Abstract 14983: Paradoxical Endothelial Dysfunction in Murine Model of Increased Endothelial Insulin Sensitivity - Role of PYK2 and Reactive Oxygen Species
Introduction: Insulin resistant type 2 diabetes, is well-established as a risk factor for the development of cardiovascular diseases. Insulin sensitizing agents such as glitazones failed to improve cardiovascular mortality rates.
Hypothesis: Therefore, we investigated the effects of enhancing insulin sensitivity specifically in the endothelium on NO bioavailability and atherosclerosis. A novel transgenic mouse was generated with over-expressing endothelial cell type A human Insulin Receptor (HIRECO) was generated.
Methods: Real time PCR, western blotting and organ baths were used to evaluate levels of human insulin receptor mRNA, protein and vascular function, respectively. Lucigenin-enhanced chemiluminescence was used to measure reactive oxygen species generation in endothelial cells.
Results: No significant morphological or metabolic changes were found in the HIRECO compared to wild type mice. HIRECO endothelial cells demonstrated increased insulin sensitivity, measured by a basal increase in tyrosine phosphorylation of insulin receptor, Akt and eNOS. HIRECO mice demonstrated significant endothelial dysfunction which was normalized by a specific inhibitor of NADPH oxidase NOX2, as well as the superoxide dismutase mimetic. HIRECO mice demonstrated a significant increase in superoxide anion production compared to WT. Moreover, expression of proline-rich tyrosine kinase (PYK2) and the phosphorylation at the inhibitory tyrosine residue 657 of eNOS were significantly increased in HIRECO endothelial cells. Decreased insulin- induced eNOS activation was improved by inhibiting PYK2. HIRECO mice crossed with atherosclerosis-prone ApoE-deficient mice, exhibited increased levels of atherosclerotic plaque development.
Conclusion: Therefore, enhancing insulin sensitivity specifically in the endothelium, leads to a paradoxical decline in endothelial function, mediated by increased tyrosine phosphorylation of eNOS and reduced bioavailability of nitric oxide through superoxide generation in endothelial cells. The findings demonstrate for the first time, that targeting PYK2 and NOX2 as potential intervention in combating diabetes-associated cardiovascular diseases.
- Insulin resistance
- Endothelial function
- Reactive oxygen intermediates
- Diabetes (Type II)
Author Disclosures: H. Viswambharan: None. N. Yuldasheva: None. P. Sukumar: None. A. Sengupta: None. R. Cubbon: None. H. Imrie: None. M. Gage: None. N. Haywood: None. A. Skromna: None. N. Makova: None. P. Shah: None. A. Shah: None. C. Santos: None. S. Wheatcroft: None. M. Kearney: None.
- © 2014 by American Heart Association, Inc.