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Scientists are closer to understanding the secret of a long and healthy life with the discovery of a gene that plays a central role in the ageing process.
The gene appears to be critical in extending the lifespan of animals that are subjected to a calorie-restricted diet - when they are slightly starved of high-calorie food but are given all the other nutrients they need.
It is well-established that calorie-restricted diets lead to longer maximum lifespans in practically every animal in which they have been studied, although the evidence is less strong for humans.
The latest study focused on a gene that is common to tiny nematode worms, mice and humans. When the gene was blocked in the nematode worms, the benefits of a calorie-restricted diet were lost and the worms lived shorter lives.
Similarly, when the scientists were able to stimulate the gene they found they could enhance the longevity of the worms so that their extended lifespans came close to matching those worms on a calorie-restricted diet.
Scientists believe that the findings could unlock a genetic treasure-chest of potential pharmacological targets for developing new drugs that could extend the lifespan without people having to follow a rigorous and difficult diet.
"After 72 years of not knowing how calorie restriction works, we finally have genetic evidence to unravel the underlying molecular programme required for increased longevity in response to calorie restriction," said Andrew Dillin, of the Salk Institute in San Diego, California.
"It's likely to play a role in the human condition, although we still don't know whether calorie restriction really works in humans. Studies in primates suggest it does," Dr Dillin said.
The first experiments in calorie-restricted diets go back to the 1930s.
Laboratory rats and mice fed a severely calorie-restricted diet, but with normal levels of vitamins and minerals, lived almost twice as long as rodents with unrestricted access to food.
Some scientists suggested it was an evolutionary adaptation to surviving hard times until there was enough food available to breed and raise offspring.
The longevity-associated gene identified by Dr Dillin and his colleagues is known as PHA-4, which is the name of the protein the gene is responsible for.
The same gene also exists in mice and humans and is known as the Foxa family of genes.
Both PHA-4 and Foxa are involved in the complex process of glucose metabolism. Dr Dillin said that there were huge potential payoffs in reducing calorie intake while maintaining a healthy diet rich in vitamins, minerals and other nutrients.
Currently it was the only strategy apart from direct genetic manipulation that consistently prolonged life and reduced the risk of cancer, diabetes and cardiovascular disease while staving off age-related degeneration in laboratory animals, he said.
Scientists from Louisiana State University are monitoring a group of 48 overweight men and women aged between 25 and 50. The study found that those who were able to cut down on their calorie intake improved in terms of metabolic markers linked to longer living - such as reduced levels of insulin in the blood stream and slower rates of DNA decay.
Luigi Fontana, who led the study, said that the findings point to ways of lowering the risk of premature ageing and death.
"It's becoming clear ... that calorie restriction does change some of the markers we associate with ageing."
- INDEPENDENT
