Abstract :
In the present study energy balance and liver respiratory activity were studied in rats fed on either a
control diet or an energy-dense diet. Liver respiration was assessed both without added substrates
and after the addition of hexanoate, glycerol, or sorbitol. The effect of ouabain on hexanoatesupported
respiration was also determined. Metabolizable energy intake and energy expenditure
increased in rats fed on an energy dense diet, but body-weight gain, as well as lipid and protein
content, remained unchanged. When net energy expenditure, obtained excluding the total cost of
storage, was expressed as a percentage of metabolizable energy, significant differences were found
between the two groups of rats. This finding supports the presence of regulatory mechanisms in rats
fed on an energy-dense diet, which are useful to counteract development of obesity. In addition,
a significant increase in liver respiratory activity was found in rats fed on an energy-dense diet,
both in the basal state and in that stimulated by added substrates. Na/K-pump-dependent O2
consumption also increased in rats fed on an energy-dense diet. The results indicate that a greater
production of metabolic heat by the liver can contribute to the increased energy expenditure found
in rats fed on an energy-dense diet.
