Abstract 18877: Novel Mouse Model for Testing NADPH Oxidase (Nox2) Role in Insulin Resistance Mediated Endothelial Dysfunction
Introduction: Insulin resistance (IR) plays a pivotal role in type 2 diabetes, obesity and hypercholesterolemia. Reactive oxygen species (ROS) play a key role in IR related endothelial dysfunction. We have reported that, superoxide (SO), an important ROS is produced at higher levels in IR and established that NADPH oxidase (Nox) is the primary source of SO in IR endothelium. Here we report our study to ascertain the role of Nox2 in IR.
Methods: A unique murine model of endothelium specific IR, Endothelial Specific Mutated Insulin Receptor Over-expression (ESMIRO) and mice with universal deletion of Nox2 gene (Nox2y/-) were used here. Nox2y/- mice was crossed with ESMIRO to generate double transgenics (ESMIRO/Nox2y/-). Endothelial function was analysed by measuring 1. aortic ring relaxation. 2. superoxide production. Expression of Nox and ROS related genes were examined by PCR and Western blotting.
Results: Realtime PCR and Western blot of organs and pulmonary endothelial cells (PEC) confirmed the total loss of Nox2 in ESMIRO/Nox2y/-. Growth rate and organ weights were unaltered in ESMIRO/Nox2y/-. However, there was a trend towards reduced BP in double transgenics (119±1 mmHg in ESMIRO Vs 114±2 mmHg in ESMIRO/Nox2y/-; p=0.06). Metabolic characteristics including ITT and GTT showed no difference between two lines. Blood insulin levels before and after glucose injection were similar. Basal superoxide in PEC of ESMIRO/Nox2y/- were 240±11% (p=0.02) reduced when compared to ESMIRO. Nitric oxide (NO) mediated vascular relaxation was improved in double transgenic animals (100±4% in response to 1000 nM Ach in ESMIRO/Nox2y/- Vs 77±6% in ESMIRO). There was no change in endothelial independent relaxation (109±5% in response to 1000 nM SNP in ESMIRO/Nox2y/- Vs 104±6% in ESMIRO). Realtime PCR showed that the important ROS scavenger superoxide dismutase 1 (SOD1) expression was increased above 300% in ESMIRO lungs compared to ESMIRO/Nox2y/-. Other Nox and ROS related genes (Nox4, p22, p47, p67, SOD2, SOD3, eNOS & catalase) expression were unchanged.
Conclusions: These results show that Nox2NADPH oxidase is a key source of the excess superoxide seen in a model of endothelium specific insulin resistance. Targeting Nox2 may be a useful therapeutic strategy in IR conditions.
- © 2012 by American Heart Association, Inc.