Effect of cold acclimation and deacclimation on energy metabolism of OLETF rats

Abstract

Long-term cold exposure to Zucker fatty rats resulted in good effects on lipid metabolism and suppression of weight-increment through growth. We investigated the effect of cold environment on energy balance of OLETF rats, another obese strain. Methods: Male OLETF and LETO rats aged 7 weeks were housed at 10°C or 25°C for 11 weeks (cold acclimated, control) and 25°C for 2 weeks after acclimation to 10°C for 9 weeks (deacclimated). Changes in body masses and food intake and oxygen uptake at 10°C and 25°C were measured. Brown adipose tissues (BAT) were isolated after 11 weeks acclimation and mass value, morphological change and expression of proteins in BAT were analyzed. Contrary to Zucker fatty rats, amounts of food intake of OLETF rats during cold exposure were markedly increased and those of oxygen consumption at 10°C were higher and were comparable to those of LETO rats. Changes in mass value and lipid content of BAT showed similar tendency as those of Zucker fatty rats but absolute values of mass were smaller. Sizes of lipid droplets of BAT were significantly smaller than those of Zucker fatty rats, though larger than those of LETO rat. These results indicate that energy expenditure of OLETF rats is greater and BAT are more active than those of Zucker fatty rats though amount of food intake is remarkably increased. Expressions of many proteins isolated from BAT were changed through cold acclimation and deacclimation and these were somewhat differed from those of Zucker rats. [Jpn J Physiol 54 Suppl:S240 (2004)]