title: Effects of oral creatine and resistance training on myogenic regulatory factor expression.
abstract: OBJECTIVE
  This study examined 12 wk of creatine (Cr) supplementation and heavy resistance training on skeletal muscle creatine kinase (M-CK) mRNA expression and the mRNA and protein expression of the myogenic regulatory factors Myo-D, myogenin, MFR-4, and Myf5.
  
  
  METHODS
  Twenty-two untrained males were randomly assigned to either a control (CON), placebo (PLC), or Cr (CRT) group in a double-blind fashion. Muscle biopsies were obtained before and after training. PLC and CRT trained thrice weekly using 3 sets of 6-8 repetitions at 85-90% 1-RM on the leg press, knee extension, and knee curl exercises. CRT ingested 6 g.d-1 of Cr for 12 wk while PLC consumed the equal amount of placebo.
  
  
  RESULTS
  After training, M-CK mRNA expression, as well as myogenin and MRF-4 mRNA and protein expression, were found to be significantly greater for CRT compared with PLC and CON, whereas PLC was also significantly different from CON (P < 0.05). For Myo-D mRNA and protein, both CRT and PLC were significantly different from CON (P < 0.05), but CRT and PLC were not different from one another. No significant differences were located for Myf5 mRNA or protein (P > 0.05). M-CK mRNA was correlated with myogenin (r = 0.916) and MRF-4 (r = 0.883) protein (P < 0.05).
  
  
  CONCLUSIONS
  When combined with heavy resistance training, Cr supplementation increases M-CK mRNA expression, likely due to concomitant increases in the expression of myogenin and MRF-4. Therefore, increases in myogenin and MRF-4 mRNA and protein may play a role in increasing myosin heavy chain expression, already shown to occur with Cr supplementation.
authors.affiliation: Department of Kinesiology, Texas Christian University, Fort Worth 76129, USA. d.willoughby@tcu.edu
authors.forename: Darryn S
authors.initials: DS
authors.lastname: Willoughby
authors.forename: John M
authors.initials: JM
authors.lastname: Rosene
mesh_terms: D000284:Administration, Oral; D000293:Adolescent; D000328:Adult; D003401:Creatine / Q000008:administration & dosage* / Q000494:pharmacology*; D003402:Creatine Kinase / Q000032:analysis / Q000096:biosynthesis*; D004311:Double-Blind Method; D005786:Gene Expression Regulation; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000187:drug effects / Q000502:physiology*; D018006:Myogenic Regulatory Factors / Q000032:analysis / Q000096:biosynthesis*; D010919:Placebos; D012333:RNA, Messenger / Q000096:biosynthesis; D014891:Weight Lifting
chemical_list: D018006:Myogenic Regulatory Factors; D010919:Placebos; D012333:RNA, Messenger; D003402:Creatine Kinase; D003401:Creatine