Submitted on April 17, 2007
Accepted on July 20, 2007
Creatine enhances differentiation of myogenic C2C12 cells by activating both p38 and Akt/PKB pathways
Louise Deldicque1, Daniel Theisen1, Luc Bertrand2, Peter J. Hespel3, Louis Hue4, and Marc Francaux1*
1 Institut d'Education physique et de Readaptation, Universite catholique de Louvain, Louvain-la-Neuve, Belgium
2 Division of Cardiology, Universite catholique de Louvain, Brussels, Belgium
3 Research Center for Exercise and Health, Faculty of Kinesiology and Rehabilitation Sciences, K.U.Leuven, Heverlee, Belgium
4 Hormone and Metabolic Research Unit, Universite catholique de Louvain, Brussels, Belgium
* To whom correspondence should be addressed. E-mail: Marc.Francaux{at}uclouvain.be.
In myogenic C2C12 cells, 5mM creatine increased the incorporation of labelled [35S] methionine into sarcoplasmic (+20%, P<0.05) and myofibrillar (+50%, P<0.01) proteins. Creatine also promoted the fusion of myoblasts assessed by an increased number of nuclei incorporated within myotubes (+40%, P<0.001). Expression of myosin heavy chain type II (MHC II, +1300%, P<0.001), troponin T (+65%, P<0.01) and titin (+40%, P<0.05) was enhanced by creatine. Neither mannitol, taurine, nor beta-alanine mimicked the effect of creatine, ruling out an osmolarity-dependent mechanism. The addition of rapamycin, the inhibitor of mammalian target of rapamycin/70kDa ribosomal S6 protein kinase (mTOR/p70s6k) pathway, and SB202190, the inhibitor of p38, completely blocked differentiation in control cells, and creatine did not reverse this inhibition, suggesting that the mTOR/p70s6k and the p38 pathways could be potentially involved in the effect induced by creatine on the differentiation. Creatine upregulated phosphorylation of protein kinase B (Akt/PKB, +60%, P<0.001), glycogen synthase kinase-3 (GSK-3, +70%, P<0.001) and p70s6k (+50%, P<0.001). Creatine also affected the phosphorylation state of p38 (-50% at 24h and +70% at 96h, P<0.05) as well as the nuclear content of its downstream targets myocyte enhancer factor-2 (MEF-2, -55% at 48h and +170% at 96h, P<0.05) and MyoD (+60%, P<0.01). In conclusion, this study points out the involvement of the p38 and the Akt/PKB-p70s6k pathways in the enhanced differentiation induced by creatine in C2C12 cells.
