Can humans live forever? Will aging soon become a thing of the past? Will immortality become the norm for the human race? According to David Harrison of The Jackson Laboratory in Bar Harbor, Maine, the only immortality humans will experience will occur in science fiction.
“Of course we’re not going to be immortal,” Harrison said. “That’s total nonsense. But, it would be nice not to have all of these awful things happen to us on such a rigid schedule…. An extra few years of healthy life span — I think that’s quite feasible.”
Harrison’s lab is just one of many conducting research on the biology of aging, with Harrison’s specialty being the use of mouse models in studying the effects of aging on a variety of physiological systems.
Harrison’s lab is part of the Interventions Testing Program, which, in coordination with the UT Health Science Center and the University of Michigan, aims to test a variety of compounds to determine their potential effects, good and bad, on the biology of aging.
“I think we have considerable human implications already, in that with the Interventions Testing Program, we have found several things that we can give to mice that increase the lifespan considerably — up to 23, 24 percent,” Harrison said.
Due to the fact that mice age 25 times faster than humans, their use in aging experiments is extremely significant. Harrison said that although mice are a good fit for aging testing, replication of the experiments and extended time are essential to the success of the research. Harrison’s lab begins testing when a mouse is 16-months old, which would make it roughly equivalent to the age of a 50-year-old human.
One of the compounds Harrison’s lab has tested is rapamycin, an immunosuppressant already used in humans to prevent organ rejection in kidney transplant patients.
Rapamycin, also known as sirolimus, was discovered in the 1970s, produced by bacteria found in soil on Easter Island, or Rapa Nui. According to “Rapamycin: One Drug, Many Effects” in the journal Cell Metabolism, Rapamycin acts as an inhibitor to the mammalian target of rapamycin(mTOR), which can be beneficial when it comes to treating a variety of diseases in humans.
With mice, Harrison said that his lab saw positive benefits from using rapamycin in testing, and that the compound increased the overall lifespan of the mice.
According to a letter published in Nature in 2009 by the three labs involved in the Interventions Testing Program, “On the basis of age at 90% mortality, rapamycin led to an increase of 14 percent for females and 9 percent for males” in terms of total lifespan. Although an increase in overall lifespan was seen, there was no difference in the disease patterns among mice treated with rapamycin and mice that were not. This suggests that rapamycin may not target any specific disease, but instead increases life span and tackles the issue of aging as whole. Harrison said that later research has supported this idea.
“Mice are very much like people in their biology,” Harrison said. “So, if you have something, which is really slowing down aging in mice, there’s a really good chance that it will slow it down in people.”
Although already used in humans for kidney transplant patients, the use of rapamycin in humans for anti-aging treatments has been limited due to possible side effects. One of the negatives associated with rapamycin is that it causes an increase in the possibility of developing type 2 diabetes.
According to Harrison, humans who receive drapamycin were 5 percent more likely to develop type 2 diabetes than people who were not given the substance.
“Certainly, if there was a reasonable chance of something slowing down the entire spectrum of complications from aging and increasing my lifespan even 5 or 10 percent, I think an increase in my risk of type 2 diabetes, which is controllable and I can watch out for, is an acceptable risk,” Harrison said. “I have a suspicion that many people would feel that way too, but that’s not the way the people that make decisions feel.”
Harrison believes that rapamycin could be extremely beneficial in humans, even with something as simple as increasing the ability of older people to benefit form the flu vaccine.
“Based on the fact that rapamycin seemed to benefit the mice even when started when they were (the mouse equivalent) 65 (human) years old, it might be possible that we could find things to benefit older people as well as young,” Harrison said.
However, significant steps in culture and law must be made before any sort of anti-aging testing can be implemented for humans.
“As a scientist, I’m dealing with reality,” Harrison said. “Legal people are dealing with make believe, that they make up. Human law can be changed with the stroke of a pen. Natural law — that’s a little tougher. It’s frustrating that lots of people (may) miss these extra healthy years because inertia of human law.”
Harrison says that if aging research is brought into human testing, the full benefits will probably not be seen until the current college-aged generation enters older adulthood.
Harrison, however, emphasized the fact that not only is eliminating aging a near impossibility, it is also not the focus of aging research in today’s day and age. Instead, Harrison said that his research is aimed at reversing or preventing some of the diseases associated with aging and providing the older generation with more healthy years as opposed to more years in general.
In terms of how long humans will live if anti-aging testing does enter the human realm, Harrison cites the story of Alex Comfort, a scientist who did the calculations of how old a human would live if aging became nonexistent. Comfort used the risk of death percentage for a 12-year-old boy and determined that if the side effects of aging were completely eliminated, the average lifespan for a human would be 800 years.