Assay of Neurodegenerative Biomarkers in Human Plasma of Patients with Parkinson’s Disease

Author(s): Wei-Che Lin, Pai-Yi Chiu, Ming-Jang Chiu, Chaur-Jong Hu, Pei-Ning Wang, Ta-Fu Chen, Fu-Chi Yang, Li-Kai Huang, Cheng-Hsien Lu, Heui-Chun Liu, Shieh-Yueh Yang

Introduction: In addition to α-synuclein, amyloid and tau pathologies have been found in patients with Parkinson’s disease (PD). Although the results of assaying these proteins in body fluid have been reported, comprehensive studies on the discriminating power between PD patients and normal controls (NCs), as well as in PD with normal cognition (PD-NC) patients and PD with dementia (PDD) patients, are rare, especially in plasma. In this study, total plasma α-synuclein, amyloid β1-42 (Aβ1-42) and total tau protein in NC, PD-NC, and PDD subjects were assayed to explore the roles of these three proteins in PD. Methods: One hundred eighty-seven NCs, one hundred twenty-eight PD-NC patients and seventy-nine PDD patients were enrolled at five hospitals in Taiwan. Plasma tau, Aβ1-42 and α-synuclein were assayed for each enrolled subject using ImmunoMagnetic Reduction (IMR). Results: Plasma Aβ1-42, tau and α-synuclein were significantly increased in PD patients compared to NCs. Further increases in plasma tau and α-synuclein were found in PDD patients compared to PD-NC patients. α-synuclein levels showed relatively strong discriminating power between PD patients and NCs, as well as between PDD and PD-NC patients. Tau levels showed a relatively strong correlation with cognitive decline. In NCs, the expression of the three proteins was independent of age. Conclusions: These results suggest that both Tau and α-synuclein play roles in the occurrence of PD and dementia in PD patients. However, tau levels are not associated with α-synuclein levels in PD patients, which implies that tau and α-synuclein should be regarded as independent biomarkers of PD.