The Gut Microbiome In Multiple Sclerosis

Gut Microbiome In Multiple Sclerosis

Welcome to my blog post ‘The Gut Microbiome In Multiple Sclerosis’ where I discuss some of the research exploring what bacteria in the gut microbiome might be involved in multiple sclerosis.

You may also be interested in the section of my blog dedicated to gut health, click here, in particular:

Perturbation of this healthy gut microbiome might be an important environmental factor in the pathogenesis of inflammatory autoimmune diseases such as multiple sclerosis (MS). Others and we have recently reported that MS patients have gut microbial dysbiosis (altered microbiota) with the depletion of some and enrichment of other bacteria.

The majority of gut bacteria are associated with certain metabolic pathways, which in turn help in the maintenance of immune homeostasis of the host.

The Gut Microbiome In Multiple Sclerosis

In the last few years, several groups including ours have profiled fecal gut microbiota from MS patients and have shown that MS patients exhibit gut microbial dysbiosis with both depletion and enrichment of certain bacteria compared with healthy controls. Within Bacteroidetes phyla Bacteroides, Prevotella, and Parabacteroides are the major genera and we observed depletion of Parabacteroides and Prevotella in relapsing remitting MS (RRMS) patients.

A Reduction In Anti-inflammatory Bacteria In Multiple Sclerosis

  • Prevotella
  • Parabacteroides
  • Lactobacillus

As mentioned previously, gut bacteria exhibit a symbiotic relationship with the host (human), which pro- vides them space and nutrients. In turn, bacteria help in maintaining a healthy state of the host by performing several physiologic functions such as digestion of food, immune system development, maintenance of the gut barrier, suppression of colonisation of pathobionts, etc. Because the gut microbiota is a community structure, some bacteria directly feed on host-provided nutrients, whereas other bacteria feed on bacterial by- products, a process called cross-feeding. Unsurprisingly, diet is one of the major factors determining our gut microbiota.

Specifically, gut microbiota help with digestion/metabolism of several compounds including starches/fibers, phytoestrogens, bile acids, and tryptophan.

Recent studies show that metabolism of food by microbiota have a strong influence on the development and function of the immune system.

Metabolism of starch/complex sugars by gut bacteria leads to the production of short-chain fatty acids (SCFAs), which are one of most studied bacterial metabolites. Firmicutes, such as Clostridium, have received much attention because certain species can produce SCFAs and aid in the maintenance of regulatory immune  cells. However, some Bacteroidetes species can also produce SCFAs. Among the bacteria showing lower abundance in MS patients, Prevotella, Parabacteroides, and Lactobacillus have the ability to induce SCFAs production. We have recently shown that Prevotella histicola, a member of the Prevotella genus, can suppress disease in experimental autoimmune encephalomyelitis (EAE), a preclinical murine model of MS

An Increase In Pro-inflammatory Bacteria In Multiple Sclerosis

  • Dorea.
  • Blautia
  • Pseudomonas
  • Mycoplana
  • Akkermansia muciniphila

Dorea might be an example of a bacterium that exhibits either pro or anti-inflamma- tory roles depending on the surrounding gut bacteria and/or available nutrients.

In a healthy individual, the gut consists of a diversified bacterial community that is responsible for maintaining the balance between pro- and anti-inflammatory immune responses. RRMS is an inflammatory disease in which the immune balance is tilted toward a pro-inflammatory state. Therefore, it is reasonable to hypothesise that gut dysbiosis can be characterised by depletion of bacteria responsible for induction/maintenance of anti-inflammatory responses and/or enrichment of bacteria with the ability to induce pro-inflammatory responses

Summary of ‘The Gut Microbiome In Multiple Sclerosis: What Bacteria Are Involved?’

The major conclusions from the research on the gut microbiome in multiple sclerosis and which bacteria might be involved are that compared with healthy controls, MS patients have:

  • Gut dysbiosis
  • Reduced Bacteroidetes phylum with lower abundance of certain genera such as Prevotella, Parabacteroides, and Bacteroides (which can induce Tregs)
  • Higher abundance of certain Firmicutes such as Akkermansia and Dorea (which can metabolize mucin and induce pro-inflammatory cytokines)
  • Depletion of ceratin Actinobacteria such as Adlercreutzia, Collinsella, and Slackia (anti-inflammatory) and Proteobacteria such as Sutterella
  • Higher abundance of certain Proteobacteria such as Acinetobacter calcoaceticus, Pseudomonas, and Mycoplana.

These data suggest that gut microbiota might sustain a healthy state of the host by maintaining immune homeostasis, and subsequent changes that perturb this homeostasis can lead to negative consequences such as inflammatory diseases.

  • It is difficult to say with certainty whether changes in gut microbiota is a cause or consequence of MS because MS patients have immunological and microbial changes months to years before clinical onset of the disease.

Altogether, MS microbiome studies suggest that there is depletion of bacteria in the gut microbiome of multiple sclerosis patients which have the ability to induce immuno-regulatory cells and enrichment of bacteria with the ability to induce pro-inflam- matory responses.

My Interview With Dr. Terry Wahls

References of ‘The Gut Microbiome In Multiple Sclerosis’:

  1. Gut microbiome in multiple sclerosis: The players involved and the roles they play: click here.
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