Network analysis identifies SOD2 mRNA as a potential biomarker for Parkinson's disease

Toxicogenomic analysis of physiologically important metals: An integrated in silico approach

Biologically important metals regulate cellular homeostasis in living systems. Anthropogenic exposure to these metals can cause adverse effects, including an increased incidence of diseases in humans such as cancer, lung, and cardiovascular defects. However, the effects of metals and the common genes/signaling pathways involved in metal toxicity have not been elucidated. Hence, the present study used toxicogenomic data mining with the comparative toxicogenomics database to explore the impact of these metals. The metals were categorized into transition, alkali, and alkali earth. The common genes were identified and subjected to functional enrichment analysis. Further, gene-gene and protein-protein interactions were assessed. Also, the top ten transcription factors and miRNAs that regulate the genes were identified. The phenotypes and diseases that have increased incidence upon alterations of these genes were detected. Overall, we were able to identify IL1B and SOD2 as the common genes, along with the AGE-RAGE signaling pathway in diabetic complications as the common pathway altered. Enriched genes and pathways specific to each metal category were also found. Further, we identified heart failure as the major diseases that have increased the incidence of these metals' exposure. In conclusion, exposure to essential metals might cause adverse effects via inflammation and oxidative stress.

Insights into Manganese Superoxide Dismutase and Human Diseases

Redox equilibria and the modulation of redox signalling play crucial roles in physiological processes. Overproduction of reactive oxygen species (ROS) disrupts the body's antioxidant defence, compromising redox homeostasis and increasing oxidative stress, leading to the development of several diseases. Manganese superoxide dismutase (MnSOD) is a principal antioxidant enzyme that protects cells from oxidative damage by converting superoxide anion radicals to hydrogen peroxide and oxygen in mitochondria. Systematic studies have demonstrated that MnSOD plays an indispensable role in multiple diseases. This review focuses on preclinical evidence that describes the mechanisms of MnSOD in diseases accompanied with an imbalanced redox status, including fibrotic diseases, inflammation, diabetes, vascular diseases, neurodegenerative diseases, and cancer. The potential therapeutic effects of MnSOD activators and MnSOD mimetics are also discussed. Targeting this specific superoxide anion radical scavenger may be a clinically beneficial strategy, and understanding the therapeutic role of MnSOD may provide a positive insight into preventing and treating related diseases.

Development of Halogenated-Chalcones Bearing with Dimethoxy Phenyl Head as Monoamine Oxidase-B Inhibitors

Two series of dimethoxy-halogenated chalcones (DM1−DM20) were synthesized and tested for their ability to inhibit monoamine oxidase (MAOs). Compound DM2 exhibited the most significant inhibition against MAO-B with an IC50 value of 0.067 µM, followed by compound DM18 (IC50 = 0.118 µM), with selectivity index (SI) values of 93.88 and >338.98, respectively. However, none of the substances successfully inhibited MAO-A. The MAO-B inhibitors DM2 and DM18 were competitive and reversible, with Ki values of 0.032 ± 0.004 and 0.045 ± 0.001 µM, respectively. DM2 was non-toxic below 100 µg/mL in the cytotoxic test using the Vero epithelial cell line by the MTT method. According to molecular docking studies, DM2 and DM18 formed very similar conformations within the MAO-B binding pocket, with the ortho-chlorine and ortho-fluorine aromatic rings sandwiched between F168 and Y326. These conformations were predicted to show better interactions with the targeted MAO-B than MAO-A. In particular, the induced-fit docking of the dimethoxy phenyl ring of DM2 facing the hydrophobic pocket made up of FAD, Y398, and Y435 had an impact on F168 in the docking pocket. Taken together, DM2 and DM18 may be suitable candidates for treating neurodegenerative conditions such as Parkinson’s disease.

hsa-miR-518-5p/hsa-miR-3135b Regulates the REL/SOD2 Pathway in Ischemic Cerebral Infarction

Objectives

Ischemic cerebral infarction (ICI) is a fatal neurovascular disorder. A bioinformatics approach based on single-cell and bulk RNA-seq analyses was applied to investigate the pathways and genes involved in ICI and study the expression profile of these genes.

Methods

First, the aberrantly regulated “small-molecule ribonucleic acids” [microRNA (miRNAs)] and messenger RNAs (mRNAs) were analyzed using transcriptome data from the ischemic brain infarction dataset of the Gene Expression Omnibus (GEO) database. In mouse cerebrovascular monocytes, the single-cell regulatory network inference and clustering (SCENIC) workflow was used to identify key transcription factors (TFs). Then, the two miRNA-TF-mRNA interaction networks were constructed. Moreover, the molecular complex detection (MCODE) extracted the core sub-networks and identified the important TFs within these sub-networks. Finally, whole blood samples were collected for validation of the expression of critical molecules in ICI.

Results

We identified four cell types and 266 regulons in mouse cerebrovascular monocytes using SCENIC analysis. Moreover, 112 differently expressed miRNAs and 3,780 differentially expressed mRNAs were identified. We discovered potential biomarkers in ICI by building a miRNA-TF-mRNA interaction network. The hsa-miR-518-5p/hsa-miR-3135b/REL/SOD2 was found to play a potential role in ICI progression. The expression of REL and superoxide dismutase 2 (SOD2) was significantly elevated in the ICI group in the clinical cohort (P < 0.05). Furthermore, a REL expression was elevated in endothelial cells and fibroblasts at the single-cell level, indicating that REL is a cell-specific regulon. Functional enrichment analyses revealed that REL is primarily engaged in neurotransmitter activity and oxidative phosphorylation.

Conclusions

Our research uncovered novel biomarkers for ICI of neurovascular disease. The hsa-miR-518-5p/hsa-miR-3135b may regulate the REL/SOD2 pathway in ICI progression.

Analysis of a precision medicine approach to treating Parkinson's disease: Analysis of the DATATOP study

INTRODUCTION

The aim of this study was to examine the potential application of a targeted proteomic predictive biomarker comprised predominantly of inflammatory proteins in distinguishing those who responded to a previously conducted clinical trial for Parkinson's disease (PD).

METHODS

Plasma samples obtained from a biorepository were assayed from a total of n = 520 DATATOP (Deprenyl And Tocopherol Antioxidative Therapy Of Parkinsonism) clinical trial participants across treatment arms. Support vector machine analyses were conducted to distinguish responder status on primary (need for Levodopa) and secondary trial endpoints (UPDRS Motor and Total Scores).

RESULTS

For the α-tocopherol and deprenyl placebo treatment arm (TOC), the targeted proteomic biomarker was able to distinguish responder status with an accuracy (area under the curve [AUC]) of 91% for the primary endpoint while it was 100% across secondary endpoints. For the deprenyl and α-tocopherol placebo treatment arm (DEP), the AUC was 93% for the primary endpoint and 99-100% for the secondary endpoints. For the combined treatment arm, AUC was 87% for the primary and 94-96% for the secondary endpoints.

DISCUSSION

The targeted proteomic predictive biomarker was highly accurate in distinguishing responder status across treatment arms thereby supporting the application of a precision medicine approach to treating PD.

S-Carboxymethyl Cysteine Protects against Oxidative Stress and Mitochondrial Impairment in a Parkinson's Disease In Vitro Model

The mucolytic agent S-carboxymethylcysteine is widely used as an expectorant for the treatment of numerous respiratory disorders. The metabolic fate of S-carboxymethyl-L-cysteine is complex. Several clinical studies have demonstrated that the metabolism of this agent differs within the same individual, with sulfur oxygenated metabolites generated upon night-time administration. It has been indicated that this drug behaves like a free radical scavenger and that, in this regard, the sulfide is the active species with sulphoxide metabolites (already oxidized) being inactive. Consequently, a night-time consumption of the drug should be more effective upon daytime administration. Still, this diurnal variation in biotransformation (deactivation) is dependent on the genetic polymorphism on which relies the patient population capacities of S-carboxymethyl-L-cysteine sulphoxidation. It has been reported that those cohorts who are efficient sulfur oxidizers will generate inactive oxygenated metabolites. In contrast, those who have a relative deficiency in this mechanism will be subjected to the active sulfide for a more extended period. In this regard, it is noteworthy that 38–39% of Parkinson’s disease patients belong to the poor sulphoxide cohort, being exposed to higher levels of active sulfide, the active antioxidant metabolite of S-carboxymethyl-L-cysteine. Parkinson’s disease is a neurodegenerative disorder that affects predominately dopaminergic neurons. It has been demonstrated that oxidative stress and mitochondrial dysfunction play a crucial role in the degeneration of dopaminergic neurons. Based on this evidence, in this study, we evaluated the effects of S-carboxymethyl cysteine in an in vitro model of Parkinson’s disease in protecting against oxidative stress injury. The data obtained suggested that an S-carboxymethylcysteine-enriched diet could be beneficial during aging to protect neurons from oxidative imbalance and mitochondrial dysfunction, thus preventing the progression of neurodegenerative processes.

Assessment of the Telomere Length and Its Effect on the Symptomatology of Parkinson's Disease

Telomeres, which are repetitive sequences that cap the end of the chromosomes, shorten with each cell division. Besides cellular aging, there are several other factors that influence telomere length (TL), in particular, oxidative stress and inflammation, which play an important role in the pathogenesis of neurodegenerative brain diseases including Parkinson’s disease (PD). So far, the majority of studies have not demonstrated a significant difference in TL between PD patients and healthy individuals. However, studies investigating the effect of TL on the symptomatology and disease progression of PD are scarce, and thus, warranted. We analyzed TL of peripheral blood cells in a sample of 204 PD patients without concomitant autoimmune diseases and analyzed its association with several PD related phenotypes. Monochrome multiplex quantitative PCR (mmqPCR) was used to determine relative TL given as a ratio of the amount of DNA between the telomere and albumin as the housekeeping gene. We found a significant difference in the relative TL between PD patients with and without dementia, where shorter TL presented higher risk for dementia (p = 0.024). However, the correlation was not significant after adjustment for clinical factors (p = 0.509). We found no correlations between TLs and the dose of dopaminergic therapy when the analysis was adjusted for genetic variability in inflammatory or oxidative factors. In addition, TL influenced time to onset of motor complications after levodopa treatment initiation (p = 0.0134), but the association did not remain significant after adjustment for age at inclusion and disease duration (p = 0.0781). Based on the results of our study we conclude that TL contributes to certain PD-related phenotypes, although it may not have a major role in directing the course of the disease. Nevertheless, this expends currently limited knowledge regarding the association of the telomere attrition and the disease severity or motor complications in Parkinson’s disease.

Analysis of the Relationship between Type II Diabetes Mellitus and Parkinson's Disease: A Systematic Review

In the early sixties, a discussion started regarding the association between Parkinson's disease (PD) and type II diabetes mellitus (T2DM). Today, this potential relationship is still a matter of debate. This review aims to analyze both diseases concerning causal relationships and treatments. A total of 104 articles were found, and studies on animal and “in vitro” models showed that T2DM causes neurological alterations that may be associated with PD, such as deregulation of the dopaminergic system, a decrease in the expression of peroxisome proliferator-activated receptor-gamma coactivator-1α (PGC-1α), an increase in the expression of phosphoprotein enriched in diabetes/phosphoprotein enriched in astrocytes 15 (PED/PEA-15), and neuroinflammation, as well as acceleration of the formation of alpha-synuclein amyloid fibrils. In addition, clinical studies described that Parkinson's symptoms were notably worse after the onset of T2DM, and seven deregulated genes were identified in the DNA of T2DM and PD patients. Regarding treatment, the action of antidiabetic drugs, especially incretin mimetic agents, seems to confer certain degree of neuroprotection to PD patients. In conclusion, the available evidence on the interaction between T2DM and PD justifies more robust clinical trials exploring this interaction especially the clinical management of patients with both conditions.

Environmental Assessment and Evaluation of Oxidative Stress and Genotoxicity Biomarkers Related to Chronic Occupational Exposure to Benzene

Environmental and occupational exposure to benzene from fuels is a major cause for concern for national and international authorities, as benzene is a known carcinogen in humans and there is no safe limit for exposure to carcinogens. The objective of this study was to evaluate the genotoxic effects of chronic occupational exposure to benzene among two groups of workers: filling station workers (Group I) and security guards working at vehicles entrances (Group II), both on the same busy highway in Rio de Janeiro, Brazil. Sociodemographic data on the workers were evaluated; the concentration of benzene/toluene (B/T) in atmospheric air and individual trans,trans-muconic acid (ttMA) and S-phenylmercapturic acid (S-PMA) were measured; oxidative stress was analyzed by catalase (CAT), glutathione S-transferase (GST), superoxide dismutase (SOD), thiol groups (THIOL) and malondialdehyde (MDA); genotoxicity was measured by metaphases with chromosomal abnormalities (MCA) and nuclear abnormalities, comet assay using the enzyme formamidopyrimidine DNA glycosylase (C-FPG), and methylation of repetitive element LINE-1, CDKN2B and KLF6 genes. Eighty-six workers participated: 51 from Group I and 35 from Group II. The B/T ratio was similar for both groups, but Group I had greater oscillation of benzene concentrations because of their work activities. No differences in ttMA and S-PMA, and no clinical changes were found between both groups, but linearity was observed between leukocyte count and ttMA; and 15% of workers had leukocyte counts less than 4.5 × 10⁹ cells L^-1, demanding close worker's attention. No differences were observed between the two groups for THIOL, MDA, MCA, or nuclear abnormalities. A multiple linear relationship was obtained for the biomarkers MCA and C-FPG. A significant correlation was found between length of time in current job and the biomarkers C-FPG, MCA, GST, and MDA. Although both populations had chronic exposure to benzene, the filling station workers were exposed to higher concentrations of benzene during their work activities, indicating an increased risk of DNA damage.

Clinical-Pharmacogenetic Predictive Models for Time to Occurrence of Levodopa Related Motor Complications in Parkinson's Disease

The response to dopaminergic treatment in Parkinson's disease depends on many clinical and genetic factors. The very common motor fluctuations (MF) and dyskinesia affect approximately half of patients after 5 years of treatment with levodopa. We did an evaluation of a combined effect of 16 clinical parameters and 34 single nucleotide polymorphisms to build clinical and clinical-pharmacogenetic models for prediction of time to occurrence of motor complications and to compare their predictive abilities. In total, 220 Parkinson's disease patients were included in the analysis. Their demographic, clinical, and genotype data were obtained. The combined effect of clinical and genetic factors was assessed using The Least Absolute Shrinkage and Selection Operator penalized regression in the Cox proportional hazards model. Clinical and clinical-pharmacogenetic models were constructed. The predictive capacity of the models was evaluated with the cross-validated area under time-dependent receiver operating characteristic curve. Clinical-pharmacogenetic model included age at diagnosis (HR = 0.99), time from diagnosis to initiation of levodopa treatment (HR = 1.24), COMT rs165815 (HR = 0.90), DRD3 rs6280 (HR = 1.03), and BIRC5 rs9904341 (HR = 0.95) as predictive factors for time to occurrence of MF. Furthermore, clinical-pharmacogenetic model for prediction of time to occurrence of dyskinesia included female sex (HR = 1.07), age at diagnosis (HR = 0.97), tremor-predominant Parkinson's disease (HR = 0.88), beta-blockers (HR = 0.95), alcohol consumption (HR = 0.99), time from diagnosis to initiation of levodopa treatment (HR = 1.15), CAT rs1001179 (HR = 1.27), SOD2 rs4880 (HR = 0.95), NOS1 rs2293054 (HR = 0.99), COMT rs165815 (HR = 0.92), and SLC22A1 rs628031 (HR = 0.80). Areas under the curves for clinical and clinical-pharmacogenetic models for MF after 5 years of levodopa treatment were 0.68 and 0.70, respectively. Areas under the curves for clinical and clinical-pharmacogenetic models for dyskinesia after 5 years of levodopa treatment were 0.71 and 0.68, respectively. These results show that clinical-pharmacogenetic models do not have better ability to predict time to occurrence of motor complications in comparison to the clinical ones despite the significance of several polymorphisms. Models could be improved by a larger sample size and by additional polymorphisms, epigenetic predictors or serum biomarkers.

Evaluation of RNA Blood Biomarkers in the Parkinson's Disease Biomarkers Program

There is a high misdiagnosis rate between Parkinson’s disease (PD) and atypical parkinsonian disorders (APD), such as progressive supranuclear palsy (PSP), the second most common parkinsonian syndrome. In our earlier studies, we identified and replicated RNA blood biomarkers in several independent cohorts, however, replication in a cohort that includes PSP patients has not yet been performed. To this end, we evaluated the diagnostic potential of nine previously identified RNA biomarkers using quantitative PCR assays in 138 blood samples at baseline from PD, PSP and healthy controls (HCs) nested in the PD Biomarkers Program. Linear discriminant analysis showed that COPZ1 and PTPN1 distinguished PD from PSP patients with 62.5% accuracy. Five biomarkers, PTPN1, COPZ1, FAXDC2, SLC14A1s and NAMPT were useful for distinguishing PSP from controls with 69% accuracy. Several biomarkers correlated with clinical features in PD patients. SLC14A1-s correlated with Unified Parkinson’s Disease Rating Scale total and part III scores. In addition, COPZ1, PTPN1 and MLST8, correlated with Montreal Cognitive Assessment (MoCA). Interestingly, COPZ1, EFTUD2 and PTPN1 were downregulated in cognitively impaired (CI) compared to normal subjects. Linear discriminant analysis showed that age, PTPN1, COPZ1, FAXDC2, EFTUD2 and MLST8 distinguished CI from normal subjects with 65.9% accuracy. These results suggest that COPZ1 and PTPN1 are useful for distinguishing PD from PSP patients. In addition, the combination of PTPN1, COPZ1, FAXDC2, EFTUD2 and MLST8 is a useful signature for cognitive impairment. Evaluation of these biomarkers in a larger study will be a key to advancing these biomarkers into the clinic.

Biological and Clinical Implications of Comorbidities in Parkinson's Disease

A wide spectrum of comorbidities has been associated with Parkinson's disease (PD), a progressive neurodegenerative disease that affects more than seven million people worldwide. Emerging evidence indicates that chronic diseases including diabetes, depression, anemia and cancer may be implicated in the pathogenesis and progression of PD. Recent epidemiological studies suggest that some of these comorbidities may increase the risk of PD and precede the onset of motor symptoms. Further, drugs to treat diabetes and cancer have elicited neuroprotective effects in PD models. Nonetheless, the mechanisms underlying the occurrence of these comorbidities remain elusive. Herein, we discuss the biological and clinical implications of comorbidities in the pathogenesis, progression, and clinical management, with an emphasis on personalized medicine applications for PD.

Individual Amino Acid Supplementation Can Improve Energy Metabolism and Decrease ROS Production in Neuronal Cells Overexpressing Alpha-Synuclein

Parkinson's disease (PD) is a neurodegenerative disorder characterized by alpha-synuclein accumulation and loss of dopaminergic neurons in the substantia nigra (SN) region of the brain. Increased levels of alpha-synuclein have been shown to result in loss of mitochondrial electron transport chain complex I activity leading to increased reactive oxygen species (ROS) production. WT alpha-synuclein was stably overexpressed in human BE(2)-M17 neuroblastoma cells resulting in increased levels of an alpha-synuclein multimer, but no increase in alpha-synuclein monomer levels. Oxygen consumption was decreased by alpha-synuclein overexpression, but ATP levels did not decrease and ROS levels did not increase. Treatment with ferrous sulfate, a ROS generator, resulted in decreased oxygen consumption in both control and alpha-synuclein overexpressing cells. However, this treatment only decreased ATP levels and increased ROS production in the cells overexpressing alpha-synuclein. Similarly, paraquat, another ROS generator, decreased ATP levels in the alpha-synuclein overexpressing cells, but not in the control cells, further demonstrating how alpha-synuclein sensitized the cells to oxidative insult. Proteomic analysis yielded molecular insights into the cellular adaptations to alpha-synuclein overexpression, such as the increased abundance of many mitochondrial proteins. Many amino acids and citric acid cycle intermediates and their ester forms were individually supplemented to the cells with L-serine, L-proline, L-aspartate, or L-glutamine decreasing ROS production in oxidatively stressed alpha-synuclein overexpressing cells, while diethyl oxaloacetate or L-valine supplementation increased ATP levels. These results suggest that dietary supplementation with individual metabolites could yield bioenergetic improvements in PD patients to delay loss of dopaminergic neurons.

Dissecting the Molecular Mechanisms of Neurodegenerative Diseases through Network Biology

Neurodegenerative diseases are rarely caused by a mutation in a single gene but rather influenced by a combination of genetic, epigenetic and environmental factors. Emerging high-throughput technologies such as RNA sequencing have been instrumental in deciphering the molecular landscape of neurodegenerative diseases, however, the interpretation of such large amounts of data remains a challenge. Network biology has become a powerful platform to integrate multiple omics data to comprehensively explore the molecular networks in the context of health and disease. In this review article, we highlight recent advances in network biology approaches with an emphasis in brain-networks that have provided insights into the molecular mechanisms leading to the most prevalent neurodegenerative diseases including Alzheimer’s (AD), Parkinson’s (PD) and Huntington’s diseases (HD). We discuss how integrative approaches using multi-omics data from different tissues have been valuable for identifying biomarkers and therapeutic targets. In addition, we discuss the challenges the field of network medicine faces toward the translation of network-based findings into clinically actionable tools for personalized medicine applications.

Evaluation of RNA Blood Biomarkers in Individuals at Risk of Parkinson's Disease

BACKGROUND

Substantial progress has been made in the discovery of blood biomarkers for Parkinson's disease (PD), a progressive neurodegenerative disease that affects more than 4 million worldwide. Olfactory dysfunction and dopamine deficits usually precede motor symptoms years before the onset of PD. A readily accessible biomarker useful for identifying patients at risk of PD is expected to accelerate clinical trials.

OBJECTIVE

To evaluate previously identified PD blood RNA biomarkers in a cohort of asymptomatic individuals at risk of PD.

METHODS

Here we tested 16 previously identified PD RNA biomarkers using quantitative PCR assays in a total of 269 blood samples at baseline from hyposmic and normosmic participants enrolled in the Parkinson's Associated Risk Syndrome study.

RESULTS

Expression levels of four biomarkers, SOD2, PKM2, ZNF134, and ZNF160 were negatively correlated with the total Unified Parkinson's Disease Rating Scale, thus suggesting these biomarkers may be useful to stratify patients prior to the onset of motor symptoms. Levels of SOD2 were upregulated in hyposmic males compared to females, whereas levels of PKM2 were upregulated in hyposmic males compared to normosmic males and hyposmic females. Further, levels of SOD2 were upregulated in males with abnormal dopamine transporter (DAT) scans compared to females with abnormal DAT scans.

CONCLUSIONS

These results suggest that some of these biomarkers may be useful for stratification of individuals at risk for PD and that there may be sex differences in the expression of some biomarkers. Future studies in larger longitudinal studies will be key to assessing the validity of these findings.

Recent developments in circulating biomarkers in Parkinson’s disease: the potential use of miRNAs in a clinical setting

Parkinson’s disease (PD) is the second most common neurodegenerative disorder, affecting 5% of the elderly population. PD diagnosis is still based on the identification of neuromotor symptoms although nonmotor manifestations emerge years prior to diagnosis. The discovery of biomarkers at the earliest stages of PD is of extreme interest. miRNAs have been considered potential biomarkers for neurodegenerative diseases, but only a limited number have been found to be PD related. This review focuses on the current findings in the field of circulating miRNAs in PD and the challenges surrounding clinical utility and validation. We briefly describe the more established circulating biomarkers in PD and provide a more thorough review of miRNAs differentially expressed in PD. We highlight their potential for being considered as biomarkers for diagnosis while emphasizing the challenges for adequate validation of the findings and how miRNAs can be envisioned in a clinical setting satisfying regulatory bodies.

Integrative transcriptomic meta-analysis of Parkinson's disease and depression identifies NAMPT as a potential blood biomarker for de novo Parkinson's disease

Emerging research indicates that depression could be one of the earliest prodromal symptoms or risk factors associated with the pathogenesis of Parkinson’s disease (PD), the second most common neurodegenerative disorder worldwide, but the mechanisms underlying the association between both diseases remains unknown. Understanding the molecular networks linking these diseases could facilitate the discovery of novel diagnostic and therapeutics. Transcriptomic meta-analysis and network analysis of blood microarrays from untreated patients with PD and depression identified genes enriched in pathways related to the immune system, metabolism of lipids, glucose, fatty acids, nicotinamide, lysosome, insulin signaling and type 1 diabetes. Nicotinamide phosphoribosyltransferase (NAMPT), an adipokine that plays a role in lipid and glucose metabolism, was identified as the most significant dysregulated gene. Relative abundance of NAMPT was upregulated in blood of 99 early stage and drug-naïve PD patients compared to 101 healthy controls (HC) nested in the cross-sectional Parkinson’s Progression Markers Initiative (PPMI). Thus, here we demonstrate that shared molecular networks between PD and depression provide an additional source of biologically relevant biomarkers. Evaluation of NAMPT in a larger prospective longitudinal study including samples from other neurodegenerative diseases, and patients at risk of PD is warranted.

Parkinson's disease between internal medicine and neurology

General medical problems and complications have a major impact on the quality of life in all stages of Parkinson's disease. To introduce an effective treatment, a comprehensive analysis of the various clinical symptoms must be undertaken. One must distinguish between (1) diseases which arise independently of Parkinson's disease, and (2) diseases which are a direct or indirect consequence of Parkinson's disease. Medical comorbidity may induce additional limitations to physical strength and coping strategies, and may thus restrict the efficacy of the physical therapy which is essential for treating hypokinetic-rigid symptoms. In selecting the appropriate medication for the treatment of any additional medical symptoms, which may arise, its limitations, contraindications and interactions with dopaminergic substances have to be taken into consideration. General medical symptoms and organ manifestations may also arise as a direct consequence of the autonomic dysfunction associated with Parkinson's disease. As the disease progresses, additional non-parkinsonian symptoms can be of concern. Furthermore, the side effects of Parkinson medications may necessitate the involvement of other medical specialists. In this review, we will discuss the various general medical aspects of Parkinson's disease.

Blood Biomarkers Associated with Cognitive Decline in Early Stage and Drug-Naive Parkinson's Disease Patients

Early diagnosis of Parkinson's disease (PD) continues to be a major challenge in the field. The lack of a robust biomarker to detect early stage PD patients has considerably slowed the progress toward the development of potential therapeutic agents. We have previously evaluated several RNA biomarkers in whole blood from participants enrolled in two independent clinical studies. In these studies, PD patients were medicated, thus, expression of these biomarkers in de novo patients remains unknown. To this end, we tested ten RNA biomarkers in blood samples from 99 untreated PD patients and 101 HC nested in the cross-sectional Parkinson's Progression Markers Initiative by quantitative real-time PCR. One biomarker out of ten, COPZ1 trended toward significance (nominal p = 0.009) when adjusting for age, sex, and educational level. Further, COPZ1, EFTUD2 and PTBP1 mRNAs correlated with clinical features in PD patients including the Hoehn and Yahr scale, Movement Disorder Society revision of Unified Parkinson's Disease Rating Scale (MDS-UPDRS) and Montreal Cognitive Assessment (MoCA) score. Levels of EFTUD2 and PTBP1 were significantly higher in cognitively normal PD patients (PD-CN) compared to cognitively impaired PD patients (PD-MCI). Interestingly, blood glucose levels were significantly higher in PD and PD-MCI patients (≥ 100 mg/dL, pre-diabetes) compared to HC. Collectively, we report the association of three RNA biomarkers, COPZ1, EFTUD2 and PTBP1 with clinical features including cognitive decline in early drug-naïve PD patients. Further, our results show that drug-naïve PD and PD-MCI patients have glucose levels characteristic of pre-diabetes patients, suggesting that impaired glucose metabolism is an early event in PD. Evaluation of these potential biomarkers in a larger longitudinal study is warranted.

Potential Biomarkers of the Earliest Clinical Stages of Parkinson's Disease

Parkinson's disease (PD) is a widespread neurodegenerative disorder. Despite the intensive studies of this pathology, in general, the picture of the etiopathogenesis has still not been clarified fully. To understand better the mechanisms underlying the pathogenesis of PD, we analyzed the expression of 10 genes in the peripheral blood of treated and untreated patients with PD. 35 untreated patients with PD and 12 treated patients with Parkinson's disease (Hoehn and Yahr scores 1-2) were studied. An analysis of the mRNA levels of ATP13A2, PARK2, PARK7, PINK1, LRRK2, SNCA, ALDH1A1, PDHB, PPARGC1A, and ZNF746 genes in the peripheral blood of patients was carried out using reverse transcription followed by real-time PCR. A statistically significant and specific increase by more than 1.5-fold in the expression of the ATP13A2, PARK7, and ZNF746 genes was observed in patients with PD. Based on these results, it can be suggested that the upregulation of the mRNA levels of ATP13A2, PARK7, and ZNF746 in untreated patients in the earliest clinical stages can also be observed in the preclinical stages of PD, and that these genes can be considered as potential biomarkers of the preclinical stage of PD.

Parkinson's Disease and Its Management: Part 1: Disease Entity, Risk Factors, Pathophysiology, Clinical Presentation, and Diagnosis

This article-the first of a five-part series-discusses possible causes, symptoms, diagnosis, and goals for treatment of Parkinson's disease. Identifying diseases that have similar presentations is an important component of the diagnostic process.

Network-based metaanalysis identifies HNF4A and PTBP1 as longitudinally dynamic biomarkers for Parkinson's disease

Environmental and genetic factors are likely to be involved in the pathogenesis of Parkinson's disease (PD), the second most prevalent neurodegenerative disease among the elderly. Network-based metaanalysis of four independent microarray studies identified the hepatocyte nuclear factor 4 alpha (HNF4A), a transcription factor associated with gluconeogenesis and diabetes, as a central regulatory hub gene up-regulated in blood of PD patients. In parallel, the polypyrimidine tract binding protein 1 (PTBP1), involved in the stabilization and mRNA translation of insulin, was identified as the most down-regulated gene. Quantitative PCR assays revealed that HNF4A and PTBP1 mRNAs were up- and down-regulated, respectively, in blood of 51 PD patients and 45 controls nested in the Diagnostic and Prognostic Biomarkers for Parkinson's Disease. These results were confirmed in blood of 50 PD patients compared with 46 healthy controls nested in the Harvard Biomarker Study. Relative abundance of HNF4A mRNA correlated with the Hoehn and Yahr stage at baseline, suggesting its clinical utility to monitor disease severity. Using both markers, PD patients were classified with 90% sensitivity and 80% specificity. Longitudinal performance analysis demonstrated that relative abundance of HNF4A and PTBP1 mRNAs significantly decreased and increased, respectively, in PD patients during the 3-y follow-up period. The inverse regulation of HNF4A and PTBP1 provides a molecular rationale for the altered insulin signaling observed in PD patients. The longitudinally dynamic biomarkers identified in this study may be useful for monitoring disease-modifying therapies for PD.

A network approach to clinical intervention in neurodegenerative diseases

Network biology has become a powerful tool to dissect the molecular mechanisms triggering neurodegeneration. Recent developments in network biology have led to the discovery of disease-causing genes, diagnostic biomarkers, and therapeutic targets for several neurodegenerative diseases including Alzheimer's, Parkinson's, and Huntington's diseases. Network-based approaches have provided the molecular rationale for the relationship among cancer, diabetes, and neurodegenerative diseases, and have uncovered unexpected links between apparently unrelated diseases. Here, we summarize the recent advances in network biology to untangle the molecular underpinnings giving rise to the most prevalent neurodegenerative diseases. We propose that network analysis provides a feasible and practical tool for identifying biologically meaningful biomarkers and potential therapeutic targets for clinical intervention in neurodegenerative diseases.

Current Challenges Towards the Development of a Blood Test for Parkinson's Disease

Parkinson’ disease (PD) is the second most prevalent neurodegenerative disease worldwide. To date, there is no disease-modifying agent, and current medical treatment only provides symptomatic benefits. Early diagnosis of PD would be useful in clinical practice to identify patients for clinical trials, test potential drugs and neuroprotective agents and track their therapeutic effect. Considerable progress has been made in the discovery and validation of diagnostic biomarkers for PD. In particular, blood-based biomarkers have shown promise in identifying PD patients in samples from independent clinical trials. Evaluation of these biomarkers in de novo patients and individuals at risk for PD remains a top priority. Here, we review the current advances and challenges toward the clinical translation of these biomarkers into a blood-based test for PD.