Posted by: 4pack | July 9, 2009

New Scientific Studies Point To A Drug, Rapamycin, That Can Extend The Elderly’s Lifespan By “Mimicking The Effects Of Dietary Restriction”

THE BENEFITS OF CALORIE RESTRICTION ARE BEING GIVEN EVEN GREATER CREDENCE BY NEW DRUG STUDIES THAT SHOW INCREASED LIFESPAN THROUGH TARGETING “SUPPRESSION OF IMMUNE SYSTEM” THAT IS PRIMARY BENEFIT OF CALORIE RESTRICTION…..

Rapamycin, a drug commonly used in humans to prevent transplanted organs from being rejected, has been found to aging in menextend the lives of mice by up to 14% — even when given to the mice late in life.

The researchers caution, however, that using this drug to extend the lifespan of humans might be problematic because it suppresses the immune system — potentially making people who take it more susceptible to infectious diseases.

Research teams at three different US institutions — the University of Texas Health Science Center in San Antonio, the University of Michigan in Ann Arbor and the Jackson Laboratory in Bar Harbor, Maine — ran the same experiment in parallel, splitting nearly 2,000 mice between them. The mice were bred to ensure that they were genetically different enough that no single strain would be more or less susceptible to ageing-related diseases or the effects of the drug. They then gave the mice food that included rapamycin.

Problems formulating the feed meant that the teams couldn’t start the treatment until the mice were rather older than they had planned — 20 months of age, or the equivalent of about 60 years in human terms.

As it happened, this delay was a fortuitous accident. Compared with the non-drug-taking group, the lifespans of the mice given rapamycin increased by up to 14%, even though they were middle-aged when treatment began. Their life expectancy at 20 months shot up by 28% for the males and 38% for the females.1

“You’ve probably heard the phrase ‘chance favours the prepared mind’, and this is an example of it,” says David Harrison, who led the arm of the experiment that took place at the Jackson Laboratory.

An independent initiative, the Interventions Testing Program overseen by the US National Institute of Aging, chose rapamycin for the three labs to test because it’s known to have effects on a cellular pathway called TOR (for target of rapamycin). This pathway is known from studies in mice, flies and worms to be involved in the age-defying effects of calorie-restricted diets.

This link could mean that rapamycin is mimicking the effects of dietary restriction, says Matt Kaeberlein, whose group at the University of Washington in Seattle works on ageing in mice, yeast and worms. “All the arrows are going in the right direction,” he says.

Harrison isn’t so sure, however — none of the mice lost body weight during their experiments, he says, and dietary restriction usually works best when started early in life, not in middle age as the rapamycin treatment was.

The big question, of course, is whether this drug could extend human life. Both Harrison and Kaeberlein are cautious. “I wouldn’t do it myself and wouldn’t encourage anyone to do it at this point,” says Harrison.

http://www.nature.com/news/2009/090708/full/news.2009.648.html

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