Untargeted 1H NMR-based metabolomics and high-pressure liquid chromatography analysis reveal sexual dimorphism in the serum metabolic profiles of Parkinson's disease patients harbouring rare genetic variants

BackgroundRecent evidence indicates that sex and genetic status significantly influence serum metabolic profiles in idiopathic Parkinsons disease (iPD) and in patients carrying at least a mutation in GBA1, LRRK2, TMEM175, PARK2, PINK1, or PARK7 genes. However, Parkinsons disease patients (PD) may also carry rare genetic variants of uncertain significance, whose effects on systemic metabolism have yet to be studied. MethodsWe combined untargeted 1H-NMR-based metabolomics to characterize serum metabolome profiles, with high-performance liquid chromatography (HPLC) to quantify D- and L-amino acids involved in neurotransmission, energy homeostasis, and oxidative stress. The study included 212 clinically and genetically well-characterized PD patients--121 with iPD and 91 with at least one rare genetic variant (rvPD) in PD-linked genes--and 140 sex-matched healthy controls (HCs). The same cohort was also investigated by targeted-association analysis of genes encoding key enzymes involved in glycine and serine metabolism, including SRR, DAO, DAOA, SHMT1, SHMT2, PHGDH, AMT, GCSH, GLDC, and N-methyl-D-aspartate receptor (NMDAR) subunits such as GRIN1, GRIN2A, and GRIN2B. Data were replicated in independent case-control datasets. ResultsNotably, integrating untargeted NMR-based analysis, demographic and genetic information, our findings revealed substantial differences in serum metabolome profiles between the rvPD and HCs groups across sexes. Significantly, male patients showed more extensive metabolic disruption in amino acid metabolism, glutathione biosynthesis, and energy-related pathways. In contrast, female patients showed fewer metabolic changes, mainly affecting metabolites implicated in lipid-related pathways. Intriguingly, multivariate analysis did not distinguish serum metabolome profiles between individuals with iPD and rvPD in either sex, indicating shared biochemical abnormalities across patients with different genotypes. Noteworthy, consistent with NMR results, HPLC analysis substantiated a significant reduction in L-glutamate levels in male, but not female, rvPD patients compared to sex-matched HCs. Furthermore, we found that in male patients with rvPD, serum levels of L-serine, glycine, L-aspartate, and L-glutamate significantly correlated with MDS-UPDRS III scores. In the same way, L-serine and L-glutamine were associated with a worsening of motor symptoms in female patients. Finally, in line with prominent dysregulation of glycine-serine metabolism, association analyses identified SHMT1, SHMT2, and GCSH as potential genetic modifiers in sex-stratified rvPD. ConclusionsIn conclusion, we found that sex differences affect serum metabolomic changes and the relationships between amino acid levels and clinical characteristics in PD patients with rare variants. Trial registrationThe study protocols have been registered in clinicaltrial.gov with the numbers NCT02403765 (Release Date: 04/01/2015), NCT04620980 (Release Date: 11/03/2020), NCT05721911 (Release Date: 30/01/2023).