Energy balance in rats with obesity-producing hypothalamic knife cuts: effects of adrenalectomy.

Rats with obesity-producing, hypothalamic knife cuts (KC) were fed a purified high fat diet for 9 wk. KC rats consumed more energy (+70-100%) and retained energy with a much higher efficiency than control rats. Adrenalectomy of KC rats 1 wk (before gross obesity was evident) or 5 wk (when KC rats were 70% overweight) after KC surgery caused a reduction in energy intake to levels approximating those of control rats. Furthermore, energy retention in adrenalectomized KC rats was depressed more than could be explained on the basis of the reduction in energy intake. Two factors associated with the reduction in energy retention, urinary excretion of norepinephrine, an indicator of sympathetic nervous system activity, and GDP binding to brown adipose tissue mitochondria, an indicator of the thermogenic capacity of the tissue, were higher in vadrenalectomized KC rats than in pair-fed KC rats. Removal of the adrenals not only suppressed hyperphagia in KC rats fed a high fat diet, but also increased energy expenditure per kilocalorie consumed.