Age-associated decrease of SIRT1 expression in rat hippocampus: prevention by late onset caloric restriction.

We have studied the effect of aging and late onset caloric restriction (CR) on the expression of SIRT1 in hippocampus and cerebral cortex of the rat. Quantitative analysis showed that there is a significant reduction of SIRT1 protein levels in hippocampus with aging. Late onset, moderate CR prevented the deleterious effect of aging on SIRT1 content. Examination of SIRT1 immunoreactivity in coronal sections from hippocampus supported these results, and confirmed that old animals are able to respond to the beneficial effects of CR by regulating SIRT1 protein expression. Differences in the amounts of SIRT1 transcripts among animal groups were not found, which suggest that post-transcriptional mechanisms could be involved in the effects of aging and CR on SIRT1 expression.