The march of old age may be unstoppable, but two new studies in mice and monkeys suggest we can at least tinker with the ageing process 鈥� and offer a glimpse at how anti-ageing medications could work.
鈥淵ou want something that鈥檚 going to give you 10 more years of relatively good health and not 10 more years of frailty,鈥� says , a biochemist at the University of Washington in Seattle, who studies ageing, but was not involved in either study.
杏吧原创s probably haven鈥檛 stumbled on that drug yet, but a drug called rapamycin, already used to suppress the immune systems of organ transplant recipients, comes close. In tests conducted at three research centres, mice that began taking the drug at a relatively old age lived substantially longer than other rodents.
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Fungus find
The researchers, led by at the Jackson Laboratory in Bar Harbor, Maine, had initially planned to begin feeding the mice rapamycin around middle age. But due to difficulties in manufacturing food that contained adequate amounts of the drug, the hundreds of mice didn鈥檛 start taking the drug until they were 600 days old 鈥� about the equivalent of a 60-year-old human.
Mice on rapamycin, which was first discovered in soil fungus from Easter Island, lived about 10 per cent longer than other mice.
Kaeberlein says that the drug鈥檚 ability to extend lifespan when taken late in life is 鈥渆xactly what you鈥檇 want from an 鈥榓nti-ageing drug'鈥�.
鈥淚t鈥檚 set a high bar for the field,鈥� agrees , a molecular biologist at Harvard University Medical School in Boston. 鈥淚t鈥檚 also the first time that a drug has worked so late in life鈥�
Rapamycin is not perfect, however. It makes a good transplant drug because it slows the expansion of immune cells and stops rejection of the implanted tissue. So scientists will need to determine whether lower doses of the drug can offer humans anti-ageing effects without compromising their immune systems, Kaeberlein says.
Diet clue
Pharmaceutical companies would also be wise to hunt for drugs that act on the same biological pathway as rapamycin. Called TOR, this pathway is involved in a cell鈥檚 response to nutrients.
Researchers had previously implicated TOR in some of the anti-ageing effects of a sparser diet that have been seen in some animals. Now, in a second study on ageing, there is the first evidence that 鈥渃aloric restriction鈥� has the same effect in primates.
For up to 20 years, a team led by , a biologist at the University of Wisconsin in Madison, followed 76 rhesus macaques, half of which consumed 30 per cent fewer calories, beginning around adulthood. Today, 37 per cent of the animals on the restricted diet are still alive, compared to just 13 per cent of monkeys who ate a normal amount of food.
鈥淚t suggests to me that the fundamental biology of caloric restriction being studied in mice, flies, worms, seems to apply nicely to primates,鈥� says Weindruch.
鈥淚t鈥檚 to the point now where, if caloric restriction does not extend human lifespan, we鈥檙e an exception on the planet,鈥� Sinclair agrees.
Healthy ageing
Not only did the calorie-restricted animals live longer than other macaques, they also led healthier lives. They were less likely to suffer from heart disease, cancer, neurodegeneration, and diabetes. The monkeys appeared healthier too, says team member Ricki Colman. 鈥淭heir coats are shinier; they have a younger-looking posture.鈥�
The breadth of these improvements is an important sign that calorie restriction slowed the process of ageing and did not simply prevent diseases related to food intake such as diabetes, Weindruch says.
Healthy ageing will also be the metric by which medicines like rapamycin are tested against in humans, says Kaeberlein. 鈥淵ou鈥檙e never going to do a clinical trial for an anti-ageing drug. You鈥檙e going to do a clinical study for Alzheimer鈥檚 or diabetes.鈥�
Journal reference (mice): (DOI: 10.1038/nature08221)
Journal reference (monkeys): (DOI: 10.1126/science.1173635)
