44-OR: Cell Intrinsic Alterations in miRNA Expression and Secretion in Muscle in Type 2 Diabetes

MicroRNAs are important regulators of metabolism in health and disease, and alterations in miRNAs can impact key metabolic pathways/processes, including insulin signaling, beta cell function, and fat/liver function. miRNAs are also secreted from cells in exosomes or small extracellular vesicles (sEVs) which can be taken up and regulate gene/protein expression in cells at a distance. To determine how T2D can modify the expression of cellular and sEV-secreted miRNAs, we have used a disease-in-a-dish model in which iPS cells from T2D patients and controls were differentiated into myoblasts (iMyos), and cellular and secreted sEV miRNAs assessed using a nuclease protection assay, which assesses all known human miRNAs. We show that, compared to controls, iMyos from T2D in vitro exhibit significant alterations in cellular expression of 71 miRNAs, with 22 up-regulated and 49 down-regulated. Overlapping the predicted miRNA-targets of the up-regulated miRNAs with global proteomics data revealed 123 proteins that were targeted and down-regulated by these miRNAs, consistent with the fact that a single miRNA has multiple targets and indicating that T2D-induced alterations in miRNA expression contribute to broad range of changes in cellular protein. In the sEVs secreted from iMyo, there were even more marked changes, with 70 up- and 296 down-regulated miRNAs, demonstrating a major alteration in regulation of miRNA secretion by muscle in T2D. Importantly, most of the T2D-regulated sEV are known to be involved in the development of insulin resistance and T2D. For example, levels of miR-1299, miR-1324, and miR-378h were elevated in T2D-derived sEVs, and we show that these miRNAs can suppress gene expression of PTEN, PGC-1α/β and FASN in adipose tissue. The dysregulated miRNA expression and secretion contribute to altered gene/protein expression in the myoblast itself, as well as targeting metabolic and signaling genes in other tissues, such as adipose tissue, thereby contributing to the pathogenesis of T2D.