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Athletes know a vigorous workout can release a flood of endorphins: “feel-good” hormones that boost mood. Now there’s evidence that exercise produces another hormone that may improve memory and protect against Alzheimer’s disease, according to a study co-led by Ottavio Arancio, MD, PhD, a researcher at Columbia University’s Vagelos College of Physicians and Surgeons and Taub Institute for Research on Alzheimer’s Disease and the Aging Brain.
The study was published in Nature Medicine.
Physical activity is known to improve memory, and studies suggest it may also reduce the risk of Alzheimer’s disease. But researchers don’t understand why.
A few years ago, exercise researchers discovered a hormone called irisin that is released into the circulation during physical activity. Initial studies suggested that irisin mainly played a role in energy metabolism. But newer research found that the hormone may also promote neuronal growth in the brain’s hippocampus, a region critical 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” says Arancio, who is a professor of pathology and cell biology and of medicine at Columbia University Vagelos College of Physicians and Surgeons.
Irisin is reduced in brains of people with Alzheimer’s
In the new study, Arancio and his colleagues at the Federal University of Rio de Janeiro in Brazil and Queens University in Canada first looked for a link between irisin and Alzheimer’s in people. Using tissue samples from brain banks, they found that irisin is present in the human hippocampus and that hippocampal levels of the hormone are reduced in individuals with Alzheimer’s.
To explore what irisin does in the brain, the team turned to mice. These experiments show that irisin, in mice, protects the brain’s synapses and the animals’ memory: When irisin was disabled in the hippocampus of healthy mice, synapses and memory weakened. Similarly, boosting brain levels of irisin improved both measures of brain health.
Swimming boosts irisin, protects memory in mice
然后研究人员研究了运动对鸢尾素和大脑的影响。在这项研究最引人注目的实验中，研究人员发现，几乎每天游泳五周的小鼠尽管注射了β淀粉样蛋白 – 这是一种与阿尔茨海默病有关的神经元堵塞，记忆抢劫蛋白，但并未发生记忆障碍。
The researchers then looked at the effect of exercise on irisin and the brain. In the study’s most compelling experiments, the researchers found that mice who swam nearly every day for five weeks did not develop memory impairment despite getting infusions of beta amyloid — the neuron-clogging, memory-robbing protein implicated in Alzheimer’s.
Blocking irisin with a drug completely eliminated the benefits of swimming, the researchers also found. Mice who swam and were treated with irisin-blocking substances performed no better on memory tests than sedentary animals after infusions with beta amyloid.
Together the findings suggest that irisin could be exploited to find a novel therapy for preventing or treating dementia in humans, Arancio says. His team is now searching for pharmaceutical compounds that can increase brain levels of the hormone or can mimic its action.
“与此同时，我当然会鼓励每个人锻炼身体，促进大脑功能和整体健康，”他说。 “但对于许多人来说，这是不可能的，特别是那些与年龄相关的疾病，如心脏病，关节炎或痴呆症。对于那些个体，特别需要能够模仿鸢尾素的作用并保护突触并防止认知能力下降的药物。 “
“In the meantime, I would certainly encourage everyone to exercise, to promote brain function and overall health,” he said. “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.”
How exercise may protect against Alzheimer’s