title: Determination of 7 alpha-hydroxy-4-cholesten-3-one level in plasma using isotope-dilution mass spectrometry and monitoring its circadian rhythm in human as an index of bile acid biosynthesis.
abstract: A highly sensitive and specific method has been developed for determination of the level of 7 alpha-hydroxy-4-cholesten-3-one in plasma. This method is based on a stable isotope-dilution technique by gas chromatography-selected-ion monitoring mass spectrometry. 7 alpha-Hydroxy-4-cholesten-3-one was extracted from plasma by saltingout extraction, and then purified by serial solid-phase extractions. The extract was treated with O-methylhydroxyl-amine hydrochloride and then dimethylethylsilylated. The resulting methyloxime-dimethylethylsilyl ether derivative was quantified by gas chromatography-selected-ion monitoring mass spectrometry with a high-resolution mode. The plasma levels of 7 alpha-hydroxy-4-cholesten-3-one were correlated with the cholesterol 7 alpha-hydroxylase activity to a higher degree than those of any other form of 7 alpha-hydroxycholesterol (r = 0.84, n = 16, p < 0.0001). The present method was applied to monitor the circadian rhythm of 7 alpha-hydroxy-4-cholesten-3-one levels in human plasma. It was concluded that the plasma level of 7 alpha-hydroxy-4-cholesten-3-one is a useful index for the monitoring of bile acid biosynthesis in the human liver.
authors.affiliation: Department of Gastroenterology, University of Tsukuba, Ibaraki, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Yoshida
authors.forename: A
authors.initials: A
authors.lastname: Honda
authors.forename: N
authors.initials: N
authors.lastname: Tanaka
authors.forename: Y
authors.initials: Y
authors.lastname: Matsuzaki
authors.forename: J
authors.initials: J
authors.lastname: Shoda
authors.forename: B
authors.initials: B
authors.lastname: He
authors.forename: T
authors.initials: T
authors.lastname: Osuga
authors.forename: H
authors.initials: H
authors.lastname: Miyazaki
mesh_terms: D000328:Adult; D000368:Aged; D001647:Bile Acids and Salts / Q000096:biosynthesis*; D002769:Cholelithiasis / Q000097:blood; D002783:Cholestenones / Q000097:blood*; D002784:Cholesterol / Q000097:blood; D002790:Cholesterol 7-alpha-Hydroxylase / Q000378:metabolism; D002940:Circadian Rhythm; D005770:Gastrointestinal Neoplasms / Q000097:blood; D006801:Humans; D006888:Hydroxycholesterols / Q000097:blood; D007700:Kinetics; D008099:Liver / Q000201:enzymology; D008297:Male; D013058:Mass Spectrometry / Q000379:methods* / Q000706:statistics & numerical data; D008875:Middle Aged; D015203:Reproducibility of Results
chemical_list: D001647:Bile Acids and Salts; D002783:Cholestenones; D006888:Hydroxycholesterols; C002656:7 alpha-hydroxy-4-cholesten-3-one; C011724:cholest-5-en-3 beta,7 alpha-diol; D002784:Cholesterol; D002790:Cholesterol 7-alpha-Hydroxylase