SAT-180 MicroRNA Library Screening Identifies a Subset of Cooperative MicroRNAs That Affects Differentiation and Glucose Metabolism of Human Skeletal Muscle Cells

Skeletal muscle is a key target tissue for regulating whole body metabolism. Decreased muscle mass during the ageing process contributes to deteriorated metabolism and, next to obesity, is a major driver for the increasing prevalence of type 2 diabetes. Strategies to improve regeneration and glucose metabolism in skeletal muscle are therefore urgently needed. microRNAs (miRNAs) are important contributors to muscle formation and potential therapeutic targets, but the relevant miRNAs to improve muscle formation and insulin action are still poorly defined. Here, we aimed to develop strategies to identify miRNA networks during muscle regeneration irrespective of aberrant expression patterns in affected muscle tissues. Using miRNA library screening we determined that miRNA cooperativity controls differentiation in muscle cells that lack endogenous miRNAs after deletion of the RNA-binding protein DiGeorge syndrome critical region gene 8 (DGCR8). A group of only six miRNAs rescued morphological and gene expression changes in these knockout cells. Conversely, combinatorial inhibition of five of the six miRNAs (let7-5p, miR-29a-3p, miR-125b-5p, miR-199a-5p, and miR-221-3p) markedly enhanced differentiation in wildtype muscle cells from mice and humans. Improved muscle differentiation translated into improved insulin stimulated glycogen synthesis (+30%, p<0.05, Ant-5x versus control myotubes). Mechanistically, miRNA add-back and loss-of-function most significantly affected genes involved in focal adhesion signalling and antagonizing the subset of miRNAs in human skeletal muscle cells enhanced phosphorylation of p38 mitogen-activated protein kinase and AKT highlighting the importance of cues from the extracellular matrix for muscle formation and the regulation of glucose metabolism.