Irisin is a hormone that circulates in the blood at nanogram levels. The discovery of irisin in 2012 was exciting because scientists had potentially found one reason why exercise keeps us healthy. Mice studies had revealed that when irisin levels were increased in the rodents, their blood and metabolism improved. A recent study has now revealed that human irisin is similar to the mouse hormone and that it circulates in the range previously reported.
Senior study author Bruce Spiegelman from Dana-Farber Cancer Institute and Harvard Medical School said, "The confusion over irisin comes down to disagreement over how irisin protein is made in skeletal muscle cells and the detection limits of protocols." The research team turned to state-of-the-art techniques to show that the human hormone uses a rare signal ATA (start codon) to initiate the production of irisin.
Furthermore, they also developed a protocol, that does not rely on antibodies, to precisely measure how much irisin increases in people after exercise. Endocrinologist Francesco Celi from the Virginia Commonwealth University's medical center, who was not involved with the study, said, "The data is compelling and clearly demonstrates the existence of irisin in blood circulation. Importantly, the authors provide a precise and reproducible protocol to measure irisin."
The findings from human studies are still mixed as to what kinds of exercise raise irisin, but data suggest that high-intensity training protocols are particularly effective. The researchers suggested that further studies are necessary to fully understand how the hormone works in humans, specifically how it relates to brown and beige fat tissue and energy use.
The study is published in Cell Metabolism.