Activation of farnesoid X receptor prevents atherosclerotic lesion formation in LDLR-/- and apoE-/- mice

Association of potential salivary biomarkers with diabetic retinopathy and its severity in type-2 diabetes mellitus: a proteomic analysis by mass spectrometry

AIM/HYPOTHESIS

The aim of our study was to characterize the human salivary proteome and determine the changes in protein expression in two different stages of diabetic retinopathy with type-2 diabetes mellitus: (1) with non-proliferative diabetic retinopathy (NPDR) and (2) with proliferative diabetic retinopathy (PDR). Type-2 diabetes mellitus without diabetic retinopathy (XDR) was designated as control.

METHOD

In this study, 45 saliva samples were collected (15 samples from XDR control group, 15 samples from NPDR disease group and 15 samples from PDR disease group). Salivary proteins were extracted, reduced, alkylated, trypsin digested and labeled with an isobaric tag for relative and absolute quantitation (iTRAQ) before being analyzed by an Orbitrap fusion tribrid mass spectrometer. Protein annotation, fold change calculation and statistical analysis were interrogated by Proteome Discoverer. Biological pathway analysis was performed by Ingenuity Pathway Analysis. Data are available via ProteomeXchange with identifiers PXD003723-PX003725.

RESULTS

A total of 315 proteins were identified from the salivary proteome and 119 proteins were found to be differentially expressed. The differentially expressed proteins from the NPDR disease group and the PDR disease group were assigned to respective canonical pathways indicating increased Liver X receptor/Retinoid X receptor (LXR/RXR) activation, Farnesoid X receptor/Retinoid X receptor (FXR/RXR) activation, acute phase response signaling, sucrose degradation V and regulation of actin-based motility by Rho in the PDR disease group compared to the NPDR disease group.

CONCLUSIONS/INTERPRETATION

Progression from non-proliferative to proliferative retinopathy in type-2 diabetic patients is a complex multi-mechanism and systemic process. Furthermore, saliva was shown to be a feasible alternative sample source for diabetic retinopathy biomarkers.

Novel bile acid therapeutics for the treatment of chronic liver diseases

Recent developments in understanding the role of bile acids (BAs) as signalling molecules in human metabolism and inflammation have opened new avenues in the field of hepatology research. BAs are no longer considered as simple molecules helping in fat digestion but as agents with real therapeutic value in treating complex autoimmune and metabolic liver diseases. BAs and their receptors such as farnesoid X receptor, transmembrane G protein-coupled receptor 5 and peroxisome proliferator-activated receptor have been identified as novel targets for drug development. Some of these novel pharmaceuticals are already in clinical evaluation with the most advanced drugs having reached phase III trials. Chronic liver diseases such as primary biliary cholangitis, primary sclerosing cholangitis and nonalcoholic fatty liver disease, for which there is no or limited pharmacotherapy, are most likely to gain from these developments. In this review we discuss recent and the most relevant basic and clinical research findings related to BAs and their implications for novel therapy for chronic liver diseases.

Roles of oxidative stress, adiponectin, and nuclear hormone receptors in obesity-associated insulin resistance and cardiovascular risk

Obesity leads to the development of type 2 diabetes mellitus, which is a strong risk factor for cardiovascular disease. A better understanding of the molecular basis of obesity will lead to the establishment of effective prevention strategies for cardiovascular diseases. Adipocytes have been shown to generate a variety of endocrine factors termed adipokines/adipocytokines. Obesity-associated changes to these adipocytokines contribute to the development of cardiovascular diseases. Adiponectin, which is one of the most well-characterized adipocytokines, is produced exclusively by adipocytes and exerts insulin-sensitizing and anti-atherogenic effects. Obese subjects have lower levels of circulating adiponectin, and this is recognized as one of the factors involved in obesity-induced insulin resistance and atherosclerosis. Another pathophysiological feature of obesity may involve the low-grade chronic inflammation in adipose tissue. This inflammatory process increases oxidative stress in adipose tissue, which may affect remote organs, leading to the development of diabetes, hypertension, and atherosclerosis. Nuclear hormone receptors (NRs) regulate the transcription of the target genes in response to binding with their ligands, which include metabolic and nutritional substrates. Among the various NRs, peroxisome proliferator-activated receptor γ promotes the transcription of adiponectin and antioxidative enzymes, whereas mineralocorticoid receptor mediates the effects of aldosterone and glucocorticoid to induce oxidative stress in adipocytes. It is hypothesized that both play crucial roles in the pathophysiology of obesity-associated insulin resistance and cardiovascular diseases. Thus, reduced adiponectin and increased oxidative stress play pathological roles in obesity-associated insulin resistance to increase the cardiovascular disease risk, and various NRs may be involved in this pathogenesis.

Use of farnesoid X receptor agonists to treat nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease is a common cause of liver related morbidity and mortality. It is closely linked to underlying insulin resistance. It has recently been shown that bile acids modulate insulin signaling and can improve insulin resistance in cell based and animal studies. These effects are mediated in part by activation of farnesoid x receptors by bile acids. In human studies, FXR agonists improve insulin resistance and have recently been shown to improve NAFLD. The basis for the use of FXR agonists for the treatment of NAFLD and early human experience with such agents is reviewed in this paper.

Bile acid signaling in metabolic disease and drug therapy

Bile acids are the end products of cholesterol catabolism. Hepatic bile acid synthesis accounts for a major fraction of daily cholesterol turnover in humans. Biliary secretion of bile acids generates bile flow and facilitates hepatobiliary secretion of lipids, lipophilic metabolites, and xenobiotics. In the intestine, bile acids are essential for the absorption, transport, and metabolism of dietary fats and lipid-soluble vitamins. Extensive research in the last 2 decades has unveiled new functions of bile acids as signaling molecules and metabolic integrators. The bile acid-activated nuclear receptors farnesoid X receptor, pregnane X receptor, constitutive androstane receptor, vitamin D receptor, and G protein-coupled bile acid receptor play critical roles in the regulation of lipid, glucose, and energy metabolism, inflammation, and drug metabolism and detoxification. Bile acid synthesis exhibits a strong diurnal rhythm, which is entrained by fasting and refeeding as well as nutrient status and plays an important role for maintaining metabolic homeostasis. Recent research revealed an interaction of liver bile acids and gut microbiota in the regulation of liver metabolism. Circadian disturbance and altered gut microbiota contribute to the pathogenesis of liver diseases, inflammatory bowel diseases, nonalcoholic fatty liver disease, diabetes, and obesity. Bile acids and their derivatives are potential therapeutic agents for treating metabolic diseases of the liver.

Dual activation of the bile acid nuclear receptor FXR and G-protein-coupled receptor TGR5 protects mice against atherosclerosis

Bile acid signaling is a critical regulator of glucose and energy metabolism, mainly through the nuclear receptor FXR and the G protein-coupled receptor TGR. The purpose of the present study was to investigate whether dual activation of FXR and TGR5 plays a significant role in the prevention of atherosclerosis progression. To evaluate the effects of bile acid signaling in atherogenesis, ApoE-/- mice and LDLR-/- mice were treated with an FXR/TGR5 dual agonist (INT-767). INT-767 treatment drastically reduced serum cholesterol levels. INT-767 treatment significantly reduced atherosclerotic plaque formation in both ApoE-/- and LDLR-/- mice. INT-767 decreased the expression of pro-inflammatory cytokines and chemokines in the aortas of ApoE-/- mice through the inactivation of NF-κB. In addition, J774 macrophages treated with INT-767 had significantly lower levels of active NF-κB, resulting in cytokine production in response to LPS through a PKA dependent mechanism. This study demonstrates that concurrent activation of FXR and TGR5 attenuates atherosclerosis by reducing both circulating lipids and inflammation.

Bile acids, obesity, and the metabolic syndrome

Bile acids are increasingly recognized as key regulators of systemic metabolism. While bile acids have long been known to play important and direct roles in nutrient absorption, bile acids also serve as signalling molecules. Bile acid interactions with the nuclear hormone receptor farnesoid X receptor (FXR) and the membrane receptor G-protein-coupled bile acid receptor 5 (TGR5) can regulate incretin hormone and fibroblast growth factor 19 (FGF19) secretion, cholesterol metabolism, and systemic energy expenditure. Bile acid levels and distribution are altered in type 2 diabetes and increased following bariatric procedures, in parallel with reduced body weight and improved insulin sensitivity and glycaemic control. Thus, modulation of bile acid levels and signalling, using bile acid binding resins, TGR5 agonists, and FXR agonists, may serve as a potent therapeutic approach for the treatment of obesity, type 2 diabetes, and other components of the metabolic syndrome in humans.

Hepatic carboxylesterase 1 is essential for both normal and farnesoid X receptor-controlled lipid homeostasis

Nonalcoholic fatty liver disease (NAFLD) is one of the major health concerns worldwide. Farnesoid X receptor (FXR) is considered a therapeutic target for treatment of NAFLD. However, the mechanism by which activation of FXR lowers hepatic triglyceride (TG) levels remains unknown. Here we investigated the role of hepatic carboxylesterase 1 (CES1) in regulating both normal and FXR-controlled lipid homeostasis. Overexpression of hepatic CES1 lowered hepatic TG and plasma glucose levels in both wild-type and diabetic mice. In contrast, knockdown of hepatic CES1 increased hepatic TG and plasma cholesterol levels. These effects likely resulted from the TG hydrolase activity of CES1, with subsequent changes in fatty acid oxidation and/or de novo lipogenesis. Activation of FXR induced hepatic CES1, and reduced the levels of hepatic and plasma TG as well as plasma cholesterol in a CES1-dependent manner.

CONCLUSION

Hepatic CES1 plays a critical role in regulating both lipid and carbohydrate metabolism and FXR-controlled lipid homeostasis.

The bile acid TGR5 membrane receptor: from basic research to clinical application

The TGR5 receptor (or GP-BAR1, or M-BAR) was characterized ten years ago as the first identified G-coupled protein receptor specific for bile acids. TGR5 gene expression is widely distributed, including endocrine glands, adipocytes, muscles, immune organs, spinal cord, and the enteric nervous system. The effect of TGR5 activation depends on the tissue where it is expressed and the signalling cascade that it induces. Animal studies suggest that TGR5 activation influences energy production and thereby may be involved in obesity and diabetes. TGR5 activation also influences intestinal motility. This review provides an overview of TGR5-bile acid interactions in health as well as the possible involvement of TGR5 in human disease.

Bile acid receptors as targets for drug development

The intracellular nuclear receptor farnesoid X receptor and the transmembrane G protein-coupled receptor TGR5 respond to bile acids by activating transcriptional networks and/or signalling cascades. These cascades affect the expression of a great number of target genes relevant for bile acid, cholesterol, lipid and carbohydrate metabolism, as well as genes involved in inflammation, fibrosis and carcinogenesis. Pregnane X receptor, vitamin D receptor and constitutive androstane receptor are additional nuclear receptors that respond to bile acids, albeit to a more restricted set of species of bile acids. Recognition of dedicated bile acid receptors prompted the development of semi-synthetic bile acid analogues and nonsteroidal compounds that target these receptors. These agents hold promise to become a new class of drugs for the treatment of chronic liver disease, hepatocellular cancer and extrahepatic inflammatory and metabolic diseases. This Review discusses the relevant bile acid receptors, the new drugs that target bile acid signalling and their possible applications.

Activation of farnesoid X receptor induces RECK expression in mouse liver

Farnesoid X receptor (FXR) belongs to the ligand-activated nuclear receptor superfamily, and functions as a transcription factor regulating the transcription of numerous genes involved in bile acid homeostasis, lipoprotein and glucose metabolism. In the present study, we identified RECK, a membrane-anchored inhibitor of matrix metalloproteinases, as a novel target gene of FXR in mouse liver. We found that FXR agonist substantially augmented hepatic RECK mRNA and protein expression in vivo and in vitro. FXR regulated the transcription of RECK through directly binding to FXR response element located within intron 1 of the mouse RECK gene. Moreover, FXR agonist reversed the down-regulation of RECK in the livers from mice fed a methionine and choline deficient diet. In summary, our data suggest that RECK is a novel transcriptional target of FXR in mouse liver, and provide clues to better understanding the function of FXR in liver.

Molecular biology of atherosclerosis

At least 468 individual genes have been manipulated by molecular methods to study their effects on the initiation, promotion, and progression of atherosclerosis. Most clinicians and many investigators, even in related disciplines, find many of these genes and the related pathways entirely foreign. Medical schools generally do not attempt to incorporate the relevant molecular biology into their curriculum. A number of key signaling pathways are highly relevant to atherogenesis and are presented to provide a context for the gene manipulations summarized herein. The pathways include the following: the insulin receptor (and other receptor tyrosine kinases); Ras and MAPK activation; TNF-α and related family members leading to activation of NF-κB; effects of reactive oxygen species (ROS) on signaling; endothelial adaptations to flow including G protein-coupled receptor (GPCR) and integrin-related signaling; activation of endothelial and other cells by modified lipoproteins; purinergic signaling; control of leukocyte adhesion to endothelium, migration, and further activation; foam cell formation; and macrophage and vascular smooth muscle cell signaling related to proliferation, efferocytosis, and apoptosis. This review is intended primarily as an introduction to these key signaling pathways. They have become the focus of modern atherosclerosis research and will undoubtedly provide a rich resource for future innovation toward intervention and prevention of the number one cause of death in the modern world.

New developments in selective cholesteryl ester uptake

PURPOSE OF REVIEW

Selective lipid uptake (SLU) is known to be a major pathway of lipoprotein cholesterol metabolism in experimental animals and humans, but remains poorly understood. This review provides a brief overview of SLU mediated by the HDL receptor scavenger receptor B-type I (SR-BI), and highlights several surprising new findings related to the impact of SLU pathways in cholesterol homeostasis.

RECENT FINDINGS

Under certain conditions, SR-BI-mediated SLU contributes to reverse cholesterol transport (RCT) independently of ABCG5/G8-mediated biliary cholesterol secretion, implying a novel trafficking mechanism. Hepatic SR-BI expression and RCT are decreased in diabetic mice. Farnesoid X receptor (FXR) and the microRNAs miR-185, miR-96 and miR-223 are emerging therapeutic targets for increasing SR-BI expression. SR-BI-independent selective cholesteryl ester uptake is a newly characterized pathway in macrophage foam cells.

SUMMARY

New findings underscore the importance of SR-BI-mediated SLU in hepatic SLU and RCT, while indicating that further investigation is needed to define SLU pathways, including SR-BI-independent macrophage selective cholesteryl ester uptake. The intracellular trafficking of cholesterol in these pathways appears to be critical to their normal function and is a major subject of ongoing studies.

Efficacy and safety of the farnesoid X receptor agonist obeticholic acid in patients with type 2 diabetes and nonalcoholic fatty liver disease

BACKGROUND & AIMS

Obeticholic acid (OCA; INT-747, 6α-ethyl-chenodeoxycholic acid) is a semisynthetic derivative of the primary human bile acid chenodeoxycholic acid, the natural agonist of the farnesoid X receptor, which is a nuclear hormone receptor that regulates glucose and lipid metabolism. In animal models, OCA decreases insulin resistance and hepatic steatosis.

METHODS

We performed a double-blind, placebo-controlled, proof-of-concept study to evaluate the effects of OCA on insulin sensitivity in patients with nonalcoholic fatty liver disease and type 2 diabetes mellitus. Patients were randomly assigned to groups given placebo (n = 23), 25 mg OCA (n = 20), or 50 mg OCA (n = 21) once daily for 6 weeks. A 2-stage hyperinsulinemic-euglycemic insulin clamp was used to measure insulin sensitivity before and after the 6-week treatment period. We also measured levels of liver enzymes, lipid analytes, fibroblast growth factor 19, 7α-hydroxy-4-cholesten-3-one (a BA precursor), endogenous bile acids, and markers of liver fibrosis.

RESULTS

When patients were given a low-dose insulin infusion, insulin sensitivity increased by 28.0% from baseline in the group treated with 25 mg OCA (P = .019) and 20.1% from baseline in the group treated with 50 mg OCA (P = .060). Insulin sensitivity increased by 24.5% (P = .011) in combined OCA groups, whereas it decreased by 5.5% in the placebo group. A similar pattern was observed in patients given a high-dose insulin infusion. The OCA groups had significant reductions in levels of γ-glutamyltransferase and alanine aminotransferase and dose-related weight loss. They also had increased serum levels of low-density lipoprotein cholesterol and fibroblast growth factor 19, associated with decreased levels of 7α-hydroxy-4-cholesten-3-one and endogenous bile acids, indicating activation of farnesoid X receptor. Markers of liver fibrosis decreased significantly in the group treated with 25 mg OCA. Adverse experiences were similar among groups.

CONCLUSIONS

In this phase 2 trial, administration of 25 or 50 mg OCA for 6 weeks was well tolerated, increased insulin sensitivity, and reduced markers of liver inflammation and fibrosis in patients with type 2 diabetes mellitus and nonalcoholic fatty liver disease. Longer and larger studies are warranted. ClinicalTrials.gov, Number: NCT00501592.

Bile acid receptors in non-alcoholic fatty liver disease

Accumulating data have shown that bile acids are important cell signaling molecules, which may activate several signaling pathways to regulate biological processes. Bile acids are endogenous ligands for the farnesoid X receptor (FXR) and TGR5, a G-protein coupled receptor. Gain- and loss-of-function studies have demonstrated that both FXR and TGR5 play important roles in regulating lipid and carbohydrate metabolism and inflammatory responses. Importantly, activation of FXR or TGR5 lowers hepatic triglyceride levels and inhibits inflammation. Such properties of FXR or TGR5 have indicated that these two bile acid receptors are ideal targets for treatment of non-alcoholic fatty liver disease, one of the major health concerns worldwide. In this article, we will focus on recent advances on the role of both FXR and TGR5 in regulating hepatic triglyceride metabolism and inflammatory responses under normal and disease conditions.

Farnesoid X receptor activation increases cholesteryl ester transfer protein expression in humans and transgenic mice

Cholesteryl ester transfer protein (CETP) activity results in a proatherogenic lipoprotein profile. In cholestatic conditions, farnesoid X receptor (FXR) signaling by bile acids (BA) is activated and plasma HDL cholesterol (HDL-C) levels are low. This study tested the hypothesis that FXR-mediated induction of CETP contributes to this phenotype. Patients with cholestasis and high plasma BA had lower HDL-C levels and higher plasma CETP activity and mass compared with matched controls with low plasma BA (each P < 0.01). BA feeding in APOE3*Leiden transgenic mice expressing the human CETP transgene controlled by its endogenous promoter increased cholesterol within apoB-containing lipoproteins and decreased HDL-C (each P < 0.01), while hepatic CETP mRNA expression and plasma CETP activity and mass increased (each P < 0.01). In vitro studies confirmed that FXR agonists substantially augmented CETP mRNA expression in hepatocytes and macrophages dependent on functional FXR expression (each P < 0.001). These transcriptional effects are likely mediated by an ER8 FXR response element (FXRE) in the first intron. In conclusion, using a translational approach, this study identifies CETP as novel FXR target gene. By increasing CETP expression, FXR activation leads to a proatherogenic lipoprotein profile. These results have clinical relevance, especially when considering FXR agonists as emerging treatment strategy for metabolic disease and atherosclerosis.

Nuclear Receptors in atherosclerosis: a superfamily with many 'Goodfellas'

Nuclear Receptors form a superfamily of 48 transcription factors that exhibit a plethora of functions in steroid hormone signaling, regulation of metabolism, circadian rhythm and cellular differentiation. In this review, we describe our current knowledge on the role of Nuclear Receptors in atherosclerosis, which is a multifactorial disease of the vessel wall. Various cell types are involved in this chronic inflammatory pathology in which multiple cellular processes and numerous genes are dysregulated. Systemic risk factors for atherosclerosis are among others adverse blood lipid profiles, enhanced circulating cytokine levels, as well as increased blood pressure. Since many Nuclear Receptors modulate lipid profiles or regulate blood pressure they indirectly affect atherosclerosis. In the present review, we focus on the functional involvement of Nuclear Receptors within the atherosclerotic vessel wall, more specifically on their modulation of cellular functions in endothelial cells, smooth muscle cells and macrophages. Collectively, this overview shows that most of the Nuclear Receptors are athero-protective in atherosclerotic lesions.

MicroRNA-144 regulates hepatic ATP binding cassette transporter A1 and plasma high-density lipoprotein after activation of the nuclear receptor farnesoid X receptor

RATIONALE

The bile acid receptor farnesoid X receptor (FXR) regulates many aspects of lipid metabolism by variouscomplex and incompletely understood molecular mechanisms. We set out to investigate the molecular mechanisms for FXR-dependent regulation of lipid and lipoprotein metabolism.

OBJECTIVE

To identify FXR-regulated microRNAs that were subsequently involved in regulating lipid metabolism.

METHODS AND RESULTS

ATP binding cassette transporter A1 (ABCA1) is a major determinant of plasma high-density lipoprotein (HDL)-cholesterol levels. Here, we show that activation of the nuclear receptor FXR in vivo increases hepatic levels of miR-144, which in turn lowers hepatic ABCA1 and plasma HDL levels. We identified 2 complementary sequences to miR-144 in the 3' untranslated region of ABCA1 mRNA that are necessary for miR-144-dependent regulation. Overexpression of miR-144 in vitro decreased both cellular ABCA1 protein and cholesterol efflux to lipid-poor apolipoprotein A-I protein, whereas overexpression in vivo reduced hepatic ABCA1 protein and plasma HDL-cholesterol. Conversely, silencing miR-144 in mice increased hepatic ABCA1 protein and HDL-cholesterol. In addition, we used tissue-specific FXR-deficient mice to show that induction of miR-144 and FXR-dependent hypolipidemia requires hepatic, but not intestinal, FXR. Finally, we identified functional FXR response elements upstream of the miR-144 locus, consistent with direct FXR regulation.

CONCLUSIONS

We have identified a novel pathway involving FXR, miR-144, and ABCA1 that together regulate plasma HDL-cholesterol.

Trimethylamine-N-oxide, a metabolite associated with atherosclerosis, exhibits complex genetic and dietary regulation

Circulating trimethylamine-N-oxide (TMAO) levels are strongly associated with atherosclerosis. We now examine genetic, dietary, and hormonal factors regulating TMAO levels. We demonstrate that two flavin mono-oxygenase family members, FMO1 and FMO3, oxidize trimethylamine (TMA), derived from gut flora metabolism of choline, to TMAO. Further, we show that FMO3 exhibits 10-fold higher specific activity than FMO1. FMO3 overexpression in mice significantly increases plasma TMAO levels while silencing FMO3 decreases TMAO levels. In both humans and mice, hepatic FMO3 expression is reduced in males compared to females. In mice, this reduction in FMO3 expression is due primarily to downregulation by androgens. FMO3 expression is induced by dietary bile acids by a mechanism that involves the farnesoid X receptor (FXR), a bile acid-activated nuclear receptor. Analysis of natural genetic variation among inbred strains of mice indicates that FMO3 and TMAO are significantly correlated, and TMAO levels explain 11% of the variation in atherosclerosis.

Loss of small heterodimer partner protects against atherosclerosis in apolipoprotein E-deficient mice

Small heterodimer partner (SHP) is involved in bile, lipid, and glucose metabolism. The aim of this study was to investigate the effect of SHP on the development of atherosclerosis. Apolipoprotein E knockout (ApoE-/-) mice were crossed with SHP knockout (SHP-/-) mice to generate double knockout (ApoE-/-SHP-/-) mice. ApoE-/- and ApoE-/-SHP-/- male mice were fed a western diet for 20 weeks. Body weight in ApoE-/-SHP-/) mice was significantly lower than that in ApoE-/- mice (37±1 g vs. 42±1 g, p<0.01). Loss of SHP in ApoE-/- mice decreased the size of adipocytes in white adipose tissue and reduced lipid accumulation in the liver. Glucose intolerance was improved in ApoE-/-SHP-/- mice as compared with ApoE-/- mice (p<0.01). There was no statistical difference in non-high density lipoprotein cholesterol levels between ApoE-/-SHP-/- mice and ApoE-/- mice despite an increase of cholesterol 7α-hydroxylase expression in the liver. The proportion of atherosclerotic lesions in the aorta was significantly lower in ApoE-/-SHP-/- mice than in ApoE-/- mice (2.8±2.0% vs. 9.1±1.9%, p<0.01). In conclusion, loss of SHP function can prevent atherosclerosis, and resistance to diet-induced obesity is the primary factor contributing to this protective effect.

Synthetic farnesoid X receptor agonists induce high-density lipoprotein-mediated transhepatic cholesterol efflux in mice and monkeys and prevent atherosclerosis in cholesteryl ester transfer protein transgenic low-density lipoprotein receptor (-/-) mice

Farnesoid X receptor (FXR), a bile acid-activated nuclear hormone receptor, plays an important role in the regulation of cholesterol and more specifically high-density lipoprotein (HDL) homeostasis. Activation of FXR is reported to lead to both pro- and anti-atherosclerotic effects. In the present study we analyzed the impact of different FXR agonists on cholesterol homeostasis, plasma lipoprotein profiles, and transhepatic cholesterol efflux in C57BL/6J mice and cynomolgus monkeys and atherosclerosis development in cholesteryl ester transfer protein transgenic (CETPtg) low-density lipoprotein receptor (LDLR) (-/-) mice. In C57BL/6J mice on a high-fat diet the synthetic FXR agonists isopropyl 3-(3,4-difluorobenzoyl)-1,1-dimethyl-1,2,3,6-tetrahydroazepino[4,5-b]indole-5-carboxylate (FXR-450) and 4-[2-[2-chloro-4-[[5-cyclopropyl-3-(2,6-dichlorophenyl)-4-isoxazolyl]methoxy]phenyl]cyclopropyl]benzoic acid (PX20606) demonstrated potent plasma cholesterol-lowering activity that affected all lipoprotein species, whereas 3-[2-[2-chloro-4-[[3-(2,6-dichlorophenyl)-5-(1-methylethyl)-4-isoxazolyl]methoxy]phenyl]ethenyl]benzoic acid (GW4064) and 6-ethyl chenodeoxycholic acid (6-ECDCA) showed only limited effects. In FXR wild-type mice, but not FXR(-/-) mice, the more efficacious FXR agonists increased fecal cholesterol excretion and reduced intestinal cholesterol (re)uptake. In CETPtg-LDLR(-/-) mice PX20606 potently lowered total cholesterol and, despite the observed HDL cholesterol (HDLc) reduction, caused a highly significant decrease in atherosclerotic plaque size. In normolipidemic cynomolgus monkeys PX20606 and 6-ECDCA both reduced total cholesterol, and PX20606 specifically lowered HDL(2c) but not HDL(3c) or apolipoprotein A1. That pharmacological FXR activation specifically affects this cholesterol-rich HDL(2) subclass is a new and highly interesting finding and sheds new light on FXR-dependent HDLc lowering, which has been perceived as a major limitation for the clinical development of FXR agonists.

Farnesoid X receptor: from medicinal chemistry to clinical applications

The farnesoid X receptor (FXR) is a bile sensor that acts in coordination with other nuclear receptors to regulate essential steps in bile acid uptake, metabolism and excretion. In addition, FXR is an ancillary receptor involved in lipid and glucose homeostasis. Steroidal and non-steroidal FXR ligands are currently available. Both groups have shown limitations in the preclinical studies regarding absorption, metabolism, specificity of target and intrinsic toxicity. FXR ligands endowed with agonistic activity are under development for the treatment of cholestatic liver diseases, including primary biliary cirrhosis and metabolic disorders linked to insulin resistance. Despite the fact that results from preclinical models are encouraging, targeting FXR holds potential for side effects (i.e., impaired cholesterol disposal and cholestasis). Thus, results from FXR gene-ablated mice and mice administered an FXR antagonist support a role for FXR antagonists or modulators (i.e., FXR agonists that selectively activate specific subsets of FXR target genes in a tissue) or co-regulator-specific manner.

Medicinal chemistry of farnesoid X receptor ligands: from agonists and antagonists to modulators

The nuclear receptor farnesoid X receptor (FXR) has emerged as a highly promising target in preclinical development in recent years. A significant amount of research has been conducted and, although none has reached clinical use, many synthetic ligands of FXR have been described. This review outlines the available knowledge regarding the medicinal chemistry and SAR of these FXR ligands, and discusses the molecular interactions of the compounds with the FXR ligand-binding domain by interpreting the existing co-crystal structures.

Bile acid receptors as targets for the treatment of dyslipidemia and cardiovascular disease

Dyslipidemia is an important risk factor for cardiovascular disease (CVD) and atherosclerosis. When dyslipidemia coincides with other metabolic disorders such as obesity, hypertension, and glucose intolerance, defined as the metabolic syndrome (MS), individuals present an elevated risk to develop type 2 diabetes (T2D) as well as CVD. Because the MS epidemic represents a growing public health problem worldwide, the development of therapies remains a major challenge. Alterations of bile acid pool regulation in T2D have revealed a link between bile acid and metabolic homeostasis. The bile acid receptors farnesoid X receptor (FXR) and TGR5 both regulate lipid, glucose, and energy metabolism, rendering them potential pharmacological targets for MS therapy. This review discusses the mechanisms of metabolic regulation by FXR and TGR5 and the utility relevance of natural and synthetic modulators of FXR and TGR5 activity, including bile acid sequestrants, in the treatment of the MS.

The role of nuclear receptors in the kidney in obesity and metabolic syndrome

Nuclear receptors are ligand-activated transcriptional regulators of several key aspects of renal physiology and pathophysiology. As such, nuclear receptors control a large variety of metabolic processes, including kidney lipid metabolism, drug clearance, inflammation, fibrosis, cell differentiation, and oxidative stress. Derangement of nuclear receptor regulation, that is, mainly due to obesity may induce metabolic syndrome, may contribute to the pathogenesis and progression of chronic renal disease and may result in end-stage renal disease. This places nuclear receptors at the forefront of novel therapeutic approaches for a broad range of kidney disorders and diseases, including glomerulosclerosis, tubulointerstitial disease, renal lipotoxicity, kidney fibrosis, and hypertension. This review focuses on the importance of the transcription factors peroxisome proliferator-activated receptor alpha, peroxisome proliferator-activated receptor beta, peroxisome proliferator-activated receptor gamma, liver X receptors, farnesoid X receptor, and the pregnane X receptor/steroid and xenobiotic receptor (PXR) on the physiology and pathophysiology of renal diseases associated with obesity and metabolic syndrome.

The farnesoid X receptor -1G>T polymorphism influences the lipid response to rosuvastatin

The bile acid-activated nuclear receptor farnesoid X receptor (FXR) plays an important role in lipid and glucose metabolism, and in addition, it regulates multiple drug transporters involved in statin disposition. We examined whether a functional single nucleotide polymorphism (SNP) in FXR (-1G>T) influenced the lipid-lowering effect of rosuvastatin. In 385 Chinese patients with hyperlipidemia who had been treated with rosuvastatin 10 mg daily for at least 4 weeks, the association between the FXR -1G>T SNP and lipid response to rosuvastatin was analyzed. The FXR -1G>T SNP was not associated with baseline lipids but was significantly associated with the LDL cholesterol (LDL-C) and total cholesterol response to rosuvastatin. Carriers of the T-variant allele (GT+TT = 68+3) had 4.4% (95% CI: 1.2, 7.5%, P = 0.006) and 2.6% (95% CI: 0.3, 5.0%; P < 0.05) greater reductions in LDL-C and total cholesterol, respectively, compared with those with homozygous wild-type alleles. The association between the FXR polymorphism and the LDL-C response to rosuvastatin remained significant after adjusting for other covariants. This association of the variant allele of the FXR -1G>T polymorphism with a greater LDL-C response to rosuvastatin may suggest that this polymorphism influences the expression of the hepatic efflux transporters involved in biliary excretion of rosuvastatin.

Farnesoid X receptor induces murine scavenger receptor Class B type I via intron binding

Farnesoid X receptor (FXR) is a nuclear receptor and a key regulator of liver cholesterol and triglyceride homeostasis. Scavenger receptor class B type I (SR-BI) is critical for reverse cholesterol transport (RCT) by transporting high-density lipoprotein (HDL) into liver. FXR induces SR-BI, however, the underlying molecular mechanism of this induction is not known. The current study confirmed induction of SR-BI mRNA by activated FXR in mouse livers, a human hepatoma cell line, and primary human hepatocytes. Genome-wide FXR binding analysis in mouse livers identified 4 putative FXR response elements in the form of inverse repeat separated by one nucleotide (IR1) at the first intron and 1 IR1 at the downstream of the mouse Sr-bi gene. ChIP-qPCR analysis revealed FXR binding to only the intronic IR1s, but not the downstream one. Luciferase assays and site-directed mutagenesis further showed that 3 out of 4 IR1s were able to activate gene transcription. A 16-week high-fat diet (HFD) feeding in mice increased hepatic Sr-bi gene expression in a FXR-dependent manner. In addition, FXR bound to the 3 bona fide IR1s in vivo, which was increased following HFD feeding. Serum total and HDL cholesterol levels were increased in FXR knockout mice fed the HFD, compared to wild-type mice. In conclusion, the Sr-bi/SR-BI gene is confirmed as a FXR target gene in both mice and humans, and at least in mice, induction of Sr-bi by FXR is via binding to intronic IR1s. This study suggests that FXR may serve as a promising molecular target for increasing reverse cholesterol transport.

Transcriptional integration of metabolism by the nuclear sterol-activated receptors LXR and FXR

Nuclear receptors are integrators of hormonal and nutritional signals, mediating changes to metabolic pathways within the body. Given that modulation of lipid and glucose metabolism has been linked to diseases including type 2 diabetes, obesity and atherosclerosis, a greater understanding of pathways that regulate metabolism in physiology and disease is crucial. The liver X receptors (LXRs) and the farnesoid X receptors (FXRs) are activated by oxysterols and bile acids, respectively. Mounting evidence indicates that these nuclear receptors have essential roles, not only in the regulation of cholesterol and bile acid metabolism but also in the integration of sterol, fatty acid and glucose metabolism.

Loss of FXR protects against diet-induced obesity and accelerates liver carcinogenesis in ob/ob mice

Farnesoid X receptor (FXR) is known to play important regulatory roles in bile acid, lipid, and carbohydrate metabolism. Aged (>12 months old) Fxr(-/-) mice also develop spontaneous liver carcinomas. In this report, we used three mouse models to investigate the role of FXR deficiency in obesity. As compared with low-density lipoprotein receptor (Ldlr) knockout (Ldlr(-/-)) mice, the Ldlr(-/-)Fxr(-/-) double-knockout mice were highly resistant to diet-induced obesity, which was associated with increased expression of genes involved in energy metabolism in the skeletal muscle and brown adipose tissue. Such a striking effect of FXR deficiency on obesity on an Ldlr(-/-) background led us to investigate whether FXR deficiency alone is sufficient to affect obesity. As compared with wild-type mice, Fxr(-/-) mice showed resistance to diet-induced weight gain. Interestingly, only female Fxr(-/-) mice showed significant resistance to diet-induced obesity, which was accompanied by increased energy expenditure in these mice. Finally, we determined the effect of FXR deficiency on obesity in a genetically obese and diabetic mouse model. We generated ob(-/-)Fxr(-/-) mice that were deficient in both Leptin and Fxr. On a chow diet, ob(-/-)Fxr(-/-) mice gained less body weight and had reduced body fat mass as compared with ob/ob mice. In addition, we observed liver carcinomas in 43% of young (<11 months old) Ob(-/-)Fxr(-/-) mice. Together these data indicate that loss of FXR prevents diet-induced or genetic obesity and accelerates liver carcinogenesis under diabetic conditions.

Sex differences in lipid metabolism and metabolic disease risk

The ability of nutrients to regulate specific metabolic pathways is often overshadowed by their role in basic sustenance. Consequently, the mechanisms whereby these nutrients protect against or promote a variety of acquired metabolic syndromes remains poorly understood. Premenopausal women are generally protected from the adverse effects of obesity despite having a greater proportion of body fat than men. Menopause is often associated with a transformation in body fat morphology and a gradual increase in the susceptibility to metabolic complications, eventually reaching the point where women and men are at equal risk. These phenomena are not explained solely by changes in food preference or nutrient intake suggesting an important role for the sex hormones in regulating the metabolic fate of nutrients and protecting against metabolic disease pathophysiology. Here, we discuss how differences in the acquisition, trafficking, and subceullular metabolism of fats and other lipid soluble nutrients in major organ systems can create overt sex-specific phenotypes, modulate metabolic disease risk, and contribute to the rise in obesity in the modern sedentary climate. Identifying the molecular mechanisms underpinning sex differences in fat metabolism requires the unravelling of the interactions among sex chromosome effects, the hormonal milieu, and diet composition. Understanding the mechanisms that give rise to sex differences in metabolism will help to rationalize treatment strategies for the management of sex-specific metabolic disease risk factors.

Non-alcoholic Fatty liver disease: the bile Acid-activated farnesoid x receptor as an emerging treatment target

Non-alcoholic fatty liver disease (NAFLD) is currently evolving as the most common liver disease worldwide. It may progress to liver cirrhosis and liver cancer and is poised to represent the most common indication for liver transplantation in the near future. The pathogenesis of NAFLD is multifactorial and not fully understood, but it represents an insulin resistance state characterized by a cluster of cardiovascular risk factors including obesity, dyslipidemia, hyperglycemia, and hypertension. Importantly, NAFLD also has evolved as independent risk factor for cardiovascular disease. Unfortunately thus far no established treatment does exist for NAFLD. The bile acid-activated nuclear farnesoid X receptor (FXR) has been shown to play a role not only in bile acid but also in lipid and glucose homeostasis. Specific targeting of FXR may be an elegant and very effective way to readjust dysregulated nuclear receptor-mediated metabolic pathways. This review discusses the body's complex response to the activation of FXR with its beneficial actions but also potential undesirable side effects.

Bile Acid signaling in liver metabolism and diseases

Obesity, diabetes, and metabolic syndromes are increasingly recognized as health concerns worldwide. Overnutrition and insulin resistance are the major causes of diabetic hyperglycemia and hyperlipidemia in humans. Studies in the past decade provide evidence that bile acids are not just biological detergents facilitating gut nutrient absorption, but also important metabolic regulators of glucose and lipid homeostasis. Pharmacological alteration of bile acid metabolism or bile acid signaling pathways such as using bile acid receptor agonists or bile acid binding resins may be a promising therapeutic strategy for the treatment of obesity and diabetes. On the other hand, bile acid signaling is complex, and the molecular mechanisms mediating the bile acid effects are still not completely understood. This paper will summarize recent advances in our understanding of bile acid signaling in regulation of glucose and lipid metabolism, and the potentials of developing novel therapeutic strategies that target bile acid metabolism for the treatment of metabolic disorders.

APOE and FABP2 Polymorphisms and History of Myocardial Infarction, Stroke, Diabetes, and Gallbladder Disease

Dysfunctional lipid metabolism plays a central role in pathogenesis of major chronic diseases, and genetic factors are important determinants of individual lipid profiles. We analyzed the associations of two well-established functional polymorphisms (FABP2 A54T and APOE isoforms) with past and family histories of 1492 population samples. FABP2-T54 allele was associated with an increased risk of past history of myocardial infarction (odds ratio (OR) = 1.51). Likewise, the subjects with APOE4, compared with E2 and E3, had a significantly increased risk of past history myocardial infarction (OR = 1.89). The OR associated with APOE4 was specifically increased in women for past history of myocardial infarction but decreased for gallstone disease. Interactions between gender and APOE isoforms were also significant or marginally significant for these two conditions. FABP2-T54 allele may be a potential genetic marker for myocardial infarction, and APOE4 may exert sex-dependent effects on myocardial infarction and gallbladder disease.

FXR an emerging therapeutic target for the treatment of atherosclerosis

Atherosclerosis is the leading cause of illness and death. Therapeutic strategies aimed at reducing cholesterol plasma levels have shown efficacy in either reducing progression of atherosclerotic plaques and atherosclerosis-related mortality. The farnesoid-X-receptor (FXR) is a member of metabolic nuclear receptors (NRs) superfamily activated by bile acids. In entero-hepatic tissues, FXR functions as a bile acid sensor regulating bile acid synthesis, detoxification and excretion. In the liver FXR induces the expression of an atypical NR, the small heterodimer partner, which subsequently inhibits the activity of hepatocyte nuclear factor 4α repressing the transcription of cholesterol 7a-hydroxylase, the critical regulatory gene in bile acid synthesis. In the intestine FXR induces the release of fibroblast growth factor 15 (FGF15) (or FGF19 in human), which activates hepatic FGF receptor 4 (FGFR4) signalling to inhibit bile acid synthesis. In rodents, FXR activation decreases bile acid synthesis and lipogenesis and increases lipoprotein clearance, and regulates glucose homeostasis by reducing liver gluconeogenesis. FXR exerts counter-regulatory effects on macrophages, vascular smooth muscle cells and endothelial cells. FXR deficiency in mice results in a pro-atherogenetic lipoproteins profile and insulin resistance but FXR^−/– mice fail to develop any detectable plaques on high-fat diet. Synthetic FXR agonists protect against development of aortic plaques formation in murine models characterized by pro-atherogenetic lipoprotein profile and accelerated atherosclerosis, but reduce HDL levels. Because human and mouse lipoprotein metabolism is modulated by different regulatory pathways the potential drawbacks of FXR ligands on HDL and bile acid synthesis need to addressed in relevant clinical settings.

Aldo-keto reductase 1B7 is a target gene of FXR and regulates lipid and glucose homeostasis

Aldo-keto reductase 1B7 (AKR1B7) is proposed to play a role in detoxification of by-products of lipid peroxidation. In this article, we show that activation of the nuclear receptor farnesoid X receptor (FXR) induces AKR1B7 expression in the liver and intestine, and reduces the levels of malondialdehyde (MDA), the end product of lipid peroxidation, in the intestine but not in the liver. To determine whether AKR1B7 regulates MDA levels in vivo, we overexpressed AKR1B7 in the liver. Overexpression of AKR1B7 in the liver had no effect on hepatic or plasma MDA levels. Interestingly, hepatic expression of AKR1B7 significantly lowered plasma glucose levels in both wild-type and diabetic db/db mice, which was associated with reduced hepatic gluconeogenesis. Hepatic expression of AKR1B7 also significantly lowered hepatic triglyceride and cholesterol levels in db/db mice. These data reveal a novel function for AKR1B7 in lipid and glucose metabolism and suggest that AKR1B7 may not play a role in detoxification of lipid peroxides in the liver. AKR1B7 may be a therapeutic target for treatment of fatty liver disease associated with diabetes mellitus.

Nuclear receptors in renal disease

Diabetes is the leading cause of end-stage renal disease in developed countries. In spite of excellent glucose and blood pressure control, including administration of angiotensin converting enzyme inhibitors and/or angiotensin II receptor blockers, diabetic nephropathy still develops and progresses. The development of additional protective therapeutic interventions is, therefore, a major priority. Nuclear hormone receptors regulate carbohydrate metabolism, lipid metabolism, the immune response, and inflammation. These receptors also modulate the development of fibrosis. As a result of their diverse biological effects, nuclear hormone receptors have become major pharmaceutical targets for the treatment of metabolic diseases. The increasing prevalence of diabetic nephropathy has led intense investigation into the role that nuclear hormone receptors may have in slowing or preventing the progression of renal disease. This role of nuclear hormone receptors would be associated with improvements in metabolism, the immune response, and inflammation. Several nuclear receptor activating ligands (agonists) have been shown to have a renal protective effect in the context of diabetic nephropathy. This review will discuss the evidence regarding the beneficial effects of the activation of several nuclear, especially the vitamin D receptor (VDR), farnesoid X receptor (FXR), and peroxisome-proliferator-associated receptors (PPARs) in preventing the progression of diabetic nephropathy and describe how the discovery and development of compounds that modulate the activity of nuclear hormone receptors may provide potential additional therapeutic approaches in the management of diabetic nephropathy. This article is part of a Special Issue entitled: Translating nuclear receptors from health to disease.

Molecular mechanisms of drug transporter regulation

Interindividual differences in drug transporter expression can result in variability in drug response. This variation in gene expression is determined, in part, by the actions of nuclear hormone receptors that act as xenobiotic- and endobiotic-sensing transcription factors. Among the ligand-activated nuclear receptors, signaling through the pregnane X receptor (PXR), constitutive androstane receptor (CAR), farnesoid X receptor (FXR), and vitamin D receptor (VDR) constitute major pathways regulating drug transporter expression in tissues. Hence, these endobiotic- and xenobiotic-sensing nuclear receptors are intrinsically involved in environmental influences of drug response. Moreover, because nuclear receptor genes are polymorphic, these transcription factors are also thought to contribute to heritability of variable drug action. In this chapter, the molecular aspects of drug transporter gene regulation by ligand-activated nuclear receptors will be reviewed including their clinical relevance.

Tuberatolides, potent FXR antagonists from the Korean marine tunicate Botryllus tuberatus

One isoprenoid, tuberatolide A (1), meroterpenoids tuberatolide B (2) and 2'-epi-tuberatolide B (3), and the known meroterpenoids yezoquinolide (4), (R)-sargachromenol (5), and (S)-sargachromenol (6) were isolated from the Korean marine tunicate Botryllus tuberatus. The structures of these compounds were elucidated by NMR, MS, and CD spectroscopic analyses. These terpenoids antagonized the chenodeoxycholic acid (CDCA)-activated human farnesoid X receptor (hFXR) in a cell-based co-transfection assay with IC(50) values as low as 1.5 μM without significant effect on steroid receptors. Furthermore, they released the co-activator peptide from the CDCA-bound hFXR ligand binding domain in cell-free surface plasmon resonance experiments.

The bile acid sensor FXR protects against dyslipidemia and aortic plaques development induced by the HIV protease inhibitor ritonavir in mice

BACKGROUND

Although human immunodeficiency virus (HIV)-related morbidity and mortality rates in patients treated with a combination of high active antiretroviral therapy (HAART) have declined, significant metabolic/vascular adverse effects associated with the long term use of HIV protease inhibitors (PIs) have emerged as a significant side effect. Here we illustrate that targeting the bile acid sensor farnesoid X receptor (FXR) protects against dyslipidemia and vascular injury induced HIV-PIs in rodents.

METHODOLOGY/PRINCIPAL FINDINGS

Administration of the HIV PI ritonavir to wild type mice increased plasma triacylglycerols and cholesterol levels and this effect was exacerbated by dosing ritonavir to mice harbouring a disrupted FXR. Dyslipidemia induced by ritonavir associated with a shift in the liver expression of signature genes, Sterol Regulatory Element-Binding Protein (SREBP)-1 and fatty acid synthase. Treating wild type mice with the FXR agonist (chenodeoxycholic acid, CDCA) protected against development of dyslipidemia induced by ritonavir. Administration of ritonavir to ApoE(-/-) mice, a strain that develop spontaneously atherosclerosis, increased the extent of aortic plaques without worsening the dyslipidemia. Treating these mice with CDCA reduced the extent of aortic plaques by 70% without changing plasma lipoproteins or the liver expression of signature genes. A beneficial effect on aortic plaques was also obtained by treating ApoE(-/-) mice with gemfibrozil, a PPARα agonist. FXR activation counter-regulated induction of expression/activity of CD36 caused by HIV-PIs in circulating monocytes and aortic plaques. In macrophages cell lines, CDCA attenuated CD36 induction and uptake of acetylated LDL caused by ritonavir. Natural and synthetic FXR ligands reduced the nuclear translocation of SREBP1c caused by ritonavir.

CONCLUSIONS/SIGNIFICANCE

Activation of the bile acid sensor FXR protects against dyslipidemia and atherosclerotic caused by ritonavir, a widely used HIV PI. From a mechanistic stand point it appears that besides reducing the liver expression of genes involved in fatty acid synthesis, FXR activation counter-regulates the expression/activity of CD36 on monocytes. FXR ligands might hold promise in the treatment dyslipidemia induced by ritonavir.

A role of the bile salt receptor FXR in atherosclerosis

This study reviews current insights into the role of bile salts and bile salt receptors on the progression and regression of atherosclerosis. Bile salts have emerged as important modifiers of lipid and energy metabolism. At the molecular level, bile salts regulate lipid and energy homeostasis mainly via the bile salt receptors FXR and TGR5. Activation of FXR has been shown to improve plasma lipid profiles, whereas Fxr(-/-) mice have increased plasma triglyceride and very-low-density lipoprotein levels. Nevertheless, high-density lipoprotein cholesterol levels are increased in these mice, suggesting that FXR has both anti- and proatherosclerotic properties. Interestingly, there is increasing evidence for a role of FXR in "nonclassical" bile salt target tissues, eg, vasculature and macrophages. In these tissues, FXR has been shown to influence vascular tension and regulate the unloading of cholesterol from foam cells, respectively. Recent publications have provided insight into the antiinflammatory properties of FXR in atherosclerosis. Bile salt signaling via TGR5 might regulate energy homeostasis, which could serve as an attractive target to increase energy expenditure and weight loss. Interventions aiming to increase cholesterol turnover (eg, by bile salt sequestration) significantly improve plasma lipid profiles and diminish atherosclerosis in animal models. Bile salt metabolism and bile salt signaling pathways represent attractive therapeutic targets for the treatment of atherosclerosis.

Functional characterization of the semisynthetic bile acid derivative INT-767, a dual farnesoid X receptor and TGR5 agonist

Two dedicated receptors for bile acids (BAs) have been identified, the nuclear hormone receptor farnesoid X receptor (FXR) and the G protein-coupled receptor TGR5, which represent attractive targets for the treatment of metabolic and chronic liver diseases. Previous work characterized 6α-ethyl-3α,7α-dihydroxy-5β-cholan-24-oic acid (INT-747), a potent and selective FXR agonist, as well as 6α-ethyl-23(S)-methyl-3α,7α,12α-trihydroxy-5β-cholan-24-oic acid (INT-777), a potent and selective TGR5 agonist. Here we characterize 6α-ethyl-3α,7α,23-trihydroxy-24-nor-5β-cholan-23-sulfate sodium salt (INT-767), a novel semisynthetic 23-sulfate derivative of INT-747. INT-767 is a potent agonist for both FXR (mean EC(50), 30 nM by PerkinElmer AlphaScreen assay) and TGR5 (mean EC(50), 630 nM by time resolved-fluorescence resonance energy transfer), the first compound described so far to potently and selectively activate both BA receptors. INT-767 does not show cytotoxic effects in HepG2 cells, does not inhibit cytochrome P450 enzymes, is highly stable to phase I and II enzymatic modifications, and does not inhibit the human ether-a-go-go-related gene potassium channel. In line with its dual activity, INT-767 induces FXR-dependent lipid uptake by adipocytes, with the beneficial effect of shuttling lipids from central hepatic to peripheral fat storage, and promotes TGR5-dependent glucagon-like peptide-1 secretion by enteroendocrine cells, a validated target in the treatment of type 2 diabetes. Moreover, INT-767 treatment markedly decreases cholesterol and triglyceride levels in diabetic db/db mice and in mice rendered diabetic by streptozotocin administration. Collectively, these preclinical results indicate that INT-767 is a safe and effective modulator of FXR and TGR5-dependent pathways, suggesting potential clinical applications in the treatment of liver and metabolic diseases.