A drug used to treat Type 2 diabetes may delay the effects of aging and increase life span, a new study in animals suggests.
Mice that were fed the drug, called metformin lived about 5 percent longer than those that were not fed the drug. The treated mice lived 160 weeks, while those not taking the drug lived about 150 weeks.
Mice on metformin were also more likely to be physically fit in their old age, and less likely to develop cataracts than those not on the drug.
The metformin treatment appeared to mimic some of the effects of caloric restriction, such as reducing cholesterol levels, and increasing expression of certain genes, the researchers said.
Caloric restriction means eating fewer calories than are burned every day, and has been shown in animal studies to increase life span. But in the new study, mice fed metformin were not put on a restrictive diet — in fact, they ate more calories than those not fed metformin.
The study suggests a possible way to reap the benefits of caloric restriction without food deprivation.
However, it's too soon to know whether the results apply to humans. For one, the mice that lived longer had blood levels of metformin that were 10 times higher than those seen in humans taking the drug to treat diabetes, the researchers said. And mice put on an even higher dose of metformin actually had a decreased life span, because the drug was toxic (it caused kidney failure). Mice were also fed a controlled diet for their whole life, which is not true of people, said study researcher Rafael de Cabo, a senior investigator at the National Institute on Aging.
Future studies are needed to determine if metformin taken at safe doses can have benefits for people who don't have diabetes, de Cabo said.
Still, the findings "raise the possibility of metformin-based interventions to promote healthy aging," the researchers wrote in the July 30 issue of the journal Nature Communications.
Previous studies in people have linked metformin treatment with a reduced risk of pancreatic cancer and breast cancer. Another study found that ovarian cancer patients who took the drug for diabetes lived longer compared with those who did not take the drug.
The new study found that metformin increased the animals' antioxidant responses to stress, and reduced inflammation, which may play a role in the drug's apparent ability to prolong life span.
It's possible that metformin may affect gut bacteria, which was not tested in the study, the researchers said.
Metformin is a relatively safe drug, de Cabo said. Potential side effects of metformin include: diarrhea, bloating, stomach pain, an unpleasant metallic taste, headache, flushing of the skin and muscle pain, according to the National Institutes of Health. Serious side effects include chest pain and rash.
Some studies in mice suggest the drug increases the risk of noncancerous growths (polyps) on the ovaries, but it's not known whether metformin increases the risk of polyps in people.