Life's Intrigues

Easter Island (Rapa Nui) is a Polynesian island in the southeastern Pacific Ocean, at the southeastern most point of the Polynesian triangle; it is widely famous for its monumental statues.

Easter Island may now boast another odd claim to fame: a midlife longevity drug. In a new study, researchers report that an antibiotic called rapamycin - after the island's Polynesian name, Rapa Nui - enabled middle-aged mice to live up to 16% longer than their rapa-free counterparts.

The discovery marks the first time a drug has been shown to lengthen life span in mammals, even when administered late in life.

Scientists first stumbled on rapamycin in soil samples taken from Easter Island in 1965. A bacterium found in the soil, Streptomyces hygroscopicus, secreted the stuff to fend off its bacterial and fungal rivals.

Rapamycin has since been used to prevent organ rejection in transplant patients and, most recently, as an antitumor drug. The compound works by inhibiting mTOR, a protein that regulates cell growth and survival.

Pharmacologist Randy Strong and molecular biologist Z. David Sharp, who headed the study's Texas arm, planned to feed young mice rapamycin and observe the drug's effects as they aged. But by the time the researchers formulated a feed that made the rapamycin stable and easily digestible, the mice had grown old (20 months old), or about 60 human years. Because calorie restriction and other life-lengthening measures work best when started young, Strong and his colleagues didn't expect the experiment to work in midlife. Yet the mice lived 28% to 38% longer than the controls from that point on, the researchers report in Nature, the equivalent of 6 to 9 extra years in humans. Their overall life expectancy rose 5% to 16%.

Rapamycin is known to raise cholesterol levels and, as a potent immune system suppressant, the compound could make its consumers more susceptible to infections.

Source: Science/AAAS