Obesity/Insulin Resistance Is Associated with Endothelial Dysfunction Implications for the Syndrome of Insulin Resistance

To test the hypothesis that obesity/insulin resistance im-pairs both endothelium-dependent vasodilation and insulin-mediated augmentation of endothelium-dependent vasodi-lation, we studied leg blood flow (LBF) responses to graded intrafemoral artery infusions of methacholine chloride (MCh) or sodium nitroprusside (SNP) during saline infu-sion and euglycemic hyperinsulinemia in lean insulin-sensi-tive controls (C), in obese insulin-resistant subjects (OB), and in subjects with non–insulin-dependent diabetes melli-tus (NIDDM). MCh induced increments in LBF were