As strange as it is to think about, many bacteria live in the human body, most of which are found in the gut (often referred to as the gut microbiome). These bodily roommates affect health in many ways that are only beginning to be understood.
In a presentation at the 2019 American Academy of Neurology annual meeting titled, “The Gut Microbiota and Pediatric Multiple Sclerosis,” Helen Tremlett, PhD, of the University of British Columbia in Canada, shared research data that explores the role of gut bacteria in pediatric multiple sclerosis (MS).
The first hint that gut bacteria might play a role in MS came from studies in mice. For example, it is much harder to experimentally induce MS in mice that have been raised in germ-free conditions (with no gut bacteria). Even if MS is induced, these mice have less severe disease than MS mice with gut bacteria.
“I couldn’t believe it when I realized there was a future in poop,” Tremlett said in her presentation, referring to how gut bacteria are typically studied via analysis of fecal samples.
Tremlett and her colleagues set out to answer two general questions about gut bacteria in pediatric MS. First, are there differences in gut bacteria between children with and without MS? And second, is the gut microbiome associated with a different likelihood of relapse in pediatric MS patients?
To assess potential gut bacterial differences between children with and without MS, the researchers collected stool samples from 18 children with the disease. The children were an average of 12 years old, and had experienced disease activity for a relatively short amount of time — 10.6 months on average. Half of the children had received some kind of MS treatment.
Stool samples were also collected from 17 children without MS (or any other autoimmune disease) to serve as controls.
Researchers then performed 16S rRNA sequencing on bacteria from the samples; this technique determines the sequence of part of the bacterial ribosome — the cell machinery that helps translate messenger RNA into proteins in cells. Differences in this sequence can distinguish between various types of bacteria, allowing researchers to obtain an overview of the type of bacteria present in each of the patients’ samples.
Importantly, results showed no massive differences between MS patients and controls — it wasn’t like controls had a “garden” of bacteria while MS patients had a “desert,” Tremlett said.
However, there were some subtle, but statistically significant, differences in the specific bacterial species present — in an extension of the analogy, Tremlett said both were gardens, but the exact types of flowers were different.
For example, MS patients had around 10 times more of the bacterial species Akkermansia muciniphila than controls. This species has been reported to have both regulatory and pro-inflammatory properties.
This indicates that differences in the gut microbiome might lead to a “pro-inflammatory milieu,” Tremlett suggested, meaning that these bacterial differences might lead to more inflammation, which could be involved in the development of MS.
To examine whether there are associations between gut bacteria and relapse risk, researchers recruited 17 children with MS, and collected and analyzed their stool samples, just as in the study discussed above. Researchers followed up with the children for 20 months, with the primary outcome being the first instance of an on-study relapse.
They found some significant associations. Children with more bacteria from the phylum Firmicutes were significantly more likely to experience a relapse than those with fewer of these bacteria. In contrast, children with more bacteria of the phylum Fusobacteria were less likely to experience a relapse.
Overall, these data suggest an association between gut bacteria and relapse risk; however, the picture is far from clear, Tremlett said, highlighting the fact that these studies were all conducted in a very small number of patients. Furthermore, it is not clear in what direction this relationship might act — gut bacteria might have an effect in MS, and having MS might also cause changes in the gut microbiome.
Therefore, further, larger studies are needed to clarify exactly how the residents of the gut affect the development and progression of MS, she said.