The microRNAs miR-375, miR-124 and let-7b suppress the translation of mRNA encoding myotrophin (MTPN). Normally, MTPN interacts with cytoskeletal elements and is thought to open the F-actin mesh, allowing access of the secretory granules to exocytotic sites. Furthermore, MTPN may activate the transcription factor NF-kappaB in the nucleus. NF-kappaB is permissive to insulin secretion, probably by activating genes that control vesicle trafficking and exocytosis. RISC, RNA-induced silencing complex; ANK, ankyrin motifs; GLP-1, glucagon-like peptide-1.