Objective: The aim of this study was to examine the association between several serum molecular markers and different measures of non-motor symptom burden in PD.

Background: There is a need of biomarkers associated with PD progression as well as with motor and non-motor features. Serum molecular markers are easily accessible and therefore have been examined for this purpose, yielding conflicting results.

Method: Patients participating in the COPPADIS-2015 study that performed blood extraction at baseline for determining molecular serum biomarkers were included. Blood sample collection for the determination of different serum biomarkers included S-100b protein, tumor necrosis factor (TNF)-ɑ, interleukin (IL)-1, IL-2, IL-6, vitamin B12, methylmalonic acid (MMA), homocysteine, uric acid, ultrasensitive CRP, ferritin, and iron. In the moment of sample collection, PD patients underwent a battery of clinical assessment to evaluate symptom severity, including motor (UPDRS, HY) and non-motor assessments (MMSE, PD-CRS, NMSS, BDI-II, NPI, QUIP-RS, PDSS, VAS-Pain, VASF-physical, VASF-mental). Univariate correlation analysis and multivariate general linear models were created, controlling for confounding variables, and were used to determine whether serum markers are associated with various symptom outcome measures.

Results: The sample consisted of 225 PD patients, mean age 61.8 years, mean disease duration 5.6 years. A significant correlation was observed between baseline serum ferritin levels and NMSS score (r= -0.24; p= 0.001). Subjects with higher non-motor symptom burden also had lower levels of ferritin (p= 0.03). We also observed a significant correlation between serum MMA levels and QUIP-RS score (r= 0.22; p=0.001). In this sense, the subjects with impulsive compulsive behaviour also had higher levels of MMA (p=0.004). The rest of the serum markers analyzed did not show significant associations with the load of non-motor symptoms measured by the different scales after correcting for confounders and multiple testing.

Conclusion: There are indications of an association, albeit weak, between serum levels of ferritin and methylmalonic acid with non-motor symptom burden and impulsive compulsive behavior, respectively, in PD. The prospective follow-up of this cohort will allow us to know whether these are useful biomarkers in Parkinson’s disease.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/serum-molecular-markers-and-non-motor-symptoms-in-parkinsons-disease/