Testing direct effects of reproduction on lifespan with controlled feeding in grasshoppers -
DESCRIPTION (provided by applicant): Increased health span could be accomplished by slowing aging and delaying the onset of age-related diseases. Recent work in C. elegans worms is beginning to reveal how reduced reproduction may extend lifespan. At the same time, reduced feeding (i.e., dietary restriction) also is well known to extend lifespan. The feeding rate
of worms upon reduced reproduction was not reported, and it may not be able to be measured reliably. Reduced reproduction can indirectly reduce feeding. Hence, studies on how reduced reproduction extends lifespan in worms may be confounded by inadvertent reductions in feeding. The present project will use a large, low-cost invertebrate to test how reduced reproduction extends lifespan, independent of daily feeding. Grasshoppers with different levels of reproduction (ovariectomized or sham-operated) but on matched daily feeding rates will be used to identify mechanisms of life-extension directly due to reduced reproduction. Because feeding is reduced upon ovariectomy, the sham-operated animals fed the same amount daily will be on dietary restriction. Transcriptomes for fat body and brain for this grasshopper have been acquired, making possible mRNA quantification and RNAi knockdown of many genes. In this way we will examine two pathways known to effect lifespan. For each, we first compare mRNA levels of pathway components in ovariectomized & full diet animals and sham-operated & dietary restricted animals with matched feeding. Second, RNAi will be used to knockdown the pathway to determine if it is required for life-extension upon ovariectomy. Aim 1 will test cellula growth by the Target of Rapamycin (TOR) pathway. Knockdown of TOR extends lifespan in worms, flies, and mice. I predict that components of the TOR pathway will be reduced upon life-extending dietary restriction, but not upon life-extending ovariectomy. Next, I predict that life-extension upon TOR knockdown be additive with life-extension by ovariectomy, but not dietary restriction. Aim 2 will examine the role of the stimulation of feeding by neuropeptide F/Y. This peptide is involved in life-extension in mice, but perhaps not via altering growth pathways. I predict that mRNA levels for neuropeptide F will increase upon dietary restriction, but not upon ovariectomy. Knockdown of neuropeptide F is predicted to increase lifespan and be additive with ovariectomy, but not dietary restriction. In addition, I will test whether neuropeptide F reduces bio-molecular damage (protein carbonyls, lipid peroxidation). A new Aim 3 will test the role of production of gaseous hydrogen sulfide from cysteine in life-extension by dietary restriction. H2S has recently been shown to be essential for the salubrious effects of dietary restriction in mice. I will test whether changes in oxidation and allocation of ingested cysteine are associated with altered H2S production. I predict H2S will be higher upon reduced diet, but not upon reduced reproduction. Understanding how reduced reproduction increases lifespan may reveal an additional target for drug development toward improving human health span. Consistent with the R15 program, students will be involved in all data collection and presentation.
