Background The metabolic disturbances that underlie antiphospholipid syndrome (APS) are currently unknown. The goal of this study is to utilize high-throughput metabolomics screening to identify new biomarkers and dysregulated pathways in primary APS patients.
Methods Fasting serum samples were collected from 20 primary APS patients and 17 healthy controls. High-throughput metabolomics screening of 247 small molecule metabolites were performed via gas chromatography coupled mass spectrometry. Multiple variate analysis, principal components analysis (PCA), partial least squares discriminant analysis (PLS-DA), and pathway analysis were completed. SYTOX Green NETosis assay was performed utilizing freshly prepared healthy donor neutrophils with various stimulants including PMA, PMA+DPI, normal human IgG, antiphospholipid antibodies (aPL), sphingosine-1 phosphate (S1P), and aPL plus various concentration of S1P.
Results 50 circulating small molecule metabolites were significantly different between primary APS patients and healthy controls. PLS-DA modeling was performed and demonstrated a clear separation between primary APS patients and healthy controls. 15 metabolic biomarkers that made the biggest contribution to the differentiation of primary APS patients and the healthy controls assessed by variable importance on projection score were identified. Pathway analysis revealed that sphingosine metabolism was the most enriched pathway among primary APS patients. To further elucidate the role of sphingosine metabolism in APS, we examined the effect of S1P, the product of sphingosine metabolism, on aPL mediated NETosis. aPL mediated NETosis was significantly potentiated by S1P in a concentration dependent manner. S1P did not trigger NETosis by itself (figure 1).
Conclusions This study comprehensively profiled the serum metabolites of primary APS patients and identified metabolic biomarkers that have the potential to be used as a diagnostic tool for differentiating APS from healthy controls. The APS metabolome analysis also revealed a potential significant role of S1P/S1PR axis in APS pathogenesis.
The effect of S1P on aPL mediated NETosis. aPL mediated NETosis was significantly potentiated by S1P in a concentration dependent manner. S1P did not trigger NETosis by itself.
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