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Dietary cholic acid lowers plasma levels of mouse and human apolipoprotein A-I primarily via a transcriptional mechanism.

To induce dietary atherosclerosis in mice, high-fat/high-cholesterol (HF) diets are frequently supplemented with cholic acid (CA). This diet produces low plasma levels of high-density lipoprotein (HDL) and high levels of low-density lipoprotein (LDL). However, HF diets without any added CA, which more closely resemble human diets, increase levels of both HDL and LDL, suggesting that CA may be responsible for the lowering of HDL. Our aim was to examine the potential mechanism responsible for the lowering of HDL. Nontransgenic (NTg) C57BL mice and apoA-I-transgenic (apoAI-Tg) mice, with greatly increased basal apoA-I and HDL levels, were used. Mice were fed the following four diets: control (C), high-fat/high-cholesterol (HF), control and 1% cholate (CA) and HF + CA. Dietary CA reduced plasma HDL levels by 35% in NTg and 250% in apoAI-Tg mice, independent of the fat or cholesterol content of the diet. Hepatic apoA-I mRNA decreased 30% in NTg and 180% in apoAI-Tg mice. Hepatic apoA-I synthesis and apoA-I mRNA transcription rates also decreased in parallel with apoA-I mRNA levels, suggesting that the CA-induced decreases in plasma apoA-I levels occurred primarily via decreasing apoA-I mRNA transcription rates. An HF diet increased HDL levels 1.8-fold in NTg and 1.5-fold in apoAI-Tg mice. Addition of CA to the HF diet lowered HDL levels by 1.6-fold in NTg and 2. 5-fold in apoAI-Tg mice. Transfection studies with the apoA-I promoter suggested the presence of a putative cis-acting element responsible for the CA-mediated down-regulation of the apoA-I promoter activity. Measurements of apoA-I regulatory protein-1 (ARP-1) mRNA, a negative regulator of the apoA-I gene in the mouse liver showed that CA increased the ARP-1 mRNA levels. Because apoA-I gene transcription alone was not sufficient to account for the lowering of plasma HDL levels, scavenger receptor-B1 (SR-B1) and hepatic lipase (HL) mRNAs levels were quantitated. The levels of SR-B1 and HL mRNA were not changed by dietary CA. These studies suggest that dietary cholate regulates plasma levels of apoA-I primarily by a transcriptional mechanism via a putative bile acid response element involving a negative regulator of apoA-I, and partly by an unidentified post-transcriptional mechanism.

Animals↗

Severe cholestasis induced by cholic acid feeding in knockout mice of sister of P-glycoprotein.

Intrahepatic cholestasis is often associated with impairment of biliary bile acid secretion, a process mediated by the sister of P-glycoprotein (Spgp or Abcb11) also known as the bile salt export pump (Bsep). In humans, mutations in the Spgp gene are associated with a fatal childhood disease, type 2 progressive familial intrahepatic cholestasis (PFIC2). However in mice, the "knockout" of Spgp only results in mild cholestasis. In this study, we fed spgp(-/-) knockout mice with a cholic acid (CA)-supplemented diet to determine whether a more pronounced PFIC2-like phenotype could be induced. Such mice developed severe cholestasis characterized by jaundice, weight loss, elevated plasma bile acid, elevated transaminase, cholangiopathy (proliferation of bile ductules and cholangitis), liver necrosis, high mortality, and wide-ranging changes in the mRNA expression of major liver genes (16/36 examined). A surprising observation was that the bile acid output and bile flow in CA-fed mutant mice was significantly higher than anticipated. This suggests that the spgp(-/-) mice are able to utilize an alternative bile salt transport system. However, unlike Spgp, this system is insufficient to protect the knockout mice from cholestasis despite its high capacity. In conclusion, the spgp(-/-) mice provide a unique model to investigate molecular pathways associated with cholestasis and related diseases.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

[Cholic acid levels in the serum of dairy cows with metabolically-caused liver diseases].

Three groups of freshly calved dairy cows suffering from fatty liver syndrome of different stages were examined for serum cholic acid (SCA) levels to assess the value of SCA-determination as a diagnostic approach to fatty liver syndrome. A. Comparison of the SCS levels between cows with and without ketonuria: Cows with ketonuria (n = 13) and with elevated plasma ASAT activity, indicating a moderate liver damage, showed a rise of their mean SCA level to 35.3 (+/- 14.9) mumol/l. Freshly calved cows without ketonuria (n = 10) had at the same time a mean SCA level of 17.9 (+/- 6.4) mumol/l, falling practically into the physiological range. The SCA level increased above the physiological range in 10 of the 13 cases with ketonuria, in seven of them even more than twice. B. Interrelationship between SCA level and hepatic lipid content: Increase in hepatic total lipid (TL) was always associated with SCA-elevation. The mean SCA level was 55 (+/- 22.0) mumol/l in cases of severe fatty liver (TL = 200-280 g/kg), and 39.5 (+/- 6.0) mumol/l in the moderate form (TL = 180-200 g/kg) of the syndrome. C. Peripartal SCA levels of cows with fatty liver: Clinically healthy cows (n = 6) with ketonuria and an elevation of serum ASAT and FFA concentrations had a mean SCA level of 35-45 mumol/l. One cow of this group, which developed acute fatty liver syndrome and died within the period of study, showed an extreme SCA level of 100 mumol/l in it's terminal stage.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

The influence of cholic acid and dehydrocholic acid on the biliary excretion of unconjugated and conjugated sulfobromophthalein in rats.

Urethane anesthetized Wistar rats with biliary fistulas were infused during 100 min with sulfobromophthalein (BSP), the glutathione conjugate of sulfobromophthalein (BSP-GSH), cholic acid (CA) and dehydrocholic acid (DCA). The dyes (594 nmol/100 g/min) and the bile acids (1200 nmol/100 g/min) were infused separately, and in combination as well. When BSP was infused, CA and DCA increased the maximal excretion of total BSP (conjugated plus unconjugated) from 1400 to 4100 and 3300 nmol/100 g/10 min. The bile flow observed with BSP plus CA was not significantly different from that with BSP plus DCA. The biliary excretion of total BSP was higher throughout with CA than with DCA because CA increased the biliary concentration of PSP while DCA did not. The bile flow attained with CA alone was significantly lower than that with BSP plus CA. The current data provide arguments for abandoning the view that choleresis per se is the crucial determinant for BSP excretion. When BSP-GSH was infused instead of BSP, the excretion rate of the dye was not altered by the additional infusion of CA whereas it was significantly reduced by DCA. The maximal biliary concentration of BSP-GSH fell from 25.9 nmol/mul to 15.3 and 9.4 nmol/mul with CA and DCA, respectively. Both CA and DCA impaired the hepatic uptake of BSP and BSP-GSH. During the infusion with CA, BSP plus CA and BSP-GSH plus CA the biliary excretion rates of bile acids did not differ significantly from each other. This favours the view that the transfer for CA from the liver to bile is different from that for BSP and BSP-GSH. A fraction of bile fluid "independent of choleretics" (viz. of bile salts, BSP and BSP-GSH) is estimated and discussed in view of the different types of infusion.

Animals↗

Ion conductors derived from cholic acid and spermine: importance of facial hydrophilicity on NA(+) transport and membrane selectivity.

A series of ion conductors have been synthesized in which the degree of facial hydrophilicity has been systematically varied. Specifically, conjugates have been prepared from cholic acid and spermine in which the hydrophilic face of each sterol bears methoxy (1), hydroxy (2), carbamate (3), or sulfate groups (4). The ability of these conjugates to promote the transport of Na(+) across phosphatidylcholine membranes of varying thickness has been investigated by (23)Na NMR spectroscopy. Examination of observed activities in three different phosphatidylcholine membranes has provided evidence for membrane-spanning dimers as the transport-active species. In the thinnest membranes investigated, made from 1,2-dimyristoleoyl-sn-glycero-3-phosphocholine (C14), Na(+)-transport activity was found to increase, substantially, with increasing facial hydrophilicity. In thicker membranes, made from 1,2-dioleoyl-sn-glycero-3-phosphocholine (C18), observed activities were found to decrease with increasing facial hydrophilicity; with a membrane of intermediate thickness, prepared from 1,2-dipalmitoleoyl-sn-glycero-3-phosphocholine (C16), ion-conducting activity increased and then decreased, with continuous increases in facial hydrophilicity. The possible origins for these variations in activity are briefly discussed.

Cholic Acid↗

Plasma conjugated cholic acid in premature and term newborns and young infants.

Bile acid handling by neonates, both premature (Group I, mean gestational age 34.3 weeks; Group II, 36.6 weeks) and full-term (Group III, 40.2 weeks) and by 3-month-old infants (Group IV) was assessed by measuring plasma concentrations of conjugated cholic acid (CCA) before and at successive intervals after feeds. The prefeeding CCA concentrations were highest in Group I (log mean 8.2; range 1.8--28.6 mumol/l) and lower in Groups II (7.5; 2.6--22.4 mumol/l), III (5.1; 2.1--11.1 mumol/L), and IV (2.2; 0.5--6.1 mumol/l). The mean postprandial increments correlated with maturity: the rises for Groups I--IV were 3.7, 4.3, 1.0 and 0.7 mumol/l, respectively. Peak values were consistently reached at 30 min after the start of the feed, i.e. strikingly earlier than in older children and adults. After the peaks the return to prefeeding levels occurred rapidly in Groups II--Iv but more slowly in the most premature infants (Group I). The rapid postprandial rise may be due to many factors, e.g., passive jejunal absorption, immature hepatic clearing mechanisms, or rapid transit of bile acids to the ileum. Hence, measurements of postprandial plasma bile acids would appear ill-suited for detection of disturbed ileal function in young infants. The high concentrations in healthy newborns suggest that caution is necessary in interpreting plasma bile acid concentrations during the first few weeks of life, especially in premature infants.

Cholic Acids↗

The effects of cholic acid and bile salt binding agents on 1,2-dimethylhydrazine-induced colon carcinogenesis in the rat.

The theory that bile salts may be colon tumour promoters was tested in the dimethylhydrazine (DMH)-induced rat colon cancer model. Fifty Wistar rats were randomly allocated to one of five experimental group (n = 10), all fed the same standard diet. One group served as saline-injected controls, while the other four groups received DMH (20 mg/kg body weight/rat/week s.c.) for 20 weeks. In addition, each of the DMH-injected groups concurrently received 20 weekly i.g. instillations of one of the following: cholic acid (a bile acid); cholestyramine or aluminium hydroxide (both bile acid binding agents), or water. After a years observation period, all the controls were alive and tumour-free, while all the DMH-injected rats had died of histologically proven colon cancer. Irrespective of the type of gastric instillate, there were no significant differences between the groups in terms of time to tumour presentation, survival, in the necropsy incidence of primary or metastatic colon cancer, or in the numbers of colon tumours per group. The data suggest that bile salts and bile salt binding agents are not colon tumour promoters in the rat. The bile salt theory of colon carcinogenesis may need reappraisal.

1,2-Dimethylhydrazine↗

Comparative topical pheromonotropic activity of insect pyrokinin/PBAN amphiphilic analogs incorporating different fatty and/or cholic acid components.

This study presents a comparison of the topical pheromonotropic activity in the tobacco budworm moth of a series of amphiphilic pseudopeptide analogs of the insect pyrokinin/PBAN peptide class incorporating fatty acids of varying chain lengths. While the C16 analog fails to penetrate the moth cuticle, and the C12 only moderately so, shorter chain analogs transmigrate the moth cuticle readily with decreasing cuticle-retention properties. A cholic acid analog topically induces twice the maximal pheromone titer of injected native hormone. From a pest management perspective, these non-aromatic hydrophobic components are expected to be more environmentally benign than benzenoid components previously used in topical insect peptide analogs.

Animals↗

Normal-phase liquid chromatography of plant hormones using reversed cholic acid micelles as the mobile phase.

When several plant hormones with similar structures are present in a sample, conventional analytical methods are not sufficiently selective to effectively differentiate them. However, the excellent selectivity of micellar liquid chromatography allows similarly structured compounds to be easily differentiated. We used reversed cholic acid micelles dissolved in tetrahydrofuran as the mobile phase in normal-phase chromatography of seven plant hormones. Our results conformed closely to those predicted by the pseudophase micellar liquid chromatography theory. The chromatographic efficiencies were calculated from the peak width and the retention times, and we compared these values with those obtained by reversed-phase chromatography using sodium dodecyl sulfate mobile phase in water. To test the efficiency of this selective method for the analysis of plant tissues that may also contain contaminants, we applied it to homogeneous suspensions of spiked maize roots. Recoveries ranged from 91 to 110%, the relative standard deviations were between 0.46 and 10.03%, and the detection limits were between 0.08 and 0.80 micrograms g-1.

Cholic Acids↗

Synthesis of biological precursors of cholic acid II.

This paper describes the partial syntheses of 3 alpha, 7 alpha, 12 alpha-trihydroxy-5 beta-cholestan-26-al, 7 alpha, 12 alpha, 26-trihydroxy-5 beta-cholestan-3-one and 7 alpha, 12 alpha-dihydroxy-3-oxo-5 beta-cholestan-26-al via Ag2CO3/Celite oxidation of 5 beta-cholestane-3 alpha, 7 alpha, 12 alpha, 26-tetrol. These bile alcohols were resolved by analytical and preparative TLC, characterized by gas-liquid chromatography and mass spectrometry. These compounds will be useful to delineate further the mechanism of oxidation of 5 beta-cholestane-3 alpha, 7 alpha, 12 alpha, 25-tetrol on the pathway to cholic acid.

Cholestanols↗

Cholic acid, a bile acid elicitor of hypersensitive cell death, pathogenesis-related protein synthesis, and phytoalexin accumulation in rice.

When plants interact with certain pathogens, they protect themselves by generating various defense responses. These defense responses are induced by molecules called elicitors. Since long ago, composts fermented by animal feces have been used as a fertilizer in plant cultivation, and recently, have been known to provide suppression of plant disease. Therefore, we hypothesized that the compounds from animal feces may function as elicitors of plant defense responses. As a result of examination of our hypothesis, an elicitor of rice defense responses was isolated from human feces, and its structure was identified as cholic acid (CA), a primary bile acid in animals. Treatment of rice (Oryza sativa) leaves with CA induced the accumulation of antimicrobial compounds (phytoalexins), hypersensitive cell death, pathogenesis-related (PR) protein synthesis, and increased resistance to subsequent infection by virulent pathogens. CA induced these defense responses more rapidly than did fungal cerebroside, a sphingolipid elicitor isolated from the rice pathogenic fungus Magnaporthe grisea. Furthermore, fungal cerebroside induced both types of rice phytoalexins, phytocassanes and momilactones, whereas CA mainly induced phytocassanes, but not momilactones. In the structure-activity relationship analysis, the hydroxyl groups at C-7 and C-12, and the carboxyl group at C-24 of CA contributed to the elicitor activity. These results indicate that CA is specifically recognized by rice and is a different type of elicitor from fungal cerebroside. This report demonstrated that bile acid induced defense responses in plants.

Bile↗

Characterization of a NADH:flavin oxidoreductase induced by cholic acid in a 7 alpha-dehydroxylating intestinal Eubacterium species.

A NADH:flavin oxidoreductase was partially purified (seven-fold) from an intestinal Eubacterium species V.P.I. 12708 using Bio-Gel A 0.5-M and DEAE-cellulose column chromatography. Enzyme activity was measured spectrophotometrically at 340 nm under anaerobic conditions. A molecular weight of 260 000 was estimated by gel filtration chromatography. The partially purified enzyme preparation exhibited single displacement kinetics with respect to the substrates NADH and FAD. The pH optimum under these conditions was 6.8. NADH:flavin oxidoreductase showed an absolute specificity for NADH as electron donor. However, methylene blue, 2,6-dichlorophenolindophenol, K3Fe(CN)6, menadione, riboflavin, FMN and molecular oxygen served as alternate electron acceptors with varying degrees of efficiency. Acriflavin, rotenone, o-phenanthroline, p-chloromercuribenzoate, dicoumarol and 2,4-dinitrophenol inhibited enzyme activity. Surprisingly, 0.1 mM cholic acid, but not 0.1 mM deoxycholic acid, rapidly induced NADH:flavin oxidoreductase activity in growing cultures.

Cell Fractionation↗

Gastroprotection of DNA with a synthetic cholic acid analog.

The oral delivery of functional DNA to the gastrointestinal system would constitute a desirable, noninvasive method for potentially treating a variety of diseases. The digestive process, however, remains a formidable barrier. This dilemma may be addressed by using targeted liposomes both to protect the polynucleotide and to deliver the therapeutic DNA with high tissue specificity. The present study represents the initial steps toward developing a novel gene delivery system designed to interact with the enterohepatic receptors of the small intestine. Two cholic acid esters were synthetically modified at position C(3) to incorporate a DNA-binding domain. These novel compounds were evaluated for their ability to protect DNA from the nucleases found in gastrointestinal segments. Additionally, the compounds were screened as a component of a gene delivery vector. Formulations containing the new bile salt derivatives protected DNA from degradation for more than 2 h and were capable of transfecting cultured NIH 3T3 cells.

3T3 Cells↗

Cerebrotendinous xanthomatosis: a defect in mitochondrial 26-hydroxylation required for normal biosynthesis of cholic acid.

Oxidation of side chain of 5 beta-cholestane-3 alpha,7 alpha,12 alpha-triol was studied in a patient with cerebrotendinous xanthomatosis (CTX) and in control subjects, using various subcellular fractions of liver homogenate and a method based on isotope dilution-mass spectrometry. In the control, 5 beta-cholestane-3 alpha,7 alpha,12 alpha-triol was converted into 5 beta-cholestane-3 alpha,7 alpha,12 alpha,26-tetrol and 3 alpha,7 alpha,12 alpha-trihydroxy-5 beta-cholestanoic acid by the mitochondrial fraction, and into 5 beta-cholestane-3 alpha,7 alpha,12 alpha,-25-tetrol by the microsomal fraction. In the CTX patient, liver mitochondria were completely devoid of 26-hydroxylase activity. The same mitochondrial fraction catalyzed 25-hydroxylation of vitamin D3. The microsomal fraction of liver of the subject with CTX contained more than 50-fold the normal amount of 5 beta-cholestane-3 alpha,7 alpha,12 alpha-triol. The basic metabolid defect in CTX appears to be a lack of the mitochondrial 26-hydroxylase. The excretion in the bile of 5 beta-cholestane-3 alpha,7 alpha,12 alpha,25-tetrol and 5 beta-cholestane-3 alpha,7 alpha,12 alpha,24 alpha,25-pentol observed in CTX patients may be secondary to the accumulation of the major substrate for the 26-hydroxylase, i. e., 5 beta-cholestane-3 alpha,7 alpha,12 alpha-triol, and exposure of this substrate to the normally less active microsomal 25-and 24-hydroxylases. It is concluded that the major pathway in the biosynthesis of cholic acid in human liver involves a mitochondrial C27-steroid 26-hydroxylation.

Cholestanols↗

Cholic acid biosynthesis: conversion of 5beta-cholestane-3alpha,7alpha,12alpha,25-tetrol into 5beta-cholestane-3alpha,7alpha, 12alpha,24beta,25-pentol by human and rat liver microsomes.

This paper describes the conversion of 5beta-cholestane-3alpha,7alpha,12alpha,25-tetrol into 5beta-cholestane-3alpha,7alpha,12alpha,24beta,25-pentol by liver microsomes. A sensitive radioactive assay for measuring the formation of 5beta-cholestane-3alpha,7alpha,12alpha,24beta,25-pentol was developed. Optimal assay conditions for human and rat microsomal systems were established. A higher 24beta-hydroxylation activity was detected in rat than in human liver under the conditions employed. The hydroxylation of 5beta-cholestane-3alpha,7alpha,12alpha,25-tetrol by the rat liver microsomal fraction fortified with NADPH was stimulated about two-fold by administration of phenobarbital. Phenobarbital treatment also stimulated hydroxylations at C-23, C-24alpha, and C-26. Carbon monoxide markedly inhibited all side-chain hydroxylations. In contrast, side-chain hydroxylase activities were not affected in animals deprived of food for 48 hr. These results are consistent with a previously postulated cholic acid biosynthetic pathway involving 5beta-cholestane-3alpha,7alpha,12alpha,24beta,25-pentol as a key intermediate in man and in the rat.

Animals↗