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Effect of Housing Temperature on Body Composition in Laboratory Mouse
Kružíková, Nikola ; Zouhar, Petr (advisor) ; Ferenčáková, Michaela (referee)
Development of obesity and associated disorders is caused by imbalance between energy intake and energy expenditure. Significant part of energy expenditure can be represented by energy cost of maintaining stable body temperature. In this thesis, the effect of thermoneutrality and high fat feeding on body composition was characterized in female C57BL/6 mice. These mice were housed either at 22 řC (standard temperature) or at 30 řC (thermoneutrality) and fed by standard chow or high fat diet for 13 weeks. Energy intake of chow-fed thermoneutral animals was lowered in comparison to mice housed at standard temperature, reflecting lower energy cost of thermogenesis. This reduction of food intake was prevented by high fat feeding resulting in adipose tissue accumulation in particular in high fat-fed thermoneutral animals. While studying this model, protocol for assessment of body composition using newly acquired dual energy X-ray absorptiometry system was validated. Reflecting the development of obesity, glucose and lipid homeostasis was deteriorated in these mice. In line with earlier notions in literature describing male mice, our data suggest critical importance of housing temperature in efficiency of high fat feeding even in female mice. Keywords: thermoneutrality, obesity, body composition, DEXA
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Non-shivering thermogenesis - UCP1 and other alternative mechanisms
Kružíková, Nikola ; Zouhar, Petr (advisor) ; Tauchmannová, Kateřina (referee)
Adaptive thermogenesis is a natural mechanism by which endothermic organisms increase their basal metabolic rate to maintain stable body temperature. During acute exposure to subthermoneutral temperatures, the first reaction of organism is shivering which is gradually replaced by nonshivering thermogenesis. Nonshivering thermogenesis in mammals is associated with a UCP1 protein located in the inner mitochondrial membrane in adipose cells. In active mode, UCP1 uncouples respiratory chain from ATP synthesis and by that significantly increases metabolic rate. Apart from UCP1, some alternative mechanisms of nonshivering thermogenesis were suggested - namely: sarcolipin uncoupling ATP hydrolysis from pumping calcium ions through SERCA pump in skeletal muscle, phosphocreatine hydrolysis in adipose tissue or futile cycling of triacylglycerols and fatty acids reesterification. However, to date, there is rather indirect and not generally accepted evidence that these mechanisms contribute significantly to adaptive nonshivering thermogenesis. Better understanding of the nonshivering thermogenesis processes would be of great clinical importance as it could allow identification of potential targets for pharmacological manipulation of energy expenditure and thus provide novel methods for reducing obesity and...
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