Defective diet-induced but normal cold-induced brown adipose tissue adaptation in hypothalamic obesity in rats.

our weeks after bilateral ventromedial hypothalamic (VMH) lesions in the female rat reared at 23 degrees C, the weight of the interscapular brown adipose tissue (IBAT) was doubled as compared to appropriate controls. Tested in vitro, the tissue of the lesioned animals showed, per unit weight, a basal and a noradrenaline--or octanoate--stimulated heat output about half of that of the tissue from the controls. However, basal and stimulated heat outputs as well as beta-oxidative capacity of IBAT from lesioned animals and their appropriate controls were the same when calculated per whole fat pad. The lesioned animals were hyperphagic, with a gross energy intake 70% larger than that of the controls. Cold acclimation at 5 degrees C for 3 weeks was found to restore the basal and stimulated heat outputs per unit weight of IBAT of the lesioned animals to the level of that of their cold acclimated controls. The weight of the tissue did not change significantly in lesioned animals upon cold exposure whereas controls exhibited the expected hypertrophy. Calculated per whole fat pad, the stimulated heat output became 33% larger in lesioned animals than in appropriate controls. The total beta-oxidative capacity increased by 3 fold in controls and 4.8 fold in lesioned animals. Cold exposure was followed by a mean increase of gross energy intake of 43% in the controls and 31% in the lesioned animals as compared to their gross energy intake at 23 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)