Exercise Hormones Are Key to Dementia Risk Reduction

Massachusetts General Hospital (MGH) scientists have uncovered how a specific hormone produced during exercise reduces amyloid beta deposits associated with Alzheimer's disease.

The research, published on September 8 in Neuron, used 3D human cell culture models of Alzheimer's previously developed by the MGH team to test whether irisin — a glucose and fat metabolizing hormone produced by muscles during exercise — impacts amyloid beta deposits in the brain.

Scientists believe the buildup of amyloid plaques between the brain's nerve cells may be a primary cause of Alzheimer's.

While previous research conducted in mice found that exercise reduces the buildup of these plaques, how and why this happens has continued to mystify scientists.

To investigate irisin's role in dementia risk reduction, the scientists added the hormone to their 3D Alzheimer's model. They found that irisin significantly reduced amyloid beta buildup by triggering specific brain cells known as astrocytes. These brain cells then ramped up the production of neprilysin, which degrades amyloid beta.

Moreover, since previous mouse research has shown that irisin can make its way into the brain when injected into the body, the research team suggests it could be a potential therapy for Alzheimer's disease.

In a press release, senior study author Rudolph Tanzi, Ph.D., director of Massachusetts General Hospital's Genetics and Aging Research Unit, said, "Our findings indicate that irisin is a major mediator of exercise-induced increases in neprilysin levels leading to reduced amyloid beta burden, suggesting a new target pathway for therapies aimed at the prevention and treatment of Alzheimer's disease."

What types of exercise promote irisin and reduce dementia risk?

While all forms of exercise promote health and increase both life and health span, a 2022 systematic review of research found that short aerobic exercise sessions have more effect on irisin levels than brief bouts of anaerobic exercise. Moreover, long-term resistance training could raise irisin levels higher than long-term aerobic and anaerobic workouts.

In addition, other 2022 research suggests that sustained moderate to high-intensity training, which includes brief intervals of highly intense activity, increases irisin levels more than other forms of exercise.

Still, a person should consider talking with their healthcare provider before beginning an exercise program for dementia risk reduction, especially if they are currently inactive or have a preexisting health condition.

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