Importance of sympathetic nerves for the stimulatory effect of cold exposure on glucose utilization in brown adipose tissue.

Abstract

The effects of cold exposure on glucose transport system in brown adipose tissue (BAT) and the role of sympathetic nerves in this response were studied in rats. The rate constant of glucose uptake in BAT increased 10-, 13-, and 14-fold after 6 h, 1 d, and 2 d of cold exposure, respectively, as compared with controls. After 2 d of cold exposure, the number of glucose transporters in the plasma membranes increased from 10.2 +/- 1.1 to 16.7 +/- 1.4 pmol/mg protein and the transporter number in the microsomal membranes decreased from 15.1 +/- 1.0 to 9.0 +/- 1.1 pmol/mg protein, as measured by cytochalasin B binding. However, the increase in glucose utilization in BAT preceded the recruitment of glucose transporters to the plasma membranes. Thus, the glucose utilization markedly increased 6 h after cold exposure without significant increase in the glucose transporter number. The apparent dissociation constant (Kd) for cytochalasin B was unchanged. The stimulatory effect of cold exposure on glucose utilization in BAT was prevented by sympathetic denervation. In denervated BAT, cold exposure conversely decreased the number of glucose transporters in the plasma membranes. These results indicate that: (1) cold exposure increases glucose utilization in BAT and promotes translocation of glucose transporters from the microsomes to plasma membranes; (2) the effects of cold exposure depend entirely upon sympathetic innervation of BAT; (3) the recruitment or redistribution of glucose transporters accounts only partly for the large increase in glucose utilization in BAT after acute cold exposure.