Exercise & Brain Health
A compelling body of research in both humans and animals has shown that exercise is good for the brain. And now a new study in mice has revealed that a hormone produced during exercise can benefit the brain by boosting the health and function of neurons, a change that improves thinking and memory in healthy animals as well as those with the mouse version of Alzheimer’s disease.
Earlier research revealed that humans produce the same hormone during exercise. Taken together the new findings suggest that regular physical activity could positively influence the trajectory of memory loss in aging and dementia.
Previous investigations have shown that exercise prompts creation of new neurons in the brain’s memory center and also helps those new cells survive, mature and integrate into the brain’s neural network, where they can contribute to thinking and remembering. In addition, large-scale epidemiological studies have indicated that populations of active people are much less likely to develop Alzheimer’s disease or other forms of dementia than people who rarely exercise.
How can working out affect the function of our brains at a molecular level? Scientists have speculated that exercise might directly change the biochemical environment inside the brain, independent of what happens within muscles. Another possibility: our muscles and other tissues might release substances during physical activity that travel to the brain and jump-start processes there, leading to subsequent improvements in brain health. If so, those substances would have to be able to pass through the protective and mostly impermeable blood-brain barrier that separates the circulation to our brains from the blood flowing to the rest of our bodies.
A decade ago, those questions were of particular interest to scientists at Harvard Medical School and other institutions. In 2012, a team led by Bruce M. Spiegelman, a Harvard professor of cell biology and medicine, identified a previously unknown hormone produced in the muscles of lab rats and people during exercise, which is released into the bloodstream. They named the new hormone irisin, afte Iris, the messenger to the gods in Greek mythology.
Mohammad R. Islam et al, “Exercise hormone irisin is a critical regulator of cognitive function,” Nature Metabolism volume 3, pages 1058-1070, August 20, 2021.
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