Sensitive LC-MS/MS method for the temporal profiling of bile acids, fatty acids and branched-chain alpha-keto acids in maternal plasma during pregnancy and cord blood plasma at delivery

Abstract

Background and aims: There are significant changes to the maternal inflammatory profile across pregnancy. Recent studies suggest that perturbations in maternal gut microbial and dietary-derived plasma metabolites over the course of pregnancy mediate inflammation through a complex interplay of immunomodulatory effects. Despite this body of evidence, there is currently no analytical method that is suitable for the simultaneous profiling of these metabolites within human plasma.

Materials and methods: We developed a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the high-throughput analysis of these metabolites in human plasma without derivatization. Plasma samples were processed using liquid-liquid extraction method with varying proportions of methyl tert-butyl ether, methanol, and water in a 3:10:2.5 ratio to reduce matrix effects.

Results: LC-MS/MS detection was sufficiently sensitive to quantify these gut microbial and dietary-derived metabolites at physiological concentrations and linear calibration curves with r² > 0.99 were obtained. Recovery was consistent across concentration levels. Stability experiments confirmed that up to 160 samples could be analyzed within a single batch. The method was validated and applied to analyse maternal plasma during the first and third trimester and cord blood plasma of 5 mothers.

Conclusion: This study validated a straightforward and sensitive LC-MS/MS method for the simultaneous quantitation of gut microbial and dietary-derived metabolites in human plasma within 9 minutes without prior sample derivatization.

Keywords: Bile acid; Branch chain alpha keto acid; Fatty acid; Liquid chromatography tandem mass spectrometry; Liquid-liquid extraction; Short chain fatty acid.