Regional cerebral glucose transport and utilization in Alzheimer's disease

We performed dynamic positron emission tomographic (PET) studies of glucose utilization, using (18F) 2-fluoro-2-deoxy-D-glucose (FDG), in patients with probable Alzheimer's disease (AD) and healthy age-matched controls, to evaluate blood-brain-barrier glucose transport and glucose utilization rates in the disease. We found no significant differences in rate constants for glucose transport (k1 and k2) and phosphorylation (k3), nor for the vascular fraction (fv), between the 2 groups, although k3 and fv were relatively depressed in temporal cortex in AD. Absolute rates of glucose use were depressed in temporal and parietal cortex, and relative rCMRglc rates were lower in frontal, temporal, parietal, and occipital cortices. These data suggest that in AD bidirectional glucose transport is intact, and that temporal-parietal hypometabolism is present upon a background of widespread cortical metabolic impairment.