title: Skeletal muscle IGF-I isoform expression in healthy women after isometric exercise.
abstract: BACKGROUND
  Little is known about the expression of skeletal muscle-specific isoforms of the insulin-like growth factor-I (IGF-I) gene in response to exercise in humans. Data for women are sparse and the influences of age and physical training status are unknown. Here we aimed to describe the expression of mRNA for the IGF-I isoforms in the quadriceps muscles of women at rest and after isometric exercise.
  
  
  OBJECTIVE
  To categorize mRNA expression of the IGF-I splice variants IGF-IEa and IGF-IEc (MGF) in healthy women, determine whether isometric exercise stimulates expression, and to determine the duration of the response.
  
  
  METHODS
  Observational study.
  
  
  METHODS
  Clinical research facility.
  
  
  METHODS
  Six healthy women (median age 38 years, range 25-43 years).
  
  
  METHODS
  Single bout of maximal isometric knee extension undertaken as 20 sets of 6 contractions. Muscle samples from the lateral mass of the quadriceps were obtained by needle biopsy at baseline, 2.5h and 50h after exercise.
  
  
  METHODS
  Quantification of mRNAs for IGF-IEa and MGF.
  
  
  RESULTS
  mRNA for the IGF-IEa transcript was significantly elevated by 50h post-exercise compared to baseline (p=0.005) and mRNA for MGF was significantly elevated by 2.5h (p=0.026). There were no statistically significant differences between measurements at 2.5h and 50h for either transcript.
  
  
  CONCLUSIONS
  We have shown that the upregulation of the muscle specific IGF-IEa and MGF isoforms occurs within 2.5h of a single bout of isometric exercise in women. The upregulation persists for at least 2 days after exercise. We have also demonstrated a potentially safe and effective way of studying the responsiveness of these isoforms to resistance exercise in future studies of older and/or frail individuals.
authors.affiliation: School of Clinical Sciences and Community Health, University of Edinburgh, Department Room F1424, Royal Infirmary Edinburgh, 51 Little France Crescent, Edinburgh EH16 5SA, United Kingdom. Cal.Greig@ed.ac.uk
authors.forename: Carolyn A
authors.initials: CA
authors.lastname: Greig
authors.forename: Mahjabeen
authors.initials: M
authors.lastname: Hameed
authors.forename: Archie
authors.initials: A
authors.lastname: Young
authors.forename: Geoffrey
authors.initials: G
authors.lastname: Goldspink
authors.forename: Brendon
authors.initials: B
authors.lastname: Noble
mesh_terms: D000328:Adult; D017398:Alternative Splicing; D015444:Exercise / Q000502:physiology*; D005260:Female; D015870:Gene Expression; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000235:genetics*; D018482:Muscle, Skeletal / Q000378:metabolism*; D020033:Protein Isoforms / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013997:Time Factors
chemical_list: D020033:Protein Isoforms; D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I