Oligomeric Synuclein Tear Content Not a Marker for Parkinson Disease Stage

The following article is part of conference coverage from the 2022 American Academy of Neurology (AAN) Annual Meeting. Neurology Advisor’s staff will be reporting breaking news associated with research conducted by leading experts in neurology. Check back for the latest news from the 2022 AAN Annual Meeting.

 

Levels of oligomeric a-synuclein in tear fluid differed significantly between patients with Parkinson disease (PD) and healthy control individuals but could not discriminate between PD stage on the basis of disease duration, according to study results presented at the 2022 American Academy of Neurology (AAN) Annual Meeting, held from April 2 to April 7 in Seattle, Washington, and virtually from April 24-26, 2022.

A previous study found that oligomeric a-synuclein was significantly elevated in basal and reflex tears among patients with PD compared with healthy control individuals. The current study sought to evaluate whether tear levels of oligomeric a-synuclein could differentiate between stages of PD on the basis of disease duration.

Patients with early PD (disease duration 4 years or less; n=77), intermediate duration disease (5-8 years; n=43), late PD (9 years or more; n=50), and 67 healthy control individuals were recruited at the Keck School of Medicine of the University of Southern California. Participants underwent an unanesthetized Schirmer’s test in both eyes and the pooled tear sample from each participant was assessed for oligomeric a-synuclein using an enzyme-linked immunosorbent assay to normalize the protein content.

Compared with healthy control individuals (mean, 0.80±0.24 ng/mg tear protein), oligomeric a-synuclein was elevated by 5.4-fold in tears from the early PD group (mean, 4.28±0.75 ng/mg tear protein; P <.001), 4.0-fold in the intermediate PD group (mean, 3.23±0.54 ng/mg tear protein; P <.001), and 3.1-fold in the late PD group (mean, 2.44±0.40 ng/mg tear protein; P <.001).

No significant gender effect was observed.

This study may have been limited by the small sample size.

These data confirmed the previously reported trend that patients with PD have elevated oligomeric α-synuclein in reflex tears. The researchers stated that oligomeric α-synuclein levels appeared to be relatively stable throughout the PD course and levels of oligomeric α-synuclein were unable to differentiate PD stage on the basis of disease duration.

“This is the first presentation of tear fluid evaluation in PD patients stratified by disease duration,” they concluded.

Reference

Lew M, Janga S, Ju Y, et al. Biomarkers for Parkinson’s Disease with Reflex Tears Stratified by Disease Duration. Presented at: the 2022 AAN Annual Meeting; April 2-7, 2022; Seattle, Washington; April 24-26, 2022; Virtual Meeting. Abstract S16.002.