S u m m a r y :
Genes promoting health and survival in the young do the opposite for the old: they drive ageing in later years, says a new study published in the journal Genes & Development.
What causes ageing? From where does it start? The new research, conducted by a team of scientists from Germany-based Institute of Molecular Biology (IMB), focuses on investigating the origin of ageing. The answer lies in the DNA, more specifically in a set of genes involved in autophagy, a process whereby the body consumes its own cells. So, when autophagy is switched off through these genes, longevity is promoted, also resulting in a better neuronal health. The findings are thought to have implications for the treatment of neurodegenerative conditions that entail autophagy, like Alzheimer’s disease and Parkinson’s.
An Evolutionary Mistake?
According to the researchers, their findings are the first genetic evidence that explains ageing. Apparently, the ageing process comes as a side-effect of evolution—this stands in stark contrast against the very meaning and implication of evolution. Driven by natural selection, as has explained Charles Darwin, the fittest individuals survive to breed, passing on their genes that code for their special traits. The characteristics that given certain individuals the upper over others in terms of reproductive success are, thus, selected more and more, leading to more individuals possessing them. So, theoretically, this should have given rise to organisms with characteristics that prevent them from ageing. Evolution should have stopped ageing. However, this is obviously not true as all of us age and die.
Natural Selection Chooses Ageing
When debating this evolutionary contradiction, George C. Williams explained, back in 1953, how natural selection and ageing can go hand in hand: while evolution promotes the genes behind reproductive success while turning a blind eye to their negative consequences on longevity, effects that would only appear after the process of reproduction. For explain, a gene mutation that leads to more offspring might be one that shortens life, and natural selection would ignore the negative effects, and further the occurrence of these genes until the latter become hard-wired into the DNA. This theory has remained without evidence though. Until now, explains lead author of the new paper, Jonathan Byrne.
“The evolutionary theory of ageing just explains everything so nicely but it lacked real evidence that it was happening in nature. Evolution becomes blind to the effects of mutations that promote ageing as long as those effects only kick in after reproduction has started. Really, ageing is an evolutionary oversight,” says Byrne.
“These AP genes haven’t been found before because it’s incredibly difficult to work with already old animals, we were the first to figure out how to do this on a large scale.”
They Let You Live, But Only When You’re Young
According to Byrne and his colleagues, 30 genes have this antagonistic aspect, that is, they confer a desired trait of development together with ageing onto the individuals bearing them. This group of 30 genes constitute the first ones that appear to be promoting ageing; this only applies to old worms though.
“Considering we tested only 0.05% of all the genes in a worm this suggests there could be many more of these genes out there to find,” says Byrne.
Ageing Accelerated and Decelerated
Even more surprising, adds co-lead author Thomas Wilhelm, is that these genes were involved in the regulation of autophagy, which is known to accelerate ageing.
Autophagy recycling process that is needed for life to continue. It, however, slows down with age, and as the new study suggests, it only gets worse in older worms. However, when the key genes were shut down and autophagy not initiated, the worms lived longer. Moreover, turning autophagy off in only one tissue of the worm boosted the health of its neurons, and the authors believe that this might be what is protecting muscles and the body in general in good health.
Hope For Alzheimer’s Patients
Wilhelm explains further that their findings might contribute to research focused on neuronal diseases linked with dysfunctional autophagy such as Alzheimer’s and Parkinson’s. The study might pave the way to prevention of these diseases.