Effects of oral creatine and resistance training on myogenic regulatory factor expression.
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.
Willoughby
Darryn S
DS
Department of Kinesiology, Texas Christian University, Fort Worth 76129, USA. d.willoughby@tcu.edu
Rosene
John M
JM
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
D018006:Myogenic Regulatory Factors; D010919:Placebos; D012333:RNA, Messenger; D003402:Creatine Kinase; D003401:Creatine