Creatine increases IGF-I and myogenic regulatory factor mRNA in C2C12 cells

Addition of creatine to the differentiation medium of C2C12 cells leads to hypertrophy of the myotubes. To investigate the implication of insulin-like growth factor I (IGF-I) and myogenic regulatory factors (MRFs) in this hypertrophy, their mRNA levels were assessed during the first 72 h of differentiation. Creatine significantly increased the IGF-I mRNA level over the whole investigated period of time, whereas the MRF mRNA levels were only augmented at precise moments, suggesting a general activation mechanism for IGF-I and a specifically regulated mechanism for MRF transcription. Our results suggest therefore that creatine-induced hypertrophy of C2C12 cells is at least partially mediated by overexpression of IGF-I and MRFs. (C) 2003 Published by Elsevier B.V. on behalf of the Federation of European Biochemical Societies.