Hormone irisin may help explain how exercise helps prevent Alzheimer’s

Summary: Exercise may help reduce obesity, boost cardiovascular health, help prevent Alzheimer’s, and prevent Alzheimer’s associated cognitive decline. However, how exercise helps boost brain health or memory has remained a mystery. But, in 2012, researchers identified a new hormone released by skeletal muscles in response to exercise called irisin. They found that many of the metabolic effects of exercise are mediated by irisin. Thus, irisin may help reduce neuroinflammation and boost cognitive function. Using irisin to treat Alzheimer’s could be an alternative approach to treatments focused on eliminating the accumulation of amyloid plaques.

 Alzheimer’s is a complex and heterogeneous disorder. The condition is caused by numerous factors, from dietary habits, lifestyle choices, brain trauma, and exposure to toxins. In addition, since it develops gradually and progresses over the years, it is a challenging disease to study by science. 

Studies suggest that people with a sedentary lifestyle are more likely to be affected by Alzheimer’s than physically active adults. On the other hand, exercise has numerous health benefits like improved mood, vascular health, glucose metabolism, insulin sensitivity, and much more1.

To date, researchers thought that most of the health benefits of exercise are related to its broader metabolic effects. For example, exercise may help improve vascular elasticity, lower blood pressure, help control obesity, and reduce inflammation. Thus, exercise may help improve cognition and lower the risk of Alzheimer’s. However, although it is true, there seems to be more to it.

The new studies show that many of the health effects of exercise could be due to or mediated by a newly discovered hormone called irisin. 

Figure 1 Irisin production in skeletal muscles2

The new hormone irisin was discovered just in 2012. Researchers found that it is secreted by muscle cells during exercise. It helps control obesity, has widespread effects on metabolism, and may even suppress inflammation. However, Irisin is yet not fully understood, and science is still exploring its health effects2.

In Alzheimer’s, the major challenge is preserving cognition and memory. Studies show that irisin may help. In addition, it appears that many of the neuroprotective effects of exercise might be due to the release of irisin.

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In the latest study, researchers impaired irisin production in mice models by using gene-editing tools. They found that it resulted in the deterioration of memory. They also found that it has a particularly negative effect on the hippocampus, a part of the brain that stores many past experiences3.

Further, they found that boosting the levels of irisin could help boost brain health and memory.

Researchers are pretty excited about these findings. They say that what is interesting about this approach is that it does not target amyloid plaques, unlike other approaches. Instead, it reduces systemic inflammation. As a result, it helps control neuroinflammation and can reduce inflammation of glial cells.

Implications of these findings are that researchers can further study the role of using this hormone for preventing or even treating Alzheimer’s. In addition, it means that many health benefits of exercise could be boosted by using this hormone.

Further, it is vital to understand that this hormone has much broader health impacts. It means that it may even promote weight loss, prevent diabetes, boost cardiovascular health. In addition, since it reduces systemic inflammation, it may have a role in preventing a range of diseases.

It is clear that irisin is a vital mediator, playing an essential role in the exercise-related benefits. Thus, there is definitely a need to study it more carefully. 

However, it is worth noticing that, at present most studies are being done on lab animals. These are still early days. It is unclear if it would be safe or beneficial for humans when used as a therapeutic agent. Nevertheless, it is an exciting finding that may change the way many diseases are treated.

References 

1. Maliszewska-Cyna E, Lynch M, Jordan Oore J, Michael Nagy P, Aubert I. The Benefits of Exercise and Metabolic Interventions for the Prevention and Early Treatment of Alzheimer’s Disease. Current Alzheimer Research. 2017;14(1):47-60.
2. Korta P, Pocheć E, Mazur-Biały A. Irisin as a Multifunctional Protein: Implications for Health and Certain Diseases. Medicina (Kaunas). 2019;55(8):485. doi:10.3390/medicina55080485
3. Islam MR, Valaris S, Young MF, et al. Exercise hormone irisin is a critical regulator of cognitive function. Nat Metab. 2021;3(8):1058-1070. doi:10.1038/s42255-021-00438-z