Insulin Regulates Expression and Secretion of Exosomal MicroRNAs in Adipocytes

Transfer of regulatory molecules, such as microRNAs (miRNAs), via small extracellular vesicles (sEVs) called exosomes represents a newly recognized mode of inter-organ communication that provides an important mechanism of metabolic regulation. We have previously shown that adipose tissue is a major contributor to the pool of circulating exosomal miRNAs and that these adipose-derived exosomal miRNAs can be taken up by target tissues and suppress gene expression. We have also shown that biogenesis, secretion, and exosomal cargo sorting is a highly regulated process and that miRNAs contain 4-8 nucleotide motifs which contribute to exosomal secretion. Several exosomal miRNAs have been linked to obesity and diabetes, yet their regulation by physiological stimuli such as insulin remains unknown. To identify the role of insulin in regulation of adipose miRNAs and their secretion in exosomes, we performed small RNA-seq on exosomes isolated from differentiated 3T3-L1 cells with and without insulin stimulation. We find that out of the 460 miRNAs detected, 39 were up- and 75 were down-regulated in exosomes in response to insulin, whereas only 14 were up- and 39 were down-regulated in cells. In some cases, exosomal secretion correlated with cellular expression of the miRNA. More interestingly, 103 of the 114 miRNAs (90.3%) that were regulated in exosomes had no significant change at the cellular level or even a change in the opposite direction, demonstrating insulin’s ability to regulate miRNA exosomal secretion independent of cellular level. These insulin-regulated exosomal miRNAs included members of the let-7 family, which have known functions in adipogenesis, as well miRNAs predicted to target mRNAs of molecules involved in fatty acid biosynthesis and insulin signaling. Thus, insulin can independently regulate miRNA expression and secretion in adipocyte-derived exosomes. These can serve as adipokines and create a novel mechanism for regulation of cell-cell and inter-organ communication. Disclosure M.Lino: None. H.Pan: None. J.Dreyfuss: None. C.Kahn: None. Funding National Institutes of Health (5R01DK082659)