Impaired local microvascular vasodilatory effects of insulin and reduced skin microvascular vasomotion in obese women.

Our study aim is to investigate whether obesity is characterized by an impairment of insulin-mediated vasodilatory effects and by a modification of basal vasomotion in the skin microvasculature. Forty healthy obese and forty healthy lean women were included. Microvascular effects of insulin as compared to a control substance were measured by cathodal iontophoresis combined with laser Doppler flowmetry. Vasomotion was examined by Fourier transform analyses of skin laser Doppler flow at rest. Locally administered insulin, as compared to the control substance, induced a microvascular vasodilatory response in lean (median (interquartile range): 31.6 (17.1-43.9) vs. 22.9 (16.4-36.7) perfusion units, P=0.04), but not in obese women (28.1 (14.4-47.1) vs. 27.5 (17.5-48.2) perfusion units, P=0.7). The relative insulin-induced increase in blood flow corrected for the control substance was higher in lean than obese women (ANOVA for repeated measures F=3.93, P=0.05). The contribution of the total frequency spectrum 0.01-1.6 Hz and of the frequency intervals 0.01-0.02 Hz and 0.02-0.06 Hz (representative of endothelial and neurogenic activity, respectively) to basal microvascular vasomotion was lower in obese than in lean women (P<0.05 for all). These findings show that obesity is characterized by an impaired direct microvascular vasodilatory effect of insulin and by decreased skin microvascular vasomotion in a way that is suggestive for alterations of endothelial and neurogenic activity.