The microbiome-gut-brain axis in Parkinson disease - from basic research to the clinic

Sleep deprivation accelerates Parkinson's disease via modulating gut microbiota associated microglial activation and oxidative stress

The interplay between Parkinson's disease (PD) and sleep disturbances suggests that sleep problems constitute a risk factor for PD progression, but the underlying mechanisms remain unclear. Microglial activation and oxidative stress are considered to play an important role in the pathogenesis of aging and neurodegenerative diseases. We hypothesized that sleep deprivation (SD) could exacerbate PD progression via modulating microglial activation and oxidative stress. To test this hypothesis, we established a PD mouse model using 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), then subjected the mice to SD. A battery of behavioral tests, including rotarod, pole, adhesive removal, and open field tests, were used to assess motor function. Our study showed that SD exacerbated motor deficits, loss of tyrosine hydroxylase (TH), microglial activation and oxidative stress damage in PD model mice. Fecal microbiota transplantation experiments revealed that SD mediated PD progression, microglial activation and oxidative stress via the gut microbiota. 16S rRNA sequencing analysis indicated that SD increased the abundances of bacteria such as Bacteroidaceae, while decreasing the abundances of bacteria including Lactobacillus. Non-targeted metabolomic analysis of gut microbiota-derived metabolites revealed that SD significantly increased the production of adenosine (ADO), a purine metabolite. Probiotic supplementation reversed the effects of SD on motor deficits, dopaminergic neuron loss, microglial activation and oxidative stress damage in PD mice; it also decreased SD-induced ADO production. Administration of Adenosine A2A receptor (A2AR) inhibitors, Istradefylline (Ist), attenuated the roles of SD and ADO in promoting microglial activation, oxidative stress and PD progression. Taken together, our findings indicate that SD accelerates PD progression via regulating microbiota associated microglial activation and oxidative stress, suggesting that efforts to improve sleep quality can be used to prevent and treat PD.

Gut microbiota-astrocyte axis: new insights into age-related cognitive decline

With the rapidly aging human population, age-related cognitive decline and dementia are becoming increasingly prevalent worldwide. Aging is considered the main risk factor for cognitive decline and acts through alterations in the composition of the gut microbiota, microbial metabolites, and the functions of astrocytes. The microbiota-gut-brain axis has been the focus of multiple studies and is closely associated with cognitive function. This article provides a comprehensive review of the specific changes that occur in the composition of the gut microbiota and microbial metabolites in older individuals and discusses how the aging of astrocytes and reactive astrocytosis are closely related to age-related cognitive decline and neurodegenerative diseases. This article also summarizes the gut microbiota components that affect astrocyte function, mainly through the vagus nerve, immune responses, circadian rhythms, and microbial metabolites. Finally, this article summarizes the mechanism by which the gut microbiota-astrocyte axis plays a role in Alzheimer's and Parkinson's diseases. Our findings have revealed the critical role of the microbiota-astrocyte axis in age-related cognitive decline, aiding in a deeper understanding of potential gut microbiome-based adjuvant therapy strategies for this condition.

Lung-specific SFTPC mutations lead to neurodevelopmental disorders with neuroinflammation

Neurodevelopmental disorders (NDDs) are characterized by diverse genetic underpinnings and abnormalities in the structure and function of the central nervous system. While the lung-specific SFTPC gene is critical for pulmonary development and homeostasis, its potential involvement in NDDs has not been previously explored. In this study, we identified compound heterozygous variants of SFTPC in two children diagnosed with NDDs, inherited from carrier parents. Bioinformatic analyses predicted these variants to be deleterious, and patient blood samples confirmed reduced SFTPC protein levels. To investigate the functional impact of these mutations, we generated a Sftpc-knock-in (Sftpc-KI) mouse model carrying the defective alleles. The Sftpc-KI mice exhibited significantly reduced Sftpc expression in both lung and blood samples. Remarkably, despite its lung-specific expression, Sftpc-KI mice displayed pronounced impairments in neurobehavioral performance. Proteomic analyses of the Sftpc-KI mouse brain revealed dysregulated proteins associated with neuroinflammation. Furthermore, primary microglial cells isolated from these mice exhibited heightened expression of M1 activation markers, indicating aberrant microglial activation. Our findings uncover a previously unrecognized connection between lung-specific SFTPC dysfunction and neurodevelopmental disorders, suggesting the existence of a novel brain-lung axis and opening new avenues for research into the molecular mechanisms underlying NDDs.

The roles of functional bacterial amyloids in neurological physiology and pathophysiology: Pros and cons for neurodegeneration

Bacterial biofilms, which are complex communities of microorganisms encapsulated in a self-produced extracellular matrix, play critical roles in various diseases. Recent research has underscored the dualistic nature of amyloids, structural proteins within these biofilms, in human health, particularly highlighting the significant role in neurodegenerative disorders such as Alzheimer's (AD) and Parkinson's disease (PD). These amyloids modulate the immune response by inducing the production of interleukin-10 (IL-10), which plays a role in anti-inflammatory processes. Additionally, they inhibit the aggregation of human amyloids and enhance the integrity of the intestinal barrier. Detrimentally, they exacerbate neuroinflammation by elevating inflammatory cytokines and promoting the aggregation of human amyloid proteins-amyloid-β (Aβ) in AD and α-synuclein (αS) in PD-through a process known as cross-seeding. Moreover, bacterial amyloids have also been shown to stimulate the production of anti-curli/DNA antibodies, which are implicated in the pathogenesis of autoimmune diseases. Given their dualistic nature, bacterial amyloids may, under specific conditions, function as beneficial proteins for human health. This understanding holds promise for the development of targeted therapeutic strategies aimed at modulating bacterial amyloids in the context of neurodegenerative diseases, such as AD and PD.

Effects of Different Cow-Milk Beta-Caseins on the Gut-Brain Axis: A Narrative Review of Preclinical, Animal, and Human Studies

The gut and brain communicate through bidirectional neural, endocrine, and immune signals to coordinate central nervous system activity with gastrointestinal function. Dysregulated inflammation can promote immune cell activation and increase entero-endocrine signaling and intestinal permeability; hence, a functional gut-brain axis is necessary for a healthy digestive system. The consumption of milk products can lead to gut discomfort via effects on gastrointestinal tract function and the inflammatory state, which, in turn, affect the brain. A1 β-casein and A2 β-casein are major components of bovine-milk protein, and their digestion may result in different physiological effects following the consumption of milk products. Peptides derived from A1 β-casein, such as β-casomorphins, may increase gut dysfunction and inflammation, thereby modulating the availability of bioactive metabolites in the bloodstream and contribute to changes in cognitive function. This narrative review examines the functional interrelationships between the consumption of cow-milk-derived β-caseins and their effect on the brain, immune system, and the gut, which together comprise the gut-brain axis.

Updated MDSGene review on the clinical and genetic spectrum of LRRK2 variants in Parkinson´s disease

Pathogenic variants in the LRRK2 gene are one of the most commonly identifiable monogenic causes of Parkinson´s disease (PD, PARK-LRRK2). This systematic MDSGene literature review comprehensively summarizes published demographic, clinical, and genetic findings related to LRRK2 variants ( https://www.mdsgene.org/ ). Data on 4660 individuals with 283 different variants were curated. The median age at onset in the PD patients with available information was 56 years, notably, with approximately one-third having PD onset <50 years. Tremor was the most frequently reported initial symptom and more common than reported in other dominantly inherited forms of PD. Of the 211 potentially PD-causing variants, 25 were classified as pathogenic or likely pathogenic, and the remaining 186 (88.2%) were variants of uncertain significance. p.G2019S was the most frequently reported pathogenic variant, followed by p.R1441G and p.R1441C. This systematic review represents the most extensive database on PARK-LRRK2 to date and provides a vital resource to improve precision medicine.

The Inflammatory Mechanism of Parkinson's Disease: Gut Microbiota Metabolites Affect the Development of the Disease Through the Gut-Brain Axis

Parkinson's disease is recognized as the second most prevalent neurodegenerative disorder globally, with its incidence rate projected to increase alongside ongoing population growth. However, the precise etiology of Parkinson's disease remains elusive. This article explores the inflammatory mechanisms linking gut microbiota to Parkinson's disease, emphasizing alterations in gut microbiota and their metabolites that influence the disease's progression through the bidirectional transmission of inflammatory signals along the gut-brain axis. Building on this mechanistic framework, this article further discusses research methodologies and treatment strategies focused on gut microbiota metabolites, including metabolomics detection techniques, animal model investigations, and therapeutic approaches such as dietary interventions, probiotic treatments, and fecal transplantation. Ultimately, this article aims to elucidate the relationship between gut microbiota metabolites and the inflammatory mechanisms underlying Parkinson's disease, thereby paving the way for novel avenues in the research and treatment of this condition.

Gut microbes of the cecum versus the colon drive more severe lethality and multi-organ damage

Intestinal perforations lead to a high risk of sepsis-associated morbidity and multi-organ dysfunctions. A perforation allows intestinal contents (IC) to enter the peritoneal cavity, causing abdominal infections. Right- and left-sided perforations have different prognoses in humans, but the mechanisms associated with different cecum and colon perforations remain unclear. This study investigates how gut flora influences outcomes from perforations at different sites in mice. Using fecal-induced peritonitis mouse model, isolated IC from the cecum or colon was injected peritoneally at 2 mg/kg. Bacterial burden was quantified with quantitative PCR, and microbial communities were analyzed using 16S rRNA gene sequencing. Survival rates were monitored, and blood biochemical indices, histological changes, cytokines expression, immunological signaling and multiple-organ damage were assessed at 16 h post-injections. The results showed cecum IC developed more severe sepsis than colon IC, with shorter median survival time and greater multi-organ damage. Mice treated with cecum IC displayed elevated tissue damage markers in the liver, heart, and kidneys, contributing to worsened pathology. This was likely driven by systematic inflammatory cytokines production and lung inflammation. Mechanistically, cecum IC triggered stronger cGAS-STING and TBK1-NF-κB signaling, promoting systemic inflammation compared to the colon IC. Moreover, bacterial analysis demonstrated that cecum IC carry a higher bacterial burden than colon IC and exhibit a different microbial community. A detailed microbiome comparison revealed an increased abundance of potentially pathogenic bacteria in the cecum IC. These findings suggest that the site of intestinal perforation influences sepsis severity, with the cecum being associated with a higher bacterial burden and a relatively increased abundance of potentially pathogenic bacteria compared to the colon. Our findings first compared the lethality associated with the microbial composition of the cecum and colon, indicating the perforation site could help providers predict the severity of sepsis, thereby introducing a novel perspective to microbiology and sepsis research.

Bacterial and bacterial derivatives-based drug delivery systems: a novel approach for treating central nervous system disorders

INTRODUCTION

Bacteria and their derivatives show great potential as drug delivery systems due to their unique chemotaxis, biocompatibility, and targeting abilities. In CNS disease treatment, bacterial carriers can cross the blood-brain barrier (BBB) and deliver drugs precisely, overcoming limitations of traditional methods. Advances in genetic engineering, synthetic biology, and nanotechnology have transformed these systems into multifunctional platforms for personalized CNS treatment.

AREAS COVERED

This review examines the latest research on bacterial carriers for treating ischemic brain injury, neurodegenerative diseases, and gliomas. Bacteria efficiently cross the blood-brain barrier via active targeting, endocytosis, paracellular transport, and the nose-to-brain route for precise drug delivery. Various bacterial drug delivery systems, such as OMVs and bacterial ghosts, are explored for their design and application. Databases were searched in Google Scholar for the period up to December 2024.

EXPERT OPINION

Future developments in bacterial drug delivery will rely on AI-driven design and high-throughput engineering, enhancing treatment precision. Personalized medicine will further optimize bacterial carriers for individual patients, but challenges such as biosafety, immune rejection, and scalability must be addressed. As multimodal diagnostic and therapeutic strategies advance, bacterial carriers are expected to play a central role in CNS disease treatment, offering novel precision medicine solutions.

Understanding Parkinson's: The microbiome and machine learning approach

OBJECTIVE

Given that Parkinson's disease is a progressive disorder, with symptoms that worsen over time, our goal is to enhance the diagnosis of Parkinson's disease by utilizing machine learning techniques and microbiome analysis. The primary objective is to identify specific microbiome signatures that can reproducibly differentiate patients with Parkinson's disease from healthy controls.

METHODS

We used four Parkinson-related datasets from the NCBI repository, focusing on stool samples. Then, we applied a DADA2-based script for amplicon sequence processing and the Recursive Ensemble Feature Selection (REF) algorithm for biomarker discovery. The discovery dataset was PRJEB14674, while PRJNA742875, PRJEB27564, and PRJNA594156 served as testing datasets. The Extra Trees classifier was used to validate the selected features.

RESULTS

The Recursive Ensemble Feature Selection algorithm identified 84 features (Amplicon Sequence Variants) from the discovery dataset, achieving an accuracy of over 80%. The Extra Trees classifier demonstrated good diagnostic accuracy with an area under the receiver operating characteristic curve of 0.74. In the testing phase, the classifier achieved areas under the receiver operating characteristic curves of 0.64, 0.71, and 0.62 for the respective datasets, indicating sufficient to good diagnostic accuracy. The study identified several bacterial taxa associated with Parkinson's disease, such as Lactobacillus, Bifidobacterium, and Roseburia, which were increased in patients with the disease.

CONCLUSION

This study successfully identified microbiome signatures that can differentiate patients with Parkinson's disease from healthy controls across different datasets. These findings highlight the potential of integrating machine learning and microbiome analysis for the diagnosis of Parkinson's disease. However, further research is needed to validate these microbiome signatures and to explore their therapeutic implications in developing targeted treatments and diagnostics for Parkinson's disease.

Environmental mycotoxins: A potential etiological factor for neurodegenerative diseases?

Mycotoxins are potential environmental risk factors for neurodegenerative diseases. These toxins penetrate the central nervous system via a compromised blood-brain barrier, which may cause oxidative stress and neuroinflammation, these can also contribute to amyloid-beta (Aβ) plaque accumulation, Tau protein hyperphosphorylation, and neurofibrillary tangle formation. Mycotoxins also activate microglia, cause neuronal apoptosis, and disrupt central nervous system function. This study examines the evidence linking mycotoxin exposure to neurodegenerative disorders like Alzheimer's and Parkinson's diseases. We explore mechanisms such as oxidative stress, mitochondrial dysfunction, blood-brain barrier disruption, neuroinflammation, and direct neurotoxic effects. Epidemiological studies show regional variations in mycotoxin prevalence and corresponding neurodegenerative disease incidences, supporting this association. We also review current approaches to mitigate mycotoxin exposure and discuss the challenges and opportunities in developing strategies to prevent or slow neurodegenerative disease progression. This work highlights the need for increased awareness and research on mycotoxins as modifiable risk factors in neurological health.

Role of nasal microbiota in regulating host anti-influenza immunity in dogs

BACKGROUND

Numerous studies have confirmed a close relationship between the pathogenicity of influenza and respiratory microbiota, but the mechanistic basis for this is poorly defined. Also, the majority of these studies have been conducted on murine models, and it remains unclear how far these findings can be extrapolated from murine models to other animals. Considering that influenza A virus is increasingly recognized as an important canine respiratory pathogen, this study investigated the cross-talk between nasal and lung tissues mediated by microbes and its association with influenza susceptibility in a beagle dog model.

RESULTS

Using 16S rRNA gene sequencing, combined with comparative transcriptomic, anatomical, and histological examinations, we investigated viral presence, gene expression profiles, and microbiota in the nasal cavity and lung after influenza infection in the beagles with antibiotic-induced nasal dysbiosis. Our data showed that dysbiosis of the nasal microbiome exacerbates influenza-induced respiratory disease and the epithelial barrier disruption, and impairs host antiviral responses in the nasal cavity and lung. Moreover, dysregulation of nasal microbiota exacerbates the influenza-induced disturbance in lung microbiota. Further, we also identified a strain of Lactobacillus plantarum isolated from canine nasal cavity with a significant antiviral effect in vitro, and found that its antiviral activity might be associated with the activation of the interferon (IFN) pathway and modulation of the impaired autophagy flux induced by influenza infection.

CONCLUSIONS

Our investigation reveals that nasal microbiota dysbiosis exerts a prominent impact on host antiviral responses, inflammation thresholds, and mucosal barrier integrity during influenza infection. Lactobacilli, as part of the nasal microbiota, may contribute to host antiviral defenses by modulating the IFN and autophagy pathways. Collectively, this study underscores the importance of nasal microbiota homeostasis in maintaining respiratory health. Video Abstract.

The Gut-Brain Axis in Parkinson's Disease

Parkinson's disease (PD) involves both the central nervous system (CNS) and enteric nervous system (ENS), and their interaction is important for understanding both the clinical manifestations of the disease and the underlying disease pathophysiology. Although the neuroanatomical distribution of pathology strongly suggests that the ENS is involved in disease pathophysiology, there are significant gaps in knowledge about the underlying mechanisms. In this article, we review the clinical presentation and management of gastrointestinal dysfunction in PD. In addition, we discuss the current understanding of disease pathophysiology in the gut, including controversies about early involvement of the gut in disease pathogenesis. We also review current knowledge about gut α-synuclein and the microbiome, discuss experimental models of PD-linked gastrointestinal pathophysiology, and highlight areas for further research. Finally, we discuss opportunities to use the gut-brain axis for the development of biomarkers and disease-modifying treatments.

Revolutionizing Neuroimmunology: Unraveling Immune Dynamics and Therapeutic Innovations in CNS Disorders

Neuroimmunology is reshaping the understanding of the central nervous system (CNS), revealing it as an active immune organ rather than an isolated structure. This review delves into the unprecedented discoveries transforming the field, including the emerging roles of microglia, astrocytes, and the blood-brain barrier (BBB) in orchestrating neuroimmune dynamics. Highlighting their dual roles in both repair and disease progression, we uncover how these elements contribute to the intricate pathophysiology of neurodegenerative diseases, cerebrovascular conditions, and CNS tumors. Novel insights into microglial priming, astrocytic cytokine networks, and meningeal lymphatics challenge the conventional paradigms of immune privilege, offering fresh perspectives on disease mechanisms. This work introduces groundbreaking therapeutic innovations, from precision immunotherapies to the controlled modulation of the BBB using nanotechnology and focused ultrasound. Moreover, we explore the fusion of immune modulation with neuromodulatory technologies, underscoring new frontiers for personalized medicine in previously intractable diseases. By synthesizing these advancements, we propose a transformative framework that integrates cutting-edge research with clinical translation, charting a bold path toward redefining CNS disease management in the era of precision neuroimmunology.

The impact of gut microbiome and diet on post-acute sequelae of SARS-CoV-2 infection

Long COVID, also known as Post COVID-19 condition by the World Health Organization or Post-Acute Sequelae of SARS-CoV-2 infection (PASC), is defined as the development of symptoms such as post-exertional malaise, dysgeusia, and partial or full anosmia three months after initial SARS-CoV-2 infection. The multisystem effects of PASC make it difficult to distinguish from its mimickers. Further, a comprehensive evaluation of the gut microbiome, nutrition, and PASC has yet to be studied. The gut-brain axis describes bidirectional immune, neural, endocrine, and humoral modulatory interactions between the gut microbiome and brain function. We explore recent studies that support an association between alterations in gut microbiome diversity and the severity of acute-phase COVID-19, and how these may be affected by diets rich in antioxidants and fiber. The Mediterranean Diet (MeDi) has demonstrated promising neuroprotective effects through its anti-inflammatory processes. Further, diets rich in fiber increase gut diversity and increase the amount of short-chain fatty acids (SCFAs) within the body-both shown to protect from acute COVID-19 complications. Long-term changes to the gut microbiome persist after acute infection and may increase susceptibility to PASC. This study builds on existing knowledge of determinants of PASC and highlights a relationship between nutrition, gut microbiome, acute-phase COVID-19, and, subsequently, PASC susceptibility.

Lycium ruthenicum Murray anthocyanin-driven neuroprotection modulates the gut microbiome and metabolome of MPTP-treated mice

Emerging evidence suggests that Parkinson's disease (PD) is strongly associated with altered gut microbiota. The present study investigated the prophylactic effects of anthocyanins (ACNs) from Lycium ruthenicum Murray on Parkinson's disease based on microbiomics and metabolomics. In this study, sixty-six adult male C57BL/6J mice were randomized into the control group, model group, positive drug (Madopar) group, and low-, medium- and high-dose ACN groups. Behavioral experiments were conducted and pathological indicators were determined. Fresh feces were collected for microbiomic analysis using 16S rRNA sequencing. Urine and serum were analyzed by the UPLC-MS method for untargeted metabolomics. The results demonstrated that ACNs ameliorated 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced motor deficits, dopamine neuron death, and glial cell activation, while 100 mg kg-1 and 200 mg kg-1 ACNs were more neuroprotective than 50 mg kg-1. Mice with PD-like phenotypes have an altered gut microbiota composition, and ACNs may regulate this disorder by causing an increase in Firmicutes/Bacteroidota ratio and abundance of norank_f__Eubacterium_coprostanoligenes_group and a decrease in the abundance of norank_f__Muribaculaceae, Coriobacteriaceae_UCG-002 and Parvibacter. Furthermore, ACNs increased 14 urinary key metabolites such as DIMBOA-Glc and tauroursodeoxycholic acid, decreased N,N-dimethyllysine, and increased 12 serum key metabolites such as 1-methylguanine and 1-nitro-5-glutathionyl-6-hydroxy-5,6-dihydronaphthalene, and decreased lamivudine-monophosphate and 5-butyl-2- methylpyridine. The present study reveals that ACNs are protective against MPTP-induced PD in mice by modulating anti-inflammatory flora in the gut and endogenous metabolites in serum/urine, and the key mechanisms may be related to Coriobacteriaceae_UCG-002 and glycerophospholipid metabolic pathways. Our findings provide new insights into the pathogenesis and potential treatment of Parkinson's disease.

Neuroimaging techniques, gene therapy, and gut microbiota: frontier advances and integrated applications in Alzheimer's Disease research

Alzheimer's Disease (AD) is a neurodegenerative disorder marked by cognitive decline, for which effective treatments remain elusive due to complex pathogenesis. Recent advances in neuroimaging, gene therapy, and gut microbiota research offer new insights and potential intervention strategies. Neuroimaging enables early detection and staging of AD through visualization of biomarkers, aiding diagnosis and tracking of disease progression. Gene therapy presents a promising approach for modifying AD-related genetic expressions, targeting amyloid and tau pathology, and potentially repairing neuronal damage. Furthermore, emerging evidence suggests that the gut microbiota influences AD pathology through the gut-brain axis, impacting inflammation, immune response, and amyloid metabolism. However, each of these technologies faces significant challenges, including concerns about safety, efficacy, and ethical considerations. This article reviews the applications, advantages, and limitations of neuroimaging, gene therapy, and gut microbiota research in AD, with a particular focus on their combined potential for early diagnosis, mechanistic insights, and therapeutic interventions. We propose an integrated approach that leverages these tools to provide a multi-dimensional framework for advancing AD diagnosis, treatment, and prevention.

Disease-modifying therapies for Parkinson disease: lessons from multiple sclerosis

The development of disease-modifying therapies (DMTs) for neurological disorders is an important goal in modern neurology, and the associated challenges are similar in many chronic neurological conditions. Major advances have been made in the multiple sclerosis (MS) field, with a range of DMTs being approved for relapsing MS and the introduction of the first DMTs for progressive MS. By contrast, people with Parkinson disease (PD) still lack such treatment options, relying instead on decades-old therapeutic approaches that provide only symptomatic relief. To address this unmet need, an in-person symposium was held in Toronto, Canada, in November 2022 for international researchers and experts in MS and PD to discuss strategies for advancing DMT development. In this Roadmap article, we highlight discussions from the symposium, which focused on therapeutic targets and preclinical models, disease spectra and subclassifications, and clinical trial design and outcome measures. From these discussions, we propose areas for novel or deeper exploration in PD using lessons learned from therapeutic development in MS. In addition, we identify challenges common to the PD and MS fields that need to be addressed to further advance the discovery and development of effective DMTs.

Gut microbiota and Parkinson's disease: potential links and the role of fecal microbiota transplantation

Parkinson's disease (PD) is the second most common neurodegenerative disease worldwide and seriously affects the quality of life of elderly patients. PD is characterized by the loss of dopaminergic neurons in the substantia nigra as well as abnormal accumulation of α-synuclein in neurons. Recent research has deepened our understanding of the gut microbiota, revealing that it participates in the pathological process of PD through the gut-brain axis, suggesting that the gut may be the source of PD. Therefore, studying the relationship between gut microbiota and PD is crucial for improving our understanding of the disease's prevention, diagnosis, and treatment. In this review, we first describe the bidirectional regulation of the gut-brain axis by the gut microbiota and the mechanisms underlying the involvement of gut microbiota and their metabolites in PD. We then summarize the different species of gut microbiota found in patients with PD and their correlations with clinical symptoms. Finally, we review the most comprehensive animal and human studies on treating PD through fecal microbiota transplantation (FMT), discussing the challenges and considerations associated with this treatment approach.

Comprehensive phage display viral antibody profiling using VirScan: potential applications in chronic immune-mediated disease

Phage immunoprecipitation sequencing (PhIP-Seq) is a high-throughput platform that uses programmable phage display for serology. VirScan, a specific PhIP-Seq library encoding viral peptides from all known human viruses, enables comprehensive quantification of past viral exposures. We review its use in immune-mediated diseases (IMDs), highlighting its utility in identifying viral exposures in the context of IMD development. Finally, we evaluate its potential for precision medicine by integrating it with other large-scale omics data sets.

Liquid-liquid Phase Separation in Aging: Novel Insights in the Pathogenesis and Therapeutics

The intricate organization of distinct cellular compartments is paramount for the maintenance of normal biological functions and the orchestration of complex biochemical reactions. These compartments, whether membrane-bound organelles or membraneless structures like Cajal bodies and RNA transport granules, play crucial roles in cellular function. Liquid-liquid phase separation (LLPS) serves as a reversible process that elucidates the genesis of membranelles structures through the self-assembly of biomolecules. LLPS has been implicated in a myriad of physiological and pathological processes, encompassing immune response and tumor genesis. But the association between LLPS and aging has not been clearly clarified. A recent advancement in the realm of aging research involves the introduction of a new edition outlining the twelve hallmarks of aging, categorized into three distinct groups. By delving into the role and mechanism of LLPS in the formation of membraneless structures at a molecular level, this review encapsulates an exploration of the interaction between LLPS and these aging hallmarks, aiming to offer novel perspectives of the intricate mechanisms underlying the aging process and deeper insights into aging therapeutics.

Gut-Brain Nexus: Mapping Multi-Modal Links to Neurodegeneration at Biobank Scale

Alzheimer's disease (AD) and Parkinson's disease (PD) are influenced by genetic and environmental factors. Using data from UK Biobank, SAIL Biobank, and FinnGen, we conducted an unbiased, population-scale study to: 1) Investigate how 155 endocrine, nutritional, metabolic, and digestive system disorders are associated with AD and PD risk prior to their diagnosis, considering known genetic influences; 2) Assess plasma biomarkers' specificity for AD or PD in individuals with these conditions; 3) Develop a multi-modal classification model integrating genetics, proteomics, and clinical data relevant to conditions affecting the gut-brain axis. Our findings show that certain disorders elevate AD and PD risk before AD and PD diagnosis including: insulin and non-insulin dependent diabetes mellitus, noninfective gastro-enteritis and colitis, functional intestinal disorders, and bacterial intestinal infections, among others. Polygenic risk scores revealed lower genetic predisposition to AD and PD in individuals with co-occurring disorders in the study categories, underscoring the importance of regulating the gut-brain axis to potentially prevent or delay the onset of neurodegenerative diseases. The proteomic profile of AD/PD cases was influenced by comorbid endocrine, nutritional, metabolic, and digestive systems conditions. Importantly, we developed multi-modal prediction models integrating clinical, genetic, proteomic and demographic data, the combination of which performs better than any single paradigm approach in disease classification. This work aims to illuminate the intricate interplay between various physiological factors involved in the gut-brain axis and the development of AD and PD, providing a multifactorial systemic understanding that goes beyond traditional approaches. Further, we have developed an interactive resource for the scientific community [https://gut-brain-nexus.streamlit.app/] where researchers can investigate components of the predictive model and can investigate feature effects on a sample level.

Systemic determinants of brain health in ageing

Preservation of brain health is a worldwide priority. The traditional view is that the major threats to the ageing brain lie within the brain itself. Consequently, therapeutic approaches have focused on protecting the brain from these presumably intrinsic pathogenic processes. However, an increasing body of evidence has unveiled a previously under-recognized contribution of peripheral organs to brain dysfunction and damage. Thus, in addition to the well-known impact of diseases of the heart and endocrine glands on the brain, accumulating data suggest that dysfunction of other organs, such as gut, liver, kidney and lung, substantially affects the development and clinical manifestation of age-related brain pathologies. In this Review, a framework is provided to indicate how organ dysfunction can alter brain homeostasis and promote neurodegeneration, with a focus on dementia. We delineate the associations of subclinical dysfunction in specific organs with dementia risk and provide suggestions for public health promotion and clinical management.

Impaired gut barrier integrity and reduced colonic expression of free fatty acid receptors in patients with Parkinson's disease

BACKGROUND

Altered gut metabolites, especially short-chain fatty acids (SCFAs), in feces and plasma are observed in patients with Parkinson's disease (PD).

OBJECTIVE

We aimed to investigate the colonic expression of two SCFA receptors, free fatty acid receptor (FFAR)2 and FFAR3, and gut barrier integrity in patients with PD and correlations with clinical severity.

METHODS

In this retrospective study, colonic biopsy specimens were collected from 37 PD patients and 34 unaffected controls. Of this cohort, 31 participants (14 PD, 17 controls) underwent a series of colon biopsies. Colonic expression of FFAR2, FFAR3, and the tight junction marker ZO-1 were assayed by immunofluorescence staining. The You Only Look Once (version 8, YOLOv8) algorithm was used for automated detection and segmentation of immunostaining signal. PD motor function was assessed with the Movement Disorder Society (MDS)-Unified Parkinson's Disease Rating Scale (UPDRS), and constipation was assessed using Rome-IV criteria.

RESULTS

Compared with controls, PD patients had significantly lower colonic expression of ZO-1 (p < 0.01) and FFAR2 (p = 0.01). On serial biopsy, colonic expression of FFAR2 and FFAR3 was reduced in the pre-motor stage before PD diagnosis (both p < 0.01). MDS-UPDRS motor scores did not correlate with colonic marker levels. Constipation severity negatively correlated with colonic ZO-1 levels (r = -0.49, p = 0.02).

CONCLUSIONS

Colonic expression of ZO-1 and FFAR2 is lower in PD patients compared with unaffected controls, and FFAR2 and FFAR3 levels decline in the pre-motor stage of PD. Our findings implicate a leaky gut phenomenon in PD and reinforce that gut metabolites may contribute to the process of PD.

Faecal intestinal permeability and intestinal inflammatory markers in older adults with age-related disorders: A systematic review and meta-analysis

This systematic review and meta-analysis appraised previous findings to uncover potential faecal intestinal permeability and intestinal inflammatory markers in older adults. A comprehensive literature search led to the identification of ten eligible studies with findings of potential faecal intestinal permeability (zonulin and alpha-1-antitrypsin) and intestinal inflammatory markers [calprotectin, lactoferrin and neutrophil gelatinase-associated lipocalin (NGAL)]. Most of the cases (n > 2) [Parkinson's disease (PD) and Alzheimer's disease (AD)] exhibited higher faecal alpha-1-antitrypsin, zonulin and calprotectin levels. The present meta-analysis confirmed significantly higher faecal alpha-1-antitrypsin in older persons with PD compared to non-PD [MD = 22.92 mg/dL; 95 % CI = 14.02-31.81, p < 0.00001; I2 = 0 % (p = 0.73)]. There was, however, no significant difference in faecal zonulin between PD and non-PD individuals [MD = 26.88 ng/mL; 95 % CI = -29.26-83.01, p = 0.35; I2 = 94 % (p < 0.0001)]. Meanwhile, faecal calprotectin was higher in older adults with GI symptoms, multiple system atrophy (MSA) or PD than the healthy controls [MD = 9.51 μg/g; 95 % CI = 0.07-18.95, p = 0.05; I2 = 84 % (p < 0.00001)]. Altogether, faecal calprotectin appears to be a potential intestinal inflammatory marker whereas previous findings on faecal alpha-1-antitrypsin as an intestinal permeability marker remain limited and require further validation.

Ageing, proteostasis, and the gut: Insights into neurological health and disease

Recent research has illuminated the profound bidirectional communication between the gastrointestinal tract and the brain, furthering our understanding of neurological ailments facilitating possible therapeutic strategies. Technological advancements in high-throughput sequencing and multi-omics have unveiled significant alterations in gut microbiota and their metabolites in various neurological disorders. This review provides a thorough analysis of the role of microbiome-gut-brain axis in neurodegenerative disease pathology, linking it to reduced age-associated proteostasis. We discuss evidences that substantiate the existence of a gut-brain cross talk ranging from early clinical accounts of James Parkinson to Braak's hypothesis. In addition to understanding of microbes, the review particularly entails specific metabolites which are altered in neurodegenerative diseases. The regulatory effects of microbial metabolites on protein clearance mechanisms, proposing their potential therapeutic implications, are also discussed. By integrating this information, we advocate for a combinatory therapeutic strategy that targets early intervention, aiming to restore proteostasis and ameliorate disease progression. This approach not only provides a new perspective on the pathogenesis of neurodegenerative diseases but also highlights innovative strategies to combat the increasing burden of these age-related disorders.

Variation in the metagenomic analysis of fecal microbiome composition calls for a standardized operating approach

The reproducibility in microbiome studies is limited due to the lack of one gold-standard operating procedure. The aim of this study was to examine the impact of protocol variations on microbiome composition using metagenomic data sets from a single center. We assessed the variation in a data set consisted of 2,722 subjects, including 9 subcohorts harboring healthy subjects and patients with various disorders, such as inflammatory bowel disease, colorectal cancer, and type 2 diabetes. Two different DNA extraction kits, with or without lyticase, and two sample storage methods were compared. Our results indicated that DNA extraction had the largest impact on gut microbiota diversity among all host factors and sample operating procedures. Healthy subjects matched by age, body mass index, and sample operating methods exhibited reduced, yet significant differences (PERMANOVA, P < 0.05) in gut microbiota composition across studies. The variations contributed by DNA extraction were primarily driven by different recovery efficiency of gram-positive bacteria, e.g., phyla Firmicutes and Actinobacteria. This was further confirmed by a parallel comparison of fecal samples from five healthy subjects and a standard mock community. In addition, the DNA extraction method influenced DNA biomass, quality, and the detection of specific lineage-associated diseases. Sample operating approach and batch effects should be considered for cohorts with large sample size or longitudinal cohorts to ensure that source data were appropriately generated and analyzed. Comparison between samples processed with inconsistent methods should be dealt with caution. This study will promote the establishment of a sample operating standard to enhance our understanding of microbiome and translating in clinical practice.IMPORTANCEThe reproducibility of human gut microbiome studies has been suboptimal across cohorts and study design choices. One possible reason for the disagreement is the introduction of systemic biases due to differences in methodologies. In our study, we utilized microbial metagenomic data sets from 2,722 fecal samples generated from a single research center to examine the extent to which sample storage and DNA extraction influence the quantification of microbial composition and compared this variable with other sources of technical and biological variation. Our research highlights the impact of DNA extraction methods when analyzing microbiome data and suggests that the microbiome profile may be influenced by differences in the extraction efficiency of bacterial species. With metagenomics sequencing being increasingly used in clinical biology, our findings provide insight into the challenges using metagenomics sequencing in clinical diagnostics, where the detection of certain species and its abundance relative to a "healthy reference" is key.

Microbial biomarker discovery in Parkinson's disease through a network-based approach

Associations between the gut microbiota and Parkinson's disease (PD) have been widely investigated. However, the replicable biomarkers for PD diagnosis across multiple populations remain elusive. Herein, we performed a meta-analysis to investigate the pivotal role of the gut microbiome in PD and its potential diagnostic implications. Six 16S rRNA gene amplicon sequence datasets from five independent studies were integrated, encompassing 550 PD and 456 healthy control samples. The analysis revealed significant alterations in microbial composition and alpha and beta diversity, emphasizing altered gut microbiota in PD. Specific microbial taxa, including Faecalibacterium, Roseburia, and Coprococcus_2, known as butyrate producers, were notably diminished in PD, potentially contributing to intestinal inflammation. Conversely, genera such as Akkermansia and Bilophila exhibited increased relative abundances. A network-based algorithm called NetMoss was utilized to identify potential biomarkers of PD. Afterwards, a classification model incorporating 11 optimized genera demonstrated high performance. Further functional analyses indicated enrichment in pathways related to neurodegeneration and metabolic pathways. These findings illuminate the intricate relationship between the gut microbiota and PD, offering insights into potential therapeutic interventions and personalized diagnostic strategies.

The potential of natural products to inhibit abnormal aggregation of α-Synuclein in the treatment of Parkinson's disease

Parkinson's disease (PD), as a refractory neurological disorder with complex etiology, currently lacks effective therapeutic agents. Natural products (NPs), derived from plants, animals, or microbes, have shown promising effects in PD models through their antioxidative and anti-inflammatory properties, as well as the enhancement of mitochondrial homeostasis and autophagy. The misfolding and deposition of α-Synuclein (α-Syn), due to abnormal overproduction and impaired clearance, being central to the death of dopamine (DA) neurons. Thus, inhibiting α-Syn misfolding and aggregation has become a critical focus in PD discovery. This review highlights NPs that can reduce α-Syn aggregation by preventing its overproduction and misfolding, emphasizing their potential as novel drugs or adjunctive therapies for PD treatment, thereby providing further insights for clinical translation.

Difference in gut microbial dysbiotic patterns between body-first and brain-first Parkinson's disease

BACKGROUND

This study aims to identify distinct microbial and functional biomarkers characteristic of body-first or brain-first subtypes of Parkinson's disease (PD). This could illuminate the unique pathogenic mechanisms within these subtypes.

METHODS

In this cross-sectional study, we classified 36 well-characterized PD patients into body-first, brain-first, or undetermined subtypes based on the presence of premotor REM sleep behavior disorder (RBD) and cardiac meta-iodobenzylguanidine (MIBG) uptake. We then conducted an in-depth shotgun metagenomic analysis of the gut microbiome for each subtype and compared the results with those from age- and sex-matched healthy controls.

RESULTS

Significant differences were found in the gut microbiome of body-first PD patients (n = 15) compared to both brain-first PD patients (n = 9) and healthy controls. The gut microbiome in body-first PD showed a distinct profile, characterized by an increased presence of Escherichia coli and Akkermansia muciniphila, and a decreased abundance of short-chain fatty acid-producing commensal bacteria. These shifts were accompanied by a higher abundance of microbial genes associated with curli protein biosynthesis and a lower abundance of genes involved in putrescine and spermidine biosynthesis. Furthermore, the combined use of premotor RBD and MIBG criteria was more strongly correlated with these microbiome differences than the use of each criterion independently.

CONCLUSIONS

Our findings highlight the significant role of dysbiotic and pathogenic gut microbial alterations in body-first PD, supporting the body-first versus brain-first hypothesis. These insights not only reinforce the gut microbiome's potential as a therapeutic target in PD but also suggest the possibility of developing subtype-specific treatment strategies.

The immune system in Parkinson's disease: what we know so far

Parkinson's disease is characterized neuropathologically by the degeneration of dopaminergic neurons in the ventral midbrain, the accumulation of α-synuclein (α-syn) aggregates in neurons and chronic neuroinflammation. In the past two decades, in vitro, ex vivo and in vivo studies have consistently shown the involvement of inflammatory responses mediated by microglia and astrocytes, which may be elicited by pathological α-syn or signals from affected neurons and other cell types, and are directly linked to neurodegeneration and disease development. Apart from the prominent immune alterations seen in the CNS, including the infiltration of T cells into the brain, more recent studies have demonstrated important changes in the peripheral immune profile within both the innate and adaptive compartments, particularly involving monocytes, CD4+ and CD8+ T cells. This review aims to integrate the consolidated understanding of immune-related processes underlying the pathogenesis of Parkinson's disease, focusing on both central and peripheral immune cells, neuron-glia crosstalk as well as the central-peripheral immune interaction during the development of Parkinson's disease. Our analysis seeks to provide a comprehensive view of the emerging knowledge of the mechanisms of immunity in Parkinson's disease and the implications of this for better understanding the overall pathogenesis of this disease.

Metagenomic Analysis Reveals Large-Scale Disruptions of the Gut Microbiome in Parkinson's Disease

BACKGROUND

Parkinson's disease (PD) has been consistently linked to alterations within the gut microbiome.

OBJECTIVE

Our goal was to identify microbial features associated with PD incidence and progression.

METHODS

Metagenomic sequencing was used to characterize taxonomic and functional changes to the PD microbiome and to explore their relation to bacterial metabolites and disease progression. Motor and non-motor symptoms were tracked using Movement Disorder Society Unified Parkinson's Disease Rating Scale (MDS-UPDRS) and levodopa equivalent dose across ≤5 yearly study visits. Stool samples were collected at baseline for metagenomic sequencing (176 PD, 100 controls).

RESULTS

PD-derived stool samples had reduced intermicrobial connectivity and seven differentially abundant species compared to controls. A suite of bacterial functions differed between PD and controls, including depletion of carbohydrate degradation pathways and enrichment of ribosomal genes. Faecalibacterium prausnitzii-specific reads contributed significantly to more than half of all differentially abundant functional terms. A subset of disease-associated functional terms correlated with faster progression of MDS-UPDRS part IV and separated those with slow and fast progression with moderate accuracy within a random forest model (area under curve = 0.70). Most PD-associated microbial trends were stronger in those with symmetric motor symptoms.

CONCLUSION

We provide further evidence that the PD microbiome is characterized by reduced intermicrobial communication and a shift to proteolytic metabolism in lieu of short-chain fatty acid production, and suggest that these microbial alterations may be relevant to disease progression. We also describe how our results support the existence of gut-first versus brain-first PD subtypes. © 2024 The Author(s). Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Therapeutic potential of the ketogenic diet: A metabolic switch with implications for neurological disorders, the gut-brain axis, and cardiovascular diseases

The Ketogenic Diet (KD) is a dietary regimen that is low in carbohydrates, high in fats, and contains adequate protein. It is designed to mimic the metabolic state of fasting. This diet triggers the production of ketone bodies through a process known as ketosis. The primary objective of KD is to induce and sustain ketosis, which has been associated with numerous health benefits. Recent research has uncovered promising therapeutic potential for KD in the treatment of various diseases. This includes evidence of its effectiveness as a dietary strategy for managing intractable epilepsy, a form of epilepsy that is resistant to medication. We are currently assessing the efficacy and safety of KD through laboratory and clinical studies. This review focuses on the anti-inflammatory properties of the KD and its potential benefits for neurological disorders and the gut-brain axis. We also explore the existing literature on the potential effects of KD on cardiac health. Our aim is to provide a comprehensive overview of the current knowledge in these areas. Given the encouraging preliminary evidence of its therapeutic effects and the growing understanding of its mechanisms of action, randomized controlled trials are warranted to further explore the rationale behind the clinical use of KD. These trials will ultimately enhance our understanding of how KD functions and its potential benefits for various health conditions. We hope that our research will contribute to the body of knowledge in this field and provide valuable insights for future studies.

Parkinson's Disease Progression and Exposure to Contaminated Water at Camp Lejeune

BACKGROUND

We recently reported an increased risk of Parkinson's disease (PD) in service members who resided at Marine Base Camp Lejeune, North Carolina, when water supplies were contaminated with trichloroethylene and other volatile organic compounds (VOCs). Prior studies suggest that environmental exposures may affect PD phenotype or progression, but this has not been reported for VOCs.

OBJECTIVE

The objective of this study was to test whether PD progression is faster in individuals exposed to VOCs in water at Camp Lejeune.

METHODS

A cohort of 172,128 marines residing at Camp Lejeune between 1975 and 1985 was previously assembled. We identified individuals with PD in Veterans Health Administration and Medicare databases between 2000 and 2021. Using estimates derived by the US Agency for Toxic Substances and Disease Registry, we classified individuals as exposed or unexposed to VOCs in residential water. We used Kaplan-Meier and Cox regression models to test differences between exposed and unexposed groups in the time from PD diagnosis until psychosis, fracture, fall, or death.

RESULTS

Among 270 persons with PD, 177 (65.6%) were exposed to VOCs in residential water. Median cumulative exposure was 4970 μg/L-months, >50-fold the permissible level. Time until psychosis, fracture, and fall were all shorter in the exposed group, with adjusted hazard ratios (HRs) exceeding 2: psychosis HR, 2.19 (95% confidence interval [CI]: 0.99-4.83); fracture HR, 2.44 (95% CI: 0.91-6.55); and fall HR, 2.64 (95% CI: 0.97-7.21). A significant dose response was observed for time to fall (P trend, 0.032). No differences were observed for time until death.

CONCLUSIONS

PD progression may be faster in persons exposed to trichloroethylene and other VOCs in water decades earlier. © 2024 The Author(s). Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

Nine Neuroimaging-AI Endophenotypes Unravel Disease Heterogeneity and Partial Overlap across Four Brain Disorders: A Dimensional Neuroanatomical Representation

Disease heterogeneity poses a significant challenge for precision diagnostics. Recent work leveraging artificial intelligence has offered promise to dissect this heterogeneity by identifying complex intermediate brain phenotypes, herein called dimensional neuroimaging endophenotypes (DNEs). We advance the argument that these DNEs capture the degree of expression of respective neuroanatomical patterns measured, offering a dimensional neuroanatomical representation for studying disease heterogeneity and similarities of neurologic and neuropsychiatric diseases. We investigate the presence of nine such DNEs derived from independent yet harmonized studies on Alzheimer's disease (AD1-2)1, autism spectrum disorder (ASD1-3)2, late-life depression (LLD1-2)3, and schizophrenia (SCZ1-2)4, in the general population of 39,178 participants in the UK Biobank study. Phenome-wide associations revealed prominent associations between the nine DNEs and phenotypes related to the brain and other human organ systems. This phenotypic landscape aligns with the SNP-phenotype genome-wide associations, revealing 31 genomic loci associated with the nine DNEs (Bonferroni corrected P-value < 5×10-8/9). The DNEs exhibited significant genetic correlations, colocalization, and causal relationships with multiple human organ systems and chronic diseases. A causal effect (odds ratio=1.25 [1.11, 1.40], P-value=8.72×10-4) was established from AD2, characterized by focal medial temporal lobe atrophy, to AD. The nine DNEs, along with their polygenic risk scores, significantly enhanced the predictive accuracy for 14 systemic disease categories, particularly for conditions related to mental health and the central nervous system, as well as mortality outcomes. These findings underscore the potential of the nine DNEs to capture the expression of disease-related brain phenotypes in individuals of the general population and to relate such measures with genetics, lifestyle factors, and chronic diseases. All results are publicly available at https://labs-laboratory.com/medicine/.

Beyond the usual suspects: multi-factorial computational models in the search for neurodegenerative disease mechanisms

From Alzheimer's disease to amyotrophic lateral sclerosis, the molecular cascades underlying neurodegenerative disorders remain poorly understood. The clinical view of neurodegeneration is confounded by symptomatic heterogeneity and mixed pathology in almost every patient. While the underlying physiological alterations originate, proliferate, and propagate potentially decades before symptomatic onset, the complexity and inaccessibility of the living brain limit direct observation over a patient's lifespan. Consequently, there is a critical need for robust computational methods to support the search for causal mechanisms of neurodegeneration by distinguishing pathogenic processes from consequential alterations, and inter-individual variability from intra-individual progression. Recently, promising advances have been made by data-driven spatiotemporal modeling of the brain, based on in vivo neuroimaging and biospecimen markers. These methods include disease progression models comparing the temporal evolution of various biomarkers, causal models linking interacting biological processes, network propagation models reproducing the spatial spreading of pathology, and biophysical models spanning cellular- to network-scale phenomena. In this review, we discuss various computational approaches for integrating cross-sectional, longitudinal, and multi-modal data, primarily from large observational neuroimaging studies, to understand (i) the temporal ordering of physiological alterations, i(i) their spatial relationships to the brain's molecular and cellular architecture, (iii) mechanistic interactions between biological processes, and (iv) the macroscopic effects of microscopic factors. We consider the extents to which computational models can evaluate mechanistic hypotheses, explore applications such as improving treatment selection, and discuss how model-informed insights can lay the groundwork for a pathobiological redefinition of neurodegenerative disorders.

Allantoin ameliorates dopaminergic neuronal damage in MPTP-induced Parkinson's disease mice via regulating oxidative damage, inflammation, and gut microbiota disorder

Parkinson's disease (PD) is a chronic progressive neurodegenerative disease that often occurs in older people. Neuroinflammation and oxidative stress are important factors in the development of PD. Gastrointestinal dysfunction is the most common non-motor symptom, and inflammation of the gut, which activates the gut-brain axis, maybe a pathogenic factor. Previous studies have attributed anti-inflammatory and antioxidant effects to Allantoin, but its function and mechanism of action in PD are unclear. This study aimed to investigate the effect and mechanism of Allantoin on 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD in mice. Our results showed that Allantoin administration ameliorated motor dysfunction and neuronal damage in mice injected with MPTP by inhibiting neuroinflammation and oxidative damage. Mechanistic studies showed that Allantoin suppresses inflammatory responses by inhibiting the overactivation of the NF-κB and MAPK signaling pathways, as well as oxidative stress by regulating the AKT/Nrf2/HO-1 signaling pathway. Notably, Allantoin also restored intestinal barrier function by modulating the gut microbiota and improving antioxidant and anti-inflammatory capacities to alleviate MPTP-induced motor deficits. In conclusion, the present study shows that the administration of Allantoin attenuated neurodegeneration in mice injected with MPTP by inhibiting neuroinflammation and oxidative stress and modulating the composition of the gut microbiome.

Fragile Guts Make Fragile Brains: Intestinal Epithelial Nrf2 Deficiency Exacerbates Neurotoxicity Induced by Polystyrene Nanoplastics

Oral ingestion is the primary route for human exposure to nanoplastics, making the gastrointestinal tract one of the first and most impacted organs. Given the presence of the gut-brain axis, a crucial concern arises regarding the potential impact of intestinal damage on the neurotoxic effects of nanoplastics (NPs). The intricate mechanisms underlying NP-induced neurotoxicity through the microbiome-gut-brain axis necessitate further investigation. To address this, we used mice specifically engineered with nuclear factor erythroid-derived 2-related factor 2 (Nrf2) deficiency in their intestines, a strain whose intestines are particularly susceptible to polystyrene NPs (PS-NPs). We conducted a 28-day repeated-dose oral toxicity study with 2.5 and 250 mg/kg of 50 nm PS-NPs in these mice. Our study delineated how PS-NP exposure caused gut microbiota dysbiosis, characterized by Mycoplasma and Coriobacteriaceae proliferation, resulting in increased levels of interleukin 17C (IL-17C) production in the intestines. The surplus IL-17C permeated the brain via the bloodstream, triggering inflammation and brain damage. Our investigation elucidated a direct correlation between intestinal health and neurological outcomes in the context of PS-NP exposure. Susceptible mice with fragile guts exhibited heightened neurotoxicity induced by PS-NPs. This phenomenon was attributed to the elevated abundance of microbiota associated with IL-17C production in the intestines of these mice, such as Mesorhizobium and Lwoffii, provoked by PS-NPs. Neurotoxicity was alleviated by in vivo treatment with anti-IL-17C-neutralizing antibodies or antibiotics. These findings advanced our comprehension of the regulatory mechanisms governing the gut-brain axis in PS-NP-induced neurotoxicity and underscored the critical importance of maintaining intestinal health to mitigate the neurotoxic effects of PS-NPs.

Distinguishing bipolar depression, bipolar mania, and major depressive disorder by gut microbial characteristics

BACKGROUND

Gut microbial disturbance has been widely confirmed in mood disorders. However, little is known about whether gut microbial characteristics can distinguish major depressive disorder (MDD), bipolar depression (BP-D), and bipolar mania (BP-M).

METHODS

This was a prospective case-control study. The composition of gut microbiota was profiled using 16S ribosomal RNA (rRNA) gene sequencing of fecal samples and compared between healthy controls (HC; n = 46), MDD (n = 51), BP-D (n = 44), and patients with BP-M (n = 45).

RESULTS

Gut microbial compositions were remarkably changed in the patients with MDD, BP-D, and BP-M. Compared to HC, distinct gut microbiome signatures were found in MDD, BP-D, and BP-M, and some gut microbial changes were overlapping between the three mood disorders. Furthermore, we identified a signature of 7 operational taxonomic units (OUT; Prevotellaceae-related OUT22, Prevotellaceae-related OUT31, Prevotellaceae-related OTU770, Ruminococcaceae-related OUT70, Bacteroidaceae-related OTU1536, Propionibacteriaceae-related OTU97, Acidaminococcaceae-related OTU34) that can distinguish patients with MDD from those with BP-D, BP-M, or HC, with area under the curve (AUC) values ranging from 0.910 to 0.996.

CONCLUSION

Our results provide the clinical rationale for the discriminative diagnosis of MDD, BP-D, and BP-M by characteristic gut microbial features.

Fecal Microbiota Transplantation for Treatment of Parkinson Disease: A Randomized Clinical Trial

Importance

Dysbiosis has been robustly demonstrated in Parkinson disease (PD), and fecal microbiota transplantation (FMT) has shown promising effects in preclinical PD models.

Objective

To assess the safety and symptomatic efficacy of colonic single-dose anaerobically prepared FMT.

Design, Setting, and Participants

This was a double-blind, placebo-controlled, randomized clinical trial conducted between November 2020 and June 2023 with a follow-up period of 12 months at 4 hospitals in Finland. Patients with PD aged 35 to 75 years in Hoehn & Yahr stage 1-3 with a mild to moderate symptom burden and dysbiosis of fecal microbiota were included. Of 229 patients screened, 48 were randomized and 47 received the intervention. One patient discontinued due to worsening of PD symptoms. Two further patients were excluded before analysis and 45 were included in the intention-to-treat analysis.

Intervention

Participants were randomized in a 2:1 ratio to receive FMT or placebo via colonoscopy.

Main Outcomes and Measures

The primary end point was the change of Movement Disorder Society Unified Parkinson's Disease Rating Scale parts I-III (part III off medication) at 6 months. Safety was assessed by recording adverse events (AEs).

Results

The median (IQR) age was 65 (52.5-70.0) years in the placebo group and 66 (59.25-69.75) years in the FMT group; 9 (60.0%) and 16 (53.3%) patients were male in the placebo group and the FMT group, respectively. The primary outcome did not differ between the groups (0.97 points, 95% CI, -5.10 to 7.03, P = .75). Gastrointestinal AEs were more frequent in the FMT group (16 [53%] vs 1 [7%]; P = .003). Secondary outcomes and post hoc analyses showed stronger increase of dopaminergic medication and improvement of certain motor and nonmotor outcomes in the placebo group. Microbiota changes were more pronounced after FMT but differed by donor. Nevertheless, dysbiosis status was reversed more frequently in the placebo group.

Conclusions and Relevance

FMT was safe but did not offer clinically meaningful improvements. Further studies-for example, through modified FMT approaches or bowel cleansing-are warranted regarding the specific impact of donor microbiota composition and dysbiosis conversion on motor and nonmotor outcomes as well as medication needs in PD.

Trial Registration

ClinicalTrials.gov Identifier: NCT04854291.

The Bifunctional Dimer Caffeine-Indan Attenuates α-Synuclein Misfolding, Neurodegeneration and Behavioral Deficits after Chronic Stimulation of Adenosine A1 Receptors

We previously found that chronic adenosine A1 receptor stimulation with N6-Cyclopentyladenosine increased α-synuclein misfolding and neurodegeneration in a novel α-synucleinopathy model, a hallmark of Parkinson's disease. Here, we aimed to synthesize a dimer caffeine-indan linked by a 6-carbon chain to cross the blood-brain barrier and tested its ability to bind α-synuclein, reducing misfolding, behavioral abnormalities, and neurodegeneration in our rodent model. Behavioral tests and histological stains assessed neuroprotective effects of the dimer compound. A rapid synthesis of the 18F-labeled analogue enabled Positron Emission Tomography and Computed Tomography imaging for biodistribution measurement. Molecular docking analysis showed that the dimer binds to α-synuclein N- and C-termini and the non-amyloid-β-component (NAC) domain, similar to 1-aminoindan, and this binding promotes a neuroprotective α-synuclein "loop" conformation. The dimer also binds to the orthosteric binding site for adenosine within the adenosine A1 receptor. Immunohistochemistry and confocal imaging showed the dimer abolished α-synuclein upregulation and aggregation in the substantia nigra and hippocampus, and the dimer mitigated cognitive deficits, anxiety, despair, and motor abnormalities. The 18F-labeled dimer remained stable post-injection and distributed in various organs, notably in the brain, suggesting its potential as a Positron Emission Tomography tracer for α-synuclein and adenosine A1 receptor in Parkinson's disease therapy.

Effects of Enterobacter cloacae insecticidal protein on the Duox-ROS system and midgut bacterial community and function of Galleria mellonella larvae

BACKGROUND

Enterobacter cloacae insecticidal proteins have been reported to kill Galleria mellonella larvae through affecting their midgut microbiome. However, the mechanisms involved remain unclear. Here we aim to investigate how the insecticidal proteins act on the midgut Duox-ROS system and microbial community of G. mellonella larvae.

METHODS

Reverse transcription qPCR and fluorescence probes were utilized to assess the Duox expression levels and to evaluate quantitative changes of the ROS levels. Sequencing of the 16S rRNA gene sequences of the midgut bacteria of G. mellonella larvae was conducted for further analyses of bacterial diversity, composition, and abundance.

RESULTS

After the injection of the insecticidal proteins, the Duox expression levels first increased within 28 h, then dramatically peaked at 36 h, and slowly decreased thereafter. Simultaneously, the ROS levels increased significantly at 36 h, peaked at 48 h, and rapidly declined to the normal level at 60 h. Responsive to the change of the ROS levels, the structure of the midgut microbial community was altered substantially, compared to that of the untreated larvae. The relative abundance of Enterobacteriaceae and other specific pathogenic bacteria increased significantly, whereas that of Lactobacillus decreased sharply. Importantly, notable shifts were observed in the crucial midgut predicted metabolic functions, including membrane transportation, carbohydrate metabolism, and amino acid metabolism.

CONCLUSION

Insecticidal proteins of E. cloacae kill G. mellonella larvae mainly through generation of high oxidative stress, alterations of the midgut microbial community and function, and damage to the physiological functions. These findings provide insights into the inhibition mechanism of E. cloacae insecticidal proteins to G. mellonella larvae.

Secondary analysis reveals gut microbiota differences in patients with Parkinson's disease and/or cognitive impairment

Background: Parkinson's disease (PD) is a neurodegenerative disorder, and the main clinical characteristics are bradykinesia and muscle stiffness. Cognitive impairment (CI) is a prevalent non-motor manifestation observed in individuals with PD. According to disease severity, it can be divided into PD with mild cognitive impairment (MCI) and PD dementia. CI in PD patients may precede motor symptoms, and the gut microbiota plays an important role in PD pathogenesis. Therefore, gut microbiota may be one of the diagnostic targets for PD-CI. Methods: This study compared the gut microbiota of 43 PD-CI patients [Montreal Cognitive Assessment (MoCA) score < 26] and 38 PD patients without CI (MoCA ≥ 26). Patients' neuropsychological conditions, depression scale, and brain structure scanned by magnetic resonance imaging (MRI) were also recorded. The fecal metagenomic datasets of patients with PD, PD-CI, and CI only were retrieved from public databases for reanalysis to explore the relationship between PD, CI, and gut microbiota. Results: We found that the cortical thickness and the volume of the hippocampus, gray matter, and thalamus were significantly reduced among patients with PD-CI compared to PD without CI (P < 0.05). Moreover, the gut microbiome in patients with PD-CI had fewer short-chain fatty acid (SCFA) producing bacteria and more pathogenic bacteria. There were also alterations in patterns of metabolic pathway-encoding genes. Additionally, PD affected gut microbiota more than CI. Conclusion: CI may aggravate the severity of PD, but it did not drastically alter subjects' gut microbiota. This study reveals the relationship between gut microbiota, PD, and CI.

The promise of molecular science in brain health. What breakthroughs are anticipated in the next 20 years?

Brain health means optimal physiological brain function across the normal life-course. It encompasses not only healthy brain aging but also brain diseases, their diagnosis and treatment. In all these areas, molecular science has advanced our understanding. This multi-disciplinary review combines viewpoints from laboratory science, clinical medicine and the bioscience industry. First, we review the advances that molecular science has brought to brain health in the past twenty years. These include therapeutic antibodies for CNS diseases (multiple sclerosis, Alzheimer disease) and the dramatic introduction of RNA-targeted therapeutics. Second, we highlight areas where greater molecular understanding is needed. Salient examples are the relation of brain structure to cognitive symptoms, and molecular biomarkers for diagnosis, target discovery and testing of interventions. Finally, we speculate on aspects of molecular science that are likely to advance brain health in the next twenty years. These include: cell senescence and chronobiology; gene editing (notably, CRISPR) and RNA targeting (RNA interference, miRNA manipulation); brain-immune interactions; novel drug targets (AQP4, HIF1, Toll-like receptors); and novel chemistry to make new drugs (molecular machines, quantum molecular modelling and "click" chemistry). Early testing of the relationships between molecular pathways and clinical manifestations will drive much-needed breakthroughs in neurology and psychiatry.

Association between Constipation and the Risk of Parkinson's Disease among Participants in the UK Biobank

INTRODUCTION

Constipation is common in patients with Parkinson's disease (PD), but its impact on incident PD remains uncertain. We aimed to prospectively investigate constipation symptoms and the risk of PD.

METHODS

Participants without PD at baseline from the UK Biobank were included in the study. Information on the regular use of laxatives, bowel movement frequency, and the frequency of hard or lumpy stools was collected. Incident PD was defined by the ICD-10 code. Cox proportional hazards models were used to assess the association between constipation symptoms and incident PD.

RESULTS

In the analysis of regular laxative use and PD, 490,797 participants were included and 2,735 incident PD were detected. The multivariable adjusted HR of PD in participants who regularly used laxatives was 1.99 (95% confidence interval [CI], 1.70-2.33) compared with those who did not. In the analysis of bowel movement frequency and hard or lumpy stools and PD, 170,017 participants were included and 519 incident PD were detected. The multivariable adjusted HRs were 2.16 (95% CI, 1.74-2.68) and 2.57 (95% CI, 2.00-3.31) for participants with a bowel movement frequency of 3-6 times/week and <3 times/week, respectively, compared with those with a bowel movement frequency of ≥7 times/week; compared with participants who never had hard or lumpy stools, multivariable adjusted HRs were 1.31 (95% CI, 1.07-1.60), 2.32 (95% CI, 1.77-3.05), and 2.94 (95% CI, 2.14-4.05) for those who sometimes had hard or lumpy stools, often had hard or lumpy stools, and most of time/always had hard or lumpy stools, respectively.

CONCLUSIONS

Constipation measured by the regular use of laxatives, bowel movement frequency, and the frequency of hard or lumpy stools was significantly associated with an increased risk of incident PD.

Unearthing the Potential Therapeutic Effects of Oxyresveratrol Based on Intrinsic Links between Pharmacological Effects: Implications for the Gut-Liver-Brain Axis

Oxyresveratrol is a stilbene compound with a simple chemical structure and various therapeutic potentials. This study summarized and analyzed the multiple pharmacological effects and mechanisms of oxyresveratrol, identifying its prominent performance in neuroprotection, hepatoprotection, and anti-inflammatory activities in the intestines. By integrating the pharmacological effects of oxyresveratrol with insights from the network pharmacology and molecular docking of its interactions with targets linked to gut-liver-brain axis disorders, it has been shown that oxyresveratrol may hold promise for the treatment of gut-liver-brain axis-related disorders. The synergistic effect between various mechanisms has inspired further research and the development of oxyresveratrol's application value.

Novel strategies in Parkinson's disease treatment: a review

An unprecedented extension of life expectancy observed during the past century drastically increased the number of patients diagnosed with Parkinson's diseases (PD) worldwide. Estimated costs of PD alone reached $52 billion per year, making effective neuroprotective treatments an urgent and unmet need. Current treatments of both AD and PD focus on mitigating the symptoms associated with these pathologies and are not neuroprotective. In this review, we discuss the most advanced therapeutic strategies that can be used to treat PD. We also critically review the shift of the therapeutic paradigm from a small molecule-based inhibition of protein aggregation to the utilization of natural degradation pathways and immune cells that are capable of degrading toxic amyloid deposits in the brain of PD patients.

[Smell the smoke before one sees the fire-The oligosymptomatic prodromal phase of neurodegenerative diseases]

BACKGROUND

With the increasing development of disease-modifying causative treatment, the importance of early diagnosis and detection of asymptomatic or oligosymptomatic early stages of neurodegenerative diseases is increasing.

OBJECTIVE

Presentation of early stages of neurodegenerative diseases, diagnostic procedures for the early detection and possible treatment consequences.

MATERIAL AND METHODS

Selective literature search, discussion of basic research and expert recommendations.

RESULTS

Many neurodegenerative diseases have a prodromal phase preceding the manifest disease that can be diagnosed with current criteria. In this prodromal phase, those affected are often oligosymptomatic but in some cases can already be identified using biomarkers. These developments are already taken into account in diagnostic criteria for some of these prodromal phases. The prodromal phase, in turn, is preceded by an asymptomatic phase which, however, already shows molecular changes and can be identified by biomarkers in some diseases. The early identification and stratification of patients is particularly important when planning studies for disease-modifying treatment, and biomarkers are already being used in clinical trials for this purpose.

DISCUSSION

Biomarker-based identification of individuals in the prodromal phase of neurodegenerative diseases is already possible for some entities. People who show the first signs of a neurodegenerative disease can be referred to centers for clinical trials and observational studies.