Alterations in nasal microbiota of patients with amyotrophic lateral sclerosis.

BACKGROUND: Links between alterations in gut microbiota composition and amyotrophic lateral sclerosis (ALS) have previously been reported. This study aimed to examine the microbiota in the nasal cavity of ALS. METHODS: Sixty-six ALS patients and 40 healthy caregivers who live in close proximity with patients were enrolled. High throughput metagenomic sequencing of the 16S ribosomal deoxyribonucleic acid (rDNA) gene V3-V4 region of nasal microbiota was used to characterize the alpha and beta diversity and relative abundance of bacterial taxa, predict function, and conduct correlation analysis between specific taxa and clinical features. RESULTS: The nasal microbiome of ALS patients showed lower alpha diversity than that of corresponding healthy family members. Genera Gaiella , Sphingomonas , Polaribacter _1, Lachnospiraceae _NK4A136_group, Klebsiella , and Alistipes were differentially enriched in ALS patients compared to controls. Nasal microbiota composition in ALS patients significantly differed from that in healthy subjects (unweighted UniFrac P = 0.001), while Linear discriminant analysis Effect Size (LEfSe) analysis indicated that Bacteroidetes and Firmicutes dominated healthy nasal communities at the phylum level, whereas Actinobacteria was the predominant phylum and Thermoleophilia was the predominant class in ALS patients. Genus Faecalibacterium and Alistipes were positively correlated with ALS functional rating scale revised (ALSFRS-R; rs = 0.349, P = 0.020 and rs = 0.393, P = 0.008), while Prevotella -9 and Bacteroides operational taxonomic units (OTUs) were positively associated with lung function (FVC) in ALS patients ( rs = 0.304, P = 0.045, and rs = 0.300, P = 0.048, respectively). Prevotella -1 was positively correlated with white blood cell counts (WBC, rs = 0.347, P = 0.021), neutrophil percentage (Neu%, rs = 0.428, P = 0.004), and neutrophil-to-lymphocyte ratio (NLR, rs = 0.411, P = 0.006), but negatively correlated with lymphocyte percentage (Lym%, rs = -0.408, P = 0.006). In contrast, Streptococcus was negatively associated with Neu% ( rs = -0.445, P = 0.003) and NLR ( rs = -0.436, P = 0.003), while positively associated with Lym% ( rs = 0.437, P = 0.003). No significant differences in nasal microbiota richness and evenness were detected among the severe and mild ALS patients. CONCLUSIONS: ALS is accompanied by altered nasal microbial community composition and diversity. The findings presented here highlight the need to understand how dysbiosis of nasal microbiota may contribute to the development of ALS.

Environmental exposure to pesticides and Amyotrophic Lateral Sclerosis in the South of Spain / Exposición ambiental a pesticidas y esclerosis lateral amiotrófica en el sur de España

Objective: To determine if there is a relationship between environmental exposure to pesticides and the prevalence of Amyotrophic Lateral Sclerosis (ALS) in Andalusia. Method: We carried out a case–control study using the logistic regression method to verify the relationship between the prevalence of ALS in the area exposed to pesticides versus the unexposed area, through the Odds Ratio statistical test. Results: The study population consisted of 519 individuals diagnosed with ALS between January 2016 and December 2018 according to the CMBD (Minimum Basic Data Set) as cases. In the control group, we have 8,384,083 individuals obtained from data from the National Institute of Statistics (INE). The Odds Ratio (OR) was used as a measure of association between cases and controls, obtaining an OR between 0.76 and 1.08 for the confidence interval of the CI (95%). Conclusions: Despite the existence of various studies that suggest a possible association between environmental exposure to pesticides and the risk of Amyotrophic Lateral Sclerosis, our analysis of the Andalusian population did not find significant evidence of this association.(AU)

Objetivo: Analizar si existe una relación entre la exposición ambiental a pesticidas y la prevalencia de esclerosis lateral amiotrófica (ELA) en Andalucía. Métodos: Realizamos un estudio de casos y controles con regresión logística para esclarecer la relación entre la prevalencia de ELA en el área expuesta a pesticidas vs. el área sin exposición, mediante el cálculo de razón de probabilidades (odds ratio [OR]). Resultados: Incluimos un grupo de casos, con 519 individuos diagnosticados de ELA entre enero de 2016 y diciembre de 2018, obtenidos del conjunto mínimo básico de datos, y un grupo control con 8.384.083 individuos obtenidos de la base de datos del Instituto Nacional de Estadística. Se utilizó la OR para medir la asociación entre casos y controles, con un intervalo de confianza del 95% de 0,76-1,08. Conclusiones: A pesar de que varios estudios sugieren una posible asociación entre la exposición ambiental a pesticidas y un aumento en el riesgo de ELA, nuestro estudio sobre la población andaluza no halló datos significativos en favor de dicha hipótesis.(AU)

Aberrant enteric neuromuscular system and dysbiosis in amyotrophic lateral sclerosis.

Amyotrophic Lateral Sclerosis is a neuromuscular disease characterized by the progressive death of motor neurons and muscle atrophy. The gastrointestinal symptoms in ALS patients were largely ignored or underestimated. The relationship between the enteric neuromuscular system and microbiome in ALS progression is unknown. We performed longitudinal studies on the enteric neuron system (ENS) and microbiome in the ALS human-SOD1G93A (Superoxide Dismutase 1) transgenic mice. We treated age-matched wild-type and ALS mice with butyrate or antibiotics to investigate the microbiome and neuromuscular functions. We examined intestinal mobility, microbiome, an ENS marker GFAP (Glial Fibrillary Acidic Protein), a smooth muscle marker (SMMHC, Smooth Muscle Myosin Heavy Chain), and human colonoids. The distribution of human-G93A-SOD1 protein was tested as an indicator of ALS progression. At 2-month-old before ALS onset, SOD1G93A mice had significantly lower intestinal mobility, decreased grip strength, and reduced time in the rotarod. We observed increased GFAP and decreased SMMHC expression. These changes correlated with consistent increased aggregation of mutated SOD1G93A in the colon, small intestine, and spinal cord. Butyrate or antibiotics treated SOD1G93A mice had a significantly longer latency to fall in the rotarod test, reduced SOD1G93A aggregation, and enhanced enteric neuromuscular function. Feces from 2-month-old SOD1G93A mice significantly enhanced SOD1G93A aggregation in human colonoids transfected with a SOD1G93A-GFP plasmid. Longitudinal studies of microbiome data further showed the altered bacterial community related to autoimmunity (e.g., Clostridium sp. ASF502, Lachnospiraceae bacterium A4), inflammation (e.g., Enterohabdus Muris,), and metabolism (e.g., Desulfovibrio fairfieldensis) at 1- and 2-month-old SOD1G93A mice, suggesting the early microbial contribution to the pathological changes. We have demonstrated a novel link between the microbiome, hSOD1G93A aggregation, and intestinal mobility. Dysbiosis occurred at the early stage of the ALS mice before observed mutated-SOD1 aggregation and dysfunction of ENS. Manipulating the microbiome improves the muscle performance of SOD1G93A mice. We provide insights into the fundamentals of intestinal neuromuscular function and microbiome in ALS.

Gut microbiome and amyotrophic lateral sclerosis: A systematic review of current evidence.

Amyotrophic lateral sclerosis (ALS), characterized by a loss of motor neurons in the brain and spinal cord, is a relatively rare but currently incurable neurodegenerative disease. The global incidence of ALS is estimated as 1.75 per 100,000 person-years and the global prevalence is estimated as 4.1-8.4 per 100,000 individuals. Contributions from outside the central nervous system to the etiology of ALS have been increasingly recognized. Gut microbiome is one of the most quickly growing fields of research for ALS. In this article, we performed a comprehensive review of the results from existing animal and human studies, to provide an up-to-date summary of the current research on gut microbiome and ALS. In brief, we found relatively consistent results from animal studies, suggesting an altered gut microbiome composition in experimental ALS. Publication bias might however be a concern. Findings from human studies are largely inconclusive. A few animal and human studies demonstrated the usefulness of intervention with microbial-derived metabolites in modulating the disease progression of ALS. We discussed potential methodological concerns in these studies, including study design, statistical power, handling process of biospecimens and sequencing data, as well as statistical methods and interpretation of results. Finally, we made a few proposals for continued microbiome research in ALS, with the aim to provide valid, reproducible, and translatable findings.

The gut microbiome: a key player in the complexity of amyotrophic lateral sclerosis (ALS).

BACKGROUND: Much progress has been made in mapping genetic abnormalities linked to amyotrophic lateral sclerosis (ALS), but the majority of cases still present with no known underlying cause. Furthermore, even in families with a shared genetic abnormality there is significant phenotypic variability, suggesting that non-genetic elements may modify pathogenesis. Identification of such disease-modifiers is important as they might represent new therapeutic targets. A growing body of research has begun to shed light on the role played by the gut microbiome in health and disease with a number of studies linking abnormalities to ALS. MAIN BODY: The microbiome refers to the genes belonging to the myriad different microorganisms that live within and upon us, collectively known as the microbiota. Most of these microbes are found in the intestines, where they play important roles in digestion and the generation of key metabolites including neurotransmitters. The gut microbiota is an important aspect of the environment in which our bodies operate and inter-individual differences may be key to explaining the different disease outcomes seen in ALS. Work has begun to investigate animal models of the disease, and the gut microbiomes of people living with ALS, revealing changes in the microbial communities of these groups. The current body of knowledge will be summarised in this review. Advances in microbiome sequencing methods will be highlighted, as their improved resolution now enables researchers to further explore differences at a functional level. Proposed mechanisms connecting the gut microbiome to neurodegeneration will also be considered, including direct effects via metabolites released into the host circulation and indirect effects on bioavailability of nutrients and even medications. CONCLUSION: Profiling of the gut microbiome has the potential to add an environmental component to rapidly advancing studies of ALS genetics and move research a step further towards personalised medicine for this disease. Moreover, should compelling evidence of upstream neurotoxicity or neuroprotection initiated by gut microbiota emerge, modification of the microbiome will represent a potential new avenue for disease modifying therapies. For an intractable condition with few current therapeutic options, further research into the ALS microbiome is of crucial importance.

The Microbiome as a Modifier of Neurodegenerative Disease Risk.

The gut microbiome is increasingly implicated in modifying susceptibility to and progression of neurodegenerative diseases (NDs). In this review, we discuss roles for the microbiome in aging and in NDs. In particular, we summarize findings from human studies on microbiome alterations in Parkinson's disease, Alzheimer's disease, amyotrophic lateral sclerosis, and Huntington's disease. We assess animal studies of genetic and environmental models for NDs that investigate how manipulations of the microbiome causally impact the development of behavioral and neuropathological endophenotypes of disease. We additionally evaluate the likely immunological, neuronal, and metabolic mechanisms for how the gut microbiota may modulate risk for NDs. Finally, we speculate on cross-cutting features for microbial influences across multiple NDs and consider the potential for microbiome-targeted interventions for NDs.

The alteration of gut microbiome and metabolism in amyotrophic lateral sclerosis patients.

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease accompanied with severe paralysis or even death, while the pathogenesis of ALS is still unclear and no effective therapy exists. The accumulating evidence has indicated the association between gut microbiota and various neurological diseases. Thus, to explore the potential role of gut microbiome in ALS, 20 patients diagnosed with probable or definite ALS and 20 healthy controls were enrolled and their fecal excrements were collected. The analysis of fecal community diversity with 16S rDNA sequencing showed an obvious change in microbial structure of ALS patients, where Bacteroidetes at the phylum level and several microbes at the genus level were up-regulated, while Firmicutes at the phylum level and Megamonas at the genus level were down-regulated compared to healthy controls. Additionally, decreased gene function associated with metabolic pathways was observed in ALS patients. The metagenomics further demonstrated the discrepancies in microflora at the species level and relevant metabolites thereof were also revealed when combined with metabolomics. In conclusion, the altered composition of the gut microbiota and metabolic products in ALS patients provided deeper insights into the pathogenesis of ALS, and these biomarkers might be established as potential therapeutic targets which deserve further exploration.

Amyotrophic lateral sclerosis and intestinal microbiota-toward establishing cause and effect.

The intestinal microbiota may be involved, through metabolic gut-brain interactions, in a variety of neurological conditions. In this addendum, we summarize the findings of our recent study investigating the potentially modulatory influence of the microbiome in a transgenic ALS mouse model, and the possible application to human disease. We found that transgenic mice show evidence of dysbiosis, even at the pre-symptomatic stage, and have a more severe disease course under germ-free conditions or after receiving broad-spectrum antibiotics. We demonstrated that Akkermansia muciniphila ameliorated the disease in mice and that this may be due to the production of nicotinamide. We then conducted a preliminary study in human ALS and identified functionally similar alterations within the metagenome. Furthermore, we found that patients with ALS had lower systemic and CSF levels of nicotinamide, suggesting that the changes observed in the mouse model may be relevant to human disease.

The role of gut microbiota, butyrate and proton pump inhibitors in amyotrophic lateral sclerosis: a systematic review.

Aim of the study: We conducted a systematic review on existing literature in humans and animals, linking the gut microbiome with amyotrophic lateral sclerosis (ALS). Additionally, we sought to explore the role of the bacterially produced metabolite butyrate as well as of proton pump inhibitors (PPIs) in these associations.Materials and methods: Following PRISMA guidelines for systematic literature reviews, four databases (Medline, Scopus, Embase and Web of Science) were searched and screened by two independent reviewers against defined inclusion criteria. Six studies in humans and six animal studies were identified, summarized and reviewed.Results: Overall, the evidence accrued to date is supportive of changes in the gut microbiome being associated with ALS risk, and potentially progression, though observational studies are small (describing a total of 145 patients with ALS across all published studies), and not entirely conclusive.Conclusions: With emerging studies beginning to apply metagenome sequencing, more clarity regarding the importance and promise of the gut microbiome in ALS can be expected. Future studies may also help establish the therapeutic potential of butyrate, and the role of PPIs in these associations.

Temporal evolution of the microbiome, immune system and epigenome with disease progression in ALS mice.

Amyotrophic lateral sclerosis (ALS) is a terminal neurodegenerative disease. Genetic predisposition, epigenetic changes, aging and accumulated life-long environmental exposures are known ALS risk factors. The complex and dynamic interplay between these pathological influences plays a role in disease onset and progression. Recently, the gut microbiome has also been implicated in ALS development. In addition, immune cell populations are differentially expanded and activated in ALS compared to healthy individuals. However, the temporal evolution of both the intestinal flora and the immune system relative to symptom onset in ALS is presently not fully understood. To better elucidate the timeline of the various potential pathological factors, we performed a longitudinal study to simultaneously assess the gut microbiome, immunophenotype and changes in ileum and brain epigenetic marks relative to motor behavior and muscle atrophy in the mutant superoxide dismutase 1 (SOD1G93A) familial ALS mouse model. We identified alterations in the gut microbial environment early in the life of SOD1G93A animals followed by motor dysfunction and muscle atrophy, and immune cell expansion and activation, particularly in the spinal cord. Global brain cytosine hydroxymethylation was also altered in SOD1G93A animals at disease end-stage compared to control mice. Correlation analysis confirmed interrelationships with the microbiome and immune system. This study serves as a starting point to more deeply comprehend the influence of gut microorganisms and the immune system on ALS onset and progression. Greater insight may help pinpoint novel biomarkers and therapeutic interventions to improve diagnosis and treatment for ALS patients.This article has an associated First Person interview with the joint first authors of the paper.

Potential roles of gut microbiome and metabolites in modulating ALS in mice.

Amyotrophic lateral sclerosis (ALS) is a complex neurodegenerative disorder, in which the clinical manifestations may be influenced by genetic and unknown environmental factors. Here we show that ALS-prone Sod1 transgenic (Sod1-Tg) mice have a pre-symptomatic, vivarium-dependent dysbiosis and altered metabolite configuration, coupled with an exacerbated disease under germ-free conditions or after treatment with broad-spectrum antibiotics. We correlate eleven distinct commensal bacteria at our vivarium with the severity of ALS in mice, and by their individual supplementation into antibiotic-treated Sod1-Tg mice we demonstrate that Akkermansia muciniphila (AM) ameliorates whereas Ruminococcus torques and Parabacteroides distasonis exacerbate the symptoms of ALS. Furthermore, Sod1-Tg mice that are administered AM are found to accumulate AM-associated nicotinamide in the central nervous system, and systemic supplementation of nicotinamide improves motor symptoms and gene expression patterns in the spinal cord of Sod1-Tg mice. In humans, we identify distinct microbiome and metabolite configurations-including reduced levels of nicotinamide systemically and in the cerebrospinal fluid-in a small preliminary study that compares patients with ALS with household controls. We suggest that environmentally driven microbiome-brain interactions may modulate ALS in mice, and we call for similar investigations in the human form of the disease.

Intestinal microbiota composition in patients with amyotrophic lateral sclerosis: establishment of bacterial and archaeal communities analyses.

BACKGROUND: Emerging evidences have indicated that the composition of gut microbiota was significantly influenced by central nervous system diseases. The digestion and metabolism disturbances of patients with amyotrophic lateral sclerosis (ALS) might be strongly associated with ALS; however, this has rarely been evaluated in these populations. This study was to evaluate bacterial and archaeal composition of gut flora and the corresponding metabolism performance of these micro-organisms in fecal samples of patients with ALS. METHODS: A comparative study was performed on the intestinal microbiota from eight patients with ALS and eight healthy individuals at Huadong Hospital during November 2017 to April 2018; meanwhile, the metabolite concentrations of human endotoxin, short-chain fatty acids (SCFA), NO2-N/NO3-N, and γ-aminobutyric acid were also evaluated by spectrophotometry methods. The correlations between intestinal microbiota and metabolite concentration were compared between the two groups using one-way analysis of variance; the relative abundance of beneficial and harmful micro-organisms in fecal samples was also analyzed. RESULTS: In general, the richness and evenness of bacterial and archaeal communities of healthy individuals were healthier than that of patients with ALS. The phylum Firmicutes/Bacteroidetes ratio, genus Methanobrevibacter showed an enhancive tendency in patients with ALS, whereas the relative abundance of beneficial micro-organisms (genera Faecalibacterium and Bacteroides) presented a significant decrease tendency in patients with ALS. In addition, the average concentrations of human endotoxin, SCFA, NO2-N/NO3-N, and γ-aminobutyric acid in patients with ALS and healthy individuals were 64.2 vs. 65.3 EU/mL, 57.5 vs. 55.3 µg/mL, 5.7 vs. 5.3 ng/mL, and 6.1 vs. 5.4 µmol/L, respectively, indicating that the digestion and metabolism functions of gastrointestinal tract of patients might decline with this disease. CONCLUSIONS: The relative abundance of beneficial and harmful micro-organisms respectively showed decrease and increase tendency in patients with ALS.

Modification of the gut microbiome to combat neurodegeneration.

The gut microbiome was extensively researched for its biological variety and its potential role in propagating diseases outside of the gastrointestinal (GI) tract. Recently, a lot of effort was focused on comprehending the gut-brain axis and the bizarre communication between the GI system and the nervous system. Ample amount of studies being carried out also revealed the involvement of the gut microbiome in enhancing the degree of many neurological disorders, including neurodegenerative diseases. It was widely observed that there were distinct microbiome profiles and dysbiosis within patients suffering from Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and multiple sclerosis. Various approaches to re-establish the balance of the gut microbiome, from antibiotic therapy, fecal microbiota transplant, or ingestion of psychobiotics, are discussed within this review within the specific context of combating neurodegenerative diseases. Present studies and clinical trials indicate that although there is an immense potential of gut microbiome modification to be preventive or therapeutic, there are still many intercalated components of the gut-brain axis at play and thus, more research needs to be carried out to delineate microbiome factors that may potentially alleviate symptoms of neurodegeneration.

Gut microbiota in ALS: possible role in pathogenesis?

Introduction: The gut microbiota has important roles in maintaining human health. The microbiota and its metabolic byproducts could play a role in the pathogenesis of neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS). Areas covered: The authors evaluate the methods of assessing the gut microbiota, and also review how the gut microbiota affects the various physiological functions of the gut. The authors then consider how gut dysbiosis could theoretically affect the pathogenesis of ALS. They present the current evidence regarding the composition of the gut microbiota in ALS and in rodent models of ALS. Finally, the authors review therapies that could improve gut dysbiosis in the context of ALS. Expert opinion: Currently reported studies suggest some instances of gut dysbiosis in ALS patients and mouse models; however, these studies are limited, and more information with well-controlled larger datasets is required to make a definitive judgment about the role of the gut microbiota in ALS pathogenesis. Overall this is an emerging field that is worthy of further investigation. The authors advocate for larger studies using modern metagenomic techniques to address the current knowledge gaps.

Fungal Neurotoxins and Sporadic Amyotrophic Lateral Sclerosis.

We review several lines of evidence that point to a potential fungal origin of sporadic amyotrophic lateral sclerosis (ALS). ALS is the most common form of motor neuron disease (MND) in adults. It is a progressive and fatal disease. Approximately 90% cases of ALS are sporadic, and 5-10% are due to genetic mutations (familial). About 25 genes implicated in familial ALS have been identified so far, including SOD1 and TARDBP, the gene encoding 43 kDa transactive response (TAR) DNA-binding protein (TDP-43). Despite intensive research over many decades, the aetiology of sporadic ALS is still unknown. An environmental cause, including grass or soil-associated fungal infections, is suggested from a range of widely diverse lines of evidence. Clusters of ALS have been reported in soccer players, natives of Guam and farmers. Grass-associated fungi are known to produce a range of neurotoxins and, in symbiotic associations, high levels of fungal SOD1. Exposure of neurons to fungal neurotoxins elicits a significant increase in glutamate production. High levels of glutamate stimulate TDP-43 translocation and modification, providing a link between fungal infection and one of the molecular and histologic hallmarks of sporadic ALS. A recent study provided evidence of a variety of fungi in the cerebrospinal fluid and brain tissue of ALS patients. This review provides a rational explanation for this observation. If a fungal infection could be confirmed as a potential cause of ALS, this could provide a straightforward treatment strategy for this fatal and incurable disease.

Infectious agents and amyotrophic lateral sclerosis: another piece of the puzzle of motor neuron degeneration.

Amyotrophic lateral sclerosis (ALS) is the most common neurodegenerative disease affecting motor neurons (MN). This fatal disease is characterized by progressive muscle wasting and lacks an effective treatment. ALS pathogenesis has not been elucidated yet. In a small proportion of ALS patients, the disease has a familial origin, related to mutations in specific genes, which directly result in MN degeneration. By contrast, the vast majority of cases are though to be sporadic, in which genes and environment interact leading to disease in genetically predisposed individuals. Lately, the role of the environment has gained relevance in this field and an extensive list of environmental conditions have been postulated to be involved in ALS. Among them, infectious agents, particularly viruses, have been suggested to play an important role in the pathogenesis of the disease. These agents could act by interacting with some crucial pathways in MN degeneration, such as gene processing, oxidative stress or neuroinflammation. In this article, we will review the main studies about the involvement of microorganisms in ALS, subsequently discussing their potential pathogenic effect and integrating them as another piece in the puzzle of ALS pathogenesis.