title: Serum irisin levels are regulated by acute strenuous exercise.
abstract: BACKGROUND
  The newly discovered myokine irisin has been proposed to affect obesity and metabolism by promoting browning of white adipose tissue. However, clinical and functional studies on the association of irisin with obesity, muscle mass, and metabolic status remain controversial. Here we assessed the effect of 4 distinct exercise regimens on serum irisin levels in children and young adults and systematically evaluated the influence of diurnal rhythm, anthropometric and metabolic parameters, and exercise on irisin.
  
  
  RESULTS
  Serum irisin levels did not show diurnal variations, nor were they affected by meal intake or defined glucose load during oral glucose tolerance testing. Irisin levels decreased with age. In adults, irisin levels were higher in men than in women, and obese subjects had significantly higher levels than lean control subjects. Irisin levels were closely correlated with muscle-associated bioimpedance parameters such as fat-free mass and body cell mass. Of the 4 exercise regimens that differed in duration and intensity, we identified a clear and immediate increase in serum irisin levels after acute strenuous exercise (cycling ergometry) and a 30-minute bout of intensive exercise in children and young adults, whereas longer (6 weeks) or chronic (1 year) increases in physical activity did not affect irisin levels.
  
  
  CONCLUSIONS
  We show that irisin levels are affected by age, sex, obesity, and particularly muscle mass, whereas diurnal rhythm and meals do not contribute to the variation in irisin levels. Short bouts of intensive exercise but not long-term elevations in physical activity, acutely and transiently increase serum irisin levels in children and adults.
authors.affiliation: Center for Paediatric Research Leipzig (D.L., K.S., D.F., J.G., J.B., K.L., I.V.W., W.K., A.K.), University Hospital for Children and Adolescents, Integrated Research and Treatment Center Adiposity Diseases (D.L., K.L., A.K.), and Leipzig Heart Centre (U.M., S.E.), Department of Cardiology, University of Leipzig, 04103 Leipzig, Germany.
authors.forename: Dennis
authors.initials: D
authors.lastname: Löffler
authors.forename: Ulrike
authors.initials: U
authors.lastname: Müller
authors.forename: Kathrin
authors.initials: K
authors.lastname: Scheuermann
authors.forename: Daniela
authors.initials: D
authors.lastname: Friebe
authors.forename: Julia
authors.initials: J
authors.lastname: Gesing
authors.forename: Julia
authors.initials: J
authors.lastname: Bielitz
authors.forename: Sandra
authors.initials: S
authors.lastname: Erbs
authors.forename: Kathrin
authors.initials: K
authors.lastname: Landgraf
authors.forename: Isabel Viola
authors.initials: IV
authors.lastname: Wagner
authors.forename: Wieland
authors.initials: W
authors.lastname: Kiess
authors.forename: Antje
authors.initials: A
authors.lastname: Körner
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D002648:Child; D002940:Circadian Rhythm; D015444:Exercise / Q000502:physiology*; D005260:Female; D005353:Fibronectins / Q000097:blood*; D005947:Glucose / Q000494:pharmacology; D006801:Humans; D006854:Hydrocortisone / Q000097:blood; D008297:Male; D062407:Meals; D055442:Metabolome / Q000187:drug effects; D063766:Pediatric Obesity / Q000097:blood* / Q000628:therapy; D005082:Physical Exertion / Q000502:physiology; D012737:Sex Factors; D055815:Young Adult
chemical_list: C577593:FNDC5 protein, human; D005353:Fibronectins; D005947:Glucose; D006854:Hydrocortisone