Adequate microvascular perfusion is essential for the regulation of tissue metabolism. Therefore, defects in microvascular function may play a role in obesity-associated insulin resistance. Steady-state hyperinsulinemia during a euglycemic hyperinsulinemic clamp stimulates endothelium-dependent vasodilation and capillary recruitment, which contribute to increased glucose uptake. These phenomena have been shown to be blunted in obesity. If insulin's effects on microcirculatory function indeed play a physiological role in regulating insulin-mediated glucose uptake, such effects should be demonstrable not only during steady-state hyperinsulinemia, but also after meal ingestion. We investigated whether similar responses occur after ingestion of a glucose load or a mixed meal. We examined the effects of a glucose drink, a mixed meal drink, or a control drink (water) on skin capillary density (i.e. baseline capillary density, hyperemic capillary recruitment, and density during venous congestion, using capillaroscopy) and skin endothelium-(in)dependent vasodilation (using laser-Doppler flowmetry with iontophoresis of acetylcholine and sodium nitroprusside) in 20 lean and 19 obese individuals. In lean individuals, neither the glucose nor the mixed meal drink induced a significant effect on capillary density or endothelium-(in)dependent vasodilation. Possibly this is related to the modest plasma insulin levels as compared to the insulin clamp. In obese individuals, the mixed meal drink, compared to the control drink, decreased baseline skin perfusion (P<0.05) and acetylcholine-mediated vasodilation (P<0.05), while no effect of the drinks on capillary density was found. Compared to lean individuals, obese individuals had impaired acetylcholine-mediated vasodilation after meal ingestion (P=0.02). The latter findings are consistent with impaired postprandial microvascular function in obesity.
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- INDUCED CAPILLARY RECRUITMENT, MUSCLE GLUCOSE-UPTAKE, HUMAN FOREARM MUSCLE, RAT SKELETAL-MUSCLE, INSULIN-RESISTANCE, MICROVASCULAR RECRUITMENT, NITRIC-OXIDE, MIXED MEAL, POTENTIAL MECHANISM, METABOLIC SYNDROME