Serum urate as a predictor of clinical and radiographic progression in Parkinson disease

Pathogenesis-targeted, disease-modifying therapies in Parkinson disease

Parkinson disease is an inexorably progressive neurodegenerative disorder. Multiple attempts have been made to establish therapies for Parkinson disease which provide neuroprotection or disease modification-two related, but not identical, concepts. However, to date, none of these attempts have succeeded. Many challenges exist in this field of research, including a complex multisystem disorder that includes dopaminergic and non-dopaminergic features; poorly understood and clearly multifaceted disease pathogenic mechanisms; a lack of reliable animal models; an absence of effective biomarkers of disease state, progression, and target engagement; and the confounding effects of potent symptomatic therapy. In this article, we will review previous, ongoing, and potential future trials designed to alter the progressive course of the disease from the perspective of the targeted underlying pathogenic mechanisms.

Relationship between serum uric acid and all-cause and cardiovascular mortality in patients treated with peritoneal dialysis

BACKGROUND

Although serum uric acid level appears to be associated with mortality in individuals treated with hemodialysis, the relationship between serum uric acid level and death is uncertain in patients treated with peritoneal dialysis (PD).

STUDY DESIGN

Cohort study.

SETTING & PARTICIPANTS

985 patients from a single PD center in South China followed up for a median of 25.3 months.

PREDICTOR

Serum uric acid level.

OUTCOMES & MEASUREMENTS

The association of baseline sex-specific uric acid level with all-cause and cardiovascular mortality was evaluated. Models were adjusted for age, body mass index, comorbidity score, residual kidney function, total Kt/V, allopurinol and angiotensin-converting enzyme inhibitor/angiotensin receptor blocker use, and laboratory test results, including hemoglobin, serum albumin, creatinine, calcium, phosphorus, triglycerides, low-density lipoprotein cholesterol, and high-sensitivity C-reactive protein.

RESULTS

Mean age was 48.3±15.4 (SD) years, and 23% had diabetes. Mean uric acid level was 7.0±1.3 (range, 3.8-19.8) mg/dL. During follow-up, 144 deaths were recorded, of which 64 were due to cardiovascular events. In multivariable models, the highest sex-specific tertile of uric acid level was associated with increased risk of all-cause mortality (HR, 1.93; 95% CI, 1.27-2.93; P=0.004) and cardiovascular mortality (HR, 3.31; 95% CI, 1.70-6.41; P<0.001) compared to the lowest tertile. Adjusted Cox regression models showed that the HRs per 1-mg/dL higher uric acid level for all-cause and cardiovascular mortality were 1.33 (95% CI, 1.14-1.56; P<0.001) and 1.44 (95% CI, 1.17-1.77; P=0.001) for men and 1.03 (95% CI, 0.86-1.24; P=0.8) and 1.16 (95% CI, 0.97-1.38; P=0.1) for women, respectively. A formal test for interaction indicated that the association of uric acid level with all-cause and cardiovascular mortality differed by sex (β = -0.06 [P=0.02] and β = -0.10 [P=0.02], respectively).

LIMITATIONS

Single measurement of uric acid at baseline. Cause of death determined by death certificates and expert consensus.

CONCLUSIONS

Elevated serum uric acid level is an independent risk factor for all-cause and cardiovascular mortality in men treated with PD.

[Advanced Parkinson's disease: clinical characteristics and treatment (part 1)]

INTRODUCTION

A large percentage of patients with Parkinson's disease (PD) develop motor fluctuations, dyskinesias, and severe non-motor symptoms within 3 to 5 years of starting dopaminergic therapy, and these motor complications are refractory to treatment. Several authors refer to this stage of the disease as advanced Parkinson's disease.

OBJECTIVE

To define the clinical manifestations of advanced PD and the risk factors for reaching this stage of the disease.

DEVELOPMENT

This consensus document has been prepared by using an exhaustive literature search and by discussion of the contents by an expert group on movement disorders of the Sociedad Española de Neurología (Spanish Neurology Society), coordinated by two of the authors (JK and MRL).

CONCLUSIONS

Severe motor fluctuations and dyskinesias, axial motor symptoms resistant to levodopa, and cognitive decline are the main signs in the clinical phenotype of advanced PD.

Uric acid is associated with the prevalence but not disease progression of multiple system atrophy in Chinese population

Oxidative stress is involved in the pathogenesis of multiple system atrophy (MSA). Uric acid has an antioxidative effect. Our aim is to clarify the correlations between serum uric acid and MSA in Chinese population. A total of 234 patients with probable MSA and 240 age- and gender- matched healthy controls were included in the study. The serum uric acid levels of all the patients and controls were evaluated. The Unified MSA Rating Scale (UMSARS) was used to assess the severity and the mean rate of annualized changes of UMSARS to assess the progression of MSA. The mean age of MSA patients was 58.90 ± 9.00 years and the mean disease duration was 2.60 ± 1.75 years. The serum uric acid levels of MSA patients were significantly lower than that of controls in males (p = 0.0001). The occurrence of MSA was increased in the lowest uric acid quartiles compared with the highest uric acid quartiles (p = 0.005). In a gender-specific analysis, increased occurrence was found in the lowest quartiles and second quartiles compared with the highest quartiles in males (p = 0.001 and p = 0.0001 respectively), but not in females. No correlation was found between the mean rate of annualized changes and serum levels of uric acid, as well as other independent factors, such as age, BMI, gender, subtype (C-type or P-type) and disease duration at the initial visit in 107 followed-up patients. MSA patients have lower levels of serum uric acid than controls. High levels of serum uric acid may be associated with a lower prevalence of MSA in the Chinese population, especially in males. However, serum uric acid does not deteriorate or ameliorate the progression of MSA.

Alcohol Consumption, Types of Alcohol, and Parkinson's Disease

Background

The epidemiologic evidence on alcohol consumption and Parkinson’s disease (PD) is equivocal. We prospectively examined total alcohol consumption and consumption of specific types of alcoholic beverage in relation to future risk of PD.

Methods

The study comprised 306,895 participants (180,235 male and 126,660 female) ages 50–71 years in 1995–1996 from the NIH-AARP Diet and Health Study. Consumption of alcoholic beverages in the past 12 months was assessed in 1995–1996. Multivariate odds ratios (OR) and 95% confidence intervals (CI) were obtained from logistic regression models.

Results

A total of 1,113 PD cases diagnosed between 2000 and 2006 were included in the analysis. Total alcohol consumption was not associated with PD. However, the association differed by types of alcoholic beverages. Compared with non-beer drinkers, the multivariate ORs for beer drinkers were 0.79 (95% CI: 0.68, 0.92) for <1 drink/day, 0.73 (95% CI: 0.50, 1.07) for 1–1.99 drinks/day, and 0.86 (95% CI: 0.60, 1.21) for ≥2 drinks/day. For liquor consumption, a monotonic increase in PD risk was suggested: ORs (95% CI) were 1.06 (0.91, 1.23), 1.22 (0.94, 1.58), and 1.35 (1.02, 1.80) for <1, 1–1.99, and ≥2 drinks/day, respectively (P for trend <0.03). Additional analyses among exclusive drinkers of one specific type of alcoholic beverage supported the robustness of these findings. The results for wine consumption were less clear, although a borderline lower PD risk was observed when comparing wine drinkers of 1–1.99 drinks/day with none drinkers (OR = 0.74, 95% CI: 0.53, 1.02).

Conclusions

Our results suggest that beer and liquor consumption may have opposite associations with PD: low to moderate beer consumption with lower PD risk and greater liquor consumption with higher risk. These findings and potential underlying mechanisms warrant further investigations.

Serum urate and the risk of Parkinson's disease: results from a meta-analysis

OBJECTIVE

Serum urate may exert protective effects against Parkinson's disease (PD) through its antioxidant capacities. In this article, we examine the hypothesis that high serum urate levels are associated with lower risk of PD.

METHODS

We searched NCBI (PubMed), ISI Web of Science and EMBASE for studies that reported the risk of PD associated with serum urate. Fixed or random effects meta-analysis was used to pool results across studies, and further analysis was used to assess the effects by gender.

RESULTS

Six studies met the inclusion criteria involving a total of 33 185 participants. Overall, we found a 33% reduction in PD incidence among persons with high serum urate level (relative risk [RR]=0.67; 95% confidence interval [CI], 0.50-0.91). Subgroup analysis was performed with 20 641 men and 12 544 women included, indicating statistically significant protective effects of serum urate in men (RR=0.60; 95% CI, 0.40-0.90) but not in women. A dose-response trend of serum urate to reduce PD risk was also observed involving 11 795 participants (RR=0.77; 95% CI, 0.68-0.88). Additionally, high serum urate levels seemed to slow the clinical decline of PD patients (RR=0.56; 95% CI, 0.43-0.72).

CONCLUSIONS

In light of these findings, our study confirms previous findings of a robust association between high serum urate level and PD risk, especially in men. It also suggests that long-term exposure to high serum urate may be linked to the delay of PD progression, however more well-designed investigations are needed.

Postmortem brain levels of urate and precursors in Parkinson's disease and related disorders

BACKGROUND

Increasing evidence suggests that urate may play an important role in neurodegenerative disease. In Parkinson's disease (PD) higher, but still normal, levels of blood and cerebrospinal fluid urate have been associated with a lower rate of disease progression.

OBJECTIVE

We explored the hypothesis that lower levels of urate and its purine precursors in brain may be associated with PD and related neurodegenerative disorders, including Alzheimer's disease (AD) and Lewy body dementia (DLB).

METHODS

Human postmortem brain tissues were obtained from PD, AD, and DLB patients and non-neurodegenerative disease controls. We measured urate and other purine pathway analytes in the frontal and temporal cortex, striatum, and cerebellum, using high-performance liquid chromatography with electrochemical and ultraviolet detection.

RESULTS

Age was well-matched among groups. Mean postmortem interval for samples was 16.3 ± 9.9 h. Urate levels in cortical and striatal tissue trended lower in PD and AD compared to controls in males only. These findings correlated with increased urate in male versus female control tissues. By contrast, in DLB urate levels were significantly elevated relative to PD and AD. Measurement of urate precursors suggested a decrease in xanthine in PD compared to AD in females only, and relative increases in inosine and adenosine in DLB and AD samples among males. Xanthine and hypoxanthine were more concentrated in striatal tissue than in other brain regions.

CONCLUSIONS

Though limited in sample size, these findings lend support to the inverse association between urate levels and PD, as well as possibly AD. The finding of increased urate in DLB brain tissue is novel and warrants further study.

Serum uric acid in patients with Parkinson's disease and vascular parkinsonism: a cross-sectional study

BACKGROUND

Elevation of serum uric acid (UA) is correlated with a decreased risk of Parkinson's disease (PD); however, the association and clinical relevance of serum UA levels in patients with PD and vascular parkinsonism (VP) are unknown.

OBJECTIVE

We performed a cross-sectional study of 160 Chinese patients with PD and VP to determine whether UA levels in patients could predict the outcomes.

METHODS

Serum UA levels were divided into quartiles and the association between UA and the severity of PD or VP was investigated in each quartile.

RESULTS

The serum levels of UA in PD were significantly lower than those in normal subjects and VP. The serum UA levels in PD patients were significantly correlated with some clinical parameters. Strong correlations were observed in male PD patients, but significant correlations were observed only between UA and the non-motor symptoms (NMS) of burden of sleep/fatigue and mood in female PD patients. PD patients in the lowest quartile of serum UA levels had significant correlations between UA and the unified Parkinson's disease rating scale, the modified Hoehn and Yahr staging scale and NMS burden for attention/memory.

CONCLUSION

Our findings support the hypothesis that subjects with low serum UA levels may be more prone to developing PD and indicate that the inverse relationship between UA and severity of PD was robust for men but weak for women. Our results strongly imply that either low serum UA level is a deteriorative predictor or that serum UA level serves as an indirect biomarker of prediction in PD but not in VP patients.

Urate in Parkinson's disease: more than a biomarker?

Parkinson's disease (PD) is a progressive neurodegenerative disease with characteristic motor manifestations. Although appreciation of PD as a multisystem disorder has grown, loss of dopaminergic neurons in the substantia nigra remains a pathological and neurochemical hallmark, accounting for the substantial symptomatic benefits of dopamine replacement therapies. However, currently no treatment has been shown to prevent or forestall the progression of the disease in spite of tremendous efforts. Among multiple environmental and genetic factors that have been implicated in the pathogenesis of PD, oxidative stress is proposed to play a critical role. A recent confluence of clinical, epidemiological, and laboratory evidence identified urate, an antioxidant and end product of purine metabolism, as not only a molecular predictor for both reduced risk and favorable progression of PD but also a potential neuroprotectant for the treatment of PD. This review summarizes recent findings on urate in PD and their clinical implications.

Uric acid as a danger signal in gout and its comorbidities

Uric acid is a waste product of purine catabolism. This molecule comes to clinical attention when it nucleates to form crystals of monosodium urate (MSU) in joints or other tissues, and thereby causes the inflammatory disease of gout. Patients with gout frequently suffer from a number of comorbid conditions including hypertension, diabetes mellitus and cardiovascular disease. Why MSU crystals trigger inflammation and are associated with comorbidities of gout has been unclear, but recent studies provide new insights into these issues. Rather than simply being a waste product, uric acid could serve a pathophysiological role as a local alarm signal that alerts the immune system to cell injury and helps to trigger both innate and adaptive immune responses. The inflammatory component of these immune responses is caused when urate crystals trigger both inflammasome-dependent and independent pathways to generate the proinflammatory cytokine IL-1. The resulting bioactive IL-1 stimulates the inflammation of gout and might contribute to the development of other comorbidities. Surprisingly, the same mechanisms underlie the inflammatory response to a number of irritant particles, many of which also cause disease. These new insights help to explain the pathogenesis of gout and point to potential new therapeutic targets for this and other sterile inflammatory diseases.

Biochemical premotor biomarkers for Parkinson's disease

A biomarker is a biological characteristic that is objectively measured and evaluated as an indicator of normal biological or pathologic processes or of pharmacologic responses to a therapeutic intervention. We reviewed the current status of target protein biomarkers (eg, total/oligomeric α-synuclein and DJ-1) in cerebrospinal fluid, as well as on unbiased processes that can be used to discover novel biomarkers. We have also provide details about strategies toward potential populations/models and technologies, including the need for standardized sampling techniques, to pursue the identification of new biochemical markers in the premotor stage of Parkinson's disease in the future.

Protection of dopaminergic cells by urate requires its accumulation in astrocytes

Urate is the end product of purine metabolism and a major antioxidant circulating in humans. Recent data link higher levels of urate with a reduced risk of developing Parkinson's disease and with a slower rate of its progression. In this study, we investigated the role of astrocytes in urate-induced protection of dopaminergic cells in a cellular model of Parkinson's disease. In mixed cultures of dopaminergic cells and astrocytes oxidative stress-induced cell death and protein damage were reduced by urate. By contrast, urate was not protective in pure dopaminergic cell cultures. Physical contact between dopaminergic cells and astrocytes was not required for astrocyte-dependent rescue as shown by conditioned medium experiments. Urate accumulation in dopaminergic cells and astrocytes was blocked by pharmacological inhibitors of urate transporters expressed differentially in these cells. The ability of a urate transport blocker to prevent urate accumulation into astroglial (but not dopaminergic) cells predicted its ability to prevent dopaminergic cell death. Transgenic expression of uricase reduced urate accumulation in astrocytes and attenuated the protective influence of urate on dopaminergic cells. These data indicate that urate might act within astrocytes to trigger release of molecule(s) that are protective for dopaminergic cells.

Nicotine as a potential neuroprotective agent for Parkinson's disease

Converging research efforts suggest that nicotine and other drugs that act at nicotinic acetylcholine receptors (nAChRs) may be beneficial in the management of Parkinson's disease. This idea initially stemmed from the results of epidemiological studies that demonstrated that smoking is associated with a decreased incidence of Parkinson's disease. The subsequent finding that nicotine administration protected against nigrostriatal damage in parkinsonian animal models led to the idea that nicotine in tobacco products may contribute to this apparent protective action. Nicotine most likely exerts its effects by interacting at nAChRs. Accumulating research indicates that multiple subtypes containing nAChRs, including α4β2, α6β2, and/or α7, may be involved. Stimulation of nAChRs initially activates various intracellular transduction pathways primarily via alterations in calcium signaling. Consequent adaptations in immune responsiveness and trophic factors may ultimately mediate nicotine's ability to reduce/halt the neuronal damage that arises in Parkinson's disease. In addition to a potential neuroprotective action, nicotine also has antidepressant properties and improves attention/cognition. Altogether, these findings suggest that nicotine and nAChR drugs represent promising therapeutic agents for the management of Parkinson's disease.

Nicotine as a potential neuroprotective agent for Parkinson's disease

Converging research efforts suggest that nicotine and other drugs that act at nicotinic acetylcholine receptors (nAChRs) may be beneficial in the management of Parkinson's disease. This idea initially stemmed from the results of epidemiological studies that demonstrated that smoking is associated with a decreased incidence of Parkinson's disease. The subsequent finding that nicotine administration protected against nigrostriatal damage in parkinsonian animal models led to the idea that nicotine in tobacco products may contribute to this apparent protective action. Nicotine most likely exerts its effects by interacting at nAChRs. Accumulating research indicates that multiple subtypes containing nAChRs, including α4β2, α6β2, and/or α7, may be involved. Stimulation of nAChRs initially activates various intracellular transduction pathways primarily via alterations in calcium signaling. Consequent adaptations in immune responsiveness and trophic factors may ultimately mediate nicotine's ability to reduce/halt the neuronal damage that arises in Parkinson's disease. In addition to a potential neuroprotective action, nicotine also has antidepressant properties and improves attention/cognition. Altogether, these findings suggest that nicotine and nAChR drugs represent promising therapeutic agents for the management of Parkinson's disease.

A molecular signature in blood identifies early Parkinson's disease

Background

The search for biomarkers in Parkinson’s disease (PD) is crucial to identify the disease early and monitor the effectiveness of neuroprotective therapies. We aim to assess whether a gene signature could be detected in blood from early/mild PD patients that could support the diagnosis of early PD, focusing on genes found particularly altered in the substantia nigra of sporadic PD.

Results

The transcriptional expression of seven selected genes was examined in blood samples from 62 early stage PD patients and 64 healthy age-matched controls. Stepwise multivariate logistic regression analysis identified five genes as optimal predictors of PD: p19 S-phase kinase-associated protein 1A (odds ratio [OR] 0.73; 95% confidence interval [CI] 0.60–0.90), huntingtin interacting protein-2 (OR 1.32; CI 1.08–1.61), aldehyde dehydrogenase family 1 subfamily A1 (OR 0.86; 95% CI 0.75–0.99), 19 S proteasomal protein PSMC4 (OR 0.73; 95% CI 0.60–0.89) and heat shock 70-kDa protein 8 (OR 1.39; 95% CI 1.14–1.70). At a 0.5 cut-off the gene panel yielded a sensitivity and specificity in detecting PD of 90.3 and 89.1 respectively and the area under the receiving operating curve (ROC AUC) was 0.96.

The performance of the five-gene classifier on the de novo PD individuals alone composing the early PD cohort (n = 38), resulted in a similar ROC with an AUC of 0.95, indicating the stability of the model and also, that patient medication had no significant effect on the predictive probability (PP) of the classifier for PD risk. The predictive ability of the model was validated in an independent cohort of 30 patients at advanced stage of PD, classifying correctly all cases as PD (100% sensitivity). Notably, the nominal average value of the PP for PD (0.95 (SD = 0.09)) in this cohort was higher than that of the early PD group (0.83 (SD = 0.22)), suggesting a potential for the model to assess disease severity. Lastly, the gene panel fully discriminated between PD and Alzheimer’s disease (n = 29).

Conclusions

The findings provide evidence on the ability of a five-gene panel to diagnose early/mild PD, with a possible diagnostic value for detection of asymptomatic PD before overt expression of the disorder.

Premotor biomarkers for Parkinson's disease - a promising direction of research

The second most serious neurodegenerative disease is Parkinson’s disease (PD). Over the past several decades, a strong body of evidence suggests that PD can begin years before the hallmark clinical motor symptoms appear. Biomarkers for PD are urgently needed to differentiate between neurodegenerative disorders, screen novel therapeutics, and predict eventual clinical PD before the onset of symptoms. Some clinical evaluations and neuroimaging techniques have been developed in the last several years with some success in this area. Moreover, other strategies have been utilized to identify biochemical and genetic markers associated with PD leading to the examination of PD progression and pathogenesis in cerebrospinal fluid, blood, or saliva. Finally, interesting results are surfacing from preliminary studies using known PD-associated genetic mutations to assess potential premotor PD biomarkers. The current review highlights recent advances and underscores areas of potential advancement.

Urate and its transgenic depletion modulate neuronal vulnerability in a cellular model of Parkinson's disease

Urate is a major antioxidant as well as the enzymatic end product of purine metabolism in humans. Higher levels correlate with a reduced risk of developing Parkinson's disease (PD) and with a slower rate of PD progression. In this study we investigated the effects of modulating intracellular urate concentration on 1-methyl-4-phenyl-pyridinium (MPP⁺)-induced degeneration of dopaminergic neurons in cultures of mouse ventral mesencephalon prepared to contain low (neuron-enriched cultures) or high (neuron-glial cultures) percentage of astrocytes. Urate, added to the cultures 24 hours before and during treatment with MPP⁺, attenuated the loss of dopaminergic neurons in neuron-enriched cultures and fully prevented their loss and atrophy in neuron-astrocyte cultures. Exogenous urate was found to increase intracellular urate content in cortical neuronal cultures. To assess the effect of reducing cellular urate content on MPP⁺-induced toxicity, mesencephalic neurons were prepared from mice over-expressing urate oxidase (UOx). Transgenic UOx expression decreased endogenous urate content both in neurons and astrocytes. Dopaminergic neurons expressing UOx were more susceptible to MPP⁺ in mesencephalic neuron-enriched cultures and to a greater extent in mesencephalic neuron-astrocyte cultures. Our findings correlate intracellular urate content in dopaminergic neurons with their toxin resistance in a cellular model of PD and suggest a facilitative role for astrocytes in the neuroprotective effect of urate.

Prospective study of statin use and risk of Parkinson disease

OBJECTIVE

To prospectively examine whether use of statins is associated with altered risk of Parkinson disease (PD).

DESIGN, SETTING, AND PARTICIPANTS

A prospective study including 38 192 men and 90 874 women participating in 2 ongoing US cohorts, the Health Professional Follow-up Study and the Nurses' Health Study, was conducted. Information on regular cholesterol-lowering drug use (≥2 times/wk) was collected in 1994 in both cohorts via questionnaire. Relative risks (RRs) and 95% CIs were computed using Cox proportional hazards models adjusting for age, smoking, caffeine intake, duration of hypercholesterolemia, and other covariates.

MAIN OUTCOME MEASURE

Incident PD.

RESULTS

During 12 years of follow-up (1994-2006), we documented 644 incident PD cases (338 women and 306 men). The risk of PD was lower among current statin users (adjusted pooled RR = 0.74; 95% CI, 0.54-1.00; P = .049) relative to nonusers. A significant association was observed in participants younger than 60 years at baseline (adjusted pooled RR = 0.31; 95% CI, 0.11-0.86; P = .02) but not among those who were older (adjusted pooled RR = 0.83; 95% CI, 0.60-1.14; P = .25) (P for interaction = .03).

CONCLUSIONS

We found that regular use of statins was associated with a modest reduction in PD risk. The possibility that some statins may reduce PD risk deserves further consideration.

Gene expression profiling and therapeutic interventions in neurodegenerative diseases: a comprehensive study on potentiality and limits

INTRODUCTION

Neurodegenerative diseases are incurable debilitating disorders of the nervous system that affect approximately 30 million people worldwide. Despite profuse efforts attempting to define the molecular mechanisms underlying neurodegeneration, many aspects of these pathologies remain elusive. The novelty of their mechanisms represents a challenge to biology, to their related biomarkers identification and drug discovery. Because of their multifactorial aspects and complexity, gene expression analysis platforms have been extensively used to investigate altered pathways during degeneration and to identify potential biomarkers and drug targets.

AREAS COVERED

This work offers an overview of the gene expression profiling studies carried out on Alzheimer's disease, Huntington's disease, Parkinson's disease and prion disease specimens. Therapeutic approaches are also discussed.

EXPERT OPINION

Although many therapeutic approaches have been tested, some of them acting on several altered cellular pathways, no effective cures for these neurodegenerative diseases have been identified. Microarray technology must be associated with functional proteomics and physiology in an effort to identify specific and selective biomarkers and druggable targets, thus allowing the successful discovery of disease-modifying therapeutic treatments.

Uric acid levels predict survival in men with amyotrophic lateral sclerosis

Elevated uric acid levels have recently been found to be associated with slower disease progression in Parkinson's disease, Huntington's disease, multiple system atrophy, and mild cognitive impairment. The aim of this study is to determine whether serum uric acid levels predict survival in amyotrophic lateral sclerosis (ALS). A total of 251 people with ALS enrolled in two multicenter clinical trials were included in our analysis. The main outcome measure was survival time, which was calculated as time to death, tracheostomy, or permanent assistive ventilation, with any event considered a survival endpoint. Cox proportional hazards models were used to estimate the hazard ratio (HR) of reaching a survival endpoint according to baseline uric acid levels after adjusting for markers of disease severity (FVC, total ALSFRS-R score, time since symptom onset, diagnostic delay, BMI, bulbar vs. spinal onset, age, and riluzole use). There was a dose-dependent survival advantage in men, but not women, with higher baseline uric acid levels (logrank test: p = 0.018 for men, p = 0.81 for women). There was a 39% reduction in risk of death during the study for men with each 1 mg/dl increase in uric acid levels (adjusted HR: 0.61, 95% CI 0.39-0.96, p = 0.03). This is the first study to demonstrate that serum uric acid is associated with prolonged survival in ALS, after adjusting for markers of disease severity. Similar to previous reports in Parkinson's disease, this association was seen in male subjects only.

Relationships between disease progression and serum levels of lipid, urate, creatinine and ferritin in Japanese patients with amyotrophic lateral sclerosis: a cross-sectional study

OBJECTIVE

Previous studies have reported distinct serological profiles of lipid, urate and ferritin in Western patients with amyotrophic lateral sclerosis (ALS). We aimed to examine the levels of these serological factors and their relationship to disease progression in Japanese ALS patients.

METHODS

Ninety-two patients with definite or probable ALS who fulfilled the revised El Escorial criteria were analyzed for clinical and serological variables. Serological data at the time diagnosed with ALS were compared to those of 92 age/sex/body mass index-matched healthy controls.

RESULTS

Compared to controls, urate and creatinine (Cr) levels were decreased and ferritin levels were increased significantly in sera of male and female patients with ALS. Significant increases of serum total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C) and triglyceride levels were found in female ALS patients. The annual decline of ALS Functional Rating Scale-Revised (ALS-FRS) and forced vital capacity (FVC) were inversely correlated with serum TC, LDL-C, Cr and urate levels, and were positively correlated with serum ferritin levels. Multivariate analysis showed that the rapid worsening of annual ALS-FRS and FVC was associated with serum levels of TC, LDL-C, Cr, urate and ferritin.

CONCLUSION

The present study indicated that serum levels of TC, LDL-C, Cr, urate and ferritin were correlated with clinical deterioration in ALS patients. These results are similar to those in Western patients. Metabolic and nutritional conditions of lipid, urate and iron could contribute to disease progression in ALS patients. Further studies investigating high nutrition diets and iron chelation for the treatment of ALS are warranted.

Parkinson's disease

Parkinson's disease (PD) is the most common age-related motoric neurodegenerative disease initially described in the 1800's by James Parkinson as the 'Shaking Palsy'. Loss of the neurotransmitter dopamine was recognized as underlying the pathophysiology of the motor dysfunction; subsequently discovery of dopamine replacement therapies brought substantial symptomatic benefit to PD patients. However, these therapies do not fully treat the clinical syndrome nor do they alter the natural history of this disorder motivating clinicians and researchers to further investigate the clinical phenotype, pathophysiology/pathobiology and etiology of this devastating disease. Although the exact cause of sporadic PD remains enigmatic studies of familial and rare toxicant forms of this disorder have laid the foundation for genome wide explorations and environmental studies. The combination of methodical clinical evaluation, systematic pathological studies and detailed genetic analyses have revealed that PD is a multifaceted disorder with a wide-range of clinical symptoms and pathology that include regions outside the dopamine system. One common thread in PD is the presence of intracytoplasmic inclusions that contain the protein, α-synuclein. The presence of toxic aggregated forms of α-synuclein (e.g., amyloid structures) are purported to be a harbinger of subsequent pathology. In fact, PD is both a cerebral amyloid disease and the most common synucleinopathy, that is, diseases that display accumulations of α-synuclein. Here we present our current understanding of PD etiology, pathology, clinical symptoms and therapeutic approaches with an emphasis on misfolded α-synuclein.

Biomarker candidates of neurodegeneration in Parkinson's disease for the evaluation of disease-modifying therapeutics

Reliable biomarkers that can be used for early diagnosis and tracking disease progression are the cornerstone of the development of disease-modifying treatments for Parkinson's disease (PD). The German Society of Experimental and Clinical Neurotherapeutics (GESENT) has convened a Working Group to review the current status of proposed biomarkers of neurodegeneration according to the following criteria and to develop a consensus statement on biomarker candidates for evaluation of disease-modifying therapeutics in PD. The criteria proposed are that the biomarker should be linked to fundamental features of PD neuropathology and mechanisms underlying neurodegeneration in PD, should be correlated to disease progression assessed by clinical rating scales, should monitor the actual disease status, should be pre-clinically validated, and confirmed by at least two independent studies conducted by qualified investigators with the results published in peer-reviewed journals. To date, available data have not yet revealed one reliable biomarker to detect early neurodegeneration in PD and to detect and monitor effects of drug candidates on the disease process, but some promising biomarker candidates, such as antibodies against neuromelanin, pathological forms of α-synuclein, DJ-1, and patterns of gene expression, metabolomic and protein profiling exist. Almost all of the biomarker candidates were not investigated in relation to effects of treatment, validated in experimental models of PD and confirmed in independent studies.

The promise of neuroprotective agents in Parkinson's disease

Parkinson’s disease (PD) is characterized by loss of dopamine neurons in the substantia nigra of the brain. Since there are limited treatment options for PD, neuroprotective agents are currently being tested as a means to slow disease progression. Agents targeting oxidative stress, mitochondrial dysfunction, and inflammation are prime candidates for neuroprotection. This review identifies Rasagiline, Minocycline, and creatine, as the most promising neuroprotective agents for PD, and they are all currently in phase III trials. Other agents possessing protective characteristics in delaying PD include stimulants, vitamins, supplements, and other drugs. Additionally, combination therapies also show benefits in slowing PD progression. The identification of neuroprotective agents for PD provides us with therapeutic opportunities for modifying the course of disease progression and, perhaps, reducing the risk of onset when preclinical biomarkers become available.

Blood-based protein biomarkers for diagnosis and classification of neurodegenerative diseases: current progress and clinical potential

Biomarker research is a rapidly advancing field in medicine. Recent advances in genomic, genetic, epigenetic, neuroscientific, proteomic, and metabolomic knowledge and technologies have opened the way to thriving research. In the most general sense, a biomarker refers to any useful characteristic that can be measured and used as an indicator of a normal biologic process, a pathogenic process, or a pharmacologic response to a therapeutic agent. Despite the extensive resources concentrated on this area, there are very few biomarkers currently available that qualify and are satisfactorily validated for mental disorders, and there is still a major lack of biomarkers for typifying neurodegenerative disorders such as Alzheimer's disease and Parkinson's disease. This article provides an overview of this field of research and focuses on recent advances in biomarker research in Alzheimer's disease and Parkinson's disease.

Serum urate and probability of dopaminergic deficit in early "Parkinson's disease"

The objective of this study was to investigate whether higher levels of urate, an antioxidant linked to a lower likelihood of developing Parkinson's disease, is also a predictor of having a dopamine transporter brain scan without evidence of dopaminergic deficit. In a cross-sectional study of 797 mildly affected, untreated parkinsonian subjects diagnosed with early Parkinson's disease in the Parkinson Research Examination of CEP-1347 Trial, we investigated the relationship at baseline between serum urate and striatal dopamine transporter density, determined by single-photon emission computed tomography of iodine-123-labeled 2-β-carboxymethoxy-3-β-(4-iodophenyl)tropane uptake. A scan without evidence of dopaminergic deficit was defined as lowest putamen iodine-123-labeled 2-β-carboxymethoxy-3-β-(4-iodophenyl)tropane > 80% age-expected putamen dopamine transporter density. The odds of having a scan without evidence of dopaminergic deficit rose across increasing quintiles of urate level, with an age- and sex-adjusted odds ratio of 3.2 comparing the highest to the lowest urate quintile (95% confidence interval, 1.5-7.2; P for trend = .0003), and remained significant after adjusting for potential confounding factors. The association was significant in men but not women, regardless of whether common or sex-specific quintiles of urate were used. Higher levels of urate were associated with a greater likelihood of a scan without evidence of dopaminergic deficit among subjects with early untreated parkinsonism in the Parkinson Research Examination of CEP-1347 Trial. The findings support the diagnostic utility of urate in combination with other determinants.

Serum cholesterol and the progression of Parkinson's disease: results from DATATOP

BACKGROUND

Recent studies have suggested that higher serum cholesterol may be associated with lower occurrence of Parkinson's disease (PD). This study is to test the hypothesis that higher serum cholesterol correlates with slower PD progression.

METHODS

Baseline non-fasting serum total cholesterol was measured in 774 of the 800 subjects with early PD enrolled between 1987 and 1988 in the Deprenyl and Tocopherol Antioxidative Therapy of Parkinsonism (DATATOP) trial. Participants were followed for up to two years, with clinical disability requiring levodopa therapy as the primary endpoint. Hazard ratios (HRs) and 95% confidence intervals (CI) were determined for increasing serum cholesterol concentration (in quintiles) for clinical disability requiring levodopa therapy, after adjusting for confounders. At baseline, only nine subjects reported use of cholesterol-lowering agents (two with statins).

RESULTS

The overall mean cholesterol level was 216 mg/dL (range 100-355). The HR of progressing to the primary endpoint decreased with increasing serum cholesterol concentrations. Compared to the lowest quintile, the HRs (95%CI), for each higher quintile (in ascending order) are 0.83 (0.59-1.16); 0.86 (0.61-1.20); 0.84 (0.60-1.18); and 0.75 (0.52-1.09). The HR for one standard deviation (SD) increase = 0.90 [(0.80-1.01), p for trend = 0.09]. This trend was found in males (HR per SD = 0.88 [(0.77-1.00), p for trend = 0.05], but not in females [HR = 1.03 (0.81-1.32)].

CONCLUSIONS

This secondary analysis of the DATATOP trial provides preliminary evidence that higher total serum cholesterol concentrations may be associated with a modest slower clinical progression of PD, and this preliminary finding needs confirmation from larger prospective studies.

Biomarkers for Parkinson's disease

Biomarkers for detecting the early stages of Parkinson's disease (PD) could accelerate development of new treatments. Such biomarkers could be used to identify individuals at risk for developing PD, to improve early diagnosis, to track disease progression with precision, and to test the efficacy of new treatments. Although some progress has been made, there are many challenges associated with developing biomarkers for detecting PD in its earliest stages.

Epidemiology and etiology of Parkinson's disease: a review of the evidence

The etiology of Parkinson's disease (PD) is not well understood but likely to involve both genetic and environmental factors. Incidence and prevalence estimates vary to a large extent-at least partly due to methodological differences between studies-but are consistently higher in men than in women. Several genes that cause familial as well as sporadic PD have been identified and familial aggregation studies support a genetic component. Despite a vast literature on lifestyle and environmental possible risk or protection factors, consistent findings are few. There is compelling evidence for protective effects of smoking and coffee, but the biologic mechanisms for these possibly causal relations are poorly understood. Uric acid also seems to be associated with lower PD risk. Evidence that one or several pesticides increase PD risk is suggestive but further research is needed to identify specific compounds that may play a causal role. Evidence is limited on the role of metals, other chemicals and magnetic fields. Important methodological limitations include crude classification of exposure, low frequency and intensity of exposure, inadequate sample size, potential for confounding, retrospective study designs and lack of consistent diagnostic criteria for PD. Studies that assessed possible shared etiological components between PD and other diseases show that REM sleep behavior disorder and mental illness increase PD risk and that PD patients have lower cancer risk, but methodological concerns exist. Future epidemiologic studies of PD should be large, include detailed quantifications of exposure, and collect information on environmental exposures as well as genetic polymorphisms.

Uric acid as a potential disease modifier in patients with multiple system atrophy

BACKGROUND

Recent studies have suggested that mitochondrial dysfunction and oxidative stress play a key role in the pathogenesis of multiple system atrophy.

METHODS

We evaluated the influence of serum uric acid levels on disease progression in 52 patients with multiple system atrophy using changes in the annualized Unified Multiple System Atrophy Rating Scale scores.

RESULTS

The mean annualized Unified Multiple System Atrophy Rating Scale changes were significantly lower in patients with the highest uric acid quartile compared with those with the lowest quartile (8.4 ± 5.1 vs 20.2 ± 16.0, P = .038). Serum uric acid levels had a significant negative correlation with the annualized Unified Multiple System Atrophy Rating Scale changes (r = -0.40, P = .004). Multiple linear regression analysis showed that only serum uric acid concentration was significantly correlated with the annualized Unified Multiple System Atrophy Rating Scale changes (β = -2.687, P = .011).

CONCLUSIONS

These data suggest that serum uric acid may act as a potential disease modifier in multiple system atrophy.

Variation in the uric acid transporter gene SLC2A9 and its association with AAO of Parkinson's disease

Based on the observed inverse association between hyperuricemia and Parkinson's disease (PD) risk, the natural antioxidant activity of uric acid has been suggested to play a protective role. SLC2A9 has been indicated as the most effective of all uric acid transporters, and SLC2A9 variants have been shown to influence circulating uric acid levels. With this study, we aimed to test the association between such SLC2A9 polymorphisms and age at onset (AAO) of PD. Variants rs733175, rs737267, rs1014290, and rs6449213 within SLC2A9 were genotyped in 664 PD individuals from three European centers. The effect of each polymorphism on AAO was estimated within each center using a linear regression model adjusted for gender and genotype at the other SNPs and assuming an additive genetic model. Results across centers were combined using inverse-variance weighted fixed-effect meta-analysis. The minor allele of rs1014290, previously shown to be associated with lower serum uric acid levels, was found to be associated with a lower AAO of PD (pooled estimate -4.56 years; 95% CI -8.13, -1.00; p=0.012). The association remained significant after adjustment for multiple comparisons and was highly consistent across centers (heterogeneity, I (2) 0%). No gender differences were observed. Our study suggests that SLC2A9 genetic variants influence age of onset of Parkinson's disease.

Discovering neuroprotection in Parkinson's disease, or getting to haphazard

Despite significant research efforts, a therapy to slow or halt the progression of Parkinson's disease ("neuroprotection") remains elusive. The discovery of such a therapy will likely require important observations from a number of perspectives: basic science investigation, clinical research, and careful observation in medical practice. Any possible insights will require confirmation in rigorous clinical trial testing. Combining the useful insights from all perspectives may be the most promising approach to discovering a neuroprotective therapy.

Urate: a novel biomarker of Parkinson's disease risk, diagnosis and prognosis

A growing number of studies have correlated higher urate levels with a lower risk of developing Parkinson's disease (PD) and with a favorable rate of disease progression, indicating that urate could be an important biomarker of the pathophysiology underlying PD. Dietary and genetic determinants of urate have also been linked to a reduced risk or delayed onset of PD. Based on the known antioxidant and metal complexing properties of urate, together with evidence for oxidative stress as a contributor to neurodegeneration in PD, urate may serve as an endogenous neuroprotectant that helps reduce the risk and rate of the disease. In this article we review the convergent biological, epidemiological and clinical data that identify urate as a promising biomarker of the risk, diagnosis and prognosis of PD.

Plasma urate and Parkinson's disease in women

Plasma urate has been consistently associated with a lower risk of Parkinson's disease in men, but it is less clear if this relation exists in women. Between 1990 and 2004, the authors conducted a nested case-control study among participants of the female-only Nurses' Health Study. In controls (n = 504), plasma urate was positively associated with age, body mass index, alcohol consumption, hypertension, and use of diuretics and was inversely associated with physical activity and postmenopausal hormone use, as expected. Mean urate levels were 5.04 mg/dL for cases (n = 101) and 4.86 mg/dL for controls (P = 0.17). The age-, smoking-, and caffeine-adjusted rate ratio comparing women in the highest (≥5.8 mg/dL) with those in the lowest (<4.0 mg/dL) quartile was 1.33 (95% confidence interval: 0.69, 2.57; P(trend) = 0.4). Further adjustment for body mass index, physical activity, history of hypertension, and postmenopausal hormone use did not change the results. Unlike in men, these findings do not support the hypothesis that urate is strongly associated with lower rates of Parkinson's disease among women.

Physical activities and future risk of Parkinson disease

OBJECTIVE

To prospectively investigate the relationship between physical activity and Parkinson disease (PD).

METHODS

We evaluated physical activity in relation to PD among 213,701 participants of the NIH-AARP Diet and Health Study cohort. Physical activities over 4 periods (ages 15-18, 19-29, and 35-39, and in the past 10 years) were noted in 1996-1997, and physician-diagnosed PD was reported on the 2004-2006 follow-up questionnaire. Only cases diagnosed after 2000 (n = 767) were included in the analyses.

RESULTS

Higher levels of moderate to vigorous activities at ages 35-39 or in the past 10 years as reported in 1996-1997 were associated with lower PD occurrence after 2000 with significant dose-response relationships. The multivariate odds ratios (OR) between the highest vs the lowest levels were 0.62 (95% CI confidence interval [CI] 0.48-0.81, p for trend 0.005) for ages 35-39 and 0.65 (95% CI 0.51-0.83, p for trend 0.0001) for in the past 10 years. Further analyses showed that individuals with consistent and frequent participation in moderate to vigorous activities in both periods had approximately a 40% lower risk than those who were inactive in both periods. Moderate to vigorous activities at earlier ages or light activities were not associated with PD. Finally, the association between higher moderate to vigorous physical activities and lower PD risk was demonstrated in a metaanalysis of prospective studies.

CONCLUSIONS

Although we cannot exclude the possibility that less participation in physical activity is an early marker of PD, epidemiologic evidence suggests that moderate to vigorous exercise may protect against PD.