Cardiovascular fitness is associated with altered cortical glucose metabolism during working memory in ɛ4 carriers.

ABSTRACT

BACKGROUND: The possibility that ɛ4 may modulate the effects of fitness in the brain remains controversial. The present exploratory FDG-PET study aimed to better understand the relationship among ɛ4, fitness, and cerebral metabolism in 18 healthy aged women (nine carriers, nine noncarriers) during working memory. METHODS: Participants were evaluated using maximal level of oxygen consumption, California Verbal Learning Test, and FDG-PET, which were collected at rest and during completion of the Sternberg working memory task. RESULTS: Resting FDG-PET did not differ between carriers and noncarriers. Significant effects of fitness on FDG-PET during working memory were noted in the ɛ4 carriers only. High fit ɛ4 carriers had greater glucose uptake in the temporal lobe than the low fit ɛ4 carriers, but low fit ɛ4 carriers had greater glucose uptake in the frontal and parietal lobes. CONCLUSIONS: We demonstrate that fitness differentially affects cerebral metabolism in ɛ4 carriers only, consistent with previous findings that the effects of fitness may be more pronounced in populations genetically at risk for cognitive decline.