Acute hyperglycaemia in the forearm induces vasodilation that is not modified by hyperinsulinaemia

Abstract

Objective: To evaluate whether acute elevations of local plasma glucose concentrations could influence forearm blood flow (FBF) and how this interacts with local hyperinsulinaemia in healthy volunteers.

Methods: Using the perfused forearm technique, in random order, glucose 20% or saline 0.9% as a control was infused in three dose steps (0.3, 1.0, and 3.0 ml/min) for 5 min each in eight healthy men. The infusion experiments were repeated, in random order, during local hyperinsulinaemia by intra-arterial infusion of insulin 0.05 mU/kg/min. The ratio of FBF of the infused over the FBF in the control arm (FR) was measured at 15-sec intervals during the infusions.

Results: Glucose infusion increased the FR dose-dependently by 172%+/-39% (M+/-SE) at the highest dose (P < 0.01). During hyperinsulinaemia the glucose-induced increase in FR was significantly (P < 0.01) less, 96%+/-26%, however, when changes in FR or forearm vascular resistance were related to the plasma glucose concentrations both glucose infusions were equipotent. The saline infusions induced small increases in FR of 27+/-5% (P < 0.01) and 24+/-11% (P > 0.05), without or with insulin respectively. The changes in FR during the saline infusions were much smaller than during the glucose infusions (P < 0.01). During the glucose infusions small but significant increases in FBF and venous plasma glucose in the non-infused forearm appeared, indicating carry-over effect and the possibility of a very low threshold for glucose-induced vascular effects.

Conclusions: High, local levels of glucose in the forearm have a vasodilator effect on resistance vessels in skeletal muscle of the forearm that is not modified by local hyperinsulinaemia. Indications were found that the threshold for this glucose-induced vasodilation may be remarkably low, but this needs to be studied more formally.