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

purposeMultiple 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.

methodWe 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. FINDING: 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.

conclusionInterventions 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.