MicroRNAs in brown and beige fat.

Brown adipose tissue (BAT) dissipates energy as heat and its activity correlates with leanness in human adults. Understanding the mechanisms behind the activation of BAT and the process of "browning", i.e. the appearance of inducible brown adipocytes called beige or brite (brown-in-white) cells in white adipose tissue (WAT), is of great interest for developing novel therapies to combat obesity. MicroRNAs (miRNAs) are small transcriptional regulators that control gene expression in a variety of tissues, including WAT and BAT. Recently, miRNAs were reported to regulate browning. Nevertheless, further studies are needed to fully understand the miRNA networks that are involved in the control of brown and beige/brite adipocytes. Particularly, most miRNAs have so far been studied in mice, underlining the importance of additional human studies. In this review, we focus on the regulation of brown fat by miRNAs including their role in promoting or inhibiting the browning process. In recent years, RNA-based therapeutical approaches have entered clinical trials for treatment of other diseases, thus miRNAs could potentially be used to enhance brown and beige fat mass and activity as novel therapies against overweight and its complications.