Journal
MEDICINE AND SCIENCE IN SPORTS AND EXERCISE
Volume 42, Issue 10, Pages 1861-1869Publisher
LIPPINCOTT WILLIAMS & WILKINS
DOI: 10.1249/MSS.0b013e3181da8a29
Keywords
CYCLINS; CYCLIN-DEPENDENT KINASES; CDK INHIBITORS; RESISTANCE EXERCISE; SKELETAL MUSCLE
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ROBERTS, M. D., V. J. DALBO, S. E. HASSELL, R. BROWN, and C. M. KERKSICK. Effects of Preexercise Feeding on Markers of Satellite Cell Activation. Med. Sci. Sports Exerc., Vol. 42, No. 10, pp. 1861-1869, 2010. Purpose: 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 (-35%, 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 postexercise time points after a conventional resistance exercise bout, a phenomenon that may seemingly be independent of preexercise macronutrient ingestion.
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