New research has discovered a network that links the brain and digestive system, with the gut sending signals about protein deficiencies.
Scientists have discovered a hitherto unknown communication network between the gut and the brain that helps animals detect protein deficiencies and adjust their eating behavior accordingly. The discovery could have important implications for obesity, metabolic disorders and appetite control.
The research was published in Science and led by Seong-Bae Suh and colleagues at Seoul National University’s Institute of Basic Sciences and Ewha Women’s University. reveals it intestine functions as an active sensory organcapable of monitoring nutritional needs and directly influencing food preferences.
Researchers found that when protein levels get too low, the gut activates a two-part signaling system. A fast neural pathway informs the brain about a lack of essential amino acids, while a slower hormonal pathway helps maintain the urge to seek out food rich in protein over time.
To investigate the mechanism, the scientists studied fruit flies, a common model for understanding feeding behavior and neural circuits. When deprived of protein, specialized intestinal cells release a hormone known as CNMa. This molecule activates neurons associated with the intestine and enters the bloodstream, creating a double channel of communication between the digestive system and the brain.
“Our study shows that the intestine is not simply a digestive organbut an active sensory system that continuously monitors nutritional status and directly guides behavioral decisions,” said Suh.
It is important to highlight that the response was not a general increase in hunger. Instead, researchers observed a targeted shift in food preferences. You protein-rich nutrients have become more attractive, while interest in sugary foods has declined.
Further analysis revealed that CNMa signaling suppressed activity in brain cells responsible for detecting sugar, effectively redirecting eating behavior towards foods that could replenish essential amino acids, explains .
The study also highlighted the role of the gut microbiome. Fruit flies lacking normal gut bacteria showed greater activation of neurons involved in protein-seeking behavior, suggesting that fruit flies microbes influence appetite affecting the availability of nutrients and the body’s internal monitoring systems.
To determine whether similar processes occur in mammals, the researchers performed experiments in mice. Animals deprived of protein also developed a strong preference for essential amino acidsindicating that this nutrient detection mechanism may be evolutionarily conserved across species.
A surprising discovery has challenged previous assumptions about the hormone FGF21, long considered a key regulator of protein appetite. You mice lacking FGF21 still exhibited protein-seeking behaviorsuggesting that there were additional biological pathways involved.
The researchers believe the discovery could help scientists better understand how the body regulates food choices and maintains nutritional balance. It can also contribute to the development of new treatments for obesityeating disorders and metabolic diseases.
“Most current medications for obesity and appetite control rely on gut hormone signaling, but still we know relatively little about how naturally produced gut signals influence the brain and behavior,” said Suh. “This study reveals fundamental principles of nutrient selection by the gut-brain axis and provides a basis for future therapeutic strategies.”
