The gut communicates bidirectionally with the brain through the microbiota-gut-brain axis. A perturbation of this axis is involved in the pathogeny of irritable bowel syndrome (IBS) and inflammatory bowel diseases (IBD) which are biopsychosocial diseases. The vagus nerve (VN), a key component of the parasympathetic nervous system, can sense the microbiota, transferring this gut information to the central nervous system which is integrated and generates an adapted or inappropriate response perpetuating a pathological condition of the gut. A dysbiosis is observed in IBS and IBD. Stress is involved in the pathogeny of IBS and IBD and modifies the gut microbiota, stimulates the sympathetic nervous system, and inhibits the VN. The VN has anti-inflammatory properties through its afferents and efferent fibers, activating respectively the hypothalamic-pituitary adrenal axis and the cholinergic anti-inflammatory pathway. The VN modulates intestinal permeability, which is perturbated in IBS and IBD. A reduction in vagal tone is observed in IBS and IBD. Monitoring vagal tone would be an interesting marker of the microbiota-gut-brain axis. Targeting vagal tone through vagus nerve stimulation, auriculotherapy, microbiota modulation, drugs activating the cholinergic system, hypnosis, meditation, cognitive behavioral therapy, deep breathing, physical activity, could restore a homeostatic microbiota-gut-brain axis.

Pr Bruno Bonaz, MD-PhD^1,2

1. Division of Hepato-Gastroenterology, University Hospital, Grenoble Alpes, France
2. Grenoble Institute of Neurosciences, Inserm U1216, University Grenoble Alpes, Grenoble, France.

References

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