The Impact Of Adiposity And Insulin Resistance On Endothelial Function In Middle-Aged Subjects

摘要

Objectives: To investigate the relationship between adiposity, adipose distribution,insulin resistance (IR) and vascular endothelial function. Methods: Flow-mediated endothelium-dependent dilation (EDD), body mass index(BMI), waist circumference, waist hip ratio and IR index (HOMA-IR) were measured in 527healthy subjects (328 males) aged between 35 to 55 years. The relations between theseparameters and endothelial function was studied using univariate and multivariate linear regression analysis. Results: Waist circumference, waist hip ratio and HOMA-IR were greater in the overweightor obese subjects (p<0.01). They were also greater in males than in females within the same body weight group (p<0.05). The incidence of vascular endothelial dysfunction in the normal body weight, overweight and obese was 30.7%, 69.5% and 75.4% respectively (p<0.05). A higher waist circumference and waist hip ratio was also found in male subjects with endothelial dysfunction than those without. A greater HOMA-IR was identified in both male and female subjects with impaired endothelial function (p<0.05). Multivariate linear regression analysis showed a small but significant inverse correlation between endothelial function and BMI (r= -0.285, p<0.001), waist hip ratio (r= -0.179, p<0.001) and HOMA-IR (r= -0.164, p<0.001). Conclusions: Adiposity and adipose distribution have an important impact on endothelial function in male subjects. An increase in HOMA-IR is associated with vascular endothelial dysfunction in both males and females. Introduction Endothelial dysfunction has been shown to be an early marker of atherosclerotic disease. 1Previous studies have demonstrated a close correlation between vascular endothelial dysfunction and insulin resistance, which was commonly seen in those who are obese. 2 To further illustrate the relationships between obesity, insulin resistance and vascular endothelial function, we investigated the adiposity and adipose distribution, insulin resistance and endothelial function in middle-aged subjects. Patients and Methods PatientsThis study was approved by the Human Ethics Committee of our hospitals. Five hundred and twenty seven healthy subjects (25-55 years old) from the city of Shijiazhuang in Northern China were enrolled in the study. Body mass index (BMI) were used to define overweight or obesity as below: normal: 18.5~24.9 kg/m2; overweight: 25~29.9 kg/m2; obese: BMI > 30 kg/m2.MethodsPlasma glucose was measured by glucose oxidase technique. Plasma insulin level was tested after 12 hours of fasting using dextran-charcoal radioimmunoassay method. Insulin resistance was estimated by the homeostasis-model assessment (HOMA-IR): insulin resistance = (fasting glucose x fasting insulin) / 22.5. 3 Weight and height were measured in light clothing without shoes. BMI was calculated as weight (kg) divided by height (m) squared and was used as an index of overall adiposity. Waist circumference was measured at the level of the umbilicus with the subject standing and breathing normally. Hip circumference was measured at the level of greatest hip girth. Waist circumference and waist hip ratio was used as a measure of body fat distribution. Vascular endothelial function was assessed from brachial artery from B-mode ultrasound images using a standard NAS-1000 HE system and a 7.0-MHz linear array transducer. The ultrasound method for assessing endothelium-dependent and independent dilatation was performed as described previously. 4, 5 The brachial artery was scanned in longitudinal section above the elbow, and the center of the artery was identified when the clearest picture of the anterior and posterior intimal layers was obtained. Depth and gain settings were set to optimize images of the lumen/arterial wall interface.In all studies, scans were obtained at rest, during reactive hyperemia (with increased flow leading to endothelium-dependent dilatation (EDD)). When a satisfactory transducer position was found, the skin was marked