The brain-gut axis is receiving more attention as a possible target for modern inflammatory bowel disease (IBD) drugs. A recent publication shows an interesting vagus nerve-spleen axis role in colitis, while older publications indicate several other brain-gut associations in ulcerative colitis (UC) and with gut microbiota.
Vagus nerve-spleen axis in colitis
The vagus nerve is mainly responsible for communicating information from the visceral organs to the brain. It also is known to promote anti-inflammatory immune responses. In a study looking at the influence of the vagus nerve on murine colitis models, Ji et al. found that increasing centrally stimulating the vagus nerve led to decreased symptoms of murine colitis and that these effects were mediated mainly via release of acetylcholine in the spleen, which interacted with a7 nicotinic acetylcholine receptor (α7nAChR) on CD11c+ cells, lowering their activation state. In general, CD11c+ cells are considered to be antigen presenting cells, which open the door for brain control of the adaptive immune response. More information about the vagus nerve and immune regulation can be also be found in a recent review by Matteoli and Boeckxstaens in July’s issue of Gut.
Different Emotional Responses in Ulcerative Colitis
To answer the question if IBD patients have different brain responses, two years ago researchers performed brain scans on patients with ulcerative colitis. Agonstini et al. imaged brains from both patients and controls after exposing them to emotional visual stimuli. It was found that the UC patients were less sensitive to positive emotional stimuli. This may play a role in why IBD sufferers have an increased incidence of depression.
Intestinal Bacteria Influence Brain Activity
In a more recent study with only healthy women, Tillisch et al. looked at the effects of the consumption of fermented milk on brain function. After four weeks of daily probiotics, changes were observed in the areas of the brain associated with emotional processing and sensation. On a practical level, this could mean that the women were more resistant to pain and stress. However, a larger study would need to be performed to be certain.
What’s your opinion regarding the brain’s involvement with IBD or do you have any personal experiences that show a link? Please share in the comment section below.
Agostini, A., Filippini, N., Cevolani, D., Agati, R., Leoni, C., Tambasco, R., et al. (2011). Brain functional changes in patients with ulcerative colitis. Inflammatory Bowel Diseases, 17(8), 1769–1777. doi:10.1002/ibd.21549
Ji, H., Rabbi, M. F., Labis, B., Pavlov, V. A., Tracey, K. J., & Ghia, J. E. (2013). Central cholinergic activation of a vagus nerve-to-spleen circuit alleviates experimental colitis. Mucosal Immunology, 1–13. doi:10.1038/mi.2013.52
Matteoli, G., & Boeckxstaens, G. E. (2013). The vagal innervation of the gut and immune homeostasis. Gut, 62(8), 1214–1222. doi:10.1136/gutjnl-2012-302550
Tillisch, K., Labus, J., Kilpatrick, L., Jiang, Z., Stains, J., Ebrat, B., et al. (2013). Consumption of Fermented Milk Product With Probiotic Modulates Brain Activity. Gastroenterology, 144(7), 1394–1401.e4. doi:10.1053/j.gastro.2013.02.043