| Summary: | A subgroup of peroxisomal disorders, peroxisome biogenesis defects (PBD), can be differentiated by elevated levels of C27 bile acids in plasma and bile. Patients with peroxisomal disorders, who lack the ability to chain-shorten the C27 bile acid intermediates into C24 bile acids, show elevated levels of C27 bile acids, notably 3α,7α-dihydroxy-5β-cholest-26-oic acid and 3α,7α,12α-trihydroxy-5β-cholestan-26-oic acid. C27 bile acids are normally estimated against other bile acid standards, by time-consuming gas chromatography-mass spectrometry and liquid chromatography-tandem mass spectrometry methods, in plasma (minimum of 50 μl). In this article we describe the quantitation of unconjugated di- and trihydroxy C27 bile acids in 5-μl plasma samples and 3-mm blood spots, using deuterium-labeled internal standards. The synthesis of 2H3-labeled di- and trihydroxycoprostanic acids is described. The sample preparation and analysis by electrospray tandem mass spectrometry (ES-MS/MS) takes less than 1 h and features dimethylaminoethyl ester derivatives. The levels of the di- and trihydroxy bile acids are significantly higher in PBD patients than in age-matched control subjects for both plasma and blood spots collected at birth (some stored for up to 18 years). Excellent correlation is observed between the C26:0/C22:0 very long chain fatty acid (VLCFA) ratio and the levels of trihydroxy C27 bile acids in plasma from PBD patients. The ES-MS/MS method can be used to rapidly screen for PBD patients in plasma samples with elevated C26:0/C22:0 VLCFA ratios and in archived collections of neonatal blood spots.—Johnson, D. W., H. J. ten Brink, R. C. Schuit, and C. Jakobs. Rapid and quantitive analysis of unconjugated C27 bile acids in plasma and blood samples by tandem mass spectrometry. J. Lipid Res. 2001. 42: 9–16.
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