title: Exercise training does not increase muscle FNDC5 protein or mRNA expression in pigs.
abstract: BACKGROUND
  Exercise training elevates circulating irisin and induces the expression of the FNDC5 gene in skeletal muscles of mice. Our objective was to determine whether exercise training also increases FNDC5 protein or mRNA expression in the skeletal muscles of pigs as well as plasma irisin.
  
  
  METHODS
  Castrated male pigs of the Rapacz familial hypercholesterolemic (FHM) strain and normal (Yucatan miniature) pigs were sacrificed after 16-20 weeks of exercise training. Samples of cardiac muscle, deltoid and triceps brachii muscle, subcutaneous and epicardial fat were obtained and FNDC5 mRNA, along with that of 6 other genes, was measured in all tissues of FHM pigs by reverse transcription polymerase chain reaction. FNDC protein in deltoid and triceps brachii was determined by Western blotting in both FHM and normal pigs. Citrate synthase activity was measured in the muscle samples of all pigs as an index of exercise training. Irisin was measured by an ELISA assay.
  
  
  RESULTS
  There was no statistically significant effect of exercise training on FNDC5 gene expression in epicardial or subcutaneous fat, deltoid muscle, triceps brachii muscle or heart muscle. Exercise-training elevated circulating levels of irisin in the FHM pigs and citrate synthase activity in deltoid and triceps brachii muscle. A similar increase in citrate synthase activity was seen in muscle extracts of exercise-trained normal pigs but there was no alteration in circulating irisin.
  
  
  CONCLUSIONS
  Exercise training in pigs does not increase FNDC5 mRNA or protein in the deltoid or triceps brachii of FHM or normal pigs while increasing circulating irisin only in the FHM pigs. These data indicate that the response to exercise training in normal pigs is not comparable to that seen in mice.
authors.affiliation: Department of Microbiology, Immunology and Biochemistry, College of Medicine, University of Tennessee Health Science Center, Memphis TN 38163, USA. Electronic address: jfain@uthsc.edu.
authors.forename: John N
authors.initials: JN
authors.lastname: Fain
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Company
authors.forename: Frank W
authors.initials: FW
authors.lastname: Booth
authors.forename: M Harold
authors.initials: MH
authors.lastname: Laughlin
authors.forename: Jaume
authors.initials: J
authors.lastname: Padilla
authors.forename: Nathan T
authors.initials: NT
authors.lastname: Jenkins
authors.forename: Suleiman W
authors.initials: SW
authors.lastname: Bahouth
authors.forename: Harold S
authors.initials: HS
authors.lastname: Sacks
mesh_terms: D000818:Animals; D002950:Citrate (si)-Synthase / Q000378:metabolism; D005353:Fibronectins / Q000235:genetics* / Q000378:metabolism*; D015870:Gene Expression / Q000235:genetics; D008297:Male; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism; D018482:Muscle, Skeletal / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism*; D010805:Physical Conditioning, Animal; D012333:RNA, Messenger / Q000235:genetics*; D050151:Subcutaneous Fat / Q000378:metabolism; D013552:Swine / Q000235:genetics / Q000378:metabolism / Q000502:physiology*
chemical_list: D005353:Fibronectins; D009124:Muscle Proteins; D012333:RNA, Messenger; D002950:Citrate (si)-Synthase
keywords: Adipose tissue; C/EBPα; CCAAT/enhancer binding protein; Cp; EAT; Exercise; FGF21; FHM pigs; FNDC5; Muscle; PGC1α; PPARγ-coactivator-1; PR-domain-missing 16; PRDM16; Pigs; RTPCR; Rapacz Familial Hypercholesterolemic pigs; UCP-1; cEAT; coronary epicardial fat; crossing point values; epicardial fat; fibroblast growth factor 21; fibronectin Type III domain-containing 5 protein; hip SAT; hip subcutaneous fat; mEAT; myocardial epicardial fat; reverse transcriptase polymerase chain reaction; uncoupling protein-1