Irisin as a muscle-derived hormone stimulating thermogenesis--a critical update.
The recently described myokine, irisin is cleaved from fibronectin type III domain containing protein 5 (FNDC5) and has been proposed to be secreted upon exercise to promote the browning of beige fat cells in white adipose tissue that results in enhanced thermogenesis and increased energy expenditure. The initial studies suggested irisin as a treatment option for obesity and associated diseases such as type 2 diabetes mellitus and stimulated further research. However, the results of subsequent studies investigating the regulation of irisin by different types of exercise are partly conflicting and effects were only shown in highly selective patient populations so far. Moreover, other parameters like body weight or fat free mass were shown to influence irisin adding more complexity to the mechanisms regulating this hormone. The present review will describe the discovery of irisin, its potential role in adipose tissue-mediated thermogenesis, its regulation by exercise and lastly, discuss current controversies and highlight gaps of knowledge to be filled by future studies.
Charité Center for Internal Medicine and Dermatology, Division of General Internal and Psychosomatic Medicine, Charité-Universitätsmedizin Berlin, Campus Mitte, Berlin, Germany.
Tobias
T
Hofmann
Charité Center for Internal Medicine and Dermatology, Division of General Internal and Psychosomatic Medicine, Charité-Universitätsmedizin Berlin, Campus Mitte, Berlin, Germany; Charité Center for Internal Medicine with Gastroenterology and Nephrology, Division of Endocrinology, Diabetes and Nutrition, Charité-Universitätsmedizin Berlin, Campus Mitte, Berlin, Germany.
Ulf
U
Elbelt
Charité Center for Internal Medicine and Dermatology, Division of General Internal and Psychosomatic Medicine, Charité-Universitätsmedizin Berlin, Campus Mitte, Berlin, Germany. Electronic address: a.stengel@gmx.de.
Andreas
A
Stengel
D052436:Adipose Tissue, White / Q000378:metabolism; D003920:Diabetes Mellitus / Q000188:drug therapy / Q000378:metabolism; D015444:Exercise / Q000502:physiology*; D005353:Fibronectins / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology*; D005947:Glucose / Q000378:metabolism; D006801:Humans; D018482:Muscle, Skeletal / Q000378:metabolism; D009765:Obesity / Q000188:drug therapy* / Q000378:metabolism; D022722:Thermogenesis / Q000502:physiology*
C577593:FNDC5 protein, human; C571428:FNDC5 protein, mouse; D005353:Fibronectins; D005947:Glucose
Brown adipose tissue; Exercise; FNDC5; Obesity