Urinary excretion of bile acid glucosides and glucuronides in extrahepatic cholestasis

Abstract

Recently the formation of bile acid glucosides has been described as a novel conjugation mechanism in vitro and in vivo. In 10 patients with extrahepatic cholestasis caused by carcinoma of the head of the pancreas we investigated excretion rates and profiles of urinary bile acid glucosides. Urinary bile acid glucosides and, for comparison, bile acid glucuronides were extracted and characterized according to established methods. In controls total urinary bile acid glucoside excretion was 0.22 +/- 0.03 mumol/24 hr (mean +/- S.E.M.)-in the range of bile acid glucuronide excretion (0.41 +/- 0.06 mumol/24 hr; mean +/- S.E.M.). A gas chromatography-mass spectrometry-characterized trihydroxy bile acid glucoside of still-unknown hydroxyl positions accounted for 65% of total urinary bile acid glucosides. In extrahepatic cholestasis total urinary bile acid glucoside excretion was 0.52 +/- 0.13 mumol/24 hr (mean +/- SEM), yet significantly lower than bile acid glucuronide excretion (1.53 +/- 0.13 mumol/24 hr; mean +/- SEM; p less than 0.001). In cholestasis the primary bile acid derivatives cholic and chenodeoxycholic acid glucosides amounted to 90%, whereas the trihydroxy bile acid glucoside had decreased to 5% of total bile acid glucoside excretion, indicating its alteration during enterohepatic circulation. The data establish the composition and quantity of urinary bile acid glucosides in healthy controls and cholestasis and constitute a quantitative comparison with another glycosidic conjugation reaction, bile acid glucuronidation.

Bile acid N-acetylglucosaminidation. In vivo and in vitro evidence for a selective conjugation reaction of 7 beta-hydroxylated bile acids in humans.

“…Besides aminoacyl amidation with glycine or taurine (1) and sulfation (2), three glycosidic conjugation pathways have been established both in vivo and in vitro during the last years: glucuronidation (3,4), glucosidation (5,6), and Nacetylglucosaminidation (7,8). Semiquantitative estimates indicated a similar urinary excretion rate for the three glycosidic conjugates, at least in healthy humans (6,7,9,10).…”

“…3a,7,8-dihydroxy-5,j-cholanoic (ursodeoxycholic), 3#,7,6-dihydroxy-5ft-cholanoic (isoursodeoxycholic) (6,7,9,10 …”

“…Total bile acids were extracted from 24-h collections of urine by repetitive use of Sep-Pak C18 cartridges. Group separation of bile acids by anion-exchange chromatography on Lipidex-DEAP was performed by a modification ofthe original method of Alme et al (17) for the estimation of glycosidic bile acid conjugates (10). Three fractions are obtained: (a) unconjugated bile acids and nonamidated bile acid glucosides and N-acetylglucosaminides; (b) glycine-or taurineconjugated bile acids and glycine-or taurine-conjugated bile acid glucosides; and (c) bile acid glucuronides.…”

“…In addition, a fraction (d) containing bile acid mono-and disulfates, was collected by elution with 15 ml 0.3 M ammonium acetate, pH 9.6, in 70% ethanol (17). Fraction (b) was treated with cholylglycine hydrolase yielding deamidated bile acids and bile acid glucosides (10), and fraction (c) was hydrolyzed with cholylglycine hydrolase and the digestive juice of Helix pomatia yielding deamidated and deglucuronidated bile acids (GlcA in Table II). Fraction (d) was solvolysed with trifluoroacetic acid in tetrahydrofuran (18) and treated with cholylglycine hydrolase (Sulfates in Table II).…”

Mutation of β-glucosidase 2 causes glycolipid storage disease and impaired male fertility

“…Bile acid glucosides, in which glucose is attached in β-linkage to carbon 3 of the bile acid (14), are normally excreted in the urine (15). Their synthesis by the liver is thought to assist in the disposal of hepatotoxic bile acids (16,17). Although GBA1 and GBA2 are both glycolipid hydrolases, the 2 enzymes apparently act on different glycolipids, do not share sequence identity, and are expressed in different tissues and subcellular compartments.…”