Biochemical premotor biomarkers for Parkinson's disease

Serum metabolomics analysis revealed metabolic disorders in Parkinson's disease

BACKGROUND

Parkinson's disease (PD) is by now the second of the most prevalent neurodegenerative diseases in the world, and its incidence is increasing rapidly as the global population ages, with 14.2 million PD patients expected worldwide by 2040.

METHODS

We gathered a completion of 45 serum samples, including 15 of healthy controls and 30 from the PD group. We used non-targeted metabolomics analysis based on liquid chromatography-mass spectrometry to identify the molecular changes in PD patients, and conducted bioinformatics analysis on this basis to explore the possible pathogenesis of PD.

RESULTS

We found significant metabolomics changes in the levels of 30 metabolites in PD patients compared with healthy controls.

CONCLUSION

Lipids and lipid-like molecules accounted for the majority of the 30 differentially expressed metabolites. Also, pathway enrichment analysis showed significant enrichment in sphingolipid metabolic pathway. These assessments can improve our perception on the underlying mechanism of PD as well as facilitate a better targeting on therapeutic interventions.

Searching for Biomarkers in the Blood of Patients at Risk of Developing Parkinson's Disease at the Prodromal Stage

Parkinson's disease (PD) is diagnosed many years after its onset, under a significant degradation of the nigrostriatal dopaminergic system, responsible for the regulation of motor function. This explains the low effectiveness of the treatment of patients. Therefore, one of the highest priorities in neurology is the development of the early (preclinical) diagnosis of PD. The aim of this study was to search for changes in the blood of patients at risk of developing PD, which are considered potential diagnostic biomarkers. Out of 1835 patients, 26 patients were included in the risk group and 20 patients in the control group. The primary criteria for inclusion in a risk group were the impairment of sleep behavior disorder and sense of smell, and the secondary criteria were neurological and mental disorders. In patients at risk and in controls, the composition of plasma and the expression of genes of interest in lymphocytes were assessed by 27 indicators. The main changes that we found in plasma include a decrease in the concentrations of l-3,4-dihydroxyphenylalanine (L-DOPA) and urates, as well as the expressions of some types of microRNA, and an increase in the total oxidative status. In turn, in the lymphocytes of patients at risk, an increase in the expression of the DA D3 receptor gene and the lymphocyte activation gene 3 (LAG3), as well as a decrease in the expression of the Protein deglycase DJ-1 gene (PARK7), were observed. The blood changes we found in patients at risk are considered candidates for diagnostic biomarkers at the prodromal stage of PD.

Synuclein-One study: skin biopsy detection of phosphorylated α-synuclein for diagnosis of synucleinopathies

Finding an easily accessible and reliable tool to diagnose the diseases collectively defined as 'synucleinopathies' is an urgent, unmet priority. The synucleinopathies include Parkinson's disease, multiple system atrophy, pure autonomic failure and dementia with Lewy bodies. There are millions of people who have a diagnosis of a synucleinopathy, with more diagnosed every year. With accessibility, ease of implementation, consistently high sensitivity (>80%) and specificity approaching 100%, skin biopsy has great potential as the clinical test of choice for the diagnosis of synucleinopathies. The large, multi-center Synuclein-One study will determine the sensitivity, specificity, accuracy and precision of α-synuclein detection within punch skin biopsies in patients with clinically established synucleinopathies using standardized, robust methods suitable for large-scale analysis. Clinical Trial Registration: NCT04700722 (ClinicalTrials.gov).

Modulation of the Interactions Between α-Synuclein and Lipid Membranes by Post-translational Modifications

Parkinson's disease is characterised by the presence in brain tissue of aberrant inclusions known as Lewy bodies and Lewy neurites, which are deposits composed by α-synuclein and a variety of other cellular components, including in particular lipid membranes. The dysregulation of the balance between lipid homeostasis and α-synuclein homeostasis is therefore likely to be closely involved in the onset and progression of Parkinson's disease and related synucleinopathies. As our understanding of this balance is increasing, we describe recent advances in the characterisation of the role of post-translational modifications in modulating the interactions of α-synuclein with lipid membranes. We then discuss the impact of these advances on the development of novel diagnostic and therapeutic tools for synucleinopathies.

[Development of early diagnosis of Parkinson's disease and comprehensive economic analysis of the effect of its implementation]

The paper summarizes the literature and author's data on the development of early (preclinical) diagnosis of Parkinson's disease (PD). Implementation of this diagnosis will promote the use of preventive therapy and change investments in diagnosis and treatment of patients. The paper declares that at present the only approach to early diagnosis of PD is positron-emission tomography of the nigrostriatal dopaminergic system, but it cannot be used for preventive examination due to its high cost. The authors consider that a less specific, but more promising approach to the development of early diagnosis of PD is the search for markers in body fluids, mainly in the blood, in patients at the prodromal stage of PD. Indeed, a number of markers as changes in the level of metabolites of monoamines, sphingolipids, urates, and indicators of oxidative stress were found in patients selected for the risk group of the prodromal stage of PD, according to characteristic premotor symptoms. In addition, it is assumed that the search for blood markers at an earlier - pre-prodromal stage is possible only in animal models of PD at the early preclinical stage. This approach can also be used to verify blood markers identified in patients at the clinical stage of PD. It is also evident that the complex socio-economic factors influencing the incidence of PD is different in developed versus developing countries. The societal and medical costs of Parkinson's are huge and efforts to improve early preclinical diagnosis of PD will lead to considerable economical and societal benefits. For instance this will allow efficient selection of patients for preclinical diagnostic tests. To assess the effectiveness of this strategy considering the uncertainty of socio-economic issues, a modification of the «cost-utility» analysis is proposed. For the first time, a Markov model of PD including preclinical diagnostic tests and possible neuroprotective therapy was developed and studied. Analytical outcomes of this process suggest that the idea of developing a new multimodal strategy is promising from a socio-economic point of view.

A case-control association of RANTES (-28C >G) and CCR5-Delta32 polymorphisms with Parkinson's disease in Indians

Recent studies have suggested that chemokines and their receptors are involved in several neurodegenerative disorders. Also, numerous lines of evidence have indicated that inflammatory processes are involved in the pathogenesis of Parkinson's disease (PD). We have examined whether single nucleotide polymorphisms at the genes encoding chemokines RANTES (-28 C > G), RANTES (-403 A > G) MCP-1 (-2518 A > G), and chemokine receptors CCR2 (+190 G > A) and CCR5 (-Δ32) were associated with sporadic PD risk in the Indian population. This pilot case-control association study included 97 PD patients and 100 control subjects, who were all genotyped with PCR-RFLP for the five polymorphisms. There was no statistically significant difference in the genotype frequencies between the cases and controls for the MCP1 (-2518 A > G), RANTES (-403 A > G) and CCR2 (+190 G > A) polymorphisms. However, the results revealed a significant difference in the frequency of the heterozygous CG genotype for the RANTES (-28 C > G) polymorphism (OR = 0.49, p = 0.03) between the cases and controls. A negative association was demonstrated in the dominant model where, compared with the GG genotype, a higher frequency of the GC + CC genotype was observed in the controls. Also, a statistically significant higher frequency of the CCR5 heterozygous genotype WT/Δ32 in the controls was observed (OR = 0.31, p = 0.04). Combined genotype analysis revealed that the allele combination of G-A-G-C of CCR2 (+190G > A), MCP-1 (-2518 A/G), RANTES (-403 A/G) and RANTES (-28 C/G) respectively had a risk association with PD (OR = 6.18, p = 0.005).

Development of early diagnosis of Parkinson's disease: Illusion or reality?

The fight against neurodegenerative diseases, Alzheimer disease and Parkinson's disease (PD), is a challenge of the 21st century. The low efficacy of treating patients is due to the late diagnosis and start of therapy, after the degeneration of most specific neurons and depletion of neuroplasticity. It is believed that the development of early diagnosis (ED) and preventive treatment will delay the onset of specific symptoms. This review evaluates methodologies for developing ED of PD. Since PD is a systemic disease, and the degeneration of certain neurons precedes that of nigrostriatal dopaminergic neurons that control motor function, the current methodology is based on searching biomarkers, such as premotor symptoms and changes in body fluids (BF) in patients. However, all attempts to develop ED were unsuccessful. Therefore, it is proposed to enhance the current methodology by (i) selecting among biomarkers found in BF in patients at the clinical stage those that are characteristics of animal models of the preclinical stage, (ii) searching biomarkers in BF in subjects at the prodromal stage, selected by detecting premotor symptoms and failure of the nigrostriatal dopaminergic system. Moreover, a new methodology was proposed for the development of ED of PD using a provocative test, which is successfully used in internal medicine.

Association of Antiviral Therapy With Risk of Parkinson Disease in Patients With Chronic Hepatitis C Virus Infection

Importance

Epidemiologic evidence suggests that hepatitis C virus (HCV) could be a risk factor for Parkinson disease (PD), but treatment for HCV infection has never been considered in these studies; hence, the association between antiviral therapy and PD incidence has remained unclear. Understanding this association may help in developing strategies to reduce PD occurrence.

Objective

To identify the risk of PD development in patients with HCV infection receiving antiviral treatment and in patients not receiving this treatment.

Design, Setting, and Participants

This cohort study obtained claims data from the Taiwan National Health Insurance Research Database. Adult patients with a new HCV diagnosis with or without hepatitis per International Classification of Diseases, Ninth Revision, Clinical Modification codes and anti-PD medications from January 1, 2003, to December 31, 2013, were selected for inclusion. After excluding participants not eligible for analysis, the remaining patients (n = 188 152) were categorized into treated and untreated groups according to whether they received antiviral therapy. Propensity score matching was performed to balance the covariates across groups for comparison of main outcomes. This study was conducted from July 1, 2017, to December 31, 2017.

Main Outcomes and Measures

Development of PD was the main outcome. A Cox proportional hazards regression model was used to compare the risk of PD, and the hazard ratio (HR) was calculated at 1 year, 3 years, and 5 years after the index date and at the end of the cohort.

Results

A total of 188 152 patients were included in the analysis. An equal number (n = 39 936) and comparable characteristics of participants were retained in the treated group (with 17 970 female [45.0%] and a mean [SD] age of 52.8 [11.4] years) and untreated group (with 17 725 female [44.4%] and a mean [SD] age of 52.5 [12.9] years) after matching. The incidence density of PD was 1.00 (95% CI, 0.85-1.15) in the treated group and 1.39 (95% CI, 1.21-1.57) per 1000 person-years in the untreated group. The advantage of antiviral therapy reached statistical significance at the 5-year follow-up (HR, 0.75; 95% CI, 0.59-0.96), and this advantage continued to increase until the end of follow-up (HR, 0.71; 95% CI, 0.58-0.87).

Conclusions and Relevance

Evidence suggested that the PD incidence was lower in patients with chronic HCV infection who received interferon-based antiviral therapy; this finding may support the hypothesis that HCV could be a risk factor for PD.

Lipid and Lipid Raft Alteration in Aging and Neurodegenerative Diseases: A Window for the Development of New Biomarkers

Lipids in the brain are major components playing structural functions as well as physiological roles in nerve cells, such as neural communication, neurogenesis, synaptic transmission, signal transduction, membrane compartmentalization, and regulation of gene expression. Determination of brain lipid composition may provide not only essential information about normal brain functioning, but also about changes with aging and diseases. Indeed, deregulations of specific lipid classes and lipid homeostasis have been demonstrated in neurodegenerative disorders such as Alzheimer's disease (AD) and Parkinson's disease (PD). Furthermore, recent studies have shown that membrane microdomains, named lipid rafts, may change their composition in correlation with neuronal impairment. Lipid rafts are key factors for signaling processes for cellular responses. Lipid alteration in these signaling platforms may correlate with abnormal protein distribution and aggregation, toxic cell signaling, and other neuropathological events related with these diseases. This review highlights the manner lipid changes in lipid rafts may participate in the modulation of neuropathological events related to AD and PD. Understanding and characterizing these changes may contribute to the development of novel and specific diagnostic and prognostic biomarkers in routinely clinical practice.

How important is tryptophan in human health?

Tryptophan (Trp) is an amino acid and an essential component of the human diet. It plays a crucial role in many metabolic functions. Clinicians can use Trp levels in the course of diagnosing various metabolic disorders and the symptoms associated with those diseases. Furthermore, supplementation with this amino acid is considered in the treatment of depression and sleep disorders, mainly due to the Trp relationship with the synthesis of serotonin (5-HT) and melatonin. It is also used in helping to resolve cognitive disorders, anxiety, or neurodegenerative diseases. Reduced secretion of serotonin is associated with autism spectrum disorder, obesity, anorexia and bulimia nervosa, and other diseases presenting peripherals symptoms. The literature strongly suggests that Trp has a significant role in the correct functionality of the brain-gut axis and immunology. This information leads to the consideration of Trp as an essential dietary component due to its role in the serotonin pathway. A reduced availability of Trp in diet and nutraceutical supplementation should be considered with greater concern than one might expect. This paper constitutes a review of the more salient aspects gleaned from the current knowledge base about the role of Trp in diseases, associated nutritional disorders, and food science, in general.

Proteomic studies associated with Parkinson's disease

INTRODUCTION

Parkinson's disease (PD) is an insidious disorder affecting more than 1-2% of the population over the age of 65. Understanding the etiology of PD may create opportunities for developing new treatments. Genomic and transcriptomic studies are useful, but do not provide evidence for the actual status of the disease. Conversely, proteomic studies deal with proteins, which are real time players, and can hence provide information on the dynamic nature of the affected cells. The number of publications relating to the proteomics of PD is vast. Therefore, there is a need to evaluate the current proteomics literature and establish the connections between the past and the present to foresee the future. Areas covered: PubMed and Web of Science were used to retrieve the literature associated with PD proteomics. Studies using human samples, model organisms and cell lines were selected and reviewed to highlight their contributions to PD. Expert commentary: The proteomic studies associated with PD achieved only limited success in facilitating disease diagnosis, monitoring and progression. A global system biology approach using new models is needed. Future research should integrate the findings of proteomics with other omics data to facilitate both early diagnosis and the treatment of PD.

Cerebrospinal fluid biomarkers for Parkinson's disease - a systematic review

Diagnosis of Parkinson's disease (PD) relies on clinical history and physical examination, but misdiagnosis is common in early stages. Identification of biomarkers for PD may allow early and more precise diagnosis and monitoring of dopamine replacement strategies and disease modifying treatments. Developments in analytical chemistry allow the detection of large numbers of molecules in plasma or cerebrospinal fluid, associated with the pathophysiology or pathogenesis of PD. This systematic review includes cerebrospinal fluid biomarker studies focusing on different disease pathways: oxidative stress, neuroinflammation, lysosomal dysfunction and proteins involved in PD and other neurodegenerative disorders, focusing on four clinical domains: their ability to (1) distinguish PD from healthy subjects and other neurodegenerative disorders as well as their relation to (2) disease duration after initial diagnosis, (3) severity of disease (motor symptoms) and (4) cognitive dysfunction. Oligomeric alpha-synuclein might be helpful in the separation of PD from controls. Through metabolomics, changes in purine and tryptophan metabolism have been discovered in patients with PD. Neurofilament light chain (NfL) has a significant role in distinguishing PD from other neurodegenerative diseases. Several oxidative stress markers are related to disease severity, with the antioxidant urate also having a prognostic value in terms of disease severity. Increased levels of amyloid and tau-proteins correlate with cognitive decline and may have prognostic value for cognitive deficits in PD. In the future, larger longitudinal studies, corroborating previous research on viable biomarker candidates or using metabolomics identifying a vast amount of potential biomarkers, could be a good approach.

The Concept of Prodromal Parkinson's Disease

Parkinson’s disease (PD) is currently clinically defined by a set of cardinal motor features centred on the presence of bradykinesia and at least one additional motor symptom out of tremor, rigidity or postural instability. However, converging evidence from clinical, neuropathological, and imaging research suggests initiation of PD-specific pathology prior to appearance of these classical motor signs. This latent phase of neurodegeneration in PD is of particular relevance in relation to the development of disease-modifying or neuroprotective therapies which would require intervention at the earliest stages of disease. A key challenge in PD research, therefore, is to identify and validate markers for the preclinical and prodromal stages of the illness. Currently, several nonmotor symptoms have been associated with an increased risk to develop PD in otherwise healthy individuals and ongoing research is aimed at validating a variety of candidate PD biomarkers based on imaging, genetic, proteomic, or metabolomic signatures, supplemented by work on tissue markers accessible to minimally invasive biopsies. In fact, the recently defined MDS research criteria for prodromal PD have included combinations of risk and prodromal markers allowing to define target populations of future disease modification trials.

Recent developments in biomarkers in Parkinson disease

PURPOSE OF REVIEW

Parkinson disease is the second most common neurodegenerative disease after Alzheimer disease, and current demographic trends indicate a life-time risk approaching 4% and predict a doubling of prevalence by 2030. Strategies are being developed to apply recent advances in our understanding of the cause of Parkinson disease to the development of biomarkers that will enable the identification of at-risk individuals, enable early diagnosis and reflect the progression of disease. The latter will be particularly important for the testing of disease-modifying therapies. This review summarizes recent advances in Parkinson disease biomarker development.

RECENT FINDINGS

Recent reports continue to reflect the application of a variety of clinical, imaging or biochemical measurements, alone or in combination, to general Parkinson disease populations. Probably the most promising is the assay of alpha-synuclein in the diagnosis and evolution of Parkinson disease. At present, detection techniques are still being refined, but once accurate and reproducible assays are available, it will be important to define the relationship of these to early diagnosis and progression. Alpha-synuclein concentrations may also be modulated by certain disease-modifying agents in development and so may represent a measure of their efficacy. It has to be accepted that no single measure currently fulfils all the necessary criteria for a biomarker in Parkinson disease, but combinations of measures are more likely to deliver benefit.

SUMMARY

The Parkinson disease biomarker field is approaching a stage when certain combinations of clinical, imaging and biochemical measures may identify a proportion of individuals at risk for developing the disease. However, their general applicability may be limited. Attention is now turning to stratification of Parkinson disease into certain at-risk groups defined by genotype. The application of multimodal screening to these populations may be more rewarding in the short term.

Lipid raft disarrangement as a result of neuropathological progresses: a novel strategy for early diagnosis?

Lipid rafts are the preferential site of numerous membrane signaling proteins which are involved in neuronal functioning and survival. These proteins are organized in multiprotein complexes, or signalosomes, in close contact with lipid classes particularly represented in lipid rafts (i.e. cholesterol, sphingolipids and saturated fatty acids), which may contribute to physiological responses leading to neuroprotection. Increasing evidence indicates that alteration of lipid composition in raft structures as a consequence of neuropathologies, such as Alzheimer's disease (AD) and Parkinson's disease (PD), causes a dramatic increase in lipid raft order. These phenomena may correlate with perturbation of signalosome activities, likely contributing to neurodegenerative progression. Interestingly, significant disruption of stable raft microenvironments has been already observed in the first stages of either AD or PD, suggesting that these alterations may represent early events in the neuropathological development. In this regard, the search for biochemical markers, such as specific metabolic products altered in the brain at the first steps of the disease, presently represents an important challenge for early diagnostic strategies. Alterations of these biomarkers may be reflected in either plasma or cerebrospinal fluid, thus representing a potential strategy to predict an accurate diagnosis. We propose that pathologically-linked lipid raft markers may be interesting candidates to be explored at this level, although it has not been studied so far to what extent alteration of different signalosome components may be reflected in peripheral fluids. In this mini-review, we will discuss on relevant aspects of lipid rafts that contribute to the modulation of neuropathological events related to AD and PD. An interesting hypothesis is that anomalies on raft biomarkers measured at peripheral fluids might mirror the lipid raft pathology observed in early stages of AD and PD.

Cerebrospinal fluid biomarkers in Parkinson disease

Clinical diagnosis of Parkinson disease (PD) is difficult in early stages of disease, with high risk of misdiagnosis. The long preclinical phase of PD provides the possibility for early therapeutic intervention once disease-modifying therapies have been developed, but lack of biomarkers for early diagnosis and monitoring of disease progression represents a major obstacle to achievement of this goal. Accordingly, research efforts aimed at identification of novel biomarkers have been increasing in the past 5 years. Cerebrospinal fluid (CSF) is an accessible source of brain-derived proteins, which mirror molecular changes that take place in the CNS. In this Review, we discuss evidence from numerous studies that have focused on identification of candidate CSF biomarkers for PD. Notably, molecular pathways related to α-synuclein, tau and β-amyloid peptides have received considerable attention. CSF levels of the protein DJ-1 are also of interest, although further investigation of this candidate marker is required. These studies support the usefulness of a combination of various CSF biomarkers of PD to increase diagnostic accuracy during early phases of the disease, and to differentiate PD from other neurodegenerative disorders.

Defining premotor Parkinson’s disease: a window of opportunity for neuroprotection?

SUMMARY The diagnosis of Parkinson’s disease (PD) is based on clinical grounds alone and requires the presence of bradykinesia and at least one further motor symptom out of tremor, rigidity or postural instability. Nevertheless, a variety of non-motor symptoms are an integral part of the clinical spectrum of the disease and may even be present before the first appearance of classical motor signs. The ultimate goal of any neuroprotective therapy will be to delay or prevent the onset of clinical disease. The current challenge is, therefore, to identify markers that would allow earlier diagnosis during the premotor stages of PD. The present review discusses potential markers of premotor PD including non-motor symptoms, neuroimaging, genetic susceptibility factors and molecular biomarkers. With the aid of such biomarkers, PD risk cohorts may eventually become sufficiently well defined to allow for ‘neuroprevention’ trials using rates of conversion to motor PD as a primary end point.

Cerebrospinal fluid biomarker candidates for parkinsonian disorders

The Parkinsonian disorders are a large group of neurodegenerative diseases including idiopathic Parkinson’s disease (PD) and atypical Parkinsonian disorders (APD), such as multiple system atrophy, progressive supranuclear palsy, corticobasal degeneration, and dementia with Lewy bodies. The etiology of these disorders is not known although it is considered to be a combination of genetic and environmental factors. One of the greatest obstacles for developing efficacious disease-modifying treatment strategies is the lack of biomarkers. Reliable biomarkers are needed for early and accurate diagnosis, to measure disease progression, and response to therapy. In this review several of the most promising cerebrospinal biomarker candidates are discussed. Alpha-synuclein seems to be intimately involved in the pathogenesis of synucleinopathies and its levels can be measured in the cerebrospinal fluid and in plasma. In a similar way, tau protein accumulation seems to be involved in the pathogenesis of tauopathies. Urate, a potent antioxidant, seems to be associated to the risk of developing PD and with its progression. Neurofilament light chain levels are increased in APD compared with PD and healthy controls. The new “omics” techniques are potent tools offering new insights in the patho-etiology of these disorders. Some of the difficulties encountered in developing biomarkers are discussed together with future perspectives.