Muscular metabolism regulation by SREBP-1 transcription factors : role of MRFs, SIRT-1 and ceramides
SREBP-1 transcription factors are involved in lipid metabolism regulation. Recently, in vitro and in vivo studies have shown that SREBP-1a or SREBP-1c overexpression induce muscular atrophy and block muscular differentiation, notably by inhibiting structural proteins and Myogenics Regulatory Factors (MRFs) expression. The aims of this work are the mecanism determination of the muscular atrophy induced by SREBP-1 overexpression and the elucidation of the role of SIRT1 proteins on SREBP-1 regulation.The muscular atrophy results from an imbalance between the amount of synthesized and degraded proteins. In our studies, we shown that SREBP-1 regulates protein synthesis and protein degradation, respectively via a negative control of MRFs expression and via a control of atrogenes expression, MuRF1 and Atrogin-1. In skeletal muscle, we shown that SIRT1 desacetylase enzyme regulates SREBP-1 transcription activity. Because of SREBP-1 and SIRT1 proteins involvement in lipid metabolism regulation, our results suggest a new signalisation pathway linking energetic metabolism and SREBP-1 transcriptionnal activity in muscle. As SIRT1 and SREBP-1 have a role on lipid and muscular metabolism, we took an interest in phospholipids involvement and more specifically in ceramides involvement in muscle mass regulation. Our studies shown that the regulation of the amount of ceramids by the TNFα regulates muscle mass. Thus, our work allows to identify new links between lipid metabolism and muscle mass and metabolism regulation.