Multiple Sclerosis

Metallomic Signature#

Metal-specific evidence in MS is sparse. No comprehensive metallomics study of MS biofluids was identified in the source literature. The relevant metal connections are indirect.

Iron: Iron accumulation in deep gray matter structures (thalamus, caudate, putamen) is documented by MRI and pathology in progressive MS, likely reflecting both neurodegeneration and impaired iron homeostasis.^{[2]Biomarkers in Multiple Sclerosis: Analysis of the Present Advantages and Look to the FutureValentina Ignatova · 2023Open reference 2 ↓} Peripherally, urine iron is significantly lower in MS patients.^{[3]Effect of heavy metals and sialic acid in multiple sclerosisServin Yesil Günal, Hikmet Saçmacı, Şerife Saçmacı et al. · 2018Open reference 3 ↓}

Ferroptosis mechanisms relevant to other neurodegenerative diseases (Parkinson's, Alzheimer's) may apply.

Zinc: Zinc is essential for oligodendrocyte function and myelin production. Zinc deficiency impairs remyelination in animal models.

Copper: Ceruloplasmin (the major copper (Cu)-carrying protein) has ferroxidase activity critical for iron homeostasis in the CNS. Disrupted copper trafficking could contribute to iron accumulation.

Manganese: manganese (Mn) is a cofactor for MnSOD and TCA cycle enzymes. The metabolic shift from oxidative phosphorylation to glycolysis observed in MS-associated T cells^{[4]Variations in diet cause alterations in microbiota and metabolites that follow changes in disease severity in a multiple sclerosis modelLibbey JE, Sanchez JM, Doty DJ et al. · 2018Open reference 4 ↓} involves manganese-dependent enzyme pathways.

The absence of a clear metallomic signature does not mean metals are irrelevant to MS—it means the research has not been done.

A Turkish case-control study (52 MS vs 41 controls) found significantly elevated urinary nickel (Ni), cadmium (Cd), lead (Pb), arsenic (As), aluminum (Al), manganese, copper, and barium (Ba) in MS patients, with nickel (OR 1.47), cadmium (OR 1.45), and lead (OR 1.32) emerging as independent risk factors.^{[3]Effect of heavy metals and sialic acid in multiple sclerosisServin Yesil Günal, Hikmet Saçmacı, Şerife Saçmacı et al. · 2018Open reference 3 ↓}

The gut microbiome evidence below suggests that metals exert their influence on MS indirectly, through reshaping the microbial communities that regulate immune function via the gut-brain axis.

Animal Model Evidence#

^{[4]Variations in diet cause alterations in microbiota and metabolites that follow changes in disease severity in a multiple sclerosis modelLibbey JE, Sanchez JM, Doty DJ et al. · 2018Open reference 4 ↓}—Diet composition alone (irradiated vs. autoclaved rodent chow) was sufficient to alter gut microbial communities and significantly change EAE severity. Key findings.

Lactobacillus abundance inversely correlated with EAE severity (Spearman r = -0.67). Therapeutic L. paracasei treatment: only 9/13 treated mice developed EAE vs. 15/15 controls (p<0.05), with significantly lower clinical scores.

Disease-associated mice showed a metabolic shift toward glycolysis and away from oxidative phosphorylation—the same metabolic shift seen in inflammatory T cells in human MS.

TCA cycle metabolites (citric acid, isocitric acid, malic acid, fumaric acid) were higher in protected mice.

The metal connection: TCA cycle enzymes require iron (Fe), manganese (Mn), and other metals as cofactors. Diet-driven changes in microbial metal availability could affect the metabolic output of gut bacteria, altering the balance of anti-inflammatory SCFA production versus pro-inflammatory metabolite generation.

^{[11]Streptococcus thermophilus ST285 Alters Pro-Inflammatory to Anti-Inflammatory Cytokine Secretion against Multiple Sclerosis Peptide in MiceDargahi N, Matsoukas J, Apostolopoulos V · 2020Open reference 11 ↓}—Streptococcus thermophilus ST285 shifted the immune response from pro-inflammatory Th1 to anti-inflammatory Th2 in MBP83-99-immunized mice. IFN-gamma (Th1): significantly reduced.

IL-4 (Th2): approximately 3-fold increase (p<0.001). IL-10 (regulatory): approximately 4-fold increase (p<0.001).

IL-5: significantly increased (p<0.01).

The IL-10 increase is particularly important: IL-10 drives naive CD4+ T cell differentiation into Tregs, supporting an anti-inflammatory phenotype. This Th1-to-Th2 shift is precisely what would be therapeutic in MS, where autoreactive Th1/Th17 responses drive demyelination.

Metal-Microbiome-Brain Pathway#

While direct metal-MS studies are lacking, the evidence supports a plausible pathway.

Dietary metals shape gut microbiome composition (extensively documented in this wiki for cadmium (Cd), lead (Pb), nickel (Ni), arsenic (As)). Gut microbiome composition determines EAE/MS severity (Libbey 2018: Lactobacillus r = -0.67). Specific probiotics shift cytokine profiles toward anti-inflammatory (Dargahi 2020: Th1 to Th2).

Cytokine shifts produce clinical improvement (Kouchaki 2017: EDSS -0.3, hs-CRP -1.3).

The missing link is step 1 applied specifically to MS. Do MS patients have altered metal exposures or handling that reshape their gut microbiome toward a pro-inflammatory, pro-demyelinating community?

Environmental Metal Exposure Links#

Direct case-control evidence links environmental metal exposure to MS risk: in a Turkish cohort, urinary nickel (Ni), cadmium (Cd), lead (Pb), aluminum (Al), arsenic (As), copper (Cu), manganese (Mn), silver (Ag), barium (Ba), Cs, Rb, and strontium (Sr) were all significantly elevated in MS patients, and Heavy Metals collectively carried ~1.5-fold increased MS risk.^{[3]Effect of heavy metals and sialic acid in multiple sclerosisServin Yesil Günal, Hikmet Saçmacı, Şerife Saçmacı et al. · 2018Open reference 3 ↓}

Beyond this. Smoking (cadmium, lead, nickel) is an established MS risk factor, increasing risk approximately 1.5-fold. Mercury from dental amalgams was historically hypothesized as an MS trigger, but epidemiological evidence does not support a causal link.

Lead exposure in childhood has been associated with increased MS risk in some studies.^{[3]Effect of heavy metals and sialic acid in multiple sclerosisServin Yesil Günal, Hikmet Saçmacı, Şerife Saçmacı et al. · 2018Open reference 3 ↓} Iron supplementation effects on MS gut microbiome have not been studied.

The gap in environmental metal-MS research is striking given the strong microbiome evidence. This represents a clear research opportunity.

Comorbidities#

Depression—depression affects 30-50% of MS patients; probiotic trials showed significant BDI improvement alongside EDSS improvement (BDI -5.6 vs -1.1, p<0.001); shared gut-brain axis disruption, SCFA depletion, and tryptophan pathway shifts toward pro-inflammatory kynurenine; depression independently worsens MS disability trajectory.

Anxiety Disorders—anxiety disorders in 20-40% of MS patients; disease unpredictability and progressive disability compound neurobiological mechanisms; shared HPA axis dysregulation and vagal tone disruption.

Inflammatory Bowel Disease (IBD)—bidirectional association: IBD patients have increased MS risk and vice versa; shared HLA-DRB1 genetic architecture; Mendelian randomization shows Crohn's increases Graves' disease risk by 30%, indicating shared autoimmune gut-immune pathways; both feature Th1/Th17 dysregulation and SCFA producer depletion.

Additional Supporting Evidence#

Bile acid metabolism—Both primary and secondary bile acid metabolites are significantly reduced in adult and pediatric MS, with TUDCA supplementation ameliorating neuroinflammation through GPBAR1 receptor signaling in EAE.^{[12]Bile acid metabolism is altered in multiple sclerosis and supplementation ameliorates neuroinflammationPavan Bhargava, Matthew D. Smith, Leah Mische et al. · 2020Open reference 12 ↓}

SCFA reduction—Fecal SCFAs and serum propionate/Butyrate are lower in MS and correlate with altered T/B cell subsets and elevated intestinal inflammation markers (calprotectin).^{[13]Short-chain fatty acids and intestinal inflammation in multiple sclerosis: modulation of female susceptibility by microbial products?Anouck Becker, Mosab Abuazab, Andreas Schwiertz et al. · 2021Open reference 13 ↓[14]Associations of serum short-chain fatty acids with circulating immune cells and serum biomarkers in patients with multiple sclerosisStephanie Trend, Jonatan Leffler, Anderson P. Jones et al. · 2021Open reference 14 ↓}

MAIT cells and gut yeasts—MS patients show elevated fecal fungal abundance (S. cerevisiae, C. albicans), and their MAIT cells are hyper-activated by fungal extracts via IL-23, producing IL-17, GM-CSF, and CCL20; MAIT cells infiltrate 53% of progressive MS brain lesions.^{[15]Proinflammatory Mucosal-Associated Invariant CD8+ T Cells React to Gut Flora Yeasts and Infiltrate Multiple Sclerosis BrainFrancesca Gargano, Gisella Guerrera, Eleonora Piras et al. · 2022Open reference 15 ↓} *Torulaspora* and *Debaryomyces* are also enriched in MS mycobiota, with Torulaspora associated with lower disability and Debaryomyces characteristic of HLA-DRB1*1501 carriers.^{[16]Exploring the Mycobiota in Multiple Sclerosis: Its Influence on Disease Development and ProgressionAne Otaegui-Chivite, Miriam Gorostidi-Aicua, Laura Martins-Almeida et al. · 2025Open reference 16 ↓}

Ketogenic diet—A 6-month ketogenic diet restored colonic microbiome mass and essential bacteria (Roseburia, Bacteroides, F. prausnitzii) in MS patients to healthy-control levels.^{[17]Reduced Mass and Diversity of the Colonic Microbiome in Patients with Multiple Sclerosis and Their Improvement with Ketogenic DietSwidsinski A, Dorfel Y, Loening-Baucke V et al. · 2017Open reference 17 ↓}

Disease-progression signatures—Commensal microbiota signatures predict clinical severity and progression in MS,^{[18]Identification of commensal gut microbiota signatures as predictors of clinical severity and disease progression in multiple sclerosisTheresa L. Montgomery, Qin Wang, Ali Mirza et al. · 2024Open reference 18 ↓} and gut microbiota composition varies with disease activity (F. prausnitzii and Gordonibacter reduced during active inflammation).^{[19]The Gut Microbiota in Multiple Sclerosis Varies with Disease ActivityThirion F, Sellebjerg F, Fan Y et al. · 2023Open reference 19 ↓}

B-cell depletion therapy—Ocrelizumab (anti-CD20) partially reverses MS-associated oral and gut dysbiosis over 12 months, shifting Bacteroidetes/Firmicutes balance toward healthy-control patterns.^{[20]B-cell-depletion reverses dysbiosis of the microbiome in multiple sclerosis patientsAlba Troci, Olga Zimmermann, Daniela Esser et al. · 2022Open reference 20 ↓}

Oral microbiome—Oral dysbiosis with a distinct metabolite signature is detectable in MS and may be more pronounced than gut dysbiosis as a disease trait.^{[21]Investigating the metabolite signature of an altered oral microbiota as a discriminant factor for multiple sclerosis: a pilot studyLéo Boussamet, Emmanuel Montassier, Camille Mathé et al. · 2024Open reference 21 ↓}

MS metabolomics—Comprehensive metabolomic profiling of MS cohorts.^{[22]An emerging potential of metabolomics in multiple sclerosis: a comprehensive overviewInsha Zahoor, Bin Rui, Junaid Khan et al. · 2021Open reference 22 ↓} Diet-MS mechanism—Dietary intake shapes MS-relevant gut-brain signaling via microbiota.^{[23]The Role of Diet in Multiple Sclerosis: Mechanistic Connections and Current EvidenceKatz Sand I · 2018Open reference 23 ↓} Mycobiota progression—Altered gut mycobiota tracks MS progression.^{[16]Exploring the Mycobiota in Multiple Sclerosis: Its Influence on Disease Development and ProgressionAne Otaegui-Chivite, Miriam Gorostidi-Aicua, Laura Martins-Almeida et al. · 2025Open reference 16 ↓}