Scapular brown fat removal enhances development of adiposity in cold-exposed obese Zucker rats.

To investigate the contribution of brown fat (BAT) to the development of obesity in genetically obese Zucker rats (fa/fa), scapular brown fat (SBAT) was removed from obese and lean 4-wk-old females. Eight weeks after surgery there was no regrowth of SBAT. Lipectomy had no effect on body weight gain, food intake, and body composition when rats were housed at 25 degrees C. Lean rats completely compensated for the lipectomy by increasing BAT mass, protein, cellularity, and activity of citrate synthase (CS) in axillary, perirenal, and thoracic depots. beta-Hydroxyacyl-coenzyme A dehydrogenase (HOAD) activity was increased, but compensation was incomplete. In lipectomized obese rats, only BAT protein and cell number were increased sufficiently for complete compensation. In a second experiment SBAT was removed from obese and lean rats, but rats were housed in the cold (10 degrees C) for 8 wk. In lean rats, although compensation was incomplete, it was sufficient to maintain a weight gain and body composition comparable with sham-operated lean rats. In obese rats, where there was little or no compensation for lipectomy, weight gain and fat deposition were greater than observed in sham-operated obese controls. These data support the hypothesis that reducing the amount of functional BAT contributes to the development of increased adiposity.