Comprehensive Identification of Amadori Compound-Modified Phosphatidylethanolamines in Human Plasma

Amadori compound modified lipids are the result of nonenzymatic glycation and play an important role in several physiological and pathological processes. However, glycation of phosphatidylethanolamine (PE), the most abundant amine-containing lipid in blood plasma, is underexplored and so far only a few glycated PEs have been reported. Herein, we report comprehensive profiling of Amadori-PE and -LysoPE species in human plasma. Using synthetic standards, we first optimized the enrichment procedure for extracting Amadori-PE/LysoPE from plasma. On the basis of the characteristic neutral losses of 303 Da in positive and 162 Da in negative ionization mode, we then applied neural loss scanning-liquid chromatography tandem mass spectrometry (LC-NLS-MS) to identify potentially glycated PE and LysoPE, which was followed by targeted product ion scanning (LC-PIS-MS) to confidently confirm the fatty acyl substitutions of the modified lipids. A total of 20 Amadori-LysoPE and 62 Amadori-PE species, including diacyl, plasmanyl, and plasmenyl, were identified. Among them, the concentrations of 12 Amarodi-LysoPE and 54 Amadori-PE were also quantified in native human plasma, using stable isotope labeled Amadori lipids as internal standards.