Not exactly a surprise, I know, but I didn’t mean you and me are getting older. I meant we are getting older, as a population. In 2001, one Canadian in eight was aged 65 or older. By 2026, one in five will be 65 or older. So what should we do with an increasingly aged population? Well, this being a North American consumer culture, the sensible thing to do is try to sell them stuff. I mean, think of the size of the market!
Right now, a significant amount of research is being devoted to aging. The main focus is to try to slow down aging (partly by developing marketable supplements and such). As some of you might know, even my own PhD thesis project is on how to slow aging in the brain. Loyal readers of ScientificChick.com will also be aware of recent articles about caloric restriction, a potential way to keep old age at bay. Thankfully, a recent publication in Nature suggests a much easier way to live longer: forget starvation, all you have to do is pop a(nother) pill!
In this article, American researchers show that mice that eat rapamycin supplements starting at 600 days of age (senior citizens in mouse years) live longer, up to 14% longer for females and 9% longer for males. What’s more, rapamycin supplementation did not change the causes of death. The researchers propose that this drug could be acting by postponing death from cancer, by delaying mechanisms of aging, or both.
How does rapamycin work? Well, as you might expect with a miracle drug like this, we’re not really sure. Rapamycin is an inhibitor of a pathway called mTOR. The mTOR pathway has many functions in your cells, like coordinating the survival response arising when there are changes in nutrient and energy availability, and dealing with potentially deadly stresses, such as oxidative stress (the kind of stress fancy juices packed with antioxidants are supposed to battle). Since the mTOR pathway acts kind of like a central sensor of cell health, it makes sense that it would be implicated in regulating lifespan. Exactly how rapamycin is working its magic, though, is probably what the researchers are trying to figure out for their next article.
Could the increase in longevity following rapamycin supplementation be related to the effects seen with caloric restriction (the “eat less, live longer” paradigm)? Well, mice on rapamycin show no change in body weight, so we know the drug is not acting through a caloric restriction mechanism. The converse, however, may be true: it is thought that the beneficial effects of diet restriction may also be due to an inhibition of the mTOR pathway.
So don’t throw out the double-stuffed Oreos just yet, but don’t eat half the box either: rapamycin pills for humans won’t be on the shelves tomorrow. While mTOR inhibitors are currently being used to treat a few conditions (transplant rejection and some cancers, for example), there’s still a lot of work to do to tease out all the potential interactions and side effects.
Longevity in pill form? To me, it would feel like cheating the system. And if there’s one thing we keep learning over and over in the life sciences, it’s that trying to cheat Mother Nature always has some unintended consequences.
A great illustration of the aging mouse by TS Rogers
Reference: Rapamycin fed late in life extends lifespan in genetically heterogeneous mice. Harrison DE, Strong R, Sharp ZD, Nelson JF, Astle CM, Flurkey K, Nadon NL, Wilkinson JE, Frenkel K, Carter CS, Pahor M, Javors MA, Fernandez E, Miller RA. Nature 2009 16;460(7253):392-5.