Differential diagnosis in patients with suspected bile acid synthesis defects

AIM: To investigate the clinical presentations associated with bile acid synthesis defects and to describe identification of individual disorders and diagnostic pitfalls. METHODS: We describe semiquantitative determination of 16 urinary bile acid metabolites by electrospray ionization-tandem mass spectrometry. Sample preparation was performed by solid-phase extraction. The total analysis time was 2 min per sample. We determined bile acid metabolites in 363 patients with suspected defects in bile acid metabolism. RESULTS: Abnormal bile acid metabolites were found in 36 patients. Two patients had bile acid synthesis defects but presented with atypical presentations. In 2 other patients who were later shown to be affected by biliary atresia and cystic fibrosis the profile of bile acid metabolites was initially suggestive of a bile acid synthesis defect. Three adult patients suffered from cerebrotendinous xanthomatosis. Nineteen patients had peroxisomal disorders, and 10 patients had cholestatic hepatopathy of other cause. CONCLUSION: Screening for urinary cholanoids should be done in every infant with cholestatic hepatopathy as well as in children with progressive neurological disease to provide specific therapy.

Flow Field-Flow Fractionation with Mass Spectrometry for Top-Down and Bottom-Up Lipidomics

As lipidomics has attracted increased attention in life science,advanced mass spectrometry(MS)technologies have been combined with other separation techniques to improve and expand the branch of study.This review intends to provide general knowledge of offline and online coupling of flow field-flow fractionation(FlFFF)—a technique that encompasses the separation of nano-to micro-scale biomolecules—with MS for analysis of blood plasma lipoproteins,processes that are considered bottomup and top-down approaches,respectively.The first part of this review focuses on the bottom-up method using multiplexed hollow fiber FlFFF(MxHF5)and nanoflow liquid chromatography electrospray-ionization tandem mass spectrometry(nLC-ESI–MS/MS)for non-targeted identification of lipids.In this protocol,plasma lipoproteins of different types are collected using MxHF5,and the lipids within the lipoproteins are then extracted and analyzed via nLC-ESI–MS/MS.The second part of the review describes the top-down approach,which uses online coupling of miniaturized FlFFF to ESI–MS for a fast screening of targeted lipids.Here,the separation of lipoproteins and detection of their component lipids are achieved simultaneously.While both methods aim to quantify the lipids within lipoproteins,the bottom-up approach provides an extensive lipidome,whereas the top-down method is suitable for high-speed targeted lipidomic analysis.This review discusses variants of FlFFF-ESI–MS/MS that offer effective analytical technologies for lipidomics.