A toxin produced in the gut could trigger the onset of multiple sclerosis (MS), according to research at the Brain and Mind Research Institute at Weill Cornell Medicine.
The past couple of decades have been revolutionary in medical science as the importance of the gut microbiome becomes clear. Twenty years ago, most of us would have raised a quizzical eyebrow upon hearing the phrase ‘gut microbiome’. But we now know that bacteria and other organisms living in the gut play a huge role in our health.
Conditions such as irritable bowel syndrome have now been strongly linked to a gut microbiome imbalance. The gut microbiome also appears to be a factor in some allergies and autoimmune diseases.
Weill Cornell Medicine’s new study builds on previous research around the composition of the gut microbiome and MS. That research identified the gut microbiome in people with MS as being different to that of those without the condition.
The new research homes in on specific bacteria found in the gut, known as C. perfringens. The research shows that people with MS are more likely to harbour C. perfringens in their gut.
What’s so bad about C. perfringens?
While C. perfringens has no direct negative affect on us, it produces a toxin that does – ETX. In attacking the covering of the body’s nerve fibres – known as the myelin sheath – ETX leaves behind scars or lesions. Each of these is known medically as a sclerosis – hence the term ‘multiple sclerosis’.
ETX is found only in C. perfringens, and the researchers found that 61 per cent of the samples from people with MS contained the ETX gene. By comparison, it was found in only 13 per cent of those from healthy controls. Additionally, they found the gut microbiota of people with MS was more likely to be colonised by ETX-positive C. perfringens.
With that link identified, the researchers took their study a step further. They injected mice known to be susceptible to developing MS symptoms. Some mice were injected with ETX. Others, though, were injected with a different toxin, PTX, which had previously been shown to induce MS-like symptoms.
The mice who were injected with ETX developed demyelination in many areas of the central nervous system. This is a similar pattern to that seen in people with MS.
The ETX-injected mice had twice as many lesions in the cerebellum as the mice that were given PTX. The cerebellum is the part of the brain responsible for balance and coordination commonly affected in those with MS.
ETX mice also had lesions in the corpus callosum, the largest compact white matter fibre bundle of the brain. These lesions were not seen in the corpus callosum of the PTX-injected mice.
Next steps
Dr Barbara Giesser, MS specialist at Pacific Neuroscience Institute, said development of a targeted treatment is now a step closer.
“The toxin helps immune cells gain access to the central nervous system,” said Dr Giesser, who was not involved in the research. “This suggests that treatments targeting the bacterium or the toxin might potentially be useful as disease-modifying therapies.”
Such treatments would need to undergo clinical trials, but the newly published study appears to be a significant step forward.
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