Bile acid sequestrants: more than simple resins

Limosilactobacillus fermentum TY-S11 ameliorates hypercholesterolemia via promoting cholesterol excretion and regulating gut microbiota in high-cholesterol diet-fed apolipoprotein E-deficient mice

Hypercholesterolemia is a metabolic disease characterized by elevated cholesterol level in the blood, which is a risk factor for many diseases. Probiotic intervention may be one of the ways to improve hypercholesterolemia. In this study, three strains with better cholesterol removal ability were selected from 60 strains of lactic acid bacteria, and were orally administered to apolipoprotein E-deficient mice on a high-cholesterol diet. Among the three strains, only Limosilactobacillus fermentum TY-S11, which was isolated from the intestine of a longevity person, significantly improved serum and liver lipid levels in hypercholesterolemic mice. Further study found that L. fermentum TY-S11 promoted the excretion of cholesterol in the feces and inhibited the absorption of cholesterol in the small intestine. As for gut microbiota, the results showed that L. fermentum TY-S11 not only prevented the reduction of diversity caused by high-cholesterol diet, but also increased the contents of short-chain fatty acids in feces. These results confirmed the ameliorative effect of L. fermentum TY-S11 on hypercholesterolemia.

Therapeutic potential of herbal medicine for the management of hyperlipidemia: latest updates

Hyperlipidemia, the most common form of dyslipidemia, is the main source of cardiovascular disorders, characterized by elevated level of total cholesterol (TC), triglycerides (TG) and low-density lipoprotein cholesterol (LDL-C) with high-density lipoprotein cholesterol (HDL-C) in peripheral blood. It is caused by a defect in lipid metabolism in the surface of Apoprotein C-II or a defect in lipoprotein lipase activity as well as reported in genetic, dietary and environmental factors. Several electronic databases were investigated as information sources, including Google Scholar, PubMed, Web of Science, Scopus, ScienceDirect, SpringerLink, Semantic Scholar, MEDLINE and CNKI Scholar. The current review focused on the risk factors of dyslipidemia, synthetic medication with their side effects and different types of medicinal plants having significant potential for the management of hyperlipidemia. The management of hyperlipidemia mostly involves a constant decrease in lipid level using different remedial drugs like statin, fibrate, bile acid sequestrates and niacin. However, this extensive review suggested that the consequences of these drugs are arguable, due to their numerous adverse effects. The selected parts of herb plants are used intact or their extracts containing active phytoconstituents to regulate the lipids in blood level. It was also noted that the Chinese herbal medicine and combination therapy is promising for the lowering of hyperlipidemia. This review intends to provide a scientific base for future endeavors, such as in-depth biological and chemical investigations into previously researched topics.

Bile Acid Sequestrants for Hypercholesterolemia Treatment Using Sustainable Biopolymers: Recent Advances and Future Perspectives

Bile acids, the endogenous steroid nucleus containing signaling molecules, are responsible for the regulation of multiple metabolic processes, including lipoprotein and glucose metabolism to maintain homeostasis. Within our body, they are directly produced from their immediate precursors, cholesterol C (low-density lipoprotein C, LDL-C), through the enzymatic catabolic process mediated by 7-α-hydroxylase (CYP7A1). Bile acid sequestrants (BASs) or amphiphilic resins that are nonabsorbable to the human body (being complex high molecular weight polymers/electrolytes) are one of the classes of drugs used to treat hypercholesterolemia (a high plasma cholesterol level) or dyslipidemia (lipid abnormalities in the body); thus, they have been used clinically for more than 50 years with strong safety profiles as demonstrated by the Lipid Research Council-Cardiovascular Primary Prevention Trial (LRC-CPPT). They reduce plasma LDL-C and can slightly increase high-density lipoprotein C (HDL-C) levels, whereas many of the recent clinical studies have demonstrated that they can reduce glucose levels in patients with type 2 diabetes mellitus (T2DM). However, due to higher daily dosage requirements, lower efficacy in LDL-C reduction, and concomitant drug malabsorption, research to develop an "ideal" BAS from sustainable or natural sources with better LDL-C lowering efficacy and glucose regulations and lower side effects is being pursued. This Review discusses some recent developments and their corresponding efficacies as bile removal or LDL-C reduction of natural biopolymer (polysaccharide)-based compounds.

A Recent Ten-Year Perspective: Bile Acid Metabolism and Signaling

Bile acids are important physiological agents required for the absorption, distribution, metabolism, and excretion of nutrients. In addition, bile acids act as sensors of intestinal contents, which are determined by the change in the spectrum of bile acids during microbial transformation, as well as by gradual intestinal absorption. Entering the liver through the portal vein, bile acids regulate the activity of nuclear receptors, modify metabolic processes and the rate of formation of new bile acids from cholesterol, and also, in all likelihood, can significantly affect the detoxification of xenobiotics. Bile acids not absorbed by the liver can interact with a variety of cellular recipes in extrahepatic tissues. This provides review information on the synthesis of bile acids in various parts of the digestive tract, its regulation, and the physiological role of bile acids. Moreover, the present study describes the involvement of bile acids in micelle formation, the mechanism of intestinal absorption, and the influence of the intestinal microbiota on this process.

Niacin Increases Atherogenic Proteins in High-Density Lipoprotein of Statin-Treated Subjects

[Figure: see text].

Colesevelam Reduces Ethanol-Induced Liver Steatosis in Humanized Gnotobiotic Mice

Alcohol-related liver disease is associated with intestinal dysbiosis. Functional changes in the microbiota affect bile acid metabolism and result in elevated serum bile acids in patients with alcohol-related liver disease. The aim of this study was to identify the potential role of the bile acid sequestrant colesevelam in a humanized mouse model of ethanol-induced liver disease. We colonized germ-free (GF) C57BL/6 mice with feces from patients with alcoholic hepatitis and subjected humanized mice to the chronic–binge ethanol feeding model. Ethanol-fed gnotobiotic mice treated with colesevelam showed reduced hepatic levels of triglycerides and cholesterol, but liver injury and inflammation were not decreased as compared with non-treated mice. Colesevelam reduced hepatic cytochrome P450, family 7, subfamily a, polypeptide 1 (Cyp7a1) protein expression, although serum bile acids were not lowered. In conclusion, our findings indicate that colesevelam treatment mitigates ethanol-induced liver steatosis in mice.

Bile acid sequestrants: a review of mechanism and design

OBJECTIVE

Bile acid sequestrants (BAS) are used extensively in the treatment of hypercholesterolaemia. This brief review aimed to describe the design and evaluation of three types of BAS: amphiphilic copolymers, cyclodextrin/poly-cyclodextrin and molecular imprinted polymers. The mechanisms underlying the action of BAS are also discussed.

KEY FINDINGS

BAS could lower plasma cholesterol, improve glycemic control in patients with type 2 diabetes and regulate balance energy metabolism via receptors or receptor-independent mediated mechanisms. Different types of BAS have different levels of ability to bind to bile acids, different stability and different in-vivo activity.

CONCLUSIONS

A growing amount of evidence suggests that bile acids play important roles not only in lipid metabolism but also in glucose metabolism. The higher selectivity, specificity, stability and in-vivo activity of BAS show considerable potential for lipid-lowering therapy.

Hepatic Autophagy Deficiency Remodels Gut Microbiota for Adaptive Protection via FGF15-FGFR4 Signaling

BACKGROUND & AIMS

The functions of the liver and the intestine are closely tied in both physiological and pathologic conditions. The gut microbiota (GM) often cause deleterious effects during hepatic pathogenesis. Autophagy is essential for liver homeostasis, but the impact of hepatic autophagy function on liver-gut interaction remains unknown. Here we investigated the effect of hepatic autophagy deficiency (Atg5Δhep) on GM and in turn the effect of GM on the liver pathology.

METHODS

Fecal microbiota were analyzed by 16S sequencing. Antibiotics were used to modulate GM. Cholestyramine was used to reduce the enterohepatic bile acid (BA) level. The functional role of fibroblast growth factor 15 (FGF15) and ileal farnesoid X receptor (FXR) was examined in mice overexpressing FGF15 gene or in mice given a fibroblast growth factor receptor-4 (FGFR4) inhibitor.

RESULTS

Atg5Δhep causes liver injury and alterations of intestinal BA composition, with a lower proportion of tauro-conjugated BAs and a higher proportion of unconjugated BAs. The composition of GM is significantly changed with an increase in BA-metabolizing bacteria, leading to an increased expression of ileal FGF15 driven by FXR that has a higher affinity to unconjugated BAs. Notably, antibiotics or cholestyramine treatment decreased FGF15 expression and exacerbated liver injury. Consistently, inhibition of FGF15 signaling in the liver enhances liver injury.

CONCLUSIONS

Deficiency of autophagy function in the liver can affect intestinal environment, leading to gut dysbiosis. Surprisingly, such changes provide an adaptive protection against the liver injury through the FGF15-FGFR4 signaling. Antibiotics use in the condition of liver injury may thus have unexpected adverse consequences via the gut-liver axis.

A Brief Review of Cardiovascular Diseases, Associated Risk Factors and Current Treatment Regimes

Cardiovascular diseases (CVDs) are the leading cause of premature death and disability in humans and their incidence is on the rise globally. Given their substantial contribution towards the escalating costs of health care, CVDs also generate a high socio-economic burden in the general population. The underlying pathogenesis and progression associated with nearly all CVDs are predominantly of atherosclerotic origin that leads to the development of coronary artery disease, cerebrovascular disease, venous thromboembolism and, peripheral vascular disease, subsequently causing myocardial infarction, cardiac arrhythmias or stroke. The aetiological risk factors leading to the onset of CVDs are well recognized and include hyperlipidaemia, hypertension, diabetes, obesity, smoking and, lack of physical activity. They collectively represent more than 90% of the CVD risks in all epidemiological studies. Despite high fatality rate of CVDs, the identification and careful prevention of the underlying risk factors can significantly reduce the global epidemic of CVDs. Beside making favorable lifestyle modifications, primary regimes for the prevention and treatment of CVDs include lipid-lowering drugs, antihypertensives, antiplatelet and anticoagulation therapies. Despite their effectiveness, significant gaps in the treatment of CVDs remain. In this review, we discuss the epidemiology and pathology of the major CVDs that are prevalent globally. We also determine the contribution of well-recognized risk factors towards the development of CVDs and the prevention strategies. In the end, therapies for the control and treatment of CVDs are discussed.

In Vitro Hypocholesterolemic Effect of Coffee Compounds

(1) Background: Cholesterol bioaccessibility is an indicator of cholesterol that is available for absorption and therefore can be a measure of hypocholesterolemic potential. In this work, the effect of commercial espresso coffee and coffee extracts on cholesterol solubility are studied in an in vitro model composed by glycodeoxycholic bile salt, as a measure of its bioaccessibility. (2) Methods: Polysaccharide extracts from coffees obtained with different extraction conditions were purified by selective precipitation with ethanol, and their sugars content were characterized by GC-FID. Hexane extraction allowed us to obtain the coffee lipids. Espresso coffee samples and extracts were tested regarding their concentration dependence on the solubility of labeled 13C-4 cholesterol by bile salt micelles, using quantitative 13C NMR. (3) Results and Discussion: Espresso coffee and coffee extracts were rich in polysaccharides, mainly arabinogalactans and galactomannans. These polysaccharides decrease cholesterol solubility and, simultaneously, the bile salts' concentration. Coffee lipid extracts were also found to decrease cholesterol solubility, although not affecting bile salt concentration. (4) Conclusions: Coffee soluble fiber, composed by the arabinogalactans and galactomannans, showed to sequester bile salts from the solution, leading to a decrease in cholesterol bioaccessibility. Coffee lipids also decrease cholesterol bioaccessibility, although the mechanism of action identified is the co-solubilization in the bile salt micelles. The effect of both polysaccharides and lipids showed to be additive, representing the overall effect observed in a typical espresso coffee. The effect of polysaccharides and lipids on cholesterol bioaccessibility should be accounted on the formulation of hypocholesterolemic food ingredients.

Lipid-lowering effects of Coffea arabica pulp aqueous extract in Caco-2 cells and hypercholesterolemic rats

BACKGROUND

Coffea arabica pulp (CP) is the first by-product obtained from coffee berries during coffee processing. The major constituents of CP, including chlorogenic acid, caffeine, and epicatechin exhibit anti-hyperlipidemic effects in in vitro and in vivo models. Whether Coffea arabica pulp aqueous extract (CPE) has a lipid-lowering effect remains unknown.

PURPOSE

This study examined the effect of CPE on cholesterol absorption, and identified the mechanisms involved in lowered cholesterol in in vitro and in vivo models.

METHODS

Uptake of [³H]-cholesterol micelles and the mode of CPE inhibition were determined using human intestinal Caco-2 cells, and subsequently, confirmed using isolated rat jejunal loops. In addition, the 12-week high-fat diet-induced hypercholesterolemic rats (HF) received either CPE (1000  mg/kg BW), a sole and high dose which was selected because it contained approximately 12  mg of CGA that was previously shown to have lipid-lowering effects, or ezetimibe (10  mg/kg BW), a cholesterol inhibitor. The rats were divided into HF, HF  ++ CPE, and HF  ++ ezetimibe groups for the next 12 weeks. Normal rats received a normal diet (ND) and CPE (ND  +  CPE). Body weights and lipid profiles were evaluated. Cholesterol transporter, Niemann-Pick C1-Like 1 (NPC1L1), protein expression and liver X receptor alpha (LXRα) mRNA expression were determined. In vitro micellar complex properties were also investigated.

RESULTS

CPE inhibited [³H]-cholesterol micelle transport in Caco-2 cells and rat jejunal loops in a dose-dependent, non-competitive manner partly by decreasing membrane NPC1L1 expression. Congruently, CPE and its major constituents activated LXRα which, in turn, down-regulated NPC1L1. Furthermore, CPE interfered with physicochemical characteristics of cholesterol mixed micelles. These data were consistent with decreased body weight and slowed body weight gain and improved lipid profiles by CPE in hypercholesterolemic rats while no change occurred in these parameters in normal rats. Down-regulated intestinal NPC1L1 expression mediated by increased LXRα mRNA were also observed in HF  ++ CPE and ND  +  CPE rats.

CONCLUSION

CPE has a cholesterol-lowering effect in in vitro and in vivo via inhibition of intestinal cholesterol absorption by down-regulating NPC1L1 mediated LXRα activation and interfering with micellar complex formation. Accordingly, CPE could be developed as nutraceutical product to prevent dyslipidemia-induced obesity and insulin resistance.

Dysregulation of Δ4-3-oxosteroid 5β-reductase in diabetic patients: Implications and mechanisms

Aldo-keto reductase family 1 member D1 (AKR1D1) is a Δ⁴-3-oxosteroid 5β-reductase required for bile acid synthesis and steroid hormone metabolism. Both bile acids and steroid hormones, especially glucocorticoids, play important roles in regulating body metabolism and energy expenditure. Currently, our understanding on AKR1D1 regulation and its roles in metabolic diseases is limited. We found that AKR1D1 expression was markedly repressed in diabetic patients. Consistent with repressed AKR1D1 expression, hepatic bile acids were significantly reduced in diabetic patients. Mechanistic studies showed that activation of peroxisome proliferator-activated receptor-α (PPARα) transcriptionally down-regulated AKR1D1 expression in vitro in HepG2 cells and in vivo in mice. Consistently, PPARα signaling was enhanced in diabetic patients. In summary, dysregulation of AKR1D1 disrupted bile acid and steroid hormone homeostasis, which may contribute to the pathogenesis of diabetes. Restoring bile acid and steroid hormone homeostasis by modulating AKR1D1 expression may represent a new approach to develop therapies for diabetes.

Animal models to study bile acid metabolism

The use of animal models, particularly genetically modified mice, continues to play a critical role in studying the relationship between bile acid metabolism and human liver disease. Over the past 20 years, these studies have been instrumental in elucidating the major pathways responsible for bile acid biosynthesis and enterohepatic cycling, and the molecular mechanisms regulating those pathways. This work also revealed bile acid differences between species, particularly in the composition, physicochemical properties, and signaling potential of the bile acid pool. These species differences may limit the ability to translate findings regarding bile acid-related disease processes from mice to humans. In this review, we focus primarily on mouse models and also briefly discuss dietary or surgical models commonly used to study the basic mechanisms underlying bile acid metabolism. Important phenotypic species differences in bile acid metabolism between mice and humans are highlighted.

Dietary Mannan Oligosaccharides Modulate Gut Microbiota, Increase Fecal Bile Acid Excretion, and Decrease Plasma Cholesterol and Atherosclerosis Development

SCOPE

Mannan oligosaccharides (MOS) have proven effective at improving growth performance, while also reducing hyperlipidemia and inflammation. As atherosclerosis is accelerated both by hyperlipidemia and inflammation, we aim to determine the effect of dietary MOS on atherosclerosis development in hyperlipidemic ApoE*3-Leiden.CETP (E3L.CETP) mice, a well-established model for human-like lipoprotein metabolism.

METHODS AND RESULTS

Female E3L.CETP mice were fed a high-cholesterol diet, with or without 1% MOS for 14 weeks. MOS substantially decreased atherosclerotic lesions up to 54%, as assessed in the valve area of the aortic root. In blood, IL-1RA, monocyte subtypes, lipids, and bile acids (BAs) were not affected by MOS. Gut microbiota composition was determined using 16S rRNA gene sequencing and MOS increased the abundance of cecal Bacteroides ovatus. MOS did not affect fecal excretion of cholesterol, but increased fecal BAs as well as butyrate in cecum as determined by gas chromatography mass spectrometry.

CONCLUSION

MOS decreased the onset of atherosclerosis development via lowering of plasma cholesterol levels. These effects were accompanied by increased cecal butyrate and fecal excretion of BAs, presumably mediated via interactions of MOS with the gut microbiota.

Therapeutic modulation of the bile acid pool by Cyp8b1 knockdown protects against nonalcoholic fatty liver disease in mice

Bile acids (BAs) are surfactant molecules that regulate the intestinal absorption of lipids. Thus, the modulation of BAs represents a potential therapy for nonalcoholic fatty liver disease (NAFLD), which is characterized by hepatic accumulation of fat and is a major cause of liver disease worldwide. Cyp8b1 is a critical modulator of the hydrophobicity index of the BA pool. As a therapeutic proof of concept, we aimed to determine the impact of Cyp8b1 inhibition in vivo on BA pool composition and as protection against NAFLD. Inhibition of Cyp8b1 expression in mice led to a remodeling of the BA pool, which altered its signaling properties and decreased intestinal fat absorption. In a model of cholesterol-induced NAFLD, Cyp8b1 knockdown significantly decreased steatosis and hepatic lipid content, which has been associated with an increase in fecal lipid and BA excretion. Moreover, inhibition of Cyp8b1 not only decreased hepatic lipid accumulation, but also resulted in the clearance of previously accumulated hepatic cholesterol, which led to a regression in hepatic steatosis. Taken together, our data demonstrate that Cyp8b1 inhibition is a viable therapeutic target of crucial interest for metabolic diseases, such as NAFLD.-Chevre, R., Trigueros-Motos, L., Castaño, D., Chua, T., Corlianò, M., Patankar, J. V., Sng, L., Sim, L., Juin, T. L., Carissimo, G., Ng, L. F. P., Yi, C. N. J., Eliathamby, C. C., Groen, A. K., Hayden, M. R., Singaraja, R. R. Therapeutic modulation of the bile acid pool by Cyp8b1 knockdown protects against nonalcoholic fatty liver disease in mice.

Nonabsorbable Iron Binding Polymers Prevent Dietary Iron Absorption for the Treatment of Iron Overload

Chronic iron overload is a serious condition that develops as a consequence of long-term accumulation of iron, eventually overwhelming iron storage systems and causing oxidative stress and subsequent organ damage. Current pharmaceuticals used to treat iron overload typically suffer from toxicities leading to relatively high rates of adverse events. To address this need, we designed a new class of nonabsorbable iron binding polymers (IBPs) that bind and sequester iron within the gastrointestinal (GI) tract. IBPs were synthesized by cross-linking polyallylamine containing various amounts of conjugated 2,3-dihydroxybenzoic acid (DHBA). In vitro studies indicated that IBPs possessed high affinity, substantial binding capacity, and excellent selectivity toward iron. Moreover, in vivo studies demonstrated that IBPs showed no signs of side effects in mice and increased fecal iron excretion when compared to a similar dose of cross-linked polyallylamine. IBPs are a novel, nonabsorbed oral therapeutic agent that may ultimately prevent iron absorption as a safe alternative to iron chelation therapies for patients with hemochromatosis or other iron overload diseases.

Bile acids and nonalcoholic fatty liver disease: Molecular insights and therapeutic perspectives

Nonalcoholic fatty liver disease (NAFLD) is a burgeoning health problem worldwide and an important risk factor for both hepatic and cardiometabolic mortality. The rapidly increasing prevalence of this disease and of its aggressive form nonalcoholic steatohepatitis (NASH) will require novel therapeutic approaches to prevent disease progression to advanced fibrosis or cirrhosis and cancer. In recent years, bile acids have emerged as relevant signaling molecules that act at both hepatic and extrahepatic tissues to regulate lipid and carbohydrate metabolic pathways as well as energy homeostasis. Activation or modulation of bile acid receptors, such as the farnesoid X receptor and TGR5, and transporters, such as the ileal apical sodium-dependent bile acid transporter, appear to affect both insulin sensitivity and NAFLD/NASH pathogenesis at multiple levels, and these approaches hold promise as novel therapies. In the present review, we summarize current available data on the relationships of bile acids to NAFLD and the potential for therapeutically targeting bile-acid-related pathways to address this growing world-wide disease. (Hepatology 2017;65:350-362).

Exploring and Understanding the Biochemical Diversity of the Human Microbiota

Recent studies have illuminated a remarkable diversity and abundance of microbes living on and within the human body. While we are beginning to appreciate associations of certain bacteria and genes with particular host physiological states, considerable information is lacking about the relevant functional activities of the human microbiota. The human gut microbiome encodes tremendous potential for the biosynthesis and transformation of compounds that are important for both microbial and host physiology. Implementation of chemical knowledge and techniques will be required to improve our understanding of the biochemical diversity of the human microbiota. Such efforts include the characterization of novel microbial enzymes and pathways, isolation of microbial natural products, and development of tools to modulate biochemical functions of the gut microbiota. Ultimately, a molecular understanding of gut microbial activities will be critical for elucidating and manipulating these organisms' contributions to human health and disease.

Randomized double blind clinical trial on the effect of oral α-cyclodextrin on serum lipids

Background

This single center, double-blinded, cross-over, placebo controlled clinical trial investigated the effect of oral α-cyclodextrin (α-CD), a soluble dietary fiber, on blood lipid and lipoprotein levels in healthy human subjects. α-CD, a cyclical polymer containing 6 glucose subunits, is currently sold as an over the counter food supplement and is also a common additive in many foods. α-CD forms a hydrophobic central cavity that binds lipids and has been shown in animal studies and in previous clinical trials to alter plasma lipid levels.

Methods

We screened for healthy subjects, males and females, between ages 18 to 75. Out of total 103 subjects interviewed, 75 subjects completed the study. Qualified individuals in each gender group were randomized into two groups in terms of which treatment arm they received first (placebo vs. α-CD, receiving 6 grams P.O. a day, for 12–14 weeks with a 7 day wash out between arms). The primary outcome variable, plasma total cholesterol, as well as other tests related to lipids and lipoprotein and glucose metabolism, were measured at baseline and at the end of each arm of the study.

Results

α-CD was well tolerated; no serious adverse events related to α-CD were observed. Approximately 8 % of the subjects on α-CD complained of minor gastrointestinal symptoms versus 3 % on placebo (p = 0.2). Small-LDL particle number decreased 10 % (p < 0.045) for subjects on α-CD versus placebo. Fasting plasma glucose (1.6 %, p < 0.05) and Insulin resistance index (11 %, p < 0.04) were also decreased when on α-CD versus placebo.

Conclusion

α-CD treatment appears to be safe and well tolerated in healthy individuals and showed a modest reduction in small LDL particles, and an improvement in glucose related parameters.

Trial registration

NCT01131299

The incretin system ABCs in obesity and diabetes - novel therapeutic strategies for weight loss and beyond

Incretins are gastrointestinal-derived hormones released in response to a meal playing a key role in the regulation of postprandial secretion of insulin (incretin effect) and glucagon by the pancreas. Both incretins, glucose-dependent insulinotropic polypeptide and glucagon-like peptide-1 (GLP-1), have several other actions by peripheral and central mechanisms. GLP-1 regulates body weight by inhibiting appetite and delaying gastric, emptying actions that are dependent on central nervous system GLP-1 receptor activation. Several other hormones and gut peptides, including leptin and ghrelin, interact with GLP-1 to modulate appetite. GLP-1 is rapidly degraded by the multifunctional enzyme dipeptidyl peptidase-4 (DPP-4). DPP-4 is involved in adipose tissue inflammation, which is associated with insulin resistance and diabetes progression, being a common pathophysiological mechanism in obesity-related complications. Furthermore, the incretin system appears to provide the basis for understanding the high weight loss efficacy of bariatric surgery, a widely used treatment for obesity, often in association with diabetes. The present review brings together new insights into obesity pathogenesis, integrating GLP-1 and DPP-4 in the complex interplay between obesity and inflammation, namely, in diabetic patients. This in turn will provide the basis for novel incretin-based therapeutic strategies for obesity and diabetes with promising benefits in addition to weight loss. © 2016 World Obesity.

Posttesticular sperm maturation, infertility, and hypercholesterolemia

Cholesterol is a key molecule in the mammalian physiology of especial particular importance for the reproductive system as it is the common precursor for steroid hormone synthesis. Cholesterol is also a recognized modulator of sperm functions, not only at the level of gametogenesis. Cholesterol homeostasis regulation is crucial for posttesticular sperm maturation, and imbalanced cholesterol levels may particularly affect these posttesticular events. Metabolic lipid disorders (dyslipidemia) affect male fertility but are most of the time studied from the angle of endocrine/testicular consequences. This review will focus on the deleterious effects of a particular dyslipidemia, i.e., hypercholesterolemia, on posttesticular maturation of mammalian spermatozoa.

Grape Seed Procyanidins and Cholestyramine Differentially Alter Bile Acid and Cholesterol Homeostatic Gene Expression in Mouse Intestine and Liver

Bile acid (BA) sequestrants, lipid-lowering agents, may be prescribed as a monotherapy or combination therapy to reduce the risk of coronary artery disease. Over 33% of adults in the United States use complementary and alternative medicine strategies, and we recently reported that grape seed procyanidin extract (GSPE) reduces enterohepatic BA recirculation as a means to reduce serum triglyceride (TG) levels. The current study was therefore designed to assess the effects on BA, cholesterol and TG homeostatic gene expression following co-administration with GSPE and the BA sequestrant, cholestyramine (CHY). Eight-week old male C57BL/6 mice were treated for 4 weeks with either a control or 2% CHY-supplemented diet, after which, they were administered vehicle or GSPE for 14 hours. Liver and intestines were harvested and gene expression was analyzed. BA, cholesterol, non-esterified fatty acid and TG levels were also analyzed in serum and feces. Results reveal that GSPE treatment alone, and co-administration with CHY, regulates BA, cholesterol and TG metabolism differently than CHY administration alone. Notably, GSPE decreased intestinal apical sodium-dependent bile acid transporter (Asbt) gene expression, while CHY significantly induced expression. Administration with GSPE or CHY robustly induced hepatic BA biosynthetic gene expression, especially cholesterol 7α-hydroxylase (Cyp7a1), compared to control, while co-administration further enhanced expression. Treatment with CHY induced both intestinal and hepatic cholesterologenic gene expression, while co-administration with GSPE attenuated the CHY-induced increase in the liver but not intestine. CHY also induced hepatic lipogenic gene expression, which was attenuated by co-administration with GSPE. Consequently, a 25% decrease in serum TG levels was observed in the CHY+GSPE group, compared to the CHY group. Collectively, this study presents novel evidence demonstrating that GSPE provides additive and complementary efficacy as a lipid-lowering combination therapy in conjunction with CHY by attenuating hepatic cholesterol synthesis, enhancing BA biosynthesis and decreasing lipogenesis, which warrants further investigation.

Metabolic effects of bile acid sequestration: impact on cardiovascular risk factors

PURPOSE OF REVIEW

This article discusses the impact of bile acid sequestrants (BAS) on cardiovascular risk factors (CVRFs), on the basis of recent (pre)clinical studies assessing the metabolic impact of modulation of enterohepatic bile acid signaling via the bile acid receptors farnesoid X receptor (FXR) and Takeda G-protein-coupled receptor 5 (TGR5).

RECENT FINDINGS

BAS decrease low-density lipoprotein-cholesterol by stimulating de novo hepatic bile acid synthesis and lowering intestinal lipid absorption, and improve glucose homeostasis in type 2 diabetes mellitus, at least in part by increasing GLP-1 production, via intestinal TGR5- and FXR-dependent mechanisms. Intestinal and peripheral FXR and TGR5 modulation also affects peripheral tissues, which can contribute to the reduction of CVRFs.

SUMMARY

Bile acids are regulators of metabolism acting in an integrated interorgan manner via FXR and TGR5. Modulation of the bile acid pool size and composition, and selective interference with their receptors could, therefore, be a therapeutic approach to decrease CVRFs. Even though clinical cardiovascular outcome studies using BAS are still lacking, the existing data point to BAS as an efficacious pharmacological approach to reduce CVRFs.

CD4(+) T-cell survival in the GI tract requires dectin-1 during fungal infection

Dectin-1 is an innate antifungal C-type lectin receptor necessary for protective antifungal immunity. We recently discovered that Dectin-1 is involved in controlling fungal infections of the gastrointestinal (GI) tract, but how this C-type lectin receptor mediates these activities is unknown. Here, we show that Dectin-1 is essential for driving fungal-specific CD4(+) T-cell responses in the GI tract. Loss of Dectin-1 resulted in abrogated dendritic cell responses in the mesenteric lymph nodes (mLNs) and defective T-cell co-stimulation, causing substantial increases in CD4(+) T-cell apoptosis and reductions in the cellularity of GI-associated lymphoid tissues. CD8(+) T-cell responses were unaffected by Dectin-1 deficiency. These functions of Dectin-1 have significant implications for our understanding of intestinal immunity and susceptibility to fungal infections.

Antilipidemic Drug Therapy Today and in the Future

The armamentarium for the treatment of dyslipidemia today comprises six different modes of action with overall around 24 different drugs. The treatment of lipid disorders was revolutionized with the introduction of statins which have become the most important therapeutic option available today to reduce and prevent atherosclerosis and its detrimental consequences like cardiovascular diseases and stroke. With and optimized reduction of elevated LDL levels with statins, the risk for cardiovascular diseases (CVD) can be reduced by 30%, indicating a residual remaining risk of 70% for the development and progression of CVD notifying still a high medical need for more effective antilipidemic drugs. Consequently, the search for novel lipid-modifying drugs is still one of the most active areas in research and development in the pharmaceutical industry. Major focus lies on approaches to LDL-lowering drugs superior to statins with regard to efficacy, safety, and patient compliance and on approaches modifying plasma levels and functionality of HDL particles based on the clinically validated inverse relationship between high-plasma HDL levels and the risk for CVD. The available drugs today for the treatment of dyslipidemia are small organic molecules or nonabsorbable polymers for binding of bile acids to be applied orally. Besides small molecules for novel targets, biological drugs such as monoclonal antibodies, antisense or gene-silencing oligonucleotides, peptidomimetics, reconstituted synthetic HDL particles and therapeutic proteins are novel approaches in clinical development are which have to be applied by injection or infusion. The promising clinical results of several novel drug candidates, particularly for LDL cholesterol lowering with monoclonal antibodies raised against PCSK9, may indicate more than a decade after the statins, the entrance of new breakthrough therapies to treat lipid disorders.

Hepatocyte β-Klotho regulates lipid homeostasis but not body weight in mice

β-Klotho (β-Kl), a transmembrane protein expressed in the liver, pancreas, adipose tissues, and brain, is essential for feedback suppression of hepatic bile acid synthesis. Because bile acid is a key regulator of lipid and energy metabolism, we hypothesized potential and tissue-specific roles of β-Kl in regulating plasma lipid levels and body weight. By crossing β-kl(-/-) mice with newly developed hepatocyte-specific β-kl transgenic (Tg) mice, we generated mice expressing β-kl solely in hepatocytes (β-kl(-/-)/Tg). Gene expression, metabolomic, and in vivo flux analyses consistently revealed that plasma level of cholesterol, which is over-excreted into feces as bile acids in β-kl(-/-), is maintained in β-kl(-/-) mice by enhanced de novo cholesterogenesis. No compensatory increase in lipogenesis was observed, despite markedly decreased plasma triglyceride. Along with enhanced bile acid synthesis, these lipid dysregulations in β-kl(-/-) were completely reversed in β-kl(-/-)/Tg mice. In contrast, reduced body weight and resistance to diet-induced obesity in β-kl(-/-) mice were not reversed by hepatocyte-specific restoration of β-Kl expression. We conclude that β-Kl in hepatocytes is necessary and sufficient for lipid homeostasis, whereas nonhepatic β-Kl regulates energy metabolism. We further demonstrate that in a condition with excessive cholesterol disposal, a robust compensatory mechanism maintains cholesterol levels but not triglyceride levels in mice.

Type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is an expanding global health problem, closely linked to the epidemic of obesity. Individuals with T2DM are at high risk for both microvascular complications (including retinopathy, nephropathy and neuropathy) and macrovascular complications (such as cardiovascular comorbidities), owing to hyperglycaemia and individual components of the insulin resistance (metabolic) syndrome. Environmental factors (for example, obesity, an unhealthy diet and physical inactivity) and genetic factors contribute to the multiple pathophysiological disturbances that are responsible for impaired glucose homeostasis in T2DM. Insulin resistance and impaired insulin secretion remain the core defects in T2DM, but at least six other pathophysiological abnormalities contribute to the dysregulation of glucose metabolism. The multiple pathogenetic disturbances present in T2DM dictate that multiple antidiabetic agents, used in combination, will be required to maintain normoglycaemia. The treatment must not only be effective and safe but also improve the quality of life. Several novel medications are in development, but the greatest need is for agents that enhance insulin sensitivity, halt the progressive pancreatic β-cell failure that is characteristic of T2DM and prevent or reverse the microvascular complications. For an illustrated summary of this Primer, visit: http://go.nature.com/V2eGfN.

Nuclear bile acid signaling through the farnesoid X receptor

Bile acids (BAs) are amphipathic molecules produced from cholesterol by the liver. Expelled from the gallbladder upon meal ingestion, BAs serve as fat solubilizers in the intestine. BAs are reabsorbed in the ileum and return via the portal vein to the liver where, together with nutrients, they provide signals to coordinate metabolic responses. BAs act on energy and metabolic homeostasis through the activation of membrane and nuclear receptors, among which the nuclear receptor farnesoid X receptor (FXR) is an important regulator of several metabolic pathways. Highly expressed in the liver and the small intestine, FXR contributes to BA effects on metabolism, inflammation and cell cycle control. The pharmacological modulation of its activity has emerged as a potential therapeutic strategy for liver and metabolic diseases. This review highlights recent advances regarding the mechanisms by which the BA sensor FXR contributes to global signaling effects of BAs, and how FXR activity may be regulated by nutrient-sensitive signaling pathways.

Metabolic effects of intestinal absorption and enterohepatic cycling of bile acids

The classical functions of bile acids include acting as detergents to facilitate the digestion and absorption of nutrients in the gut. In addition, bile acids also act as signaling molecules to regulate glucose homeostasis, lipid metabolism and energy expenditure. The signaling potential of bile acids in compartments such as the systemic circulation is regulated in part by an efficient enterohepatic circulation that functions to conserve and channel the pool of bile acids within the intestinal and hepatobiliary compartments. Changes in hepatobiliary and intestinal bile acid transport can alter the composition, size, and distribution of the bile acid pool. These alterations in turn can have significant effects on bile acid signaling and their downstream metabolic targets. This review discusses recent advances in our understanding of the inter-relationship between the enterohepatic cycling of bile acids and the metabolic consequences of signaling via bile acid-activated receptors, such as farnesoid X nuclear receptor (FXR) and the G-protein-coupled bile acid receptor (TGR5).

Sevelamer in a diabetologist's perspective: a phosphate-binding resin with glucose-lowering potential

Sevelamer is a calcium-free and metal-free phosphate-binding oral drug used in the management of hyperphosphataemia in chronic kidney disease. Preclinical and clinical trials have shown glucose and lipid-lowering effects of sevelamer, thereby giving rise to a potential role of the drug in the treatment of patients with type 2 diabetes. These 'novel' effects are most probably derived from the bile acid-binding properties of sevelamer. The proposed potential is supported by the approval of the bile acid sequestrant colesevelam in the United States for the treatment of type 2 diabetes and hypercholesterolaemia. This article offers a brief review on the effects of sevelamer and a perspective on the potential mechanisms behind the glucose-lowering effect of the drug.

Precision microbiome reconstitution restores bile acid mediated resistance to Clostridium difficile

The gastrointestinal tracts of mammals are colonized by hundreds of microbial species that contribute to health, including colonization resistance against intestinal pathogens¹. Many antibiotics destroy intestinal microbial communities and increase susceptibility to intestinal pathogens². Among these, Clostridium difficile, a major cause of antibiotic-induced diarrhea, greatly increases morbidity and mortality in hospitalized patients³. Which intestinal bacteria provide resistance to C. difficile infection and their in vivo inhibitory mechanisms remain unclear. By treating mice with different antibiotics that result in distinct microbiota changes and lead to varied susceptibility to C. difficile, we correlated loss of specific bacterial taxa with development of infection. Mathematical modeling augmented by microbiota analyses of hospitalized patients identified resistance-associated bacteria common to mice and humans. Using these platforms, we determined that Clostridium scindens, a bile acid 7-dehydroxylating intestinal bacterium, is associated with resistance to C. difficile infection and, upon administration, enhances resistance to infection in a secondary bile acid-dependent fashion. Using a workflow involving mouse models, clinical studies, metagenomic analyses and mathematical modeling, we identified a probiotic candidate that corrects a clinically relevant microbiome deficiency. These findings have implications for rational design of targeted antimicrobials as well as microbiome-based diagnostics and therapeutics for individuals at risk for C. difficile infection.

Bile acid malabsorption assessed by 7 alpha-hydroxy-4-cholesten-3-one in pediatric inflammatory bowel disease: correlation to clinical and laboratory findings

BACKGROUND AND AIMS

Measurement of 7 alpha-hydroxy-4-cholesten-3-one (C4) in serum is a semiquantitative test for bile acid malabsorption (BAM). We have previously established pediatric normal values for C4 with an upper limit of normal of 66.5 ng/mL, independent of age and sex. Here we performed the C4 test in 58 pediatric patients with Crohn's disease (CD) and ulcerative colitis (UC).

METHODS

C4 was measured using high performance liquid chromatography (HPLC) in fasting serum samples of 44 patients with CD (range 7-19 years) and 14 with UC (4-18 years). Disease activity was assessed by the pediatric CD and UC activity indices (PCDAI and PUCAI, respectively) plus serum (CRP, ESR) and fecal inflammatory markers (calprotectin).

RESULTS

C4 concentrations were increased in 10 CD (23%) (range: 70.8-269.3 ng/mL) but only one UC patient (72.9 ng/mL). CD patients with diarrhea (n=12) had higher C4-values compared to those without (76.9 vs. 30.4 ng/mL; p=0.0043). Ileal resection in CD patients (n=10) was associated with increased C4 concentrations (81.2 vs. 24.3 ng/mL, p=0.0004). No correlation was found between C4 values and inflammatory markers. Six of 7 CD patients with persistent diarrhea but quiescent disease (PCDAI ≤12.5) had C4 values indicating BAM.

CONCLUSION

Elevated C4 concentrations indicating BAM are common in children with CD. They are associated with ileal resection and non-bloody diarrhea in the absence of active disease or elevated inflammatory markers. The C4-test identifies a subgroup of CD patients with persistent diarrhea in spite of clinical remission which may benefit from bile acid binding therapy.

Glucose-lowering effects of intestinal bile acid sequestration through enhancement of splanchnic glucose utilization

Intestinal bile acid (BA) sequestration efficiently lowers plasma glucose concentrations in type 2 diabetes (T2D) patients. Because BAs act as signaling molecules via receptors, including the G protein-coupled receptor TGR5 and the nuclear receptor FXR (farnesoid X receptor), to regulate glucose homeostasis, BA sequestration, which interrupts the entero-hepatic circulation of BAs, constitutes a plausible action mechanism of BA sequestrants. An increase of intestinal L-cell glucagon-like peptide-1 (GLP-1) secretion upon TGR5 activation is the most commonly proposed mechanism, but recent studies also argue for a direct entero-hepatic action to enhance glucose utilization. We discuss here recent findings on the mechanisms of sequestrant-mediated glucose lowering via an increase of splanchnic glucose utilization through entero-hepatic FXR signaling.

Toward individualized cholesterol-lowering treatment in end-stage renal disease

There is broad evidence that lowering low-density lipoprotein (LDL) cholesterol will reduce cardiovascular risk. However, in patients on maintenance hemodialysis treatment, lowering LDL cholesterol is not as effective in preventing cardiovascular complications as in the general population. Cholesterol is either endogenously synthesized or absorbed from the intestine. It has been suggested that the benefit of using statins to prevent atherosclerotic complications is less pronounced in people with high absorption of cholesterol. Recent data indicate that patients on hemodialysis have high absorption of cholesterol. Therefore, these patients may benefit from dietary counseling to reduce cholesterol intake, from functional foods containing plant sterols and stanols, and from drugs that interfere with intestinal absorption of sterols (i.e., ezetimibe, bile acid resins, and sevelamer). This review discusses cholesterol homeostasis and the perspective of personalized treatment of hypercholesterolemia in hemodialysis.

Bile acid sequestrants: glucose-lowering mechanisms and efficacy in type 2 diabetes

Bile acids are synthesized in the liver from cholesterol and have traditionally been recognized for their role in absorption of lipids and in cholesterol homeostasis. In recent years, however, bile acids have emerged as metabolic signaling molecules that are involved in the regulation of lipid and glucose metabolism, and possibly energy homeostasis, through activation of the bile acid receptors farnesoid X receptor (FXR) and TGR5. Bile acid sequestrants (BASs) constitute a class of drugs that bind bile acids in the intestine to form a nonabsorbable complex resulting in interruption of the enterohepatic circulation. This increases bile acid synthesis and consequently reduces serum low-density lipoprotein cholesterol. Also, BASs improve glycemic control in patients with type 2 diabetes. Despite a growing understanding of the impact of BASs on glucose metabolism, the mechanisms behind their glucose-lowering effect in patients with type 2 diabetes remain unclear. This article offers a review of the mechanisms behind the glucose-lowering effect of BASs, and the efficacy of BASs in the treatment of type 2 diabetes.

Human insulin resistance is associated with increased plasma levels of 12α-hydroxylated bile acids

Bile acids (BAs) exert pleiotropic metabolic effects, and physicochemical properties of different BAs affect their function. In rodents, insulin regulates BA composition, in part by regulating the BA 12α-hydroxylase CYP8B1. However, it is unclear whether a similar effect occurs in humans. To address this question, we examined the relationship between clamp-measured insulin sensitivity and plasma BA composition in a cohort of 200 healthy subjects and 35 type 2 diabetic (T2D) patients. In healthy subjects, insulin resistance (IR) was associated with increased 12α-hydroxylated BAs (cholic acid, deoxycholic acid, and their conjugated forms). Furthermore, ratios of 12α-hydroxylated/non-12α-hydroxylated BAs were associated with key features of IR, including higher insulin, proinsulin, glucose, glucagon, and triglyceride (TG) levels and lower HDL cholesterol. In T2D patients, BAs were nearly twofold elevated, and more hydrophobic, compared with healthy subjects, although we did not observe disproportionate increases in 12α-hydroxylated BAs. In multivariate analysis of the whole dataset, controlling for sex, age, BMI, and glucose tolerance status, higher 12α-hydroxy/non-12α-hydroxy BA ratios were associated with lower insulin sensitivity and higher plasma TGs. These findings suggest a role for 12α-hydroxylated BAs in metabolic abnormalities in the natural history of T2D and raise the possibility of developing insulin-sensitizing therapeutics based on manipulations of BA composition.

Diagnosis and management of familial dyslipoproteinemias

The three major pathways of lipoprotein metabolism provide a superb paradigm to delineate systematically the familial dyslipoproteinemias. Such understanding leads to improved diagnosis and treatment of patients. In the exogenous (intestinal) pathway, defects in LPL, apoC-II, APOA-V, and GPIHBP1 disrupt the catabolism of chylomicrons and hepatic uptake of their remnants, producing very high TG. In the endogenous (hepatic) pathway, six disorders affect the activity of the LDLR and markedly increase LDL. These include FH, FDB, ARH, PCSK9 gain-of-function mutations, sitosterolemia and loss of 7 alpha hydroxylase. Hepatic overproduction of VLDL occurs in FCHL, hyperapoB, LDL subclass pattern B, FDH and syndrome X, often due to insulin resistance and resulting in high TG, elevated small LDL particles and low HDL-C. Defects in APOB-100 and loss-of-function mutations in PCSK9 are associated with low LDL-C, decreased CVD and longevity. An absence of MTP leads to marked reduction in chylomicrons and VLDL, causing abetalipoproteinemia. In the reverse cholesterol pathway, deletions or nonsense mutations in apoA-I or ABCA1 transporter disrupt the formation of the nascent HDL particle. Mutations in LCAT disrupt esterification of cholesterol in nascent HDL by LCAT and apoA-1, and formation of spherical HDL. Mutations in either CETP or SR-B1 and familial high HDL lead to increased large HDL particles, the effect of which on CVD is not resolved. The major goal is to prevent or ameliorate the major complications of many familial dyslipoproteinemias, namely, premature CVD or pancreatitis. Dietary and drug treatment specific for each inherited disorder is reviewed.

Laxative treatment with polyethylene glycol decreases microbial primary bile salt dehydroxylation and lipid metabolism in the intestine of rats

Polyethylene glycol (PEG) is a frequently used osmotic laxative that accelerates gastrointestinal transit. It has remained unclear, however, whether PEG affects intestinal functions. We aimed to determine the effect of PEG treatment on intestinal sterol metabolism. Rats were treated with PEG in drinking water (7%) for 2 wk or left untreated (controls). We studied the enterohepatic circulation of the major bile salt (BS) cholate with a plasma stable isotope dilution technique and determined BS profiles and concentrations in bile, intestinal lumen contents, and feces. We determined the fecal excretion of cholesterol plus its intestinally formed metabolites. Finally, we determined the cytolytic activity of fecal water (a surrogate marker of colorectal cancer risk) and the amount and composition of fecal microbiota. Compared with control rats, PEG treatment increased the pool size (+51%; P < 0.01) and decreased the fractional turnover of cholate (-32%; P < 0.01). PEG did not affect the cholate synthesis rate, corresponding with an unaffected fecal primary BS excretion. PEG reduced fecal excretion of secondary BS and of cholesterol metabolites (each P < 0.01). PEG decreased the cytolytic activity of fecal water [54 (46-62) vs. 87 (85-92)% erythrocyte potassium release in PEG-treated and control rats, respectively; P < 0.01]. PEG treatment increased the contribution of Verrucomicrobia (P < 0.01) and decreased that of Firmicutes (P < 0.01) in fecal flora. We concluded that PEG treatment changes the intestinal bacterial composition, decreases the bacterial dehydroxylation of primary BS and the metabolism of cholesterol, and increases the pool size of the primary BS cholate in rats.

Clinical relevance of target identity and biology: implications for drug discovery and development

Many of the most commonly used drugs precede techniques for target identification and drug specificity and were developed on the basis of efficacy and safety, an approach referred to as classical pharmacology and, more recently, phenotypic drug discovery. Although substantial gains have been made during the period of focus on target-based approaches, particularly in oncology, these approaches have suffered a high overall failure rate and lower productivity in terms of new drugs when compared with phenotypic approaches. This review considers the importance of target identity and biology in clinical practice from the prescriber's viewpoint. In evaluating influences on prescribing behavior, studies suggest that target identity and mechanism of action are not significant factors in drug choice. Rather, patients and providers consistently value efficacy, safety, and tolerability. Similarly, the Food and Drug Administration requires evidence of safety and efficacy for new drugs but does not require knowledge of drug target identity or target biology. Prescribers do favor drugs with novel mechanisms, but this preference is limited to diseases for which treatments are either not available or suboptimal. Thus, while understanding of drug target and target biology is important from a scientific perspective, it is not particularly important to prescribers, who prioritize efficacy and safety.

Role of bile acids in liver injury and regeneration following acetaminophen overdose

Bile acids play a critical role in liver injury and regeneration, but their role in acetaminophen (APAP)-induced liver injury is not known. We tested the effect of bile acid modulation on APAP hepatotoxicity using C57BL/6 mice, which were fed a normal diet, a 2% cholestyramine (CSA)-containing diet for bile acid depletion, or a 0.2% cholic acid (CA)-containing diet for 1 week before treatment with 400 mg/kg APAP. CSA-mediated bile acid depletion resulted in significantly higher liver injury and delayed regeneration after APAP treatment. In contrast, 0.2% CA supplementation in the diet resulted in a moderate delay in progression of liver injury and significantly higher liver regeneration after APAP treatment. Either CSA-mediated bile acid depletion or CA supplementation did not affect hepatic CYP2E1 levels or glutathione depletion after APAP treatment. CSA-fed mice exhibited significantly higher activation of c-Jun N-terminal protein kinases and a significant decrease in intestinal fibroblast growth factor 15 mRNA after APAP treatment. In contrast, mice fed a 0.2% CA diet had significantly lower c-Jun N-terminal protein kinase activation and 12-fold higher fibroblast growth factor 15 mRNA in the intestines. Liver regeneration after APAP treatment was significantly faster in CA diet-fed mice after APAP administration secondary to rapid cyclin D1 induction. Taken together, these data indicate that bile acids play a critical role in both initiation and recovery of APAP-induced liver injury.