Cerebrospinal fluid samples taken from people with multiple sclerosis show high levels of different toxic substances, produced by gut bacteria.
- Multiple sclerosis affects the central nervous system: the immune system attacks myelin, which makes up the sheath of nerve fibres.
- The intestinal microbiota is implicated in inflammatory and autoimmune diseases.
- Bacteria in the intestines can produce compounds that are toxic to nerve cells.
The gut is sometimes referred to as the second brain. In fact, it has a great influence on our body: it has an impact on the immune, cardiovascular and bone systems. Works published in the journal Brain show that it would also be involved in the onset of certain neurodegenerative diseases. Its authors found that gut bacteria were linked to multiple sclerosis (MS).
What motivated this research?
Previously published scientific studies have shown that an imbalance in the intestinal microbiota, i.e. all the microorganisms present in the human intestines, can be the cause of a series of neurological disorders. In the case of multiple sclerosis, certain intestinal bacteria are in higher or lower quantity in MS patients compared to healthy individuals. But until now the precise links between these bacteria and the appearance of the neurodegenerative disease were unknown.
Three abnormally present substances
In this work, the research team analyzed samples of blood and cerebrospinal fluid from volunteer patients, followed Multiple Sclerosis Center of Northeastern, At New York. The samples were taken before and after the administration of dimethyl fumarate (DMF), a preventive treatment against multiple sclerosis flare-ups, which is said to have a profound effect on the intestinal microbiota of people with MS. The data allowed the researchers to identify an over-representation of three toxic metabolites, i.e. organic compounds, in MS patients not treated with DMF compared to the test sample, i.e. a group of people not affected by the disease. These substances are produced by intestinal bacteria. “Our results suggest that gut bacteria from MS patients produce and release large amounts of p-cresol sulfate, indoxyl sulfate and N-phenylacetylglutamine into the bloodstream.explains Hye-Jin Park, one of the main authors of the study, and they end up reaching the cerebrospinal fluid” Thanks to this liquid, the toxic metabolites are present all around the brain and spinal cord. According to this researcher, this allows them to “potentially play a role in destroying the myelin sheath that protects the nerves“, the destruction of this sheath is one of the main mechanisms of MS.
Future treatments?
The research also allowed the authors to see that treatment with DMF had an effect on the phenomenon: the level of metabolites fell after administration of the drug. “This is an exciting and important discoverysays Patrizia Casaccia, co-author of the study. This work not only improves our understanding of the role of gut-brain communication in neurodegenerative disease progression, but also provides a potential metabolic target for the development of novel MS therapies.”
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