The antibiotic called rapamycin is already used to treat some cancers and even suppress the immune system in patients who have had organ transplants. Researchers at the Jackson Laboratory, the University of Michigan; and the University of Texas Health Science Center have reported this finding online, but have added they do not know how this antibiotic exerts the anti-aging effect.

Rapamycin is an inhibitor of the mTOR pathway, which is known to be associated with the aging process. The researchers report that they already knew inhibition of the TOR (Target of Rapamycin) pathway extends lifespan in invertebrates, but the role of the mTOR pathway in mammals was not known.

In their study they found that even older mice fed with rapamycin lived longer than normal. In female mice, lifespan was extended by 14%, while it increased by 9% in male mice.

“While other results have been promising, the rapamycin effect is bigger, and worked even when started in late middle age,” said a released statement by University of Michigan scientist Richard A. Miller, M.D., Ph.D . "We do not know if the good effects of rapamycin in our mice are due to its anti-immune effects, its anti-cancer effects, or some other effect."

In another study, the researchers report similar findings in mice that were fed the antibiotic at 270 days of age. The extension of survival was seen both in male as well as female mice.

The three trials on anti-aging are funded by the National Institute on Aging, a part of the National Institutes of Health. Anti-aging medications are in huge demand and this trial may actually spur development of medicines tailored to extend life. However researchers warn that consumers must not start taking rapamycin until further recommendations following human trials can be made.

Rapamycin is an antibiotic that was found in soil samples on Easter Island. While the drug's anti-aging effects are a pleasant surprise, it must be noted that it suppresses immune system and reduces the ability of the body to fight infections.

The details of the study are due to appear in the July 16 issue of Nature.