Gut hormone CNMa rewires the brain to crave protein when diets fall short

Scientists have uncovered a new way the gut communicates with the brain to control food choices, particularly when protein is scarce. Research led by Director Seong-Bae Suh at the Institute for Basic Science (IBS) reveals how a gut-derived hormone, CNMa, drives animals to seek out protein-rich foods over time. The study focused on Drosophila melanogaster to map how the body responds to a lack of essential amino acids. When protein levels drop, gut epithelial cells release CNMa, a peptide hormone. This hormone then activates enteric neurons, sending urgent signals to the brain’s feeding centres within moments.

CNMa does more than just trigger short-term hunger. It systematically influences specific brain neurons, reinforcing a long-term preference for protein-heavy meals. The gut’s microbiome also plays a role—flies without gut bacteria showed stronger activation of amino acid-sensitive neurons, suggesting microbes help regulate this response. The mechanism isn’t unique to flies. Protein-deficient mice displayed a similar drive to consume essential amino acids, indicating this gut-brain pathway is conserved across species. The findings highlight the gut as an active sensory organ, constantly monitoring nutrient levels and directing behaviour to correct deficiencies.

This research identifies CNMa as a key regulator of protein-seeking behaviour, linking gut signals to brain-driven food choices. The discovery sheds light on how animals—including humans—prioritise essential nutrients for survival. It also opens avenues for understanding how diet and gut microbes shape long-term eating habits.