelium. Expression of p65, an NFκB regulatory subunit, was 43% higher in diabetic patients (P=0.04) whereas expression of IκBα, an inhibitor of NFκB, was 48% lower (P=0.03). Intracellular adhesion molecule, an inflammatory gene regulated by NFκB, was 117% higher in diabetic patients (P<0.01). Patients with diabetes demonstrated endothelial dysfunction evidenced by lower flow-mediated dilation compared to controls (7.5±0.5% vs. 14.5±1.6%, P<0.01). Insulin-mediated eNOS phosphorylation was associated with flow-mediated dilation (r=0.78, P=0.01). We provide direct evidence for the presence of inflammatory activation and insulin resistance in the endothelium of humans with diabetes. Our findings are consistent with the possibility that abnormal eNOS signaling, in conjunction with NFκB upregulation, may contribute to endothelial dysfunction in diabetes.
- © 2011 by American Heart Association, Inc.