title: Actions of short-term fasting on human skeletal muscle myogenic and atrogenic gene expression.
abstract: BACKGROUND
  Skeletal muscle mass is governed by multiple IGF-1-sensitive positive regulators of muscle-specific protein synthesis (myogenic regulatory factors which includes myoD, myogenin and Myf5) and negative regulators, including the atrogenic proteins myostatin, atrogin-1 and muscle ring finger 1 (MuRF-1). The coordinated control of these myogenic and atrogenic factors in human skeletal muscle following short-term fasting is currently unknown.
  
  
  METHODS
  Healthy adults (n = 6, age 27.6 years) undertook a 40-hour fast. Skeletal muscle biopsy (vastus lateralis) and venous blood samples were taken 3, 15 and 40 h into the fast after an initial standard high-carbohydrate meal. Gene expression of the myogenic regulator factors (myoD, myogenin and Myf5) and the atrogenic factors (myostatin, atrogin-1 and MuRF-1) were determined by real-time PCR analysis. Plasma myostatin and IGF-1 were determined by ELISA.
  
  
  RESULTS
  There were no significant alterations in either the positive or negative regulators of muscle mass at either 15 or 40 h, when compared to gene expression measured 3 h after a meal. Similarly, plasma myostatin and IGF-1 were also unaltered at these times.
  
  
  CONCLUSIONS
  Unlike previous observations in catabolic and cachexic diseased states, short-term fasting (40 h) fails to elicit marked alteration of the genes regulating both muscle-specific protein synthesis or atrophy. Greater periods of fasting may be required to initiate coordinated inhibition of myogenic and atrogenic gene expression.
authors.affiliation: School of Exercise and Nutrition Sciences, Deakin University, Burwood, Vic, Australia.
authors.forename: A E
authors.initials: AE
authors.lastname: Larsen
authors.forename: R J
authors.initials: RJ
authors.lastname: Tunstall
authors.forename: K A
authors.initials: KA
authors.lastname: Carey
authors.forename: G
authors.initials: G
authors.lastname: Nicholas
authors.forename: R
authors.initials: R
authors.lastname: Kambadur
authors.forename: T C
authors.initials: TC
authors.lastname: Crowe
authors.forename: D
authors.initials: D
authors.lastname: Cameron-Smith
mesh_terms: D000328:Adult; D001707:Biopsy, Needle; D005215:Fasting / Q000378:metabolism*; D005260:Female; D005786:Gene Expression Regulation; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D008297:Male; D009124:Muscle Proteins / Q000378:metabolism; D018482:Muscle, Skeletal / Q000378:metabolism*; D017570:MyoD Protein / Q000378:metabolism; D051787:Myogenic Regulatory Factor 5 / Q000378:metabolism; D018006:Myogenic Regulatory Factors / Q000378:metabolism*; D018008:Myogenin / Q000378:metabolism; D055435:Myostatin; D016133:Polymerase Chain Reaction / Q000379:methods; D012333:RNA, Messenger / Q000378:metabolism*; D044843:SKP Cullin F-Box Protein Ligases / Q000378:metabolism; D013997:Time Factors; D016212:Transforming Growth Factor beta / Q000097:blood / Q000378:metabolism; D000070584:Tripartite Motif Proteins; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism
chemical_list: C525911:MSTN protein, human; D009124:Muscle Proteins; D017570:MyoD Protein; D051787:Myogenic Regulatory Factor 5; D018006:Myogenic Regulatory Factors; D018008:Myogenin; D055435:Myostatin; D012333:RNA, Messenger; D016212:Transforming Growth Factor beta; D000070584:Tripartite Motif Proteins; D007334:Insulin-Like Growth Factor I; C440907:FBXO32 protein, human; D044843:SKP Cullin F-Box Protein Ligases; C440908:TRIM63 protein, human; D044767:Ubiquitin-Protein Ligases