Sex-Specific Systemic Signatures in Parkinson's Disease: Integrated Biochemical and Metabolomic Evidence

Background/Objectives: Parkinson's disease (PD) exhibits marked sexual dimorphism, with a higher incidence and earlier onset in men than in women. However, the impact of biological sex on systemic molecular alterations in PD remains poorly understood. This pilot study aimed to identify sex-specific circulating signatures associated with PD. Methods: Serum samples from a selected cohort of PD patients and healthy controls (HC) of both sexes were analyzed using an integrated biochemical and ¹H NMR-based metabolomic approach. Oxidative stress markers, antioxidant proteins, inflammatory mediators, matrix metalloproteinases, α-synuclein species, and circulating antibodies were evaluated. Results: This analysis indicated that, while global oxidative stress markers were unchanged, sex-related differences in antioxidant pathways were observed as suggested by the reduced Nrf2 expression observed in PD females and increased IL-6 levels, above all in male PD patients. MMP3 levels were significantly higher in female PD patients compared with males. Male patients showed higher levels of 52 kDa protease-resistant α-synuclein species, while females exhibited increased antibody titers against both monomeric and aggregated forms. Metabolomic profiling suggested a disease-associated metabolic remodeling in PD, with distinct sex-related metabolic signatures and a more pronounced and widespread metabolic dysregulation in males. Conclusions: These findings suggest that biological sex may contribute to systemic molecular heterogeneity in PD, with trends indicating more pronounced inflammatory and metabolic alterations in males and distinct immune-related responses in females. Given the exploratory nature of the study and the limited sample size, these observations should be interpreted cautiously and require validation in larger, independent cohorts. Nevertheless, the results support the importance of considering sex-related molecular differences in future biomarker studies and precision medicine approaches for PD.