Propionic Acid Shapes the Multiple Sclerosis Disease Course by an Immunomodulatory Mechanism.

Short-chain fatty acids are processed from indigestible dietary fibers by gut bacteria and have immunomodulatory properties. Here, we investigate propionic acid (PA) in multiple sclerosis (MS), an autoimmune and neurodegenerative disease. Serum and feces of subjects with MS exhibited significantly reduced PA amounts compared with controls, particularly after the first relapse. In a proof-of-concept study, we supplemented PA to therapy-naive MS patients and as an add-on to MS immunotherapy. After 2 weeks of PA intake, we observed a significant and sustained increase of functionally competent regulatory T (Treg) cells, whereas Th1 and Th17 cells decreased significantly. Post-hoc analyses revealed a reduced annual relapse rate, disability stabilization, and reduced brain atrophy after 3 years of PA intake. Functional microbiome analysis revealed increased expression of Treg-cell-inducing genes in the intestine after PA intake. Furthermore, PA normalized Treg cell mitochondrial function and morphology in MS. Our findings suggest that PA can serve as a potent immunomodulatory supplement to MS drugs.

Dietary Fatty Acids Directly Impact Central Nervous System Autoimmunity via the Small Intestine.

Growing empirical evidence suggests that nutrition and bacterial metabolites might impact the systemic immune response in the context of disease and autoimmunity. We report that long-chain fatty acids (LCFAs) enhanced differentiation and proliferation of T helper 1 (Th1) and/or Th17 cells and impaired their intestinal sequestration via p38-MAPK pathway. Alternatively, dietary short-chain FAs (SCFAs) expanded gut T regulatory (Treg) cells by suppression of the JNK1 and p38 pathway. We used experimental autoimmune encephalomyelitis (EAE) as a model of T cell-mediated autoimmunity to show that LCFAs consistently decreased SCFAs in the gut and exacerbated disease by expanding pathogenic Th1 and/or Th17 cell populations in the small intestine. Treatment with SCFAs ameliorated EAE and reduced axonal damage via long-lasting imprinting on lamina-propria-derived Treg cells. These data demonstrate a direct dietary impact on intestinal-specific, and subsequently central nervous system-specific, Th cell responses in autoimmunity, and thus might have therapeutic implications for autoimmune diseases such as multiple sclerosis.

Implications of Diet and The Gut Microbiome in Neuroinflammatory and Neurodegenerative Diseases.

Within the last century, human lifestyle and dietary behaviors have changed dramatically. These changes, especially concerning hygiene, have led to a marked decrease in some diseases, i.e., infectious diseases. However, other diseases that can be attributed to the so-called 'Western' lifestyle have increased, i.e., metabolic and cardiovascular disorders. More recently, multifactorial disorders, such as autoimmune and neurodegenerative diseases, have been associated with changes in diet and the gut microbiome. In particular, short chain fatty acid (SCFA)-producing bacteria are of high interest. SCFAs are the main metabolites produced by bacteria and are often reduced in a dysbiotic state, causing an inflammatory environment. Based on advanced technologies, high-resolution investigations of the abundance and composition of the commensal microbiome are now possible. These techniques enable the assessment of the relationship between the gut microbiome, its metabolome and gut-associated immune and neuronal cells. While a growing number of studies have shown the indirect impact of gut metabolites, mediated by alterations of immune-mediated mechanisms, the direct influence of these compounds on cells of the central nervous system needs to be further elucidated. For instance, the SCFA propionic acid (PA) increases the amount of intestine-derived regulatory T cells, which furthermore can positively affect the central nervous system (CNS), e.g., by increasing remyelination. However, the question of if and how PA can directly interact with CNS-resident cells is a matter of debate. In this review, we discuss the impact of an altered microbiome composition in relation to various diseases and discuss how the commensal microbiome is shaped, starting from the beginning of human life.

Interferon-beta affects mitochondrial activity in CD4+ lymphocytes: Implications for mechanism of action in multiple sclerosis.

BACKGROUND: Whereas cellular immune function depends on energy supply and mitochondrial function, little is known on the impact of immunotherapies on cellular energy metabolism. OBJECTIVE: The objective of this paper is to assess the effects of interferon-beta (IFN-ß) on mitochondrial function of CD4(+) T cells. METHODS: Intracellular adenosine triphosphate (iATP) in phytohemagglutinin (PHA)-stimulated CD4(+) cells of multiple sclerosis (MS) patients treated with IFN-ß and controls were analyzed in a luciferase-based assay. Mitochondrial-transmembrane potential (ΔΨm) in IFN-ß-treated peripheral blood mononuclear cells (PBMCs) was investigated by flow cytometry. Expression of genes involved in mitochondrial oxidative phosphorylation (OXPHOS) in CD4(+) cells of IFN-ß-treated individuals and correlations between genetic variants in the key metabolism regulator PGC-1α and IFN-ß response in MS were analyzed. RESULTS: IFN-ß-treated MS patients exhibited a dose-dependent reduction of iATP levels in CD4(+) T cells compared to controls (p < 0.001). Mitochondrial effects were reflected by depolarization of ΔΨm. Expression data revealed changes in the transcription of OXPHOS-genes. iATP levels in IFN-ß-responders were reduced compared to non-responders (p < 0.05), and the major T allele of the SNP rs7665116 of PGC-1α correlated with iATP-levels. CONCLUSION: Reduced iATP-synthesis ex vivo and differential expression of OXPHOS-genes in CD4(+) T cells point to unknown IFN-ß effects on mitochondrial energy metabolism, adding to potential pleiotropic mechanisms of action.

Propionic acid promotes neurite recovery in damaged multiple sclerosis neurons.

Neurodegeneration in the autoimmune disease multiple sclerosis still poses a major therapeutic challenge. Effective drugs that target the inflammation can only partially reduce accumulation of neurological deficits and conversion to progressive disease forms. Diet and the associated gut microbiome are currently being discussed as crucial environmental risk factors that determine disease onset and subsequent progression. In people with multiple sclerosis, supplementation of the short-chain fatty acid propionic acid, as a microbial metabolite derived from the fermentation of a high-fiber diet, has previously been shown to regulate inflammation accompanied by neuroprotective properties. We set out to determine whether the neuroprotective impact of propionic acid is a direct mode of action of short-chain fatty acids on CNS neurons. We analysed neurite recovery in the presence of the short-chain fatty acid propionic acid and butyric acid in a reverse-translational disease-in-a-dish model of human-induced primary neurons differentiated from people with multiple sclerosis-derived induced pluripotent stem cells. We found that recovery of damaged neurites is induced by propionic acid and butyric acid. We could also show that administration of butyric acid is able to enhance propionic acid-associated neurite recovery. Whole-cell proteome analysis of induced primary neurons following recovery in the presence of propionic acid revealed abundant changes of protein groups that are associated with the chromatin assembly, translational, and metabolic processes. We further present evidence that these alterations in the chromatin assembly were associated with inhibition of histone deacetylase class I/II following both propionic acid and butyric acid treatment, mediated by free fatty acid receptor signalling. While neurite recovery in the presence of propionic acid is promoted by activation of the anti-oxidative response, administration of butyric acid increases neuronal ATP synthesis in people with multiple sclerosis-specific induced primary neurons.

Functional and structural readouts for early detection of retinal involvement in multiple sclerosis.

Introduction: The retina, a window into the brain, allows for the investigation of many disease-associated inflammatory and neurodegenerative changes affecting the central nervous system (CNS). Multiple sclerosis (MS), an autoimmune disease targeting the CNS, typically impacts on the visual system including the retina. Hence, we aimed to establish innovative functional retinal measures of MS-related damage, e.g., spatially resolved non-invasive retinal electrophysiology, backed by established morphological retinal imaging markers, i.e., optical coherence tomography (OCT). Methods: 20 healthy controls (HC) and 37 people with MS [17 without history of optic neuritis (NON) and 20 with (HON) history of optic neuritis] were included. In this work, we differentially assessed photoreceptor/bipolar cells (distal retina) and retinal ganglion cell (RGC, proximal retina) function besides structural assessment (OCT). We compared two multifocal electroretinography-based approaches, i.e., the multifocal pattern electroretinogram (mfPERG) and the multifocal electroretinogram to record photopic negative response (mfERG PhNR ). Structural assessment utilized peripapillary retinal nerve fiber layer thickness (pRNFL) and macular scans to calculate outer nuclear thickness (ONL) and macular ganglion cell inner plexiform layer thickness (GCIPL). One eye was randomly selected per subject. Results: In NON, photoreceptor/bipolar cell layer had dysfunctional responses evidenced by reduced mfERG PhNR -N1 peak time of the summed response, but preserved structural integrity. Further, both NON and HON demonstrated abnormal RGC responses as evidenced by the photopic negative response of mfERG PhNR (mfPhNR) and mfPERG indices (P < 0.05). Structurally, only HON had thinned retina at the level of RGCs in the macula (GCIPL, P < 0.01) and the peripapillary area (pRNFL, P < 0.01). All three modalities showed good performance to differentiate MS-related damage from HC, 71-81% area under curve. Conclusion: In conclusion, while structural damage was evident mainly for HON, functional measures were the only retinal read-outs of MS-related retinal damage that were independent of optic neuritis, observed for NON. These results indicate retinal MS-related inflammatory processes in the retina prior to optic neuritis. They highlight the importance of retinal electrophysiology in MS diagnostics and its potential as a sensitive biomarker for follow-up in innovative interventions.

Propionic acid beneficially modifies osteoporosis biomarkers in patients with multiple sclerosis.

Background: The impact of the gut and its microbiota are increasingly appreciated in health and disease. Short-chain fatty acids (SCFAs) are among the main metabolites synthesized from bacterial fermentation. Recently, we showed the anti-inflammatory and potentially neuroprotective effect of propionic acid (PA) in multiple sclerosis (MS). Osteoporosis is one of the most common co-morbidities for MS patients with limited therapeutic options available. Osteoporosis is closely linked to an imbalance of cells of the immune system and an immune-mediated impact on bone structure via the gut has been shown. Interestingly, intake of SCFA leads to bone mass increase and concomitant reduction of inflammation-induced bone loss in mice. Objective: To determine the impact of PA supplementation on markers of bone metabolism in MS patients. Methods: We investigated the influence of 14 days supplementation with PA on bone metabolism in 20 MS patients. To this end, ß-CrossLaps and osteocalcin, established markers of bone metabolism, were measured in serum before and after PA intake and correlated with phenotypic and functional immunodata. Results: Supplementation with PA induced a significant increase in serum levels of osteocalcin, a surrogate marker for bone formation. Levels of ß-CrossLaps, a marker for bone resorption, were significantly decreased after therapy. Regulatory T-cell (Treg) numbers and suppressive capacity positively correlated with serum levels of osteocalcin while Th17 cell numbers showed an inverse correlation. Our findings are in line with animal studies showing that SCFA induced increased bone formation and reduced bone resorption. Conclusion: In addition to its immune regulatory, disease-modifying effect on MS disease course, supplementation with PA beneficially influences serum levels of ß-CrossLaps and osteocalcin and may thus also protect against osteoporosis, a common co-morbidity in MS.

Propionic Acid Rescues High-Fat Diet Enhanced Immunopathology in Autoimmunity via Effects on Th17 Responses.

High-fat diets (HFD) are linked to obesity and associated comorbidities and induce pathogenic T helper (Th) 17 cells while decreasing regulatory T cells (Treg). This pro-inflammatory environment also aggravates immunopathology in experimental autoimmune encephalomyelitis (EAE) as a prototype model of T cell mediated autoimmunity. The strong association of HFD to obesity as well as the increasing risk of autoimmunity in the Western world stresses the importance to identify compounds that counteract this metabolically induced pro-inflammatory state in humans. One prominent candidate is the short-chain fatty acid propionate (PA) that was recently identified as potent therapy in the autoimmune disease multiple sclerosis by enhancing Treg cell frequencies and functionality. Mice were fed a HFD rich lauric acid (LA) and treated either with water or PA during MOG35-55-EAE. We analyzed Treg and Th17 cell frequencies in different tissues, antigen-specific cell proliferation and cytokine secretion, investigated Treg cell functionality by suppression assays and IL-10 signaling blockade and employed Western blotting to investigate the involvement of p38-MAPK signaling. Finally, we performed an explorative study in obese and non-obese MS patients, investigating fecal PA concentrations as well as peripheral Th17 and Treg frequencies before and after 90 days of daily PA intake. As compared to controls, mice on a HFD displayed a more severe course of EAE with enhanced demyelination and immune cell infiltration in the spinal cord. PA treatment prevented this disease enhancing effect of HFD by inhibiting Th17 mediated inflammatory processes in the gut and the spleen. Blocking experiments and signaling studies revealed p38-MAPK and IL-10 signaling as important targets linking the beneficial effects of PA treatment and reduced inflammation due to enhanced Treg frequency and functionality. An explorative study in a small group of MS patients revealed reduced PA concentrations in fecal samples of obese MS patients compared to the non-obese group, coinciding with increased Th17 but decreased Treg cells in obese patients. Importantly, PA intake could restore the Treg-Th17 homeostasis. Our data thus identify Th17 responses as an important target for the beneficial effects of PA in HFD and obesity in addition to the recently identified potential of PA as a Treg inducing therapy in T cell mediated autoimmunity.

Interventional Influence of the Intestinal Microbiome Through Dietary Intervention and Bowel Cleansing Might Improve Motor Symptoms in Parkinson's Disease.

The impact of the gut microbiome is being increasingly appreciated in health and in various chronic diseases, among them neurodegenerative disorders such as Parkinson's disease (PD). In the pathogenesis of PD, the role of the gut has been previously established. In conjunction with a better understanding of the intestinal microbiome, a link to the misfolding and spread of alpha-synuclein via inflammatory processes within the gut is discussed. In a case-control study, we assessed the gut microbiome of 54 PD patients and 32 healthy controls (HC). Additionally, we tested in this proof-of-concept study whether dietary intervention alone or additional physical colon cleaning may lead to changes of the gut microbiome in PD. 16 PD patients underwent a well-controlled balanced, ovo-lacto vegetarian diet intervention including short fatty acids for 14 days. 10 of those patients received additional treatment with daily fecal enema over 8 days. Stool samples were collected before and after 14 days of intervention. In comparison to HC, we could confirm previously reported PD associated microbiome changes. The UDPRS III significantly improved and the levodopa-equivalent daily dose decreased after vegetarian diet and fecal enema in a one-year follow-up. Additionally, we observed a significant association between the gut microbiome diversity and the UPDRS III and the abundance of Ruminococcaceae. Additionally, the abundance of Clostridiaceae was significantly reduced after enema. Dietary intervention and bowel cleansing may provide an additional non-pharmacologic therapeutic option for PD patients.

Predictors for Therapy Response to Intrathecal Corticosteroid Therapy in Multiple Sclerosis.

Objective: The autoimmune disease Multiple Sclerosis (MS) represents a heterogeneous disease pattern with an individual course that may lead to permanent disability. In addition to immuno-modulating therapies patients benefit from symptomatic approaches like intrathecal corticosteroid therapy (ICT), which is frequently applied in a growing number of centers in Germany. ICT reduces spasticity, which elongates patient's walking distance and speed, thus improves quality of life. Methods: In our study we set out to investigate cerebrospinal fluid (CSF) parameters and clinical predictors for response to ICT. Therefore, we analyzed 811 CSF samples collected from 354 patients over a time period of 12 years. Patients who received ICT were divided in two groups (improving or active group) depending on their EDSS-progress. As control groups we analyzed data of ICT naïve patients, who were divided in the two groups as well. Additionally we observed the clinical progress after receiving ICT by comparison of patients in both groups. Results: The results showed clinical data had a significant influence on the probability to benefit from ICT. The probability (shown by Odds Ratio of 1.77-2.43) to belong to the improving group in contrast to the active group is significantly (p < 0.0001) higher at later stages of disease with early disease onset (< 35 years, OR = 2.43) and higher EDSS at timepoint of ICT-initiation (EDSS > 6, OR = 2.06). Additionally, we observed lower CSF cell counts (6.68 ± 1.37 µl) and lower total CSF protein (412 ± 18.25 mg/l) of patients who responded to ICT compared to patients who did not (p < 0.05). In the control group no significant differences were revealed. Furthermore analyses of our data revealed patients belonging to the improving group reach an EDSS of 6 after ICT-initiation less often than patients of the active group (after 13 years 39.8% in the improving group, 67.8% in the active group). Conclusion: Our study implies two relevant messages: (i) although the study was not designed to prospectively assess clinical data, in this cohort no severe side effects were observed under ICT; (ii) disease onset, EDSS, CSF cell count, and total protein may serve as predictive markers for therapy response.

Peripheral CD19+ B-cell counts and infusion intervals as a surrogate for long-term B-cell depleting therapy in multiple sclerosis and neuromyelitis optica/neuromyelitis optica spectrum disorders.

BACKGROUND: With ocrelizumab another drug is available for the treatment of multiple sclerosis (MS). Little is known on the long-term use of ocrelizumab on immune cell subsets, and no surrogate markers are available. Rituximab (RTX) has been in off-label use for the treatment of MS, neuromyelitis optica (NMO) and neuromyelitis optica spectrum disorder (NMOSD) for > 10 years. OBJECTIVE: We evaluated the long-term depletion and repopulation rate of peripheral CD19+ B-cells as a potential surrogate for the clinical outcome, and whether it may serve for dosage and time-to-infusion decision making. METHODS: We evaluated the CD19+ and CD4+/8+ T-cell counts in n = 153 patients treated with RTX (132 MS, 21 NMO/NMOSD). The dosages ranged from 250 to 2000 mg RTX. Depletion/repopulation rates of CD19+ B-cells as well as long-term total lymphocyte cell counts, were assessed and corroborated with EDSS, ARR (annualized relapse rate), MRI, and time to reinfusion. RESULTS: CD19+ B-cells' repopulation rate significantly varied depending on the dosage applied leading to individualized application intervals (mean 9.73 ± 0.528 months). Low/absent CD19+ B-cell counts were associated with reduced ARR, EDSS, and GD+-MRI-lesions. Long-term B-cell-depleting therapy led to a transiently skewed CD4+/8+ T-cell ratio due to reduced CD4+ T-cells and absolute lymphocyte counts, which recovered after the second cycle. CONCLUSION: Our data suggest that CD19+ B-cell repopulation latency may serve as surrogate marker for individualized treatment strategies in MS and NMO/NMOSD, which proved clinically equally effective in our cohort as evaluated by previous studies.

Induction of Regulatory Properties in the Intestinal Immune System by Dimethyl Fumarate in Lewis Rat Experimental Autoimmune Neuritis.

Objective: Dimethyl fumarate (DMF) exerts immunomodulatory and neuroprotective effects in the animal model of experimental autoimmune neuritis (EAN) in the Lewis rat. DMF has been shown to modulate gut microbiota in veterinary medicine, however the effects of oral DMF on the gut-associated lymphoid tissue (GALT) remain unknown. Methods: Lewis rats were treated orally twice daily with DMF up to day 10 after immunization with immunogenic P2 peptide. Histological, flow cytometric and RT-PCR analyses of the GALT (intraepithelial layer, lamina propria, and Peyer patches) in duodenum, jejunum, and ileum were performed ex vivo. Moreover, cell transfer experiments were used to examine the protective effects of GALT regulatory T cells of the Peyer patches. Results: In the upper layers of duodenum, DMF induced a reduction of the toll-like receptor 4 (TLR4) mRNA expression. This was combined by a decrease of the pro-inflammatory lamina propria IFN-γ mRNA expression. In the ileum, we detected an immunoregulatory phenotype characterized by an increase of FoxP3 mRNA expression and of the nuclear factor (erythroid-derived-2)- like 2 (Nrf2) downstream molecule heme oxygenase-1 (HO-1) mRNA. Finally, CD4+ CD25+ regulatory T cells were increased in the Peyer patches. In vivo, the protective effect of these regulatory cells was verified by cell transfer into recipient EAN rats. Conclusions: Our results identified a novel immunomodulatory effect of DMF through the different regions and layers of the small intestine, which led to an increase of regulatory T cells, exerting a protective role in experimental neuritis.

Elevated levels of miR-181c and miR-633 in the CSF of patients with MS: A validation study.

OBJECTIVE: To validate a previously discovered microRNA (miRNA) panel in the CSF of patients with MS, we now tested the diagnostic value of CSF-derived candidate miRNAs in a case-control study in a larger MS cohort. METHODS: The levels of miR-181c, miR-633, and miR-922 were analyzed in the CSF of 218 patients with MS and 211 patients with other neurologic diseases (OND) by real-time quantitative reverse transcriptase PCR. RESULTS: CSF levels of both miR-181c (p < 0.001 and miR-633 p < 0.001) were higher in patients with MS patients compared with patients with OND. Both miR-181c (area under the curve [AUC] 0.75, 95% CI 0.70-0.80, p < 0.001) and miR-633 (AUC 0.75, 95% CI 0.68-0.83, p < 0.001) differentiated MS from OND. Combining both miRNAs yielded a sensitivity of 62% and specificity of 89% to differentiate MS from OND. miR-922 was not confirmed to be differentially expressed in this validation cohort. CONCLUSIONS: The results of this so far largest study on CSF-based miRNAs confirm the diagnostic value of miR-181c and miR-633 for MS. The present study may help to extend the diagnostic tools for patients with suspected MS and may add further knowledge to the pathology of the disease. CLASSIFICATION OF EVIDENCE: This study provides Class III evidence that CSF-derived miR-181c and miR-633 distinguish patients with MS from patients with OND.

The NRF2 pathway as potential biomarker for dimethyl fumarate treatment in multiple sclerosis.

OBJECTIVE: Immunological studies have demonstrated a plethora of beneficial effects of dimethyl fumarate (DMF) on various cell types. However, the cellular and molecular targets are incompletely understood and response markers are scarce. Here, we focus on the relation between nuclear factor (erythroid-derived 2)-like 2 (NRF2) pathway induction under DMF therapy and the composition of the blood immune cell compartment and clinical efficacy in relapsing-remitting multiple sclerosis (MS) patients. METHODS: We explored effects of DMF on peripheral immune cell subsets by flow cytometric and transcriptional analysis of serial blood samples obtained from 43 MS patients during the first year of therapy. RESULTS: Gene expression analysis proved activation of NRF2 signaling under DMF therapy that was paralleled by a temporal expansion of FoxP3+ regulatory T cells, CD56bright natural killer cells, plasmacytoid dendritic cells, and a decrease in CD8+ T cells, B cells, and type 1 myeloid dendritic cells. In a subgroup of 28 patients with completely available clinical data, individuals with higher levels of the NRF2 target gene NAD(P)H quinone dehydrogenase 1 (NQO1) 4-6 weeks after DMF therapy initiation were more likely to achieve no evidence of disease activity status 1 year later. The degree of NQO1 induction further correlated with patient age. INTERPRETATION: We demonstrate that positive effects of DMF on the clinical outcome are paralleled by induction of the antioxidant NRF2 transcriptional pathway and a shift toward regulatory immune cell subsets in the periphery. Our data identify a role of the NRF2 pathway as potential biomarker for DMF treatment in MS.

The immunomodulatory effect of laquinimod in CNS autoimmunity is mediated by the aryl hydrocarbon receptor.

Though several functional properties of laquinimod have been identified, our understanding of the underlying mechanisms is still incomplete. Since the compound elicits similar immunomodulatory effects to ligands of the aryl hydrocarbon receptor (AhR), we compared the efficacy of laquinimod in experimental autoimmune encephalomyelitis (EAE)-afflicted wild-type and AhR-deficient mice. Laquinimod failed to ameliorate clinical symptoms and leukocyte infiltration in AhR-deficient mice; however, treatment exerted neuroprotection by elevation of brain-derived neurotrophic factor (BDNF) independent of genetic profile. Thus, our data identify the AhR pathway in these mutant mice as crucial for the immunomodulatory, but not neuroprotective, efficacy of laquinimod in EAE.