Abstract
Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized by motor and non-motor symptoms. The absence of reliable fluid biomarkers continues to hinder early diagnosis and effective monitoring of disease progression. Circulating microRNAs (cmiRNAs) are potential candidates, given their stability in biofluids and their ability to mirror pathological processes. We conducted a longitudinal study in 30 early-stage levodopa-naive PD patients (22 men, 8 women). Serum samples were collected at baseline (T0) and at a follow-up time point two years later (T2). A panel of MicroRNAs (miRNAs) (miR-146a-5p, miR-34a-5p, miR-155-5p, miR-29a-3p, miR-106a-5p) were quantified by quantitative real-time PCR. Data were expressed as relative expression (2^-ΔCt), and statistical analyses included sex-stratified comparisons and paired tests for longitudinal changes. At baseline, no significant differences were found in the expression of the miRNAs between male and female PD patients. In contrast, longitudinal within-subject analysis revealed a highly significant upregulation in miR-146a-5p expression from T0 to T2 in both sexes (p < 0.0001). No other miRNAs in the panel exhibited significant changes over time. CmiR-146a-5p levels rise markedly over time in PD patients, independent of sex, suggesting that this miRNA could be a dynamic biomarker of disease progression.