9:00 a.m. CT Saturday, June 13
Mice are not simply small humans. Because mice are used widely to study diabetes and obesity, understanding their thermal biology is critical to translating observations from mice to humans. In humans, the heat needed to maintain body temperature is virtually all created as a byproduct of metabolic processes. People generally live in a “thermoneutral zone”, a ~10 degrees C range of ambient temperatures over which core body temperature is maintained without increasing metabolic rate. In contrast, mice typically live below thermoneutrality. At room temperature (~20-22 degrees C) about half of food intake is used to generate heat. Surprisingly, we found for mice no ambient temperature range over which energy expenditure and body temperature remained constant. Rather, we propose the concept of a thermoneutral point (TNP), a single ambient temperature, below which energy expenditure increases and above which body temperature increases. The mouse TNP was 29 degrees C in the resting/light phase and 33 degrees C in active/dark phase, a four-degree change every 12 hours. Thus, studying mice “at thermoneutrality” is not feasible. These results inform how mice can be used to model human obesity physiology and drug development.