August 24, 2023

Thermal Physiology The Effects of Environmental Temperatures on Energy Expenditure in Mice

Marc Reitman, MD, PhD and Oksana Gavrilova, PhD, give an in-depth overview of thermal physiology, energy expenditure, and thermoneutrality in a mouse model.

Mice are generally an excellent model of human biology with nearly identical metabolic pathways. In contrast, the 3000-fold difference in body mass causes huge differences in thermal physiology and energy homeostasis. Humans generally live in a thermoneutral environment, while mice live and are typically studied below thermoneutrality. A mouse housed singly at 22 °C devotes 42% of its energy expenditure to maintaining its body temperature; the corresponding value in humans is approximately 0%. Understanding this different physiology is important, allowing one to avoid incorrect application of mouse observations to humans. It also boosts elucidation of physiology that is subtle or difficult to study in humans.

The goal is to understand thermal physiology and to use it to develop conditions under which mice better model humans. This is important for studying the effectiveness of drug treatments for metabolic diseases, like obesity and diabetes. Marc and Oksana discuss what thermoneutrality means in the mouse and the concept of the thermoneutral point. They also explore the effects of cold, hot, and near-thermoneutral environments on mouse energy expenditure, body temperature, and behavior.