Obesity is associated with increased cardiovascular morbidity. The skin is a unique site allowing simple, noninvasive assessment of capillary density and endothelial function. In the present study, we measured skin capillary density and endothelial function in a group of normotensive overweight/obese nondiabetic individuals and healthy lean controls.
Methods and results
We examined 120 relatively insulin-sensitive overweight individuals (BMI 27.9 ± 2.7 kg/m2, mean ± SD) with normal blood pressure and fasting plasma glucose and 130 lean (BMI 22.4 ± 1.7 kg/m2) controls. We used video microscopy to measure skin capillary density in the resting state and during venous occlusion. Laser Doppler flowmetry, combined with iontophoresis of acetylcholine (endothelial-dependent vasodilation) and following skin heating (endothelial-independent dilation), was performed. Resting capillary density was negatively correlated with BMI (r = −0.130, P < 0.05). Resting capillary density (mean ± SE) was lower, however nonsignificantly, in overweight as compared with the lean individuals (88.6 ± 1.5 vs. 91.8 ± 1.4, P = 0.117). Capillary recruitment, defined as the percentage increase in capillary density during venous congestion, was higher in overweight (9.5 ± 1.0%) than in controls (5.4 ± 0.9%, P = 0.003), which remained significant after adjustment for age, sex, mean arterial pressure and fasting glucose. As a consequence, capillary density during venous occlusion was similar between the groups. Endothelial-dependent and independent cutaneous vasodilation was also similar between groups. No correlations were found between capillary density and plasma markers of adiposity, inflammation or endothelial dysfunction.
BMI was inversely correlated with resting capillary density. This suggests a lower baseline tissue perfusion associated with higher vasomotor tone. Despite this, capillary recruitment was higher in overweight as compared with lean individuals, resulting in similar capillary density during venous congestion. Our results suggest that skin microcirculation abnormalities, in the absence of endothelial dysfunction, may be one of the earliest detectable alterations in vascular function in overweight individuals.