Adrenalectomy increases brown adipose tissue metabolism in ob/ob mice housed at 35 degrees C

Adrenalectomy arrests the development of obesity in ob/ob mice fed a high-starch diet and housed at a normal room temperature (20-25 degrees C) partly by stimulating the low thermogenic activity of brown adipose tissue (BAT). The present study was undertaken to determine if adrenalectomy would also lower energy retention and stimulate BAT metabolism in ob/ob mice housed in a warm environment (35 degrees C) where BAT thermoregulatory heat production is not needed. Adrenalectomy prevented hyperphagia and hyperinsulinemia and lowered the efficiency of energy retention in ob/ob mice housed at 35 degrees C, which is comparable to results obtained at 20-25 degrees C. Sympathetic nervous system stimulation of BAT (interscapular and subscapular depots) assessed by norepinephrine turnover was increased in adrenalectomized ob/ob mice. Thermogenic activity of BAT in adrenalectomized ob/ob mice (as assessed by GDP binding to isolated BAT mitochondria, GDP-inhibitable acetate-induced BAT mitochondrial swelling, and Mg2(/)-activated GDP binding to BAT mitochondria) was not elevated when results were expressed per milligram of mitochondrial protein but was elevated approximately 65% when expressed per interscapular and subscapular depots because adrenalectomy increased BAT mitochondrial mass. Adrenalectomy lowers the efficiency of energy retention and stimulates BAT metabolism even when ob/ob mice are housed in a warm environment.