“Mythical” Exercise Hormone Confirmed

The hotly-debated “feel good” exercise hormone irisin does in fact exist, according to a new study.

The hormone was first discovered in 2012 by Bruce Spiegelman, a cell biologist at the Dana-Farber Cancer Institute and professor at Harvard Medical School. His initial research revealed that when mice were injected with irisin, their fat cells consumed more oxygen and burned more calories. In addition, the presence of irisin induced weight loss in the mice and improved blood sugar regulation, lowering their risk of diabetes.

While many scientists were quick to suggest that the hormone could form the basis for medications used to combat metabolic disease and obesity, others contended that the methods implemented in the hormone’s discovery were insufficient to prove its existence at all.

Now, Spiegelman’s team has used a far more precise technique called quantitative mass spectrometry to isolate irisin and to observe its relationship to exercise.

The team monitored irisin levels in blood samples collected from two groups: people who did not exercise at all, and people who had completed an intense 12-week trial of aerobic training. They found that although irisin was present only in small quantities, it was far more abundant in those who exercised than in those who did not.

“Our paper definitively confirms that irisin circulates and is altered with exercise in humans,” Spiegelman said.

The purported effects of irisin extend far beyond the familiar warm, giddy feeling that follows a hard workout. In addition to transmuting sedentary white fat into metabolically active brown fat, irisin could improve cardiovascular and cognitive functions. Given that its structure is identical in mice and humans alike, its demonstrated effects on weight loss and blood sugar regulation in mice raise tantalizing questions about its possible medicinal applications.

If irisin really does mimic the effects of exercise, could scientists be on the cusp of harnessing a therapeutic capable of treating obesity, hypertension, heart disease, and diabetes?

Researchers agree that further study will be necessary in order to prove a correlation between the hormone and the positive effects of exercise. For now, at least, Spiegelman’s work has unequivocally settled the issue of the hormone’s existence.


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