Untargeted metabolomics in a prospective cross-sectional observational study reveals differences in plasma and cerebrospinal fluid between asymptomatic neurosyphilis and serofast syphilis

Asymptomatic neurosyphilis (ANS), a diagnostically elusive complication of Treponema pallidum infection, necessitates invasive cerebrospinal fluid (CSF) analysis for detection. This study investigated metabolic differences between patients with ANS and those with serofast syphilis. Using untargeted metabolomics, we analyzed plasma and CSF from 15 patients with ANS, 15 patients with serofast syphilis, and 16 healthy controls via liquid chromatography-mass spectrometry. Univariate statistical analyses identified differential metabolites, followed by pathway enrichment through Kyoto encyclopedia of genes and genomes enrichment analysis and biomarker evaluation. Plasma analysis identified dysregulated tryptophan metabolism as a central feature in ANS, with key alterations in 4-(2-aminophenyl)-2,4-dioxobutanoic acid and 2-formylaminobezaldehyde. Comparative analysis further distinguished ANS through perturbations in inositol phosphate metabolism in both plasma and CSF. Spearman correlation analysis identified positive associations of the plasma biomarkers 1D-myo-inositol-1,3,4,6-tetrakisphosphate, inositol-1,3-bisphosphate, 4-(2-aminophenyl)-2,4-dioxobutanoic acid, and 2-formylaminobezaldehyde with CSF total protein. Our findings suggest that dysregulation in tryptophan and inositol phosphate metabolism may play an important role in ANS pathogenesis, warranting further confirmatory studies.