Be kind to your brain, go work out
A hormone that is released during exercise may improve brain health and lessen the damage and memory loss that occur during dementia, a new study finds. The study, published this month in Nature Medicine, involved mice, but its findings could help to explain how, at a molecular level, exercise protects our brains and possibly preserves memory and thinking skills, even in people whose pasts are fading.
Considerable scientific evidence already demonstrates that exercise remodels brains and affects thinking. Researchers have shown in rats and mice that running ramps up the creation of new brain cells in the hippocampus, a part of the brain devoted to memory formation and storage. Exercise also can improve the health and function of the synapses between neurons there, letting brain cells communicate better.
In people, epidemiological research indicates that being physically active reduces the risk for Alzheimer’s disease and other dementias and may slow disease progression.
But many questions remain on just how exercise alters the inner workings of the brain and whether the effects are a result of changes elsewhere in the body that also happen to be good for the brain or whether the changes actually occur within the brain itself. Those issues attracted the attention of an international consortium of scientists – some neuroscientists, others cell biologists – all focused on preventing, treating and understanding Alzheimer’s disease.
Those concerns had brought a hormone called irisin into their sphere of interest. Irisin, first identified in 2012 and named for Iris, the gods’ messenger in Greek mythology, is produced by muscles during exercise. The hormone jump-starts multiple biochemical reactions throughout the body, most of them related to energy metabolism.
Because Alzheimer’s disease is believed to involve, in part, changes in how brain cells use energy, the scientists reasoned that exercise might be helping to protect brains by increasing levels of irisin there.
But if so, they realized, irisin would have to exist in human brains. To see if it did, they gathered tissues from brain banks and, using sophisticated testing, found irisin there. Gene expression patterns in those tissues also suggested that much of this irisin had been created in the brain itself. Levels of the hormone were especially high in the brains of people free of dementia when they died, but were barely detectable in the brains of people who had died with Alzheimer’s.
The scientists involved in the study hope soon to test a pharmaceutical form of irisin as a treatment for dementia in animals and eventually people.