Dietary bile acids reduce liver lipid deposition via activating farnesoid X receptor, and improve gut health by regulating gut microbiota in Chinese perch (Siniperca chuatsi)

The aim of this study is to explore the effects of dietary bile acids (BAs) supplementation on lipid metabolism and gut health of Chinese perch (Siniperca chuatsi), and its possible mechanisms. Two isonitrogenous and isolipidic diets were formulated to supplement different levels of BAs (0 and 900 mg BAs kg^-1 diet, respectively). All fish (Initial mean body weight: 171.29 ± 0.77g) were randomly divided into 2 groups (triplicate, 54 fish/group) and were fed with different experimental diets for 56 days, respectively. Dietary exogenous BAs supplementation at the concentration of 900 mg kg^-1 significantly increased weight gain and survival rate, and decreased feed conversion ratio. BAs could inhibit lipid synthesis and promote lipid oxidation to reduce lipid deposition by activating farnesoid X receptor (FXR). Dietary BAs supplementation increased the abundance of Lactobacilli in Firmicutes, and the increase of Lactobacillus caused the increase of lactic acid level and the decrease of pH, which might be the reason for the gut villus length and gut wall high in this study. Dietary BAs supplementation increased the levels of catalase and superoxide dismutase and decreased the level of malondialdehyde in the gut and plasma, which might be contributed to the regulating the antioxidant stress phenotype of gut microbiota by the increased abundance of Firmicutes. Then it caused the increase of the globulin level in the plasma, meaning the enhancement of immune state. The increased immunity might also be thought to be responsible for increased survival rate. These results suggest dietary BAs reduce liver lipid deposition via activating FXR, and improve gut health by regulating gut microbiota in Chinese perch.

Differential effects of bile acids on the postprandial secretion of gut hormones: a randomized crossover study

Bile acids (BA) regulate postprandial metabolism directly and indirectly by affecting the secretion of gut hormones like glucagon-like peptide-1 (GLP-1). The postprandial effects of BA on the secretion of other metabolically active hormones are not well understood. The objective of this study was to investigate the effects of oral ursodeoxycholic acid (UDCA) and chenodeoxycholic acid (CDCA) on postprandial secretion of GLP-1, oxyntomodulin (OXM), peptide YY (PYY), glucose-dependent insulinotropic peptide (GIP), glucagon, and ghrelin. Twelve healthy volunteers underwent a mixed meal test 60 min after ingestion of UDCA (12-16 mg/kg), CDCA (13-16 mg/kg), or no BA in a randomized crossover study. Glucose, insulin, GLP-1, OXM, PYY, GIP, glucagon, ghrelin, and fibroblast growth factor 19 were measured prior to BA administration at -60 and 0 min (just prior to mixed meal) and 15, 30, 60, 120, 180, and 240 min after the meal. UDCA and CDCA provoked differential gut hormone responses; UDCA did not have any significant effects, but CDCA provoked significant increases in GLP-1 and OXM and a profound reduction in GIP. CDCA increased fasting GLP-1 and OXM secretion in parallel with an increase in insulin. On the other hand, CDCA reduced postprandial secretion of GIP, with an associated reduction in postprandial insulin secretion. Exogenous CDCA can exert multiple salutary effects on the secretion of gut hormones; if these effects are confirmed in obesity and type 2 diabetes, CDCA may be a potential therapy for these conditions.NEW & NOTEWORTHY Oral CDCA and UDCA have different effects on gut and pancreatic hormone secretion. A single dose of CDCA increased fasting secretion of the hormones GLP-1 and OXM with an accompanying increase in insulin secretion. CDCA also reduced postprandial GIP secretion, which was associated with reduced insulin. In contrast, UDCA did not change gut hormone secretion fasting or postprandially. Oral CDCA could be beneficial to patients with obesity and diabetes.

Synergistic activity of bile salts and their derivatives in combination with conventional antimicrobial agents against Acinetobacter baumannii

ETHNOPHARMACOLOGICAL RELEVANCE

Bile traditionally was used in wound healing, having erodent, antioxidant and antimicrobial potential. Acinetobacter baumannii is a frequent etiological agent of wound infections, exhibiting high level of resistance to conventional antibiotics.

AIM OF THE STUDY

To determine the effect of selected bile acid sodium salts and their 3-dehydro (i.e. 3-oxo) derivatives, as well as their combinations with commercial antibiotics against A. baumanniia, to confirm bile ethnopharmacological application in wound healing from aspect of microbiology.

MATERIALS AND METHODS

The sensitivity of reference and multidrug resistant (MDR) A. baumannii strains to bile salts, their derivatives and conventional antibiotics were examined by a microtiter plate method. The interaction of bile salts/derivatives and antibiotics was examined by a checkerboard method and time kill curve method. The interaction of bile salts with ciprofloxacin in terms of micelles formation was examined by DOSY NMR technique.

RESULTS

The bile salts sodium deoxycholate (Na-DCA) and sodium chenodeoxycholate (Na-CDCA), as well as their derivatives sodium 3-dehydro-deoxycholate (Na-3DH-DCA) and sodium 3-dehydro-chenodeoxycholate (Na-3DH-CDCA), potentiate antibiotic activity and resensitize A. baumannii. The bile salts and their derivatives enhance A. baumannii sensitivity to antibiotics, particularly those that should penetrate cell to exhibit activity. The sodium salts of bile acid derivatives, namely Na-3DH-DCA and Na-3DH-CDCA, showed synergy against both reference and MDR strain in combination with ciprofloxacin or gentamicin, while synergy with gentamicin was obtained in all combinations, regardless of bile salt type and bacterial strains. The synergy with Na-3DH-CDCA was further confirmed by the time-kill curve method, as bacterial number decreased after 12 h. NMR experiment revealed that this bile salt derivative and ciprofloxacin form co-aggregates when bile salts concentration was higher than critical micelle concentrations (CMC), which indicate the possibility that bile salts enhance ciprofloxacin cell penetration by membrane destabilization, contributing to the synergy.

CONCLUSION

The synergistic interactions between bile salts or derivatives with ciprofloxacin and particularly gentamicin represent a promising strategy for the treatment of A. baumannii wound infections.

Pharmacokinetics of CamSA, a potential prophylactic compound against Clostridioides difficile infections

Clostridioides difficile infections (CDI) are the leading cause of nosocomial antibiotic-associated diarrhea. C. difficile produces dormant spores that serve as infectious agents. Bile salts in the gastrointestinal tract signal spores to germinate into toxin-producing cells. As spore germination is required for CDI onset, anti-germination compounds may serve as prophylactics. CamSA, a synthetic bile salt, was previously shown to inhibit C. difficile spore germination in vitro and in vivo. Unexpectedly, a single dose of CamSA was sufficient to offer multi-day protection from CDI in mice without any observable toxicity. To study this intriguing protection pattern, we examined the pharmacokinetic parameters of CamSA. CamSA was stable to the gut of antibiotic-treated mice but was extensively degraded by the microbiota of non-antibiotic-treated animals. Our data also suggest that CamSA's systemic absorption is minimal since it is retained primarily in the intestinal lumen and liver. CamSA shows weak interactions with CYP3A4, a P450 hepatic isozyme involved in drug metabolism and bile salt modification. Like other bile salts, CamSA seems to undergo enterohepatic circulation. We hypothesize that the cycling of CamSA between the liver and intestines serves as a slow-release mechanism that allows CamSA to be retained in the gastrointestinal tract for days. This model explains how a single CamSA dose can prevent murine CDI even though spores are present in the animal's intestine for up to four days post-challenge.

Bile acids drive the newborn's gut microbiota maturation

Following birth, the neonatal intestine is exposed to maternal and environmental bacteria that successively form a dense and highly dynamic intestinal microbiota. Whereas the effect of exogenous factors has been extensively investigated, endogenous, host-mediated mechanisms have remained largely unexplored. Concomitantly with microbial colonization, the liver undergoes functional transition from a hematopoietic organ to a central organ of metabolic regulation and immune surveillance. The aim of the present study was to analyze the influence of the developing hepatic function and liver metabolism on the early intestinal microbiota. Here, we report on the characterization of the colonization dynamics and liver metabolism in the murine gastrointestinal tract (n = 6-10 per age group) using metabolomic and microbial profiling in combination with multivariate analysis. We observed major age-dependent microbial and metabolic changes and identified bile acids as potent drivers of the early intestinal microbiota maturation. Consistently, oral administration of tauro-cholic acid or β-tauro-murocholic acid to newborn mice (n = 7-14 per group) accelerated postnatal microbiota maturation.

Effects of supplemental dietary bile acids on growth, liver function and immunity of juvenile largemouth bass（Micropterus salmoides）fed high-starch diet

The present study was conducted to investigate the effects of bile acids (BAs) on the growth, liver function and immunity of the largemouth bass fed high-starch diet. The experiment set three isonitrogenous and isoenergetic semi-purified diets, LS: low-starch diet (5%), HS: high-starch diet (19%) and SB: high-starch diet with BAs (350 mg/kg diet). An 8-week feeding trial was conducted in largemouth bass of initial weight 23.69 ± 0.13 g. The results indicated that the weight gain (WG) and protein efficiency ratio (PER) of fish fed LS and SB were significantly higher than HS treatment. The superoxide dismutase (SOD) and catalase (CAT) activities of SB group were significantly increased, while malondialdehyde (MDA) content significantly reduced in liver compared with HS group. The activities of alanine aminotransferase (ALT), aspartate transaminase (AST), alkaline phosphatase (ALP) and glucose contents in plasma of SB group were significantly lower than HS treatment, whereas the content of triglyceride (TG) and total cholesterol (TC) in plasma were significantly higher than HS treatment. Additionally, the plasma immunoglobulin count, lysozyme activity and the blood leukocyte count (WBC) in SB group were significantly higher than HS group. The results of paraffin section of liver showed the histopathological alterations were significantly reduced in the SB group compared to HS group. All in all, this study revealed that bile acids supplement could significantly improve growth performance, enhance liver function and immune ability, and alleviate stress responses of M. salmoides fed high-starch diet.

Supplementation exogenous bile acid improved growth and intestinal immune function associated with NF-κB and TOR signalling pathways in on-growing grass carp (Ctenopharyngodon idella): Enhancement the effect of protein-sparing by dietary lipid

This study investigated the effects of bile acid (BA) supplementation on growth performance, intestinal immune function and the mRNA expression of the related signalling molecules in on-growing grass carp (Ctenopharyngodon idella). A total of 540 healthy grass carp (mean weight 179.85 ± 1.34 g) were fed a normal protein and lipid (NPNL) diet containing 29% crude protein (CP) and 5% ether extract (EE), and five low-protein and high-lipid (LPHL) diets (26% CP, 6% EE) with graded levels of BA (0-320 mg/kg diet) for 50 days. The fish were then challenged with Aeromonas hydrophila for 14 days. The results indicated that compared with the NPNL diet, the LPHL diet (unsupplemented BA) suppressed the growth performance, intestinal development and enteritis resistance capability and impaired the partial intestinal immune function of on-growing grass carp. Whereas in the LPHL diet, optimal BA supplementation significantly improved fish growth performance (percent weight gain, specific growth rate, feed intake and feed efficiency) and intestinal growth and function (intestine weight, intestine length and intestosomatic index), increased beneficial bacteria Lactobacillus and Bifidobacterium amounts, decreased harmful bacteria Aeromonas and Escherichia coli amounts, elevated lysozyme and acid phosphatase activities, increased complement (C3 and C4) and immunoglobulin M contents, and upregulated β-defensin-1, hepcidin, liver expressed antimicrobial peptide 2A (LEAP-2A), LEAP-2B, Mucin2, interleukin 10 (IL-10), IL-11, transforming growth factor (TGF)-β1, TGF-β2, IL-4/13A (not IL-4/13B), TOR, S6K1 and inhibitor of κBα (IκBα) mRNA levels. In addition, optimal BA supplementation in the LPHL diet downregulated tumour necrosis factor α (TNF-α), interferon γ2 (IFN-γ2), IL-1β, IL-6, IL-8, IL-15, IL-17D, IL-12p35, IL-12p40 (rather than proximal intestine (PI) or mid intestine (MI), nuclear factor kappa B p65 (NF-κB p65) (except NF-κB p52), c-Rel, IκB kinase β (IKKβ), IKKγ (except IKKα), eIF4E-binding proteins (4E-BP)1 and 4E-BP2 mRNA levels in all three intestinal segments of on-growing grass carp (P < 0.05). These findings suggest that BA supplementation in the LPHL diet improves growth and intestinal immune function of fish. Furthermore, 240 mg/kg BA supplementation in the LPHL diet was superior to the NPNL diet in improving growth and enhancing intestinal immune function of fish. Finally, based on percent weight gain, feed intake, protecting fish against enteritis, lysozyme activity in MI and acid phosphatase activity in distal intestine (DI), the optimal BA supplementation for on-growing grass carp were estimated to be 168.98, 170.23, 166.67, 176.50 and 191.97 mg/kg diet, respectively.

Microbiota-Derived Metabolic Factors Reduce Campylobacteriosis in Mice

BACKGROUND & AIMS

Campylobacter jejuni, a prevalent foodborne bacterial pathogen, exploits the host innate response to induce colitis. Little is known about the roles of microbiota in C jejuni-induced intestinal inflammation. We investigated interactions between microbiota and intestinal cells during C jejuni infection of mice.

METHODS

Germ-free C57BL/6 Il10-/- mice were colonized with conventional microbiota and infected with a single dose of C jejuni (109 colony-forming units/mouse) via gavage. Conventional microbiota were cultured under aerobic, microaerobic, or anaerobic conditions and orally transplanted into germ-free Il10-/- mice. Colon tissues were collected from mice and analyzed by histology, real-time polymerase chain reaction, and immunoblotting. Fecal microbiota and bile acids were analyzed with 16S sequencing and high-performance liquid chromatography with mass spectrometry, respectively.

RESULTS

Introduction of conventional microbiota reduced C jejuni-induced colitis in previously germ-free Il10-/- mice, independent of fecal load of C jejuni, accompanied by reduced activation of mammalian target of rapamycin. Microbiota transplantation and 16S ribosomal DNA sequencing experiments showed that Clostridium XI, Bifidobacterium, and Lactobacillus were enriched in fecal samples from mice colonized with microbiota cultured in anaerobic conditions (which reduce colitis) compared with mice fed microbiota cultured under aerobic conditions (susceptible to colitis). Oral administration to mice of microbiota-derived secondary bile acid sodium deoxycholate, but not ursodeoxycholic acid or lithocholic acid, reduced C jejuni-induced colitis. Depletion of secondary bile acid-producing bacteria with antibiotics that kill anaerobic bacteria (clindamycin) promoted C jejuni-induced colitis in specific pathogen-free Il10-/- mice compared with the nonspecific antibiotic nalidixic acid; colitis induction by antibiotics was associated with reduced level of luminal deoxycholate.

CONCLUSIONS

We identified a mechanism by which the microbiota controls susceptibility to C jejuni infection in mice, via bacteria-derived secondary bile acids.

Long-term Administration of Nuclear Bile Acid Receptor FXR Agonist Prevents Spontaneous Hepatocarcinogenesis in Abcb4-/- Mice

Altered bile acid (BA) signaling is associated with hepatotoxicity. The farnesoid X receptor (FXR) is a nuclear receptor that transcriptionally regulates BA homeostasis. Mice with FXR ablation present hepatocarcinoma (HCC) due to high toxic BA levels. Mice with Abcb4 ablation accumulate toxic BA within the bile ducts and present HCC. We have previously shown that intestinal specific activation of FXR by transgenic VP16-FXR chimera is able to reduce BA pool size and prevent HCC. Here we tested chemical FXR activation by administering for 15 months the dual FXR/ membrane G protein-coupled receptor (TGR5) agonist INT-767 (6α-ethyl-3α,7α,23-trihydroxy-24-nor-5β-cholan-23-sulphate) to Fxr-/- and Abcb4-/- mice. HCC number and size were significantly reduced by INT-767 administration. In contrast, no changes in HCC tumor number and size were observed in Fxr-/- mice fed with or without INT-767. Notably, INT-767 preserved the hepatic parenchyma, improved hepatic function and down-regulated pro-inflammatory cytokines. Moreover, in Abcb4-/- mice INT-767 prevented fibrosis by reducing collagen expression and deposition. Thus, long term activation of FXR is able to reduce BA pool, reprogram BA metabolism and prevent HCC. These data provide the impetus to address the bona fide therapeutic potential of FXR activation in disease with BA-associated development of HCC.

The bile acid chenodeoxycholic acid directly modulates metabolic pathways in white adipose tissue in vitro: insight into how bile acids decrease obesity

Obesity is a worldwide epidemic, and associated pathologies, including type 2 diabetes and cardiovascular alterations, are increasingly escalating morbidity and mortality. Despite intensive study, no effective simple treatment for these conditions exists. As such, the need for go-to drugs is serious. Bile acids (BAs) present the possibility of reversing these problems, as various in vivo studies and clinical trials have shown significant effects with regard to weight and obesity reduction, insulin sensitivity restoration and cardiovascular improvements. However, the mechanism of action of BA-induced metabolic improvement has yet to be fully established. The currently most accepted model involves non-shivering thermogenesis for energy waste, but this is disputed. As such, we propose to determine whether the BA chenodeoxycholic acid (CDCA) can exert anti-obesogenic effects in vitro, independent of thermogenic brown adipose tissue activation. By exposing differentiated 3 T3-L1 adipocytes to high glucose and CDCA, we demonstrate that this BA has anti-obesity effects in vitro. Nuclear magnetic resonance spectroscopic analysis of metabolic pathways clearly indicates an improvement in metabolic status, as these cells become more oxidative rather than glycolytic, which may be associated with an increase in fatty acid oxidation. Our work demonstrates that CDCA-induced metabolic alterations occur in white and brown adipocytes and are not totally dependent on endocrine/nervous system signaling, as thought until now. Furthermore, future exploration of the mechanisms behind these effects will undoubtedly reveal interesting targets for clinical modulation.

Bile acid binding resin improves hepatic insulin sensitivity by reducing cholesterol but not triglyceride levels in the liver

AIMS

Bile acid binding resin (BAR) improves glycaemic control in patients with type 2 diabetes. Although the mechanism is hypothesised to involve the clearance of excess hepatic triglyceride, this hypothesis has not been examined in appropriately designed studies. Therefore, we investigated whether reduced hepatic triglyceride deposition is involved in BAR-mediated improvements in glycaemic control in spontaneous fatty liver diabetic mice without dietary interventions.

METHODS

Male 6-week-old fatty liver Shionogi (FLS) mice were fed a standard diet without or with 1.5% BAR (colestilan) for 6 weeks. Glucose tolerance, insulin sensitivity, hepatic lipid content, and gene expression were assessed. A liver X receptor (LXR) agonist was also administered to activate the LXR pathway. We also retrospectively analysed the medical records of 21 outpatients with type 2 diabetes who were treated with colestilan for ≥6 months.

RESULTS

BAR enhanced glucose tolerance and insulin sensitivity in FLS mice without altering fat mass. BAR improved hepatic insulin sensitivity, increased IRS2 expression, and decreased SREBP expression. BAR reduced hepatic cholesterol levels but not hepatic triglyceride levels. BAR also reduced the expression of LXR target genes, and LXR activation abolished the BAR-mediated improvements in glycaemic control. Colestilan significantly lowered serum cholesterol levels and improved glycaemic control in patients with type 2 diabetes.

CONCLUSIONS

BAR improved hepatic insulin resistance in FLS mice by reducing hepatic cholesterol without affecting hepatic triglyceride levels or body fat distribution. Our study revealed that BAR improves glycaemic control at least in part by downregulating the hepatic cholesterol-LXR-IRS2 pathway.

Homologue gene of bile acid transporters ntcp, asbt, and ost-alpha in rainbow trout Oncorhynchus mykiss: tissue expression, effect of fasting, and response to bile acid administration

Bile acid transporters belonging to the SLC10A protein family, Na+ taurocholate cotransporting polypeptide (NTCP or SLC10A1), apical sodium-dependent bile salt transporter (ASBT or SLC10A2), and organic solute transporter alpha (Ost-alpha) have been known to play critical roles in the enterohepatic circulation of bile acids in mammals. In this study, ntcp, asbt, and ost-alpha-1/-2 cDNA were cloned, their tissue distributions were characterized, and the effects of fasting and bile acid administration on their expression were examined in rainbow trout Oncorhynchus mykiss. The structural characteristics of Ntcp, Asbt, and Ost-alpha were well conserved in trout, and three-dimensional structure analysis showed that Ntcp and Asbt were similar to each other. Tissue distribution analysis revealed that trout asbt was primarily expressed in the hindgut, while ntcp expression occurred in the brain, and ost-alpha-1/-2 was mainly expressed in the liver or ovary. Although asbt and ost-alpha-1 mRNA levels in the gut increased in response to fasting for 4 days, ost-alpha-1 expression in the liver decreased. Similarly, bile acid administration increased asbt and ost-alpha-1 expression levels in the gut, while those of ntcp and ost-alpha-2 in the liver decreased. These results suggested that the genes asbt, ntcp, and ost-alpha are involved in bile acid transport in rainbow trout.

Prolonged stimulation of pancreatic serous secretions by bile and sodium taurocholate in anaesthetized rats

There have been numerous reports that infusion of either natural bile or bile salts into the duodenum evokes a rapid increase in pancreatic secretion through the release of the hormone secretin from the duodenal mucosa. We have extended this observation by the demonstration of an additional late increase in secretion which persisted for many hours and have sought to identify the processes underlying this increase. In anaesthetised rats, infusion of 20 mM taurocholate into the duodenum caused a staircase-like increase in the weight of pancreatic secretion which extended over many hours during which, the HCO[Formula: see text] and protein output of the secretion showed only minimal changes. This effect was also reproduced with intra-duodenal infusion of natural bile which was inferred to act though its taurocholate content. Since the stimulatory action was also obtained with superfusion of taurocholate or natural bile onto the small intestine and by intravenous injection of taurocholate, it was concluded that taurocholate acted by being absorbed into the bloodstream and then by exerting a stimulatory action on the exocrine pancreas. This action was inhibited by puromycin (a protein synthesis inhibitor), by furosemide (a Na( + )/K( + )/2Cl(-) cotransporter inhibitor), though not by SITS (an inhibitor of Cl(-)/HCO[Formula: see text] exchange). The long lasting increase in pancreatic serous secretion would be consistent with the possible activation of gene transcription by taurocholate leading to increased activity of the Na( + )/K( + )/2Cl(-) cotransporter through which the acinar cells increased their secretions.

[Biochemical characteristics of operating bile composition in different types of cholecystolithiasis]

With a view to predicting the outcomes of surgical treatment of cholelithiasis, depending on the composition of concretions by high performance liquid chromatography was studied lipid composition and the spectrum of the operating bile acids in 10 patients with bile pigment cholelithiasis, 15--with cholesterol cholelithiasis, 15--with a combination of cholesterol cholelithiasis, and scab forms cholesterosis gallbladder, 6--to polypous-mesh form cholesterosis gallbladder. As a control, use the operating bile 6 patients with adenomatous and fibro-adenomatous polyps of the gallbladder. Based on the results of the study was proved the need for correction of biliary insufficiency in patients operated on for cholesterin associated pathology of the gallbladder. Spectrum of bile acids of operating bile helped justify holding litholytic therapy to prevent aggregation of bile.

Effects of intestinal constituents and lipids on intestinal formation and pharmacokinetics of desethylamiodarone formed from amiodarone

To model the impact of intestinal components associated with a high fat meal on metabolism of amiodarone, rat everted intestinal sacs were evaluated for their ability to metabolize the drug to its active metabolite (desethylamiodarone) under a variety of conditions. The preparations were obtained from fasted rats or rats pretreated with 1% cholesterol in peanut oil. After isolation of the tissues, the intestinal segments were immersed in oxygenated Krebs Henseleit buffer containing varying concentrations of bile salts, cholesterol, lecithin and lipase with or without soybean oil emulsion as a source of triglycerides. Amiodarone uptake was similar between the five 10-cm segments isolated distally from the stomach. Desethylamiodarone was measurable in all segments. Based on the metabolite-to-drug concentration ratio within the tissues, there was little difference in metabolic efficiency between segments for any of the treatments. Between treatments, however, it appeared that the lowest level of metabolism was noted in rats pretreated with 1% cholesterol in peanut oil. This reduction in metabolic efficiency was not observed in gut sacs from the fasted rats to which soybean oil emulsion was directly added to the incubation media. Despite the apparent reduction in intestinal metabolism, there was no apparent change in the ratio of metabolite-to-drug area under the plasma concentration versus time ratios of fasted rats and those given 1% cholesterol in peanut oil, suggesting that the intestinal presystemic formation of desethylamiodarone is not substantial.

Liphophilic complexation of heparin based on bile acid for oral delivery

Oral delivery of heparin will offer great advantages over injectable heparin therapy in the treatment of patients with deep vein thrombosis. Since heparin absorption in the intestine is restricted due to its physicochemical properties, we designed a bile acid derivative, cationic deoxycholylethylamine (DCEA), to be complexed with anionic low molecular weight heparin (LMWH). Complexation between LMWH and DCEA was saturated above 1:10 molar ratio and improved lipophilicity of LMWH. The LMWH/DCEA complex was completely solubilized in 80% propylene glycol solution. The oral absorption of LMWH in rats was proportional to the molar ratio of DCEA and the administered dose of complex. The C(max) values to the complex molar ratios of 1:0, 1:3, 1:5 and 1:10 were about 0.07, 0.27, 0.83, and 0.47 IU/ml, respectively, and the C(max) values to the doses of 10, 25, 50 mg/kg were 0.16, 0.44, and 0.83 IU/ml, respectively. The LMWH/DCEA complex was found to be absorbable through all regions of the small intestine of rats without causing tissue damage. This study demonstrates the feasibility of oral heparin delivery using the cationic DCEA for chronic administration in clinical trials as an effective therapy.

Intestinal bile salt absorption in Atp8b1 deficient mice

BACKGROUND/AIMS

Mutations in the ATP8B1 gene can cause Progressive Familial Intrahepatic Cholestasis type 1. We have previously reported that Atp8b1(G308V/G308V) mice, a model for PFIC1, have slightly, but significantly, higher baseline serum bile salt (BS) concentrations compared to wt mice. Upon BS feeding, serum BS concentrations strongly increased in Atp8b1-deficient mice. Despite these findings, we observed only mildly impaired canalicular BS transport. In the present report we tested the hypothesis that Atp8b1(G308V/G308V) mice hyperabsorb BS in the intestine during BS feeding.

METHODS

Intestinal BS absorption was measured in intestinal perfusion and in intestinal explants. In addition, we measured BS concentrations in portal blood. Ileal expression of the Fxr-targets Asbt, Ilbp and Shp was assessed.

RESULTS

In wt and Atp8b1(G308V/G308V) mice, intestinal taurocholate absorption is primarily mediated by the ileal bile salt transporter Asbt. Neither of the experimental systems revealed enhanced absorption of BS in Atp8b1(G308V/G308V) mice compared to wt mice. In line with these observations, we found no difference in the ileal protein expression of Asbt. Induction of Shp expression during BS feeding also demonstrated that Fxr signalling is intact in Atp8b1(G308V/G308V) mice.

CONCLUSIONS

The accumulation of BS in plasma of Atp8b1(G308V/G308V) mice during BS feeding is not caused by increased intestinal BS absorption.

Involvement of membrane-type bile acid receptor M-BAR/TGR5 in bile acid-induced activation of epidermal growth factor receptor and mitogen-activated protein kinases in gastric carcinoma cells

Bile acids, which have been implicated in gastrointestinal-tract cell carcinogenesis, share properties with tumor promoters in that both affect signal transduction pathways responsible for cell proliferation and apoptosis. In the present study, we demonstrate that EGFR-ERK1/2 is activated following treatment of AGS human gastric carcinoma cells with bile acids. EGFR phosphoactivation is ligand-dependent, since treatment of cells with HB-EGF antisera or CM197 (a selective inhibitor of HB-EGF) markedly inhibits deoxycholate (DC)-promoted activation. Membrane-type bile acid receptor (M-BAR)/TGR5 is a recently identified G-protein-coupled receptor (GPCR). In AGS cells, siRNAs that target M-BAR suppress DC-induced phosphorylation of EGFR. Furthermore, introduction of siRNAs targeting ADAM17 transcripts resulted in suppression of DC-induced activation of EGFR and ERK1/2. These results suggest that in AGS cells, DC transactivates EGFR through M-BAR- and ADAM/HB-EGF-dependent mechanisms.

Deoxycholic acid differentially regulates focal adhesion kinase phosphorylation: role of tyrosine phosphatase ShP2

Environmental factors, including dietary fats, are implicated in colonic carcinogenesis. Dietary fats modulate secondary bile acids including deoxycholic acid (DCA) concentrations in the colon, which are thought to contribute to the nutritional-related component of colon cancer risk. Here we demonstrate, for the first time, that DCA differentially regulated the site-specific phosphorylation of focal adhesion kinase (FAK). DCA decreased adhesion of HCA-7 cells to the substratum and induced dephosphorylation of FAK at tyrosine-576/577 (Tyr-576/577) and Tyr-925. Tyrosine phosphorylation of FAK at Tyr-397 remained unaffected by DCA stimulation. Interestingly, we found that c-Src was constitutively associated with FAK and DCA actually activated Src, despite no change in FAK-397 and an inhibition of FAK-576 phosphorylation. DCA concomitantly and significantly increased association of tyrosine phosphatase ShP2 with FAK. Incubation of immunoprecipitated FAK, in vitro, with glutathione-S-transferase-ShP2 fusion protein resulted in tyrosine dephosphorylation of FAK in a concentration-dependent manner. Antisense oligodeoxynucleotides directed against ShP2 decreased ShP2 protein levels and attenuated DCA-induced FAK dephosphorylation. Inhibition of FAK by adenoviral-mediated overexpression of FAK-related nonkinase and gene silencing of Shp2 both abolished DCA's effect on cell adhesion, thus providing a possible mechanism for inside-out signaling by DCA in colon cancer cells. Our results suggest that DCA differentially regulates focal adhesion complexes and that tyrosine phosphatase ShP2 has a role in DCA signaling.

Bifendate treatment attenuates hepatic steatosis in cholesterol/bile salt- and high-fat diet-induced hypercholesterolemia in mice

Effects of bifendate, a synthetic intermediate of schisandrin C (a dibenzocyclooctadiene derivative), on liver lipid contents were investigated in experimentally-induced hypercholesterolemia in mice. Hypercholesterolemia was induced by either chronic administration of cholesterol/bile salt or feeding a high-fat diet containing cholesterol and/or bile salt. Hepatic and serum total cholesterol levels were significantly increased (42-268% and 23-124%, respectively) in cholesterol or high-fat diet-treated mice, when compared with control animals receiving vehicle or normal diet. Hepatic triglyceride level was increased (up to 108%), but serum triglyceride level was significantly reduced by 23-63% in hypercholesterolemic mice. Daily administration of bifendate (0.03-1.0 g/kg, i.g.) for 4 days decreased hepatic levels of total cholesterol (9-37%) and triglyceride (10-37%) in hypercholesterolemic mice. Supplementing the high-fat diet with bifendate (0.25%, w/w) caused decreases in hepatic total cholesterol (25-56%) and triglyceride (22-44%) levels following 7 or 14 days of experiment, respectively, when compared with animals fed with high-fat diet not supplemented with bifendate. While fenofibrate treatment decreased both hepatic and serum lipid levels in hypercholesterolemic mice, bifendate treatment did not reduce serum lipid levels. Bifendate and fenofibrate caused an increase (10-41% and 59-98%, respectively) in hepatic index of hypercholesterolemic mice. The results indicate that bifendate treatment can invariably decrease hepatic (but not serum) lipid levels in various mouse models of hypercholesterolemia.

Bile acids stimulate PKCalpha autophosphorylation and activation: role in the attenuation of prostaglandin E1-induced cAMP production in human dermal fibroblasts

The aim was to identify the specific PKC isoform(s) and their mechanism of activation responsible for the modulation of cAMP production by bile acids in human dermal fibroblasts. Stimulation of fibroblasts with 25-100 microM of chenodeoxycholic acid (CDCA) and ursodeoxycholic acid (UDCA) led to YFP-PKCalpha and YFP-PKCdelta translocation in 30-60 min followed by a transient 24- to 48-h downregulation of the total PKCalpha, PKCdelta, and PKCepsilon protein expression by 30-50%, without affecting that of PKCzeta. Increased plasma membrane translocation of PKCalpha was associated with an increased PKCalpha phosphorylation, whereas increased PKCdelta translocation to the perinuclear domain was associated with an increased accumulation of phospho-PKCdelta Thr505 and Tyr311 in the nucleus. The PKCalpha specificity on the attenuation of cAMP production by CDCA was demonstrated with PKC downregulation or inhibition, as well as PKC isoform dominant-negative mutants. Under these same conditions, neither phosphatidylinositol 3-kinase, p38 MAP kinase, p42/44 MAP kinase, nor PKA inhibitors had any significant effect on the CDCA-induced cAMP production attenuation. CDCA concentrations as low as 10 microM stimulated PKCalpha autophosphorylation in vitro. This bile acid effect required phosphatidylserine and was completely abolished by the presence of Gö6976. CDCA at concentrations less than 50 microM enhanced the PKCalpha activation induced by PMA, whereas greater CDCA concentrations reduced the PMA-induced PKCalpha activation. CDCA alone did not affect PKCalpha activity in vitro. In conclusion, although CDCA and UDCA activate different PKC isoforms, PKCalpha plays a major role in the bile acid-induced inhibition of cAMP synthesis in fibroblasts. This study emphasizes potential consequences of increased systemic bile acid concentrations and cellular bile acid accumulation in extrahepatic tissues during cholestatic liver diseases.

Expression of transporters potentially involved in the targeting of cytostatic bile acid derivatives to colon cancer and polyps

Drug targeting might help to overcome resistance to chemotherapy. Here we investigated whether colon cancer and polyps do express functional carriers involved in the uptake of cytostatic bile acid derivatives, in this case Bamet-UD2 [cis-diammine-bisursodeoxycholate-platinum(II)], which has been reported to be taken up by colon cancer cells "in vitro", efficiently induce apoptosis and overcome resistance to cisplatin. Although at lower levels than in ileum, a detectable expression of ASBT, OATP8/1B3, OCT1 and OSTalpha in colon tissue was found, which was not impaired in colon cancer or polyps. The expression of OATP-A/1A2 and OSTbeta was also found in colon, but this was markedly decreased in neoplastic colon tissue. In contrast, the expression of OATP-C/1B1 was low in colon but significantly enhanced in neoplastic colon tissue. MDR1 and MRP2 were poorly expressed in colon as compared with ileum, whereas MRP3 expression was higher in colon than in ileum. The abundance of mRNA for these ABC proteins was not changed in colon cancer or polyps. When RNA from different tissues was injected to Xenopus laevis oocytes their ability to take up taurocholate and Bamet-UD2 was enhanced (healthy ileum>healthy colon approximately neoplastic colon tissue). In all cases, uptake was lower for taurocholate than for Bamet-UD2, probably due to that ASBT mediates sodium-dependent uptake of both substrates, whereas additional transporters expressed in these tissues can participate in Bamet-UD2 uptake. In conclusion, our results suggest that the use of cytostatic bile acid derivatives might be a good pharmacological strategy for the treatment of colon tumors.

Nuclear Receptor-Dependent Bile Acid Signaling Is Required for Normal Liver Regeneration

Liver mass depends on one or more unidentified humoral signals that drive regeneration when liver functional capacity is diminished. Bile acids are important liver products, and their levels are tightly regulated. Here, we identify a role for nuclear receptor-dependent bile acid signaling in normal liver regeneration. Elevated bile acid levels accelerate regeneration, and decreased levels inhibit liver regrowth, as does the absence of the primary nuclear bile acid receptor FXR. We propose that FXR activation by increased bile acid flux is a signal of decreased functional capacity of the liver. FXR, and possibly other nuclear receptors, may promote homeostasis not only by regulating expression of appropriate metabolic target genes but also by driving homeotrophic liver growth.

Colestilan, a New Bile Acid-Sequestering Resin, Reduces??Bodyweight in Postmenopausal??Women Who??have??Dieted Unsuccessfully

OBJECTIVE

Bile acid-sequestering resins are known to be potent hypocholesterolaemic drugs, and a feeling of abdominal fullness has been reported as the most frequent adverse effect associated with their use. However, this unique adverse effect of colestilan, abdominal fullness, may have the potential to reduce total food intake. The aim of this study was to investigate the effect of colestilan, a new bile acid-sequestering resin, on the bodyweight of postmenopausal women who had previously dieted unsuccessfully.

METHODS

Forty postmenopausal women who failed to diet successfully over a 4-week period were enrolled in this randomised, open-label, controlled study. Subjects were randomised to two groups: the colestilan group received four colestilan tablets administered in divided doses with three glasses of water before dinner and bedtime for 12 weeks; the control group received three glasses of water before dinner and bedtime for 12 weeks. All patients were monitored and were given the same diet instructions.

RESULTS

Twelve weeks' administration of colestilan in addition to diet instruction significantly reduced bodyweight and body mass index from 62.9 +/- 5.7kg to 58.0 +/- 5.4kg (mean +/- SD) and from 26.1 +/- 2.0 kg/m2 to 23.9 +/- 2.0 kg/m2, respectively. There were no significant differences in bodyweight before and after 12 weeks of treatment in the control group.

CONCLUSION

Colestilan may be useful for appetite control and exerts anti-obesity effects when used in conjunction with a weight-management programme.

[New therapy strategies in secondary hyperparathyroidism on dialysis (I): new concepts, new treatments]

Secondary hyperparathyroidism (SHP) is still an early and frequent complication of chronic renal disease (CRD). Currently, CRD is an independent cardiovascular risk factor, and calcium-phosphorus metabolism is one of the modifiable related factors. In this first article, we summarize the recent SHP treatment paradigm shift in dialysis patients, derived from the better knowledge and understanding of vascular calcification. We analyze the most recent guidelines (K/DOQI), and describe the general implications of hyperphosphatemia, as well as our therapeutic approach with phosphorus-binders. Since sevelamer additionally presents some pleiotropic effects and it attenuates the progression of vascular calcification, we consider it in the first-line of treatment despite it is not yet demonstrated a survival benefit. We also minimize the use of elemental calcium to a maximum of 1000 to 1500 mg/day. Lanthanum carbonate may well be an important therapeutic agent in the near future, especially if security concerns related to metal accumulation are overcome. Ferric citrate, colestilan and nicotinamide may soon play a role. All these drugs, isolated or in combination, are important in the treatment of SHP since a great deal of its success and the avoidance of some dialysis-related complications depend on an efficient phosphorus control.

Faecal sterol output is increased by arachidyl amido cholanoic acid (Aramchol) in rats

Fatty acid-bile acid conjugates (FABACs) were shown recently to have important and multiple effects on cholesterol metabolism. In human fibroblasts, they were found to markedly enhance cholesterol efflux by an ATP-binding cassette transporter A1-dependent pathway. In C57L/J mice, they increased CYP7A1 activity and RNA expression, while decreasing moderately 3-hydroxy-3-methylglutaryl-CoA reductase activity. In C57L/J mice and in hamsters, they also decreased serum cholesterol levels, whereas in other animals, this effect was not seen in short-term experiments. In the present study, we investigated potential mechanisms of action of arachidyl amido cholanoic acid (Aramchol), with particular reference to biliary and faecal sterol outputs in rats. Supplementation with Aramchol at a dose of 150 mg x kg(-1) x day(-1) increased neutral sterol output by approx. 50%, while the faecal outputs of bile salts and total sterols increased by almost 2-fold. Biliary lipid outputs were not significantly different between the control and FABAC-supplemented animals. These findings indicate an overall catabolic effect of FABACs on body cholesterol.

Unique inhibition of bile salt-induced apoptosis by lecithins and cytoprotective bile salts in immortalized mouse cholangiocytes

Bile duct epithelium is physiologically exposed to high concentrations of bile salts, suggesting the presence of a cytoprotective mechanism(s). The aim of this study was to clarify whether bile salts cause bile duct cell damage and to elucidate the mechanism(s) providing protection against such an action of bile salts. Immortalized mouse cholangiocytes were incubated with taurocholate, taurochenodeoxycholate, glycochenodeoxycholate (GCDC), taurodeoxycholate, and tauroursodeoxycholate (TUDC), followed by flow-cytometric analysis and caspase activity assay to evaluate the induction of apoptosis. GCDC time-dependently induced caspase 3 (3.4-fold)- and caspase 9 (1.4-fold)-mediated apoptosis of cholangiocytes, but this was inhibited by lecithins and TUDC. Further, expression of cholangiocyte bile salt transporters (apical sodium-dependent bile salt transporter [Asbt] and multidrug resistance protein 3 [Mrp3]) was examined by RT-PCR and western blotting, and cholangiocyte bile salt uptake was determined using radiolabeled bile salts. Expression of cholangiocyte Asbt and Mrp3 was increased by bile salts, whereas lecithins interestingly reduced bile salt uptake to inhibit cholangiocyte apoptosis. In conclusion, bile salts themselves cause cholangiocyte apoptosis when absorbed by and retained inside the cell, but this is inhibited by washing out cytotoxic bile salts according to Mrp3, a rescue exporting molecule. Biliary lecithin is seemingly another cytoprotective player against cytotoxic bile salts, reducing their uptake, and this is associated with a reduced expression of Mrp3.

Resistance of SHP-null mice to bile acid-induced liver damage

The orphan nuclear hormone receptor SHP (gene designation NROB2) is an important component of a negative regulatory cascade by which high levels of bile acids repress bile acid biosynthesis. Short term studies in SHP null animals confirm this function and also reveal the existence of additional pathways for bile acid negative feedback regulation. We have used long term dietary treatments to test the role of SHP in response to chronic elevation of bile acids, cholesterol, or both. In contrast to the increased sensitivity predicted from the loss of negative feedback regulation, the SHP null mice were relatively resistant to the hepatotoxicity associated with a diet containing 0.5% cholic acid and the much more severe effects of a diet containing both 0.5% cholic acid and 2% cholesterol. This was associated with decreased hepatic accumulation of cholesterol and triglycerides in the SHP null mice. There were also alterations in the expression of a number of genes involved in cholesterol and bile acid homeostasis, notably cholesterol 12alpha-hydroxylase (CYP8B1), which was strongly reexpressed in the SHP null mice, but not the wild type mice fed either bile acid containing diet. This contrasts with the strong repression of CYP8B1 observed with short term bile acid feeding, as well as the effects of long term feeding on other bile acid biosynthetic enzymes such as cholesterol 7alpha-hydroxylase (CYP7A1). CYP8B1 expression could contribute to the decreased toxicity of the chronic bile acid treatment by increasing the hydrophilicity of the bile acid pool. These results identify an unexpected role for SHP in hepatotoxicity and suggest new approaches to modulating effects of chronically elevated bile acids in cholestasis.

Fatty acid bile acid conjugates inhibit atherosclerosis in the C57BL/6 mouse model

OBJECTIVE

The aim of the current research was to study whether fatty acid bile acid conjugates (FABACs) have a beneficial effect on atherosclerosis progression and blood lipid levels in mice.

METHODS

C57BL/6 female mice, fed a high-fat Paigen diet, were administered an oral dose of FABAC or DDH2O daily. Quantification of atherosclerotic fatty-streak lesions at the aortic sinus was performed.

RESULTS

The FABAC-treated mice showed a significant reduction in the atherosclerotic lesion areas as compared to the control group (p = 0.019). A significant elevation in total cholesterol levels was observed in both the FABAC and control groups. Higher FABAC levels were measured in the high-density lipoprotein fraction as compared to the very-low-density and low-density lipoprotein fractions.

CONCLUSION

Our findings demonstrate that FABACs, given orally, reduce the development of atherosclerosis in mice fed a high-fat high-cholesterol diet, despite a lack of effect on plasma lipid levels.

Bile acid composition in snake bile juice and toxicity of snake bile acids to rats

We determined the bile acid profiles in bile juice of snake gallbladders by HPLC on a silica gel RP-18 reversed-phase column. Cholic acid and chenodeoxycholic acid were predominant components in three of four snake species. To elucidate the toxic effect of snake bile acids on rats, a synthetic bile acid mixture was prepared mimicking the bile acid composition of a snake Naja naja atra bile juice. Twenty-four male Wistar rats were divided into four groups and treated orally at 3-day intervals with saline (control group) and different doses (1-3x doses) of the bile acid mixture. After treatment, the following parameters increased: the relative ratios of liver and kidney mass to body mass, the concentrations of red blood cell, hemoglobin and hematocrit in the blood, aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, plasma urea nitrogen and creatinine in the plasma, and the levels of urine urea nitrogen and creatinine in the urine. Body mass of rats and the levels of Na+, K+, Ca++ in the urine of rats were significantly decreased, especially for groups treated with 2x and 3x doses of the bile acid mixture. Examination of liver and kidney pathology also showed cell enlargement and lesion in cell integrity in treated groups, especially for groups treated with 2x and 3x bile acid mixture, indicating that short-term toxicity of snake N. naja atra bile acids was significant in rats.

Enterohepatic cycling of bilirubin as a cause of 'black' pigment gallstones in adult life

In contrast to bile salts, which undergo a highly efficient enterohepatic circulation with multiple regulatory and physiologic functions, glucuronic acid conjugates of bilirubin are biliary excretory molecules that in health do not have a continuing biologic life. Intestinal absorptive cells are devoid of recapture transporters for bilirubin conjugates, and their large size and polarity prevent absorption by passive diffusion. However, unconjugated bilirubin, the beta-glucuronidase hydrolysis product of bilirubin glucuronides can be absorbed passively from any part of the small and large intestines. This can occur only if unconjugated bilirubin is kept in solution and does not undergo rapid bacterial reduction to form urobilinoids. Here we collect, and in some cases reinterpret, experimental and clinical evidence to show that in addition to the well-known occurrence in newborns, enterohepatic cycling of unconjugated bilirubin can reappear in adult life. This happens as a result of several common conditions, particularly associated with bile salt leakage from the small intestine, the most notable ileal dysfunction resulting from any medical or surgical cause. We propose that when present in excess, colonic bile salts solubilize unconjugated bilirubin, delay urobilinoid formation, prevent calcium complexing of unconjugated bilirubin and promote passive absorption of unconjugated bilirubin from the large intestine. Following uptake, reconjugation, and resecretion into bile, this source of 'hyperbilirubinbilia' may be the important pathophysiological risk factor for 'black' pigment gallstone formation in predisposed adult humans.

Effects of microflora status, dietary bile salts and guar gum on lipid digestibility, intestinal bile salts, and histomorphology in broiler chickens

The aim of the present study was to reexamine the effects of intestinal viscosity, microflora, and bile salts, and their interactions in order to clarify the mechanisms that explain the effect of intestinal viscosity on lipid digestibility, especially those that could involve microflora. Effects of intestinal viscosity, microflora status, and dietary bile salts on lipid digestibility, intestinal bile salts, and intestinal histomorphology were tested in a 2 x 2 x 2 factorial experiment. The effect of microflora status was examined by comparing conventional chickens to chickens with limited microflora obtained by rearing birds in sterilized conditions. Viscosity and dietary bile salts were tested with guar gum (0 or 0.5% in diets) and sodium taurocholate (0 or 0.3% in diets), respectively. Guar gum was autoclaved and added to the gamma-irradiated diets by mixing inside the sterile isolators. The intestinal concentration of lactic acid and cecal concentration of short-chain fatty acids were both very low in birds with limited microflora compared to conventional birds (P = 0.0001). Chickens with limited microflora had higher gain:feed ratios (P = 0.002), higher fecal lipid digestibility (P = 0.0001), more intestinal conjugated bile salts (P = 0.0001), less intestinal unconjugated bile salts (P = 0.0001), and their gastrointestinal compartments were smaller (P < 0.05) than those of conventional chickens. Addition of bile salts in diets increased the lipid digestibility (P = 0.0001) with a more pronounced effect in conventional birds (P = 0.0001) and in birds fed on guar gum diets (P = 0.002). Feeding the guar gum diets increased the intestinal supernatant viscosity (P = 0.0001) for both microflora status. Guar gum addition increased (P < 0.05) the lactic acid concentration in the small intestine of conventional chickens. Guar gum decreased the fecal lipid digestibility (P = 0.0001) and the intestinal conjugated bile salts (P = 0.0001) for both microflora status. However, the magnitude of lipid digestibility decrease due to guar gum was lower (P = 0.05) in birds with limited microflora than in conventional birds, and the negative effect of guar gum on intestinal conjugated bile salts was more pronounced (P = 0.02) in birds with limited microflora. Bile salt addition reduced the negative effect of guar gum on lipid digestibility (P = 0.02) for both microflora status. The mean lipid digestibilities were negatively correlated (P = 0.0001) with the ratio [Ln(viscosity)/total bile salt] measured in intestinal digesta. Except for gizzard, size of digestive compartments and villus heights increased (P < 0.05) with feed efficiency and digestibility decreased. In conclusion, the results provided evidences that the negative effect of guar gum on lipid digestibility was mainly mediated by its direct effect on intestinal bile salt concentration and efficiency. The small interaction between guar gum and microflora status effects on lipid digestibility had to be accounted for by the low basal level of intestinal bile salts in conventional chickens.

Measurement of intestinal cholesterol absorption by plasma and fecal dual-isotope ratio, mass balance, and lymph fistula methods in the mouse: an analysis of direct versus indirect methodologies

The rate of intestinal cholesterol (Ch) absorption is an important criterion for quantitation of Ch homeostasis. However, studies in the literature suggest that percent Ch absorption, measured usually by a fecal dual-isotope ratio method, spans a wide range, from 20% to 90%, in healthy inbred mice on a chow diet. In the present study, we adapted four standard methods, one direct (lymph collection) and three indirect (plasma and fecal dual-isotope ratio, and sterol balance) measurements of Ch absorption and applied them to mice. Our data establish that all methodologies can be valid in mice, with all methods supporting the concept that gallstone-susceptible C57L mice absorb significantly more Ch (37 +/- 5%) than gallstone-resistant AKR mice (24 +/- 4%). We ascertained that sources of error in the literature leading to marked differences in Ch absorption efficiencies between laboratories relate to a number of technical factors, most notably expertise in mouse surgery, complete solubilization and delivery of radioisotopes, appropriate collection periods for plasma and fecal samples, and total extraction of radioisotopes from feces. We find that all methods provide excellent interexperimental agreement, and the ranges obtained challenge previously held beliefs regarding the spread of intestinal Ch absorption efficiencies in mice. The approaches documented herein provide quantifiable methodologies for exploring genetic mechanisms of Ch absorption, and for investigating the assembly and secretion of chylomicrons, as well as intestinal lipoprotein metabolism in mice.

Oral bile acids reduce bacterial overgrowth, bacterial translocation, and endotoxemia in cirrhotic rats

Experiments were performed to test whether conjugated bile acid administration would decrease bacterial overgrowth, bacterial translocation, and endotoxemia in ascitic cirrhotic rats. Cholylsarcosine, a deconjugation-dehydroxylation resistant and cholylglycine, a deconjugation-dehydroxylation susceptible bile acid were used. Rats with CCl(4)-induced cirrhosis and ascites were fed cholylsarcosine, cholylglycine (both at 70 mg/kg/d), or placebo for 2 weeks. Healthy rats, as controls, were treated similarly. In cirrhotic rats receiving placebo, bile secretion from an acute biliary fistula was lower than in healthy rats (27.2 +/- 6.5 vs. 53.0 +/- 3.1 microL/kg/min; mean +/- SE, P<.05). The administration of conjugated bile acids to cirrhotic rats normalized bile secretion (cholylsarcosine, 51.8 +/- 6.29; cholylglycine, 52.72 +/- 8.9 microL/kg/min). Total ileal bacterial content was 6-fold higher in ascitic cirrhotic rats than in healthy rats. Conjugated bile acid administration reduced bacterial content to normal levels. Bacterial translocation was less in cirrhotic animals receiving conjugated bile acids (cholylsarcosine, 33%; cholylglycine, 26%) than in animals receiving placebo (66%). Endotoxemia was decreased in cirrhotic rats by conjugated bile acid feeding (cholylsarcosine, 0.098 +/- 0.002; cholylglycine 0.101 +/- 0.007 EU/mL) compared with placebo (0.282 +/- 0.124, P <.001). Survival was greater in animals receiving conjugated bile acids (cholylsarcosine, 10/15; cholylglycine, 11/15; placebo, 5/15). In conclusion, the administration of conjugated bile acids to ascitic cirrhotic rats increased bile acid secretion, eliminated intestinal bacterial overgrowth, decreased bacterial translocation, decreased endotoxemia, and increased survival. Oral conjugated bile acids may be useful in preventing bacterial translocation, endotoxemia, and spontaneous bacterial perotonitis in cirrhotic patients.

What future for combination therapies?

For most patients who require lipid-lowering treatment, statin monotherapy is the appropriate treatment. However, in those patients where statin monotherapy does not produce optimal lipid levels, the combination of a statin with niacin, a bile acid sequestrant, a fibric acid derivative, a cholesterol absorption inhibitor or a fish oil preparation may provide improved control. The choice of combination therapy depends upon the patient's lipid profile and tolerability of the medication. Combination of a statin with niacin, a bile acid sequestrant or ezetimibe, a cholesterol absorption inhibitor, should be considered for patients with very high low-density lipoprotein cholesterol (LDL-C) levels, while combination with either a fibric acid derivative or a fish oil should be considered for patients with high LDL-C and high triglyceride levels. A number of new lipid-lowering agents are currently in development, including cholesteryl ester transfer protein (CETP) inhibitors, acyl coenzyme A: cholesterol acyltransferase (ACAT) inhibitors, ileal bile acid transport (IBAT) inhibitors, microsomal triglyceride transfer protein (MTP) inhibitors and dual peroxisome proliferator-activated receptor (PPAR) alpha and gamma agonists. Introduction of these novel therapies will provide opportunities for developing different combination strategies that may help to optimise lipid profiles in patients who are currently difficult to treat. The introduction of new combinations will require careful study to ensure that the risks of drug interactions and adverse events are minimised.

Usefulness of liposomes loaded with cytostatic bile acid derivatives to circumvent chemotherapy resistance of enterohepatic tumors

We have investigated the sensitivity of the cisplatin-resistant enterohepatic tumor cell lines LS174T/R (human colon adenocarcinoma), WIF-B9/R (rat hepatoma-human fibroblast hybrid), and Hepa 1-6/R (mouse hepatoma) to free and liposome-encapsulated cytostatic bile acid derivatives Bamet-R2 and bamet-UD2. Expression of resistance associated genes was measured by quantitative reverse transcription-polymerase chain reaction or Western blotting. Drug uptake was determined by atomic absorption spectrophotometry. In resistant cells, overexpression of MRP1 and MRP2 was accompanied by reduced accumulation of cisplatin. The expression of MDR1 and GST-P was only enhanced in LS 174T/R. A higher expression of p53 was seen in LS 174T/R and Hepa 1-6/R cell lines but not in WIF-B9/R cells. In wild-type counterparts, uptake and cytostatic ability of Bamets were markedly higher (UD2 > R2) than that of cisplatin. Both effects were further enhanced by liposome formulation. Bamets were able to overcome cisplatin resistance in all cell lines. Cisplatin prolonged the survival time of nude mice in whose livers a Hepa 1-6 tumor had been implanted, but failed to exert a beneficial effect when the tumor was Hepa 1-6/R. In both cases, tissue distribution of cisplatin was: kidney >> liver > tumor. Survival was markedly longer in animals receiving Bamet-UD2, even if the implanted tumor was resistant. The accumulation of Bamet-UD2 in tissues was: liver > tumor > kidney. Liposome formulation further enhanced the beneficial properties of Bamet-UD2. Thus, the amount of drug in the tumor was increased and that in liver and kidney was reduced (tumor > liver > kidney), and life span was prolonged. In conclusion, liposomal Bamet-UD2 may be a useful tool to circumvent resistance to chemotherapy, particularly in tumors of the enterohepatic circuit.

The effect of taurine on the cholesterol metabolism in rats fed diets supplemented with cholestyramine or high amounts of bile acid

The effects of taurine on serum cholesterol levels and hepatic cholesterol 7alpha-hydroxylase activity (CYP7A1) were studied in rats fed cholestyramine or high amounts of sodium cholate in order to alter the intestinal pool of bile acids. Rats were fed a diet supplemented with 1% cholesterol and 0.25% sodium cholate (high cholesterol, control; C), and C supplemented with 4% cholestyramine (CH) or 0.75% sodium cholate (BA) for 14 d. Taurine groups were fed the diet supplemented with 3% taurine (CT, CHT and BAT). Compared to rats fed C and BA diets, serum cholesterol levels were significantly reduced in rats fed CT and BAT diets, but a significant reduction of serum cholesterol by taurine feeding was not observed in the CHT group as compared to the CH group. An increase in hepatic CYP7A1 activity due to taurine intake was observed in the CT and BAT groups. However, the simultaneous administration of cholestyramine and taurine (CHT group) did not increase hepatic CYP7A1 activity compared the intake of cholestyramine only (CH group). A significant increase in fecal bile acid excretion due to taurine intake was found only in rats fed the CT diet. In conclusion, it is suggested that taurine facilitates hepatic CYP7A1 activity regardless of the enlarged intestinal pool of bile acids due to increased intake of exogenous bile acid, and then reduces the serum cholesterol concentration.

Effect of Mixed Micelle Formulations Including Terpenes on the Transdermal Delivery of Diclofenac

The significant inhibitory action of diclofenac formulated in mixed micelles of lecithin with cholate or deoxycholate was observed on the rat hind paw edema induced by carrageenan. In the primary stage, mixed micelle formulation of deoxycholate was more effective compared with that of cholate. However, in the final term, the inhibitory action was similar in both formulations. In a previous study, the flux of diclofenac was greater in the mixed micelle formulation of deoxycholate compared with that of cholate. It was suggested that the permeation rate of diclofenac through skin was proportional to the pharmacological activity. The hind paw edema was quickly inhibited when cyclic monoterpene such as d-limonene or l-menthol was included in the formulations. All the micelle formulations significantly decreased the value of AUC estimated the hind paw thickness-time profile. This suggests that the micelle formulation of cholate in addition to deoxycholate showed significant anti-inflammatory activity to hind paw edema of rats. Incorporation of d-limonene or l-menthol was more effective on the decrease of AUC. A pharmacological study revealed that micelle formulations were able to reduce the skin irritation of chemicals.

Oral absorption of insulin encapsulated in artificial chyles of bile salts, palmitic acid and alpha-tocopherol dispersions

The hypoglycemic effect of orally given insulin was studied on rabbits, using different bile salts as absorption promoters, in two different carriers to form an artificial chyloform system ready to be absorbed by intestinal mucosa. The rank order of enhancement by bile salts in the presence of 1% ethanol was deoxycholate>cholate>glycocholate>glycodeoxycholate>taurodeoxycholate>no bile salts. The dose response studies with increased insulin loaded in the chyle showed a greater corresponding hypoglycemic effect with the system of cholate-palmitic-alpha-tocopherol dispersions than the cholate-palmitic acid dispersions. A more effective hypoglycemic effect was achieved using lower doses of the deoxycholate-palmitate-tocopherol-chyle dispersions.

Dietary bile acids inhibit potentially elemental diet-induced small intestinal atrophy in rats

The mechanism responsible for elemental diet (ED)-induced small intestinal atrophy is still unknown. However, it is possible that bile acids in the gut lumen influence this process. The aim of this study was to evaluate the effects of oral bile acid administration during ED feeding. Specific pathogen-free male Sprague-Dawley rats, 10 weeks old, were fed an ED only, ED plus 0.1% (w/w) hyocholic acid, or ED plus 0.1% (w/w) hyodeoxycholic acid ad libitum for 4 weeks. The control rats were fed standard chow ad libitum for 4 weeks. After 4 weeks, the wet weight and whole length of the small intestine, and the mucosal diamine oxidase (DAO) and alkaline phosphatase (ALP) activities were measured. Microscopic histological observation was also performed. ED feeding induced atrophy and elevations in the mucosal DAO and ALP activities in the small intestine. Hyocholic acid and hyodeoxycholic acid administration both tended to inhibit these alterations. In conclusion, ED feeding induced atrophy and elevations in the mucosal DAO and ALP activities in the small intestine. Oral bile acid administration may prevent this atrophy and the elevations in mucosal DAO and ALP activities, which may lead to new therapeutic strategies in patients managed with ED.

Tauroursodeoxycholic acid, a bile acid, is neuroprotective in a transgenic animal model of Huntington's disease

Huntington's disease (HD) is an untreatable neurological disorder caused by selective and progressive degeneration of the caudate nucleus and putamen of the basal ganglia. Although the etiology of HD pathology is not fully understood, the observed loss of neuronal cells is thought to occur primarily through apoptosis. Furthermore, there is evidence in HD that cell death is mediated through mitochondrial pathways, and mitochondrial deficits are commonly associated with HD. We have previously reported that treatment with tauroursodeoxycholic acid (TUDCA), a hydrophilic bile acid, prevented neuropathology and associated behavioral deficits in the 3-nitropropionic acid rat model of HD. We therefore examined whether TUDCA would also be neuroprotective in a genetic mouse model of HD. Our results showed that systemically administered TUDCA led to a significant reduction in striatal neuropathology of the R6/2 transgenic HD mouse. Specifically, R6/2 mice began receiving TUDCA at 6 weeks of age and exhibited reduced striatal atrophy, decreased striatal apoptosis, as well as fewer and smaller size ubiquitinated neuronal intranuclear huntingtin inclusions. Moreover, locomotor and sensorimotor deficits were significantly improved in the TUDCA-treated mice. In conclusion, TUDCA is a nontoxic, endogenously produced hydrophilic bile acid that is neuroprotective in a transgenic mouse model of HD and, therefore, may provide a novel and effective treatment in patients with HD.

Dissolution of cholesterol gallstones in mice by the oral administration of a fatty acid bile acid conjugate

Gallstones, mostly cholesterol stones, affect some 15% of the population. Oral bile salts dissolve human cholesterol gallstones, but with low efficacy, and surgery remains the main therapeutic option. Fatty acid bile acid conjugates (FABACs) were shown to prevent formation of cholesterol gallstones in experimental animals. The aim of this study was to test whether these compounds could dissolve preexisting cholesterol gallstones via oral administration. Inbred, gallstone-susceptible C57J/L mice were given a lithogenic diet for 2 months, and the presence of gallstones was ascertained. The mice were then switched to a regular diet while part of them were given in addition C20-FABAC, by gavage, at a dose of 0.5 or 3 mg per animal per day. All mice tested had cholesterol gallstones after 2 months on the lithogenic diet. In study I, after 2 months on the regular diet, 3 of 4 (75%) of the controls had gallstones, whereas none of the 6 FABAC-fed animals (3 mg/d) had stones (P =.033). In study II, evaluating 2 FABAC doses, after 2 months on the regular diet, 8 of 8 (100%) of the controls had gallstones, which were found in 2 of 7 (28%) and 1 of 8 (12%) of the mice supplemented with 0.5 mg/d (P =.007) or 3 mg/d (P =.001) FABAC, respectively. On a molar basis, the dose of 0.5 mg FABAC is equivalent to 14 mg/kg/d of a bile acid. In conclusion, FABACs given orally can dissolve preexisting cholesterol gallstones in mice. This was accomplished with a dose of FABAC equivalent to the dose of bile acids used in human gallstone dissolution.

Cytokeratins as targets for bile acid-induced toxicity

Cholestasis is associated with retention of potentially toxic bile acids and profound cytoskeletal alterations of hepatocytes. Given the well-established cytoprotective role of hepatocyte keratins this study aimed to determine the effects of cholestasis on the cytokeratin (CK) intermediate filament network in mouse liver. Mice were subjected to common bile duct ligation or sham operation. Mice were also fed a cholic acid or ursodeoxycholic acid (UDCA)-supplemented diet (0.1%, 0.5%, and 1%) or control diet for 7 days. CK 8 and CK 18 expression was studied by competitive reverse transcriptase-polymerase chain reaction, in situ hybridization, Western blot analysis, and immunofluorescence microscopy. Common bile duct ligation and cholic acid feeding significantly stimulated CK 8 and CK 18 mRNA and protein levels compared to controls, whereas UDCA had no effect. CK overexpression was accompanied by pronounced phosphorylation. Our results show that potentially toxic bile acids induce hepatocytic CK 8 and CK 18 expression and phosphorylation whereas nontoxic UDCA has no effect on CKs. Thus, increased hepatocellular CK expression and phosphorylation in cholestasis may be caused by retention of toxic bile acids and reflect a hepatocellular stress response with potential beneficial effects.

Therapy of microcirculatory disorders in severe acute pancreatitis: what mediators should we block?

OBJECTIVE

To compare the effect of different vasoactive mediator antagonists in the same model of severe acute pancreatitis (AP) and to evaluate whether combinations of the agents exhibit synergistic effects.

DESIGN

Prospective experimental study.

SETTING

Microcirculation and pancreas research laboratory at an university hospital.

PARTICIPANTS

Hundred eighty anesthetized male Sprague-Dawley rats.

INTERVENTIONS

Six hours after inducing AP by intra-ductal bile salt infusion and i.v. cerulein in 168 rats, these were randomized for therapy with (1) saline, (2) endothelin receptor antagonist (ET-RA), (3) platelet activating factor receptor antagonist (PAF-RA), (4) intercellular adhesion molecule-1 antibody (ICAM-1-AB) or different combinations (5-7). After 24 h the animals underwent a second laparotomy for intra-vital microscopic determination of pancreatic and colonic capillary permeability, blood flow and leukocyte-endothelial interaction.

RESULTS

AP induction decreased capillary blood flow and increased permeability and leukocyte rolling. ET-RA, PAF-RA and ICAM-1-AB decreased capillary permeability, increased blood flow and reduced leukocyte rolling. ET-RA was most effective in decreasing capillary permeability in both organs as well as in increasing pancreatic capillary blood flow. Combining vasoactive mediator blockers did not further improve target parameters.

CONCLUSIONS

This study supports previous observations that ET-RA, PAF-RA and ICAM-1-AB improve microcirculation in AP and that ET-RA is more effective than PAF-RA or ICAM-1-AB, especially in counteracting capillary leakage. Although this may suggest that they act through different mechanisms, antagonist combinations failed to improve microcirculation further. We conclude that ET-RA is the most promising candidate for a clinical trial to reduce capillary leakage in patients with AP.

Beneficial effects of glycocholic acid (GCA) on gut mucosal damage in bile duct ligated rats

In order to investigate the effect of bile acids on gastrointestinal inflammations, bile duct ligated rats (BDL) were treated with GCA (25 mM/ml, oral or colonic) or saline I h before ethanol challenge and twice daily for 3 days in the ileitis group, while GCA was given twice daily for 3 days in the colitis group. BDL reduced the macroscopic and microscopic damage scores in the ileitis group compared to sham operated group, while it had no significant effect on ulcer or colitis groups. However, GCA given in BDL group reduced the ulcer index and microscopic damage in colitis group compared to saline-treated groups, but had no effect in ileitis group. Both BDL and GCA administration in BDL group reduced ileitis- or colitis-induced elevations in MPO levels. GCA administration in BDL group inhibited gastric acid output and volume. Our results suggest that oral or colonic administration of primary bile acids may be useful for the treatment of gastrointestinal inflammations.

Farnesoid X-activated receptor induces apolipoprotein C-II transcription: a molecular mechanism linking plasma triglyceride levels to bile acids

The farnesoid X-activated receptor (FXR; NR1H4), a member of the nuclear hormone receptor superfamily, induces gene expression in response to several bile acids, including chenodeoxycholic acid. Here we used suppression subtractive hybridization to identify apolipoprotein C-II (apoC-II) as an FXR target gene. Retroviral expression of FXR in HepG2 cells results in induction of the mRNA encoding apoC-II in response to several FXR ligands. EMSAs demonstrate that recombinant FXR and RXR bind to two FXR response elements that are contained within two important distal enhancer elements (hepatic control regions) that lie 11 kb and 22 kb upstream of the transcription start site of the apoC-II gene. A luciferase reporter gene containing the hepatic control region or two copies of the wild-type FXR response element was activated when FXR-containing cells were treated with FXR ligands. In addition, we report that hepatic expression of both apoC-II and phospholipid transfer protein mRNAs increases when mice are fed diets supplemented with cholic acid, an FXR ligand, and this induction is attenuated in FXR null mice. Finally, we observed decreased plasma triglyceride levels in mice fed cholic acid- containing diets. These results identify a mechanism whereby FXR and its ligands lower plasma triglyceride levels. These findings may have important implications in the clinical management of hyperlipidemias.