Scientists discover hormone produced by exercise may prevent Alzheimer’s disease

NEW YORK — Endorphins are a well-known exercise by-product, the result of hormones being released that can significantly boost one’s mood. Now scientists say exercise also releases another hormone that may protect the brain against Alzheimer’s disease later in life.

Previous research has long shown that regular physical activity improves memory and may reduce the risk of Alzheimer’s, but researchers didn’t understand why. Researchers at Columbia University sought to shed light on the mystery, honing in on a hormone produced by exercise that was only discovered a few years ago.

Scientists studying the effect of exercise on the body discovered the hormone, called irisin, and believed it was primarily involved in energy metabolism. But more recent research showed that the hormone could also improve the hippocampus area of the brain, a region needed for learning and memory.

“This raised the possibility that irisin may help explain why physical activity improves memory and seems to play a protective role in brain disorders such as Alzheimer’s disease” explains Dr. Ottavio Arancio, lead researcher and professor of pathology and cell biology and of medicine at Columbia University Vagelos College of Physicians and Surgeons, in a university release.

After examining human samples from brain banks and finding high irisin levels in individuals who didn’t suffer from Alzheimer’s disease and low levels in Alzheimer’s-affected brains, the research team tested their hypothesis on mice. Their experiments showed that irisin protected the brain synapses of the mice and their memory. When the researchers disabled the effects of irisin, their synapses and memory weakened.

In another experiment involving mice, Dr. Arancio’s team found that mice that swam nearly every day for five weeks did not suffer from memory impairment in spite of beta amyloid infusions, a neuron-clogging, memory-robbing protein thought to be a cause of Alzheimer’s. Blocking irisin with another drug was found to eliminate the positive effects from the swimming.

Arancio and his team are now looking to create drugs that could increase levels of the hormone or mimic its effects.

“In the meantime, I would certainly encourage everyone to exercise to promote brain function and overall health,” he says. “But that’s not possible for many people, especially those with age-related conditions like heart disease, arthritis, or dementia. For those individuals, there’s a particular need for drugs that can mimic the effects of irisin and protect synapses and prevent cognitive decline.”

The study was published in the journal Nature Medicine.

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