Word: rapamycin
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Scientists think rapamycin's cellular target - called mTOR for "mammalian target of rapamycin" - helps regulate the body's response to nutrients and may also, according to Strong, "gear up responses to stress," such as the oxidative stress that damages proteins and DNA and contributes to disease development. "What we're doing with rapamycin," Strong says, "is we're actually tricking the cells into thinking that they're depleted of nutrients. Rather than the animals losing weight - we haven't noticed any weight loss - they may be just using their proteins more efficiently, and then repairing proteins more efficiently...
...this cellular efficiency, perhaps, that delays aging and helps preserve animals' good health. The findings suggest that rapamycin does not affect or prevent any one disease specifically - the mice in the study died of various causes, with no real difference between mice that received rapamycin and those that didn't - but rather that it slows aging overall. (Read a TIME cover story on the science of aging...
...Rapamycin's life-extending effect has been demonstrated by other researchers in past studies of worms, fruit flies and yeast; the drug appears to interfere with a similar cellular process in those species too. "I think this is a big leap from those invertebrate species to mammals," says Strong, who is also a senior research scientist for the Department of Veteran Affairs. "This gives us a good idea that perhaps it would work in humans...
Earlier human trials have shown, however, that rapamycin can have serious side effects. Because it is an immunosuppressant, it can make users susceptible to opportunistic infections. It has also been linked to hyperlipidemia, or high levels of triglycerides in the blood, which can lead to heart disease. It's unclear whether these problems would counteract any longevity benefit that rapamycin might provide in humans. Says Strong, "I think more immediately, people are starting to look at [rapamycin] for age-related diseases like Alzheimer's disease, Parkinson's disease or kidney disease." The drug has also recently entered clinical trials...
...agents for extending life, other drugs may be further along in the pipeline - resveratrol, for one, which has also prolonged life in lab mice. But the new finding by Strong and his colleagues "more clearly identifies the [target of rapamycin] pathway as important across species." It may guide researchers to target different proteins in the same pathway. "If those proteins react the same way to extend lifespan, then we might be able to get rid of unwanted side effects," says Strong...