British scientists have poured cold water on US research that claimed to have identified a gene responsible for ageing.
The gene controls the production of a substance, sirtuin, which has been widely exploited by cosmetics firms to sell anti-wrinkle creams.
Studies of yeast, the nematode worm and the fruit fly had shown that when an organism's genes overproduced sirtuin, its lifespan was significantly extended, in nematodes by as much as 50 percent.
A connection was also found between sirtuins and dietary restriction - known to extend lifespan in many organisms - indicating that dietary restriction produced this effect by activating the production of sirtuins.
Predictably, the sirtuin-producing gene was dubbed the 'longevity gene', and a number of anti-ageing creams were launched which containeda substance claimed to activate sirtuins.
But in a study published yesterday in the journal Nature, Dr David Gems of University College London provides what he calls 'almost conclusive' evidence that the effects on animal longevity seen in earlier experiments were actually unconnected to sirtuin.
His team, together with researchers in the US and Hungary, first examined two different strains of nematode worm, each from a different prior study. The worms had been genetically manipulated so that the sirtuin gene was overactive.
As expected, these worms lived longer than the control 'wild-type' worms. The team found, however, that this difference disappeared once precautions were taken to ensure that the only difference between control and test worms was the level of sirtuin production.
Suspecting that some other genetic factor must have caused the longevity, they identified a mutation in a gene involved in the development of nerve cells as the cause.
Similar results were found in fruit flies - indeed, the team actually created a new strain of fruit fly with even higher sirtuin levels, but found it wasn't particularly long-lived.
Finally, the teams re-tested the claim that dietary restriction increases lifespan by activating sirtuins. Taking mutant fruit flies that lacked the sirtuin gene, the researchers showed that dietary restriction still increased lifespan.
"Sirtuins, far from being a key to longevity, appear to have nothing to do with extending life," says Dr Gems.
"But I think this is good news in a way: after all, revising old ideas can be as important as presenting new ones to assure scientific progress. This work should help to redirect scientific efforts toward those processes that really do control ageing."