Abstract 12049: Reactive Oxygen Species Causes Vascular Dysfunction in Murine Model of Endothelial Insulin Sensitivity via Activation of Nox2 and Reduction of eNOS Activity
The increasing number of individuals suffering from Type 2 Diabetes is a significant health burden. It is well-established that insulin stimulates generation of the endothelium-derived anti-atherosclerotic signalling radical, nitric oxide. We investigated the hypothesis that increasing insulin sensitivity in the endothelium leads to incraesed NO bioavailability and vascular function. A novel transgenic mouse over-expressing Type A human Insulin Receptor (HIRECO) in the endothelium, driven by the Tie-2 promoter-enhancer was generated to explore the effects of increasing insulin signalling in the vasculature. Tissues and pulmonary endothelial cells from the HIRECO mice were analysed using RT-PCR to confirm significant levels of human insulin receptor mRNA. Lucigenin-enhanced chemiluminescence was used to measure superoxide anion levels while vasomotor function was assessed in thoracic aortic rings in organ baths. No significant morphological, metabolic phenotype or blood pressure abnormalities were found in HIRECO mice compared to wild type (WT) littermates. HIRECO mice exhibited significant endothelial dysfunction with a blunted response to acetylcholine. The impaired aortic response to acetylcholine was normalized by the NADPH oxidase inhibitor peptide, gp91ds-tat. Basal nitric oxide bioactivity and insulin-stimulated eNOS activation were significantly decreased in HIRECO compared to WT littermates. However, basal eNOS and Akt phosphorylation in endothelial cells of HIRECO mice was enhanced 1.56 fold compared to WT littermates. HIRECO mice had a 1.65-fold increase in the level of superoxide anion production compared to WT. Additionally, increased expressions of NADPH oxidase isoform, Nox2 and redox-sensitive transcription factor, Nrf2 were detected in HIRECO endothelial cells.These data clearly suggest that enhanced oxidative stress in a novel murine model of increased endothelial insulin signalling, leads to reduced bioavailability of nitric oxide and vascular dysfunction. These data demonstrate for the first time, that increased insulin sensitivity in the endothelium increases the generation of free radical generation via regulation of NOX2 protein levels and reduces nitric oxide bioavailability.
- © 2013 by American Heart Association, Inc.