Metformin limits ceramide-induced senescence in C2C12 myoblasts

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, 50 mu M C2-ceramide (8 h), and/or 2 mM 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-BPI, regardless of the presence of insulin. The ceramide treated myoblasts displayed higher beta-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-ct 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. (C) 2013 Published by Elsevier Ireland Ltd.