Discovery of candidate phospholipid biomarkers in human lipoproteins with coronary artery disease by flow field-flow fractionation and nanoflow liquid chromatography–tandem mass spectrometry

In this study, an analytical method is demonstrated to identify and develop potential phospholipid (PL) biomarkers of high density lipoprotein (HDL) and low density lipoprotein (LDL) in plasma from individuals with coronary artery disease (CAD) by employing a combination of off-line multiplexed hollow fiber flow field-flow fractionation (MxHF5) and nanoflow liquid chromatography–electrospray ionization-tandem mass spectrometry (nLC–ESI-MS–MS). HDL and LDL particles of human plasma were sorted by size at a semi-preparative scale using MxHF5, after which PL extracts of each lipoprotein fraction were qualitatively and quantitatively analyzed by nLC–ESI-MS–MS. Experiments were performed using plasma samples from 10 CAD patients and 10 controls. Quantitative analysis of the 93 PL species identified yielded a selection of 19 species from HDL fractions and 10 from LDL fractions exhibiting at least a five fold change in average concentration in CAD patients. Among the selected species, only a few were found exclusively in patient HDL fractions (18:3-LPA and 20:2/16:0-PG), control HDL fractions (16:0/16:1-PC, 20:1/20:4-PE, and 16:1-LPA), and control LDL fractions (16:0/22:3-PG). Moreover, 16:1/18:2-PC was detected from both HDL and LDL fractions of controls but disappeared in CAD patients. Although the typical change in lipoproteins for CAD is well known, with decreased levels of HDLs and reduced LDL particle size, the current study provides fundamental information on the molecular level of lipoprotein variation which can be utilized for diagnostic and therapeutic tracking.