AJP - Endocrinology and Metabolism, Vol 246, Issue 4 319-E326, Copyright © 1984 by American Physiological Society
Energy metabolism in rats with ventromedial hypothalamic lesions
B. E. Hustvedt, J. Jeszka, A. Christophersen and A. Lovo
Rats with ventromedial hypothalamic lesions (VMH) have increased ability to
accumulate energy. The aim of this investigation was to characterize the
main processes responsible for the reduced energy expenditure, using
indirect calorimetry, nitrogen, and energy balance techniques. Metabolism
was studied during different metabolic conditions created by a strict
feeding regimen with concentrated feeding periods. A computerized system
for indirect calorimetry enabled continuous study of individual animals for
prolonged time periods. We found a mean decrease of 15.5% in total energy
expenditure and decreased nitrogen retention in VMH rats. Calculation of
respiratory quotient (RQ), energy expenditure, and the metabolic mixture
demonstrated fluctuations in metabolism in accordance with the feeding
regimen. The same percent reduction in resting postabsorptive energy
expenditure was found as in total expenditure. Quantitatively, this main
finding means that metabolic processes that occurred both in the resting
and postabsorptive state were responsible for two-thirds of the total
reduction in energy expenditure, whereas only one-third could be attributed
to differences in dietary-induced thermogenesis and/or physical activity.
It is concluded that VMH-animals spent as much as 10.3% of their total
energy expenditure on liponeogenesis compared with 2.5% in controls.
