Researchers have discovered a cluster of brain cells that could be harnessed to help control food intake and body weight, which may aid the development of a new obesity medication that doesn't cause nausea.
A study at the University of Aberdeen found that these cells create a chemical called gamma-aminobutyric acid—'GABA', for short—which is a neurotransmitter that blocks signals between nerve cells in the brain.
In their experiments, which were conducted with mice, the team recorded the activity of individual brain cells. They also measured changes in daily food intake and body weight in the animals.
The team found a new connection between a group of neurons in the brainstem that sense food consumption, and neurons in another part of the brain that stimulate hunger. The former turn off the latter, with GABA playing a key role in this process.
"Think of GABA as the brain's 'stop sign'—it directly talks to cells and makes them stop, and it stops communication between other cells," paper author professor Lora Heisler told Newsweek.
"Our study investigated the function of GABA cells within a part of the brain called the brainstem. New cutting-edge tools have been developed recently that allow researchers to establish the function of small groups specific of cells in particular parts of the brain."
"Our study was the first time these brainstem GABA cells have been selectively switched on with such exquisite precision, and this allowed us to discover that they control food intake and body weight," Heisler explained.
"Given GABA's job in the brain, we thought that the way it reduces food intake and body weight is likely by communicating with cells that govern hunger and stopping them for a bit," she added.
"We went on to examine this and found that brainstem GABA cells dampen the activity of the main cells in the brain that stimulate hunger."
Although excess body weight is primarily caused by eating more calories than the body needs or burns off, feeling hungry can make it difficult for people to regulate their weight. Obesity medications can help people lose weight by reducing hunger.
One interesting feature of these brainstem GABA cells, Heisler added, is that the widely prescribed obesity medication liraglutide uses them to reduce food intake. Liraglutide, which is commonly sold under the brand names Victoza and Saxenda, is used to treat type 2 diabetes and chronic obesity. However, dizziness and sickness are common side effects.
Heisler told Newsweek: "It is not yet known how drugs such as liraglutide act in the brain to treat obesity. A common side effect of liraglutide and similar drugs is nausea. Our research and others suggest that one group of cells that is important in liraglutide's effects is brainstem GABA cells.
"What is really interesting is that we found that only activating brainstem GABA neurons can abate hunger but does not cause nausea," she added. "This suggests that the side effect of nausea is caused by liraglutide acting at other cells.
"Excitingly, this means it may be possible to develop drugs targeting brainstem GABA cells as future obesity medications that don't cause nausea."
Dr Pablo Blanco Martínez de Morentin, who led the study while at Aberdeen but now works at the University of Leeds, added: "This is exciting news as it opens up the potential for new strategies for weight regulation."
The full findings of the study were published in the journal Current Biology.
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