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Role of bile acids and bile acid binding agents in patients with collagenous colitis.

BACKGROUND: In a retrospective study bile acid malabsorption was observed in patients with collagenous colitis. AIMS: To study the occurrence of bile acid malabsorption and the effect of bile acid binders prospectively in patients with chronic diarrhoea and collagenous colitis. METHODS: Over 36 months all patients referred because of chronic diarrhoea completed a diagnostic programme, including gastroscopy with duodenal biopsy, colonoscopy with biopsies, and the (75)Se-homocholic acid taurine ((75)SeHCAT) test for bile acid malabsorption. Treatment with a bile acid binder (cholestyramine in 24, colestipol in three) was given, irrespective of the results of the (75)SeHCAT test. RESULTS: Collagenous colitis was found in 28 patients (six men, 22 women), 27 of whom had persistent symptoms and completed the programme. Four patients had had a previous cholecystectomy or a distal gastric resection. The (75)SeHCAT test was abnormal in 12/27 (44%) of the collagenous colitis patients with (75)SeHCAT values 0.5-9.7%, and normal in 15 patients (56%). Bile acid binding treatment was followed by a rapid, marked, or complete improvement in 21/27 (78%) of the collagenous colitis patients. Rapid improvement occurred in 11/12 (92%) of the patients with bile acid malabsorption compared with 10/15 (67%) of the patients with normal (75)SeHCAT tests. CONCLUSION: Bile acid malabsorption is common in patients with collagenous colitis and is probably an important pathophysiological factor. Because of a high response rate without serious side effects, bile acid binding treatment should be considered for collagenous colitis, particularly patients with bile acid malabsorption.

Adult↗

Bile acids in the rat: studies in experimental occlusion of the bile duct.

Bile acids in the plasma, urine, and small intestine of adult male rats with occluded bile ducts have been studied using a method of high specificity for their determination. After bile duct ligation cholic acid rapidly accumulates in the plasma for 8 hr, remains high for a further 8 hr, and subsequently diminishes; bile acids disappear from the small intestine. During the first 12 hr after bile duct ligation the excretion of trihydroxy acids in the urine was 10 times that of the dihydroxy acids. Subsequently the two excretion rates became equal. Because bile acids have been implicated in the etiology of hepatic damage following bile duct ligation, studies have been made of the effect on the liver of removing (with cholestyramine) and supplementing (with cholic acid) the intestinal bile acid pool. The addition of cholestyramine to the stock diet prevented the rise in trihydroxy bile acids after bile duct ligation, but did not prevent the development of histological abnormalities in the liver. Supplementing the diet with cholic acid raised the plasma cholic acid levels but had little effect on the hepatic histological findings.

Animals↗

Cholesterol and bile acid absorption during bile acid therapy in obese subjects undergoing weight reduction.

One of the potential complications of bile acid therapy for gallstone disease is the promotion of intestinal absorption of cholesterol, thereby increasing the influx of cholesterol in body pools. To determine whether bile acid feeding is associated with an increased absorption of intestinal cholesterol, absorption measurements were made in 8 obese subjects given chenodeoxycholic acid (CCDA) or Bilron (750 mg/day). The bile acids were given in random order, separated by control periods, in patients undergoing weight reduction. Absorption of cholesterol (mass and percent) and of bile acids were determined by a technique of combined measurements of biliary lipid secretion and fecal steroid excretion. Our data showed that during treatment with either bile acid, a marked increase in pool size and hepatic secretion of bile acids occurred. However, despite an increased flux of bile acids through the intestinal tract, there was no significant increase in cholesterol absorption as compared to control periods. Absorption rates during administration of the two bile acids were approximately the same. Furthermore, plasma cholesterol concentrations were stable throughout both control and treatment periods. Bile acid absorption remained highly efficient (greater than 96%) during all periods, even with administration of exogenous bile acids.

Adult↗

Bile-fat relationships in gastric secretory inhibition and bile flow stimulation.

The effect of intraduodenal infusion of olive oil, bile, or a mixture of olive oil and bile on pentagastrin-stimulated gastric secretion, bile flow, and serum immunoreactive secretin levels was studied in dogs. Bile alone had no effect on gastric secretion, but the mixture of bile and olive oil induced prompt, statistically significant gastric secretory inhibition. Bile had the early choleretic effect that would be expected to result from the absorption of bile salts, whereas the bile--olive oil mixture brought about a delayed amd much greater increase in bile flow rates. None of the agents given intraduodenally produced a significant change in the serum secretin level. Intravenous pentagastrin infusion caused a significant increase in rate of bile flow.

Animals↗

Changes of intrahepatic bile duct dilatation after surgery for congenital dilatation of the bile duct.

Of 47 patients suffering from congenital dilatation of the bile duct whose intrahepatic bile ducts could be clearly demonstrated by operative cholangiogram or preoperative ERCP, 39 patients (83%) had dilatation of the intrahepatic bile ducts. Follow-up studies in infants and children ranging from 1 year to 11 years after their corrective operation for congenital dilatation of the common bile duct showed no morbidity that was attributed to the presence of the dilatation of the intrahepatic bile ducts. ECHO grams in 21 patients revealed marked decrease in size of the intrahepatic bile ducts except for two patients with huge cystic dilatation of the intrahepatic bile ducts. These findings justify the employment of the standard operative procedure for the treatment of congenital dilatation of the bile duct even if it is associated with dilatation of the intrahepatic bile ducts.

Adolescent↗

Effect of acute bile acid pool depletion on total and ionized calcium concentrations in human bile.

Although calcium salts are important components of gallstones, there are few data on the total and ionized calcium content of human bile. Therefore, in 14 fasting T-tube patients studied 7-11 days after cholecystectomy, we measured bile flow, bile acid [BA], total [CaTOT] and free ionized [Ca++] calcium concentrations, in 20-30 min bile collections during acute BA pool depletion induced by 6-8 h of continuous bile drainage. During washout of the BA pool there were parallel falls in bile flow, BA output and total calcium output (correlation coefficients ranging from 0.59 to 0.99; P < 0.02-0.001). In 12 of the 14 patients, [CaTOT] also fell (from 1.84 +/- 0.29 to 1.32 +/- 0.34 mmol L-1) in parallel with [BA] (from 34.0 +/- 14.0 to 8.2 +/- 8.0 mmol L-1; r = 0.75-0.98; P < 0.005). In contrast, biliary [Ca++] remained virtually unchanged. These data suggest that the BAs are linked to the bound, rather than to the free, ionized, fraction of biliary calcium, which is consistent with in vivo calcium binding by BAs. A model is proposed in which BA-induced biliary calcium secretion results from (i) bile acid-induced water flow via solvent drag; and (ii) calcium binding in the bile canaliculus by bile acids, which induces paracellular diffusion of Ca++, thereby maintaining [Ca++] independent of [BA].

Adult↗

Influence of bile salts on the endogenous excretion of bile pigments.

Effect of the infusion of glycodeoxycholate (GDC), taurocholate (TC) and dehydrocholate (DHC) on bile flow and on bile salt, biliary lipid and bile pigment secretion, has been studied in pentobarbital-anesthetized rabbits. GDC increased bile flow the most, while DHC increased it more than TC. The different choleretic actions of these bile salts cannot be explained by means of variations in their capacity to form micelles. Only GDC and TC were able to stimulate biliary lipid secretion, which suggests that both bile salts increase the formation of mixed micelles. GDC and TC to a lesser extent increased bile pigment excretion, DHC being without effect. These results favour the hypothesis that micellar binding could be an important factor responsible for the effect of bile acids on bile pigment excretion and should not be completely ruled out.

Animals↗

Choleretic action of diosgenin is based upon the increases in canalicular membrane fluidity and transporter activity mediating bile acid independent bile flow.

It is known that diosgenin alters the lipid composition of hepatic plasma membranes as well as bile lipids. We recently reported that changes in the lipid composition of the canalicular membrane bilayer were associated with alterations of membrane fluidity. Therefore, the present study was performed to determine the effect of diosgenin on bile secretion, focusing on canalicular membrane composition, membrane fluidity, transporter expression, and transporter activity. METHODS: SD rats were fed a diet with or without diosgenin. Bile duct cannulation was done and the bile acid pool was depleted, followed by infusion of sodium taurocholate for 120 min to collect bile samples. Bile flow and the biliary output of cholesterol (Ch), phospholipids, bile salt, and total glutathione (GSH+GSSG) were estimated. Liver canalicular membrane vesicles (CMV) were prepared for the assessment of lipid composition, ATP-dependent transporters, and membrane fluidity. RESULTS: Bile flow, especially bile acid-independent fraction, was increased significantly by diosgenin. Biliary output of Ch and total glutathione were significantly increased by diosgenin. CMV fluidity and Mrp2 expression were increased by diosgenin. CONCLUSION: The fact that diosgenin increased bile flow and biliary cholesterol and glutathione output indicates a choleretic action along with enhancement of solute secretion. The increase of CMV fluidity and Mrp2 suggests that the choleretic action of diosgenin was based upon both the direct stimulation of transporter expression and indirect transporter activation by an increase of membrane fluidity.

Journal Article↗

The effect of bile, bile acids and detergents on calcium absorption in the chick.

1. Bile from rachitic or normal chicks causes an immediate increase in the intestinal absorption of soluble calcium in rachitic and vitamin D(3)-treated chicks as tested in vivo by intestinal-loop and oral-dosing methods. 2. This effect is apparently solely due to the taurine-conjugated bile acids present in the bile and is independent of the action of vitamin D. 3. Chick bile and bile acids can increase the solubility and the absorption of calcium presented as sparingly soluble calcium hydrogen phosphate. 4. In addition, bile is necessary to some extent at least for the intestinal absorption of vitamin D(3) in the chick and this would indirectly enhance the absorption of calcium. 5. Thus bile is capable of a threefold action in the absorption of calcium in the chick. It is suggested that the direct action on sparingly soluble forms of calcium is of considerable physiological importance since most of the calcium in the normal bird's diet would be in this form. 6. Bile acids enhance the absorption of calcium in all regions of the small intestine of the chick. 7. Of a range of bile acids and detergents tested for enhancement of calcium absorption, various taurine-conjugated bile acids and sodium lauryl sulphate, an anionic detergent, are effective. A non-ionic detergent (Tween 80) and a cationic detergent (Zephiran) are without effect. 8. The ability of a substance to increase directly the intestinal absorption of soluble calcium appears to depend to some extent on an anionic detergent action, i.e. the ability to form a salt or complex soluble to some extent in both aqueous and lipid phases. 9. In chicks the immediate deposition of calcium ((45)Ca) in the bones closely reflects any increase in plasma calcium radioactivity regardless of the cause of the increase and regardless of the vitamin D(3) status. Although sodium lauryl sulphate can increase markedly the calcium absorption from the gut and the immediate deposition in the bones it has no significant effect on rickets. 10. Some of the implications of these findings are discussed.

Journal Article↗

Liver receptor homologue-1 mediates species- and cell line-specific bile acid-dependent negative feedback regulation of the apical sodium-dependent bile acid transporter.

Intestinal reclamation of bile salts is mediated in large part by the apical sodium-dependent bile acid transporter (ASBT). The bile acid responsiveness of ASBT is controversial. Bile acid feeding in mice results in decreased expression of ASBT protein and mRNA. Mouse but not rat ASBT promoter activity was repressed in Caco-2, but not IEC-6, cells by chenodeoxycholic acid. A potential liver receptor homologue-1 (LRH-1) cis-acting element was identified in the bile acid-responsive region of the mouse but not rat promoter. The mouse, but not rat, promoter was activated by LRH-1, and this correlated with nuclear protein binding to the mouse but not rat LRH-1 element. The short heterodimer partner diminished the activity of the mouse promoter and could partially offset its activation by LRH-1. Interconversion of the potential LRH-1 cis-elements between the mouse and rat ASBT promoters was associated with an interconversion of LRH-1 and bile acid responsiveness. LRH-1 protein was found in Caco-2 cells and mouse ileum, but not IEC-6 cells or rat ileum. Bile acid response was mediated by the farnesoid X receptor, as shown by the fact that overexpression of a dominant-negative farnesoid X-receptor eliminated the bile acid mediated down-regulation of ASBT. In addition, ASBT expression in farnesoid X receptor null mice was unresponsive to bile acid feeding. In summary cell line- and species-specific negative feedback regulation of ASBT by bile acids is mediated by farnesoid X receptor via small heterodimer partner-dependent repression of LRH-1 activation of the ASBT promoter.

Animals↗

Nitric oxide and guanosine 3',5'-cyclic monophosphate stimulate bile secretion in isolated rat hepatocyte couplets, but not in isolated bile duct units.

Nitric oxide (NO) and guanosine 3',5'-cyclic monophosphate (cGMP) have recently been shown to stimulate bile acid-independent bile flow in the isolated perfused rat liver (IPRL). However, the cellular origin and mechanisms of this choleresis have not yet been determined. To address these questions, we examined the effects of NO and cGMP on bile secretion in isolated rat hepatocyte couplets (IRHC) and in isolated bile duct units (IBDU), both of which are isolated cell systems in which cell polarity is maintained and secretion can be measured directly. Changes in the area of the canalicular and ductular lumens were determined in IRHC and IBDU, respectively, as indicators of the rate of fluid secretion using video microscopy. In addition, Cl-/HCO3- exchanger activity in IBDU was evaluated by measuring changes in intracellular pH (pHi) after Cl- removal/readmission by microfluorometric methods. In the presence of HCO3-, both the NO donor, S-nitroso-acetyl-penicillamine (SNAP), and the cell-permeant cGMP analogue, dibutyryl cGMP (DBcGMP), stimulated canalicular bile secretion (P <.05), as did the cell-permeant cAMP analogue, dibutyryl cAMP (DBcAMP) (P <.05). Removal of HCO3- from the buffer completely abolished the choleretic effects of DBcGMP, but had no effect on NO-induced choleresis. In contrast, secretion in IBDU was not stimulated following incubations with SNAP or DBcGMP over 30 minutes, whereas DBcAMP and secretin, a cholangiocyte secretagogue and cAMP agonist, both had a marked effect on ductular secretion over this same time interval (P <.05). SNAP also had no effect on Cl-/HCO3- exchanger activity in IBDU, and inhibition of endogenous NO synthesis by NG-monomethyl-L-arginine (L-NMMA) did not alter secretin-induced stimulation of ductular bile secretion and Cl-/HCO3- exchanger activity. In summary, NO and cGMP stimulate bile secretion exclusively at the the level of hepatocytes, whereas cAMP mediates choleresis at both hepatocyte and bile duct levels. These findings may have important implications for the regulation of ductular bile secretion by hormones and neuropeptides, as well as under pathological conditions with increased hepatic NO synthesis.

Animals↗

Dissolution kinetics of cholesterol in simulated bile II: influence of simulated bile composition.

Normal human gallbladder bile and gallbladder bile of patients undergoing chenodeoxycholic acid therapy were simulated by using appropriate combinations of taurine and glycine conjugates of cholic, chenodeoxycholic, and deoxycholic acids. Also, the total bile acid concentration and the total bile acid to lecithin ratio were varied over physiological ranges. Dissolution rates of cholesterol monohydrate pellets (model gallstone) in these solutions were 90--99% interfacially controlled. Even under conditions favorable for dissolution, i.e., high bile acid concentration and high bile acid to lecithin ratio, the interfacial resistances were extremely large. These results are of the same order of magnitude as those found in the limited studies with actual gallbladder bile and suggest that the bile acids, lecithin, and the electrolytes are the primary determinants of the interfacial resistance for cholesterol dissolution. Furthermore, the kinetics of dissolution were always much faster with the chenodeoxycholic acid-rich compositions than with the corresponding normal compositions. This finding suggests, therefore, that in addition to desaturating bile with respect to cholesterol, the feeding of chenodeoxycholic acid further facilitates cholesterol gallstone dissolution by reducing the interfacial resistance of the process.

Bile↗

Hydrophilic bile salts protect bile duct epithelium during cold preservation: a scanning electron microscopy study.

Prolonged graft preservation is associated with postoperative bile duct strictures after liver transplantation. We previously showed that hydrophilic bile salts mitigate bile duct preservation injury in a pig model. Because this injury occurs at the epithelial level, scanning electron microscopy was performed to further characterize this effect in vitro. Swine livers were harvested after the intravenous infusion of 1 of 3 solutions: saline (n = 7), tauroursodeoxycholate ([TUDC] hydrophilic; n = 4), or taurodeoxycholate ([TDC] hydrophobic; n = 4). Livers were perfused with University of Wisconsin solution. The bile ducts were flushed retrograde, and the liver was stored at 0 degrees C to 1 degrees C for 20 hours. Bile duct samples were obtained at the time of harvest and 8, 12, 16, and 20 hours thereafter. In saline-infused controls at time 0, the epithelium was intact and composed of uniform cuboidal cells covered with fine regular microvilli. There were no spaces between individual cells. After 8 to 12 hours of preservation, cells were more irregular in shape, with loss of cell-cell contact. The cell surfaces showed fewer microvilli. Surface erosions suggested loss of cell-wall integrity. TUDC was protective, evidenced by normal-appearing cells with uniform microvilli after 16 hours. In contrast, TDC accelerated the injury process, causing cell-surface erosions, blebs, and loss of microvilli as early as time 0. Scanning electron microscopy is an excellent tool to study injury to bile duct epithelium. This study supports the hypothesis that hydrophilic bile salts protect bile ducts during preservation. To determine whether treatment with hydrophilic bile salts can prevent postoperative stricture, in vivo transplantation studies are needed.

Animals↗

Effects of calmodulin antagonists on secretion of bile and bile acid.

In the isolated perfused rat liver, the effects of calmodulin (CaM) antagonists, chlorpromazine (CPZ), trifluoperazine (TFP), W-7 and W-5, on secretion of bile and bile acid were compared. Without addition of taurocholic acid to the perfusate, TFP (200 microM or higher), CPZ (200 microM) and W-7 (400 microM) decreased the bile flow transiently. In contrast, W-5 did not decrease the bile flow. Taking into consideration the binding of TFP and CPZ to bovine serum albumin in the perfusate, they diminished the bile flow by inhibiting CaM function. This was also supported by the difference between the effects of W-7 and W-5. These findings suggested that CaM was involved in the secretion of bile. Under the constant infusion of taurocholic acid into the perfusate, CaM antagonists decreased the secretion of bile acid. However this might be due to the inhibition of bile acid uptake, because these agents inhibited the uptake into isolated rat hepatocytes. The concentrations required for inhibition of the uptake were near to those which decreased the viability, suggesting that the inhibition was due to their non-specific cytotoxic effect. Future studies must be carried out to determine whether CaM is involved in the secretion of bile acid.

Animals↗

Reappraisal of cholesterol solubilization in bile salt-lecithin solution and the stability of bile.

On the basis obtained in a preceding study, cholesterol solubilization in aqueous bile salt-lecithin solution was investigated. The alteration of mixing sequence was found to yield differences not only in the rate but also in the magnitude of cholesterol solubilization. Both the rate and the magnitude were remarkably bigger in the system solubilizing cholesterol and lecithin mixture by bile salt than that solubilizing cholesterol crystal by bile salt with solubilized lecithin. A linear relation between the quantity of solubilized cholesterol and the concentration of bile salt except for lower concentration range was obtained for every bile salt-lecithin system. Values of k, the slope of the partial straight line, determined for cholate, chenodeoxycholate, deoxycholate and equimolar cholate-deoxycholate systems were 5.85 X 10(-2), 7.60 X 10(-2), 9.50 X 10(-2) and 7.17 X 10(-2), respectively. Cholesterol solubilizing power of bile salt was thus enhanced by the addition of lecithin. Since the solubilizing power could be given by the ratio of the solubilizate to the solubilizer, it was expressed graphically by the ratio of cholesterol to bile salt as ordinate and the concentration of bile salt as abscissa. The saturability of cholesterol solubilization in bile was purposefully exhibited in this graph by plotting assayed data of biliary lipid components.

Bile↗

An angulated common bile duct predisposes to recurrent symptomatic bile duct stones after endoscopic stone extraction.

BACKGROUND: Endoscopic sphincterotomy and stone extraction are standard procedures for the removal of bile duct stones. Stone recurrence can, however, occur in up to 25% of cases. Risk factors have been poorly defined, but are believed to be related to bile stasis. This study investigated whether an angulated common bile duct (CBD) that may predispose to bile stasis influences symptomatic stone recurrence after successful endoscopic therapy. METHODS: This study included 232 consecutive patients (mean age, 64.1 years; 86 men) who had undergone therapeutic endoscopic retrograde cholangiopancreatography for bile duct stones. Data from the follow-up period (36 +/- 17 months) were obtained from medical records and patient questioning. Common bile duct angulation and diameter were measured from the cholangiogram after stone removal. RESULTS: Symptomatic bile duct stones recurred in 16% of the patients (36/232). Three independent risk factors were identified by multivariate analysis: an angulated CBD (angle, < or = 145 degrees; relative risk [RR], 5.2; 95% confidence interval [CI], 2.2-12.5; p = 0.0002), a dilated CBD (diameter, > or = 13 mm; RR, 2.6; 95% CI, 1.2-5.7; p = 0.017), and a previous open cholecystectomy (RR, 2.7; 95% CI, 1.3-5.9; p = 0.0117). Gender, age, urgency of procedure, or a periampullary diverticulum did not influence the recurrence rate. CONCLUSIONS: Angulation of the CBD (< or = 145 degrees) on endoscopic cholangiography, a dilated CBD, and a previous open cholecystectomy are independent risk factors for symptomatic recurrence of bile duct stones. The findings support the role of bile stasis in stone recurrence. Further studies using these data prospectively to identify high-risk patients are warranted.

Adolescent↗

The effects of bile salt hydrophobicity on model bile vesicle morphology.

The addition of bile salts to vesicles supersaturated with cholesterol induces cholesterol precipitation, an important step in the formation of cholesterol gallstones. To investigate the effects of bile salt hydrophobicity on vesicle morphology, vesicles obtained from supersaturated model bile by density gradient ultracentrifugation, were incubated with mixtures of deoxycholate (DC) and ursodeoxycholate (UDC) with a constant total bile salt concentration of 30 mM but with a varying hydrophobicity index ranging from -0.31 (UDC alone) up to +0.72 (DC alone) depending on the composition of the mixture. Five days after addition of bile salts to vesicles, cholesterol precipitation was determined microscopically and incubation samples were again subjected to ultracentrifugation to assess the lipid distribution among residual vesicles, mixed micelles, and cholesterol crystals. Structure and size of the isolated residual vesicles were studied by freeze fracture electron microscopy. The control, and samples exposed to hydrophilic bile salt mixtures, consisted of unilamellar vesicles of which more than 75% had a diameter of 50-80 nm. After addition of increasingly hydrophobic bile salt mixtures, multilamellar vesicles with progressively greater diameters (up to 1300 nm) were found, suggesting that vesicle fusion and aggregation took place and might hence be important in the cholesterol precipitation process. Accordingly, crystallization was positively correlated with bile salt hydrophobicity. We conclude that cholesterol crystallization from vesicles depends on the hydrophobicity of the bile salts added, and apparently occurs from fused or aggregated vesicles of extended magnitude and with a multilamellar constitution.

Bile↗

Enhancing effects of vasoconstrictors on bile flow and bile acid excretion in the isolated perfused rat liver.

The effects of vasoconstrictors on bile flow and bile acid excretion were examined in single-pass isolated perfused rat livers. Administration of norepinephrine (NE), 4 nmol/min, plus continuous infusion of taurocholate (TC) (1.0 mumol/min) rapidly increased bile flow in 1 min, and from min 5 until the end of NE administration (late period) bile flow remained above the basal level (111.7 +/- 2.2%), as did bile acid output (114.6 +/- 1.8%). Without TC infusion, administration of NE produced no increase in the late period. Administration of NE plus taurochenodeoxycholate (1.0 mumol/min) increased bile flow and bile acid output in the late period to 121.9 +/- 7.0 and 137.1 +/- 6.8%, respectively. With NE plus taurodehydrocholate, the respective values were only 105.4 +/- 1.6 and 104.1 +/- 4.0%. When horseradish peroxidase (HRP) (25 mg) was infused over 1 min with continuous NE, the late peak (20-25 min) of HRP elimination into bile significantly exceeded that of untreated controls (P < 0.01). These observations suggest that vasoconstrictors enhance biliary excretion of more hydrophobic bile acids, in part by stimulating vesicular transport.

Animals↗