Bile Acid Derivatives Research Articles

Intrauterine growth retardation affects liver bile acid metabolism in growing pigs: effects associated with the changes of colonic bile acid derivatives

BackgroundIntrauterine growth retardation (IUGR) is associated with severely impaired nutrient metabolism and intestinal development of pigs. Our previous study found that IUGR altered intestinal microbiota and metabolites in the colon. However, the consequences of IUGR on bile acid metabolism in pigs remained unclear. The present study aimed to investigate the bile acid metabolism in the liver and the profile of bile acid derivatives in the colon of growing pigs with IUGR using bile acid targeted metabolomics. Furthermore, we determined correlations between colonic microbiota composition and metabolites of IUGR and normal birth weight (NBW) pigs at different growth stages that were 7, 21, and 28-day-old, and the average body weight (BW) of 25, 50, and 100 kg of the NBW pigs.ResultsThe results showed that the plasma total bile acid concentration was higher (P < 0.05) at the 25 kg BW stage and tended to increase (P = 0.08) at 28-day-old in IUGR pigs. The hepatic gene expressions related to bile acid synthesis (CYP7A1, CYP27A1, and NTCP) were up-regulated (P < 0.05), and the genes related to glucose and lipid metabolism (ATGL, HSL, and PC) were down-regulated (P < 0.05) at the 25 kg BW stage in IUGR pigs when compared with the NBW group. Targeted metabolomics analysis showed that 29 bile acids and related compounds were detected in the colon of pigs. The colonic concentrations of dehydrolithocholic acid and apocholic acid were increased (P < 0.05), while isodeoxycholic acid and 6,7-diketolithocholic acid were decreased (P < 0.05) in IUGR pigs, when compared with the NBW pigs at the 25 kg BW stage. Moreover, Spearman’s correlation analysis revealed that colonic Unclassified_[Mogibacteriaceae], Lachnospira, and Slackia abundances were negatively correlated (P < 0.05) with dehydrolithocholic acid, as well as the Unclassified_Clostridiaceae abundance with 6,7-diketolithocholic acid at the 25 kg BW stage.ConclusionsThese findings suggest that IUGR could affect bile acid and glucolipid metabolism in growing pigs, especially at the 25 kg BW stage, these effects being paralleled by a modification of bile acid derivatives concentrations in the colonic content. The plausible links between these modified parameters are discussed.

Synthesis and in silico study of chenodeoxycholic acid and its analogues as an alternative inhibitor of spike glycoprotein of SARS-CoV-2

COVID-19, caused by SARS-CoV-2, is a viral infection that has generated one of the most significant health problems in the world. Spike glycoprotein is a crucial enzyme in viral replication and transcription mediation. There are reports in the literature on using bile acid in the fight against this virus through in vitro tests. This work presents the synthesis of nine chenodeoxycholic acid derivatives (1-9), which were prepared by oxidation, acetylation, formylation, and esterification reactions, and the analogs 6-9 have not yet been reported in the literature and the possibility of conducting an in silico study of bile acid derivatives as a therapeutic alternative to combat the virus using glycoprotein as a macromolecular target. As a result, five compounds (1, 6-9) possessed favorable competitive interactions with the lowest energies compared to the native ligand (BLA), and the highlighted compound 9 got the best scores. At the same time, analog 1 presented the best ADME filter result. Molecular dynamics also simulated these compounds to verify their stability within the active protein site to seek new therapeutic propositions to fight against the pandemic. Physical and spectroscopic data have fully characterized all the compounds. Communicated by Ramaswamy H. Sarma

Synthesis and biological activity evaluation of podophyllotoxin-linked bile acid derivatives as potential anti-liver cancer agents

Podophyllotoxin’s undifferentiated cytotoxicity and poor selectivity limit its clinical application. To improve above disadvantages, conjugation of bile acids with podophyllotoxin could improve cell line selectivity of liver cancer to achieve clinical translation further. Enlightened by the bile acids’ moiety magic characters, thirty podophyllotoxin-linked bile acid derivatives had been designed and synthesized. The cytotoxicity of these compounds in vitro was evaluated on HepG2, HCT-116, A549 and MDCK cell lines. After conjunction with bile acids, most of the derivatives (IC50 = 0.066–0.831 μM) were more potent against above three types of tumor cells than Etoposide (VP-16, IC50 = 4.319–41.080 μM) and exhibited similar antitumor activity compared with doxorubicin (DOX, IC50 = 0.230–0.745 μM). Moreover, structure–activity relationship displayed the length of the linker chain between podophyllotoxin and bile acids affected the cytotoxicity. Especially, compound 23 exhibited strong activity against HepG2 cell lines (IC50 = 0.188 ± 0.01 μM) than MDCK cell lines (IC50 = 4.780 ± 0.50 μM) and its SI (IC50MDCK/IC50HepG2) value of compound 23 was 25.4. Further antitumor mechanism studies showed that compound 23 acted as Topo Ⅱ inhibition and induced cell apoptosis with S cell cycle arrest. In particular, compound 23 showed valid antitumor efficacy at 10 mg/kg by intraperitoneal administration with a tumor inhibition rate of 60.9% in the Hepa1-6 xenograft mice model. The current research displayed that introduction of bile acids contributed to improve selectivity and activity to cell, and compound 23 could be a promising anti-tumor candidate.

Feasibility study of separation and purification of bile acid derivatives by HPLC on C18 and F5 columns

Organic synthesis could be very demanding, usually due to difficulties related to the separation of main reaction products from by-products. Steroidal compounds could have similar lipophilicity, which is mostly based on the lipophilicity of the steroidal core. This causes many problems during purification, i.e. in obtaining a pure single steroidal compound. In this research, a group of bile acid derivatives were subjected to HPLC analysis using four experimental systems, which presented combinations of C18 and F5 columns with methanol-water and acetonitrile-water as mobile phases. Retention parameters and retention order of the compounds were established and indicated that all experimental systems could be applicable in order to separate and/or purify some individual compounds or a mixture of a few compounds. However, the only experimental system that could separate a mixture of all investigated derivatives proved to be a C18 column with acetonitrile-water as a mobile phase. Since complex interactions between F5 column and the analytes exist, molecular surface polarity (MSP) was tested as a lipophilicity parameter, and also compared with logP using multivariate statistics. Retention parameters obtained on F5 column were used as descriptors, both with MSP and with logP, concluding that logP has shown to be a better lipophilicity descriptor.

Mechanism of Bile Acid-Induced Programmed Cell Death and Drug Discovery against Cancer: A Review.

Bile acids are major signaling molecules that play a significant role as emulsifiers in the digestion and absorption of dietary lipids. Bile acids are amphiphilic molecules produced by the reaction of enzymes with cholesterol as a substrate, and they are the primary metabolites of cholesterol in the body. Bile acids were initially considered as tumor promoters, but many studies have deemed them to be tumor suppressors. The tumor-suppressive effect of bile acids is associated with programmed cell death. Moreover, based on this fact, several synthetic bile acid derivatives have also been used to induce programmed cell death in several types of human cancers. This review comprehensively summarizes the literature related to bile acid-induced programmed cell death, such as apoptosis, autophagy, and necroptosis, and the status of drug development using synthetic bile acid derivatives against human cancers. We hope that this review will provide a reference for the future research and development of drugs against cancer.

Tauroursodeoxycholic acid inhibits TGF-β1-induced renal fibrosis markers in cultured renal mesangial cells by regulating endoplasmic reticulum stress.

Chronic kidney disease (CKD) has a worldwide prevalence of higher than 10% with an increasing mortality rate. As it involves the deterioration of renal function, it represents a serious risk to human health and, if left untreated, significantly lowers the quality of the patient's life. CKD is characterized by renal fibrosis. Studies have shown that transforming growth factor β1 (TGF-β1), a key driving factor of renal fibrosis, is closely related to the activation of renal fibrosis pathways such as endoplasmic reticulum stress (ERS). Tauroursodeoxycholic acid (TUDCA), an endogenous bile acid derivative, can effectively inhibit endogenous ERS. Here, we explored the effects and actions of TUDCA on renal fibrosis by establishing a renal mesangial cell (RMC) model. The RMC was stimulated with TGF-β1, and PCR and western blotting were used to detect the expression of ERS-related chaperone proteins and fibrotic indicators. The expression of glucose-regulated protein 78 (GRP78) was silenced in RMC cells to investigate the role of GRP78 in renal fibrosis. Finally, PCR and western blotting were used to detect the effects of TUDCA on the expression of GRP78, C/EBP homologous protein (CHOP), α-smooth muscle actin (α-SMA), and fibronectin (FN) in the TGF-β1-stimulated RMCs. The results showed that TUDCA significantly downregulated TGF-β1-induced levels of GRP78, CHOP, α-SMA and FN in RMCs. In addition, downregulation of GRP78 inhibited the expression of FN and α-SMA in the RMCs. In conclusion, downregulation of GRP78 and CHOP expression is one of the mechanisms by which TUDCA inhibits TGF-β1-induced renal mesangial cell fibrosis.

Bile acids directly bind and allosterically regulate the epithelial sodium channel

Bile acids are critical for the digestion and absorption of dietary fats and have important roles as signaling molecules. Bile acids are normally restricted to the enterohepatic circulation, but can be elevated in the blood and urine of patients with advanced liver diseases. The epithelial sodium channel (ENaC) mediates Na+ transport in the biliary epithelium, where it regulates bile viscosity, and in the aldosterone‐sensitive distal nephron, where it regulates extracellular fluid volume. We previously showed that bile acid regulation of ENaC depends on the position and stereochemistry of specific functional groups, but not on their chemico‐physical properties. To determine whether bile acids regulate ENaC in ex vivo native tissues, we performed patch clamp experiments on isolated split open renal tubules from mice, using recording pipettes backfilled with taurocholic acid (t‐CA) or taurohyodeoxycholic acid (t‐HDCA). Consistent with in vitro experiments, t‐CA increased ENaC open probability (PO) by 2‐fold while t‐HDCA decreased ENaC PO by nearly two‐thirds. To determine whether bile acids regulate ENaC through direct binding, we performed photoaffinity labeling experiments. We employed a bile acid derivative (p‐DCA) with diazirine and terminal alkyne groups that facilitate uv‐crosslinking and affinity purification, respectively. Using cultured Fisher Rat Thyroid cells transfected with ENaC, we found that the deoxycholic acid derivative (p‐DCA) crosslinked to the α, β, and γ subunits. To determine whether crosslinking was specific, we performed experiments in the presence of competing bile acids. Crosslinking to the β subunit was significantly reduced in the presence of deoxycholic acid (DCA). Crosslinking to the γ subunit was significantly reduced by taurocholic acid (t‐CA). These data suggest direct binding and multiple sites. To determine the effect of subunit composition on regulation, we measured the effect of t‐CA on Li+ currents in Xenopusoocytes expressing different functional ENaC subunit combinations. Channels composed of α subunits alone were strongly activated by t‐CA, followed by αβγ‐ and αβ‐ channels, suggesting that the α subunit is sufficient for ENaC sensitivity to t‐CA. Our data are consistent with bile acids directly binding all three ENaC subunits at multiple sites. Bile acid moieties provide for selective preferences for each of the sites, resulting in distinct effects for each bile acid.

Synthesis of Novel C/D Ring Modified Bile Acids.

Bile acid receptors have been identified as important targets for the development of new therapeutics to treat various metabolic and inflammatory diseases. The synthesis of new bile acid analogues can help elucidate structure–activity relationships and define compounds that activate these receptors selectively. Towards this, access to large quantities of a chenodeoxycholic acid derivative bearing a C-12 methyl and a C-13 to C-14 double bond provided an interesting scaffold to investigate the chemical manipulation of the C/D ring junction in bile acids. The reactivity of this alkene substrate with various zinc carbenoid species showed that those generated using the Furukawa methodology achieved selective α-cyclopropanation, whereas those generated using the Shi methodology reacted in an unexpected manner giving rise to a rearranged skeleton whereby the C ring has undergone contraction to form a novel spiro–furan ring system. Further derivatization of the cyclopropanated steroid included O-7 oxidation and epimerization to afford new bile acid derivatives for biological evaluation.

Self-Assembly of an Amphiphilic Bile Acid Dimer: A Combined Experimental and Theoretical Study of Its Medium-Responsive Fluorescence.

This work describes the synthesis and aggregation behavior of a dimeric bile acid derivative in which two steroid cores are bridged by a p-di(phenylethynyl)phenylene fluorophore. The studied compound contains three key characteristics: (a) restricted conformational equilibrium in solution, (b) efficient fluorescence conferred by the bridge, and (c) medium responsiveness encoded in the steroid fragments. The incorporation of the three components afforded a compound that generates nano- and micrometric spherical particles with aggregation-responsive fluorescence emission. The observed self-assembly process of the featured molecule was induced by the gradual addition of water to the tetrahydrofuran (THF) solution. This aggregation led to significant changes in fluorescence that went from two bands at λem values of 370 and 390 nm in pure THF to a new spectrum with two maxima at λem values of 395 and 418 nm at high water contents, without a decrease in emission. The observed changes can be ascribed to weakly coupled aggregation, a hypothesis supported by multiscale molecular modeling, which sheds light on the mechanism of the self-assembly of this unconventional amphiphile.

A molecular mechanism of UDCA engagement with GPBAR and subsequent G protein interaction revealed by scattered alanine scanning

As the most known therapeutic component of bear bile acids, ursodeoxycholic acid (UDCA) is an FDA-approved drug for the treatment of primary biliary cirrhosis (PBC), the dissolution of cholesterol gallstones. UDCA produces many beneficial effects on metabolism and immune responses via its interaction with the membrane G protein-coupled bile acid receptor (GPBAR); however, how UDCA interacts with GPBAR and its selective cellular effects remain elusive. In this study, we delineated the interaction of UDCA with GPBAR and activation mechanism of GPBAR by scattered alanine scanning and molecular docking. Our results indicated that transmembrane helix 2 (TM2), TM3, TM5 and TM6 of GPBAR contribute to the interaction of UDCA in GPBAR binding pocket. Moreover, we predicted that the engagement of the 3-OH of UDCA with phenolic oxygen of Y2406.51 in GPBAR plays a key role in GPBAR activation. Unexpectedly, in addition to the well-known roles of intracellular loop2 (ICL2) residues, we identified that ICL3 residues play an important role in G protein coupling to GPBAR in response to UDCA binding. Our study provides a preliminary molecular mechanism of how GPBAR recognizes UDCA and subsequent activation and G protein interaction, which may facilitate the development of new bile acid derivatives as therapeutics.

Protein-Protein Interaction Inhibitors Targeting the Eph-Ephrin System with a Focus on Amino Acid Conjugates of Bile Acids.

The role of the Eph-ephrin system in the etiology of pathological conditions has been consolidated throughout the years. In this context, approaches directed against this signaling system, intended to modulate its activity, can be strategic therapeutic opportunities. Currently, the most promising class of compounds able to interfere with the Eph receptor-ephrin protein interaction is composed of synthetic derivatives of bile acids. In the present review, we summarize the progresses achieved, in terms of chemical expansions and structure-activity relationships, both in the steroidal core and the terminal carboxylic acid group, along with the pharmacological characterization for the most promising Eph-ephrin antagonists in in vivo settings.

Design and synthesis of bile acid derivatives and their activity against colon cancer.

Bile acids (BAs) containing both hydrophilic hydroxyl and carboxyl groups and hydrophobic methyl and steroid nuclei can promote the absorption of fat and other substances in the intestine, and they are synthesized by cholesterol in the liver and then returned to the liver through enteric liver circulation. Because there are many BA receptors on the cell membrane of colon tissues, BAs can improve the specific delivery and transport of medicines to colon tissues. Moreover, BAs have a certain anticancer and inflammation activity by themselves. Based on this theory, a series of BA derivatives against colon cancer including cholic acid (CA), chenodeoxycholic acid (CDCA), ursodeoxycholic acid (UDCA) and lithocholic acid (LCA) were designed and synthesized, and their antitumor activity was evaluated. For in vitro anti-tumor tests, all the compounds displayed cell proliferative inhibition to nine human malignant tumor cell lines to some degree, and in particular they showed stronger inhibition to the colon cancer cells than the other cell lines. Among them, four compounds (4, 5, 6, and 7) showed stronger activity than the other compounds as well as the positive control 5-FU against HCT116 cells, and their IC50 was between 21.32 μmol L-1 and 28.90 μmol L-1; cell clone formation and migration tests showed that they not only effectively inhibited the formation of HCT116 cell colonies, but also inhibited the HCT116 cell migration and invasion; moreover, they induced apoptosis, arrested the mitotic process at the G2/M phase of the cell cycle, reduced the mitochondrial membrane potential, increased the intracellular ROS levels, and reduced the expression of Bcl-2 and p-STAT3 in HCT 116 cells. In addition, they also displayed intermediate anti-inflammatory activity by inhibiting inflammatory mediators NO and downregulating TNF-α expression, which also is one of the causes of colon cancer. This suggests that they deserve to be further investigated as candidates for colon cancer treatment drugs.

Discovery of Bile Acid Derivatives as Potent ACE2 Activators by Virtual Screening and Essential Dynamics.

The angiotensin-converting enzyme II (ACE2) is a key molecular player in the regulation of vessel contraction, inflammation, and reduction of oxidative stress. In addition, ACE2 has assumed a prominent role in the fight against the COVID-19 pandemic-causing virus SARS-CoV-2, as it is the very first receptor in the host of the viral spike protein. The binding of the spike protein to ACE2 triggers a cascade of events that eventually leads the virus to enter the host cell and initiate its life cycle. At the same time, SARS-CoV-2 infection downregulates ACE2 expression especially in the lung, altering the biochemical signals regulated by the enzyme and contributing to the poor clinical prognosis characterizing the late stage of the COVID-19 disease. Despite its important biological role, a very limited number of ACE2 activators are known. Here, using a combined in silico and experimental approach, we show that ursodeoxycholic acid (UDCA) derivatives work as ACE2 activators. In detail, we have identified two potent ACE2 ligands, BAR107 and BAR708, through a docking virtual screening campaign and elucidated their mechanism of action from essential dynamics of the enzyme observed during microsecond molecular dynamics calculations. The in silico results were confirmed by in vitro pharmacological assays with the newly identified compounds showing ACE2 activity comparable to that of DIZE, the most potent ACE2 activator known so far. Our work provides structural insight into ACE2/ligand-binding interaction useful for the design of compounds with therapeutic potential against SARS-CoV-2 infection, inflammation, and other ACE2-related diseases.

Tauroursodeoxycholic acid alleviates secondary injury in spinal cord injury mice by reducing oxidative stress, apoptosis, and inflammatory response

BackgroundTauroursodeoxycholic acid (TUDCA) is a hydrophilic bile acid derivative, which has been demonstrated to have neuroprotective effects in different neurological disease models. However, the effect and underlying mechanism of TUDCA on spinal cord injury (SCI) have not been fully elucidated. This study aims to investigate the protective effects of TUDCA in the SCI mouse model and the related mechanism involved.MethodsThe primary cortical neurons were isolated from E16.5 C57BL/6 mouse embryos. To evaluate the effect of TUDCA on axon degeneration induced by oxidative stress in vitro, the cortical neurons were treated with H2O2 with or without TUDCA added and immunostained with Tuj1. Mice were randomly divided into sham, SCI, and SCI+TUDCA groups. SCI model was induced using a pneumatic impact device at T9-T10 level of the vertebra. TUDCA (200 mg/kg) or an equal volume of saline was intragastrically administrated daily post-injury for 14 days.ResultsWe found that TUDCA attenuated axon degeneration induced by H2O2 treatment and protected primary cortical neurons from oxidative stress in vitro. In vivo, TUDCA treatment significantly reduced tissue injury, oxidative stress, inflammatory response, and apoptosis and promoted axon regeneration and remyelination in the lesion site of the spinal cord of SCI mice. The functional recovery test revealed that TUDCA treatment significantly ameliorated the recovery of limb function.ConclusionsTUDCA treatment can alleviate secondary injury and promote functional recovery by reducing oxidative stress, inflammatory response, and apoptosis induced by primary injury, and promote axon regeneration and remyelination, which could be used as a potential therapy for human SCI recovery.

(E)-7-Ethylidene-lithocholic Acid (7-ELCA) Is a Potent Dual Farnesoid X Receptor (FXR) Antagonist and GPBAR1 Agonist Inhibiting FXR-Induced Gene Expression in Hepatocytes and Stimulating Glucagon-like Peptide-1 Secretion From Enteroendocrine Cells.

Bile acids (BAs) are key signaling steroidal molecules that regulate glucose, lipid, and energy homeostasis via interactions with the farnesoid X receptor (FXR) and G-protein bile acid receptor 1 (GPBAR1). Extensive medicinal chemistry modifications of the BA scaffold led to the discovery of potent selective or dual FXR and GPBAR1 agonists. Herein, we discovered 7-ethylidene-lithocholic acid (7-ELCA) as a novel combined FXR antagonist/GPBAR1 agonist (IC50 = 15 μM/EC50 = 26 nM) with no off-target activation in a library of 7-alkyl substituted derivatives of BAs. 7-ELCA significantly suppressed the effect of the FXR agonist obeticholic acid in BSEP and SHP regulation in human hepatocytes. Importantly, 7-ELCA significantly stimulated the production of glucagon-like peptide-1 (GLP-1), an incretin with insulinotropic effect in postprandial glucose utilization, in intestinal enteroendocrine cells. We can suggest that 7-ELCA may be a prospective approach to the treatment of type II diabetes as the dual modulation of GPBAR1 and FXR has been supposed to be effective in the synergistic regulation of glucose homeostasis in the intestine.

Dual Agonist of Farnesoid X Receptor and Takeda G Protein-Coupled Receptor 5 Inhibits Hepatitis B Virus Infection In Vitro and In Vivo.

Chronic HBV infection is a major health problem worldwide. Currently, the first-line treatment for HBV is nucleos(t)ide analogs or interferons; however, efficient therapeutic approaches that enable cure are lacking. Therefore, anti-HBV agents with mechanisms distinct from those of current drugs are needed. Sodium taurocholate cotransporting polypeptide (NTCP) was previously identified as an HBV receptor that is inhibited by several compounds. Farnesoid X receptor (FXR) activation also inhibits NTCP function. In this study, we investigated the inhibitory effect of bile acid (BA) derivatives-namely obeticholic acid (OCA), 6α-ethyl-24-nor-5β-cholane-3α,7α,23-triol-23 sulfate sodium salt (INT-767; a dual agonist of FXR and Takeda G protein-coupled receptor [TGR5]), and 6α-ethyl-23(S)-methyl-cholic acid (INT-777; a TGR5 agonist)-3-(2,6-dichlorophenyl)-4-(3'-carboxy-2-chlorostilben-4-yl)oxymethyl-5-isopropylisoxazole (GW4064; a FXR agonist), cyclosporin A, and irbesartan. OCA and INT-777 suppressed HBV infection in HepG2-human NTCP-C4 cells. Interestingly, INT-767 showed potent inhibition by attaching to HBV particles rather than binding to NTCP. As an entry inhibitor, INT-767 was stronger than various natural BAs. Furthermore, in chimeric mice with humanized liver, INT-767 markedly delayed the initial rise of HBsAg, HBeAg, and HBV DNA and reduced covalently closed circular DNA. The strong inhibitory effect of INT-767 may be due to the cumulative effect of its ability to inhibit the entry of HBV and to stimulate FXR downstream signaling, which affects the postentry step. Our results suggest that BA derivatives, particularly INT-767, are prospective candidate anti-HBV agents. Clarifying the underlying mechanisms of BA derivatives would facilitate the development of anti-HBV agents.

Diet Quality, Gut Microbiome and Metabolism

ObjectivesDietary pattern is associated with circulatory and gut metabolome variation. However, it is unclear if this association is mediated by gut microbiome composition. We investigated whether the interaction between diet quality and gut microbiome influenced circulatory and gut metabolites. MethodsWe conducted a cross-sectional study among 75 healthy adults in the ABO Study. Diet quality was assessed using the Healthy Eating Index (HEI). Metabolome profiling (800 circulatory and 767 gut metabolites) was performed at Metabolon Inc. Two gut microbiome Enterotypes (1 and 2) were identified using the Partitioning Around Medoids method. Metabolite set enrichment analysis was performed using Metaboanalyst 4.0. Multivariable linear regression was conducted to test for an interaction between the gut microbiome-HEI and metabolite levels. ResultsDiet quality was significantly higher in participants with Enterotype 2, compared to those with Enterotype 1 (P = 0.01). The gut microbiome-HEI interaction (Enterotype 2 and higher HEI) was directly related to omega-3/omega-6 poly-unsaturated fatty acids (PUFAs) and acetyl/acyl derivatives of amino acids. It was inversely linked to polar lipids including 1-palmitoyl-2-linoleoyl-GPC (16:0/18:2), which demonstrated the most significant association (β = 0.008, P = 0.0009) among circulatory metabolites. Considering gut metabolome, however, the interaction directly associated with metabolites involved in DNA synthesis including thymidine 5′-monophosphate, which showed the strongest association (β = 0.041, P = 0.0007), and bile acids derivatives. It inversely associated with fatty acids and branch chain amino acids. ‘Glycine and serine metabolism’ was the only pathway that was significantly enriched by the interaction (P = 0.044). ConclusionsFuture research is warranted; however, these findings suggest that the efficacy of dietary interventions targeted at altering metabolism (the metabolism of lipids (PUFAs and polar lipids), amino acids and nucleotides) may be dependent on gut microbiome composition. Funding SourcesThe National Institutes of Health.

Bile acids directly bind and allosterically regulate the epithelial sodium channel

Bile acids are abundant in the biliary tree and intestinal tract, and can be elevated in the urine of patients with advanced liver disease. Our previous work showed that bile acids carrying specific moieties regulate the epithelia Na+ channel (ENaC). ENaC mediates Na+ transport in several epithelia, including the biliary epithelium and aldosterone-sensitive distal nephron and colon. Based on our work showing no dependence on bile acid physicochemical properties or membrane permeability, we hypothesize that bile acids regulate ENaC through direct binding. To test this, we performed crosslinking experiments using bile acid derivatives that facilitate uv-crosslinking and affinity purification. Using ENaC heterologously expressed in Fisher Rat Thyroid cells, we found that the deoxycholic acid derivative (p-DCA) crosslinked to the α, β, and γ subunits. To determine whether crosslinking was specific, we performed experiments in the presence of different competing bile acids. We found that crosslinking to the β subunit was significantly reduced in the presence of deoxycholic acid (DCA). We also found that crosslinking to the γ subunit was significantly reduced by taurocholic acid (t-CA). These data suggest that bile acids directly bind ENaC, with different bile acids preferentially binding different sites. We also examined the effect of subunit composition on bile acid regulation. Using Xenopus oocytes, we measured the effect of t-CA on Li+ currents conducted by different functional ENaC subunit combinations. We found that α-only channels were greatly activated by t-CA, followed by αβγ- and αβ- channels, suggesting that the α subunit is sufficient for ENaC sensitivity to t-CA. To determine whether bile acid regulation is voltage-sensitive, we measured the effect of different doses of t-CA on ENaC activation while varying voltage from -140 mV to 40 mV. We found that t-CA activated ENaC in a voltage-dependent manner, with greater activation at less negative potentials. Models of regulation having a single t-CA binding site fit the data poorly. Hypothesizing multiple binding sites, our data fit well to an allosteric model with at least two binding sites, one of which is voltage-sensitive. Our data are consistent with bile acids directly binding all three ENaC subunits at multiple sites, with one site associated with the transmembrane domains. Bile acid moieties provide for selective preferences for each of the sites, resulting in distinct effects for each bile acid.

Design of Dimeric Bile Acid Derivatives as Potent and Selective Human NTCP Inhibitors.

Dimeric bile acid derivatives (DBADs) were developed and tested for their anti-HBV and anti-HDV activities as sodium taurocholate cotransporting polypeptide (NTCP) inhibitors. DBADs exhibited strong and persistent potency of NTCP inhibition, whereas diverse linkers and constitutions showed distinct inhibition features. Motif aa157-165 on NTCP was shown to be a possible binding site of DBADs; therefore, we determined DBADs' selectivity among NTCPs from different species. A cyclized DBAD scaffold DBA-41 exhibited a high affinity to human NTCP (hNTCP). Intraperitoneal administration of DBA-41 to hNTCP-tg mice induced serum total bile acid elevation. DBA-41 may serve as a biological tool to study NTCP physiological function.

Chiral Biobased Ionic Liquids with Cations or Anions including Bile Acid Building Blocks as Chiral Selectors in Voltammetry

AbstractChiral ionic liquids (CILs), or ionic liquids (ILs) with chiral additives, are very attractive chiral media for enantioselective electroanalysis, on account of their high chiral structural order at the electrochemical interphase. A family of molecular salts with CIL properties is now introduced, based on the chiral steroid building block of deoxycholic acid implemented either in the anion or cation. Testing them as chiral additives in a commercial achiral IL, they enable voltammetric discrimination of the enantiomers of a model chiral probe on disposable screen‐printed electrodes in terms of peak potential differences, which is the most desirable transduction mode of the enantiorecognition event. The probe enantiomer sequence is the same for all selectors, consistent with their sharing the same chiral building block configuration. This proof‐of‐concept widens the application fields of bile acid derivatives as chiral selectors, while also enriching the still very few CIL families so far explored for applications in chiral electroanalysis.