Mitochondrial respiratory chain activity in the human brain as a function of age.

Age-associated changes in mitochondrial respiratory chain activity were investigated in human brain tissue collected at autopsy. Four brain regions, the frontal cortex, superior temporal cortex, cerebellum and putamen, were studied to map any regional variation. A significant decrease in cytochrome c oxidase activity was seen in all regions studied with increasing age (P<0.05). Although a small decrease in succinate dehydrogenase-cytochrome c oxidoreductase and NADH: ubiquinone oxidoreductase activities was observed, this was not statistically significant. This study has shown that the age-related fall in cytochrome c oxidase activity affects the frontal cortex, superior temporal cortex, cerebellum and putamen. The variation in the extent of age-related oxidative phosphorylation decline was striking. We hypothesize that individuals with more severe age-related decline may be predisposed to neuronal dysfunction, whereas individuals with well preserved oxidative phosphorylation may enjoy some degree of neuronal protection.