Screening biomarkers for diagnosis of COPD by multiplex-high-resolution mass spectrometry based pseudotargeted lipidomics

Abstract

Triple quadrupole (QQQ) MS based pseudotargeted lipidomics combines high coverage and quantitative accuracy, is commonly established by selecting the most responsive lipid ion pairs identified from high-resolution mass spectrometry (HRMS), then sending them to QQQ MS for quantification by multiple reaction monitoring. Due to the low resolution of QQQ MS, it may result in faulty peak identification in integration and method transition from HRMS to QQQ MS, thus, directly establish pseudotargeted lipidomics on HRMS is needed to improve the accuracy of present methods. We propose a method for rapidly screening high-resolution ion pairs for constructing multiplex-HRMS-based pseudotargeted lipidomics (MHPL). Firstly, high-resolution precursor and product ions for lipid quantification were obtained by HRMS. To solve the problem of lower acquisition speed in HRMS, we used the multiplex mode to simultaneously fragment co-eluting lipid precursor ions within one isolation window, scan the MS/MS mass spectra, and quantify the unique product ions (UPI) of co-eluting lipid (defined as Quan-PIs). Meanwhile, we provide a group of scripts for searching for lipid Quan-PIs in multiplex mode. The proposed MHPL strategy could ensure accurate quantification of 460 lipids within 5 injections, and was applied in serum differential lipid discovery for chronic obstructive pulmonary disease (COPD) patients. As a result, 47 differential lipids were found to comprise a potential biomarker panel for COPD diagnosis. The lipid identification and quantification in this work were conducted in the same instrument, and faulty peak identification was considerably reduced in integration and when transitioning methods from HRMS to QQQ MS.