Bile acid synthesis in man: metabolism of 7 -hydroxycholesterol- 14 C and 26-hydroxycholesterol- 3 H

Female sex steroid induced epithelial changes in the gallbladder of the ovariectomized Syrian hamster

Ovariectomized Syrian hamsters treated by female sex steroids during a 1-month period show gallbladder surface epithelial changes in the fundic area consistent with apical bulging and decapitations of the epithelial cells. These events were detected in the infundibulum and the fundic or body regions of estrogen- and estrogen+progesterone-treated hamsters. In control hamsters, these events were restricted to the region in the vicinity of the bile duct. Following steroid treatment, intraluminal deposits detected resembled Ca-bilirubinate deposits described in previous studies while decapitations are similar to endometrial epithelium changes associated with hormonal physiological changes or treatments. Moreover some small electron-dense deposits are comparable to those found in human cholesterol gallstones. This report indicates that, besides an alteration in bile composition, cell fragments originating from the surface epithelium of the bile duct and/or of the gallbladder mucosal epithelium could participate in gallstone nucleation.

Cyclosporin A blocks bile acid synthesis in cultured hepatocytes by specific inhibition of chenodeoxycholic acid synthesis

Bile acid synthesis, determined by conversion of [4-14C]cholesterol into bile acids in rat and human hepatocytes and by measurement of mass production of bile acids in rat hepatocytes, was dose-dependently decreased by cyclosporin A, with 52% (rat) and 45% (human) inhibition of 10 microM. The decreased bile acid production in rat hepatocytes was due only to a fall in the synthesis of beta-muricholic and chenodeoxycholic acids (-64% at 10 microM-cyclosporin A), with no change in the formation of cholic acid. In isolated rat liver mitochondria, 26-hydroxylation of cholesterol was potently inhibited by the drug (concn. giving half-maximal inhibition = 4 microM). These results suggest that cyclosporin A blocks the alternative pathway in bile acid synthesis, which leads preferentially to the formation of chenodeoxycholic acid.

Potential bile acid precursors in plasma--possible indicators of biosynthetic pathways to cholic and chenodeoxycholic acids in man

The plasma concentrations of 3 beta-hydroxy-5-cholestenoic acid, 3 beta,7 alpha-dihydroxy-5-cholestenoic acid and 7 alpha-hydroxy-3-oxo-4-cholestenoic acid have been compared with that of 7 alpha-hydroxy-4-cholesten-3-one in healthy subjects and in patients with an expected decrease or increase of the bile acid production. In controls and patients with liver disease, the level of 7 alpha-hydroxy-3-oxo-4-cholestenoic acid was positively correlated to that of 3 beta,7 alpha-dihydroxy-5-cholestenoic acid and not to that of 7 alpha-hydroxy-4-cholesten-3-one. In patients with stimulated bile acid formation the levels of the acids were not correlated to each other but there was a significant positive correlation between the levels of 7 alpha-hydroxy-3-oxo-4-cholestenoic acid and 7 alpha-hydroxy-4-cholesten-3-one. These findings indicate that the precursor of 7 alpha-hydroxy-3-oxo-4-cholestenoic acid differs depending on the activity of cholesterol 7 alpha-hydroxylase. Since the activity of this enzyme is reflected by the level of 7 alpha-hydroxy-4-cholesten-3-one in plasma the findings are compatible with a formation of 7 alpha-hydroxy-3-oxo-4-cholestenoic acid from 3 beta,7 alpha-dihydroxy-5-cholestenoic acid when the rate of bile acid formation is normal or reduced and from 7 alpha-hydroxy-4-cholesten-3-one under conditions of increased bile acid synthesis. In support of this interpretation, 7 alpha,26-dihydroxy-4-cholesten-3-one was identified at elevated levels in plasma from patients with ileal resection or treated with cholestyramine. The levels of 7 alpha,12 alpha-dihydroxy-4-cholesten-3-one were also higher than normal in these patients. Based on these findings and previous knowledge, a model is proposed for the biosynthesis of bile acids in man. Under normal conditions, two major pathways, one "neutral" and one "acidic" or "26-oxygenated", lead to the formation of cholic acid and chenodeoxycholic acid, respectively. These pathways are separately regulated. When the activity of cholesterol 7 alpha-hydroxylase is high, the "neutral" pathway is most important whereas the reverse is true when cholesterol 7 alpha-hydroxylase activity is low. In cases with enhanced activity of cholesterol 7 alpha-hydroxylase, the "neutral" pathway is connected to the "acidic" pathway via 7 alpha,26-dihydroxy-4-cholesten-3-one, whereas a flow from the acidic pathway to cholic acid appears to be of minor importance.

Metabolism of 3 beta-hydroxycholest-5-en-26-oic acid in hamsters

Metabolism of 26-hydroxycholesterol to 3 beta-hydroxychol-5-en-24-oic acid and other C24-bile acids has been expected to occur by way of 3 beta-hydroxycholest-5-en-26-oic acid in studies in vitro. 3 beta-Hydroxycholest-5-en-26-oic acid was infused intravenously into bile fistula hamsters and the following C24-bile acids were identified: 3 beta-hydroxychol-5-en-24-oic acid, lithocholic acid, chenodeoxycholic acid, and a small amount of cholic acid.

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.

The role of peroxisomal fatty acyl-CoA beta-oxidation in bile acid biosynthesis

The physiological role of the peroxisomal fatty acyl-CoA beta-oxidizing system (FAOS) is not yet established. We speculated that there might be a relationship between peroxisomal degradation of long-chain fatty acids in the liver and the biosynthesis of bile acids. This was investigated using [1-14C]butyric acid and [1-14C]lignoceric acid as substrates of FAOS in mitochondria and peroxisomes, respectively. The incorporation of [14C]lignoceric acid into primary bile acids was approximately four times higher than that of [14C]butyric acid (in terms of C-2 units). The pools of these two fatty acids in the liver were exceedingly small. The incorporations of radioactivity into the primary bile acids were strongly inhibited by administration of aminotriazole, which is a specific inhibitor of peroxisomal FAOS in vivo [F. Hashimoto and H. Hayashi (1987) Biochim. Biophys. Acta 921, 142-150]. Aminotriazole inhibited preferentially the formation of cholate, the major primary bile acid, from both [14C]lignoceric acid and [14C]butyric acid, rather than the formation of chenodeoxycholate. The former inhibition was about 70% and the latter was approximately 40-50%. In view of reports that cholate is biosynthesized from endogenous cholesterol, the above results indicate that peroxisomal FAOS may have an anabolic function, supplying acetyl CoA for bile acid biosynthesis.

Cholesterol and bile acid synthesis in Hep G2 cells. Metabolic effects of 26- and 7 alpha-hydroxycholesterol

1. Using a human hepatoma (Hep G2) cell line that continually synthesizes 3 beta-hydroxy-5-cholenoic acid, lithocholic acid, chenodeoxycholic acid and cholic acid we have determined the metabolism and biological effects of 26-hydroxycholesterol and 7 alpha-hydroxycholesterol. 2. Addition of 26-hydroxycholesterol to the medium (6 microM) downregulated cholesterol and chenodeoxycholic acid synthesis. 3. The predominant metabolite of 26-hydroxycholesterol was 3 beta-hydroxy-5-cholenoic acid. 4. Cholesterol synthesis was not affected by the addition of 7 alpha-hydroxycholesterol (6 and 12 microM). The predominant metabolite of 7 alpha-hydroxycholesterol was chenodeoxycholic acid. 5. In Hep G2 cells 7 alpha-hydroxylation of 26-hydroxycholesterol is not well expressed.

Delta 4-3-oxosteroid 5 beta-reductase deficiency described in identical twins with neonatal hepatitis. A new inborn error in bile acid synthesis

A new inborn error in bile acid synthesis, manifest in identical infant twins as severe intrahepatic cholestasis, is described involving the delta 4-3-oxosteroid 5 beta-reductase catalyzed conversion of the key intermediates, 7 alpha-hydroxy-4-cholesten-3-one and 7 alpha,12 alpha-dihydroxy-4-cholesten-3-one for chenodeoxycholic and cholic acid synthesis, to the respective 3 alpha-hydroxy-5 beta (H) products. This defect was detected by fast atom bombardment ionization-mass spectrometry from an elevated excretion and predominance of taurine conjugated unsaturated hydroxy-oxo-bile acids. Gas chromatography-mass spectrometry confirmed these to be 7 alpha-hydroxy-3-oxo-4-cholenoic and 7 alpha,12 alpha-dihydroxy-3-oxo-4-cholenoic acids (75-92% of total). Fasting serum bile acid concentrations were greater than 37 mumol/liter; chenodeoxycholic acid was the major bile acid, but significant amounts of allo(5 alpha-H)-bile acids (approximately 30%) were present. Biliary bile acid concentration was less than 2 mumol/liter and consisted of chenodeoxycholic, allo-chenodeoxycholic, and allo-cholic acids. These biochemical findings, which were identical in both infants, indicate a defect in bile acid synthesis involving the conversion of the delta 4-3-oxo-C27 intermediates into the corresponding 3 alpha-hydroxy-5 beta(H)-structures, a reaction that is catalyzed by a delta 4-3-oxosteroid-5 beta reductase enzyme. This defect resulted in markedly reduced primary bile acid synthesis and concomitant accumulation of delta 4-3-oxo-and allo-bile acids. These findings indicate a pathway in bile acid synthesis whereby side chain oxidation can occur despite incomplete alterations to the steroid nucleus, and lend support for an active delta 4-3-oxosteroid 5 alpha-reductase catalyzing the conversion of the delta 4-3-oxosteroid intermediates to the respective 3 alpha-hydroxy-5 alpha(H)-structures.

Alcohol protects against cholesterol gallstone formation

Epidemiologic studies have suggested that alcohol intake may protect against cholelithiasis. Gallstone formation was studied in 20 prairie dogs fed a 0.4% cholesterol-supplemented liquid diet. In ten animals, ethanol provided 35% of total calories. In ten pair-fed controls, ethanol was replaced with isocaloric maltose. After 3 months the gallbladders were inspected for gallstones, and gallbladder bile was analyzed. Cholesterol macroaggregates were present in all controls and pigment concretions were noted in five. No stones were observed in ethanol-fed animals. Bile in the ethanol group contained less cholesterol than the controls (5.60 +/- 0.71 vs. 9.16 +/- 0.61 mmol/L, p less than 0.05) while phospholipids, total bile acids, and bilirubin were unchanged. The resulting cholesterol saturation index was reduced in the ethanol group (0.81 vs. 1.22, p less than 0.05). The ratios of trihydroxy to dihydroxy bile acids were also different (2.07 +/- 0.25 in ETOH vs. 3.29 in controls, p less than 0.05). The bile calcium concentration was higher in control animals presumably secondary to the use of complex sugars (5.36 +/- 0.37 vs. 3.77 +/- 0.32 mmol/L, p less than 0.05). These results confirm that ethanol inhibits cholesterol gallstone formation. They further suggest that this effect is dependent on reductions of biliary cholesterol and selective changes in bile acid concentrations.

Cholesterol synthesis in the pathogenesis of lithocholic acid-induced cholestasis

Lithocholic acid (LCA)-induced intrahepatic cholestasis is associated with increased de novo synthesis of hepatic cholesterol and augmented cholesterol content of the liver cell plasma membrane fraction enriched in bile canalicular complexes (BCM). To determine whether inhibition of cholesterol synthesis could prevent LCA-induced cholestasis, adult male Wistar rats were treated daily with the hypocholesterolemic agents, clofibrate (250 mg/kg) or mevinolin (25 mg/kg), for one, two or four days. After bile duct cannulation and bile collection for one hr, the animals were injected intravenously with 120 mumoles/kg of LCA or its carrier (albumin). Cholesterol synthesis was measured in liver homogenates, and its contribution to the BCM was estimated. LCA reduced bile flow by 51%, 35% and 25% after clofibrate pretreatment for one, two and four days, respectively, and by 51%, 30% and 42% in mevinolin-pretreated animals after one, two and four days. In control animals, cholesterol synthesis and the contribution of newly synthesized cholesterol in the BCM were increased after LCA injection. However, despite that cholesterol synthesis and the contribution of newly synthesized cholesterol in the BCM were reduced in drug-pretreated rats, LCA injection caused a relative increase in these parameters of a magnitude similar to that observed in controls. Thus, the ability of LCA injection to augment de novo cholesterol synthesis and its transport to the BCM may be an important pathogenetic step in the development of cholestasis.

Regulation of low density lipoprotein metabolism by 26-hydroxycholesterol in human fibroblasts

Oxygenated derivatives of cholesterol are believed to play a role in cellular cholesterol homeostasis through the feed-back control of its biosynthesis. We report that 26-hydroxycholesterol inhibits the specific binding, uptake and degradation of 125I-LDL in human fibroblasts. The effect is dose-dependent, and saturation kinetics indicates a reduction of LDL-binding sites with no effect on ligand affinity. The results support a possible role of 26-hydroxycholesterol, a physiological oxysterol, in the regulation of cellular cholesterol homeostasis.

Regurgitant bile acids and mucosal injury of the gastric remnant after partial gastrectomy

Three groups, each consisting of seven patients who had undergone either Billroth I, Billroth II, or pylorus-preserving gastrectomies, were evaluated more than 18 months postoperatively in terms of concentration and amount of bile acids in the gastric aspirate and histologic changes in the gastric remnant mucosa. Concentrations of bile acids were determined by gas chromatography and mucosal specimens were obtained by endoscopic biopsy. The total bile acid concentration and all of the individual fractional bile acid levels, whether free or conjugated, were significantly higher in the Billroth II group than in the other two groups. The amount of gastric aspirate was also highest in the Billroth II group. Endoscopic biopsy revealed glandular dysplasia to be predominantly in the Billroth II group. The presence of bile acids in the gastric remnant may contribute to mucosal injury, possibly leading to cancer in the gastric remnant, especially after the Billroth II operation.

Familial giant cell hepatitis associated with synthesis of 3 beta, 7 alpha-dihydroxy-and 3 beta,7 alpha, 12 alpha-trihydroxy-5-cholenoic acids

Urinary bile acids from a 3-mo-old boy with cholestatic jaundice were analyzed by ion exchange chromatography and gas chromatography-mass spectrometry (GC-MS). This suggested the presence of labile sulfated cholenoic acids with an allylic hydroxyl group, a conclusion supported by analysis using fast atom bombardment mass spectrometry (FAB-MS). The compounds detected by FAB-MS were separated by thin layer chromatography and high performance liquid chromatography. The sulfated bile acids could be solvolyzed in acidified tetrahydrofuran, and glycine conjugates were partially hydrolyzed by cholylglycine hydrolase. Following solvolysis, deconjugation, and methylation with diazomethane, the bile acids were identified by GC-MS of trimethylsilyl derivatives. The major bile acids in the urine were 3 beta,7 alpha-dihydroxy-5-cholenoic acid 3-sulfate, 3 beta,7 alpha,12 alpha-trihydroxy-5-cholenoic acid monosulfate, and their glycine conjugates. Chenodeoxycholic acid and cholic acid were undetectable in urine and plasma. The family pedigree suggested that abnormal bile acid synthesis was an autosomal recessive condition leading to cirrhosis in early childhood.

Effects of bile acids and endotoxin on the function and morphology of cultured hamster Kupffer cells

The mechanisms of hepatic reticuloendothelial cell dysfunction in obstructive jaundice were investigated using cultured hamster Kupffer cells. The introduction of free bile acids, cholic acid (CA) at concentrations over 2 mM and chenodeoxycholic acid (CDCA) over 1 mM inhibited colloidal carbon pinocytosis. CA and CDCA at concentrations over 0.5 mM inhibited IgG-coated sheep red blood cell phagocytosis. With the application of conjugated bile acid and endotoxin at concentrations over 50 micrograms/ml, endocytic function was inhibited. With bile acids, a dose-dependent increase in the concentration of beta-glucuronidase occurred in the culture medium, and with endotoxin a time-dependent increase in beta-glucuronidase was noted. Bile acids produced alterations in cell organelles before destruction of the cell membrane. The presence of endotoxin led to the appearance of large vacuoles in the cytoplasm. These observations suggest that bile acids and endotoxin inhibit Kupffer cells by different mechanisms. We tentatively conclude that bile acids rather than endotoxin influence Kupffer cells in vivo.

Bile acids in deermice lacking liver alcohol dehydrogenase

Liver alcohol dehydrogenase (EC 1.1.1.1) is believed to catalyze the oxidation of 26-hydroxylated intermediates in the biosynthesis of bile acids from cholesterol. We have therefore analyzed the composition and size of the bile acid pool in deer-mice genetically lacking alcohol dehydrogenase. Cholic acid was found to be the major primary bile acid accompanied by small amounts of chenodeoxycholic acid. Variable amounts of secondary bile acids were also present, mainly deoxycholic acid and 3 alpha, 12 alpha-dihydroxy-7-oxo-5 beta-cholanoic acid. The same bile acids were found in animals with normal levels of alcohol dehydrogenase. The pool of bile acids in the gallbladder, small intestine and large intestine varied between 4.2 and 8.4 mumol in four animals lacking alcohol dehydrogenase and between 6.0 and 8.4 mumol in four control animals. Ethanol did not influence pool size or composition of bile acids in the animal studied. It is concluded that alcohol dehydrogenase is not obligatory for normal bile acid biosynthesis.

Deoxycholic and sulpholithocholic acid concentrations in serum during infancy and childhood

The concentrations of the two secondary bile acids (deoxycholic (DCA) and sulpholithocholic (SLCA) acid) were determined by radioimmunoassays in the serum of infants and children at ages ranging from 1 hour to 15 years. The same bile acids were measured also in the umbilical cord serum. The concentrations of the secondary bile acids in the serum of 1-hour old infants corresponded to those in the umbilical cord serum. Secondary bile acid serum concentrations were after the age of 7 days and up to the age of 3 to 6 months significantly lower than those in the umbilical cord serum. After the age of 6 months a significant increase in DCA serum concentrations could be shown. During the first 6 months of life DCA concentrations were clearly lower than those of SLCA. Our observations suggest that in the perinatal period DCA is mainly of maternal origin and that an alternate hepatic pathway may exist for the synthesis of lithocholic acid in early infancy.

Preparation and antigenic property of methyl 3 beta-hydroxy-19-oxo-5-cholen-24-oate 19-(O-carboxymethyl) oxime-bovine serum albumin conjugate

The preparation and antigenic property of 3 beta-hydroxy-5-cholen-24-oic acid-bovine serum albumin (BSA) conjugate in which the hapten is linked to the carrier protein through an (O-carboxymethyl) oxime bridge at the C-19 position on the steroid nucleus is described. Antibody raised against antigen in the rabbit possessed high titer and specificity to 3 beta-hydroxy-5-cholen-24-oic acid, exhibiting no significant cross-reactions with various bile acids.

Cholest-5-ene-3 beta, 26-diol: synthesis and biomedical use of a deuterated compound

To further studies of the metabolism of 26-hydroxycholesterol in fetal and neonatal life, a deuterated compound was prepared from kryptogenin by Clemmensen reduction. The spectra of the deuterated 26-hydroxycholesterol showed that five to nine deuterium atoms were incorporated per 26-hydroxycholesterol molecule, with the maximum incorporation of eight deuterium atoms. The deuterated compound was recovered unchanged from the feces of a child following oral administration. Comparison of the ratio of deuterated to protium compound indicated the presence of an endogenous pool of 26-hydroxycholesterol. Parenteral administration of the compound to a hamster indicated metabolism to deuterated chenodeoxycholic acid. The compound is useful as an isotope tracer for studies of the endogenous metabolism of 26-hydroxycholesterol.

Bile acid metabolism in cirrhosis. VIII. Quantitative evaluation of bile acid synthesis from [7 beta-3H]7 alpha-hydroxycholesterol and [G-3H]26-hydroxycholesterol

In order to evaluate more definitively the observed aberrations in the synthesis of cholic and chenodeoxycholic acids in patients with advanced cirrhosis, two bile acid biosynthesis pathways were examined by determining the efficiency of conversion of [3H]7 alpha-hydroxycholesterol and [3H] 26-hydroxycholesterol to primary bile acids. Bile acid kinetics were determined by administration of [14C]cholic and [14C]chenodeoxycholic acids. Cholic acid synthesis in cirrhotic patients was markedly depressed (170 vs. 927 mumoles per day)( while chenodeoxycholic acid synthesis was reduced to a much lesser degree (227 vs. 550 mumoles per day). The administration of [3H]7 alpha-hydroxycholesterol allowed for an evaluation of the major pathway of bile acid synthesis via the 7 alpha-hydroxylation of cholesterol. This compound was efficiently incorporated into primary bile acids by the two normal subjects (88 and 100%) and two cirrhotic patients (77 and 91%). However, the recovery of the label in cholic acid was slightly less in cirrhotic patients than in normal subjects. [3H]26-hydroxycholesterol was administered to ascertain the contribution of the 26-hydroxylation pathway to bile acid synthesis. All study subjects showed poor conversion (9 to 22%) of this intermediate into bile acids. The results of this study suggest that a major block in the bile acid synthesis pathway in cirrhosis is at the level of 7 alpha-hydroxylation of cholesterol (impairment of 7 alpha-hydroxylase) and /or in the feedback triggering mechanism regulating bile acid synthesis. The data also suggest that the 26-hydroxylation pathway in normal subjects and patients with cirrhosis is a minor contributor to synthesis of the primary bile acids. Therefore, the relative sparing of chenodeoxycholic acid synthesis observed in cirrhotic patients is not due to preferential synthesis of this bile acid via the 26-hydroxylation pathway.

A quantitative evaluation of the conversion of 25-hydroxycholesterol to bile acids in man

The present study was directed toward providing additional information in man on the nature of a potential alternative pathway to cholic acid not involving an initial 7 alpha-hydroxylation of cholesterol. Two bile fistula patients and one normal subject each received 25-hydroxy[G-3H]cholesterol; [14C]cholic and [14C]chenodeoxycholic acids were also simultaneously administered to one bile fistula patient and normal subject. The labeled 25-hydroxycholesterol was found to be poorly converted to primary bile acids by all three patients; the range of conversion was 9.7 to 18.9%. Cholic acid was favored over chenodeoxycholic acid by a margin of about 1.4/1. It is concluded that a pathway to primary bile acid via the 25-hydroxylation of cholesterol is of minor importance under conditions of normal or accelerated synthesis in man.

Effects of acute and chronic ethanol intake on bile acid metabolism

Ethanol has been demonstrated to cause aberrations in lipoprotein metabolism, cholesterol synthesis, biliary secretion, and bile acid synthesis. Although there is interdependency of cholesterol and bile acid metabolism, a role of ethanol-induced lipid abnormalities in altering bile acid synthesis has not been found. The direct effects of ethanol administration on bile acid metabolism have been studied in animals and vary with the experimental design. Acutely, ethanol causes decreased bile acid secretion and synthesis, but other effects are less well defined. Chronic ethanol use in man may result in cirrhosis, a condition in which abnormalities of bile acid metabolism have been described in detail. Cholic acid synthesis and pool size are markedly depressed in advanced cirrhosis. Chenodeoxycholic acid synthesis is affected less than cholic acid synthesis, probably because 12 alpha-hydroxylase activity is markedly depressed in cirrhosis, although other steps may also be influenced such as 7 alpha-hydroxylation of cholesterol or availability of cholesterol precursor. The deoxycholic acid pool is depressed probably because of changes in fecal flora. Despite the decrease in total bile acid pool, lithogenicity of bile is not increased in cirrhotic patients because of a concomitant decline in cholesterol and phospholipid secretion. Changes in hepatic blood flow and hepatic extraction cause an increase in plasma bile acid levels which may have clinical relevance.

Microflora and deconjugation of bile acids in alkaline reflux after partial gastrectomy

It has been postulated that reflux of bile into the stomach promotes gastric carcinogenesis. Bile-stained aspirates from 50 asymptomatic patients, partially gastrectomized more than 10 years earlier, were examined bacteriologically and with regard to conjugated and deconjugated bile acids. Endoscopic biopsies showed atrophic gastritis in all patients, cancer in two and severe dysplasia in another two. pH in the reflux aspirates was 7.3 +/- 0.4 (mean +/- standard deviation). Bacterial cultures were positive in all patients studied. Fecal type flora, mostly E. coli, klebsiella and Clostridium perfringens, was found in 85% of the patients. Total bile acids were found to be 2.6 +/- 2.0 mg/ml, 23% of which were deconjugated. Deoxycholic acid, known to promote carcinogenesis in animals, amounted to 27% of total bile acids and deconjugated deoxycholic acid was 5% of total bile acids. The mostly anaerobic microflora and the presence of mainly free secondary and primary bile acids may contribute to the high incidence of cancer in the gastric remnant observed after Billroth I or II operations.

[Atypical bile acids (author's transl)]

The metabolism of bile acids in man is disturbed under the conditions of cholestasis. Besides of the main bile acids atypical bile acids can be found, which are mainly eliminated by renal excretion as sulphate esters and glucuronides. The pattern of urinary bile acids up to now renders no conclusions with respect to the underlying disease, although intrahepatic cholestasis seems to be in some way connected with disturbances in the metabolism of 3 beta-hydroxy-5-cholenoic acid, a bile acid, which exerts cholestatic effects by itself. The metabolites to be found seem to reflect a derepression of a genotypical synthesis program, which is not phenotypically apparent in healthy adults, but which may have been active during prenatal developmental stages of the liver.

Solution properties of sulfated monohydroxy bile salts. Relative insolubility of the disodium salt of glycolithocholate sulfate

Physical-chemical properties of the major sulfated monohydroxy bile salts of man are described. In general, the sulfates are significantly more water-soluble than the non-sulfated species as a result of lower critical micellar temperatures, high aqueous monomeric solubilities and critical micellar concentrations. Nevertheless, at 37 degrees C the disodium salt of glycolithocholate sulfate, the major monohydroxy bile salt of man is not more soluble than its non-sulfated form. Since aqueous solubility correlates inversely with the cholestatic potential of bile salts, our results suggest that this sulfate may be potentially hepatoxic. Micellar solubility of phosphatidylcholine and cholesterol by the majority of non-sulfated and sulfated monohydroxy bile salts is slight. Nonetheless, phosphatidylcholine is very well solubilized by taurolithocholate sulfate but cholesterol solubility is not increased appreciably. Cholesterol saturation in model bile systems of taurochenodeoxycholate and phosphatidylcholine is impaired by the addition of sulfated lithocholate conjugates but with physiological bile salt compositions this reduction is not significant.

Itch in liver disease: facts and speculations

Pruritus in hepatobiliary disease is commonly believed to be caused by retention of bile acids with their sequestration in the skin. HOwever, we have recently demonstrated that skin levels of bile acids in patients with cholestasis correlate poorly with pruritus. In this report, we present additional data concerning the relationship of pruritus to bile acid retention: (1) the urinary excretion of sulfated and nonsulfated bile acids was not significantly different in patients with cholestasis who itched compared to those who did not; (2) one patient with itch associated with a liver abscess had normal levels of bile acids in serum, skin, and urine; (3) patients with primary biliary cirrhosis who itched had lower serum bile acid levels than patients with mechanical biliary obstruction who did not itch.These studies support our premise that pruritus in hepatobiliary diseases is not directly related to bile acid retention. They suggest that the type of cholestatic disorder, and not simply the magnitude of the cholestasis, as estimated by the elevation of serum bile acids, is important. We propose that the agent responsible for pruritus is produced in response to cholestasis, possibly through activation of the alternate pathway of bile acid synthesis. Properties of the hypothetical pruritogen are discussed.