X-Message-Number: 29482
From: 
Date: Wed, 02 May 2007 23:47:39 -0500
Subject: Gene Discovered that Enables Calorie Restriction to Extend Li...

Now if they can only figure out how to utilize it!

http://news.independent.co.uk/world/science_technology/article2504640.ece

Scientists find the gene that decides how long we live 
The science of ageing 
By Steve Connor, Science Editor 
Published: 03 May 2007 


Scientists have come a step closer to understanding the secret of a long, 
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 it not as strong for humans.


The latest study focussed on a gene common to nematode worms, mice and humans. 
When the gene was blocked in the 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 that 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 drugs that can extend the human
lifespan without 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."


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. Experiments with other creatures found that the 
phenomenon appeared to be ubiquitous in the animal kingdom. Some scientists 
suggested it was an evolutionary adaptation to surviving hard times until enough
food became available.


The longevity-associated gene identified by Dr Dillin and his colleagues is 
known as PHA-4 - the name of the protein for which the gene is responsible. 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. In mammals, the gene is linked with a hormone called glucagon which 
increases levels of glucose in the bloodstream to maintain the body's energy 
balance especially during fasting.


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 that are linked to longer living. 


The accepted view among scientists is that there is probably an absolute upper 
limit to human lifespan of no more than about 125 years - the oldest person with
an authenticated birth record was a Frenchwoman called Jeanne Calment, who died
aged 122 years, five months and 14 days. People in the West are living longer, 
but the extra years are not necessarily healthy ones - an ageing population is 
leading to a dramatic rise in senile dementia.


There has been a dramatic increase in longevity over the past couple of 
centuries due to improvements in housing and sanitation, nutrition and health.


Some 60 per cent of boys and 70 per cent of girls born in 1981 are expected to 
survive to celebrate their 75th birthday in 2056. In 1881, only a third of girls
and just one in five boys reached the same age.


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