On the turnover and excretory products of cholic and chenodeoxycholic acid in man.
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The preservation of the functional polarity of hepatocytes in liver snips (1 x 2 x 4 mm) was demonstrated by fluorescent microscopic studies using the sodium salt of (N-[7-(4-nitrobenzo-2-oxa-1,3-diazol)]-3 beta-amino-7 alpha,12 alpha- dihydroxy-5 beta-cholan-24-oyl)-2-aminoethanesulfonic acid. This fluorescent bile salt derivative is not only taken up by hepatocytes of several cell layers at the surface of the snips but also secreted into bile canaliculi. The intact hepatobiliary transport of bile salts by hepatocytes of liver snips demonstrates that they are a useful system for the investigation of those transcellular transport processes which require the integrity of hepatic structure. Photoaffinity labelling of liver snips with the sodium salt of (7,7-azo-3 alpha,12 alpha-dihydroxy-5 beta-[3 beta-3H]cholan- 24-oyl)-2-aminoethanesulfonic acid revealed that the bile-salt-binding membrane polypeptides with apparent Mr values of 54,000 and 48,000 are exclusively located in the sinusoidal membrane, whereas a single bile-salt-binding polypeptide with an apparent Mr of 100,000 is located in the bile-canalicular membrane. Photoaffinity labelling of liver snips at 4 degrees C, when transcellular bile-salt transport is insignificant, resulted in the labelling of the two sinusoidal membrane polypeptides and practically no labelling of the polypeptide with an apparent Mr of 100,000. This latter polypeptide was also not labelled when Ca2 deprivation abolished bile secretion completely. These results indicate that the directed hepatobiliary transport of bile salts in hepatocytes is accomplished by transport systems which are different for sinusoidal uptake and canalicular secretion.
Bile salts of ten species of frogs of the family Ranidae were examined by means of thin-layer chromatography, gas-liquid chromatography, and gas-liquid chromatography-mass spectrometry. Their major bile alcohols were ranol, cyprinol, or bufol. Four species of frogs contained lesser amounts of higher bile acids, and in two species C24 bile acids were present. A higher bile acid that has not been previously described was detected in Rana plancyi. On the basis of the spectral data and the direct comparison with a synthetic sample, the chemical structure of the new bile acid was established to be 3 alpha, 7 alpha, 12 alpha, 26-tetrahydroxy-5 beta-cholestanoic acid.
Biliary excretion of certain bile acids is mediated by multidrug resistance associated protein 2 (Mrp2) and the bile salt export pump (Bsep). In the present study, the transport properties of several bile acids were characterized in canalicular membrane vesicles (CMVs) isolated from Sprague--Dawley (SD) rats and Eisai hyperbilirubinemic rats (EHBR) whose Mrp2 function is hereditarily defective and in membrane vesicles isolated from Sf9 cells infected with recombinant baculovirus containing cDNAs encoding Mrp2 and Bsep. ATP-dependent uptake of [(3)H]taurochenodeoxycholate sulfate (TCDC-S) (K(m)=8.8 microM) and [(3)H]taurolithocholate sulfate (TLC-S) (K(m)=1.5 microM) was observed in CMVs from SD rats, but not from EHBR. In addition, ATP-dependent uptake of [(3)H]TLC-S (K(m)=3.9 microM) and [(3)H]taurocholate (TC) (K(m)=7.5 microM) was also observed in Mrp2- and Bsep-expressing Sf9 membrane vesicles, respectively. TCDC-S and TLC-S inhibited the ATP-dependent TC uptake into CMVs from SD rats with IC(50) values of 4.6 microM and 1.2 microM, respectively. In contrast, the corresponding values for Sf9 cells expressing Bsep were 59 and 62 microM, respectively, which were similar to those determined in CMVs from EHBR (68 and 33 microM, respectively). By co-expressing Mrp2 with Bsep in Sf9 cells, IC(50) values for membrane vesicles from these cells shifted to values comparable with those in CMVs from SD rats (4.6 and 1.2 microM). Moreover, in membrane vesicles where both Mrp2 and Bsep are co-expressed, preincubation with the sulfated bile acids potentiated their inhibitory effect on Bsep-mediated TC transport. These results can be accounted for by assuming that the sulfated bile acids trans-inhibit the Bsep-mediated transport of TC.
Microbial bile salt hydrolase (BSH) plays a central role in shaping bile acid composition and gut-liver metabolic signaling, yet its therapeutic potential in metabolic dysfunction-associated steatohepatitis (MASH) remains incompletely defined. Here, we evaluated the efficacy of the non-absorbable BSH inhibitor GR-7 in a diet induced mouse model of steatohepatitis using early and late intervention strategies with different dosing regimens. GR-7 reduced food intake and exerted stage- and dose-dependent therapeutic effects, with early intervention robustly suppressing hepatic fibrosis even at low dose, whereas late-stage administration of high-dose GR-7 markedly reduced hepatic steatosis and inflammation, as evidenced by decreased liver weight, hepatic triglyceride and cholesterol levels, and plasma ALT. Although late intervention did not result in statistically significant histological reversal of fibrosis, a trend toward improvement was observed, together with suppression of fibrogenic gene expression, suggesting that prolonged treatment may further enhance antifibrotic efficacy. Mechanistically, GR-7 effectively inhibited microbial BSH activity in vivo, leading to reduced cecal unconjugated primary and secondary bile acids-including deoxycholic acid and lithocholic acid, which was associated with improved gut barrier integrity and reduced hepatic inflammation. In parallel, BSH inhibition reprogrammed hepatic bile acid metabolism toward activation of the alternative CYP27A1-mediated synthesis pathway, accompanied by reduced food intake, thereby contributing to improved hepatic lipid accumulation. Furthermore, late-stage high-dose treatment selectively remodeled the hepatic immune landscape rather than fully restoring homeostasis, highlighting immune recalibration as a key component of therapeutic response. Together, these findings identify microbial BSH inhibition as a promising microbiome-targeted therapeutic strategy for MASH.
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.
Studies in experimental animals and in humans have shown a definite interaction of dietary fiber with bile acid metabolism. In experimental animals, some types of fiber have been shown to increase bile acid excretion as well as increase pool size and turnover of bile acids. In man, increases in bile acid excretion have been observed but not consistently. Alternations in excretion and biliary bile acid levels indicate an influence of dietary fiber in bile acid metabolism. In vitro experiments have attempted to determine the nature of the fiber-bile acid interaction. Some types of fiber and some components of fiber have been shown to bind bile acids and bile salts in appreciable quantities. The capacity for various types of fiber to bind bile acids or bile salts is quite variable, and a high capacity seems to correspond with a hypocholesteremic effect. A great deal of research is still needed for elucidation of these interactions of fiber and bile acid metabolism and the resultant beneficial effects on cholesterol metabolism and the disease-related abnormalities in cholesterol metabolism.
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Effects of dietary bile acids and their sodium salts on the development of pepsinogen-altered pyloric glands (PAPG) were examined in male WKY/N Crj rats initially given a single dose of 160 mg/kg body weight of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) by gastric intubation. From week 3 the animals were administered basal diet containing 0.5% supplements of cholic acid (CA), deoxycholic acid (DCA), chenodeoxycholic acid (CDCA) or their sodium salts (Na-C, Na-DC and Na-CDC), or 5% ascorbic acid (ASA) or its salt (Na-AS) for 18 weeks. The concentration of DCA and Na-DC was reduced to 0.3% from week 12. At week 20, animals were killed and the numbers of immunohistochemically-demonstrated PAPG were determined. Values were significantly higher with Na-C and Na-CDC than with the corresponding parent acids, and in the Na-C case PAPG development was greater than with MNNG alone. In addition, Na-CDC itself induced the numbers of PAPG significantly. These results suggest that bile salts are possible intrinsic promoters of gastric carcinogenesis. They were without effect, however, on forestomach lesions.
The biliary and urinary excretion and the choleretic effect of iopanoic acid (Telepaque) were studied in nonanesthetized bile-fistula dogs using a stepwise increase of infusion rates of iopanoic acid and a constant infusion of sodium taurocholate at a rate of either 0.5 or 2.0 mumoles/min./kg. The maximum rate of bile excretion (0.671 mumoles/min./kg) when taurocholate was infused at the lower rate nearly doubled (1.325 mumoles/min./kg) when given at the higher rate. Maximum biliary concentrations of iopanoic acid at both rates of taurocholate infusion (70-77 mumoles/ml) were almost double the maximum concentration previously determined for iodipamide (Cholografin) (42 mumoles/ml).
A chitosan (CS) powder treated with cinnamic acid and an analogue compound (CN) was prepared as CS-CN. Using it, bile acid adsorption by CS-CN and the release of CN were investigated in vitro. When CS-CN was soaked in a taurocholate solution, it released CN and simultaneously adsorbed the bile acid. For CS-CN prepared with cinnamic acid, the amount of CN released was 0.286 +/- 0.001 mmol/g CS-CN; the amount of taurocholate adsorbed was 0.284 +/- 0.003 mmol/g CS-CN. These two functions were recognized on alginate or pectin gel beads containing CS-CN. The amount of released CN was altered extensively by the species of CN used for gel-bead preparation. Results suggest that CS-CN is a candidate for complementary medicine to prevent lifestyle-related diseases.
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