Humans are known as homeothermic endotherms. To ensure thermic balance at rest when exposed to cold, they dispose of two main thermogenic processes: shivering thermogenesis (ST) and non-shivering thermogenesis (NST). ST consists of involuntary muscle contractions and NST represents the component of Hprod that is not ST. While ST is difficult to tolerate, it is not yet known which nutrients and how much are required to stimulate NST and lower ST in the cold. Whether or not food caloric intake has an impact on the relative contribution of ST and NST to total Hprod remains to be determined. Therefore, the purpose of this thesis was 1) to quantify the effects of ingesting two quantities (1507 vs 3015 kJ) of same relative compositions on cold-induced whole-body Hprod and 2) to establish the effects of these two quantities of food on the relative contribution of ST and NST to total Hprod. Five healthy male participants were exposed to a 3h mild cold, using a liquid conditioned suit with water flowing at 15°C (COLD) or 33 °C (CON) for a total of 4 trials. Thermal, metabolic and shivering responses were measured at baseline, before and after shake ingestion. Results demonstrated that Hprod and ST intensity increased in the cold, while no significant differences were found between the ingested shakes at two different caloric equivalents. In addition, ST intensity did not change, which confirmed that NST remained the same between the two conditions. Thus, knowing that the caloric intake will not maximize the thermogenic effects in the cold (i.e. improve the comfort of the individual), is it more advantageous to bring food or additional clothing, for any activity? Clearly, more research on the exact pathways of each processes in the cold with food consumption needs to be made. To that extent, the investigation of the effect of food quality on changes in the thermogenic processes during cold exposure strikes us as a fascinating area for future research.

京都大学 / 0048 / 新制・課程博士 / 博士(薬科学) / 甲第20311号 / 薬科博第80号 / 新制||薬科||9(附属図書館) / 京都大学大学院薬学研究科医薬創成情報科学専攻 / (主査)教授 岡村 均, 教授 竹島 浩, 准教授 平澤 明 / 学位規則第4条第1項該当 / Doctor of Pharmaceutical Sciences / Kyoto University / DGAM

The large capacity of brown adipose tissue (BAT) to expend energy as heat makes it an interesting potential player in weight regulation and other metabolic conditions. This is of particular interest as it has been recognized that adult humans possess BAT. The protein responsible for the heat production is uncoupling protein 1 (UCP1), which, as the name implies, uncouples the respiratory chain from ATP production; instead heat is produced. Cold is the strongest recruiter and activator of BAT. However, also obesogenic food has a low but nonetheless significant effect on the recruitment and activation of UCP1, although the significance of this has been discussed. In the present thesis, I have studied the effect of diet on BAT and the possibilities for it to be obesity-protective. This can be done by comparing responses in wild-type mice and in UCP1-ablated mice. Since the effect of diet on BAT is low, it is of importance to control the temperature and maintain thermoneutrality. Other confounding factors to keep in mind are differences in actual energy and composition of food and also cohort differences. When controlling all the parameters mentioned and giving the mice the same obesogenic diet, the mice possessing UCP1 compared to UCP1-ablated mice had higher energy expenditure, and lower weight gain, despite eating more. This confirms the presence of a UCP1-dependent diet-induced thermogenesis. Thus, the conclusion must be that possessing UCP1 does result in obesity protection at thermoneutrality. However, the relevance for human energy balance is still not established. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: Manuscript. Paper 2: Manuscript. Paper 3: Manuscript.</p>