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Conjugation of cholic acid with taurine and glycine by rat liver peroxisomes.

We have previously shown that rat liver peroxisomes catalyze conversion of 3 alpha,7 alpha,12 alpha-trihydroxy-5 beta-cholestanoic acid into cholic acid as the CoA-ester (1). In the present work it is shown that addition of taurine or glycine to the reaction mixture, choloyl-CoA is further converted to taurocholic or glycocholic acid, respectively. The identity of these products was verified by fast atom bombardment-mass spectrometry. The peroxisomal fraction catalyzed conjugation of cholic acid with taurine (22.3 nmol X mg-1 X h-1) or glycine (18.6 nmol X mg-1 X h-1) at rates twice those observed with the microsomal fraction. The results indicate that conjugation of newly formed bile acids may be an important function of liver peroxisomes.

Animals↗

Cholic acid accumulation and its diminution by short-chain fatty acids in bifidobacteria.

Cholic acid (CA) transport was investigated in nine intestinal Bifidobacterium strains. Upon energization with glucose, all of the bifidobacteria accumulated CA. The driving force behind CA accumulation was found to be the transmembrane proton gradient (Delta pH, alkaline interior). The levels of accumulated CA generally coincided with the theoretical values, which were calculated by the Henderson-Hasselbalch equation using the measured internal pH values of the bifidobacteria, and a pK(a) value of 6.4 for CA. These results suggest that the mechanism of CA accumulation is based on the diffusion of a hydrophobic weak acid across the bacterial cell membrane, and its dissociation according to the Delta pH value. A mixture of short-chain fatty acids (acetate, propionate and butyrate) at the appropriate colonic concentration (117 mM in total) reduced CA accumulation in Bifidobacterium breve JCM 1192(T). These short-chain fatty acids, which are weak acids, reduced the Delta pH, thereby decreasing CA accumulation in a dose-dependent manner. The bifidobacteria did not alter or modify the CA molecule. The probiotic potential of CA accumulation in vivo is discussed in relation to human bile acid metabolism.

Acetic Acid↗

Microbiological degradation of bile acids. The conjugation of a certain cholic acid metabolite with amino acids in Corynebacterium equi.

1. (4R)-4[4alpha-(2-Carboxyethyl)-3aalpha-hexahydro-7abeta-methyl-5-oxoindan-1beta-yl]valeric acid (II) could not be utilized by Arthrobacter simplex, even though the acid was one of the metabolites formed from cholic acid (I) by this organism. Therefore the further degradation of the acid (II) by Corynebacterium equi was investigated to identify the intermediates involved in the cholic acid degradation. 2. The organism, cultured in a medium containing the acid (II) as the sole source of carbon, produced unexpected metabolites, the conjugates of this original acid (II) with amino acids or their derivatives, although the yield was very low. These new metabolites were isolated and identified by chemical synthesis as the Na-((4R)-4-[4alpha-(2-carboxyethyl)-3a alpha-hexahydro-7a beta-methyl-5-oxoindan-1 beta-yl]-valeryl) derivatives of L-alanine, glutamic acid, O-acetylhomoserine and glutamine, i.e. compounds (IIIa), (IIIb), (IIId) respectively. 3. The possibility that the bacterial synthetic reaction observed in the acid (II) metabolism with C. equi is analogous to peptide conjugation known in both animals and higher plants is discussed. A possible mechanism for this bacterial conjugation is also considered.

Alanine↗

Selective activity of several cholic acid derivatives against human immunodeficiency virus replication in vitro.

Several cholic acid derivatives such as taurolithocholic acid, lithocholic acid 3-sulfate, taurolithocholic acid 3-sulfate, and glycolithocholic acid 3-sulfate were shown to inhibit selectively the replication of human immunodeficiency virus type 1 (HIV-1) in vitro. These compounds completely protected MT-4 cells against HIV-1-induced cytopathogenicity at a concentration of 100 micrograms/ml, whereas no toxicity for the host cells was observed at 200 micrograms/ml. They also inhibited HIV-1 antigen expression in HIV-1-infected CEM cells. The bile acids (cholic acid, deoxycholic acid, chenodeoxycholic acid, and lithocholic acid) did not show any inhibitory effect on HIV-1 replication at concentrations that were not toxic to the host (MT-4) cells. From a structure-function analysis of a number of cholic acid derivatives, the presence of either a sulfonate (as in the tauro conjugates) or a sulfate group as well as the "litho" configuration appeared to be necessary for the expression of anti-HIV-1 activity. The active cholic acid derivatives did not directly inactivate the virus particles at the concentrations that were not toxic to the host cells. Lithocholic acid 3-sulfate, taurolithocholic acid 3-sulfate, and glycolithocholic acid 3-sulfate, but not taurolithocholic acid, partially inhibited virus adsorption to MT-4 cells. These three compounds were also inhibitory to the reverse transcriptase activity associated with HIV-1.

Adsorption↗

Microbiological degradation of bile acids. Nitrogenous hexahydroindane derivatives formed from cholic acid by Streptomyces rubescens.

The metabolism of cholic acid (I) by Streptomyces rubescens was investigated. This organism effected ring A cleavage, side-chain shortening and amide bond formation and gave the following metabolites: (4R)-4-[4alpha-(2-carboxyethyl)-3aalpha-hexahydro-7abeta-methyl-5-oxoindan-1 beta-yl]valeric acid (IIa) and its mono-amide (valeramide) (IIb); and 2,3,4,6, 6abeta,7,8,9,9aalpha,9bbeta-decahydro-6abeta-methyl-1H-cyclopenta[f]quinoline-3,7-dione(IIIe)and its homologues with the beta-oriented side chains, valeric acid, valeramide, butanone and propionic acid, in the place of the oxo group at C-7, i.e.compounds (IIIa), (IIIb), (IIIc) and (IIId) respectively. All the nitrogenous metabolites were new compounds, and their structures were established by partial synthesis except for the metabolite (IIIc). The mechanism of formation of these metabolites is considered. A degradative pathway of cholic acid (I) into the metabolites is also tentatively proposed.

Cholic Acids↗

Effect of simvastatin, ursodeoxycholic acid and simvastatin plus ursodeoxycholic acid on biliary lipid secretion and cholic acid kinetics in nonfamilial hypercholesterolemia.

It has been recently shown that the newest hypocholesterolemic agent, simvastatin, lowers the biliary cholesterol saturation index and that its association with ursodeoxycholic acid renders it more effective. To determine the mechanism by which simvastatin decreases the biliary cholesterol saturation index, we evaluated hepatic secretion rates of cholesterol, bile acids and phospholipids, and cholic acid pool size, turnover and synthesis in eight hyperlipidemic patients (five women and three men, age range = 38 to 65 yr). These assessments were conducted before treatment, after 4 wk of simvastatin (40 mg/day), after 4 wk of ursodeoxycholic acid (600 mg/day) and after a further 4 wk of a combination therapy of simvastatin (40 mg/day) plus ursodeoxycholic acid (600 mg/day). The cholesterol saturation index was significantly reduced with simvastatin (from 1.51 +/- 0.10 to 0.94 +/- 0.05, mean +/- S.E.; p less than 0.02), with ursodeoxycholic acid (from 1.51 +/- 0.10 to 0.86 +/- 0.03, mean +/- S.E.; p less than 0.02) and with the combination of simvastatin plus ursodeoxycholic acid (from 1.51 +/- 0.01 to 0.70 +/- 0.05, p less than 0.02). The cholesterol saturation index during combination therapy was significantly lower (p less than 0.02) than that reached during the use of simvastatin and ursodeoxycholic acid. Both simvastatin and ursodeoxycholic acid significantly reduced the hepatic secretion rate of cholesterol (from 130 +/- 14 mumols/hr to 81 +/- 12 mumols/hr, p less than 0.01, and 70 +/- 9 mumols/hr, p less than 0.01) without affecting bile acid and phospholipid outputs.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

Synthesis of the specific monosulfates of cholic acid.

The three isomeric cholic acid-monosulfates were synthetized and characterized. Cholic acid-3-sulfate was obtained by reacting cholic acid for 2 min with chlorosulfonic acid in pyridine and chromatography of the resulting bile salt mixture on Sephadex LH-20. The 7- and the 12-monosulfate were prepared by sulfation of the corresponding monohydroxy-diacetates followed by removal of the acetyl groups by alkaline hydrolysis and purification by chromatography on Sephadex LH-20. On TLC in n-butanol-acetic acid-water (10:1:1, v/v) the Rf values were 0.59 for cholic acid-3-sulfate, 0.52 for cholic acid-7-sulfate and 0.48 for cholic acid-12-sulfate. The time required for complete solvolysis at 37 degrees C in acid methanol-acetone (1:9) was 3 h for cholic acid-3-sulfate, 12 h for the 12-monosulfate and 18 h for the 7-monosulfate.

Cholic Acids↗

Effect of ursodeoxycholic acid on the kinetics of cholic acid and chenodeoxycholic acid in patients with primary sclerosing cholangitis.

Treatment of patients with cholestatic liver diseases with ursodeoxycholic acid has been shown to have beneficial effects that may be related to a shift in the balance between hydrophilic and hydrophobic bile acids in favor of hydrophilic bile acids. During treatment of patients with primary sclerosing cholangitis with ursodeoxycholic acid, plasma concentrations of some endogenous bile acids decrease. To test whether the changes in plasma bile acids are due to decreases of their pool sizes or synthesis rates, we determined bile acid kinetics of cholic and chenodeoxycholic acid in six patients with primary sclerosing cholangitis, of whom four also had ulcerative colitis. All patients were studied before and 3 mo after the start of ursodeoxycholic acid treatment. Six healthy subjects served as controls. In patients with primary sclerosing cholangitis, pool sizes of cholic and chenodeoxycholic acid were considerably smaller than those in healthy controls; after ursodeoxycholic acid treatment they were unchanged. Fractional turnover and synthesis of cholic acid increased significantly after ursodeoxycholic acid administration. Fractional turnover of chenodeoxycholic acid also increased significantly, whereas synthesis of this bile acid was unchanged. Our data indicate that in patients with primary sclerosing cholangitis, pool sizes of bile acids are reduced. The decrease of levels of endogenous bile acids in plasma under ursodeoxycholic acid treatment despite unchanged bile acid pool sizes indicates redistribution of the bile acids into the enterohepatic circulation, probably because of improved hepatic clearance after ursodeoxycholic acid treatment.

Adult↗

Microbiological degradation of bile acids, further degradation of a cholic acid metabolite containing the hexahydroindane nucleus by Corynebacterium equi.

1. The further degradation of a cholic acid (I) metabolite, (4R)-4-[4alpha-(2-carboxyethyl)-3aalpha-hexahydro-7abeta-methyl-5-oxoindan-1beta-yl]valeric acid (IIa), by Corynebacterium equi was investigated. This organism effected ring-opening and gave (4R)-4-[2alpha-(2-carboxyethyl)-3beta-(3-carboxypropionyl)-2beta-methylcyclopent-1beta-yl]valeric acid (VI). The new metabolite was isolated as its trimethyl ester and identified by partical synthesis. It was not utilized by C. equi. 2. (4R)-4[4alpha-(2-Carboxyethyl)-3aalpha-decahydro-8abeta-methyl5-oxa-6-oxoazulen-1beta-yl]valeric acid (IVa), which is a hypothetical initial oxidation product in the above degradation, was not converted by C. equi into the expected metabolite (VI), but into 3 - [2beta - [(2S) - tetrahydro - 5 - oxofur - 2 - yl] - 1beta - methyl - 5 - oxocyclopent - 1alpha - yl]-propionic acid (VIII), the structure of which was established by partial synthesis. 3. Both the possible precursors of the metabolite (VI), an isomer of the epsilon-lactone (IVa), the gamma-lactone (XIa), and the open form of these lactones, the hydroxytricarboxylic acid (V), were also not utilized by C. equi. 4. Under some incubation conditions, C. equi also converted compound (IIa) and 3-(3aalpha-hexahydro-7abeta-methyl-1,5-dioxoindan-4alpha-yl)propionic acid (IIb) into 5-methyl-4-oxo-octane-1,8-dioic acid (III), (4R)-4-(2,3,4,6,6abeta,7,8,9,9aalpha,9bbeta-decahydro-6abeta-methyl-3-oxo-1H-cyclopenta[f]quinolin-7beta-yl)valeric acid (VII) and probably a monohydroxy derivative of compound (IIa) and compound (III), respectively. 5. The possibility that an initial step in the degradation of compound (IIa) by C. equi is oxygenation of the Baeyer-Villiger type, yielding compound (IVa), is discussed. Metabolic pathways of compound (IIa) to compounds (III), (VI), (VII) and (VIII) are also considered.

Cholic Acids↗

Cholic acid binding to isolated rat liver plasma membranes.

Cholic acid binding to isolated rat liver plasma membranes was studied using a centrifugal filtration technique which allowed independent determination of free and membrane-bound cholic acid. Binding of cholic acid was very rapid and reversible. Scatchard analysis revealed at least three binding sites with high, medium and low affinity. The high affinity binding a) displayed saturability and isotope replacement, b) was not present in rat liver mitochondria and red blood cell ghosts and c) was temperature dependent. This binding has a very low capacity with a dissociation constant in the physiological range of plasma cholic acid concentration and has an affinity for other common bile acids. Cholic acid binding to the high affinity binding site was not inhibited by estrone, beta-estradiol or cholesterol. These results would suggest that the high affinity binding site represents a specific binding site for cholic acid and may also be specific for other common bile acids. This binding was not dependent on Na and was inhibited by bromosulfophthalein. Cholic acid binding to the high affinity site has some features in common with cholic acid uptake by isolated rat hepatocytes, and this would suggest that the high affinity binding site could be the postulated carrier for hepatic uptake of cholic acid.

Animals↗

Crystal structure of chicken liver basic fatty acid-binding protein complexed with cholic acid.

Two paralogous groups of liver fatty acid-binding proteins (FABPs) have been described: the mammalian type liver FABPs and the basic type (Lb-FABPs) characterized in several vertebrates but not in mammals. The two groups have similar sequences and share a highly conserved three-dimensional structure, but their specificity and stoichiometry of binding are different. The crystal structure of chicken Lb-FABP complexed with cholic acid and that of the apoprotein refined to 2.0 A resolution are presented in this paper. The two forms of the protein crystallize in different space groups, and significant changes are observed between the two conformations. The holoprotein binds two molecules of cholate in the interior cavity, and the contacts observed between the two ligands can help to explain the reason for this stoichiometry of binding. Most of the amino acids involved in ligand binding are conserved in other members of the Lb-FABP family. Since the amino acid sequence of the Lb-FABPs is more similar to that of the bile acid-binding proteins than to that of the L-FABPs, the possibility that the Lb-FABPs might be more appropriately called liver bile acid-binding proteins (L-BABPs) is suggested.

Amino Acid Sequence↗

[Study on radiosterilization of crude drug pill involving bezoar bovis--radiolysis of bilirubin and cholic acids in hydrous starch pellet (author's transl)].

Radiolysis of bilirubin and cholic acids (cholic acid, desoxycholic acid and lithocholic acid) in hydrous pellet have been investigated with following parameters, which were hydrous content, radiation dose and the dose rate, to discuss the application of gamma-irradiation for sterilization of crude drug pill involving bezoar bovis. At 774 C/kg (3.0 MR) irradiation for 5% and 10% hydrous contents pellets, the radiolysis percent of those components were less than 5%. However, the higher hydrous pellet, the radiolysis percents of those are more increase. At the same irradiated condition for 20% hydrous contents pellets, the radiolysis percents of those were 15-22%. The hydrous percent of commercial crude drug pill involving bezoar bovis are about 9%, so that the radiolysis of those components will be less than 5% on the sterilization. The radiolysis percent of bilirubin are constant to variation of radiation dose rate between 51.6-722.5 C/kg.hr (0.2-2.8 MR/hr). But, the values of cholic acids don't definite such as that of bilirubin, because of larger analytical error.

Animals↗

Cholelithiasis in hamsters: effects of cholic acid and calcium on gallstone formation.

Dietary cholic acid (0.1%) and/or calcium (2.6% as calcium carbonate) were added to a semipurified diet containing cholesterol and ethynyl estradiol to determine whether the incidence of pigment and/or cholesterol gallstones would be changed. Male golden Syrian hamsters were fed the experimental diets for 96 days (Group 1, control; Group 3, cholic acid plus calcium) or only an average of 60 days (Group 2, 0.1% cholic acid). Animals in Group 2 became ill (weight loss, low food intake, diarrhea) possibly due to cholic acid (or deoxycholic acid) toxicity. Cholesterol gallstones and crystals were absent in all experimental groups. The incidence of pigment gallstones was: control, Group 1, 12/16; 0.1% cholic acid, Group 2, 3/13; and 0.1% cholic acid plus calcium, Group 3, 11/22. Cholic acid with or without calcium produced an elevation of both liver and plasma cholesterol: Group 2, 80.1 mg/g and 501 mg/dl; Group 3, 103.7 mg/g and 475 mg/dl vs Group 1, 65 mg/g and 209 mg/dl, respectively. The lithogenic indices of the bile were lower in Groups 2 and 3 compared to Group 1, controls, 0.45 and 0.58 vs 1.16, respectively. The extent of the portal tract pathology could not be correlated with the presence or absence of pigment gallstones or with the levels of lithocholic acid in the hamster bile. In summary, when semipurified diets were supplemented with ethynyl estradiol and cholic acid, with and without calcium supplementation, no cholesterol gallstones formed and the incidence of pigment gallstones was not altered.

Animals↗

Formation of cholic acid from 3 alpha, 7 alpha, 12 alpha-trihydroxy-5 beta-cholestanoic acid by rat liver peroxisomes.

In a previous study, it was shown that the peroxisomal fraction of rat liver, isolated by Percoll gradient centrifugation of a light mitochondrial fraction, was able to catalyze conversion of 3 alpha, 7 alpha, 12 alpha-trihydroxy-5 beta-cholestanoic acid (THCA) into cholic acid (Pedersen, J. I., and J. Gustafsson, 1980. FEBS Lett. 121: 345-348). In the present work, this peroxisomal THCA-oxidizing system has been studied in more detail. The peroxisomes were prepared by sucrose gradient centrifugation. By use of different marker enzymes, it was confirmed that the major part of the activity in the light mitochondrial fraction was located in the peroxisomes. The reaction was absolutely dependent on the presence of Mg2+, CoA, ATP, and NAD+ in the reaction medium. In addition to cholic acid, small amounts of 3 alpha, 7 alpha, 12 alpha, 24-tetrahydroxy-5 beta-cholestanoic acid were detected as product. Provided the peroxisomes were preincubated with ATP and CoA, the reaction was linear with time up to 75 min. It was linear with peroxisomal protein and the pH optimum was 8. The reaction was stimulated by FAD (ca. 50%), by cytosolic protein (about twofold), by microsomal protein (about twofold), bovine serum albumin (about sevenfold), and by KCN (75% at 1 mM). In the absence of bovine serum albumin in the medium the K'm for the overall reaction was 1.4 X 10(-6) M and the maximum rate was 4.3 nmol X mg-1 X hr-1. In the presence of bovine serum albumin, the K'm increased to 6.3 X 10(-6) M and the maximum rate to about 32 nmol X mg-1 X hr-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗