Irisin May Have a Future as Treatment to Reduce Brain Inflammation, Preserve Memory
The protective benefits of regular exercise on cognition are well established, but researchers are still learning more about the relationship between physical activity and robust memory and thinking skills later in life. A study published in the journal Nature Metabolism and led by Massachusetts General Hospital (MGH) researchers sheds new light on a hormone called irisin, which holds promise as a potential key to treating or preventing Alzheimer’s disease or other neurodegenerative diseases.
Irisin is a cleaved version of the protein known as FNDC5, which is secreted by muscles during exercise. Irisin is the circulating form of FNDC5. In studies of mice, genetic deletion of irisin was shown to impair cognitive function, while elevated irisin levels in the bloodstream showed improved cognition and reduced neuroinflammation.
“Preserving cognitive function is a major challenge in an increasingly aging population,” says Christiane Wrann, DVM, PhD, leader of the Program in Neuroprotection in Exercise at MGH and senior author of the study. “Exercise is known to have positive effects on brain health, which is why identifying key mediators of those neuroprotective benefits, like irisin, has become such a critical goal of research.”
Irisin as Medicine?
One of the more encouraging aspects of the studies is that the addition of irisin led to cognitive improvements in mice with advanced Alzheimer’s disease. Though leveraging irisin for human treatment could be years away, researchers are hopeful that the hormone could be developed into an effective medication with the potential of reversing or at least delaying progression of Alzheimer’s or other similar diseases. “This could have implications for intervention in humans with Alzheimer’s disease where therapy typically starts after patients have become symptomatic,” Dr. Wrann says.
Regular exercise continues to be the primary prescription for enduring brain health and overall fitness. But for people who may have physical limitations, the idea of a medication that confers similar benefits is an inspiring goal. “It’s hard to imagine anything better for brain health than daily exercise,” says study co-author Rudy Tanzi, PhD, co-director of the McCance Center for Brain Health at MGH. “Our findings shed new light on the mechanism involved: protecting against neuroinflammation, perhaps the biggest killer of brain neurons as we age.”
Cooling Inflammation
Neuroinflammation, an inflammatory response in the spinal cord or brain, continues to be an active area of research. In recent years, its role as a factor in the development and progression of Alzheimer’s and other causes of dementia has become clearer. Potential treatments or preventive interventions for Alzheimer’s disease, for example, have largely focused on amyloid and tau proteins and the damage they cause neurons in people with the disease. But several major studies suggest that neuroinflammation may not only create an environment for those toxic proteins to take hold, but may help hasten the death of brain cells, too.
In addition to Alzheimer’s disease, neuroinflammation is associated with conditions such as Parkinson’s disease and amyotrophic lateral sclerosis (ALS, or Lou Gehrig’s disease). “Since irisin does not specifically target amyloid plaques, but rather neuroinflammation directly, we’re optimistic it could have beneficial effects on neurodegenerative diseases beyond just Alzheimer’s,” Dr. Wrann says.
Interestingly, irisin appears to confer at least one other benefit. Early research on the hormone, led by Bruce Spiegelman, PhD, of the Dana Farber Cancer Institute and Harvard Medical School, found that irisin is absorbed by fat cells and triggers a series of biochemical reactions that help convert white fat into brown fat, which is more metabolically active. As a result, irisin improves calorie burning and revs up the body’s metabolism.
Takeaway
It may be a long time before irisin treatments are available at your doctor’s office, so in the meantime, the best way to boost your own production of this helpful hormone is through regular exercise. In addition, exercise helps the brain by promoting the birth and maturation of new neurons in the hippocampus—the brain region largely responsible for memory. Numerous large-scale studies have found a strong association between being physically active and having a lower risk of Alzheimer’s disease and other forms of dementia.
Aim for 30 to 40 minutes of moderate-intensity exercise a day. One of the next areas of irisin research will look at which exercises are the most effective and productive in pumping this brain-boosting hormone into your bloodstream.
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