Regulation of UCP1, UCP2, and UCP3 mRNA expression in brown adipose tissue, white adipose tissue, and skeletal muscle in rats by estrogen

The effects of ovariectomy (OVX) and estrogen substitution on body weight, body composition, food intake, weight gain, and expression of uncoupling pr oteins (UCPs) in brown adipose tissue (BAT), white adipose tissue (WAT), an d skeletal muscle were studied in four groups of rats: (1) Sham-operated ra ts (N = 8), (2) ovariectomized rats (OVX - E) (N = 8), (3) estrogen-treated OVX rats (OVX + E) (N = 8), and (4) OVX rats on energy restriction (OVX - E + D) (N = 8). OVX was associated with an increase in food intake and body weight gain during a 5-week study period compared to sham-operated rats. T he estrogen-substituted rats had a significantly lower food intake and weig ht gain during the 5 weeks compared to the sham-operated group. However, we also included a nontreated OVX group that was allowed to eat only enough c how to match the weight gain of the sham-operated group. To match the weigh t gain in the two groups, the OVX group had to consume 16% less chow than t he sham-operated group. In BAT, the UCP1 expression was significantly lower in estrogen-deficient rats compared to either intact rats or estrogen-subs tituted rats, whereas UCP2 and UCP3 mRNA expression was similar in BAT from all four groups. In WAT, both estrogen-deficient groups had significantly lower UCP2 mRNA expression compared to the control rats and estrogen-treate d rats; In contrast, the UCP3 mRNA expression in WAT was similar in all fou r groups. Finally, in skeletal muscle the OVX group on mild energy restrict ion had reduced UCP3 mRNA expression compared to control, OVX, and estrogen -treated rats. In contrast, the UCP2 mRNA expression in skeletal muscle was similar in all four groups. Thus, the findings that estrogen deficiency is followed by reduced UCP1 expression in BAT and reduced UCP2 expression in WAT in association with weight gain probably caused by a decrease in energy expenditure might indicate that UCPs play a role for the estrogen-mediated changes in body weight and energy expenditure. (C) 2001 Academic Press.