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Insulin resistance does not diminish eNOS expression, phosphorylation, or binding to HSP-90
David Fulton1, M Brennan Harris, Bruce E Kemp
1Vascular Biology Center, Medical College of Georgia, 1459 Laney Walker Blvd., Augusta, GA 30912, USA. dfulton@mcg.edu
Summary
Vascular dysfunction in obese rats is not due to changes in endothelial nitric oxide synthase (eNOS) expression or its regulation. Other factors likely contribute to this condition in insulin resistance.
Area of Science:
- Cardiovascular Physiology
- Metabolic Syndrome Research
- Molecular Biology
Background:
- Obese Zucker rats (OZR) exhibit impaired endothelium-dependent vasodilation, a hallmark of vascular dysfunction.
- Insulin resistance is associated with cardiovascular complications, but the underlying molecular mechanisms remain unclear.
Purpose of the Study:
- To investigate if reduced expression or altered posttranslational regulation of endothelial nitric oxide synthase (eNOS) contributes to vascular dysfunction in OZR.
- To examine eNOS regulation in other models of insulin resistance.
Main Methods:
- Quantitative analysis of eNOS expression and mRNA levels in various tissues of OZR and lean Zucker rats (LZR).
- Assessment of eNOS phosphorylation at key sites (S632, T494, S1176) and its association with heat shock protein 90.
- In vivo studies using ob/ob mice and fructose-fed rats, and in vitro studies with endothelial cells.
Main Results:
- No significant differences in eNOS expression or mRNA levels were found between LZR and OZR.
- While phosphorylation at S632 and T494 was unchanged, S1176 phosphorylation was enhanced in OZR, but not consistently across all insulin-resistant models.
- The association of heat shock protein 90 with eNOS was similar in both groups.
Conclusions:
- Altered eNOS expression or posttranslational regulation does not appear to be the primary cause of vascular dysfunction in insulin-resistant OZR.
- Other mechanisms, including altered eNOS localization, cofactor/substrate availability, or increased superoxide production, may be responsible for the observed vascular deficits.