Serum uric acid levels in Parkinson's disease and related disorders

Biomarkers of Parkinson's Disease: From Basic Research to Clinical Practice

Parkinson's disease (PD) is a common neurodegenerative disease characterized pathologically by dopaminergic neuron loss and the formation of Lewy bodies, which are enriched with aggregated α-synuclein (α-syn). PD currently has no cure, but therapeutic strategies are available to alleviate symptoms. Early diagnosis can greatly improve therapeutic interventions, but the clinical diagnosis of PD remains challenging and depends mainly on clinical features and imaging tests. Efficient and specific biomarkers are crucial for the diagnosis, monitoring, and evaluation of PD. Here, we reviewed the biomarkers of PD in different tissues and biofluids, along with the current clinical biochemical detection methods. We found that the sensitivity and specificity of single biomarkers are limited, and selecting appropriate indicators for combined detection can improve the diagnostic accuracy of PD.

Elevated Serum Xanthine Oxidase and Its Correlation with Antioxidant Status in Patients with Parkinson's Disease

Parkinson's disease (PD) is a neurodegenerative movement disorder associated with a loss of dopamine neurons in the substantia nigra. The diagnosis of PD is sensitive since it shows clinical features that are common with other neurodegenerative diseases. In addition, most symptoms arise at the late stage of the disease, where most dopaminergic neurons are already damaged. Several studies reported that oxidative stress is a key modulator in the development of PD. This condition occurs due to excess reactive oxygen species (ROS) production in the cellular system and the incapability of antioxidants to neutralize it. In this study, we focused on the pathology of PD by measuring serum xanthine oxidase (XO) activity, which is an enzyme that generates ROS. Interestingly, the serum XO activity of patients with PD was markedly upregulated compared to patients with other neurological diseases (ONDs) as a control. Moreover, serum XO activity in patients with PD showed a significant correlation with the disease severity based on the Hoehn and Yahr (HY) stages. The investigation of antioxidant status also revealed that serum uric acid levels were significantly lower in the severe group (HY ≥ 3) than in the ONDs group. Together, these results suggest that XO activity may contribute to the development of PD and might potentially be a biomarker for determining disease severity in patients with PD.

Hyperuricemia may be associated with muscle wellness in older adults

PURPOSE

Sarcopenia, associated with morbidity and mortality, is a common geriatric syndrome in older adults. In this study, we investigated the relationship between uric acid, which is a powerful antioxidant and has intracellular proinflammatory activity, and sarcopenia in older adults.

METHODS

This is a cross-sectional retrospective study involving a total of 936 patients. The diagnosis of sarcopenia was evaluated based on the EGWSOP 2 criteria. The patients were divided into two groups according to hyperuricemia (for females > 6 mg/dl, for males > 7 mg/dl); hyperuricemia and control.

RESULTS

The frequency of hyperuricemia was 65.40%. Patients with hyperuricemia were older than the control group and female gender frequency was higher (p = 0.001, p < 0.001, respectively). Sarcopenia was negatively associated with hyperuricemia as a result of the adjustment analysis made according to demographic characteristics, comorbidities, laboratory results, malnutrition, and malnutrition risk. (p = 0.034). Besides, muscle mass and muscle strength were associated with hyperuricemia (p = 0.026 and p = 0.009, respectively).

CONCLUSIONS

Considering the positive effect of hyperuricemia on sarcopenia, avoiding aggressive uric acid-lowering therapy may be a good option in older adults with asymptomatic hyperuricemia.

Serum Uric Acid Levels in Neurodegenerative Disorders: A Cross-Sectional Study

Background: Excessive oxidative stress may contribute to neurodegeneration by leading to protein aggregation and mitochondrial dysfunction. Uric acid (UA) is an important endogenous antioxidant that protects against oxidative stress, yet its exact role in neurodegeneration remains unclear. Objective: To explore the performance of serum UA in neurodegenerative disorders. Methods: A total of 839 controls and 840 patients, including Alzheimer’s disease (AD), Parkinson’s disease (PD), multiple system atrophy (MSA), progressive supranuclear palsy (PSP), frontotemporal dementia (FTD), dementia with Lewy bodies (DLB), motor neuron disease (MND), Creutzfeldt-Jakob disease (CJD), and mixed dementia (MixD) were enrolled. Fasting serum UA levels were measured in all participants and compared between patients and controls. Linear regression models were utilized to explore possible relationships of serum UA with cognition, disease duration, age, and age of onset. Results: Compared to controls (355.48 ± 85.38 μmol/L), serum UA was significantly lower in AD (291.29 ± 83.49 μmol/L, p < 0.001), PD (286.95 ± 81.78 μmol/L, p < 0.001), PSP (313.32 ± 88.19 μmol/L, p < 0.001), FTD (313.89 ± 71.18 μmol/L, p = 0.001), and DLB (279.23 ± 65.51 μmol/L, p < 0.001), adjusting for confounding factors including age, gender, education, etc. In addition, serum UA was positively correlated with cognitive levels in all patients (Mini-Mental State Examination: r = 0.136, p = 0.001; and Montreal Cognitive Assessment Scale: r = 0.108, p = 0.009). Conclusion: Decreased levels of serum UA were correlated with AD, PD, PSP, FTD, and DLB, offering significant potential as a promisingly relevant, less-invasive marker of multiple neurodegenerative disorders.

Correlation of Serum Uric Acid with Cognition, Severity, and Stage of Disease in Patients with Idiopathic Parkinson’s Disease and Vascular Parkinsonism: A Cross-Sectional Study

Background:

Uric acid (UA) being a potent antioxidant may reduce the oxidative stress and progression of Parkinson’s disease. However, the role of UA is not yet established in people with Idiopathic Parkinson’s disease (IPD) and Vascular Parkinsonism (VP).

Objectives:

We aimed i) to compare the serum UA levels in IPD, VP, and healthy adults and ii) to find a relation between UA levels with disease severity, disease stage, and cognitive function in people with IPD and VP.

Methods:

A cross-sectional study was conducted among people with IPD (n=70), VP (n=70), and healthy adults (n=70). Demographics details, body mass index, duration of illness, levodopa usage, comorbidities, MDS-UPDRS scores, modified H&Y scale, MMSE, and serum UA levels were collected from participants. Pearson’s correlation coefficient was used to find the correlation between UA levels, MDS-UPDRS, H & Y, and MMSE scores.

Results:

The age of the participants ranged from 59 to 80 years. Results showed that serum UA level in healthy control (5.41±0.99; p=0.001) and VP groups (5.27 ± 0.99; p=0.001) were significantly higher compared to IPD group (4.34 ±1.03). We found a significant negative correlation between UA and MDS-UPDRS (r=-0.68, p<0.01) and H & Y scores (r = -0.61, p<0.01) and a significant positive correlation of UA with MMSE (r=0.55, p<0.01) in the IPD group. UA levels in the VP group were not correlated with any of the outcome measures.

Conclusion:

In people with IPD, serum UA level was negatively correlated with severity and progression of the disease but positively correlated with cognitive ability.

Cognition, motor symptoms, and glycolipid metabolism in Parkinson's disease with depressive symptoms

Depressive symptoms and abnormal glycolipid metabolisms are common in patients with Parkinson's disease (PD), but their relationship has not been fully reported. It is not clear whether glycolipid impairments lead to poor cognitive and motor function, and aggravate depressive symptoms. Therefore, we aimed to explore the relationships between glycolipid variables, cognition, motor and depressive symptoms in PD patients cross-sectionally. Two hundred ten PD patients were recruited. Glycolipid parameters and Uric acid (UA) were measured. Depressive symptoms, cognitive function and motor symptoms were assessed using the Hamilton Depression Rating Scale-17 (HAMD-17), the Montreal Cognitive Assessment (MOCA) and the Movement Disorder Society Unified Parkinson's Disease Rating Scale Part-III (UPDRS-III). Depressive PD patients had significantly worse motor symptoms and higher levels of fasting plasma glucose (FPG) than those in non-depressive patients (F = 24.145, P < 0.001). Further, logistic regression analysis indicated that UPDRS-III (OR = 1.039, 95% CI 1.019-1.057, P = 0.044), FPG (OR = 1.447, 95% CI 1.050-1.994, P = 0.024) were independently associated with depression. In PD patients without depression, UA (β = - 0.068, t = - 2.913, P = 0.005) and cholesterol (CHOL) (β = - 3.941, t = - 2.518, P = 0.014) were independent predictors of the UPDRS-III score; in addition, UPDRS-III score was negatively associated with MOCA score (β = - 0.092, t = - 2.791, P = 0.007). FPG levels and motor symptoms were related to depressive symptoms in PD patients. Further, in non-depressive PD patients, UA and CHOL showed putative biomarkers of motor symptoms.

Serum Cystatin C as a Potential Predictor of the Severity of Multiple System Atrophy With Predominant Cerebellar Ataxia: A Case-Control Study in Chinese Population

Objective: Multiple system atrophy (MSA) is a serious neurodegenerative disease that is charactered by progressive neurological disability. The aim of this study was to investigate the correlation of serum oxidant factors with the severity of MSA.

Methods: A total of 52 MSA patients and 52 age- and gender- matched healthy subjects were retrospectively enrolled in this study. Enzymatic colorimetric methods were used to assay the concentrations of uric acid (UA), serum creatinine (Scr), blood urea nitrogen (BUN), and cystatin C (Cys-C). Disease severity was evaluated by the Unified Multiple System Atrophy Rating Scale (UMSARS). The disease progression rate was defined by the change in UMSARS-IV (global disability score, GDS) over a 1-year period.

Results: Comparisons between the two groups revealed that there were no significant differences in terms of serum Scr (70.81 ± 13.88 vs. 70.92 ± 14.19 μmol/L, p = 0.967). However, the serum levels of the other three biomarkers were significantly higher in the MSA patients (UA: 325.31 ± 84.92 vs. 291.19 ± 64.14 μmol/L, p = 0.023; BUN: 5.68 ± 1.67 vs. 4.60 ± 1.24 mmol/L, p < 0.001; Cys-C: 0.96 ± 0.15 vs. 0.89 ± 0.14 mg/L, p = 0.024). In addition, Pearson correlation analyses revealed that only serum Cys-C was significantly correlated to GDS (r = 0.281, p = 0.044). Subgroup analysis further demonstrated that serum Cys-C was the only factor that was positively associated with the disease severity in patients with MSA and predominant cerebellar ataxia (MSA-C) (r = 0.444, p = 0.018); there was no significant association in MSA patients with predominant Parkinsonism (MSA-P) (r = 0.118, p = 0.582). MSA-C patients with severe disability were shown to express higher serum levels of Cys-C than patients with mild disability (1.03 ± 0.13 vs. 0.88 ± 0.12 mg/L, p = 0.009). Finally, Kaplan-Meier plots revealed a significant difference in the 5-year probability of survival from severe disability between MSA-C patients with high- and low-concentrations of serum Cys-C (Log-rank test: X² = 4.154, p = 0.042). ROC curve analysis confirmed that serum Cys-C exhibits good performance as a biomarker (AUC = 0.847).

Conclusion: Our research indicated that oxidative stress plays a vital role in MSA. Serum Cys-C represents a potential prognostic biomarker to evaluate the severity of disease in patients with MSA-C.

The Influence of Serum Uric Acid Level on Non-Motor Symptoms Occurrence and Severity in Patients with Idiopathic Parkinson's Disease and Atypical Parkinsonisms-A Systematic Review

Background and Objectives: A growing number of studies correlated higher levels of serum uric acid (UA) with both: lower risk of Parkinson’s Disease (PD) occurrence and slower progression of the disease. Similar conclusions were made where studies correlated UA with atypical Parkinsonisms (AP) progression. A few researchers have studied the issue of the influence of serum UA on the occurrence of non-motor symptoms (NMS) in PD and AP. Our systematic review is the first review completely dedicated to this matter. Materials and Methods: A comprehensive evaluation of the literature was performed to review the relationship between UA and NMS in PD and AP. The systematic review was conducted according to PRISMA Statement guidelines. The following databases were searched starting in April 2021: MEDLINE via PubMed, Embase, and Scopus. During the research, the following filters were used: >2010, articles in English, concerning humans. The study was not registered and received no external funding. Results: Seven articles meeting all inclusion criteria were included in this study. Collectively, data on 1104 patients were analyzed. A correlation between serum UA concentration and a few NMS types has been provided by the analyzed studies. In four papers, sleep disorders and fatigue were related to UA for both advanced and early PD. Other commonly appearing NMS domains were Attention/memory (4 studies), Depression/anxiety (3 studies), Cardiovascular (3 studies), Gastrointestinal (1 study), Perceptual (1 study), and Miscellaneous (1 study). For AP, no significant correlation between UA and worsening of NMS has been found. Conclusions: Based on the analyzed studies, a correlation between serum UA level and the occurrence and worsening of NMS in PD and APs cannot be definitively determined. Large-scale studies with a more diverse patient population and with more accurate methods of NMS assessment in Parkinsonism are needed.

Novel Therapies for Parkinsonian Syndromes-Recent Progress and Future Perspectives

Background: Atypical parkinsonian syndromes are rare, fatal neurodegenerative diseases associated with abnormal protein accumulation in the brain. Examples of these syndromes include progressive supranuclear palsy, multiple system atrophy, and corticobasal degeneration. A common clinical feature in parkinsonism is a limited improvement with levodopa. So far, there are no disease-modifying treatments to address these conditions, and therapy is only limited to the alleviation of symptoms. Diagnosis is devastating for patients, as prognosis is extremely poor, and the disease tends to progress rapidly. Currently, potential causes and neuropathological mechanisms involved in these diseases are being widely investigated. Objectives: The goal of this review is to summarize recent advances and gather emerging disease-modifying therapies that could slow the progression of atypical parkinsonian syndromes. Methods: PubMed and Google Scholar databases were searched regarding novel perspectives for atypical parkinsonism treatment. The following medical subject headings were used: "atypical parkinsonian syndromes-therapy," "treatment of atypical parkinsonian syndromes," "atypical parkinsonian syndromes-clinical trial," "therapy of tauopathy," "alpha-synucleinopathy treatment," "PSP therapy/treatment," "CBD therapy/treatment," "MSA therapy/treatment," and "atypical parkinsonian syndromes-disease modifying." All search results were manually reviewed prior to inclusion in this review. Results: Neuroinflammation, mitochondrial dysfunction, microglia activation, proteasomal impairment, and oxidative stress play a role in the neurodegenerative process. Ongoing studies and clinical trials target these components in order to suppress toxic protein accumulation. Various approaches such as stem cell therapy, anti-aggregation/anti-phosphorylation agent administration, or usage of active and passive immunization appear to have promising results. Conclusion: Presently, disease-modifying strategies for atypical parkinsonian syndromes are being actively explored, with encouraging preliminary results. This leads to an assumption that developing accurate, safe, and progression-halting treatment is not far off. Nevertheless, the further investigation remains necessary.

Patients with REM sleep behavior disorder have higher serum levels of allantoin

INTRODUCTION

Rapid eye movement (REM) sleep behavior disorder (RBD) is associated with an increased risk of developing Parkinson's disease (PD). Low uric acid (UA) levels are associated with the risk of development and progression of PD. Allantoin is the major oxidation product of UA and is considered as a biomarker of oxidative stress. We aimed to compare serum levels of UA, allantoin, and allantoin/UA ratio in RBD patients with those in healthy controls, and to examine their associations with clinical severity.

METHODS

We evaluated serum levels of UA, allantoin, and allantoin/UA ratio in 38 RBD patients (one female, mean age 66.8 (SD 6.3) years) and in 47 controls (four females, 66.8 (7.6) years). All RBD patients were assessed according to an examination protocol, which included structured interview, Montreal Cognitive Assessment (MoCA), Movement Disorder Society-Unified Parkinson's Disease Rating Scale (MDS-UPDRS), and dopamine transporter single-photon emission computed tomography (DAT-SPECT). The lower putaminal binding ratio from both hemispheres was used for analysis.

RESULTS

Mean serum allantoin concentration and allantoin/UA ratio were significantly increased in the RBD group compared to controls (2.6 (1.8) vs. 1.4 (0.7) μmol/l, p = 0.0004, and 0.008 (0.004) vs. 0.004 (0.002), p < 0.0001, respectively). There were no significant differences in UA levels between the two groups. No significant associations between any biochemical parameter and RBD duration, putaminal binding ratio on DAT-SPECT, MDS-UPDRS, or MoCA score were found.

CONCLUSION

Serum allantoin and allantoin/UA ratio are increased in RBD patients in comparison to controls, which may reflect increased systemic oxidative stress in prodromal synucleinopathy.

Gout and Levodopa: An unknown adverse effect?

We report the case of a 77-year-old man with Parkinson's disease (PD) who experimented for the first time gout crisis after the initiation of levodopa. Levodopa was withdrawn, and colchicine and allopurinol were initiated to treat the gout crisis. Because of PD progression, levodopa was reintroduced, and the patient presented relapse of gout flare. To further explore the association between gout and levodopa, we extracted and synthetized all Individual Case Safety Reports of gout associated with levodopa in the World Health Organization pharmacovigilance database, VigiBase^® , up to April 2021. 43 cases of gout were reported in VigiBase^® with drugs from N04BA ATC class. Levodopa was suspected in fifteen cases among which improvement was noticed in six cases (two after levodopa withdrawal, two despite treatment continuation, and two cases lacking details about action taken with levodopa); three cases did not recover; in the remaining six cases, evolution was not known. "Hyperuricemia" was not mentioned in the Summary of Product Characteristics of medicine containing levodopa; however, "abnormality biologics test with uric acid" was mentioned. Despite few cases of recovery after reduced doses of levodopa, the above-described case of positive reintroduction was an argument in favor of the role of levodopa in gout flare. This study highlights a potential association between levodopa and gout through an analysis of the cases reported in the WHO pharmacovigilance database.

Intragastric Administration of Casein Leads to Nigrostriatal Disease Progressed Accompanied with Persistent Nigrostriatal-Intestinal Inflammation Activited and Intestinal Microbiota-Metabolic Disorders Induced in MPTP Mouse Model of Parkinson's Disease

Gut microbial dysbiosis and alteration of gut microbiota composition in Parkinson's disease (PD) have been increasingly reported, no recognized therapies are available to halt or slow progression of PD and more evidence is still needed to illustrate its causative impact on gut microbiota and PD and mechanisms for targeted mitigation. Epidemiological evidence supported an association between milk intake and a higher incidence of Parkinson's disease (PD), questions have been raised about prospective associations between dietary factors and the incidence of PD. Here, we investigated the significance of casein in the development of PD. The mice were given casein (6.75 g/kg i.g.) for 21 days after MPTP (25 mg/kg i.p. × 5 days) treatment, the motor function, dopaminergic neurons, inflammation, gut microbiota and fecal metabolites were observed. The experimental results revealed that the mice with casein gavage after MPTP treatment showed a persisted dyskinesia, the content of dopamine in striatum and the expression of TH in midbrain and ileum were decreased, the expression of Iba-1, CD4, IL-22 in midbrain and ileum increased continuously with persisted intestinal histopathology and intestinal barrier injury. Decreased intestinal bile secretion in addition with abnormal digestion and metabolism of carbohydrate, lipids and proteins were found, whereas these pathological status for the MPTP mice without casein intake had recovered after 24 days, no significant differences were observed with regard to only treated with casein. Our study demonstrates that intestinal pathologic injury, intestinal dysbacteriosis and metabolism changes promoted by casein in MPTP mice ultimately exacerbated the lesions to dopaminergic neurons.

The association between multiple risk factors, clinical correlations and molecular insights in Parkinson's disease patients from Tamil Nadu population, India

Parkinson's disease (PD) is a neurodegenerative disease with multifactorial aetiology that influences the quality of life. However, the association of possible factors with PD is need to be investigated in Indian population, hence we aimed to determine the association of lifestyle, environmental factors, biochemical parameters and genetic insights of MT-ND1 gene in PD patients. Using a standardised questionnaire, PD patients and control group of about 146 subjects were interviewed on demographic, lifestyle and environmental factors. The subjects includes n = 73 Parkinson's patients [juvenile (n = 4); early-onset (n = 8); late-onset (n = 61)] with equal number of age and sex matched controls, further we had obtained institutional ethical clearance and informed consent from study participants. Biomarker investigations and MT-ND1 alterations were investigated by appropriate molecular techniques. During the average follow-up years of 5.1, significant association was observed among smoking, alcohol, caffeinated drinks, surgery, pesticide exposure at p < 0.05 in varied PD age groups. Occupational exposure to agriculture and industry showed an increased risk among the late-onset group. The biomarkers uric acid (UA) and dopamine (DA) were significant at p < 0.05 in all the three PD age groups. The MT-ND1 alteration with A3843 G variant was significant at p < 0.05 for AG allele in all the three PD groups but the highest prevalence was observed in late-onset group. From our study, smoking, alcohol, caffeinated drinks, occupational influence of agriculture and industry and pesticide exposure had more association with PD occurrence. Hence, to the best of our knowledge, this is the first kind of study in Tamil Nadu population, India to validate the various factors with PD. Therefore we suggest that further research is mandatory to detect other possible associations among PD, using comprehensive larger sample size.

Lipoprotein-Associated Phospholipase A2 Is a Risk Factor for Patients With Parkinson's Disease

Objective

To explore the association between lipoprotein-related phospholipase A2 (Lp-PLA2) and the risk of Parkinson's disease (PD).

Methods

A case-control study involving 58 hospitalized PD patients and 60 healthy controls was carried out. Serum Lp-PLA2 level was detected. According to the disease course and severity, PD patients were subdivided to analyze the clinical value of Lp-PLA2. Relationship between Lp-PLA2 and PD risk was analyzed by logistic regression. Diagnostic value of Lp-PLA2 in PD patients was investigated using receiver's operator characteristic curves.

Results

Lp-PLA2 level was significantly higher in the PD patients compared with the controls, and was significantly and positively correlated with the Hoehn-Yahr (H&Y) stage. The serum Lp-PLA2 level and H&Y stage of PD patients with a longer disease course were significantly higher than those with a shorter disease course. PD patients with milder conditions had significantly lower serum Lp-PLA2 levels than patients with severe conditions. Multivariable logistic regression analysis indicated higher Lp-PLA2 level was an independent risk factor of PD patients. Moreover, the area under the curve for Lp-PLA2 was 0.703, which was between those of homocysteine and serum amylase A.

Conclusion

To our knowledge, this is the first study to show that increased level of Lp-PLA2 is associated with the risk of PD. Lp-PLA2 may be used for early detection of PD, and provides an effective intervention target for clinical treatment of PD.

Urate is closely linked to white matter integrity in multiple system atrophy

Objective

We aimed to investigate the association of the serum urate level with cortical thickness and white matter integrity in multiple system atrophy (MSA).

Methods

We recruited 75 MSA patients and 42 controls who underwent brain MRI and measured serum urate level at baseline. Using cortical thickness and tract‐based spatial statistics analyses, we investigated the correlation between serum urate levels and cortical thickness or diffusion tensor imaging (DTI) measures in controls and MSA patients. Interaction effects were analyzed to find different patterns of correlation according to sex and clinical subtype. We evaluated the relationship between serum urate levels, DTI measures, and total UMSARS score, using path analysis.

Results

Serum urate levels showed a positive correlation with FA values in the corpus callosum and a negative correlation with MD values in widespread regions including cerebellar, brainstem, and cerebral white matter in patients with MSA. Both sexes showed a negative correlation between serum urate levels and MD values without significant interaction effect. In subgroup analysis according to subtype, patients with cerebellar subtype showed a negative correlation. Serum urate levels did not correlated with cortical thickness. Path analysis showed that MD values in middle and inferior cerebellar peduncle mediated the association between serum urate level and total UMSAR score.

Interpretation

The present study demonstrated that serum urate levels played a pivotal role in white matter disintegrity and clinical disability in MSA. It would provide an evidence of the role of urate as a potential neuroprotective factor against white matter neurodegeneration in MSA.

Serum Uric Acid in LRRK2 Related Parkinson's Disease: Longitudinal Data from the PPMI Study

BACKGROUND

Previous studies have highlighted serum uric acid as a putative idiopathic Parkinson's disease (iPD) biomarker. Only one study, so far, showed higher levels of serum uric acid in leucine-rich repeat kinase 2 (LRRK + 2) carriers compared to those who developed PD, however a longitudinal comparison between LRRK2 + PD and healthy controls (HC) has not been performed.

OBJECTIVE

The aim of this study was to determine whether there are longitudinal differences in serum uric acid between iPD, LRRK2 + PD and HC and their association with motor and non-motor features.

METHODS

Longitudinal data of uric acid of 282 de novo iPD, 144 LRRK2 + PD patients, and 195 age-matched HC were obtained from the Parkinson's Progression Markers Initiative (PPMI) database. We also used longitudinal Montreal Cognitive Assessment (MoCA), Movement Disorder Society-Unified Parkinson's Disease Rating Scale part III (MDS-UPDRS-III), Geriatric Depression Scale (GDS) scores, and DaTSCAN striatal binding ratios (SBRs).

RESULTS

Longitudinal uric acid measurements were significantly lower in LRRK2 + PD patients compared to HC up to 5 years follow-up. There was no significant impact or correlation of adjusted or unadjusted uric acid levels with MoCA, MDS-UPDRS III, or GDS scores, the presence of RBD or DAT-SCAN SBRs.

CONCLUSION

LRRK2 + PD group had significantly lower uric acid concentrations compared to HC after adjusting for age, sex and baseline BMI up to 5 years follow-up. There were no significant associations between uric acid levels and indices of disease severity. These findings identify serum uric acid as a marker linked to LRRK2 + PD.

Shared perturbations in the metallome and metabolome of Alzheimer's, Parkinson's, Huntington's, and dementia with Lewy bodies: A systematic review

Despite differences in presentation, age-related dementing diseases such as Alzheimer's (AD), Parkinson's (PD), and Huntington's diseases (HD), and dementia with Lewy bodies (DLB) may share pathogenic processes. This review aims to systematically assemble and compare findings in various biochemical pathways across these four dementias. PubMed and Google Scholar were screened for articles reporting on brain and biofluid measurements of metals and/or metabolites in AD, PD, HD, or DLB. Articles were assessed using specific a priori-defined inclusion and exclusion criteria. Of 284 papers identified, 198 met criteria for inclusion. Although varying coverage levels of metals and metabolites across diseases and tissues made comparison of many analytes impossible, several common findings were identified: elevated glucose in both brain tissue and biofluids of AD, PD, and HD cases; increased iron and decreased copper in AD, PD and HD brain tissue; and decreased uric acid in biofluids of AD and PD cases. Other analytes were found to differ between diseases or were otherwise not covered across all conditions. These findings indicate that disturbances in glucose and purine pathways may be common to AD, PD, and HD. However, standardisation of methodologies and better coverage in some areas - notably of DLB - are necessary to validate and extend these findings.

Association of sleep quality and sleep duration with serum uric acid levels in adults

OBJECTIVE

To date, the association between sleep duration or sleep quality and hyperuricemia has remained unclear. In addition, sleep duration and quality were not considered concomitantly in previous studies. Thus, this study was aimed toward an examination of the association of sleep duration and quality with uric acid level in a Taiwanese population.

METHODS

A total of 4,555 patients aged ≥18 years were enrolled in this study. The sleep duration was classified into three groups: short (<7 h), normal (7-9 h), and long (≥9 h). The Pittsburgh Sleep Quality Index (PSQI) was used to evaluate sleep quality, and poor sleep quality was defined as a global PSQI score of >5.

RESULTS

Poor sleepers were younger and had lower body mass index, blood pressure, uric acid, blood sugar, cholesterol, creatinine level, shorter sleep duration, and engaged in less exercise but had a higher white blood cell count and prevalence of smoking as compared to good sleepers. There were also differences in body mass index, blood pressure, uric acid, blood sugar, lipid profiles, and sleep quality among subjects with different sleep durations. After adjusting for other variables, poor sleep quality was associated with lower uric acid levels. In addition, short sleep duration was positively associated with higher uric acid levels.

CONCLUSIONS

Poor sleep quality was related to lower uric acid levels, whereas short sleep duration was associated with higher uric acid levels.

Diagnostic utility of fluid biomarkers in multiple system atrophy: a systematic review and meta-analysis

BACKGROUND

Multiple system atrophy (MSA) is an adult onset, fatal neurodegenerative disease. However, no reliable biomarker is currently available to guide clinical diagnosis and help to determine the prognosis. Thus, a comprehensive meta-analysis is warranted to determine effective biomarkers for MSA and provide useful guidance for clinical diagnosis.

METHODS

A comprehensive literature search was made of the PubMed, Embase, Cochrane and Web of Science databases for relevant clinical trial articles for 1984-2019. Two review authors examined the full-text records, respectively, and determined which studies met the inclusion criteria. We estimated the mean difference, standard deviation and 95% confidence intervals.

RESULTS

A total of 28 studies and 11 biomarkers were included in our analysis. Several biomarkers were found to be useful to distinguish MSA patients from healthy controls, including the reduction of phosphorylated tau, α-synuclein (α-syn), 42-amino-acid form of Aβ and total tau (t-tau), the elevation of neurofilament light-chain protein (NFL) in cerebrospinal fluid, the elevation of uric acid and reduction of homocysteine and coenzyme Q10 in plasma. Importantly, α-syn, NFL and t-tau could be used to distinguish MSA from Parkinson's disease (PD), indicating that these three biomarkers could be useful biomarkers in MSA diagnosis.

CONCLUSION

The findings of our meta-analysis demonstrated diagnostic biomarkers for MSA. Moreover, three biomarkers could be used in differential diagnosis of MSA and PD. The results could be helpful for the early diagnosis of MSA and the accuracy of MSA diagnosis.

Serum Uric Acid, Serum Uric Acid to Serum Creatinine Ratio and Serum Bilirubin in Patients With Parkinson's Disease: A Case-Control Study

Background

Studies have shown that a low serum uric acid (SUA) level associates with Parkinson’s disease (PD), but many of them did not exclude patients with impaired renal function. Studies on the association between serum bilirubin level and PD also are limited. This study determined the association between SUA level, SUA/serum creatinine (SCr) ratio and serum bilirubin levels in PD patients with normal renal and liver functions.

Methods

The PD patients from a neurological clinic, and the controls from the club for the elderly, were recruited into this study. The PD stage and motor and non-motor function were determined by the Hoehn-Yahr (H&Y) scale and unified Parkinson’s disease rating scale (UPDRS), respectively.

Results

Sixty-one PD patients and 135 controls participated. The SUA/SCr ratio, but not SUA, was significantly lower in the PD patients than in the controls (4.12 ± 0.90 vs. 4.59 ± 1.04, P = 0.003). Serum total bilirubin (TB) and indirect bilirubin (IDB) were significantly higher in the PD patients (7.92 ± 3.67 µmol/L vs. 6.59 ± 2.78 µmol/L, P = 0.003 and 4.52 ± 2.48 µmol/L vs. 3.26 ± 1.82 µmol/L, P < 0.001), respectively. Serum TB and IDB, but not SUA or SUA/SCr ratio, were associated negatively with PD stages (P = 0.010 and P = 0.014, respectively). There was no association between TB, IDB, SUA or SUA/SCr ratio and PD disease duration or motor subtypes. No significant correlation was found between SUA or SUA/SCr ratio, serum TB and IDB.

Conclusion

The SUA/SCr ratio is more sensitive than SUA in determining their association with PD. The high serum TB and IDB levels in PD patients compared with the controls suggest that serum bilirubin might play a role in the pathogenesis of PD. However, the lack of association between SUA or the SUA/SCr ratio and serum TB or IDB suggests that these two biomarkers play a different role in the etiopathogenesis of PD.

Assessment of serum uric acid levels in patients with restless legs syndrome

In our study, the aim was to collect data in relation to our hypothesis that oxidative stress is effective in the etiopathogenesis of restless legs syndrome (RLS) by assessing the serum uric acid levels, an important biomarker of oxidative stress, among RLS patients. The study included a total of 281 patients with restless legs syndrome diagnosis according to the "2012 Revised International Restless Legs Syndrome Study Group Diagnostic Criteria". Disease severity was assessed according to the "International Restless Legs Syndrome Study Group Severity Scale". The control group comprised 237 healthy individuals with the same age and gender features as the control group. The result showed no statistically significant difference in the mean age and gender between RLS and control group (p = 0.923; p = 0.433). The hemoglobin, ferritin, and uric acid levels of patients with RLS were found to be low (p < 0.001). Total iron-binding capacity level was higher in patients (p < 0.01; p < 0.05). In RLS patients, the serum uric acid level was not affected by disease severity (p > 0.05). Variables affecting uric acid level in RLS patients were determined to be age, disease duration, and hemoglobin level. The hypothesis that uric acid level, accepted as a biomarker of oxidative stress, is important in the pathogenesis of restless legs syndrome is supported by our study.

Shortage of Cellular ATP as a Cause of Diseases and Strategies to Enhance ATP

Germline mutations in cellular-energy associated genes have been shown to lead to various monogenic disorders. Notably, mitochondrial disorders often impact skeletal muscle, brain, liver, heart, and kidneys, which are the body’s top energy-consuming organs. However, energy-related dysfunctions have not been widely seen as causes of common diseases, although evidence points to such a link for certain disorders. During acute energy consumption, like extreme exercise, cells increase the favorability of the adenylate kinase reaction 2-ADP -> ATP+AMP by AMP deaminase degrading AMP to IMP, which further degrades to inosine and then to purines hypoxanthine -> xanthine -> urate. Thus, increased blood urate levels may act as a barometer of extreme energy consumption. AMP deaminase deficient subjects experience some negative effects like decreased muscle power output, but also positive effects such as decreased diabetes and improved prognosis for chronic heart failure patients. That may reflect decreased energy consumption from maintaining the pool of IMP for salvage to AMP and then ATP, since de novo IMP synthesis requires burning seven ATPs. Similarly, beneficial effects have been seen in heart, skeletal muscle, or brain after treatment with allopurinol or febuxostat to inhibit xanthine oxidoreductase, which catalyzes hypoxanthine -> xanthine and xanthine -> urate reactions. Some disorders of those organs may reflect dysfunction in energy-consumption/production, and the observed beneficial effects related to reinforcement of ATP re-synthesis due to increased hypoxanthine levels in the blood and tissues. Recent clinical studies indicated that treatment with xanthine oxidoreductase inhibitors plus inosine had the strongest impact for increasing the pool of salvageable purines and leading to increased ATP levels in humans, thereby suggesting that this combination is more beneficial than a xanthine oxidoreductase inhibitor alone to treat disorders with ATP deficiency.

Association between serum uric acid level and multiple system atrophy: A meta-analysis

OBJECTIVES

Lower serum uric acid (UA) levels are considered to be related to the risk to develop many neurodegenerative disorders. However, the association between serum UA level and multiple system atrophy (MSA) remains controversial. The aim of this meta-analysis was to evaluate the relationship between serum UA level and MSA.

PATIENTS AND METHODS

PubMed, Web of Science, Embase, Cochrane Library and China National Knowledge Infrastructure (CNKI) were searched for eligible studies. Standardized mean difference (SMD) and 95% confidence intervals (95% CI) were calculated in a fixed-effects model or a random-effects model when appropriate. Subgroup analyses were carried out based on gender. A total of 6 eligible studies involving 547 MSA patients and 637 healthy individuals were identified.

RESULTS

Meta-analysis results revealed that individuals with MSA had lower sera levels of UA as compared with healthy controls (pooled SMD is -0.51, 95%CI: -0.88 to -0.14; p = 0.006). The subgroup analysis to detect sex differences showed that the pooled SMD was -0.61 (95% CI: -0.82 to -0.40; p < 0.0001) for males and -0.22 (95% CI: -0.55 to 0.10; p = 0.18) for females compared with healthy controls.

CONCLUSION

Our meta-analysis revealed that lower serum level of UA is associated with an increased risk of MSA and the relationship is significant in men but not in women.

What Is the Evidence for Treat-to-Target Serum Urate in Gout?

PURPOSE OF REVIEW

Most current clinical guidelines for gout management advocate a treat-to-target serum urate approach, although notable differences exist. Serum urate is a rational target for gout treatment given the central role of urate in disease causality, its association with key outcomes and its practicality of use in clinical practice. This review analyses the evidence for this strategy in gout.

RECENT FINDINGS

Recent studies have confirmed the efficacy of urate-lowering therapy in achieving serum urate targets, both in trials using fixed doses and those applying a treat-to-target strategy. In a limited number of long-term studies (> 12-month duration), interventions that incorporate a treat-to-target serum urate approach have been shown to promote regression of tophi, reduce the frequency of gout flares and improve MRI-detected synovitis. A strong case can be made for a treat-to-target serum urate strategy in gout, supported by existing knowledge of disease pathophysiology, outcomes from urate-lowering therapy studies and emerging results of randomised strategy trials of sufficient duration.

Urate promotes SNCA/α-synuclein clearance via regulating mTOR-dependent macroautophagy

Serum urate levels are reported to be significantly lowered in patients with Parkinson's disease (PD) and inversely correlated to the risk and progression of PD. However, the mechanism by which urate affects PD is poorly understood. Here we showed that treatment with uric acid (UA) resulted in an autophagy activity enhancement in PC12 cells in dose- and time-dependent manners, as indicated by LC3-II increase and P62 decrease. Moreover, UA was still able to increase the LC3-II level and the number of LC3 puncta in the presence of Bafilomycin A1, a lysosomal inhibitor. These changes of autophagic markers were preceded by mTOR inhibition and ULK1 activation. Co-treatment with 3-benzyl-5-((2-nitrophenoxy) methyl)-dihydrofuran-2(3H)-one (3BDO), an mTOR activator, abolished the UA-induced LC3-II increase. More importantly, UA reduced SNCA/α-synuclein accumulation in PC12 cells that overexpress wildtype or A53T mutant SNCA, and this was blocked by Bafilomycin A1 co-treatment. The in vivo study showed that UA administration was able to modulate the levels of autophagy markers, increase the autophagosome/autolysosome formation, and reduce SNCA accumulation in the midbrain of SNCA^A53T transgenic mice. Taken together, our findings suggest that UA could induce autophagy activation via an mTOR-dependent signaling and ameliorate SNCA accumulation. This implicates that urate-elevating agent may become a potential strategy for PD therapy.

Targeting urate to reduce oxidative stress in Parkinson disease

Oxidative stress has been implicated as a core contributor to the initiation and progression of multiple neurological diseases. Genetic and environmental factors can produce oxidative stress through mitochondrial dysfunction leading to the degeneration of dopaminergic and other neurons underlying Parkinson disease (PD). Although clinical trials of antioxidants have thus far failed to demonstrate slowed progression of PD, oxidative stress remains a compelling target. Rather than prompting abandonment of antioxidant strategies, these failures have raised the bar for justifying drug and dosing selections and for improving study designs to test for disease modification by antioxidants. Urate, the main antioxidant found in plasma as well as the end product of purine metabolism in humans, has emerged as a promising potential neuroprotectant with advantages that distinguish it from previously tested antioxidant agents. Uniquely, higher urate levels in plasma or cerebrospinal fluid (CSF) have been linked to both a lower risk of developing PD and to a slower rate of its subsequent progression in numerous large prospective epidemiological and clinical cohorts. Laboratory evidence that urate confers neuroprotection in cellular and animal models of PD, possibly via the Nrf2 antioxidant response pathway, further strengthened its candidacy for rapid clinical translation. An early phase trial of the urate precursor inosine demonstrated its capacity to safely produce well tolerated, long-term elevation of plasma and CSF urate in early PD, supporting a phase 3 trial now underway to determine whether oral inosine dosed to elevate urate to concentrations predictive of favorable prognosis in PD slows clinical decline in people with recently diagnosed, dopamine transporter-deficient PD.

Serum uric acid levels and freezing of gait in Parkinson's disease

Uric acid (UA) is a natural antioxidant and iron scavenger in the human body, which has been hypothesized to exert an anti-oxidative effect in Parkinson's disease (PD). This study aimed to investigate the relationship between serum UA levels and freezing of gait (FOG) in PD. A total of 321 Chinese PD patients with fasting serum UA evaluated were included in the cross-sectional study. Demographics, clinical features, and therapeutic regimen were collected. The Unified PD Rating Scale (UPDRS) III and Hoehn and Yahr (H and Y) stage were used to evaluate the severity of disease, and the Frontal Assessment Battery (FAB) and Montreal Cognitive Assessment (MoCA) scales were used to assess the cognitive function. Patients with FOG showed lower proportion of male, longer disease duration, lower body mass index, lower concentrations of serum UA, higher total levodopa equivalent daily dosage, higher UPDRS III score, greater median H and Y stage, lower scores of FAB and MoCA, and higher frequencies of motor fluctuation, dyskinesia, falls, and festination compared to patients without FOG (P < 0.05). The binary logistic regression model indicated that high UPDRS III score (OR = 1.049, P < 0.001), fluctuation (OR = 2.677, P = 0.035), dyskinesia (OR = 6.294, P = 0.003), festination (OR = 3.948, P < 0.001), falls (OR = 7.528, P < 0.001), and low serum UA levels (OR = 0.990, P < 0.001) were associated with FOG. Our study suggests that low serum UA concentration is associated with the occurrence of FOG in PD.

Serum uric acid levels in Parkinson's disease and related disorders

OBJECTIVE

Serum uric acid (UA) levels are reported to be decreased in patients with Parkinson's disease (PD) and multiple system atrophy (MSA). However, clinical correlates of serum UA levels are still unclear in PD-related disorders. We conducted a cross-sectional study to evaluate the associations between serum UA levels and disease duration, disease severity, and motor function among PD, MSA, and progressive supranuclear palsy (PSP) patients.

METHODS

A total of 100 patients with PD, 42 patients with MSA, 30 patients with PSP, and 100 controls were included in this study. Serum UA levels were determined, and associations among serum UA levels and disease duration, disease severity, and motor function in PD, PSP, and MSA patients were evaluated.

RESULTS

Serum UA levels were significantly lower in male PD, MSA, and PSP patients compared with the controls, but not in female patients. Serum UA levels were negatively correlated with disease duration and severity in MSA and PSP patients, but no correlations were observed in PD patients. The serum UA levels were significantly decreased in the tauopathy group (PSP patients) compared with the synucleinopathy group (PD and MSA patients) after adjusting for age, gender, and body mass index.

CONCLUSION

We found decreased serum UA levels in male patients with PD-related disorders (PD, MSA, and PSP) compared with male controls, and significant correlations between serum UA levels and disease severity in MSA and PSP patients.