HMN 2026: How High-fat diet-linked dysbiosis may send gut bacteria to the brain via vagus nerve

Gut dysbiosis caused by a high-fat diet can allow bacteria to move from the gut to the brain in mice, according to a new study by David Weiss and Arash Grakoui from Emory University, U.S., and colleagues published in the open-access journal PLOS Biology.

The gut microbiome is known to indirectly interact with the brain through immune pathways, neuroendocrine signaling, or secretion of metabolites. However, how gut bacteria may directly interact with the brain is poorly understood.

Researchers fed mice a high-fat diet, which is known to change the composition of the gut microbiome and increase gut permeability. They found that a small number of bacteria translocated from the gut to the brain, likely via the vagus nerve. When mice were returned to a normal diet, the bacteria in the brain disappeared.

The team also detected low numbers of bacteria in mouse models of Alzheimer’s disease, Parkinson’s disease, and autism spectrum disorder without any dietary changes.

The findings add to growing evidence that the gut–brain axis plays a role in neurological disorders. More research is needed to understand whether a similar phenomenon occurs in humans and what role, if any, these bacteria may play in neurological disorders.

The authors add, “While the incidence of multiple neurological conditions is increasing, the initiating causes are largely unknown. This novel pathway of gut bacteria reaching the brain could be a trigger of numerous neurological diseases.”

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