Separation and analysis of mono-glucosylated lipids in brain and skin by hydrophilic interaction chromatography based on carbohydrate and lipid moiety

Abstract

Mono-glycosylated sphingolipids and glycerophospholipids play important roles in diverse biological processes and are linked to a variety of pathologies, such as Parkinson disease. The precise identification of the carbohydrate head group of these lipids is complicated by their isobaric nature and by substantial differences in concentration in different biological samples. To overcome these obstacles, we developed a zwitterionic (ZIC)-hydrophilic interaction chromatography (HILIC) electrospray ionization tandem mass spectrometry method. ZIC-HILIC preferentially retains inositol, followed by glucose- and galactose-featuring lipids. Comparison with unmodified silica gel HILIC stationary phase revealed different retention specificity. To evaluate the precision of ZIC-HILIC, we quantified glucosyl- (GlcCer) and galactosylceramides (GalCer) in seven different regions of the mouse brain and discovered that GlcCer and GalCer concentrations are inversely related. The highest GalCer (lowest GlcCer) content was found in the medulla oblongata and hippocampus, whereas the highest GlcCer (lowest GalCer) content was found in other regions. With a neutral loss scan, ZIC-HILIC resolved glucosylceramide species featuring non-hydroxylated fatty acid, hydroxylated fatty acid, and trihydroxy sphingoid bases in mouse epidermis samples. This demonstrates that our ZIC-HILIC-based approach is a valuable tool for characterizing the structural diversity of mono-glucosylated lipids in biological material and for quantifying these important lipids.

Keywords: Glucosylated lipid; Glucosylceramide; Hydrophilic interaction chromatography; Lipid isomer; Mass spectrometry; Phopsphatidylglucoside; Zwitterionic phase.