Gastrointestinal manifestations in Parkinson’s disease: prevalence and occurrence before motor symptoms. J Neurol. 2013;260:1332-1338. [PMID: 23263478 DOI: 10.1007/s00415-012-6801-2]

Oral administration of Proteus mirabilis damages dopaminergic neurons and motor functions in mice

Recently, studies on the relationship between gut dysbiosis and Parkinson's disease (PD) have increased, but whether a specific gut bacterium may cause PD remains unexplored. Here, we report, for the first time, that a specific gut bacterium directly induces PD symptoms and dopaminergic neuronal damage in the mouse brain. We found that the number of Enterobacteriaceae, particularly Proteus mirabilis, markedly and commonly increased in PD mouse models. Administration of P. mirabilis isolated from PD mice significantly induced motor deficits, selectively caused dopaminergic neuronal damage and inflammation in substantia nigra and striatum, and stimulated α-synuclein aggregation in the brain as well as in the colon. We found that lipopolysaccharides, a virulence factor of P. mirabilis, may be associated in these pathological changes via gut leakage and inflammatory actions. Our results suggest a role of P. mirabilis on PD pathogenesis in the brain.

Stomaching the Possibility of a Pathogenic Role for Helicobacter pylori in Parkinson's Disease

While a small subset of Parkinson's disease cases have genetic causes, most cases are sporadic and may have an environmental contributor that has largely remained enigmatic. Remarkably, gastrointestinal symptoms in PD patients serve as a prodrome for the eventual motor dysfunctions. Herein, we review studies exploring a possible link between the gastric human pathogen Helicobacter pylori and PD. We provide plausible and testable hypotheses for how this organism might contribute to PD: 1) a toxin(s) produced by the bacteria; 2) disruption of the intestinal microbiome; 3) local inflammation that crosses the gut-brain axis, leading to neuroinflammation; and 4) manipulation of the pharmacokinetics of the PD drug levodopa by H. pylori, even in those not receiving exogenous levodopa. Key findings are: 1) people with PD are 1.5-3-fold more likely to be infected with H. pylori than people without PD; 2) H. pylori-infected PD patients display worse motor functions than H. pylori-negative PD patients; 3) eradication of H. pylori improves motor function in PD patients over PD patients whose H. pylori was not eradicated; and 4) eradication of H. pylori improves levodopa absorption in PD patients compared to that of PD patients whose H. pylori was not eradicated. Evidence is accumulating that H. pylori has a link with PD, but the mechanism is unclear. Future work should explore the effects of H. pylori on development of PD in defined PD animal models, focusing on the roles of H. pylori toxins, inflammation, levodopa absorption, and microbiome dysbiosis.

Mitochondria and α-Synuclein: Friends or Foes in the Pathogenesis of Parkinson's Disease?

Parkinson’s disease (PD) is a movement disorder characterized by dopaminergic nigrostriatal neuron degeneration and the formation of Lewy bodies (LB), pathological inclusions containing fibrils that are mainly composed of α-synuclein. Dopaminergic neurons, for their intrinsic characteristics, have a high energy demand that relies on the efficiency of the mitochondria respiratory chain. Dysregulations of mitochondria, deriving from alterations of complex I protein or oxidative DNA damage, change the trafficking, size and morphology of these organelles. Of note, these mitochondrial bioenergetics defects have been related to PD. A series of experimental evidence supports that α-synuclein physiological action is relevant for mitochondrial homeostasis, while its pathological aggregation can negatively impinge on mitochondrial function. It thus appears that imbalances in the equilibrium between the reciprocal modulatory action of mitochondria and α-synuclein can contribute to PD onset by inducing neuronal impairment. This review will try to highlight the role of physiological and pathological α-synuclein in the modulation of mitochondrial functions.

The Gut Microbiome Feelings of the Brain: A Perspective for Non-Microbiologists

Objectives: To comprehensively review the scientific knowledge on the gut-brain axis. Methods: Various publications on the gut-brain axis, until 31 July 2017, were screened using the Medline, Google, and Cochrane Library databases. The search was performed using the following keywords: "gut-brain axis", "gut-microbiota-brain axis", "nutrition microbiome/microbiota", "enteric nervous system", "enteric glial cells/network", "gut-brain pathways", "microbiome immune system", "microbiome neuroendocrine system" and "intestinal/gut/enteric neuropeptides". Relevant articles were selected and reviewed. Results: Tremendous progress has been made in exploring the interactions between nutrients, the microbiome, and the intestinal, epithelium-enteric nervous, endocrine and immune systems and the brain. The basis of the gut-brain axis comprises of an array of multichannel sensing and trafficking pathways that are suggested to convey the enteric signals to the brain. These are mediated by neuroanatomy (represented by the vagal and spinal afferent neurons), the neuroendocrine-hypothalamic-pituitary-adrenal (HPA) axis (represented by the gut hormones), immune routes (represented by multiple cytokines), microbially-derived neurotransmitters, and finally the gate keepers of the intestinal and brain barriers. Their mutual and harmonious but intricate interaction is essential for human life and brain performance. However, a failure in the interaction leads to a number of inflammatory-, autoimmune-, neurodegenerative-, metabolic-, mood-, behavioral-, cognitive-, autism-spectrum-, stress- and pain-related disorders. The limited availability of information on the mechanisms, pathways and cause-and-effect relationships hinders us from translating and implementing the knowledge from the bench to the clinic. Implications: Further understanding of this intricate field might potentially shed light on novel preventive and therapeutic strategies to combat these disorders. Nutritional approaches, microbiome manipulations, enteric and brain barrier reinforcement and sensing and trafficking modulation might improve physical and mental health outcomes.

Merging Clinical and Imaging Biomarkers to Tackle Parkinson's Disease

Background

In Parkinson's disease, biomarkers represent tools that are potentially suitable for either clinical or research settings and are useful in predicting onset, confirming diagnosis, detecting progression, and evaluating response to potential disease-modifying treatments. The range of available biomarkers in Parkinson's disease is fast expanding and includes an increasing amount of laboratory, clinical, and imaging data. Indeed, the latter 2 represent the cornerstones of the diagnostic criteria for Parkinson's disease recently proposed by the International Parkinson and Movement Disorders Society Task Force on the definition of Parkinson's disease.

Methods and Results

In this review, we describe current knowledge and emerging findings on clinical (with emphasis on nonmotor symptoms) and imaging biomarkers for Parkinson's disease, with a focus on prodromal, diagnostic, and middle/advanced phases.

Conclusion

An increasing body of evidence suggests that merging clinical and imaging biomarkers through disease stages may be the best, fastest track to tackle Parkinson's disease.

Premotor Diagnosis of Parkinson's Disease

Typical Parkinsonian symptoms consist of bradykinesia plus rigidity and/or resting tremor. Some time later postural instability occurs. Pre-motor symptoms such as hyposmia, constipation, REM sleep behavior disorder and depression may antecede these motor symptoms for years. It would be ideal, if we had a biomarker which would allow to predict who with one or two of these pre-motor symptoms will develop the movement disorder Parkinson's disease (PD). Thus, it is interesting to learn that biopsies of the submandibular gland or colon biopsies may be a means to predict PD, if there is a high amout of abnormally folded alpha-synuclein and phosphorylated alpha-synuclein. This would be of relevance if we would have available means to stop the propagation of abnormal alpha-synuclein which is otherwise one of the reasons of this spreading disease PD.

Constipation in Parkinson's Disease

Constipation is one of the main and disabling nonmotor symptoms in Parkinson's disease (PD), with a prevalence ranging from 24.6% to 63% according to the different diagnostic criteria used to define chronic constipation. Constipation is currently recognized as a risk factor of PD in relation to the number of evacuation per week and its severity. Moreover, several studies have demonstrated that constipation may precede the occurrence of motor symptoms underlying an earlier involvement of the enteric nervous system and the dorsal motor nucleus of the vagus in the α-synuclein pathology. In PD, constipation is mainly due to slower colonic transit or puborectalis dyssynergia, but the concomitant use of antiparkinsonian, pain, and antidepressant medications may worsen it. An accurate diagnosis and an adequate treatment of constipation it is pivotal to prevent complications such as intestinal occlusion and to ensure an optimal clinical response to levodopa.

The Gut and Nonmotor Symptoms in Parkinson's Disease

Gastrointestinal (GI) symptoms are one of the most common nonmotor symptoms (NMS) in patients with Parkinson's disease (PD) involving the whole GI tract (GIT) and being evident throughout the whole course of the disease. Furthermore, constipation serves as a risk factor for PD as well as an early prodromal NMS of PD. The gut as gateway to the environment with its enteric nervous system (ENS) plays a crucial role in the neurodegenerative process that leads to PD. Alpha-synucleinopathy as the pathological hallmark of PD could be found within the whole GIT in a rostrocaudal gradient interacting with the ENS, the gut microbiome, and enteric glial cells. Bidirectional interactions between the ENS and the central nervous system (CNS) via a brain-gut-enteric microbiota axis have been reported. As well as there is evidence out of animal, autopsy, and epidemiological studies that α-synuclein spreads via rostrocranial transmission by transsynaptic cell-to-cell transfer via the sympathetic and parasympathetic nervous system to the CNS causing the typical neuropathological changes of PD. Recognition of GI NMS as prodromal markers of PD as well as a better understanding of the brain-gut connection offers new insights in the pathophysiology of PD and might provide the opportunity of PD diagnosis before CNS involvement. Hereby the opportunity for development of neuroprotective and disease-modifying therapeutics, respectively, seem to be promising. This chapter covers the variety of GI NMS and its consequences in PD as well as the important role of the gut as part of the pathological process in PD.

Neuropathology of Nonmotor Symptoms of Parkinson's Disease

Parkinson's disease (PD), a multiorgan neurodegenerative disorder associated with α-synuclein deposits throughout the nervous system and many organs, is clinically characterized by motor and nonmotor features, many of the latter antedating motor dysfunctions by 20 or more years. The causes of the nonmotor manifestations such as olfactory, autonomic, sensory, neuropsychiatric, visuospatial, sleep, and other disorders are unlikely to be related to single lesions. They are mediated by the involvement of both dopaminergic and nondopaminergic systems, and diverse structures outside the nigrostriatal system that is mainly responsible for the motor features of PD. The nonmotor alterations appear in early/prodromal stages of the disease and its further progression, suggesting a topographical and chronological spread of the lesions. This lends further support for the notion that PD is a multiorgan proteinopathy, although the exact relationship between presymptomatic and later developing nonmotor features of PD and neuropathology awaits further elucidation.

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

BACKGROUND

There is mounting evidence for a connection between the gut and Parkinson's disease (PD). Dysbiosis of gut microbiota could explain several features of PD.

OBJECTIVE

The objective of this study was to determine if PD involves dysbiosis of gut microbiome, disentangle effects of confounders, and identify candidate taxa and functional pathways to guide research.

METHODS

A total of 197 PD cases and 130 controls were studied. Microbial composition was determined by 16S rRNA gene sequencing of DNA extracted from stool. Metadata were collected on 39 potential confounders including medications, diet, gastrointestinal symptoms, and demographics. Statistical analyses were conducted while controlling for potential confounders and correcting for multiple testing. We tested differences in the overall microbial composition, taxa abundance, and functional pathways.

RESULTS

Independent microbial signatures were detected for PD (P = 4E-5), participants' region of residence within the United States (P = 3E-3), age (P = 0.03), sex (P = 1E-3), and dietary fruits/vegetables (P = 0.01). Among patients, independent signals were detected for catechol-O-methyltransferase-inhibitors (P = 4E-4), anticholinergics (P = 5E-3), and possibly carbidopa/levodopa (P = 0.05). We found significantly altered abundances of the Bifidobacteriaceae, Christensenellaceae, [Tissierellaceae], Lachnospiraceae, Lactobacillaceae, Pasteurellaceae, and Verrucomicrobiaceae families. Functional predictions revealed changes in numerous pathways, including the metabolism of plant-derived compounds and xenobiotics degradation.

CONCLUSION

PD is accompanied by dysbiosis of gut microbiome. Results coalesce divergent findings of prior studies, reveal altered abundance of several taxa, nominate functional pathways, and demonstrate independent effects of PD medications on the microbiome. The findings provide new leads and testable hypotheses on the pathophysiology and treatment of PD. © 2017 International Parkinson and Movement Disorder Society.

Exploring Braak's Hypothesis of Parkinson's Disease

Parkinson’s disease (PD) is a neurodegenerative disorder for which there is no cure. Most patients suffer from sporadic PD, which is likely caused by a combination of genetic and environmental factors. Braak’s hypothesis states that sporadic PD is caused by a pathogen that enters the body via the nasal cavity, and subsequently is swallowed and reaches the gut, initiating Lewy pathology (LP) in the nose and the digestive tract. A staging system describing the spread of LP from the peripheral to the central nervous system was also postulated by the same research group. There has been criticism to Braak’s hypothesis, in part because not all patients follow the proposed staging system. Here, we review literature that either supports or criticizes Braak’s hypothesis, focused on the enteric route, digestive problems in patients, the spread of LP on a tissue and a cellular level, and the toxicity of the protein αSynuclein (αSyn), which is the major constituent of LP. We conclude that Braak’s hypothesis is supported by in vitro, in vivo, and clinical evidence. However, we also conclude that the staging system of Braak only describes a specific subset of patients with young onset and long duration of the disease.

LRRK2 and the Immune System

Polymorphisms in leucine-rich repeat kinase 2 (LRRK2) have been linked to familial Parkinson's disease, increased risk of sporadic Parkinson's disease, increased risk of Crohn's inflammatory bowel disease, and increased susceptibility to leprosy. As well as LRRK2 mutations, these diseases share in common immune dysfunction and inflammation. LRRK2 is highly expressed in particular immune cells and has been biochemically linked to the intertwined pathways regulating inflammation, mitochondrial function, and autophagy/lysosomal function. This review outlines what is currently understood about LRRK2 function in the immune system and the potential implications of LRRK2 dysfunction for diseases genetically linked to this enigmatic enzyme.

Intestinal dysfunction in Parkinson's disease: Lessons learned from translational studies and experimental models

BACKGROUND

Symptoms of digestive dysfunction in patients with Parkinson's disease (PD) occur at all stages of the disease, often preceding the onset of central motor symptoms. On the basis of these PD-preceding symptoms it has been proposed that PD could initiate in the gut, and that the presence of alpha-synuclein aggregates, or Lewy bodies in the enteric nervous system might represent one of the earliest signs of the disease. Following this hypothesis, much research has been focused on the digestive tract to unravel the mechanisms underlying the onset and progression of PD, with particular attention to the role of alterations in enteric neurotransmission in the pathophysiology of intestinal motility disturbances. There is also evidence suggesting that the development of central nigrostriatal neurodegeneration is associated with the occurrence of gut inflammation, characterized by increments of tissue pro-inflammatory markers and oxidative stress, which might support conditions of bowel neuromotor abnormalities.

PURPOSE

The present review intends to provide an integrated and critical appraisal of the available knowledge on the alterations of enteric neuromuscular pathways regulating gut motor activity both in humans and preclinical models of PD. Moreover, we will discuss the possible involvement of neuro-immune mechanisms in the pathophysiology of aberrant gastrointestinal gut transit and neuromuscular activity in the small and large bowel.

The Threshold Theory for Parkinson's Disease

Parkinson's disease (PD) is recognized by the accumulation of α-synuclein within neurons. In contrast to the current ascending theory where α-synuclein would propagate from neuron to neuron, we now propose the threshold theory for PD based on evidence of parallel degeneration of both central nervous system (CNS) and peripheral nervous system (PNS) in PD. The functional threshold is lower for the emergence of early symptoms before the classical motor symptoms of PD. This is due to the larger functional reserve of the midbrain dopamine and integrated basal ganglia motor systems to control movement. This threshold theory better accounts for the current neurobiology of PD symptom progression compared to the hypothesis that the disease ascends from the PNS to the CNS as proposed by Braak's hypothesis.

Nonmotor gastrointestinal disorders in older patients with Parkinson's disease: is there hope?

Despite the fact that nonmotor symptoms (NMS) like gastrointestinal (GI) complaints are frequently reported in Parkinson’s disease (PD), no therapeutic guidelines are available. This study aimed to manage some lower GI-NMS in a group of patients with PD. A total of 40 patients (17 males, 23 females; mean age 76.05±2.09 years) were randomly selected for this study. Patients were confirmed to have PD (modified Hoehn–Yars scale: 2.075±0.4) who had undergone levodopa or dopamine agonist treatment. In the non-motor symptoms questionnaire (NMS-Quest), regarding GI complaints, the following were recorded: abdominal pain, bloating, and constipation of mild-to-moderate severity. Laboratory studies, abdominal ultrasound, and upper and lower digestive endoscopies were performed to rule out organic issues. All patients increased their water intake to 2 L/d and alimentary fiber to 20–25 g/d. Twenty patients received trimebutine 200 mg three times daily half an hour before meals. The other 20 patients received probiotics (60 mg per-tablet of two lactic bacteria: Lactobacillus acidophilus and Bifidobacterium infantis), 2×/d, 1 hour after meals for 3 months along with the reassessment of GI complaints. Our results demonstrated that there were significant statistical differences in all assessed symptoms in the first group: 1.55±0.51 vs 0.6±0.5 (P<0.0001) for abdominal pain; 1.6±0.5 vs 0.45±0.51 (P<0.0001) for bloating; and 1.5±0.51 vs 0.85±0.67 (P=0.0014) for constipation with incomplete defecation. The second group displayed statistical differences only for abdominal pain 1.45±0.51 vs 1.05±0.69 (P=0.00432) and bloating 1.4±0.5 vs 0.3±0.47 (P<0.0001). For constipation with incomplete defecation, there was a slight improvement. Thus, there was no significant statistical difference: 1.35±0.49 vs 1.15±0.49 (P=0.2040). In conclusion, lower GI-NMS are frequently present, isolated or associated with other autonomic issues, even before the diagnosis of PD. Treatment with probiotics could improve abdominal pain and bloating as much as with trimebutine, but less for constipation with incomplete evacuation, where trimebutine showed better results.

New concepts in the pathogenesis and presentation of Parkinson's disease

Parkinson's disease (PD) was first described by James Parkinson in 1817. He noted the complex nature of this condition and that non-motor symptoms (NMS) underpinned the classic motor symptoms of PD. The concept of what PD is has therefore undergone substantial changes and it is now recognised that PD is a combined motor and non-motor syndrome and NMS are present during the prodromal phase of PD, starting up to 20 years before the first clinical motor signs emerge. PD may originate from pathology in the gut, olfactory bulb and lower brainstem rather than in the substantia nigra. Complex phenotypes of PD may exist where clinical NMS overshadow motor features. Therapy needs to be adjusted based on motor and non-motor loads, ideally using validated tools. Recently, a multimodal biomarker battery in PD has emerged and might play an important role in the future.

High-resolution Anorectal Manometry in Parkinson Disease With Defecation Disorder: A Comparison With Functional Defecation Disorder

GOAL

To investigate the characteristics of high-resolution anorectal manometry (HR-ARM) in Parkinson disease (PD) patients with defecation disorder (DD) compared with patients with functional defecation disorder (FDD).

BACKGROUND

DD is a common gastrointestinal symptom in PD. HR-ARM is a relatively new and reliable method for detecting DD.

STUDY

A cohort of PD patients with DD was matched with FDD patients. Defecatory symptoms were investigated by questionnaire. Anorectal motility and sensation were evaluated by HR-ARM. Differences in defecatory symptoms, sensorimotor parameters, and DD type were analyzed. Defecatory symptoms and manometric variables obtained in early-stage PD were compared with advanced stage, and relationships between manometric parameters and evacuatory symptoms explored.

RESULTS

Straining and sensation of blockage was experienced significantly more in PD than FDD, and stool consistency more severely affected. Maximum squeeze and intrarectal pressure during defecation in PD was lower than in FDD. Anal resting and residual pressures, duration of sustained squeeze, threshold volumes for first sensation, urgency, and maximum discomfort were similar between groups. PD patients presented predominantly with inadequate propulsive forces, whereas FDD patients showed dyssynergic defecation. Defecatory symptoms and manometric parameters did not differ between stages of PD.

CONCLUSIONS

PD patients with DD experienced more straining and sensation of blockage than FDD patients, possibly related to inadequate anorectal motility and paradoxical anal contraction of pelvic floor. Impaired squeeze response and inadequate propulsive forces are specific to anorectal function of PD patients with DD, compared with FDD, with abnormalities unchanged between early and advanced PD.

Constipation: an emerging risk factor for Parkinson's disease?

Constipation is the most prominent and disabling manifestation of lower gastrointestinal (GI) dysfunction in Parkinson's disease (PD). The prevalence of constipation in PD patients ranges from 24.6% to 63%; this variability is due to the different criteria used to define constipation and to the type of population enrolled in the studies. In addition, constipation may play an active role in the pathophysiological changes that underlie motor fluctuations in advanced PD through its negative effects on absorption of levodopa. Several clinical studies now consistently suggest that constipation may precede the first occurrence of classical motor features in PD. Studies in vivo, using biopsies of the GI tract and more recently functional imaging investigations, showed the presence of α-synuclein (α-SYN) aggregates and neurotransmitter alterations in enteric tissues. All these findings support the Braak proposed model for the pathophysiology of α-SYN aggregates in PD, with early pathological involvement of the enteric nervous system and dorsal motor nucleus of the vagus. Therefore, constipation could have the potential sensitivity to be used as a clinical biomarker of the prodromal phase of the disease. The use of colonic biopsies to look at α-SYN pathology, once confirmed by larger prospective studies, might eventually represent a feasible, albeit partially invasive, new diagnostic biomarker for PD.

Parkinson Disease-Mediated Gastrointestinal Disorders and Rational for Combinatorial Therapies

A gradual loss of dopamine-producing nerve cells gives rise to a common neurodegenerative Parkinson’s disease (PD). This disease causes a neurotransmitter imbalance in the brain and initiates a cascade of complications in the rest of the body that appears as distressing symptoms which include gait problems, tremor, gastrointestinal (GI) disorders and cognitive decline. To aid dopamine deficiency, treatment in PD patients includes oral medications, in addition to other methods such as deep brain stimulation and surgical lesioning. Scientists are extensively studying molecular and signaling mechanisms, particularly those involving phenotypic transcription factors and their co-regulatory proteins that are associated with neuronal stem cell (SC) fate determination, maintenance and disease state, and their role in the pathogenesis of PD. Advancement in scientific research and “personalized medicine” to augment current therapeutic intervention and minimize the side effects of chemotherapy may lead to the development of more effective therapeutic strategies in the near future. This review focuses on PD and associated GI complications and summarizes the current therapeutic modalities that include stem cell studies and combinatorial drug treatment.

Brain-gut-microbiota axis in Parkinson's disease

Parkinson’s disease (PD) is characterized by alpha-synucleinopathy that affects all levels of the brain-gut axis including the central, autonomic, and enteric nervous systems. Recently, it has been recognized that the brain-gut axis interactions are significantly modulated by the gut microbiota via immunological, neuroendocrine, and direct neural mechanisms. Dysregulation of the brain-gut-microbiota axis in PD may be associated with gastrointestinal manifestations frequently preceding motor symptoms, as well as with the pathogenesis of PD itself, supporting the hypothesis that the pathological process is spread from the gut to the brain. Excessive stimulation of the innate immune system resulting from gut dysbiosis and/or small intestinal bacterial overgrowth and increased intestinal permeability may induce systemic inflammation, while activation of enteric neurons and enteric glial cells may contribute to the initiation of alpha-synuclein misfolding. Additionally, the adaptive immune system may be disturbed by bacterial proteins cross-reacting with human antigens. A better understanding of the brain-gut-microbiota axis interactions should bring a new insight in the pathophysiology of PD and permit an earlier diagnosis with a focus on peripheral biomarkers within the enteric nervous system. Novel therapeutic options aimed at modifying the gut microbiota composition and enhancing the intestinal epithelial barrier integrity in PD patients could influence the initial step of the following cascade of neurodegeneration in PD.

The treatment of gastroparesis, constipation and small intestinal bacterial overgrowth syndrome in patients with Parkinson's disease

INTRODUCTION

Parkinson's disease (PD) affects the nerves of the entire gastrointestinal (GI) tract and may result in profound gastrointestinal (GI) dysfunction leading to poor patient outcomes. Common GI disturbances in patients with PD include gastroparesis (GP), constipation and small intestinal bacterial overgrowth syndrome (SIBO). In particular, GP is difficult to treat due to the limited options available and precautions, contraindications and adverse effects associated with the approved treatments. Moreover, some commonly used medications can worsen pre-existing PD.

AREAS COVERED

Our review will focus on treatment options for GP and SIBO with motilin agonists, dopamine receptor antagonists, Ghrelin agonists muscarinic agonists, 5-HT4 receptor agonists, antibiotics, probiotics and herbal formulation such as iberogast. Constipation occurs in the majority of patients with PD and fortunately many treatments are now available. Our review is based on original papers or reviews selected from PUBMED search and Cochrane reviews.

EXPERT OPINION

Motility disorders of the GI tract are found frequently in patients with PD and treating the underlying GI disorders caused by PD with various prokinetics and laxatives is paramount in achieving improvements in patient's motor function. Various prokinetics and laxatives are now available to provide some relief of the GI morbidity caused by PD leading even to better absorption of even the PD treatments.

Modern treatment in Parkinson's disease, a personal approach

There are many guidelines available concerning the treatment of Parkinson's disease. Most of these advocate treating young-onset patients with a dopamine agonist and older patients with levodopa. The rationale behind this recommendation has its origins in the side effects associated with each of these drug classes: whilst levodopa leads to dyskinesia, which may not be relevant for patients with a limited life-expectancy, dopamine agonists have a much longer plasma half life which probably leads to more continuous dopamine receptor stimulation and thus decreases the occurrence and severity of dyskinesia. However, the side effects associated with the use of dopamine agonists, such as sleepiness, orthostatic problems, hallucinations and impulse control disorders are a drawback. In this overview, the hypothesis will be put forward that perhaps such a strict distinction is no longer needed. A new idea may be the early combination of levodopa with a dopamine agonist which would provide good clinical efficacy and, because of the relatively low doses involved, would reduce the side effects associated with both substances. MAO-B inhibitors may be a good option for early treatment and especially for patients who experience first motor fluctuations. Similarly, and particularly if a wearing-off symptom is present, COMT inhibitors smoothen and prolong the action of levodopa. More invasive escalation therapy comes into play when patients reach the advanced stages with problems of insufficient motor control, such as bradykinesia, rigidity and resting tremor, combined with on-time dyskinesia. The use of all oral and invasive treatment has to be individualized to gain a good motor and non-motor control and especially a good quality of life.

Visuomotor control of neck surface electromyography in Parkinson's disease

OBJECTIVE

To compare performance of individuals with Parkinson's disease (PD) and age-matched controls on a visuomotor tracking task controlled via surface electromyography (sEMG).

METHODS

Twenty-seven adults with PD and twenty-four older controls produced dry swallows and completed a visuomotor tracking task utilizing both static and dynamic targets. sEMG was recorded at the anterior neck and submental surface during both tasks.

RESULTS

There was no significant difference in visuomotor tracking ability between cohorts. Post hoc analyses indicated that there was no significant difference between participant groups in the strength or duration of swallows as measured by sEMG but that participants with PD showed a trend for decreased swallow durations at the anterior neck (padj = 0.067) whereas controls showed a trend for increased durations at the anterior neck (padj = 0.112), compared to the submental surface. However, there were no significant correlations between swallowing behavior and visuomotor tracking ability.

CONCLUSION

There were no significant differences in visuomotor tracking performance between individuals with PD and controls. Furthermore, there was no relationship between tracking ability and swallowing behavior. We conclude that sEMG-mediated biofeedback may have limited promise as a tool for treating PD-related dysphagia.

Gastrointestinal Autonomic Dysfunction in Patients with Parkinson's Disease

Currently, gastrointestinal dysfunctions in Parkinson’s disease (PD) are well-recognized problems and are known to be an initial symptom in the pathological process that eventually results in PD. Gastrointestinal symptoms may result from the involvement of either the central or enteric nervous systems, or these symptoms may be side effects of antiparkinsonian medications. Weight loss, excessive salivation, dysphagia, nausea/gastroparesis, constipation, and defecation dysfunction all may occur. Increased identification and early detection of these symptoms can result in a significant improvement in the quality of life for PD patients.

Gastrointestinal Biopsies for the Diagnosis of Alpha-Synuclein Pathology in Parkinson's Disease

The diagnosis of Parkinson's disease (PD) relies on clinical features whereas pathological confirmation is only possible with autopsy examination. The neuropathological hallmarks of PD are neuronal loss and the presence of inclusions termed Lewy bodies/neurites in affected regions. A major component of these inclusions is phosphorylated alpha-synuclein (α-SYN) protein. There is evidence that α-SYN pathology is widely distributed outside the central nervous system in patients with PD. The gastrointestinal tract is importantly affected by α-SYN containing inclusions and typically there is a rostrocaudal gradient for the distribution of the pathology. The highest amounts of Lewy bodies/neurites are found at the submandibular gland together with the lower esophagus and the lowest amounts are found in the rectum. Autopsy findings prompted research aimed at achieving in vivo pathological diagnosis of PD by demonstrating the presence of α-SYN pathology in biopsy material of these peripheral accessible tissues. So far, biopsy studies of the gut have demonstrated the presence of α-SYN pathology in the salivary glands, stomach, duodenum, colon, and rectum. Further research is necessary in order to determine which are the most sensitive targets for in vivo α-SYN pathology detection and the safest techniques for these approaches in patients with PD.

Decrease in plasma levels of α-synuclein is evident in patients with Parkinson's disease after elimination of heterophilic antibody interference

There is substantial biochemical, pathological, and genetic evidence that α-synuclein (A-syn) is a principal molecule in the pathogenesis of Parkinson disease (PD). We previously reported that total A-syn levels in cerebrospinal fluid (CSF), measured with the specific enzyme-linked immunosorbent assay (ELISA) developed by ourselves, were decreased in patients with PD, and suggested the usefulness of A-syn in CSF and plasma as a biomarker for the diagnosis of PD. After our report, a considerable number of studies have investigated the levels A-syn in CSF and in blood, but have reported inconclusive results. Such discrepancies have often been attributed not only to the use of different antibodies in the ELISAs but also to interference from hemolysis. In this study we measured the levels of A-syn in CSF and plasma by using our own sandwich ELISA with or without heterophilic antibody (HA) inhibitor in 30 patients with PD and 58 age-matched controls. We thereby revealed that HA interfered with ELISA measurements of A-syn and are accordingly considered to be an important confounder in A-syn ELISAs. HA produced falsely exaggerated signals in A-syn ELISAs more prominently in plasma samples than in CSF samples. After elimination of HA interference, it was found that hemolysis did not have a significant effect on the signals obtained using our A-syn ELISA. Furthermore, plasma levels of A-syn were significantly lower in the PD group compared with the control group following elimination of HA interference with an HA inhibitor. Our results demonstrate that HA was a major confounder that should be controlled in A-syn ELISAs, and that plasma A-syn could be a useful biomarker for the diagnosis of PD if adequately quantified following elimination of HA interference.

Structural alterations of the intestinal epithelial barrier in Parkinson's disease

Functional and morphological alterations of the intestinal epithelial barrier (IEB) have been consistently reported in digestive disorders such as irritable bowel syndrome and inflammatory bowel disease. There is mounting evidence that Parkinson's disease (PD) is not only a brain disease but also a digestive disorder. Gastrointestinal involvement is a frequent and early event in the course of PD, and it may be critically involved in the early development of the disease. We therefore undertook the present survey to investigate whether changes in the IEB function and/or morphology occur in PD. Colonic biopsies were performed in 31 PD patients and 11 age-matched healthy controls. The para- and transcellular permeability were evaluated by measuring sulfonic acid and horseradish peroxidase flux respectively, in colonic biopsies mounted in Ussing chambers. The expression and localization of the two tight junctions proteins ZO-1 and occludin were analyzed by Western blot and immunofluorescence, respectively. The para- and transcellular permeability were not different between PD patients and controls. The expression of occludin, but not ZO-1, was significantly lower in colonic samples from PD patients as compared to controls and the cellular distribution of both proteins was altered in colonic mucosal specimens from PD patients. Our findings provide evidence that the IEB is morphologically altered in PD and further reinforce the potential role of the gastrointestinal tract in the initiation and/or the progression of the disease.

Early and persistent expression of phosphorylated α-synuclein in the enteric nervous system of A53T mutant human α-synuclein transgenic mice

Alpha-synuclein is a key protein in Parkinson disease (PD) and dementia with Lewy bodies. It is found in Lewy bodies in the brains of PD patients and has been reported in the peripheral nervous system in postmortem tissues from PD patients and in biopsies from patients in the preclinical phase of PD. Here, we used a transgenic mouse model of human synucleinopathies expressing the A53T mutant α-synuclein (TgM83) in which a neurodegenerative process associated with α-synuclein occurs spontaneously and increases with age. In particular, α-synuclein protein phosphorylated at serine 129 (pSer129 α-synuclein) naturally and progressively increases in diseased brains. We examined the time course of pSer129 α-synuclein presence in the gut of these mice between 1.5 and 22 months of age using immunohistochemistry and paraffin-embedded tissue blots. The pSer129 α-synuclein accumulated early (before the onset of motor signs) and persistently in the enteric nervous system and was concomitantly found in the brain. These results suggest that the accumulation of phosphorylated α-synuclein in the enteric and central nervous systems may result from parallel pathologic processes when the disease is linked to a mutation of α-synuclein.

Saliva α-Synuclein and A High Extinction Coefficient Protein: A Novel Approach in Assessment Biomarkers of Parkinson's Disease

BACKGROUND

The pathological hallmark of Parkinson's disease (PD) is the appearance of intracytoplasmic inclusions known as Lewy bodies in which its principal component is α-synuclein.

AIM

This study aimed to determine salivary α-synuclein and the extinction coefficient of the saliva protein as biomarkers of PD.

MATERIALS AND METHODS

This observational study was done in Department of Pharmacology, College of Medicine in cooperation with Department of Oral Medicine, College of Dentistry at Al-Mustansiriya University in Baghdad, Iraq from September 2013 to March 2014. A total number of 20 PD patients and 20 healthy subjects were enrolled in the study. Unstimulated saliva obtained from each participant obtained for determination of salivary flow rate, saliva protein and α-synuclein using enzyme linked immune sorbent assay (ELISA) technique.

RESULTS

Total saliva protein and uncontaminated protein with nucleic acids are significantly higher in PD compared with healthy subjects. The mean extinction coefficient of that protein is 27.25 M.cm(-1) which significantly (P < 0.001) less than corresponding value of healthy subjects (33.48 M.cm(-1) ). Saliva α-synuclein level is significantly less in PD (65 ± 52.2 pg/ml) than healthy subjects (314.01 ± 435.9 pg/ml).

CONCLUSIONS

We conclude that saliva α-synuclein serves as a biomarker for PD if its level compared with healthy subjects, and a specific protein with extinction coefficient 27.25 M.cm-1 is detected in saliva of Parkinson's patients.

An update on the rotenone models of Parkinson's disease: their ability to reproduce the features of clinical disease and model gene-environment interactions

Parkinson's disease (PD) is the second most common neurodegenerative disorder that is characterized by two major neuropathological hallmarks: the degeneration of dopaminergic neurons in the substantia nigra (SN) and the presence of Lewy bodies in the surviving SN neurons, as well as other regions of the central and peripheral nervous system. Animal models have been invaluable tools for investigating the underlying mechanisms of the pathogenesis of PD and testing new potential symptomatic, neuroprotective and neurorestorative therapies. However, the usefulness of these models is dependent on how precisely they replicate the features of clinical PD with some studies now employing combined gene-environment models to replicate more of the affected pathways. The rotenone model of PD has become of great interest following the seminal paper by the Greenamyre group in 2000 (Betarbet et al., 2000). This paper reported for the first time that systemic rotenone was able to reproduce the two pathological hallmarks of PD as well as certain parkinsonian motor deficits. Since 2000, many research groups have actively used the rotenone model worldwide. This paper will review rotenone models, focusing upon their ability to reproduce the two pathological hallmarks of PD, motor deficits, extranigral pathology and non-motor symptoms. We will also summarize the recent advances in neuroprotective therapies, focusing on those that investigated non-motor symptoms and review rotenone models used in combination with PD genetic models to investigate gene-environment interactions.

Dysautonomia in Parkinson disease

Dysautonomias are conditions in which altered function of one or more components of the autonomic nervous system (ANS) adversely affects health. This review updates knowledge about dysautonomia in Parkinson disease (PD). Most PD patients have symptoms or signs of dysautonomia; occasionally, the abnormalities dominate the clinical picture. Components of the ANS include the sympathetic noradrenergic system (SNS), the parasympathetic nervous system (PNS), the sympathetic cholinergic system (SCS), the sympathetic adrenomedullary system (SAS), and the enteric nervous system (ENS). Dysfunction of each component system produces characteristic manifestations. In PD, it is cardiovascular dysautonomia that is best understood scientifically, mainly because of the variety of clinical laboratory tools available to assess functions of catecholamine systems. Most of this review focuses on this aspect of autonomic involvement in PD. PD features cardiac sympathetic denervation, which can precede the movement disorder. Loss of cardiac SNS innervation occurs independently of the loss of striatal dopaminergic innervation underlying the motor signs of PD and is associated with other nonmotor manifestations, including anosmia, REM behavior disorder, orthostatic hypotension (OH), and dementia. Autonomic dysfunction in PD is important not only in clinical management and in providing potential biomarkers but also for understanding disease mechanisms (e.g., autotoxicity exerted by catecholamine metabolites). Since Lewy bodies and Lewy neurites containing alpha-synuclein constitute neuropathologic hallmarks of the disease, and catecholamine depletion in the striatum and heart are characteristic neurochemical features, a key goal of future research is to understand better the link between alpha-synucleinopathy and loss of catecholamine neurons in PD.

Prevalence and risk of developing comorbid conditions in patients with chronic constipation

OBJECTIVE

To estimate the prevalence of gastrointestinal (GI) and non-GI comorbidities and the risk of incident comorbidities among patients with and without chronic constipation (CC).

RESEARCH DESIGN AND METHODS

Adults with CC were identified from a large retrospective US claims database. Each CC patient was matched 1:3 to CC-free patients by birth year, sex, and region of residence.

MAIN OUTCOME MEASURES

Prevalence of GI and non-GI comorbidities was measured over a 1-year period. Relative risk of new comorbidities was also estimated among patients who were free of the studied comorbidity prior to the index date.

RESULTS

Mean age was 61.9 years; 33.3% of patients were male. The 1-year prevalence of GI comorbidities was significantly higher in CC (N = 28,854) vs. CC-free (N = 86,562) patients (all p < 0.05). The risk of developing new GI conditions was also significantly higher in CC patients for all studied conditions except ulcerative colitis: megacolon (hazard ratio [95% confidence interval] HR [CI] = 11.96 [8.16-17.53]), intestinal impaction (10.56 [9.22-12.10]), volvulus (7.12 [5.42-9.35]), other specified functional intestinal disorders (6.67 [5.57-8.00]), and other unspecified functional disorders of intestine (4.60 [3.61-5.87]). Similarly, 1-year prevalence of non-GI comorbidities was higher in CC patients, as was the risk of developing new conditions: depression and mood disorder (HR [CI] = 1.84 [1.77-1.90]), neurological disorders (1.68 [1.62-1.74]), iron deficiency anemia (1.52 [1.47-1.57]), hypothyroidism (1.40 [1.34-1.46]), and peripheral vascular disorders (1.40 [1.34-1.46]).

LIMITATIONS

An algorithm was used to define CC as there is no specific diagnosis code to identify CC.

CONCLUSIONS

CC patients had significantly higher prevalence and were at increased risk of developing new GI and non-GI comorbidities than age-, gender- and region-matched CC-free patients. Future research is warranted to better understand these associations.

The frequency and severity of gastrointestinal symptoms in patients with early Parkinson's disease

Objective

Although gastrointestinal dysfunctions occur in the majority of patients with Parkinson’s disease (PD), they are often unrecognized because many patients remain relatively asymptomatic in the early stage. We investigated the frequency of gastrointestinal symptoms in patients with PD using newly developed gastrointestinal symptom questionnaires.

Methods

Early PD patients with a symptom duration not exceeding 3 years were included in this study. All PD patients were evaluated using a questionnaire, which consisted of three relevant domains: oropharyngoesophageal (10 items); gastric (3 items); and intestinal-anorectal (7 items). The frequency of symptoms was calculated as a proportion with an item score ≥ 2.

Results

Of the 54 patients enrolled, 48 patients (88.9%) responded that bowel symptoms developed before the onset of Parkinsonian motor symptoms, and four patients reported that the onset of two types of symptoms (i.e., bowel and neurological) occurred approximately simultaneously, with only months between them. The frequencies of gastrointestinal symptoms are as follows: speech disturbance (40.7%), drooling (24.1%), sense of getting stuck (31.5%), choking (27.8%), globus pharyngis (16.7%), repetitive deglutition (29.6%), pain during swallowing (5.6%), food regurgitation (3.7%), acid reflux (7.4%), nausea/vomiting (11.1%), early satiety (16.7%), postprandial fullness (14.8%), epigastric soreness (9.3%), abdominal pain (3.7%), constipation (46.3%), excessive strain during defecation (33.3%), fecal incontinence (7.4%), tenesmus (20.4%), loose stool or diarrhea (3.7%), and difficulty in relaxing anal sphincter (11.1%). Two patients were scored at zero.

Conclusions

Our findings confirm that gastrointestinal dysfunction occurs in early PD in relatively high frequency.

Parkinson disease and sleep: sleep-wake changes in the premotor stage of Parkinson disease; impaired olfaction and other prodromal features

Parkinson disease (PD) has a premotor stage where neurodegeneration occurs before parkinsonism becomes apparent. Identification of individuals at this stage provides an opportunity to study early disease progression and test disease-modifying interventions. Hyposmia, constipation, depression and hypersomnia are part of this premotor phase and predictive of future development of PD. However, these features are common in the general population, and they are most often the result of causes other than incipient PD. In contrast, most individuals with idiopathic REM sleep behavior disorder (IRBD) eventually develop PD and other synucleinopathies. IRBD individuals with hyposmia, substantia nigra hyperechogenicity, and abnormal striatal dopamine transporter imaging findings have increased short-term risk of developing a synucleinopathy. IRBD is an optimal target to test disease-modifying agents in the PD prodromal phase. Serial dopamine transporter imaging, but not olfactory tests, may serve to monitor the disease process in future disease-modifying trials in IRBD.

Progression of intestinal permeability changes and alpha-synuclein expression in a mouse model of Parkinson's disease

Parkinson's disease (PD) is a multifocal degenerative disorder for which there is no cure. The majority of cases are sporadic with unknown etiology. Recent data indicate that untreated patients with de novo PD have increased colonic permeability and that both de novo and premotor patients have pathological expression of α-synuclein (α-syn) in their colon. Both endpoints potentially can serve as disease biomarkers and even may initiate PD events through gut-derived, lipopolysaccharide (LPS)-induced neuronal injury. Animal models could be ideal for interrogating the potential role of the intestines in the pathogenesis of PD; however, few current animal models of PD encompass these nonmotor features. We sought to establish a progressive model of PD that includes the gastrointestinal (GI) dysfunction present in human patients. C57/BL6 mice were systemically administered one dose of either LPS (2.5 mg/kg) or saline and were sacrificed in monthly intervals (n = 5 mice for 5 months) to create a time-course. Small and large intestinal permeability was assessed by analyzing the urinary output of orally ingested sugar probes through capillary column gas chromatography. α-Syn expression was assessed by counting the number of mildly, moderately, and severely affected myenteric ganglia neurons throughout the GI tract, and the counts were validated by quantitative optical density measurements. Nigrostriatal integrity was assessed by tyrosine hydroxylase immunohistochemistry stereology and densitometry. LPS caused an immediate and progressive increase in α-syn expression in the large intestine but not in the small intestine. Intestinal permeability of the whole gut (large and small intestines) progressively increased between months 2 and 4 after LPS administration but returned to baseline levels at month 5. Selective measurements demonstrated that intestinal permeability in the small intestine remained largely intact, suggesting that gut leakiness was predominately in the large intestine. Phosphorylated serine 129-α-syn was identified in a subset of colonic myenteric neurons at months 4 and 5. Although these changes were observed in the absence of nigrostriatal degeneration, an abrupt but insignificant increase in brainstem α-syn was observed that paralleled the restoration of permeability. No changes were observed over time in controls. LPS, an endotoxin used to model PD, causes sequential increases in α-syn immunoreactivity, intestinal permeability, and pathological α-syn accumulation in the colon in a manner similar to that observed in patients with PD. These features are observed without nigrostriatal degeneration and incorporate PD features before the motor syndrome. This allows for the potential use of this model in testing neuroprotective and disease-modifying therapies, including intestinal-directed therapies to fortify intestinal barrier integrity.

Delayed gastric emptying in Parkinson's disease

Gastrointestinal symptoms are evident in all stages of Parkinson's disease (PD). Most of the gastrointestinal abnormalities associated with PD are attributable to impaired motility. At the level of the stomach, this results in delayed gastric emptying. The etiology of delayed gastric emptying in PD is probably multifactorial but is at least partly related to Lewy pathology in the enteric nervous system and discrete brainstem nuclei. Delayed gastric emptying occurs in both early and advanced PD but is underdetected in routine clinical practice. Recognition of delayed gastric emptying is important because it can cause an array of upper gastrointestinal symptoms, but additionally it has important implications for the absorption and action of levodopa. Delayed gastric emptying contributes significantly to response fluctuations seen in people on long-term l-dopa therapy. Neurohormonal aspects of the brain-gut axis are pertinent to discussions regarding the pathophysiology of delayed gastric emptying in PD and are also hypothesized to contribute to the pathogenesis of PD itself. Ghrelin is a gastric-derived hormone with potential as a therapeutic agent for delayed gastric emptying and also as a novel neuroprotective agent in PD. Recent findings relating to ghrelin in the context of PD and gastric emptying are considered. This article highlights the pathological abnormalities that may account for delayed gastric emptying in PD. It also considers the wider relevance of abnormal gastric pathology to our current understanding of the etiology of PD.

Parkinson's disease: an update on pathogenesis and treatment

The Parkinson's disease research field is a rapidly moving one, as many of the relevant processes underlying PD neurodegeneration are being deciphered, enabling novel approaches to treatment to be assessed both in the laboratory and in the clinic. This review aims to highlight the most relevant updates in the PD field, with emphasis on research that may help lead towards an improvement in the treatment of this condition.