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

Uric acid and alterations of purine recycling disorders in Parkinson's disease: a cross-sectional study

The relationship between reduced serum uric acid (UA) levels and Parkinson's disease (PD), particularly purine metabolic pathways, is not fully understood. Our study compared serum and cerebrospinal fluid (CSF) levels of inosine, hypoxanthine, xanthine, and UA in PD patients and healthy controls. We analyzed 132 samples (serum, 45 PD, and 29 age- and sex-matched healthy controls; CSF, 39 PD, and 19 age- and sex-matched healthy controls) using liquid chromatography-tandem mass spectrometry. Results showed significantly lower serum and CSF UA levels in PD patients than in controls (p < 0.0001; effect size r = 0.5007 in serum, p = 0.0046; r = 0.3720 in CSF). Decreased serum hypoxanthine levels were observed (p = 0.0002; r = 0.4338) in PD patients compared to controls with decreased CSF inosine and hypoxanthine levels (p < 0.0001, r = 0.5396: p = 0.0276, r = 0.2893). A general linear model analysis indicated that the reduced UA levels were mainly due to external factors such as sex and weight in serum and age and weight in CSF unrelated to the purine metabolic pathway. Our findings highlight that decreased UA levels in PD are influenced by factors beyond purine metabolism, including external factors such as sex, weight, and age, emphasizing the need for further research into the underlying mechanisms and potential therapeutic approaches.

Progression of cognitive impairment in Parkinson's disease correlates with uric acid concentration

Introduction

This study assessed the relationship between the progression of Parkinson's disease (PD) with cognitive impairment and changes in serum uric acid (UA) and homocysteine (Hcy) concentrations and explored the factors influencing PD with cognitive impairment.

Methods

The study randomly selected 74 patients with PD and evaluated their cognitive function using the Montreal Cognitive Assessment Scale (MoCA). Patients with PD were divided into two subgroups: those with and without cognitive impairment. PD severity was evaluated and graded using the Hoehn and Yahr (H-Y) scale. Another 60 middle-aged and older individuals without PD during the same period were selected as a control group. Blood UA and Hcy concentrations in each group were measured to assess the relationship between PD, cognitive impairment, and changes in UA and Hcy concentrations.

Results

The PD group with cognitive impairment had a lower UA concentration and higher Hcy concentration. The UA concentration was significantly higher in the early PD stages than in the middle and late stages (P<0.05). A significant negative relationship between MoCA scores and serum UA levels was found in patients with PD, whereas a positive relationship existed between MoCA scores and serum Hcy concentrations. Regression analysis showed that a higher UA concentration was an independent protective factor for PD with cognitive impairment, while a higher Hcy concentration was a risk factor (P<0.05). A serum UA concentration of 212.9 mmol/L and Hcy concentration of 13.35 mmol/L could distinguish between patients with PD with or without cognitive impairment with a sensitivity of 93.2% and specificity of 43.3%.

Conclusion

PD and cognitive impairment were associated with a decrease in UA concentration; the later the H-Y stage was, the lower the UA concentration was. The increase in Hcy concentration was related to PD and its cognitive impairment, whereas it is not significantly correlated with PD progression.

Moderating effects of uric acid and sex on cognition and psychiatric symptoms in asymmetric Parkinson's disease

BACKGROUND

Non-motor symptoms are an important early feature of Parkinson's disease (PD), encompassing a variety of cognitive and psychiatric symptoms that seem to manifest differently depending on motor symptom asymmetry. Different factors, such as uric acid (UA) and sex, seem to influence cognitive and psychiatric expression in PD, however their interplay remains to be better understood.

METHODS

Participants taking part in the Parkinson's Progression Marker Initiative were studied based on the side of motor symptom asymmetry and sex. Three-way interaction modeling was used to examine the moderating effects of sex and UA on cognitive functions and psychiatric symptoms.

RESULTS

Significant three-way interactions were highlighted at 1-year follow-up between motor symptom asymmetry, UA and sex for immediate and long-term memory in female patients exhibiting predominantly left-sided motor symptoms, and for processing speed and sleepiness in female patients exhibiting predominantly right-sided motor symptoms. No significant interactions were observed for male patients. Moreover, female patients exhibiting predominantly right-sided motor symptoms demonstrated lower serum UA concentrations and had overall better outcomes, while male patients with predominantly right-sided motor symptoms demonstrated particularly poor outcomes.

CONCLUSIONS

These findings suggest that in the earliest stages of the disease, UA and sex moderate cognitive functions and psychiatric symptoms differently depending on motor asymmetry, holding important clinical implications for symptom management in patients.

Serum but not cerebrospinal fluid levels of allantoin are increased in de novo Parkinson's disease

Oxidative stress supposedly plays a role in the pathogenesis of Parkinson's disease (PD). Uric acid (UA), a powerful antioxidant, is lowered in PD while allantoin, the oxidation product of UA and known biomarker of oxidative stress, was not systematically studied in PD. We aim to compare serum and cerebrospinal fluid (CSF) levels of UA, allantoin, and allantoin/UA ratio in de novo PD patients and controls, and evaluate their associations with clinical severity and the degree of substantia nigra degeneration in PD. We measured serum and CSF levels of UA, allantoin, and allantoin/UA ratio in 86 PD patients (33 females, mean age 57.9 (SD 12.6) years; CSF levels were assessed in 51 patients) and in 40 controls (19 females, 56.7 (14.1) years). PD patients were examined using Movement Disorder Society-Unified Parkinson's Disease Rating Scale (MDS-UPDRS), Montreal Cognitive Assessment (MoCA), Scales for Outcomes in Parkinson Disease-Autonomic (SCOPA-AUT), the University of Pennsylvania Smell Identification Test (UPSIT), one-night video-polysomnography, and dopamine transporter single-photon emission computed tomography (DAT-SPECT). Serum allantoin and allantoin/UA ratio were significantly increased in the PD group compared to controls (p < 0.001 and p = 0.002, respectively). Allantoin/UA ratios in serum and CSF were positively associated with the SCOPA-AUT score (p = 0.005 and 0.031, respectively) and RBD presence (p = 0.044 and 0.028, respectively). In conclusion, serum allantoin and allantoin/UA ratio are elevated in patients with de novo PD. Allantoin/UA ratio in serum and CSF is associated with autonomic dysfunction and RBD presence, indicating that higher systemic oxidative stress occurs in PD patients with more diffuse neurodegenerative changes.

Serum Uric Acid as a Putative Biomarker in Prodromal Parkinson's Disease: Longitudinal Data from the PPMI Study

BACKGROUND

The role of blood uric acid as a biomarker in symptomatic motor PD has been increasingly established in the literature.

OBJECTIVE

Our present study assessed the role of serum uric acid as a putative biomarker in a prodromal PD cohort [REM Sleep Behavior disorder (RBD) and Hyposmia] followed longitudinally.

METHODS

Longitudinal 5-year serum uric acid measurement data of 39 RBD patients and 26 Hyposmia patients with an abnormal DATSCAN imaging were downloaded from the Parkinson's Progression Markers Initiative database. These cohorts were compared with 423 de novo PD patients and 196 healthy controls enrolled in the same study.

RESULTS

After adjusting for age, sex, body mass index, and concomitant disorders (hypertension/gout), baseline and longitudinal serum uric acid levels were higher in the RBD subgroup as compared to the established PD cohort (p = 0.004 and p = 0.001). (Baseline RBD 6.07±1.6 vs. Baseline PD 5.35±1.3 mg/dL and Year-5 RBD 5.7±1.3 vs. Year-5 PD 5.26±1.33). This was also true for longitudinal measurements in the Hyposmic subgroup (p = 0.008) (Baseline Hyposmic 5.7±1.6 vs. PD 5.35±1.3 mg/dL and Year-5 Hyposmic 5.58±1.6 vs. PD 5.26±1.33).

CONCLUSION

Our results indicate that serum uric acid levels are higher in prodromal PD subjects with ongoing dopaminergic degeneration compared to those with manifest PD. These data indicate that the well-established decrease in the levels of serum uric acid occurs with the transition from prodromal to clinical PD. Whether the higher levels of serum uric acid observed in prodromal PD may provide protection against conversion to full-blown clinical PD will require further study.

Uric Acid in Parkinson's Disease: What Is the Connection?

Numerous studies have linked Parkinson's disease (PD) with low levels of uric acid (UA). Low UA has been associated with the risk of developing PD, and its progression and severity. The biological mechanisms underlying these relationships have never been firmly established. The most frequently proposed mechanism is that UA is an antioxidant. Low UA is thought to predispose to oxidative stress, which contributes to dopamine neuron degeneration, and leads to initial appearance of symptoms of PD and its worsening over time. Several recent studies have questioned this explanation. In this review, we describe the biology of UA, its many links with PD, evidence regarding UA as an antioxidant, and we question whether UA causes PD or contributes to its progression. We also address the possibility that something about PD causes low UA (reverse causation) or that low UA is a biomarker of some other more relevant mechanism in PD. We hope the evidence provided here will stimulate additional studies to better understand the links between UA and PD. Elucidating these mechanisms remains important, because they may provide new insights into the pathogenesis of PD or novel approaches to treatments. © 2022 International Parkinson and Movement Disorder Society.

Association between gout and the development of Parkinson's disease: a systematic review and meta-analysis

BACKGROUND

As a natural antioxidant, uric acid plays a protective role against neurodegenerative disorders, including Parkinson's disease (PD). Therefore, the risk of PD has been found to be lower in people with hyperuricemia. In this article, we conducted a systematic review and meta-analysis to investigate whether gout affects the future risk of developing PD.

METHODS

We searched PubMed, Scopus, the Web of Science, and Google Scholar to find relevant studies, up to March 16, 2022. Studies investigating the risk of PD, following a gout diagnosis, were included if they were cross-sectional, case-control or cohort studies. The Newcastle Ottawa Scale (NOS) checklist was used to assess the quality of all included studies. The meta-analysis was performed using STATA 17.0.

RESULTS

Ten studies were included, which were comprised of three case-controls, six cohort studies and one nested case-control study. We found no significant association between gout and the risk of PD among both sexes (RR = 0.94, 95% CI: 0.86-1.04), although the association was significant for females (RR = 1.09; 95% CI: 1.02-1.17). Subgroup analysis also showed no significant findings by age group, whether they were receiving treatment for gout, study design, quality assessment score, and method of gout ascertainment. In contrast, the studies that defined PD according to the use of drugs showed significant results (RR = 0.82; 95% CI: 0.76-0.89). There was a significant publication bias on the association between gout and PD.

CONCLUSIONS

The presence of gout had no significant effect on the risk of subsequently developing PD. Further analyses are recommended to investigate the effects of demographic and behavioral risk factors.

Serum Uric Acid Levels in Parkinson’s Disease: A Cross-Sectional Electronic Medical Record Database Study from a Tertiary Referral Centre in Romania

Background and Objectives: Parkinson’s disease (PD) is a prevalent neurodegenerative condition responsible for progressive motor and non-motor symptoms. Currently, no prophylactic or disease-modifying interventions are available. Uric acid (UA) is a potent endogenous antioxidant, resulting from purine metabolism. It is responsible for about half of the antioxidant capacity of the plasma. Increasing evidence suggests that lower serum UA levels are associated with an increased risk of developing PD and with faster disease progression. Materials and Methods: We conducted an electronic medical record database study to investigate the associations between UA levels and different characteristics of PD. Results: Out of 274 datasets from distinct patients with PD, 49 complied with the predefined inclusion and exclusion criteria. Lower UA levels were significantly associated with the severity of parkinsonism according to the Hoehn and Yahr stage (r_s = 0.488, p = 0.002), with the motor complications of long-term dopaminergic treatment (r = 0.333, p = 0.027), and with the presence of neurocognitive impairment (r = 0.346, p = 0.021). Conclusions: Oxidative stress is considered a key player in the etiopathogenesis of PD, therefore the involvement of lower UA levels in the development and progression of PD is plausible. Data on the potential therapeutic roles of elevating serum UA (e.g., by precursor administration or diet manipulation) are scarce, but considering the accumulating epidemiological evidence, the topic warrants further research.