Biliary Bile Acid Profile Research Articles

Exercise Enhances Whole-Body Cholesterol Turnover in Mice

Regular exercise reduces cardiovascular risk in humans by reducing cholesterol levels, but the underlying mechanisms have not been fully explored. Exercise might provoke changes in cholesterol and bile acid metabolism and thereby reduce cardiovascular risk. We examined whether voluntary wheel running in mice modulates cholesterol and bile acid metabolism. Male mice (10 wk old) were randomly assigned to have access to a voluntary running wheel for 2 wk (RUN group) or remained sedentary (SED group). Running wheel activity was recorded daily. In a first experiment, fecal sterol outputs, fecal bile acid profiles, plasma parameters, and expression levels of genes involved in cholesterol and bile acid metabolism were determined. In a second experiment, bile flow, biliary bile acid profile, and biliary secretion rates of cholesterol, phospholipids, and bile acids were determined. The RUN group ran an average of 10 km.d and displayed lower plasma cholesterol compared with SED (P = 0.030). Fecal bile acid loss was induced by approximately 30% in running mice compared with SED (P = 0.0012). A approximately 30% increase in fecal cholesterol output in RUN (P = 0.014) was consistent with changes in parameters of cholesterol absorption, such as reduced plasma plant sterol-cholesterol ratio (P = 0.044) and decreased jejunal expression of Npc1l1 (P = 0.013). Supportive of an increased cholesterol synthesis to compensate for fecal sterol loss were increased hepatic mRNA levels of HMGCoA reductase (P = 0.006) and an increased plasma lathosterol-cholesterol ratio (P = 0.0011) in RUN. Voluntary wheel running increased cholesterol turnover in healthy mice owing to an increased fecal bile acid excretion and a decreased intestinal cholesterol absorption. Enhanced cholesterol turnover may contribute to the established reduction of cardiovascular risk induced by regular exercise.

Effects of ionizing radiation on the activity of the major hepatic enzymes implicated in bile acid biosynthesis in the rat

In the days following high-dose radiation exposure, damage to small intestinal mucosa is aggravated by changes in the bile acid pool reaching the gut. Intestinal bile acid malabsorption, as described classically, may be associated with altered hepatic bile acid biosynthesis, which was the objective of this work. The activity of the main rate-limiting enzymes implicated in the bile acid biosynthesis were evaluated in the days following an 8-Gy γ 60Co total body irradiation of rats, with concomitant determination of biliary bile acid profiles and intestinal bile acid content. Modifications of biliary bile acid profiles, observed as early as the first post-irradiation day, were most marked at the third and fourth day, and resulted in an increased hydrophobicity index. In parallel, the intestinal bile acids' content was enhanced and hepatic enzymatic activities leading to bile acids were changed. A marked increase of sterol 12α-hydroxylase and decrease of oxysterol 7α-hydroxylase activity was observed at day 3, whereas both cholesterol 7α-hydroxylase and oxysterol 7α-hydroxylase activities were decreased at day 4 after irradiation. These results show, for the first time, radiation-induced modifications of hepatic enzymatic activities implicated in bile acid biosynthesis and suggest that they are mainly a consequence of radiation-altered intestinal absorption, which induces a physiological response of the enterohepatic bile acid recirculation. To cite this article: M. Souidi et al., C. R. Biologies 330 (2007).

Biliary bile acid profiles in patients with familial adenomatous polyposis before and after colectomy.

The development of colorectal polyps and cancer in patients with familial adenomatous polyposis (FAP) is directly linked to inactivation of the APC gene. Other, epigenetic, mechanisms may be involved in tumorigenesis and a previous study suggested that an intrinsic difference in the biliary bile acid profile of untreated patients with FAP persisted after colectomy. Gas chromatography and gas chromatography-mass spectrometry were used to examine the biliary bile acid profiles of four groups of patients with normal gallbladders: 20 patients with an intact colon comprising 12 with FAP and eight controls; and 26 patients after colectomy comprising 12 with FAP and 14 controls. Comparison of ten different bile acids from both amidate fractions (glycine and taurine) revealed a small increase in the molar percentage of a minor bile acid (12-oxolithocholic acid) in patients with FAP and an intact colon compared with the matching control group. Colectomy was associated with a dramatic reduction in levels of secondary bile acids but with little difference between patients with FAP and controls.

Biliary bile acid profiles in familial adenomatous polyposis

Patients with familial adenomatous polyposis have an excess risk for adenomas and cancers of the upper and lower gastrointestinal tract. In the upper intestine these lesions occur mainly around the ampulla of Vater and they parallel mucosal exposure to bile. In view of this finding and of evidence that bile acids play a role in colorectal carcinogenesis, biliary bile acid profiles were determined in 29 patients with familial adenomatous polyposis (12 before colectomy, 17 after colectomy) and in 28 patients without familial adenomatous polyposis (all with colons in situ). Patients with familial adenomatous polyposis had a higher total biliary bile acid concentration than the others. The bile of patients with polyposis had a greater proportion of chenodeoxycholic acid and a lower proportion of deoxycholic acid than did the bile of patients without polyposis. The ratio of chenodeoxycholic acid and its metabolite lithocholic acid to cholic acid and its metabolite deoxycholic acid, which is related to subsequent bile acid profiles in the colon, was higher in patients with polyposis. Because bile acids influence cellular proliferation, these findings may be of importance with respect to intestinal adenoma and cancer growth.

Effects of dietary 27-hydroxycholesterol on cholesterol metabolism and bile acid biosynthesis in the hamster.

27-hydroxycholesterol (27OH-Chol) is an important endogenous oxysterol resulting from the action of sterol 27-hydroxylase (CYP27A1) on cholesterol in the liver and numerous extrahepatic tissues. It may act as a modulator of cholesterol and bile acid metabolism. The effects of 27OH-Chol on the main enzymes and receptors of cholesterol metabolism were investigated by feeding male hamsters a diet supplemented with 27OH-Chol (0.1% w/w) for 1 week. Intestinal scavenger class B, type I (SR-BI) protein level was decreased (-65%), but hepatic expression was increased (+34%). Liver 3beta-hydroxy-3beta-methyl glutaryl coenzyme A reductase (-58%), cholesterol 7alpha-hydroxylase (-54%), oxysterol 7alpha-hydroxylase (-44%), and sterol 12alpha-hydroxylase (-70%) activities were all decreased. Bile acid composition was changed (fourfold increase in the chenodeoxycholic/cholic acid ratio). This study demonstrates that dietary 27OH-Chol modulates major enzymes of cholesterol metabolism and alters the biliary bile acid profile, making it more hydrophobic, at least at this level of intake. Its effects on SR-BI protein levels are organ dependent. The properties of 27OH-Chol or its metabolites on cholesterol metabolism probably result from the activation of specific transcription factors.

Determination of bile acids in biological fluids by liquid chromatography-electrospray tandem mass spectrometry

A simple, sensitive, and specific liquid chromatography-electrospray tandem mass spectrometry (LC-MS/MS) method for the determination of bile acids in human bile has been developed. The bile acids were extracted with a C18 (octadecyl) reversed-phase column and identified and quantified by simultaneous monitoring of their parent and daughter ions, using the multiple reaction monitoring mode. Identification and quantification of conjugated bile acids in bile was achieved in 5 min. The detection limit was 1 ng, and the determination was linear for concentrations up to 100 ng. The percent recovery of standards made of single conjugated (glycine and taurine) bile acid or of mixture of glycine- or taurine-conjugated cholic acid, chenodeoxycholic acid, deoxycholic acid, ursodeoxycholic acid, and lithocholic acid averaged 71.73% to 95.92%. The percent recovery of the same standard bile acids was also determined by gas chromatography-mass spectrometry (GC-MS), using the selected ion monitoring mode, and averaged 66% to 96%. A biliary bile acid profile of human gallbladder bile was obtained by LC-MS/MS and GC-MS. The results showed a good correlation between the two techniques and no significant differences between the two methods were observed. The LC-MS/MS method was also used for the analysis of serum, urine, and fecal bile acids. In conclusion, LC-MS/MS is a simple, sensitive, and rapid technique for the analysis of conjugated bile acids in bile and other biological samples.—Perwaiz, S., B. Tuchweber, D. Mignault, T. Gilat, and I. M. Yousef. Determination of bile acids in biological fluids by liquid chromatography-electrospray tandem mass spectrometry. J. Lipid Res. 2001. 42: 114–119.

Impact of β-cyclodextrin and resistant starch on bile acid metabolism and fecal steroid excretion in regard to their hypolipidemic action in hamsters

To examine the impact on bile acid metabolism and fecal steroid excretion as a mechanism involved in the lipid-lowering action of β-cyclodextrin and resistant starch in comparison to cholestyramine, male golden Syrian hamsters were fed 0% (control), 8% or 12% of β-cyclodextrin or resistant starch or 1% cholestyramine. Resistant starch, β-cyclodextrin and cholestyramine significantly lowered plasma total cholesterol and triacylglycerol concentrations compared to control. Distinct changes in the bile acid profile of gallbladder bile were caused by resistant starch, β-cyclodextrin and cholestyramine. While cholestyramine significantly reduced chenodeoxycholate independently of its taurine–glycine conjugation, β-cyclodextrin and resistant starch decreased especially the percentage of taurochenodeoxycholate by −75% and −44%, respectively. As a result, the cholate:chenodeoxycholate ratio was significantly increased by 100% with β-cyclodextrin and by 550% with cholestyramine while resistant starch revealed no effect on this ratio. β-Cyclodextrin and resistant starch, not cholestyramine, significantly increased the glycine:taurine conjugation ratio demonstrating the predominance of glycine conjugated bile acids. Daily fecal excretion of bile acids was 4-times higher with 8% β-cyclodextrin and 19-times with 1% cholestyramine compared to control. β-Cyclodextrin and cholestyramine also induced a 2-fold increase in fecal neutral sterol excretion, demonstrating the sterol binding capacity of these two compounds. Resistant starch had only a modest effect on fecal bile acid excretion (80% increase) and no effect on excretion of neutral sterols, suggesting a weak interaction with intestinal steroid absorption. These data demonstrate the lipid-lowering potential of β-cyclodextrin and resistant starch. An impaired reabsorption of circulating bile acids and intestinal cholesterol absorption leading to an increase in fecal bile acid and neutral sterol excretion is most likely the primary mechanism responsible for the lipid-lowering action of β-cyclodextrin. In contrast, other mechanisms involving the alterations in the biliary bile acid profile or repressed hepatic lipogenesis, e.g., VLDL production, appear to be involved in the hypolipidemic effect of resistant starch.

Dietary Inulin Lowers Plasma Cholesterol and Triacylglycerol and Alters Biliary Bile Acid Profile in Hamsters

The mechanisms by which inulin may elicit its lipid-lowering effect are not well elucidated. To examine the lipid-lowering potential of inulin and especially its effect on bile acid metabolism, male golden Syrian hamsters were fed semipurified diets containing 20 g/100 g fat, 0.12 g/100 g cholesterol and 0 (control), 8, 12 or 16% inulin for 5 wk. Plasma total cholesterol concentrations were significantly lowered by 18, 15 and 29% in hamsters fed 8, 12 and 16% inulin, respectively. Dietary inulin specifically decreased VLDL cholesterol, which was significantly lower in hamsters fed 16% inulin compared with controls (1.1 ± 0.3 vs. 2.9 ± 0.6 mmol/L). LDL and HDL cholesterol were not significantly affected by dietary inulin. Plasma triacylglycerol was significantly reduced by 40 and 63% in hamsters fed 12 and 16% inulin, respectively. Hepatic total cholesterol and particularly esterified cholesterol accumulation were significantly lower in hamsters fed 8% inulin compared with controls. All three levels of dietary inulin caused distinct alterations in the bile acid profile of gallbladder bile. Taurochenodeoxycholic acid was significantly lower, whereas glycocholic and glycodeoxycholic acid were greater in hamsters fed inulin. Daily fecal bile acid excretion (μmol/d) tended to be greater (P = 0.056) in inulin-fed hamsters compared with controls, whereas daily neutral sterol excretion was not affected. These data demonstrate that the lipid-lowering action of inulin is possibly due to several mechanisms, including altered hepatic triacylglycerol synthesis and VLDL secretion and impaired reabsorption of circulating bile acids.

Biliary bile acid profiles of domestic fowl as determined by high performance liquid chromatography and fast atom bombardment mass spectrometry

1. 1. The biliary bile acid profiles of domestic chickens ( Gallus domesticus), turkeys ( Meleagris gallopavo), and ducks ( Anas platyrhynchos) were determiend by high performance liquid chromatography (HPLC) and fast atom bombardment mass spectrometry (FAB-MS). 2. 2. Chenodeoxycholyltaurine and cholyltaurine were the predominant bile acids in chicken and turkey bile, whereas duck bile contained primarily chenodeoxycholyltaurine and phocaecholyltaurine. 3. 3. Allocholyltaurine was also detected in chicken and turkey bile, but not in duck bile. 4. 4. FAB-MS analyses of individual HPLC peak fractions from chicken and duck bile extracts confirmed the presence of either taurine-conjugated dihydroxy- or trihydroxycholanoates. 5. 5. Direct FAB-MS analyses of avian bile extracts not subjected to HPLC permitted a rapid assessment of the relative proportion of taurine-conjugated dihydroxy- to trihydroxycholanoates.

Oleic acid-induced cholelithiasis in the rabbit: conversion of dietary oleic acid to cholestanol as a cause of calcium-bile salt gallstones.

Rabbits fed a diet rich in oleic acid develop gallstones consisting of calcium salts of (5 alpha)-glyco-allodeoxycholic acid. To study the metabolic pathway of oleic acid, we followed the changes in plasma, hepatic and biliary lipids in this animal model. In addition, to also determine the role played by intestinal microflora on biliary lipid metabolism, we added kanamycin to the oleic acid diet. Oleic acid-fed rabbits rapidly developed hypercholesterolemia. This was associated with an increase in liver 3-hydroxy-3-methylglutaryl coenzyme A reductase activity, accumulation of cholesterol as well as cholestanol in the liver and progressive saturation of cholesterol in bile. [14C]oleic acid fed orally to rabbits was recovered in liver extracts as both cholesterol and cholestanol. With oleic acid feeding, there was a progressive increase in glyco-allodeoxycholic acid culminating in the formation of gallstones. Kanamycin supplement to the oleic acid diet resulted in the same changes in plasma and hepatic sterol metabolism compared with oleic acid-fed rabbits. There was, however, a striking difference in the biliary bile acid profile. Kanamycin supplementation dramatically reduced the proportion of 5 alpha-dihydroxy bile acids, increased the proportion of 5 beta-trihydroxy bile acids and completely abolished gallstone formation. We postulate that, in the rabbit, oleic acid is used as a carbon source for cholesterol synthesis, and a high oleic acid diet increases hepatic cholesterogenesis. Hepatic cholesterol is then metabolized to form cholestanol, followed by (5 alpha)-glyco-allocholic acid which is secreted into bile and transformed by gut bacteria to form (5 alpha)-allodeoxycholic acid. Kanamycin abolished gallstone formation by inhibiting intestinal bacterial dehydroxylation.

Effect of petroleum hydrocarbons on the biliary bile acid composition of rainbow trout ( Salmo gairdneri)

1. 1. Biliary bile acid profiles were investigated by thin layer and gas liquid chromatography in fish exposed per os with a Venezuelan crude petroleum or a triglyceride rich oil, olive oil. 2. 2. Neither volume of bile nor bile acid pools were affected, compared to controls, in fish fed either petroleum or olive oil. 3. 3. The response was not uniform, but a small increase in the ratio of the primary bile acids, cholic to chenodeoxycholic, was observed in a number of fish exposed to petroleum. 4. 4. Petroleum appeared not to simply mimic a fatty food source in altering the cholic to chenodeoxycholic acid ratio. 5. 5. The hypothesis that the elevation of mixed function oxygenase enzymes by such potent inducers as petroleum hydrocarbons could markedly alter bile acid profiles, or result in the production of novel bile acid metabolites, was not supported in this study.

Prediction of the bile acid composition of bile from serum bile acid analysis during gallstone dissolution therapy

The relationship between the relative concentrations of individual bile acids in fasting serum and bile collected simultaneously was determined in 28 patients with gallstones. Seven of these patients were being treated with chenodeoxycholic acid (15 mg/kg/day). The relative concentrations of deoxycholic acid, chenodeoxycholic acid, and ursodeoxycholic acid were found to be higher in serum than in bile, while the reverse was true for cholic acid. A highly significant correlation (P < 0.001) was found between the relative proportions of each of deoxycholic acid, cholic acid, chenodeoxycholic acid and ursodeoxycholic acid in fasting serum and bile. Each correlation was defined by linear regression analysis, and regression equations were used to predict the bile acid composition of bile from the relative concentrations of the individual bile acids in serum. Although some error was obtained between predicted and actual values in individual patients, in all 7 gallstone dissolution patients treated with chenodeoxycholic acid, both the actual and predicted cholic acid concentrations in bile were < 20 moles %, and the chenodeoxycholic acid concentrations were > 70 moles %. This latter value almost always indicates biliary cholesterol unsaturation in nonobese patients. Other studies in T-tube patients confirmed that changes in biliary bile acid profiles produced by chenodeoxycholic acid treatment could be readily followed via the serum. Serum bile acid analysis is therefore a useful alternative to bile analysis for the biochemical monitoring of patients treated with chenodeoxycholic acid, and avoids duodenal intubation for bile collection.