The sirtuins represent a distinct class of trichostatin A-insensitive lysyl-deacetylases (class III HDACs) and have been shown to catalyze a reaction that couples lysine deacetylation to the formation of nicotinamide and O-acetyl-ADP-ribose from NAD+ and the abstracted acetyl group. This SIRT family of genes is highly conserved from prokaryotes to eukaryotes and is involved in diverse processes including transcriptional regulation, cell cycle progression, DNA damage repair and aging. SIRT1 has been shown to be induced by caloric restriction (CR) in several tissues and SIRT1 mediated deacetylase activity attenuates B-amyloid content in the brain during CR. SIRT1 also regulates the p53-dependent DNA damage response pathway by binding to and deacetylating p53.