Meeting Abstract

S9.3-2  Tuesday, Jan. 7 14:00  Ingestion and allocation of macronutrients underlying reduced reproduction and life extension in grasshoppers HATLE, JD; Univ. of North Florida jhatle@unf.edu

Reduced reproduction and reduced diet (aka. dietary restriction) each extend lifespan in many animals. Because the degree of dietary restriction needed to extend lifespan usually reduces fecundity, the dogma has been that both manipulations work through the same means. We have addressed this hypothesis by measuring feeding rates, physiological parameters of stress, and storage. In many ways, the two treatments produce similar responses. Reduced reproduction (via ovariectomy or RNAi on vitellogenin) reduced feeding ~35% in old females and increased lifespan by ~18%. Similarly, reduced diet (i.e., ~30% less than that consumed by intact individuals fed ad libitum) reduced egg production about 30% and increased lifespan ~18%. Females upon ovariectomy and females on dietary restriction had similar total anti-oxidant activities in the hemolymph and muscle, similar numbers of mitochondria in the fat body and muscle, and similar mRNA expressions of vitellogenin and storage protein in the fat body. In stark contrast to these similarities, ovariectomy doubled fat body mass and hemolymph volume, while dietary restriction did not. In addition, we tracked ingested macronutrients to somatic tissues using stable isotopes. Ovariectomy, despite increasing somatic storage, does not alter allocation of ingested nutrients to muscle, storage proteins, or fat body (i.e., the metabolic organ). A parallel experiment testing allocation of ingested nitrogen upon dietary restriction is underway, and its results will be compared to ovariectomy. Last, we are measuring metabolic rates upon ovariectomy or matched-fed controls (which are thereby under dietary restriction). Overall, these data suggest that life-extending reductions in reproduction and diet result in similar feeding rates but greatly different investments in storage.