title: Effects of elevated circulating hormones on resistance exercise-induced Akt signaling.
abstract: OBJECTIVE
  Hormones and muscle contraction alter protein kinase B (Akt) signaling via distinct mechanisms. Therefore, the purpose of this study was to determine whether physiologically elevated circulating hormones modulate resistance exercise (RE)-induced signaling of Akt and its downstream targets. We hypothesized that elevated circulating hormones would potentiate the signaling response.
  
  
  METHODS
  Seven healthy men (mean +/- SD age, 27 +/- 4 yr; body mass, 79.1 +/- 13.6 kg; body fat, 16% +/- 7%) performed two identical lower-body RE protocols (five sets of five maximal repetitions of knee extensions) in a randomized order and separated by 1-3 wk: one protocol was preceded by rest [low-circulating hormonal concentration (LHC) trial], and the other was preceded by a bout of high-volume upper-body RE using short rest periods designed to elicit a large increase in circulating hormones [high-circulating hormonal concentration (HHC) trial].
  
  
  RESULTS
  The HHC trial invoked significantly (P < or = 0.05) greater growth hormone (GH) and cortisol concentrations compared with the LHC trial. There were minimal differences between trials in insulin and insulin-like growth factor-I (IGF-I) concentrations. Contrary to our hypothesis, 70-kDa ribosomal protein S6 kinase (p70 S6K) threonine (Thr) 389 phosphorylation within the vastus lateralis was attenuated at 180 min post-RE during the HHC trial. RE did not affect Akt or glycogen synthase kinase-3beta (GSK-3beta) phosphorylation nor were there differences between trials. Immediately post-RE, eukaryotic initiation factor (eIF) 4E binding protein-1 (4E-BP1) phosphorylation declined, and adenosine monophosphate-activated protein kinase (AMPK) phosphorylation increased; however, there were no differences between trials in these variables.
  
  
  CONCLUSIONS
  p70 S6K Thr 389 phosphorylation was attenuated during the HHC trial despite dramatically greater (>2.5-fold) circulating GH concentrations; this was potentially due to cortisol-induced inhibition of p70 S6K Thr 389 phosphorylation.
authors.affiliation: Human Performance Laboratory, Department of Kinesiology, University of Connecticut, Storrs, CT 06269, USA.
authors.forename: Barry A
authors.initials: BA
authors.lastname: Spiering
authors.forename: William J
authors.initials: WJ
authors.lastname: Kraemer
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Anderson
authors.forename: Lawrence E
authors.initials: LE
authors.lastname: Armstrong
authors.forename: Bradley C
authors.initials: BC
authors.lastname: Nindl
authors.forename: Jeff S
authors.initials: JS
authors.lastname: Volek
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Judelson
authors.forename: Michael
authors.initials: M
authors.lastname: Joseph
authors.forename: Jakob L
authors.initials: JL
authors.lastname: Vingren
authors.forename: Disa L
authors.initials: DL
authors.lastname: Hatfield
authors.forename: Maren S
authors.initials: MS
authors.lastname: Fragala
authors.forename: Jen-Yu
authors.initials: JY
authors.lastname: Ho
authors.forename: Carl M
authors.initials: CM
authors.lastname: Maresh
mesh_terms: D000328:Adult; D015444:Exercise / Q000502:physiology*; D006006:Glycogen Synthase / Q000378:metabolism; D013006:Growth Hormone / Q000378:metabolism; D006801:Humans; D006854:Hydrocortisone / Q000502:physiology; D008297:Male; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000502:physiology*; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000378:metabolism*; D015398:Signal Transduction; D014891:Weight Lifting / Q000502:physiology
chemical_list: D013006:Growth Hormone; D006006:Glycogen Synthase; D051057:Proto-Oncogene Proteins c-akt; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D006854:Hydrocortisone