Gut Feeling: Tracing the Microbial Link to Multiple Sclerosis

by: Ma. Shereena Tabur (Chromoplexy)

What if the trigger to a mysterious brain disease has been hiding in your gut all along?

    Multiple sclerosis (MS) is a condition where the immune system mistakenly attacks myelin, the protective layer surrounding nerve fibers (Multiple sclerosis, n.d.). This disrupts communication between the brain and body, leading to symptoms like numbness, weakness, vision problems, and difficulty walking. Over time, MS can cause lasting damage to the nerves. Scientists have been looking for possible causes for this disease and now, research points to an unlikely suspect: your intestinal microbial composition (Yoon et al., 2025).

Photo from Mayo Foundation For Medical Education and Research

    The gut-brain axis (GBA) is a two-way communication network that links the brain and the gut by regulating emotional, cognitive, and digestive processes. A 2015 study led by Marilia Carabotti highlighted the critical role of gut microbiota in this connection, showing that these microbes send signals to the brain and receive responses with the help of various biological pathways. It is important to note that this link goes beyond mere biological curiosity; it is an emerging research that now suggests that disturbances in gut microbiota could be tied to neurological diseases, including MS. Such findings suggest that imbalances in the gut's microbial community might influence the immune system's attack on nerve fibers. 

    To test this theory, researchers turned to a unique study model: identical twins. Since a common genome is shared between twins, the significant difference would lie in their gut microbiome. The gut microbiota is unique to each individual, which makes identical twins ideal for studying the association between gut health and MS. By comparing the microbiomes of twins, with one having MS and the other does not, scientists can better understand the influence of gut bacteria on the development and progression of neurological disorders.

    The researchers assembled 81 pairs of identical twins, one with MS and one without. This allowed the researchers to focus on gut-related differences by simply eliminating genetic and early environmental differences. They collected samples from the ileum, a gut region known for housing proinflammatory immune cells, from selected twin pairs. These samples were then transplanted into germ-free transgenic mice that were genetically predisposed to develop MS-like symptoms, known as experimental autoimmune encephalomyelitis (EAE), upon microbial colonization. The results were striking as mice colonized with microbiota from the MS-affected twins developed EAE at significantly higher rates than those receiving samples from their healthy siblings. An equally compelling discovery was that female mice showed greater susceptibility to the disease, mirroring the higher prevalence of MS in women.

    Further analysis identified two key bacterial organisms, Eisenbergiella tayi and Lachnoclostridium sp., as likely contributors to this heightened immune response. Both belong to the Lachnospiraceae family, which has been linked to inflammation and immune modulation. This experiment marked a significant breakthrough as it not only revealed the correlation between gut bacteria and MS, but also provided clear evidence to disease progression due to MS in a living model. Moreover, the findings from the twin study and animal model experiments can open the door to new therapeutic possibilities for MS. If certain bacterial species indeed influence the development of MS, then targeting them could be a game-changer, and treatments for MS can switch from a neurological approach to a more gut-centric treatment.

    The notion that tiny gut bacteria could influence a tragic brain condition such as multiple sclerosis is both disturbing and innovative. These findings emphasize the strong link between the gut and the brain, perhaps leading to new treatments aimed at restoring microbial equilibrium. It's possible that the key to understanding and possibly providing a cure for MS is not in the brain, but in the massive, unseen world of bacteria living within us.

SOURCES

Carabotti, M., Scirocco, A., Maselli, M. A., & Severi, C. (2015). The gut-brain axis: interactions between enteric microbiota, central and enteric nervous systems. Annals of gastroenterology, 28(2), 203–209.

Multiple sclerosis. (n.d.). Mayo Clinic. Retrieved May 11, 2025, from https://www.mayoclinic.org/diseases-conditions/multiple-sclerosis/symptoms-causes/syc-20350269

Yoon, H., Gerdes, L. A., Beigel, F., Sun, Y., Kövilein, J., Wang, J., Kuhlmann, T., Flierl-Hecht, A., Haller, D., Hohlfeld, R., Baranzini, S. E., Hartmut Wekerle, & Peters, A. (2025). Multiple sclerosis and gut microbiota: Lachnospiraceae from the ileum of MS twins trigger MS-like disease in germfree transgenic mice—An unbiased functional study. Proceedings of the National Academy of Sciences, 122(18). https://doi.org/10.1073/pnas.2419689122

This article was originally published in the GENEWS May 2025 Issue.