Islet β cell: An endocrine cell secreting miRNAs.

The pancreas is an important endocrine organ. Pancreatic beta (β) cells secrete insulin to regulate the metabolism of glucose and maintain the stability of blood glucose. MicroRNAs (miRNAs), small (20-25 nt) non-coding RNA molecules, function in target gene silencing through post-transcriptional patterns, and multiple miRNAs regulate insulin secretion, insulin signaling pathways in pancreatic β cells and islet activity. In recent years, it has been found that many types of cells can secrete regulatory miRNA, but whether islet cells can secrete miRNA has not been clarified yet. In this study, we detected miRNA expressions in cell culture medium of primary mouse islet cells and islet cell line MIN6. And we found that islet cells can selectively and actively secrete miRNAs, mainly through the way of exosome package, and that miRNA secretion profiling patterns vary according to different insulin secretion stimulating conditions (high Glucose, high Kcl, high Arginine and high Free fat acid (FFA)). Additionally, we found that these miRNAs secreted by islet cells can be transported and have gene-regulating functions on recipient tissue cells, such as liver and muscles. In conclusion, we find another secretory function of the islet β cells: not only insulin, but also miRNAs.