Obesity is an independent risk factor for the development of coronary artery disease and is associated with endothelial dysfunction (ED), a critical early event in atherogenesis. We aimed to explore the relationship between measures of fat distribution and flow-mediated vasodilatation (FMD), a surrogate marker for endothelial function, and the influence of weight loss on this.
We assessed endothelial function in 73 subjects (37 ± 10 years old, mean ± S.D., 60 % female) over a range of body mass indexes (BMI, 18-73 kg m-2). No subject had diabetes or a history of cardiovascular disease. Height, weight and waist and hip circumferences were measured. Brachial artery FMD was assessed after an overnight fast and analysed using an automated wall-tracking system. Blood for lipid profile and glucose was taken. Correlations were assessed with non-parametric tests.
FMD showed a weak negative correlation with BMI (r = -0.31, P < 0.01). When dichotomised by the upper limit of normal for BMI (30 kg m-2), FMD was worse in the obese group (6.8 ± 3.1 vs. 9.3 ± 3.4 %, P < 0.001, Student’s unpaired t test). Waist-hip ratio (WHR), which gives an indication of visceral adiposity, was closely negatively correlated with FMD (r = -0.60, P < 0.0001). Weight (r = -0.43, P < 0.02) and waist circumference (r = -0.53, P < 0.01) showed modest correlations with FMD. When dichotomised by upper limit of normal for WHR (0.95 for men, 0.8 for women) FMD was worse in the higher WHR group (6.7 ± 2.9 vs. 9.4 ± 3.5 %, P < 0.0005). Higher WHR was associated with raised LDL cholesterol (P < 0.005), triglyceride (P < 0.005) and systolic blood pressure (P < 0.0005), but not fasting glucose.
Of this cohort, eight underwent laparoscopic gastric banding or gastric bypass in order to achieve weight loss. FMD was reassessed after a minimum of 6 months or 10 % weight loss, whichever occurred earlier. Two patients gained a small amount of weight post-operatively whilst the remaining six lost between 6 and 38 kg. Percentage change in body weight was very closely correlated with absolute change in FMD (r = 0.90, P < 0.002); of the other anthropometric measures, change in waist circumference best predicted improvement in endothelial function (r = 0.79, P < 0.02).
These data demonstrate a close association between FMD and WHR. WHR may be a better marker than BMI when assessing patients’ cardiovascular risk profile. Weight loss is associated with an improvement in FMD, probably through a reduction in visceral adiposity, and may significantly improve endothelial function in subjects who, despite weight reduction, remain morbidly obese.
This work was supported by the BHF.