The novel adipokine CTRP5 is a negative regulator of white adipose tissue browning

The browning of white adipose tissue predominantly emerges as an adaptation to environmental cues, such as cold exposure. The enhanced browning of adipose tissue results in improved energy and glucose homeostasis and reduced fat mass and body weight, which is greatly beneficial for the treatment of obesity and other metabolic diseases. C1q/TNF-related protein 5 (CTRP5) is a novel adipokine associated with a variety of endocrine and metabolic diseases; however, whether it can regulate the metabolism of adipose tissue itself remains unknown. In this study, we demonstrated that the expression of CTRP5 in murine subcutaneous white adipose tissue (scWAT) was significantly decreased when the mice were exposed to cold temperatures. The lentivirus-mediated overexpression of CTRP5 in mice repressed the adipose tissue browning, leading to reduced heat production, decreased expression of the browning marker uncoupling protein 1 (UCP1) and decreased browning-related gene expression. Mechanistically, we found that autophagy was inhibited after cold exposure, but this inhibition was alleviated after CTRP5 overexpression. In primary cultured adipocytes, CTRP5 suppressed UCP1 expression, whereas 3-MA (an autophagy inhibitor) rescued the suppression. All of these results demonstrated that CTRP5 is a negative regulator of adipose browning. CTRP5 exerts its effect, at least in part, by suppressing adipocyte autophagy. Our findings indicated that CTRP5 is a novel promising therapeutic target for obesity and other metabolic diseases.