title: l-glutamine Improves Skeletal Muscle Cell Differentiation and Prevents Myotube Atrophy After Cytokine (TNF-α) Stress Via Reduced p38 MAPK Signal Transduction.
abstract: Tumour Necrosis Factor-Alpha (TNF-α) is chronically elevated in conditions where skeletal muscle loss occurs. As l-glutamine can dampen the effects of inflamed environments, we investigated the role of l-glutamine in both differentiating C2C12 myoblasts and existing myotubes in the absence/presence of TNF-α (20 ng · ml(-1) ) ± l-glutamine (20 mM). TNF-α reduced the proportion of cells in G1 phase, as well as biochemical (CK activity) and morphological differentiation (myotube number), with corresponding reductions in transcript expression of: Myogenin, Igf-I, and Igfbp5. Furthermore, when administered to mature myotubes, TNF-α induced myotube loss and atrophy underpinned by reductions in Myogenin, Igf-I, Igfbp2, and glutamine synthetase and parallel increases in Fox03, Cfos, p53, and Bid gene expression. Investigation of signaling activity suggested that Akt and ERK1/2 were unchanged, JNK increased (non-significantly) whereas P38 MAPK substantially and significantly increased in both myoblasts and myotubes in the presence of TNF-α. Importantly, 20 mM l-glutamine reduced p38 MAPK activity in TNF-α conditions back to control levels, with a corresponding rescue of myoblast differentiation and a reversal of atrophy in myotubes. l-glutamine resulted in upregulation of genes associated with growth and survival including; Myogenin, Igf-Ir, Myhc2 & 7, Tnfsfr1b, Adra1d, and restored atrophic gene expression of Fox03 back to baseline in TNF-α conditions. In conclusion, l-glutamine supplementation rescued suppressed muscle cell differentiation and prevented myotube atrophy in an inflamed environment via regulation of p38 MAPK. l-glutamine administration could represent an important therapeutic strategy for reducing muscle loss in catabolic diseases and inflamed ageing. J. Cell. Physiol. 9999: 231: 2720-2732, 2016. © 2016 Wiley Periodicals, Inc.
authors.affiliation: Stem Cells, Ageing and Molecular Physiology Research Unit, Exercise Metabolism and Adaptation Research Group, Research Institute for Sport and Exercise Sciences (RISES), Liverpool John Moores University, Liverpool, United Kingdom.
authors.forename: Matthew
authors.initials: M
authors.lastname: Girven
authors.affiliation: Stem Cells, Ageing and Molecular Physiology Research Unit, Exercise Metabolism and Adaptation Research Group, Research Institute for Sport and Exercise Sciences (RISES), Liverpool John Moores University, Liverpool, United Kingdom.
authors.forename: Hannah F
authors.initials: HF
authors.lastname: Dugdale
authors.affiliation: Stem Cells, Ageing and Molecular Physiology Research Unit, Exercise Metabolism and Adaptation Research Group, Research Institute for Sport and Exercise Sciences (RISES), Liverpool John Moores University, Liverpool, United Kingdom.|Sorbonne Universités, UPMC University of Paris 06, INSERM UMRS974, CNRS FRE3617, Centre de Recherche en Myologie (CRM), GH Pitié Salpêtrière, Paris 13, France.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Owens
authors.affiliation: Stem Cells, Ageing and Molecular Physiology Research Unit, Exercise Metabolism and Adaptation Research Group, Research Institute for Sport and Exercise Sciences (RISES), Liverpool John Moores University, Liverpool, United Kingdom.|Department of Neurobiology, Physiology and Behavior, University of California Davis, Davis, California.
authors.forename: David C
authors.initials: DC
authors.lastname: Hughes
authors.affiliation: Stem Cells, Ageing and Molecular Physiology Research Unit, Exercise Metabolism and Adaptation Research Group, Research Institute for Sport and Exercise Sciences (RISES), Liverpool John Moores University, Liverpool, United Kingdom.
authors.forename: Claire E
authors.initials: CE
authors.lastname: Stewart
authors.affiliation: Stem Cells, Ageing and Molecular Physiology Research Unit, Exercise Metabolism and Adaptation Research Group, Research Institute for Sport and Exercise Sciences (RISES), Liverpool John Moores University, Liverpool, United Kingdom.
authors.forename: Adam P
authors.initials: AP
authors.lastname: Sharples
mesh_terms: D000818:Animals; D001284:Atrophy; D002454:Cell Differentiation / Q000187:drug effects*; D002459:Cell Fusion; D048430:Cell Shape / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects / Q000235:genetics; D005786:Gene Expression Regulation / Q000187:drug effects; D005973:Glutamine / Q000494:pharmacology*; D020935:MAP Kinase Signaling System / Q000187:drug effects*; D051379:Mice; D024510:Muscle Development / Q000187:drug effects; D018485:Muscle Fibers, Skeletal / Q000187:drug effects / Q000201:enzymology* / Q000473:pathology*; D032448:Myoblasts, Skeletal / Q000473:pathology*; D010766:Phosphorylation / Q000187:drug effects; D013312:Stress, Physiological / Q000187:drug effects; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
chemical_list: D014409:Tumor Necrosis Factor-alpha; D005973:Glutamine; D048051:p38 Mitogen-Activated Protein Kinases