miRNAs play important roles in regulating differentiation and metabolism of brown adipocytes.We recently identified miR-30 as a key regulator in promoting thermogenesis and the development of beige adipocytes.We found that over-expression and knock-down of miR-30b and-30c induced and suppressed,respectively, the expression of thermogenic genes such as UCP1 and Cidea in brown adipocytes.Forced expression of miR-30b/c also significantly increased thermogenic gene expression and mitochondrial respiration activity in adipocytes derived from subcutaneous white adipose tissue, demonstrating a promoting effect of the miRNAs on the development of beige fat.In addition, knockdown of miR-30b/c repressed UCP1 expression in the brown adipose tissue in vivo.miR-30b/c targeted the 3'UTR of the receptor-interacting protein 140 (RIP140) and inhibiting RIP140 transcription could be an important mechanism by which miR-30b/c promotes thermogenesis.Taken together, our study identifies miR-30b/c as a key regulator of thermogenesis and uncovers a new mechanism underlying the regulation of brown adipose tissue function and the development of beige fat.