Scientists have discovered a gene that accelerates aging after reproductive years
Aging isn't random? A gene switches off the search for food after procreation.
When C. elegans roundworms finish reproducing, they still retain their mobility and generally function normally - but dramatically lose the ability to recognise some of the food odours that used to lead them to eat. Researchers at Nagoya University found that this decline triggers a specific gene that literally "turns off" the perception of food odour in aging animals.
The work is published in the journal Aging Cell. The authors believe that this is one of the first examples to discover a gene that actively causes age-related decline in sensory function - not through the accumulation of damage, but through a genetically controlled "switch-off".
Why the "fifth day" is important
C. elegans live only 2-3 weeks: they mature in three days, reproduce for a few days, then age and die. Thanks to their short lifespan, scientists can observe aging processes in weeks rather than years.
According to project leader Kentaro Noma, day five is the moment just after the end of the reproductive period. That's when worms typically experience a sharp dip in their ability to smell diacetyl, the odour emitted by the bacteria that serve as their food.
How the "switch" was found
The team created a line of worms with random mutations and tested them on the fifth day of life. Most, like normal worms, were already bad at "smelling" food. But some of the mutants retained the ability. What they had in common was a defect in the nhr-76 gene - which pointed to its role.
As explained by lead author Rikuo Yokosawa, nhr-76 encodes a protein that in sensory neurons suppresses the activity of genes responsible for the recognition of food odours. The researchers suggest that this protein may be switched on by chemical signalling - that is, the body's "ageing" physiology itself triggers the switch-off mechanism.
Why would evolution need a harmful gene?
Scientists discuss two hypotheses.
Evolution does not "remove" such genes because they show a negative effect after reproduction - when the genes have had time to be passed on to offspring anyway.
A decline in food search may be beneficial to the population: if older individuals compete less for resources, the young have a better chance of survival. In this case, it may not be a "breakdown", but an evolutionarily fixed strategy.
Are there parallels with humans?
The authors emphasise that mammals also have similar proteins (nuclear hormone receptors) and can now be specifically tested for their involvement in age-related changes. There is no direct evidence of a similar mechanism in humans yet, but a model on C. elegans may suggest where to look.