Interaction between heat acclimation and exogenous insulin in brown adipose tissue of rats |
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Authors: | H Ohno H Yamashita N Sato Y Habara S Gasa J Nagasawa Y Sato M Ishikawa M Segawa M Yamamoto |
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Institution: | (1) Departments of Hygiene, National Defense Medical College, 359 Tokorozawa, Japan;(2) Molecular Pharmacology Group, Tsukuba Research Laboratories, Nippon Glaxo Ltd., 300-42 Tsukuba, Japan;(3) Laboratory of Cellular Metabolism, Department of Molecular Physiology, National Institute for Physiological Science, 444 Okazaki, Japan;(4) Biochemistry Laboratory, Cancer Institute, Hokkaido University School of Medicine, 060 Sapporo, Japan;(5) Research Center of Health, Physical Fitness and Sports, Nagoya University, 464 Nagoya, Japan;(6) Department of Obstetrics and Gynecology, Asahikawa Medical Collge, 078 Asahikawa, Japan;(7) Departments of Biochemistry, National Defense Medical College, 359 Tokorozawa, Japan |
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Abstract: | Seventy-one male Wistar strain rats (7 weeks old) were kept at 5, 25, or 34° C, respectively, for 2 weeks with or without insulin administration. Insulin (Novo Lente MC) was given subcutaneously in a dose of 3.62 nmol/125 µl saline per 100 g body weight. An apparent effect of insulin treatment was noted only in heat-exposed rats, resulting in a remarkable gain in inter-scapular brown adipose tissue (BAT) mass of heat-acclimated, insulin-treated rats in terms of weight or weight per unit body weight. The BAT from heat-acclimated, insulin-treated rats had significantly higher levels of protein, DNA, RNA, and triglyceride than BAT from heat-acclimated, saline-treated rats. Therefore, it seems likely that the growth of BAT in heat-acclimated, insulin-treated rats was mostly due to the anabolic effects of insulin. The uncoupling protein mRNA was, however, present in BAT of heat-acclimated, insulin-treated rats at rather a depressed level, explaining a corresponding decrease in cold tolerance. On the other hand, the expression of insulin receptor mRNA was attenuated in BAT of rats from all the insulin-treated groups, possibly due to the down-regulation of insulin. Thus, there appeared to be some linkage among BAT, heat acclimation, and insulin. |
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Keywords: | Heat acclimation Insulin Brown adipose tissue Uncoupling protein Cold tolerance |
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