The effect of euglucaemic hyperinsulinaemia on forearm blood flow and glucose uptake in the human forearm

Insulin-mediated stimulation of blood flow to skeletal muscle has been prop osed to be of major importance for insulin-mediated glucose uptake. The aim of this study was to investigate the relative importance of blood flow and glucose extraction as determinants of insulin-mediated glucose uptake in t he human forearm. Forearm blood flow (FBF), glucose extraction and oxygen c onsumption were evaluated for 100 min during the euglycaemic hyperinsulinae mic clamp (92 mU/l) in nine healthy subjects. FBF was measured by venous oc clusion plethysmography. Forearm glucose uptake increased sevenfold during the hyperinsulinaemic (P<0.001). Forearm glucose extraction showed a minor increase during the first 10 min of hyperinsulinaemia, but the most marked increase took place between 10 and 20 min (+170%). Thereafter, only a minor further increase was seen. During the first 10 min of hyperinsulinaemia FB F was unchanged. Thereafter, FBF increased steadily to a plateau reached af ter 60 min (+50%, P<0.001). A close relationship between whole body glucose uptake and FBF was seen at the end of the clamp (r = 0.75, P<0.02), but at this time the relationship between whole body glucose uptake and forearm g lucose extraction was not significant. The modest increase in O-2 consumpti on seen at the beginning of the clamp (+19%) was not related to FBF during the early phase of the clamp. In conclusion, the early course of insulin-me diated glucose uptake in the human fore arm was mainly due to an increase i n glucose extraction. However, with time the insulin-mediated increase in b lood flow increased in importance and after 100 min of hyperinsulinaemia FB F was the major determinant of glucose uptake.