Single myofibers from Mus musculus Raw sequence reads. Mus musculus strain:CD1 | isolate:Not applicable | breed:Not applicable | cultivar:Not applicable

Skeletal muscle has a central role in whole body metabolism with myofibers that represent its functional units. These are differentiated cells with different contraction power and metabolic traits. Faster contracting myofibers preferentially use glucose as substrate for energy production, while slower use lipids. Myofibers can plastically change phenotypic traits in response to pathophysiological stimuli. Since post-transcriptional mechanisms should administer the changes of these post-mitotic cells, we profiled mRNAs and miRNAs of all myofiber types of mouse hindlimb. We integrated these signatures and obtained myofiber-specific miRNA-mRNA regulatory networks that allowed focusing on two miRNAs that influence myofiber fuel availability and mitochondrial morphology. In vitro and in vivo experiments demonstrate that miR-27a-3p regulates glycogen utilization targeting Gaa and Pgm2, whereas miR-142-3p regulates lipid utilization targeting Fndc5. Our work provides a complete catalogue of genes and miRNAs expressed in myofibers and establishes miR-27a-3p and miR-142-3p as focal regulators of muscle metabolism.