Human cecal bile acids: concentration and spectrum.
To obtain information on the concentration and spectrum of bile acids in human cecal content, samples were obtained from 19 persons who had died an unnatural death from causes such as trauma, homicide, suicide, or drug overdose. Bile acid concentration was measured via an enzymatic assay for 3alpha-hydroxy bile acids; bile acid classes were determined by electrospray ionization mass spectrometry and individual bile acids by gas chromatography mass spectrometry and liquid chromatography mass spectrometry. The 3alpha-hydroxy bile acid concentration (mumol bile acid/ml cecal content) was 0.4 +/- 0.2 mM (mean +/- SD); the total 3-hydroxy bile acid concentration was 0.6 +/- 0.3 mM. The aqueous concentration of bile acids (supernatant after centrifugation) was identical, indicating that most bile acids were in solution. By liquid chromatography mass spectrometry, bile acids were mostly in unconjugated form (90 +/- 9%, mean +/- SD); sulfated, nonamidated bile acids were 7 +/- 5%, and nonsulfated amidated bile acids (glycine or taurine conjugates) were 3 +/- 7%. By gas chromatography mass spectrometry, 10 bile acids were identified: deoxycholic (34 +/- 16%), lithocholic (26 +/- 10%), and ursodeoxycholic (6 +/- 9), as well as their primary bile acid precursors cholic (6 +/- 9%) and chenodeoxycholic acid (7 +/- 8%). In addition, 3beta-hydroxy derivatives of some or all of these bile acids were present and averaged 27 +/- 18% of total bile acids, indicating that 3beta-hydroxy bile acids are normal constituents of cecal content. In the human cecum, deconjugation and dehydroxylation of bile acids are nearly complete, resulting in most bile acids being in unconjugated form at submicellar and subsecretory concentrations.
Hamilton
James P
JP
Division of Gastroenterology and Hepatology, Department of Medicine, Veterans Affairs Maryland Health Care System and University of Maryland School of Medicine, 22 S. Greene Street, Baltimore, MD 21201, USA.
Xie
Guofeng
G
Raufman
Jean-Pierre
JP
Hogan
Susan
S
Griffin
Terrance L
TL
Packard
Christine A
CA
Chatfield
Dale A
DA
Hagey
Lee R
LR
Steinbach
Joseph H
JH
Hofmann
Alan F
AF
D001647:Bile Acids and Salts / Q000032:analysis*; D002432:Cecum / Q000737:chemistry*; D002635:Chenodeoxycholic Acid / Q000032:analysis; D002793:Cholic Acids / Q000032:analysis; D002853:Chromatography, Liquid; D003840:Deoxycholic Acid / Q000032:analysis; D008401:Gas Chromatography-Mass Spectrometry; D005766:Gastrointestinal Contents / Q000737:chemistry*; D006801:Humans; D008095:Lithocholic Acid / Q000032:analysis; D021241:Spectrometry, Mass, Electrospray Ionization; D053719:Tandem Mass Spectrometry; D014580:Ursodeoxycholic Acid / Q000032:analysis
D001647:Bile Acids and Salts; D002793:Cholic Acids; D003840:Deoxycholic Acid; D002635:Chenodeoxycholic Acid; D008095:Lithocholic Acid; D014580:Ursodeoxycholic Acid