Hyodeoxycholic acid: a new approach to gallstone prevention

Hyodeoxycholic acid attenuates cholesterol gallstone formation via modulation of bile acid metabolism and gut microbiota

BACKGROUND & AIMS

Hyodeoxycholic acid (HDCA), a hydrophilic bile acid (BA), may prevent and suppress the formation of cholesterol gallstones (CGs). However, the mechanism by which HDCA prevents CGs formation remains unclear. This study aimed to investigate the underlying mechanism of HDCA in preventing CG formation.

METHODS

C57BL/6J mice were fed either a lithogenic diet (LD), a chow diet, or LD combined with HDCA. The concentration of BAs in the liver and ileum were determined using liquid chromatography-mass spectrometry (LC-MS/MS). Genes involved in cholesterol and BAs metabolism were detected using polymerase chain reaction (PCR). The gut microbiota in the faeces was determined using 16S rRNA.

RESULTS

HDCA supplementation effectively prevented LD-induced CG formation. HDCA increased the gene expression of BA synthesis enzymes, including Cyp7a1, Cyp7b1, and Cyp8b1, and decreased the expression of the cholesterol transporter Abcg5/g8 gene in the liver. HDCA inhibited LD-induced Nuclear farnesoid X receptor (Fxr) activation and reduced the gene expression of Fgf15 and Shp in the ileum. These data indicate that HDCA could prevent CGs formation partly by promoting BA synthesis in the liver and reduced the cholesterol efflux. In addition, HDCA administration reversed the LD-induced decrease in the abundance of norank_f_Muribaculaceae, which was inversely proportional to cholesterol levels.

CONCLUSIONS

HDCA attenuated CG formation by modulating BA synthesis and gut microbiota. This study provides new insights into the mechanism by which HDCA prevents CG formation.

LAY SUMMARY

In this study, we found that HDCA supplementation suppressed LD-induced CGs in mice by inhibiting Fxr in the ileum, enhancing BA synthesis, and increasing the abundance of norank_f_Muribaculaceae in the gut microbiota. HDCA can also downregulate the level of total cholesterol in the serum, liver, and bile.

In vivo gallbladder bile diffusion coefficient measurement by diffusion-weighted echo planar imaging in hamster fed normal and lithogenic diets

It is shown that in vivo measurement of bile water apparent diffusion coefficient (ADC) by diffusion-weighted echo-planar imaging (EPI) in hamster gallbladder is possible providing motion artifact-free ADC values. These ADC values are used to estimate bile viscosity variation induced by normal diets, cholesterol gallstone-inducing diets, and an antilithiasic drug, and to determine if a link exists between bile viscosity and cholesterol gallstone formation. Measurements were performed at 4.7 T with respiratory triggering in five groups of hamsters fed a commercial (RC) or a semisynthetic (SSD) diet, a SSD containing 0.2% hyodeoxycholic acid (SSD+HDC) and two lithogenic diets (LD5, LD10). ADC decreased significantly in LD10 (2.15+/-0.07x 10(-3) mm(2)s(-1)) and SSD+HDC (2.03+/-0.04) compared to RC (2.40+/-0.05) but not in the most lithogenic LD5 diet (2.33+/-0.06). No direct relationship was found between bile viscosity and gallstone incidence; however, viscosity seems to be related to lipid contents of diets. Magn Reson Med 43:854-859, 2000.

Taurohyodeoxycholic acid protects against taurochenodeoxycholic acid-induced cholestasis in the rat

The prevention of the hepatotoxic effects produced by intravenous infusion of taurochenodeoxycholic acid (TCDCA) by coinfusion with taurohyodeoxycholic acid (THDCA) was evaluated in bile fistula rats; the hepatoprotective effects of the latter were also compared with those of tauroursodeoxycholic acid (TUDCA). Rats infused with TCDCA at a dose of 8 micromol/min/kg showed reduced bile flow and calcium secretion, as well as increased biliary release of alkaline phosphatase (AP) and lactate dehydrogenase (LDH). This was associated with a very low biliary secretion rate of TCDCA (approximately 1 micromol/min/kg). Simultaneous infusion of THDCA or TUDCA at the same dose preserved bile flow and almost totally abolished the pathological leakage of the two enzymes into bile. The effect was slightly more potent for THDCA. The maximum secretion rate of TCDCA increased to the highest value (8 micromol/min/kg) when coinfused with either of the two hepatoprotective bile acids (BA), which were efficiently and completely secreted in the bile, without metabolism. Calcium output was also restored and phospholipid (PL) secretion increased with respect to the control saline infusion. This increase was higher in the THDCA study. These data show that THDCA is highly effective in the prevention of hepatotoxicity induced by intravenous infusion of TCDCA by facilitating its biliary secretion and reducing its hepatic residence time; this was associated with selective stimulation of PL biliary secretion.

Dissolution of human cholesterol gallstones in bile salt/lecithin mixtures: effect of bile salt hydrophobicity and various pHs

BACKGROUND

Unconjugated bile salts currently available for gallstone dissolution are poorly effective. We evaluated in vitro the litholytic potency of taurine-amidated bile salts against human cholesterol gallstones.

METHODS

Seventy radiolucent gallstones with similar size and composition (cholesterol content, 70.1 +/- 0.9%) from a single patient were incubated in model biles composed of 100 mM of either taurochenodeoxycholate (TCDC), taurocholate (TC), taurohyodeoxycholate (THDC) or tauroursodeoxycholate (TUDC) and of 45 mM egg yolk lecithin in saline buffered with tris/HCl (at pHs 7 and 8) or phosphate (at pHs 4 and 6). Biles (total lipids, 10 g/dl; cholesterol saturation, 99%) were incubated at 37 degrees C for 40 days. Gallstones were periodically weighed and returned to the dissolution vials, and the biliary cholesterol concentration was monitored.

RESULTS

Model biles remained optically clear during the initial 48 h of incubation. Then, biles containing THDC and TUDC, but not those with TC and TCDC, became progressively turbid until, after several days, a white precipitate surrounded the residual stone. Abundant liquid crytalline droplets were observed at polarizing microscopy in biles containing TUDC and THDC. Gallstone dissolution was closely related to cholesterol solubilization and decreased in the order TCDC > THDC > or = TC > TUDC, being highest at pH 8. At the physiologic pH of 7 THDC was more litholythic than TC.

CONCLUSIONS

In vitro, the litholytic potency of bile salts on cholesterol gallstones primarily depends on their hydrophobicity. THDC is a new potential gallstone-dissolving agent, deserving in vivo studies.

Effect of taurohyodeoxycholic acid, a hydrophilic bile salt, on bile salt and biliary lipid secretion in the rat

Taurohyodeoxycholic acid is a natural 6 alpha-hydroxylated bile acid with an apparent hydrophilicity intermediate between those of tauroursodeoxycholic and taurocholic acids. We investigated in the rat the hepatobiliary metabolism, choleretic properties, and biliary maximum secretory rate (SRmax) of taurohyodeoxycholic in comparison with these two bile salts. Each compound was infused intravenously, at a rate increased in a stepwise manner from 100 to 300 nmol/min/100 g body wt, in bile salt-depleted bile fistula rats. The three bile salts appeared rapidly starting with the infusion and increased to represent more than 95% of the total bile salts. No apparent biliary metabolites were formed. All the bile salts caused a dose-dependent increase in bile flow and biliary lipid output. The absolute increase in bile flow was lower in rats infused with taurohyodeoxycholic acid, yet the volume of bile formed per nanomole of secreted bile salt was 13.8 nl for taurohyodeoxycholic, 6.4 nl for tauroursodeoxycholic acid, and 10.9 nl for taurocholic. The SRmax values were 1080, 3240, and 960 nmol/min/100 g, respectively. At all infusion rates, taurohyodeoxycholic acid caused a greater (P < 0.001) secretion of biliary lecithin compared to the other bile salts. There were no significant differences in the biliary secretion of cholesterol and proteins. Electron microscopy showed the recruitment of vesicles and lamellar bodies around and within bile canaliculi. In conclusion, taurohyodeoxycholic promotes a biliary lecithin secretion greater than expected from physicochemical predictions, representing a novel secretory property with potential pharmacological relevance.

Metabolism and effects on biliary lipid secretion of murocholic acid in the hamster

The metabolism of murocholic acid (MC), a 6 beta-hydroxylated bile acid, was investigated after intravenous (i.v.), intraduodenal (i.d.) or intragastric (i.g.) administration to bile fistula hamsters. The effects on biliary cholesterol and phospholipid secretion were measured during intravenous infusions of increasing doses of [3H]MC. At an infusion rate of 0.1 or 1 mumol.min-1.kg-1, the hepatic uptake was effective. More than 90% of the dose was recovered in bile within 4 h. A bolus injection of 500 micrograms of [3H]MC in the duodenum led to a rapid and efficient biliary secretion of radioactivity. Increasing i.v. infused doses of MC had no effect on bile flow or biliary cholesterol output compared to the controls. Phospholipid secretion was significantly reduced (0.113 mumol.min-1.kg-1 versus 0.238 mumol.min-1.kg-1 in in controls per mumol.min-1.kg-1 of excreted bile acids) as MC progressively replaced the endogenous bile acid pool in bile. After i.v. and i.d. administration, MC was secreted in bile as glyco and tauro conjugates without additional hepatic hydroxylation, sulfation or glucuronidation. The i.g. ingestion of MC followed by the faecal analysis of metabolites showed the formation of hyodeoxycholic acid and 3 alpha-OH-6-oxo-5 beta-cholan-24-oic acid. An equivalent experiment with hyodeoxycholic acid gave MC and the same oxo bile acid. We concluded that MC is metabolized by the hamster liver as an endogenous bile acid, which undergoes intestinal bacterial transformation into a 6-oxo derivative and is then reduced into hyodeoxycholic acid. This process is completely reversible.(ABSTRACT TRUNCATED AT 250 WORDS)

Bile acids substituted in the 6 position prevent cholesterol gallstone formation in the hamster

The aim of the present study is to examine the efficacy of 6-hydroxy substituted bile acids on the prevention of cholesterol gallstones in a new hamster model of cholesterol cholelithiasis. Male golden Syrian hamsters were fed a nutritionally adequate semipurified lithogenic diet consisting of casein, cornstarch, soluble starch, butterfat, corn oil, and cellulose plus 0.3% cholesterol. Six different bile acids were added to this diet at the 0.05% level: chenodeoxycholic acid, ursodeoxycholic acid, hyodeoxycholic acid, murideoxycholic acid, 6 beta-methyl-hyodeoxycholic acid, and 6 alpha-methyl-murideoxycholic acid. At the end of the 6-wk feeding period, the control group receiving the lithogenic diet had a 55% incidence of gallstones. It was found that all bile acids had inhibited the formation of cholesterol gallstones; complete prevention of gallstones was observed with all 4 3,6-dihydroxy bile acids, whereas chenodeoxycholic acid and ursodeoxycholic acid were somewhat less effective (80% and 75% prevention, respectively). The accumulation of cholesterol in serum and liver induced by the lithogenic diet was inhibited to some extent by all of the bile acids; hyodeoxycholic acid, murideoxycholic acid, and 6 beta-methyl hyodeoxycholic acid were most effective in this respect. The administered bile acids tended to predominate in bile in the case of chenodeoxycholic acid, hyodeoxycholic acid, and 6 beta-methyl-hyodeoxycholic acid. In contrast, ursodeoxycholic acid seemed to be converted to chenodeoxycholic acid and murideoxycholic acid to hyodeoxycholic acid. Only 4% of the 6-methyl analogue of murideoxycholic acid, 6 alpha-methyl-murideoxycholic acid, was recovered in gallbladder bile. These experiments show that the new hamster model of cholesterol cholelithiasis is suitable for gallstone-prevention studies. It was not possible to draw definite conclusions concerning the mechanism of action of the administered bile acids on the basis of cholesterol saturation or the presence of liquid crystals. The detailed mechanism of gallstone prevention by hydrophilic bile acids in this model remains to be elucidated.

Classical bile acids in animals, beta-phocaecholic acid in ducks

1. Bile samples of different animals were analysed and the percentage content of classical bile acids was determined. 2. Herbivorous birds mostly excreted a large proportion of chenodeoxycholic acid. 3. The anteater (Myrmecophaga tridactyla) excreted deoxycholic acid most probably as a primary bile acid. 4. In the bile of ducks (Anas platyrhynchos) a large amount of (23R)3 alpha, 7 alpha, 23-trihydroxy-5 beta-cholan-24-oic acid (beta-phocaecholic acid) was found.

7-Methyl bile acids: effects of chenodeoxycholic acid, cholic acid, and their 7 beta-methyl analogues on the formation of cholesterol gallstones in the prairie dog

The purpose of this study was to compare the effects of the naturally occurring bile acids (chenodeoxycholic acid and cholic acid) with their 7-methyl analogues (3 alpha,7 alpha-dihydroxy-7 beta-methyl-5 beta-cholanoic acid and 3 alpha,7 alpha,12 alpha-trihydroxy-7 beta-methyl-5 beta-cholanoic acid) on gallstone formation and prevention and cholesterol metabolism in the prairie dog. Sixty animals were fed a semipurified diet, containing 0.4% cholesterol, with one of the following acids (0.1%): chenodeoxycholic, cholic, 3 alpha,7 alpha-dihydroxy-7 beta-methyl-5 beta-cholanoic, or 3 alpha,7 alpha,12 alpha-trihydroxy-7 beta-methyl-5 beta-cholanoic acid. This concentration of dietary bile acids amounts to a dose of 27-30 mg/kg.day. After 8 wk, 89% of control animals had gallstones and 94% had cholesterol crystals. Chenodeoxycholic and 3 alpha,7 alpha-dihydroxy-7 beta-methyl-5 beta-cholanoic acids decreased the incidence of gallstones to 50%. Cholic acid and 3 alpha,7 alpha,12 alpha-tri-hydroxy-7 beta-methyl-5 beta-cholanoic acid did not prevent gallstone formation. The liver cholesterol level was decreased by chenodeoxycholic acid, whereas cholic and 3 alpha,7 alpha,12 alpha-trihydroxy-7 beta-methyl-5 beta-cholanoic acids increased serum and liver cholesterol. Each administered bile acid became the predominant biliary bile acid and 7-methyl analogues did not increase secondary bile acids. Fecal analysis of radioactive metabolites using 14C-labeled 7-methyl analogues showed that these compounds are resistant to bacterial 7-dehydroxylation. It was concluded that 3 alpha,7 alpha-dihydroxy-7 beta-methyl-5 beta-cholanoic acid inhibited gallstone formation as effectively as chenodeoxycholic acid, whereas both cholic and 3 alpha,7 alpha,12 alpha-trihydroxy-7 beta-methyl-5 beta-cholanoic acids were not effective. The effects of 7-methyl analogues on the parameters of cholesterol metabolism that we studied were similar to those of their parent compounds, chenodeoxycholic and cholic acids. Thus, 3 alpha,7 alpha-dihydroxy-7 beta-methyl-5 beta-cholanoic acid but not 3 alpha,7 alpha,12 alpha-trihydroxy-7 beta-methyl-5 beta-cholanoic acid offers promise in cholelitholytic therapy for the prevention and possibly dissolution of cholesterol gallstones.

Dissolution of cholesterol gallstones by bile acids in the prairie dog

The effect of chenodeoxycholic acid, ursodeoxycholic acid and hyodeoxycholic acid on gallstone dissolution was studied in the prairie dog. Cholesterol gallstones were found in all animals after feeding a semipurified diet plus 1.2% cholesterol for six wk. Gallstone regression was examined by feeding a chow diet containing the bile acids (chenodeoxycholic acid, ursodeoxycholic acid or hyodeoxycholic acid) alone (30 mg/kg/day) or in combination (chenodeoxycholic acid plus ursodeoxycholic acid) for an additional six wk. Chenodeoxycholic acid was effective in dissolving established cholesterol gallstones (two out of 16 animals still had stones) and cholesterol crystals (six out of 16 animals had crystals); the hydrophilic bile acids, ursodeoxycholic acid and hyodeoxycholic acid, were ineffective in the six-wk regression study. The lithogenic indices averaged 1.09 at the end of the induction period; all biles became unsaturated with respect to cholesterol after the six-wk regression period (group 1, 0.82; group 2, 0.66; group 3, 0.81; group 4, 0.84; group 5, 0.66). Cholesterol levels in liver, plasma and bile were elevated after the six-wk induction phase (4.59 mg/g, 610 mg/dl and 0.36 mg/ml, respectively) but returned to near normal levels after the six-wk regression period. Biliary bile acids contained increased levels of the dietary bile acid administered to each group. This experiment shows that relatively hydrophobic bile acids may be more effective than hydrophilic bile acids for gallstone dissolution during the period studied.

A hydrophilic bile acid effects partial dissolution of cholesterol gallstones in the prairie dog

Gallstone formation and dissolution were studied in a prairie dog model of cholesterol (CH) cholelithiasis. Gallstones were induced in 49 prairie dogs by feeding 1.2% CH in a nutritionally adequate semisynthetic diet for 6 wk (period 1). At 6 wk, gallstones had developed in all animals examined. The diets were modified by reducing the amounts of CH to 0.4, 0.2, 0.1 and 0.0% (diets 1-4); hyodeoxycholic acid (HDA; 30 mg/kg/day) was added to these diets (diets 5-8). All animals were fed the modified experimental diets for an additional 8 wk (period 2). At week 14, spontaneous gallstone dissolution had not occurred, even in the groups given no added dietary CH during period 2 (group 4). Addition of HDA to the diet tended to reduce the incidence of biliary CH crystals and the size and number of CH gallstones. Biliary CH remained elevated and the lithogenic indices in all groups were found to be greater than 1.0 at the end of the experiment. Liver and plasma CH levels tended to be lower in the groups fed HDA. In these groups, HDA and 6 beta HDA became the major biliary bile acids. This study demonstrates that HDA achieved partial dissolution of gallstones in bile supersaturated with CH.

Gallstone prevention in prairie dogs: comparison of chow vs. semisynthetic diets

The effects of a standard rodent chow were compared with those of a semisynthetic diet of known composition (with and without added cholesterol) in the prairie dog model of cholesterol cholelithiasis. Gallstone incidence was 40% higher in animals fed a semisynthetic diet plus cholesterol compared to chow plus cholesterol. The semisynthetic diet plus cholesterol caused significant increases in tissue cholesterol levels (serum, liver and bile) and lithogenic index, but significant decreases in the activity of hepatic 3-hydroxy-3-methyl-glutaryl coenzyme A reductase and cholesterol 7 alpha-hydroxylase compared to chow plus cholesterol. Histologic study of liver sections revealed that the semisynthetic diet plus cholesterol resulted in moderate to marked portal tract changes characterized by bile duct proliferation, inflammatory infiltration and fibrosis, whereas the cholesterol-supplemented chow diet caused only slight bile duct proliferation with minimal inflammation and fibrosis in the portal areas. Dietary hyodeoxycholic acid prevented cholesterol gallstones and biliary cholesterol crystals when added to either chow plus cholesterol or semisynthetic plus cholesterol diets. The hyodeoxycholic acid supplements also prevented the development of severe histopathologic alterations along the portal tracts. Biliary cholesterol levels were elevated in prairie dogs fed cholesterol plus hyodeoxycholic acid; these animals had liquid crystals in the bile, and hyodeoxycholic acid and its 6 beta-isomer became the major biliary bile acids. A semisynthetic diet plus cholesterol is superior to a high cholesterol chow diet for gallstone formation and prevention studies, but in prolonged feeding experiments, the potential hepatotoxicity of this diet in the prairie dog must be appreciated.

Medical management of cholesterol gallstones

Cholesterol gallstones are a significant cause of morbidity in the U.S. Methods used to treat gallstones include cholecystectomy or medical dissolution. The primary drugs used for the dissolution of cholesterol gallstones are two bile acids, chenodeoxycholic acid and ursodeoxycholic acid. Complete or partial gallstone dissolution rates using chenodeoxycholic acid have ranged from 30 to 80 percent. Factors affecting gallstone dissolution using the bile acids include the dosage and administration schedule, obesity, the stone characteristics, diet, and the duration of therapy. The adverse effects of chenodeoxycholic acid include gastrointestinal complaints, hepatotoxicity, and increased serum cholesterol. Ursodeoxycholic acid, which is investigational, differs from chenodeoxycholic acid in its mechanism of action. Ursodeoxycholic acid has similar efficacy with chenodeoxycholic acid, at a lower daily dosage, with less gastrointestinal and hepatic adverse effects. If appropriate patient selection is used, the response rate to medical therapy can range from 50 to 80 percent.