Beige adipocytes independently improve impaired glucose metabolism in the absence of brown adipose tissues in vivo

Abstract

Beige adipocytes are emerging as an interesting issue in obesity and metabolism research. There is a neglected possibility that brown adipocytes are equally activated when external stimuli induce beige adipocytes. Thus, a question is whether beige adipocytes have the same functions as brown adipocytes when brown adipose tissue (BAT) is lacking. This question has not been well studied. Therefore we determine the beneficial effects of beige adipocytes upon cold challenge or CL316243 treatments in animal models of BAT ablation by surgical denervation. The data show that beige adipocytes partly contribute to impaired glucose metabolism resulting from denervated BAT. Whereas, we found that denervated BAT were activated by cold exposure and CL316243. Thus, we further used BAT-removal animal models to abolish BAT functions completely. We found that beige adipocytes upon cold challenge or CL316243 treatments independently improved impaired glucose metabolism in BAT-removal mice. The insulin signaling was activated in BAT-removal mice upon cold exposure. Whereas, both the activation of insulin signaling and up-regulation of glucose transporter expression were observed in BAT-removal mice with CL316243 treatments. The data show that beige adipocytes induced by cold exposure or CL316243 may have different mechanisms to improve impaired glucose metabolism. Beige adipocytes can also enhance energy expenditure and lipolytic activity of white adipose tissue when BAT is lacking. We provide direct evidences for the beneficial effect of beige adipocytes in glucose metabolism and energy expenditure in the absence of BAT in vivo.