Background/Purpose: The metabolic disturbances that underlie antiphospholipid syndrome (APS) are currently unknown. The goal of this study was 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, 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 normal human IgG, polyclonal antiphospholipid antibodies (aPL), sphingosine-1 phosphate (S1P), and polyclonal aPL plus various concentrations 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 (Figure 1). 15 metabolic molecules that contributed most to the differentiation of primary APS patients and the healthy controls (assessed by variable importance on projection score) had the highest potential to be clinically relevant biomarkers. Pathway analysis revealed that sphingosine metabolism was the most enriched pathway among primary APS patients. Sphingosine metabolism plays paramount roles in membrane biology and provides many bioactive metabolites that regulate cellular function. To further elucidate the role of sphingosine metabolism in APS, we examined the effect of S1P (a product of sphingosine metabolism) on aPL-mediated neutrophil extracellular trap release (NETosis). aPL-mediated NETosis was significantly potentiated by S1P. Importantly, S1P had no impact on NETosis in the absence of aPL (Figure 2).

Conclusion: This study identified metabolomic differences in the serum of primary APS patients and healthy controls. One of the most significant pathways was sphingolipid metabolism. One product of this pathway is S1P, implicated in immunological pathology. The ability of this compound to augment aPL in provoking NETosis suggests a potential role of S1P/S1PR axis in APS pathogenesis.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/metabolomics-analysis-identifies-biomarkers-for-aps-and-suggests-a-potential-new-pathway-related-to-aps-pathogenesis/