A genetic experiment to unlock the secrets of the ageing process has created organisms that live six times their usual lifespan, raising hopes that it might be possible to slow ageing in humans.
The geneticists behind the study say the increase in lifespan is so striking, they may have tapped into one of the most fundamental mechanisms that controls the rate at which living creatures age.
The tests were carried out in single-celled organisms, forcing them into what the researchers refer to as ”extreme survival mode”. Instead of growing quickly and showing signs of ageing, the organisms became resilient to damage and were better able to repair the genetic defects that build up with age, often leading to cancer in later life.
”When you do this genetic manipu-lation, you can get some of the longest lifespans ever described,” said Valter Longo, a biomedical gerontologist at the University of Southern California. ”We have good reason to believe this genetic effect is conserved in other organisms. We’re working with mice and human cells now, and are already starting to see the same response.”
A large body of research has already shown that severely restricting diet can boost the lifespan of flies, worms and mice by around 40%. Scientists believe that drastically cutting calories triggers a switch in an organism’s behaviour, from growing and being able to reproduce to a state of stasis in which growth and ageing are put on hold, at the expense of reproductive capability, until more food is available.
Scientists are now trying to mimic the effect by tinkering with genes in the hope of developing anti-ageing treatments that work without having to cut food intake.
”We’re not too far from being able to start thinking about drugs that can put humans in anti-ageing mode. That doesn’t mean we’ll live six times longer, but we could slow down the DNA damage we accumulate as we age, and that could protect us from cancer,” he said.
In the experiment, Longo’s team took yeast cells and knocked out two key genes, namely Sir2 and SCH9. The latter governs the cells’ ability to convert nutrients into energy. The team found that, instead of dying after a week, the cells lived for up to six weeks.
Longo said parallel experiments on human liver cells appeared to replicate the effect, but he refused to elaborate until the results have been published.
The researchers believe the Sir2 gene plays a role in restricting an organism’s lifespan, allowing energy from the food it eats to be directed into growth and reproduction. By blocking the gene, the cells were essentially tricked into believing food was scarce and they switched to survival mode.
”When you start increasing lifespan, you’re really playing with the life and death programmes of organisms. We’re telling the organisms to go into a completely different mode of slow ageing,” said Longo. ”What they’re doing is saying ‘I cannot afford to age. I still have to generate offspring, but I don’t have enough food to do it now.”’
Research has begun to test whether the effect works in mice. According to Longo, lab mice bred with the equivalent gene knocked out appear to live longer, but are smaller, infertile and often suffer muscular defects. This suggests the gene is necessary for normal foetal development.
The research is a big step in a small field that has been progressing at pace since the advent of the new tools of genetics. Another paper published recently in the American journal Science describes the discovery of 10 new genes that are thought to regulate longevity in yeast cells. ”Even though yeast is a simple, single-cell organism, it’s still capable of revealing mechanisms in the ageing process,” said the study’s lead researcher, Stanley Field of the University of Washington in Seattle. — Â