Identification of unusual oxysterols and bile acids with 7-oxo or 3β,5α,6β-trihydroxy functions in human plasma by charge-tagging mass spectrometry with multistage fragmentation

William J Griffiths, Ian Gilmore, Eylan Yutuc, Jonas Abdel-Khalik, Peter J Crick, Thomas Hearn, Alison Dickson, Brian W Bigger, Teresa Hoi-Yee Wu, Anu Goenka, Arunabha Ghosh, Simon A Jones, Yuqin Wang

Research output: Contribution to journalArticle (Academic Journal)peer-review

Abstract

7-Oxocholesterol (7-OC), 5,6-epoxycholesterol (5,6-EC), and its hydrolysis product cholestane-3β,5α,6β-triol (3β,5α,6β-triol) are normally minor oxysterols in human samples; however, in disease, their levels may be greatly elevated. This is the case in plasma from patients suffering from some lysosomal storage disorders, e.g., Niemann-Pick disease type C, or the inborn errors of sterol metabolism, e.g., Smith-Lemli-Opitz syndrome and cerebrotendinous xanthomatosis. A complication in the analysis of 7-OC and 5,6-EC is that they can also be formed ex vivo from cholesterol during sample handling in air, causing confusion with molecules formed in vivo. When formed endogenously, 7-OC, 5,6-EC, and 3β,5α,6β-triol can be converted to bile acids. Here, we describe methodology based on chemical derivatization and LC/MS with multistage fragmentation (MSn) to identify the necessary intermediates in the conversion of 7-OC to 3β-hydroxy-7-oxochol-5-enoic acid and 5,6-EC and 3β,5α,6β-triol to 3β,5α,6β-trihydroxycholanoic acid. Identification of intermediate metabolites is facilitated by their unusual MSn fragmentation patterns. Semiquantitative measurements are possible, but absolute values await the synthesis of isotope-labeled standards.

Original languageEnglish
Pages (from-to)1058-1070
Number of pages13
JournalJournal of Lipid Research
Volume59
Issue number6
DOIs
Publication statusPublished - Jun 2018

Bibliographical note

Copyright © 2018 Griffiths et al. Published under exclusive license by The American Society for Biochemistry and Molecular Biology, Inc.

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