New Exercise Hormone may Protect Against Brain Changes in Dementia
Tuesday, April 2nd, 2019
We know exercise is good for our brain, but how?
It is well known that regular exercise protects against cognitive decline. The evidence underpins the World Health Organization recommendation that adults aged 65 years and over participate in a minimum 150 minutes of aerobic exercise each week. However, researchers haven’t yet been able to identify how or why exercise is so good for us.
In last month’s issue of Nature Medicine, a team of Brazilian and Canadian scientists suggest that the recently discovered hormone, irisin, released by our muscles during exercise to promote energy metabolism, may hold the key. Their study formed three parts.
Irisin was reduced in brains of people with Alzheimer’s
They first found that irisin levels are reduced in the hippocampi of individuals with Alzheimer’s disease – the area of the brain critical for memory and learning.
Irisin protected against the unhealthy brain changes that occur in dementia
Next, the team sought to identify precisely what the hormone does to the brain by experimenting with mice. They found that reducing irisin levels in mice brains impaired their memory; and that then boosting levels of irisin rescued these impairments. Interestingly, they found that giving mice irisin, reduced the unhealthy brain changes that occur in response to the build-up of beta-amyloid, a key culprit in brain cell death and the development of Alzheimer’s disease.
Irisin facilitated the beneficial effects of exercise on memory
Lastly, the researchers tested the link between exercise and memory and the brain, by giving the mice an infusion of beta-amyloid and making them swim an hour every day, five days a week, for five weeks. Swimming increased irisin levels in the mice and reduced or stopped the unhealthy brain changes and memory loss associated with beta-amyloid. Compellingly, when the mice had their irisin production blocked, the benefits of swimming on memory and the brain were completely eliminated.
A reason to sweat
Taken together, these early findings suggest that exercise protects against dementia via the production of irisin. They add to the mounting evidence supporting the relationship between lifestyle factors and dementia, and provide another source of encouragement to exercise and keep healthy. For many people, especially those with age-related conditions such as heart disease, arthritis, or dementia, it may not be possible to exercise regularly, and drugs designed to mimic the effects of irisin could potentially bring some of the benefits of physical activity to people who are less able to exercise. The findings have only been validated in mice, and such ideas lay far into the future, with any new drug needing to go through several years of testing before it is trialled with humans; but for now, the findings open a promising new area of research.
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