Ageing in worms mainly results from the direct action of genes and not from random wear and tear or loss of function, and the same is likely to be true in humans, according to research by UCL, Lancaster University and Queen Mary University of London scientists.
The study, published in Current Biology and funded by Wellcome, shows that normal biological processes which are useful early on in life, continue to 'run-on' pointlessly in later life causing age-related diseases.
The deteriorative part of ageing, called 'senescence', is the main cause of disease and death worldwide as it leads to dementia, cancer, cardiovascular disease and chronic obstructive pulmonary disease, but scientists have struggled to identify what causes it.
To address this, researchers have focused on discovering the basic principles of ageing by studying simple animals such as Caenorhabditis elegans, a nematode worm used in this study which lives on fruit, and dies of old age after only 2-3 weeks.
"Discovering the causes of ageing in these little creatures could provide the key to understanding human ageing, and where late-life diseases come from," said Professor David Gems (UCL Institute of Healthy Ageing), corresponding author who led the team.
"I've been studying ageing in C. elegans for 25 years, and it's amazing to see its underlying mechanisms revealed. It is so important, because if you want to treat a disease you really need to understand what causes it. And senescence has really become the mother of all diseases, so understanding it is good news for all of us."
The study describes how biological processes that make young worms better able to reproduce run-on pointlessly in older worms, causing disease.
"Since genes we've found driving the destructive processes of ageing in worms are known to control lifespan in mammals, we think the findings are applicable to humans and mark a real paradigm shift in our understanding of ageing," said Dr Marina Ezcurra (UCL and Queen Mary), first author of the study.
Specifically, they focused on autophagy, where body cells consume their own biomass to recycle components and extract energy. They found that the worms' intestine consumes itself (autophagy) to create the yolk needed for eggs, and in elderly worms, this process causes severe deterioration of the intestine and obesity from a build-up of pooled fats. In turn, this further impacts on the health of the worm by promoting growth of tumours in the uterus, and shortens lifespan.
"This really surprised us since autophagy is usually thought to protect against ageing rather than cause it," said Dr Alex Benedetto, a lead author on the study, formerly at UCL but now at Lancaster University.
"It seems that worms crank-up autophagy, which is considered good, to maximise reproductive success, which is good too, but they end up overdoing it, causing senescence," he added.
The finding suggests parallels with bone erosion in lactating mammals. In women, a process originally designed to leach calcium from bone to create milk for breastfeeding may have negative effects after menopause, when it instead contributes to osteoporosis, osteoarthritis and calcified blood vessels.
When useful biological programmes run-on in later life, they can become disease-causing 'quasi-programmes'. Such programmes were recently proposed and the findings support that they are indeed a major underlying cause of ageing.
This does not mean that aging is programmed but instead, that it is a continuation of developmental growth driven by genetic pathways to the point where these becomes harmful. Other examples include an increase in blood pressure causing hypertension and an increase to the eyes' near vision point causing long-sightedness and a need for reading glasses.
The results of this study are consistent with the results of another recent study from the same team at UCL showing how the futile activation of genes in unfertilized eggs, which are programmed to generate embryos, cause tumours to form in ageing worms.
"For decades scientists studying ageing have thought of ageing bodies as wearing out much like cars do, from a build-up of damage. What's exciting about this new work is that it shows something completely different. It turns out that we are not like cars - what kills us when we're old is not random damage, but our own genes. It seems that natural selection is short-sighted and ageing is the price we pay," concluded Dr Benedetto.
Notes to Editors
For more information or to speak to the researchers involved, please contact:
Dr Rebecca Caygill, UCL Media Relations. T: +44 (0)20 3108 3846 / +44 (0)7733 307 596, E: firstname.lastname@example.org
Gillian Whitworth, Lancaster University Media Relations. T: 01524 592612, E: Gillian.email@example.com
Ezcurra, M., Benedetto, A., Sornda, T., Gilliat, A.F., Au, C., Zhang, Q., van Schelt, S., Petrache, A.L., Wang, H., de la Guardia, Y., Bar-Nun, S., Tyler, E., Wakelam, M.J., Gems, D, 'C. elegans Eats its Own Intestine to Make Yolk Leading to Multiple Senescent Pathologies' will be published in Current Biology on Wednesday 9 August 2018, 16:00 UK time / 11:00 US Eastern time and is under a strict embargo until this time.
The DOI for this paper will be 10.1016/j.cub.2018.06.035
Related, recent paper also cited:
Wang, H., Zhao, Y., Ezcurra, M., Benedetto, A., Gilliat, A.F., Hellberg, J., Ren, Z., Galimov, E.R., Athigapanich, T., Girstmair, J., Telford, M.J., Dolphin, C.T., Zhang, Z., Gems, D, 'A Parthenogenetic Quasi-program Causes Teratoma-like Tumors During Aging in Wild-type C. elegans' npj Aging and Mechanisms of Disease 4: 6 published 13 June 2018.
About UCL (University College London)
UCL was founded in 1826. We were the first English university established after Oxford and Cambridge, the first to open up university education to those previously excluded from it, and the first to provide systematic teaching of law, architecture and medicine. We are among the world's top universities, as reflected by performance in a range of international rankings and tables. UCL currently has over 41,500 students from 150 countries and over 12,800 staff. Our annual income is more than £1 billion.
About Lancaster University
Lancaster is a research intensive university that combines world-class research with excellent teaching and high levels of student satisfaction. Rated top ten in the three major UK league tables, Lancaster was named University of the Year by The Times and The Sunday Times Good University Guide 2018. The University also received the TEF Gold (2017) award for outstanding teaching, an outstanding learning environment and delivering excellent employment outcomes for its students. This is the highest possible rating a university can achieve. For more information please see http://www.
About Queen Mary University of London
Queen Mary University of London is one of the UK's leading universities with 25,332 students representing more than 160 nationalities.
A member of the Russell Group, we work across the humanities and social sciences, medicine and dentistry, and science and engineering, with inspirational teaching directly informed by our research. In the most recent national assessment of the quality of research, we were placed ninth in the UK amongst multi-faculty universities (Research Excellence Framework 2014).
As well as our main site at Mile End - which is home to one of the largest self-contained residential campuses in London - we have campuses at Whitechapel, Charterhouse Square, and West Smithfield dedicated to the study of medicine and dentistry, and a base for legal studies at Lincoln's Inn Fields.
Queen Mary began life as the People's Palace, a Victorian philanthropic project designed to bring culture, recreation and education to the people of the East End. We also have roots in Westfield College, one of the first colleges to provide higher education to women; St Bartholomew's Hospital, one of the first public hospitals in Europe; and The London, one of England's first medical schools.