Periodic Reporting for period 3 - GermlineAgeingSoma (Getting to the root of ageing: somatic decay as a cost of germline maintenance) Reporting period: 2020-09-01 to 2022-02-28 Summary of the context and overall objectives of the project Ageing is an evolutionary paradox but it is also a debilitating condition in humans, which explains why it commands such high level of interest among scientists and general public alike. The research on ageing proceeds along two main trajectories: evolutionary biologists focus on the fundamental causes of ageing, while biogerontologists study medical interventions that extend lifespan and alleviate the health implications of growing old. Recent developments in both of these fields suggest that we are witnessing a major change in our understanding of the basics of ageing process. This project builds on key latest discoveries and offers an integrative interdisciplinary framework to test the exciting theories in an area where PI is an expert. This project is uniquely using advances in biogerontology to test fundamental questions about evolutionary biology of ageing and it will also have important lessons for applied research community.Recent discoveries in the multi-disciplinary study of ageing questioned the very foundation of the evolutionary theory of ageing – the reproduction cost of longevity. This project will empirically test the novel ideas that can resolve the paradox of cost-free lifespan extension. By harnessing the power of evolutionary approach we will be able to inform biomedical scientists and general public about the potential risks associated with genetic and/or pharmacological manipulations to boost investment into somatic maintenance. For example, the drug metformin, which is currently being considered for the first-in-history clinical anti-ageing trials in humans has negatve effects on reproduciton in model organisms. At the same time, metformin is a successful anti-diabetic drug, which is also reducing rates of different cancers, as well as overall mortality, suggesting that it may be involved in reallocation of resources from reproduction and germline maintenance to somatic maintenance, thereby potentially compromising reproductive performance of both adults and their offspring. Specifically, the proposed work is testing whether some of the current research programs aimed at manipulating nutrient-sensing signalling in humans are safe to apply to post-reproductive population only because otherwise they may cause health problems in adult offspring. However, a different theory suggests instead that ageing is caused by suboptimal gene expression in adulthood because the force of natural selection on gene expression is maximal during pre-adult development and weakens with increasing adult age. This theory predicts that experimental optimisation of gene expression in adulthood can simultaneously increase lifespan, healthspan and reproductive performance and may even have beneficial effects on the resulting offspring. Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far We established that adulthood-only downregulation of evolutionarily conserved insulin signalling in Caenorhabditis elegans nematodes improved parental survival and offspring fitness. These result are in line with the idea that ageing results, in part, from suboptimal levels of gene expression in adulthood, suggesting that optimising adulthood-only gene expression can simultaneously improve lifespan and healthspan. We investigated whether these effects persist under a range of stressful conditions, whether they can be transferred over several generations and whether can be beneficial to healthspan and evolutionary fitness under multivariate stress. We established 800 mutation accumulation lines where we downregulate insulin signalling using daf-2 RNA interference (RNAi) approach. We studies extinction and fitness under mutation accumulation when mutations accumulate spontaneously or induced by low-level UV radiation. We investigated the evolutionary response of C. elegans con-gener, C. remanei, to low-level UV radiation over several generation on experimental laboratory evolution design. We studied the evolutionary costs of experimental upregulation of autophagy in C. elegans and discovered that downregulating autophagy both in long-lived and wildtype animals results in increased reproduction. This suggests that lifespan extension via upregulated autophagy is likely to result in decreased reproduction and reduced fitness, supporting the main tenet of the disposable soma theory of ageing. We also established an experimental set-up to evaluate the effect intermittent fasting on the soma and the germline in zebrafish, Dario rerio. We collected preliminary data on reproduction, growth and investment into soma. This is the work in progress and the main results are expected by the end of the project. Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far) The most important achievements of the project so far are:1. The discovery that downregulation on insulin signalling pathway in parents can increase offspring fitness. This is a novel and very significant finding that has important implications for our understanding of the biology of ageing and for translational research. This work has been published.2. We revealed how multigenerational downregulation of insulin signalling pathway in adulthood affects the soma and the germline under mutation accumulation. This work has been just completed and will be made available to the scientific community and general public via pre-print service bioRxiv shortly. 3. We just started to investigate, for the first time, how downregulation of insulin signalling pathway in adulthood affects lifespan, healthspan, reproduction and Darwinian fitness in complex and variable environments. This is a very exciting part of the project because environmental complexity may have very different effects of age-specific fitness compared to organismal performance in benign and predictable environments. This is one of the most promising avenues for future research within this project, and beyond, as the results suggest that organismal health in old age could be improved by environmental modification in realistic, ecologically relevant conditions.By the end of the project, we are expecting to provide a comprehensive evaluation of age-specific and transgenerational trade-offs associated with the regulation of lifespan, healthspan and reproductive ageing by insulin signalling pathway in nematodes. By looking at the effects of the germline and the soma, we will be able cover all aspects of fitness, from age-specific survival and reproduction to germline mutation and offspring quality to long-term transgenerational effects on distant descendants. Nematodes
