Brown adipose tissue lipectomy leads to increased fat deposition in Osborne-Mendel rats

Inter- and subscapular brown adipose tissue depots were removed from nine female Osborne-Mendel rats. These lipectomized animals and nine sham-operated controls recovered from surgery for 7 days at 25 degrees C and were then placed on a highly palatable liquid diet. All animals were maintained for a 2nd wk at 25 degrees C before being switched to 8 degrees C. After 9 wk in the cold, animals were killed, and the brown adipose tissue was dissected from scapular, cervical, thoracic, perirenal, and axillary regions. Total brown fat pad mass, protein content, brown adipocyte number, citrate synthase activity, and beta-hydroxyacyl CoA dehydrogenase activity in each of the dissected brown fat depots were significantly less than those of the sham-operated controls. Thus there was incomplete metabolic compensation in the remaining brown fat depots after the removal of the scapular brown fat in the lipectomized rats. The mass and lipid content of the retroperitoneal white adipose depot were significantly increased in the lipectomized rats as was their carcass fat content (up 14%). Food intake of the lipectomized rats was slightly but significantly decreased. These data indicate that a reduction in the amount of functional brown fat is accompanied by increased body fat accretion and are thus consistent with the hypothesis that decreased brown adipose thermogenesis can lead to altered energy balance and increased white fat deposition.