title: Creatine-induced activation of antioxidative defence in myotube cultures revealed by explorative NMR-based metabonomics and proteomics.
abstract: BACKGROUND
  Creatine is a key intermediate in energy metabolism and supplementation of creatine has been used for increasing muscle mass, strength and endurance. Creatine supplementation has also been reported to trigger the skeletal muscle expression of insulin like growth factor I, to increase the fat-free mass and improve cognition in elderly, and more explorative approaches like transcriptomics has revealed additional information. The aim of the present study was to reveal additional insight into the biochemical effects of creatine supplementation at the protein and metabolite level by integrating the explorative techniques, proteomics and NMR metabonomics, in a systems biology approach.
  
  
  METHODS
  Differentiated mouse myotube cultures (C2C12) were exposed to 5 mM creatine monohydrate (CMH) for 24 hours. For proteomics studies, lysed myotubes were analyzed in single 2-DGE gels where the first dimension of protein separation was pI 5-8 and second dimension was a 12.5% Criterion gel. Differentially expressed protein spots of significance were excised from the gel, desalted and identified by peptide mass fingerprinting using MALDI-TOF MS. For NMR metabonomic studies, chloroform/methanol extractions of the myotubes were subjected to one-dimensional 1H NMR spectroscopy and the intracellular oxidative status of myotubes was assessed by intracellular DCFH2 oxidation after 24 h pre-incubation with CMH.
  
  
  RESULTS
  The identified differentially expressed proteins included vimentin, malate dehydrogenase, peroxiredoxin, thioredoxin dependent peroxide reductase, and 75 kDa and 78 kDa glucose regulated protein precursors. After CMH exposure, up-regulated proteomic spots correlated positively with the NMR signals from creatine, while down-regulated proteomic spots were negatively correlated with these NMR signals. The identified differentially regulated proteins were related to energy metabolism, glucose regulated stress, cellular structure and the antioxidative defence system. The suggested improvement of the antioxidative defence was confirmed by a reduced intracellular DCFH2 oxidation with increasing concentrations of CMH in the 24 h pre-incubation medium.
  
  
  CONCLUSIONS
  The explorative approach of this study combined with the determination of a decreased intracellular DCFH2 oxidation revealed an additional stimulation of cellular antioxidative mechanisms when myotubes were exposed to CMH. This may contribute to an increased exercise performance mediated by increased ability to cope with training-induced increases in oxidative stress.
authors.affiliation: Department of Food Science, Faculty of Agricultural Sciences, University of Aarhus, Denmark. JetteF.Young@agrsci.dk.
authors.forename: Jette F
authors.initials: JF
authors.lastname: Young
authors.forename: Lotte B
authors.initials: LB
authors.lastname: Larsen
authors.forename: Anders
authors.initials: A
authors.lastname: Malmendal
authors.forename: Niels Chr
authors.initials: NC
authors.lastname: Nielsen
authors.forename: Ida K
authors.initials: IK
authors.lastname: Straadt
authors.forename: Niels
authors.initials: N
authors.lastname: Oksbjerg
authors.forename: Hanne C
authors.initials: HC
authors.lastname: Bertram