URIC ACID: THE ROLE IN THE PATHOPHYSIOLOGY AND THE PREDICTION IN THE DIAGNOSIS OF PARKINSON'S DISEASE: A TURKISH-BASED STUDY

Background and purpose - Oxidative stress has been associated as an essential contributor to the development of neurodegenerative diseases. Recent developments in the field of Parkinson's Disease (PD) pathophysiology have led to a renewed interest in this field. As an antioxidant, uric acid (UA) has arisen as a potential neuroprotectant. Higher concentrations of UA are linked to reducing the risk of the development of the disease and preventing its progression. However, the expositions are unsatisfactory because the outcomes of these reports have not been consistent. This study is set out to assess the association of whether lower UA concentrations increased the PD risk by investigating its relationship with patients' demographic and clinical data, and to determine whether previous studies are compatible with the Turkish-sampled population. Furthermore, we aimed to determine UA's probability of being an early-stage diagnostic marker. Methods - A total of 305 patients and 100 healthy controls were included. Serum UA levels of patients and controls were compared with clinical features. We classified the patients into three motor subtypes and determined the disease severity by modified Hoehn&Yahr Staging Scale (mH&Y) and Unified Parkinson's Disease Rating Scale (UPDRS). Standardized Mini-Mental State Examination (MMSE-TR) was assessed for cognition. Results - There were not any significant differences of age and sex between patients and controls (p=0.030, p=0.132). The mean UA was 5.06 +/- 1.33 mg/dL in patients and 5.46-+/- 1.44 in controls, and a statistical significance was detected (p=0.022). The mean MMSE-TR were 24.83 +/- 4.35 in patients and 27.09 +/- 2.13 in controls, and statistical significance was revealed (p=0.001). The mean duration of the disease was 6.31 +/- 4.16 years, mean UPDRS scores were 59.74 +/- 22.33, and mH&Y scores were 2.29 +/- 0.91. In binary comparisons, patients with tremor-dominant motor subtype had lower UA concentrations than controls (p=0.014). ROC curve analysis revealed UA's cut-off as 59.15, the specificity was <= 99.3, the sensitivity was 10.0, and the area under the curve was 0.576 (p<0.005). Regression analysis revealed age as an independent risk factor on UA values. Oxidative stress might be a factor in the development of PD, and UA may be a possible prospective protecting factor in the clinical course of the disease. However, it does not affect the severity. Conclusion - Our results support that lower uric acid concentrations are associated with PD; however, it is not a powerful indicator for predicting PD risk. As we reveal more about UA and its effect in further investigations, its significant role will become well-defined.