Meeting Abstract
Dietary restriction (energy deficit diet without malnutrition; DR) extends the lifespan of a wide range of animals. Recent studies show that restriction of protein is vital to this extension. Lifespan extension is also achieved through RNAi knockdown of the Target of Rapamycin pathway (a cellular growth pathway; TOR). The TOR pathway is potently stimulated by leucine, which may contribute to the life-shortening effects of a protein-rich diet. Given the energy deficit upon DR, we hypothesize that DR extends lifespan in part through enhanced oxidation of leucine (which would render leucine unable to activate TOR). We predict that female Lubber grasshoppers on DR would oxidize dietary leucine at higher rates than grasshoppers fed ad libitum. In past work, leucine oxidation has been observed to increase significantly in some trials and non-significantly in others, with high variability across individuals. In this experiment, grasshoppers (total n=28) each were fed either ad libitum or DR for ~40 days, then measured for leucine oxidation (trial 1). These same lubbers were then switched to the other feeding level (ad libitum to DR; DR to ad libitum) for an additional ~40 days before a second leucine oxidation measurement (trial 2). Oxidation rates did not differ in trial 1, but in trial 2 leucine oxidation rates were higher from 4-8 hr after tracer ingestion (all P<0.05; 90-187% increases). These results suggest that leucine can be oxidized at higher rates in lubber grasshoppers upon DR. High variation exists but is not due to individual differences. Overall our results are consistent with previous work in the lab: leucine oxidation can be higher upon DR, but it is not consistently higher.
