SirT1, the mammalian ortholog of Sir2, is a nuclear protein implicated in the regulation of many cellular processes, including apoptosis, cellular senescence, endocrine signaling, glucose homeostasis, aging, and longevity. Targets of SirT1 include acetylated p53, p300, Ku70, forkhead (FoxO) transcription factors, PPARγ, and the PPARγ coactivator-1α (PGC-1α) protein. Deacetylation of p53 and FoxO transcription factors represses apoptosis and increases cell survival. SirT1 deacetylase activity is inhibited by nicotinamide and activated by resveratrol.