Aging is influenced by complex interactions between genetic and environmental parameters. Sirtuins are a family of nicotinamide adenine dinucleotide (NAD)–dependent protein deacetylases (which remove acetyl groups from protein molecules) and adenosine diphosphate (ADP)–ribosyltransferases (which catalyze the transfer of the ADP-ribose moiety from NAD⁺ onto specific substrates) that are thought to play an important role in modulating these interactions. Mammalian sirtuins have been recently implicated in a variety of aging-related processes, and it has been suggested that these enzymes may prove to be effective therapeutic targets for treating age-associated diseases in humans.