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Hartshorne, L.

Publications and source records attributed to Hartshorne, L..

2 recordsLinked to original sources

Age-dependent effects of reduced mTor signalling on life expectancy through distinct physiology

Research on the mechanisms of ageing has identified ways via which lifespan can be extended in model organisms, increasing the potential for translation of these findings to our own species. However, the large majority of research on animal models involves dietary, genetic or pharmacological treatments throughout life - limiting translational potential and ignoring age-dependent effects. Previously, we have suggested using demographic meta-analysis that reduced mTor signalling has the potential to instantly rejuvenate. We have now tested this prediction experimentally using large-scale demographic data (N > 10,000) combined with conditional knockdown of mTor in Drosophila melanogaster. Indeed, reduced mTor decreased mortality rate when applied during old age. Interestingly, we found that transient treatment during early adult life had long-lasting benefits. Age-dependent deep-RNAseq indicated that these effects arose from distinct physiology and implicate alternative splicing as a potential mechanism for the long-lasting benefits of transient mTor reduction. These findings suggest that reducing mTor short term or during old age could be used to combat ageing. In addition, our findings suggest that the results from experimental research on mTor signalling, and potentially other mechanisms of ageing, that employ life-long interventions are likely to be a complex composite of age-dependent effects that counteract or enhance each other.

physiology

The hidden costs of dietary restriction: implications for its evolutionary and mechanistic origins

Dietary restriction (DR) consistently and universally extends health-and lifespan across taxa. Despite efforts to uncover the mechanisms underpinning DR - and ultimately translate its beneficial outcomes to humans - precise and universal mechanisms have not been identified. In biomedical science, the effects of DR are interpreted as regulating pro-longevity molecular pathways. This reasoning is guided by the conviction that DR evolved as an adaptive, pro-longevity physiological response to restricted food intake. Current evolutionary theory states that organisms should invest in their soma more heavily during periods of DR, and, when their resource availability improves, should outcompete age-matched rich-fed controls in survival and/or reproduction. Here we present a formal test of these key predictions utilising a large-scale demographic approach detailing mortality and fecundity in Drosophila melanogaster fed alternating dietary regimes (N > 66,000 flies across 11 genetic lines). Our experiments reveal surprising and substantial mortality costs when returning to a rich diet after periods of DR. These results suggest the effects of DR are not necessarily intrinsically pro-longevity and could be considered an escape from costs incurred under nutrient-rich conditions, in addition to novel, discrete costs associated with restricting dietary protein. These insights question the relevance of current evolutionary explanations of DR in interpreting the mechanistic basis of dietary restriction.

evolutionary biology