SIRT1 but not its increased expression is essential for lifespan extension in caloric restricted mice

The SIRT1 deacetylase is one of the best-studied potential mediators of some of the anti-aging effects of calorie restriction (CR); but its role in CR-dependent lifespan extension has not been demonstrated. We previously found that mice lacking both copies of SIRT1 displayed a shorter median lifespan than wild type mice on an ad libitum diet. Here we report that median lifespan extension in CR heterozygote SIRT1+/- mice was identical (51%) to that observed in wild type mice but SIRT1+/- mice displayed a higher frequency of some certain pathologies. Although larger studies in different genetic backgrounds are necessary , these results provide strong initial evidence for the requirement of SIRT1 for the anti-aging effects of CR, but suggest that its high expression is not required for CR-induced lifespan extension. Key words: SIRT1, caloric restriction, lifespan, anti-aging 2-5 month old male mice of 3 different genotypes (SIRT1+/+, SIRT1+/-, and SIRT1-/-) that had normal, reduced or no expression of SIRT1 were treated with either a 40% caloric restricted diet (CR) or an ad libitum diet (AL). 2-4 replicates of each experimental condition were used in the analysis.