Objective: Uric acid (UA) has been shown to be potentially neuroprotective in Parkinson’s disease (PD), a progressive neurodegenerative disorder that is clinically characterised by motor disturbances. PD patients often present with non-motor symptoms such as depression, hallucination, and fatigue. This study aims to investigate the relationship between serum UA levels and motor subtypes, as well as non-motor symptoms in early PD patients.

Background: Oxidative stress plays a major role in PD pathogenesis. UA is a natural antioxidant and its level in serum has been found to correlate well with its level in cerebrospinal fluid (CSF). Previous studies have shown that PD patients have lower serum UA levels as compared to non-PD individuals. In addition, serum UA was found to be associated with certain motor and non-motor symptoms, specifically tremor dominant motor subtype, mild cognitive impairment, mood disturbances, and cardiovascular symptoms.

Methods: 125 early PD patients were recruited from two large tertiary hospitals in Singapore. Fasting serum UA levels were measured. Demographic, clinical, motor and non-motor assessments were performed. Patients were categorized into four motor subtypes: tremor-dominant (TD), akinesia-rigidity (AR), postural instability/gait difficulty (PIGD), and mixed. Patients’ non-motor symptoms were classified as present or absent based on appropriate cut-offs of each non-motor symptom instrument.

Results: Most patients had TD (n=51, 40.8%) and AR (n=47, 37.6%) motor subtypes, while a minority had PIGD (n=11, 8.8%) and mixed (n=16, 12.8%) subtypes. Using the AR subtype as reference, patients with higher serum UA level were more likely to have TD (p=0.0361; OR=1.492) and PIGD (p=0.0049, OR=3.103) subtypes. For non-motor symptoms, high serum UA was significantly associated with less fatigue (p=0.0460, OR=0.726) and less hallucination/delusion (p=0.0403, OR=0.636).

Conclusions: Higher serum UA level was associated with reduced likelihood of AR subtype, fatigue, and hallucination/delusion in early PD, which could be related to its anti-oxidative properties. Our findings provide new insights into uric acid’s neuroprotection in PD.

References: Lolekha, P., Wongwan, P., & Kulkantrakorn, K. (2015). Association between serum uric acid and motor subtypes of Parkinson’s disease. Journal of Clinical Neuroscience, 22(8), 1264-1267. Moccia, M., Picillo, M., Erro, R., Vitale, C., Longo, K., Amboni, M., … & Santoro, L. (2014). Is serum uric acid related to non-motor symptoms in de-novo Parkinson’s disease patients?. Parkinsonism & related disorders, 20(7), 772-775.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/higher-levels-of-serum-uric-acid-associated-with-motor-non-motor-symptoms-in-early-parkinsons-disease/