Postprandial thermic effect of chicken involves thyroid hormones and hepatic energy metabolism in rats

Calculating Diet-Induced Thermogenesis in Mice

Diet-induced thermogenesis (DIT) is the increase in energy expenditure (EE) associated with food intake. Increasing DIT may lead to weight loss, so it is expected that increasing DIT will decrease body mass index and body fat mass. DIT in humans has been measured in various ways, but there is no way to calculate absolute DIT values in mice. Therefore, we developed a method to measure DIT in mice by applying a method more commonly used in humans. First, we measure the energy metabolism of mice under fasting conditions. EE is then plotted against the square root of activity, and a linear regression equation is fitted to the data. Next, we measure the energy metabolism of mice fed ad libitum and plotted EE in the same way. DIT is calculated by subtracting the predicted EE value from the EE value of mice fed at the same activity count. This method not only allows observation of the time course of the absolute value of DIT but also allows calculation of the ratio of DIT to caloric intake and the ratio of DIT to EE.

The Role and Regulatory Mechanism of Brown Adipose Tissue Activation in Diet-Induced Thermogenesis in Health and Diseases

Brown adipose tissue (BAT) has been considered a vital organ in response to non-shivering adaptive thermogenesis, which could be activated during cold exposure through the sympathetic nervous system (SNS) or under postprandial conditions contributing to diet-induced thermogenesis (DIT). Humans prefer to live within their thermal comfort or neutral zone with minimal energy expenditure created by wearing clothing, making shelters, or using an air conditioner to regulate their ambient temperature; thereby, DIT would become an important mechanism to counter-regulate energy intake and lipid accumulation. In addition, there has been a long interest in the intriguing possibility that a defect in DIT predisposes one to obesity and other metabolic diseases. Due to the recent advances in methodology to evaluate the functional activity of BAT and DIT, this updated review will focus on the role and regulatory mechanism of BAT biology in DIT in health and diseases and whether these mechanisms are applicable to humans.

A novel method for measuring diet-induced thermogenesis in mice

Diet-induced thermogenesis (DIT) refers to energy expenditure (EE) related to food consumption. Enhancing DIT can lead to weight loss. Factors that increase DIT are expected to lower body mass index and body fat mass. Although various methods have been developed for measuring DIT in humans, there is currently no method available for calculating absolute DIT values in mice. Therefore, we attempted to measure DIT in mice by applying the method more commonly used for humans. Mouse energy metabolism was first measured under fasting conditions; EE was plotted against the square root of the activity count, and a linear regression equation was fit to the data. Then, energy metabolism was measured in mice that were allowed to feed ad libitum, and EE was plotted in the same way. We calculated the DIT by subtracting the predicted EE value from the fed EE value for the same activity count. The methodology for measuring DIT in mice may be helpful for researching ways of combatting obesity by increasing DIT.

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The methodology for measuring absolute DIT values in mice is developed.

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For mice, the proportion of DIT compared with calorie intake and EE are 12.3% and 21.7%, respectively.

Diet-Induced Thermogenesis and Expression Levels of Thyroid Hormone Target Genes and Their Products in Rats Differ between Meat Proteins

We compared the effects of purified meat proteins on postprandial thermogenesis and on the secretion of and responsiveness to thyroid hormones (THs) in rats. Body temperatures at 2 h after feeding were significantly higher in the chicken and mutton protein groups than in the other groups, and these proteins seem to have a strong thermogenic effect. There were no significant differences in plasma TH concentrations among the groups, but levels of TH-responsive Spot 14 protein in the liver and brown adipose tissue were significantly higher in the chicken and mutton protein groups than in the other groups. Levels of malic enzyme 1 protein in the liver and brown adipose tissue were significantly higher in the chicken protein group than in the other groups except for the mutton protein group. Furthermore, levels of uncoupling protein 1 were higher in the chicken and mutton protein groups than in the other groups. The results suggest that the difference in postprandial thermogenesis of meat is strongly dependent on meat proteins; chicken and mutton proteins are strong promoters of postprandial thermogenesis, and THs may contribute to this effect. Since strong postprandial thermogenesis and high expression levels of TH target genes and their products were not observed in the amino acid group, chicken and mutton proteins or their digested peptides might contribute to these effects.