title: Myokine Expression in Muscle and Myotubes in Response to Exercise Stimulation.
abstract: OBJECTIVE
  Myokines have been shown to affect muscle physiology and exert systemic effects. We endeavored to investigate a panel of myokine mRNA expression after a single exercise bout (studies 1 and 2) to measure myokine mRNA in primary human myotubes in an in vitro exercise model (study 2).
  
  
  METHODS
  Vastus lateralis muscle biopsies were obtained from 20 healthy males (age, 24.0 ± 4.5 yr; BMI, 23.6 ± 1.8 kg·m)(-2) before and after a single exercise bout (650 kcal at 50% V˙O2max). Primary myotubes from active and sedentary male donors were treated with a pharmacological cocktail (palmitate, forskolin, and ionomycin (PFI)) to mimic exercise-stimulated contractions in vitro.
  
  
  RESULTS
  Interleukin 6 and 8 (IL-6 and IL-8), leukocyte-inducing factor, and connective tissue growth factor (CTGF) mRNA levels increased approximately 10-fold after a single exercise bout (all P < 0.001), whereas myostatin levels decreased (P < 0.05). Key correlations between myokine expression and parameters of muscle and whole-body physiology were found: myostatin versus skeletal muscle citrate synthase activity (r = -0.69, P < 0.001), V˙O2max (r = -0.64, P = 0.002) and the percentage of Type I fibers (r = -0.55, P = 0.01); IL-6 versus the RER (r = 0.45, P = 0.04), homeostatic model assessment of insulin resistance (r = 0.44, P = 0.05), and serum lactate (r = 0.50, P = 0.02). Myokine expressions in myotubes from sedentary donors for CTGF and myostatin decreased, whereas IL-6 and IL-8 increased after PFI treatment. In myotubes from active donors, myokine expression increased for IL-6, CTGF, and myostatin but decreased for IL-8 after PFI treatment.
  
  
  CONCLUSIONS
  These data offer insight into the differences in regulation of myokine expression and their possible physiologic relationships.
authors.affiliation: 1Pennington Biomedical Research Center, Baton Rouge, LA; 2School of Medicine, Louisiana State University Health Sciences Center, New Orleans, LA; 3The Charles Perkins Centre and The School of Biological Sciences, University of Sydney, NSW, AUSTRALIA; 4Department of Kinesiology, University of Texas in El Paso, El Paso, TX; and 5School of Medicine, Pontificia Universidad Catolica de Chile, Santiago, CHILE.
authors.forename: Jeffrey D
authors.initials: JD
authors.lastname: Covington
authors.forename: Charmaine S
authors.initials: CS
authors.lastname: Tam
authors.forename: Sudip
authors.initials: S
authors.lastname: Bajpeyi
authors.forename: Jose E
authors.initials: JE
authors.lastname: Galgani
authors.forename: Robert C
authors.initials: RC
authors.lastname: Noland
authors.forename: Steven R
authors.initials: SR
authors.lastname: Smith
authors.forename: Leanne M
authors.initials: LM
authors.lastname: Redman
authors.forename: Eric
authors.initials: E
authors.lastname: Ravussin
mesh_terms: D000328:Adult; D001706:Biopsy; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D055513:Connective Tissue Growth Factor / Q000378:metabolism; D015444:Exercise / Q000502:physiology*; D006801:Humans; D007333:Insulin Resistance; D015850:Interleukin-6 / Q000378:metabolism; D016209:Interleukin-8 / Q000378:metabolism; D015759:Ionomycin / Q000494:pharmacology; D019344:Lactic Acid / Q000097:blood; D008297:Male; D018485:Muscle Fibers, Skeletal / Q000187:drug effects / Q000378:metabolism*; D055435:Myostatin / Q000378:metabolism; D010168:Palmitates / Q000494:pharmacology; D052097:Quadriceps Muscle / Q000378:metabolism*; D055815:Young Adult
chemical_list: C526317:CCN2 protein, human; C508606:CXCL8 protein, human; C508600:IL6 protein, human; D015850:Interleukin-6; D016209:Interleukin-8; C525911:MSTN protein, human; D055435:Myostatin; D010168:Palmitates; D055513:Connective Tissue Growth Factor; D005576:Colforsin; D019344:Lactic Acid; D015759:Ionomycin