ABSTRACT. There are several benefits to a high-fat diet for animals exposed to cold, including improved tolerance to severe cold conditions and increased survival rates in cold environments. It is therefore of interest to examine whether animals exposed to cold will selectively consume lipids. We examined the intake of safflower oil (SO) by rats exposed to cold (4 ± 2°C) under a feeding condition in which the rats were given free access to SO. Rats exposed to cold consumed more SO than those housed at 25 ± 2°C. This finding suggests that rats prefer SO in a cold environment. There was no significant difference in the ratio of calories of SO ingested to that of matter (standard laboratory chow plus SO) ingested between rats exposed to cold and those at 25 ± 2°C. The high SO intake also affected cold tolerance and metabolite kinetics in the rats. Factors that affected the SO intake of rats exposed to cold are also discussed. KEY WORDS: cold exposure, cold tolerance, interscapular adipose tissue, rats, safflower oil.J. Vet. Med. Sci. 67 (7): [653][654][655][656][657][658] 2005 There are several benefits to a high-fat diet for animals exposed to cold, including improved tolerance to severe cold conditions and increased survival rates in cold environments [5,15,18]. Previous studies have examined diets that included a higher portion of lipid than standard diets. Thus, animals were forced to eat a high-fat diet to satisfy their energy needs and to obtain essential nutrients. However, whether animals prefer lipids in a cold environment has not been studied. It is therefore of interest to examine whether animals exposed to cold will selectively consume lipids. Safflower oil (SO) has often been used as a lipid in experiments related to diet [8, 20-22, 26, 27]. Thus, in the present study we examined the SO intake of rats exposed to cold (4 ± 2°C) under a free-feeding condition in which both SO and a standard laboratory chow were available ad libitum. We also measured rectal temperature upon acute cold exposure (ACE: -20°C in a cold room, 60 min) to evaluate the effect of ingestion of SO on cold tolerance of rats compared with rats not given SO [15]. Changes in the blood levels of glucose, nonesterified fatty acids (NEFA), and β-hydroxybutyrate caused by ACE were also measured to evaluate changes in the use of these substances by cold exposure [15]. The interscapular brown adipose tissue (IBAT) was weighed to assess its generation of heat [10,15]. MATERIALS AND METHODSMale Slc: Wistar rats 9 week of age (Japan SLC, Shizuoka, Japan) were divided into 4 groups with 2 rats per cage (Fig. 1). Two groups were housed at room temperature (25 ± 2°C) for 4 week and then exposed to cold (4 ± 2°C, using a cold room) for the following 3 week period. The 1st group served as controls exposed to the cold environment (CECNT), and the 2nd group had access to SO (CESO). The other 2 groups were fed at room temperature for 7 week.One group served as controls housed at room temperature (RTCNT), and the other group had access to SO (RTSO). A...

Chronic exposure to cold increases the growth of brown adipose tissue and the resistance to more severe cold, thus improving thermogenesis. The present study examined the possibility that dietary compounds can modify cold acclimation. Adenosine (ADO) or adenine (ADE) were administered in drinking water (0.05%, w/v) for 5 weeks to male ddY strain mice from 4 weeks of age. At 5 weeks of age, the mice were exposed to 4°C for 4 weeks. After termination of this period, the interscapular brown adipose tissue (IBAT) and rectal temperature on acute exposure to severe cold (–20°C) for 60 min were measured. Chronic exposure to cold increased the weight of IBAT and made mice resistant to a fall in rectal temperature on exposure to severe cold. The growth of IBAT and improvement in thermogenesis can be used as a cold acclimation profile in ddY mice. The growth of IBAT was selectively prevented by ingestion of ADO. The improvement in thermogenesis was reduced, but only a little, by the ingestion of either ADO or ADE. Thus, growth of brown adipocytes might not be necessary for cold acclimation in mice.

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