| The aim of this study was to examine the effects of dietary macronutrient composition on energy homeostasis. Uncoupling protein (UCP) has the ability to uncouple oxidative phosphorylation, and is postulated to have a role on the regulation of energy metabolism. At the first stage (study 1), iso-caloric high-fat (50% of total energy) and high-carbohydrate diets were used to feed C57/B6 lean mice to compare their effects on weight gain. At the second stage, the iso-caloric high-fat and high-carbohydrate diets were given to lean and ob/ob mice. Weight gain, metabolic changes and UCP expressions were recorded 2- (study 2) and four-weeks (study 3). Subsequently, a dietary and exercise treatment study was conducted on lean mice to explore the role of high-fat diet and physical activity in UCP expression and energy metabolism (study 4). A significant negative correlation between body weight gain and UCP3 mRNA expression was found in both stages of the experiment (r = −0.7861 & −0.4286, respectively, p < 0.05). There was a significant positive correlation between inactive metabolic rate and UCP3 mRNA expression (r = 0.4, p = 0.035), as well as oxygen consumption and UCP3 mRNA expression (r = 0.4128, p = 0.03). High fat treated lean mice gained weight at a significantly greater rate during the first two weeks of dietary treatment; however, the difference disappeared at the end of the four-week treatment. High-fat diet increased brown fat UCP1 expression in lean and ob/ob mice after the two-week treatment. High-fat treated ob/ob mice gained more weight than high-carbohydrate treated mice throughout the four-week dietary treatment, and this change was accompanied by a lower UCP2 mRNA expression in the liver. These results suggest that whole-body energy expenditure is affected by the rate of UCP expression in specific tissues. The ability to express UCP could therefore be an important marker of susceptibility to obesity. |
