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Decreased concentrations of deoxycholic acid in serum of uraemic patients with diarrhoea.

The fasting peripheral serum concentrations of cholic acid, chenodeoxycholic acid, deoxycholic acid and ursodeoxycholic acid were determined in a total of 32 patients with uraemia. Eighteen of the patients suffered from diarrhoea. A highly accurate and specific mass-fragmentographic technique with high sensitivity was used to measure the concentrations of the individual bile acids. The total amount of bile acids was normal in the two groups of patients. Patients with diarrhoea had 50% lower concentrations of deoxycholic acid than a corresponding group of healthy subjects. It is suggested that the low level of deoxycholic acid may contribute to diarrhoea in these patients.

Adult↗

Bile acid structure-activity relationship: evaluation of bile acid lipophilicity using 1-octanol/water partition coefficient and reverse phase HPLC.

Two independent methods have been developed and compared to determine the lipophilicity of a representative series of naturally occurring bile acids (BA) in relation to their structure. The BA included cholic acid (CA), chenodeoxycholic acid (CDCA), ursodeoxycholic acid (UDCA), deoxycholic acid (DCA), hyodeoxycholic acid (HDCA), ursocholic acid (UCA), hyocholic acid (HCA), as well as their glycine and taurine amidates. Lipophilicity was determined using a 1-octanol/water shake-flask procedure and the experiments were performed at different pH and ionic strengths and at initial BA concentrations below their critical micellar concentrations (CMC) and the water solubility of the protonated form. The experimental data show that both the protonated (HA) and ionized (A-) forms of BA can distribute in 1-octanol, and consequently a partition coefficient for HA (logP' HA) and for A- (logP' A-) must be defined. An equation to predict a weighted apparent distribution coefficient (D) value as a function of pH and pKa has been developed and fits well with the experimental data. Differences between logP for protonated and ionized species for unconjugated BA were in the order of 1 log unit, which increased to 2 for glycine-amidate BA. The partition coefficient of the A- form increased with Na+ concentration and total ionic strength, suggesting an ion-pair mechanism for its partition into 1-octanol. Lipophilicity was also assessed using reverse phase chromatography (C-18-HPLC), and a capacity factor (K') for ionized species was determined. Despite a broad correlation with the logP data, some BA behaved differently. The logP values showed that the order of lipophilicity was DCA greater than CDCA greater than UDCA greater than HDCA greater than HCA greater than CA greater than UCA for both the protonated and ionized unconjugated and glycine-amidate BA, while the K' data showed an inversion for some BA, i.e., DCA greater than CDCA greater than CA greater than HCA greater than UDCA greater than HDCA greater than UCA. The logP data fitted well with other indirect measurements of BA monomeric lipophilicity such as albumin binding or accessible total hydrophobic surface area data calculated by energy minimization and molecular computer graphics. Differences between unconjugated and amidated BA are consistent with the presence of an amide bond and a lower pKa when pH dependence was studied. Capacity factors, on the other hand, were related to properties of BA micelles such as cholesterol-solubilizing capacity and membrane disruption, reflecting the BA detergency.(ABSTRACT TRUNCATED AT 400 WORDS)

Bile Acids and Salts↗

Hypocalcemia and steatorrhea--clues to etiology.

Two boys with idiopathic hypoparathyroidism had extensive studies of gastrointestinal function during hypocalcemia accompanied by steatorrhea. No evidence of generalized gastrointestinal moniliasis or abnormal mucosal structure or function was observed. Studies of pancreatic function and bile salt metabolism during hypocalcemia demonstrated deficient meal-stimulated intraluminal pancreatic enzyme concentrations in both subjects and reduced bile salt concentrations in one subject. However, following stimulation with exogenous octapeptide of cholecystokinin, intraluminal pancreatic enzyme and bile salt concentrations were normal in both. Cholic acid pool sizes were markedly increased in both subjects during hypocalcemia (9 and 12 times larger than during normocalcemia) and cholic acid turnover was reduced during hypocalcemia in one subject. Our findings suggest that during hypocalcemia, insufficient endogenous cholecystokinin is released by the duodenal mucosa during a meal stimulus to stimulate normal gallbladder contraction and pancreatic enzyme secretion.

Adolescent↗

Influence of dehydrocholic acid on the secretion of bile acids and biliary lipids in rats.

This study investigated the influence of dehydrocholic acid (DHCA) infusion on the secretion of endogenous bile acids, and biliary lipids in rats in an attempt to explain the reduction of biliary lipid secretion associated with DHCA infusion. DHCA increased bile flow and the bile acids produced during the infusion were composed of three hydroxy-oxo metabolites (83-93%), and cholic acid (6-14%). Very little DHCA was secreted unchanged (less than 2%). The secretions of all the endogenous biliary bile acids were diminished within 30-60 min of infusion. DHCA furthermore reduced the secretion of exogenous cholic acid when co-infused with DHCA. Phospholipid secretion declined to an undetectable amount and cholesterol declined to 10% of the base value by the end of the infusion. The reduction of biliary lipid secretion during DHCA infusion was attributed to the diminished secretion of endogenous bile acids. These data show that DHCA infusion induces choleresis associated with reduced secretion of endogenous and/or exogenous biliary components.

Animals↗

Metabolism of beta-muricholic acid in the hamster and prairie dog.

The metabolism of beta-muricholic acid was investigated in the prairie dog and the hamster. Intravenous infusion into bile fistula hamsters showed that beta-muricholic acid was extracted by the liver and secreted into the bile (> 85% in 1 h). Hepatic extraction of this compound and cholic acid in the prairie dog was not as rapid as in the hamster. In the bile of the prairie dog, most (93%) of the administered beta-muricholic acid was present as the taurine conjugate. In the hamster, 28% of infused beta-muricholic acid was secreted in unconjugated form, 43% as the taurine conjugate, and 22% as the glycine conjugate. In both species, the administered compound underwent little biotransformation. After intraduodenal injection of [6 alpha-3H]-labeled beta-muricholic acid into bile fistula hamsters, the bile acid was rapidly secreted into the bile; more than 80% of the administered radioactivity was recovered in 3 h. In the prairie dog, biliary recovery after intraduodenal administration of either beta-muricholic acid (43% in 3 h) or cholic acid (22% in 3 h) was slower than in the hamster. After intragastric administration, more than 80% of beta-muricholic acid was recovered unchanged in feces of both animal species.

Animals↗

Stereochemistry of the side chain oxidation of 5 beta-cholestane-3 alpha,7 alpha,12 alpha-triol in man.

Previous in vitro studies have shown that the oxidation of the side chain of bile acid precursors can start with either microsomal or mitochondrial enzyme systems. The microsomal system oxidizes the terminal methyl group (C-26) of the side chain that originates from C-2 of mevalonic acid, and the mitochondrial system oxidizes the terminal methyl group (C-27) derived from C'-3 of mevalonic acid. We administered [2-14C]-mevalonic acid to a patient with a complete bile fistula and isolated from the bile 3 alpha,7 alpha,12 alpha-trihydroxy[1,7,15,22,26-14C]5 beta-cholestanoic acid, a precursor in the synthesis of cholic acid which has undergone partial oxidation of the side chain. This compound was chemically decarboxylated and the liberated CO2 was trapped and counted. The recovery from control experiments using [24-14C]cholic acid was 82.6 +/- 2.3% (+/- 1 S.D.). However, following decarboxylation of 3 alpha,7 alpha,12 alpha-trihydroxy[14C5]5 beta-cholestanoic acid, only 7.5 +/- 0.58% (+/- S.D.) of the C-26 radioactivity was recovered. This study suggests that the major pathway of side chain oxidation of 5 beta-cholestane-3 alpha,7 alpha,12 alpha-triol starts with hydroxylation of the methyl group derived from C'-3 of mevalonate (C-27) by mitochondrial enzymes. It is also concluded that the 3 alpha,7 alpha,12 alpha-trihydroxy-5 beta-cholestan-27-oic acid formed in man has the R configuration at carbon 25.

Bile↗

Early nutrition with a high-cholesterol diet alters normal age-related changes in intestinal active transport.

This study was undertaken in the young and growing rabbit to establish the effect of feeding a high-cholesterol (2%) diet on the intestinal in vitro uptake of glucose, galactose, leucine, and cholic acid. Three groups of animals were fed standard Purina chow for 14, 28, and 42 days. A fourth group was fed chow for 14 days followed by high-cholesterol diet for 10 days followed by chow for 4 days. A fifth group was fed chow for 14 days followed by the high-cholesterol diet for 10 days followed by chow for 18 days. Short-term feeding with a high-cholesterol diet reversed the normal developmental decline in the jejunal uptake of some nutrients (e.g., glucose), enhanced the age-related uptake of other nutrients (e.g., galactose and leucine), but had no effect on others (e.g., jejunal uptake of cholic acid). Two weeks after stopping the high-cholesterol diet, there was enhanced jejunal uptake of all nutrients. Colonic uptake of glucose, galactose, and leucine was unresponsive to the effects of early development or of a high-cholesterol diet, whereas the colonic uptake of cholic acid did increase. This altered uptake is not explained by nonspecific mechanisms such as changes in body weight gain, intestinal mass, or effective resistance of the intestinal unstirred water layer. In summary, early feeding of rabbits for a short interval with a high-cholesterol diet is associated with transport changes that may persist, progress, or appear for the first time when the animals are switched from the high-cholesterol diet back to chow. Thus, early feeding with a high-cholesterol diet alters the normal development of intestinal transport function.

Aging↗

Bile acid and very low density lipoprotein production by cultured hepatocytes from hypo- or hyperresponsive rabbits fed cholesterol.

Two groups of rabbits, either hyperresponsive or hyporesponsive to dietary cholesterol, were selected after ten weeks of cholesterol feeding (0.2 g cholesterol/kg body weight per day). Bile acids and very low density lipoprotein (VLDL) production were determined in primary hepatocyte cultures from control, hyper- and hyporesponsive rabbits. Free cholesterol and cholesteryl ester contents in hepatocytes of the hyperresponsive rabbits was significantly increased. In contrast, lipid composition in hepatocytes of the hyporesponders was similar to that of control cells. Cholic acid was the predominant bile acid in the culture medium of hepatocytes together with small amounts of chenodeoxycholic and deoxycholic acids. The rate of cholic acid production by hepatocytes in the hyporesponsive group was two times higher than that in the hyperresponsive group. Bile acid production by control hepatocytes was slightly higher than in the hyperresponsive group. In contrast, secretion of VLDL cholesteryl ester was significantly increased by hepatocytes of the hyperresponsive rabbits. Similar differences in bile acid production were found between hypo- and hyperresponsive rabbits selected after five days of cholesterol feeding and subsequent maintenance on a low cholesterol diet for a period of one month. The results suggest that the increased rate of bile acid production could contribute to the apparent resistance of hyporesponders to the atherogenic diet.

Animals↗

Correction of maternal serum bile acid profile during ursodeoxycholic acid therapy in cholestasis of pregnancy.

BACKGROUND/AIMS: Intrahepatic cholestasis of pregnancy is characterized by pruritus and increased levels of serum bile acids, and is often associated with premature delivery, fetal distress, and perinatal mortality. The aims of the present study were: (i) to better define the serum bile acid profile in intrahepatic cholestasis of pregnancy and its potential usefulness for differential diagnosis; (ii) to investigate the effect of ursodeoxycholic acid treatment on the bile acid pool; and (iii) to investigate possible adverse effects of therapy. METHODS: Fifteen patients with intrahepatic cholestasis of pregnancy were enrolled in this study. Ursodeoxycholic acid (14 mg/kg body weight per day) was administered for 13 +/- 5 days. Twenty normal pregnant women served as controls. Serum bile acid profile was analyzed by high-performance liquid chromatography. RESULTS: Patients with cholestasis of pregnancy showed significant alterations in the proportion of primary bile acids, with an increase in cholic acid (64.0 +/- 3.0% vs. 32.2 +/- 1.8%, p < 0.01), and a decrease in chenodeoxycholic acid (20.8 +/- 1.4% vs. 31.9 +/- 1.3%, p < 0.01), as compared to controls, resulting in a marked elevation in the cholic/chenodeoxycholic acid ratio (3.4 +/- 0.5 vs. 1.1 +/- 0.1, p < 0.01). The glycine/taurine ratio was reduced in cholestasis of pregnancy (0.8 +/- 0.1 vs. 1.4 +/- 0.1, p < 0.01). During ursodeoxycholic acid administration its proportion in serum increased from 1.4 +/- 0.6% (0.6 +/- 0.2 micromol/l) at baseline to 24.7 +/- 2.3% (5.9 +/- 1.9 micromol/l) with therapy (p < 0.01). This increment was accompanied by a significant decrease in the percentage of cholic acid (28.2 +/- 2.6%, p < 0.01) and an elevation in chenodeoxycholic acid proportion (25.0 +/- 1.9%, N.S.). Although lithocholic acid concentration in serum was maintained with treatment (1.2 +/- 0.2 micromol/l vs. 1.7 +/- 0.5 micromol/l), there was a significant increase in lithocholic acid proportion (p < 0.01) from 3.3 +/- 0.5% at baseline to 7.4 +/- 1.3% during therapy. The glycine/taurine ratio of serum bile acid pool returned to normal after ursodeoxycholic acid administration (1.7 +/- 0.3). CONCLUSIONS: These results establish the importance of ursodeoxycholic acid treatment for the correction of maternal serum bile acid profile in cholestasis of pregnancy, indicating that ursodeoxycholic acid may improve fetal prognosis.

Adult↗

Use of serum bile acids in the identification of vinyl chloride hepatotoxicity.

Most previous studies proposing serum bile acids as indicators of hepatic function have been performed in hospitalized patients in whom overt symptomatic liver disease was present. The ability of fasting levels of serum bile acids to identify mild, clinically inapparent chemical liver injury in an occupational setting was compared with that of indocyanine green clearance and routine biochemical liver tests in 67 asymptomatic chemical workers in whom liver biopsies had been performed for medical indications. Histologically, 15 were found to have chemical liver injury, 27 had nonchemical liver disease, and 25 were normal. Two serum bile acids, cholylglycine and conjugates of cholic acid, were determined by radioimmunoassay, using 466 "normal" males from the same worker cohort as a reference range. The geometric mean concentrations of cholylglycine in patients with chemical liver injury, patients with nonchemical liver disease, and normal subjects were 47.9, 19.1, and 20.0 micrograms/dl, respectively (p = 0.036 by analysis of variance). Conjugates of cholic acid showed similar differences (p = 0.027), as did indocyanine green clearance with mean half-life of 4.2, 3.2, and 3.3 minutes in the three biopsy subgroups, respectively (p = 0.043). Such differences were not observed for biochemical liver tests. The fasting level of serum bile acids provided high specificity but lower sensitivity in the detection of all types of liver disease. However, serum bile acids and indocyanine green clearance provided a higher specificity and sensitivity for chemical liver injury than for nonchemical liver disease. An index of average exposure to vinyl chloride was significantly greater in the subgroup with chemical liver injury than in the other two groups, further supporting the association of chemical type injury with impaired anion uptake. These data identify the fasting level of serum bile acids as a clinically usable indicator of early chemical injury in chemically exposed asymptomatic worker populations with liver dysfunction. Further investigation is needed in other occupational hepatotoxic environments to determine if this association is limited to vinyl monomer type injury.

Adult↗

Conjugates of gadolinium complexes to bile acids as hepatocyte-directed contrast agents for magnetic resonance imaging.

A series of structurally different Gd(III) conjugates incorporating a bile acid moiety have been prepared. Polyaminopolycarboxylic ligands such as diethylenetriaminepentaacetic acid (DTPA) and 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetracetic acid (DOTA) have been selected as chelating subunit for the Gd(III) ion. Cholic acid, cholylglycine, and cholyltaurine have been incorporated as the bile acid moieties. In first generation conjugates the Gd(III) complex is linked to the carboxyl group of cholic acid. Second generation conjugates feature the attachment of the Gd(III) complex to the 3 position of the steroidic backbone of the bile acid. Finally, in third generation conjugates the Gd(III) complex is attached to the epsilon nitrogen atom of cholyllysine. The conjugates are eliminated through the biliary route to a various extent (7.5 to 77% in rats) according to their structural features. Among the most promising terms, a second generation conjugate in which the Gd(III) complex is linked to cholic acid through the 3alpha hydroxy group seems to enter hepatocytes using the Na(+)/taurocholate transporter. Noticeably, some of the second generation conjugates are characterized by very high tolerabilities (LD(50) up to 9.5 mmol/kg) after intravenous administration in mice.

Animals↗

The effect of a natural high-fibre diet on faecal and biliary bile acids, faecal pH and whole-gut transit time in man. A controlled study.

Dietary fibre possibly protects against colonic cancer by effects on bile acid metabolism. We investigated the effect of a natural high-fibre diet on secondary bile acid formation. Twelve healthy subjects on an habitual low-fibre diet (for 4 weeks) consumed a high-fibre menu for 10 weeks (experimental group). A control group of 10 subjects consumed their regular high-fibre diet during this period. Faecal and biliary acid composition, faecal weight, faecal pH and gut transit time were studied before and after 6 and 10 weeks of fibre addition. Changes in the experimental group were compared to changes in the control group. The concentration, but not the excretion, of the secondary faecal bile acids was reduced in the experimental group. Faecal weight increased, faecal pH dropped and gut transit time was not altered. The biliary deoxycholic acid content decreased and the cholic acid content increased after 6 weeks, but returned to baseline values after 10 weeks of fibre addition. This study shows that a natural high-fibre diet lowers secondary faecal bile acid concentration through an increase in stool weight. The 7 alpha-dehydroxylation of primary bile acids is probably not or only transiently inhibited.

Adult↗

Expression of the bile acid-inducible NADH:flavin oxidoreductase gene of Eubacterium sp. VPI 12708 in Escherichia coli.

The intestinal microorganism Eubacterium sp. VPI 12708 synthesizes a bile acid-inducible NADH:flavin oxidoreductase (NADH:FOR) which presumably functions in the 7 alpha-dehydroxylation of cholic acid to deoxycholic acid. The baiH gene encoding NADH:FOR was subcloned into an IPTG-inducible expression vector, pBaiH2.2. Escherichia coli DH5 alpha cells transformed with pBaiH2.2 expressed 10-fold higher levels of NADH:FOR upon induction with IPTG than did Eubacterium sp. VPI 12708 cells induced with cholic acid. The NADH:FOR produced by E. coli DH5 alpha(pBaiH2.2) was purified to > 95% electrophoretic homogeneity in three steps. The purified NADH:FOR was similar to that of Eubacterium sp. VPI 12708 in subunit and native M(r) (ca. 72,000 and 210,000, respectively), pH optimum, sensitivity to inhibitors, and electron acceptor specificity. It contained 1 mol of FAD, up to 2 mol of iron, and 1 mol of copper per mol of subunit. The enzyme reduced synthetic quinones, dyes, flavins, and O2 with NADH as the electron donor, but did not reduce disulfide compounds, various unsaturated bile acids, cytochrome c, physiological quinones, or cell fractions from Eubacterium sp. VPI 12708. Addition of purified NADH:FOR to Eubacterium sp. VPI 12708 cell extracts altered the balance of oxidized and reduced bile acid intermediates produced during cholic acid 7 alpha-dehydroxylation, suggesting that the enzyme may regulate the cellular ratio of NAD to NADH.

Amino Acid Sequence↗

A case of cerebrotendinous xanthomatosis: effects of ursodeoxycholic acid administration on serum bile acids and cholestanol.

Cerebrotendinous xanthomatosis (CTX) is a rare familiar disease characterized by tendon xanthomas, cataracts, cerebellar ataxia, dementia and an elevated serum cholestanol level. In this paper, a 50-year-old man with typical signs and symptoms of CTX is described. Serum cholestanol and chelesterol concentrations were 17.9-28.6 micrograms/ml and 109-153 mg/dl, respectively. The determination of non-sulfated bile acid concentration in the serum assayed by mass fragmentography disclosed an abnormal profile. The concentration of cholic acid (0.30-0.52 microgram/ml) was higher than normal, while those of chenodeoxycholic acid, ursodeoxycholic acid, deoxycholic acid and lithocholic acid were extremely low or undetectable. Administration of ursodeoxycholic acid (300 mg per day, orally) for 2 weeks resulted in a marked reduction of serum cholic acid concentration. However, serum cholestanol levels remained unchanged.

Bile Acids and Salts↗

Two loci on chromosome 9 control bile acid composition: evidence that a strong candidate gene, Cyp8b1, is not the culprit.

An intercross between C57BL/6J and CASA/Rk mice was used to study the genetics of biliary bile acid composition. In parental strains, male C57BL/6J mice had significantly higher cholic acid (CA; 14%) and lower beta-muricholic acid (betaMC; 27%) than CASA/Rk mice, whereas females did not differ. However, quantitative trait locus analysis of F2 mice revealed no significant chromosome 9 loci in males but loci in females on chromosome 9 for percentage CA (%CA) at 72 centimorgan (cM) [logarithm of the odds (LOD) 5.89] and %betaMC at 54 cM (LOD 4.09). Chromosome 9 congenic and subcongenic strains representing CASA/Rk intervals 38-73 cM (9KK) and 68-73 cM (9DKK) on the C57BL/6J background were made. In 9KK and 9DKK males, %CA was increased and %betaMC was unchanged, whereas in 9KK but not 9DKK females, %CA was increased and %betaMC was decreased. Sterol 12alpha-hydroxylase (Cyp8b1) channels bile acid precursors into CA and maps at chromosome 9 (73 cM). However, there was no significant difference in Cyp8b1 mRNA or enzymatic activity between parental mice, parental-congenic-subcongenic mice, or high-low biliary %CA F2 mice. In summary, two chromosome 9 loci control sexually dimorphic effects on biliary bile acid composition: a distal (68-73 cM) major determinant in males, and a more proximal (38-68 cM) major determinant in females. In this intercross, Cyp8b1, a strong candidate, does not appear to be responsible.

Animals↗

Influence of primary bile acid feeding on cholesterol metabolism and hepatic function in the rhesus monkey.

In three healthy rhesus monkeys fed chenodeoxycholic (chenic) acid, there was no consistent increase in the total exchangeable cholesterol pool or input to the cholesterol pool. In three similar monkeys fed cholic acid, the total exchangeable pool increased in all animals and input to the cholesterol pool increased in two. Serum glutamic-pyruvic transaminase (SGPT) increased transiently in two animals in each group. Morphologic abnormalities (triaditis with atypical ductular proliferation) were noted in one animal; this animal was ingesting chenic acid but had normal liver test results at the time of biopsy. Biliary bile acids contained 8 to 14 percent lithocholic acid in the chenic acid group and 48 to 72 percent deoxycholic acid in the cholic acid group.

Alanine Transaminase↗

Effect of phototherapy and exchange transfusion on primary bile acids in the serum of hyperbilirubinaemic newborns.

Serum primary bile acid (cholic (CA) and chenodeoxycholic (CDCA) acid) concentrations were measured in 14 preterm and 11 full-term hyperbilirubinaemic newborns at the beginning and end of, and 24 and 72 hours following phototherapy. Only in the preterm newborns with gestational ages of 35-38 weeks there was a significant decrease of mean serum bile acid concentrations which could be shown 72 hours after the beginning of phototherapy. It can be hypothesized that the decrease was a result of a direct effect of light on the excretory liver function. Serum CA and CDCA concentrations were also measured in 5 hyperbilirubinaemic newborns at the beginning and end, and 24, 48 and 72 hours after the end of exchange transfusion. Exchange transfusion caused a clear immediate decrease in the mean serum primary bile acid concentrations. However, on day 2 after exchange transfusion the mean serum concentration of CA was about 150% and that of CDCA about 110% of the initial values. The most hyperbilirubinaemic newborns had extremely high primary bile acid serum concentrations before therapy. As bile acids compete with bilirubin for albumin binding it should be considered whether high bile acids in the serum of hyperbilirubinaemic newborns presuppose exchange transfusions.

Bilirubin↗