Apical Sodium-dependent Bile Acid Transporter Research Articles

Bile acid dysmetabolism in inflammatory bowel diseases

Aim: To summarize the state-of-the-art data on the molecular mechanisms of bile acid (BA) synthesis and absorption, their impaired absorption and receptor-dependent signaling, as well as on the effects of the gut microbiota on BA metabolism in inflammatory bowel diseases (IBD).
 Key messages: BA malabsorption is one of the relevant mechanisms in the development of diarrhea in IBD. It may occur due to various disorders of the ileum, such as terminal ileitis, ileocolitis or ileocecal resection in Crohn's disease and ileoanal reservoir in ulcerative colitis. Molecular mechanisms of BA malabsorption in IBD are related to a defect in the BA uptake by the apical sodium dependent bile acid transporter (ASBT), as well as to a decrease in the expression of pregnane X receptor (PXR) and farnesoid X receptor (FXR), whose activation by glucocorticoids results in an increase in the BA reabsorption in the ileum and a decrease in hologenic diarrhea. The metabolic profile of luminal BA in IBD is characterized by an increased content of conjugated and 3-OH-sulfated BA and reduced levels of secondary BA. The decrease in the relative abundance of the Lachnospiraceae and Oscillospiraceae spp. in IBD patients leads to a decrease in the efficiency of microbial biotransformation of BA. Changes in the BA metabolic profile in IBD affect the gut microbiota, and impaired interaction with the FXR, PXR, G protein-coupled bile acid receptor (GPBAR1), retinoid-related orphan receptors (RORs) and vitamin D receptor (VDR) results in a pro-inflammatory response and increased intestinal permeability, bacterial translocation, and IBD progression. BA metabolism in IBD-associated primary sclerosing cholangitis (PSC-IBD) is characterized by a significant decrease in the luminal BA pool, and the microbiota composition is remarkable for an increase in the relative abundance of Fusobacterium and Ruminococcus spp., and a decrease in Veillonella, Dorea, Blautia, Lachnospira and Roseburia.
 Conclusion: Disordered synergistic interplay of BA with intestinal microbiota results in disruption of the ligand-receptor interaction and BA metabolic transformation, which contributes to the activation of the immune system, formation of a vicious circle of chronic inflammation and IBD progression. Further studies into mutual influence of the gut microbiota, BA metabolism and receptor signaling may promote the development of new methods for the diagnosis and treatment of IBD.

Lrig1+ small intestinal progenitor cells require MYO5B for proper crypt proliferation and enterocyte maturation

Microvillus inclusion disease (MVID) is a congenital disorder characterized by severe diarrhea. MVID is caused by inactivating mutations in myosin Vb (MYO5B), a motor protein. Mice lacking MYO5B in their intestinal epithelium have demonstrated the importance of MYO5B in enterocyte brush border formation and epithelial cell differentiation. Additionally, the proliferative zone of the intestinal crypt of MYO5B-deficient mice is elongated compared to controls. We hypothesize that the progenitor cell-specific Cre driver under Lrig1 demonstrates crypt-specific effects caused by MYO5B loss. Lrig1-CreERT2;R26R-YFP and Myo5bfl/fl mice were crossbred to generate Lrig1-CreERT2;R26R-YFP;MYO5B fl/fl (Lrig1 ΔMYO5B ) mice. Adult Lrig1 ΔMYO5B mice and control littermates received tamoxifen injection at day 0. GI tissues were collected 2.5, 3, 4, and 5 days after tamoxifen administration for histological characterization. Lrig1 ΔMYO5B mice began experiencing significant weight loss 4 days after tamoxifen injection and lost 20% of their starting body weight on day 5. At day 5, the Lrig1 ΔMYO5B mouse colon was devoid of solid feces and their small intestine contained clear luminal contents, together suggesting a watery diarrheal phenotype. Enterocytes of Lrig1DMYO5B mice on day 5 contained abnormal cytoplasmic accumulation of PAS staining. Fewer goblet cells were apparent in intestinal sections from day 3 and 5 Lrig1 ΔMYO5B mice compared to controls. Crypts were elongated starting at day 3. Similarly, the PCNA+ epithelial region was expanded in Lrig1 ΔMYO5B mice, even reaching into the villi at day 5. The time course of the PCNA+ region expansion corresponded to the wave of MYO5B-loss beginning at the base of crypts. MYO5B expression was diminished in the crypts at day 3 and nearly absent from the epithelium by day 5. Interestingly, expression of 3-hydroxy-3-methylglutaryl-CoA synthase 2 (HMGCS2), the rate-limited enzyme of ketogenesis that is important for stem cell function, was expanded in the crypt at day 3 and 5 after tamoxifen. Sodium/glucose cotransporter 1 (SGLT1), which is present along the apical surface of mature enterocytes, was progressively diminished and mis-localized away from the apical surface after tamoxifen administration. Apical sodium-dependent bile acid transporter (ASBT), found in the distal small intestine, demonstrated a similar mis-localization away from the apical membrane in enterocytes.We established a novel mouse model that demonstrates progressive MYO5B loss in the intestinal epithelium, starting at the base of the crypt and reaching villi tips over the course of 5 days following Cre induction. This Lrig1 ΔMYO5B strain will allow for lineage tracing studies to better understand the effect of MYO5B loss on intestinal epithelial differentiation and progenitor function. NSF GFRP, NIH R01DK128190 This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Klebsiella quasipneumoniae in intestine damages bile acid metabolism in hematopoietic stem cell transplantation patients with bloodstream infection

BackgroundBloodstream infection (BSI) is a serious hematopoietic stem cell transplantation (HSCT) complication. The intestinal microbiome regulates host metabolism and maintains intestinal homeostasis. Thus, the impact of microbiome on HSCT patients with BSI is essential.MethodsStool and serum specimens of HSCT patients were prospectively collected from the pretransplant conditioning period till 4 months after transplantation. Specimens of 16 patients without BSI and 21 patients before BSI onset were screened for omics study using 16S rRNA gene sequencing and untargeted metabolomics. The predictive infection model was constructed using LASSO and the logistic regression algorithm. The correlation and influence of microbiome and metabolism were examined in mouse and Caco-2 cell monolayer models.ResultsThe microbial diversity and abundance of Lactobacillaceae were remarkably reduced, but the abundance of Enterobacteriaceae (especially Klebsiella quasipneumoniae) was significantly increased in the BSI group before onset, compared with the non-BSI group. The family score of microbiome features (Enterobacteriaceae and Butyricicoccaceae) could highly predict BSI (AUC = 0.879). The serum metabolomic analysis showed that 16 differential metabolites were mainly enriched in the primary bile acid biosynthesis pathway, and the level of chenodeoxycholic acid (CDCA) was positively correlated with the abundance of K. quasipneumoniae (R = 0.406, P = 0.006). The results of mouse experiments confirmed that three serum primary bile acids levels (cholic acid, isoCDCA and ursocholic acid), the mRNA expression levels of bile acid farnesol X receptor gene and apical sodium-dependent bile acid transporter gene in K. quasipneumoniae colonized mice were significantly higher than those in non-colonized mice. The intestinal villus height, crypt depth, and the mRNA expression level of tight junction protein claudin-1 gene in K. quasipneumoniae intestinal colonized mice were significantly lower than those in non-colonized mice. In vitro, K. quasipneumoniae increased the clearance of FITC-dextran by Caco-2 cell monolayer.ConclusionsThis study demonstrated that the intestinal opportunistic pathogen, K. quasipneumoniae, was increased in HSCT patients before BSI onset, causing increased serum primary bile acids. The colonization of K. quasipneumoniae in mice intestines could lead to mucosal integrity damage. The intestinal microbiome features of HSCT patients were highly predictive of BSI and could be further used as potential biomarkers.

Active enterohepatic cycling is not required for the choleretic actions of 24-norUrsodeoxycholic acid in mice.

The pronounced choleretic properties of 24-norUrsodeoxycholic acid (norUDCA) to induce bicarbonate-rich bile secretion have been attributed to its ability to undergo cholehepatic shunting. The goal of this study was to identify the mechanisms underlying the choleretic actions of norUDCA and the role of the bile acid transporters. Here, we show that the apical sodium-dependent bile acid transporter (ASBT), organic solute transporter-α (OSTα), and organic anion transporting polypeptide 1a/1b (OATP1a/1b) transporters are dispensable for the norUDCA stimulation of bile flow and biliary bicarbonate secretion. Chloride channels in biliary epithelial cells provide the driving force for biliary secretion. In mouse large cholangiocytes, norUDCA potently stimulated chloride currents that were blocked by siRNA silencing and pharmacological inhibition of calcium-activated chloride channel transmembrane member 16A (TMEM16A) but unaffected by ASBT inhibition. In agreement, blocking intestinal bile acid reabsorption by coadministration of an ASBT inhibitor or bile acid sequestrant did not impact norUDCA stimulation of bile flow in WT mice. The results indicate that these major bile acid transporters are not directly involved in the absorption, cholehepatic shunting, or choleretic actions of norUDCA. Additionally, the findings support further investigation of the therapeutic synergy between norUDCA and ASBT inhibitors or bile acid sequestrants for cholestatic liver disease.

The Pathological Effects of Circulating Hydrophobic Bile Acids in Alzheimer's Disease.

Recent clinical studies have revealed that the serum levels of toxic hydrophobic bile acids (deoxy cholic acid, lithocholic acid [LCA], and glycoursodeoxycholic acid) are significantly higher in patients with Alzheimer's disease (AD) and amnestic mild cognitive impairment (aMCI) when compared to control subjects. The elevated serum bile acids may be the result of hepatic peroxisomal dysfunction. Circulating hydrophobic bile acids are able to disrupt the blood-brain barrier and promote the formation of amyloid-β plaques through enhancing the oxidation of docosahexaenoic acid. Hydrophobic bile acid may find their ways into the neurons via the apical sodium-dependent bile acid transporter. It has been shown that hydrophobic bile acids impose their pathological effects by activating farnesoid X receptor and suppressing bile acid synthesis in the brain, blocking NMDA receptors, lowering brain oxysterol levels, and interfering with 17β-estradiol actions such as LCA by binding to E2 receptors (molecular modelling data exclusive to this paper). Hydrophobic bile acids may interfere with the sonic hedgehog signaling through alteration of cell membrane rafts and reducing brain 24(S)-hydroxycholesterol. This article will 1) analyze the pathological roles of circulating hydrophobic bile acids in the brain, 2) propose therapeutic approaches, and 3) conclude that consideration be given to reducing/monitoring toxic bile acid levels in patients with AD or aMCI, prior/in combination with other treatments.

Combining ASBT inhibitor and FGF15 treatments enhances therapeutic efficacy against cholangiopathy in female but not male Cyp2c70 KO mice

Therapeutic reduction of hydrophobic bile acids exposure is considered beneficial in cholestasis. The Cyp2c70 KO mice lack hydrophilic muricholic acids and have a human-like hydrophobic bile acid pool resulting in hepatobiliary injury. This study investigates if combining an apical sodium-dependent bile acid transporter inhibitor GSK2330672 (GSK) and fibroblast growth factor-15 (FGF15) overexpression, via simultaneous inhibition of bile acid synthesis and gut bile acid uptake, achieves enhanced therapeutic efficacy in alleviating hepatobiliary injury in Cyp2c70 KO mice. The effects of GSK, adeno-associated virus (AAV)-FGF15, and the combined treatment on bile acid metabolism and cholangiopathy were compared in Cyp2c70 KO mice. In female Cyp2c70 KO mice with more severe cholangiopathy than male Cyp2c70 KO mice, the combined treatment was more effective in reversing portal inflammation, ductular reaction, and fibrosis than AAV-FGF15, while GSK was largely ineffective. The combined treatment reduced bile acid pool by ∼80% compared to ∼50% reduction by GSK or AAV-FGF15, and enriched tauro-conjugated ursodeoxycholic acid in the bile. Interestingly, the male Cyp2c70 KO mice treated with AAV-FGF15 or GSK showed attenuated cholangiopathy and portal fibrosis but the combined treatment was ineffective despite reducing bile acid pool. Both male and female Cyp2c70 KO mice showed impaired gut barrier integrity. AAV-FGF15 and the combined treatment, but not GSK, reduced gut exposure to lithocholic acid and improved gut barrier function. In conclusion, the combined treatment improved therapeutic efficacy against cholangiopathy than either single treatment in the female but not male Cyp2c70 KO mice by reducing bile acid pool size and hydrophobicity.

Apple juice relieves loperamide-induced constipation in rats by downregulating the intestinal apical sodium-dependent bile acid transporter ASBT.

Apples are known to exhibit various beneficial effects on human health. In the present study, we investigated the effect of continuous intake of apple juice (AJ) on constipation status. A single dose of loperamide in rats as the constipation model markedly decreased the weight and number of fecal pellets compared to saline-administered rats as a control. After the administration of AJ twice a day for seven days, recovery of defecation close to that of the control was observed in loperamide-treated rats. In addition, the total bile acid content in the feces increased from day 4 after the administration of AJ. Among hepatic and intestinal transporters and enzymes that regulate bile acids, the mRNA expression of the apical sodium-dependent bile acid transporter (Asbt, slc10a2) was decreased by AJ in rats. Furthermore, the Asbt-mediated bile acid transport activity in the rat ileum decreased after AJ administration. Moreover, in human colonic cancer-derived Caco-2 cells, AJ exposure for 24 and 48 h decreased the expressions of ASBT mRNA and protein, and the uptake activity of taurocholic acid in both 7- and 21-d cultures. Several components of AJ, such as procyanidins, decreased the expression of ASBT in Caco-2 cells. In conclusion, ASBT downregulation is a possible mechanism responsible for the constipation-relieving effect of apples, and procyanidins may play a role in downregulating ASBT, which leads to the beneficial effects of apples against constipation. Although it is generally agreed that the common dietary compositions play a role in constipation relief, the novel specific mechanism of apples found in this study would facilitate understanding food functions.

Intestinal in vitro transport assay combined with physiologically based kinetic modeling as a tool to predict bile acid levels in vivo.

Bile acid homeostasis is vital for numerous metabolic and immune functions in humans. The enterohepatic circulation of bile acids is extremely efficient, with ~95% of intestinal bile acids being reabsorbed. Disturbing intestinal bile acid uptake is expected to substantially affect intestinal and systemic bile acid levels. Here, we aimed to predict the effects of apical sodium-dependent bile acid transporter (ASBT)-inhibition on systemic plasma levels. For this, we combined in vitro Caco-2 cell transport assays with physiologically based (PBK) modeling. We used the selective ASBT-inhibitor odevixibat (ODE) as a model compound. Caco-2 cells grown on culture inserts were used to obtain transport kinetic parameters of glycocholic acid (GCA). The apparent Michaelis-Menten constant (Km,app), apparent maximal intestinal transport rate (Vmax,app), and ODE’s inhibitory constant (Ki) were determined for GCA. These kinetic parameters were incorporated into a PBK model and used to predict the ASBT inhibition effects on plasma bile acid levels. GCA is transported over Caco-2 cells in an active and sodium-dependent manner, indicating the presence of functional ASBT. ODE inhibited GCA transport dose-dependently. The PBK model predicted that oral doses of ODE reduced conjugated bile acid levels in plasma. Our simulations match in vivo data and provide a first proof-of-principle for the incorporation of active intestinal bile acid uptake in a bile acid PBK model. This approach could in future be of use to predict the effects of other ASBT-inhibitors on plasma and intestinal bile acid levels.

Modeling of a Novel Patient-Based MYO5B Point Mutation Reveals Insights Into MVID Pathogenesis

Modeling of a Novel Patient-Based MYO5B Point Mutation Reveals Insights Into MVID Pathogenesis

Conjoint hepatobiliary-enterohepatic cycles for amyloid excretion and enhancing its drug-induced clearance: a systems biology approach to Alzheimer’s disease

The liver is the major organ responsible for metabolism of amyloid-beta, the primary toxic misfolded protein responsible for Alzheimer’s disease (AD). The present study focuses on the crucial role of liver in AD. We have developed a framework that formulates and integrates two reciprocal transport processes of amyloid, via hepato-biliary and enterohepatic circulations (EHC). Our system analysis approach shows that activating the liver X-receptor (LXR) can reduce amyloid-beta formation by increasing expression of the genes: ATP-binding-cassette-transporter (ABCA1) and Stearoyl-CoA-desaturase (SCD). Besides, activating the pregnane-X-receptor (PXR) can enhance the clearance of amyloid-beta by increasing the expression of the genes: ATP-Binding-Cassette-Superfamily-G-member-2 (ABCG2) and multidrug-resistance protein-1 (MDR1). We also identified receptor-like apical sodium-dependent bile-acid transporter (ASBT) of intestinal enterocyte, showing affinity towards amyloid-beta, suggesting amyloid-beta’s possible reuptake from intestinal contents to the systemic circulation through this receptor. Further, we have performed protein-protein interaction to evaluate the binding affinity of amyloid-beta to these receptors. Moreover, we undertook molecular docking and molecular dynamic simulation of some repurposed drugs (rifampicin, 24-hydroxycholesterols, resveratrol, cilostazol) which can target the aforesaid receptors to enhance amyloid-beta’s fecal clearance, reduce amyloid-beta formation, and prevent the reuptake of amyloid-beta from intestinal feces. Additionally, network pharmacology and synergism analysis were utilized to validate our hypothesis and identify the drug combinations, respectively. Gene-ontology investigation, network pharmacology, and consolidated pathway analysis validate the alteration of the above-mentioned gene expression profiles. Furthermore, our neuropharmacological synergism study identifies the optimal combination of the repurposed drugs. Finally, our findings on candidate drugs are substantiated by clinical-trial outcomes. Communicated by Ramaswamy H. Sarma

Novel nitroxide-bile acid conjugates inform substrate requirements for human bile acid transporters

Transport of bile acids within the enterohepatic circulation from the liver to the intestines via the gallbladder and back to the liver via the portal vein plays a critical role in bile acid regulation and homeostasis. Deficiency of fibroblast growth factor 19 (FGF19), a hormone whose role is to suppress de novo hepatic bile acid synthesis to maintain homeostatic levels, results in bile acid diarrhea (BAD). FGF19 also modulates gallbladder motility so that bile acids are concentrated in the gallbladder until postprandial contraction. To assess bile acid transport and diagnose ailments like BAD that are associated with altered bile acid synthesis and transport, we created bile acid conjugates with nitroxide radicals. Because nitroxides are paramagnetic and can promote proton relaxation, we reasoned that these paramagnetic conjugates should act as contrast agents in in vivo magnetic resonance imaging (MRI). We tested substrate capability by assessing the inhibitory potential of these novel agents against taurocholate uptake by the apical sodium dependent bile acid transporter (ASBT) and the Na+/taurocholate cotransporting polypeptide (NTCP). Surprisingly, neither the paramagnetic compounds CA-Px-1 and CA-Px-2, nor their reduced forms, CA-Px-1H and CA-Px-2H, inhibited hASBT- or hNTCP-mediated taurocholate uptake. Therefore, the new conjugates cannot serve as contrast agents for MRI in vivo. However, our findings identify important structural constraints of transportable bile acid conjugates and suggest potential modifications to overcome these limitations.

Enhanced Oral Absorption and Liver Distribution of Polymeric Nanoparticles through Traveling the Enterohepatic Circulation Pathways of Bile Acid.

The intestinal epithelium is known to be a main hindrance to oral delivery of nanoparticles. Even though surface ligand modification can enhance cellular uptake of nanoparticles, the "easy entry and hard across" was frequently observed for many active targeting nanoparticles. Here, we fabricated polymeric nanoparticles relayed by bile acid transporters with monomethoxy poly(ethylene glycol)-poly(D,l-lactide) and deoxycholic acid-conjugated poly(2-ethyl-2-oxazoline)-poly(D,l-lactide) based on structural characteristics of intestine epithelium and the absorption characteristics of endogenous substances. As anticipated, deoxycholic acid-modified polymeric nanoparticles featuring good stability in simulated gastrointestinal fluid could notably promote the internalization of their payload by Caco-2 cells through mediation of apical sodium-dependent bile acid transporter (ASBT) and transmembrane transport of the nanoparticles across Caco-2 cell monolayers via relay-guide of ASBT, ileal bile acid-binding protein, and the heteromeric organic solute transporter (OSTα-OSTβ) along with multidrug resistance-associated protein 3 (MRP3) evidenced by competitive inhibition and fluorescence immunoassay, which was further visually confirmed by the stronger fluorescence from C6-labeled nanoparticles inside enterocytes and the basal side of the intestinal epithelium of mice. The transcellular transport of deoxycholic acid-modified nanoparticles in an intact form was mediated by caveolin/lipid rafts and clathrin with intracellular trafficking trace of endosome-lysosome-ER-Golgi apparatus and bile acid transport route. Furthermore, the increased uptake by HepG2 cells compared with unmodified nanoparticles evidenced the target ability of deoxycholic acid-modified nanoparticles to the liver, which was further supported by ex vivo imaging of excised major organs of mice. Thus, this study provided a feasible and potential strategy to further enhance transepithelial transport efficiency and liver-targeted ability of nanoparticles by means of the specific enterohepatic circulation pathways of bile acid.

Systemic ASBT inactivation protects against liver damage in obstructive cholestasis in mice

Background & AimsNon-absorbable inhibitors of the apical sodium-dependent bile acid transporter (ASBT; also called ileal bile acid transporter [IBAT]) are recently approved or in clinical development for multiple cholestatic liver disorders and lead to a reduction in pruritus and (markers for) liver injury. Unfortunately, non-absorbable ASBT inhibitors (ASBTi) can induce diarrhoea or may be ineffective if cholestasis is extensive and largely precludes intestinal excretion of bile acids. Systemically acting ASBTi that divert bile salts towards renal excretion may alleviate these issues.MethodsBile duct ligation (BDL) was performed in ASBT-deficient (ASBT knockout [KO]) mice as a model for chronic systemic ASBT inhibition in obstructive cholestasis. Co-infusion of radiolabelled taurocholate and inulin was used to quantify renal bile salt excretion after BDL. In a second (wild-type) mouse model, a combination of obeticholic acid (OCA) and intestine-restricted ASBT inhibition was used to lower the bile salt pool size before BDL.ResultsAfter BDL, ASBT KO mice had reduced plasma bilirubin and alkaline phosphatase compared with wild-type mice with BDL and showed a marked reduction in liver necrotic areas at histopathological analysis, suggesting decreased BDL-induced liver damage. Furthermore, ASBT KO mice had reduced bile salt pool size, lower plasma taurine-conjugated polyhydroxylated bile salt, and increased urinary bile salt excretion. Pretreatment with OCA + ASBTi in wild-type mice reduced the pool size and greatly improved liver injury markers and liver histology.ConclusionsA reduced bile salt pool at the onset of cholestasis effectively lowers cholestatic liver injury in mice. Systemic ASBT inhibition may be valuable as treatment for cholestatic liver disease by lowering the pool size and increasing renal bile salt output even under conditions of minimal faecal bile salt secretion.Lay summaryNovel treatment approaches against cholestatic liver disease (resulting in reduced or blocked flow of bile) involve non-absorbable inhibitors of the bile acid transport protein ASBT, but these are not always effective and/or can cause unwanted side effects. In this study, we demonstrate that systemic inhibition/inactivation of ASBT protects mice against developing severe cholestatic liver injury after bile duct ligation, by reducing bile salt pool size and increasing renal bile salt excretion.

Safety and Efficacy of Elobixibat, an Ileal Bile Acid Transporter Inhibitor, in Elderly Patients With Chronic Idiopathic Constipation According to Administration Time: Interim Analysis of Post-marketing Surveillance.

Background/AimsElobixibat, an ileal bile acid transporter (apical sodium-dependent bile acid transporter) inhibitor, was recently launched in Japan for the treatment of chronic idiopathic constipation. We conducted an interim analysis of post-marketing surveillance to evaluate the safety and efficacy of elobixibat in elderly patients with chronic constipation and compared the efficacy according to administration time.MethodsSafety and efficacy outcomes were evaluated through patient interviews for 4 weeks.ResultsAdverse drug reactions (ADRs) were observed in 5.24% of the 1049 patients analyzed; diarrhea (2.19%) and abdominal pain (1.81%) were the most common. A serious ADR of death was reported in one patient (0.10%). The incidence of ADRs in the ≥ 65-year old or ≥ 75-year-old subpopulation was similar to that in the total patient population. Mean bowel movements per week significantly increased from 2.9 ± 2.5 at baseline to 5.0 ± 3.1 (P < 0.001) at Week 2 and 5.3 ± 2.6 (P < 0.001) at Week 4. The mean Bristol Stool Form Scale score significantly increased from 2.3 ± 1.4 at baseline to 3.8 ± 1.3 (P < 0.001) at Week 2 and 3.9 ± 1.1 at Week 4 (P < 0.001). Bowel movements significantly increased in the elderly population and subpopulations receiving elobixibat before breakfast, lunch, or dinner. The median time to bowel movement was 5 hours.ConclusionThe results suggested that elobixibat was well-tolerated and efficacious in elderly patients with chronic constipation and can be administered before any meals.

MiR-203 is an anti-obese microRNA by targeting apical sodium-dependent bile acid transporter

SummaryObesity is characterized by excessive fat deposition within the body. Bile acids (BA) are important regulators for controlling the absorption of lipid. Here we show that miR-203 exerts weight-loss and lipid-lowering effects by increasing total BA excretion in obese rodents. miR-203 overexpression transgenic mice are resistant to high-fat diet (HFD)-induced obesity and dyslipidemia. Moreover, the knockdown of miR-203 deteriorates metabolic disorders. ASBT plays important role in regulating BA homeostasis and is a direct target of miR-203. In human intestinal epithelial cells, overexpression of miR-203 decreases the cellular uptake of BA by inhibiting ASBT. Furthermore, TCF7L2 is downregulated in obese mice and acts as a transcription factor of miR-203. The ASBT mRNA level was positively correlated with the body mass index (BMI) of population, while the miR-203 level was negatively associated with BMI. Taken together, these data suggest miR-203 could be a new therapeutic BA regulator for obesity and dyslipidemia.

OS019 - Novel anti-cholestatic treatment strategies by combining inhibition of the Apical sodium-dependent bile acid transporter with stimulation of urinary bile salt excretion or lowering bile salt synthesis

OS019 - Novel anti-cholestatic treatment strategies by combining inhibition of the Apical sodium-dependent bile acid transporter with stimulation of urinary bile salt excretion or lowering bile salt synthesis

Biomimetic and temporal-controlled nanocarriers with ileum transporter targeting for achieving oral administration of chemotherapeutic drugs

BackgroundOral chemotherapy is preferred for patients with cancer owing to its multiple advantages, including convenience, better patient compliance, and improved safety. Nevertheless, various physical barriers exist in this route that hamper the development of oral chemotherapeutic formulations, including destruction of drugs in the gastrointestinal tract (GIT), low permeability in enterocytes, and short residence time in the intestine. To overcome these limitations, it is necessary to design an efficient oral drug delivery system with high efficacy and improved safety.ResultsHerein, we designed novel glycocholic acid (GCA)-functionalized double layer nanoparticles (GCA-NPs), which can act via an endogenous pathway and in a temporally controlled manner in the intestine, to enhance the oral bioavailability of hydrophobic chemotherapeutic drugs such as paclitaxel (PTX). GCA-NPs were composed of quercetin (Qu)-modified liposomes (QL) coated with GCA-chitosan oligosaccharide conjugate (GCOS). The GCA-NPs thus prepared showed prolonged intestinal retention time and good GIT stability due to the presence of chitosan oligosaccharide (COS) and enhanced active transportation via intestinal apical sodium-dependent bile acid transporter (ASBT) due to the presence of GCA. GCA-NPs also efficiently inhibited intestinal P-gp induced by Qu. PTX-loaded GCA-NPs (PTX@GCA-NPs) had a particle size of 84 nm and an entrapment efficiency of 98% with good stability. As a result, the oral bioavailability of PTX was increased 19-fold compared to that of oral Taxol® at the same dose. Oral PTX@GCA-NPs displayed superior antitumor efficacy and better safety than Taxol® when administered intravenously.ConclusionsOur novel drug delivery system showed remarkable efficacy in overcoming multiple limitations and is a promising carrier for oral delivery of multiple drugs, which addresses several challenges in oral delivery in the clinical context.Graphical

Bile Acid Conjugation on Solid Nanoparticles Enhances ASBT‐Mediated Endocytosis and Chylomicron Pathway but Weakens the Transcytosis by Inducing Transport Flow in a Cellular Negative Feedback Loop

Bile acid‐modified nanoparticles provide a convenient strategy to improve oral bioavailability of poorly permeable drugs by exploiting specific interactions with bile acid transporters. However, the underlying mechanisms are unknown, especially considering the different absorption sites of free bile acids (ileum) and digested fat molecules from bile acid‐emulsified fat droplets (duodenum). Here, glycocholic acid (GCA)‐conjugated polystyrene nanoparticles (GCPNs) are synthesized and their transport in Caco‐2 cell models is studied. GCA conjugation enhances the uptake by interactions with apical sodium‐dependent bile acid transporter (ASBT). A new pathway correlated with both ASBT and chylomicron pathways is identified. Meanwhile, the higher uptake of GCPNs does not lead to higher transcytosis to the same degree compared with unmodified nanoparticles (CPNs). The pharmacological and genomics study confirm that GCA conjugation changes the endocytosis mechanisms and downregulates the cellular response to the transport at gene levels, which works as a negative feedback loop and explains the higher cellular retention of GCPNs. These findings offer a solid foundation in the bile acid‐based nanomedicine design, with utilizing advantages of the ASBT‐mediated uptake, as well as inspiration to take comprehensive consideration of the cellular response with more developed technologies.

Acrylamide induced glucose metabolism disorder in rats involves gut microbiota dysbiosis and changed bile acids metabolism

Acrylamide (AA) is a common food contaminant that causes glucose metabolism disorders (GMD). However, the underlying mechanism remains unclear. Female Sprague Dawley (SD) rats were treated with AA via gavage for 21 days, and the glucose and insulin levels, gut microbiota, intestinal barrier, and metabolism were analyzed. The results revealed that AA elevated serum glucose levels, reduced insulin levels and caused intestinal barrier injury. The 16S amplicon sequencing and non-targeted metabolomics showed that AA induced gut microbiota dysbiosis and bile acids (BAs) metabolism disorder. Specifically, AA decreased the abundance of Lactobacillus and Bacteroides in the cecal contents, and increased the cholic acid (CA) content in feces. Meanwhile, the expression of ileum apical sodium-dependent bile acid transporter (ASBT) responsible for CA reabsorption was suppressed. Further analysis indicated that BAs sensing nuclear receptor farnesoid X receptor (FXR) gene was activated and glucagon-like peptide-1 (GLP-1) which stimulates insulin secretion was downregulated. In addition, activation of FXR increased the expression of fibroblast growth factor 15 (FGF15), which resulted in the inhibition of hepatic BAs synthesis. Overall, this study demonstrated that AA-induced GMD is associated with the gut-microbiota-CA-FXR/GLP-1 axis. These findings add new knowledge to the AA-induced GMD and provide a basis for potential AA toxicity mitigation by manipulation of the gut microbiota.

Structural insights into the HBV receptor and bile acid transporter NTCP

Around 250 million people are infected with hepatitis B virus (HBV) worldwide1, and 15 million may also carry the satellite virus hepatitis D virus (HDV), which confers even greater risk of severe liver disease2. The HBV receptor has been identified as sodium taurocholate co-transporting polypeptide (NTCP), which interacts directly with the first 48 amino acid residues of the N-myristoylated N-terminal preS1 domain of the viral large protein3. Despite the pressing need for therapeutic agents to counter HBV, the structure of NTCP remains unsolved. This 349-residue protein is closely related to human apical sodium-dependent bile acid transporter (ASBT), another member of the solute carrier family SLC10. Crystal structures have been reported of similar bile acid transporters from bacteria4,5, and these models are believed to resemble closely both NTCP and ASBT. Here we have used cryo-electron microscopy to solve the structure of NTCP bound to an antibody, clearly showing that the transporter has no equivalent of the first transmembrane helix found in other SLC10 proteins, and that the N terminus is exposed on the extracellular face. Comparison of our structure with those of related proteins indicates a common mechanism of bile acid transport, but the NTCP structure displays an additional pocket formed by residues that are known to interact with preS1, presenting new opportunities for structure-based drug design.