Researchers have discovered that a pill used to treat type 2 diabetes has improved health and lifespan in middle-aged male mice. The study was recently published in Nature Communications.

Researchers at the National Institute of Aging (NIA), a part of the National Institutes of Health (NIH) in the US, tested the type 2 diabetes drug metformin on the mice.

Metformin has been prescribed for diabetes since the 1960s. It is known to prompt sugar conversion to energy in the body, as well as to prevent the build up of sugar in the liver, which enhances insulin sensitivity.

As well as treating type 2 diabetes, the drug is also known to have beneficial effects in reducing the the risk of metabolic syndrome, a condition that can lead to heart disease and stroke.

Rafael de Cabo of the NIA’s Intramural Research Program and lead author of the study, says:

“Aging is a driving force behind metabolic syndrome and diabetes. Given that metformin is clinically proven to alleviate symptoms of these conditions and reduce risk of cancer, we thought perhaps it was a good candidate to study for its broader effects on health and lifespan.”

The researchers tested a 0.1% dosage of metformin on middle-aged male mice and compared these with a control group of mice on a standard diet with no metformin.

Results of the experiment showed that the mice who received the drug had a 5.83 % increase in lifespan, compared with the control group.

The researchers say that additionally, the mice showed improved general fitness and weighed less compared with the control group, even though they had consumed more calories.

The study authors add that the mice given metformin increased their use of fat for energy and preserved bodyweight with age. They add that this is something usually associated with increased survival in other studies.

The drug also increased antioxidant protection in the mice and, less surprisingly, prevented the development of metabolic syndrome.

Richard Hodes, director of the NIA, says of the study:

There is increasing interest in exploring how drugs for one use might be repurposed for another.

It is exciting to discover that a drug already known to be safe and effective in humans might be further studied for a possible, alternate use for healthy aging.”

However, when the metformin dosage was increased to 1%, the drug had a “toxic” effect on the mice. They showed a 14.4% shorter lifespan compared with the mice who did not have the drug. The researchers add that this could be due to kidney failure.

The researchers say that more detailed testing is needed on the effects of metformin before the drug can be explored for use in people’s healthy aging.

“Further studies are required to determine the effects of chronic exposure levels to biguanides in health and aging in humans,” they say.