Differences in the Composition of Gut Microbiota between Patients with Parkinson's Disease and Healthy Controls: A Cohort Study

Protection of Alzheimer's disease progression by a human-origin probiotics cocktail

Microbiome abnormalities (dysbiosis) significantly contribute to the progression of Alzheimer's disease (AD). However, the therapeutic efficacy of microbiome modulators in protecting against these ailments remains poorly studied. Herein, we tested a cocktail of unique probiotics, including 5 Lactobacillus and 5 Enterococcus strains isolated from infant gut with proven microbiome modulating capabilities. We aimed to determine the probiotics cocktail's efficacy in ameliorating AD pathology in a humanized AD mouse model of APP/PS1 strains. Remarkably, feeding mice with 1 × 1011 CFU per day in drinking water for 16 weeks significantly reduced cognitive decline (measured by the Morris Water Maze test) and AD pathology markers, such as Aβ aggregation, microglia activation, neuroinflammation, and preserved blood-brain barrier (BBB) tight junctions. The beneficial effects were linked to a reduced inflammatory microbiome, leading to decreased gut permeability and inflammation in both systemic circulation and the brain. Although both male and female mice showed overall improvements in cognition and biological markers, females did not exhibit improvements in specific markers related to inflammation and barrier permeability, suggesting that the underlying mechanisms may differ depending on sex. In conclusion, our results suggest that this unique probiotics cocktail could serve as a prophylactic agent to reduce the progression of cognitive decline and AD pathology. This is achieved by beneficially modulating the microbiome, improving intestinal tight junction proteins, reducing permeability in both gut and BBB, and decreasing inflammation in the gut, blood circulation, and brain, ultimately mitigating AD pathology and cognitive decline.

Gut-brain axis and brain health: modulating neuroinflammation, cognitive decline, and neurodegeneration

The microbiota-gut-brain axis is a pivotal medium of crosstalk between the central nervous system (CNS) and the gastrointestinal tract. It is an intricate network of synergistic molecular pathways that exert their effects far beyond their local vicinity and even affect the systemic functioning of the body. The current review explores the involvement of the gut-brain axis (GBA) in the functioning of the nervous system, with a special emphasis on the neurodegeneration, cognitive decline, and neuroinflammation that occur in Alzheimer's disease (AD) and Parkinson's disease (PD). Gut-derived microbial metabolites play an important role in facilitating this interaction. We also highlighted the complex interaction between gut-derived metabolites and CNS processes, demonstrating how microbial dysbiosis might result in clinical disorders. Short-chain fatty acids have neuroprotective properties, whereas branched-chain amino acids, trimethylamine-N-oxide (TMAO), and tryptophan derivatives such as indole have negative effects at high concentrations. Furthermore, we cover pharmaceutical and nonpharmacological approaches for restoring the gut microbial balance and promoting neurological health. We further expanded on nutritional therapies and lifestyle changes, such as the Mediterranean diet and exercise. Next, we focused on food-controlling habits such as caloric restriction and intermittent fasting. Moreover, interventional techniques such as prebiotics, probiotics, and pharmacological medications have also been utilized to modify the GBA. Historical microbiome research from early discoveries to recent studies linking gut health to cognitive and emotional well-being has increased our understanding of the GBA.

Microbiome-based therapies for Parkinson's disease

The human gut microbiome dysbiosis plays an important role in the pathogenesis of Parkinson's disease (PD). The bidirectional relationship between the enteric nervous system (ENS) and central nervous system (CNS) under the mediation of the gut-brain axis control the gastrointestinal functioning. This review article discusses key mechanisms by which modifications in the composition and function of the gut microbiota (GM) influence PD progression and motor control loss. Increased intestinal permeability, chronic inflammation, oxidative stress, α-synuclein aggregation, and neurotransmitter imbalances are some key factors that govern gastrointestinal pathology and PD progression. The bacterial taxa of the gut associated with PD development are discussed with emphasis on the enteric nervous system (ENS), as well as the impact of gut bacteria on dopamine production and levodopa metabolism. The pathophysiology and course of the disease are associated with several inflammatory markers, including TNF-α, IL-1β, and IL-6. Emerging therapeutic strategies targeting the gut microbiome include probiotics, prebiotics, synbiotics, postbiotics, and fecal microbiota transplantation (FMT). The article explored how dietary changes may affect the gut microbiota (GM) and the ways that can affect Parkinson's disease (PD), with a focus on nutrition-based, Mediterranean, and ketogenic diets. This comprehensive review synthesizes current evidence on the role of the gut microbiome in PD pathogenesis and explores its potential as a therapeutic target. Understanding these complex interactions may assist in the development of novel diagnostic tools and treatment options for this neurodegenerative disorder.

Atypical gut microbiota composition in a mouse model of developmental stuttering

Developmental stuttering is a complex neurodevelopmental disorder characterized by disfluent speech. It has been associated with mutations in genes involved in lysosomal enzyme trafficking. Mice with mutations in one such gene, Gnptab, exhibit atypical vocalizations analogous to stuttering in humans. This mouse model has enabled the study of various molecular mechanisms related to the disorder. Simultaneously, an increasing number of reports have suggested the role of gut microbiota in altered brain function and development in neurological disorders. In this study, we compared gut microbiota profiles from Gnptab mutant mice to wildtype control mice. Microbiome analysis demonstrated a distinct microbiota profile in Gnptab mutant mice. The most significant alteration was an increased relative abundance of Akkermansia, a genus of mucin degrading bacteria, which has previously been associated with multiple neurological disorders. Moreover, the altered microbiota profile of these mice was predicted to result in differences in abundance of several metabolic pathways, including short chain fatty acid and lipopolysaccharide synthesis. These pathways may play a role in the onset, progression and persistence of developmental stuttering. This is the first study to show a potential link between developmental stuttering and changes in the gut microbiota, laying the groundwork for a new research direction.

The Microbiota-Gut-Brain Axis and Neurological Disorders: A Comprehensive Review

Microbes have inhabited the earth for hundreds of millions of years longer than humans. The microbiota-gut-brain axis (MGBA) represents a bidirectional communication pathway. These communications occur between the central nervous system (CNS), the enteric nervous system (ENS), and the emotional and cognitive centres of the brain. The field of research on the gut-brain axis has grown significantly during the past two decades. Signalling occurs between the gut microbiota and the brain through the neural, endocrine, immune, and humoral pathways. A substantial body of evidence indicates that the MGBA plays a pivotal role in various neurological diseases. These include Alzheimer's disease (AD), autism spectrum disorder (ASD), Rett syndrome, attention deficit hyperactivity disorder (ADHD), non-Alzheimer's neurodegeneration and dementias, fronto-temporal lobe dementia (FTLD), Wilson-Konovalov disease (WD), multisystem atrophy (MSA), Huntington's chorea (HC), Parkinson's disease (PD), multiple sclerosis (MS), amyotrophic lateral sclerosis (ALS), temporal lobe epilepsy (TLE), depression, and schizophrenia (SCZ). Furthermore, the bidirectional correlation between therapeutics and the gut-brain axis will be discussed. Conversely, the mood of delivery, exercise, psychotropic agents, stress, and neurologic drugs can influence the MGBA. By understanding the MGBA, it may be possible to facilitate research into microbial-based interventions and therapeutic strategies for neurological diseases.

Probiotics and the microbiota-gut-brain axis in neurodegeneration: Beneficial effects and mechanistic insights

Neurodegenerative diseases (NDs) are a group of heterogeneous disorders with a high socioeconomic burden. Although pharmacotherapy is currently the principal therapeutic approach for the management of NDs, mounting evidence supports the notion that the protracted application of available drugs would abate their dopaminergic outcomes in the long run. The therapeutic application of microbiome-based modalities has received escalating attention in biomedical works. In-depth investigations of the bidirectional communication between the microbiome in the gut and the brain offer a multitude of targets for the treatment of NDs or maximizing the patient's quality of life. Probiotic administration is a well-known microbial-oriented approach to modulate the gut microbiota and potentially influence the process of neurodegeneration. Of note, there is a strong need for further investigation to map out the mechanistic prospects for the gut-brain axis and the clinical efficacy of probiotics. In this review, we discuss the importance of microbiome modulation and hemostasis via probiotics, prebiotics, postbiotics and synbiotics in ameliorating pathological neurodegenerative events. Also, we meticulously describe the underlying mechanism of action of probiotics and their metabolites on the gut-brain axis in different NDs. We suppose that the present work will provide a functional direction for the use of probiotic-based modalities in promoting current practical treatments for the management of neurodegenerative-related diseases.

Update of the list of qualified presumption of safety (QPS) recommended microbiological agents intentionally added to food or feed as notified to EFSA 20: Suitability of taxonomic units notified to EFSA until March 2024

The qualified presumption of safety (QPS) process was developed to provide a safety assessment approach for microorganisms intended for use in food or feed chains. In the period covered by this statement, no new information was found that would change the status of previously recommended QPS TUs. The TUs in the QPS list were updated based on a verification, against their respective authoritative databases, of the correctness of the names and completeness of synonyms. A new procedure has been established to ensure the TUs are kept up to date in relation to recent taxonomical insights. Of 83 microorganisms notified to EFSA between October 2023 and March 2024 (47 as feed additives, 25 as food enzymes or additives, 11 as novel foods), 75 were not evaluated because: 15 were filamentous fungi, 1 was Enterococcus faecium, 10 were Escherichia coli, 1 was a Streptomyces (all excluded from the QPS evaluation) and 48 were TUs that already have a QPS status. Two of the other eight notifications were already evaluated for a possible QPS status in the previous Panel Statement: Heyndrickxia faecalis (previously Weizmannia faecalis) and Serratia marcescens. One was notified at genus level so could not be assessed for QPS status. The other five notifications belonging to five TUs were assessed for possible QPS status. Akkermansia muciniphila and Actinomadura roseirufa were still not recommended for QPS status due to safety concerns. Rhizobium radiobacter can be recommended for QPS status with the qualification for production purposes. Microbacterium arborescens and Burkholderia stagnalis cannot be included in the QPS list due to a lack of body of knowledge for its use in the food and feed chain and for B. stagnalis also due to safety concerns. A. roseirufa and B. stagnalis have been excluded from further QPS assessment.

Microbiota-brain axis: Exploring the role of gut microbiota in psychiatric disorders - A comprehensive review

Mental illness is a hidden epidemic in modern science that has gradually spread worldwide. According to estimates from the World Health Organization (WHO), approximately 10% of the world's population suffers from various mental diseases each year. Worldwide, financial and health burdens on society are increasing annually. Therefore, understanding the different factors that can influence mental illness is required to formulate novel and effective treatments and interventions to combat mental illness. Gut microbiota, consisting of diverse microbial communities residing in the gastrointestinal tract, exert profound effects on the central nervous system through the gut-brain axis. The gut-brain axis serves as a conduit for bidirectional communication between the two systems, enabling the gut microbiota to affect emotional and cognitive functions. Dysbiosis, or an imbalance in the gut microbiota, is associated with an increased susceptibility to mental health disorders and psychiatric illnesses. Gut microbiota is one of the most diverse and abundant groups of microbes that have been found to interact with the central nervous system and play important physiological functions in the human gut, thus greatly affecting the development of mental illnesses. The interaction between gut microbiota and mental health-related illnesses is a multifaceted and promising field of study. This review explores the mechanisms by which gut microbiota influences mental health, encompassing the modulation of neurotransmitter production, neuroinflammation, and integrity of the gut barrier. In addition, it emphasizes a thorough understanding of how the gut microbiome affects various psychiatric conditions.

Relationships Between Rapid Eye Movement Sleep Behavior Disorder and Parkinson's Disease: Indication from Gut Microbiota Alterations

Rapid eye movement sleep behavior disorder (RBD) has a close relationship with Parkinson's disease (PD) and was even regarded as the most reliable hallmark of prodromal PD. RBD might have similar changes in gut dysbiosis to PD, but the relationship between RBD and PD in gut microbial alterations is rarely studied. In this study, we aim to investigate whether there were consistent changes between RBD and PD in gut microbiota, and found some specific biomarkers in RBD that might indicate phenoconversion to PD. Alpha-diversity showed no remarkable difference and beta-diversity showed significant differences based on the unweighted (R = 0.035, P = 0.037) and weighted (R = 0.0045, P = 0.008) UniFrac analysis among idiopathic RBD (iRBD), PD with RBD, PD without RBD and normal controls (NC). Enterotype distribution indicated iRBD, PD with RBD and PD without RBD were Ruminococcus-dominant while NC were Bacteroides-dominant. 7 genera (4 increased: Aerococcus, Eubacterium, Gordonibacter and Stenotrophomonas, 3 decreased: Butyricicoccus, Faecalibacterium and Haemophilus) were consistently changed in iRBD and PD with RBD. Among them, 4 genera (Aerococcus, Eubacterium, Butyricicoccus, Faecalibacterium) remained distinctive in the comparison between PD with RBD and PD without RBD. Through clinical correlation analysis, Butyricicoccus and Faecalibacterium were found negatively correlated with the severity of RBD (RBD-HK). Functional analysis showed iRBD had similarly increased staurosporine biosynthesis to PD with RBD. Our study indicates that RBD had similar gut microbial changes to PD. Decreased Butyricicoccus and Faecalibacterium might be potential hallmarks of phenoconversion of RBD to PD.

Does gut brain axis has an impact on Parkinson's disease (PD)?

Parkinson's Disease (PD) is becoming a growing global concern by being the second most prevalent disease next to Alzheimer's Disease (AD). Henceforth new exploration is needed in search of new aspects towards the disease mechanism and origin. Evidence from recent studies has clearly stated the role of Gut Microbiota (GM) in the maintenance of the brain and as a root cause of various diseases and disorders including other neurological conditions. In the case of PD, with an unknown etiology, the GM is said to have a larger impact on the disease pathophysiology. Although GM and its metabolites are crucial for maintaining the normal physiology of the host, it is an undeniable fact that there is an influence of GM in the pathophysiology of PD. As such the Enteroendocrine Cells (EECs) in the epithelium of the intestine are one of the significant regulators of the gut-brain axis and act as a communication mediator between the gut and the brain. The communication is established via the molecules of neuroendocrine which are said to have a crucial part in neurological diseases such as AD, PD, and other psychiatry-related disorders. This review is focused on understanding the proper role of GM and EECs in PD. Here, we also focus on some of the metabolites and compounds that can interact with the PD genes causing various dysfunctions in the cell and facilitating the disease conditions using bioinformatical tools. Various mechanisms concerning EECs and PD, their identification, the latest studies, and available current therapies have also been discussed.

Alterations of gut microbiota and its correlation with the liver metabolome in the process of ameliorating Parkinson's disease with Buyang Huanwu decoction

ETHNOPHARMACOLOGICAL RELEVANCE

Buyang Huanwu decoction (BHD), a famous traditional Chinese medicine (TCM) formula, was first recorded in Qing Dynasty physician Qingren Wang's Yi Lin Gai Cuo. BHD has been widely utilized in the treatment of patients with neurological disorders, including Parkinson's disease (PD). However, the underlying mechanism has not been fully elucidated. In particular, little is known about the role of gut microbiota.

AIM OF THE STUDY

We aimed to reveal the alterations and functions of gut microbiota and its correlation with the liver metabolome in the process of improving PD with BHD.

MATERIALS AND METHODS

The cecal contents were collected from PD mice treated with or without BHD. 16S rRNA gene sequencing was performed on an Illumina MiSeq-PE250 platform, and the ecological structure, dominant taxa, co-occurrence patterns, and function prediction of the gut microbial community were analyzed by multivariate statistical methods. The correlation between differential microbial communities in the gut and differentially accumulated metabolites in the liver was analyzed using Spearman's correlation analysis.

RESULTS

The abundance of Butyricimonas, Christensenellaceae, Coprococcus, Peptococcaceae, Odoribacteraceae, and Roseburia was altered significantly in the model group, which was by BHD. Ten genera, namely Dorea, unclassified_Lachnospiraceae, Oscillospira, unidentified_Ruminococcaceae, unclassified_Clostridiales, unidentified_Clostridiales, Bacteroides, unclassified_Prevotellaceae, unidentified_Rikenellaceae, and unidentified_S24-7, were identified as key bacterial communities. According to the function prediction of differential genera, the mRNA surveillance pathway might be a target of BHD. Integrated analysis of gut microbiota and the liver metabolome revealed that several gut microbiota genera such as Parabacteroides, Ochrobactrum, Acinetobacter, Clostridium, and Halomonas, were positively or negatively correlated with some nervous system-related metabolites, such as L-carnitine, L-pyroglutamic acid, oleic acid, and taurine.

CONCLUSIONS

Gut microbiota might be a target of BHD in the process of ameliorating PD. Our findings provide novel insight into the mechanisms underlying the effects of BHD on PD and contribute to the development of TCM.

Microglia regulation of central nervous system myelin health and regeneration

Microglia are resident macrophages of the central nervous system that have key functions in its development, homeostasis and response to damage and infection. Although microglia have been increasingly implicated in contributing to the pathology that underpins neurological dysfunction and disease, they also have crucial roles in neurological homeostasis and regeneration. This includes regulation of the maintenance and regeneration of myelin, the membrane that surrounds neuronal axons, which is required for axonal health and function. Myelin is damaged with normal ageing and in several neurodegenerative diseases, such as multiple sclerosis and Alzheimer disease. Given the lack of approved therapies targeting myelin maintenance or regeneration, it is imperative to understand the mechanisms by which microglia support and restore myelin health to identify potential therapeutic approaches. However, the mechanisms by which microglia regulate myelin loss or integrity are still being uncovered. In this Review, we discuss recent work that reveals the changes in white matter with ageing and neurodegenerative disease, how this relates to microglia dynamics during myelin damage and regeneration, and factors that influence the regenerative functions of microglia.

Akkermansia in the gastrointestinal tract as a modifier of human health

Akkermansia sp are common members of the human gut microbiota. Multiple reports have emerged linking the abundance of A. muciniphila to health benefits and disease risk in humans and animals. This review highlights findings linking Akkermansia species in the gastrointestinal (GI) tract to health outcomes across a spectrum of disorders, encompassing those that affect the digestive, respiratory, urinary, and central nervous systems. The mechanism through which Akkermansia exerts a beneficial versus a detrimental effect on health is likely dependent on the genetic makeup of the host metabolic capacity and immunomodulatory properties of the strain, the competition or cooperation with other members of the host microbiota, as well as synergy with co-administered therapies.

Potential Effects of Akkermansia Muciniphila in Aging and Aging-Related Diseases: Current Evidence and Perspectives

Akkermansia muciniphila (A. muciniphila) is an anaerobic bacterium that widely colonizes the mucus layer of the human and animal gut. The role of this symbiotic bacterium in host metabolism, inflammation, and cancer immunotherapy has been extensively investigated over the past 20 years. Recently, a growing number of studies have revealed a link between A. muciniphila, and aging and aging-related diseases (ARDs). Research in this area is gradually shifting from correlation analysis to exploration of causal relationships. Here, we systematically reviewed the association of A. muciniphila with aging and ARDs (including vascular degeneration, neurodegenerative diseases, osteoporosis, chronic kidney disease, and type 2 diabetes). Furthermore, we summarize the potential mechanisms of action of A. muciniphila and offer perspectives for future studies.

Dysbiosis of the Beneficial Gut Bacteria in Patients with Parkinson's Disease from India

Objectives

Recent advancement in understanding neurological disorders has revealed the involvement of dysbiosis of the gut microbiota in the pathophysiology of Parkinson's disease (PD). We sequenced microbial DNA using fecal samples collected from PD cases and healthy controls (HCs) to evaluate the role of gut microbiota.

Methods

Full-length bacterial 16S rRNA gene sequencing of fecal samples was performed using amplified polymerase chain reaction (PCR) products on the GridION Nanopore sequencer. Sequenced data were analyzed using web-based tools BugSeq and MicrobiomeAnalyst.

Results

We found that certain bacterial families like Clostridia UCG 014, Cristensenellaceae, and Oscillospiraceae are higher in abundance, and Lachinospiracea, Coriobacteriaceae and genera associated with short-chain fatty acid production, Faecalibacterium, Fusicatenibacter, Roseburia and Blautia, are lower in abundance among PD cases when compared with the HC. Genus Akkermansia, Dialister, Bacteroides, and Lachnospiraceae NK4A136 group positively correlated with constipation in PD.

Conclusion

Observations from this study support the other global research on the PD gut microbiome background and provide fresh insight into the gut microbial composition of PD patients from a south Indian population. We report a higher abundance of Clostridia UCG 014 group, previously not linked to PD.

From-Toilet-to-Freezer: A Review on Requirements for an Automatic Protocol to Collect and Store Human Fecal Samples for Research Purposes

The composition, viability and metabolic functionality of intestinal microbiota play an important role in human health and disease. Studies on intestinal microbiota are often based on fecal samples, because these can be sampled in a non-invasive way, although procedures for sampling, processing and storage vary. This review presents factors to consider when developing an automated protocol for sampling, processing and storing fecal samples: donor inclusion criteria, urine-feces separation in smart toilets, homogenization, aliquoting, usage or type of buffer to dissolve and store fecal material, temperature and time for processing and storage and quality control. The lack of standardization and low-throughput of state-of-the-art fecal collection procedures promote a more automated protocol. Based on this review, an automated protocol is proposed. Fecal samples should be collected and immediately processed under anaerobic conditions at either room temperature (RT) for a maximum of 4 h or at 4 °C for no more than 24 h. Upon homogenization, preferably in the absence of added solvent to allow addition of a buffer of choice at a later stage, aliquots obtained should be stored at either -20 °C for up to a few months or -80 °C for a longer period-up to 2 years. Protocols for quality control should characterize microbial composition and viability as well as metabolic functionality.

The gut-brain vascular axis in neuroinflammation

The multifaceted microbiota characterizing our gut plays a crucial role in maintaining immune, metabolic and tissue homeostasis of the intestine as well as of distal organs, including the central nervous system. Microbial dysbiosis is reported in several inflammatory intestinal diseases characterized by the impairment of the gut epithelial and vascular barriers, defined as leaky gut, and it is reported as a potential danger condition associated with the development of metabolic, inflammatory and neurodegenerative diseases. Recently, we pointed out the strict connection between the gut and the brain via a novel vascular axis. Here we want to deepen our knowledge on the gut-brain axis, with particular emphasis on the connection between microbial dysbiosis, leaky gut, cerebral and gut vascular barriers, and neurodegenerative diseases. The firm association between microbial dysbiosis and impairment of the vascular gut-brain axis will be summarized in the context of protection, amelioration or boosting of Alzheimer, Parkinson, Major depressive and Anxiety disorders. Understanding the relationship between disease pathophysiology, mucosal barrier function and host-microbe interaction will foster the use of the microbiome as biomarker for health and disease as well as a target for therapeutic and nutritional advances.

Akkermansia muciniphila in neuropsychiatric disorders: friend or foe?

An accumulating body of evidence suggests that the bacterium Akkermansia muciniphila exhibits positive systemic effects on host health, mainly by improving immunological and metabolic functions, and it is therefore regarded as a promising potential probiotic. Recent clinical and preclinical studies have shown that A. muciniphila plays a vital role in a variety of neuropsychiatric disorders by influencing the host brain through the microbiota-gut-brain axis (MGBA). Numerous studies observed that A. muciniphila and its metabolic substances can effectively improve the symptoms of neuropsychiatric disorders by restoring the gut microbiota, reestablishing the integrity of the gut mucosal barrier, regulating host immunity, and modulating gut and neuroinflammation. However, A. muciniphila was also reported to participate in the development of neuropsychiatric disorders by aggravating inflammation and influencing mucus production. Therefore, the exact mechanism of action of A. muciniphila remains much controversial. This review summarizes the proposed roles and mechanisms of A. muciniphila in various neurological and psychiatric disorders such as depression, anxiety, Parkinson's disease, Alzheimer's disease, multiple sclerosis, strokes, and autism spectrum disorders, and provides insights into the potential therapeutic application of A. muciniphila for the treatment of these conditions.

A Critical Perspective on the Supplementation of Akkermansia muciniphila: Benefits and Harms

Akkermansia muciniphila is a mucin-degrading bacterium of the intestinal niche, exerting beneficial effects on the host metabolic profile. Accumulating evidence indicated Akkermansia as a promising therapeutic probiotic against metabolic disorders such as obesity, type 2 diabetes and cardiovascular diseases. However, in specific intestinal microenvironments, its excessive enrichment may be not beneficial. Conditions like inflammatory bowel disease (IBD), Salmonella typhimurium infection or post-antibiotic reconstitution may not benefit from Akkermansia supplementation. Furthermore, using Akkermansia in patients with endocrine and gynecological disorders-such as polycystic ovary syndrome (PCOS) or endometriosis-that have a higher risk of developing IBD, should be critically evaluated. In addition, a cautionary note comes from the neurological field, as the gut microbiota of patients suffering from Parkinson's disease or multiple sclerosis exhibits a characteristic signature of Akkermansia municiphila abundance. Overall, considering these controversial points, the use of Akkermansia should be evaluated on an individual basis, avoiding risking unexpected effects.

Health and Disease: Akkermansia muciniphila, the Shining Star of the Gut Flora

Akkermansia muciniphila (A. muciniphila) has drawn much attention as an important gut microbe strain in recent years. A. muciniphila can influence the occurrence and development of diseases of the endocrine, nervous, digestive, musculoskeletal, and respiratory systems and other diseases. It can also improve immunotherapy for some cancers. A. muciniphila is expected to become a new probiotic in addition to Lactobacillus and Bifidobacterium. An increase in A. muciniphila abundance through direct or indirect A. muciniphila supplementation may inhibit or even reverse disease progression. However, some contrary findings are found in type 2 diabetes mellitus and neurodegenerative diseases, where increased A. muciniphila abundance may aggravate the diseases. To enable a more comprehensive understanding of the role of A. muciniphila in diseases, we summarize the relevant information on A. muciniphila in different systemic diseases and introduce regulators of A. muciniphila abundance to promote the clinical transformation of A. muciniphila research.

Dysbiosis of Gut Microbiota from the Perspective of the Gut-Brain Axis: Role in the Provocation of Neurological Disorders

The gut-brain axis is a bidirectional communication network connecting the gastrointestinal tract and central nervous system. The axis keeps track of gastrointestinal activities and integrates them to connect gut health to higher cognitive parts of the brain. Disruption in this connection may facilitate various neurological and gastrointestinal problems. Neurodegenerative diseases are characterized by the progressive dysfunction of specific populations of neurons, determining clinical presentation. Misfolded protein aggregates that cause cellular toxicity and that aid in the collapse of cellular proteostasis are a defining characteristic of neurodegenerative proteinopathies. These disorders are not only caused by changes in the neural compartment but also due to other factors of non-neural origin. Mounting data reveal that the majority of gastrointestinal (GI) physiologies and mechanics are governed by the central nervous system (CNS). Furthermore, the gut microbiota plays a critical role in the regulation and physiological function of the brain, although the mechanism involved has not yet been fully interpreted. One of the emerging explanations of the start and progression of many neurodegenerative illnesses is dysbiosis of the gut microbial makeup. The present understanding of the literature surrounding the relationship between intestinal dysbiosis and the emergence of certain neurological diseases, such as Alzheimer's disease, Parkinson's disease, Huntington's disease, and multiple sclerosis, is the main emphasis of this review. The potential entry pathway of the pathogen-associated secretions and toxins into the CNS compartment has been explored in this article at the outset of neuropathology. We have also included the possible mechanism of undelaying the synergistic effect of infections, their metabolites, and other interactions based on the current understanding.

Microbiota: Not Just a Gut Feeling

Every year, an increasing number of scientific papers are published on the gut microbiome [...].

The Interplay between Gut Microbiota and Parkinson's Disease: Implications on Diagnosis and Treatment

The bidirectional interaction between the gut microbiota (GM) and the Central Nervous System, the so-called gut microbiota brain axis (GMBA), deeply affects brain function and has an important impact on the development of neurodegenerative diseases. In Parkinson’s disease (PD), gastrointestinal symptoms often precede the onset of motor and non-motor manifestations, and alterations in the GM composition accompany disease pathogenesis. Several studies have been conducted to unravel the role of dysbiosis and intestinal permeability in PD onset and progression, but the therapeutic and diagnostic applications of GM modifying approaches remain to be fully elucidated. After a brief introduction on the involvement of GMBA in the disease, we present evidence for GM alterations and leaky gut in PD patients. According to these data, we then review the potential of GM-based signatures to serve as disease biomarkers and we highlight the emerging role of probiotics, prebiotics, antibiotics, dietary interventions, and fecal microbiota transplantation as supportive therapeutic approaches in PD. Finally, we analyze the mutual influence between commonly prescribed PD medications and gut-microbiota, and we offer insights on the involvement also of nasal and oral microbiota in PD pathology, thus providing a comprehensive and up-to-date overview on the role of microbial features in disease diagnosis and treatment.

Oral ingestion of the environmental toxicant trichloroethylene in rats induces alterations in the gut microbiome: Relevance to idiopathic Parkinson's disease

Microbial alterations within the gut microbiome appear to be a common feature of individuals with Parkinson's disease (PD), providing further evidence for the role of the gut-brain axis in PD development. As a major site of contact with the environment, questions have emerged surrounding the cause and effect of alterations to the gut microbiome by environmental contaminants associated with PD risk, such as pesticides, metals, and organic solvents. Recent data from our lab shows that ingestion of the industrial byproduct and environmental pollutant trichloroethylene (TCE) induces key Parkinsonian pathology within aged rats, including the degeneration of dopaminergic neurons, α-synuclein accumulation, neuroinflammation, and endolysosomal deficits. As TCE is the most common organic contaminant within drinking water, we postulated that ingestion of TCE associated with PD-related neurodegeneration may alter the gut microbiome to a similar extent as observed in persons with PD. To assess this, we collected fecal samples from adult rats treated with 200 mg/kg TCE over 6 weeks via oral gavage - the dose that produced nigrostriatal neurodegeneration - and analyzed the gut microbiome via whole genome shotgun sequencing. Our results showed changes in gut microorganisms reflective of the microbial signatures observed in individuals with idiopathic PD, such as decreased abundance of short-chain fatty acid producing Blautia and elevated lactic-acid producing Bifidobacteria, as well as genera who contain species previously reported as opportunistic pathogens such as Clostridium. From these experimental data, we postulate that TCE exposure within contaminated drinking water could induce alterations of the gut microbiome that contributes to chronic disease risk, including idiopathic PD.