Identification of Two Sulfated Cholesterol Metabolites Found in the Urine of a Patient with Niemann–Pick Disease Type C as Novel Candidate Diagnostic Markers

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In the urine of a Niemann–Pick disease type C (NPC) patient, we have identified three characteristic intense peaks that have not been observed in the urine of a 3β-hydroxysteroid-Δ⁵-C₂₇-steroid dehydrogenase deficiency patient or a healthy infant and adult. Based on accurate masses of the protonated molecules, we focused on two of them as candidate NPC diagnostic markers. Two synthesized authentic preparations agreed with the two compounds found in NPC patient urine in regard to both chromatographic behavior and accurate masses of the deprotonated molecules. Moreover, the isotopic patterns of the deprotonated molecules, twin peaks unique to the sulfur-containing compounds appearing in their second isotope positions, and accurate masses of product ions observed at m/z 97 also agreed between the target compounds and authentic preparations. We identified the two compounds as the sulfated cholesterol metabolites as 3β-sulfooxy-7β-hydroxy-5-cholen-24-oic acid and 3β-sulfooxy-7-oxo-5-cholen-24-oic acid. These two compounds represent more promising candidate diagnostic markers for NPC diagnosis than three other candidates that are multiple conjugates of cholesterol metabolites, 3β-sulfooxy-7β-N-acetylglucosaminyl-5-cholen-24-oic acid and its glycine and taurine conjugates, although we have reported an analytical method for determining the urinary levels of these compounds using liquid chromatography/electrospray ionization tandem mass spectrometry, because of their lack of N-acetylglucosamine conjugation.