Clearance Of Bile Salts Research Articles

Inhibition of hepatic bile salt uptake by Bulevirtide reduces atherosclerosis in Oatp1a1−/−Ldlr−/− mice

Bile salts can strongly influence energy metabolism through systemic signaling, which can be enhanced by inhibiting the hepatic bile salt transporter Na+ taurocholate cotransporting polypeptide (NTCP), thereby delaying hepatic reuptake of bile salts to increase systemic bile salt levels. Bulevirtide is an NTCP inhibitor and was originally developed to prevent NTCP-mediated entry of Hepatitis B and D into hepatocytes. We previously demonstrated that NTCP inhibition lowers body weight, induces glucagon-like peptide-1 (GLP1) secretion, and lowers plasma cholesterol levels in murine obesity models. In humans, a genetic loss-of-function variant of NTCP has been associated with reduced plasma cholesterol levels. Here, we aimed to assess if Bulevirtide treatment attenuates atherosclerosis development by treating female Ldlr−/− mice with Bulevirtide or vehicle for 11 weeks. Since this did not result in the expected increase in plasma bile salt levels, we generated Oatp1a1−/−Ldlr−/− mice, an atherosclerosis-prone model with human-like hepatic bile salt uptake characteristics. These mice showed delayed plasma clearance of bile salts and elevated bile salt levels upon Bulevirtide treatment. At the study endpoint, Bulevirtide-treated female Oatp1a1−/−Ldlr−/− mice had reduced atherosclerotic lesion area in the aortic root that coincided with lowered plasma LDL-c levels, independent of intestinal cholesterol absorption. In conclusion, Bulevirtide, which is considered safe and is EMA-approved for the treatment of Hepatitis D, reduces atherosclerotic lesion area by reducing plasma LDL-c levels. We anticipate that its application may extend to atherosclerotic cardiovascular diseases, which warrants clinical trials.

Low-Dose Lipopolysaccharide Causes Biliary Injury by Blood Biliary Barrier Impairment in a Rat Hepatic Ischemia/Reperfusion Model.

This study explored whether bacterial endotoxins, in the form of lipopolysaccharides (LPS), could have an injurious effect on the biliary tract in conjunction with ischemia. A total of 64 rats were randomly assigned to 4 groups: sham operation (sham group), 1 mg/kg LPS intraperitoneal (LPS group), hepatic ischemia/reperfusion (IR; IR group), and IR combined with LPS (IR+LPS group). Following 1 or 6 hours of reperfusion, serum liver tests, bile duct histology, immunofluorescence microscopy (zonula occludens-1 [ZO-1]), bile composition (bile salts, phospholipids, lactate dehydrogenase), hepatic gene expression (bile salt transporters and inflammatory mediators), as well as serum and biliary cytokine concentrations were quantified and compared between the study groups. In addition, the integrity of the blood biliary barrier (BBB) was assayed in vivo using horseradish peroxidase (HRP). LPS administration induced severe small bile duct injury following 6 hours of reperfusion. Furthermore, total bile salts and bilirubin concentrations in serum were increased in the LPS groups compared with sham controls (LPS, + 3.3-fold and +1.9-fold; IR+LPS, + 3.8-fold and +1.7-fold, respectively). The BBB was impaired in the LPS groups as evidenced by elevated levels of HRP in bile (+4.9-fold), and decreased expression of claudin 1 (-6.7-fold) and claudin 3 (-3.6-fold). LPS was found to be a potent inducer of small bile duct injury following hepatic ischemia and 6 hours of reperfusion. This injury was associated with increased permeability of the BBB and impaired hepatic bile salt clearance. Liver Transplantation 23 194-206 2017 AASLD.

Erratum to “Heterogeneity of rat liver parenchyma in taurocholate uptake” [Hepatol. Res. 27 (3) (2003) 238–247

Periportal and perivenous hepatocytes were isolated from rat liver by digitonin/collagenase perfusion for investigating the acinar distribution of taurocholate uptake. Statistical analysis revealed that uptake of taurocholate by periportal, perivenous and regular (whole acinus) hepatocytes in Na + -containing and -free buffer was best described by one saturable component. Total taurocholate uptake measured in Na + -containing buffer was significantly higher in perivenous (V max =7.5 nmol/(min mg protein)) than in periportal hepatocytes (V max =5.4 nmol/(min mg protein)). Uptake by regular hepatocytes was well between the values of periportal and perivenous hepatocytes (V max =6.7 nmol/(min mg protein)). The K m -values were not different among the zonal regions. In Na + -free buffer, K m and V max of taurocholate uptake calculated for all fractions were similar. During cultivation of hepatocytes as monolayer total taurocholate uptake strongly decreased and the zonal differences observed in freshly isolated cells in suspension disappeared. Initial uptake rates of Na + -independent taurocholate uptake and the ATP-content of the hepatocytes were constant. Our results indicate an acinar gradient of Na + -dependent taurocholate uptake activity, which may improve the clearance of bile salts from portal blood and protect periportal hepatocytes against a too high intracellular bile salt concentration.

Heterogeneity of rat liver parenchyma in taurocholate uptake

Periportal and perivenous hepatocytes were isolated from rat liver by digitonin/collagenase perfusion for investigating the acinar distribution of taurocholate uptake. Statistical analysis revealed that uptake of taurocholate by periportal, perivenous and regular (whole acinus) hepatocytes in Na +-containing and -free buffer was best described by one saturable component. Total taurocholate uptake measured in Na +-containing buffer was significantly higher in perivenous (V max=7.5 nmol/(min mg protein)) than in periportal hepatocytes (V max=5.4 nmol/(min mg protein)). Uptake by regular hepatocytes was well between the values of periportal and perivenous hepatocytes (V max=6.7 nmol/(min mg protein)). The K m-values were not different among the zonal regions. In Na +-free buffer, K m and V max of taurocholate uptake calculated for all fractions were similar. During cultivation of hepatocytes as monolayer total taurocholate uptake strongly decreased and the zonal differences observed in freshly isolated cells in suspension disappeared. Initial uptake rates of Na +-independent taurocholate uptake and the ATP-content of the hepatocytes were constant. Our results indicate an acinar gradient of Na +-dependent taurocholate uptake activity, which may improve the clearance of bile salts from portal blood and protect periportal hepatocytes against a too high intracellular bile salt concentration.

Functional expression of the canalicular bile salt export pump of human liver

Background & Aims: Hepatic bile salt secretion is an essential function of vertebrate liver. Rat and mouse bile salt export pump (Bsep) are adenosine triphosphate (ATP)-dependent bile salt transporters. Mutations in human BSEP were identified as the cause of progressive familial intrahepatic cholestasis type 2. BSEP protein is highly identical with its rat and mouse orthologs and has not yet been functionally characterized; the effect of BSEP mutations on its function has also not been studied. Therefore, the aim of this study was to functionally characterize human BSEP. Methods: Complementary DNA for BSEP was isolated from human liver and expressed with the baculovirus system in Sf9 cells. ATP-dependent bile salt transport assays were performed with Sf9 cell vesicles expressing BSEP and a rapid filtration assay. Results: Cloning of human BSEP required the inactivation of a bacterial cryptic promoter motif within its coding region. BSEP expressed in Sf9 cells transports different bile salts in an ATP-dependent manner with Michaelis constant values as follows: taurocholate, 7.9 ± 2.1 μmol/L; glycocholate, 11.1 ± 3.3 μmol/L; taurochenodeoxycholate, 4.8 ± 1.7 μmol/L; tauroursodeoxycholate, 11.9 ± 1.8 μmol/L. The rank order of the intrinsic clearance of bile salts was taurochenodeoxycholate > taurocholate > tauroursodeoxycholate > glycocholate. Conclusions: This study characterizes human BSEP as an ATP-dependent bile salt export pump with transport properties similar to its rat and mouse orthologs. Expression of BSEP in Sf9 cells will enable functional characterization of the consequences of mutations in the human BSEP gene.GASTROENTEROLOGY 2002;123:1659-1666

Relationships amongst liver bile salt clearance, bile secretion and infusion of lipids in calves.

In order to study the influence of portal lipid loading on the extraction rate of bile salts by the liver, four cholecystectomized calves (mean body weight 103 kg) were fitted with permanent cannulae to the common bile duct, duodenum and portal vein. A venflon catheter was also set up in the jugular vein to collect blood for analysis of fatty acids (FA) and bile salts (PBS) in plasma. The experiments were divided into two parts. In the first part sodium taurocholate (TCHNa) was infused for at least 2 h at a rate of 25 mumol/min into the duodenum to stabilize the bile flow and bile salt output in bile and the concentration in plasma. In the second part, as well as TCHNa, Intralipid (Itlp) (infusible 10% of lipid compounds) was also infused into the portal vein. Itlp was infused for 40 min, starting at a rate of 3 ml/min at the beginning of the 3rd hour of TCHNa infusion followed by a rate of 6 ml/min at the beginning of the 4th hour of TCHNa infusion. During TCHNa infusion the plasma bile salt concentrations were in the range 15.69-20.21 mumol/l, similar to that of the pre-infusion period. Introduction of Itlp to the infusion of TCHNa resulted in a significant (P < 0.05) increase of PBS, about 2 times higher at an Itlp infusion rate of 3 ml/min, and 3 times higher (62.82 +/- 16.42 mumol/l) at 6 ml/min. Under Itlp infusion, all common plasma FA increased, but the largest increases were in levels of linolenic, palmitic and oleic acids. During TCHNa infusion, the bile flow and the content of bile salts in bile did not change. The infusion of TCHNa with Itlp at the rate of 6 ml/min caused a 2-fold decrease both of the bile flow and of the output of bile salts from 18.58 +/- 3.04 microliters/min/kg and from 0.58 +/- 0.07 mumol/min/kg observed at the beginning of both infusions to 9.51 +/- 2.95 microliters/min/kg and 0.28 +/- 0.05 mumol/min/kg, respectively, at the end of the collecting period. When only TCHNa was infused, almost all of it was secreted to the bile, while with the additional infusion of Itlp only about half of the infused TCHNa was secreted to the bile. These results indicate that the extraction rate of PBS by the liver is decreased by loading of the portal blood by lipids, allowing more bile salts to escape into the systemic circulation, and thus reducing bile production.

Passive jejunal bile salt absorption alters the enterohepatic circulation in immature rats

Background: Developmental changes in passive bile salt absorption may alter the enterohepatic circulation. Methods: 14-, 21-, and 40-day-old anesthetized male Sprague-Dawley rats were studied. Jejunum and ileum were isolated, cannulated, and injected or perfused with a taurocholate, [3H]taurocholate, and nonabsorbable marker solution. Bile was collected. Results: Using bolus injection, jejunal taurocholate absorption rates and total taurocholate absorption were nonsaturable, linearly related to taurocholate dose, and decreased from 14 days (1.62 nmol · cm−1 · min−1) to 21 days (1.05 nmol · cm−1 · min−1) and 40 days (0.54 nmol · cm−1 · min−1). While total taurocholate absorption decreased (14 days, 52.4%; 21 days, 43.7%; 40 days, 30.5%), hepatic taurocholate clearance increased (14 days, 18.2%; 21 days, 23.7%; 40 days, 37.3%). Hepatic taurocholate clearance was saturated only at 14 days. Using jejunal perfusion, total taurocholate absorption (14 days, 62.0%; 21 days, 43.1%; 40 days, 45.3%) and taurocholate absorption rate decreased with age (14 days, 941.13 nmol · cm−2 · min−1 per micromole of taurocholate; 21 days, 411.28 nmol · cm −2 · min−1 per micromole of taurocholate; 40 days, 334.50 nmol · cm−2 · min−1 per micromole of taurocholate). Conclusions: Passive jejunal bile salt absorption and decreased hepatic bile salt clearance could account for the low intraluminal and high serum bile salt levels observed in immature animals and in human neonates.

The effect of age on the intravenous sodium glycocholate test

The clearance of an injected dose of sodium glycocholate has been studied in a group of 23 control subjects who had no evidence of liver disease. A significant correlation was found between bile salt clearance and age. No significant difference was found between the bile salt clearance of male and female subjects. Data derived from a simple compartmental model indicated that decreased clearance of bile salt with age was not specifically related to degenerative changes in hepatocellular integrity, hepatic uptake of bile salts or bile flow.