The Vagus Nerve, Immunity and Metabolism

The role of the vagus nerve in regulating inflammation and its broader implications for immunity and metabolism have been analyzed by Valentin A. Pavlov and Kevin J. Tracey in the article, “The vagus nerve and the inflammatory reflex—linking immunity and metabolism.”

The two scientists describe the inflammatory reflex as a neural circuit where the vagus nerve modulates immune responses by inhibiting excessive inflammation.
Vagus nerve fibers that go up, also called afferent fibers, detect inflammatory signals (e.g., cytokines) and relay them to the brain, which then activates efferent (going down) vagus nerve signals to release acetylcholine, a neurotransmitter that suppresses pro-inflammatory cytokine production in organs like the spleen. This process prevents tissue damage from overactive immune responses, as seen in conditions like sepsis or autoimmune diseases.

The article also highlights the vagus nerve’s role in the brain-gut axis.
The vagus nerve influences metabolism by regulating insulin, glucose, and appetite.
Vagus nerve stimulation (VNS) is discussed as a therapeutic approach, showing promise in treating inflammatory disorders (e.g., rheumatoid arthritis, Crohn’s disease) and metabolic conditions (e.g., obesity, diabetes).

The integration of neural and immune systems via the vagus nerve suggests new avenues for treating diseases where inflammation and metabolism intersect, such as cardiovascular disease and obesity-related disorders.

Source: Pavlov, V. A., & Tracey, K. J. (2012). The vagus nerve and the inflammatory reflex—linking immunity and metabolism. Nature Reviews Endocrinology, 8(12), 743–754. https://pmc.ncbi.nlm.nih.gov/articles/PMC4082307/