Investigation of bile acids by LC-MS/MS in cholestasis patients and determination of possible biomarkers

Inborn errors of bile acid synthesis (IEBAS) are autosomal recessively inherited disorders that are resulted from the deficiencies in the structure or function of the enzymes involved in the synthesis of bile acids, causing the accumulation of unusual intermediate metabolites of bile acid synthesis. If untreated, progressive neurological symptoms and fatal liver disease is prominent, thus early diagnosis is important. In this study, it was aimed to determine the method that can be used in the early diagnosis of these rare, difficult to diagnose but treatable diseases and possible biomarkers for them. Sixty-eight bile acid intermediate metabolites were evaluated by targeted metabolomic analysis in urine samples impregnated on dry paper by LC-MS/MS method. In plasma samples, 5α-cholestanol and 7-dehydrocholesterol intermediate metabolite and cholesterol measurement were evaluated by GC-MS method. A significant difference was observed between total bile acid values (p=0.001), classical bile acid values (p=0.001), hydroxylated bile acid values (p=0.001), 3β-hydroxy-Δ5-bile acid values (p=0.002) and 3-oxo-∆⁴-bile acid values (p=0.001) of patients and healthy individuals. Urinary bile acid bile metabolites compatible with 3β-hydroxy-Δ5-steroid dehydrogenase deficiency in one patient, oxisterol-7α-hydroxylase deficiency in one patient, and cerebrotendinous xanthomatosis in 3 patients were detected. There was no significant difference between cholesterol and cholestanol values (p=0.570 and p=0.099). A significant difference was found between 7-dehydrocholesterol values (p=0.008). Our findings show that the targeted mass spectrometry technology is effective in detecting the intermediate bile acid metabolites in urine and plasma and predicting enzyme deficiencies involved in bile acid synthesis pathways.