Sodium-dependent Bile Acid Transporter Research Articles

Defining Substrate Binding Site in Sodium-Dependent Bile Acid Transporters

Bile acids are stored in the gallbladder and excreted into the digestive tract where they assist absorption of lipids and vitamins. Bile acids are synthesized from cholesterol in the liver before they are stored and entered into the small intestine. In the small intestine, more than 95% of the bile acids are absorbed and sent back to the liver through a process known as enterohepatic circulation. In humans, there are two Na+-dependent transporters that play an essential role in enterohepatic circulation—Na+-taurocholate co-transporting polypeptide (NTCP) and apical sodium-dependent bile acid transporter (ASBT). NTCP and ASBT share 35% sequence identity and both belong to the solute carrier 10 (Slc10A) family of secondary transporters. NTCP, in addition to its role in bile acid transport, is required for infection of hepatitis B virus because it serves as a co-receptor for human hepatitis B and D virus. ASBT is crucial to enterohepatic circulation as it has been correlated to multiple digestive illnesses, and has become a potential drug target for hypercholesterolaemia, type 2 diabetes, and constipation. Crystals structures of two bacterial homologs of human ASBT, ASBTNm and ASBTYf, have been reported, however, the two reports differ in their definition of the bile acid binding site. We will better define the bile acid binding site and its selectivity to various bile acids by making mutations to solvent exposed residues on the ASBTYf transporter and measure binding and transport of bile acids. These studies will give a better understanding of the substrate binding site of ASBT.

Bile Acid Transport by the Symporter ASBTNM: Substrate Binding and Conformational Change

The apical sodium-dependent bile acid transporter (ASBT) allows reabsorption of bile acids from the intestine by coupling bile acid movement to the sodium gradient. Such transporters are attractive targets for drug delivery and in the treatment for hypercholesterolaemia. Several structures of bacterial homologues in both inward and outward facing conformations have been obtained experimentally, including a substrate-bound inward facing structure of the homologue from Neisseria meningitidis (ASBTNM). However, many details surrounding the binding of substrates and the conformational transition remain unclear. We have used experimental and computational methods to explore these details at an atomistic scale using the homologue ASBTNM and the bile acid taurocholate. Models of apo and substrate-bound ASBTNM in the outward-facing conformation were generated. Biased molecular dynamics simulations and free energy calculations were used to explore conformational changes and possible movement of taurocholate during the transition by an elevator mechanism. Probability distributions and the residues important for binding of sodium and taurocholate in wild type and mutant ASBTNM were investigated with unbiased simulations, revealing alternative sodium binding sites. These results further our understanding of the important molecular details of ASBT function.

An Update on Further Progression of NAFLD, NASH with Prospective Therapies Like L-Carnitine (LC), Nicotinamide Ribose (NR) Combination, as well as Apical Sodium Dependent Bile Acids Transporter (ASBT) or Volixibat and Silybin as Alternatives

An Update on Further Progression of NAFLD, NASH with Prospective Therapies Like L-Carnitine (LC), Nicotinamide Ribose (NR) Combination, as well as Apical Sodium Dependent Bile Acids Transporter (ASBT) or Volixibat and Silybin as Alternatives

Bile Acid Receptor Therapeutics Effects on Chronic Liver Diseases.

In the past ten years, our understanding of the importance of bile acids has expanded from fat absorption and glucose/lipid/energy homeostasis into potential therapeutic targets for amelioration of chronic cholestatic liver diseases. The discovery of important bile acid signaling mechanisms, as well as their role in metabolism, has increased the interest in bile acid/bile acid receptor research development. Bile acid levels and speciation are dysregulated during liver injury/damage resulting in cytotoxicity, inflammation, and fibrosis. An increasing focus to target bile acid receptors, responsible for bile acid synthesis and circulation, such as Farnesoid X receptor and apical sodium-dependent bile acid transporter to reduce bile acid synthesis have resulted in clinical trials for treatment of previously untreatable chronic liver diseases such as non-alcoholic steatohepatitis and primary sclerosing cholangitis. This review focuses on current bile acid receptor mediators and their effects on parenchymal and non-parenchymal cells. Attention will also be brought to the gut/liver axis during chronic liver damage and its treatment with bile acid receptor modulators. Overall, these studies lend evidence to the importance of bile acids and their receptors on liver disease establishment and progression.

The alpha-glucosidase inhibitor miglitol increases hepatic CYP7A1 activity in association with altered short-chain fatty acid production in the gut of obese diabetic mice

PurposeBile acids (BAs) have been shown to contribute to glucose and energy homeostasis. We have recently reported that miglitol, an alpha-glucosidase inhibitor, increases fecal BA excretion and ameliorate insulin resistance and obesity in mice. The aim of this study was to clarify the mechanisms by which miglitol affects BA metabolism. The expression of genes regulating BA metabolism, gut microbiome and short-chain fatty acids (SCFA) were examined. ProceduresNSY mice, representing an obese type 2 diabetic model, were fed with a high-fat diet with or without miglitol for 4 weeks. The expression of BA-related genes in the liver and the lower intestine were measured. Alterations in fecal microbiome, fecal SCFA along with plasma lipid levels were also evaluated. Major findingsMiglitol significantly increased fecal BA secretion and markedly upregulated the mRNA expression, protein levels and enzyme activity of hepatic cholesterol 7α-hydroxylase, a rate-limiting enzyme of BA synthesis. In the intestine, miglitol treatment significantly suppressed the mRNA expression of apical sodium-dependent bile acid transporter and ATP-binding cassette transporter G5 and G8. In fecal microbiome, the prevalence of prevotella was remarkably reduced and that of clostridium subcluster XIVa was increased by miglitol. Miglitol elevated formic and n-butyric acids along with total SCFA concentration in feces, while succinic acid was decreased. There was no change in plasma total cholesterol levels. ConclusionsCollectively, miglitol may affect BA metabolism via enhanced CYP7A1 activity resulting from at least in part the alterations in gut microbiome and SCFA production in obese diabetic mice.

The inhibitors of the apical sodium-dependent bile acid transporter (ASBT) as promising drugs

Inhibition of the apical sodium-dependent bile acid transporter (ASBT, also known as IBAT - ileal bile acid transporter, SLC10A2) leads to disruption of the enterohepatic circulation of bile acids and their excretion with fecal masses. This is accompanied by cholesterol utilization for synthesis of new bile acids. ASBT inhibitors are promising drugs for the treatment of such diseases as non-alcoholic fatty liver disease, non-alcoholic steatohepatitis, type 2 diabetes mellitus, necrotic enterocolitis, chronic constipation, atherosclerosis. To date the most known chemically synthesized inhibitors are: A3309, SHP626, A4250, 264W94, GSK2330672, SC-435. All of them are at different stages of clinical trials, which confirm the high efficacy and good tolerance of these inhibitors. Current trends in this field also include directed chemical synthesis of ASBT inhibitors, as well as their search among substances of plant origin.

Maralixibat Treatment Significantly Reduces Pruritus and Serum Bile Acids in Patients with Alagille Syndrome: Results from a Randomized Phase II Study with 4 Years of Follow-Up

Background: Alagille syndrome (ALGS) is a rare genetic disease that often presents with severe cholestasis and pruritus. There are no approved drugs for management. Maralixibat, an apical sodium-dependent bile acid transport inhibitor, prevents enterohepatic bile acid recirculation. We evaluated the safety and efficacy of maralixibat for children with cholestasis in ALGS. Methods: ICONIC was a randomized, placebo-controlled, drug-withdrawal, Phase IIb study with open-label extension in children with ALGS (NCT02160782). Eligible participants had >3x normal serum bile acid (sBA) levels and intractable pruritus. After 18 weeks of maralixibat 380 μg/kg once daily, participants were randomized 1:1 to continue maralixibat or receive placebo for 4 weeks. Subsequently, all participants received open-label maralixibat to Week 48. During the long-term extension (204 weeks reported), doses were increased up to 380 μg/kg twice daily. The primary endpoint was the mean sBA change during the randomized withdrawal in participants with ≥50% sBA reduction by Week 18. Cholestasis was assessed using pruritus (observer-, patient- and clinician-rated; 0-4 scale), growth and liver function. Findings: Between October 2014 and August 2015, 31 participants (mean age: 5.4 years) were enrolled and 28 analyzed at Week 48. In the randomized-withdrawal period, participants switched to placebo experienced significant increases in sBA (+94 µmol/L; p=0.0130) and pruritus (+1.7 pts; p<0.0001), whereas those continuing maralixibat maintained treatment response. From Baseline to Week 48, sBA (‑96 µmol/L; p=0.0058), pruritus (-1.6 pts, p<0.0001), xanthomas (-0.9 pts; p=0.0006), height (+0.18 z-score; p=0.0704) and quality of life (+9 pts; p=0.0200) improved. In those continuing to Week 204 (n=15) all improvements were maintained. Throughout, no increase in adverse event frequency or severity was observed. Interpretation: In children with ALGS, maralixibat is the first agent to demonstrate significant, durable, and clinically meaningful improvements in cholestasis. Maralixibat represents a new treatment paradigm for chronic cholestasis in ALGS. Trial Registration: NCT02160782 Funding: Funded by Mirum Pharmaceuticals. Declaration of Interests: EG has received consultancy fees from Mirum Pharmaceuticals, Albireo, and Laboratoires CTRS. AB has received grants and research support from Mirum Pharmaceuticals. ES has received consultancy fees from Mirum Pharmaceuticals and Albireo and has received travel support from Albireo. KDRS has received consultancy fees from Retrophin and Sanitarium Health and Wellbeing Company and is a stockholder in Asklepion Pharmaceuticals, LLC, Ausio Pharmaceuticals, LLC, and Aliveris s.r.l. CK and TJ are shareholders in Mirum Pharmaceuticals. NKD is a stockholder in and employee of Takeda. PV and AJW are stockholders in and employees of Mirum Pharmaceuticals. EJ has received consultancy fees from Laboratoires CTRS and is a stockholder of Laboratoires CTRS and Vivet Therapeutics AD was an employee of Lumina Pharmaceuticals and has received personal fees from Shire Pharmaceuticals. WH, MS, LH, AL, FL, AL, and JS have no conflicts of interest to declare. Ethics Approval Statement: This study was conducted in accordance with the Declaration of Helsinki and Good Clinical Practice Guidelines and approved by institutional review boards and ethics committees. Informed consent (and assent) was obtained from the participant or their legal guardian.

Primary biliary cholangitis: pathogenesis and therapeutic opportunities.

Primary biliary cholangitis is a chronic, seropositive and female-predominant inflammatory and cholestatic liver disease, which has a variable rate of progression towards biliary cirrhosis. Substantial progress has been made in patient risk stratification with the goal of personalized care, including early adoption of next-generation therapy with licensed use of obeticholic acid or off-label fibrate derivatives for those with insufficient benefit from ursodeoxycholic acid, the current first-line drug. The disease biology spans genetic risk, epigenetic changes, dysregulated mucosal immunity and altered biliary epithelial cell function, all of which interact and arise in the context of ill-defined environmental triggers. A current focus of research on nuclear receptor pathway modulation that specifically and potently improves biliary excretion, reduces inflammation and attenuates fibrosis is redefining therapy. Patients are benefiting from pharmacological agonists of farnesoid X receptor and peroxisome proliferator-activated receptors. Immunotherapy remains a challenge, with a lack of target definition, pleiotropic immune pathways and an interplay between hepatic immune responses and cholestasis, wherein bile acid-induced inflammation and fibrosis are dominant clinically. The management of patient symptoms, particularly pruritus, is a notable goal reflected in the development of rational therapy with apical sodium-dependent bile acid transporter inhibitors.

Gluco-Metabolic Effects of Pharmacotherapy-Induced Modulation of Bile Acid Physiology.

The discovery and characterization of the bile acid specific receptors farnesoid X receptor (FXR) and Takeda G protein-coupled receptor 5 (TGR5) have facilitated a wealth of research focusing on the link between bile acid physiology and glucose metabolism. Modulation of FXR and TGR5 activation have been demonstrated to affect the secretion of glucagon-like peptide 1, insulin, and glucagon as well as energy expenditure and gut microbiota composition, with potential beneficial effects on glucose metabolism. A search strategy based on literature searches in on PubMed with various combinations of the key words FXR, TGR5, agonist, apical sodium-dependent bile acid transporter (ASBT), bile acid sequestrant, metformin, and glucose metabolism has been applied to obtain material for the present review. Furthermore, manual searches including scanning of reference lists in relevant papers and conference proceedings have been performed. This review provides an outline of the link between bile acid and glucose metabolism, with a special focus on the gluco-metabolic impact of treatment modalities with modulating effects on bile acid physiology; including FXR agonists, TGR5 agonists, ASBT inhibitors, bile acid sequestrants, and metformin. Any potential beneficial gluco-metabolic effects of FXR agonists remain to be established, whereas the clinical relevance of TGR5-based treatment modalities seems limited because of substantial safety concerns of TGR5 agonists observed in animal models. The glucose-lowering effects of ASBT inhibitors, bile acid sequestrants, and metformin are at least partly mediated by modulation of bile acid circulation, which might allow an optimization of these bile acid-modulating treatment modalities. (J Clin Endocrinol Metab XX: 00-00, 2019).

Efficient reabsorption of transintestinally excreted cholesterol is a strong determinant for cholesterol disposal in mice

Transintestinal cholesterol excretion (TICE) is a major route for eliminating cholesterol from the body and a potential therapeutic target for hypercholesterolemia. The underlying mechanism, however, is largely unclear, and its contribution to cholesterol disposal from the body is obscured by the counteracting process of intestinal cholesterol reabsorption. To determine the quantity of TICE independent from its reabsorption, we studied two models of decreased intestinal cholesterol absorption. Cholesterol absorption was inhibited either by ezetimibe or, indirectly, by the genetic inactivation of the intestinal apical sodium-dependent bile acid transporter (ASBT; SLC10A2). Both ezetimibe treatment and Asbt inactivation virtually abrogated fractional cholesterol absorption (from 46% to 4% and 6%, respectively). In both models, fecal neutral sterol excretion and net intestinal cholesterol balance were considerably higher than in control mice (5- and 7-fold, respectively), suggesting that, under physiological conditions, TICE is largely reabsorbed. In addition, the net intestinal cholesterol balance was increased to a similar extent but was not further increased when the models were combined, suggesting that the effect on cholesterol reabsorption was already maximal under either condition alone. On the basis of these findings, we hypothesize that the inhibition of cholesterol (re)absorption combined with stimulating TICE will be most effective in increasing cholesterol disposal.

Impaired Intestinal Farnesoid X Receptor Signaling in Cystic Fibrosis Mice.

Background & AimsThe bile acid (BA)-activated farnesoid X receptor (FXR) controls hepatic BA synthesis and cell proliferation via the intestinal hormone fibroblast growth factor 19. Because cystic fibrosis (CF) is associated with intestinal dysbiosis, anomalous BA handling, and biliary cirrhosis, we investigated FXR signaling in CF.MethodsIntestinal and hepatic expression of FXR target genes and inflammation markers was assessed in Cftr null mice and controls. Localization of the apical sodium-dependent BA transporter was assessed, and BAs in gastrointestinal tissues were analyzed. The CF microbiota was characterized and FXR signaling was investigated in intestinal tissue and organoids.ResultsIleal murine fibroblast growth factor 19 ortholog (Fgf15) expression was strongly reduced in CF mice, compared with controls. Luminal BA levels and localization of apical sodium-dependent BA transporter was not affected, and BAs induced Fgf15 up to normal levels in CF ileum, ex vivo, and CF organoids. CF mice showed a dysbiosis that was associated with a marked up-regulation of genes involved in host–microbe interactions, including those involved in mucin glycosylation, antimicrobial defense, and Toll-like receptor signaling. Antibiotic treatment reversed the up-regulation of inflammatory markers and restored intestinal FXR signaling in CF mice. Conversely, FXR-dependent gene induction in ileal tissue and organoids was repressed by bacterial lipopolysaccharide and proinflammatory cytokines, respectively. Loss of intestinal FXR activity was associated with a markedly blunted hepatic trophic response to oral BA supplementation, and with impaired repression of Cyp7a1, the gene encoding the rate-limiting enzyme in BA synthesis.ConclusionsIn CF mice, the gut microbiota represses intestinal FXR activity, and, consequently, FXR-dependent hepatic cell proliferation and feedback control of BA synthesis.

The Origin of Follicular Bile Acids in the Human Ovary

Bile acids (BAs) are present in ovarian follicular fluid (FF) and are linked to embryo development. However, information on the source of ovarian BA is scarce. Therefore, we aimed to explore local ovarian synthesis and BA transport from blood into FF. BA levels were determined in matching FF and serum from women undergoing invitro fertilization. Invitro BA production by human mural granulosa cells (MGCs) and cumulus granulosa cells (CGCs) was measured by mass spectrometry. Gene and protein expression were quantified in MGC and CGC and in human ovarian tissue by quantitative PCR and Western blot/immunohistochemistry, respectively. BA levels in blood and FF were significantly correlated (rs=0.186, P=0.027) but were almost twofold higher in FF (P<0.001). Primary BA levels were increased in FF, indicating that, in addition to passive diffusion, other sources of ovarian BA might exist. The key BA synthesis enzyme cytochrome P450 A1 was absent in MGC and CGC; BA production invitro was undetectable. Therefore, local ovarian BA production is unlikely. However, common BA importers (Na+/taurocholate cotransporting polypeptide, apical sodium-dependent bile acid transporter) and an exporter (ATP-binding cassette subfamily C member 3) were identified in GC, theca cells, and oocyte. In summary, these results suggest that passive and active transport of BAs from blood into FF constitute sources of FF BA.

Single small molecule-assembled nanoparticles mediate efficient oral drug delivery.

Oral drug delivery, which requires surviving the harsh environment in the gastrointestinal (GI) tract and penetrating the intestinal epithelium, has not been achieved using simple formulation nanoparticles (NPs). Medicinal natural products (MNPs) have been widely used in traditional medicine for disease management through oral consumption. However, most pharmacologically active compounds within MNPs do not have the properties suitable for oral applications. We hypothesize that some MNPs contain natural nanomaterials that can convert those compounds into oral formulations by forming NPs. After screening 66 MNPs, we identified five classes of small molecules that form NPs, many of which are capable of efficient drug encapsulation and GI penetration. We show that one of them, dehydrotrametenolic acid (DTA), is capable of mediating oral delivery for effective disease treatment. We determine that DTA NPs assemble through hydrogen bonding and penetrate the GI tract via apical sodium-dependent bile acid transporter. Our study reveals a novel class of single component, small molecule- assembled NPs for oral drug delivery, and suggests a novel approach to modernizing MNPs through nanomaterial discovery.

Homo- and heterodimerization is a common feature of the solute carrier family SLC10 members.

The solute carrier family SLC10 consists of seven members, including the bile acid transporters Na+/taurocholate co-transporting polypeptide (NTCP) and apical sodium-dependent bile acid transporter (ASBT), the steroid sulfate transporter SOAT as well as four orphan carriers (SLC10A3, SLC10A4, SLC10A5 and SLC10A7). Previously, homodimerization of NTCP, ASBT and SOAT was described and there is increasing evidence that carrier oligomerization is an important regulatory factor for protein sorting and transport function. In the present study, homo- and heterodimerization were systematically analyzed among all SLC10 carriers (except for SLC10A3) using the yeast-two-hybrid membrane protein system. Strong homodimerization occurred for NTCP/NTCP, ASBT/ASBT and SLC10A7/SLC10A7. Heterodimerization was observed for most of the SLC10 carrier combinations. Heterodimerization of NTCP was additionally investigated by co-localization of NTCP-GFP and NTCP-mScarlet with respective SLC10 carrier constructs. NTCP co-localized with SLC10A4, SLC10A5, SOAT and SLC10A7. This co-localization was most pronounced for SLC10A4 and was additionally confirmed by co-immunoprecipitation. Interestingly, SLC10 carrier co-expression decreased the taurocholate transport function of NTCP for most of the analyzed constructs, indicating that SLC10 carrier heterodimerization is of functional relevance. In conclusion, homo- and heterodimerization is a common feature of the SLC10 carriers. The relevance of this finding for regulation and transport function of the SLC10 carriers in vivo needs further investigation.

Apical sodium-dependent bile acid transporter inhibition with volixibat improves metabolic aspects and components of non-alcoholic steatohepatitis in Ldlr-/-.Leiden mice.

Interruption of bile acid recirculation through inhibition of the apical sodium-dependent bile acid transporter (ASBT) is a promising strategy to alleviate hepatic cholesterol accumulation in non-alcoholic steatohepatitis (NASH), and improve the metabolic aspects of the disease. Potential disease-attenuating effects of the ASBT inhibitor volixibat (5, 15, and 30 mg/kg) were investigated in high-fat diet (HFD)-fed Ldlr-/-.Leiden mice over 24 weeks. Plasma and fecal bile acid levels, plasma insulin, lipids, and liver enzymes were monitored. Final analyses included liver histology, intrahepatic lipids, mesenteric white adipose tissue mass, and liver gene profiling. Consistent with its mechanism of action, volixibat significantly increased the total amount of bile acid in feces. At the highest dose, volixibat significantly attenuated the HFD-induced increase in hepatocyte hypertrophy, hepatic triglyceride and cholesteryl ester levels, and mesenteric white adipose tissue deposition. Non-alcoholic fatty liver disease activity score (NAS) was significantly lower in volixibat-treated mice than in the HFD controls. Gene profiling showed that volixibat reversed the inhibitory effect of the HFD on metabolic master regulators, including peroxisome proliferator-activated receptor-γ coactivator-1β, insulin receptor, and sterol regulatory element-binding transcription factor 2. Volixibat may have beneficial effects on physiological and metabolic aspects of NASH pathophysiology.

Tyrosine Phosphorylation Regulates Plasma Membrane Expression and Stability of the Human Bile Acid Transporter ASBT (SLC10A2).

The human apical sodium-dependent bile acid transporter (hASBT; SLC10A2) is responsible for the reclamation of bile acids from the intestinal lumen, providing a primary mechanism for bile acid and cholesterol homeostasis. However, the regulation of hASBT at the post-translational level is not well understood. In the present study, we investigated the role of Src family kinases (SFKs) and protein tyrosine phosphatases (PTPs) in the regulation of surface expression and function of hASBT. Inhibition of Src family kinases, via treatment with PP2, significantly reduced hASBT function, while the inhibition of PTPs by activated orthovanadate significantly induced function. Src family kinase inhibition by PP2 was associated with a concomitant decrease in maximum transport velocity (Jmax) correlated with a decrease in hASBT surface expression. Interestingly, PP2-mediated suppression of hASBT protein expression was rescued by the proteasome inhibitor MG132, suggesting that dephosphorylation impacts protein stability with the subsequent proteasome-dependent degradation of hASBT. Consequently, single-point mutations were introduced at five intracellular tyrosine residues: Y148F, Y216F, Y308F, Y311F, and Y337F. Although all mutants had significantly altered hASBT function without changes in total cellular expression, sequential tyrosine mutations at the five residues above rendered hASBT nonfunctional with diminished protein expression. Furthermore, orthovanadate-induced transport activity of single-point tyrosine mutants suggested a role for multiple tyrosine residues in the regulation of hASBT function and membrane expression. Overall, our data confirms that tyrosine phosphorylation mediated by Src family kinases (SFKs), in particular, regulates surface expression, function, and stability of hASBT.

Western Diet-Induced Dysbiosis Is Associated with Intestinal Hyperplasia and Dysregulation of FXR-FGF19 Gene Expression in Juvenile Iberian Pigs (OR26-03-19)

ObjectivesThe Western diet has been associated with increased risk of colon cancer, partially due to changes in bile acid (BA) homeostasis. While diet-induced proliferation of intestinal mucosa has been documented in adults, it is unclear whether it can develop in pediatric populations. We hypothesize that feeding a high-fat high-fructose (HFF) diet to neonatal pigs will increase BA levels in liver and plasma, and cell proliferation in intestinal mucosa. In addition, we hypothesize that supplementation of a probiotic mixture with Pediococcus, Lactobacillus and Bacillus at 6.2 × 104 cfu/mL will ameliorate the HFF pro-proliferative effect. MethodsTo test the hypothesis we used 10-d old Iberian pigs, which have a leptin-resistant phenotype resulting in rapid development of obesity and dyslipidemia. Diets contained (g/kg body weight × d) 0 g fructose, 11 g fat and 199 kcal (CON-N; n = 8), 22 g fructose, 16 g fat and 300 kcal (HFF-N; n = 6), CON + probiotic (CON-P; n = 6), or HFF + probiotic (HFF-P; n = 6). Pigs were euthanized at 80 d of age. Liver and plasma BA levels were analyzed by LC-MS. Hyperplasia in colon and distal ileum (DI) was assessed by hematoxylin-eosin and Ki-67 staining. Bacteria in colon content were quantified at genus level by 16S ribosomal RNA analysis. Gene expression of farnesoid X receptor (FXR), small heterodimer partner (SHP), fibroblast growth factor 19 (FGF19), organic solute transporter (OST) α, apical sodium-dependent BA transporter (ASBT), tumor necrosis factor (TNF) α, tumor growth factor (TGF) β, takeda G-protein receptor (TGR) 5, and epidermal growth factor receptor (EGFR) was measured by qPCR. ResultsHFF-N an HFF-P increased taurocholate and glyocholate in liver and plasma (P ≤ 0.0001), crypt depth, villi length and Ki-67 + cells/crypt (P ≤ 0.01) in colon and DI, and Clostridium, Bacteroides, Synergistes, and Bilophila populations in colon content (P ≤ 0.05). HFF-N and HFF-P increased expression of SHP, OSTα, and ASBT and decreased FGF19 in DI (P ≤ 0.05), and increased SHP and decreased TNFα and TGFβ in colon (P ≤ 0.05). FXR, TGR5 and EGFR did not differ between groups. ConclusionsA high-fructose high-fat diet increased liver and plasma BA levels and downregulated FGF19 expression in DI. Colonic hyperplasia, proliferation of BA tolerant bacteria and changes in SHP, TNFα and TGFβ may be related to increased secondary BA in the colon. Funding SourcesARI, AcornSeekers, STRIDE.

Bile Acid Transporters Are Expressed and Heterogeneously Distributed in Rat Bile Ducts.

Background/AimsCholangiocytes are capable of reabsorbing bile salts from bile, but the pathophysiological significance of this process is unclear. To this end, we detected the expression and distribution of bile acid transport proteins in cholangiocytes from normal rat liver and analyzed the possible pathophysiological significance.MethodsBile duct tissues of Sprague-Dawley rats were isolated by enzymatic digestion and mechanical isolation, and then divided into large and small bile duct tissues. Immunohistochemistry, real-time polymerase chain reaction and Western blotting were used to determine the expression of the apical sodium-dependent bile acid transporter (ASBT), ileal bile acid binding protein (IBABP), and basolateral organic solute transporter α (Ostα) in the biliary tract system of rats. Differences in the expression and distribution of these proteins were analyzed.ResultsIn cholangiocytes, ASBT and IBABP were mainly expressed in cholangiocytes of the large bile ducts, in which the expression of both was significantly higher than that in the small ducts (p<0.05). Ostα was simultaneously expressed in cholangiocytes of both the large and small bile ducts, showing no significant difference in expression between the two groups of bile ducts (p>0.05).ConclusionsBile acid transporters are expressed and heterogeneously distributed in rat bile ducts, indicating that bile acid reabsorption by cholangiocytes might mainly occur in the large bile ducts. These findings may help explore the physiology of bile ducts and the pathogenesis of various cholangiopathies.

1093 – A Novel Role of S-Acylation in the Modulation of Ileal Apical Sodium-Dependent Bile Acid Transporter (ASBT) Function

1093 – A Novel Role of S-Acylation in the Modulation of Ileal Apical Sodium-Dependent Bile Acid Transporter (ASBT) Function

330 – Pharmacological Inhibition of the Apical Sodium-Dependent Bile Acid Transporter (ASBT) Protects Ileal Enterocytes from Bile Acid-Induced Injury in Adult Organic Anion Transporter-Alpha (OSTα) Null Mice

330 – Pharmacological Inhibition of the Apical Sodium-Dependent Bile Acid Transporter (ASBT) Protects Ileal Enterocytes from Bile Acid-Induced Injury in Adult Organic Anion Transporter-Alpha (OSTα) Null Mice