Insulin-mediated vasodilation and glucose uptake are functionally linked in humans

Intra-arterial infusion of insulin in physiological doses causes forearm va sodilation which is augmented by co-infusion of D-glucose, leading us to sp eculate that local insulin-mediated vasodilation may depend on insulin-medi ated glucose uptake. We have examined the relationship between whole-body i nsulin sensitivity and forearm vasodilation in response to local infusion o f insulin/glucose, thus avoiding any confounding effects of sympathetic sti mulation on peripheral blood flow. Eighteen healthy, normotensive male volu nteers (age, 26+/-5.4 years) attended on two separate occasions for measure ment of: (1) whole-body insulin sensitivity with use of the hyperinsulinemi c euglycemic clamp; (2) forearm vasodilation in response to an intra-arteri al infusion of insulin/glucose with use of bilateral venous occlusion pleth ysmography. Insulin-mediated glucose uptake (M) for the group (mean+/-SD) w as 10.0+/-2.2 mg.kg(-1).min(-1), and the percentage change in forearm blood flow ratio (%FBFR) for the group (median, interquartile range) was 28.2% ( 13.6, 48.6). In univariate analysis, M was significantly correlated with %F BFR (r(s)=0.60, P<0.05), but not with body mass index (BMI) (r(s)=-0.42), a ge (r=-0.39)or mean arterial pressure (r=0.13). In multiple regression anal ysis, %FBFR remained a significant independent predictor of M (R-2 (adj)=0. 48, t=3.23, P<0.01) in a model involving BMI, age, and blood pressure. Thes e data support the concept of a significant functional relationship between insulin's metabolic and vascular actions, possibly at an endothelial level .