Diabetes Drug may Repair Injured Brains

Here’s a good brain teaser for a Wednesday.  What do an old diabetes drug, brain injury and Alzheimer’s Disease have in common?

Here’s some clues to help you solve the riddle.

(i)           Metformin is a widely used treatment for type II diabetes

(ii)          An increasing proportion of people with Alzheimer’s Disease also have diabetes

(iii)         Hyperinsulinemia (excess levels of insulin in the blood) may enhance the onset and progression of neurodegeneration

Have you solved it?  If so, congratulations!

If not, the answer, according to data just published in the journal Cell Stem Cell is that the former may hold the clue to treating the latter.

In other words, the study suggests that metformin, an anti-diabetes drug first discovered in the 1920’s, is able to help activate the mechanism that signals stem cells to generate brain cells.

Principal investigator, Freda Miller, a Professor from the Department of Molecular Genetics at the University of Toronto
says “If you could take stem cells that normally reside in our brains and somehow use drugs to recruit them into becoming appropriate neural cell types, then you may be able to promote repair and recovery in at least some of the many brain disorders and injuries for which we currently have no treatment.”

The research involved laboratory experiments using both mouse and human brain stem cells, as well as learning and memory tests performed on live mice given the drug.

Miller and her colleagues started by adding metformin to stem cells from the brains of mice, then repeated the experiment with human brain stem cells generated in the lab. In both cases, the stem cells gave rise to new brain cells.

They then tested the drug in lab mice and found that those given daily doses of metformin for two or three weeks had increased brain cell growth and outperformed rodents not given the drug in learning and memory tasks.

In the key experiment, mice were forced to learn the position of a platform hidden under the surface of a water-filled maze and then asked rapidly to learn a new position.

Mice were injected with either metformin or saline for 38 days. On days 22 through 38, they learned the initial position of the platform, which provided an escape from the water-filled maze.  Then the platform was moved to the opposite side of the maze, and the animals were asked again to learn its position. In both tasks, the mice learned the platform positions with equivalent speed.

But when they were put back in the maze – this time with the platform removed – control mice spent more time searching for it in the original position, while the metformin-treated animals preferentially looked in the new region.

The implication  is that metformin helped the mice form their new memories of the second platform position. Further analysis showed that their enhanced ability was paralleled by an increase in the number of  neurons.

In a separate study researchers have shown that metformin can increase lifespan and delay the onset of cognitive impairment in a mouse model of Huntington’s disease.

Taken together, these findings raise the possibility that metformin’s ability to enhance neurogenesis might have a positive impact in some nervous system disorders.

Miller’s team is already planning a pilot study to test metformin in young patients with acquired brain damage, either as result of treating a childhood brain tumor or from a traumatic head injury.

We will report back to you with results, as they are published.

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