Contrary to earlier research wherein scientists concluded that rapamycin extends life by slowing aging, here another group proposes that the extended life observed in laboratory animals results from cancer suppression, and aging isn't greatly impacted. Drugs that can slow aging are in any case a sideshow, a line of research that will require decades and billions but is incapable of producing ways to rejuvenate the old. Only SENS and similar repair-based research programs have the potential to result in therapies that will extend the healthy lives of the elderly and restore their lost vigor and youth. So if the scientific community is going to spend the few decades between now and my old age working on new medicine, I'd rather they ditched the old-style drug discovery pipeline in favor of a research strategy that is actually likely to benefit me. As to the debate on rapamycin:
Rapamycin is used in recipients of organ transplants, as it keeps the immune system in check and can consequently prevent rejection of the foreign tissue. In 2009, US scientists discovered another effect: Mice treated with rapamycin lived longer than their untreated counterparts. "Rapamycin was the first drug shown to extend maximal lifespan in a mammalian species. This study has created quite a stir. We wanted to address if rapamycin slows down aging in mice or, alternatively, if it has an isolated effect on lifespan - without broadly modulating aging."
"Our results indicate that rapamycin extends lifespan, but it has only limited effects on the aging process itself. Most aging traits were not affected by rapamycin treatment. Although we did observe positive effects on some aging traits, such as memory impairments and reduced red blood cell counts, our studies showed that similar drug effects are also seen in young mice, indicating that rapamycin did not influence these measures by slowing aging, but rather via other, aging-independent, mechanisms."
The researchers believe that such aging-independent drug effects also underlie rapamycin's effect on lifespan. "We assume that the lifespan of mice is extended because rapamycin inhibits tumor formation. This is a well-known rapamycin effect, which we were able to confirm. Cancer is the leading cause of death in the relevant mouse strains. Rapamycin, therefore, seems to have isolated effects on specific life-limiting pathology, but lacks broad effects on aging in mice."
"Generally speaking, our studies show that a number of different parameters have to be considered when assessing the efficacy of possible anti-aging interventions. The interpretation of the data depends heavily on the overall picture of findings. Lifespan measures alone are not a reliable indicator of anti-aging effects. This makes the search for anti-aging medicines tedious, but it is also very promising, because such substances could open up new possibilities for medicine. However, this is still some way off."