The role of insulin in human brain glucose metabolism: an 18fluoro-deoxyglucose positron emission tomography study.
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. kg(-1). min(-1) somatostatin to suppress endogenous insulin production. In one study 0.3 mU. kg(-1). min(-1) 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. kg(-1). min(-1) without insulin and 0.245 +/- 0.021 mmol. kg(-1). min(-1) with insulin (P = 0.008, an average difference of 15.3 +/- 12.5%). Regional analysis using statistical parametric mapping showed that the effect of basal insulin was significantly less in the cerebellum (Z = 5.53, corrected P = 0.031). We conclude that basal insulin has a role in regulating global brain glucose uptake in humans, mostly marked in cortical areas.
Bingham
Emma M
EM
GKT School of Medicine, King's College Hospital, London SE5 9PJ, U.K. emma.bingham@kcl.ac.uk
Hopkins
David
D
Smith
Diarmuid
D
Pernet
Andrew
A
Hallett
William
W
Reed
Laurence
L
Marsden
Paul K
PK
Amiel
Stephanie A
SA
D000328:Adult; D001921:Brain / Q000000981:diagnostic imaging / Q000378:metabolism*; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics; D005947:Glucose / Q000378:metabolism*; D006801:Humans; D007328:Insulin / Q000494:pharmacology / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D011897:Random Allocation; D014018:Tissue Distribution; D014055:Tomography, Emission-Computed
D007328:Insulin; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18; D005947:Glucose