# Modulating the Gut Microbiome as a Therapeutic Approach in Multiple Sclerosis: Implications for Gut‐Brain Interactions and Immune Pathways: A Narrative Review

## TL;DR

This review explores how gut microbiome changes contribute to multiple sclerosis and how restoring gut health could help manage the disease.

## Contribution

The paper provides a narrative synthesis of how gut microbiome dysbiosis affects immune pathways in MS and evaluates microbiome-targeted therapies.

## Key findings

- MS patients show reduced SCFA-producing bacteria and increased pro-inflammatory species.
- Microbiome interventions like probiotics and FMT show modest improvements in relapse rates and fatigue.
- Larger trials are needed to confirm clinical benefits and identify responder profiles.

## Abstract

Multiple sclerosis (MS) is a chronic autoimmune disease of the central nervous system characterized by progressive disability. Emerging evidence has implicated gut microbiome dysbiosis, characterized by decreased short‐chain fatty acids (SCFAs)‐producing taxa and increased pro‐inflammatory species, in disturbed immune signaling, T‐helper17/T‐regulatory cells imbalance, disturbed tryptophan metabolism, and disrupted integrity of the blood–brain barrier. In this review, we summarize the mechanistic and therapeutic insights from studies that have explored the gut microbiome in MS.

We performed a literature search in PubMed, Scopus, Web of Science, and ClinicalTrials.gov from database inception to January 2025; only English‐language articles were included, comprising human MS cohorts and preclinical experimental autoimmune encephalomyelitis models. Of these, approximately 95 human and preclinical studies fulfilled the inclusion criteria. Evidence synthesis was narrative, without meta‐analysis.

There has been a consistent depletion of beneficial genera such as Faecalibacterium and Roseburia, expansion of Akkermansia muciniphila, and reduction in microbial metabolites such as butyrate, propionate, and neuroactive indole derivatives in MS patients across studies. These changes promote intestinal permeability, exaggerated pro‐inflammatory cytokine responses, and microglial activation. The therapeutic approach of restoring microbial balance includes therapies such as probiotics, prebiotics, synbiotics, fecal microbiota transplantation, and dietary interventions. Early trials have shown modest improvements in relapse rates, fatigue, immune profiles, and microbiome composition. Results across randomized studies are heterogeneous, with no significant clinical benefit in several. Pilot trials report modest reductions in relapse rate (RR ≈ 0.85) and fatigue (Cohen's d ≈ 0.3), but several double‑blind RCTs showed no significant benefit (p  >  0.05) in up to 40% of participants, highlighting variable effect sizes.

Interventions aimed at the microbiome are promising as adjunct approaches to the treatment of MS, acting principally through the restoration of SCFAs, immune modulation, and strengthening of the gut‐brain axis. Larger, longer‐term randomized trials are required to confirm clinical efficacy, define responder phenotypes, and inform personalized microbiome‐based therapies.

The gut microbiome in multiple sclerosis (MS) shows consistent depletion of short‐chain fatty acid (SCFA)‐producing bacteria, expansion of pro‐inflammatory species, and reduced levels of butyrate, propionate, and indole metabolites. These alterations increase intestinal permeability, disrupt immune balance, and contribute to blood–brain barrier dysfunction and neuroinflammation. Microbiome‐targeted interventions, including probiotics, prebiotics, synbiotics, fecal microbiota transplantation, and dietary strategies, aim to restore microbial balance and modulate immune and gut–brain pathways. Early clinical studies report modest improvements in relapse activity, fatigue, immune markers, and microbiome composition, although findings are variable across trials.