Expression Of Bile Acid Transporters Research Articles

Treatment of a Mouse Model of Cholestasis with a Thyromimetic Improves Biliary Injury But Exacerbates Hepatocyte Injury

Chronic cholestasis results from bile secretory defects or impairment of bile flow, and there are few effective medical therapies available. Thyroid hormone T3 and synthetic thyroid hormone receptor agonists are known to cause induction of hepatocyte proliferation during liver regeneration. However, whether these drugs have therapeutic benefits in cholestatic liver disease is unknown. In this study, we administered GC‐1, a thyromimetic that preferentially acts through the TRb receptor found predominantly in liver, to Mdr2 knockout (KO) mice, which is a commonly used model of sclerosing cholangitis characterized by bile acid (BA) regurgitation, periductular inflammation, and fibrosis. We determined Mdr2 KO mice fed 5mg/kg GC‐1 diet had decreased bilirubin, liver to body weight ratios, serum alkaline phosphatase, but increased serum alanine aminotransferase and aspartate aminotransferase compared to KO mice fed normal diet as early as 1 week on diet. Histologically, KO mice on GC‐1 diet had decreased ductular response, less bridging fibrosis, and fewer SOX9 positive hepatocytes compared to KO on normal diet. Although total liver BA were higher in KO mice fed GC‐1 diet for 2 weeks compared to normal diet, they normalized to KO levels at 4 weeks of diet. To elucidate the mechanism of increased BA accumulation and liver injury, we examined expression of BA transporters and detoxification enzymes. KO mice on GC‐1 diet had decreased bilirubin transport and detoxification genes, such as Mrp3, Cyp2b10, and Oatp4, compared to KO mice on normal diet, with the net result being retention of BA in the hepatocyte. Affymetrix gene array data also indicates that KO mice on GC‐1 have normalized bile acid synthesis compared to WT expression levels. Thus, GC‐1 reduces cholangiocyte injury during cholestasis by inducing retention of BA in hepatocytes, causing injury to the hepatocytes; this occurs through as‐yet unknown mechanisms that are upstream of BA transporters and biosynthesis enzymes and appears to be b‐catenin independent.Support or Funding InformationNational Institute of Biomedical Imaging and Bioengineering of the National Institute of Health under Award Number T32EB0010216UPP Academic Foundation Award 1R01DK103775This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Defective FXR-FGF15 signaling and bile acid homeostasis in cystic fibrosis mice can be restored by the laxative polyethylene glycol.

The gastrointestinal phenotype of cystic fibrosis (CF) features intestinal bile acid (BA) malabsorption, impaired intestinal farnesoid X receptor (FXR) activation, and consequently reduced fibroblast growth factor 19 (FGF19, FGF15 in mice) production. The osmotic laxative polyethylene glycol (PEG) has been shown to decrease intestinal mucus accumulation in CF mice and could, by doing so, improve BA reabsorption. Here we determined the effect of PEG on BA excretion and FXR-FGF15 signaling in CF mice. Male Cftr-/-tm1Unc (CF) and wild-type (WT) littermates were administered PEG 4000 in drinking water and fed either chow or a semisynthetic diet. PEG was withdrawn for 3 days before termination. Fecal BA excretion was measured at PEG dosages of 37 g/l (100%) and 0 g/l (0%). Ileal FXR activation was assessed by gene expression of its downstream targets Fgf15 and small heterodimer partner ( Shp). In CF mice, PEG withdrawal increased fecal BA excretion on either diet compared with full PEG dosage (chow, 2-fold, P = 0.06; semisynthetic, 4.4-fold, P = 0.007). PEG withdrawal did not affect fecal BA excretion in WT mice on either diet. After PEG withdrawal, gene expression levels of intestinal FXR target genes Fgf15 and Shp were decreased in CF mice but unaffected in WT littermates. PEG did not affect the gene expression of the main intestinal BA transporter apical sodium-dependent bile acid transporter (ASBT). PEG treatment ameliorates intestinal BA malabsorption in CF mice and restores intestinal FXR-FGF15 signaling, independent from Asbt gene expression. These findings highlight the potential of PEG in the prevention and treatment of the gastrointestinal phenotype of CF. NEW & NOTEWORTHY A gastrointestinal feature of cystic fibrosis is bile acid malabsorption and consequent impairment of farnesoid X receptor (FXR)-fibroblast growth factor 15 (FGF15) signaling. FXR-FGF15 signaling regulates various metabolic processes and could be implicated in metabolic and gastrointestinal complications of cystic fibrosis, such as diabetes and liver disease. In cystic fibrosis mice, treatment with the osmotic laxative polyethylene glycol is associated with decreased fecal bile acid loss and restoration of FXR-FGF15 signaling.

Identification of amniotic fluid metabolomic and placental transcriptomic changes associated with abnormal development of cloned pig fetuses.

Piglets cloned by somatic cell nuclear transfer (SCNT) show a high incidence of malformations and a high death rate during the perinatal period. To investigate the underlying mechanisms for abnormal development of cloned pig fetuses, we compared body weight, amniotic fluid (AF) metabolome, and placental transcriptome between SCNT- and artificial insemination (AI)-derived pig fetuses. Results showed that the body weight of SCNT pig fetuses was significantly lower than that of AI pig fetuses. The identified differential metabolites between the two groups of AF were mainly involved in bile acids and steroid hormones. The levels of all detected bile acids in SCNT AF were significantly higher than those in AI AF. The increase in the AF bile acid levels in SCNT fetuses was linked with the downregulation of placental bile acid transporter expression and the abnormal development of placental folds (PFs), both of which negatively affected the transfer of bile acids from AF across the placenta into the mother's circulation. Alteration in the AF steroid hormone levels in cloned fetuses was associated with decreased expression of enzymes responsible for steroid hormone biosynthesis in the placenta. In conclusion, cloned pig fetuses undergo abnormal intrauterine development associated with alteration of bile acid and steroid hormone levels in AF, which may be due to the poor development of PFs and the erroneous expression of bile acid transporters and enzymes responsible for steroid hormone biosynthesis in the placentas.

N-3 Fatty Acids Abrogate Dyslipidemia-Induced Changes in Bile Acid Uptake, Synthesis, and Transport in Young and Aged Dyslipidemic Rats.

In this study, the effect of n-3 fatty acids (FA) [α-linolenic acid (ALA) and eicosapentaenoic acid (EPA) + docosahexaenoic acid (DHA)] on the intestinal bile acid (BA) uptake, hepatic BA synthesis, and enterohepatic bile acid transporters (BAT) was assessed in young and aged dyslipidemic rats. Dyslipidemia was induced in young and aged rats by feeding a high-fat (HF) diet. Experimental groups received diets containing canola oil (HF + CNO) and fish oil (HF + FO) as a source of ALA and EPA + DHA, respectively. After 60 days of feeding, intestinal BA uptake and expression of apical sodium-dependent bile acid transporter (Asbt), organic solute transporter-alpha/beta (Osta/b) messenger RNA (mRNA), and hepatic expression of Na+ taurocholate cotransporting polypeptide (Ntcp), bile salt export pump (Bsep), cholesterol 7-α hydroxylase A1 (Cyp7a1), Farnesoid X receptor (Fxr), small heterodimer partner-1 (Shp), liver receptor homolog-1 (Lrh-1), and hepatic nuclear factor-4 alpha (Hnf4a) mRNA were measured. Hepatic 3-hydroxy-3-methyl-glutaryl-coenzyme A (HMG-CoA) reductase activity and total BA in serum, liver, and feces were assessed. The dyslipidemic HF group had: (1) increased intestinal BA uptake and Asbt and Osta/b mRNA expression, (2) increased BA in serum, (3) decreased hepatic expression of Ntcp, Bsep, and Cyp7a1 mRNA, (4) increased activity of HMG-CoA reductase, (5) increased hepatic expression of Fxr and Shp mRNA, (6) decreased hepatic expression of Lrh-1 and Hnf4a mRNA, and (7) decreased BA in feces, when compared to control, HF + CNO, and HF + FO groups. Immunostaining revealed increased expression of intestinal Asbt and hepatic Ntcp protein in the HF group when compared to control, HF + CNO, and HF + FO groups. n-3 FA abrogated dyslipidemia-induced changes in the intestinal uptake, hepatic synthesis, and enterohepatic transporters of BA in both young and aged rats. EPA + DHA was more effective than ALA in modulating dyslipidemia-induced changes.

Validation of hepatobiliary transport PET imaging in liver function assessment: Evaluation of 3β-[18F]FCA in mouse models of liver disease

Recently, our research group reported on the development of 3β-[18F]Fluorocholic acid (3β-[18F]FCA), a 18F labeled bile acid to detect drug interference with the bile acid transporters (drug-induced cholestasis). It was hypothesized that 3β-[18F]FCA could also be used as a non-invasive tool to monitor (regional) liver function in vivo in different liver diseases through altered expression of bile acid transporters. MethodsHepatobiliary transport of 3β-[18F]FCA was evaluated in four murine liver disease models. Acute liver injury was induced by oral gavage of an acetaminophen (APAP) overdose (300 mg/kg). Chronic cholangiopathy and non-alcoholic steatohepatitis (NASH) were induced by feeding mice 3,5-diethoxycarbonyl- 1,4-dihydrocollidine (DDC) diet or methionine and choline deficient (MCD) diet, respectively. Hepatocellular carcinoma (HCC) was evoked by intraperitoneal injection of 35 mg/kg diethylnitrosamine (DEN) once a week for 23 weeks. Gene expression of the murine bile acid transporters was determined by RT-qPCR. ResultsHepatobiliary transport of 3β-[18F]FCA was not significantly altered after an APAP overdose. Mice fed the DDC or MCD diet showed impaired transport of 3β-[18F]FCA compared to baseline, which was associated with altered expression of the bile acid transporters ntcp, oatp4 and mrp2. After recovery from DDC- and MCD-induced liver injury, 3β-[18F]FCA parameters returned to baseline. Global hepatobiliary transport of 3β-[18F]FCA in HCC bearing mice was not significantly different compared to control mice. However, HCC lesions showed reduced hepatic uptake of the tracer (tumor-to-background: 0.45 ± 0.13), which was in line with decreased in expression of basolateral bile acid uptake transporters nctp and oatp4 in tumor tissue. Conclusion3β-[18F]FCA is a useful tool to assess and longitudinally follow-up liver function in several mouse models for liver diseases that are associated with altered expression of the bile acid transporters. These results point towards the (pre)clinical utility of 3β-[18F]FCA as a PET tracer to monitor altered liver functionality in patients with chronic liver diseases.

Bile acid malabsorption is associated with diarrhea in acute phase of colitis

The enterohepatic circulation of bile acids (BAs) critically depends on BA transporters and enzymes, which can be affected by inflammatory bowel disease. Diarrhea in colitis is believed to result in part from BA malabsorption. The work aimed to investigate whether diarrhea in colitis was associated with the expression of BA transporters, enzymes, and nuclear receptors. RT-qPCR and Western blot techniques were used to evaluate the gene and protein levels of Cyp7a1, Asbt, SHP, FXR, Ostβ in a 2,4,6-trinitrobenzenesulfonic-acid-induced rat model of colitis. The total BAs (TBAs) levels were assayed using ELISA kits, and the individual BAs were measured by LC-MS/MS. Results showed that the fecal excretions of TBAs were significantly increased by 1.6-fold in acute stage of colitis. In ileum, Asbt was significantly decreased; however, there was a compensatory increase in Cyp7a1 level in liver. Moreover, FXR has a decreased tendency and the downstream target gene SHP was downregulated. Contrary to acute stage, molecular changes were completely reversible during the remission phase. Our results indicated that the expression of Asbt and Cyp7a1 were altered in acute colitis, which performed vital roles in maintaining BA homeostasis. Early medical manipulation of BA transporters and enzymes may help prevent diarrhea.

Hepatoprotective Activity of the Ethanolic Extract of Polygonum multiflorum Thunb. against Oxidative Stress-Induced Liver Injury.

Oxidative stress is an important pathological mechanism in various liver diseases. Polygonum multiflorum Thunb. (PM) can be used for the treatment of diseases associated with aging, hyperlipidemia, and oxidative stress in traditional Chinese medicine. In this study, we examined the hepatoprotective effects of the ethanolic extract of PM (PME) in in vitro and in vivo models. The PME induced expression of antioxidant-response-element- (ARE-) related genes in HepG2 cells showed a dose-dependent manner. Pretreatment of HepG2 cell with PME suppressed H2O2- and acetaminophen- (APAP-) induced cellular reactive oxygen species (ROS) generation and cytotoxicity. In APAP-induced mouse liver injury, pretreatment with PME also showed ability to increase the survival rate and reduce the severity of liver injury. Treatment with PME attenuated bile duct ligation-induced extrahepatic cholestatic liver injury and further increased multidrug resistance protein 4 (MRP4) and reduced organic anion-transporting polypeptide (OATP) expression. Furthermore, increased nuclear translocation of the nuclear factor erythroid 2-related factor 2 (Nrf2) was observed after treatment with PME in both in vivo models. In conclusion, the current study showed the hepatoprotective activity of PME by regulating the redox state in liver injury through Nrf2 activation and controlling hepatic bile acid homeostasis in obstructive cholestasis, through bile acid transporter expression modulation.

Comparison of intestinal expression of the apical sodium-dependent bile acid transporter between dogs with and without chronic inflammatory enteropathy.

BackgroundIntestinal absorption of bile acids is mediated by the apical sodium‐dependent bile acid transporter (ASBT). Fecal bile acid dysmetabolism has been reported in dogs with chronic inflammatory enteropathy (CIE).ObjectiveCharacterization of ASBT distribution along the intestinal tract of control dogs and comparison to dogs with CIE.AnimalsTwenty‐four dogs with CIE and 11 control dogs.MethodsThe ASBT mRNA and protein expression were assessed using RNA in situ hybridization and immunohistochemistry, respectively. The concentrations of fecal bile acids were measured by gas chromatography‐mass spectrometry. The fecal microbiota dysbiosis index was assessed with a quantitative polymerase chain reaction panel.ResultsIn control dogs, ASBT mRNA expression was observed in enterocytes in all analyzed intestinal segments, with highest expression in the ileum. The ASBT protein expression was restricted to enterocytes in the ileum, cecum, and colon. Dogs with CIE had significantly decreased expression of ASBT protein in the ileum (P = .001), which was negatively correlated with histopathological score (ρ = −0.40; P corr = .049). Additionally, dogs with CIE had a significantly increased percentage of primary bile acids in feces compared to controls (P = .04). The fecal dysbiosis index was significantly higher in dogs with CIE than in control dogs (P = .01).Conclusions and Clinical ImportanceThese findings indicate that ileal protein expression of ASBT is downregulated in dogs with CIE. This change may be linked to the inflammatory process, intestinal dysbiosis, and fecal bile acid dysmetabolism observed in these patients.

Diet-Induced Dysbiosis and Genetic Background Synergize With Cystic Fibrosis Transmembrane Conductance Regulator Deficiency to Promote Cholangiopathy in Mice.

The most typical expression of cystic fibrosis (CF)–related liver disease is a cholangiopathy that can progress to cirrhosis. We aimed to determine the potential impact of environmental and genetic factors on the development of CF‐related cholangiopathy in mice. Cystic fibrosis transmembrane conductance regulator (Cftr)−/− mice and Cftr +/+ littermates in a congenic C57BL/6J background were fed a high medium‐chain triglyceride (MCT) diet. Liver histopathology, fecal microbiota, intestinal inflammation and barrier function, bile acid homeostasis, and liver transcriptome were analyzed in 3‐month‐old males. Subsequently, MCT diet was changed for chow with polyethylene glycol (PEG) and the genetic background for a mixed C57BL/6J;129/Ola background (resulting from three backcrosses), to test their effect on phenotype. C57BL/6J Cftr −/− mice on an MCT diet developed cholangiopathy features that were associated with dysbiosis, primarily Escherichia coli enrichment, and low‐grade intestinal inflammation. Compared with Cftr +/+ littermates, they displayed increased intestinal permeability and a lack of secondary bile acids together with a low expression of ileal bile acid transporters. Dietary‐induced (chow with PEG) changes in gut microbiota composition largely prevented the development of cholangiopathy in Cftr −/− mice. Regardless of Cftr status, mice in a mixed C57BL/6J;129/Ola background developed fatty liver under an MCT diet. The Cftr −/− mice in the mixed background showed no cholangiopathy, which was not explained by a difference in gut microbiota or intestinal permeability, compared with congenic mice. Transcriptomic analysis of the liver revealed differential expression, notably of immune‐related genes, in mice of the congenic versus mixed background. In conclusion, our findings suggest that CFTR deficiency causes abnormal intestinal permeability, which, combined with diet‐induced dysbiosis and immune‐related genetic susceptibility, promotes CF‐related cholangiopathy.

Evidence that decreased expression of sinusoidal bile acid transporters accounts for the inhibition by rapamycin of bile flow recovery following liver ischemia

Rapamycin is employed as an immunosuppressant following organ transplant and, in patients with hepatocellular carcinoma, to inhibit cancer cell regrowth following liver surgery. Preconditioning the liver with rapamycin to induce the expression of antioxidant enzymes is a potential strategy to reduce ischemia reperfusion (IR) injury. However, pre-treatment with rapamycin inhibits bile flow, especially following ischemia. The aim was to investigate the mechanisms involved in this inhibition. In a rat model of segmental hepatic ischemia and reperfusion, acute administration of rapamycin by intravenous injection did not inhibit the basal rate of bile flow. Pre-treatment of rats with rapamycin for 24 h by intraperitoneal injection inhibited the expression of mRNA encoding the sinusoidal influx transporters Ntcp, Oatp1 and 2 and the canalicular efflux transporter Bsep, and increased expression of canalicular Mrp2. Dose-response curves for the actions of rapamycin on the expression of Bsep and Ntcp in cultured rat hepatocytes were biphasic, and monophasic for effects on Oatp1. In cultured tumorigenic H4IIE liver cells, several bile acid transporters were not expressed, or were expressed at very low levels compared to hepatocytes. In H4IIE cells, rapamycin increased expression of Ntcp, Oatp1 and Mrp2, but decreased expression of Oatp2. It is concluded that the inhibition of bile flow recovery following ischemia observed in rapamycin-treated livers is principally due to inhibition of the expression of sinusoidal bile acid transporters. Moreover, in tumorigenic liver tissue the contribution of tumorigenic hepatocytes to total liver bile flow is likely to be small and is unlikely to be greatly affected by rapamycin.

Intestinal de novo phosphatidylcholine synthesis is required for dietary lipid absorption and metabolic homeostasis

De novo phosphatidylcholine (PC) synthesis via CTP:phosphocholine cytidylyltransferase-α (CTα) is required for VLDL secretion. To determine the precise role of de novo PC synthesis in intestinal lipid metabolism, we deleted CTα exclusively in the intestinal epithelium of mice (CTαIKO mice). When fed a chow diet, CTαIKO mice showed normal fat absorption despite a ∼30% decrease in intestinal PC concentrations relative to control mice, suggesting that biliary PC can fully support chylomicron secretion under these conditions. However, when fed a high-fat diet, CTαIKO mice showed impaired passage of FAs and cholesterol from the intestinal lumen into enterocytes. Impaired intestinal lipid uptake in CTαIKO mice was associated with lower plasma triglyceride concentrations, higher plasma glucagon-like peptide 1 and peptide YY, and disruption of intestinal membrane lipid transporters after a high-fat meal relative to control mice. Unexpectedly, biliary bile acid and PC secretion was enhanced in CTαIKO mice due to a shift in expression of bile-acid transporters to the proximal intestine, indicative of accelerated enterohepatic cycling. These data show that intestinal de novo PC synthesis is required for dietary lipid absorption during high-fat feeding and that the reacylation of biliary lyso-PC cannot compensate for loss of CTα under these conditions.

Impact of Clinical Use of Parenteral Lipid Emulsions on Bile Acid Metabolism and Composition in Neonatal Piglets.

Neonates with intestinal failure dependent on parenteral nutrition (PN) are at risk of intestinal failure-associated liver disease (IFALD). PN lipid composition relates to the risk of IFALD, but the mechanisms are poorly understood. We investigated the effects of soybean oil (SO), a mixed-lipid (ML) emulsion containing fish oil (FO), and a pure FO. We hypothesized FO-containing PN lipids would result in increased gene expression of canalicular bile acid transporters and a larger, more hydrophilic bile acid pool, predictive of increased bile flow. Neonatal piglets were allocated to receive 1 of SO, ML, or FO throughout 14 days of PN feeding. Relative expression of genes involved in bile acid synthesis and transport were determined through quantitative polymerase chain reaction. Bile secreted from the liver was collected and measured. Bile acid composition was determined using tandem mass spectrometry. Regression analysis was used to determine predictors of bile flow. PN reduced bile acid secretion (P < .001). FO-containing PN lipids were associated with greater expression of bile acid and organic solute transport genes (P < .05) and greater secretion of hydrophobic bile acids (P < .001). Farnesoid X receptor (P = .01), bile salt export pump (P < .01), multidrug resistant protein 2 (P < .01), and unconjugated hyocholic acid (P < .001) independently predicted bile flow. PN lipid modulation altered bile acid metabolism and composition. These alterations may explain the hepatoprotective effects of FO-containing PN lipids and support their use in the prevention and treatment of IFALD.

Liver Inflammation Relates to Decreased Canalicular Bile Transporter Expression in Pediatric Onset Intestinal Failure

Although liver disease is a major complication of parenteral nutrition (PN) for intestinal failure (IF), its pathogenesis remains unclear. We investigated potential molecular mechanisms of liver injury in pediatric onset IF. Liver expression of canalicular phospholipid (ABCB4), bile acid (ABCB11), and sterol (ABCG5/8) transporters, their upstream regulators LXR and FXR as well as pro-inflammatory cytokines interleukin-6 (IL6) and tumor necrosis factor (TNF) were investigated among patients with IF [age median 3.8 (IQR 1.2 to 11)] in relation to biochemical and histologic liver injury, PN, serum plant sterols, fibroblast growth factor 19, and α-tocopherol. Patients receiving PN currently (n = 18) showed more advanced liver injury than patients after weaning off PN (n = 30). Histologic portal inflammation strongly segregated PN-dependent (44%) from weaned off patients (3%, P = 0.001) and coupled with progression of cholestasis and liver fibrosis. Patients with portal inflammation demonstrated markedly induced liver RNA expression of IL6 and TNF, repression of FXR and its canalicular bile transporter target gene RNA expression, including ABCB4 and ABCB11 as well as decreased protein expression of ABCB11 and ABCB4. Furthermore, upregulation of LXR and ABCG5/8 RNA expression was suppressed in patients with portal inflammation. Current PN, increased serum levels of plant sterols stigmasterol, avenasterol, and sitosterol along with serum citrulline, a marker of enterocyte mass, predicted portal inflammation. In pediatric onset IF, current PN delivery synergistically with intestinal compromise promote liver inflammation, which associates with progression of biochemical and histologic liver injury, while reducing expression of canalicular bile transporters.

Enterohepatic Circulation of Bile Acids Is Activated by Bariatric Surgery before Weight Loss Becomes Apparent

Bariatric surgery induces metabolic improvement before weight loss occurs. Plasma levels of bile acids (BA) are increased after bariatric surgery and this change is reported to contribute significantly to metabolic improvement. In this study, we investigated rats with duodeno-jejunal bypass (DJB) surgery to assess the mechanism underlying the increase in plasma BA after bariatric surgery, especially before weight loss was detectable. Sprague-Dawley rats were fed a high-fat diet for 10 weeks and then were subjected to DJB surgery. Significant weight loss was noted in the DJB rats from 4 weeks after surgery. However, plasma triglycerides (TG) and the hepatic TG content were reduced at 2 weeks after surgery, although food intake was comparable between DJB rats and sham-operated rats. Plasma levels of total BA were elevated from 2 weeks after DJB surgery. In week 2, plasma levels of cholate and chenodeoxycholate were about 5-fold higher in DJB rats than in sham-operated rats, while cecal levels of both BA were lower in DJB rats compared with sham-operated rats. The increase in plasma BA was suppressed by administration of one of bile acid sequestrants, colestimide. Intestinal expression of BA transporters (ASBT, ABCC3, and OSTα) was up-regulated in DJB rats, and hepatic expression of Cyp7A1 was also up-regulated in DJB rats at 2 weeks after surgery. These findings suggest that activation of de novo biosynthesis and increased enterohepatic circulation of BA contribute to elevation of plasma BA levels after DJB surgery before weight loss becomes apparent. These changes led to alteration of gut microbiota in DJB rats, and the resting core body temperature of DJB rats was increased over that of sham-operated rats from 2 weeks after surgery. Therefore, elevation of plasma BA levels early after bariatric surgery by activation of de novo BA synthesis and enterohepatic circulation may play an important role in postoperative metabolic improvement and weight loss. Disclosure Y. Kitahara: Employee; Self; Ajinomoto Co., Inc. H. Kawanabe: Employee; Self; Ajinomoto Co., Inc. M. Hasumura: Employee; Self; Ajinomoto Co., Inc. Y. Iwai: Employee; Self; Ajinomoto Co., Inc. Y. Okamatsu: Employee; Self; Ajinomoto Co., Inc..

Hypocholesterolaemic effect of whole-grain highland hull-less barley in rats fed a high-fat diet.

Whole-grain highland hull-less barley (WHLB) contains high amounts of bioactive compounds that potentially exhibit cholesterol-lowering effects. This study investigated the hypocholesterolaemic effect of WHLB. A total of seventy-two male Sprague-Dawley rats were divided into four groups and were fed with the normal control diet, high-fat diet (HFD) and HFD containing low or high dose (10 or 48·95 %) of WHLB. High dose of WHLB significantly decreased the organ indexes of liver and abdominal fat and lipid levels of plasma and liver in HFD rats. The lipid regulation effect of WHLB, which was reconfirmed through hepatocyte morphologic observation, was accompanied by a large excretion of bile acids in the small intestinal contents and the faeces. Real-time PCR analyses, which were further reconfirmed through Western blot analyses, revealed that a high dose of WHLB significantly enhanced the hepatic expressions of AMP-activated protein kinase α, cholesterol 7α-hydroxylase, LDL receptor, liver X receptor, and PPARα and decreased the expression of 3-hydroxy-3-methylglutaryl coenzyme A reductase. It also enhanced the ileal expression of farnesoid X receptor and resulted in the decrease of expression of apical sodium-dependent bile acid transporter. WHLB exhibited hypocholesterolaemic effects mainly by inhibiting cholesterol synthesis, cholesterol accumulation in peripheral tissue, and bile acid reabsorption and by stimulating bile acid synthesis.

Treatment of a Mouse Model of Cholestasis with a Thyromimetic Improves Biliary Injury But Exacerbates Hepatocyte Injury

Chronic cholestasis results from bile secretory defects or impairment of bile flow, and there are few effective medical therapies available. Thyroid hormone T3 and synthetic thyroid hormone receptor agonists are known to cause induction of hepatocyte proliferation during liver regeneration through activation of b‐catenin. However, whether these drugs have therapeutic benefits in cholestatic liver disease is unknown. In this study, we administered GC‐1, a thyromimetic that preferentially acts through the TRb receptor found predominantly in liver, to Mdr2 knockout (KO) mice, which is a commonly used model of sclerosing cholangitis characterized by bile acid (BA) regurgitation, periductular inflammation, and fibrosis. We determined Mdr2 KO mice fed 5mg/kg GC‐1 diet had decreased bilirubin, liver to body weight ratios, serum alkaline phosphatase, but increased serum alanine aminotransferase and aspartate aminotransferase compared to KO mice fed normal diet as early as 1 week on diet. Histologically, KO mice on GC‐1 diet had decreased ductular response, less bridging fibrosis, and fewer SOX9 positive hepatocytes compared to KO on normal diet. Although total liver BA were higher in KO mice fed GC‐1 diet for 2 weeks compared to normal diet, they normalized to KO levels at 4 weeks of diet. To elucidate the mechanism of increased BA accumulation and liver injury, we examined expression of BA transporters and detoxification enzymes. KO mice on GC‐1 diet had decreased bilirubin transport and detoxification genes, such as Mrp2, Mrp3, Cyp2b10, and Oatp4, compared to KO mice on normal diet, with the net result being retention of BA in the hepatocyte. Interestingly, KO mice on GC‐1 diet had decreased total and phosphorylated, active b‐catenin compared to KO mice on normal diet, suggesting an alternate mechanism for GC‐1 activation in this model. Thus, GC‐1 reduces cholangiocyte injury during cholestasis by inducing retention of BA in hepatocytes, causing injury to the hepatocytes; this occurs through as‐yet unknown mechanisms that are upstream of BA transporters and biosynthesis enzymes and appears to be b‐catenin independent.Support or Funding InformationNational Institute of Biomedical Imaging and Bioengineering of the National Institute of Health under Award Number T32EB0010216UPP Academic Foundation Award 1R01DK103775This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Diet-induced obesity and weight loss alter bile acid concentrations and bile acid–sensitive gene expression in insulin target tissues of C57BL/6J mice

Bile acids (BAs) influence the metabolism of glucose, lipids, and energy expenditure. We hypothesized that BA concentrations and related gene expression would be altered in lean (low-fat diet fed; LFD) vs diet-induced obese (high-fat diet fed; HFD) groups of mice and that some detected changes would remain after weight loss in an HFD group switched to the LFD (SW). Taurine conjugates dominated the bile acid composition of the liver, epididymal white adipose tissue (eWAT), and hypothalamus, with the latter having lower levels (~95%, ~95%, and ~80%, respectively; P<.05). Plasma conjugated bile acids were elevated in the HFD relative to the LFD and SW animals. Total hepatic BA concentrations decreased in obese mice fed HFD, and levels returned to preobese levels in the SW group. Subtle changes in unconjugated bile acids were detected in the eWAT, hypothalamus, and muscle. Liver expression of a variety of enzymes involved in BA synthesis (eg, Cyp27a1, Acox2), BA transport (eg, Slc22a8), and BA-sensitive receptors (Fxr, Tgr5) were unchanged by HFD feeding but decreased with SW. Other hepatic enzymes were induced in the SW group (eg, Amacr and Bal). In eWAT, Cyp27a1 and Acox2 also declined in the SW group, whereas the HFD group showed reduced expression of BA transporters (eg, Abcc3), and changes in Fxr and Tgr5 were unclear. Therefore, although most detectable changes in BA metabolism associated with diet-induced obesity are reversed by diet-induced weight loss, some effects on BA composition, concentrations, and gene expression can persist after weight loss.

Bile acids and intestinal microbiota in autoimmune cholestatic liver diseases.

Autoimmune cholestatic liver diseases, including primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC), are manifested as an impairment of normal bile flow and excessive accumulation of potentially toxic bile acids. Endogenous bile acids are involved in the pathogenesis and progression of cholestasis. Consequently, chronic cholestasis affects the expression of bile acid transporters and nuclear receptors, and results in liver injury. Several lines of evidence suggest that intestinal microbiota plays an important role in the etiopathogenesis of cholestatic liver diseases by regulating metabolism and immune responses. However, progression of the disease may also affect the composition of gut microbiota, which in turn exacerbates the progression of cholestasis. In addition, the interaction between intestinal microbiota and bile acids is not unidirectional. Bile acids can shape the gut microbiota community, and in turn, intestinal microbes are able to alter bile acid pool. In general, gut microbiota actively communicates with bile acids, and together play an important role in the pathogenesis of PBC and PSC. Targeting the link between bile acids and intestinal microbiota offers exciting new perspectives for the treatment of those cholestatic liver diseases. This review highlights current understanding of the interactions between bile acids and intestinal microbiota and their roles in autoimmune cholestatic liver diseases. Further, we postulate a bile acids-intestinal microbiota-cholestasis triangle in the pathogenesis of autoimmune cholestatic liver diseases and potential therapeutic strategies by targeting this triangle.

Tauroursodeoxycholic acid protects bile acid homeostasis under inflammatory conditions and dampens Crohn's disease-like ileitis

Bile acids regulate the expression of intestinal bile acid transporters and are natural ligands for nuclear receptors controlling inflammation. Accumulating evidence suggests that signaling through these receptors is impaired in inflammatory bowel disease. We investigated whether tauroursodeoxycholic acid (TUDCA), a secondary bile acid with cytoprotective properties, regulates ileal nuclear receptor and bile acid transporter expression and assessed its therapeutic potential in an experimental model of Crohn's disease (CD). Gene expression of the nuclear receptors farnesoid X receptor, pregnane X receptor and vitamin D receptor and the bile acid transporters apical sodium-dependent bile acid transporter and organic solute transporter α and β was analyzed in Caco-2 cell monolayers exposed to tumor necrosis factor (TNF)α, in ileal tissue of TNFΔARE/WT mice and in inflamed ileal biopsies from CD patients by quantitative real-time polymerase chain reaction. TNFΔARE/WT mice and wild-type littermates were treated with TUDCA or placebo for 11 weeks and ileal histopathology and expression of the aforementioned genes were determined. Exposing Caco-2 cell monolayers to TNFα impaired the mRNA expression of nuclear receptors and bile acid transporters, whereas co-incubation with TUDCA antagonized their downregulation. TNFΔARE/WT mice displayed altered ileal bile acid homeostasis that mimicked the situation in human CD ileitis. Administration of TUDCA attenuated ileitis and alleviated the downregulation of nuclear receptors and bile acid transporters in these mice. These results show that TUDCA protects bile acid homeostasis under inflammatory conditions and suppresses CD-like ileitis. Together with previous observations showing similar efficacy in experimental colitis, we conclude that TUDCA could be a promising therapeutic agent for inflammatory bowel disease, warranting a clinical trial.

From the Cover: MechanisticInsights in Cytotoxic and Cholestatic Potential of the Endothelial Receptor Antagonists Using HepaRG Cells.

Several endothelin receptor antagonists (ERAs) have been developed for the treatment of pulmonary arterial hypertension (PAH). Some of them have been related to clinical cases of hepatocellular injury (sitaxentan [SIT]) and/or cholestasis (bosentan [BOS]). We aimed to determine if ambrisentan (AMB) and macitentan (MAC), in addition to BOS and SIT, could potentially cause liver damage in man by use of human HepaRG cells. Our results showed that like BOS, MAC-induced cytotoxicity and cholestatic disorders characterized by bile canaliculi dilatation and impairment of myosin light chain kinase signaling. Macitentan also strongly inhibited taurocholic acid and carboxy-2',7'-dichlorofluorescein efflux while it had a much lower inhibitory effect on influx activity compared to BOS and SIT. Moreover, these three drugs caused decreased intracellular accumulation and parallel increased levels of total bile acids (BAs) in serum-free culture media. In addition, all drugs except AMB variably deregulated gene expression of BA transporters. In contrast, SIT was hepatotoxic without causing cholestatic damage, likely via the formation of reactive metabolites and AMB was not hepatotoxic. Together, our results show that some ERAs can be hepatotoxic and that the recently marketed MAC, structurally similar to BOS, can also cause cholestatic alterations in HepaRG cells. The absence of currently known or suspected cases of cholestasis in patients suffering from PAH treated with MAC is rationalized by the lower therapeutic doses and Cmax, and longer receptor residence time compared to BOS.