Effects of preexercise feeding on markers of satellite cell activation.
OBJECTIVE
The purpose of this study was to determine if consuming isoenergetic (25 g) doses of carbohydrate or protein versus a noncaloric placebo before conventional resistance training affected the myogenic expression of cell cycle-regulating genes as well as the muscle [DNA] acutely after exercise.


METHODS
Ten untrained men (mean +/- SD: age = 22 +/- 4 yr, body mass = 77.8 +/- 8.3 kg, percent body fat = 17.8 +/- 4.0) participated in three resistance exercise sessions (three sets of 10 repetitions at 80% one-repetition maximum for the bilateral hack squat, leg press, and leg extension exercises) in a crossover fashion, which were preceded by carbohydrate, protein, or placebo ingestion 30 min before training. Presupplement/preexercise and 2- and 6-h postexercise muscle biopsies were obtained during each session and analyzed for fold changes in CDK4, CYCLIN D1, MGF, MYOD, P21(CIP1), and P27(KIP1) messenger RNA expression using real-time reverse transcriptase-polymerase chain reaction as well as muscle [DNA] using cuvette-based fluorometric methods.


RESULTS
Nonparametric statistics were completed, and no conditions x time interaction effects were revealed. Several exercise-mediated responses were found to occur independent of condition: 1) muscle [DNA] increased at 6 h (+40%, P < 0.05), 2) CDK4 expression increased at 6 h (+86%, P < 0.05), 3) MYOD expression increased at 6 h (+98%, P < 0.05), 4) P27(KIP1) expression decreased at 2 h (j35%, P < 0.05) and 6 h (-59%, P < 0.001), and 5) P21(CIP1) expression substantially increased 2 and 6 h postexercise (+1.250% and +4.670%, respectively, P < 0.001).


CONCLUSIONS
The tandem DNA and cell cycle regulator gene expression analyses provide preliminary evidence to suggest that satellite cell activation and proliferation may be occurring at early post-exercise time points after a conventional resistance exercise bout, a phenomenon that may seemingly be independent of preexercise macronutrient ingestion.
Roberts
Michael D
MD
Health and Exercise Science Department, University of Oklahoma, Norman, OK 73019-6081, USA.
Dalbo
Vincent J
VJ
Hassell
Scott E
SE
Brown
Ryan
R
Kerksick
Chad M
CM
D000328:Adult; D015415:Biomarkers / Q000378:metabolism; D019938:Cyclin D1 / Q000032:analysis; D051358:Cyclin-Dependent Kinase 4 / Q000032:analysis; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000032:analysis; D050760:Cyclin-Dependent Kinase Inhibitor p27; D004435:Eating / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D015870:Gene Expression / Q000502:physiology; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000032:analysis; D008297:Male; D009124:Muscle Proteins / Q000378:metabolism; D018482:Muscle, Skeletal / Q000378:metabolism; D017570:MyoD Protein / Q000032:analysis; D055070:Resistance Training; D050799:STAT5 Transcription Factor / Q000032:analysis; D032496:Satellite Cells, Skeletal Muscle / Q000378:metabolism / Q000502:physiology*; D025521:Tumor Suppressor Proteins / Q000032:analysis; D055815:Young Adult
D015415:Biomarkers; C493956:CDKN1A protein, human; C436291:CDKN1B protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D047908:Intracellular Signaling Peptides and Proteins; D009124:Muscle Proteins; D017570:MyoD Protein; D050799:STAT5 Transcription Factor; C494092:STAT5A protein, human; D025521:Tumor Suppressor Proteins; D019938:Cyclin D1; D050760:Cyclin-Dependent Kinase Inhibitor p27; C495900:CDK4 protein, human; D051358:Cyclin-Dependent Kinase 4