Cerebral transport and metabolism of 1-11C-D-glucose during stepped hypoglycemia

Attempts to measure blood-to-brain glucose transport and cerebral glucose metabolism with 11C-glucose have been hampered by methods that require jugular venous sampling or do not adequately account for the efflux of labeled metabolites from the brain. We performed eight positron emission tomography studies with 1-11C-D-glucose in macaques at arterial plasma glucose concentrations of 8.43 to 1.51 mumol ml-1 (152-27 mg dl-1) using a model that includes a fourth rate constant to account for regional egress of all 11C-metabolites. Values for blood-to-brain glucose influx, cerebral glucose metabolism, and brain free glucose concentration agreed closely with values obtained in mammals by other investigators. Values for net extraction fraction corresponded closely to simultaneously measured arteriovenous values. We demonstrated that utilization of a model that includes a fourth rate constant to account for regional egress of all 11C-metabolites with positron emission tomography and 1-11C-D-glucose provides accurate measurements of blood-to-brain glucose transport and cerebral glucose metabolism in vivo without need for jugular venous sampling, even under conditions of severe hypoglycemia.