title: Metformin limits ceramide-induced senescence in C2C12 myoblasts.
abstract: High lipid and ceramide concentrations are hallmarks of obese and/or insulin resistant skeletal muscle, yet little is known about its role on cell cycle and senescence. The purpose of this study was to examine the role of ceramide on muscle senescence, and whether metformin limited this response.
  
  
  METHODS
  Low passage, proliferating C2C12 myoblasts were treated with a control, 50μM C2-ceramide (8h), and/or 2mM metformin, then examined for insulin sensitivity, cell senescence, cell proliferation, cell cycle, protein expression of cell cycle regulators.
  
  
  RESULTS
  Ceramide treatment caused a dephosphorylation (p<0.05) of Akt and 4E-BP1, regardless of the presence of insulin. The ceramide treated myoblasts displayed higher β-galactosidase staining (p<0.05), reduced BrDu incorporation and total number of cells (p<0.05), and an increased proportion of cells in G2-phase (p<0.05) versus control cultures. Ceramide treatment also upregulated (p<0.05) p53 and p21 protein expression, that was reversed by either pifithrin-α or shRNA for p53. Metformin limited (p<0.05) ceramide's effects on insulin signaling, senescence, and cell cycle regulation.
  
  
  CONCLUSIONS
  High ceramide concentrations reduced myoblast proliferation that was associated with aberrant cell cycle regulation and a senescent phenotype, which could provide an understanding of skeletal muscle cell adaptation during conditions of high intramuscular lipid deposition and/or obesity.
authors.affiliation: Department of Exercise and Nutrition Sciences, University at Buffalo SUNY, Buffalo, NY 14214, USA.
authors.forename: Kavita S
authors.initials: KS
authors.lastname: Jadhav
authors.affiliation: Department of Exercise and Nutrition Sciences, University at Buffalo SUNY, Buffalo, NY 14214, USA.
authors.forename: Cory M
authors.initials: CM
authors.lastname: Dungan
authors.affiliation: Department of Exercise and Nutrition Sciences, University at Buffalo SUNY, Buffalo, NY 14214, USA. Electronic address: davidwil@buffalo.edu.
authors.forename: David L
authors.initials: DL
authors.lastname: Williamson
mesh_terms: D000375:Aging; D000818:Animals; D002453:Cell Cycle; D002460:Cell Line; D049109:Cell Proliferation; D002470:Cell Survival; D016922:Cellular Senescence; D002518:Ceramides / Q000494:pharmacology*; D005786:Gene Expression Regulation; D007004:Hypoglycemic Agents / Q000494:pharmacology; D007328:Insulin / Q000378:metabolism; D007333:Insulin Resistance; D008055:Lipids / Q000737:chemistry; D008687:Metformin / Q000494:pharmacology*; D051379:Mice; D010766:Phosphorylation; D034741:RNA, Small Interfering / Q000378:metabolism; D013997:Time Factors; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism
chemical_list: D002518:Ceramides; D007004:Hypoglycemic Agents; D007328:Insulin; D008055:Lipids; D034741:RNA, Small Interfering; D016159:Tumor Suppressor Protein p53; D008687:Metformin
keywords: Cell cycle; Lipid; Proliferation; p21; p53