Overexpression of several enzymes of the NAD+ salvage pathway, including nicotinate phosphoribosyltransferase (PNC1) and nicotinamide mononucleotide adenylyltransferase 1 (NMNAT1) have been shown to extend lifespan in rat models by activating SIRT1 and promoting p53 deacetylation (van der Veer et al., 2007; Porcu and Chiarugi, 2005; Arraki et al., 2004; Berger et al., 2004; Bedalov and Simon, 2004).