Objective: The aim of this study is to measure alpha-synuclein (a-syn) total, a-syn oligomers (a-syn olig) and total tau protein concentration in the saliva of patients affected by PD and PSP in order to test whether salivary analysis can be used for differential diagnosis between PD and PSP.

Background: A-syn aggregation and tau deposition are respectively the pathological hallmarks of PD and PSP. In PD patients, we have detected lower salivary a-syn total and higher a-syn oligomers than healthy subjects and we have found that salivary a-syn total correlates with patients ‘clinical scores (Vivacqua et al., 2016).

Methods: 100 PD patients and 20 patients affected by PSP were admitted to the study, together with 80 age and sex matched healthy subjects. Samples of saliva were collected following the protocol of previous study (Vivacqua et al., 2016). ELISA analysis was performed using three specific ELISA kits: SensoLyte 55550 for a-syn total, MyBioSource MBS043824 for a-syn olig and Life Technologies KHB0041 for total tau. Statistical significance was evaluated by Mann-Whitney U test. Spearmann Rank correlation coefficient was used for clinical correlations and Receiving Operating Analysis (ROC) was applied to determine sensitivity and specificity.

Results: A-syn total is significantly lower in PD patients confronting to healthy subjects, whereas a-syn olig is significantly higher (p<0.05). Conversely, in PSP patients salivary a-syn total is comparable to healthy subjects. Salivary tau total is significantly higher in both PD and PSP patients confronting to healthy subjects (p<0.05) but no significant differences were detected between PD and PSP patients (p>0.05). ROC analysis revealed that salivary a-syn total is able to differentiate PD patients from PSP patients with a sensitivity of 100% and a specificity of 96,51%. Conversely salivary tau total is able to distinguish PD and PSP patients from healthy subjects, but it cannot differentiate PD and PSP patients.

Conclusions: Decreased salivary a-syn total is likely to be specific of PD, whereas salivary tau total is significantly increased in both PD and PSP patients may leading to the occurrence of peripheral neuropathy involving the small autonomic fibers. Our data support salivary a-syn detection as a promising biomarker for differential diagnosis between PD and PSP.

References: Vivacqua G, Latorre A, Suppa A, Nardi M, Pietracupa S, Mancinelli R, Fabbrini G, Colosimo C, Gaudio E, Berardelli A. Abnormal Salivary Total and Oligomeric Alpha-Synuclein in Parkinson’s Disease. PLoS One. 2016 Mar 24;11(3):e0151156. doi: 10.1371/journal.pone.0151156. eCollection 2016.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/salivary-alpha-synuclein-and-tau-in-parkinsons-disease-and-progressive-supranuclear-palsy/