RedGage

Description

The effect of basal insulin on global and regional brain glucose uptake and metabolism in humans was studied using 18-fluorodeoxyglucose and positron emission tomography (FDG-PET). Eight healthy male volunteers aged 49.3 5.1 years were studied twice in random order. On each occasion, they received an infusion of 0.1 mg kg1 min1 somatostatin to suppress endogenous insulin production. In one study 0.3 mU kg1 min1 insulin was infused to replace basal circulating insulin levels, and in the other study a saline infusion was used as control. We sought stimulatory effects of basal insulin on brain glucose metabolism particularly in regions with deficiencies in the blood-brain barrier and high density of insulin receptors. Insulin levels were 27.07 1.3 mU/l with insulin replacement and 3.51 0.4 mU/l without ( P = 0.001). Mean global rate of brain glucose utilization was 0.215 0.030 mmol kg1 min1 without insulin and 0.245 0.021 mmol kg1 min1 with insulin ( P = 0.008, an average difference of