Parkinson's disease and Parkinson's disease medications have distinct signatures of the gut microbiome

Inclusive Education and Health Performance in Sub Saharan Africa

The study assesses the effect of inclusive education on health performance in 48 Sub Saharan African countries from 2000 to 2020. The study adopted the Driscoll/Kraay technique to address cross-sectional dependence and the GMM strategy to address potential endogeneity. The study employed three indicators of health performance which are the total life expectancy, the female life expectancy and the male life expectancy. Three gender parity index of educational enrolments are employed: primary education, secondary and the tertiary education as indicators of inclusive education. The findings of the study reveal that inclusive education enhances the health situation of individuals in Sub Saharan Africa. The findings further show that the health situation of both the male and the female are improved by inclusive education. The study recommends policymakers in this region to invest more in the education and the health sector so as to enhance the health performance of the citizens.

Gut microbiota in dementia with Lewy bodies

Gut microbiota and fecal bile acids were analyzed in 278 patients with α-synucleinopathies, which were comprised of 28 patients with dementia with Lewy bodies (DLB), 224 patients with Parkinson's disease (PD), and 26 patients with idiopathic rapid eye movement sleep behavior disorder (iRBD). Similarly to PD, short-chain fatty acids-producing genera were decreased in DLB. Additionally, Ruminococcus torques and Collinsella were increased in DLB, which were not changed in PD. Random forest models to differentiate DLB and PD showed that high Ruminococcus torques and high Collinsella, which presumably increase intestinal permeability, as well as low Bifidobacterium, which are also observed in Alzheimer's disease, were predictive of DLB. As Ruminococcus torques and Collinsella are also major secondary bile acids-producing bacteria, we quantified fecal bile acids and found that the production of ursodeoxycholic acid (UDCA) was high in DLB. Increased UDCA in DLB may mitigate neuroinflammation at the substantia nigra, whereas neuroinflammation may not be critical at the neocortex. Theraeutic intervention to increase Bifidobacteirum and its metabolites may retard the development and progression of DLB.

Mangosteen Pericarp Extract Supplementation Boosts Antioxidant Status via Rebuilding Gut Microbiota to Attenuate Motor Deficit in 6-OHDA-Induced Parkinson's Disease

Oxidative stress and gut dysbiosis have been known to precede Parkinson's disease (PD). An antioxidant-rich product, mangosteen pericarp (MP), has the ability to counterbalance excessive free radicals and the imbalanced gut microbiota composition, suggesting the MP's capacity to delay PD progression. In this study, we explored the effects of two doses of MP extract in a unilateral 6-hydroxydopamine (6-OHDA)-induced PD rat model. We revealed that the 8-week supplementation of a low dose (LMP) and a high dose of the MP extract (HMP) improved motor function, as observed in decreased contralateral rotation, improved time spent on rod, and higher dopamine binding transporter (DAT) in the substantia nigra pars compacta (SNc). The MP extract, especially the HMP, also increased antioxidant-related gene expressions, restored muscle mitochondrial function, and remodeled fecal microbiota composition, which were followed by reduced reactive oxygen species levels in brain and inflammation in plasma. Importantly, bacterial genera Sutterella, Rothia, and Aggregatibacter, which were negatively correlated with antioxidant gene expressions, decreased in the HMP group. It is imperative to note that in addition to directly acting as an antioxidant to reduce excessive free radicals, MP extract might also increase antioxidant state by rebuilding gut microbiota, thereby enhanced anti-inflammatory capacity and restored mitochondrial function to attenuate motor deficit in 6-OHDA-induced PD-like condition. All in all, MP extract is a potential candidate for auxiliary therapy for PD.

Emerging insights between gut microbiome dysbiosis and Parkinson's disease: Pathogenic and clinical relevance

Parkinson's disease (PD) is a complicated neurodegenerative disease, of which gastrointestinal disturbance appears prior to motor symptoms. Numerous studies have shed light on the roles of gastrointestinal tract and its neural connection to brain in PD pathology. In the past decades, the fields of microbiology and neuroscience have become ever more entwined. The emergence of gut microbiome has been considered as one of the key regulators of gut-brain function. With the advent of multi-omics sequencing techniques, gut microbiome of PD patients has been shown unique characteristics. The resident gut microbiota can exert considerable effects in PD and there are suggestions of a link between gut microbiome dysbiosis and PD progression. In this review, we summarize the latest progresses of gut microbiome dysbiosis in PD pathogenesis, further highlight the clinical relevance of gut microbiota and its metabolites in both the non-motor and motor symptoms of PD. Furthermore, we draw attention to the complex interplay between gut microbiota and PD drugs, with the purpose of improving drug efficacy and prescription accordingly. Further studies at specific strain level and longitudinal prospective clinical trials using optimized methods are still needed for the development of diagnostic markers and novel therapeutic regimens for PD.

Toward manipulating serotonin signaling via the microbiota-gut-brain axis

It is now well established in humans that there is a bidirectional pathway of communication between the central and enteric nervous systems in which members of the microbiome participate. This microbiota-gut-brain axis (MGBA) is crucial for normal development and physiology, and its dysregulation has been implicated in a range of neurological and intestinal disorders. Investigations into the mechanistic underpinnings of the MGBA have identified serotonin as a molecule of particular interest. In this review, we highlight recent advances toward understanding the role of endogenous serotonin in microbial communities, how microbial communities bidirectionally interact with host serotonin, and potential future engineering opportunities to leverage these novel mechanisms for biomedical applications.

Approaching the Gut and Nasal Microbiota in Parkinson's Disease in the Era of the Seed Amplification Assays

Parkinson's disease (PD) is a neurodegenerative disorder often associated with pre-motor symptoms involving both gastrointestinal and olfactory tissues. PD patients frequently suffer from hyposmia, hyposalivation, dysphagia and gastrointestinal dysfunctions. During the last few years it has been speculated that microbial agents could play a crucial role in PD. In particular, alterations of the microbiota composition (dysbiosis) might contribute to the formation of misfolded α-synuclein, which is believed to be the leading cause of PD. However, while several findings confirmed that there might be an important link between intestinal microbiota alterations and PD onset, little is known about the potential contribution of the nasal microbiota. Here, we describe the latest findings on this topic by considering that more than 80% of patients with PD develop remarkable olfactory deficits in their prodromal disease stage. Therefore, the nasal microbiota might contribute to PD, eventually boosting the gut microbiota in promoting disease onset. Finally, we present the applications of the seed amplification assays to the study of the gut and olfactory mucosa of PD patients, and how they could be exploited to investigate whether pathogenic bacteria present in the gut and the nose might promote α-synuclein misfolding and aggregation.

Metagenomics of Parkinson's disease implicates the gut microbiome in multiple disease mechanisms

Parkinson's disease (PD) may start in the gut and spread to the brain. To investigate the role of gut microbiome, we conducted a large-scale study, at high taxonomic resolution, using uniform standardized methods from start to end. We enrolled 490 PD and 234 control individuals, conducted deep shotgun sequencing of fecal DNA, followed by metagenome-wide association studies requiring significance by two methods (ANCOM-BC and MaAsLin2) to declare disease association, network analysis to identify polymicrobial clusters, and functional profiling. Here we show that over 30% of species, genes and pathways tested have altered abundances in PD, depicting a widespread dysbiosis. PD-associated species form polymicrobial clusters that grow or shrink together, and some compete. PD microbiome is disease permissive, evidenced by overabundance of pathogens and immunogenic components, dysregulated neuroactive signaling, preponderance of molecules that induce alpha-synuclein pathology, and over-production of toxicants; with the reduction in anti-inflammatory and neuroprotective factors limiting the capacity to recover. We validate, in human PD, findings that were observed in experimental models; reconcile and resolve human PD microbiome literature; and provide a broad foundation with a wealth of concrete testable hypotheses to discern the role of the gut microbiome in PD.

Probiotic Pediococcus pentosaceus ameliorates MPTP-induced oxidative stress via regulating the gut microbiota–gut–brain axis

Recent evidence demonstrated that functional bacteria were involved in the regulation of Parkinson’s disease (PD). However, the mechanism of probiotics in improving PD was unclear. Here the antioxidant effect and the mechanism of probiotics Pediococcus pentosaceus (PP) on PD were studied by regulating the gut–brain axis. In this study, male C57BL/6J mice were injected with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) intraperitoneally to establish a PD model and were then treated with PP for 4 weeks. Subsequently, a series of neurobehavioral tests to evaluate the motor function of the mice was performed. Additionally, degeneration of dopaminergic neurons, accumulation of α-synuclein, the production of an oxidative stress response, and the expression of nuclear factor erythroid 2-related factor 2 (Nrf2) pathway-related proteins were evaluated. Moreover, the gut microbial composition and the level of metabolite γ-aminobutyric acid (GABA) were assessed. The results showed that PP treatment could improve MPTP-induced motor deficits, the degeneration of dopaminergic neurons, and the accumulation of α-synuclein. Moreover, PP treatment significantly increased the levels of SOD1, Gpx1, and Nrf2, while it decreased the levels of Keap1 in the brain of MPTP-induced mice. Notably, PP treatment improved the gut microbial dysbiosis and increased the level of GABA in MPTP-induced mice. These findings indicated that PP might represent a promising candidate, due to the metabolite of GABA, that could be used for the treatment of PD.

What Are the Key Gut Microbiota Involved in Neurological Diseases? A Systematic Review

There is a growing body of evidence highlighting there are significant changes in the gut microbiota composition and relative abundance in various neurological disorders. We performed a systematic review of the different microbiota altered in a wide range of neurological disorders (Alzheimer's disease (AD), Parkinson's disease (PD), multiple sclerosis (MS), amyotrophic lateral sclerosis, and stroke). Fifty-two studies were included representing 5496 patients. At the genus level, the most frequently involved microbiota are Akkermansia, Faecalibacterium, and Prevotella. The overlap between the pathologies was strongest for MS and PD, sharing eight genera (Akkermansia, Butyricicoccus, Bifidobacterium, Coprococcus, Dorea, Faecalibacterium, Parabacteroides, and Prevotella) and PD and stroke, sharing six genera (Enterococcus, Faecalibacterium, Lactobacillus, Parabacteroides, Prevotella, and Roseburia). The identification signatures overlapping for AD, PD, and MS raise the question of whether these reflect a common etiology or rather common consequence of these diseases. The interpretation is hampered by the low number and low power for AD, ALS, and stroke with ample opportunity for false positive and false negative findings.

Vagus Nerve and Underlying Impact on the Gut Microbiota-Brain Axis in Behavior and Neurodegenerative Diseases

The gut microbiota is the most abundant and diverse microbiota in the human body and the vagus nerve is the most widely distributed and complex nerve in the body, both of them are essential in maintaining homeostasis. The most important phenomenon is how they coordinate to regulate functions, which has attracted the great attention of scientists. The academic literature on the correlation with a host of intestinal diseases and even systemic diseases has revealed the bidirectional communication between the gut microbiota and the brain, which can be carried out via multiple patterns. In the review, firstly, we have a general overview of the gut microbiota and the gut microbiota-brain axis. Secondly, according to the distribution characteristics of the vagus nerve, we analyzed and summarized its function in the intestinal tract. At the same time, we have summarized the underlying mechanism of some behavior changes such as depressive and anxiety-like behaviors and related neurodegenerative diseases caused by the vagus nerve and intestinal microecological environment disorders, and then we also analyzed inconsistency of the experimental evidence in order to propose novel strategies for the clinical practice.

The interplay between the gut-brain axis and the microbiome: A perspective on psychiatric and neurodegenerative disorders

What is the effect of our gut microbial flora on brain? Does the gut microbiome have any role in the causation of psychiatric and neurodegenerative diseases? Does the effect of gut microbiota traverse the gut-brain axis? Questions like these have captured the interest and imagination of the scientific community for quite some time now. Research in the quest for answers to these questions, to unravel the potential role of the microbiota inhabiting the gut in controlling brain functions, has progressed manifold over the last two decades. Although the possibility of microbiome as a key susceptibility factor for neurological disorders viz. Parkinson's disease, Alzheimer's disease, multiple sclerosis, and autism spectrum disorder has bolstered by an increase in the clinical and preclinical evidence, the field is still in its infancy. Given the fact that the diversity of the gut microbiota is affected by various factors including the diet and exercise, the interpretation of such data becomes all the more difficult. Also, such studies have been mostly conducted on animal models, so there is a need for randomized controlled trials in human subjects, corroborated by longitudinal studies, to establish if modulating the gut microbiota can unravel novel therapeutic interventions. Exploring the genomic, metagenomic and metabolomic data from clinical subjects with psychiatric and neurological diseases can prove to be a helpful guide in individual treatment selection.

Gut bacterial profiles in Parkinson's disease: A systematic review

INTRODUCTION

Recent advances have highlighted the relationships between gut dysbiosis and Parkinson's disease (PD). Microbiota transplantation from PD patients to mice can induce increased alpha-synuclein-mediated motor deficits. Human studies have identified differences in the gut microbiota of PD patients compared to healthy controls. We undertook a systematic review to evaluate the available evidence for the involvement of gut bacteria in the etiology of PD.

METHODS

The PubMed databank, the China National Knowledge Infrastructure databank, and Wanfang Data were searched from inception until June 2021 to identify human case-control studies that investigated relationships between PD and microbiota quantified from feces. We evaluated the resulting studies focusing on bacterial taxa that were different between PD patients and healthy controls.

RESULTS

Twenty-six studies were found in which 53 microbial families and 98 genera exhibited differences between patients with PD and healthy controls. The genera identified by more than two studies as increased in PD were Bifidobacterium, Alistipes, Christensenella, Enterococcus, Oscillospira, Bilophila, Desulfovibrio, Escherichia/Shigella, and Akkermansia, while Prevotella, Blautia, Faecalibacterium, Fusicatenibacter, and Haemophilus had three or more reports of being lower in PD patients. More than one report demonstrated that Bacteroides, Odoribacter, Parabacteroides, Butyricicoccus, Butyrivibrio, Clostridium, Coprococcus, Lachnospira, Lactobacillus, Megasphaera, Phascolarctobacterium, Roseburia, Ruminococcus, Streptococcus, and Klebsiella were altered in both directions.

CONCLUSION

Our review shows that the involvement of the gut microbiome in the etiology of PD may involve alterations of short-chain fatty acids (SCFAs)-producing bacteria and an increase in putative gut pathobionts. SCFAs-producing bacteria may vary above or below an "optimal range," causing imbalances. Considering that Bifidobacterium, Lactobacillus, and Akkermansia are beneficial for human health, increased Bifidobacterium and Lactobacillus in the PD gut microbiome may be associated with PD medications, especially COMT inhibitors, while a high level of Akkermansia may be associated with aging.

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.

Fecal microbiome alterations in treatment-naive de novo Parkinson's disease

Gut microbiota alterations in Parkinson's disease (PD) have been found in several studies and are suggested to contribute to the pathogenesis of PD. However, previous results could not be adequately adjusted for a potential confounding effect of PD medication and disease duration, as almost all PD participants were already using dopaminergic medication and were included several years after diagnosis. Here, the gut microbiome composition of treatment-naive de novo PD subjects was assessed compared to healthy controls (HC) in two large independent case-control cohorts (n = 136 and 56 PD, n = 85 and 87 HC), using 16S-sequencing of fecal samples. Relevant variables such as technical batches, diet and constipation were assessed for their potential effects. Overall gut microbiome composition differed between PD and HC in both cohorts, suggesting gut microbiome alterations are already present in de novo PD subjects at the time of diagnosis, without the possible confounding effect of dopaminergic medication. Although no differentially abundant taxon could be replicated in both cohorts, multiple short chain fatty acids (SCFA) producing taxa were decreased in PD in both cohorts. In particular, several taxa belonging to the family Lachnospiraceae were decreased in abundance. Fewer taxonomic differences were found compared to previous studies, indicating smaller effect sizes in de novo PD.

Role of the gut-microbiota-metabolite axis in the rotenone model of early-stage Parkinson's Disease

Gastrointestinal symptoms are common in the early-stage Parkinson's disease (PD), but its potential pathogenesis remains unclear. Therefore, in the present study, we used the 16S ribosomal RNA gene sequencing and gas chromatography coupled with mass spectrometry-based metabolomics to investigate the alterations of gut microbiome and serum amino acid levels in the early-stage PD mice model induced with rotenone. The results demonstrated that the microbial taxa at phylum, family and genus levels remarkably altered in rotenone-induced mice relative to vehicle-induced mice. The rotenone-induced mice had higher relative abundance of Flavobacteriaceae, Staphylococcaceae, and Prevotellaceae as well as lower relative abundance of Lachnospiraceae_UCG-001, Ruminiclostridium, and Prevotellaceae_NK3B31_group than vehicle-induced mice. The evaluation of serum amino acids revealed the alterations in several classes of amino acids, including L-proline, L-alanine, L-serine, L-asparagine, L-threonine, L-glutamine, L-methionine, and L-4-hydroxyproline. Notably, the altered serum amino acid levels were significantly associated with the abundance of gut microbiota, especially Ruminococcaceae and Ruminiclostridium. Our study explored the possible role of the gut-microbiota-metabolite axis in the early-stage PD and provided the possibility of prevention and treatment of PD by gut-microbiota-metabolite axis in the future.

Inflammasome Activation in Parkinson’s Disease

Chronic sterile inflammation and persistent immune activation is a prominent pathological feature of Parkinson’s disease (PD). Inflammasomes are multi-protein intracellular signaling complexes which orchestrate inflammatory responses in immune cells to a diverse range of pathogens and host-derived signals. Widespread inflammasome activation is evident in PD patients at the sites of dopaminergic degeneration as well as in blood samples and mucosal biopsies. Inflammasome activation in the nigrostriatal system is also a common pathological feature in both neurotoxicant and α-synuclein models of PD where dopaminergic degeneration occurs through distinct mechanisms. The NLRP3 (NLR Family Pyrin Domain Containing 3) inflammasome has been shown to be the primary driver of inflammatory neurotoxicity in PD and other neurodegenerative diseases. Chronic NLRP3 inflammasome activation is triggered by pathogenic misfolded α-synuclein aggregates which accumulate and spread over the disease course in PD. Converging lines of evidence suggest that blocking inflammasome activation could be a promising therapeutic strategy for disease modification, with both NLRP3 knockout mice and CNS-permeable pharmacological inhibitors providing robust neuroprotection in multiple PD models. This review summarizes the current evidence and knowledge gaps around inflammasome activation in PD, the pathological mechanisms by which persistent inflammasome activation can drive dopaminergic degeneration and the therapeutic opportunities for disease modification using NLRP3 inhibitors.

Does the Gut Microbial Metabolome Really Matter? The Connection between GUT Metabolome and Neurological Disorders

Herein we gathered updated knowledge regarding the alterations of gut microbiota (dysbiosis) and its correlation with human neurodegenerative and brain-related diseases, e.g., Alzheimer’s and Parkinson’s. This review underlines the importance of gut-derived metabolites and gut metabolic status as the main players in gut-brain crosstalk and their implications on the severity of neural conditions. Scientific evidence indicates that the administration of probiotic bacteria exerts beneficial and protective effects as reduced systemic inflammation, neuroinflammation, and inhibited neurodegeneration. The experimental results performed on animals, but also human clinical trials, show the importance of designing a novel microbiota-based probiotic dietary supplementation with the aim to prevent or ease the symptoms of Alzheimer’s and Parkinson’s diseases or other forms of dementia or neurodegeneration.

Zinc Supplementation Partially Decreases the Harmful Effects of a Cafeteria Diet in Rats but Does Not Prevent Intestinal Dysbiosis

Zinc (Zn) plays an important role in metabolic homeostasis and may modulate neurological impairment related to obesity. The present study aimed to evaluate the effect of Zn supplementation on the intestinal microbiota, fatty acid profile, and neurofunctional parameters in obese male Wistar rats. Rats were fed a cafeteria diet (CAF), composed of ultra-processed and highly caloric and palatable foods, for 20 weeks to induce obesity. From week 16, Zn supplementation was started (10 mg/kg/day). At the end of the experiment, we evaluated the colon morphology, composition of gut microbiota, intestinal fatty acids, integrity of the intestinal barrier and blood-brain barrier (BBB), and neuroplasticity markers in the cerebral cortex and hippocampus. Obese rats showed dysbiosis, morphological changes, short-chain fatty acid (SCFA) reduction, and increased saturated fatty acids in the colon. BBB may also be compromised in CAF-fed animals, as claudin-5 expression is reduced in the cerebral cortex. In addition, synaptophysin was decreased in the hippocampus, which may affect synaptic function. Our findings showed that Zn could not protect obese animals from intestinal dysbiosis. However, an increase in acetate levels was observed, which suggests a partial beneficial effect of Zn. Thus, Zn supplementation may not be sufficient to protect from obesity-related dysfunctions.

Clostridioides difficile and neurological disorders: New perspectives

Despite brain physiological functions or pathological dysfunctions relying on the activity of neuronal/non-neuronal populations, over the last decades a plethora of evidence unraveled the essential contribution of the microbial populations living and residing within the gut, called gut microbiota. The gut microbiota plays a role in brain (dys)functions, and it will become a promising valuable therapeutic target for several brain pathologies. In the present mini-review, after a brief overview of the role of gut microbiota in normal brain physiology and pathology, we focus on the role of the bacterium Clostridioides difficile, a pathogen responsible for recurrent and refractory infections, in people with neurological diseases, summarizing recent correlative and causative evidence in the scientific literature and highlighting the potential of microbiota-based strategies targeting this pathogen to ameliorate not only gastrointestinal but also the neurological symptoms.

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.

Microbiome-Based Therapies in Parkinson's Disease: Can Tuning the Microbiota Become a Viable Therapeutic Strategy?

Progressive neurodegenerative disorders such as Parkinson's disease (PD) have continued to baffle medical science, despite strides in the understanding of their pathology. The inability of currently available therapies to halt disease progression is a testament to an incomplete understanding of pathways crucial to disease initiation, progression and management. Science has continued to link the activities and equilibrium of the gut microbiome to the health and proper functioning of brain neurons. They also continue to stir interest in the potential applications of technologies that may shift the balance of the gut microbiome towards achieving a favourable outcome in PD management. There have been suggestions that an improved understanding of the roles of the gut microbiota is likely to lead to the emergence of an era where their manipulation becomes a recognized strategy for PD management. This review examines the current state of our journey in the quest to understand how the gut microbiota can influence several aspects of PD. We highlight the relationship between the gut microbiome/microbiota and PD pathogenesis, as well as preclinical and clinical evidence evaluating the effect of postbiotics, probiotics and prebiotics in PD management. This is with a view to ascertaining if we are at the threshold of discovering the application of a usable tool in our quest for disease modifying therapies in PD.

Protocol for rapid obtention and fractionation of anaerobic bacterial conditioned media to study calcium signaling in enteroendocrine cells

Gut microbiota influences neurodevelopment, behavior and contributes to neurodegenerative disorders. One possible mechanism is the direct modulation of calcium (Ca²⁺) signaling and protein homeostasis in enteroendocrine cells (EECs), a component of the gut epithelium. Here, we present a protocol to isolate fractions of conditioned media (CM) from the anaerobic bacteria Akkermansia muciniphila and the utilization of this CM to monitor Ca²⁺ fluctuation in EECs by imaging. This protocol can be adapted and applied to various bacterial cultures and cell types.

For complete details on the use and execution of this protocol, please refer to Amorim Neto et al. (2022).

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Protocol for rapid obtention and fractionation of anaerobic bacterial conditioned media

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Protocol can be applied to different anaerobic bacterial strains

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Isolated media can be used to study Ca²⁺ signaling in several mammalian cells

Publisher’s note: Undertaking any experimental protocol requires adherence to local institutional guidelines for laboratory safety and ethics.

Curcumin-driven reprogramming of the gut microbiota and metabolome ameliorates motor deficits and neuroinflammation in a mouse model of Parkinson's disease

Background

Parkinson's disease (PD) is a common neurodegenerative disorder, accompanied by motor deficits as well as gastrointestinal dysfunctions. Recent studies have proved that the disturbance of gut microbiota and metabolism contributes to the pathogenesis of PD; however, the mechanisms underlying these effects have yet to be elucidated. Curcumin (CUR) has been reported to provide neuroprotective effects on neurological disorders and modulate the gut flora in intestinal-related diseases. Therefore, it is of significant interest to investigate whether CUR could exert a protective effect on PD and whether the effect of CUR is dependent on the intestinal flora and subsequent changes in metabolites.

Methods

In this study, we investigated the neuroprotective effects of CUR on a mouse model of PD induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). 16S rRNA sequencing was performed to explore the profile of the gut microbiota among controls, MPTP-treated mice and CUR-treated mice. Then, antibiotic treatment (ABX) and fecal microbiota transplantation (FMT) experiments were conducted to examine the role of intestinal microbes on the protective effects of CUR in PD mice. Furthermore, ultra-high-performance liquid chromatography-mass spectrometry (UHPLC-MS)-based metabolomics analysis was used to identify the landscape of the CUR-driven serum metabolome. Finally, Pearson's analysis was conducted to investigate correlations between the gut flora-metabolite axis and CUR-driven neuroprotection in PD.

Results

Our results showed that CUR intervention effectively improved motor deficits, glial cell activation, and the aggregation of α-synuclein (α-syn) in MPTP-treated mice. 16S rRNA sequencing showed elevated abundances of Muribaculaceae, Lactobacillaceae, Lachnospiraceae and Eggerthellaceae but depleted abundances of Aerococcaceae and Staphylococcaceae in CUR-treated mice when compared with MPTP mice. ABX and FMT experiments further confirmed that the gut microbiota was required for CUR-induced protection in PD mice. Serum metabolomics analysis showed that CUR notably upregulated the levels of tyrosine, methionine, sarcosine and creatine. Importantly, strong correlations were identified among crucial taxa (Aerococcaceae, Staphylococcaceae, Muribaculaceae, Lactobacillaceae, Lachnospiraceae and Eggerthellaceae), pivotal metabolites (tyrosine, methionine, sarcosine and creatine) and the motor function and pathological results of mice. CUR treatment led to a rapid increase in the brain levels of tyrosine and levodopa (dopa) these changes were related to the abundances of Lactobacillaceae and Aerococcaceae.

Conclusions

CUR exerts a protective effect on the progression of PD by modulating the gut microbiota-metabolite axis. Lactobacillaceae and Aerococcaceae, along with key metabolites such as tyrosine and dopa play a dominant role in CUR-associated neuroprotection in PD mice. Our findings offer unique insights into the pathogenesis and potential treatment of PD.

Intestinal microbiota and neuroinflammation in Parkinson's disease: At the helm of the gut-brain axis

Emerging data suggest that disrupted intestinal microbiota, or dysbiosis, may be responsible for multiple features of Parkinson's disease (PD), from initiation, to progression, to therapeutic response. We have progressed greatly in our understanding of microbial signatures associated with PD, and have gained important insights into how dysbiosis and intestinal permeability promote neurodegeneration through neuroinflammation and Lewy body formation. These insights underscore the potential of microbiota-directed therapies, which include dietary, pharmacologic, and lifestyle interventions.

Microbiome influences on neuro-immune interactions in neurodegenerative disease

Mounting evidence points to a role for the gut microbiome in a wide range of central nervous system diseases and disorders including depression, multiple sclerosis, Alzheimer's disease, Parkinson's disease, and autism spectrum disorder. Moreover, immune system involvement has also been implicated in these diseases, specifically with inflammation being central to their pathogenesis. In addition to the reported changes in gut microbiome composition and altered immune states in many neurological diseases, how the microbiome and the immune system interact to influence disease onset and progression has recently garnered much attention. This chapter provides a review of the literature related to gut microbiome influences on neuro-immune interactions with a particular focus on neurological diseases. Gut microbiome-derived mediators, including short-chain fatty acids and other metabolites, lipopolysaccharide, and neurotransmitters, and their impact on neuro-immune interactions as well as routes by which these interactions may occur are also discussed.

Microbiota Dysbiosis in Parkinson Disease—In Search of a Biomarker

Numerous studies have highlighted the role of the gastrointestinal system in Parkinson disease pathogenesis. It is likely triggered by proinflammatory markers produced by specific gut bacteria. This review’s aim is to identify gut bacterial biomarkers of Parkinson disease. A comprehensive search for original research papers on gut microbiota composition in Parkinson disease was conducted using the PubMed, Embase, and Scopus databases. Research papers on intestinal permeability, nasal and oral microbiomes, and interventional studies were excluded. The yielded results were categorized into four groups: Parkinson disease vs. healthy controls; disease severity; non-motor symptoms; and clinical phenotypes. This review was conducted in accordance with the PRISMA 2020 statement. A total of 51 studies met the eligibility criteria. In the Parkinson disease vs. healthy controls group, 22 bacteria were deemed potentially important. In the disease severity category, two bacteria were distinguished. In the non-motor symptoms and clinical phenotypes categories, no distinct pathogen was identified. The studies in this review report bacteria of varying taxonomic levels, which prevents the authors from reaching a clear conclusion. Future research should follow a unified methodology in order to identify potential biomarkers for Parkinson disease.

Individual Nutrition Is Associated with Altered Gut Microbiome Composition for Adults with Food Insecurity

Diet is widely recognized as a key contributor to human gut microbiome composition and function. However, overall nutrition can be difficult to compare across a population with varying diets. Moreover, the role of food security in the relationship with overall nutrition and the gut microbiome is unclear. This study aims to investigate the association between personalized nutrition scores, variation in the adult gut microbiome, and modification by food insecurity. The data originate from the Survey of the Health of Wisconsin and the Wisconsin Microbiome Study. Individual nutrition scores were assessed using My Nutrition Index (MNI), calculated using data from food frequency questionnaires, and additional health history and demographic surveys. Food security and covariate data were measured through self-reported questionnaires. The gut microbiome was assessed using 16S amplicon sequencing of DNA extracted from stool samples. Associations, adjusted for confounding and interaction by food security, were estimated using Weighted Quantile Sum (WQS) regression models with Random Subset and Repeated Holdout extensions (WQSRSRH), with bacterial taxa used as components in the weighted index. Of 643 participants, the average MNI was 66.5 (SD = 31.9), and 22.8% of participants were food insecure. Increased MNI was significantly associated with altered gut microbial composition (β = 2.56, 95% CI = 0.52−4.61), with Ruminococcus, Oscillospira, and Blautia among the most heavily weighted of the 21 genera associated with the MNI score. In the stratified interaction WQSRSRH models, the bacterial taxa most heavily weighted in the association with MNI differed by food security, but the level of association between MNI and the gut microbiome was not significantly different. More bacterial genera are important in the association with higher nutrition scores for people with food insecurity versus food security, including Streptococcus, Parabacteroides Faecalibacterium, and Desulfovibrio. Individual nutrition scores are associated with differences in adult gut microbiome composition. The bacterial taxa most associated with nutrition vary by level of food security. While further investigation is needed, results showed a higher nutrition score was associated with a wider range of bacterial taxa for food insecure vs. secure, suggesting nutritional quality in food insecure individuals is important in maintaining health and reducing disparities.

Multi-omic Analysis of the Gut Microbiome in Rats with Lithium-Pilocarpine-Induced Temporal Lobe Epilepsy

Evidence supports that the gut microbiota and bacteria-dependent metabolites influence the maintenance of epileptic brain activity. However, the alterations in the gut microbiota between epileptic versus healthy individuals are poorly understood. We used a multi-omic approach to evaluate the changes in the composition of gut metagenome as well in the fecal metabolomic profile in rats before and after being submitted to status epilepticus (SE)-induced temporal lobe epilepsy (TLE). The 16S ribosomal RNA (rRNA) sequencing of fecal samples coupled to bioinformatic analysis revealed taxonomic, compositional, and functional shifts in epileptic rats. The species richness (Chao1 index) was significantly lower in the post-TLE group, and the β-diversity analysis revealed clustering separated from the pre-TLE group. The taxonomic abundance analysis showed a significant increase of phylum Desulfobacterota and a decrease of Patescibacteria in the post-TLE group. The DESEq2 and LEfSe analysis resulted in 18 genera significantly enriched between post-TLE and pre-TLE groups at the genus level. We observed that epileptic rats present a peculiar metabolic phenotype, including a lower concentration of D-glucose and L-lactic acid and a higher concentration of L-glutamic acid and glycine. The microbiota-host metabolic correlation analysis showed that the genera differentially abundant in post-TLE rats are associated with the altered metabolites, especially the proinflammatory Desulfovibrio and Marvinbryantia, which were enriched in epileptic animals and positively correlated with these excitatory neurotransmitters and carbohydrate metabolites. Therefore, our data revealed a correlation between dysbacteriosis in epileptic animals and fecal metabolites that are known to be relevant for maintaining epileptic brain activity by enhancing chronic inflammation, an excitatory-inhibitory imbalance, and/or a metabolic disturbance. These data are promising and suggest that targeting the gut microbiota could provide a novel avenue for preventing and treating acquired epilepsy. However, the causal relationship between these microbial/metabolite components and the SRS occurrence still needs further exploration.

The many genomes of Parkinson's disease

Genetic component of Parkinson's disease, once firmly believed non-existent, involves the human genome, mitochondrial genome, and the microbiome. Understanding the genomics of PD requires identification of PD-relevant genes and learning how they interact within the hologenome and with their environment. This chapter is an evidence-based perspective of a geneticist on how far we have come in this endeavor. The contemporary scientific society started with a naive and simplistic view of PD, evolved to accept that Parkinson's disease is probably the most complex disease there is, the progress we have made in discovering the genes and elucidating their functions, and now assembling the parts to create the whole.

Management of dysphagia and gastroparesis in Parkinson's disease in real-world clinical practice - Balancing pharmacological and non-pharmacological approaches

Gastrointestinal (GI) issues are commonly experienced by patients with Parkinson's disease (PD). Those that affect the lower GI tract, such as constipation, are the most frequently reported GI problems among patients with PD. Upper GI issues, such as swallowing dysfunction (dysphagia) and delayed gastric emptying (gastroparesis), are also common in PD but are less well recognized by both patients and clinicians and, therefore, often overlooked. These GI issues may also be perceived by the healthcare team as less of a priority than management of PD motor symptoms. However, if left untreated, both dysphagia and gastroparesis can have a significant impact on the quality of life of patients with PD and on the effectiveness on oral PD medications, with negative consequences for motor control. Holistic management of PD should therefore include timely and effective management of upper GI issues by utilizing both non-pharmacological and pharmacological approaches. This dual approach is key as many pharmacological strategies have limited efficacy in this setting, so non-pharmacological approaches are often the best option. Although a multidisciplinary approach to the management of GI issues in PD is ideal, resource constraints may mean this is not always feasible. In 'real-world' practice, neurologists and PD care teams often need to make initial assessments and treatment or referral recommendations for their patients with PD who are experiencing these problems. To provide guidance in these cases, this article reviews the published evidence for diagnostic and therapeutic management of dysphagia and gastroparesis, including recommendations for timely and appropriate referral to GI specialists when needed and guidance on the development of an effective management plan.

Rotenone aggravates PD-like pathology in A53T mutant human α-synuclein transgenic mice in an age-dependent manner

Multiple factors such as genes, environment, and age are involved in developing Parkinson’s disease (PD) pathology. However, how various factors interact to cause PD remains unclear. Here, 3-month and 9-month-old hα-syn^+⁣/− mice were treated with low-dose rotenone for 2 months to explore the mechanisms that underline the environment–gene–age interaction in the occurrence of PD. We have examined the behavior of mice and the PD-like pathologies of the brain and gut. The present results showed that impairments of the motor function and olfactory function were more serious in old hα-syn^+/– mice with rotenone than that in young mice. The dopaminergic neuron loss in the SNc is more in old hα-syn^+/– mice with rotenone than in young mice. Expression of hα-syn^+/– is increased in the SNc of hα-syn^+/– mice following rotenone treatment for 2 months. Furthermore, the number of activated microglia cells increased in SNc and accompanied the high expression of inflammatory cytokines, namely, TNF-α and IL-18 in the midbrain of old hα-syn^+/– mice treated with rotenone. Meanwhile, we found that after treatment with rotenone, hα-syn positive particles deposited in the intestinal wall, intestinal microflora, and T lymphocyte subtypes of Peyer’s patches changed, and intestinal mucosal permeability increased. Moreover, these phenomena were age-dependent. These findings suggested that rotenone aggravated the PD-like pathologies and affected the brain and gut of human α-syn^+/– transgenic mice in an age-dependent manner.

Specific gut microbiota alterations in essential tremor and its difference from Parkinson's disease

Essential tremor (ET) is the most common movement disorder and share overlapping symptoms with Parkinson’s disease (PD), making differential diagnosis challenging. Gut dysbiosis is regarded crucial in the pathogenesis of PD. Since ET patients also has comorbidity in gastrointestinal disorders, the relationship between gut microbiota and ET really worth investigating and may help distinguishing ET from PD. Fecal samples from 54 ET, 67 de novo PD and 54 normal controls (NC) were collected for 16S ribosomal RNA gene sequencing and quantitative real-time PCR. ET showed lower species richness (Chao1 index) than NC and PD. ET was with Bacteroides-dominant enterotype, while PD was with Ruminococcus-dominant enterotype. Compared with NC, 7 genera were significantly reduced in ET, 4 of which (Ruminococcus, Romboutsia, Mucispirillum, and Aeromonas) were identified to be distinctive with an area under the curve (AUC) of 0.705. Compared to PD, 26 genera were found significantly different from ET, 4 of which (Bacteroides, Fusobacterium, Phascolarctobacterium, and Lachnospira) were found distinguishable with an AUC of 0.756. Clinical association results indicated that Proteus was associated with disease severity (TETRAS) of ET, while Klebsiella was linked to depression and anxiety in ET. Functional predictions revealed that 4 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways were altered in ET. This study reveals gut dysbiosis in ET and it provides new insight into the pathogenesis of ET and helps distinguishing ET from PD.

Role of the Gut-Brain Axis, Gut Microbial Composition, Diet, and Probiotic Intervention in Parkinson's Disease

Parkinson's disease (PD) is the second-most prevalent neurodegenerative or neuropsychiatric disease, affecting 1% of seniors worldwide. The gut microbiota (GM) is one of the key access controls for most diseases and disorders. Disturbance in the GM creates an imbalance in the function and circulation of metabolites, resulting in unhealthy conditions. Any dysbiosis could affect the function of the gut, consequently disturbing the equilibrium in the intestine, and provoking pro-inflammatory conditions in the gut lumen, which send signals to the central nervous system (CNS) through the vagus enteric nervous system, possibly disturbing the blood-brain barrier. The neuroinflammatory conditions in the brain cause accumulation of α-syn, and progressively develop PD. An important aspect of understanding and treating the disease is access to broad knowledge about the influence of dietary supplements on GM. Probiotics are live microorganisms which, when administered in adequate amounts, confer a health benefit on the host. Probiotic supplementation improves the function of the CNS, and improves the motor and non-motor symptoms of PD. Probiotic supplementation could be an adjuvant therapeutic method to manage PD. This review summarizes the role of GM in health, the GM-brain axis, the pathogenesis of PD, the role of GM and diet in PD, and the influence of probiotic supplementation on PD. The study encourages further detailed clinical trials in PD patients with probiotics, which aids in determining the involvement of GM, intestinal mediators, and neurological mediators in the treatment or management of PD.

Role of the gut microbiota in the development of various neurological diseases

INTRODUCTION

In recent years, the scientific evidence supporting a relationship between the microbiota and various diseases has increased significantly; this trend has also been observed for neurological diseases. This has given rise to the concept of the gut-brain axis and the idea of a relationship between the gut microbiota and several neurological diseases whose aetiopathogenesis is yet to be clearly defined.

DEVELOPMENT

We review the role of the gut microbiota in the gut-brain axis and analyse those neurological diseases in which alterations in the gut microbiota have been described as a result of human studies: specifically, Parkinson's disease, Alzheimer disease, amyotrophic lateral sclerosis, neuromyelitis optica, and multiple sclerosis.

CONCLUSIONS

The body of evidence linking the gut microbiota to various neurological diseases has grown considerably. Several interesting studies show a relationship between the gut microbiota and Parkinson's disease, Alzheimer disease, neuromyelitis optica, and multiple sclerosis, whereas other controversial studies implicate it in amyotrophic lateral sclerosis. Many of these studies place considerable emphasis on modulation of inflammation, particularly by bacteria capable of producing short-chain fatty acids. Despite these encouraging results, many questions remain, and there is a need to demonstrate causality, determine the role of fungi or viruses, and research possible treatment through diet, probiotics, or faecal microbiota transplantation.

Role of the gut microbiota in the development of various neurological diseases

INTRODUCTION

In recent years, the scientific evidence supporting a relationship between the microbiota and various diseases has increased significantly; this trend has also been observed for neurological diseases. This has given rise to the concept of the gut-brain axis and the idea of a relationship between the gut microbiota and several neurological diseases whose aetiopathogenesis is yet to be clearly defined.

DEVELOPMENT

We review the role of the gut microbiota in the gut-brain axis and analyse those neurological diseases in which alterations in the gut microbiota have been described as a result of human studies: specifically, Parkinson's disease, Alzheimer disease, amyotrophic lateral sclerosis, neuromyelitis optica, and multiple sclerosis.

CONCLUSIONS

The body of evidence linking the gut microbiota to various neurological diseases has grown considerably. Several interesting studies show a relationship between the gut microbiota and Parkinson's disease, Alzheimer disease, neuromyelitis optica, and multiple sclerosis, whereas other controversial studies implicate it in amyotrophic lateral sclerosis. Many of these studies place considerable emphasis on modulation of inflammation, particularly by bacteria capable of producing short-chain fatty acids. Despite these encouraging results, many questions remain, and there is a need to demonstrate causality, determine the role of fungi or viruses, and research possible treatment through diet, probiotics, or faecal microbiota transplantation.

The role of LRRK2 in the periphery: link with Parkinson's disease and inflammatory diseases

Parkinson's disease (PD) is currently considered a multisystemic disorder rather than a pure brain disease, in line with the multiple hit hypothesis from Braak. However, despite increasing evidence that the pathology might originate in the periphery, multiple unknown aspects and contradictory data on the pathological processes taking place in the periphery jeopardize the interpretation and therapeutic targeting of PD. Mutations in the leucine-rich-repeat kinase 2 (LRRK2) gene have been widely linked with familial and sporadic PD cases. However, the actual role of LRRK2 in PD pathophysiology is far from understood. There is evidence that LRRK2 may be involved in alpha-synuclein (α-synuclein) pathology and immune cell regulation, but it has also been associated with inflammatory diseases such as inflammatory bowel disease, tuberculosis, leprosy, and several other bacterial infections. In this review, we focus on the different roles of LRRK2 in the periphery. More specifically, we discuss the involvement of LRRK2 in the propagation of α-synuclein pathology and its regulatory role in peripheral inflammation. A deeper understanding of the multidimensional functions of LRRK2 will pave the way for more accurate characterization of PD pathophysiology and its association with other inflammatory diseases.

Overlapping Mechanisms of Action of Brain-Active Bacteria and Bacterial Metabolites in the Pathogenesis of Common Brain Diseases

The involvement of the gut microbiota and the metabolites of colon-residing bacteria in brain disease pathogenesis has been covered in a growing number of studies, but comparative literature is scarce. To fill this gap, we explored the contribution of the microbiota-gut-brain axis to the pathophysiology of seven brain-related diseases (attention deficit hyperactivity disorder, autism spectrum disorder, schizophrenia, Alzheimer's disease, Parkinson's disease, major depressive disorder, and bipolar disorder). In this article, we discussed changes in bacterial abundance and the metabolic implications of these changes on disease development and progression. Our central findings indicate that, mechanistically, all seven diseases are associated with a leaky gut, neuroinflammation, and over-activated microglial cells, to which gut-residing bacteria and their metabolites are important contributors. Patients show a pro-inflammatory shift in their colon microbiota, harbouring more Gram-negative bacteria containing immune-triggering lipopolysaccharides (LPS) in their cell walls. In addition, bacteria with pro-inflammatory properties (Alistipes, Eggerthella, Flavonifractor) are found in higher abundances, whereas lower abundances of anti-inflammatory bacteria (Bifidobacterium, Coprococcus, Eucbacterium, Eubacterium rectale, Faecalibacterium, Faecalibacterium prasunitzii, Lactobacillus, Prevotella, Roseburia) are reported, when compared to healthy controls. On the metabolite level, aberrant levels of short-chain fatty acids (SCFAs) are involved in disease pathogenesis and are mostly found in lower quantities. Moreover, bacterial metabolites such as neurotransmitters (acetylcholine, dopamine, noradrenaline, GABA, glutamate, serotonin) or amino acids (phenylalanine, tryptophan) also play an important role. In the future, defined aberrations in the abundance of bacteria strains and altered bacterial metabolite levels could likely be possible markers for disease diagnostics and follow-ups. Moreover, they could help to identify novel treatment options, underlining the necessity for a deeper understanding of the microbiota-gut-brain axis.

Heat-inactivated Lacticaseibacillus paracasei N1115 alleviates the damage due to brain function caused by long-term antibiotic cocktail exposure in mice

Critical development period of intestinal microbiota occurs concurrently with brain development, and their interaction is influenced by the microbiota–gut–brain axis. This study examined how antibiotics exposure affected gut microbiota and brain development and analyzed the possible benefits of heat-inactivated Lacticaseibacillus paracasei N1115 (N1115). Thirty neonatal male mice were randomly divided into three groups and treated with sterilized water (control), an antibiotic cocktail (Abx), or antibiotics plus heat-inactivated N1115 (Abx + N1115) for 84 days. We found that while the mRNA levels of GABA_Aα1, GABA_b1, and glucocorticoid receptor (GR) in the hippocampus and brain-derived neurotrophic factor (BDNF), GABA_Aα1, GABA_b1, and nerve growth factor (NGF) in the prefrontal cortex were higher, the mRNA levels of 5-HT_1A were lower in the Abx group. The Abx + N1115 group had lower mRNA levels of GABA_Aα1, GABA_b1, and GR in the hippocampus and BDNF, GABA_b1, and NGF in the prefrontal cortex than the Abx group. The latency period was longer in the Morris water maze test while longer rest time was seen in tail suspension test in the Abx group than the control and Abx + N1115 groups. In the open field test, the moving time and distance of the Abx group were reduced. Further, the alpha-diversity indexes of the Abx and Abx + N1115 groups were significantly lower than the control. Further, long-term exposure to antibiotics disrupted the intestinal microbiota as evidenced by decreased Bacteroides, Firmicutes, and Lactobacillus, and increased Proteobacteria and Citrobacter. However, N1115 significantly decreased the abundance of Citrobacter when compared with those in the Abx group. These results indicate that antibiotics can substantially damage the intestinal microbiota and cognitive function, causing anxiety and depression, which can be alleviated by heat-inactivated N1115 via modulation of the microbiota–gut–brain axis.

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

Evidence for a close bidirectional link between the brain and the gut has led to a paradigm shift in neurology, especially in the case of Parkinson disease (PD), in which gastrointestinal dysfunction is a prominent feature. Over the past decade, numerous high-quality preclinical and clinical publications have shed light on the highly complex relationship between the gut and the brain in PD, providing potential for the development of new biomarkers and therapeutics. With the advent of high-throughput sequencing, the role of the gut microbiome has been specifically highlighted. Here, we provide a critical review of the literature on the microbiome-gut-brain axis in PD and present perspectives that will be useful for clinical practice. We begin with an overview of the gut-brain axis in PD, including the potential roles and interrelationships of the vagus nerve, α-synuclein in the enteric nervous system, altered intestinal permeability and inflammation, and gut microbes and their metabolic activities. The sections that follow synthesize the proposed roles of gut-related factors in the development and progression of, in responses to PD treatment, and as therapeutic targets. Finally, we summarize current knowledge gaps and challenges and delineate future directions for the field.

Gut Microbiota: A Novel Therapeutic Target for Parkinson’s Disease

Parkinson’s disease (PD) is the second most common neurodegenerative disease characterized by motor dysfunction. Growing evidence has demonstrated that gut dysbiosis is involved in the occurrence, development and progression of PD. Numerous clinical trials have identified the characteristics of the changed gut microbiota profiles, and preclinical studies in PD animal models have indicated that gut dysbiosis can influence the progression and onset of PD via increasing intestinal permeability, aggravating neuroinflammation, aggregating abnormal levels of α-synuclein fibrils, increasing oxidative stress, and decreasing neurotransmitter production. The gut microbiota can be considered promising diagnostic and therapeutic targets for PD, which can be regulated by probiotics, psychobiotics, prebiotics, synbiotics, postbiotics, fecal microbiota transplantation, diet modifications, and Chinese medicine. This review summarizes the recent studies in PD-associated gut microbiota profiles and functions, the potential roles, and mechanisms of gut microbiota in PD, and gut microbiota-targeted interventions for PD. Deciphering the underlying roles and mechanisms of the PD-associated gut microbiota will help interpret the pathogenesis of PD from new perspectives and elucidate novel therapeutic strategies for PD.

Alteration of gut microbiota during narrowband ultraviolet B therapy: A preliminary study

BACKGROUND

Gut microbiome dysbiosis is associated with psoriasis development. A relationship between gut microbiota and psoriasis treatment response has been reported. No study has reported the effect of narrowband ultraviolet B (NBUVB) therapy, a standard treatment of psoriasis, on gut microbiota.

QUESTION ADDRESSED

This study aimed to evaluate gut microbiota change during NBUVB therapy.

EXPERIMENTAL DESIGN

Stool samples from 22 participants, including 13 patients with chronic plaque psoriasis and nine healthy controls, were recruited. Fecal microbiota composition was analyzed using 16S rRNA sequencing before and after NBUVB therapy. Serum 25-OH Vitamin D of patients with psoriasis was evaluated simultaneously.

RESULTS

The most abundant phyla of gut microbiota in patients with psoriasis were Firmicutes, Bacteroidetes, Proteobacteria, and Actinobacteria in all participants. Bilophila, Paraprevotella, Alistipes, Sutterella, Romboutsia, Clostridium sensu stricto, and Agathobacter are significantly more enriched in healthy controls. Lactobacillales and Ruminococus torques appeared more enriched after NBUVB treatment in responders but not non-responders. Serum Vitamin D levels significantly increased after NBUVB treatment.

CONCLUSIONS&PERSPECTIVE

The present study revealed that gut microbiota altered after NBUVB treatment. The change might be treatment-specific and influence the treatment response.

The Gut Microbiome-Brain Crosstalk in Neurodegenerative Diseases

The gut–brain axis (GBA) is a complex interactive network linking the gut to the brain. It involves the bidirectional communication between the gastrointestinal and the central nervous system, mediated by endocrinological, immunological, and neural signals. Perturbations of the GBA have been reported in many neurodegenerative diseases, suggesting a possible role in disease pathogenesis, making it a potential therapeutic target. The gut microbiome is a pivotal component of the GBA, and alterations in its composition have been linked to GBA dysfunction and CNS inflammation and degeneration. The gut microbiome might influence the homeostasis of the central nervous system homeostasis through the modulation of the immune system and, more directly, the production of molecules and metabolites. Small clinical and preclinical trials, in which microbial composition was manipulated using dietary changes, fecal microbiome transplantation, and probiotic supplements, have provided promising outcomes. However, results are not always consistent, and large-scale randomized control trials are lacking. Here, we give an overview of how the gut microbiome influences the GBA and could contribute to disease pathogenesis in neurodegenerative diseases.

The role of nutrition on Parkinson's disease: a systematic review

BACKGROUND

Parkinson's disease (PD) in elderly patients is the second most prevalent neurodegenerative disease. The pathogenesis of PD is associated with dopaminergic neuron degeneration of the substantia nigra in the basal ganglia, causing classic motor symptoms. Oxidative stress, mitochondrial dysfunction, and neuroinflammation have been identified as possible pathways in laboratory investigations. Nutrition, a potentially versatile factor from all environmental factors affecting PD, has received intense research scrutiny.

METHODS

A systematic search was conducted in the MEDLINE, EMBASE, and WEB OF SCIENCE databases from 2000 until the present. Only randomized clinical trials (RCTs), observational case-control studies, and follow-up studies were included.

RESULTS

We retrieved fifty-two studies that met the inclusion criteria. Most selected studies investigated the effects of malnutrition and the Mediterranean diet (MeDiet) on PD incidence and progression. Other investigations contributed evidence on the critical role of microbiota, vitamins, polyphenols, dairy products, coffee, and alcohol intake.

CONCLUSIONS

There are still many concerns regarding the association between PD and nutrition, possibly due to underlying genetic and environmental factors. However, there is a body of evidence revealing that correcting malnutrition, gut microbiota, and following the MeDiet reduced the onset of PD and reduced clinical progression. Other factors, such as polyphenols, polyunsaturated fatty acids, and coffee intake, can have a potential protective effect. Conversely, milk and its accessory products can increase PD risk. Nutritional intervention is essential for neurologists to improve clinical outcomes and reduce the disease progression of PD.

Microbiome Impact on Amyloidogenesis

Our life is closely linked to microorganisms, either through a parasitic or symbiotic relationship. The microbiome contains more than 1,000 different bacterial species and outnumbers human genes by 150 times. Worryingly, during the last 10 years, it has been observed a relationship between alterations in microbiota and neurodegeneration. Several publications support the hypothesis that amyloid structures formed by microorganisms may trigger host proteins aggregation. In this review, we collect pieces of evidence supporting that the crosstalk between human and microbiota amyloid proteins could be feasible and, probably, a more common event than expected before. The combination of their outnumbers, the long periods of time that stay in our bodies, and the widespread presence of amyloid proteins in the bacteria Domain outline a worrying scenario. However, the identification of the exact microorganisms and the mechanisms through with they can influence human disease also opens the door to developing a new and diverse set of therapeutic strategies.

Amyloid-β Inspired Short Peptide Amphiphile Facilitates Synthesis of Silver Nanoparticles as Potential Antibacterial Agents

An amyloid-β inspired biocompatible short peptide amphiphile (sPA) molecule was used for controlled and targeted delivery of bioactive silver nanoparticles via transforming sPA nanostructures. Such sPA-AgNPs hybrid structures can be further used to develop antibacterial materials to combat emerging bacterial resistance. Due to the excellent antibacterial activity of silver, the growth of clinically relevant bacteria was inhibited in the presence of AgNPs-sPA hybrids. Bacterial tests demonstrated that the high biocompatibility and low cytotoxicity of the designed sPA allow it to work as a model drug delivery agent. It therefore shows great potential in locally addressing bacterial infections. The results of our study suggest that these nanodevices have the potential to trap and then engage in the facile delivery of their chemical payload at the target site, thereby working as potential delivery materials. This system has potential therapeutic value for the treatment of microbiota triggered progression of neurodegenerative diseases.

Whole-Genome Sequencing Reveals Age-Specific Changes in the Human Blood Microbiota

Based on several reports that indicate the presence of blood microbiota in patients with diseases, we became interested in identifying the presence of bacteria in the blood of healthy individuals. Using 37 samples from 5 families, we extracted sequences that were not mapped to the human reference genome and mapped them to the bacterial reference genome for characterization. Proteobacteria account for more than 95% of the blood microbiota. The results of clustering by means of principal component analysis showed similar patterns for each age group. We observed that the class Gammaproteobacteria was significantly higher in the elderly group (over 60 years old), whereas the arcsine square root-transformed relative abundance of the classes Alphaproteobacteria, Deltaproteobacteria, and Clostridia was significantly lower (p < 0.05). In addition, the diversity among the groups showed a significant difference (p < 0.05) in the elderly group. This result provides meaningful evidence of a consistent phenomenon that chronic diseases associated with aging are accompanied by metabolic endotoxemia and chronic inflammation.

Urolithins: potential biomarkers of gut dysbiosis and disease stage in Parkinson's patients

Gut microbiota alteration (gut dysbiosis) occurs during the onset and progression of Parkinson's disease. Gut dysbiosis biomarkers could be relevant to prodromal disease. Urolithins, anti-inflammatory metabolites produced from some dietary polyphenols by specific gut microbial ecologies (urolithin metabotypes), have been proposed as biomarkers of gut microbiota composition and functionality. However, this has not been explored in Parkinson's disease patients. The current study aimed to assess associations between urolithin metabotypes, gut dysbiosis and disease severity in Parkinson's disease patients. Participants (52 patients and 117 healthy controls) provided stool samples for microbiota sequencing and urine samples for urolithin profiling before and after consuming 30 g of walnuts for three days. Data on demographics, medication, disease duration and Hoehn and Yahr disease stage were collected. We observed a significant gradual increase of urolithin non-producers (metabotype-0) as the disease severity increased. The gut microbiome of metabotype-0 patients and patients with the greatest severity was characterized by a more altered bacterial composition, i.e., increased pro-inflammatory Enterobacteriaceae and reduced protective bacteria against autoimmune and inflammatory processes, including butyrate and urolithin-producing bacteria (Lachnospiraceae members and Gordonibacter). Besides, their microbiome was characterized by predictive functions of lipopolysaccharide biosynthesis and metabolism of glutathione, cysteine and methionine that could indirectly reflect the gut pro-inflammatory status. Urolithin detection in urine is a feasible, non-invasive and fast approach that can reflect gut microbiome dysbiosis and intestinal inflammation in Parkinson's disease patients. Our current study could provide novel strategies for improving diagnostics, and for preventing and treating disease progression in microbiota-based interventions.