Hormone secreted when exercising halts Parkinson’s decline in mice
A hormone believed to be released by muscles during exercise has been found to reduce levels of a toxic protein associated with Parkinson’s disease. The promising animal studies indicate future therapies could be developed based on the way this hormone improves brain health.
In 2012 a team of researchers from Harvard Medical School published a landmark study reporting the discovery of a new hormone released by muscles during exercise. The researchers named the hormone irisin.
For several years the scientific community debated whether irisin, originally detected in mice, was actually present in humans. By 2015 the argument was ultimately settled, with new research affirming irisin is real and secreted by skeletal muscles in humans during exercise. Of course, that led to a new debate over what effects this hormone actually has on human health.
Interesting clues to the effects of irisin on the brain came early, as studies showed the hormone can cross the blood-brain barrier, and potentially trigger beneficial activity in the hippocampus. A 2019 mouse study found boosting irisin levels in Alzheimer’s animal models improved brain plasticity and memory.
This new study came about when Bruce Spiegelman, one of the authors on the original 2012 irisin discovery study, joined forces with neurodegenerative disease researcher Ted Dawson to explore the effects of irisin on Parkinson’s disease. Exercise has long been found to be extraordinarily beneficial for Parkinson’s patients, often slowing progression of the disease. So Dawson and Spiegelman wondered whether irisin could be playing a specific role in improving signs of Parkinson’s.
Across several mouse experiments the new research showed irisin can prevent the degeneration of dopamine neurons associated with Parkinson’s disease. The study also found irisin reduces accumulation of alpha synuclein, proteins known to clump together and lead to Parkinson’s neurodegeneration.
One interesting finding in the study is the suggestion that irisin therapy could reverse the effects of Parkinson’s. One particular animal experiment did offer promising signs that irisin could reverse some aspects of the disease, but the researchers are cautious to point out plenty more work will be needed to understand this mechanism.
“It will be important for any future human therapy to determine whether irisin can arrest the progression of experimental PD after neurological symptoms have started and to determine the effects of irisin in other PD models,” the researchers write in the study. “Nevertheless, since irisin treatment was begun well after the pathogenic cascade was initiated by the α-syn PFF injection, there is considerable promise that it might be developed as a disease-modifying therapy for the treatment of PD.”
How this all translates to a human therapy is still unclear. Better understanding of how irisin could disrupt the cascade of degenerative events that lead to Parkinson’s may help researchers develop specific protein or gene therapies. However, in the short term these findings offer strong clues to how exercise can be especially beneficial in patients with Parkinson’s disease.
The new study was published in the journal PNAS.
Source: John Hopkins Medicine