title: Plasma Irisin Modestly Increases during Moderate and High-Intensity Afternoon Exercise in Obese Females.
abstract: OBJECTIVE
  Irisin is an exercise-responsive myokine that has been proposed to exert anti-obesity benefits; yet its response during exercise in obese women is not described. This study characterized plasma irisin levels during a single bout of afternoon isocaloric-exercise of different intensities (moderate- vs high-intensity) in obese females.
  
  
  METHODS
  Eleven obese females participated in 3 randomized study days beginning at 1600h: 1) no exercise (NoEx), 2) moderate exercise (ModEx; 55%VO2max) and 3) high intensity interval exercise (IntEx; 4 min (80%VO2max)/3 min (50% VO2max). Frequent blood samples were analyzed for glucose and lactate (whole-blood), and insulin, c-peptide, glucagon, and irisin (plasma) throughout 190 min of testing.
  
  
  RESULTS
  Plasma irisin increased above baseline during ModEx and IntEx (P<0.05), but not NoEx (P>0.05). Peak irisin levels during ModEx and IntEx exercise were 11.9± 3.4% and 12.3 ± 4.1% relative to baseline (P<0.05), respectively, with no differences between exercise intensities (P>0.05). Irisin levels remained elevated above resting for 125 minutes post-exercise during ModEx, whereas levels returned to baseline within 15 minutes post-exercise during IntEx. Similarly, no associations were found between plasma irisin levels and circulating lactate, glucose, insulin, c-peptide, or glucagon among study days (P>0.05). However, there was an inverse association between basal irisin and lean mass (r = -0.70, P = 0.01).
  
  
  CONCLUSIONS
  A single bout of moderate and high intensity afternoon exercise induces modest increases in circulating irisin concentrations during exercise; however the regulation post-exercise appears to be dimorphic between exercise intensity in obese females. Future studies are needed to compare morning and afternoon exercise on irisin secretion.
authors.affiliation: Department of Nutrition and Exercise Physiology, University of Missouri, Columbia, Missouri, United States of America.
authors.forename: Nathan C
authors.initials: NC
authors.lastname: Winn
authors.affiliation: Department of Nutrition and Exercise Physiology, University of Missouri, Columbia, Missouri, United States of America.
authors.forename: Zachary I
authors.initials: ZI
authors.lastname: Grunewald
authors.affiliation: Department of Nutrition and Exercise Physiology, University of Missouri, Columbia, Missouri, United States of America.
authors.forename: Ying
authors.initials: Y
authors.lastname: Liu
authors.affiliation: East Carolina Diabetes and Obesity Institute and Department of Kinesiology, East Carolina University, Greenville, North Carolina, United States of America.
authors.forename: Timothy D
authors.initials: TD
authors.lastname: Heden
authors.affiliation: Department of Nutrition and Exercise Physiology, University of Missouri, Columbia, Missouri, United States of America.
authors.forename: Lauren M
authors.initials: LM
authors.lastname: Nyhoff
authors.affiliation: Department of Nutrition and Exercise Physiology, University of Missouri, Columbia, Missouri, United States of America.
authors.forename: Jill A
authors.initials: JA
authors.lastname: Kanaley
mesh_terms: D000328:Adult; D001786:Blood Glucose; D015992:Body Mass Index; D002096:C-Peptide / Q000097:blood; D015444:Exercise; D005260:Female; D005353:Fibronectins / Q000097:blood* / Q000235:genetics; D015870:Gene Expression; D005934:Glucagon / Q000097:blood; D006801:Humans; D007328:Insulin; D019344:Lactic Acid; D009765:Obesity / Q000097:blood*; D010101:Oxygen Consumption / Q000502:physiology; D011897:Random Allocation; D013997:Time Factors
chemical_list: D001786:Blood Glucose; D002096:C-Peptide; C577593:FNDC5 protein, human; D005353:Fibronectins; D007328:Insulin; D019344:Lactic Acid; D005934:Glucagon