The intestinal flora (intestinal microbiome) appears to play an important role in multiple sclerosis (MS). Some intestinal microbiota are associated with adverse effects, while others appear to have a protective effect. The new findings also open up promising new therapeutic approaches.
In a recent review, a Polish research team led by Dr. Anna Pokryszko-Dragan from the Wroclaw Medical University discussed the connections between the intestinal flora and MS as well as the therapeutic implications derived from this. The results are published in the specialist magazine “Gut Microbes”.
The intestinal flora and MS
Previous studies have suggested that intestinal flora influences the risk of multiple sclerosis and that there is a connection between intestinal flora and MS.
The research team has now analyzed what these connections are based on and what therapeutic implications can be derived from them based on a comprehensive evaluation of the studies published so far.
A number of pharmacological, dietary and other interventions that target the intestinal microbiome and are said to have positive effects on the progression of MS were also taken into account.
The researchers also determined to what extent known MS risk factors such as smoking, obesity, nutritional aspects, vitamin D3 levels, stress and infections may be related to the disease through their effects on the intestinal flora.
In addition, the gut-brain axis, which describes the bidirectional communication between the gastrointestinal system and the central nervous system via endocrine, metabolic, immunological and neurotransmitting connections, received particular attention.
Dysbiosis a risk factor
Overall, the intestinal microbiome appears to play a special role in the development and dynamics of MS, with a so-called dysbiosis of the intestinal flora being associated with an increased risk of disease and negative effects on the course of the disease, the researchers report.
The intestinal flora of people with MS shows significant changes compared to healthy people, including an increased relative frequency of the bacterial strains Akkermansia and Streptococcus.
According to the researchers, the bacterial taxa whose presence is reduced in MS include Bacteroides, Faecalibacterium, Prevotella and Roseburia. A decline in Lactobacillaceae is also associated with the onset and progression of the disease.
However, differences did occur in the available studies and the composition of the intestinal flora also varied between the different forms of MS.
Nevertheless, the evaluated in vivo data overall indicate that intestinal dysbiosis is functionally linked to a shift from regulatory components of the autoimmune reaction to pro-inflammatory components, the researchers report.
This is probably related to the microbial metabolites, mainly short-chain fatty acids. The experimental and clinical studies show links between gut dysbiosis in MS and the dysregulated immune response and altered metabolic pathways, the research team said.
The ability of commensal bacteria to have either a pro-inflammatory or anti-inflammatory effect via various mechanisms plays a crucial role here.
Interestingly, a protective, anti-inflammatory effect was observed in some bacteria (Clostridia, Bacteroides, Prevotella), which may be related to special components such as polysaccharide A and lipid 654, the experts add.
New MS treatment approaches
The researchers also analyzed various treatment approaches that affect the gut microbiome, including the use of probiotics, drugs (e.g. antibiotics), dietary changes and fecal transplants.
According to experts, there is insufficient evidence of a positive effect of probiotics in MS, although individual studies have observed, for example, reduced expression of pro-inflammatory cytokines.
The use of antibiotics only has a limited effect and can even lead to worsening. Although long-term treatment with antibiotics has had positive effects in individual studies, the undesirable effects (including the development of resistant pathogens) are a significant obstacle here.
Nutritional interventions in MS
It has long been known that diet can have an impact on the intestinal flora. The team explains that it is also possible to positively influence the course of the disease in MS by changing your diet.
For example, studies on mice have shown that fasting and a ketogenic diet can delay the onset of the disease and alleviate symptoms, the researchers report. There was a decrease in cognitive symptoms, but also in inflammatory infiltration and demyelination in the spinal cord.
Intermittent fasting also led to an enrichment of Bacteroidaceae, Prevotellaceae and Lactobacillaceae in the animals’ intestines and improved microbial antioxidant metabolic pathways.
To date, however, only a small amount of research has examined the effects of nutritional interventions on the intestinal flora and the associated effects on MS, which is why further studies are required to make clear statements.
Can fecal transplants help?
Investigating the therapeutic potential of fecal transplants in MS was inspired by case reports in which people with MS were treated with this method for severe gastrointestinal problems and subsequently experienced long-term disease stabilization, the research team explains.
In recent studies it has become clear that the improvements were accompanied by, among other things, changed microbial parameters and increased concentrations of acetate, propionate and butyrate, the researchers report. There is also evidence that fecal transplants reduce what is known as intestinal permeability.
Clinical trials currently underway are expected to provide further data on the effects, tolerability and optimal procedure of fecal transplants, which would further support the implementation of this method in MS treatment, experts said.
Intestinal flora in the focus of new therapies
Overall, the researchers come to the conclusion that, in addition to conventional MS therapy, other approaches that target the intestinal microbiota can definitely have a positive influence on the course of the disease. However, further randomized clinical trials are needed to clearly confirm the beneficial effects of these interventions in MS. (fp)