Mass Spectrometry-Based Comparative Analysis of N-Glycosylation Alterations in Three Human Body Fluids in Parkinson’s Disease

Parkinson’s disease (PD) is a progressive neurodegenerative disorder lacking definitive diagnostic tests. To identify new diagnostic biomarkers, we employed glycoproteomics-mass spectrometry (MS) to investigate dynamic changes in protein N-glycosylation across the serum, urine, and saliva of PD patients. Our comparative analysis of differentially expressed glycoproteins (DEGs) between PD patients and healthy controls (HCs) revealed distinct patterns. Specifically, ATPase phospholipid transporter 11B (ATP11B) was significantly upregulated in the serum of PD patients, while urine and saliva showed an opposite trend. Other key findings included elevated myeloperoxidase (MPO) in urine and clusterin (CLU) in serum. Zinc-α-2-glycoprotein (AZGP1), detected in all three biofluids, displayed increased sialylation and core fucosylation in serum but decreased levels in the saliva and urine of PD patients, along with a distinct bifucosylation pattern in saliva. These glycoprotein expression changes were further validated using enzyme-linked immunoassay (ELISA). Pathway analysis indicated that these DEGs are primarily involved in inflammatory response, complement activation, and synaptic plasticity, suggesting that glycosylation dysregulation may contribute to PD progression by modulating neuroinflammation and protein homeostasis. This study represents the first comprehensive analysis of multibiofluid N-glycosylation in PD. The findings offer potential biomarkers and provide insights into the molecular mechanisms of the disease, which could ultimately inform early diagnosis and the development of targeted therapies.