Exercise training blunts microvascular rarefaction in the metabolic syndrome

Physiol 291: H2483–H2492, 2006. First published June 23, 2006; doi:10.1152/ajpheart.00566.2006.—Reduced skeletal muscle mi-crovessel density (MVD) in the obese Zucker rat (OZR) model of the metabolic syndrome is a function of a chronic reduction in vascular nitric oxide (NO) bioavailability. Previous studies suggest that exercise can improve NO bioavailability and reduce chronic inflammation and that low vascular NO bioavailability may be associated with impaired angiogenic responses via increased ma-trix metalloproteinase (MMP)-2 and MMP-9 activity. As such, we hypothesized that chronic exercise (EX) would increase NO bio-availability in OZR and blunt microvascular rarefaction through reduced MMP activity, and potentially via altered plasma cytokine levels. Ten weeks of treadmill exercise (1 h/day, 5 days/wk, 22 m/min) reduced body mass and fasting insulin and triglyceride levels in EX-OZR vs. sedentary (SED) OZR. In EX-OZR, gastroc