July 10, 2009 -- A drug first found in the soil of Easter Island in the South Pacific may hold the elusive key to slowing the aging process.
New research shows rapamycin extended the life expectancy of middle-aged mice by 28%-38%. Researchers say that's more than the expected benefit in extra years of life that would be achieved by knocking out both heart disease and cancer in humans.
"We believe this is the first convincing evidence that the aging process can be slowed and life span can be extended by a drug therapy starting at an advanced age," says researcher Randy Strong, PhD, in a news release. Strong directs the Aging Interventions Testing Center in San Antonio.
The Aging Interventions Testing program is funded by the National Institute on Aging and is designed to test compounds for potential antiaging effects on mice. Several compounds have already been tested, but researchers say rapamycin is the first to significantly increase the life span of mice at all three testing centers and in both male and female mice.
Rapamycin was first discovered in the 1970s in the soil of Easter Island. Its immunosuppressant properties led to its use in transplant patients to prevent organ rejection. It's also being studied as a potential anticancer drug.
In the study, published in Nature, researchers added rapamycin to the diets of mice who were the human equivalent of about 60 years old.
At first, the drug was not readily absorbed into the bloodstream of the mice, so a specialized feed was developed with an encapsulated, timed-release form of rapamycin.
The results showed that the average life span of the mice was increased significantly with rapamycin.
Researchers write that "rapamycin may extend life span by postponing death from cancer, by retarding mechanisms of ageing, or both." The effects of rapamycin may be due to its effect on an enzyme involved in cell metabolism.
Although the results are promising, experts say it is still much too soon to assume it will have the same effect in humans.
"In no way should anyone consider using this particular drug to try to extend their own life span, as rapamycin suppresses immunity. While the lab mice were protected from infection, that's simply impossible in the human population,” says Lynne Cox, a researcher in aging at the University of Oxford, England, in a news release.
"What the study does is to highlight an important molecular pathway that new, more specific drugs might be designed to work on. Whether it's a sensible thing to try to increase life span this way is another matter: perhaps increasing health span rather than overall life span might be a better goal," says Cox.