When 14th-century Spanish explorer Ponce de Leon set out on his famous sea voyage in search of the Fountain of Youth, he landed on the shores of a verdant, unexplored land. As legend has it, he found a magical spring capable of reversing the aging process and curing illness. He named this new territory "La Florida" for Pascua Florida, the Spanish Easter festival of rebirth.
Turns out, what Ponce de Leon was looking for wasn't to be found in a warm Floridian spring, but instead in the soil of a tiny dot of land off the coast of Chile: Easter Island. He had the Easter part right, it seems.
Medicine of Youth?
In 1964, 450 years after Ponce de Leon's voyage, a group of Canadian scientists discovered a bacterium in the soils of Easter Island that secreted a powerful antifungal antibiotic they named rapamycin that prevented natives of the island from getting tetanus. Since then, the compound has been used as an immunosuppressant to help the bodies of organ transplant patients accept their new organs, and as an ingredient in anticancer drugs, due to the fact that it suppresses the division of cells. It also seems to have a lot of potential as a pharmaceutical Fountain of Youth, as drug trials have found it can extend the lifespan of a mouse by up to 60 percent.
"The most exciting aspect of rapamycin therapy is the potential it has to improve health-span, not just lifespan," says Dr. Suzette Tardif of the Barshop Institute for Longevity and Aging Studies at UT San Antonio, who published a study last year on the long-term consequences of rapamycin on marmoset monkeys. "The goal of much aging research these days is not to extend human life but to extend the period of healthy life — delaying the onset of common age-related conditions such as cardiovascular disease, diabetes, cancer, and Alzheimer's. Studies in rodents suggest that rapamycin may be able to do just that."
Since the 2009 discovery that rapamycin could extend the lifespans of mice, aging and longevity researchers have been hustling to get to the bottom of whether the drug might be used to reinvigorate and extend the lives of aging humans. There are concerns that high doses of rapamycin may increase the risk of cancer, diabetes, and infection, and studies have found that male and female mice seem to respond to the drug differently. And then there's the small matter of nobody understanding exactly how rapamycin works to improve the health and extend the lifespans of its test subjects.
"We're still investigating the effects of rapamycin within cells," says Dr. Corinna Ross, an assistant biology professor at Texas A&M University San Antonio, and lead author on last year's marmoset study. "On a systemic level, it appears to be mimicking caloric restriction, which is the gold standard to increase health and lifespan."
The workings of rapamycin on a cellular level seem to be more mysterious:
"It seems to be suppressing a cellular signalling pathway that's associated with cell growth and proliferation, but beyond this investigators are still examining the pathways," says Ross.
Pooch de Leon?
Humans can't yet take rapamycin as a treatment for aging, but soon you might be able to give it to your dog. Researchers at the University of Washington's Dog Aging Project have tested rapamycin on a small group of companion dogs, and although results of this study haven't yet been published, the website claims "there were no significant side effects associated with the rapamycin treatment, and there were statistically significant improvements in heart function in the dogs that received rapamycin relative to those that received the placebo."
Since our pet dogs are such an important part of our lives, but most breeds don't live past the age of 15, the Dog Aging Project is seeking funding to conduct a large-scale longitudinal study on 10,000 dogs from all over the U.S. Some of the dogs in the study will receive a rapamycin treatment.
"For me, the most exciting thing about the potential of rapamycin is the large impact that it could have on healthy longevity for both dogs and people," says Dr. Matt Kaeberlein, co-director of the Dog Aging Project and University of Washington professor of pathology. "The traditional biomedical approach of targeting one disease at a time is not particularly effective. Even if we could cure all forms of cancer — which isn't happening — that would only result in about a 3-to-5-year increase in life expectancy for a typical 50-year-old woman.
"By targeting the aging process directly, we have the potential to increase healthy life expectancy to a much greater degree, and I believe this is actually less challenging than 'curing' individual diseases. Rapamycin is our best bet for the first drug that actually does this effectively, which is very exciting."
So ... maybe we have discovered the Fountain of Youth. Now all we have to do is figure out the dosage.