The neural effects of the drug, called metformin, also found to help mice become smarter, according to the study, published in the journal Cell Stem Cell.
The discovery is an important step toward therapies that aim to repair the brain not by introducing new stem cells but rather by spurring those that are already present into action, said lead study author Freda Miller of the Hospital for Sick Children affiliated to the University of Toronto.
The fact that it's a drug that is so widely used and so safe makes the news all that much better, she said.
Earlier work by Miller's team highlighted a pathway known as aPKC-CBP for its essential role in telling neural stem cells where and when to differentiate into mature neurons.
As it happened, others had found before them that the same pathway is important for the metabolic effects of the drug metformin, but in liver cells.
"We put two and two together," Miller said. If metformin activates the CBP pathway in the liver, they thought, may be it could also do that in neural stem cells of the brain to encourage brain repair.
The new evidence lends support to that promising idea in both mouse brains and human cells.
Mice taking metformin not only showed an increase in the birth of new neurons, but they were also better able to learn the location of a hidden platform in a standard maze test of spatial learning.
While it remains to be seen whether the very popular diabetes drug might already be serving as a brain booster for those who are now taking it, there are already some early hints that it may have cognitive benefits for people with Alzheimer's disease.
It had been thought those improvements were the result of better diabetes control, Miller says, but it now appears that metformin may improve Alzheimer's symptoms by enhancing brain repair.
Miller said they now hope to test whether metformin might help repair the brains of those who have suffered brain injury due to trauma or radiation therapies for cancer.
