Endothelial Nitric Oxide Synthase Uncoupling and Perivascular Adipose Oxidative Stress and Inflammation Contribute to Vascular Dysfunction in a Rodent Model of Metabolic Syndrome

The metabolic syndrome represents a constellation of cardiovascular risk factors that promote the development of cardiovascular disease. Oxidative stress is a mediator of endothelial dysfunction and vascular remodeling. We investigated vascular dysfunction in the metabolic syndrome and the oxidant mechanisms involved. New Zealand obese (NZO) mice with metabolic syndrome and New Zealand black control mice were studied. NZO mice showed insulin resistance and increased visceral fat and blood pressure compared with New Zealand black mice. Mesenteric resistance arteries from NZO mice exhibited increased media: lumen ratio and media cross-sectional area, demonstrating hypertrophic vascular remodeling. Endothelium-dependent relaxation to acetylcholine, assessed by pressurized myography, was impaired in NZO mice, not affected by NG-nitro-L-arginine methyl ester, inhibitor of endothelial NO synthase, and improved by the antioxidant Tempol, suggesting reduced NO bioavailability and increased oxidative stress. Dimer: monomer ratio of endothelial NO synthase was decreased in NZO mice compared with New Zealand black mice, suggesting endothelial NO synthase uncoupling. Furthermore, vascular superoxide and peroxynitrite production was increased, as well as adhesion molecule expression. Perivascular adipose tissue of NZO mice showed increased superoxide production and NADPH oxidase activity, as well as adipocyte hypertrophy, associated with inflammatory Mac-3-positive cell infiltration. Vasoconstriction to norepinephrine decreased in the presence of perivascular adipose tissue in New Zealand black mice but was unaffected by perivascular adipose tissue in NZO mice, suggesting loss of perivascular adipose tissue anticontractile properties. Our data suggest that this rodent model of metabolic syndrome is associated with perivascular adipose inflammation and oxidative stress, hypertrophic resistance artery remodeling, and endothelial dysfunction, the latter a result of decreased NO and enhanced superoxide generated by uncoupled endothelial NO synthase. (Hypertension. 2009; 54: 1384-1392.)