Chronic exercise training improves vascular function and microvessel density in skeletal muscle of obese Zucker rats

Abstract

Previous studies have demonstrated that development of the metabolic syndrome is associated with impairments to the bioavailability of endothelium derived nitric oxide, vascular reactivity and skeletal muscle microvessel density. The present study used 7 week old lean (LZR) and obese Zucker rats to determine if chronic exercise training (9 weeks of treadmill running, 1 hour/day) would alleviate these impairments. Following completion of the exercise regimen, OZR experienced significant improvements in body weight, mean arterial pressure, insulin sensitivity and dyslipidemia as compared to their sedentary counterparts. Associated with these improvements in the indices of the metabolic syndrome were significant increases in the levels of vascular nitric oxide bioavailability under resting conditions and in response to challenge with acetylcholine. Vascular dilator reactivity in response to acetylcholine and prostacyclin was improved, and hyperconstrictor responses to adrenergic agonists were lessened. Gastrocnemius muscle microvessel density was improved in trained OZR, although not restored to the levels in LZR. As a result of these improvements in vascular structure and reactivity, functional hyperemia of in situ gastrocnemius muscle was improved in trained OZR as compared to sedentary animals. These results suggest that chronic exercise training can improve vascular function and skeletal muscle perfusion in OZR, and that this is correlated with an improvement in the indices of the metabolic syndrome. (NIH R01 DK64668; AHA 330194N)