Integration of body temperature into the analysis of energy expenditure in the mouse

• Objectives: We quantified the effect of environmental temperature on mouse energy homeostasis and body temperature.Methods: The effect of environmental temperature (4e33 C) on body temperature, energy expenditure, physical activity, and food intake invarious mice (chow diet, high-fat diet, Brs3-/y, lipodystrophic) was measured using continuous monitoring.Results: Body temperature depended most on circadian phase and physical activity, but also on environmental temperature. The amounts ofenergy expenditure due to basal metabolic rate (calculated via a novel method), thermic effect of food, physical activity, and cold-inducedthermogenesis were determined as a function of environmental temperature. The measured resting defended body temperature matchedthat calculated from the energy expenditure using Fourier’s law of heat conduction. Mice defended a higher body temperature during physicalactivity. The cost of the warmer body temperature during the active phase is 4e16% of total daily energy expenditure. Parameters measured indiet-induced obese and Brs3-/y mice were similar to controls. The high post-mortem heat conductance demonstrates that most insulation in miceis via physiological mechanisms.Conclusions: At 22 C, cold-induced thermogenesis isw120% of basal metabolic rate. The higher body temperature during physical activity isdue to a higher set point, not simply increased heat generation during exercise. Most insulation in mice is via physiological mechanisms, with littlefrom fur or fat. Our analysis suggests that the definition of the upper limit of the thermoneutral zone should be re-considered. Measuring bodytemperature informs interpretation of energy expenditure data and improves the predictiveness and utility of the mouse to model human energyhomeostasis.

Ämnesord

NATURVETENSKAP  -- Biologi -- Biokemi och molekylärbiologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Biochemistry and Molecular Biology (hsv//eng)

Nyckelord

Thermoneutrality

Basal metabolic rate

Cold-induced thermogenesis

Body temperature

Energy expenditure

Heat conductance

fysiologi

Physiology

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