Age-related changes of glucose metabolism in rat cerebral cortex with reference to glucose-derived amino acids

The parietal cortical slices obtained from 8 week-old (young) and 78 week-old (middle-aged) male Wistar rats were incubated with D-[U-14C]glucose in oxygen-saturated Gey's balanced salt solution. Subsequently, the radioactivities of liberated CO2 and glucose-derived amino acids (alanine, aspartate, GABA, glutamate and glutamine) obtained from the slices were measured. In the middle-aged rats as compared to the young rats, the amount of radioactivity of CO2 (P less than 0.01) and glutamate (P less than 0.05) showed a significant reduction with glutamine unchanged, while that of alanine (P less than 0.01), aspartate (P less than 0.05) and GABA (P less than 0.05) increased significantly. The results indicate that with advancing age the overall glucose oxidation in the cerebral cortex declines but the metabolic pathway to form amino acids is not uniformly suppressed. Therefore, the above characteristic glucose metabolism could be related to the development of heterogeneous enzyme activities associated with aging in the brain.