By Press Association
Published: 16:00 GMT, 7 January 2019 | Updated: 17:33 GMT, 7 January 2019
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A hormone released during exercise may protect the brain against Alzheimer's disease, research suggests.
Irisin is a messenger protein generated by muscle tissue that is carried around the body in the bloodstream.
The new evidence indicates that it may be behind the known positive effects on mental performance of taking exercise.
US and Brazilian scientists found lower levels of the hormone in the brains of Alzheimer's patients compared with healthy individuals.
Bostering irisin, either with drugs or through exercise, could provide a 'novel strategy' for preventing cognitive decline in patients with Alzheimer's disease, said the scientists
The same was true for the precursor protein from which irisin is derived, FNDC5.
The team's findings were based on samples of brain tissue from people who had dementia when they died and the blood and spinal fluid of living patients.
Then, in tests on genetically engineered mice, the scientists induced learning and memory deficits by cutting out irisin.
They were able to reverse these effects by restoring the hormone.
When irisin signalling was blocked in mice with a rodent version
