Shotgun lipidomics combined targeted MRM reveals sphingolipid signatures of coronary artery disease

Sphingolipids (SPLs) are bioactive lipids that manifest structural diversity and complexity in eukaryotes. However, the distributions and functions of these molecules in mammalian tissues/cells have not been systematically investigated. Herein, we integrated shotgun lipidomics with targeted LC-MRM/MS approach to comprehensively analyze SPL species in various biological samples with high accuracy. Preliminarily, 1311 SPL molecules were identified in 18 kinds of mammalian samples, including 3 groups of human sera, 10 mouse tissues and 5 cell lines via 26 sphingoid long-chain bases scanning. The sphingolipidome compositions and distributions were systematically characterized and distinct qualitative and quantitative profiles were clearly exhibited in various samples, indicating unique biological functions of the sphingolipidomes. Next, targeted SPLs analysis by LC-MRM/MS with critical criteria monitoring two characteristic fragments of one precursor was applied to human serum samples from 24 coronary artery disease (CAD) patients and 12 healthy controls, which successfully quantified 170 SPL molecules. Ten novel SPL molecules were discovered as a potential diagnostic panel for CAD patients via multivariate exploratory receiver operating characteristic curve-based biomarker analysis. The diagnostic panel with the 10 SPL molecules achieved 97.2% accuracy, with a favorable auxiliary diagnostic value (AUC = 1.000), for the detection of CAD. These results clearly support the sphingolipidomic approach in application to discovering disease biomarker panel as well as deep investigation of biological functions of complex SPLs in mammalian samples.