title: Amino acid infusion alters the expression of growth-related genes in multiple skeletal muscles.
abstract: BACKGROUND
  Exercise and nutritional interventions have been examined independently as countermeasures to offset the loss of skeletal muscle mass with unloading, yet a protocol to completely preserve the soleus has not been identified. Little is known regarding the combined effect of exercise and nutrition on factors regulating skeletal muscle growth. The purpose of this investigation was to evaluate the influence of amino acid (AA) infusion on myogenic (MRF-4, MyoD, and Myogenin), proteolytic (MuRF-1, Atrogin-1, FOXO3A, Calpain-1, Calpain-2, Caspase-3, Cathepsin L1), and cytokine (IL-6, IL-8, and IL-15) mRNA transcripts in two skeletal muscles that respond distinctly to microgravity unloading.
  
  
  METHODS
  Muscle biopsies were obtained from the vastus lateralis (VL) and soleus of eight male subjects prior to and after 4 h of AA infusion for analysis of mRNA expression. All subjects performed a standardized exercise bout (45-min treadmill run) 24 h prior to the AA infusion.
  
  
  RESULTS
  In the VL, proteolytic factors MuRF-1 and FOXO3A were reduced (44 +/- 9 and 28 +/- 6%, respectively) in response toAA infusion. In the soleus, mRNA transcripts of myogenic factor MRF-4 (91 +/- 36%) and cytokines IL-6, IL-8, and IL-15 were elevated while the proteolytic marker FOXO3A mRNA was reduced by 19 +/- 9%.
  
  
  CONCLUSIONS
  These data suggest that the expression of genes related to skeletal muscle remodeling is altered during acute AA infusion 24 h post-exercise. It appears that increased amino acid availability in concert with exercise may create an intramuscular environment favorable for the prevention of muscle atrophy associated with unloading, which may be particularly beneficial for the soleus.
authors.affiliation: Ball State University, Muncie, IN 47306, USA.
authors.forename: Miranda K
authors.initials: MK
authors.lastname: Suer
authors.forename: Justin D
authors.initials: JD
authors.lastname: Crane
authors.forename: Todd A
authors.initials: TA
authors.lastname: Trappe
authors.forename: Bozena
authors.initials: B
authors.lastname: Jemiolo
authors.forename: Scott W
authors.initials: SW
authors.lastname: Trappe
authors.forename: Matthew P
authors.initials: MP
authors.lastname: Harber
mesh_terms: D000328:Adult; D000596:Amino Acids / Q000494:pharmacology*; D003546:Cysteine Endopeptidases / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D016207:Cytokines / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D015444:Exercise / Q000502:physiology; D015870:Gene Expression / Q000187:drug effects*; D006801:Humans; D008297:Male; D009124:Muscle Proteins / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism*; D018006:Myogenic Regulatory Factors / Q000235:genetics / Q000378:metabolism; D052097:Quadriceps Muscle / Q000187:drug effects / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D055815:Young Adult
chemical_list: D000596:Amino Acids; D016207:Cytokines; D009124:Muscle Proteins; D018006:Myogenic Regulatory Factors; D012333:RNA, Messenger; D003546:Cysteine Endopeptidases