|| Checking for direct PDF access through Ovid
Experimentally restricting dietary calories, while maintaining adequate dietary nutrient content, extends lifespan in phylogenetically diverse species; thus suggesting the existence of conserved pathways which can modify lifespan in response to energy intake. However, in some cases the impact on longevity may depend on the quality of the energy source. In Drosophila, restriction of dietary yeast yields considerable lifespan extension whereas isocaloric restriction of dietary sugar yields only modest extension, indicating that other diet-responsive pathways can modify lifespan in this species. In rodents, restricting intake of a single amino acid - methionine - extends lifespan. Here we show that dietary methionine can modify lifespan in adult female, non-virgin Oregon-R strain Drosophila fed a chemically defined media. Compared to a diet containing 0.135% methionine and 15% glucose, high dietary methionine (0.405%) shortened maximum lifespan by 2.33% from 86 to 84 days and mean lifespan by 9.55% from 71.7 to 64.9 days. Further restriction of methionine to 0.045% did not extend maximum lifespan and shortened mean lifespan by 1.95% from 71.1 to 70.3 days. Restricting glucose from 15% to 5% while holding methionine at a concentration of 0.135%, modestly extended maximum lifespan by 5.8% from 86 to 91 days, without extending mean lifespan. All these diet-induced changes were highly significant (log-rank p < 0.0001). Notably, all four diets resulted in considerably longer life spans than those typically reported for flies fed conventional yeast and sugar based diets. Such defined diets can be used to identify lifespan-modifying pathways and specific gene-nutrient interactions in Drosophila.