Bile acids and their sulphated and glucuronidated derivatives in bile, plasma, and urine of children with intrahepatic cholestasis: effects of phenobarbital treatment

Review of paediatric gastrointestinal physiology relevant to the absorption of orally administered medicines

Despite much progress in regulations to improve paediatric drug development, there remains a significant need to develop better medications for children. For the design of oral dosage forms, a detailed understanding of the specific gastrointestinal (GI) conditions in children of different age categories and how they differ from GI conditions in adults is essential. Several review articles have been published addressing the ontogeny of GI characteristics, including luminal conditions in the GI tract of children. However, the data reported in most of these reviews are of limited quality because (1) information was cited from very old publications and sometimes low quality sources, (2) data gaps in the original data were filled with textbook knowledge, (3) data obtained on healthy and sick children were mixed, (4) average data obtained on groups of patients were mixed with data obtained on individual patients, and (5) results obtained using investigative techniques that may have altered the outcome of the respective studies were considered. Consequently, many of these reviews draw conclusions that may be incorrect. The aim of the present review was to provide a comprehensive and updated overview of the available original data on the ontogeny of GI luminal conditions relevant to oral drug absorption in the paediatric population. To this end, the PubMed and Web of Science metadatabases were searched for appropriate studies that examined age-related conditions in the oral cavity, esophagus, stomach, small intestine, and colon. Maturation was observed for several GI parameters, and corresponding data sets were identified for each paediatric age group. However, it also became clear that the ontogeny of several GI traits in the paediatric population is not yet known. The review article provides a robust and valuable data set for the development of paediatric in vitro and in silico biopharmaceutical tools to support the development of age-appropriate dosage forms. In addition, it provides important information on existing data gaps and should provide impetus for further systematic and well-designed in vivo studies on GI physiology in children of specific age groups in order to close existing knowledge gaps and to sustainably improve oral drug therapy in children.

Global profiling and identification of bile acids by multi-dimensional data mining to reveal a way of eliminating abnormal bile acids

Bile acids (BAs), as crucial endogenous metabolites, are closely related to cholestasis, metabolic disorders, and cancer. To better understand their function and disease pathogenesis, global profiling of BAs is necessary. Here, multidimensional data mining was developed for the discovery and identification of potentially unknown BAs in cholestasis rats. Based on an in-house theoretical BA database and using a newly established liquid chromatography-tandem high-resolution mass spectrometry (LC-HRMS/MS) method, four-dimensional (4D) data including the retention times (RT), abundances, HRMS, and HRMS/MS spectra were acquired and elucidated. And 491 BAs were totally profiled. Then, the relationships between RT with different conjugation types, different positions and configurations of hydroxyl/ketone groups as well as fragmentation rules of hydroxyl, ortho-hydroxyl, ketone, and conjugated groups of BAs were summarized to assist BA identification for the first time. Finally, 292 BAs were assigned with molecular formulas, 201 of which were putatively identified by integrating the 4D data, applying structure-driven relative retention time rules, and a comparison with synthetic BAs. The estimated concentrations of 201 BAs, including 93 reported and 108 newly identified BAs, were quantified by using surrogate standards with similar structure. Among 201 BAs, 38 BAs were detected in both humans and rats for the first time. Our strategy has expanded the scope of BAs and provides a way to identify a class of metabolites. Compared to normal rats, the significantly increased sulfated and glucuronide conjugated BAs in urine and feces from experimentally cholestatic rats may reveal a way to diagnose intrahepatic cholestasis.

Advances in oral peptide therapeutics

Protein and peptide therapeutics require parenteral administration, which can be a deterrent to medication adherence. For this reason, there have been extensive efforts to develop alternative delivery strategies, particularly for peptides such as insulin that are used to treat endocrine disorders. Oral delivery is especially desirable, but it faces substantial barriers related to the structural organization and physiological function of the gastrointestinal tract. This article highlights strategies designed to overcome these barriers, including permeation enhancers, inhibitors of gut enzymes, and mucus-penetrating and cell-penetrating peptides. It then focuses on the experience with oral peptides that have reached clinical trials, including insulin, calcitonin, parathyroid hormone and vasopressin, with an emphasis on the advances that have recently led to the landmark approval of an oral formulation of the glucagon-like peptide 1 receptor agonist semaglutide for the treatment of type 2 diabetes.

Upregulation of UGT2B4 Expression by 3'-Phosphoadenosine-5'-Phosphosulfate Synthase Knockdown: Implications for Coordinated Control of Bile Acid Conjugation

During cholestasis, the bile acid-conjugating enzymes, SULT2A1 and UGT2B4, work in concert to prevent the accumulation of toxic bile acids. To understand the impact of sulfotransferase deficiency on human hepatic gene expression, we knocked down 3'-phosphoadenosine-5'-phosphosulfate synthases (PAPSS) 1 and 2, which catalyze synthesis of the obligate sulfotransferase cofactor, in HepG2 cells. PAPSS knockdown caused no change in SULT2A1 expression; however, UGT2B4 expression increased markedly (∼41-fold increase in UGT2B4 mRNA content). Knockdown of SULT2A1 in HepG2 cells also increased UGT2B4 expression. To investigate the underlying mechanism, we transfected PAPSS-deficient HepG2 cells with a luciferase reporter plasmid containing ∼2 Kb of the UGT2B4 5'-flanking region, which included a response element for the bile acid-sensing nuclear receptor, farnesoid X receptor (FXR). FXR activation or overexpression increased UGT2B4 promoter activity; however, knocking down FXR or mutating or deleting the FXR response element did not significantly decrease UGT2B4 promoter activity. Further evaluation of the UGT2B4 5'-flanking region indicated the presence of distal regulatory elements between nucleotides -10090 and -10037 that negatively and positively regulated UGT2B4 transcription. Pulse-chase analysis showed that increased UGT2B4 expression in PAPSS-deficient cells was attributable to both increased mRNA synthesis and stability. Transfection analysis demonstrated that the UGT2B4 3'-untranslated region decreased luciferase reporter expression less in PAPSS-deficient cells than in control cells. These data indicate that knocking down PAPSS increases UGT2B4 transcription and mRNA stability as a compensatory response to the loss of SULT2A1 activity, presumably to maintain bile acid-conjugating activity.

Regulation of the cytosolic sulfotransferases by nuclear receptors

The cytosolic sulfotransferases (SULTs) are a multigene family of enzymes that catalyze the transfer of a sulfonate group from the physiologic sulfate donor, 3'-phosphoadenosine-5'-phosphosulfate, to a nucleophilic substrate to generate a polar product that is more amenable to elimination from the body. As catalysts of both xenobiotic and endogenous metabolism, the SULTs are major points of contact between the external and physiological environments, and modulation of SULT-catalyzed metabolism can not only affect xenobiotic disposition, but it can also alter endogenous metabolic processes. Therefore, it is not surprising that SULT expression is regulated by numerous members of the nuclear receptor (NR) superfamily that function as sensors of xenobiotics as well as endogenous molecules, such as fatty acids, bile acids, and oxysterols. These NRs include the peroxisome proliferator-activated receptors, pregnane X receptor, constitutive androstane receptor, vitamin D receptor, liver X receptors, farnesoid X receptor, retinoid-related orphan receptors, and estrogen-related receptors. This review summarizes current information about NR regulation of SULT expression. Because species differences in SULT subfamily composition and tissue-, sex-, development-, and inducer-dependent regulation are prominent, these differences will be emphasized throughout the review. In addition, because of the central role of the SULTs in cellular physiology, the effect of NR-mediated SULT regulation on physiological and pathophysiological processes will be discussed. Gaps in current knowledge that require further investigation are also highlighted.

Expression of bile acid synthesis and detoxification enzymes and the alternative bile acid efflux pump MRP4 in patients with primary biliary cirrhosis

BACKGROUND

Bile acid synthesis, transport and metabolism are markedly altered in experimental cholestasis. Whether such coordinated regulation exists in human cholestatic diseases is unclear. We therefore investigated expression of genes for bile acid synthesis, detoxification and alternative basolateral export and regulatory nuclear factors in primary biliary cirrhosis (PBC).

MATERIAL/METHODS

Hepatic CYP7A1, CYP27A1, CYP8B1 (bile acid synthesis), CYP3A4 (hydroxylation), SULT2A1 (sulphation), UGT2B4/2B7 (glucuronidation), MRP4 (basolateral export), farnesoid X receptor (FXR), retinoid X receptor (RXR), short heterodimer partner (SHP), hepatocyte nuclear factor 1alpha (HNF1alpha) and HNF4alpha expression was determined in 11 patients with late-stage PBC and this was compared with non-cholestatic controls.

RESULTS

CYP7A1 mRNA was repressed in PBC to 10-20% of controls, while CYP27 and CYP8B1 mRNA remained unchanged. SULT2A1, UGT2B4/2B7 and CYP3A4 mRNA levels were unaltered or only mildly reduced in PBC. MRP4 protein levels were induced three-fold in PBC, whereas mRNA levels remained unchanged. Expression levels of FXR, RXR, SHP, PXR, CAR, HNF1alpha and HNF4alpha were moderately reduced in PBC without reaching statistical significance.

SUMMARY/CONCLUSIONS

Repression of bile acid synthesis and induction of basolateral bile acid export may represent adaptive mechanisms to limit bile acid burden in chronic cholestasis. As these changes do not sufficiently counteract cholestatic liver damage, future therapeutic strategies should aim at stimulation of bile acid detoxification pathways.

An enzymatic cycling method for the determination of serum total bile acids with recombinant 3alpha-hydroxysteroid dehydrogenase

A highly sensitive enzymatic cycling method was developed for the serum total bile acids assay. We constructed a prokaryotic expression system to prepare the recombinant 3alpha-hydroxysteroid dehydrogenase in place of the natural enzyme and for the first time used it in the total bile acids assay. The production rate of thio-NADH correlated with the bile acids concentration and was measured by the change of absorbance at 405/660 nm. The enzymatic cycling method could detect 0.22 micromol/L total bile acids in serum. Within-run and between-run imprecisions were 1.2-3.7% and 2.3-4.8%, respectively. The calibration curve for total bile acids in serum was linear between 0.5 and 180 micromol/L. This method was free from interference by bilirubin, hemoglobin, ascorbate, and lactate dehydrogenase. In conclusion, serum total bile acids could be measured by the enzymatic cycling method with recombinant 3alpha-hydroxysteroid dehydrogenase as the tool enzyme.

Taurolithocholic acid-3 sulfate induces CD95 trafficking and apoptosis in a c-Jun N-terminal kinase-dependent manner

BACKGROUND & AIMS

Prevention of bile acid-induced apoptosis is of therapeutic interest and requires the understanding of underlying mechanisms.

METHODS

The effect of tauroursodeoxycholate (TUDC) on taurolithocholic acid-3 sulfate (TLCS)-induced apoptosis was studied in cultured rat hepatocytes.

RESULTS

TLCS induced activation of caspases 8, 9, and 3 and hepatocyte apoptosis. These effects were abolished by TUDC in a PI 3-kinase-/protein kinase B (PKB)-, p38(MAPK)-, and extracellular signal-regulated kinase-2 (Erk-2)-independent manner. These protein kinases were activated by both TLCS and TUDC, however, with different kinetics. TLCS, but not TUDC, led to a sustained activation of c-Jun N-terminal kinase (JNK) and CD95 trafficking to the plasma membrane; both TLCS effects were prevented by TUDC. Inhibition of JNK1 or protein kinase C prevented TLCS-induced CD95 membrane trafficking and blunted the apoptotic response. The apoptotic potency of other bile acids paralleled their ability to induce sustained JNK activation.

CONCLUSIONS

Protection by TUDC against TLCS-induced apoptosis starts upstream of caspase 8 activation and is independent of a PI 3-kinase-dependent survival pathway. JNK activation may be important for bile acid-induced apoptosis by triggering ligand-independent CD95 surface trafficking and activation of apoptosis.

Bilirubin and bile acids may modulate their own metabolism via regulating uridine diphosphate-glucuronosyltransferase expression in the rat

BACKGROUND AND AIMS

Uridine diphosphate (UDP)-glucuronosyltransferase (UGT) is a critical enzyme in the elimination of bilirubin and it also plays a role in the metabolism of bile acids. The aim of this study was to determine whether bilirubin and bile acids could modulate their own metabolism by regulating UGT levels in cultured rat hepatocytes.

METHODS AND RESULTS

Incubation of hepatocytes with bilirubin (48 micromol/L) for 24 h significantly increased the mRNA expression of UGT1A1 and UGT1A5, two UGT isoforms responsible for the conjugation of bilirubin. The induction of UGT1A1 and UGT1A5 by bilirubin was concentration and time dependent. Treatment with chenodeoxycholic acid, cholic acid, deoxycholic acid, hyodeoxycholic acid and lithocholic acid at a concentration of 100 micromol/L for 48 h significantly enhanced the mRNA expression of UGT2B1, a UGT isoform responsible for the glucuronidation of bile acids. The UGT2B3 mRNA level was also increased by hyodeoxycholic acid. The regulation of UGT2B1 mRNA by chenodeoxycholic acid and hyodeoxycholic acid was dose and time dependent.

CONCLUSION

Our results suggest that bilirubin and bile acids can induce UGT expression and as a result, these compounds may modulate their own metabolism. Such regulation could play a compensatory role in the pathological increased concentrations of these compounds in some hepatobiliary diseases.

Binding proteins for cyclic and linear oligopeptides in plasma membranes and the cytosol of rat hepatocytes

Using a cyclolinopeptide A analogue, the hydrophobic cyclic peptide c(-Ala-Lys-Pro-Phe-Phe-Ala-Lys-Pro-Phe-Phe-), termed CDP (cyclodecapeptide), as ligand in affinity chromatography, hepatocellular peptide binding proteins were isolated from the integral part of plasma membranes and the cytosol. The sequence of the isolated protein with MW of 50 kDa from the integral part of the plasma membrane fraction was identical to cytochrome P450 II C13 and cytochrome P450 II C22, whereas the sequence of the 54 kDa protein was identical to 3-hydroxyandrogen-UDP-glucuronosyltransferase. These proteins have also been described as binding proteins for bile acids. As shown in earlier studies, bile acids and CDP also compete for uptake into hepatocytes. In the cytosol, a further known bile acid binding protein, the glutathione-S-transferase (G-S-T) subunit Yb1, was isolated and sequenced as binding protein for CDP and also for a further cyclopeptide, the somatostatin analogue OO8, and a linear peptide with renin-inhibiting activity, EMD 55068. As shown in uptake studies using isolated basolateral plasma membrane vesicles, G-S-T was able to increase the uptake of EMD 51921, a linear peptide with renin-inhibiting potency, into the vesicles when the latter were preloaded with G-S-T. The binding of the substrate to the outside of the preloaded vesicles was not different than binding to unloaded vesicles. The maximal transport rate of the carrier-mediated/facilitated diffusion and the rate of permeation, however, were doubled in the presence of G-S-T, pointing to the involvement of intracellular binding proteins such as G-S-T in the unloading of the carrier protein and in the reduction of the free substrate concentration.

Direct enzymatic assay of urinary sulfated bile acids to replace serum bilirubin testing for selective screening of neonatal cholestasis

Direct enzymatic assay of urinary sulfated bile acids is a sensitive, rapid, minimally invasive, and convenient method of detecting cholestasis in young infants. It may replace measurement of serum direct bilirubin for selective screening for biliary atresia and neonatal hepatitis syndrome at 1 month of age.

Stimulation of bile acid 6 alpha-hydroxylation by rifampin

BACKGROUND

Rifampin was shown to relieve pruritus in cholestatic liver diseases. There has been much speculation about the origin of pruritus, but it has not yet been comprehensively explained. The role of bile acids in producing pruritus is obscure and still under debate. Since rifampin both inhibits the uptake of bile acids into the hepatocyte and strongly induces mixed-function oxidases in the liver, the beneficial effects of this drug might be a consequence of altered bile acid metabolism.

METHODS

We investigated the influence of rifampin on urinary bile acid excretion with special respect to glucuronide and sulphate conjugates in 14 healthy volunteers before and after administration of rifampin, 600 mg x 7 days, using each subject as his or her own control.

RESULTS

Bile acid glucuronide excretion increased from 0.55 to 1.19 mumol/24 h. This was in particular due to a significant increase of the urinary excretion of the 6 alpha-hydroxylated hyocholic and hyodeoxycholic acids, the relative amounts of which accounted for about two thirds of the urinary bile acid excretion. Excretion of sulphates, however, decreased from 1.40 to 0.86 mumol/24 h due to a significantly reduced excretion of lithocholic acid sulphate. No changes in the excretion rates of other primary and secondary bile acids and no changes in their conjugation patterns were observed.

CONCLUSIONS

The results provide evidence that rifampin induces 6 alpha-hydroxylation of bile acids. The products are subsequently glucuronidated at the 6 alpha-hydroxy group, thus stimulating renal excretion of potentially toxic bile acids.

Bile acids in the diagnosis, pathology, and therapy of hepatobiliary diseases

Bile acids are normally confined in the enterohepatic circulation in which they play an important role in bile formation, biliary lipid excretion, and intestinal lipid absorption. In hepatobiliary diseases, bile acids escape the confinement of the enterohepatic circulation, allowing the measurement of the serum total bile acid concentration as a diagnostic indicator. Accumulation of certain bile acids within the hepatocyte, amplified as a consequence of cholestatic hepatobiliary disease, probably enhances cytotoxicity and leads to secondary pathology. Ursodeoxycholate, a bile acid with atypical physiological effects, may be useful in the treatment of various long-term cholestatic hepatobiliary diseases. Presently, most of the information on the toxicity and therapeutic usefulness of bile acids are based on studies in humans and experimental animals. Further studies, both basic and clinical, are needed to determine the pathologic as well as the therapeutic effects of bile acids in domestic animals.

Bile salt sulphotransferase activity in the liver of cholestatic infants

A simple assay of bile salt sulphotransferase activity in human liver was developed. The system used glycolithocholate and PAPS as substrates. Km values for glycolithocholate and PAPs were 2.8 microM and 11.5 microM, respectively. Furthermore bile salt sulphation capacity in infants with cholestasis was investigated by measuring the activity of the bile salt sulphotransferase in the liver. No significant difference was found between the sulphotransferase activity in cholestatic infants and non-cholestatic adults. In addition the magnitude of the bile salt sulphotransferase activity in as neonatal liver did not differ from the enzymatic activity in adult liver. It is thus considered unlikely that low degree of sulphation of bile salts in infants is due to reduced capacity of this enzyme system.

Evidence for defective primary bile acid secretion in children with progressive familial intrahepatic cholestasis (Byler disease)

To clarify the relationship of progressive familial intrahepatic cholestasis (Byler disease) to bile acid metabolism, we analysed, by high performance liquid chromatography, the bile acid composition of serum and bile in seven children with Byler disease and in eight control children with other cholestatic diseases. In serum, total bile acid concentration was increased in patients with Byler disease (0.30 +/- 0.05 mmol/l) and in control patients (0.21 +/- 0.08 mmol/l). Cholate (C) and chenodeoxycholate (CDC) comprised the major proportion of total bile acids in patients with Byler disease as in control patients. Hyocholate (HC) was only detected in patients with Byler disease and lithocholate was only present in control children. In bile, total bile acid concentration was very low in patients with Byler disease (1.1 +/- 1.4 mmol/l) compared to control patients (88.9 +/- 83.2 mmol/l). C and CDC were the major bile acids in control patients, whereas C and HC comprised the major proportion of bile acids in patients with Byler disease. These results suggest the existence of a defect of primary bile acid secretion in Byler disease characterized by the presence of high concentration of bile acids in serum and absence or very low concentration of bile acids in bile.

Pan-sulfation of bile salts markedly increases hydrophilicity and essentially abolishes self- and hetero-association with lecithin

In chronic liver disease, partially and to a lesser extent completely (pan-)sulfated common bile salts are synthesized, yet little information is available concerning their physical-chemical characteristics. We studied solution properties of pan-sulfated common free, taurine and glycine-conjugated bile salts, and the interactions of taurodeoxycholate di-sulfate (TDC-S) with lecithin. By reverse-phase HPLC, pan-sulfated glycine and taurine-conjugated bile salts were very hydrophilic, with hydrophobic indices 1.7 to 2.5 units lower than their non-sulfated congeners. In contrast to non-sulfated species, pan-sulfated free and glycine-conjugated bile salts produced simple potentiometric titration curves without precipitation of bile salt below the pK'A of the carboxylic acids. By quasi-elastic light scattering, critical micellar concentrations of TDC-S fell from 28 mM in 0.15 M NaCl to 3 mM in 4.0 M NaCl, a value slightly higher than that of TDC. TDC-S formed very small micelles (hydrodynamic radii approx. 11A) that, in contrast to TDC, did not grow with increases in bile salt (7-66 mM) or NaCl (0.15-2.0 M) concentrations. TDC-S formed mixed micelles with lecithin in 0.15 M NaCl, but with a micellar zone drastically reduced compared with that of the non-sulfated congener. However, in 4 M NaCl, the micellar zone of TDC-S expanded and approached that of the non-sulfated parent compound. Therefore, under physiological conditions, pan-sulfation of common bile salts should largely eliminate their capacity to form mixed micelles with membrane lipids.

Use of the conjugate of disulphated ursodeoxycholic acid with p-aminobenzoic acid for the detection of intestinal bacteria

The disulphate ester of ursodeoxycholyl-p-aminobenzoic acid (PABA-UCDA) was synthesised and compared with PABA-UDCA for its use in detection of intestinal bacteria. This compound, PABA-UDCA disulphate, had characters in common with PABA-UDCA in that it was deconjugated by cholylglycine hydrolase to release free PABA and bacteria that split glycocholic acid deconjugated PABA-UDCA disulphate. Further, in rat experiments urinary excretions of PABA were measured for six hours after oral administration of 15 mg PABA-UDCA disulphate. Ten control rats excreted (mean (SE) 188.2 (13.6) micrograms of PABA; 10 rats with an intestinal stagnant loop excreted more (530.1 (30.1) micrograms; p < 0.001): whereas 10 rats in each of three groups pretreated by oral administration of various antibiotics excreted less (polymixin B+tinidazole, 4.9 (1.6) micrograms; kanamycin, 31.0 (4.7) micrograms; clindamycin 40.9 (5.5) micrograms; p < 0.001). By contrast with PABA-UDCA, PABA-UDCA disulphate was not actively absorbed from any part of the small intestine in everted gut sac experiments, and showed poor recovery from bile after its intraileal instillation in rats. This indicated that PABA-UDCA disulphate is a single pass type substance in the gut and its oral administration test reflects the sum of the activities of bacteria in the small intestine and colon. The disulphate was easily soluble in water and this allowed its application in an in vitro test involving PABA-UDCA disulphate incubation with intraperitoneal pus (PABA-UDCA disulphate incubation test) from patients with peritonitis. This test was carried out on six patients with peritonitis, and the severity of bacterial peritonitis was expressed quantitatively. From the results obtained PABA-UDCA disulphate was considered a good material to detect intestinal bacteria.

Biotransformation of orally administered ursodeoxycholic acid in man as observed in gallbladder bile, serum and urine

The aim of this study was to evaluate the biotransformation of orally administered ursodeoxycholic acid in man. The distribution of ursodeoxycholic acid and its metabolites in gallbladder bile, in serum and in urine with emphasis on separation of their unconjugated, amidated and sulfated species in particular, was investigated. Seven gallstone patients were given 750 mg of ursodeoxycholic acid daily for 2-3 weeks. Six gallstone patients who did not receive ursodeoxycholic acid served as controls. Ursodeoxycholic acid became the major bile acid in gallbladder bile contributing 43% to total bile acids. 2% of biliary ursodeoxycholic acids were in the unconjugated form, 87% in the amidated form and 11% in the sulfated form. Iso-ursodeoxycholic acid was found in bile in small amounts and was present only as the sulfated species and not as the amidated one. Other metabolites of ursodeoxycholic acid tentatively identified in bile were 1 beta, 12 beta, 6 alpha- and 21,22-hydroxylated derivatives of ursodeoxycholic acid. Lithocholic acid in bile tended to increase under ursodeoxycholic acid treatment and was positively correlated to ursodeoxycholic acid. The concentration of cholic acid in bile decreased significantly whereas the levels of deoxycholic acid and chenodeoxycholic acid did not change. Total bile acid concentration in serum and excretion of bile acids in urine increased from 5.4 +/- 1.1 to 18.4 +/- 9.5 mumol l-1 (mean +/- SD, P < 0.005) and from 5.6 +/- 1.3 to 13.1 +/- 7.9 mumol g-1 creatinine (mean +/- SD, P < 0.05) after ursodeoxycholic acid ingestion mainly due to spillover and excretion of ursodeoxycholic acid.(ABSTRACT TRUNCATED AT 250 WORDS)

Pathogenesis of lithocholate-induced intrahepatic cholestasis: role of glucuronidation and hydroxylation of lithocholate

It has been shown that lithocholic glucuronide is more cholestatic than lithocholic acid (LCA), as well as its taurine and glycine conjugates. Furthermore, LCA hydroxylation is thought to be a major detoxifying mechanism. Therefore, the role of LCA glucuronidation and hydroxylation was investigated during the development of LCA-induced cholestasis and recovery from it. Male rats received a bolus intravenous injection of [14C]LCA (12 mumol/100 g body weight) and bile samples were collected every 30 min for 5 h. Bile flow (BF) was reduced immediately after LCA injection, dropping to 40% of basal BF at 60 min. It then started to increase, reaching normal bile flow values at 3.5 h. Morphologically, canalicular lesions were dominant at 60 min and virtually absent at 2 h. At 60 min (maximal cholestasis), 30% of the LCA injected was secreted in bile, 20% was found in plasma while the other 50% was recovered in the liver and distributed mainly in plasma membranes, microsomes and cytosol. At the end of the experiment (normal BF), 20% of the LCA injected was still in the liver but was present mainly in the cytosol. In bile, within 30 min after injection, 46% of the LCA secreted was lithocholic glucuronide, 24% was conjugated with taurine and glycine, and 21% was in the form of hydroxylated bile acids. During the recovery period, lithocholic glucuronide secretion decreased to 18-25%. Taurine and glycine conjugate secretion increased to a maximum of 43% at 60 min, after which it was reduced to 21-28%. In contrast, hydroxylated metabolites were elevated during the recovery periods, reaching a maximum (45%) at 120 min and remaining constant thereafter. These results suggest that: (i) LCA binding to plasma membranes and microsomes appeared to correlate with the development of cholestasis; (ii) LCA glucuronidation may initiate and/or contribute to LCA-induced cholestasis; and (iii) hydroxylation predominates during recovery from cholestasis.

Cytotoxic effect and uptake mechanism by isolated rat hepatocytes of lithocholate and its glucuronide and sulfate

The hepatotoxicity and uptake mechanism of lithocholate and its glucuronide and sulfate were studied using isolated rat hepatocytes. Cytotoxicity was in the order of lithocholate greater than lithocholate-glucuronide greater than lithocholate-sulfate; their 50% cytotoxic concentrations on hepatocytes were 50, 150 and 700 microM, respectively. Thus, glucuronidation as well as sulfation acted to detoxify lithocholate, not relating to the previously reported higher cholestatic effect of lithocholate-glucuronide than lithocholate. Lithocholate uptake was linear up to 50 microM, whereas the uptakes of lithocholate-glucuronide and sulfate were saturable with an apparent Km and Vmax of 32 microM and 6.4 nmol/min per 10(6) cells for lithocholate-glucuronide and 26 microM and 11.8 nmol/min per 10(6) cells for lithocholate-sulfate. Na+ replacement by choline+ had no effect on the uptake of lithocholate and lithocholate-glucuronide, whereas it slightly inhibited lithocholate-sulfate uptake. Lithocholate-glucuronide uptake was inhibited by lithocholate-sulfate and sulfobromophthalein, whereas lithocholate-glucuronide and sulfobromophthalein had no effect on lithocholate-sulfate uptake. These data indicate that hepatic lithocholate uptake is mediated by simple diffusion, and that hepatic uptake of lithocholate-glucuronide and sulfate is mainly mediated by a Na(+)-independent carrier.

Cholestasis induced by lithocholate and its glucuronide: their biliary excretion and metabolism

We studied the effects of the infusion of lithocholate and lithocholate-3-sulfate and 3-glucuronide in rats (0.29 mumol/min per 100 g body weight for 40 min) on bile flow, together with their biliary excretion and metabolism. Lithocholate-glucuronide had a higher cholestatic effect than lithocholate, whereas lithocholate-sulfate had almost no effect on bile flow. Lithocholate was mainly converted to taurine or glucuronide conjugates in the bile, serum and liver and hydroxylation of the tauro-conjugate proceeded. Lithocholate-sulfate was almost completely excreted in the bile, mainly as tauro-conjugate. Lithocholate-glucuronide was excreted in bile almost without conjugation, while some taurine conjugation occurred in the serum and liver. These results suggest that the poor biotransformation of lithocholate-glucuronide is related to its higher cholestatic potency than lithocholate.

The ursodeoxycholate dose-dependent formation of ursodeoxycholate-glucuronide in the rat and the choleretic potencies

The reason for the discrepancy between bile flow and biliary bile acid excretion during ursodeoxycholate infusion in rats is unknown. We found that ursodeoxycholate-glucuronide is formed during ursodeoxycholate infusion at higher doses. Ursodeoxycholate infusion (1 to 3 mumol/min/100 gm body weight) for 90 min caused marked hypercholeresis, and the previously reported discrepancy between bile flow and biliary bile acid excretion was observed when bile acid concentrations were measured by regular enzymatic methods. However, the appearance of ursodeoxycholate-glucuronide was observed on thin-layer chromatography analysis and up to 30% of the ursodeoxycholate in bile was found to be glucuronidated when determined by the enzymatic method after beta-glucuronidase treatment. The choleretic activity of ursodeoxycholate-glucuronide (25.2 microliters/mumol) was about 3 times higher than that of ursodeoxycholate (8.9 microliters/mumol) when infused at 0.25 mumol/min/100 gm body weight and ursodeoxycholate-glucuronide also stimulated higher biliary bicarbonate excretion than ursodeoxycholate. These results indicate that the discrepancy between bile flow and biliary bile acid excretion caused by high-dose infusion of ursodeoxycholate into rats can be explained by glucuronide conjugation of ursodeoxycholate that cannot be detected by the regular enzymatic method. The glucuronidation of ursodeoxycholate might also be important in the ursodeoxycholate-induced increase in biliary bicarbonate excretion.

Cholesterol 7 alpha-hydroxylase activity and bile acid synthesis in hepatocytes of unweaned and weaned pigs in monolayer culture

Activity of cholesterol 7 alpha-hydroxylase (EC 1.14.13.17) in freshly isolated hepatocytes from unweaned piglets (2 to 3 weeks old) was 16-times lower as compared to hepatocytes from weaned piglets (7 to 8 weeks old). The monolayer culture activity of the enzyme remained low in unweaned piglet hepatocytes. In contrast, in cultured hepatocytes from weaned piglets, cholesterol 7 alpha-hydroxylase activity declined during the first day of culture, but was restored during the next 2 culture days, provided that fetal bovine serum (10%) was added to the culture medium. Addition of dexamethasone (50 nM) and insulin (135 nM) to the medium, further enhanced cholesterol 7 alpha-hydroxylase activity to values similar to those in freshly isolated hepatocytes and retarded the decline of enzyme activity after the 3rd culture day. Cultured hepatocytes from weaned and unweaned piglets synthesized similar types of bile acids from [14C]cholesterol, among which hyocholic acid (the most prominent), hyodeoxycholic acid, chenodeoxycholic acid, murocholic acid and lithocholic acid could be identified. 95% of radiolabelled bile acids synthesized was conjugated, mainly with glycine, but also with taurine, sulfate and glucuronic acid. The rate of mass production of bile acids by cultured hepatocytes of weaned piglets (as measured by gas-chromatography) parallelled cholesterol 7 alpha-hydroxylase activity, and was low in the absence of serum, but increased in medium containing fetal bovine serum, dexamethasone and insulin to a rate lying in the range of 75% of the in vivo bile acid production during the 3rd culture day. Bile acid production by unweaned piglet hepatocytes was 3-times lower under these conditions. It is concluded that hepatocytes from young weaned pigs cultured in medium containing 10% fetal bovine serum, offer a suitable in vitro model for the study of bile acid synthesis, in view of the high cholesterol 7 alpha-hydroxylase activities and bile acid production rates.

Comparison of biliary excretion and metabolism of lithocholic acid and its sulfate and glucuronide conjugates in rats

Biliary excretion and biotransformation of tracer doses of [14C]lithocholic acid and its sulfate and glucuronide intravenously injected into bile-drainaged rats were compared. Biliary excretion efficiency was in the order of unconjugate sulfate glucuronide and all conjugates were completely excreted into bile within 60 min after injection. Only tracer doses of radioactivity were found in the liver and urine. About 90% of radiolabeled bile acids in bile were conjugated with taurine immediately after injection of lithocholic acid, whereas lithocholic acid-glucuronide was only partly conjugated with taurine all the time (less than 6%) and excreted into bile mainly as native compound. In the first 10 min, 66% of lithocholic acid-sulfate was conjugated with taurine and it gradually proceeded up to 87%. Hydroxylation at C-6 and C-7 positions of lithocholic acid proceeded time-dependently up to 45%. No hydroxylation was observed with lithocholic acid-sulfate or glucuronide. Differences of biliary excretion rate of these conjugates may be one of the reasons for the delayed decrease of sulfated and glucuronidated bile acids in serum after bile drainage to patients with obstructive jaundice of during the recovery of acute hepatitis than non-esterified bile acids.

Taurine and glycine conjugation and sulfation of lithocholate in primary hepatocyte cultures

Rat primary liver cells were used to study taurine and glycine conjugation and sulfation of lithocholate. After addition of [14C]lithocholate to the tissue culture medium, synthesis and excretion of amidated and/or sulfated products were investigated for up to 24 h. After incubation for 1 h, more than 83% of the labeled bile salt was amidated but not sulfated and between 5 and 11% was sulfated, with more than 80% of the sulfated bile salts being also amidated. After 24 h, the proportion of sulfated lithocholate had increased to about 23% and more than 99% of the lithocholate sulfate was additionally conjugated with glycine or taurine. Both sulfates and non-sulfates were preferably amidated with taurine. We conclude that in primary rat hepatocytes, (1) lithocholate is rapidly and almost completely conjugated with glycine or taurine (amidated), whereas sulfation of lithocholate (and its amidates) proceeds slowly and even after 24 h represents only a small proportion of the total lithocholate metabolites, and (2) sulfated and unsulfated bile salts are both preferably amidated with taurine.

Enzymatic determination of serum 12 alpha-hydroxy bile acid concentration with 12 alpha-hydroxysteroid dehydrogenase

A simple colorimetric enzymatic assay for determination of serum 12 alpha-hydroxy bile acids was developed using 12 alpha-hydroxysteroid dehydrogenase (HSD). The enzymes were extracted from Bacillus sphaericus. The principle of the method is as follows: 12 alpha-hydroxy bile acids are converted to 12-oxo bile acids using 12 alpha-HSD with the conocomitant reduction of NAD to NADH, and then the hydrogen of the generated NADH is transferred by diaphorase to NTB to yield diformazan. Finally, the color of resultant diformazan was measured. The specificity and precision of this assay method were satisfactory. A linear relationship was noted between the amount of 12 alpha-hydroxy bile acids and the degree of absorbance in the range of 6.7 to 215 microM. The fasting values for serum 12 alpha-hydroxy bile acid in 10 patients with liver diseases ranged widely from 7.6 to 91.1 microM, and values obtained with this assay agreed closely with those obtained by gas-liquid chromatography (r = 0.94, p less than 0.001). The assay is convenient, rapid, and specific for the measurement of 12 alpha-hydroxy bile acid concentrations in the serum of patients with liver diseases.

Intestinal absorption of bile acid glucuronides in rats

While the intestinal absorption of taurine, glycine, and sulfate conjugates of bile acids has been studied extensively, nothing is known about the absorption of bile acid glucuronides. In the present study, the intestinal phase of the enterohepatic circulation of two bile acid glucuronides was examined. [3 beta-3H]cholic acid 3-O-beta-D-glucuronide or [3 beta-3H]lithocholic acid 3-O-beta-D-glucuronide was perfused through isolated segments of ileum or jejunum with intact blood supply in rats prepared with a biliary fistula. [14C]Taurocholic acid was perfused simultaneously with each glucuronide to compare glucuronide absorption with that of an actively transported bile acid. Intestinal absorption was determined by measuring the rate of secretion of labeled bile acid in bile. The absorption of [3H]cholic acid glucuronide by the ileum and jejunum was one fortieth and one eighth, respectively, that of [14C]taurocholic acid. Comparison of the two glucuronides show that [3H]lithocholic acid glucuronide absorption was 18 and 10 times greater than [3H]cholic acid glucuronide absorption from the jejunum and ileum, respectively. Collectively, the above observations suggest that glucuronidation of bile acids markedly reduces absorption from the small intestine.

Inhibition of Na+/H+ exchange in the rat is associated with decreased ursodeoxycholate hypercholeresis, decreased secretion of unconjugated urodeoxycholate, and increased ursodeoxycholate glucuronidation

In the perfused rat liver, ursodeoxycholate in high dose produces an HCO3- -rich hypercholeresis which we have shown previously to be inhibited by replacement of perfusate Na+ with Li+ or by addition of amiloride (or amiloride analogues). In the present studies, we have determined whether such inhibition is associated with altered ursodeoxycholate biotransformation. Under control conditions, ursodeoxycholate infusion produced a 3.7-fold increase in bile flow and a 9.2-fold increase in biliary HCO3- output. By thin-layer chromatography, ursodeoxycholate radioactivity in bile was present in unconjugated form (15%) or as glycine or taurine amidates. Glucuronide conjugates of ursodeoxycholate accounted for less than 1% of biliary bile acids. Li+/Na+ substitution decreased ursodeoxycholate-stimulated bile flow and HCO3- secretion by greater than 90%, but decreased recovery of ursodeoxycholate and metabolites by only 25%. Amiloride or amiloride analogues decreased ursodeoxycholate-stimulated choleresis and HCO3- output by 38%-76%, yet did not cause decreased recovery of ursodeoxycholate and metabolites. Inhibition of the hypercholeresis was associated with a decrease in unconjugated ursodeoxycholate to less than 2% of total biliary bile acids, a striking increase in ursodeoxycholate glucuronides, and a reciprocal decrease in glycine and taurine amidates. With Li+/Na+ substitution, the predominant metabolites were a mixture of the 24-ester and the 3-aketal (ethereal) glucuronide (29%), and amidation with glycine appeared to be selectively inhibited; with amiloride or its analogues, only the 3-ethereal glucuronide was formed (20%-60% of biliary bile acids), and both taurine and glycine amidation were inhibited. Thus, maneuvers that decrease Na+/H+ exchange inhibit ursodeoxycholate hypercholeresis and cause replacement of unconjugated ursodeoxycholate in bile by its glucuronide. The secretion of unconjugated ursodeoxycholate, a lipophilic bile acid, appears to be necessary for hypercholeresis induced by high-dose ursodeoxycholate infusion.

Separate transport systems for biliary secretion of sulfated and unsulfated bile acids in the rat

Biliary secretion of 3 alpha-sulfated bile acids has been studied in Wistar rats with an autosomal recessive defect in the hepatic transport of bilirubin. Liver function, established by measurement of various enzymes in plasma, by enzyme histochemical methods, and by electron microscopy, appeared to be normal in these rats. Serum levels of unconjugated, monoglucuronidated, and diglucuronidated bilirubin were 0.62, 1.62, and 6.16 mumol/liter, respectively, compared with 0.17, 0.08, and 0.02 mumol/liter in control rats. Biliary bilirubin secretion was strongly reduced in the mutant animals: 0.21 +/- 0.03 vs. 0.39 +/- 0.03 nmol/min per 100 g body wt in control rats. Despite normal biliary bile acid output, bile flow was markedly impaired in the mutant animals, due to a 53% reduction of the bile acid-independent fraction of bile flow. The transport maximum for biliary secretion of dibromosulphthalein (DBSP) was also drastically reduced (-53%). Biliary secretion of intravenously administered trace amounts of the 3 alpha-sulfate esters of 14C-labeled taurocholic acid (-14%), taurochenodeoxycholic acid (-39%), taurolithocholic acid (-73%), and glycolithocholic acid (-91%) was impaired in the jaundiced rats compared with controls, in contrast to the biliary secretion of the unsulfated parent compounds. Hepatic uptake of sulfated glycolithocholic acid was not affected in the jaundiced animals. Preadministration of DBSP (15 mumol/100 g body wt) to normal Wistar rats significantly impaired the biliary secretion of sulfated glycolithocholic acid, but did not affect taurocholic acid secretion. We conclude that separate transport systems in the rat liver exist for biliary secretion of sulfated and unsulfated bile acids; the sulfates probably share secretory pathways with the organic anions bilirubin and DBSP. The described genetic defect in hepatic transport function is associated with a reduced capacity to secrete sulfated bile acids into bile; this becomes more pronounced with a decreasing number of hydroxyl groups on the sulfated bile acid's molecule.

Effective glucuronidation of 6 alpha-hydroxylated bile acids by human hepatic and renal microsomes

The glucuronidation of bile acids is an established metabolic pathway in different human organs. The hepatic and renal UDP-glucuronyltransferase activities vary according to the bile acids concerned. Thus, hyodeoxycholic acid is clearly differentiated from other bile acids by its high rate of glucuronidation and elevated urinary excretion in man. To determine whether such in vivo observations are related to variations in bile acid structure, human hepatic and renal microsomes were prepared and time courses of bile acid glucuronidation measured with the bile acids possessing hydroxyl groups in different positions. Eleven [24-14C]bile acids were chosen or synthesized in respect of their specific combination of hydroxyl and oxo groups at the 3, 6, 7 and 12 positions and of their alpha or beta hydroxyl configurations. The results clearly demonstrate that bile acids with an hydroxyl group in the 6 alpha position underwent a high degree of glucuronidation. Apparent kinetic Km and Vmax values for UDP-glucuronyltransferase activities ranged over 78-66 microM and 1.8-3.3 nmol.min-1.mg-1 protein in the liver and over 190-19 microM and 0.5-9.2 nmol.min-1.mg-1 protein in the kidney. All the other bile acids tested, each of which possessed a 3 alpha-hydroxyl group and whose second or third hydroxyl was bound at the 6 beta, 7 or 12 positions, were glucuronidated to a degree far below that of the 6 alpha-hydroxylated bile acids. We conclude that an active and highly specific UDP-glucuronyltransferase activity for 6 alpha-hydroxylated bile acids exists in human liver and kidneys. Moreover, this activity results in the linkage of glucuronic acid to the 6 alpha-hydroxyl group and not to the usual 3 alpha-hydroxyl group of bile acids.

Advances in the application of biochemical tests to diseases of the liver and biliary tract: their role in diagnosis, prognosis, and the elucidation of pathogenetic mechanisms

Despite the biochemical complexity of the liver, few laboratory tests provide discriminatory diagnostic information in patients with hepatobiliary disease. Recent efforts have concentrated upon tests which assess the function of the liver, the severity of the disease state, and underlying pathological processes. Bile Acids: The emergence of facile technology and widespread application has brought the realization that these assays are not as sensitive in detecting liver disease as previously believed, although the cholate/chenate ratio may be useful in distinguishing cholestasis from chronic liver disease. The presence of unusual bile acids in serum or urine may be helpful in some cases. Drug Metabolism: A number of tests provide good evidence about liver function, hepatic blood flow and portal shunting, but the aminopyrine breath tests is the most useful, giving prognostic information in acetaminophen overdose and alcoholic liver disease. The antipyrine half-life identifies surgical cases at risk from poor hepatic function. Proteins and Immunochemical Tests: Interest has developed in plasma proteins such as prealbumin and retinol-binding protein to monitor hepatic protein synthetic function. Secretory IgA is more elevated in biliary tract disease, unlike the native protein which is increased principally in cirrhosis. Type III procollagen can be measured in serum, and correlates with the activity of collagen synthesis and the degree of fibrosis in biopsy samples. Reye's Syndrome: Biochemical tests play an essential role in diagnosis of this recently discovered disease. These will be presented and discussed.

Glucuronidated and sulfated bile acids in serum of patients with acute hepatitis

The concentrations of glucuronidated and sulfated bile acids in the serum of 15 patients with acute hepatitis were determined by mass fragmentography. Total serum bile acid levels were 13.79-444.10 mumol/liter, and the percentages of glucuronidated and sulfated bile acids were in the wide ranges of 1.7-33% and 2.4-49%, respectively. In four of the five patients for whom serum bile acids were analyzed serially from the acute to the recovery stages of acute hepatitis, the decrease of the glucuronidated and sulfated bile acids was slower than that of nonglucuronidated, nonsulfated bile acids. Thus, the relative proportion of the glucuronides and sulfates in total bile acids apparently increased during the recovery phase. The mechanism for the relative predominance of bile acid esters in serum during recovery is unknown but might reflect an improved excretion of the nonesterified bile acids into bile after the rapid recovery of intrahepatic cholestasis.

Determination of 3 beta-hydroxy-5-cholenoic acid in serum of hepatobiliary diseases--its glucuronidated and sulfated conjugates

3 beta-Hydroxy-5-cholenoic acid in the serum of control subjects and 62 patients with various hepatobiliary diseases was quantitated by mass fragmentography after separation into nonglucuronidated-nonsulfated, glucuronidated, and sulfated fractions. Deuterium-labeled deoxycholic acid and its glucuronide and sulfate were used as internal standards. Mean concentrations of total 3 beta-hydroxy-5-cholenoic acid in serum (mumole/liter) were as follows: Control subjects (14), 0.184; obstructive jaundice (15), 6.783; liver cirrhosis, compensated (12), 0.433, and decompensated (12), 1.636; chronic hepatitis (12), 0.241; and acute hepatitis (11), 2.364. Most of the 3 beta-hydroxy-5-cholenoic acid was glucuronidated or sulfated. Only in patients with obstructive jaundice did glucuronidation (60 +/- 14%) exceed sulfation (31 +/- 14%), sulfation exceeding glucuronidation in the others. The UDP-glucuronyltransferase might have different substrate specificities for 3 beta-hydroxy-5-cholenoic acid and other common bile acids, especially in the cholestatic state.

Serum concentrations of glucuronidated and sulfated bile acids in children with cholestasis

Serum concentrations of nonglucuronidated-nonsulfated, glucuronidated, and sulfated bile acids in 9 control children and 16 children with cholestasis were quantitated by mass fragmentography. Total bile acid levels in control children were 19.55 +/- 2.78 mumol/liter (mean +/- SEM), and glucuronidated and sulfated bile acids comprised 2.6 +/- 0.5 and 17 +/- 3.1%, respectively. In 9 patients with congenital biliary atrasia, total bile acid levels were 167.34 +/- 11.18 mumole/liter of which 2.1 +/- 0.3% were glucuronidated and 15 +/- 1.4% were sulfated. Lithocholic and 3 beta-hydroxy-5-cholenoic acids, which have hepatotoxic effects, were presented in only small amounts in cholestatic children, and they were almost all glucuronidated or sulfated. The percentages of glucuronidated bile acids in control and cholestatic children were lower than in healthy and cholestatic adults, which may be explained by the lower activity of UDP-glucuronyltransferase in neonatal liver.

Biliary and urinary excretion of sulfated, glucuronidated and tetrahydroxylated bile acids in cirrhotic patients

In patients with hepatobiliary diseases, considerable amounts of sulfated and glucuronidated bile acids are excreted in urine. Information on the biliary excretion of these compounds is lacking. We used an intestinal perfusion method to determine the biliary excretion of sulfated and glucuronidated bile acids in eight patients with alcoholic cirrhosis and moderately severe cholestasis and compared results with urinary excretion rates. In bile, the patients excreted 508.7 mumoles per hr (mean) nonsulfated, nonglucuronidated bile acids, 8.1 mumoles per hr sulfated bile acids and 4.0 mumoles per hr glucuronidated bile acids. In urine, these patients excreted 0.27 mumoles per hr nonsulfated, nonglucuronidated bile acids, 0.88 mumoles per hr sulfated bile acids and 0.02 mumoles per hr glucuronidated bile acids. Sulfates and glucuronides of mono-, di- and trihydroxy bile acids were detected in urine and bile. In urine, tetrahydroxy bile acids were only excreted as nonsulfated and nonglucuronidated forms. The bile:urine excretion ratio of sulfated bile acids was 9:1 and of glucuronidated bile acids was 226:1. In alcoholic cirrhosis with cholestasis, biliary excretion is an important excretory route of sulfated and glucuronidated bile acids.

Unusual serum bile acid pattern in children with the syndrome of hepatic ductular hypoplasia

Fasting bile acids in serum of eight children with the syndrome of hepatic ductular hypoplasia were analyzed by gas chromatography. The children did not receive any kind of treatment during the month before the analysis. Serum concentrations of total bile acids ranged from 110.8-303.7 mumol/1. The predominant bile acids were chenodeoxycholic and cholic acids accounting for 62.8-86.5% of the total. The ratio of cholic acid to chenodeoxycholic acid ranged between 0.43 and 1.11. Monohydroxylated bile acids were found in increased amounts in all patients (5.1-23.9%), 3 beta-hydroxy-5-cholenoic acid being the major monohydroxylated bile acid (3.1-17.1%). Other unusual bile acids such as ursodeoxycholic acid and 12-oxo-3 alpha, 7 alpha-dihydroxy-5 beta-cholanoic acid (7.3-14.9%) were also detected. Neither 3 beta-hydroxy-5-cholenoic nor lithocholic acid levels were statistically correlated to cholic or chenodeoxycholic acids. However, a statistically significant correlation between total bile acid levels and 12-oxo-3 alpha, 7 alpha-dihydroxy-5 beta-cholanoic acid levels was found. These findings are interesting as far as the origin of the unusual bile acids found in this cholestatic syndrome is concerned. The large amounts of 3 beta-hydroxy-5-cholenoic acid measured in children with the syndrome of hepatic ductular hypoplasia could indicate the existence of an alternative fetal pathway of bile acid synthesis.

The diagnostic value of fasting individual serum bile acids in anicteric alcoholic liver disease: relation to liver morphology

The aim of the present study was to evaluate the diagnostic value of measuring individual serum bile acids in patients with suspected alcoholic liver disease. A highly accurate and specific mass-fragmentographic technique with high sensitivity was used. Anicteric patients with fatty liver (n = 10) and liver cirrhosis (n = 9) were compared with healthy controls (n = 27). The measurement of serum bile acids did not discriminate patients with fatty liver from controls. In general, an increased serum level of cholic acid indicated more serious liver disease. Determination of chenodeoxycholic acid and deoxycholic acid did not add any further diagnostic information.

Profiles of bile acids and their glucuronide and sulphate conjugates in the serum, urine and bile from patients undergoing bile drainage

Bile acid profiles in serum, urine, and bile from patients undergoing bile drainage and the changes of serum bile acids after bile drainage were studied. Bile acids were separated into non-glucuronidate-non-sulphate, glucuronidated, and sulphated fractions and were measured by mass fragmentography using conjugates of deuterium labelled bile acids as internal standards. Glucuronidated and sulphated bile acids contribute 14-32% and 16-44% of serum bile acids, 4-11% and 61-82% of urine bile acids and 0.2-1% and 0.3-2% of biliary bile acids respectively. After bile drainage the concentration of serum non-glucuronidated-non-sulphated bile acids decreased more rapidly than glucuronidated and sulphated bile acids. There was little biliary excretion of the glucuronidated and sulphated bile acids. Such conjugation appears to have a role in facilitating bile acid excretion by the urinary route.

Effects of phenobarbital on biliary lipid metabolism in children with chronic intrahepatic cholestasis

The effects of phenobarbital (5.4-7.5 mg/kg body weight) for 14 days were studied in four children with severe intrahepatic cholestasis (group I) and in four with a syndromatic type of paucity of intralobular bile ducts (group II). Phenobarbital administration resulted in a moderate improvement of pruritus in all patients. There was a significant decrease of bilirubin in serum (group I: from 4.8 to 2.7 mg/dl; group II: from 6.1 to 2.1 mg/dl); total bile acids (group I: from 416 to 337 mumol/l; group II: from 156 to 123 mumol/l) and cholesterol (group I: from 248 to 207 mg/dl; group II: from 351 to 292 mg/dl). Alkaline phosphatase activity increased from 929 to 1126 U/l in group I and from 1751 to 2360 U/l in group II. SGOT and SGPT activities remained unchanged in both groups. In group I total biliary lipid concentration and bile acid output increased from 0.09 to 0.17 g/dl and from 3.9 to 7.2 mumol/kg per 30 min, respectively. Molar percentages of cholesterol, phospholipids and bile acids in bile remained unchanged. In group II total lipid concentrations and bile acid output increased from 1.62 to 2.0 g/dl and from 27.8 to 39.1 mumol/kg per 30 min, respectively. The molar percentage of cholesterol decreased from 5.6 to 3.5 mol%. The present results indicate that short term administration of phenobarbital has only minimal effects on biliary lipid metabolism in children with chronic intrahepatic cholestasis.

Lithocholate glucuronide is a cholestatic agent

Lithocholic acid and its taurine, glycine, and sulfate derivatives are potent cholestatic agents. Lithocholate glucuronide is present in the plasma and urine of patients with cholestatic syndromes, but little is known of its metabolism, excretion, and cholestatic potential. [3 beta-3H]lithocholate 3-O-beta-D-glucuronide was synthesized, and chemical and radiochemical purity were established. The aqueous solubility of lithocholate glucuronide was determined and found to be greater than that of lithocholic acid or several of its derivatives. In the range of concentrations examined, calcium ions precipitated lithocholate glucuronide stoichiometrically. The material was administered to rats prepared with an external biliary fistula. When 17-25 micrograms quantities were administered, 89.1 +/- 4.5% (mean +/- SEM) of the radiolabel was secreted in bile within the first 20 h after administration, the major fraction being secreted in less than 20 min. Four-fifths of the radiolabeled material in bile was the administered unaltered parent compound, while a minor fraction consisted of a more polar derivative(s). We showed that increasing biliary concentrations of more polar derivatives were observed with milligram doses of [3H]lithocholate glucuronide, and with time after the administration of these loading doses. Milligram doses of [3H]lithocholate glucuronide resulted in partial or complete cholestasis. When induced cholestasis was partial, secretion in bile remained the primary excretory route (82.5-105.6% recovery in bile), while, when complete cholestasis was induced, wide tissue distribution of radiolabel was observed. Cholestasis developed rapidly during infusion of [3H]lithocholate glucuronide. Bile flow was diminished within 10-20 min of the start of an infusion of 0.05 mumol, 100 g-1 body weight, minute-1, administered concomitantly with an equimolar infusion of taurocholate. The results establish that lithocholate glucuronide exerts cholestatic effects comparable to those exerted by unconjugated lithocholic acid.

Unconjugated, glycine-conjugated, taurine-conjugated bile acid nonsulfates and sulfates in urine of young infants with cholestasis

A direct assay system for conjugated bile acids using an enzymatic procedure and high-performance liquid chromatography was used for the analysis of urinary bile acid profiles in young infants with intrahepatic cholestasis (idiopathic neonatal hepatitis syndrome) or extra-hepatic biliary atresia. The major urinary bile acids were cholate and chenodeoxycholate conjugates, but a small amount of deoxycholate and 3 beta-hydroxy-5-cholenate conjugates were detected. Although there was no significant difference in total bile acid excretion between patients with intrahepatic cholestasis and extrahepatic biliary atresia, mean ratios of cholate to chenodeoxycholate and sulfated to total urinary bile acids were different between the two groups examined (5.63 +/- 2.83 vs. 2.50 +/- 1.25, p less than 0.05, 15.8 +/- 9.9 vs. 34.5 +/- 9.9%, p less than 0.005). The proportion of taurine-conjugated chenodeoxycholate in the sulfate fraction to the total bile acid was lower in intrahepatic cholestasis, compared with that in biliary atresia (7.7 +/- 7.5 vs 22.7% +/- 7.8%, p less than 0.005). The greater ratio of cholate to chenodeoxycholate and the reduced excretion of sulfated urinary bile acids in intrahepatic cholestasis was due to decreased taurine-conjugated chenodeoxycholate sulfate excretion.

Urinary concentrations of bile acid glucuronides and sulfates in hepatobiliary diseases

Urinary bile acids in normal subjects and patients with obstructive jaundice and liver cirrhosis were quantitated by mass fragmentography after separation into nonglucuronidated-nonsulfated, glucuronidated and sulfated fractions. Mean values of total bile acids in urine were as follows: Control subjects (n = 7), 1.90 +/- 0.67; obstructive jaundice (n = 9), 77.90 +/- 40.39; liver cirrhosis, compensated (n = 6), 15.14 +/- 8.97, and decompensated (n = 6), 11.84 +/- 9.32 (mean +/- SD, mg/day). The percentages of each conjugate was 19-29% in the non-glucuronidated-nonsulfated fraction, 6-14% in the glucuronidated fraction and 60-74% in the sulfated fraction. Bile acids in urine and serum correlated well in each fraction (r = 0.82-0.84, p less than 0.001). The clearance of the three conjugates was the highest in the sulfates, and the clearance of glucuronides was higher than that of non-esterified bile acids. The glucuronidation and sulfation of bile acids play an important role in the detoxication of bile acids by excreting them into urine, especially in patients with elevated serum bile acids.