Author:

Keywords:

Adaptor Proteins, Signal Transducing, Adult, Biopsy, Carrier Proteins, Creatine, Cross-Over Studies, Double-Blind Method, Exercise, Humans, Insulin-Like Growth Factor I, Insulin-Like Growth Factor II, Male, Muscle, Skeletal, Phosphoproteins, Phosphorylation, RNA, Messenger, Ribosomal Protein S6 Kinases, 70-kDa, Time Factors, Science & Technology, Life Sciences & Biomedicine, Sport Sciences, resistance exercise, protein synthesis, P70(S6K), 4E-BP1, real-time RT-PCR, GROWTH-FACTOR-I, P70 S6 KINASE, MAMMALIAN TARGET, PHAS-I, PROTEIN-SYNTHESIS, PHOSPHORYLATION, EXERCISE, TRANSLATION, STRENGTH, Cell Cycle Proteins, 1106 Human Movement and Sports Sciences, 1116 Medical Physiology, 1117 Public Health and Health Services, 3202 Clinical sciences, 3208 Medical physiology, 4207 Sports science and exercise

Abstract:

PURPOSE: We hypothesized that creatine supplementation would facilitate muscle anabolism by increasing the expression of growth factors and the phosphorylation of anabolic signaling molecules; we therefore tested the responses of mRNA for IGF-I and IGF-II and the phosphorylation state of components of anabolic signaling pathways p70(s6k) and 4E-BP1 to a bout of high-intensity resistance exercise after 5 d of creatine supplementation. METHODS: In a double-blind cross-over design, muscle biopsies were taken from the m. vastus lateralis at rest and 3 and 24 h postexercise in subjects who had taken creatine or placebo for 5 d (21 g x d(-1)). For the first 3 h postexercise, the subjects were fed with a drink containing maltodextrin (0.3 g x kg(-1) body weight x h(-1)) and protein (0.08 g x kg(-1) body weight x h(-1)). RESULTS: After creatine supplementation, resting muscle expressed more mRNA for IGF-I (+30%, P < 0.05) and IGF-II (+40%, P = 0.054). Exercise caused an increase by 3 h postexercise in IGF-I (+24%, P < 0.05) and IGF-II (+48%, P < 0.05) and by 24 h postexercise in IGF-I (+29%, P < 0.05), but this effect was not potentiated by creatine supplementation. The phosphorylation states of p70(s6k) and 4E-BP1 were not affected by creatine at rest; phosphorylation of both increased (150-400%, P < 0.05) to similar levels under placebo and creatine conditions at 3 h postexercise plus feeding. However, the phosphorylation state of 4E-BP1 was higher in the creatine versus placebo condition at 24 h postexercise. CONCLUSION: The increase in lean body mass often reported after creatine supplementation could be mediated by signaling pathway(s) involving IGF and 4E-BP1.