title: Oestrogen-dependent satellite cell activation and proliferation following a running exercise occurs via the PI3K signalling pathway and not IGF-1.
abstract: OBJECTIVE
  The purpose of this study was to determine whether 17β-estradiol (E2) enhances the activation, proliferation and differentiation of muscle satellite cells (SC) following eccentric exercise either via insulin-like growth factor-1 (IGF-1) or through phosphatidylinositol 3-kinase (PI3K) signalling.
  
  
  METHODS
  This study used 64, 9-week-old, ovariectomized Sprague-Dawley rats that were divided into eight treatments groups based on oestrogen status (0.25 mg oestrogen pellet or sham), exercise status (90 min run @ 17 m min(-1), -13.5° or unexercised) and PI3K signalling inhibition (0.7 mg wortmannin kg(-1) body weight or DMSO control).
  
  
  RESULTS
  Significant increases in total SCs were found in both soleus and white gastrocnemius muscles (immunofluorescent co-localization of Pax7(+) nuclei) 72 h following eccentric exercise (P < 0.05). Oestrogen supplementation caused a further enhancement in total SCs in exercised rats (P < 0.05). In animals where the PI3K pathway was inhibited, regardless of oestrogen or exercise status, there was no significant enhancement of SC number in both the soleus or white gastrocnemius muscles. Interestingly, oestrogen supplementation lowered muscle levels of IGF-1 with this effect being most prominent in the soleus muscle. While IGF-1 was increased following exercise (P < 0.05), oestrogen supplementation abrogated this increase back to sedentary levels.
  
  
  CONCLUSIONS
  These data suggest that the increase in SC population following exercise in oestrogen-supplemented females may be mediated via PI3K pathway signalling and not IGF-1.
authors.affiliation: Departments of Kinesiology and Physical Education and Health Sciences, Wilfrid Laurier University, Waterloo, ON, Canada.
authors.forename: G
authors.initials: G
authors.lastname: Mangan
authors.forename: E
authors.initials: E
authors.lastname: Bombardier
authors.forename: A S
authors.initials: AS
authors.lastname: Mitchell
authors.forename: J
authors.initials: J
authors.lastname: Quadrilatero
authors.forename: P M
authors.initials: PM
authors.lastname: Tiidus
mesh_terms: D000818:Animals; D049109:Cell Proliferation / Q000187:drug effects; D004958:Estradiol / Q000494:pharmacology*; D004967:Estrogens / Q000494:pharmacology*; D005260:Female; D005455:Fluorescent Antibody Technique; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D010052:Ovariectomy; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D010805:Physical Conditioning, Animal / Q000502:physiology*; D011863:Radioimmunoassay; D051381:Rats; D017207:Rats, Sprague-Dawley; D032496:Satellite Cells, Skeletal Muscle / Q000187:drug effects / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology
chemical_list: D004967:Estrogens; D004958:Estradiol; D007334:Insulin-Like Growth Factor I; D019869:Phosphatidylinositol 3-Kinases
keywords: insulin-like growth factor-1; muscle; oestrogen; phosphatidylinositol-3 kinase; satellite cells