| Co-Investigator(Kenkyū-buntansha) |
TSUJITA Junzo Hyogo College of Medicine, Medical Dept.Assistant Prof., 医学部, 講師 (30104235)
SASAKI Sadao Hyogo College of Medicine, Medical Dept.Associate Prof., 医学部, 助教授 (20104276)
HORI Seiki Hyogo College of Medicine, Medical Dept.Professor, 医学部, 教授 (80068452)
KANOH Naoyuki Hyogo College of Medicine, Medical Dept.Research Associate, 医学部, 助手 (20152829)
NAKAGAKI Ikuko Hyogo College of Medicine, Medical Dept.Assistant Prof., 医学部, 講師 (90084904)
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| Research Abstract |
Thermoregulatory thermogenesis (non-shivering thermogenesis) during cold exposure is mainly caused by the enhanced thermogenesis in brown adipose tissue (BAT). An increase in non-shivering thermogenesis is usually caused by the increased mass of BAT accompanied by an increase in the amount of mitochondrial uncoupling protein 1 (UCP1), thermogenin, lessening of the volume of lipid droplets as well as the increased blood flow through BAT.UCP1 creates proton leak across the inner mitochonrial membrane resulting uncoupling oxidative phosphorylation from ATP synthesis. However, adaptive changes induced by reacclimation to warm environment after long- term cold acclimation have not yet been fully elucidated.
Obesity results from many factors such as energy expenditure, energy intake and so on.
In the present investigation, we studied energy balance during cold acclimation and deacclimation in normal rats and obese rats. In male Wistar and Zucker lean rats, mass of adrenal glands and food intak
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e increased while the rate of increase in body mass decreased during cold acclimation. After 2 weeks of deacclimation, body mass of cold acclimated rats reached closer to that of warm acclimated rats. Mass of BAT, amounts of UCP1 and GLUT4 protein increased during cold acclimation and these changes obtained by cold acclimation were almost maintained after deacclimation. Volume of droplets and fat contents in BAT increased slightly during deacclimation. Values of respiratory quotient of deacclimated rats were small and similar to those of cold acclimated rats, and considerably smaller at 10℃ compared with those of warm acclimated rats, that is, state of cold acclimation concerning thermogenesis was maintained. Effects of cold acclimation and deacclimation of thermoregultory thermogenesis in these rats were similar to those in Zucker obese rats. However, increase in metabolic rate and non-shivering thermogenesis induced by cold acclimation in obese rats tended to be greter than those in lean rats. Decrease in metabolic rate in obese rats by deacclimation was approximately the same as that of lean rats. In deacclimated obese rats, an increase in metabolic rate induced by cold exposure (10℃) was greater compared with lean rats. In obese rats, orexigenic effect by cold exposure was not found, body mass reducing effect by cold exposure was greater compared with lean rats. Increase in body mass during deacclimation was smaller in obese rats than in lean rats. Greater increase in metabolic rate, marked decreases in concentrations of plasma glucose and lipid as well as body mass by cold acclimation indicate that the health risk of obesity and diabetes might be attenuated by long-term exposure to cold environment. Less
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