Motor fluctuations and Helicobacter pylori in Parkinson’s disease. J Neurol. 2013;260:2974-2980. [PMID: 24002418 DOI: 10.1007/s00415-013-7089-6]

Helicobacter pylori infection and Parkinson's Disease: etiology, pathogenesis and levodopa bioavailability

Parkinson's disease (PD), a neurodegenerative disorder with an unknown etiology, is primarily characterized by the degeneration of dopamine (DA) neurons. The prevalence of PD has experienced a significant surge in recent years. The unidentified etiology poses limitations to the development of effective therapeutic interventions for this condition. Helicobacter pylori (H. pylori) infection has affected approximately half of the global population. Mounting evidences suggest that H. pylori infection plays an important role in PD through various mechanisms. The autotoxin produced by H. pylori induces pro-inflammatory cytokines release, thereby facilitating the occurrence of central inflammation that leads to neuronal damage. Simultaneously, H. pylori disrupts the equilibrium of gastrointestinal microbiota with an overgrowth of bacteria in the small intestinal known as small intestinal bacterial overgrowth (SIBO). This dysbiosis of the gut flora influences the central nervous system (CNS) through microbiome-gut-brain axis. Moreover, SIBO hampers levodopa absorption and affects its therapeutic efficacy in the treatment of PD. Also, H. pylori promotes the production of defensins to regulate the permeability of the blood-brain barrier, facilitating the entry of harmful factors into the CNS. In addition, H. pylori has been found to induce gastroparesis, resulting in a prolonged transit time for levodopa to reach the small intestine. H. pylori may exploit levodopa to facilitate its own growth and proliferation, or it can inflict damage to the gastrointestinal mucosa, leading to gastrointestinal ulcers and impeding levodopa absorption. Here, this review focused on the role of H. pylori infection in PD from etiology, pathogenesis to levodopa bioavailability.

A functional role for alpha-synuclein in neuroimmune responses

Alpha-synuclein is a neuronal protein with unclear function but is associated with the pathogenesis of Parkinson's disease and other synucleinopathies. In this review, we discuss the emerging functional role of alpha-synuclein in support of the unique immune responses in the nervous system. Recent data now show that alpha-synuclein functions to support interferon signaling within neurons and is released from neurons to support chemoattraction and activation of local glial cells and infiltrating immune cells. Inflammatory activation and interferon signaling also induce post-translational modifications of alpha-synuclein that are commonly associated with Parkinson's disease pathogenesis. Taken together, emerging data implicate complex interactions between alpha-synuclein and host immune responses that may contribute to the pathogenesis of Parkinson's disease. Additional study of the function of alpha-synuclein in the brain's immune response may provide disease-modifying therapeutic targets for Parkinson's disease in the future.

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.

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

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

Gut brain axis: an insight into microbiota role in Parkinson's disease

Parkinson's disease (PD) is one of the most common progressive neurodegenerative diseases. It is characterized neuropathologically by the presence of alpha-synuclein containing Lewy Bodies in the substantia nigra of the brain with loss of dopaminergic neurons in the pars compacta of the substantia nigra. The presence of alpha-synuclein aggregates in the substantia nigra and the enteric nervous system (ENS) drew attention to the possibility of a correlation between the gut microbiota and Parkinson's disease. The gut-brain axis is a two-way communication system, which explains how through the vagus nerve, the gut microbiota can affect the central nervous system (CNS), including brain functions related to the ENS, as well as how CNS can alter various gut secretions and immune responses. As a result, this dysbiosis or alteration in gut microbiota can be an early sign of PD with reported changes in short chain fatty acids, bile acids, and lipids. This gave rise to the use of probiotics and faecal microbiota transplantation as alternative approaches to improve the symptoms of patients with PD. The aim of this review is to discuss investigations that have been done to explore the gastrointestinal involvement in Parkinson's disease, the effect of dysbiosis, and potential therapeutic strategies for PD.

Gastro-intestinal dysfunctions in Parkinson's disease (Review)

In patients with Parkinson's disease (PD), gastrointestinal dysfunction occurs from the early stages of the disease and even in the pre-motor phase. This condition can include the entire digestive tract, with symptoms ranging from delays in gastric emptying to dysphagia, constipation and even malnutrition. Excess saliva accumulates in the mouth due to the low frequency of swallowing. Dysphagia develops in about 50% of patients and may be a reflection of both central nervous system and enteric nervous system disorder. Gastroparesis can cause a variety of symptoms, including nausea, and also may be responsible for some of the motor fluctuations observed with levodopa therapy. Intestinal dysfunction in PD may be the result of both delayed colon transit and impaired anorectal muscle coordination. In addition, recent studies have demonstrated the role of Helicobacter pylori infection in the pathogenesis of diseases but also the occurrence of motor fluctuations by affecting the absorption of anti-parkinsonian medication. In this review, the main gastrointestinal dysfunctions associated with PD are presented.

Helicobacter pylori infection is associated with a poor response to levodopa in patients with Parkinson's disease: a systematic review and meta-analysis

BACKGROUND

Helicobacter pylori (HP) infection has been reported to be associated with increased severity of Parkinson's disease (PD) and have negative effects on drug response in patients. We aimed to investigate the influence of HP infection on patients with PD using a systematic review and meta-analysis approach.

METHODS

PubMed and EMBASE databases for relevant articles published before October 2020 were searched. Two authors independently screened records, extracted data, and evaluated the quality of the included studies. The odds ratios (ORs) or standardized mean differences (SMDs) with their corresponding 95% confidence intervals (CIs) were used to calculate the pooled results by employing a random or fixed-effects model. Sensitivity analyses were conducted, and potential publication bias was assessed.

RESULTS

A total of 13 studies were included in our meta-analysis. Overall, PD patients with HP infection had significantly higher levodopa equivalent daily dose (UPDRS) motor scores (SMD = 0.266; 95% CI 0.065-0.467; P = 0.009) and more units of levodopa equivalent daily dose (LEDD) (SMD = 0.178; 95% CI 0.004-0.353; P = 0.046) than those of patients without HP infection. Additionally, the time to achieve 'ON' state was significantly longer (SMD = 0.778; 95% CI 0.337-1.220; P = 0.001) and the duration of 'ON' state was significantly shorter (SMD = -0.539; 95% CI = -0.801 to  -0.227; P = 0.001) in patients with HP infection than in those without HP infection.

CONCLUSION

Our pooled results of this meta-analysis demonstrated that HP infection was associated with worse motor symptoms, higher LEDD, and worse response to drugs in patients with PD. This evidence emphasizes the importance of considering subsequent eradication of HP infection in patients with PD.

Infection and Risk of Parkinson's Disease

Parkinson’s disease (PD) is thought to be caused by a combination of genetic and environmental factors. Bacterial or viral infection has been proposed as a potential risk factor, and there is supporting although not entirely consistent epidemiologic and basic science evidence to support its role. Encephalitis caused by influenza has included parkinsonian features. Epidemiological evidence is most compelling for an association between PD and hepatitis C virus. Infection with Helicobacter pylori may be associated not only with PD risk but also response to levodopa. Rapidly evolving knowledge regarding the role of the microbiome also suggests a role of resident bacteria in PD risk. Biological plausibility for the role for infectious agents is supported by the known neurotropic effects of specific viruses, particular vulnerability of the substantia nigra and even the promotion of aggregation of alpha-synuclein. A common feature of implicated viruses appears to be production of high levels of cytokines and chemokines that can cross the blood-brain barrier leading to microglial activation and inflammation and ultimately neuronal cell death. Based on multiple avenues of evidence it appears likely that specific bacterial and particularly viral infections may increase vulnerability to PD. The implications of this for PD prevention requires attention and may be most relevant once preventive treatments for at-risk populations are developed.

Effects of Helicobacter pylori on Levodopa Pharmacokinetics

BACKGROUND

Infection with Helicobacter pylori seems overrepresented in Parkinson's disease. Clinical observations suggest a suboptimal treatment effect of levodopa in Helicobacter positive patients.

OBJECTIVE

Describe and explain the connection between a Helicobacter pylori infection of the upper gut and changes in pharmacokinetics of oral levodopa treatment in Parkinson's disease.

METHODS

PubMed, Google Scholar, and Cross Reference search was done using the key words and combined searches: Bioavailability, drug metabolism, dyskinesia, Helicobacter, L-dopa, levodopa, motor control, pharmacodynamics, pharmacokinetics, prevalence, unified Parkinson's disease rating scale.

RESULTS

The prevalence of Helicobacter pylori in Parkinson's disease patients is reported to be about 1.6-fold higher than in a control population in some studies. Helicobacter has therefore been assumed to be linked to Parkinson's disease, but the mechanism is unclear. As regards symptoms and treatment, patients with Parkinson's disease on levodopa therapy and with Helicobacter pylori infection display worse motor control than those without Helicobacter infection. Eradication of the infection improves levodopa response in Parkinson's disease, likely as a consequence of an increased oral pre-systemic bioavailability of levodopa, likely to be explained by reduced Helicobacter-dependent levodopa consumption in the stomach. In addition, small intestinal bacterial overgrowth may also have an impact on the therapeutic setting for levodopa treatment but is less well established.

CONCLUSION

Eradication of Helicobacter pylori improves levodopa bioavailability resulting in improved motor control. Eradication of Helicobacter should be considered in patients with poor symptomatic control and considerable motor fluctuations.

[The role of the gut microbiome in idiopathic Parkinson's disease]

BACKGROUND

In recent years studies have provided increasing evidence suggesting an association between the (gut) microbiome and idiopathic Parkinson's disease (IPD).

OBJECTIVE

The aim of this article is to summarize and evaluate existing evidence with respect to the relevance of the (gut) microbiome for IPD.

MATERIAL AND METHODS

An analysis and critical review of studies in the field of IPD and (gut) microbiome were carried out. The resulting potential perspectives and therapeutic strategies are discussed.

RESULTS

Despite partially divergent results between different studies (potentially due to the applied methods and variance in the composition of the investigated cohorts), there is an overlap between studies indicating an association between IPD, the microbiome and microbial metabolites. Nevertheless, the cause-effect relationship between IPD and the microbiome has still not been clarified. Taken together, existing evidence supports a potentially relevant role for the microbiome with respect to typical disease symptoms and pathogenesis of the disease.

CONCLUSION

Over the past 5 years there has been an enormous increase in the evidence with respect to the relevance of the microbiome for IPD. While early work in this field was mainly descriptive, new diagnostic methods provide evidence for the underlying mechanisms and the complex interactions between man as the host, the human immune system, the enteric nervous system, gut microbiota and microbial metabolites. A relatively novel and clinically relevant field of research is how the gut microbiome can influence the success of oral pharmacotherapy and whether substitution of specific microbiome components might be used either for future therapeutic or prophylactic strategies.

Role of Helicobacters in Neuropsychiatric Disease: A Systematic Review in Idiopathic Parkinsonism

Interest in an aetiopathogenic role for Helicobacter in neuropsychiatric diseases started with idiopathic parkinsonism (IP), where the cardinal signs can be assessed objectively. This systematic review, using an EMBASE database search, addresses Oxford Centre for Evidence-Based Medicine based questions on the inter-relationship of Helicobacter and IP, the benefits of eradicating Helicobacter in IP and the outcome of not treating. The search strategy was based on Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines: 21 of 204 articles met the inclusion criteria. The results show that the assumption that any benefit of Helicobacter eradication results from improved levodopa bioavailability is unjustified. The inter-relationship between Helicobacter and IP is well-established. H. pylori virulence markers (associated with autoimmunity and immune tolerance) influence the risk, severity and progression of IP. The birth cohort effect for virulence marker antibodies, seen in controls, is obliterated in IP, suggesting causality. Successful H. pylori eradication in IP is disease-modifying (even in anti-parkinsonian treatment-naïve patients) but not preventive. Hypokinesia regresses with eradication and overall motor severity lessens. Eradication may influence gastrointestinal microbiota adversely, unlocking the next stage in the natural history, the development of rigidity. Failed eradication worsens hypokinesia, as does the presence/persistence of H. pylori at molecular level only. Adequate prognostic assessment of the consequences of not treating Helicobacter, for IP, is prevented by a short follow-up. We conclude that Helicobacter is a pathophysiological driver of IP.

Clinical implications of gastric complications on levodopa treatment in Parkinson's disease

Disorders of the gastrointestinal (GI) tract are common and distressing nonmotor symptoms of Parkinson's disease (PD) that can adversely affect levodopa absorption and lead to OFF periods, also known as motor fluctuations. Gastroparesis, which is primarily defined as delayed gastric emptying (DGE), and Helicobacter pylori infection, which is present with increased frequency in PD, are among the most common and important GI disorders reported in PD that may impair oral levodopa absorption and increase OFF time. Symptoms of gastroparesis include nausea, vomiting, postprandial bloating, fullness, early satiety, abdominal pain, and weight loss. DGE has been reported in a substantial fraction of individuals with PD. Symptoms of H. pylori infection include gastritis and peptic ulcers. Studies have found that DGE and H. pylori infection are correlated with delayed peak levodopa plasma levels and increased incidence of motor fluctuations. Therapeutic strategies devised to minimize the potential that gastric complications will impair oral levodopa absorption and efficacy in PD patients include treatments that circumvent the GI tract, such as apomorphine injection, levodopa intestinal gel delivery, levodopa inhalation powder, and deep brain stimulation. Other strategies aim at improving gastric emptying in PD patients, primarily including prokinetic agents.

An overview of the neuroendocrine system in Parkinson's disease: what is the impact on diagnosis and treatment?

Introduction: A growing body of evidence indicates that neuroendocrine interactions may occur at all levels of the brain-gut-microbiota axis, which is directly involved in the pathogenesis of Parkinson's disease (PD).Areas covered: The review presents some current and emerging concepts regarding the organization and functioning of the neuroendocrine system as well as the role of neuroendocrine disturbances in the pathophysiology and symptomatology of PD. The concept of the brain-gut-microbiota triad interactions in the neuroendocrine system and PD is proposed. In PD, dysregulation of the main neuroendocrine axes coordinated by the hypothalamus is accompanied by disruptions at the peripheral level, which involve enteroendocrine cells producing numerous neuropeptides. Moreover, the important role of the gut microbiota as a main coordinator of immune and neuroendocrine interactions is discussed. The potential diagnostic and therapeutic implications in the context of the recent developments in the fields of neuroendocrinology and neurodegeneration are also presented.Expert opinion: Unraveling complex neuroendocrine interactions in the course of PD may provide crucial diagnostic implications and novel therapeutic approaches including the application of gut neuropeptides and gut microbiota modification.

Contributions of Gut Bacteria and Diet to Drug Pharmacokinetics in the Treatment of Parkinson's Disease

Parkinson's disease is the second-most common neurodegenerative disorder worldwide. Besides deciphering the mechanisms that underlie the etiology of the disease, it is important to elucidate the factors that influence the efficacy of the treatment therapeutics. Levodopa, which remains the golden treatment of the disease, is absorbed in the proximal small intestine. A reduction in levodopa absorption, leads to reduction in striatal dopamine levels and, in turn, an "off"-episode. In fact, motor fluctuations represent a major problem during the progression of the disease and alteration between "on" (mobility often with dyskinesia) and "off" (immobility, akinesia) episodes contribute to a decreased quality of life. Dietary amino acids can interfere with the absorption of levodopa from the gut lumen and its transport through the blood brain barrier. In addition, higher abundance of specific gut bacteria that restrict levodopa absorption plays a significant role in motor fluctuations in a subset of Parkinson's disease patients. Here, we review the impact of factors potentially interfering with levodopa absorption, focusing on levodopa transport, diet, and gut bacterial interference with the bioavailability of levodopa.

H. pylori and Parkinson's disease: Meta-analyses including clinical severity

The exact etiology of Parkinson's disease (PD) remains unclear. Some evidence supports Helicobacter pylori infection as a trigger or driving event, but detection and eradication of H. pylori are not part of PD management. The aims of this case-control study and meta-analysis were to determine (i) the prevalence of H. pylori infection in PD patients, (ii) associations between H. pylori infection and clinical status, and (iii) differences in motor status in PD patients before and after H. pylori eradication. A literature search was performed using the PubMed database. The prevalence of H. pylori infection in PD, its association with the unified Parkinson's disease rating scale (UPDRS), and the association of H. pylori eradication therapy with the UPDRS-III score were determined by calculating the odds ratios (OR) and the standardized mean differences (SMD) with 95% confidence intervals (CI). Fixed- and random-effects models were applied. Ten studies were included in the first meta-analysis (5043 PD patients, 23,449 HCs); H. pylori infection prevalence was higher in PD patients than in HCs [OR (95% CI): 1.47 (1.27, 1.70), P_z<0.00001]. In seven studies reporting UPDRS scores (150 H. pylori infected, 228 non-infected PD patients), there was a significant association between H. pylori infection and mean UPDRS scores [SMD (95% CI): 0.33 (0.12, 0.54), P_z = 0.003]. Regarding H. pylori eradication, in five studies (90 PD patients), there was a significant reduction in UPDRS-III scores after treatment [SMD (95% CI): 6.83 (2.29, 11.38), P_z = 0.003]. In conclusion, the present meta-analysis revealed a higher prevalence of H. pylori infection in PD patients suggesting that H. pylori may contribute to PD pathophysiology. In addition, the significantly lower UPDRS scores in non-infected PD patients and in patients after H. pylori eradication therapy demonstrate that the infection may deteriorate the clinical severity of the disease.

Clinimetrics of the 9- and 19-Item Wearing-Off Questionnaire: A Systematic Review

The treatment of Parkinson's disease (PD) with dopaminergic therapy improves functionality and quality of life. However, as the disease progresses, the wearing-off phenomenon develops, which necessitates complex posology adjustment or adjuvant therapy. This phenomenon may not be well recognized, especially if it is mild or involves nonmotor symptoms. Questionnaires were developed to improve the recognition of the wearing-off phenomenon. The questionnaires consist of a list of symptoms that patients must check if they have and if the symptoms improve with medication. A recent review by the Movement Disorder Society suggested the 19-item (WOQ-19) and 9-item (WOQ-9) questionnaires as screening tools for the wearing-off phenomenon. However, there has not been a systematic review to assess the questionnaires' clinimetric properties, such as sensitivity, specificity, test-retest reliability, and responsiveness. We conducted an extensive search for studies using these two tools. We identified 3 studies using WOQ-19 and 5 studies using WOQ-9. Both questionnaires seem to have good sensitivity (0.81–1). WOQ-19 has variable specificity (0.39–0.8), depending on the number of positive items, while WOQ-9 lacks specificity (0.1–0.69). Only one study using WOQ-19 reported test-retest, and only two studies reported responsiveness. Thus, this report describes the first independent systematic review to exam quantitatively the clinimetric properties of these two questionnaires.

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.

Helicobacter pylori infection is associated with an increased risk of Parkinson's disease: A population-based retrospective cohort study

BACKGROUND

Several studies have evaluated the association of Parkinson's disease with Helicobacter pylori (HP) infection, although no cohort studies have evaluated this association among the general population.

OBJECTIVE

This study aimed to investigate the risk of Parkinson's disease after HP infection in the general Taiwanese population.

METHODS

This study of Taiwanese health insurance data (2000-2012) evaluated 9105 cases of HP infection and 9105 controls matched with propensity scoring. Univariate and multivariate Cox proportional hazards regression models were used to assess the risk of subsequent Parkinson's disease.

RESULTS

We observed 64 cases of Parkinson's disease in the HP infection group (1.7/1000 person-years), and 25 cases in the control group (0.7/1000 person-years). Overall, there was a significantly higher risk of Parkinson's disease in the HP infection group (adjusted hazard ratio [aHR]: 2.29, 95% confidence interval [CI]: 1.44-3.66). HP infection was significantly associated with an increased risk of Parkinson's disease among individuals who were ≥60 years old (aHR: 2.53, 95% CI: 1.47-4.35), but not among those <60 years old (aHR: 1.86, 95% CI: 0.69-4.98). Furthermore, HP infection was associated with an increased risk of Parkinson's disease among both men (aHR: 2.14, 95% CI: 1.15-3.96) and women (aHR: 2.84, 95% CI: 1.37-5.89). Nonetheless, eradication therapy was not significantly associated with the risk of Parkinson's disease (aHR: 1.07, 95% CI: 0.63-1.82).

CONCLUSION

Although HP infection was associated with an increased risk of Parkinson's disease, eradication therapy did not ameliorate this association. Further research is needed to explore the underlying biological mechanisms.

Motor Complications of Dopaminergic Medications in Parkinson's Disease

Motor complications are a consequence of the chronic treatment of Parkinson's disease (PD) and include motor fluctuations (wearing-off phenomenon) and levodopa-induced dyskinesia. Both can have a significant impact on functionality and quality of life; thus, proper recognition and management is essential. The phenomenology and temporal relationship of motor complications to the schedule of levodopa dosing can be helpful in characterizing them. There are several therapeutic approaches to motor complications, including pharmacological and surgical options. The authors summarize the different types of motor complications according to phenomenology and the currently available medical treatments, including ongoing trials for the management of this condition.

Association between Parkinson's Disease and Helicobacter Pylori

Helicobacter pylori (HP) is a common infection of the gastrointestinal system that is usually related to peptic ulcers. However, recent studies have revealed relationships between HP and many other diseases. Although the exact mechanism is unknown, HP can prevent the absorption of certain drugs. A high prevalence of HP has been found in patients with Parkinson's disease, and this bacterium causes motor fluctuations by affecting the absorption of levodopa, which is the main drug used to treat Parkinson's disease. Eradicating HP from patients with Parkinson's disease by applying antibiotic treatment will increase the absorption of levodopa and decrease their motor fluctuations.

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.

Helicobacter pylori and neurological diseases: Married by the laws of inflammation

The purpose of this paper is to review current information about the role of inflammation caused by Helicobacter pylori (H. pylori) infection in neurological diseases such as Parkinson’s disease, Alzheimer’s disease, Guillain-Barré syndrome, multiple sclerosis, and other inflammatory diseases including ischemic stroke. Infection with H. pylori usually persists throughout life, resulting in a chronic inflammatory response with local secretion of numerous inflammatory mediators including chemokines [interleukin (IL)-8, macrophage chemotactic protein (MCP)-1, growth-regulated oncogene (GRO)-α] and cytokines [IL-1β, tumor necrosis factor (TNF)-α, IL-6, IL-12, interferon (IFN)-γ], which can pass into the circulation and have a systemic effect. The persistence of detectable systemic and local concentrations of inflammatory mediators is likely to alter the outcome of neurological diseases. These proinflammatory factors can induce brain inflammation and the death of neurons and could eventually be associated to Parkinson’s disease and also may be involved in the development of Alzheimer’s disease. However, most neurological diseases are the result of a combination of multiple factors, but the systemic inflammatory response is a common component and determinant in the onset, evolution, and outcome of diseases. However, more studies are needed to allow understanding of the effects and mechanisms by which the inflammatory response generated by H. pylori infection affects neurological diseases.

Beyond the stomach: An updated view of Helicobacter pylori pathogenesis, diagnosis, and treatment

Helicobacter pylori (H. pylori) is an extremely common, yet underappreciated, pathogen that is able to alter host physiology and subvert the host immune response, allowing it to persist for the life of the host. H. pylori is the primary cause of peptic ulcers and gastric cancer. In the United States, the annual cost associated with peptic ulcer disease is estimated to be $6 billion and gastric cancer kills over 700000 people per year globally. The prevalence of H. pylori infection remains high (> 50%) in much of the world, although the infection rates are dropping in some developed nations. The drop in H. pylori prevalence could be a double-edged sword, reducing the incidence of gastric diseases while increasing the risk of allergies and esophageal diseases. The list of diseases potentially caused by H. pylori continues to grow; however, mechanistic explanations of how H. pylori could contribute to extragastric diseases lag far behind clinical studies. A number of host factors and H. pylori virulence factors act in concert to determine which individuals are at the highest risk of disease. These include bacterial cytotoxins and polymorphisms in host genes responsible for directing the immune response. This review discusses the latest advances in H. pylori pathogenesis, diagnosis, and treatment. Up-to-date information on correlations between H. pylori and extragastric diseases is also provided.

Helicobacter pylori infection and drugs malabsorption

Drug absorption represents an important factor affecting the efficacy of oral drug treatment. Gastric secretion and motility seem to be critical for drug absorption. A causal relationship between impaired absorption of orally administered drugs and Helicobacter pylori (H. pylori) infection has been proposed. Associations have been reported between poor bioavailability of l-thyroxine and l-dopa and H. pylori infection. According to the Maastricht Florence Consensus Report on the management of H. pylori infection, H. pylori treatment improves the bioavailability of both these drugs, whereas the direct clinical benefits to patients still await to be established. Less strong seems the association between H. pylori infection and other drugs malabsorption, such as delavirdine and ketoconazole. The exact mechanisms forming the basis of the relationship between H. pylori infection and impaired drugs absorption and/or bioavailability are not fully elucidated. H. pylori infection may trigger a chronic inflammation of the gastric mucosa, and impaired gastric acid secretion often follows. The reduction of acid secretion closely relates with the wideness and the severity of the damage and may affect drug absorption. This minireview focuses on the evidence of H. pylori infection associated with impaired drug absorption.