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.