Fatty Acyl-Specific Macrolipidomics and Microlipidomics for Nutritional Research

Abstract

The field of lipidomics can further our understanding of the biochemical processes of human health and disease. Generally, lipidomics methods utilize high-performance liquid chromatography (HPLC) for lipid separation, followed by detection using tandem mass spectrometry (MS/MS). The joint use of HPLC and MS/MS has increased dramatically over the past few years, and novel technologies continue to increase the versatility and practical usability of various lipidomics methods. However, a lack of harmonized language, nomenclature and standardized analytical strategies can result in lipid misannotations, improper analyte identifications, and incorrect quantitative results. In this thesis, the importance of adopting appropriate analytical strategies to answer research hypothesis(es) will be highlighted. Specifically, this entails a comparison between analytical platforms and four HPLC-MS/MS data acquisition strategies for untargeted/global lipidomic profiling of highly-abundant lipids including phospholipids, triacylglycerols and cholesteryl esters in human whole blood. In addition, the advantages of targeted analytical approaches for the measurement of specific lipid classes will be examined through the development of a tailored method for the determination of regioisomers of lysophosphatidic acid in plasma (mouse), the acyl species of triacylglycerols in cooking oil (sunflower), and the acyl species of phospholipids in brain tissue (mouse). Finally, comprehensive profiling of various lipid classes in whole blood using a novel retention time-based negative/positive ion mode switching method will be used to screen for potential blood biomarkers of omega-3 polyunsaturated fatty acid intake. This will include samples from a cross-sectional dietary assessment study in humans, and an acute/chronic docosahexaenoic acid supplementation study in rats. The methods presented in this thesis have the potential to be expanded for use in agriculture, nutrition, research and clinical settings.