The Major Metabolites of Ursodeoxycholic Acid in Human Urine Are Conjugated With N –Acetylglucosamine

Abstract

Ursodeoxycholic acid (750 mg/day) was administered orally to ten healthy subjects over a period of 10 days; 24 hr urine samples were collected the day before and on the last day of the study. Urinary bile acids were extracted, separated into groups of conjugates and analyzed by gas chromatography-mass spectrometry and fast atom bombardment mass spectrometry. Excretion of ursodeoxycholic acid rose from 70 to 2,915 micrograms/24 h. The highest increase was observed among N-acetylglucosamine conjugates, 90% of which constituted the previously unknown double conjugate of ursodeoxycholic acid with N-acetylglucosamine and glycine. Excretion of isoursodeoxycholic acid increased from 50 to 738 micrograms/24 h. This isomerization product of ursodeoxycholic acid was excreted almost exclusively as N-acetylglucosamine conjugate. In total, N-acetylglucosamine conjugates constituted 50% of urinary metabolites of ursodeoxycholic acid. In addition, metabolites of ursodeoxycholic acid hydroxylated at carbon atoms 1, 6, 22 and possibly 21 were observed. These compounds were also found as conjugates with N-acetylglucosamine. Their formation from ursodeoxycholic acid was definitely demonstrated by 13C-labeling after giving [24-13C]ursodeoxycholic acid to one of the healthy subjects and to a patient with extrahepatic cholestasis in whom hydroxylation of ursodeoxycholic acid at C-23 was also observed. The patient was also found to excrete the double conjugate of ursodeoxycholic acid with N-acetylglucosamine and taurine. The N-acetylglucosaminidation of ursodeoxycholic acid in vivo was shown to occur at C-7.(ABSTRACT TRUNCATED AT 250 WORDS)

Identification of novel bile acids as biomarkers for the early diagnosis of Niemann‐Pick C disease

“…This compound was prepared by solvolysis 31 of the 3‐sulfate 28 and used as a reference standard for the UPLC‐MS/MS analyses. Solvolysis of 3β‐sulfoxy‐7β‐ N ‐acetyl‐glucosaminyl‐5‐cholenoic acid 28 produced a bile acid with [M−H] − of m / z 592, consistent with the expected 3β‐hydroxy‐7β‐ N ‐acetyl‐glucosaminyl‐5‐cholenoic acid and a main product ion of m / z 389, after the neutral loss of 203 mass units attributable to the cleavage of the O ‐GlcNAc bond.…”

“…We considered a possible cause of failure to detect the bile acids conjugated with N ‐acetyl‐glucosamine in NPC patients. A common homozygous polymorphism/mutation in the UGT3A1 gene, c.T361G, leads to an amino acid substitution (p.C121G) and absence of activity of the encoded 7β‐hydroxy bile acid UDP N ‐acetylglucosaminyl transferase 30, 31: homozygosity for c.T361G is present in about 20% of Asian and Caucasian populations.…”

A two-year prospective study of the effect of ursodeoxycholic acid on urinary bile acid excretion and liver morphology in cystic fibrosis-associated liver disease

“…IsoUDCA could not be separated from UDCA with our method. The urine from five patients was also analyzed for glycosidic bile acid conjugates by a modification of the methods of Marschall et al 19 and Yamaga et al 20 The U fraction was eluated with 15 mL 0.1 mol/L HAc in ethanol at pH 3.85; the G and T fraction combined (GT), including glucuronides, was eluted with 25 mL 0.15 mol/L HAc in 70% ethanol at pH 6.6 and 20 mL 0.25 mol/L HCOOH in 70% ethanol. The S fraction was eluated with 15 mL 0.3 mol/L HAc in 70% ethanol at pH 9.6, and the S and GT fractions were evaporated, dissolved in water, and once more passed through a Sep-Pak C18 cartridge and eluated with 5 mL methanol.…”

“…Four patients were analyzed after separation of bile acid fractions as described by Marschall et al, 19 using FABMS to verify the efficacy of the method used in the present study. There was good separation, with no overlapping between the fractions except for a slight peak of dihydroxycholylglycine in the S fraction.…”

“…One other bile acid, tentatively identified as -muricholic acid, which is also considered to be a metabolite of UDCA, 22 was found occasionally. The total excretion of (right), at 0, 3, 12, and 18 and II ϭ including glycosidic conjugates 19 at the start and after 24 months of treatment of UDCA. For explanation, see Table 3 and text.…”