American scientists have studied how winter temperatures trigger the brain to increase appetite.
- American researchers have identified specific brain circuits that cause mammals, including humans, to eat more in cold weather.
- When mice search for food in the face of low temperatures, they do so only after a delay of about six hours.
- According to the authors, cold temperatures provide a distinct signal that must be present for changes in appetite to occur.
When exposed to cold, mammals automatically burn more calories to maintain normal body temperature. This increase in energy expenditure triggers an increase in appetite. “The neural mechanism that controls this is not well understood,” indicated researchers from the Scripps Research Institute (United States). But recently, they identified brain circuits that make mammals want to eat more when exposed to cold temperatures.
Eat more because of energy expenditure rather than feeling cold
As part of their study, published in the journal Nature, scientists conducted behavioral and metabolic experiments on mice. When cold temperatures arrived, mice only increased their foraging after a delay of about six hours, suggesting that this change in behavior was not simply a direct result of exposure to cold. cold. To identify the neural mechanisms underlying cold-induced foraging, the authors compared the activity of neurons in the brain when it was cold and hot. The team discovered that “the xiphoid (Xi), a small nucleus located in the midline of the thalamus, was selectively activated by prolonged cold associated with high energy expenditure, but not by acute cold exposure.”
When the authors artificially activated these neurons, the rodents increased their foraging, but not other activities. Likewise, when they inhibited the activity of these neurons, the animals decreased their search for food. These effects only appeared when it was cold, implying that cold temperatures provide a distinct signal that must also be present for changes in appetite to occur. In a final experiment, the scientists showed that these neurons in the xiphoid nucleus project to a region of the brain called the nucleus accumbens, an area long known for its role in integrating reward and aversion signals to guide behavior, including eating behavior.
Block cold-induced appetite by targeting neurons in the xiphoid nucleus
According to the researchers, these findings may have clinical relevance because they suggest the possibility of blocking the usual cold-induced increase in appetite, which would allow relatively simple cold exposure regimens to cause loss weight much more efficiently. The group of neurons, which function like a “switch”, is “a fundamental adaptive mechanism in mammals and targeting it with future treatments could help enhance the metabolic benefits of cold or other forms of fat burning,” concluded Li Ye, lead author of the study, in a statement.
