The Gut-Brain Axis in Multiple Sclerosis. Is Its Dysfunction a Pathological Trigger or a Consequence of the Disease?

Environmental factors related to multiple sclerosis progression

Multiple Sclerosis (MS) is a complex neurological disease which prevalence is increasing worldwide. The impact of environmental factors on MS susceptibility has already been defined and highlighted in many previous reports, particularly vitamin D or ultraviolet B light exposure, Epstein-Barr virus (EBV) infection, obesity, and smoking. There is increasing evidence that environmental and lifestyle factors are not only important in triggering MS but are also implicated in MS progression. Low sun exposure and vitamin D deficiency exhibit a strong relationship with disease progression in both animal and human studies. The gestational period seems also to impact long-term disease progression as January's babies had a higher risk of requiring walking assistance than those born in other months. The implication of EBV in neurodegeneration and MS progression was also suggested even though its specific targets and mechanisms are still unclear. Cigarette smoking is correlated with faster clinical progression. The association of obesity and smoking seems to be associated with a faster progression and an increased rate of brain atrophy. Although the effect of air pollution on MS pathogenesis remains not fully understood, exposure to polluted air can stimulate several mechanisms that might contribute to MS severity. People with MS with active disease have an altered microbiota compared to patients in the remission phase. Cardiovascular comorbidities, epilepsy, and depression are also associated with a more severe disability accrual. Knowledge about MS modifiable risk factors of progression need to be incorporated into everyday clinical practice in order to ameliorate disease outcomes.

Life history of a brain autoreactive T cell: From thymus through intestine to blood-brain barrier and brain lesion

Brain antigen-specific autoreactive T cells seem to play a key role in inducing inflammation in the central nervous system (CNS), a characteristic feature of human multiple sclerosis (MS). These T cells are generated within the thymus, where they escape negative selection and become integrated into the peripheral immune repertoire of immune cells. Typically, these autoreactive T cells rest in the periphery without attacking the CNS. When autoimmune T cells enter gut-associated lymphatic tissue (GALT), they may be stimulated by the microbiota and its metabolites. After activation, the cells migrate into the CNS through the blood‒brain barrier, become reactivated upon interacting with local antigen-presenting cells, and induce inflammatory lesions within the brain parenchyma. This review describes how microbiota influence autoreactive T cells during their life, starting in the thymus, migrating through the periphery and inducing inflammation in their target organ, the CNS.

Perivascular B cells link intestinal angiogenesis to immunity and to the gut-brain axis during neuroinflammation

Disruption of gut barrier function and intestinal immune cell homeostasis are increasingly considered critical players in pathogenesis of extra-intestinal inflammatory diseases, including multiple sclerosis (MS) and its prototypical animal model, the experimental autoimmune encephalomyelitis (EAE). Breakdown of epithelial barriers increases intestinal permeability and systemic dissemination of microbiota-derived molecules. However, whether the gut-vascular barrier (GVB) is altered during EAE has not been reported. Here, we demonstrate that endothelial cell proliferation and vessel permeability increase before EAE clinical onset, leading to vascular remodeling and expansion of intestinal villi capillary bed during disease symptomatic phase in an antigen-independent manner. Concomitant to onset of angiogenesis observed prior to neurological symptoms, we identify an increase of intestinal perivascular immune cells characterized by the surface marker lymphatic vessel endothelial hyaluronic acid receptor 1 (LYVE-1). LYVE-1+ is expressed more frequently on B cells that show high levels of CD73 and have proangiogenic properties. B cell depletion was sufficient to mitigate enteric blood endothelial cell proliferation following immunization for EAE. In conclusion, we propose that altered intestinal vasculature driven by a specialized LYVE-1+ B cell subset promotes angiogenesis and that loss of GVB function is implicated in EAE development and autoimmunity.

Concurrent inflammation-related brain reorganization in multiple sclerosis and depression

BACKGROUND

Neuroinflammation affects brain tissue integrity in multiple sclerosis (MS) and may have a role in major depressive disorder (MDD). Whether advanced magnetic resonance imaging characteristics of the gray-to-white matter border serve as proxy of neuroinflammatory activity in MDD and MS remain unknown.

METHODS

We included 684 participants (132 MDD patients with recurrent depressive episodes (RDE), 70 MDD patients with a single depressive episode (SDE), 222 MS patients without depressive symptoms (nMS), 58 MS patients with depressive symptoms (dMS), and 202 healthy controls (HC)). 3 T-T1w MRI-derived gray-to-white matter contrast (GWc) was used to reconstruct and characterize connectivity alterations of GWc-covariance networks by means of modularity, clustering coefficient, and degree. A cross-validated support vector machine was used to test the ability of GWc to stratify groups according to their depression symptoms, measured with BDI, at the single-subject level in MS and MDD independently.

FINDINGS

MS and MDD patients showed increased modularity (ANOVA partial-η2 = 0.3) and clustering (partial-η2 = 0.1) compared to HC. In the subgroups, a linear trend analysis attested a gradient of modularity increases in the form: HC, dMS, nMS, SDE, and RDE (ANOVA partial-η2 = 0.28, p < 0.001) while this trend was less evident for clustering coefficient. Reduced morphological integrity (GWc) was seen in patients with increased depressive symptoms (partial-η2 = 0.42, P < 0.001) and was associated with depression scores across patient groups (r = -0.2, P < 0.001). Depressive symptoms in MS were robustly classified (88 %).

CONCLUSIONS

Similar structural network alterations in MDD and MS exist, suggesting possible common inflammatory events like demyelination, neuroinflammation that are caught by GWc analyses. These alterations may vary depending on the severity of symptoms and in the case of MS may elucidate the occurrence of comorbid depression.

Applied physiology: gut microbiota and antimicrobial therapy

The gut microbiota plays an important role in maintaining human health and in the pathogenesis of several diseases. Antibiotics are among the most commonly prescribed drugs and have a significant impact on the structure and function of the gut microbiota. The understanding that a healthy gut microbiota prevents the development of many diseases has also led to its consideration as a potential therapeutic target. At the same time, any factor that alters the gut microbiota becomes important in this approach. Exercise and antibacterial therapy have a direct effect on the microbiota. The review reflects the current state of publications on the mechanisms of intestinal bacterial involvement in the pathogenesis of cardiovascular, metabolic, and neurodegenerative diseases. The physiological mechanisms of the influence of physical activity on the composition of the gut microbiota are considered. The mechanisms of the common interface between exercise and antibacterial therapy will be considered using the example of several socially important diseases. The aim of the study is to show the physiological relationship between the effects of exercise and antibiotics on the gut microbiota.

Causal effects of gut microbiota on multiple sclerosis: A two-sample Mendelian randomization study

BACKGROUND

Gut microbiota alterations in multiple sclerosis (MS) patients have been reported in observational studies, but whether these associations are causal is unclear.

OBJECTIVE

We performed a Mendelian randomization study (MR) to assess the causal effects of gut microbiota on MS.

METHODS

Independent genetic variants associated with 211 gut microbiota phenotypes were selected as instrumental variables from the largest genome-wide association studies (GWAS) previously published by the MiBioGen study. GWAS data for MS were obtained from the International Multiple Sclerosis Genetics Consortium (IMSGC) for primary analysis and the FinnGen consortium for replication and collaborative analysis. Sensitivity analyses were conducted to evaluate heterogeneity and pleiotropy.

RESULTS

After inverse-variance-weighted and sensitivity analysis filtering, seven gut microbiota with potential causal effects on MS were identified from the IMSGC. Only five metabolites remained significant associations with MS when combined with the FinnGen consortium, including genus Anaerofilum id.2053 (odds ratio [OR] = 1.141, 95% confidence interval [CI]: 1.021-1.276, p = .021), Ruminococcus2 id.11374 (OR = 1.190, 95% CI: 1.007-1.406, p = .042), Ruminococcaceae UCG003 id.11361 (OR = 0.822, 95% CI: 0.688-0.982, p = .031), Ruminiclostridium5 id.11355 (OR = 0.724, 95% CI: 0.585-0.895, p = .003), Anaerotruncus id.2054 (OR = 0.772, 95% CI: 0.634-0.940, p = .010).

CONCLUSION

Our MR analysis reveals a potential causal relationship between gut microbiota and MS, offering promising avenues for advancing mechanistic understanding and clinical investigation of microbiota-mediated MS.

Impact of high-salt diet in health and diseases and its role in pursuit of cancer immunotherapy by modulating gut microbiome

Cancer chemotherapy remains an area of concern, as many of the therapies are uncomfortable involving side effects and unpleasant experiences. These factors could further reduce patient's quality of life, and even endanger their life. Many therapeutic strategies have been tried to reduce the unpleasant side effects and increase the treatment effectiveness; however, none have shown to have promising effects. One of the main hindrances to cancer therapy is the escape strategies by tumor cells to the immune attack. Promoting inflammation in the tumor microenvironment is the cornerstone and key therapeutic target in cancer chemotherapy. High-salt diet (HSD) intake, though it has deleterious effects on human health by promoting chronic inflammation, is found to be advantageous in the tumor microenvironment. Studies identified HSD favors an increased abundance of Bifidobacterium species in the tumor environment due to gut barrier alteration, which, in turn, promotes inflammation and favors improved response to cancer chemotherapy. A review of the literature was carried out to find out the effects of an HSD on health and diseases, with special mention of its effect on cancer chemotherapy. Studies emphasized HSD would block the myeloid-derived suppressor cells which will enhance the tumor immunity. Exploration of the precise mechanism of simple HSD regime/ingestion of specific bacterial species as probiotics will be effective and essential to formulate the game-changing cancer chemotherapy. With the modern era of healthcare moving toward precision medicine where the physician can choose the treatment option suitable for the individual, HSD regime/ingestion of specific bacterial species can be considered.

Improvements in Gut Microbiome Composition and Clinical Symptoms Following Familial Fecal Microbiota Transplantation in a Nineteen-Year-Old Adolescent With Severe Autism

This case report describes a novel therapy for patients with severe autism spectrum disorder (ASD) that is worth further investigation. A 19-year-old male adolescent with ASD, who was not responding to standard treatment received fecal microbiota transplant (FMT) using donor material from his typically developing female sibling. The patient's ASD symptoms were assessed by assessors who were blind to the patient's past ASD symptomatology. Assessors used the Childhood Autism Rating Scale (CARS), an observation-based rating scale to assess developmental delay in children with autism (range of CARS scores is 15 - 60; a score > 28 is indicative of autism; higher score is positively correlated with degree of severity), at baseline and again at six timepoints post-FMT. The patient experienced marked improvements in microbiome diversity and composition over the year and a half period that followed the FMT procedure. Additionally, the patient who was previously nonverbal said his first two words and experienced a reduction in aggression 1-month post-FMT. To the authors' knowledge, this is the first report to demonstrate the use of familial FMT in an adolescent patient with ASD. Given that ASD symptom improvements post-FMT tend to occur in younger patients, the authors hypothesize that the use of a familial donor may be an important factor that contributed to the improved outcomes experienced by this older child.

Animal model of multiple sclerosis: Experimental autoimmune encephalomyelitis

Multiple sclerosis (MS) is a very complex and heterogeneous disease, with an unknown etiology and which, currently, remains incurable. For this reason, animal models are crucial to investigate this disease, which has increased in prevalence in recent years, affecting 2.8 million people worldwide, and is the leading cause of non-traumatic disability in young adults between the ages of 20-30years. Of all the models developed to replicate MS, experimental autoimmune encephalomyelitis (EAE) best reflects the autoimmune pathogenesis of MS. There are different methods to induce it, which will give rise to different types of EAE, which will vary in clinical presentation and severity. Of the EAE models, the most widespread and used is the one induced in rodents due to its advantages over other species. Likewise, EAE has become a widely used model in the development of therapies for the treatment of MS. Likewise, it is very useful to define the cellular and molecular mechanisms involved in the pathogenesis of MS and to establish therapeutic targets for this disease. For all these reasons, the EAE model plays a key role in improving the understanding of MS.

In-silico characterization of GABAT protein found in gut-brain axis associated bacteria of healthy individuals and multiple sclerosis patients

Background

Multiple sclerosis (MS) is a neurodegenerative disease characterized by inflammation and demyelination of neurons. There is evidence to suggest that level of a neurotransmitter gamma-aminobutyric acid (GABA), due to the degradation by γ-aminobutyric acid transaminase (GABAT), is reduced in certain areas of the brain in MS patients. MS is always accompanied by gut bacteria dysbiosis. In healthy individuals, Faecalibacterium sp. while in MS patients A. calcoaceticus, Clostridium sp. and S. typhimurium are found abundantly. Although all these microbes produce GABAT but only in MS patients this enzyme significantly degrades GABA.

Objective

Present study is an attempt to characterize the GABAT protein sequences of these bacteria.

Methodology

Sequences of GABAT protein were retrieved from Uniprot database. Sequences were analyzed by Protparam, Gneg-mPLoc, SOSUI, PFP-FunDSeqE, Pepwheel program, PROTEUS and Alphafold and SAVES servers, MEME suite and HDOCK server.

Results

In healthy individuals gastrointestinal tract (GIT) bacteria, GABAT protein was present in inner-membrane with α helix content (61 and 62%) and β sheet content (5%), 4-helical cytokines functional domains. It has greater number of B-cell epitopes and more complex 3D configuration as compared to MS patients GIT bacterial enzymes.

Conclusion

Present study might enable us to modify the GABAT encoding gene and enzyme through site-directed mutagenesis in pathogenic bacteria thus reducing their potential of causing MS.

Milk and multiple sclerosis: A possible link?

Despite having been formally defined over 150 years ago, the etiology of multiple sclerosis (MS) is still relatively unknown. However, it is now recognized as a multifactorial disease in which genetics, infection, immune function, and environment play a role. We propose an additional piece to the puzzle: milk. In this review, milk is highlighted as a potential risk factor for MS. We examine the overall correlation between bovine milk consumption and the incidence of MS. We then discuss possible mechanisms that may explain the positive association between milk consumption and the development of MS. For instance, butyrophilin (BTN), a milk glycoprotein, can provide molecular mimicry of myelin oligodendrocyte glycoprotein and induce an autoinflammatory response against myelin. Other milk components such as casein, gangliosides, xanthine oxidase, and saturated fats are also analyzed for their potential involvement in the pathophysiology of MS. Finally, we fit milk alongside other well known risk factors of MS: vitamin D levels, Epstein Barr virus infection, and gut dysbiosis. In conclusion, this review summarizes potential mechanisms linking milk as an underappreciated potential risk factor for the development of MS.

Current knowledge on multiple sclerosis pathophysiology, disability progression assessment and treatment options, and the role of autologous hematopoietic stem cell transplantation

Multiple sclerosis (MS) is an autoimmune disease of the central nervous system (CNS) that affects nearly 2.8 million people each year. MS distinguishes three main types: relapsing-remitting MS (RRMS), secondary progressive MS (SPMS) and primary progressive MS (PPMS). RRMS is the most common type, with the majority of patients eventually progressing to SPMS, in which neurological development is constant, whereas PPMS is characterized by a progressive course from disease onset. New or additional insights into the role of effector and regulatory cells of the immune and CNS systems, Epstein-Barr virus (EBV) infection, and the microbiome in the pathophysiology of MS have emerged, which may lead to the development of more targeted therapies that can halt or reverse neurodegeneration. Depending on the type and severity of the disease, various disease-modifying therapies (DMTs) are currently used for RRMS/SPMS and PPMS. As a last resort, and especially in highly active RRMS that does not respond to DMTs, autologous hematopoietic stem cell transplantation (AHSCT) is performed and has shown good results in reducing neuroinflammation. Nevertheless, the question of its potential role in preventing disability progression remains open. The aim of this review is to provide a comprehensive update on MS pathophysiology, assessment of MS disability progression and current treatments, and to examine the potential role of AHSCT in preventing disability progression.

Risk of Common Neurological Disorders in Adult Patients with Inflammatory Bowel Disease: A Systematic Review and Meta-analysis

BACKGROUND

Several studies investigated the risks of neurological conditions in patients with inflammatory bowel disease (IBD), with some variability in findings. We aimed to perform a systematic review and meta-analysis of available evidence to elucidate the association between IBD and the risks of common neurological disorders.

METHODS

We conducted a literature search through Embase, PubMed, Scopus, and ProQuest databases from inception to June 30, 2023, to identify cohort studies assessing the risk of developing stroke, all-cause dementia, Parkinson's disease (PD), multiple sclerosis (MS), seizure/epilepsy, and peripheral neuropathy in adult IBD patients compared with non-IBD population. We combined hazard ratios (HRs) with 95% confidence intervals (CIs) to compute pooled estimates using a random-effects model.

RESULTS

In total, 22 cohort studies were included, of which 9 studies reported 7074 stroke events in 202 460 IBD patients, 5 studies reported 3783 all-cause dementia diagnoses in 109 602 IBD patients, 7 studies reported 932 PD diagnoses in 354 792 IBD patients, and 1 study reported 6 MS events in 35 581 IBD patients. We observed increased risks of incident stroke (pooled HR = 1.19; 95% CI, 1.06-1.31), all-cause dementia (pooled HR = 1.22; 95% CI, 1.05-1.38), PD (pooled HR = 1.39; 95% CI, 1.20-1.58), and MS (HR = 2.89; 95% CI, 1.02-8.42). No eligible studies were found on peripheral neuropathy and seizure/epilepsy.

CONCLUSIONS

Inflammatory bowel disease may be modestly associated with increased risks of stroke, all-cause dementia, and PD. Further longitudinal studies are warranted to investigate potential links with MS, seizure/epilepsy, and peripheral neuropathy, as well as their clinical significance.

Impact of Disease-Modifying Therapies on Gut-Brain Axis in Multiple Sclerosis

Multiple sclerosis is a chronic, autoimmune-mediated, demyelinating disease whose pathogenesis remains to be defined. In past years, in consideration of a constantly growing number of patients diagnosed with multiple sclerosis, the impacts of different environmental factors in the pathogenesis of the disease have been largely studied. Alterations in gut microbiome composition and intestinal barrier permeability have been suggested to play an essential role in the regulation of autoimmunity. Thus, increased efforts are being conducted to demonstrate the complex interplay between gut homeostasis and disease pathogenesis. Numerous results confirm that disease-modifying therapies (DMTs) used for the treatment of MS, in addition to their immunomodulatory effect, could exert an impact on the intestinal microbiota, contributing to the modulation of the immune response itself. However, to date, the direct influence of these treatments on the microbiota is still unclear. This review intends to underline the impact of DMTs on the complex system of the microbiota-gut-brain axis in patients with multiple sclerosis.

Association of intestinal dysbiosis with susceptibility to multiple sclerosis: Evidence from different population studies (Review)

Understanding the relationship between microorganisms that live in our intestines and neuroinflammatory and neurodegenerative pathologies of the central nervous system (CNS) is essential, since they have been shown to have an immunomodulatory effect in neurological disorders, such as multiple sclerosis (MS). The gut microbiota can be affected by several environmental factors, including infections, physical and emotional stress and diet, the latter known as the main modulator of intestinal bacteria. An abrupt shift in the gut microbiota composition and function is known as dysbiosis, a state of local and systemic inflammation produced by pathogenic bacteria and its metabolites responsible for numerous neurological symptoms. It may also trigger neuronal damage in patients diagnosed with MS. Intestinal dysbiosis affects the permeability of the intestine, allowing chronic low-grade bacterial translocation from the intestine to the circulation, which may overstimulate immune cells and cells resident in the CNS, break immune tolerance and, in addition, alter the permeability of the blood-brain barrier (BBB). This way, toxins, inflammatory molecules and oxidative stress molecules can pass freely into the CNS and cause extensive damage to the brain. However, commensal bacteria, such as the Lactobacillus genus and Bacteroides fragilis, and their metabolites (with anti-inflammatory potential), produce neurotransmitters such as γ-aminobutyric acid, histamine, dopamine, norepinephrine, acetylcholine and serotonin, which are important for neurological regulation. In addition, reprogramming the gut microbiota of patients with MS with a healthy gut microbiota may help improve the integrity of the gut and BBB, by providing clinically protective anti-inflammatory effects and reducing the disease's degenerative progression. The present review provides valuable information about the relationship between gut microbiota and neuroinflammatory processes of the CNS. Most importantly, it highlights the importance of intestinal bacteria as an environmental factor that may mediate the clinical course of MS, or even predispose to the outbreak of this disease.

Bibliometric analysis of global research trends on regulatory T cells in neurological diseases

This bibliometric study aimed to summarize and visualize the current research status, emerging trends, and research hotspots of regulatory T (Treg) cells in neurological diseases. Relevant documents were retrieved from the Web of Science Core Collection. Tableau Public, VOSviewer, and CiteSpace software were used to perform bibliometric analysis and network visualization. A total of 2,739 documents were included, and research on Treg cells in neurological diseases is still in a prolific period. The documents included in the research were sourced from 85 countries/regions, with the majority of them originating from the United States, and 2,811 organizations, with a significant proportion of them coming from Harvard Medical School. Howard E Gendelman was the most prolific author in this research area. Considering the number of documents and citations, impact factors, and JCR partitions, Frontiers in Immunology was the most popular journal in this research area. Keywords "multiple sclerosis," "inflammation," "regulatory T cells," "neuroinflammation," "autoimmunity," "cytokines," and "immunomodulation" were identified as high-frequency keywords. Additionally, "gut microbiota" has recently emerged as a new topic of interest. The study of Treg cells in neurological diseases continues to be a hot topic. Immunomodulation, gut microbiota, and cytokines represent the current research hotspots and frontiers in this field. Treg cell-based immunomodulatory approaches have shown immense potential in the treatment of neurological diseases. Modifying gut microbiota or regulating cytokines to boost the numbers and functions of Treg cells represents a promising therapeutic strategy for neurological diseases.

Impaired intestinal permeability in patients with multiple sclerosis

BACKGROUND

A number of recent studies have shown that the intestinal microbiome, part of the brain-gut axis, is implicated in the pathophysiology of multiple sclerosis. An essential part of this axis, is the intestinal barrier and gastrointestinal disorders with intestinal barrier dysregulation appear to be linked to CNS demyelination, and hence involved in the etiopathogenesis of multiple sclerosis (MS).

OBJECTIVE

The aim of this study was to evaluate the integrity of the intestinal barrier in patients with clinically definite multiple sclerosis (CDMS) and clinically isolated syndrome (CIS) using two serum biomarkers, claudin-3 (CLDN3), a component of tight epithelial junctions, and intestinal fatty acid binding protein (I-FABP), a cytosolic protein in enterocytes.

METHODS

Serum levels of CLDN3 in 37 MS patients and 22 controls, and serum levels of I-FABP in 46 MS patients and 51 controls were measured using commercial ELISA kits. Complete laboratory tests excluded the presence of gluten-related disorders in all subjects. Thirty MS patients received either disease-modifying drugs (DMD), immunosuppression (IS) or corticosteroid treatment.

RESULTS

CLDN3 levels were only significantly higher in the MS patients treated with DMD or IS compared to the control group (P=0.006). There were no differences in I-FABP serum levels between the groups. Serum CLDN3 levels did not correlate with serum I-FABP levels in CDMS, in CIS patients or controls.

CONCLUSIONS

In multiple sclerosis patients, the intestinal epithelium may be impaired with increased permeability, but without significant enterocyte damage characterized by intracellular protein leakage. Based on our data, CLDN3 serum levels appear to assess intestinal dysfunction in MS patients but mainly in treated ones.

An appraisal of emerging therapeutic targets for multiple sclerosis derived from current preclinical models

INTRODUCTION

Multiple sclerosis (MS) is a chronic inflammatory, demyelinating, and neurodegenerative condition affecting the central nervous system (CNS). Although therapeutic approaches have become available over the last 20 years that markedly slow the progression of disease, there is no cure for MS. Furthermore, the capacity to repair existing CNS damage caused by MS remains very limited.

AREAS COVERED

Several animal models are widely used in MS research to identify potential druggable targets for new treatment of MS. In this review, we look at targets identified since 2019 in studies using these models, and their potential for effecting a cure for MS.

EXPERT OPINION

Refinement of therapeutic strategies targeting key molecules involved in the activation of immune cells, cytokine, and chemokine signaling, and the polarization of the immune response have dominated recent publications. While some progress has been made in identifying effective targets to combat chronic demyelination and neurodegeneration, much more work is required. Progress is largely limited by the gaps in knowledge of how the immune system and the nervous system interact in MS and its animal models, and whether the numerous targets present in both systems respond in the same way in each system to the same therapeutic manipulation.

Multiple Sclerosis-Related Dietary and Nutritional Issues: An Updated Scoping Review with a Focus on Pediatrics

PURPOSE

Lifestyle/dietetic habits play an important role in the development and progression of multiple sclerosis (MS) disease. Here, we examine the basic pathomechanisms underlying intestinal and brain barrier modifications in MS and consider diets and dietary supplementations proposed over time to complement pharmacological therapies for improving disease outcome both in adults and in children.

METHODS

Scoping literature search about evidence-based findings in MS-related gut-brain axis (GBA) pathophysiology and nutritional issues at all ages.

FINDINGS

Data show that (1) no universal best diet exists, (2) healthy/balanced diets are, however, necessary to safeguard the adequate intake of all essential nutrients, (3) diets with high intakes of fruits, vegetables, whole grains, and lean proteins that limit processed foods, sugar, and saturated fat appear beneficial for their antioxidant and anti-inflammatory properties and their ability to shape a gut microbiota that respects the gut and brain barriers, (4) obesity may trigger MS onset and/or its less favorable course, especially in pediatric-onset MS. Vitamin D and polyunsaturated fatty acids are the most studied supplements for reducing MS-associated inflammation.

CONCLUSIONS

Pending results from other and/or newer approaches targeting the GBA (e.g., pre- and probiotics, engineered probiotics, fecal-microbiota transplantation), accurate counseling in choosing adequate diet and maintaining physical activity remains recommended for MS prevention and management both in adults and children.

Anti-CD20 monoclonal antibody (mAb) therapy and colitis: A case series and review

The US Food and Drug Administration (FDA) recently issued a warning regarding ocrelizumab due to reports of colitis among patients taking this medication. Since it is the only FDA-approved therapy for primary progressive multiple sclerosis (PPMS), further research on this adverse event is necessary, and healthcare professionals should be informed of potential treatment options. In this review, we summarize the available data on the incidence of inflammatory colitis associated with anti-CD20 monoclonal antibodies (mAbs), such as ocrelizumab and rituximab, used in MS treatment. Although the exact pathophysiology of anti-CD20-induced colitis remains unknown, immunological dysregulation through treatment-mediated B-cell depletion has been proposed as a possible mechanism. Our study highlights the importance of clinicians being aware of this potential side effect, and patients taking these medications should be closely monitored for any new-onset gastrointestinal symptoms or diarrheal illness. Research indicates that prompt intervention with endoscopic examination and medical or surgical therapies can ensure timely and effective management, thus improving patient outcomes. However, large-scale studies are still needed to determine the associated risk factors and to establish definitive guidelines for the clinical evaluation of MS patients on anti-CD20 medications.

Impact of the mother's gut microbiota on infant microbiome and brain development

The link between the gut microbiome and health has recently garnered considerable interest in its employment for medicinal purposes. Since the early microbiota exhibits more flexibility compared to that of adults, there is a considerable possibility that altering it will have significant consequences on human development. Like genetics, the human microbiota can be passed from mother to child. This provides information on early microbiota acquisition, future development, and prospective chances for intervention. The succession and acquisition of early-life microbiota, modifications of the maternal microbiota during pregnancy, delivery, and infancy, and new efforts to understand maternal-infant microbiota transmission are discussed in this article. We also examine the shaping of mother-to-infant microbial transmission, and we then explore possible paths for future research to advance our knowledge in this area.

Adrenoceptors as potential target for add-on immunomodulatory therapy in multiple sclerosis

This review summarizes recent findings related to the role of the sympathetic nervous system (SNS) in pathogenesis of multiple sclerosis (MS) and its commonly used experimental model - experimental autoimmune encephalomyelitis (EAE). They indicate that noradrenaline, the key end-point mediator of the SNS, acting through β-adrenoceptor, has a contributory role in the early stages of MS/EAE development. This stage is characterized by the SNS hyperactivity (increased release of noradrenaline) reflecting the net effect of different factors, such as the disease-associated inflammation, stress, vitamin D hypovitaminosis, Epstein-Barr virus infection and dysbiosis. Thus, the administration of propranolol, a non-selective β-adrenoceptor blocker, readily crossing the blood-brain barrier, to experimental rats before the autoimmune challenge and in the early (preclinical/prodromal) phase of the disease mitigates EAE severity. This phenomenon has been ascribed to the alleviation of neuroinflammation (due to attenuation of primarily microglial activation/proinflammatory functions) and the diminution of the magnitude of the primary CD4+ T-cell autoimmune response (the effect associated with impaired autoantigen uptake by antigen presenting cells and their migration into draining lymph nodes). The former is partly related to breaking of the catecholamine-dependent self-amplifying microglial feed-forward loop and the positive feedback loop between microglia and the SNS, leading to down-regulation of the SNS hyperactivity and its enhancing influence on microglial activation/proinflammatory functions and the magnitude of autoimmune response. The effects of propranolol are shown to be more prominent in male EAE animals, the phenomenon important as males (like men) are likely to develop clinically more severe disease. Thus, these findings could serve as a firm scientific background for formulation of a new sex-specific immune-intervention strategy for the early phases of MS (characterized by the SNS hyperactivity) exploiting anti-(neuro)inflammatory and immunomodulatory properties of propranolol and other relatively cheap and safe adrenergic drugs with similar therapeutic profile.

COVID-19 and Multiple Sclerosis: A Complex Relationship Possibly Aggravated by Low Vitamin D Levels

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is an exceptionally transmissible and pathogenic coronavirus that appeared at the end of 2019 and triggered a pandemic of acute respiratory disease, known as coronavirus disease 2019 (COVID-19). COVID-19 can evolve into a severe disease associated with immediate and delayed sequelae in different organs, including the central nervous system (CNS). A topic that deserves attention in this context is the complex relationship between SARS-CoV-2 infection and multiple sclerosis (MS). Here, we initially described the clinical and immunopathogenic characteristics of these two illnesses, accentuating the fact that COVID-19 can, in defined patients, reach the CNS, the target tissue of the MS autoimmune process. The well-known contribution of viral agents such as the Epstein-Barr virus and the postulated participation of SARS-CoV-2 as a risk factor for the triggering or worsening of MS are then described. We emphasize the contribution of vitamin D in this scenario, considering its relevance in the susceptibility, severity and control of both pathologies. Finally, we discuss the experimental animal models that could be explored to better understand the complex interplay of these two diseases, including the possible use of vitamin D as an adjunct immunomodulator to treat them.

Association between exposure to combustion-related air pollution and multiple sclerosis risk

BACKGROUND

Smoking and occupational pulmonary irritants contribute to multiple sclerosis (MS) development. We aimed to study the association between ambient air pollution and MS risk and potential interaction with the human leukocyte antigen (HLA)-DRB1*15:01 allele.

METHODS

Exposure to combustion-related air pollution was estimated as outdoor levels of nitrogen oxides (NOx) at the participants' residence locations, by spatially resolved dispersion modelling for the years 1990-18. Using two population-based case-control studies (6635 cases, 8880 controls), NOx levels were associated with MS risk by calculating odds ratios (OR) with 95% confidence intervals (CI) using logistic regression models. Interaction between high NOx levels and the HLA-DRB1*15:01 allele regarding MS risk was calculated by the attributable proportion due to interaction (AP). In addition, a register study was performed comprising all MS cases in Sweden who had received their diagnosis between 1993 and 2018 (n = 22 173), with 10 controls per case randomly selected from the National Population register.

RESULTS

Residential air pollution was associated with MS risk. NOx levels (3-year average) exceeding the 90th percentile (24.6 µg/m3) were associated with an OR of 1.37 (95% CI 1.10-1.76) compared with levels below the 25th percentile (5.9 µg/m3), with a trend of increasing risk of MS with increasing levels of NOx (P <0.0001). A synergistic effect was observed between high NOx levels (exceeding the lower quartile among controls) and the HLA-DRB1*15:01 allele regarding MS risk (AP 0.26, 95% CI 0.13-0.29).

CONCLUSIONS

Our findings indicate that moderate levels of combustion-related ambient air pollution may play a role in MS development.

Key role of the gut-microbiota-brain axis via the subdiaphragmatic vagus nerve in demyelination of the cuprizone-treated mouse brain

Multiple sclerosis (MS) is the most common demyelinating disease that attacks the central nervous system. Dietary intake of cuprizone (CPZ) produces demyelination resembling that of patients with MS. Given the role of the vagus nerve in gut-microbiota-brain axis in development of MS, we performed this study to investigate whether subdiaphragmatic vagotomy (SDV) affects demyelination in CPZ-treated mice. SDV significantly ameliorated demyelination and microglial activation in the brain compared with sham-operated CPZ-treated mice. Furthermore, 16S ribosomal RNA analysis revealed that SDV significantly improved the abnormal gut microbiota composition of CPZ-treated mice. An untargeted metabolomic analysis demonstrated that SDV significantly improved abnormal blood levels of metabolites in CPZ-treated mice compared with sham-operated CPZ-treated mice. Notably, there were correlations between demyelination or microglial activation in the brain and the relative abundance of several microbiome populations, suggesting a link between gut microbiota and the brain. There were also correlations between demyelination or microglial activation in the brain and blood levels of metabolites. Together, these data suggest that CPZ produces demyelination in the brain through the gut-microbiota-brain axis via the subdiaphragmatic vagus nerve.

[Gut microbiota in patients with relapsing-remitting multiple sclerosis]

Microorganisms in human life play a huge role: in particular, those that coexist with the host organism, inhabiting the skin, upper respiratory tract, external genitalia and especially the digestive tract. The intestinal microbiota, including bacteriome, mycobiome and virome, not only takes part in the digestion process, but also provides the synthesis of a number of vitamins. The intestinal microbiome also serves as the basis for a system of extensive bidirectional neuroendocrine pathways that connect microbiota with various regions of the central nervous system, the hypothalamic-pituitary-adrenal system, and the peripheral parts of the autonomic nervous system. This system of connections has got the name of gut-brain axis and has attracted close attention of scientists over the past two decades, since a targeted impact on the intestinal flora is potentially capable of changing the nature of nervous system regulatory influences on the whole body. It is especially important to study patterns of functioning of the gut-brain axis in patients with the nervous system pathology, namely neurodegenerative and demyelinating diseases. Methods for their treatment continue to improve, and perhaps the correction of the gut microbiotic composition will serve as an additional therapeutic approach. The review article describes current views on the role of the intestinal microbiota, provides the latest data on the composition of bacteriome, mycobiome, and virome in patients with relapsing-remitting multiple sclerosis.

Possible role of the NLRP3 inflammasome and the gut-brain axis in multiple sclerosis-related depression

Multiple sclerosis (MS) is an autoimmune and demyelinating disease of the central nervous system that results from complex interactions between genetic and environmental determinants. Patients with MS exhibit a high risk of depression, however, the exact pathomechanisms remain largely unknown. It is becoming widely accepted that the gut-brain axis (GBA) disorders may exert an influence on neuroinflammation and psychiatric symptoms, including so-called MS-related depression. The element suggested as a bridge between intestinal disorders, depression, and MS is an inflammatory response with the central role of the NLR family pyrin domain containing 3 (NLRP3) inflammasome. The pro-inflammatory activity of effector cytokines of the NLRP3 inflammasome forms the hypothesis that it is actively involved in the development of inflammatory and autoimmune diseases. Despite extensive reviews considering the possible origins of MS-related depression, its complex pathophysiology prevents any easy determination of its underlying mechanisms. This paper aims to discuss molecular mechanisms related to the GBA axis that can mediate dysbiosis, intestinal barrier dysfunction, disruption of blood-brain barrier integrity, neuroinflammation, and subsequent manifestation of MS-related major depressive disorder.

Gut immune cell trafficking: inter-organ communication and immune-mediated inflammation

Immune cell trafficking is a complex and tightly regulated process that is indispensable for the body's fight against pathogens. However, it is also increasingly acknowledged that dysregulation of cell trafficking contributes to the pathogenesis of immune-mediated inflammatory diseases (IMIDs) in gastroenterology and hepatology, such as inflammatory bowel disease and primary sclerosing cholangitis. Moreover, altered cell trafficking has also been implicated as a crucial step in the immunopathogenesis of other IMIDs, such as rheumatoid arthritis and multiple sclerosis. Over the past few years, a central role of the gut in mediating these disorders has progressively emerged, and the partly microbiota-driven imprinting of particular cell trafficking phenotypes in the intestine seems to be crucially involved. Therefore, this Review highlights achievements in understanding immune cell trafficking to, within and from the intestine and delineates its consequences for immune-mediated pathology along the gut-liver, gut-joint and gut-brain axes. We also discuss implications for current and future therapeutic approaches that specifically interfere with homing, retention, egress and recirculation of immune cells.

Probiotic Influences on Motor Skills: A Review

The effects of probiotics have mostly been shown to be favorable on measures of anxiety and stress. More recent experiments indicate single- and multi-strain probiotics in treating motorrelated diseases. Initial studies in patients with Parkinson's disease and Prader-Willi syndrome are concordant with this hypothesis. In addition, probiotics improved motor coordination in normal animals and models of Parkinson's disease, multiple sclerosis, and spinal cord injury as well as grip strength in hepatic encephalopathy. Further studies should delineate the most optimal bacterial profile under each condition.

Global trends in research on irritable bowel syndrome and the brain–gut axis: Bibliometrics and visualization analysis

Irritable bowel syndrome (IBS) is a gastrointestinal disorder with no structural damage, and its pathogenesis remains unclear. Studies have shown that the brain–gut axis is closely related to the occurrence of IBS. However, studies of IBS related to the brain–gut axis have not been systematically analyzed by bibliometrics and visual analysis. This study is based on 631 publications in the Web of Science Core Collection (WoSCC) to analyze hot spots and trends in this field. The collaborations between different authors, institutions, countries, and keywords were bibliometrically analyzed by CiteSpace software. Meanwhile, VOSviewer analyzed the references. The results show that since 2012, the number of publications has been growing rapidly. According to the collaborative network analysis, the United States, the National University of Ireland, Cork, and J.F. Cryan are the countries, institutions, and authors contributing the most, respectively. Through keywords and literature analysis, mechanisms and therapy associated with IBS and the brain–gut axis have still been a research focus in recent years. Furthermore, the physiological and pathological mechanisms of the brain–gut axis influencing IBS (related to gastrointestinal dysfunction, vagus nerve, visceral pain, intestinal flora, serotonin, tryptophan metabolism, stress, brain-derived neurotrophic factor (BDNF), and malonyldialdehyde) are the future research trends, especially the mechanisms related to intestinal flora. This is the first bibliometric and visualization analysis of IBS and brain–gut axis-related literature to explore research hotspots and trends.

Advances in the study of the relationship between Alzheimer's disease and the gastrointestinal microbiome

There are many trillions of bacteria in the gastrointestinal microbiome (GM). Their ecological dysregulation can contribute to the development of certain neurodegenerative diseases, including Alzheimer's disease (AD). AD is common dementia and its incidence is increasing year by year. However, the relationship between GM and AD is unclear. Therefore, this review discusses the relationship between GM and AD, elaborates on the possible factors that can affect this relationship through the inflammation of the brain induced by blood-brain damage and accumulation of amyloid deposit, and proposes feasible ways to treat AD through GM-related substances, such as probiotics, Mega-3, and gut hormones, including their shortcomings as well.

Gut microbiome in multiple sclerosis-related cognitive impairment

Cognition is one of the most evaluated neurologic subjects with which the gut microbiome is supposed to be associated. Cognitive impairment is a prevalent finding in patients with multiple sclerosis (MS). Here, we are about to study the current evidence on the effect of gut microbiota on cognition and MS. Although no direct evidence is in hand, putting all indirect research together, one could think of the hypothetical benefit of brain-gut axis interventions (possibly diet changes, probiotic administration, microbiota transplant) to solve the drastic problem of cognitive impairment in MS. Hence, researchers are encouraged to scan this horizon in order to fill the knowledge gaps in the field.

The antimicrobial peptide cathelicidin drives development of experimental autoimmune encephalomyelitis in mice by affecting Th17 differentiation

Multiple sclerosis (MS) is a highly prevalent demyelinating autoimmune condition; the mechanisms regulating its severity and progression are unclear. The IL-17-producing Th17 subset of T cells has been widely implicated in MS and in the mouse model, experimental autoimmune encephalomyelitis (EAE). However, the differentiation and regulation of Th17 cells during EAE remain incompletely understood. Although evidence is mounting that the antimicrobial peptide cathelicidin profoundly affects early T cell differentiation, no studies have looked at its role in longer-term T cell responses. Now, we report that cathelicidin drives severe EAE disease. It is released from neutrophils, microglia, and endothelial cells throughout disease; its interaction with T cells potentiates Th17 differentiation in lymph nodes and Th17 to exTh17 plasticity and IFN-γ production in the spinal cord. As a consequence, mice lacking cathelicidin are protected from severe EAE. In addition, we show that cathelicidin is produced by the same cell types in the active brain lesions in human MS disease. We propose that cathelicidin exposure results in highly activated, cytokine-producing T cells, which drive autoimmunity; this is a mechanism through which neutrophils amplify inflammation in the central nervous system.

Thinking outside the box: non-canonical targets in multiple sclerosis

Multiple sclerosis (MS) is an immune-mediated disease of the central nervous system that causes demyelination, axonal degeneration and astrogliosis, resulting in progressive neurological disability. Fuelled by an evolving understanding of MS immunopathogenesis, the range of available immunotherapies for clinical use has expanded over the past two decades. However, MS remains an incurable disease and even targeted immunotherapies often fail to control insidious disease progression, indicating the need for new and exceptional therapeutic options beyond the established immunological landscape. In this Review, we highlight such non-canonical targets in preclinical MS research with a focus on five highly promising areas: oligodendrocytes; the blood-brain barrier; metabolites and cellular metabolism; the coagulation system; and tolerance induction. Recent findings in these areas may guide the field towards novel targets for future therapeutic approaches in MS.

Pelvic Floor Dysfunctions and Their Rehabilitation in Multiple Sclerosis

Urinary, bowel, and sexual dysfunctions are the most frequent and disabling pelvic floor (PF) disorders in patients with multiple sclerosis (MS). PF dysfunction negatively impacts the performance of daily living activities, walking, and the physical dimension of quality of life (QoL) in people with MS. Patient-reported outcomes on sphincteric functioning could be useful to detect PF disorders and their impact on patients’ lives. PF rehabilitation proposed by Kegel is based on a series of regularly repeated exercises for “the functional restoration of the perineal muscles”. Over time, various therapeutic modalities have been added to PF muscles exercises, through the application of physical or instrumental techniques, such as intravaginal neuromuscular electrical stimulation, electromyographic biofeedback, transcutaneous tibial nerve stimulation. PF rehabilitation has been applied in MS treatment, with improvements of lower urinary tract symptoms severity, QoL, level of anxiety and depression, and sexual dysfunction. This review aims to examine the different PF disorders in MS to evaluate the application of PF rehabilitation in MS and to highlight its advantages and limits, suggesting a multidisciplinary management of PF disorders, with a well-deserved space reserved for PF rehabilitation.

The Enclosed Intestinal Microbiome: Semiochemical Signals from the Precambrian and Their Disruption by Heavy Metal Pollution

It is increasingly likely that many non-communicable diseases of humans and associated animals are due to the degradation of their intestinal microbiomes, a situation often referred to as dysbiosis. An analysis of the resultant diseases offers an opportunity to probe the function of these microbial partners of multicellular animals. In our view, it now seems likely that vertebrate animals and their microbiomes have coevolved throughout the Ediacaran-Cambrian transition and beyond, operating by semiochemical messaging between the multicellular host and its microbial community guest. A consideration of the overall role of the mutualistic intestinal microbiome as an enclosed bioreactor throws up a variety of challenging concepts. In particular: the significance of the microbiome with respect to the immune system suggests that microeukaryotes could act as microbial sentinel cells; the ubiquity of bacteriophage viruses implies the rapid turnover of microbial composition by a viral-shunt mechanism; and high microbial diversity is needed to ensure that horizontal gene transfer allows valuable genetic functions to be expressed. We have previously postulated that microbes of sufficient diversity must be transferred from mother to infant by seemingly accidental contamination during the process of natural birth. We termed this maternal microbial inheritance and suggested that it operates alongside parental genetic inheritance to modify gene expression. In this way, the adjustment of the neonate immune system by the microbiome may represent one of the ways in which the genome of a vertebrate animal interacts with its microbial environment. The absence of such critical functions in the neonate may help to explain the observation of persistent immune-system problems in affected adults. Equally, granted that the survival of the guest microbiome depends on the viability of its host, one function of microbiome-generated semiochemicals could be to facilitate the movement of food through the digestive tract, effectively partitioning nutrition between host and guest. In the event of famine, downregulation of microbial growth and therefore of semiochemical production would allow all available food to be consumed by the host. Although it is often thought that non-communicable diseases, such as type 2 diabetes, are caused by consumption of food containing insufficient dietary fibre, our hypothesis suggests that poor-quality food is not the prime cause but that the tendency for disease follows the degradation of the intestinal microbiome, when fat build-up occurs because the relevant semiochemicals can no longer be produced. It is the purpose of this paper to highlight the possibility that the origins of the microbiome lie in the Precambrian and that the disconnection of body and microbiome gives rise to non-communicable disease through the loss of semiochemical signalling. We further surmise that this disconnect has been largely brought about by heavy metal poisoning, potentially illuminating a facet of the exposome, the sum total of environmental insults that influence the expression of the genetic inheritance of an animal.