Severe obesity is associated with impaired arterial smooth muscle function in young adults

Abstract

The degree of arterial dilatation induced by exogenous nitrates (nitrate-mediated dilatation, NMD) has been similar in obese and normal-weight adults after single high-dose glyceryl trinitrate (GTN). We examined whether NMD is impaired in obesity by performing a GTN dose-response study, as this is a potentially more sensitive measure of arterial smooth muscle function. In this cross-sectional study, subjects were 19 obese (age 31.0±1.2 years, 10 male, BMI 44.1±2.1) and 19 age- and sex-matched normal-weight (BMI 22.4±0.4) young adults. Blood pressure (BP), triglycerides, high-density lipoprotein (HDL), and low-density lipoprotein (LDL)-cholesterol, glucose, insulin, high-sensitivity C-reactive protein (hs-CRP), carotid intima-media thickness (CIMT), and flow-mediated dilatation (FMD) were measured. After incremental doses of GTN, brachial artery maximal percent dilatation (maximal NMD) and the area under the dose-response curve (NMD AUC) were calculated. Maximal NMD (13.4 0.9% vs. 18.3±1.1%, P = 0.002) and NMD AUC (54,316 362 vs. 55,613±375, P = 0.018) were lower in obese subjects. The obese had significantly higher hs-CRP, insulin, and CIMT and lower HDL-cholesterol. Significant bivariate associations existed between maximal NMD or NMD AUC and BMI-group (r = 0.492, P = 0.001 or r = 0.383, P = 0.009), hs-CRP (r = 0.419, P = 0.004 or r = 0.351, P = 0.015), and HDL-cholesterol (r = 0.374, P = 0.01 or r = 0.270, P = 0.05). On multivariate analysis, higher BMI-group remained as the only significant determinant of maximal NMD (r2 = 0.242, Β = 0.492, P = 0.002) and NMD AUC (r2 = 0.147, Β = 0.383, P = 0.023). In conclusion, arterial smooth muscle function is significantly impaired in the obese. This may be important in their increased cardiovascular risk. © 2010 The Obesity Society.