Distinct effects of three bile salts on cholesterol solubilization by oleate-monoolein-bile salt micelles.

Micellar cholesterol solubilities in bile salt-monoolein-oleic acid systems have been determined. Whatever the bile salt/oleyl compounds ratio, taurochenodeoxycholate solubilizes more cholesterol than taurocholate and much more than tauroursodeoxycholate. At pH 6.7, the cholesterol solubility limit is about the same with either oleate or monoolein. Cholesterol solubility falls in oleate-bile acid mixtures as the pH is raised. The capacity for supersaturation with cholesterol is greater for bile salt-monoolein than for bile salt-oleate micelles. For the latter it decreases as pH increases.

beta-Muricholic acid; potentiometric and cholesterol-dissolving properties.

Some physicochemical properties of beta-muricholic acid (3 alpha,6 beta,7 beta-trihydroxy-5 beta-cholanic acid), a major bile acid biosynthesized by rat liver, were determined and compared to those of ursodeoxycholic and chenodeoxycholic acids. From potentiometric studies, the following characteristics of beta-muricholic acid were shown: a low monomer solubility (13 microM), a high equilibrium precipitation pH (7.92 for 30 mM solution), an apparent critical micellar concentration of 4 mM, and a very low micellar capacity of the bile salt to dissolve the protonated bile acid. Sodium beta-muricholate solution (30 mM) poorly solubilized cholesterol, as indicated by a bile salt/cholesterol molar ratio of 1430, whereas saturation ratios obtained with chenodeoxycholate and ursoseoxycholate were 24 and 384, respectively. Sodium beta-muricholate (30 mM)/phosphatidylcholine/cholesterol mixtures contained non-micellar aggregates from very low cholesterol concentrations. At physiological phosphatidylcholine concentrations, sodium beta-muricholate (100 mM) dissolved cholesterol crystals via essentially lamellar liquid-crystal formation. These solubilizing properties might have important physiological relevance to the dissolution of cholesterol gallstones in man.

Ursodeoxycholate protects against ethanol-induced liver mitochondrial injury.

The purpose of this work was to examine whether ursodeoxycholate (UDC), a hydrophilic bile salt, could reduce mitochondrial liver injury from chronic ethanol consumption in rats. Animals were pair-fed liquid diets containing 36% of calories as ethanol or isocaloric carbohydrates. They were randomly assigned into 4 groups of 7 rats each and received a specific treatment for 5 weeks: control diet, ethanol diet, control diet + UDC, and ethanol diet + UDC. Respiratory rates of isolated liver mitochondria were measured using a Clark oxygen electrode with sodium succinate as substrate. Mitochondria from rats chronically fed ethanol demonstrated an impaired ability to produce energy. At the fatty liver stage, the ADP-stimulated respiration (V3) was depressed by 33%, the respiratory control ratio (RC) by 25% and the P/O ratio by 15%. In ethanol-fed rats supplemented with UDC, both the rate and efficiency of ATP synthesis via the oxidative phosphorylation were improved: V3 was increased by 35%, P/O by 8%. All the respiratory parameters were similar in control group and control + UDC group. On the other hand, the number and size of mitochondria were assessed by electron microscopy and computer-assisted quantitative analysis. The number of mitochondria from ethanol-treated rats was decreased by 29%, and they were enlarged by 74%. Both parameters were normalized to control values by UDC treatment. These studies demonstrate that UDC has a protective effect against ethanol-induced mitochondrial injury by improving ATP synthesis and preserving liver mitochondrial morphology. These UDC positive effects may contribute to the observed decrease in fat accumulation and may delay the progression of alcoholic injury to more advanced stages.

CYP2E1 and CYP3A1/2 gene expression is not associated with the ursodeoxycholate effect on ethanol-induced lipoperoxidation.

Ethanol is a well-known hepatotoxicant inducing steatosis and membrane lipoperoxidation. The aim of the present study was to investigate in rats, whether the protective effect of UDC on ethanol-induced lipid peroxidation may be related with CYP2E1 and CYP3A1/2 gene expression. We showed that UDC treatment in ethanol-fed rats induced a significant decrease in liver triglyceride concentration which was closely correlated with a reduction in malondialdehyde and hydroxyalkenal levels. In chronically ethanol-fed rats, CYP2E1 and CYP3A1/2 gene expressions were increased by a post-transcriptional mechanism. These inductions, mainly of CYP2E1, could take part in alcohol-induced hepatic lipoperoxidation. UDC modified neither the specific activity, nor the protein level, nor the mRNA level of CYP2E1 when compared with control. UDC supplementation to alcohol diet did not prevent the increase in CYP2E1 expression of ethanol-fed rats. Furthermore, CYP3A1/2 protein levels were similarly increased by ethanol and ethanol plus UDC treatment. Therefore, UDC protective effect against ethanol-induced lipoperoxidation was not associated with a modification of CYP2E1 and CYP3A1/2 expression.

Ursodeoxycholate improves hepatobiliary dysfunction induced by valproate-carbamazepine treatment in the rat.

Carbamazepine (CBZ) and valproate (VPA) are commonly used antiepileptic drugs. These drugs, either alone or combined, may produce hepatotoxicity. We report results of a biochemical and histological study of the liver in rats treated for eight days with VPA (500 mg/Kg/day), CBZ (200 mg/Kg/day) and VPA plus CBZ. A hepatoprotective bile salt, ursodeoxycholate (UDC, 60 mg/Kg/day) was given as a supplement to rats treated with the VPA+CBZ combination. VPA strongly modified the biliary biochemical parameters inducing hypercholeresis and hyposecretion of phospholipids. Microscopically, hepatocytes showed intense vacuolation of the peripheral cytoplasm and alterations of the mitochondrial matrix. CBZ produced increased choleresis but had no effect on biliary lipid parameters. Ultrastructurally, CBZ induced marked proliferation of the smooth endoplasmic reticulum of hepatocytes. The VPA+CBZ association produced a combination of the alterations induced independently by each drug. In both bile and plasma, increased CBZ-epoxide and decreased VPA levels were observed. The addition of UDC restored the biliary phospholipid secretion, decreased cytoplasmic vacuoles and mitochondrial alterations, and diminished the hypertrophy of smooth endoplasmic reticulum, indicating a clear beneficial effect of UDC on hepatobiliary dysfunction induced by the VPA+CBZ combination. Furthermore, the supplementation with UDC did not significantly change the plasma levels of the antiepileptic drugs.

Ursodeoxycholic acid modulates cyclosporin A oral absorption in liver transplant recipients.

The aim was to study the ursodeoxycholic acid (UDC) effect on the cyclosporin A (CsA) pharmacokinetics after oral administration of the microemulsion formulation Neoral (CsA-ME) in liver transplant recipients, and test the potential protective effect of this bile acid on liver and renal CsA-ME-induced toxicity. At entry into the study, 12 patients who underwent orthotopic liver transplantation received CsA-ME, for at least 6 months. They then received a cotreatment CsA-ME plus UDC (13.8 mg x kg(-1) x day(-1)) for three months. Blood concentrations of CsA were measured using a monoclonal antibody specific for the parent compound. The kinetic data were analysed by a mathematical model incorporating a time dependent rate coefficient for CsA intestinal absorption, before and after UDC treatment. Changes in serum markers of hepatic and renal injury were assessed. Individual serum bile acids were determined by chromatography. Serum levels of UDC increased from 3 to about 45% of total serum bile acids after UDC treatment. The estimated model parameters indicate that UDC administration modulates CsA intestinal absorption. In the nine non-cholestatic patients, UDC reduced the absorption rate and the bioavailability of CsA without modifying the elimination rate constant of CsA and the CsA pre-drug levels. In contrast, in the three cholestatic patients, the bioavailability tended to be higher and the absorption rate faster when CsA was combined with UDC. UDC significantly decreased elevated gamma-glutamyl transferase and creatinine serum levels and induced some clinical improvements such as disappearance of headaches in four patients. In conclusion, a 3-month UDC treatment modifies CsA intestinal absorption without affecting CsA elimination rate constant. On the other hand, UDC supplementation appears to improve CsA tolerability.

Glycodihydrofusidate: biliary excretion and its effect on biliary secretion of the rat.

Glycodihydrofusidate, which has the same detergent properties a bile salts, is excreted almost exclusively by the bile duct after intravenous injection in the rat. As with bile salts, it leads to a significant (P less tthan or equal to 0.05) increase in excretion of lecithins and cholesterol (0.15 mumol lecithin and 0.026 mumol cholesterol per 1 mumol of glycodihydrofusidate excreted). In addition, this drug simulataneously inhibits excretion of both endogenous bile salts and bile pigments.

[Contact litholysis of common bile duct calculi. Study of 44 patients]. / Litholyse de contact des calculs de la voie biliaire principale. Etude chez 44 malades.

OBJECTIVES: Endoscopic sphincterotomy has become a generally accepted method for extracting common bile duct stones in high risk or cholecystectomized patients. However, stone extraction is impossible by the usual methods in 5 to 10% of cases. The purpose of this study was to evaluate the effect of a recently developed solvent system in patients with large bile duct stones. METHODS: Forty four patients (15 men and 29 women, median age of years) underwent contact dissolution after unsuccessful Dormia extraction. Solvents were administered via a nasobiliary catheter in 41 patients following papillotomy and through a T-tube in 3 patients. Solvent mixtures (26 mM ethylene diamine tetraacetic acid, 40 mM sodium deoxycholate and 30% dimethyl sulfoxide in an alkaline aqueous solution; and a 70/30 dimethyl sulfoxide/methyl tert-butyl ether mixture) were infused continuously and alternatively for 2 hours. RESULTS: Bile duct stones disappeared in 13-24 hours of infusion in 11 patients. In 29 patients, a clear reduction in stone volume occurred, allowing complete endoscopic extraction of the fragments. In 4 patients, the size of the stone did not change. Only mild and transient side-effects including abdominal pain (68%), nausea (72%), vomiting (52%), diarrhea and sleepiness (50%) were observed. CONCLUSION: Direct dissolution therapy could be an effective method for the non-surgical management of large bile duct stones in selected patients when intra- or extracorporeal lithotripsy is unsuccessful.

[Ursodeoxycholic acid and prevention of tacrine-induced hepatotoxicity: a pilot study]. / Acide ursodésoxycholique et prévention de l'hépatotoxicité de la tacrine: une étude pilote.

Ursodeoxycholic acid is a protective agent against liver toxicity caused by some drugs. In the present pilot study, we assessed the effect of this bile acid on tacrine-induced hepatotoxicity. Fourteen patients with a diagnosis of Alzheimer's disease received tacrine and ursodeoxycholic acid (13 mg/kg/day) for 105 days. Serum ALAT was the main evaluation criterion. Serum levels of ALAT were compared with those of 100 patients who had been treated with tacrine in the same centre. In patients receiving ursodeoxycholic acid, ALAT serum levels were normal in 93 per cent of cases vs. 69 per cent in control patients and moderate hepatotoxicity (ULN < ALAT < 3 ULN) did not occur while it was present in 25 per cent of controls (p = 0.036). In contrast, the percentage of patients with ALAT > 3 ULN was similar in the two groups (7 per cent vs. 6 per cent). These present findings suggest that UDC could prevent moderate tacrine-induced hepatotoxicity. These results should be confirmed in a controlled therapeutical trial.

Effect of hyocholic acid on the prevention and dissolution of biliary cholesterol crystals in mice.

Gallstone prevention and dissolution were studied in a mouse model of cholesterol cholelithiasis using hyocholic acid (3 alpha, 6 alpha, 7 alpha-trihydroxy-5 beta-cholanic acid). Addition of hyocholic acid, 0.1 or 0.3%, in the lithogenic diet (1% cholesterol + 0.5% cholic acid) prevented the formation of cholesterol monohydrate crystals in 70 and 90% of cases, respectively. On the other hand, chow diet supplemented with 0.1 or 0.3% hyocholic acid dissolved cholesterol crystals in lithiasic mice in, respectively, 80 and 100% of cases within 12 days. In both protocols, biles were largely supersaturated with cholesterol; lecithin-cholesterol lamellar liquid crystals were responsible for the transport of the excess cholesterol content. The percentage of hydrophilic bile salts (hyocholic acid, hyodeoxycholic acid, beta-muricholic acid) in bile, although moderate (15-50% of total bile salts), appears to induce such liquid crystalline dispersion. This study demonstrates that the balance between hydrophilic and hydrophobic bile salts plays a major role in the prevention and dissolution of cholesterol crystals. It is also shown that the desaturation of biliary cholesterol is not a prerequisite for gallstone dissolution.

Contact solvents for common bile duct stones. Study in an in vitro system.

Cholesterol and brown pigment stones found in the common bile duct are often radiolucent and therefore indistinguishable. The purpose of this study was to define contact solvent systems able to dissolve both stone types. The influence of mucolytic agents on in vitro pigment stone dissolution was first determined. It was shown that dithioerythritol induced more rapid dissolution than N-acetylcysteine. Alternating treatment with an aqueous alkaline solvent (pH = 9.5), composed of sodium deoxycholate 50 mM, ethylenediaminetetraacetate 26 mM and dithioerythritol 50 mM, for 45 min, and an organic solvent methyl tert-butyl ether/dimethyl sulfoxide (90/10) for 15 min, was more effective for bilirubin, cholesterol, and fatty acid solubilization (p < 0.01) than using these solvents separately. The dissolution of brown stones was nearly completed within 9 h and that of mixed cholesterol stones was obtained within 3 h. We conclude that the alternating treatment described is very effective for the rapid in vitro dissolution of the two major stone types present in the bile ducts, and deserves further assessment in vivo.

Ursodeoxycholate alleviates alcoholic fatty liver damage in rats.

The hydrophilic bile salt ursodeoxycholate (UDC) improves cholestasis in several liver diseases and is in vitro an efficient membrane stabilizer. However, its action on chronic ethanol-induced liver damage is not established. We thus sought to determine the effect of UDC on chronic ethanol-induced steatosis and on liver plasma membrane fluidity in rats. Male rats were pair-fed liquid diets containing 36% of calories as ethanol (alcohol diet) or an isocaloric maltose-dextrin mixture (control diet). Four groups of 10 animals received, respectively, during 30 days: the control diet, the control diet + UDC (90 mg/kg/day), the alcohol diet, and the alcohol diet + UDC. Bile was collected for assessment of bile flow, biliary lipids, and individual bile salts. Liver lipid contents and lipid peroxidation were determined. Plasma membrane fluidity was assessed by fluorescence polarization of various probes. Alcohol treatment caused a 4-fold increase in liver triacylglycerol and cholesterol ester levels. UDC supplementation significantly reduced these increases by 50% and 40%, respectively. UDC intake was associated with a marked decrease in alcohol-induced lipid peroxidation. Bile flow, bile salt, and phospholipid secretion were slightly increased by alcohol intake. The addition of UDC-enriched bile with tauroursodeoxycholate (38%) without significantly affecting the biliary parameters. Lastly, UDC treatment almost totally prevented the 20% increase in liver plasma membrane fluidity due to chronic alcohol intake. This study shows that UDC intake, concomitant with alcohol diet, exerts a clear-cut membrane protective effect that might alleviate ethanol-induced lipid disorders.

Experimental lymphatic obstruction and fat absorption in the rabbit.

Using a previously published procedure of experimental abdominal lymphatic duct obstruction, we were unable to confirm increased faecal fat excretion after the operation. Nevertheless, the completeness of the obstruction and the huge dilatation of the lymph ducts of the villi have been verified. A spontaneous seasonal variation of faecal fat excretion has been observed in the rabbit with a maximum in October and November.

Dissolution of human brown pigment biliary stones.

The chemical dissolution of human brown pigment stones was studied using various monophasic multicomponent solvents. Among the nine solutions tested for stone powder dissolution capacity, the two most active were retained for further analysis. The solvent containing 26 mM ethylenediaminetetraacetate, 40 mM sodium deoxycholate, 10 mM monoolein and 30% dimethylsulfoxide was efficient for calcium and bilirubin solubilization. The other solvent containing dimethylsulfoxide/methyl tert-butyl ether (70:30) had a high capacity for dissolution of cholesterol and bilirubin. From in vitro stone dissolution experiments, we found that alternating treatment every 2 h with these two mixtures was more effective than using these solvents separately. Within 24 h, 90% of cholesterol, 80% of bilirubin, and 70% of calcium were dissolved. In vivo, we studied the dissolution of human stones surgically implanted in the gallbladder of 6 rabbits. Alternating perfusions with the solvents selected led to complete disappearance of stones within 16 h in 5 out of 6 cases. The residual histological toxicity in the gallbladder wall, 15 days after perfusion, was low and blood parameters did not differ from the normal values.

Hepatic uptake and biliary excretion of a bile salt analog : glycodihydrofusidate.

Glyco-24, 25-dihydrofusidate is efficiently excreted in the bile by the liver. This compound partially inhibits hepatobiliary transport of bile salts and bilirubin. In order to determine if bile salts and glycodihydrofusidate share common pathways at the hepatocyte level, we studied the effect of sodium dehydrocholate on the blood clearance of glycodihydrofusidate. Two groups of rats were perfused, controls with 0.15M NaCl, and test animals with 10 micronmol + min-(1) + kg(1) of dehydrocholate; both groups received 1 micronCi of 14C-glycodihydrofusidate intravenously. Carotid blood was removed every minute and the disappearance of radioactivity from the blood was monitored. The results are consisgent with a theoretical model of two compartments. The experimental curves were fit to the sum of exponentials.

Comparative effects of cholic, chenodeoxycholic, and ursodeoxycholic acids on micellar solubilization and intestinal absorption of cholesterol.

Cholesterol absorption was studied in mice receiving cholic, chenodeoxycholic, or ursodeoxycholic acids (0.2% of the diet) for 2 months. Cholesterol absorption was greater with cholic acid (79%) than with chenodeoxycholic acid feeding (60%) and the lowest levels were observed during ursodeoxycholic acid feeding (37%). Under the three diets, bile acid pool and bile acid secretion were not different. Biliary cholesterol secretion was increased by cholic acid. The bile acid fed represents at least 80% of total bile acids. Micellar solubilization of oleic acid and cholesterol in the presence of each tauro-conjugated bile salt (10 mM) was determined in vitro by the coprecipitation method. Whatever the pH conditions, taurochenodeoxycholate solubilized significantly more cholesterol and more oleic acid than taurocholate. Tauroursodeoxycholate had the poorest detergent properties for both lipids. The differences between the three bile salts for cholesterol solubilization were enlarged by lowering pH and by high oleic acid concentration. Therefore the decrease in cholesterol absorption observed during ursodeoxycholic acid feeding could be explained by the poor detergent properties of this bile salt species. On the other hand, there is no relationship between the detergent properties of taurochenodeoxycholate and taurocholate and their effects on cholesterol absorption in mice. These results suggest that, in this particular case, micellar solubilization is not the rate limiting step in cholesterol absorption.

Effect of endoscopic sphincterotomy on bile lithogenicity in patients with gallbladder in situ.

BACKGROUND AND STUDY AIMS: Endoscopic sphincterotomy results in a continuous flow of bile into the duodenum and consequently leads to an increase in the frequency of enterohepatic bile acid cycling. Because bile acids are the driving force of biliary secretion, sphincterotomy may affect bile genesis. The present study was undertaken to determine the influence of endoscopic sphincterotomy on bile composition. PATIENTS AND METHODS: The cholesterol saturation index and the bile acid pattern were determined in the gallbladder bile of lithiasis patients with (group III) or without sphincterotomy (group I), and in the hepatic bile of patients with gallbladder in situ who were checked at 3 months after the endoscopic procedure (group II). Stones from each patient were examined for chemical composition and microstructure. RESULTS: All the patients had cholesterol stones. After endoscopic sphincterotomy the molar percentages of cholesterol in the gallbladder bile of group III and in the hepatic bile of group II were significantly lower (-31% and -46% respectively) than in group I. Similarly, the cholesterol saturation index in the hepatic bile (0.79) and the gallbladder bile (0.86) from patients who had undergone sphincterotomy indicated undersaturation whereas bile from group I was oversaturated (1.25). On the other hand, endoscopic sphincterotomy did not modify the hydrophobicity index of the bile acid pool, even though deoxycholate content increased. CONCLUSIONS: Endoscopic sphincterotomy causes a marked decrease in the lithogenicity of bile and thus may prevent the risk of recurrence of cholesterol lithiasis.

Effects of tauroursodeoxycholate solutions on cyclosporin A bioavailability in rats.

Cyclosporin A (CsA) exhibits poor bioavailability after oral administration of Sandimmune, with wide intra- and interindividual variations. Our study sought to determine the effect of the coadministration of CsA standard oily formulation and tauroursodeoxycholate (TUDC) and that of an aqueous micellar solution containing TUDC, monoolein, and CsA in promoting and regulating CsA bioavailability in the rat Pharmacokinetic parameters of CsA were determined in fasted rats after either an intravenous administration (5 mg/kg) or a single oral CsA dose of 10 mg/kg. Compared with oral Sandimmune, the CsA micellar solution significantly improved the CsA bioavailability by 160% and decreased the interindividual variability in bioavailability expressed as percent coefficient of variation from 32% to 15%. The concentration-time profile was modified with a 3.5-fold increase in C(max), a reduction of t(max), and an increased trough concentration. Bioavailability slightly improved in rats receiving standard oily solution plus concomitant TUDC, although not significantly. Data indicate that the structure of the CsA carriers greatly affect drug bioavailability and that aqueous micellar solutions of CsA-TUDC-monoolein constitute efficient vehicles, thus providing for CsA high absorption with low variability.