Fat and brain talk, the discovery of scientists

“Overheard sensory neurons”. Also Patapoutian Medicine Nobel 2021 in the team

Fat and brain talk to each other, they do it through a newly discovered entity, sensory neurons, and a team of scientists – including a Nobel Prize – has ‘overheard’ their exchange of messages. What Does Brain Fat Say? Researchers from the Scripps Research Institute reveal this in ‘Nature’. For years it was thought that passively floating hormones in the blood were the way fat tissue could send information related to stress and metabolism to the brain. Instead the experts discovered a direct line: sensory neurons carry a flow of messages from fat to the brain.

“This is another example of how important sensory neurons are to the health and disease of the human body,” says co-senior author Ardem Patapoutian, 2021 Nobel Prize in Medicine researcher Howard Hughes Medical Institute. “The discovery of these neurons – adds senior co-author Li Ye, associate professor of neuroscience at Scripps Research – suggests for the first time that your brain is actively examining your fat, rather than passively receiving messages about it. The implications. of this discovery are profound “.

In short words, sensory neurons could eventually be co-opted to treat obesity or metabolic diseases. In mammals, adipose tissue stores energy in the form of fat cells, and when the body needs energy, it releases these reserves. It also controls a number of hormones and signaling molecules related to hunger and metabolism. In diseases such as diabetes, fatty liver, atherosclerosis and obesity, energy storage and signaling often go wrong.

Researchers have long known that nerves extend into fat tissue, but they suspected they weren’t sensory neurons carrying data to the brain. Most speculated that the nerves in fat belonged primarily to the sympathetic nervous system, the network responsible for our fight-or-flight (‘Fight-or-Flight’) response, which activates fat-burning pathways during times of stress. and physical activity. After all, it is difficult to study them because deep in the adipose tissue the nerves are difficult to see or to stimulate. Ye and colleagues developed two new methods that allowed them to overcome obstacles. One is an imaging approach that made the mouse tissues transparent, allowing the pathways of the neurons to be better traced as they snaked through the adipose tissue.

The researchers found that nearly half of these neurons did not connect to the sympathetic nervous system, but to the dorsal root ganglia, an area of ​​the brain from which all sensory neurons originate. A second new technique, which the scientists called Root, was used to better probe the role of these neurons. “This research was really made possible by the way these new methods were put together,” says lead author Yu Wang. So what have the scientists overheard? Meanwhile, they have seen that when the brain does not receive sensory messages from adipose tissue, the programs activated by the sympathetic nervous system, related to the conversion of white fat to brown fat, become excessively active in the fat cells, and the result is larger fat. than normal with particularly high levels of brown fat, which breaks down other fat and sugar molecules to produce heat.

Indeed, animals with blocked sensory neurons and high levels of sympathetic signaling had an increased body temperature. The results suggest that sensory neurons and sympathetic neurons may have two opposite functions: the sympathetic ones serve to activate fat burning and brown fat production, the sensory needed to lower these programs. “Therefore, there is not only a one-size-fits-all instruction that the brain sends adipose tissue – says Li – these two types of neurons act as an accelerator pedal and a brake to burn fat.” Scientists now know that connections and communications are key to keeping fat healthy. And they are planning future research into what neurons detect and whether other similar cells exist in other internal organs.