Urate as a predictor of the rate of clinical decline in Parkinson disease

Magnetic resonance imaging as a potential biomarker for Parkinson's disease

Although a magnetic resonance imaging (MRI) biomarker for Parkinson's disease (PD) remains an unfulfilled objective, there have been numerous developments in MRI methodology and some of these have shown promise for PD. With funding from the National Institutes of Health and the Michael J Fox Foundation there will be further validation of structural, diffusion-based, and iron-focused MRI methods as possible biomarkers for PD. In this review, these methods and other strategies such as neurochemical and metabolic MRI have been covered. One of the challenges in establishing a biomarker is in the selection of individuals as PD is a heterogeneous disease with varying clinical features, different etiologies, and a range of pathologic changes. Additionally, longitudinal studies are needed of individuals with clinically diagnosed PD and cohorts of individuals who are at great risk for developing PD to validate methods. Ultimately an MRI biomarker will be useful in the diagnosis of PD, predicting the course of PD, providing a means to track its course, and provide an approach to select and monitor treatments.

The Role of Uric Acid and Methyl Derivatives in the Prevention of Age-Related Neurodegenerative Disorders

High uric acid (UA levels have been correlated with a reduced risk of many neurodegenerative diseases through mechanisms involving chelating Fenton reaction transitional metals, antioxidant quenching of superoxide and hydroxyl free radicals, and as an electron donor that increases antioxidant enzyme activity (e.g. SOD. However, the clinical usefulness of UA is limited by its' low water solubility and propensity to form inflammatory crystals at hyperuricemic levels. This review focuses on the role of UA in neuroprotection, as well as potential strategies aimed at increasing UA levels in the soluble range, and the potential therapeutic use of more water-soluble methyl-UA derivatives from the natural catabolic end-products of dietary caffeine, theophylline, and theobromine.

Monitoring of 30 marker candidates in early Parkinson disease as progression markers

OBJECTIVE

This was a longitudinal single-center cohort study to comprehensively explore multimodal progression markers for Parkinson disease (PD) in patients with recently diagnosed PD (n = 123) and age-matched, neurologically healthy controls (HC; n = 106).

METHODS

Thirty tests at baseline and after 24 months covered nonmotor symptoms (NMS), cognitive function, and REM sleep behavior disorder (RBD) by polysomnography (PSG), voxel-based morphometry (VBM) of the brain by MRI, and CSF markers. Linear mixed-effect models were used to estimate differences of rates of change and to provide standardized effect sizes (d) with 95% confidence intervals (CI).

RESULTS

A composite panel of 10 informative markers was identified. Significant relative worsening (PD vs HC) was seen with the following markers: the Unified Parkinson's Disease Rating Scale I (d 0.39; CI 0.09-0.70), the Autonomic Scale for Outcomes in Parkinson's Disease (d 0.25; CI 0.06-0.46), the Epworth Sleepiness Scale (d 0.47; CI 0.24-0.71), the RBD Screening Questionnaire (d 0.44; CI 0.25-0.64), and RBD by PSG (d 0.37; CI 0.19-0.55) as well as VBM units of cortical gray matter (d -0.2; CI -0.3 to -0.09) and hippocampus (d -0.15; CI -0.27 to -0.03). Markers with a relative improvement included the Nonmotor Symptom (Severity) Scale (d -0.19; CI -0.36 to -0.02) and 2 depression scales (Beck Depression Inventory d -0.18; CI -0.36 to 0; Montgomery-Åsberg Depression Rating Scale d -0.26; CI -0.47 to -0.04). Unexpectedly, cognitive measures and select laboratory markers were not significantly changed in PD vs HC participants.

CONCLUSIONS

Current CSF biomarkers and cognitive scales do not represent useful progression markers. However, sleep and imaging measures, and to some extent NMS, assessed using adequate scales, may be more informative markers to quantify progression.

Micronutrients and Risk of Parkinson's Disease: A Systematic Review

Parkinson’s disease (PD) is the second most common neurodegenerative disorder. Although the precise pathogenetic mechanisms of PD remain undetermined, there appears to be both genetic and environmental factors that contribute to the risk of developing PD. With regard to environmental risk factors, there has been significant interest related to the role of diet, nutrition, and nutrients on the onset and progression of PD. As the current treatments are predominantly focused on symptomatic management, efforts must be directed toward prevention of the PD and identification of potentially modifiable risk and preventive factors. This comprehensive review gives an overview of studies examining the role of micronutrients in PD, and provides guidance on the value of the reported outcomes.

Onset and progression factors in Parkinson's disease: A systematic review

Current research has identified several factors thought to be associated with the onset and progression of Parkinson's Disease (PD); however, whether certain factors contribute to or are protective against PD remains unclear. As such, a systematic search of the literature was performed using variations of MeSH and keyword search terms to identify and summarize systematic reviews and primary studies pertaining to factors associated with the onset and progression of PD. Factors referred to both traditional risk factors and prodromal markers. The following databases were searched: MEDLINE, MEDLINE In-Process, EMBASE, PsycINFO, Scopus, Web of Science, Cochrane Database of Systematic Reviews, Cumulative Index to Nursing and Allied Health Literature (CINAHL), ProQuest Dissertations & Theses, AARP AgeLine, and PDGene. A quality assessment of included systematic reviews was completed using the validated Assessment of the Methodological Quality of Systematic Reviews (AMSTAR) tool. Data extraction targeted reported factors, risk estimates, and 95% confidence intervals (CI). Findings identified 11 systematic reviews of sufficient quality reporting factors for PD onset, and no systematic reviews reporting factors for PD progression. In addition, 93 primary articles were identified, of which, 89 articles addressed factors related to PD onset and 4 articles addressed factors related to the PD progression. Pesticide exposure, rural living, well-water drinking, and farming occupation were consistently found to be positively associated with the onset of PD. Moreover, family history and polymorphisms to key genes were also found to be positively associated with the onset of PD. Conversely, coffee consumption, cigarette smoking, and some polymorphisms were consistently found to be negatively associated with the onset of PD. Urate was the only identified factor linked to the progression of PD; it was mostly found to be negatively associated with PD. In sum, the evidence was systematically found and summarized in the literature pertaining to factors related to the onset and progression of PD.

GWAS and transcriptional analysis prioritize ITPR1 and CNTN4 for a serum uric acid 3p26 QTL in Mexican Americans

Background

The variation in serum uric acid concentrations is under significant genetic influence. Elevated SUA concentrations have been linked to increased risk for gout, kidney stones, chronic kidney disease, and cardiovascular disease whereas reduced serum uric acid concentrations have been linked to multiple sclerosis, Parkinson’s disease and Alzheimer’s disease. Previously, we identified a novel locus on chromosome 3p26 affecting serum uric acid concentrations in Mexican Americans from San Antonio Family Heart Study. As a follow up, we examined genome-wide single nucleotide polymorphism data in an extended cohort of 1281 Mexican Americans from multigenerational families of the San Antonio Family Heart Study and the San Antonio Family Diabetes/Gallbladder Study. We used a linear regression-based joint linkage/association test under an additive model of allelic effect, while accounting for non-independence among family members via a kinship variance component.

Results

Univariate genetic analysis indicated serum uric acid concentrations to be significant heritable (h² = 0.50 ± 0.05, p < 4 × 10⁻³⁵), and linkage analysis of serum uric acid concentrations confirmed our previous finding of a novel locus on 3p26 (LOD = 4.9, p < 1 × 10⁻⁵) in the extended sample. Additionally, we observed strong association of serum uric acid concentrations with variants in following candidate genes in the 3p26 region; inositol 1,4,5-trisphosphate receptor, type 1 (ITPR1), contactin 4 (CNTN4), decapping mRNA 1A (DCP1A); transglutaminase 4 (TGM4) and rho guanine nucleotide exchange factor (GEF) 26 (ARHGEF26) [p < 3 × 10⁻⁷; minor allele frequencies ranged between 0.003 and 0.42] and evidence of cis-regulation for ITPR1 transcripts.

Conclusion

Our results confirm the importance of the chromosome 3p26 locus and genetic variants in this region in the regulation of serum uric acid concentrations.

Current disease modifying approaches to treat Parkinson's disease

Parkinson's disease (PD is a progressive neurological disorder characterized by the degeneration and death of midbrain dopamine and non-dopamine neurons in the brain leading to motor dysfunctions and other symptoms, which seriously influence the quality of life of PD patients. The drug L-dopa can alleviate the motor symptoms in PD, but so far there are no rational therapies targeting the underlying neurodegenerative processes. Despite intensive research, the molecular mechanisms causing neuronal loss are not fully understood which has hampered the development of new drugs and disease-modifying therapies. Neurotrophic factors are by virtue of their survival promoting activities attract candidates to counteract and possibly halt cell degeneration in PD. In particular, studies employing glial cell line-derived neurotrophic factor (GDNF) and its family member neurturin (NRTN), as well as the recently described cerebral dopamine neurotrophic factor (CDNF) and the mesencephalic astrocyte-derived neurotrophic factor (MANF) have shown positive results in protecting and repairing dopaminergic neurons in various models of PD. Other substances with trophic actions in dopaminergic neurons include neuropeptides and small compounds that target different pathways impaired in PD, such as increased cell stress, protein handling defects, dysfunctional mitochondria and neuroinflammation. In this review, we will highlight the recent developments in this field with a focus on trophic factors and substances having the potential to beneficially influence the viability and functions of dopaminergic neurons as shown in preclinical or in animal models of PD.

Association Between Change in Body Mass Index, Unified Parkinson's Disease Rating Scale Scores, and Survival Among Persons With Parkinson Disease: Secondary Analysis of Longitudinal Data From NINDS Exploratory Trials in Parkinson Disease Long-term Study 1

IMPORTANCE

Greater body mass index (BMI, calculated as weight in kilograms divided by height in meters squared) is associated with improved survival among persons with Huntington disease or amyotrophic lateral sclerosis. Weight loss is common among persons with Parkinson disease (PD) and is associated with worse quality of life.

OBJECTIVE

To explore the association between change in BMI, Unified Parkinson's Disease Rating Scale (UPDRS) motor and total scores, and survival among persons with PD and to test whether there is a positive association between BMI at randomization and survival.

DESIGN, SETTING, AND PARTICIPANTS

Secondary analysis (from May 27, 2014, to October 13, 2015) of longitudinal data (3-6 years) from 1673 participants who started the National Institute of Neurological Disorders and Stroke Exploratory Trials in PD Long-term Study-1 (NET-PD LS-1). This was a double-blind randomized placebo-controlled clinical trial of creatine monohydrate (10 g/d) that was performed at 45 sites throughout the United States and Canada. Participants with early (within 5 years of diagnosis) and treated (receiving dopaminergic therapy) PD were enrolled from March 2007 to May 2010 and followed up until September 2013.

MAIN OUTCOMES AND MEASURES

Change across time in motor UPDRS score, change across time in total UPDRS score, and time to death. Generalized linear mixed models were used to estimate the effect of BMI on the change in motor and total UPDRS scores after controlling for covariates. Survival was analyzed using Cox proportional hazards models of time to death. A participant's BMI was measured at randomization, and BMI trajectory groups were classified according to whether participants experienced weight loss ("decreasing BMI"), weight stability ("stable BMI"), or weight gain ("increasing BMI") during the study.

RESULTS

Of the 1673 participants (mean [SD] age, 61.7 [9.6] years; 1074 [64.2%] were male), 158 (9.4%) experienced weight loss (decreasing BMI), whereas 233 (13.9%) experienced weight gain (increasing BMI). After adjusting for covariates, we found that the weight-loss group's mean (SE) motor UPDRS score increased by 1.48 (0.28) (P < .001) more points per visit than the weight-stable group's mean (SE) motor UPDRS score. The weight-gain group's mean (SE) motor UPDRS score decreased by -0.51 (0.24) (P = .03) points per visit, relative to the weight-stable group. While there was an unadjusted difference in survival between the 3 BMI trajectory groups (log-rank P < .001), this was not significant after adjusting for covariates.

CONCLUSIONS AND RELEVANCE

Change in BMI was inversely associated with change in motor and total UPDRS scores in the NET-PD LS-1. Change in BMI was not associated with survival; however, these results were limited by the low number of deaths in the NET-PD LS-1.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00449865.

Gout and the risk of Alzheimer's disease: a population-based, BMI-matched cohort study

OBJECTIVE

While gout is associated with cardiovascular (CV)-metabolic comorbidities and their sequelae, the antioxidant effects of uric acid may have neuroprotective benefits. We evaluated the potential impact of incident gout on the risk of developing Alzheimer's disease (AD) in a general population context.

METHODS

We conducted an age-matched, sex-matched, entry-time-matched and body mass index (BMI)-matched cohort study using data from The Health Improvement Network, an electronic medical record database representative of the UK general population, from 1 January 1995 to 31 December 2013. Up to five non-gout individuals were matched to each case of incident gout by age, sex, year of enrolment and BMI. We compared incidence rates of AD between the gout and comparison cohorts, excluding individuals with prevalent gout or dementia at baseline. Multivariate hazard ratios (HRs) were calculated, while adjusting for smoking, alcohol use, physician visits, social deprivation index, comorbidities and medication use. We repeated the same analysis among patients with incident osteoarthritis (OA) as a negative control exposure.

RESULTS

We identified 309 new cases of AD among 59 224 patients with gout (29% female, mean age 65 years) and 1942 cases among 238 805 in the comparison cohort over a 5-year median follow up (1.0 vs 1.5 per 1000 person-years, respectively). Univariate (age-matched, sex-matched, entry-time-matched and BMI-matched) and multivariate HRs for AD among patients with gout were 0.71 (95% CI 0.62 to 0.80) and 0.76 (95% CI 0.66 to 0.87), respectively. The inverse association persisted among subgroups stratified by sex, age group (<75 and ≥75 years), social deprivation index and history of CV disease. The association between incident OA and the risk of incident AD was null.

CONCLUSIONS

These findings provide the first general population-based evidence that gout is inversely associated with the risk of developing AD, supporting the purported potential neuroprotective role of uric acid.

Purines: forgotten mediators in traumatic brain injury

Recently, the topic of traumatic brain injury has gained attention in both the scientific community and lay press. Similarly, there have been exciting developments on multiple fronts in the area of neurochemistry specifically related to purine biology that are relevant to both neuroprotection and neurodegeneration. At the 2105 meeting of the National Neurotrauma Society, a session sponsored by the International Society for Neurochemistry featured three experts in the field of purine biology who discussed new developments that are germane to both the pathomechanisms of secondary injury and development of therapies for traumatic brain injury. This included presentations by Drs. Edwin Jackson on the novel 2',3'-cAMP pathway in neuroprotection, Detlev Boison on adenosine in post-traumatic seizures and epilepsy, and Michael Schwarzschild on the potential of urate to treat central nervous system injury. This mini review summarizes the important findings in these three areas and outlines future directions for the development of new purine-related therapies for traumatic brain injury and other forms of central nervous system injury. In this review, novel therapies based on three emerging areas of adenosine-related pathobiology in traumatic brain injury (TBI) were proposed, namely, therapies targeting 1) the 2',3'-cyclic adenosine monophosphate (cAMP) pathway, 2) adenosine deficiency after TBI, and 3) augmentation of urate after TBI.

New and emerging medical therapies in Parkinson's disease

INTRODUCTION

Parkinson's disease (PD) is one of the most challenging neurodegenerative disorders to treat as it manifests with a large variety of troublesome, and often disabling, motor and non-motor symptoms. Despite limitations, such as motor and other complications, levodopa remains the most effective drug in the treatment of PD.

AREAS COVERED

In this review, we focus on phase 2 and 3 studies describing new and emerging medical therapies in PD. We discuss new formulations of levodopa, medications that prolong levodopa response and ameliorate levodopa-induced dyskinesias, and innovative delivery methods that are currently being evaluated in clinical trials or are in development with the promise of better efficacy and tolerability. We also describe novel non-dopaminergic drugs that have been identified for treatment of motor and non-motor symptoms. A specific section is designated for potential disease modifying therapies.

EXPERT OPINION

Alternative formulations of levodopa appear to be promising especially to help with the motor fluctuations either by providing sustained benefits with controlled released formulations or ameliorate sudden OFF by formulations such as inhaled levodopa. Several different medications affecting non-dopaminergic pathways are being evaluated which may aide levodopa. As the understanding of the disease grows further, numerous novel neuroprotective or disease modifying therapies have been suggested. This along with development of medications to treat various non-motor symptoms will help improve quality of life of patients with PD.

Relationship between uric acid levels and progressive supranuclear palsy

INTRODUCTION

The pathophysiology of both PD and PSP is characterized by a pro-oxidant state. Uric acid is an oxidative stress marker. High uric acid blood levels have been associated with a reduced risk of PD and a decreased rate of disease progression. We investigated whether a low serum concentration of uric acid is also associated with PSP.

METHODS

We measured serum uric acid concentrations in a subsample of the ENGENE PSP Cohort that included 75 cases and 75 frequency-matched-by-sex healthy controls (69 spouses, 6 in-laws) from four centers willing to participate (Case Western, Rush University, University of Utah, and University of Louisville). Case severity was characterized using the total PSP-Rating Scale, UPDRS, and Mattis Dementia Rating Scale. Unconditional logistic regression, Pearson's chi-squared test, and analysis of variance were used, as appropriate.

RESULTS

The mean uric acid level among cases (4.0 mg/dL) was not significantly lower than that of controls (4.1 mg/dL). When controlling for sex, there were no between-group statistical differences in uric acid levels. Uric acid levels were not correlated with disease severity.

CONCLUSIONS

The results of this study do not provide evidence of uric acid having a protective role in PSP, even if oxidative injury is important in the pathophysiology of this disorder. The lack of statistical significance suggests that there is no direct association between uric acid levels and PSP. However, a small inverse association cannot be excluded. © 2016 Movement Disorder Society.

Serum uric acid level and association with cognitive impairment and dementia: systematic review and meta-analysis

Serum uric acid (sUA) level may be associated with cognitive impairment/dementia. It is possible this relationship varies with dementia subtype, particularly between vascular dementias (VaD) and Alzheimer's (AD) or Parkinson's disease (PDD)-related dementia. We aimed to present a synthesis of all published data on sUA and relationship with dementia/cognition through systematic review and meta-analysis. We included studies that assessed the association between sUA and any measure of cognitive function or a clinical diagnosis of dementia. We pre-defined subgroup analyses for patients with AD, VaD, PDD, mild cognitive impairment (MCI), and mixed or undifferentiated. We assessed risk of bias/generalizability, and where data allowed, we performed meta-analysis to describe pooled measures of association across studies. From 4811 titles, 46 papers (n = 16,688 participants) met our selection criteria. Compared to controls, sUA was lower in dementia (SDM -0.33 (95%CI)). There were differences in association by dementia type with apparent association for AD (SDM -0.33 (95%CI)) and PDD (SDM -0.67 (95%CI)) but not in cases of mixed dementia (SDM 0.19 (95%CI)) or VaD (SDM -0.05 (95%CI)). There was no correlation between scores on Mini-Mental State Examination and sUA level (summary r 0.08, p = 0.27), except in patients with PDD (r 0.16, p = 0.003). Our conclusions are limited by clinical heterogeneity and risk of bias in studies. Accepting this caveat, the relationship between sUA and dementia/cognitive impairment is not consistent across all dementia groups and in particular may differ in patients with VaD compared to other dementia subtypes.

Environmental risk factors and Parkinson's disease: An umbrella review of meta-analyses

BACKGROUND

Parkinson's disease is a neurological disorder with complex pathogenesis implicating both environmental and genetic factors. We aimed to summarise the environmental risk factors that have been studied for potential association with Parkinson's disease, assess the presence of diverse biases, and identify the risk factors with the strongest support.

METHODS

We searched PubMed from inception to September 18, 2015, to identify systematic reviews and meta-analyses of observational studies that examined associations between environmental factors and Parkinson's disease. For each meta-analysis we estimated the summary effect size by random-effects and fixed-effects models, the 95% confidence interval and the 95% prediction interval. We estimated the between-study heterogeneity expressed by I(2), evidence of small-study effects and evidence of excess significance bias.

RESULTS

Overall, 75 unique meta-analyses on different risk factors for Parkinson's disease were examined, covering diverse biomarkers, dietary factors, drugs, medical history or comorbid diseases, exposure to toxic environmental agents and habits. 21 of 75 meta-analyses had results that were significant at p < 0.001 by random-effects. Evidence for an association was convincing (more than 1000 cases, p < 10(-6) by random-effects, not large heterogeneity, 95% prediction interval excluding the null value and absence of hints for small-study effects and excess significance bias) for constipation, and physical activity.

CONCLUSION

Many environmental factors have substantial evidence of association with Parkinson's disease, but several, perhaps most, of them may reflect reverse causation, residual confounding, information bias, sponsor conflicts or other caveats.

Prospective study of plasma urate and risk of Parkinson disease in men and women

OBJECTIVE

To examine whether higher plasma urate concentrations are associated with a lower risk of developing Parkinson disease (PD) and whether there is a sex difference in the potential urate-PD relationship.

METHODS

We conducted a nested case-control study based on 90,214 participants of 3 ongoing US cohorts. We identified 388 new PD cases (202 men and 186 women) since blood collection, which were then matched to 1,267 controls. PD cases were confirmed by medical record review. Conditional logistic regression estimated relative risks (RRs) and 95% confidence intervals (95% CIs), after adjustment for age, smoking, caffeine intake, plasma concentrations of cholesterol and ferritin, and other covariates. We also conducted a meta-analysis to combine our study with 3 previously published prospective studies on urate and PD risk.

RESULTS

In the present nested case-control study, the multivariate-adjusted RRs of PD comparing extreme quartiles of urate were 0.63 (95% CI 0.35, 1.10; ptrend = 0.049) in men and 1.04 (95% CI 0.61, 1.78; ptrend = 0.44) in women (pheterogeneity = 0.001). In the meta-analysis, the pooled RRs comparing 2 extreme quartiles of urate were 0.63 (95% CI 0.42, 0.95) in men and 0.89 (95% CI 0.57, 1.40) in women.

CONCLUSION

We observed that men, but not women, with higher urate concentrations had a lower future risk of developing PD, suggesting that urate could be protective against PD risk or could slow disease progression during the preclinical stage of disease.

ALS biomarkers for therapy development: State of the field and future directions

Biomarkers have become the focus of intense research in the field of amyotrophic lateral sclerosis (ALS), with the hope that they might aid therapy development efforts. Notwithstanding the discovery of many candidate biomarkers, none have yet emerged as validated tools for drug development. In this review we present a nuanced view of biomarkers based on the perspective of the Food and Drug Administration; highlight the distinction between discovery and validation; describe existing and emerging resources; review leading biological fluid-based, electrophysiological, and neuroimaging candidates relevant to therapy development efforts; discuss lessons learned from biomarker initiatives in related neurodegenerative diseases; and outline specific steps that we, as a field, might take to hasten the development and validation of biomarkers that will prove useful in enhancing efforts to develop effective treatments for ALS patients. Most important among these is the proposal to establish a federated ALS Biomarker Consortium in which all interested and willing stakeholders may participate with equal opportunity to contribute to the broader mission of biomarker development and validation.

Neuroprotective effects of urate are mediated by augmenting astrocytic glutathione synthesis and release

Urate has emerged as a promising target for neuroprotection based on epidemiological observations, preclinical models, and early clinical trial results in multiple neurologic diseases, including Parkinson's disease (PD). This study investigates the astrocytic mechanism of urate's neuroprotective effect. Targeted biochemical screens of conditioned medium from urate- versus vehicle-treated astrocytes identified markedly elevated glutathione (GSH) concentrations as a candidate mediator of urate's astrocyte-dependent neuroprotective effects. Urate treatment also induced the nuclear translocation of the nuclear factor (erythroid-derived 2)-like 2 (Nrf2) protein and transcriptional activation of its key target genes in primary astrocytic cultures. Urate's neuroprotective effect was attenuated when GSH was depleted in the conditioned media either by targeting its synthesis or release by astrocytes. Overall, these results implicate GSH as the extracellular astrocytic factor mediating the protective effect of urate in a cellular model of PD. These results also show that urate can employ a novel indirect neuroprotective mechanism via induction of the Nrf2 signaling pathway, a master regulator of the response to oxidative stress, in astrocytes.

Genome-wide variant by serum urate interaction in Parkinson's disease

OBJECTIVE

Serum urate levels have been associated with risk for and progression of Parkinson's disease (PD). Urate-related compounds are therapeutic candidates in neuroprotective efforts to slow PD progression. A urate-elevating agent is currently under investigation as a potential disease-modifying strategy in people with PD. However, PD is a heterogeneous disorder, and genetic variation may explain divergence in disease severity and progression.

METHODS

We conducted a genome-wide association study to identify gene variant × serum urate interaction effects on the striatal (123) I-ioflupane (DaTscan) binding ratio measured using single photon emission computed tomography in patients with possible PD from the Parkinson's Progression Markers Initiative (PPMI, n = 360). Follow-up analyses were conducted to assess gene variant × serum urate interaction effects on magnetic resonance imaging-derived regional brain volumes and clinical status. We then attempted to replicate our primary analysis in patients who entered the Parkinson Research Examination of CEP-1347 Trial (PRECEPT) with a clinical diagnosis of PD (n = 349).

RESULTS

Rs1109303 (T>G) variant within the INPP5K gene on chromosome 17p13.3 demonstrated a genome-wide significant interaction with serum urate level to predict striatal dopamine transporter density among all PPMI participants (n = 359) with possible PD (p = 2.01 × 10(-8) ; after excluding participants with SWEDD [scan without evidence of dopaminergic deficit]: p = 1.12 × 10(-9) ; n = 316). Independent of striatal dopamine transporter density, similar effects on brain atrophy, bradykinesia, anxiety, and depression were observed. No effect was present in the PRECEPT sample at baseline; however, in non-SWEDD PD participants in PRECEPT (n = 309), we observed a significant longitudinal genotype × serum urate interaction effect, consistent in direction with the PPMI sample, on progression of striatal dopamine transporter density over the 22-month follow-up.

INTERPRETATION

Genetic profile combined with serum urate level can be used to predict disease severity and potential disease progression in patients with PD. These results may be relevant to therapeutic efforts targeting the urate pathway.

Longitudinal Metabolomics Profiling of Parkinson's Disease-Related α-Synuclein A53T Transgenic Mice

Metabolic homeostasis is critical for all biological processes in the brain. The metabolites are considered the best indicators of cell states and their rapid fluxes are extremely sensitive to cellular changes. While there are a few studies on the metabolomics of Parkinson's disease, it lacks longitudinal studies of the brain metabolic pathways affected by aging and the disease. Using ultra-high performance liquid chromatography and tandem mass spectroscopy (UPLC/MS), we generated the metabolomics profiling data from the brains of young and aged male PD-related α-synuclein A53T transgenic mice as well as the age- and gender-matched non-transgenic (nTg) controls. Principal component and unsupervised hierarchical clustering analyses identified distinctive metabolites influenced by aging and the A53T mutation. The following metabolite set enrichment classification revealed the alanine metabolism, redox and acetyl-CoA biosynthesis pathways were substantially disturbed in the aged mouse brains regardless of the genotypes, suggesting that aging plays a more prominent role in the alterations of brain metabolism. Further examination showed that the interaction effect of aging and genotype only disturbed the guanosine levels. The young A53T mice exhibited lower levels of guanosine compared to the age-matched nTg controls. The guanosine levels remained constant between the young and aged nTg mice, whereas the aged A53T mice showed substantially increased guanosine levels compared to the young mutant ones. In light of the neuroprotective function of guanosine, our findings suggest that the increase of guanosine metabolism in aged A53T mice likely represents a protective mechanism against neurodegeneration, while monitoring guanosine levels could be applicable to the early diagnosis of the disease.

Metabolomics Approach Reveals Integrated Metabolic Network Associated with Serotonin Deficiency

Serotonin is an important neurotransmitter that broadly participates in various biological processes. While serotonin deficiency has been associated with multiple pathological conditions such as depression, schizophrenia, Alzheimer's disease and Parkinson's disease, the serotonin-dependent mechanisms remain poorly understood. This study therefore aimed to identify novel biomarkers and metabolic pathways perturbed by serotonin deficiency using metabolomics approach in order to gain new metabolic insights into the serotonin deficiency-related molecular mechanisms. Serotonin deficiency was achieved through pharmacological inhibition of tryptophan hydroxylase (Tph) using p-chlorophenylalanine (pCPA) or genetic knockout of the neuronal specific Tph2 isoform. This dual approach improved specificity for the serotonin deficiency-associated biomarkers while minimizing nonspecific effects of pCPA treatment or Tph2 knockout (Tph2-/-). Non-targeted metabolic profiling and a targeted pCPA dose-response study identified 21 biomarkers in the pCPA-treated mice while 17 metabolites in the Tph2-/- mice were found to be significantly altered compared with the control mice. These newly identified biomarkers were associated with amino acid, energy, purine, lipid and gut microflora metabolisms. Oxidative stress was also found to be significantly increased in the serotonin deficient mice. These new biomarkers and the overall metabolic pathways may provide new understanding for the serotonin deficiency-associated mechanisms under multiple pathological states.

A systems-level "misunderstanding": the plasma metabolome in Huntington's disease

Objective

Huntington’s disease (HD) is a rare neurodegenerative disease caused by the expansion of an N-terminal repeat in the huntingtin protein. The protein is expressed in all cells in the body; hence, peripheral tissues, such as blood, may recapitulate processes in the brain. The plasma metabolome may provide a window into active processes that influence brain health and a unique opportunity to noninvasively identify processes that may contribute to neurodegeneration. Alterations in metabolic pathways in brain have been shown to profoundly impact HD. Therefore, identification and quantification of critical metabolomic perturbations could provide novel biomarkers for disease onset and disease progression.

Methods

We analyzed the plasma metabolomic profiles from 52 premanifest (PHD), 102 early symptomatic HD, and 140 healthy controls (NC) using liquid chromatography coupled with a highly sensitive electrochemical detection platform.

Results

Alterations in tryptophan, tyrosine, purine, and antioxidant pathways were identified, including many related to energetic and oxidative stress and derived from the gut microbiome. Multivariate statistical modeling demonstrated mutually distinct metabolomic profiles, suggesting that the processes that determine onset were likely distinct from those that determine progression. Gut microbiome-derived metabolites particularly differentiated the PHD metabolome, while the symptomatic HD metabolome was increasingly influenced by metabolites that may reflect mutant huntingtin toxicity and neurodegeneration.

Interpretation

Understanding the complex changes in the delicate balance of the metabolome and the gut microbiome in HD, and how they relate to disease onset, progression, and phenotypic variability in HD are critical questions for future research.

Clinically meaningful parameters of progression and long-term outcome of Parkinson disease: An international consensus statement

Parkinson disease (PD) is associated with a clinical course of variable duration, severity, and a combination of motor and non-motor features. Recent PD research has focused primarily on etiology rather than clinical progression and long-term outcomes. For the PD patient, caregivers, and clinicians, information on expected clinical progression and long-term outcomes is of great importance. Today, it remains largely unknown what factors influence long-term clinical progression and outcomes in PD; recent data indicate that the factors that increase the risk to develop PD differ, at least partly, from those that accelerate clinical progression and lead to worse outcomes. Prospective studies will be required to identify factors that influence progression and outcome. We suggest that data for such studies is collected during routine office visits in order to guarantee high external validity of such research. We report here the results of a consensus meeting of international movement disorder experts from the Genetic Epidemiology of Parkinson's Disease (GEO-PD) consortium, who convened to define which long-term outcomes are of interest to patients, caregivers and clinicians, and what is presently known about environmental or genetic factors influencing clinical progression or long-term outcomes in PD. We propose a panel of rating scales that collects a significant amount of phenotypic information, can be performed in the routine office visit and allows international standardization. Research into the progression and long-term outcomes of PD aims at providing individual prognostic information early, adapting treatment choices, and taking specific measures to provide care optimized to the individual patient's needs.

Clinical associations between gout and multiple sclerosis, Parkinson's disease and motor neuron disease: record-linkage studies

BACKGROUND

Uric acid has antioxidant effects on neurons. Abnormally high levels of uric acid are, however, associated with gout. Previous studies have suggested that high levels of uric acid (and the presence of gout) may exert a protective effect against the risk of developing some neurological diseases. We aimed to investigate this hypothesis in a large database of hospital admissions in England.

METHODS

We analysed a database of linked statistical records of hospital admissions and death registrations in England (1999-2012). A cohort of people with gout was constructed and followed for development of multiple sclerosis (MS), Parkinson's disease (PD) or motor neuron disease (MND). Then, conversely, cohorts of all people in the database with MS, PD or MND were constructed and followed for subsequent gout. Rate ratios (RRs) were determined, comparing these cohorts with people in a reference cohort.

RESULTS

In the gout cohort, we observed a modest elevation of the overall risk of subsequent MS, PD and MND (respectively, RR = 1.27 (95% confidence interval 1.03-1.55), 1.11 (1.05-1.17) and 1.28 (1.11-1.48) which was largely attributable to an increased risk observed in the early years after hospitalisation for gout. The increased risk of neurological disease did not remain after 5 years. In the cohorts of people with MS or PD, there was a significantly reduced risk of subsequent gout admission (RR = 0.79 (0.69-0.89) and 0.83 (0.79-0.87), respectively). This inverse association was sustained over time. There was also a reduced risk of MND following gout which only emerged more than five years following initial gout admission (RR at 5+ years 0.35 (0.15-0.68)).

CONCLUSIONS

This study investigated the epidemiological evidence for a protective role of high serum concentration of uric acid, for which we used gout as a proxy, in the aetiology of MS, PD or MND. Our observations do not support this hypothesis. However, when the order was reversed, and we retrospectively followed up patients with MS, PD and MND for a number of years, we found a statistically significant deficit of gout. This suggests that there is relationship between some aspects of these neurodegenerative diseases and metabolism of uric acid.

Uric acid relates to dopamine transporter availability in Parkinson's disease

BACKGROUND

Diagnosing Parkinson's disease (PD) and tracking its progression may require the combination of reliable biomarkers. Among them, both serum uric acid (UA) and dopamine transporter (DaT) binding deserve more investigations.

AIMS OF THE STUDY

We aimed to investigate the relationship between serum UA levels and DaT availability in newly diagnosed, drug-naïve PD patients, by means of semiquantitative [(123) I]FP-CIT-SPECT.

METHODS

We recruited 52 newly diagnosed, drug-naïve PD patients, and performed serum UA dosage and [(123) I]FP-CIT-SPECT.

RESULTS

Pearson's correlation analysis showed that UA levels were significantly higher in patients with higher averaged, ipsilateral and contralateral DaT binding in caudate, putamen, and striatum.

CONCLUSIONS

We showed, for the first time, by regional semiquantitative analysis of DaT binding in PD patients that UA levels significantly correlates with the severity of dopaminergic impairment in caudate, putamen, and striatum. This study broadens our knowledge on the importance of UA as a biomarker of PD.

ABCG2 variant has opposing effects on onset ages of Parkinson's disease and gout

Uric acid (urate) has been suggested to play a protective role in Parkinson's disease onset through its antioxidant activity. Dysfunction of ABCG2, a high-capacity urate exporter, is a major cause for early-onset gout based on hyperuricemia. In this study, the effects of a dysfunctional ABCG2 variant (Q141K, rs2231142) were analyzed on the ages at onset of gout patients (N = 507) and Parkinson's disease patients (N = 1015). The Q141K variant hastened the gout onset (P = 0.0027), but significantly associated with later Parkinson's disease onset (P = 0.025). Our findings will be helpful for development of more effective prevention of Parkinson's disease.

What is the Clinical Significance of Cerebrospinal Fluid Biomarkers in Parkinson's disease? Is the Significance Diagnostic or Prognostic?

The clinical diagnostic criteria of Parkinson's disease (PD) have limitations in detecting the disease at early stage and in differentiating heterogeneous clinical progression. The lack of reliable biomarker(s) for early diagnosis and prediction of prognosis is a major hurdle to achieve optimal clinical care of patients and efficient design of clinical trials for disease-modifying therapeutics. Numerous efforts to discover PD biomarkers in CSF were conducted. In this review, we describe the molecular pathogenesis of PD and discuss its implication to develop PD biomarkers in CSF. Next, we summarize the clinical utility of CSF biomarkers including alpha-synuclein for early and differential diagnosis, and prediction of PD progression. Given the heterogeneity in the clinical features of PD and none of the CSF biomarkers for an early diagnosis have been developed, research efforts to develop biomarkers to predict heterogeneous disease progression is on-going. Notably, a rapid cognitive decline followed by the development of dementia is a risk factor of poor prognosis in PD. In connection to this, CSF levels of Alzheimer's disease (AD) biomarkers have received considerable attention. However, we still need long-term longitudinal observational studies employing large cohorts to evaluate the clinical utility of CSF biomarkers reflecting Lewy body pathology and AD pathology in the brain. We believe that current research efforts including the Parkinson's Progression Markers Initiative will resolve the current needs of early diagnosis and/or prediction of disease progression using CSF biomarkers, and which will further accelerate the development of disease-modifying therapeutics and optimize the clinical management of PD patients.

The ongoing pursuit of neuroprotective therapies in Parkinson disease

Many agents developed for neuroprotective treatment of Parkinson disease (PD) have shown great promise in the laboratory, but none have translated to positive results in patients with PD. Potential neuroprotective drugs, such as ubiquinone, creatine and PYM50028, have failed to show any clinical benefits in recent high-profile clinical trials. This 'failure to translate' is likely to be related primarily to our incomplete understanding of the pathogenic mechanisms underlying PD, and excessive reliance on data from toxin-based animal models to judge which agents should be selected for clinical trials. Restricted resources inevitably mean that difficult compromises must be made in terms of trial design, and reliable estimation of efficacy is further hampered by the absence of validated biomarkers of disease progression. Drug development in PD dementia has been mostly unsuccessful; however, emerging biochemical, genetic and pathological evidence suggests a link between tau and amyloid-β deposition and cognitive decline in PD, potentially opening up new possibilities for therapeutic intervention. This Review discusses the most important 'druggable' disease mechanisms in PD, as well as the most-promising drugs that are being evaluated for their potential efficiency in treatment of motor and cognitive impairments in PD.

Cerebrospinal fluid biochemical studies in patients with Parkinson's disease: toward a potential search for biomarkers for this disease

The blood-brain barrier supplies brain tissues with nutrients and filters certain compounds from the brain back to the bloodstream. In several neurodegenerative diseases, including Parkinson's disease (PD), there are disruptions of the blood-brain barrier. Cerebrospinal fluid (CSF) has been widely investigated in PD and in other parkinsonian syndromes with the aim of establishing useful biomarkers for an accurate differential diagnosis among these syndromes. This review article summarizes the studies reported on CSF levels of many potential biomarkers of PD. The most consistent findings are: (a) the possible role of CSF urate on the progression of the disease; (b) the possible relations of CSF total tau and phosphotau protein with the progression of PD and with the preservation of cognitive function in PD patients; (c) the possible value of CSF beta-amyloid 1-42 as a useful marker of further cognitive decline in PD patients, and (d) the potential usefulness of CSF neurofilament (NFL) protein levels in the differential diagnosis between PD and other parkinsonian syndromes. Future multicentric, longitudinal, prospective studies with long-term follow-up and neuropathological confirmation would be useful in establishing appropriate biomarkers for PD.

Complementary & alternative management of Parkinson's disease: an evidence-based review of eastern influenced practices

The prevalence of Parkinson’s disease (PD) appears to be lower in Asia compared to the Western world. It is unclear if this is related to the ubiquitous use of traditional medicine in Eastern healthcare, but the use of complementary and alternative medicine (CAM) modalities in countries like Korea may be as high as 76%. Among patients with PD, herbal medicines, health supplement foods, and acupuncture are interventions which are increasingly used throughout the world. Countries like Korea, China, India, and Japan have long embraced and incorporated traditional medicine into modern management of conditions such as PD, but research into various CAM modalities remains in its infancy limiting evidence-based recommendations for many treatments. We reviewed the literature on CAM treatments for PD, focusing on mind-body interventions and natural products. Based on evidence limited to randomized-controlled trials we found that mind-body interventions are generally effective forms of physical activity that are likely to foster good adherence and may reduce disability associated with PD. Based on the current data, modalities like Tai Chi and dance are safe and beneficial in PD, but better studies are needed to assess the effects of other frequently used modalities such as yoga and acupuncture. Furthermore, despite centuries of experience using medicinal herbs and plants in Eastern countries, and despite substantial preclinical data on the beneficial effects of nutritional antioxidants as neuroprotective agents in PD, there is insufficient clinical evidence that any vitamin, food additive, or supplement, can improve motor function or delay disease progression in PD.

The PRO-ACT database: design, initial analyses, and predictive features

OBJECTIVE

To pool data from completed amyotrophic lateral sclerosis (ALS) clinical trials and create an open-access resource that enables greater understanding of the phenotype and biology of ALS.

METHODS

Clinical trials data were pooled from 16 completed phase II/III ALS clinical trials and one observational study. Over 8 million de-identified longitudinally collected data points from over 8,600 individuals with ALS were standardized across trials and merged to create the Pooled Resource Open-Access ALS Clinical Trials (PRO-ACT) database. This database includes demographics, family histories, and longitudinal clinical and laboratory data. Mixed effects models were used to describe the rate of disease progression measured by the Revised ALS Functional Rating Scale (ALSFRS-R) and vital capacity (VC). Cox regression models were used to describe survival data. Implementing Bonferroni correction, the critical p value for 15 different tests was p = 0.003.

RESULTS

The ALSFRS-R rate of decline was 1.02 (±2.3) points per month and the VC rate of decline was 2.24% of predicted (±6.9) per month. Higher levels of uric acid at trial entry were predictive of a slower drop in ALSFRS-R (p = 0.01) and VC (p < 0.0001), and longer survival (p = 0.02). Higher levels of creatinine at baseline were predictive of a slower drop in ALSFRS-R (p = 0.01) and VC (p < 0.0001), and longer survival (p = 0.01). Finally, higher body mass index (BMI) at baseline was associated with longer survival (p < 0.0001).

CONCLUSION

The PRO-ACT database is the largest publicly available repository of merged ALS clinical trials data. We report that baseline levels of creatinine and uric acid, as well as baseline BMI, are strong predictors of disease progression and survival.

Mendelian randomization of serum urate and parkinson disease progression

OBJECTIVE

Higher serum urate concentrations predict more favorable prognosis in individuals with Parkinson disease (PD). The purpose of this study was to test the causality of this association using a Mendelian randomization approach.

METHODS

The study was conducted among participants in DATATOP and PRECEPT, 2 randomized trials among patients with early PD. The 808 patients with available DNA were genotyped for 3 SLC2A9 single nucleotide polymorphisms (SNPs) that identify an allele associated with lower urate concentrations, and for selected SNPs in other genes encoding urate transporters that have modest or no effect on serum urate levels. An SLC2A9 score was created based on the total number of minor alleles at the 3 SLC2A9 loci. Primary outcome was disability requiring dopaminergic treatment.

RESULTS

Serum urate concentrations were 0.69mg/dl lower among individuals with ≥4 SLC2A9 minor alleles as compared to those with ≤2 (p = 0.0002). The hazard ratio (HR) for progression to disability requiring dopaminergic treatment increased with increasing SLC2A9 score (HR = 1.16, 95% confidence interval [CI] = 1.00-1.35, p = 0.056). In a comparative analysis, the HR was 1.27 (95% CI = 1.00-1.61, p = 0.0497) for a 0.5mg/dl genetically conferred decrease in serum urate, and 1.05 (95% CI = 1.01-1.10, p = 0.0133) for a 0.5mg/dl decrease in measured serum urate. No associations were found between polymorphisms in other genes associated with urate that do not affect serum urate and PD progression.

INTERPRETATION

This Mendelian randomization analysis adds to the evidence of a causal protective effect of high urate levels.

Serum uric acid level is associated with the prevalence but not with survival of amyotrophic lateral sclerosis in a Chinese population

Oxidative stress is involved in the pathogenesis of amyotrophic lateral sclerosis (ALS). Serum uric acid (UA) has anti-oxidative effect. To clarify the associations between UA and sporadic ALS (SALS) in Chinese population. A total of 512 SALS patients and 501 age- and gender- matched healthy controls were included, with fasting serum UA evaluated. The ALS functional rating scale-Revised was used to assess disease severity, and the mean change of ALSFRS-R per month (△ALS-FRS-R/m) to assess its progression. Four hundred forty-five patients were followed up. Survival and progression were estimated according to quartiles and gender-specific quartiles of UA. The mean age of SALS patients was 53.3 ± 11.7 years. UA level of SALS was significantly lower than controls (p = 0.001). Male SALS had higher UA than female (p = 0.001). The occurrence of SALS was increased in the lowest, second and third quartiles compared with the highest quartile (p = 0.001). In the gender-specific analysis, increased occurrence was found in the lowest and second quartiles compared with third and fourth quartiles in both males and females SALS (p(f) = 0.001 and p(m) < 0.05). No correlation was found between △ALS-FRS-R/m and UA (p > 0.05), nor between SALS survival and UA. SALS patients have low level of serum UA than controls. Low level of uric acid may be associated with increased occurrence of SALS in Chinese population. Uric acid level may not contribute to the survival or progression of SALS.

A review of the clinical evidence for complementary and alternative therapies in Parkinson's disease

OPINION STATEMENT

No conventional treatment has been convincingly demonstrated to slow or stop the progression of Parkinson's disease (PD). Dopaminergic therapy is the gold standard for managing the motor disability associated with PD, but it falls short of managing all of the aspects of the disease that contribute to quality of life. Perhaps for this reason, an increasing number of patients are searching for a more holistic approach to healthcare. This is not to say that they are abandoning the standard and effective symptomatic therapies for PD, but rather are complementing them with healthy living, mind-body practices, and natural products that empower patients to be active participants in their healthcare and widen the net under which disease modification might one day be achieved. Despite high rates of utilization of complementary and alternative medicine (CAM) practices, data on efficacy is generally limited, restricting physicians in providing guidance to interested patients. Exercise is now well-established as integral in the management of PD, but mind-body interventions such as Tai Chi that incorporate relaxation and mindfulness with physical activity should be routinely encouraged as well. While no comment can be made about neuroplastic or disease-modifying effects of mind-body interventions, patients should be encouraged to be as active as possible and engage with others in enjoyable and challenging activities such as dance, music therapy, and yoga. Many PD patients also choose to try herbs, vitamins, and neutraceuticals as part of a healthy lifestyle, with the added expectation that these products may lower free radical damage and protect them against further cell death. Evidence for neuroprotection is limited, but patients can be encouraged to maintain a healthy diet rich in "high-power," low-inflammatory foods, while at the same time receiving education that many promising natural products have produced disappointing results in clinical trials. It is vital that the science of holistic medicine reaches a point where all neutraceuticals are investigated with the same rigor as conventional drugs. A number of agents discussed here that have a proposed role in the treatment of neurodegenerative diseases (and PD in particular), including cannabis, mucuna pruriens, and Chinese herbals, deserve more attention from basic science researchers and clinical investigators before they can be either safely utilized or dismissed.