Scientists have determined irisin, a hormone thought previously to be a myth in humans, does in fact reside in humans. The hormone is also shown to have increased levels within individuals who undergo aerobic interval training.
The article journaling the discovery was published on Aug. 13, 2015 in Cell Metabolism journal. According to scientist Mark P. Jedrychowskim who wrote the article, “Irisin is an exercise-induced myokine [protein secreted from skeletal muscle] with beneficial metabolic functions.”
The discovery comes following an experiment by Jedrychowskim, et al. using tandem mass spectrometry, a fairly recent tool in the scientific world that detects molecules by their weight and/or mass. The experiment used plasma samples from two test groups: one, where the subjects (6 males, roughly 25 years old, with an average BMI of 24.3) exercised 3 days out of the week on a cycle ergometer at 90% peak aerobic capacity; and a second, sedentary group (4 males, roughly 26 years old, with an average BMI of 26.1), who did not participate in the aerobic exercise training.
The level of iris in present in the sedentary individuals was ~3.6 ng/ml, while levels in the individuals who participated in aerobic activity were at ~4.3 ng/ml. According to Jedrychoskim, this suggests human irisin is regulated by exercise.
For the moment, human irisin’s exact functions remain unknown, though its discovery is certain to lead scientists to determine irisin’s relationship with the human body.