Dysbiosis of gut microbiota and microbial metabolites in Parkinson's Disease

Periphery and brain, innate and adaptive immunity in Parkinson's disease

Parkinson’s disease (PD) is a neurodegenerative disorder where alpha-synuclein plays a central role in the death and dysfunction of neurons, both, in central, as well as in the peripheral nervous system. Besides the neuronal events observed in patients, PD also includes a significant immune component. It is suggested that the PD-associated immune response will have consequences on neuronal health, thus opening immunomodulation as a potential therapeutic strategy in PD. The immune changes during the disease occur in the brain, involving microglia, but also in the periphery with changes in cells of the innate immune system, particularly monocytes, as well as those of adaptive immunity, such as T-cells. This realization arises from multiple patient studies, but also from data in animal models of the disease, providing strong evidence for innate and adaptive immune system crosstalk in the central nervous system and periphery in PD. Here we review the data showing that alpha-synuclein plays a crucial role in the activation of the innate and adaptive immune system. We will also describe the studies suggesting that inflammation in PD includes early changes in innate and adaptive immune cells that develop dynamically through time during disease, contributing to neuronal degeneration and symptomatology in patients. This novel finding has contributed to the definition of PD as a multisystem disease that should be approached in a more integratory manner rather than a brain-focused classical approach.

Association Between Microscopic Colitis and Parkinson's Disease in a Swedish Population

BACKGROUND

Gastrointestinal inflammation has been linked with Parkinson's disease (PD). Microscopic colitis (MC) is an intestinal inflammatory disease with unknown relationship with PD.

OBJECTIVE

This study aimed to examine the association of MC with PD risk.

METHODS

In this nationwide matched cohort study in Sweden, PD incidence was compared between 12,609 patients with histologically confirmed MC and a matched population cohort of 58,879 MC-free individuals and a sibling cohort comprising all unaffected siblings of the MC patients (N_MC /N_Sibling  = 6281/12,351). Hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated using Cox regression models.

RESULTS

During a mean follow-up of ~7 years, we identified 449 incident PD diagnoses among the MC patients and the population cohort. Overall, MC was associated with an adjusted HR of 1.76 for PD, but the association attenuated substantially during follow-up. In the time-varying effects model, PD hazard was 3.45-fold (95% CI: 2.42, 4.93) higher during the first 2 years after biopsy and 1.80-fold (95% CI: 1.23, 2.64) higher during the following 3 years among MC versus MC-free individuals but was not different beyond 5 years after biopsy (HR: 1.03; 95% CI: 0.68, 1.54). This temporal pattern of MC-PD associations persisted when comparing MC patients to their siblings. In a post hoc case-control analysis, we also detected a strong association between MC and preexisting PD (odds ratio: 3.46; 95% CI: 2.91, 4.12).

CONCLUSIONS

Our findings suggest that MC may not be a risk factor for PD; instead, it may co-occur with PD as a comorbidity or develop after a diagnosis of PD. © 2021 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Unravelling the potential of gut microbiota in sustaining brain health and their current prospective towards development of neurotherapeutics

Increasing incidences of neurological disorders, such as Parkinson's disease (PD), multiple sclerosis (MS), Alzheimer's disease (AD) and amyotrophic lateral sclerosis (ALS) are being reported, but an insight into their pathology remains elusive. Findings have suggested that gut microbiota play a major role in regulating brain functions through the gut-brain axis. A unique bidirectional communication between gut microbiota and maintenance of brain health could play a pivotal role in regulating incidences of neurodegenerative diseases. Contrarily, the present life style with changing food habits and disturbed circadian rhythm may contribute to gut homeostatic imbalance and dysbiosis leading to progression of several neurological disorders. Therefore, dysbiosis, as a primary factor behind intestinal disorders, may also augment inflammation, intestinal and blood-brain barrier permeability through microbiota-gut-brain axis. This review primarily focuses on the gut-brain axis functions, specific gut microbial population, metabolites produced by gut microbiota, their role in regulating various metabolic processes and role of gut microbiota towards development of neurodegenerative diseases. However, several studies have reported a decrease in abundance of a specific gut microbial population and a corresponding increase in other microbial family, with few findings revealing some contradictions. Reports also showed that colonization of gut microbiota isolated from patients suffering from neurodegenerative disease leads to the development of enhance pathological outcomes in animal models. Hence, a systematic understanding of the dominant role of specific gut microbiome towards development of different neurodegenerative diseases could possibly provide novel insight into the use of probiotics and microbial transplantation as a substitute approach for treating/preventing such health maladies.

The Contribution of Gut Microbiota-Brain Axis in the Development of Brain Disorders

Different bacterial families colonize most mucosal tissues in the human organism such as the skin, mouth, vagina, respiratory, and gastrointestinal districts. In particular, the mammalian intestine hosts a microbial community of between 1,000 and 1,500 bacterial species, collectively called "microbiota." Co-metabolism between the microbiota and the host system is generated and the symbiotic relationship is mutually beneficial. The balance that is achieved between the microbiota and the host organism is fundamental to the organization of the immune system. Scientific studies have highlighted a direct correlation between the intestinal microbiota and the brain, establishing the existence of the gut microbiota-brain axis. Based on this theory, the microbiota acts on the development, physiology, and cognitive functions of the brain, although the mechanisms involved have not yet been fully interpreted. Similarly, a close relationship between alteration of the intestinal microbiota and the onset of several neurological pathologies has been highlighted. This review aims to point out current knowledge as can be found in literature regarding the connection between intestinal dysbiosis and the onset of particular neurological pathologies such as anxiety and depression, autism spectrum disorder, and multiple sclerosis. These disorders have always been considered to be a consequence of neuronal alteration, but in this review, we hypothesize that these alterations may be non-neuronal in origin, and consider the idea that the composition of the microbiota could be directly involved. In this direction, the following two key points will be highlighted: (1) the direct cross-talk that comes about between neurons and gut microbiota, and (2) the degree of impact of the microbiota on the brain. Could we consider the microbiota a valuable target for reducing or modulating the incidence of certain neurological diseases?

Gut microbiome dysbiosis alleviates the progression of osteoarthritis in mice

Gut microbiota dysbiosis has been studied under the pathological conditions of osteoarthritis (OA). However, the effect of antibiotic-induced gut flora dysbiosis on OA remains incompletely understood at present. Herein, we used a mouse (8 weeks) OA model of destabilization of the medial meniscus (DMM) and gut microbiome dysbiosis induced by antibiotic treatment with ampicillin and neomycin for 8 weeks. The results show that antibiotic-induced intestinal microbiota dysbiosis reduced the serum level of lipopolysaccharide (LPS) and the inflammatory response, such as suppression of the levels of tumour necrosis factor-α (TNF-α) and interleukin-6 (IL-6), which can lead to decreased matrix metalloprotease-13 (MMP-13) expression and improvement of OA after joint injury. In addition, trabecular thickness (Tb.Th) and osteophyte scores were increased significantly in antibiotic-induced male mice compared with female mice. We further used network correlation analysis to verify the effect of gut microbiota dysbiosis on OA. Therefore, the present study contributes to our understanding of the gut-joint axis in OA and reveals the relationship between the inflammatory response, sex and gut microbiota, which may provide new strategies to prevent the symptoms and long-term sequelae of OA. Conclusion: Our data showed that gut microbiome dysbiosis alleviates the progression of OA.

Clostridium butyricum Alleviates Gut Microbiota Alteration-Induced Bone Loss after Bariatric Surgery by Promoting Bone Autophagy

Bariatric surgery is the most common and effective treatment of severe obesity; however, these bariatric procedures always result in detrimental effects on bone metabolism by underlying mechanisms. This study aims to investigate the skeletal response to bariatric surgery and to explore whether Clostridium butyricum alleviates gut microbiota alteration-induced bone loss after bariatric surgery. Consequently, male SD rats received Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG) surgery, respectively, followed by body weight recording. The bone loss after bariatric surgery was further determined by dual-energy X-ray absorptiometry (DXA), micro-CT measurement, histologic analyses, and Western blot. Besides, 16S rDNA gene sequencing was performed to determine the gut microbiota alteration after surgery, and intervention with fecal microbiota from RYGB donor was conducted in obese SD rats, followed by C. butyricum administration. Accordingly, rats in the RYGB and SG groups maintained sustained weight loss, and DXA and micro-CT measurement further demonstrated significant bone loss after bariatric surgery. Besides, histologic and Western blot analyses validated enhanced osteoclastogenesis and inhibited osteoblastogenesis and defective autophagy after surgery. The 16S rDNA gene sequencing suggested a significant alteration of gut microbiota composition in the RYGB group, and intervention with fecal microbiota from RYGB donor further determined that this kind of alteration contributed to the bone loss after RYGB. Meanwhile, C. butyricum might protect against this postoperative bone loss by promoting osteoblast autophagy. In summary, this study suggests novel mechanisms to clarify the skeletal response to bariatric surgery and provides a potential candidate for the treatment of bone disorder among bariatric patients. SIGNIFICANCE STATEMENT: The significance of this study is the discovery of obvious bone loss and defective autophagy after bariatric surgery. Besides, it is revealed that gut microbiota alterations could be the reason for impaired bone mass after bariatric surgery. Furthermore, Clostridium butyricum could alleviate the gut microbiota alteration-induced bone loss after bariatric surgery by promoting osteoblast autophagy.

Comprehensive metabolic profiling of Parkinson's disease by liquid chromatography-mass spectrometry

Background

Parkinson’s disease (PD) is a prevalent neurological disease in the elderly with increasing morbidity and mortality. Despite enormous efforts, rapid and accurate diagnosis of PD is still compromised. Metabolomics defines the final readout of genome-environment interactions through the analysis of the entire metabolic profile in biological matrices. Recently, unbiased metabolic profiling of human sample has been initiated to identify novel PD metabolic biomarkers and dysfunctional metabolic pathways, however, it remains a challenge to define reliable biomarker(s) for clinical use.

Methods

We presented a comprehensive metabolic evaluation for identifying crucial metabolic disturbances in PD using liquid chromatography-high resolution mass spectrometry-based metabolomics approach. Plasma samples from 3 independent cohorts (n = 460, 223 PD, 169 healthy controls (HCs) and 68 PD-unrelated neurological disease controls) were collected for the characterization of metabolic changes resulted from PD, antiparkinsonian treatment and potential interferences of other diseases. Unbiased multivariate and univariate analyses were performed to determine the most promising metabolic signatures from all metabolomic datasets. Multiple linear regressions were applied to investigate the associations of metabolites with age, duration time and stage of PD. The combinational biomarker model established by binary logistic regression analysis was validated by 3 cohorts.

Results

A list of metabolites including amino acids, acylcarnitines, organic acids, steroids, amides, and lipids from human plasma of 3 cohorts were identified. Compared with HC, we observed significant reductions of fatty acids (FFAs) and caffeine metabolites, elevations of bile acids and microbiota-derived deleterious metabolites, and alterations in steroid hormones in drug-naïve PD. Additionally, we found that L-dopa treatment could affect plasma metabolome involved in phenylalanine and tyrosine metabolism and alleviate the elevations of bile acids in PD. Finally, a metabolite panel of 4 biomarker candidates, including FFA 10:0, FFA 12:0, indolelactic acid and phenylacetyl-glutamine was identified based on comprehensive discovery and validation workflow. This panel showed favorable discriminating power for PD.

Conclusions

This study may help improve our understanding of PD etiopathogenesis and facilitate target screening for therapeutic intervention. The metabolite panel identified in this study may provide novel approach for the clinical diagnosis of PD in the future.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13024-021-00425-8.

Understanding the host-microbe interactions using metabolic modeling

The human gut harbors an enormous number of symbiotic microbes, which is vital for human health. However, interactions within the complex microbiota community and between the microbiota and its host are challenging to elucidate, limiting development in the treatment for a variety of diseases associated with microbiota dysbiosis. Using in silico simulation methods based on flux balance analysis, those interactions can be better investigated. Flux balance analysis uses an annotated genome-scale reconstruction of a metabolic network to determine the distribution of metabolic fluxes that represent the complete metabolism of a bacterium in a certain metabolic environment such as the gut. Simulation of a set of bacterial species in a shared metabolic environment can enable the study of the effect of numerous perturbations, such as dietary changes or addition of a probiotic species in a personalized manner. This review aims to introduce to experimental biologists the possible applications of flux balance analysis in the host-microbiota interaction field and discusses its potential use to improve human health. Video abstract.

The effect of taxonomic classification by full-length 16S rRNA sequencing with a synthetic long-read technology

Characterizing the microbial communities inhabiting specimens is one of the primary objectives of microbiome studies. A short-read sequencing platform for reading partial regions of the 16S rRNA gene is most commonly used by reducing the cost burden of next-generation sequencing (NGS), but misclassification at the species level due to its length being too short to consider sequence similarity remains a challenge. Loop Genomics recently proposed a new 16S full-length-based synthetic long-read sequencing technology (sFL16S). We compared a 16S full-length-based synthetic long-read (sFL16S) and V3-V4 short-read (V3V4) methods using 24 human GUT microbiota samples. Our comparison analyses of sFL16S and V3V4 sequencing data showed that they were highly similar at all classification resolutions except the species level. At the species level, we confirmed that sFL16S showed better resolutions than V3V4 in analyses of alpha-diversity, relative abundance frequency and identification accuracy. Furthermore, we demonstrated that sFL16S could overcome the microbial misidentification caused by different sequence similarity in each 16S variable region through comparison the identification accuracy of Bifidobacterium, Bacteroides, and Alistipes strains classified from both methods. Therefore, this study suggests that the new sFL16S method is a suitable tool to overcome the weakness of the V3V4 method.

Role of pattern recognition receptors and the microbiota in neurological disorders

In recent years, the gut microbiota has been increasingly implicated in the development of many extraintestinal disorders, including neurodevelopmental and neurodegenerative disorders. Despite this growing connection, our understanding of the precise mechanisms behind these effects is currently lacking. Pattern recognition receptors (PRRs) are important innate immune proteins expressed on the surface and within the cytoplasm of a multitude of cells, both immune and otherwise, including epithelial, endothelial and neuronal. PRRs comprise four major subfamilies: the Toll-like receptors (TLRs), the nucleotide-binding oligomerization domain leucine rich repeats-containing receptors (NLRs), the retinoic acid inducible gene 1-like receptors and the C-type lectin receptors. Recognition of commensal bacteria by PRRs is critical for maintaining host-microbe interactions and homeostasis, including behaviour. The expression of PRRs on multiple cell types makes them a highly interesting and novel target for regulation of host-microbe signalling, which may lead to gut-brain signalling. Emerging evidence indicates that two of the four known families of PRRs (the NLRs and the TLRs) are involved in the pathogenesis of neurodevelopmental and neurodegenerative disorders via the gut-brain axis. Taken together, increasing evidence supports a role for these PRRs in the development of neurological disorders, including Alzheimer's disease, Parkinson's disease and multiple sclerosis, via the microbiota-gut-brain axis.

Is Gut Dysbiosis an Epicenter of Parkinson's Disease?

Once recognized as one of the most esoteric diseases of the central nervous system, Parkinson's disease (PD) is now deemed to be a chronic illness contributed by the central, autonomic and enteric nervous systems. Most likely, an accumulation of α-synuclein in the central and enteric nervous systems is the key that supports this viewpoint. Constipation, one of the non-motor hallmarks in roughly two-third of PD patients, is regulated by the composition of gut bacteria, which is assumed to set off the enteric α-synuclein accrual. Vagus nerve is suggested to direct the signal for α-synuclein over-expression and accumulation to the brain. While trillions of microorganisms reside in the intestinal tract, only one third of the proportion inhabits evenly in all individuals. Existence of an impaired gut-microbe-brain axis consonant with dysbiosis could be an epicenter of this inexplicable disorder. Any alteration in the structure and function of the gastrointestinal tract owing to exposure of endogenous or exogenous chemicals or toxicants could lead to dysbiosis. However, inconsistency in the symptoms even after exposure to same chemical or toxicant in PD patients emphatically creates a conundrum. While the level of a few specific neurotransmitters and metabolites is influenced by microbes, implication of dysbiosis is still debatable. Nevertheless, the scientific literature is overflowing with the remarkable observations supporting the role of dysbiosis in PD. Lack of specificity to differentially diagnose PD with non-PD or PD-plus syndrome, to identify highly precise drug targets and to develop therapeutic stratagems to encounter the disease on the basis of this approach, causes us to be open-minded about the dysbiosis theory. The article reviews the facts supporting gut dysbiosis as the foremost trigger for PD onset along with disagreements.

Altered physiology of gastrointestinal vagal afferents following neurotrauma

The adaptability of the central nervous system has been revealed in several model systems. Of particular interest to central nervous system-injured individuals is the ability for neural components to be modified for regain of function. In both types of neurotrauma, traumatic brain injury and spinal cord injury, the primary parasympathetic control to the gastrointestinal tract, the vagus nerve, remains anatomically intact. However, individuals with traumatic brain injury or spinal cord injury are highly susceptible to gastrointestinal dysfunctions. Such gastrointestinal dysfunctions attribute to higher morbidity and mortality following traumatic brain injury and spinal cord injury. While the vagal efferent output remains capable of eliciting motor responses following injury, evidence suggests impairment of the vagal afferents. Since sensory input drives motor output, this review will discuss the normal and altered anatomy and physiology of the gastrointestinal vagal afferents to better understand the contributions of vagal afferent plasticity following neurotrauma.

Gut Microbiota and Parkinson's Disease: Implications for Faecal Microbiota Transplantation Therapy

Parkinson's disease (PD) ranks the second place among neurodegenerative diseases in terms of its morbidity, which affects 1-2% people aged over 65 years. In addition to genetics, some environmental factors may exert vital parts in PD occurrence as well. At present, more and more studies are conducted to elucidate the association between gut microbial dysbiosis and the incidence of PD. Gut microbial dysbiosis has a certain effect on both the central nervous system (CNS) and the enteric nervous system (ENS), which indicates that there is a gut-microbiota-brain axis that induces CNS disorders. Some gut microbial strains are suggested to suppress or weaken the neuroinflammation- and gut-inflammation-immune responses, which suggests the protective and pathogenic effects of certain gut microbial species on PD progression. Therefore, gut microbiome may contain plenty of targets for preventing and managing PD. Faecal microbiota transplantation (FMT) may serve as a direct and useful treatment for PD in the future. Nonetheless, there is little available scientific research in this field. The present work reviewed the latest research to examine the association of gut microbiota with PD, and the future prospects of FMT treatment.

Probiotic Clostridium butyricum ameliorated motor deficits in a mouse model of Parkinson's disease via gut microbiota-GLP-1 pathway

A connection between gut microbiota and Parkinson's disease (PD) indicates that dysbiosis of the gut microbiota might represent a risk factor for PD. Microbiota-targeted interventions, including probiotic Clostridium butyricum (Cb), have been recently shown to have favorable effects in PD by regulating microbiota-gut-brain axis. However, the potential beneficial roles and its mechanisms of Cb on PD were still unknown. Male C57BL/6 mice were subjected to a PD model-induced by 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP) and were treated intragastrically with Cb for 4 weeks. The motor functions were assessed by a series of behavioral tests including pole test, beam walking teat, forced swimming test and open field test. The dopaminergic neuron loss, synaptic plasticity and microglia activation, as well as the levels of colonic glucagon-like peptide-1 (GLP-1), colonic G protein-coupled receptors GPR41/43 and cerebral GLP-1 receptors were assessed. Gut microbial composition was assessed by 16S rRNA sequencing analysis. Our results showed that oral administration of Cb could improve motor deficits, dopaminergic neuron loss, synaptic dysfunction and microglia activation in the MPTP-induced mice. Meanwhile, Cb treatment could reverse the dysbiosis of gut microbiota and the decreased levels of colonic GLP-1, colonic GPR41/43 and cerebral GLP-1 receptor in the MPTP-induced mice. These findings indicated that the neuroprotective mechanism of Cb on PD might be related to the improvement of abnormal gut microbiota-gut-brain axis.

Gut microbiota and metabolome distinctive features in Parkinson disease: Focus on levodopa and levodopa-carbidopa intrajejunal gel

BACKGROUND AND PURPOSE

Recent data suggest that imbalances in the composition of the gut microbiota (GM) could exacerbate the progression of Parkinson disease (PD). The effects of levodopa (LD) have been poorly assessed, and those of LD-carbidopa intestinal gel (LCIG) have not been evaluated so far. The aim of this study was to identify the effect of LD and LCIG, in particular, on the GM and metabolome.

METHODS

Fecal DNA samples from 107 patients with a clinical diagnosis of PD were analyzed by next-generation sequencing of the V3 and V4 regions of the 16S rRNA gene. PD patients were classified in different groups: patients on LCIG (LCIG group, n = 38) and on LD (LD group, n = 46). We also included a group of patients (n = 23) without antiparkinsonian medicaments (Naïve group). Fecal metabolic extracts were evaluated by gas chromatography mass spectrometry.

RESULTS

The multivariate analysis showed a significantly higher abundance in the LCIG group of Enterobacteriaceae, Escherichia, and Serratia compared to the LD group. Compared to the Naïve group, the univariate analysis showed a reduction of Blautia and Lachnospirae in the LD group. Moreover, an increase of Proteobacteria, Enterobacteriaceae, and a reduction of Firmicutes, Lachnospiraceae, and Blautia was found in the LCIG group. No significant difference was found in the multivariate analysis of these comparisons. The LD group and LCIG group were associated with a metabolic profile linked to gut inflammation.

CONCLUSIONS

Our results suggest that LD, and mostly LCIG, might significantly influence the microbiota composition and host/bacteria metabolism, acting as stressors in precipitating a specific inflammatory intestinal microenvironment, potentially related to the PD state and progression.

Gastrointestinal dysfunction in the synucleinopathies

Interest in gastrointestinal dysfunction in Parkinson's disease has blossomed over the past 30 years and has generated a wealth of investigation into this non-motor aspect of the disorder, research that has encompassed its pathophysiology, its clinical features, and its impact on quality of life. The question of gastrointestinal dysfunction in the other synucleinopathies has not received nearly as much attention, but information and knowledge are growing. In this review, the current knowledge, controversies, and gaps in our understanding of the pathophysiology of gastrointestinal dysfunction in Parkinson's disease and the other synucleinopathies will be addressed, and extended focus will be directed toward the clinical problems involving saliva management, swallowing, gastric emptying, small intestinal function, and bowel function that are so problematic in these disorders.

Characterization of the intestinal microbiota during Citrobacter rodentium infection in a mouse model of infection-triggered Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder that has been shown to be influenced by the intestinal milieu. The gut microbiota is altered in PD patients, and murine studies have begun suggesting a causative role for the gut microbiota in progression of PD. We have previously shown that repeated infection with the intestinal murine pathogen Citrobacter rodentium resulted in the development of PD-like pathology in Pink1^-/- mice compared to wild-type littermates. This addendum aims to expand this work by characterizing the gut microbiota during C. rodentium infection in our Pink1^-/- PD model. We observed little disturbance to the fecal microbiota diversity both between infection timepoints and between Pink1^-/- and wild-type control littermates. However, the level of short-chain fatty acids appeared to be altered over the course of infection with butyric acid significantly increasing in Pink1^-/- mice and isobutyric acid increasing in wild-type mice.

Fecal microbiota transplantation therapy for Parkinson's disease: A preliminary study

Imbalances in the gut microbiota mediate the progression of neurodegenerative diseases such as Parkinson's disease (PD). Fecal microbiota transplantation (FMT) is currently being explored as a potential therapy for PD. The objective of this study was to assess the efficacy and safety of FMT on PD. Fifteen PD patients were included, 10 of them received FMT via colonoscopy (colonic FMT group) and 5 received FMT via nasal-jejunal tube (nasointestinal FMT group). The score of PSQI, HAMD, HAMA, PDQ-39, NMSQ and UPDRS-III significantly decreased after FMT treatment (all P < .05). Colonic FMT group showed significant improvement and longer maintenance of efficacy compared with nasointestinal FMT (P = .002). Two patients achieved self-satisfying outcomes that last for more than 24 months. However, nasointestinal FMT group had no significant therapeutic effect, although UPDRS-III score slightly reduced. There were no patients were satisfied with nasointestinal FMT for more than 3 months. Among 15 PD patients, there were 5 cases had adverse events (AEs), including diarrhea (2 cases), abdominal pain (2 cases) and flatulence (1 case). These AEs were mild and self-limiting. We conclude that FMT can relieve the motor and non-motor symptoms with acceptable safety in PD. Compared with nasointestinal FMT, colonic FMT seems better and preferable.

Clostridium difficile infection and risk of Parkinson's disease: a Swedish population-based cohort study

BACKGROUND AND PURPOSE

Gastrointestinal inflammation has been implicated in Parkinson's disease (PD). The aim of this study was to examine whether individuals with a history of Clostridium difficile infection (CDI) are at elevated risk of PD.

METHODS

We performed a population-based cohort study using Swedish national register data. Adults aged ≥35 years were identified from the Swedish Population and Housing Census 1990 and followed during the period 1997-2013. Diagnoses of CDI and PD were extracted from the National Patient Register. Associations of CDI history with PD risk were estimated using Cox proportional hazards regression. We also explored whether the association differed by the source of CDI diagnosis (inpatient vs. outpatient), presence of recurrent infections, and pre-infection use of antibiotics.

RESULTS

Amongst the study population (N = 4 670 423), 34 868 (0.75%) had a history of CDI. A total of 165 and 47 035 incident PD cases were identified from individuals with and without CDI history, respectively. Across the entire follow-up, a 16% elevation of PD risk was observed among the CDI group [hazard ratio 1.16, 95% confidence interval (CI)1.00-1.36], which was mainly driven by increased PD risk within the first 2 years after CDI diagnosis (hazard ratio 1.38, 95% CI 1.12-1.69). In longer follow-up, CDI was not associated with subsequent PD occurrence. This temporal pattern of CDI-PD associations was generally observed across all CDI subgroups.

CONCLUSIONS

Clostridium difficile may be associated with an increased short-term PD risk, but this might be explained by reverse causation and/or surveillance bias. Our results do not imply that CDI history affects long-term PD risk.

Perspectives in lung microbiome research

Our understanding of the existence and role of the lung microbiome has grown at a slower pace than other microbiome research areas. This is likely a consequence of the original dogma that the lung was a sterile environment although there are other barriers that are worth discussing. Here we will not be conducting an exhaustive review of the current literature on the lung microbiome, but rather we will focus on what we see as some important challenges that the field needs to face in order to improve our mechanistic understanding of the lung microbiome and its role on human health.

Regulation of immune-driven pathogenesis in Parkinson's disease by gut microbiota

Parkinson's disease (PD) is one of the most significant medical and social burdens of our time. The prevalence of PD increases with age and the number of individuals diagnosed with PD is expected to double from 6.9 million in 2015 to 14.2 million in 2040. To date, no drugs can stop the ongoing neurodegeneration caused by PD due to its unclear and complex pathogenic mechanisms. It has been wildly recognized that both gut microbiota and neuro-immunity are involved in the pathology of PD. In this review, we intend to provide a comprehensive overview of current knowledge on how gut microbiota involved in immune-driven pathogenesis of PD, and its potential as a new target of dietary and/or therapeutic interventions for PD.

Butyrate Protects Against Salsolinol-Induced Toxicity in SH-SY5Y Cells: Implication for Parkinson's Disease

Parkinson's disease (PD), a progressive neurodegenerative disorder, is associated with the destruction of dopamine neurons in the substantia nigra (SN) and the formation of Lewy bodies in basal ganglia. Risk factors for PD include aging, as well as environmental and genetic factors. Recent converging reports suggest a role for the gut microbiome and epigenetic factors in the onset and/or progression of PD. Of particular relevance and potential therapeutic targets in this regard are histone deacetylases (HDACs), enzymes that are involved in chromatin remodeling. Butyrate, a short-chain fatty acid (FA) produced in the gut and presumably acting via several G protein-coupled receptors (GPCRs) including FA3 receptors (FA3Rs), is a well-known HDAC inhibitor that plays an important role in maintaining homeostasis of the gut-brain axis. Recently, its significance in regulation of some critical brain functions and usefulness in neurodegenerative diseases such as PD has been suggested. In this study we sought to determine whether butyrate may have protective effects against salsolionl (SALS)-induced toxicity in SH-SY5Y cells. SALS, an endogenous product of aldehyde and dopamine condensation, may be selectively toxic to dopaminergic neurons. SH-SY5Y cells, derived from human neuroblastoma cells, are used as a model of these neurons. Exposure of SH-SY5Y cells for 24 h to 400 μM SALS resulted in approximately 60% cell death, which was concentration-dependently prevented by butyrate. The effects of butyrate in turn were significantly attenuated by beta-hydroxy butyrate (BHB), a selective FA3R antagonist. Moreover, a selective FA3R agonist (AR 420626) also provided protective effects against SALS, which was totally blocked by BHB. These findings provide further support that butyrate or an agonist of FA3R may be of therapeutic potential in PD.

Is Porphyromonas gingivalis involved in Parkinson's disease?

Porphyromonas gingivalis, a major subgingival plaque bacterium in periodontitis, has recently attracted much attention as a possible microbial driver in Alzheimer's disease. In the present paper, another common neuroinflammatory disease, Parkinson's disease (PD), is discussed. A recent study found major virulence factors of P. gingivalis such as gingipain R1 (RgpA) and lipopolysaccharide in the blood circulation of a PD population. The current review reveals how features such as systemic inflammation, hypercoagulation, presence of amyloid fibrin(ogen) in plasma, and marked ultrastructural changes in platelets, probably induced by P. gingivalis, may affect the development of PD. Several other clinical studies have also demonstrated an association between periodontitis and PD. Even if the risk of periodontal diseases causing neurological disorders needs to be better substantiated, that should not keep us from trying to prevent them by performing careful daily dental hygiene.

Parkinson's Disease and the Gut: Future Perspectives for Early Diagnosis

Parkinson's disease (PD) is a neurodegenerative disease characterized by progressive degeneration of dopaminergic neurons, and at the cellular level by the formation of Lewy bodies in the central nervous system (CNS). However, the onset of the disease is believed to be localized to peripheral organs, particularly the gastrointestinal tract (GIT) and the olfactory bulb sooner before neuropathological changes occur in the CNS. Patients already in the pre-motor stage of PD suffer from various digestive problems and/or due to significant changes in the composition of the intestinal microbiome in this early stage of the disease. Detailed analyses of patient biopsies and autopsies as well as animal models of neuropathological changes characteristic of PD provided important information on the pathology or treatment of PD symptoms. However, presently is not clarified (i) the specific tissue in the GIT where the pathological processes associated with PD is initiated; (ii) the mechanism by which these processes are disseminated to the CNS or other tissues within the GIT; and (iii) which neuropathological changes could also serve as a reliable diagnostic marker of the premotor stages of PD, or (iv) which type of GIT tissue would be the most appropriate choice for routine examination of patient biopsies.

LRRK2 at the Interface Between Peripheral and Central Immune Function in Parkinson's

It is becoming increasingly accepted that there is an interplay between the peripheral immune response and neuroinflammation in the pathophysiology of Parkinson's disease (PD). Mutations in the leucine-rich-repeat kinase 2 (LRRK2) gene are associated with familial and sporadic cases of PD but are also found in immune-related disorders, such as inflammatory bowel disease (IBD) and leprosy. Furthermore, LRRK2 has been associated with bacterial infections such as Mycobacterium tuberculosis and Salmonella typhimurium. Recent evidence suggests a role of LRRK2 in the regulation of the immune system and modulation of inflammatory responses, at a systemic level, with LRRK2 functionally implicated in both the immune system of the central nervous system (CNS) and the periphery. It has therefore been suggested that peripheral immune signaling may play an important role in the regulation of neurodegeneration in LRRK2 as well as non-LRRK2-associated PD. This review will discuss the current evidence for this hypothesis and will provide compelling rationale for placing LRRK2 at the interface between peripheral immune responses and neuroinflammation.

Bioactive Polyphenols and Neuromodulation: Molecular Mechanisms in Neurodegeneration

The interest in dietary polyphenols in recent years has greatly increased due to their antioxidant bioactivity with preventive properties against chronic diseases. Polyphenols, by modulating different cellular functions, play an important role in neuroprotection and are able to neutralize the effects of oxidative stress, inflammation, and apoptosis. Interestingly, all these mechanisms are involved in neurodegeneration. Although polyphenols display differences in their effectiveness due to interindividual variability, recent studies indicated that bioactive polyphenols in food and beverages promote health and prevent age-related cognitive decline. Polyphenols have a poor bioavailability and their digestion by gut microbiota produces active metabolites. In fact, dietary bioactive polyphenols need to be modified by microbiota present in the intestine before being absorbed, and to exert health preventive effects by interacting with cellular signalling pathways. This literature review includes an evaluation of the literature in English up to December 2019 in PubMed and Web of Science databases. A total of 307 studies, consisting of research reports, review articles and articles were examined and 146 were included. The review highlights the role of bioactive polyphenols in neurodegeneration, with a particular emphasis on the cellular and molecular mechanisms that are modulated by polyphenols involved in protection from oxidative stress and apoptosis prevention.

Microcystin-LR-induced changes of hepatopancreatic transcriptome, intestinal microbiota, and histopathology of freshwater crayfish (Procambarus clarkii)

As a hepatotoxin, microcystin-LR (MC-LR) poses a great threat to aquatic organisms. In this research, the hepatopancreatic transcriptome, intestinal microbiota, and histopathology of Procambarus clarkii (P. clarkii) in response to acute MC-LR exposure were studied. RNA-seq analysis of hepatopancreas identified 372 and 781 differentially expressed genes (DEGs) after treatment with 10 and 40 μg/L MC-LR, respectively. Among the DEGs, 23 genes were immune-related and 21 genes were redox-related. GO functional enrichment analysis revealed that MC-LR could impact nuclear-transcribed mRNA catabolic process, cobalamin- and heme-related processes, and sirohydrochlorin cobaltochelatase activity of P. clarkii. In addition, the only significantly enriched KEGG pathway induced by MC-LR was galactose metabolism pathway. Meanwhile, sequencing of the bacterial 16S rRNA gene demonstrated that MC-LR decreased bacterial richness and diversity, and altered the intestinal microbiota composition. At the phylum level, after 96 h, the abundance of Verrucomicrobia decreased after treatment with 10 and 40 μg/L MC-LR, while Firmicutes increased in the 40 μg/L MC-LR-treated group. At the genus level, the abundances of 15 genera were significantly altered after exposure to MC-LR. Our research demonstrated that MC-LR exposure caused histological alterations such as structural damage of hepatopancreas and intestines. This research provides an insight into the mechanisms associated with MC-LR toxicity in aquatic crustaceans.

Neurobiological findings underlying depressive behavior in Parkinson's disease: A review

Parkinson's disease (PD) is one of the most prevalent neurodegenerative diseases in the world with a harmful impact on the quality of life. Although its clinical diagnosis is based on motor symptoms such as resting tremor, postural instability, slow gait, and muscle stiffness, this disorder is also characterized by the presence of early emotional impairment, including features such as depression, anxiety, fatigue, and apathy. Depression is the main emotional manifestation associated with PD and the mechanisms involved in its pathophysiology have been extensively investigated however, it is not yet completely elucidated. In addition to monoaminergic imbalance, immunological and gut microbiota changes have been associated with depression in PD. Besides, a patient group appears be refractory to the treatment available currently. This review emphasizes the mainly neuromolecular findings of the PD-associated depression as well as discuss novel and potential pharmacological and non-pharmacological therapeutic strategies.

Effects of cadmium on intestinal histology and microbiota in freshwater crayfish (Procambarus clarkii)

In this study, Procambarus clarkii (P. clarkii) were exposed to different concentrations (0, 2, 5 and 10 mg/L) of cadmium (Cd). We studied the effects of Cd exposure on intestinal histology and microbiota in P. clarkii. The results demonstrated that exposure to Cd caused histological alterations in the intestines of P. clarkii. Meanwhile, high-throughput sequencing analysis revealed that Cd exposure could alter the richness, diversity, and composition of intestinal microbiota in P. clarkii. At the phylum level, the relative abundances of the prevalent phyla Firmicutes, Proteobacteria, Bacteroidetes, Fusobacteria, and Actinobacteria changed significantly after exposure to Cd. At the genus level, the most prevalent genera with significant difference in relative abundance were Bacteroides, Clostridium XlVb, Hafnia, Buttiauxella, Shewanella, Anaerorhabdus, Alistipes, Arcobacter, Azoarcus, Chryseobacterium, and so on. Furthermore, functional prediction analysis of intestinal microbial communities showed that Cd exposure could significantly alter the pathways related to metabolism, diseases, cellular processes, and so on. Taken together, exposure to Cd could induce intestinal histological damage and affect intestinal microbiota composition and functions of P. clarkii. Our study can be an important step toward a better understanding of the toxic effects of Cd on aquatic crustaceans.

Identification of plasmalogens in Bifidobacterium longum, but not in Bifidobacterium animalis

Plasmalogens are glycerophospholipids that contain a vinyl ether bond at the sn-1 position of glycerol backbone instead of an ester bond. Plasmalogens are indicated to have many important functions in mammalian cells. On the other hand, it is suggested that some gut microbiota plays many probiotic functions to human health. Presence of plasmalogens in Clostridium strains in gut microbiota is well-known, but presence of plasmalogens in Bifidobacterium longum (B. longum) strain, one of the most important probiotic gut microbiota, has not been reported. We identified plasmalogens in lipid extract from some B. longum species, but not from Bifidobacterium animalis (B. animalis) species which are another important strain of probiotic bifidobacteria. Major phospholipid classes of plasmalogens in B. longum species were cardiolipin, phosphatidylglycerol and phosphatidic acid. Almost all of the phospholipids from B. longum examined were indicated to be plasmalogens. Although major phospholipid classes of plasmalogens in human brain and major phospholipid classes of plasmalogens in B. longum are different, it is interesting to note that many reported functions of microbiota-gut-brain axis on human neurodegenerative diseases and those functions of plasmalogens on neurodegenerative diseases are overlapped. The presence of plasmalogens in B. longum species may play important roles for many probiotic effects of B. longum to human health.

Sodium butyrate causes α-synuclein degradation by an Atg5-dependent and PI3K/Akt/mTOR-related autophagy pathway

Aggregation of α-Synuclein is central to the pathogenesis of Parkinson's disease (PD). However, these α-Synuclein inclusions are not only present in brain, but also in gut. Enteroendocrine cells (EECs), which are directly exposed to the gut lumen, can express α-Synuclein and directly connect to α-Synuclein-containing nerves. Dysbiosis of gut microbiota and microbial metabolite short-chain fatty acids (SCFAs) has been implicated as a driver for PD. Butyrate is an SCFA produced by the gut microbiota. Our aim was to demonstrate how α-Synuclein expression in EECs responds to butyrate stimulation. Interestingly, we found that sodium butyrate (NaB) increases α-Synuclein mRNA expression, enhances Atg5-mediated autophagy (increased LC3B-II and decreased SQSTM1 (also known as p62) expression) in murine neuroendocrine STC-1 cells. Further, α-Synuclein mRNA was decreased by the inhibition of autophagy by using inhibitor bafilomycin A1 or by silencing Atg5 with siRNA. Moreover, the PI3K/Akt/mTOR pathway was significantly inhibited and cell apoptosis was activated by NaB. Conditioned media from NaB-stimulated STC-1 cells induced inflammation in SH-SY5Y cells. Collectively, NaB causes α-Synuclein degradation by an Atg5-dependent and PI3K/Akt/mTOR-related autophagy pathway.

The sex-specific interaction of the microbiome in neurodegenerative diseases

Several neurologic diseases exhibit different prevalence and severity in males and females, highlighting the importance of understanding the influence of biologic sex and gender. Beyond host-intrinsic differences in neurologic development and homeostasis, evidence is now emerging that the microbiota is an important environmental factor that may account for differences between men and women in neurologic disease. The gut microbiota is composed of trillions of bacteria, archaea, viruses, and fungi, that can confer benefits to the host or promote disease. There is bidirectional communication between the intestinal microbiota and the brain that is mediated via immunologic, endocrine, and neural signaling pathways. While there is substantial interindividual variation within the microbiota, differences between males and females can be detected. In animal models, sex-specific microbiota differences can affect susceptibility to chronic diseases. In this review, we discuss the ways in which neurologic diseases may be regulated by the microbiota in a sex-specific manner.

The gut microbiota to the brain axis in the metabolic control

The regulation of glycemia is under a tight neuronal detection of glucose levels performed by the gut-brain axis and an efficient efferent neuronal message sent to the peripheral organs, as the pancreas to induce insulin and inhibit glucagon secretions. The neuronal detection of glucose levels is performed by the autonomic nervous system including the enteric nervous system and the vagus nerve innervating the gastro-intestinal tractus, from the mouth to the anus. A dysregulation of this detection leads to the one of the most important current health issue around the world i.e. diabetes mellitus. Furthemore, the consequences of diabetes mellitus on neuronal homeostasis and activities participate to the aggravation of the disease establishing a viscious circle. Prokaryotic cells as bacteria, reside in our gut. The strong relationship between prokaryotic cells and our eukaryotic cells has been established long ago, and prokaryotic and eukaryotic cells in our body have evolved synbiotically. For the last decades, studies demonstrated the critical role of the gut microbiota on the metabolic control and how its shift can induce diseases such as diabetes. Despite an important increase of knowledge, few is known about 1) how the gut microbiota influences the neuronal detection of glucose and 2) how the diabetes mellitus-induced gut microbiota shift observed participates to the alterations of autonomic nervous system and the gut-brain axis activity.

Twice subacute MPTP administrations induced time-dependent dopaminergic neurodegeneration and inflammation in midbrain and ileum, as well as gut microbiota disorders in PD mice

Parkinson's disease (PD) is a common progressive neurodegenerative disease. PD produces a pathological state in the intestine and disordered gut microbiota (GM), which may be important for the pathogenesis and progression of PD, but it is not clear. To explore the conditions and characteristics of intestinal pathology and GM disorders when PD-related injuries occur, we used twice 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) subacute administration with an interval of 3 weeks (each was an intraperitoneal injection of 25 mg/kg MPTP for 5 consecutive days). We observed the changes in intestinal and brain immune status, intestinal barrier function and GM in different injury states one day, one week, and three weeks after the first stimulus and one day and one week after the second stimulus. Our study found that two subacute administrations of MPTP induced dopaminergic (DAergic) neuron injury and inflammation in the midbrain and ileum, impaired intestinal barrier function and GM disorders closely related to administration. These changes recovered after the first administration, but after repeated administration, some indicators showed more dramatic changes than during the first administration. Our results suggest that the intestinal tract is sensitive to PD-related injury, and the GM is susceptible to disturbances caused by intestinal function, which may be concerned in local immune disorders of the intestine.

Undigested Food and Gut Microbiota May Cooperate in the Pathogenesis of Neuroinflammatory Diseases: A Matter of Barriers and a Proposal on the Origin of Organ Specificity

As food is an active subject and may have anti-inflammatory or pro-inflammatory effects, dietary habits may modulate the low-grade neuroinflammation associated with chronic neurodegenerative diseases. Food is living matter different from us, but made of our own nature. Therefore, it is at the same time foreign to us (non-self), if not yet digested, and like us (self), after its complete digestion. To avoid the efflux of undigested food from the lumen, the intestinal barrier must remain intact. What and how much we eat shape the composition of gut microbiota. Gut dysbiosis, as a consequence of Western diets, leads to intestinal inflammation and a leaky intestinal barrier. The efflux of undigested food, microbes, endotoxins, as well as immune-competent cells and molecules, causes chronic systemic inflammation. Opening of the blood-brain barrier may trigger microglia and astrocytes and set up neuroinflammation. We suggest that what determines the organ specificity of the autoimmune-inflammatory process may depend on food antigens resembling proteins of the organ being attacked. This applies to the brain and neuroinflammatory diseases, as to other organs and other diseases, including cancer. Understanding the cooperation between microbiota and undigested food in inflammatory diseases may clarify organ specificity, allow the setting up of adequate experimental models of disease and develop targeted dietary interventions.

Metabolomics for Investigating Physiological and Pathophysiological Processes

Metabolomics uses advanced analytical chemistry techniques to enable the high-throughput characterization of metabolites from cells, organs, tissues, or biofluids. The rapid growth in metabolomics is leading to a renewed interest in metabolism and the role that small molecule metabolites play in many biological processes. As a result, traditional views of metabolites as being simply the "bricks and mortar" of cells or just the fuel for cellular energetics are being upended. Indeed, metabolites appear to have much more varied and far more important roles as signaling molecules, immune modulators, endogenous toxins, and environmental sensors. This review explores how metabolomics is yielding important new insights into a number of important biological and physiological processes. In particular, a major focus is on illustrating how metabolomics and discoveries made through metabolomics are improving our understanding of both normal physiology and the pathophysiology of many diseases. These discoveries are yielding new insights into how metabolites influence organ function, immune function, nutrient sensing, and gut physiology. Collectively, this work is leading to a much more unified and system-wide perspective of biology wherein metabolites, proteins, and genes are understood to interact synergistically to modify the actions and functions of organelles, organs, and organisms.

In vitro Characterization of Gut Microbiota-Derived Bacterial Strains With Neuroprotective Properties

Neurodegenerative diseases are disabling, incurable, and progressive conditions characterized by neuronal loss and decreased cognitive function. Changes in gut microbiome composition have been linked to a number of neurodegenerative diseases, indicating a role for the gut-brain axis. Here, we show how specific gut-derived bacterial strains can modulate neuroinflammatory and neurodegenerative processes in vitro through the production of specific metabolites and discuss the potential therapeutic implications for neurodegenerative disorders. A panel of fifty gut bacterial strains was screened for their ability to reduce pro-inflammatory IL-6 secretion in U373 glioblastoma astrocytoma cells. Parabacteroides distasonis MRx0005 and Megasphaera massiliensis MRx0029 had the strongest capacity to reduce IL-6 secretion in vitro. Oxidative stress plays a crucial role in neuroinflammation and neurodegeneration, and both bacterial strains displayed intrinsic antioxidant capacity. While MRx0005 showed a general antioxidant activity on different brain cell lines, MRx0029 only protected differentiated SH-SY5Y neuroblastoma cells from chemically induced oxidative stress. MRx0029 also induced a mature phenotype in undifferentiated neuroblastoma cells through upregulation of microtubule-associated protein 2. Interestingly, short-chain fatty acid analysis revealed that MRx0005 mainly produced C1-C3 fatty acids, while MRx0029 produced C4-C6 fatty acids, specifically butyric, valeric and hexanoic acid. None of the short-chain fatty acids tested protected neuroblastoma cells from chemically induced oxidative stress. However, butyrate was able to reduce neuroinflammation in vitro, and the combination of butyrate and valerate induced neuronal maturation, albeit not to the same degree as the complex cell-free supernatant of MRx0029. This observation was confirmed by solvent extraction of cell-free supernatants, where only MRx0029 methanolic fractions containing butyrate and valerate showed an anti-inflammatory activity in U373 cells and retained the ability to differentiate neuroblastoma cells. In summary, our results suggest that the pleiotropic nature of live biotherapeutics, as opposed to isolated metabolites, could be a promising novel drug class in drug discovery for neurodegenerative disorders.

Probiotics for Parkinson's Disease

Parkinson's disease (PD) is a complex neurological disorder classically characterized by impairments in motor system function associated with loss of dopaminergic neurons in the substantia nigra. After almost 200 years since the first description of PD by James Parkinson, unraveling the complexity of PD continues to evolve. It is now recognized that an interplay between genetic and environmental factors influences a diverse range of cellular processes, reflecting on other clinical features including non-motor symptoms. This has consequently highlighted the extensive value of early clinical diagnosis to reduce difficulties of later stage management of PD. Advancement in understanding of PD has made remarkable progress in introducing new tools and strategies such as stem cell therapy and deep brain stimulation. A link between alterations in gut microbiota and PD has also opened a new line. Evidence exists of a bidirectional pathway between the gastrointestinal tract and the central nervous system. Probiotics, prebiotics and synbiotics are being examined that might influence gut-brain axis by altering gut microbiota composition, enteric nervous system, and CNS. This review provides status on use of probiotics for PD. Limitations and future directions will also be addressed to promote further research considering use of probiotics for PD.

Polyphenols in the management of brain disorders: Modulation of the microbiota-gut-brain axis

The modulation of the microbiota-gut-brain axis with a view to preventing and treating brain disorders became recently a hot topic for the scientific community. Dietary polyphenols are multifaceted compounds that have demonstrated to be highly advantageous to counteract inflammation, oxidative stress, and neurodegeneration, among other pathological conditions, being useful in the prevention and treatment of several chronic disorders. The potential of these compounds to prevent and treat brain disorders has not been only related to their capacity to reach the brain, depending on their chemical structure, and interact directly with brain cells, but also to their ability to modulate the communication between the brain and the gut, interfering with multiple branches of this axis. Preclinical studies have demonstrated the potential of these food bioactive compounds in brain diseases, namely, neurodevelopmental, such as Down's syndrome and Autism spectrum disorder, neurodegenerative, such as Parkinson's disease and Alzheimer's disease, and psychiatric disorders, such as depression and anxiety. Until now, dietary polyphenols have been recognized as promising nutraceuticals to combat brain disorders. However, the impact of these compounds on the gut-brain interconnection remains poorly elucidated. Also, clinical assays are crucial to further support the beneficial effects of these compounds as demonstrated in preclinical research.

Efficacy of Routine Fecal Microbiota Transplantation for Treatment of Recurrent Clostridium difficile Infection: A Retrospective Cohort Study

Background

Patients with recurrent Clostridium difficile infections (CDIs) constitute an increasing treatment problem. Fecal microbiota transplantation (FMT) has shown promising results of treating recurrent CDI, where treatment with antibiotics fails repeatedly. Our study describes retrospective cohort treated with FMT at two major hospitals in Stockholm.

Methods

Medical records of all patients with recurrent CDI treated with FMT during the period 2013–2017 were reviewed. We evaluated cure of CDI-related diarrhea without relapse 10 weeks after FMT.

Results

47 patients were included. One treatment cured 25 patients (53%), and more than one treatment cured 32 patients (68%). Treatment outcome did not vary significantly with treatment with fresh donor feces or frozen fecal culture, days of use of antibiotics or days of hospitalization prior to CDI, and renal function or time from the first CDI to therapy. Treatment failure was associated with a significantly lower Karnofsky performance status score (70 points vs 90, p=0.02).

Conclusion

Fecal instillation, for the treatment of relapsing CDI, is a promising approach, with 68% success rate reported in this study. The success rate of FMT is high, regardless of multiple comorbidities, extended use of antibiotics, or long time hospitalization. Although generally FMT is performed with fresh donor feces, our data show that the usage of frozen fecal culture could be an effective treatment alternative in recurrent CDI.

A nutritional approach to microbiota in Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disease characterized by motor impairment and the accumulation of alpha-synucleinopathy (α-syn), which can affect different levels of the brain-gut axis. There is a two-way communication between the gastrointestinal tract, and brain that includes the gut microbiota. This bidirectional communication between the gut microbiota and the brain includes many pathways, such as immune mechanisms, the vagus nerve, and microbial neurometabolite production. The common cause of constipation in PD is thought to be the accumulation of α-syn proteins in the enteric nervous system. Recent studies have focused on changes in microbial metabolites and gut microbiota dysbiosis. Microbiota dysbiosis is associated with increased intestinal permeability, intestinal inflammation, and neuroinflammation. Many factors, such as unbalanced nutrition, antibiotic use, age, and infection, result in alteration of microbial metabolites, triggering α-syn accumulation in the intestinal mucosa cells. Increased evidence indicates that the amount, type, and balance of dietary macronutrients (carbohydrates, proteins, and fats); high consumption of vegetables, fruits, and omega-3 fatty acids; and healthy diet patterns such as the Mediterranean diet may have a great protective impact on PD. This review focuses on the potential benefits of prebiotics, probiotics, and synbiotics to regulate microbiota dysbiosis along with the effect of diet on the gut microbiota in PD.

Infectious Etiologies of Parkinsonism: Pathomechanisms and Clinical Implications

Extensive research in recent decades has expanded our insights into the pathogenesis of Parkinson's disease (PD), though the underlying cause remains incompletely understood. Neuroinflammation have become a point of interest in the interconnecting areas of neurodegeneration and infectious diseases. The hypothesis concerning an infectious origin in PD stems from the observation of Parkinson-like symptoms in individuals infected with the influenza virus who then developed encephalitis lethargica. The implications of infectious pathogens have later been studied in neuronal pathways leading to the development of Parkinsonism and PD, through both a direct association and through synergistic effects of infectious pathogens in inducing neuroinflammation. This review explores the relationship between important infectious pathogens and Parkinsonism, including symptoms of Parkinsonism following infectious etiologies, infectious contributions to neuroinflammation and neurodegenerative processes associated with Parkinsonism, and the epidemiologic correlations between infectious pathogens and idiopathic PD.

Why targeting the microbiome is not so successful: can randomness overcome the adaptation that occurs following gut manipulation?

The microbiome is explored as a potential target for therapy of bowel and systemic diseases. Fecal microbiota transplantation (FMT) has demonstrated efficacy in Clostridium difficile infection. However, clinical results regarding other diseases are modest, despite the abundant research on the microbiome over the last decade. Both high rate variability of the microbiome and adaptation to gut manipulations may underlie the lack of ultimate effects of FMT, probiotics, prebiotics, synbiotics, and antibiotics, which are aimed at restoring a healthier microbiome. The present review discusses the inherent variability of the microbiome and multiple factors that affect its diversity, as possible causes of the adaptation of the gut microbiome to chronic manipulation. The potential use of randomness is proposed, as a means of overcoming the adaptation and of restoring some of the inherent variability, with the goal of improving the long-term efficacy of these therapies.

Microbiota and gut neuropeptides: a dual action of antimicrobial activity and neuroimmune response

The gut microbiota is comprised of a vast variety of microbes that colonize the gastrointestinal tract and exert crucial roles for the host health. These microorganisms, partially via their breakdown of dietary components, are able to modulate immune response, mood, and behavior, establishing a chemical dialogue in the microbiota-gut-brain interphase. Changes in the gut microbiota composition and functionality are associated with multiple diseases, in which altered levels of gut-associated neuropeptides are also detected. Gut neuropeptides are strong neuroimmune modulators; they mediate the communication between the gut microbiota and the host (including gut-brain axis) and have also recently been found to exert antimicrobial properties. This highlights the importance of understanding the interplay between gut neuropeptides and microbiota and their implications on host health. Here, we will discuss how gut neuropeptides help to maintain a balanced microbiota and we will point at the missing gaps that need to be further investigated in order to elucidate whether these molecules are related to neuropsychiatric disorders, which are often associated with gut dysbiosis and altered gut neuropeptide levels.