But researchers don't understand why. In previous studies, exercise researchers uncovered the hormone's efficiency in increasing memory and energy metabolism.
Irisin is a messenger protein generated by muscle tissue that is carried around the body in the bloodstream. This new research has shown that irisin is capable of promoting new neuron growth in the brain.
USA and Brazilian scientists found lower levels of the hormone in the brains of Alzheimer's patients compared with healthy individuals.
Arancio and his colleagues looked for a link between irisin and Alzheimer's. The experiments showed that irisin protects the brain's synapses and memory. When irisin levels were raised, there was an improvement in brain health, the researchers noted. The researchers developed an optic probe that glows over 100 times more brightly when it detects fiber or fibrils of amyloid beta proteins; the concentrated light then oxidizes the fibers to prevent them from accumulating in the brain and affecting patient cognitive ability, and a specific binding site for the harmful proteins was identified which may pave the way for new drug treatments.
Mice who swam almost every day for five weeks did not develop memory impairment despite getting infusions of beta amyloid - the brain-cell clogging 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. Following this experiment, the researchers are hopeful that they can build on these findings to ultimately treat or prevent memory issues, like dementia and Alzheimer's, in humans.
"I would certainly encourage everyone to exercise, to promote brain function and overall health", said Dr Ottavio Arancio, professor of pathology and cell biology and of medicine at Columbia University. His team is now searching for pharmaceutical compounds that can increase brain levels of the hormone or can mimic its action. But that's not possible for many people, especially those with age-related conditions like heart disease, arthritis, or dementia. Note: material may have been edited for length and content. (2019). Exercise-linked FNDC5/irisin rescues synaptic plasticity and memory defects in Alzheimer's models.