A molecule released during exercise drastically improves the health of brain-damaged mice, massively increasing their life expectancy, as well as their ability to walk and balance, according to a new study. In fact, mice in the study that were given just six weeks to live originally lived for a whole year after exercise.
The results, from The Ottawa Hospital and the University of Ottawa in Canada, are published in the journal Cell Reports.
Having identified the compound involved and figured out how it produces this effect, researchers now hope to use it to create new treatments for neurodegenerative disorders such as multiple sclerosis.
The team bred mice that were missing a gene called Snf2h, resulting in them being born with an underdeveloped cerebellum – the part of the brain that coordinates balance and movement. These mice struggled to walk and tended to die within six weeks of being born.
However, the researchers discovered that if these mice were given regular access to a running wheel, they not only became better at walking, but also lived for up to a whole year. Yet if the running wheel was removed, the condition of these mice deteriorated once again, suggesting that these benefits can only be sustained with regular exercise.
When examining the brains of mice that had been granted access to running wheels, they found that they did not have any more neurons than those that did not exercise, but they did have more oligodendrocytes. These are cells that produce the myelin sheath that insulates neurons, which therefore became more efficient at transmitting impulses.
Myelin coats nerve fibers and allows neurons to function. When it is damaged it can cause neurodegeneration. Designua/Shutterstock
"We saw that the existing neurons became better insulated and more stable," said the study's lead author Matías Alvarez-Saavedra from the New York University School of Medicine in a statement. "This means that the unhealthy neurons worked better and the previously damaged circuits in the brain became stronger and more functional."
This led the study authors to suspect that continued exercise produces certain epigenetic changes in mice, meaning it alters the way that certain genes are expressed. When analyzing the rodents’ RNA, they found a number of differences between those that were allowed to run and those that were not. Significantly, genes that code for a molecule called VGF nerve growth factor were found to be upregulated in the exercising mice.
Given that VGF is known to stimulate the creation of new oligodendrocytes – a process called oligondendrogenesis – and has previously been found to be released during exercise, the researchers suspected that this molecule may be responsible for the running mice’s improvements. To investigate, they injected VGF into the brains of mice that were not given access to any exercise equipment, and found that they experienced the same benefits as those that were allowed to run on a regular basis.
Based on this discovery, researcher David Picketts from the University of Ottawa explained that “VGF is important to kick-start healing in damaged areas of the brain,” adding that it could one day be used to treat neurological disorders in humans.
