Gastrointestinal dysfunction in Parkinson's disease

Small molecule modulators of alpha-synuclein aggregation and toxicity: Pioneering an emerging arsenal against Parkinson's disease

Parkinson's disease (PD) is primarily characterized by loss of dopaminergic neurons in the substantia nigra pars compacta region of the brain and accumulation of aggregated forms of alpha-synuclein (α-Syn), an intrinsically disordered protein, in the form of Lewy Bodies and Lewy Neurites. Substantial evidences point to the aggregated/fibrillar forms of α-Syn as a central event in PD pathogenesis, underscoring the modulation of α-Syn aggregation as a promising strategy for PD treatment. Consequently, numerous anti-aggregation agents, spanning from small molecules to polymers, have been scrutinized for their potential to mitigate α-Syn aggregation and its associated toxicity. Among these, small molecule modulators like osmoprotectants, polyphenols, cellular metabolites, metals, and peptides have emerged as promising candidates with significant potential in PD management. This article offers a comprehensive overview of the effects of these small molecule modulators on the aggregation propensity and associated toxicity of α-Syn and its PD-associated mutants. It serves as a valuable resource for identifying and developing potent, non-invasive, non-toxic, and highly specific small molecule-based therapeutic arsenal for combating PD. Additionally, it raises pertinent questions aimed at guiding future research endeavours in the field of α-Syn aggregation remodelling.

Consensus practice recommendations for management of gastrointestinal dysfunction in Parkinson disease

BACKGROUND

Gastrointestinal (GI) dysfunction is a common non-motor feature of Parkinson disease (PD). GI symptoms may start years before the onset of motor symptoms and impair quality of life. Robust clinical trial data is lacking to guide screening, diagnosis and treatment of GI dysfunction in PD.

OBJECTIVE

To develop consensus statements on screening, diagnosis, and treatment of GI dysfunction in PD.

METHODS

The application of a modified Delphi panel allowed for the synthesis of expert opinions into clinical statements. Consensus was predefined as a level of agreement of 100 % for each item. Five virtual Delphi rounds were held. Two movement disorders neurologists reviewed the literature on GI dysfunction in PD and developed draft statements based on the literature review. Draft statements were distributed among the panel that included five movement disorder neurologists and two gastroenterologists, both experts in GI dysmotility and its impact on PD symptoms. All members reviewed the statements and references in advance of the virtual meetings. In the virtual meetings, each statement was discussed, edited, and a vote was conducted. If there was not 100 % consensus, further discussions and modifications ensued until there was consensus.

RESULTS

Statements were developed for screening, diagnosis, and treatment of common GI symptoms in PD and were organized by anatomic segments: oral cavity and esophagus, stomach, small intestine, and colon and anorectum.

CONCLUSIONS

These consensus recommendations offer a practical framework for the diagnosis and treatment of GI dysfunction in PD.

Neuroimmune Connectomes in the Gut and Their Implications in Parkinson's Disease

The gastrointestinal tract is the largest immune organ and it receives dense innervation from intrinsic (enteric) and extrinsic (sympathetic, parasympathetic, and somatosensory) neurons. The immune and neural systems of the gut communicate with each other and their interactions shape gut defensive mechanisms and neural-controlled gut functions such as motility and secretion. Changes in neuroimmune interactions play central roles in the pathogenesis of diseases such as Parkinson's disease (PD), which is a multicentric disorder that is heterogeneous in its manifestation and pathogenesis. Non-motor and premotor symptoms of PD are common in the gastrointestinal tract and the gut is considered a potential initiation site for PD in some cases. How the enteric nervous system and neuroimmune signaling contribute to PD disease progression is an emerging area of interest. This review focuses on intestinal neuroimmune loops such as the neuroepithelial unit, enteric glial cells and their immunomodulatory effects, anti-inflammatory cholinergic signaling and the relationship between myenteric neurons and muscularis macrophages, and the role of α-synuclein in gut immunity. Special consideration is given to the discussion of intestinal neuroimmune connectomes during PD and their possible implications for various aspects of the disease.

Dopaminergic neuron loss in mice due to increased levels of wild-type human α-Synuclein only takes place under conditions of accelerated aging

Understanding the intricate pathogenic mechanisms behind Parkinson's disease (PD) and its multifactorial nature presents a significant challenge in disease modeling. To address this, we explore genetic models that better capture the disease's complexity. Given that aging is the primary risk factor for PD, this study investigates the impact of aging in conjunction with overexpression of wild-type human α-synuclein (α-Syn) in the dopaminergic system. This is achieved by introducing a novel transgenic mouse strain overexpressing α-Syn under the TH-promoter within the senescence-accelerated SAMP8 (P8) genetic background. Behavioral assessments, conducted at both 10 and 16 months of age, unveil motor impairments exclusive to P8 α-SynTg mice, a phenomenon conspicuously absent in α-SynTg mice. These findings suggest a synergistic interplay between heightened α-Syn levels and the aging process, resulting in motor deficits. These motor disturbances correlate with reduced dopamine (DA) levels, increased DA turnover, synaptic terminal loss, and notably, the depletion of dopaminergic neurons in the substantia nigra and noradrenergic neurons in the locus coeruleus. Furthermore, P8 α-SynTg mice exhibit alterations in gut transit time, mirroring early PD symptoms. In summary, P8 α-SynTg mice effectively replicate parkinsonian phenotypes by combining α-Syn transgene expression with accelerated aging. This model offers valuable insights into the understanding of PD and serves as a valuable platform for further research.

The critical role of gut-brain axis microbiome in mental disorders

The Gut-brain axis is a bidirectional neural and humoral signaling that plays an important role in mental disorders and intestinal health and connects them as well. Over the past decades, the gut microbiota has been explored as an important part of the gastrointestinal tract that plays a crucial role in the regulation of most functions of various human organs. The evidence shows several mediators such as short-chain fatty acids, peptides, and neurotransmitters that are produced by the gut may affect the brain's function directly or indirectly. Thus, dysregulation in this microbiome community can give rise to several diseases such as Parkinson's disease, depression, irritable bowel syndrome, and Alzheimer's disease. So, the interactions between the gut and the brain are significantly considered, and also it provides a prominent subject to investigate the causes of some diseases. In this article, we reviewed and focused on the role of the largest and most repetitive bacterial community and their relevance with some diseases that they have mentioned previously.

α-Synuclein seeding activity in duodenum biopsies from Parkinson's disease patients

Abnormal deposition of α-synuclein is a key feature and biomarker of Parkinson's disease. α-Synuclein aggregates can propagate themselves by a prion-like seeding-based mechanism within and between tissues and are hypothesized to move between the intestine and brain. α-Synuclein RT-QuIC seed amplification assays have detected Parkinson's-associated α-synuclein in multiple biospecimens including post-mortem colon samples. Here we show intra vitam detection of seeds in duodenum biopsies from 22/23 Parkinson's patients, but not in 6 healthy controls by RT-QuICR. In contrast, no tau seeding activity was detected in any of the biopsies. Our seed amplifications provide evidence that the upper intestine contains a form(s) of α-synuclein with self-propagating activity. The diagnostic sensitivity and specificity for PD in this biopsy panel were 95.7% and 100% respectively. End-point dilution analysis indicated up to 106 SD50 seeding units per mg of tissue with positivity in two contemporaneous biopsies from individual patients suggesting widespread distribution within the superior and descending parts of duodenum. Our detection of α-synuclein seeding activity in duodenum biopsies of Parkinson's disease patients suggests not only that such analyses may be useful in ante-mortem diagnosis, but also that the duodenum may be a source or a destination for pathological, self-propagating α-synuclein assemblies.

Beyond the Microbiota: Understanding the Role of the Enteric Nervous System in Parkinson's Disease from Mice to Human

The enteric nervous system (ENS) is a nerve network composed of neurons and glial cells that regulates the motor and secretory functions of the gastrointestinal (GI) tract. There is abundant evidence of mutual communication between the brain and the GI tract. Dysfunction of these connections appears to be involved in the pathophysiology of Parkinson's disease (PD). Alterations in the ENS have been shown to occur very early in PD, even before central nervous system (CNS) involvement. Post-mortem studies of PD patients have shown aggregation of α-synuclein (αS) in specific subtypes of neurons in the ENS. Subsequently, αS spreads retrogradely in the CNS through preganglionic vagal fibers to this nerve's dorsal motor nucleus (DMV) and other central nervous structures. Here, we highlight the role of the ENS in PD pathogenesis based on evidence observed in animal models and using a translational perspective. While acknowledging the putative role of the microbiome in the gut-brain axis (GBA), this review provides a comprehensive view of the ENS not only as a "second brain", but also as a window into the "first brain", a potentially crucial element in the search for new therapeutic approaches that can delay and even cure the disease.

Behavioural interventions for swallowing in subjects with Parkinson's disease: A mixed methods systematic review

BACKGROUND

Dysphagia is prevalent in subjects with Parkinson's disease (PD). Swallowing intervention to improve or maintain swallowing function is of major importance as dysphagia may considerably impact physical and psycho-social health.

AIMS

A mixed methods systematic review was conducted to summarize and appraise literature reporting (1) effects of behavioural interventions for swallowing in individuals with PD; and (2) participants' perspectives of swallowing interventions.

METHODS & PROCEDURES

Electronic databases were searched systematically in July 2020 for articles published between 2014 and 2020. In addition, studies published between 2000 and 2014 were identified non-systematically through previous reviews. Peer-reviewed quantitative and qualitative research in English or German documenting behavioural interventions for swallowing in individuals with a diagnosis of PD was eligible for inclusion. Participants at all disease stages were included. Behavioural interventions included rehabilitative and compensatory strategies. Studies reporting swallowing outcomes with and without a comparative group were included. For each study, the National Health and Medical Research Council level of evidence was defined. Included studies were critically appraised using the Standard Quality Assessment Criteria for Evaluating Primary Research Papers from a Variety of Fields. An integrated synthesis was performed after separate analysis of effect data and data reflecting participants' experiences. This review was conducted based on published JBI methodology and the guideline from the Preferred Reporting Items for Systematic Reviews and Meta-Analysis system was followed.

MAIN CONTRIBUTION

A total of 33 studies published in English met the inclusion criteria. Thirty-one studies reported quantitative data, one was qualitative and one was mixed methods. Intervention effects on swallowing function, swallowing safety and swallowing-related quality of life were reported for various treatment approaches. Three studies explored how participants perceived the intervention. Overriding themes including subjects' views regarding treatment schedules and levels of effort or comfort associated with the intervention were identified across these studies. Combining evidence of intervention effects and subjects' experiences was possible for one rehabilitative and one compensatory intervention.

CONCLUSIONS & IMPLICATIONS

Beneficial effects of swallowing interventions have been reported; however, most experiments were case studies of variable methodological quality. Randomized-controlled trials with robust methodology to explore treatment effects in larger samples is needed to guide clinical practice. Research reporting subjects' views is scarce. More studies exploring how individuals perceive behavioural interventions for swallowing are necessary to inform clinical decision-making.

WHAT THIS PAPER ADDS

What is already known on the subject Dysphagia is common in individuals with PD. Swallowing intervention is of major importance as dysphagia may negatively affect physical and psycho-social health of subjects with PD. What this study adds Beneficial effects of behavioural interventions for swallowing, including rehabilitative and compensatory strategies, have been reported; however, available data are mostly based on case studies of variable quality. Data on how participants perceive specific behavioural interventions are lacking. Based on the available data, integration of efficacy data and individuals' experiences is limited. What are the clinical implications of this work? Given the current evidence of intervention effects and individuals' views on behavioural treatment strategies, interventions implemented into clinical practice require careful evaluation on a case-by-case basis. More high-quality research is needed to examine interventions' short- and long-term effects in larger samples to guide clinical practice. In addition to studies evaluating intervention effects, research exploring participants' experiences with interventions is required as a foundation for clinical decision-making.

Gastrointestinal barriers to levodopa transport and absorption in Parkinson's disease

Levodopa is the gold standard for the symptomatic treatment of Parkinson's disease (PD). There are well documented motor and non-motor fluctuations, however, that occur almost inevitably once levodopa is started after a variable period in people with PD. Whilst brain neurodegenerative processes play a part in the pathogenesis of these fluctuations, a range of barriers across the gastrointestinal (GI) tract can alter levodopa pharmacokinetics, ultimately contributing to non-optimal levodopa response and symptoms fluctuations. GI barriers to levodopa transport and absorption include dysphagia, delayed gastric emptying, constipation, Helicobacter pylori infection, small intestinal bacterial overgrowth and gut dysbiosis. In addition, a protein-rich diet and concomitant medication intake can further alter levodopa pharmacokinetics. This can result in unpredictable or sub-optimal levodopa response, 'delayed on' or 'no on' phenomena. In this narrative review, we provided an overview on the plethora of GI obstacles to levodopa transport and absorption in PD and their implications on levodopa pharmacokinetics and development of motor fluctuations. In addition, management strategies to address GI dysfunction in PD are highlighted, including use of non-oral therapies to bypass the GI tract.

Laterality in Parkinson's disease: A neuropsychological review

Laterality of motor symptom onset in Parkinson's disease is both well-known and under-appreciated. Treatment of disorders that have asymmetric pathological features, such as stroke and epilepsy, demonstrate the importance of incorporating hemispheric lateralization and specialization into therapy and care planning. These practices could theoretically extend to Parkinson's disease, providing increased diagnostic accuracy and improved treatment outcomes. Additionally, while motor symptoms have generally received the majority of attention, non-motor features (e.g., autonomic dysfunction) also decrease quality of life and are influenced by asymmetrical neurodegeneration. Due to the laterality of cognitive and behavioral processes in the two brain hemispheres, analysis of hemibody side of onset can potentially give insight into expected symptom profile of the patient and allow for increased predictive accuracy of disease progression and outcome, thus opening the door to personalized and improved therapy in treating Parkinson's disease patients. This review discusses motor and non-motor symptoms (namely autonomic, sensory, emotional, and cognitive dysfunction) of Parkinson's disease in respect to hemispheric lateralization from a theoretical perspective in hopes of providing a framework for future research and personalized treatment.

The Microbiome-Gut-Brain Axis and Dementia: A Bibliometric Analysis

BACKGROUND

Associations between the microbiome-gut-brain axis and dementia have attracted considerable attention in research literature. This study examined the microbiome-gut-brain axis and dementia-related research from a bibliometric perspective.

METHODS

A search for original research and review articles on the microbiome-gut-brain axis and dementia was conducted in the Web of Science Core Collection (WOSCC) database. The R package "bibliometrix" was used to collect information on countries, institutions, authors, journals, and keywords. VOSviewer software was used to visualize the co-occurrence network of keywords.

RESULTS

Overall, 494 articles met the study inclusion criteria, with an average of 29.64 citations per article. Corresponding authors of published articles were mainly from China, the United States and Italy. Zhejiang University in China and Kyung Hee University in Korea were the most active institutions, while the Journal of Alzheimer's Disease and Nutrients published the most articles in this field. Expected main search terms, "Parkinson disease" and "chain fatty-acids" were high-frequency keywords that indicate current and future research directions in this field.

CONCLUSIONS

This bibliometric study helped researchers to identify the key topics and trends in the microbiome-gut-brain axis and dementia-related research. High-frequency keywords identified in this study reflect current trends and possible future directions in this field related to methodologies, mechanisms and populations of interest.

Heparan sulfate proteoglycans mediate prion-like α-synuclein toxicity in Parkinson's in vivo models

This study offers new Caenorhabditis elegans models in which feeding with α-synuclein pre-formed fibrils results in prion-like aggregation of host α-synuclein and dopamine neuron degeneration, and these disease phenotypes are regulated by the heparan sulfate proteoglycan pathway.

Parkinson’s disease (PD) is a debilitating neurodegenerative disorder characterized by progressive motor decline and the aggregation of α-synuclein protein. Growing evidence suggests that α-synuclein aggregates may spread from neurons of the digestive tract to the central nervous system in a prion-like manner, yet the mechanisms of α-synuclein transmission and neurotoxicity remain poorly understood. Animal models that are amenable to high-throughput investigations are needed to facilitate the discovery of disease mechanisms. Here we describe the first Caenorhabditis elegans models in which feeding with α-synuclein preformed fibrils (PFFs) induces dopaminergic neurodegeneration, prion-like seeding of aggregation of human α-synuclein expressed in the host, and an associated motor decline. RNAi-mediated knockdown of the C. elegans syndecan sdn-1, or other enzymes involved in heparan sulfate proteoglycan synthesis, protected against PFF-induced α-synuclein aggregation, motor dysfunction, and dopamine neuron degeneration. This work offers new models by which to investigate gut-derived α-synuclein spreading and propagation of disease.

Electroacupuncture Modulates 5-HT4R-Mediated cAMP/PKA Signaling to Improve Intestinal Motility Disorders in a Thy1-αSyn Parkinson's Mouse Model

Constipation is one of the most common nonmotor symptoms in patients with Parkinson's disease (PD) and often occurs before motor symptoms. Electroacupuncture effectively improves the symptoms of constipation in patients with PD. In the present study, we used thymus cell antigen 1-α-synuclein (Thy1-αSyn) transgenic mice as a model of intestinal motility disorders in PD to determine the therapeutic effect of electroacupuncture and the underlying mechanisms. Electroacupuncture significantly improved fecal excretion and accelerated the rate of small-intestinal propulsion in Thy1-αSyn mice by upregulating the serotonin concentration and the expression of the serotonin 4 receptor. Consequently, the downstream cyclic AMP/protein kinase A (cAMP/PKA) pathway was affected, and to upregulate and downregulate, the expression of substance P was upregulated, and the expression of calcitonin gene-related peptide was downregulated. In summary, electroacupuncture improved intestinal motility in PD mice by affecting serotonin levels, serotonin 4 receptor expression, and the cAMP/PKA pathway, providing a potentially effective and promising complementary and alternative therapy for relieving constipation symptoms in patients with PD.

Human Induced Pluripotent Stem Cell Phenotyping and Preclinical Modeling of Familial Parkinson's Disease

Parkinson's disease (PD) is primarily idiopathic and a highly heterogenous neurodegenerative disease with patients experiencing a wide array of motor and non-motor symptoms. A major challenge for understanding susceptibility to PD is to determine the genetic and environmental factors that influence the mechanisms underlying the variations in disease-associated traits. The pathological hallmark of PD is the degeneration of dopaminergic neurons in the substantia nigra pars compacta region of the brain and post-mortem Lewy pathology, which leads to the loss of projecting axons innervating the striatum and to impaired motor and cognitive functions. While the cause of PD is still largely unknown, genome-wide association studies provide evidence that numerous polymorphic variants in various genes contribute to sporadic PD, and 10 to 15% of all cases are linked to some form of hereditary mutations, either autosomal dominant or recessive. Among the most common mutations observed in PD patients are in the genes LRRK2, SNCA, GBA1, PINK1, PRKN, and PARK7/DJ-1. In this review, we cover these PD-related mutations, the use of induced pluripotent stem cells as a disease in a dish model, and genetic animal models to better understand the diversity in the pathogenesis and long-term outcomes seen in PD patients.

Intestine-derived α-synuclein initiates and aggravates pathogenesis of Parkinson's disease in Drosophila

Background

Aberrant aggregation of α-synuclein (α-syn) is a key pathological feature of Parkinson’s disease (PD), but the precise role of intestinal α-syn in the progression of PD is unclear. In a number of genetic Drosophila models of PD, α-syn was frequently ectopically expressed in the neural system to investigate the pathobiology.

Method

We investigated the potential role of intestinal α-syn in PD pathogenesis using a Drosophila model. Human α-syn was overexpressed in Drosophila guts, and life span, survival, immunofluorescence and climbing were evaluated. Immunofluorescence, Western blotting and reactive oxygen species (ROS) staining were performed to assess the effects of intestinal α-syn on intestinal dysplasia. High‐throughput RNA and 16S rRNA gene sequencing, quantitative RT‐PCR, immunofluorescence, and ROS staining were performed to determine the underlying molecular mechanism.

Results

We found that the intestinal α-syn alone recapitulated many phenotypic and pathological features of PD, including impaired life span, loss of dopaminergic neurons, and progressive motor defects. The intestine-derived α-syn disrupted intestinal homeostasis and accelerated the onset of intestinal ageing. Moreover, intestinal expression of α-syn induced dysbiosis, while microbiome depletion was efficient to restore intestinal homeostasis and ameliorate the progression of PD. Intestinal α-syn triggered ROS, and eventually led to the activation of the dual oxidase (DUOX)–ROS–Jun N-terminal Kinase (JNK) pathway. In addition, α-syn from both the gut and the brain synergized to accelerate the progression of PD.

Conclusions

The intestinal expression of α-syn recapitulates many phenotypic and pathologic features of PD, and induces dysbiosis that aggravates the pathology through the DUOX–ROS–JNK pathway in Drosophila. Our findings provide new insights into the role of intestinal α-syn in PD pathophysiology.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40035-022-00318-w.

Probiotics for constipation and gut microbiota in Parkinson's disease

INTRODUCTION

Constipation is one of the common non-motor symptoms in Parkinson's disease that significantly impacts patient quality of life. Probiotics supplementation may improve constipation symptoms, but its effect on the gut microbiota population is unclear.

METHODS

In this randomized controlled study, 46 PD patients with constipation according to Rome Ⅲ criteria were recruited. The number of complete bowel movements per week, degree of defecation effort, Bristol stool Scale (BSS), Patient Assessment of Constipation symptom (PAC-SYM) and Patient assessment of constipation quality of life questionnaire (PAC-QOL) were collected pre- and post-intervention to evaluate the constipation symptoms. In addition, fresh feces of subjects before and after intervention and healthy controls were collected for 16s rRNA gene V3-V4 region sequencing to compare bacterial flora differences.

RESULTS

Compared with the control group, the treatment group increased the average number of complete bowel movements per week (1.09 ± 1.24 vs. 0.04 ± 0.64, P < 0.001). Probiotics supplementation reduced the BSS score (0.65 ± 0.93 vs. -0.17 ± 0.94, P = 0.004), PAC-SYM score (4.09 ± 6.31 vs. -1.83 ± 4.14, P < 0.001), PAC-QOL score (10.65 ± 16.53 vs. 0.57 ± 12.82, P = 0.042), and degree of defecation effort score (1.00 ± 0.80 vs. 0.00 ± 0.30, P < 0.001). The improvement rate of constipation in the probiotics group was significantly higher than that in the control group (52.2% vs. 8.7%, P = 0.001). PD patients showed intestinal flora disorders compared to healthy controls. After 12 weeks of probiotics treatment, g_Christensenella_sp._Marseille-P2437 significantly increased, while g_Eubacterium_oxidoreducens_group, g_Eubacterium_hallii_group and s_Odoribacter_sp._N54.MGS-14 decreased (p < 0 0.05).

CONCLUSIONS

Probiotics treatment can effectively improve the constipation symptoms of PD patients and positively affected the gut microbiota.

Antibiotic Consumption Patterns in European Countries Are Associated with the Prevalence of Parkinson’s Disease; the Possible Augmenting Role of the Narrow-Spectrum Penicillin

Parkinson’s disease: Parkinson’s disease (PD) is the second-most common neurodegenerative disease, affecting at least 0.3% of the worldwide population and over 3% of those over 80 years old. According to recent research (2018), in 2016, 6.1 million (95% uncertainty interval (UI) 5.0–7.3) individuals had Parkinson’s disease globally, compared with 2.5 million (2.0–3.0) in 1990. The pandemic-like spreading of PD is considered a slow-moving disaster. Most recent studies indicated the possible role of an altered microbiome, dysbiosis, in the development of PD, which occurs long before the clinical diagnosis of PD. Antibiotics are considered as major disruptors of the intestinal flora and we have hypothesized that, as different classes of antibiotics might induce different dysbiosis, certain classes of antibiotics could trigger the PD-related dysbiosis as well. Comparative analyses were performed between the average yearly antibiotic consumption of 30 European countries (1997–2016) and the PD prevalence database (estimated for 2016). We divided the time frame of antibiotic consumption of 1997–2016 into four subsections to estimate the possible time lapse between antibiotic exposure and the prevalence, prevalence change, and PD-related death rates estimated for 2016. Our results indicated that countries with high consumption of narrow-spectrum penicillin experienced a higher increase in PD prevalence than the others. Countries reporting a decline in PD from 1990 to 2016 demonstrated a reduction in the consumption of narrow-spectrum penicillin in this period.

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.

Changes in the expression of TRPV4 and TRPM8 channels in the colon of rats with 6-OHDA-induced Parkinson’s disease

Parkinson’s disease (PD) is neurodegenerative disease, which is accompanied by degeneration of dopaminergic neurons in subtantia nigra. Non-motor symptoms, in particular, disorders of the gastrointestinal (GI) tract are observed in 20-80% of patients some 15-20 years before clinically diagnosed PD and are not a least important feature of PD pathogenesis. The transient receptor potential (TRP) channels are expressed throughout the GI tract, where they play an important role in taste, thermoregulation, pain, mucosal function and homeostasis, control of interstitial motility etc. The aim of this study was to investigate the contribution of TRPV4 and TRPM8 channels in the GI motor function in the colon of rats with PD, incduced by injection of the 12 μg 6-hydroxydopamine (6-OHDA). The studies were performed on the 4th week and the 7th month after PD induction The rats were randomly divided into: I group – the sham-lesioned rats, 4 μl 0.9% NaCl, autopsy 4 weeks after injection (n = 5); II group – the 6-OHDA-PD rats, 4 μl 12 μg of 6-OHDA, autopsy 4 weeks after injection (n = 5); III group – the sham-lesioned rats, 4 μl 0.9% NaCl, autopsy 7 months after injection (n = 4); IV group – the 6-OHDA-PD rats, 4 μl 12 μg of 6-OHDA, autopsy 7 months after injection (n = 5). We evaluated the body weight of rats, GI transit time, the cecum weight index and immunohistochemical identification of tyrosine hydroxylase (TH) -positive cells, and TRPV4, TRPM8 expression in rat’s colon. We showed that on the 7th month of the experiment, the GI transit time doubles over time; the cecum weight index of 6-OHDA rats increased by 57%; the number of TH-positive cells in colon rats decreased 2-fold, while TRPM8 ion channels were downregulated in PD rats and TRPV4 ion channels were upregulated in the colon of rats with 6-OHDA-PD. It was concluded that TRPV4 and TRPM8 ion channels may be considered pharmacological targets in the progression of PD pathology.

Nutritional Intake and Gut Microbiome Composition Predict Parkinson's Disease

Background

Models to predict Parkinson's disease (PD) incorporating alterations of gut microbiome (GM) composition have been reported with varying success.

Objective

To assess the utility of GM compositional changes combined with macronutrient intake to develop a predictive model of PD.

Methods

We performed a cross-sectional analysis of the GM and nutritional intake in 103 PD patients and 81 household controls (HCs). GM composition was determined by 16S amplicon sequencing of the V3-V4 region of bacterial ribosomal DNA isolated from stool. To determine multivariate disease-discriminant associations, we developed two models using Random Forest and support-vector machine (SVM) methodologies.

Results

Using updated taxonomic reference, we identified significant compositional differences in the GM profiles of PD patients in association with a variety of clinical PD characteristics. Six genera were overrepresented and eight underrepresented in PD patients relative to HCs, with the largest difference being overrepresentation of Lactobacillaceae at family taxonomic level. Correlation analyses highlighted multiple associations between clinical characteristics and select taxa, whilst constipation severity, physical activity and pharmacological therapies associated with changes in beta diversity. The random forest model of PD, incorporating taxonomic data at the genus level and carbohydrate contribution to total energy demonstrated the best predictive capacity [Area under the ROC Curve (AUC) of 0.74].

Conclusion

The notable differences in GM diversity and composition when combined with clinical measures and nutritional data enabled the development of a predictive model to identify PD. These findings support the combination of GM and nutritional data as a potentially useful biomarker of PD to improve diagnosis and guide clinical management.

The Gut-Brain Axis and Its Relation to Parkinson's Disease: A Review

Parkinson's disease is a chronic neurodegenerative disease characterized by the accumulation of misfolded alpha-synuclein protein (Lewy bodies) in dopaminergic neurons of the substantia nigra and other related circuitry, which contribute to the development of both motor (bradykinesia, tremors, stiffness, abnormal gait) and non-motor symptoms (gastrointestinal issues, urinogenital complications, olfaction dysfunction, cognitive impairment). Despite tremendous progress in the field, the exact pathways and mechanisms responsible for the initiation and progression of this disease remain unclear. However, recent research suggests a potential relationship between the commensal gut bacteria and the brain capable of influencing neurodevelopment, brain function and health. This bidirectional communication is often referred to as the microbiome-gut-brain axis. Accumulating evidence suggests that the onset of non-motor symptoms, such as gastrointestinal manifestations, often precede the onset of motor symptoms and disease diagnosis, lending support to the potential role that the microbiome-gut-brain axis might play in the underlying pathological mechanisms of Parkinson's disease. This review will provide an overview of and critically discuss the current knowledge of the relationship between the gut microbiota and Parkinson's disease. We will discuss the role of α-synuclein in non-motor disease pathology, proposed pathways constituting the connection between the gut microbiome and the brain, existing evidence related to pre- and probiotic interventions. Finally, we will highlight the potential opportunity for the development of novel preventative measures and therapeutic options that could target the microbiome-gut-brain axis in the context of Parkinson's disease.

Long-Term Risks of Parkinson's Disease, Surgery, and Colorectal Cancer in Patients With Slow-Transit Constipation

BACKGROUND & AIMS

Long-term outcomes of constipation have not been evaluated fully. We investigated the incidence of Parkinson's disease, constipation-related surgery, and colorectal cancer (CRC) in patients with constipation and slow-transit constipation (STC), followed up for up to 20 years.

METHODS

We collected data from 2165 patients (33.1% men; median patient age, 54 y; median symptom duration, 5.0 y) with a diagnosis of constipation (based on Rome II criteria) who underwent an anorectal function test and a colonic transit time study, from 2000 through 2010, at a tertiary university hospital in Seoul, South Korea. The presence of STC was determined from colonic transit time. We used the Kaplan-Meier method to analyze and compare cumulative probabilities of a new diagnosis of Parkinson's disease or CRC according to the presence of STC. The patients were followed up until the end of 2019.

RESULTS

During a median follow-up period of 4.7 years (interquartile range, 0.7-8.3 y), 10 patients underwent constipation-related surgery. The cumulative probabilities of constipation-related surgery were 0.7% at 5 years and 0.8% at 10 years after a diagnosis of constipation. Twenty-nine patients (1.3%) developed Parkinson's disease; the cumulative probabilities were 0.4% at 1 year, 1.0% at 5 years, and 2.6% at 10 years after a diagnosis of constipation. At 10 years, 1.3% of patients with STC required constipation-related surgery and 3.5% of patients with STC developed Parkinson's disease; in contrast, none of the patients without STC required constipation-related surgery (P = .003), and 1.5% developed Parkinson's disease (P = .019). In multivariate analysis, patient age of 65 years or older at the diagnosis of constipation (hazard ratio, 4.834; 95% CI, 2.088-11.190) and the presence of STC (hazard ratio, 2.477; 95% CI, 1.046-5.866) were associated independently with the development of Parkinson's disease. Only 5 patients had a new diagnosis of CRC during the follow-up period. The risk of CRC did not differ significantly between patients with vs without STC (P = .575).

CONCLUSIONS

In a long-term follow-up study of patients with constipation in Korea, most patients had no severe complications. However, patients older than age 65 years with a new diagnosis of STC might be considered for Parkinson's disease screening.

Association between Parkinson's disease and the faecal eukaryotic microbiota

Parkinson's disease (PD) is one of the most common neurodegenerative disease, and is so far not considered curable. PD patients suffer from several motor and non-motor symptoms, including gastrointestinal dysfunctions and alterations of the enteric nervous system. Constipation and additional intestinal affections can precede the classical motor symptoms by several years. Recently, we reported effects of PD and related medications on the faecal bacterial community of 34 German PD patients and 25 age-matched controls. Here, we used the same collective and analysed the V6 and V7 hypervariable region of PCR-amplified, eukaryotic 18S rRNA genes using an Illumina MiSeq platform. In all, 53% (18) of the PD samples and 72% (18) of the control samples yielded sufficient amplicons for downstream community analyses. The PD samples showed a significantly lower alpha and a different beta eukaryotic diversity than the controls. Most strikingly, we observed a significantly higher relative abundance of sequence affiliated with the Geotrichum genus in the PD samples (39.7%), when compared to the control samples (0.05%). In addition, we observed lower relative abundances of sequences affiliated with Aspergillus/Penicillium, Charophyta/Linum, unidentified Opisthokonta and three genera of minor abundant zooflagellates in the PD samples. Our data add knowledge to the small body of data about the eukaryotic microbiota of PD patients and suggest a potential association of certain gut eukaryotes and PD.

Alpha-synuclein alters the faecal viromes of rats in a gut-initiated model of Parkinson's disease

Parkinson's disease (PD) is a chronic neurological disorder associated with the misfolding of alpha-synuclein (α-syn) into aggregates within nerve cells that contribute to their neurodegeneration. Recent evidence suggests α-syn aggregation may begin in the gut and travel to the brain along the vagus nerve, with microbes potentially a trigger initiating α-syn misfolding. However, the effects α-syn alterations on the gut virome have not been investigated. In this study, we show longitudinal faecal virome changes in rats administered either monomeric or preformed fibrils (PFF) of α-syn directly into their enteric nervous system. Differential changes in rat viromes were observed when comparing monomeric and PFF α-syn, with alterations compounded by the addition of LPS. Changes in rat faecal viromes were observed after one month and did not resolve within the study's five-month observational period. These results suggest that virome alterations may be reactive to host α-syn changes that are associated with PD development.

Gastrointestinal disorders in hyperkinetic movement disorders and ataxia

BACKGROUND

Gastrointestinal (GI) disorders have been thoroughly investigated in hypokinetic disorders such as Parkinson's disease, but much less is known about GI disorders in hyperkinetic movement disorders and ataxia. The aim of this review is to draw attention to the GI disorders that are associated with these movement disorders.

METHODS

References for this systematic review were identified by searches of PubMed through May 2020. Only publications in English were reviewed.

RESULTS

Data from 249 articles were critically reviewed, compared, and integrated. The most frequently reported GI symptoms overall in hyperkinetic movement disorders and ataxia are dysphagia, sialorrhea, weight changes, esophago-gastritis, gastroparesis, constipation, diarrhea, and malabsorption. We report in detail on the frequency, characteristics, pathophysiology, and management of GI symptoms in essential tremor, restless legs syndrome, chorea, and spinocerebellar ataxias. The limited available data on GI disorders in dystonias, paroxysmal movement disorders, tardive dyskinesias, myoclonus, and non-SCA ataxias are also summarized.

CONCLUSION

The purpose of our systematic review is to draw attention that, although primarily motor disorders, hyperkinetic movement disorders and ataxia can involve the GI system. Raising awareness about the GI symptom burden in hyperkinetic movement disorders and ataxia could contribute to a new research interest in that field, as well as improved patient care.

Cohort Study in Parkinsonism: Delayed Transit, Accelerated Gastric Emptying, and Prodromal Dysmotility

Objective

To evaluate gastric emptying (GE) and colonic transit in a cohort of patients with Parkinson disease and other parkinsonism disorders and to determine whether abnormal gut transit precedes motor onset of parkinsonism.

Methods

Medical record review of 84 patients with parkinsonism who underwent clinically indicated transit studies at Mayo Clinic (2001-2019) and 11 patients with transit studies who subsequently developed parkinsonism. Data are summarized as median (interquartile range).

Results

The 84 patients (52% female) with parkinsonism were aged 72 (66-76) years with a disease duration of 5 (2-8) years: Parkinson disease = 70, multiple system atrophy = 7, dementia with Lewy bodies = 4, progressive supranuclear palsy = 2, and parkinsonian syndrome = 1. Ten had delayed GE, 10 slow colonic transit, 16 accelerated GE (14 Parkinson disease, 1 multiple system atrophy, and 1 parkinsonian syndrome), and 49 normal transit. One patient with parkinsonian syndrome had both slow colonic and accelerated gastric transit. Longer disease duration and higher levodopa equivalent daily dose were observed for Parkinson disease compared with other parkinsonisms and with slow compared with normal colonic transit. Of 11 patients (5 female) with transit studies who later developed motor parkinsonism after 4 (3-5) years, 1 had accelerated GE, 1 had delayed GE, and 1 had both delayed GE and colonic transit.

Conclusions

Accelerated GE was newly identified in patients with parkinsonism, in addition to delayed GE or colonic transit. Furthermore, gut dysmotility was objectively identified to precede the motor onset of parkinsonism.

Efficacy and safety of botulinum toxin for treating sialorrhea: A systematic review and meta-analysis

BACKGROUND AND PURPOSE

Sialorrhea often happens in patients with neurologic disorders, and botulinum toxin (BoNT), which inhibits acetylcholine activation, may be an effective treatment for drooling. This systematic review and meta-analysis of randomized control trials aims to evaluate the efficacy and safety of BoNT in adults and children with sialorrhea due to neurological disorders.

METHODS

The PubMed, Embase, and Cochrane databases were searched for relevant studies published before August 2021. The pooled estimate of outcomes was calculated using a random effect model.

RESULTS

The review included 17 studies involving 981 patients. Compared with placebo, both BoNT type A (BoNT-A) and BoNT type B (BoNT-B) alleviated drooling frequency and severity (mean difference, 95% CI; BoNT-A: -1.20, -1.89 to -0.51; BoNT-B: -1.62, -2.07 to -1.17), reduced saliva weight (BoNT-A: -1.70, -2.30 to -1.10; BoNT-B: -1.12, -1.97 to -0.27), and improved global impression of change (BoNT-A: -1.30, -1.73 to -0.86; BoNT-B: -1.58, -1.95 to -1.21) in adults 4 weeks postinjection. BoNT-B remained effective at 12 weeks. In children, BoNT-A and BoNT-B alleviated sialorrhea symptoms (BoNT-A: -1.63, -2.42 to -0.85; BoNT-B: -5.20, -6.03 to -4.37) and BoNT-A reduced saliva weight (-0.77, -1.54 to 0.00) at 4 weeks postinjection. After 12 weeks, BoNT-B remained efficacious. Most adverse effects (AEs) were mild to moderate and self-limited.

CONCLUSIONS

There is moderate certainty of evidence (COE) that either BoNT-A or BoNT-B could relieve sialorrhea after 4 and 12 weeks of follow-up without significantly more severe AEs in adults. However, the COE is very low to low in children.

Enteric glia in homeostasis and disease: From fundamental biology to human pathology

Glia, the non-neuronal cells of the nervous system, were long considered secondary cells only necessary for supporting the functions of their more important neuronal neighbors. Work by many groups over the past two decades has completely overturned this notion, revealing the myriad and vital functions of glia in nervous system development, plasticity, and health. The largest population of glia outside the brain is in the enteric nervous system, a division of the autonomic nervous system that constitutes a key node of the gut-brain axis. Here, we review the latest in the understanding of these enteric glia in mammals with a focus on their putative roles in human health and disease.

Bilateral Subthalamic Nucleus Deep Brain Stimulation Improves Gastric Emptying Time in Parkinson Disease

BACKGROUND

It is well-established that deep brain stimulation (DBS) can improve motor function in those with Parkinson disease (PD); however, its effects on gastrointestinal disorders remain unclear.

METHODS

From January 2019 to December 2020, 26 patients with PD who had undergone subthalamic nucleus (STN) DBS were included in our study. The evaluated items included the pre- and postoperative dose of levodopa, Unified Parkinson's Disease Rating Scale, part III, scores with and without medication and stimulation, and gastric emptying time (expressed as the peak time of carbon-¹³C dioxide excretion in the ¹³C-acetate breath test). Sex-, age-, and body weight-matched controls were recruited to test the gastric emptying time in healthy individuals.

RESULTS

All the patients benefited from DBS. The Unified Parkinson's Disease Rating Scale, part III, scores had decreased from 48.5 ± 13.77 to 25.23 ± 8.59 without medication and 31.23 ± 11.4 to 13.92 ± 5.27 with medication. The levodopa equivalent dose had decreased from 1009.8 ± 291 mg to 707.65 ± 193.79 mg. The gastric emptying time was significantly prolonged in the patients with PD before DBS compared with the healthy control group (29.23 ± 6.58 minutes) and had improved to 35.19 ± 10.14 minutes with medication and 38.07 ± 11.17 minutes without medication after 3 months of STN stimulation. At 6 months postoperatively, the gastric emptying time was 32.3 ± 10.02 minutes without medication and 33.84 ± 10.79 minutes with medication.

CONCLUSIONS

A delayed gastric emptying time is associated with greater PD severity. Antiparkinsonian medications did not affect gastric emptying in patients with PD. STN DBS can improve both movement function and gastrointestinal motility in patients with PD in the long term. The exact mechanism by which DBS improves gastric emptying requires further exploration.

Managing Advanced Parkinson Disease

Advanced Parkinson disease (PD) is associated with treatment-related motor fluctuations and reduced ability to perform activities of daily living. Progression of non-motor symptoms and medication-induced adverse effects complicate focused approach to motor symptom management, frequently accelerating reduced quality of life. It is thus critical for clinicians to consider disease progression versus therapeutic contributions when balancing management decisions. Such an approach requires careful recognition of inflection points resulting from therapeutic decisions and should prompt consideration of reduced pharmacologic burden and increased reliance on non-pharmacologic strategies in advanced disease. The successful approach to advanced PD requires a multidisciplinary effort focused on improving the patient's and family's quality of life, sometimes requiring sacrifice of motor symptom benefit. Here, we emphasize management strategies in advanced PD, focusing on the need to balance the therapeutic approach across advancing motor symptoms, progressive non-motor features, and potential pharmacologic adverse effects.

Fecal microbiota transplant as a potential treatment for Parkinson's disease - A case series

OBJECTIVE

We aimed to determine whether fecal microbiota transplant (FMT) is safe and possibly efficacious in treating constipation, motor, and non-motor symptoms in Parkinson's disease (PD) patients.

METHODS

Patients with PD, constipation and an indication for screening colonoscopy were treated with FMT. The study was conducted from December 2017 to November 2019, and clinical outcomes assessing motor, non-motor and constipation symptoms were compared at baseline (week 0) and at 2, 4, 8, 12, 16, 20, and 24 weeks after the FMT.

RESULTS

Six patients (3 men, age range 47-73, median age 52) were treated with FMT. Four weeks following the FMT, motor, non-motor and constipation scores were improved in 5 of 6 patients. At week 24, compared to before the FMT, the changes in motor scores ranged from - 13-7 points, in non-motor scores from - 2 to - 45 points, and in constipation scores from - 12-1 point. One patient had a serious adverse event requiring admission for observation only, and no adverse events were observed in all other patients.

CONCLUSIONS

In this preliminary uncontrolled case series of 6 PD patients, a treatment with donor FMT infused via colonoscopy, was safe and resulted in improvement of PD motor and non-motor symptoms, including constipation, at 6 months. Further research is needed to assess longer-term maintenance of efficacy and safety, including in large scale randomized controlled trials.

TRIAL REGISTRATION

ClinicalTrials.gov - NCT03876327.

A comparison of swallow-related submandibular contraction amplitude and duration in people with Parkinson's disease and healthy controls

PURPOSE

To compare the contraction amplitude and contraction duration of submandibular muscles during the pharyngeal stage of swallowing in people with Parkinson's disease (PD) compared to normal controls.

METHOD

A prospective cross-sectional study design was utilised to recruit 24 participants from the regional area. A total of 14 people with PD and 10 healthy controls (HC) were recruited. Participants swallowed three volumes of thin liquid (5mL, 10mL, 15mL) while the activity of the submandibular muscles was recorded using surface electromyography. Measurements of contraction amplitude ratio (normalised to a maximum voluntary contraction) and contraction duration were computed from recorded electromyographic signals. Receiver Operating Characteristics (ROC) were computed for variables associated with significant main effects.

RESULT

Analyses revealed a significant effect of group on contraction amplitude ratio but not contraction duration. There were no significant effects of bolus volume on the dependent variables. ROC analysis indicated that contraction amplitude ratio accurately predicted group assignment in 77% cases.

CONCLUSION

Findings revealed that a majority of people with PD in this study utilised a greater percentage of their maximum contraction force in submandibular muscles when swallowing compared to normal controls. Further research is needed to determine if this inefficiency is consistent across larger samples and whether it is due to elevated baseline muscle activity, a compensatory behaviour to accomplish a more effective swallow, or both.

"Janus-Faced" α-Synuclein: Role in Parkinson's Disease

Parkinson's disease (PD) is a pathological condition characterized by the aggregation and the resultant presence of intraneuronal inclusions termed Lewy bodies (LBs) and Lewy neurites which are mainly composed of fibrillar α-synuclein (α-syn) protein. Pathogenic aggregation of α-syn is identified as the major cause of LBs deposition. Several mutations in α-syn showing varied aggregation kinetics in comparison to the wild type (WT) α-syn are reported in PD (A30P, E46K, H 50Q, G51D, A53E, and A53T). Also, the cell-to-cell spread of pathological α-syn plays a significant role in PD development. Interestingly, it has also been suggested that the pathology of PD may begin in the gastrointestinal tract and spread via the vagus nerve (VN) to brain proposing the gut-brain axis of α-syn pathology in PD. Despite multiple efforts, the behavior and functions of this protein in normal and pathological states (specifically in PD) is far from understood. Furthermore, the etiological factors responsible for triggering aggregation of this protein remain elusive. This review is an attempt to collate and present latest information on α-syn in relation to its structure, biochemistry and biophysics of aggregation in PD. Current advances in therapeutic efforts toward clearing the pathogenic α-syn via autophagy/lysosomal flux are also reviewed and reported.

The association of enteric neuropathy with gut phenotypes in acute and progressive models of Parkinson's disease

Parkinson's disease (PD) is associated with neuronal damage in the brain and gut. This work compares changes in the enteric nervous system (ENS) of commonly used mouse models of PD that exhibit central neuropathy and a gut phenotype. Enteric neuropathy was assessed in five mouse models: peripheral injection of MPTP; intracerebral injection of 6-OHDA; oral rotenone; and mice transgenic for A53T variant human α-synuclein with and without rotenone. Changes in the ENS of the colon were quantified using pan-neuronal marker, Hu, and neuronal nitric oxide synthase (nNOS) and were correlated with GI function. MPTP had no effect on the number of Hu+ neurons but was associated with an increase in Hu+ nuclear translocation (P < 0.04). 6-OHDA lesioned mice had significantly fewer Hu+ neurons/ganglion (P < 0.02) and a reduced proportion of nNOS+ neurons in colon (P < 0.001). A53T mice had significantly fewer Hu+ neurons/area (P < 0.001) and exhibited larger soma size (P < 0.03). Treatment with rotenone reduced the number of Hu+ cells/mm2 in WT mice (P < 0.006) and increased the proportion of Hu+ translocated cells in both WT (P < 0.02) and A53T mice (P < 0.04). All PD models exhibited a degree of enteric neuropathy, the extent and type of damage to the ENS, however, was dependent on the model.

Polymorphisms of Dopamine Receptor Genes and Parkinson's Disease: Clinical Relevance and Future Perspectives

Parkinson’s disease (PD) is a neurodegenerative disease caused by loss of dopaminergic neurons in the midbrain. PD is clinically characterized by a variety of motor and nonmotor symptoms, and treatment relies on dopaminergic replacement. Beyond a common pathological hallmark, PD patients may present differences in both clinical progression and response to drug therapy that are partly affected by genetic factors. Despite extensive knowledge on genetic variability of dopaminergic receptors (DR), few studies have addressed their relevance as possible influencers of clinical heterogeneity in PD patients. In this review, we summarized available evidence regarding the role of genetic polymorphisms in DR as possible determinants of PD development, progression and treatment response. Moreover, we examined the role of DR in the modulation of peripheral immunity, in light of the emerging role of the peripheral immune system in PD pathophysiology. A better understanding of all these aspects represents an important step towards the development of precise and personalized disease-modifying therapies for PD.

Systematic analysis of gut microbiome reveals the role of bacterial folate and homocysteine metabolism in Parkinson's disease

Parkinson's disease (PD) is the most common progressive neurological disorder compromising motor functions. However, nonmotor symptoms, such as gastrointestinal (GI) dysfunction, precede those affecting movement. Evidence of an early involvement of the GI tract and enteric nervous system highlights the need for better understanding of the role of gut microbiota in GI complications in PD. Here, we investigate the gut microbiome of patients with PD using metagenomics and serum metabolomics. We integrate these data using metabolic modeling and construct an integrative correlation network giving insight into key microbial species linked with disease severity, GI dysfunction, and age of patients with PD. Functional analysis reveals an increased microbial capability to degrade mucin and host glycans in PD. Personalized community-level metabolic modeling reveals the microbial contribution to folate deficiency and hyperhomocysteinemia observed in patients with PD. The metabolic modeling approach could be applied to uncover gut microbial metabolic contributions to PD pathophysiology.

Clinical Phenotypes of Parkinson's Disease Associate with Distinct Gut Microbiota and Metabolome Enterotypes

Parkinson’s disease (PD) is a clinically heterogenic disorder characterized by distinct clinical entities. Most studies on motor deficits dichotomize PD into tremor dominant (TD) or non-tremor dominant (non-TD) with akinetic-rigid features (AR). Different pathophysiological mechanisms may affect the onset of motor manifestations. Recent studies have suggested that gut microbes may be involved in PD pathogenesis. The aim of this study was to investigate the gut microbiota and metabolome composition in PD patients in relation to TD and non-TD phenotypes. In order to address this issue, gut microbiota and the metabolome structure of PD patients were determined from faecal samples using 16S next generation sequencing and gas chromatography–mass spectrometry approaches. The results showed a reduction in the relative abundance of Lachnospiraceae, Blautia, Coprococcus, Lachnospira, and an increase in Enterobacteriaceae, Escherichia and Serratia linked to non-TD subtypes. Moreover, the levels of important molecules (i.e., nicotinic acid, cadaverine, glucuronic acid) were altered in relation to the severity of phenotype. We hypothesize that the microbiota/metabolome enterotypes associated to non-TD subtypes may favor the development of gut inflammatory environment and gastrointestinal dysfunctions and therefore a more severe α-synucleinopathy. This study adds important information to PD pathogenesis and emphasizes the potential pathophysiological link between gut microbiota/metabolites and PD motor subtypes.

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.

Self-Medication with Ganoderma lucidum ("Reishi") to Combat Parkinson's Disease Symptoms: A Single Case Study

Parkinson's disease (PD) is a prevalent neurodegenerative disease for which only symptomatic treatments, mainly focused on motor symptoms. In contrast, conventional pharmacological treatments do not address cognitive impairment and emotional dysfunction. Together with potential treatment side effects, these can cause distress, lower the quality of life, and increase motor impairment in patients. Preclinical research suggests that the Traditional Chinese Medicine Ganoderma lucidum (“Reishi”) can alleviate symptoms in neurological disorders like PD. However, no clinical research to date has addressed this. An (unmedicated) patient, 50 years of age and diagnosed with PD for 5 years, approached the author as he decided to initiate self-treatment with Reishi, lasting 3 months. He wanted to evaluate the effects and decide to continue self-treatment or not. He agreed to be followed during this period, using questionnaires asking him about his (non-)motor symptoms. The most notable finding was the increase in Mindfulness, 3 months after self-treatment started. The motor symptoms stayed stable, there were no extreme changes in quality of life, and emotion regulation seemed to deteriorate over time while slightly improving at the 3-month assessment. While the findings do not allow firm conclusions seen the nature (N = 1) of this study, the small positive changes in some facets of affective behavior and the patient's experience, combined with the evidence from preclinical research, warrant clinical studies in this patient population.

Lactobacillus plantarum PS128 alleviates neurodegenerative progression in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced mouse models of Parkinson's disease

Evidence suggests that the Parkinson's disease (PD) pathogenesis is strongly associated with bidirectional pathways in the microbiota-gut-brain axis (MGBA), and psychobiotics may inhibit PD progression. We previously reported that the novel psychobiotic strain, Lactobacillus plantarum PS128 (PS128), ameliorated abnormal behaviors and modulated neurotransmissions in dopaminergic pathways in rodent models. Here, we report that orally administering PS128 for 4 weeks significantly alleviated the motor deficits, elevation in corticosterone, nigrostriatal dopaminergic neuronal death, and striatal dopamine reduction in 1-methyl-4-phenyl-1,2,3,6-tetrathydropyridine (MPTP)-induced PD mouse models. PS128 ingestion suppressed glial cell hyperactivation and increased norepinephrine and neurotrophic factors in the striatum of the PD-model mice. PS128 administration also attenuated MPTP-induced oxidative stress and neuroinflammation in the nigrostriatal pathway. Fecal analysis showed that PS128 modulated the gut microbiota. L. plantarum abundance was significantly increased along with methionine biosynthesis-related microbial modules. PS128 also suppressed the increased family Enterobacteriaceae and lipopolysaccharide and peptidoglycan biosynthesis-related microbial modules caused by MPTP. In conclude, PS128 ingestion alleviated MPTP-induced motor deficits and neurotoxicity.PS128 supplementation inhibited neurodegenerative processes in PD-model mice and may help prevent PD.

Neuroprotective effects of probiotics bacteria on animal model of Parkinson's disease induced by 6-hydroxydopamine: A behavioral, biochemical, and histological study

Parkinson's disease (PD) is an age-associated, progressive, and common neurodegenerative disorder. It is characterized by dopaminergic neuron degeneration in the substantia nigra pars compacta. The involvement of oxidative stress, inflammation, and dysbiosis in PD has been confirmed and probiotics also have the ability to regulate the mentioned mechanisms. Here, we assessed probiotics supplementation effects on experimental model of PD. Thirty Male Wistar rats were divided into three groups for a 14-day treatment. It was shown that a mixture of probiotics containing Lactobacillus acidophilus, Bifidobacterium bifidum, Lactobacillus reuteri, and Lactobacillus fermentum could improve rotational behavior, cognitive function, lipid peroxidation, and neuronal damage in the group received probiotic supplementation compared to the other groups (P < 0001, P < .001, and P = .026, respectively). Taken together, these findings revealed that probiotics supplementation could be an appropriate complementary treatment for PD.

Study on the Clinical Features of Parkinson's Disease With Probable Rapid Eye Movement Sleep Behavior Disorder

Objective: To investigate the clinical features and factors associated with Parkinson's disease (PD) patients with probable rapid eye movement sleep behavior disorder (PD-pRBD).

Methods: A total of 2,440 patients with clinically established or clinically probable PD were divided into two groups: PD-pRBD and PD without pRBD (PD-NRBD), according to the RBD questionnaire—Hong Kong. Data collection included demographic data, basic clinical history, and motor and non-motor symptoms. Based on the onset time of pRBD and the motor symptoms in PD, PD-pRBD patients were further divided into the pRBD prior to PD (PD-prRBD) group and the pRBD posterior to PD (PD-poRBD) group. Clinical features were compared between the PD-pRBD and PD-NRBD groups, as well as the PD-prRBD and PD-poRBD groups. The associated factors of pRBD were also explored.

Results: The prevalence of pRBD was 41.4% (1,010 out of the total of 2,440) in our PD cohort. Further, compared with the PD-NRBD group, the PD-pRBD group had longer disease duration and more severe motor symptoms. Moreover, the PD-pRBD group had significantly higher levodopa equivalent daily dose and a higher ratio of dyskinesia, wearing-off, and offset of the Hoehn–Yahr stage. The scores on the non-motor symptom rating scale (NMSS), cognitive impairment, Parkinson's disease sleep scale (PDSS), excessive daytime sleepiness, constipation, hyposmia, depression, and the 39-item Parkinson's disease questionnaire also appeared worse in the PD-pRBD group. Significant differences in the educational level, disease duration, disease progression, Unified Parkinson's Disease Rating Scale (UPDRS)-II, UPDRS-III, tremor, rigidity, bradykinesia, posture gait, frozen gait, levodopa equivalent daily dose, dyskinesia, wearing-off, Hoehn–Yahr stage, NMSS-6, PDSS, and communication score widely existed between the PD-prRBD and PD-poRBD groups. Late-onset PD, long disease duration, high UPDRS-I score, high NMSS-4 score, low PDSS score, constipation, and hyposmia were all identified as the risk factors for PD-pRBD.

Conclusions: Compared with the PD-NRBD group, the PD-pRBD group may have more severe motor symptoms, motor complications, and non-motor symptoms as well as a substandard quality of life. Further, late-onset PD, long disease duration, high UPDRS-I score, high NMSS-4 score, low PDSS score, constipation, and hyposmia can be risk factors for RBD in PD. Differences also occurred between the PD-prRBD and PD-poRBD groups.

Autonomic Dysfunction in Parkinson's Disease

Recognition of the importance of nonmotor dysfunction as a component of Parkinson's disease has exploded over the past three decades. Autonomic dysfunction is a frequent and particularly important nonmotor feature because of the broad clinical spectrum it covers. Cardiovascular, gastrointestinal, urinary, sexual, and thermoregulatory abnormalities all can appear in the setting of Parkinson's disease. Cardiovascular dysfunction is characterized most prominently by orthostatic hypotension. Gastrointestinal dysfunction can involve virtually all levels of the gastrointestinal tract. Urinary dysfunction can entail either too frequent voiding or difficulty voiding. Sexual dysfunction is frequent and frustrating for both patient and partner. Alterations in sweating and body temperature are not widely recognized but often are present. Autonomic dysfunction can significantly and deleteriously impact quality of life for individuals with Parkinson's disease. Because effective treatment for many aspects of autonomic dysfunction is available, it is vitally important that assessment of autonomic dysfunction be a regular component of the neurologic history and exam and that appropriate treatment be initiated and maintained.

Modulation of the Microbiome in Parkinson's Disease: Diet, Drug, Stool Transplant, and Beyond

The gastrointestinal microbiome is altered in Parkinson's disease and likely plays a key role in its pathophysiology, affecting symptoms and response to therapy and perhaps modifying progression or even disease initiation. Gut dysbiosis therefore has a significant potential as a therapeutic target in Parkinson's disease, a condition elusive to disease-modifying therapy thus far. The gastrointestinal environment hosts a complex ecology, and efforts to modulate the relative abundance or function of established microorganisms are still in their infancy. Still, these techniques are being rapidly developed and have important implications for our understanding of Parkinson's disease. Currently, modulation of the microbiome can be achieved through non-pharmacologic means such as diet, pharmacologically through probiotic, prebiotic, or antibiotic use and procedurally through fecal transplant. Novel techniques being explored include the use of small molecules or genetically engineered organisms, with vast potential. Here, we review how some of these approaches have been used to date, important areas of ongoing research, and how microbiome modulation may play a role in the clinical management of Parkinson's disease in the future.

The Microbiome as a Modifier of Neurodegenerative Disease Risk

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

Clinical Perspectives of Parkinson's Disease for Ophthalmologists, Otorhinolaryngologists, Cardiologists, Dentists, Gastroenterologists, Urologists, Physiatrists, and Psychiatrists

Parkinson's disease (PD) is a multisystemic disorder characterized by various non-motor symptoms (NMS) in addition to motor dysfunction. NMS include sleep, ocular, olfactory, throat, cardiovascular, gastrointestinal, genitourinary, or musculoskeletal disorders. A range of NMS, particularly hyposmia, sleep disturbances, constipation, and depression, can even appear prior to the motor symptoms of PD. Because NMS can affect multiple organs and result in major disabilities, the recognition and multidisciplinary and collaborative management of NMS by physicians is essential for patients with PD. Therefore, the aim of this review article is to provide an overview of the organs that are affected by NMS in PD together with a brief review of pathophysiology and treatment options.

Systems Biology Approaches to Understand the Host-Microbiome Interactions in Neurodegenerative Diseases

Neurodegenerative diseases (NDDs) comprise a broad range of progressive neurological disorders with multifactorial etiology contributing to disease pathophysiology. Evidence of the microbiome involvement in the gut-brain axis urges the interest in understanding metabolic interactions between the microbiota and host physiology in NDDs. Systems Biology offers a holistic integrative approach to study the interplay between the different biologic systems as part of a whole, and may elucidate the host–microbiome interactions in NDDs. We reviewed direct and indirect pathways through which the microbiota can modulate the bidirectional communication of the gut-brain axis, and explored the evidence of microbial dysbiosis in Alzheimer’s and Parkinson’s diseases. As the gut microbiota being strongly affected by diet, the potential approaches to targeting the human microbiota through diet for the stimulation of neuroprotective microbial-metabolites secretion were described. We explored the potential of Genome-scale metabolic models (GEMs) to infer microbe-microbe and host-microbe interactions and to identify the microbiome contribution to disease development or prevention. Finally, a systemic approach based on GEMs and ‘omics integration, that would allow the design of sustainable personalized anti-inflammatory diets in NDDs prevention, through the modulation of gut microbiota was described.