t0901317 and Fatty-Liver

Protective effect of omega-3 polyunsaturated fatty acids (n-3 PUFA) on non-alcoholic fatty liver disease has been demonstrated. FFA4 (also known as GPR120; a G protein-coupled receptor) has been suggested to be a target of n-3 PUFA. FFA4 expression in hepatocytes has also been reported from liver biopsies in child fatty liver patients. In order to assess the functional role of FFA4 in hepatic steatosis, we used an in vitro model of liver X receptor (LXR)-mediated hepatocellular steatosis. FFA4 expression was confirmed in Hep3B and HepG2 human hepatoma cells. T0901317 (a specific LXR activator) induced lipid accumulation and docosahexaenoic acid (DHA; a representative n-3 PUFA) inhibited lipid accumulation. This DHA-induced inhibition was blunted by treatment of AH7614 (a FFA4 antagonist) and by transfection of FFA4 siRNA. SREBP-1c (a key transcription factor of lipogenesis) was induced by treatment with T0901317, and SREBP-1c induction was also inhibited by DHA at mRNA and protein levels. DHA-induced suppression of SREBP-1c expression was also blunted by FFA4-knockdown. Furthermore, DHA inhibited T0901317-induced lipid accumulation in primary hepatocytes from wild type mice, but not in those from FFA4 deficient mice. In addition, DHA-induced activations of G

Topics: AMP-Activated Protein Kinases; Animals; Calcium-Calmodulin-Dependent Protein Kinase Kinase; Carcinoma, Hepatocellular; Docosahexaenoic Acids; Fatty Liver; Gene Knockdown Techniques; Hep G2 Cells; Humans; Hydrocarbons, Fluorinated; Liver Neoplasms; Mice; Mice, Knockout; Neoplasm Proteins; Receptors, G-Protein-Coupled; Sterol Regulatory Element Binding Protein 1; Sulfonamides

Fat-specific protein 27 (FSP27) is highly expressed in the fatty liver of genetically obese ob/ob mice and promotes hepatic triglyceride (TG) accumulation. The nuclear hormone receptor liver X receptor α (LXRα) also plays a critical role in the control of TG levels in the liver. The present study demonstrated transcriptional regulation of Fsp27a and Fsp27b genes by LXRα. Treatment with the LXR ligand T0901317 markedly increased Fsp27a and Fsp27b mRNAs in wild-type C57BL/6J and ob/ob mouse livers. A reporter assay indicated that two LXR-responsive elements (LXREs) are necessary for LXRα-dependent induction of Fsp27a and Fsp27b promoter activities. Furthermore, the LXRα/retinoid X receptor α complex is capable of directly binding to the two LXREs both in vitro and in vivo. These results suggest that LXRα positively regulates Fsp27a and Fsp27b expression through two functional LXREs. Fsp27a/b are novel LXR target genes in the ob/ob fatty liver.

Topics: Animals; Base Sequence; Exons; Fatty Liver; Gene Expression Regulation; HEK293 Cells; Humans; Hydrocarbons, Fluorinated; Liver; Liver X Receptors; Mice, Inbred C57BL; Mice, Obese; Promoter Regions, Genetic; Protein Binding; Protein Multimerization; Proteins; Response Elements; Sulfonamides

Oxyresveratrol (OXY) is a naturally occurring polyhydroxylated stilbene that is abundant in mulberry wood (Morus alba L.), which has frequently been supplied as a herbal medicine. It has been shown that OXY has regulatory effects on inflammation and oxidative stress, and may have potential in preventing or curing nonalcoholic fatty liver disease (NAFLD). This study examined the effects of OXY on in vitro model of NAFLD in hepatocyte by the liver X receptor α (LXRα)-mediated induction of lipogenic genes and in vivo model in mice along with its molecular mechanism. OXY inhibited the LXRα agonists-mediated sterol regulatory element binding protein-1c (SREBP-1c) induction and expression of the lipogenic genes and upregulated the mRNA of fatty acid β-oxidation-related genes in hepatocytes, which is more potent than genistein and daidzein. OXY also induced AMP-activated protein kinase (AMPK) activation in a time-dependent manner. Moreover, AMPK activation by the OXY treatment helped inhibit SREBP-1c using compound C as an AMPK antagonist. Oral administration of OXY decreased the Oil Red O stained-positive areas significantly, indicating lipid droplets and hepatic steatosis regions, as well as the serum parameters, such as fasting glucose, total cholesterol, and low density lipoprotein-cholesterol in high fat diet fed-mice, as similar with orally treatment of atorvastatin. Overall, this result suggests that OXY has the potency to inhibit hepatic lipogenesis through the AMPK/SREBP-1c pathway and can be used in the development of pharmaceuticals to prevent a fatty liver.

Topics: AMP-Activated Protein Kinase Kinases; AMP-Activated Protein Kinases; Animals; Cell Line, Tumor; Enzyme Activation; Fatty Acids; Fatty Liver; Gene Expression Regulation; Humans; Hydrocarbons, Fluorinated; Lipogenesis; Liver; Liver X Receptors; Male; Mice, Inbred C57BL; Non-alcoholic Fatty Liver Disease; Oxidation-Reduction; Plant Extracts; Protein Serine-Threonine Kinases; Sterol Regulatory Element Binding Protein 1; Stilbenes; Sulfonamides

Lipid dysregulation is a common hepatic adverse outcome after exposure to toxic drugs and chemicals. A donor-free rat hepatocyte-like (B-13/H) cell was therefore examined as an in vitro model for investigating mechanisms. The B-13/H cell irreversibly accumulated triglycerides (steatosis) in a time- and dose-dependent manner when exposed to fatty acids, an effect that was potentiated by the combined addition of hyperglycaemic levels of glucose and insulin. B-13/H cells also expressed the LXR nuclear receptors and exposure to their activators - T0901317 or GW3965 - induced luciferase expression from a transfected LXR-regulated reporter gene construct and steatosis in a dose-dependent manner with T0901317. Exposing B-13/H cells to a variety of cationic amphiphilic drugs - but not other hepatotoxins - also resulted in a time- and dose-dependent accumulation of phospholipids (phospholipidosis), an effect that was reduced by over-expression of lysosomal phospholipase A2. Through application of this model, hepatotoxin methapyrilene exposure was shown to induce phospholipidosis in both B-13 and B-13/H cells in a time- and dose-dependent manner. However, methapyrilene was only toxic to B-13/H cells and inhibitors of hepatotoxicity enhanced phospholipidosis, suggesting phospholipidosis is not a pathway in toxicity for this withdrawn drug. In contrast, pre-existing steatosis had minimal effect on methapyrilene hepatotoxicity in B-13/H cells. These data demonstrate that the donor free B-13 cell system for generating hepatocyte-like cells may be employed in studies of fatty acid- and LXR activator-induced steatosis and phospholipidosis and in the dissection of pathways leading to adverse outcomes such as hepatotoxicity.

Topics: Animals; Benzoates; Benzylamines; Cell Line; Chemical and Drug Induced Liver Injury; Dose-Response Relationship, Drug; Fatty Acids; Fatty Liver; Hepatocytes; Hydrocarbons, Fluorinated; Lipid Metabolism; Liver X Receptors; Methapyrilene; Phospholipids; Rats; Sulfonamides; Time Factors; Triglycerides

Non-alcoholic fatty liver disease is the most commonly occurring chronic liver disease, and hepatic steatosis, a condition defined as extensive lipid accumulation in hepatocytes, is associated with liver dysfunction and metabolic diseases, such as, obesity and type II diabetes. Apelin is an adipokine that acts on a G protein-coupled receptor named APJ, and has been established to play pivotal roles in various physiological conditions. However, the function of apelin in hepatocytes has not been fully investigated. In order to assess the functional roles of apelin and APJ in hepatocytes, we used an in vitro model of liver X receptor (LXR)-mediated hepatocellular steatosis. In Hep3B human hepatoma cells, T0901317 (a specific LXR activator) induced lipid accumulation and this was inhibited by apelin. T0901317 also induced the expression of SREBP-1c, a key transcription factor for lipogenesis. Apelin not only inhibited SREBP-1c induction at the mRNA and protein levels but also induced lipolytic PPARα expression. Furthermore, these protective effects of apelin were inhibited by apelin F13A (a specific APJ antagonist). Furthermore, silencing of APJ by siRNA transfection also inhibited the actions of apelin. Specific inhibitors of cellular signaling components showed inhibition of lipid accumulation by apelin was mediated through G

Topics: AMP-Activated Protein Kinase Kinases; Animals; Apelin; Apelin Receptors; Cell Line, Tumor; Fatty Liver; Female; Hepatocytes; Humans; Hydrocarbons, Fluorinated; Intercellular Signaling Peptides and Proteins; Lipogenesis; Liver X Receptors; Mice; Mice, Inbred BALB C; PPAR alpha; Primary Cell Culture; Protein Kinases; Sterol Regulatory Element Binding Protein 1; Sulfonamides

Gomisin N (GN) is a phytochemical derived from Schisandra chinensis. It has been reported to exert a protective effect against hepatic steatosis by attenuating endoplasmic reticulum (ER) stress. However, the detailed mechanism by which GN inhibits hepatic steatosis remains to be elucidated. In this study, we examined whether GN activates AMP-activated protein kinase (AMPK) and exerts therapeutic effects on liver X receptor (LXR)- or palmitic acid (PA)-induced triglyceride (TG) accumulation in HepG2 cells. Furthermore, in vivo protective effects of GN against hepatic steatosis were assessed in high-fat diet (HFD)-induced obese mice. GN stimulated the phosphorylation of AMPK, acetyl-CoA carboxylase (ACC), and sterol regulatory element-binding protein 1c (SREBP1c) in HepG2 cells. It decreased the expression of lipogenesis genes, but increased the expression of fatty acid oxidation genes. Additionally, GN decreased the expression of lipogenesis genes induced by the LXR agonist T0901317 or PA in HepG2 cells, resulting in reduced intracellular TG content. However, preincubation with compound C, an AMPK inhibitor, prevented GN-mediated effects. Administration of GN to HFD-induced obese mice decreased HFD-induced liver weight, hepatic TG accumulation, and cytoplasmic lipid droplet. These findings demonstrate that GN activates the AMPK pathway and ameliorates HFD-induced hepatic steatosis.

Topics: AMP-Activated Protein Kinase Kinases; Animals; Anti-Inflammatory Agents; Cyclooctanes; Cytoplasm; Fatty Acids; Fatty Liver; Hep G2 Cells; Humans; Hydrocarbons, Fluorinated; Lignans; Lipogenesis; Liver; Liver X Receptors; Male; Mice; Mice, Inbred C57BL; Mice, Obese; Phosphorylation; Phytochemicals; Polycyclic Compounds; Protein Kinases; Sterol Regulatory Element Binding Protein 1; Sulfonamides; Triglycerides

Liver X receptors (LXRs) are transcription factors essential for cholesterol homeostasis and lipogenesis. LXRα has been implicated in regulating hepatic triglyceride (TG) accumulation upon both influx of adipose-derived fatty acids (FAs) during fasting and stimulation of de novo FA synthesis by chemical agonism of LXR. However, whether or not a convergent mechanism is employed to drive deposition of FAs from these 2 different sources in TGs is undetermined. Here, we report that the G0/G1 Switch Gene 2 (G0S2), a selective inhibitor of intracellular TG hydrolysis/lipolysis, is a direct target gene of LXRα. Transcriptional activation is conferred by LXRα binding to a direct repeat 4 (DR4) motif in the G0S2 promoter. While LXRα

Topics: Animals; Arabidopsis Proteins; Cell Cycle Proteins; Cholesterol, HDL; Fasting; Fatty Liver; Hydrocarbons, Fluorinated; Hydrolysis; Hypertriglyceridemia; Lipolysis; Liver; Liver X Receptors; Mice; Mice, Knockout; Repetitive Sequences, Nucleic Acid; Sulfonamides; Triglycerides

Numerous studies have shown that dietary omega-3 polyunsaturated fatty acids (PUFAs), particularly eicosapentaenoic acid (EPA), improve lipid metabolism. The beneficial effects of PUFA-derived oxidation products have been increasingly reported. However, EPA is easily oxidized in food products and in the human body, generating various derivatives of oxidized EPA (oxEPA), such that these oxidation products may partially contribute to EPA's effect. We previously reported that oxEPA was more potent than intact EPA in reducing liver-X-receptor α (LXRα)-induced cellular triacylglycerol (TG) accumulation. However, the in vivo hypolipidemic effects of oxEPA remain unclear. In the present study, we evaluated the effect of oral administration of EPA and oxEPA on hepatic steatosis in mice induced by a high-sucrose diet and a synthetic LXRα agonist, TO-901317. Both EPA and oxEPA reduced TG accumulation in the liver and plasma biomarkers of liver injury. Furthermore, they suppressed the expression of lipogenic genes, but not β-oxidation genes, in a similar pattern as the biomarkers. Our results suggest that oxEPA and intact EPA suppress de novo lipogenesis to ameliorate hepatic steatosis.

Topics: Administration, Oral; Animals; Biomarkers; Dietary Sucrose; Eicosapentaenoic Acid; Fatty Liver; Hydrocarbons, Fluorinated; Hypolipidemic Agents; Lipogenesis; Liver; Liver X Receptors; Male; Mice, Inbred ICR; Oxidation-Reduction; Sulfonamides; Triglycerides

Liver X receptor (LXR) agonists exert potent antiatherosclerotic actions but simultaneously induce excessive triglyceride (TG) accumulation in the liver. To obtain a detailed insight into the underlying mechanism of hepatic TG accumulation, we used a novel computational modeling approach called analysis of dynamic adaptations in parameter trajectories (ADAPT). We revealed that both input and output fluxes to hepatic TG content are considerably induced on LXR activation and that in the early phase of LXR agonism, hepatic steatosis results from only a minor imbalance between the two. It is generally believed that LXR-induced hepatic steatosis results from increased de novo lipogenesis (DNL). In contrast, ADAPT predicted that the hepatic influx of free fatty acids is the major contributor to hepatic TG accumulation in the early phase of LXR activation. Qualitative validation of this prediction showed a 5-fold increase in the contribution of plasma palmitate to hepatic monounsaturated fatty acids on acute LXR activation, whereas DNL was not yet significantly increased. This study illustrates that complex effects of pharmacological intervention can be translated into distinct patterns of metabolic regulation through state-of-the-art mathematical modeling.

Topics: Animals; Atherosclerosis; Computer Simulation; Fatty Acids, Nonesterified; Fatty Liver; Hydrocarbons, Fluorinated; Lipogenesis; Lipoproteins, VLDL; Liver; Liver X Receptors; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Mice, Transgenic; Models, Biological; Orphan Nuclear Receptors; PPAR gamma; Sulfonamides; Systems Biology; Triglycerides

Activation of liver X receptor (LXR) inhibits atherosclerosis but induces hypertriglyceridemia. In vitro, it has been shown that mitogen-activated protein kinase kinase 1/2 (MEK1/2) inhibitor synergizes LXR ligand-induced macrophage ABCA1 expression and cholesterol efflux. In this study, we determined whether MEK1/2 (U0126) and LXR ligand (T0901317) can have a synergistic effect on the reduction of atherosclerosis while eliminating LXR ligand-induced fatty livers and hypertriglyceridemia. We also set out to identify the cellular mechanisms of the actions.. Wild-type mice were used to determine the effect of U0126 on a high-fat diet or high-fat diet plus T0901317-induced transient dyslipidemia and liver injury. ApoE deficient (apoE(-/-)) mice or mice with advanced lesions were used to determine the effect of the combination of T0901317 and U0126 on atherosclerosis and hypertriglyceridemia. We found that U0126 protected animals against T0901317-induced transient or long-term hepatic lipid accumulation, liver injury, and hypertriglyceridemia. Meanwhile, the combination of T0901317 and U0126 inhibited the development of atherosclerosis in a synergistic manner and reduced advanced lesions. Mechanistically, in addition to synergistic induction of macrophage ABCA1 expression, the combination of U0126 and T0901317 maintained arterial wall integrity, inhibited macrophage accumulation in aortas and formation of macrophages/foam cells, and activated reverse cholesterol transport. The inhibition of T0901317-induced lipid accumulation by the combined U0126 might be attributed to inactivation of lipogenesis and activation of lipolysis/fatty acid oxidation pathways.. Our study suggests that the combination of mitogen-activated protein kinase kinase 1/2 inhibitor and LXR ligand can function as a novel therapy to synergistically reduce atherosclerosis while eliminating LXR-induced deleterious effects.

Topics: Animals; Aorta; Aortic Diseases; Apolipoproteins E; Atherosclerosis; Butadienes; Chemical and Drug Induced Liver Injury; Cholesterol; Disease Models, Animal; Drug Synergism; Drug Therapy, Combination; Fatty Liver; Female; Foam Cells; Hep G2 Cells; Humans; Hydrocarbons, Fluorinated; Hypertriglyceridemia; Liver; Liver X Receptors; Male; Mice, Inbred C57BL; Mice, Knockout; Mitogen-Activated Protein Kinase 1; Mitogen-Activated Protein Kinase 3; Nitriles; Orphan Nuclear Receptors; Protein Kinase Inhibitors; Signal Transduction; Sulfonamides

The nuclear hormone receptors liver X receptor α (LXRα) and peroxisome proliferator-activated receptor γ (PPARγ) play key roles in the development of fatty liver. To determine the link between hepatic PPARγ and LXRα signaling and the development of fatty liver, a LXRα-specific ligand, T0901317, was administered to normal OB/OB and genetically obese (ob/ob) mice lacking hepatic PPARγ (Pparγ(ΔH)). In ob/ob-Pparγ(ΔH) and OB/OB-Pparγ(ΔH) mice, as well as ob/ob-Pparγ(WT) and OB/OB-Pparγ(WT) mice, the liver weights and hepatic triglyceride levels were markedly increased in response to T0901317 treatment. These results suggest that hepatic PPARγ and LXRα signals independently contribute to the development of fatty liver.

Topics: Animals; Anticholesteremic Agents; Blood Glucose; Fatty Liver; Hydrocarbons, Fluorinated; Hypoglycemic Agents; Lipogenesis; Liver; Liver X Receptors; Mice; Mice, Knockout; Mice, Obese; Orphan Nuclear Receptors; PPAR gamma; Sulfonamides

Liver X receptor (LXR) has been identified as a potential target for treatment of atherosclerosis and diabetes. Activation of LXR, however, is associated with increased lipogenesis and fat accumulation in the liver. The objective of the current study was to examine the effect of resveratrol on LXR activator-induced fat accumulation in liver using mice as an animal model. Three groups of C57BL/6 mice were studied. Animals in group 1 were treated with T0901317, a potent activator of LXR in mice. Animals in group 2 served as the control and were treated with carrier solution and those in group 3 were treated with T0901317/resveratrol combination. Using histochemical and biochemical methods, we demonstrate that resveratrol treatment significantly suppressed fat accumulation in the liver induced by T0901317. In addition, resveratrol completely blocked elevation of blood levels of triglyceride and cholesterol and reduced blood glucose level. Quantitative PCR analysis revealed that resveratrol treatment did not change the mRNA levels of abca1, abcg1, cyp7a1, srebp-1c, chrebp, and acc genes compared to that of animals treated with T0901317 alone but reduced pepck and g6p gene expressions. Immunohistochemistry and Western blot analyses show resveratrol treatment activated AMP-activated protein kinase (AMPK) and increased phosphorylation of acetyl-CoA carboxylase. Treatment with T0901317 on hepatocytes increased intracellular fat accumulation and this increase was suppressed by resveratrol; the suppressive effect of resveratrol was greatly repressed by Compound C which is an inhibitor of AMPK. Collectively, these data suggest that resveratrol blocks T0901317-induced lipid accumulation in the liver and can be considered for inclusion into the treatment of diseases involving activation of liver X receptor.

Topics: Animals; Cells, Cultured; Fatty Liver; Hepatocytes; Hydrocarbons, Fluorinated; Liver X Receptors; Male; Mice; Mice, Inbred C57BL; Orphan Nuclear Receptors; Resveratrol; Stilbenes; Sulfonamides

Liver X receptor (LXR) activation improves glucose homeostasis in obesity. This improvement, however, is associated with several side effects including hyperlipidemia and hepatic steatosis. Activation of peroxisome proliferator-activated receptor alpha (PPARα), on the other hand, increases fatty acid oxidation, leading to a reduction of hyperlipidemia. The objective of this study was to investigate whether concurrent activation of LXR/PPARα can produce synergistic benefits in treating obesity-associated metabolic disorders. Treatment of high fat diet-induced obese mice with T0901317, an LXR activator, or fenofibrate, the PPARα agonist, or in combination alleviated insulin resistance and improved glucose tolerance. The combined treatment dramatically exacerbated hepatic steatosis. Gene expression analysis in the liver showed that combined treatment increased the expression of genes involved in lipogenesis and fatty acid transport, including srebp-1c, chrebp, acc1, fas, scd1 and cd36. Histochemistry and ex vivo glycerol releasing assay showed that combined treatment accelerated lipid mobilization in adipose tissue. Combined treatment also increased the transcription of glut4, hsl, atgl and adiponectin, and decreased that of plin1, cd11c, ifnγ and leptin. Combined treatment markedly elevated the transcription of fgf21 in liver but not in adipose tissue. These results suggest that concurrent activation of LXR and PPARα as a strategy to control glucose and lipid metabolism in obesity is beneficial but could lead to elevation of lipid accumulation in the liver.

Topics: Adipocytes; Adipose Tissue, White; Animals; Blood Glucose; Cell Size; Cholesterol; Diet, High-Fat; Fatty Acids; Fatty Liver; Fenofibrate; Gene Expression Regulation; Glucose Tolerance Test; Hydrocarbons, Fluorinated; Insulin; Insulin Resistance; Liver; Liver X Receptors; Male; Mice; Mice, Inbred C57BL; Mice, Obese; Orphan Nuclear Receptors; PPAR alpha; Sulfonamides; Triglycerides

Drugs designed specifically to activate liver X receptors (LXRs) have beneficial effects on lowering cholesterol metabolism and inflammation but unfortunately lead to severe hepatic steatosis. The transcription factor CCAAT/enhancer binding protein beta (C/EBPβ) is an important regulator of liver gene expression but little is known about its involvement in LXR-based steatosis and cholesterol metabolism. The present study investigated the role of C/EBPβ expression in LXR agonist (T0901317)-mediated alteration of hepatic triglyceride (TG) and lipogenesis in mice. C/EBPβ deletion in mice prevented LXR agonist-mediated induction of lipogenic gene expression in liver in conjunction with significant reduction of liver TG accumulation. Surprisingly, C/EBPβ(-/-) mice showed a major increase in liver mitochondrial electron chain function compared to WT mice. Furthermore, LXR activation in C/EBPβ(-/-) mice increased the expression of liver ATP-binding cassette transporter ABCG1, a gene implicated in cholesterol efflux and reducing blood levels of total and LDL-cholesterol. Together, these findings establish a central role for C/EBPβ in the LXR-mediated steatosis and mitochondrial function, without impairing the influence of LXR activation on lowering LDL and increasing HDL-cholesterol. Inactivation of C/EBPβ might therefore be an important therapeutic strategy to prevent LXR activation-mediated adverse effects on liver TG metabolism without disrupting its beneficial effects on cholesterol metabolism.

Topics: Animals; Anticholesteremic Agents; CCAAT-Enhancer-Binding Protein-beta; Cholesterol, HDL; Fatty Liver; Gene Deletion; Hydrocarbons, Fluorinated; Lipogenesis; Liver X Receptors; Male; Mice; Mice, Mutant Strains; Mitochondria, Liver; Orphan Nuclear Receptors; Sulfonamides; Triglycerides

The effect of activation of liver X receptor by N-(2,2,2-trifluoroethyl)-N-[4-[2,2,2-trifluoro-1-hydroxy-1(trifluoromethyl)ethyl]phenyl] benzenesulfonamide (T0901317) on high fat diet (HFD)-induced obesity and insulin resistance was examined in C57BL/6 mice. When on HFD continuously for 10 weeks, C57BL/6 mice became obese with an average body weight of 42 g, insulin resistant, and glucose intolerant. Twice weekly intraperitoneal injections of T0901317 at 50 mg/kg in animals on the same diet completely blocked obesity development, obesity-associated insulin resistance, and glucose intolerance. Quantitative real-time PCR analysis showed that T0901317-treated animals had significantly higher mRNA levels of genes involved in energy metabolism, including Ucp-1, Pgc1a, Pgc1b, Cpt1a, Cpt1b, Acadm, Acadl, Aox, and Ehhadh. Transcription activation of Cyp7a1, Srebp-1c, Fas, Scd-1, and Acc-1 genes was also seen in T0901317-treated animals. T0901317 treatment induced reversible aggregation of lipids in the liver. These results suggest that liver X receptor could be a potential target for prevention of obesity and obesity-associated insulin resistance.

Topics: Adipose Tissue; Animals; Body Composition; Diet, High-Fat; Eating; Energy Metabolism; Fatty Liver; Glucose; Hydrocarbons, Fluorinated; Insulin Resistance; Liver X Receptors; Male; Mice; Mice, Inbred C57BL; Obesity; Orphan Nuclear Receptors; Pancreas; Sulfonamides

The protein, thyroid hormone-responsive SPOT 14 homolog (Thrsp), has been reported to be a lipogenic gene in cultured hepatocytes, implicating an important role of Thrsp in the pathogenesis of nonalcoholic fatty liver disease (NAFLD). Thrsp expression is known to be regulated by a variety of transcription factors, including thyroid hormone receptor, pregnane X receptor, and constitutive androstane receptor. Emerging in vitro evidence also points to a critical role of liver X receptor (LXR) in regulating Thrsp transcription in hepatocytes. In the present study, we showed that Thrsp was up-regulated in livers of db/db mice and high-fat-diet-fed mice, two models of murine NAFLD. Hepatic overexpression of Thrsp increased triglyceride accumulation with enhanced lipogenesis in livers of C57Bl/6 mice, whereas hepatic Thrsp gene silencing attenuated the fatty liver phenotype in db/db mice. LXR activator TO901317 induced Thrsp expression in livers of wild-type (WT) and LXR-β gene-deficient mice, but not in LXR-α or LXR-α/β double-knockout mice. TO901317 treatment significantly enhanced hepatic sterol regulatory element-binding protein 1c (SREBP-1c) expression and activity in WT mice, but failed to induce Thrsp expression in SREBP-1c gene-deficient mice. Sequence analysis revealed four LXR response-element-like elements and one sterol regulatory element (SRE)-binding site within a -2,468 ∼+1-base-pair region of the Thrsp promoter. TO901317 treatment and LXR-α overexpression failed to induce, whereas overexpression of SREBP-1c significantly increased Thrsp promoter activity. Moreover, deletion of the SRE site completely abolished SREBP-1c-induced Thrsp transcription.. Thrsp is a lipogenic gene in the liver that is induced by the LXR agonist through an LXR-α-mediated, SREBP-1c-dependent mechanism. Therefore, Thrsp may represent a potential therapeutic target for the treatment of NAFLD.

Topics: Animals; Anticholesteremic Agents; Cells, Cultured; Diet, High-Fat; Disease Models, Animal; Fatty Liver; Hydrocarbons, Fluorinated; Lipogenesis; Liver; Liver X Receptors; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Mice, Mutant Strains; Non-alcoholic Fatty Liver Disease; Nuclear Proteins; Orphan Nuclear Receptors; Signal Transduction; Sterol Regulatory Element Binding Protein 1; Sulfonamides; Transcription Factors; Transcription, Genetic

Nonalcoholic fatty liver disease (NAFLD) is classically associated with insulin resistance and the inflammatory response, especially in the nonalcoholic steatohepatitis phase. The liver X receptors (LXRs) play a critical role in the regulation of cholesterol metabolism and inflammatory processes.. Wild-type C57BL/6 mice were fed a normal diet (ND) or a high-fat (HF) diet for 8 weeks. Some ND- and HF-fed mice were treated (i.p.) with the LXR agonist T0901317 (30 mg/kg/day) for 7 days. Lipopolysaccharide (LPS, 50 μg/mouse) was then injected intraperitoneally to induce liver injury. The activation of MAPKs, NF-κB and the PI3K pathway was evaluated using Western blot. Bone marrow-derived macrophages (MDMs) were isolated from the femurs of C57BL/6 mice and cultured with or without T0901317 (20 μmol/l). The expression of tumor necrosis factor-alpha (TNF-α) and inducible nitric oxide synthase (iNOS) was evaluated in vitro or in vivo using real-time PCR, immunohistochemistry, or Western blot.. The LXR agonist T0901317 attenuated LPS-induced liver injury in a murine model of NAFLD, reflected by reduced serum alanine aminotransferase and aspartate aminotransferase levels, and reduced liver histology changes. Activation of LXRs reduced TNF-α and iNOS expression through inhibiting JNK and the PI3K signaling pathway. An in vitro study demonstrated that the activation of LXR inhibited the expression of TNF-α and iNOS in the MDMs of mice.. Activation of LXRs attenuates LPS-induced liver injury in murine NAFLD through inhibiting the pro-inflammatory activity of macrophages.

Topics: Alanine Transaminase; Animals; Aspartate Aminotransferases; Blotting, Western; Fatty Liver; Hydrocarbons, Fluorinated; Immunohistochemistry; Lipogenesis; Lipopolysaccharides; Liver; Liver X Receptors; Male; Mice; Mice, Inbred C57BL; Mitogen-Activated Protein Kinases; NF-kappa B; Nitric Oxide Synthase Type II; Non-alcoholic Fatty Liver Disease; Orphan Nuclear Receptors; Sulfonamides; Tumor Necrosis Factor-alpha

Liver X receptor-α (LXRα) functions as a major regulator of lipid homeostasis through activation of sterol regulatory element binding protein-1c (SREBP-1c), which promotes hepatic steatosis and steatohepatitis. NF-E2-related factor 2 (Nrf2) is the crucial transcription factor that is necessary for the induction of antioxidant enzymes. This study investigated the potential of liquiritigenin (LQ), a hepatoprotective flavonoid in licorice, to inhibit LXRα-induced hepatic steatosis, and the underlying mechanism of the action. LQ treatment attenuated fat accumulation and lipogenic gene induction in the liver of mice fed a high fat diet. Also, LQ had the ability to inhibit oxidative liver injury, as shown by decreases in thiobarbituric acid reactive substances formation and nitrotyrosinylation. Moreover, LQ treatment antagonized LXRα agonist (T0901317)-mediated SREBP-1c activation, and transactivation of the lipogenic target genes. LQ was found to activate Nrf2, and the ability of LQ to inhibit LXRα-mediated SREBP-1c activation was reversed by Nrf2 deficiency, which supports the inhibitory role of Nrf2 in LXRα-dependent lipogenesis. Consistently, treatment with other Nrf2 activators or forced expression of Nrf2 also inhibited LXRα-mediated SREBP-1c activation. Our results demonstrate that LQ has an efficacy to activate Nrf2, which contributes to inhibiting the activity of LXRα that leads to SREBP-1c induction and hepatic steatosis.

Topics: Animals; Antioxidants; Cell Line; Dietary Fats; Fatty Liver; Flavanones; Gene Expression Regulation; Glycyrrhiza; Hep G2 Cells; Humans; Hydrocarbons, Fluorinated; Lipogenesis; Liver; Liver X Receptors; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; NF-E2-Related Factor 2; Orphan Nuclear Receptors; Oxidative Stress; Rats; Signal Transduction; Sterol Regulatory Element Binding Protein 1; Sulfonamides

The nuclear receptor liver X receptor-α (LXRα) stimulates lipogenesis, leading to steatosis. Nuclear factor erythroid-2-related factor-2 (Nrf2) contributes to cellular defense mechanism by upregulating antioxidant genes, and may protect the liver from injury inflicted by fat accumulation. However, whether Nrf2 affects LXRα activity is unknown. This study investigated the inhibitory role of Nrf2 in hepatic LXRα activity and the molecular basis.. A deficiency of Nrf2 enhanced the ability of LXRα agonist to promote hepatic steatosis, as mediated by lipogenic gene induction. In hepatocytes, Nrf2 overexpression repressed gene transactivation by LXR-binding site activation. Consistently, treatment of mice with sulforaphane (an Nrf2 activator) suppressed T0901317-induced lipogenesis, as confirmed by the experiments using hepatocytes. Nrf2 activation promoted deacetylation of farnesoid X receptor (FXR) by competing for p300, leading to FXR-dependent induction of small heterodimer partner (SHP), which was responsible for the repression of LXRα-dependent gene transcription. In human steatotic samples, the transcript levels of LXRα and SREBP-1 inversely correlated with those of Nrf2, FXR, and SHP.. Our findings offer the mechanism to explain how decrease in Nrf2 activity in hepatic steatosis could contribute to the progression of NAFLD, providing the use of Nrf2 as a molecular biomarker to diagnose NAFLD. As certain antioxidants have the abilities to activate Nrf2, clinicians might utilize the activators of Nrf2 as a new therapeutic approach to prevent and/or treat NAFLD.. Nrf2 activation inhibits LXRα activity and LXRα-dependent liver steatosis by competing with FXR for p300, causing FXR activation and FXR-mediated SHP induction. Our findings provide important information on a strategy to prevent and/or treat steatosis.

Topics: Acetylesterase; Animals; Blotting, Western; Chromatin Immunoprecipitation; Fatty Liver; Hep G2 Cells; Hepatocytes; Humans; Hydrocarbons, Fluorinated; Immunoprecipitation; Isothiocyanates; Lipogenesis; Liver; Liver X Receptors; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; NF-E2-Related Factor 2; Orphan Nuclear Receptors; Protein Binding; Real-Time Polymerase Chain Reaction; Receptors, Cytoplasmic and Nuclear; Sterol Regulatory Element Binding Protein 1; Sulfonamides; Sulfoxides; Thiocyanates

Liver X receptor (LXR) agonists slow atherogenesis, but cause hepatic steatosis and dysfunction in part by increasing expression of sterol regulatory element binding protein 1-c (SREBP1-c), a transcription factor that upregulates fatty acid (FA) synthesis. n-3 FAs decrease hepatic FA synthesis by down-regulating SREBP1-c. To test the hypothesis that n-3 FAs decrease hepatic steatosis in mice given LXR agonist, C57BL/6 mice received daily gavage of an LXR agonist T0901317 (LXR(T)) or vehicle for 4weeks with concomitant intakes chow or high-fat diets enriched in saturated fat (SAT) or n-3 fat (n-3). Mice on LXR(T) and SAT developed hepatomegaly with a large increase in size and number of hepatic lipid droplets; an n-3 diet reduced liver weight/body weight with decreased hepatic steatosis and triglyceride levels. Effects of n-3 diet on hepatic lipogenesis were linked to a blunting of LXR(T) upregulation of hepatic SREBP1-c and FA synthase mRNA. n-3 diets also normalized LXR(T)-mediated increases of plasma ALT and AST levels, whereas SAT diet increased these markers.. These studies suggest that n-3 FAs when given together with LXR agonists have the potential to improve both hepatic steatosis and hepatotoxicity in humans that might receive LXR agonists to decrease risk of atherosclerosis.

Topics: Alanine Transaminase; Animals; Aspartate Aminotransferases; Dietary Fats; Dietary Supplements; Fatty Acid Synthases; Fatty Acids; Fatty Acids, Omega-3; Fatty Liver; Humans; Hydrocarbons, Fluorinated; Liver; Liver X Receptors; Male; Mice; Mice, Inbred C57BL; Orphan Nuclear Receptors; Sterol Regulatory Element Binding Protein 1; Sulfonamides

Sauchinone, as an AMP-activated kinase (AMPK)-activating lignan in Saururus chinensis, has been shown to prevent iron-induced oxidative stress and liver injury. Sterol regulatory element binding protein-1c (SREBP-1c) plays a key role in hepatic steatosis, which promotes oxidative stress in obese subjects. Previously, we identified the role of AMPK in liver X receptor-alpha (LXRalpha)-mediated SREBP-1c-dependent lipogenesis. Because sauchinone as an antioxidant has the ability to activate AMPK, this study investigated its effects on SREBP-1c-dependent lipogenesis in hepatocytes and in high-fat diet (HFD)-induced hepatic steatosis and oxidative injury. Sauchinone prevented the ability of an LXRalpha agonist (T0901317) to activate SREBP-1c, repressing transcription of the fatty acid synthase, acetyl-CoA carboxylase, stearoyl-CoA desaturase-1, ATP-binding cassette transporter A1, and LXRalpha genes. Consistent with this, an HFD in mice caused fat accumulation in the liver with SREBP-1c induction, which was attenuated by sauchinone treatment. Also, sauchinone had the ability to inhibit oxidative stress as shown by decreases in thiobarbituric acid-reactive substance formation, nitrotyrosinylation, and 4-hydroxynonenal production. Moreover, it prevented not only the liver injury, but also the AMPK inhibition elicited by HFD feeding. These results demonstrate that sauchinone has the capability to inhibit LXRalpha-mediated SREBP-1c induction and SREBP-1c-dependent hepatic steatosis, thereby protecting hepatocytes from oxidative stress induced by fat accumulation.

Topics: AMP-Activated Protein Kinases; Animals; Fatty Liver; Gene Expression Regulation, Enzymologic; Hepatocytes; Humans; Hydrocarbons, Fluorinated; Lignans; Liver; Liver X Receptors; Male; Mice; Mice, Inbred C57BL; Orphan Nuclear Receptors; Oxidative Stress; Plant Extracts; Rats; Saururaceae; Sterol Regulatory Element Binding Protein 1; Sulfonamides

There is increasing evidence that the metabolic state of the mother during pregnancy affects long-term glucose and lipid metabolism of the offspring. The liver X receptors (LXR)α and -β are key regulators of cholesterol, fatty acid, and glucose metabolism. LXRs are activated by oxysterols and expressed in fetal mouse liver from day 10 of gestation onward. In the present study, we aimed to elucidate whether in utero pharmacological activation of LXR would influence fetal fatty acid and glucose metabolism and whether this would affect lipid homeostasis at adult age. Exposure of pregnant mice to the synthetic LXR agonist T0901317 increased hepatic mRNA expression levels of Lxr target genes and hepatic and plasma triglyceride levels in fetuses and dams. T0901317 treatment increased absolute de novo synthesis and chain elongation of hepatic oleic acid in dams and fetuses. T0901317 exposure in utero influenced lipid metabolism in adulthood in a sex-specific manner; hepatic triglyceride content was increased (+45%) in male offspring and decreased in female offspring (-42%) when they were fed a regular chow diet compared with untreated sex controls. Plasma and hepatic lipid contents and hepatic gene expression patterns in adult male or female mice fed a high-fat diet were not affected by T0901317 pretreatment. We conclude that LXR treatment of pregnant mice induces immediate effects on lipid metabolism in dams and fetuses. Despite the profound changes during fetal life, long-term effects appeared to be rather mild and sex selective without modulating the lipid response to a high-fat diet.

Topics: Animals; Diet, High-Fat; Dietary Fats; Fatty Acids, Nonesterified; Fatty Liver; Female; Fetal Development; Fetus; Glucose; Homeostasis; Hydrocarbons, Fluorinated; Insulin; Lipids; Lipogenesis; Liver X Receptors; Male; Mice; Mice, Inbred C57BL; Oleic Acids; Orphan Nuclear Receptors; Pregnancy; Real-Time Polymerase Chain Reaction; RNA; Sex Characteristics; Sulfonamides

HBV (hepatitis B virus) is a primary cause of chronic liver disease, which frequently results in hepatitis, cirrhosis and ultimately HCC (hepatocellular carcinoma). Recently, we showed that HBx (HBV protein X) expression induces lipid accumulation in hepatic cells mediated by the induction of SREBP1 (sterol-regulatory-element-binding protein 1), a key regulator of lipogenic genes in the liver. However, the molecular mechanisms by which HBx increases SREBP1 expression and transactivation remain to be clearly elucidated. In the present study, we demonstrated that HBx interacts with LXRalpha (liver X receptor alpha) and enhances the binding of LXRalpha to LXRE (LXR-response element), thereby resulting in the up-regulation of SREBP1 and FAS (fatty acid synthase) in the presence or absence of the LXR agonist T0901317 in the hepatic cells and HBx-transgenic mice. Furthermore, HBx also augments the ability to recruit ASC2 (activating signal co-integrator 2), a transcriptional co-activator that controls liver lipid metabolic pathways, to the LXRE with LXRalpha. These studies place LXRalpha in a key position within the HBx-induced lipogenic pathways, and suggest a molecular mechanism through which HBV infection can stimulate the SREBP1-mediated control of hepatic lipid accumulation.

Topics: Animals; Carcinoma, Hepatocellular; Cell Line; Cell Line, Tumor; DNA-Binding Proteins; Fatty Acid Synthases; Fatty Liver; Genes, Reporter; Hepatitis B; Hepatitis C; Humans; Hydrocarbons, Fluorinated; Lipids; Liver Neoplasms; Liver X Receptors; Mice; Mice, Transgenic; Orphan Nuclear Receptors; Receptors, Cytoplasmic and Nuclear; Reverse Transcriptase Polymerase Chain Reaction; RNA Interference; Sterol Regulatory Element Binding Protein 1; Sulfonamides; Trans-Activators; Transfection; Viral Regulatory and Accessory Proteins

The ATP-binding cassette transporter ABCA1 is essential for high density lipoprotein (HDL) formation and considered rate-controlling for reverse cholesterol transport. Expression of the Abca1 gene is under control of the liver X receptor (LXR). We have evaluated effects of LXR activation by the synthetic agonist T0901317 on hepatic and intestinal cholesterol metabolism in C57BL/6J and DBA/1 wild-type mice and in ABCA1-deficient DBA/1 mice. In wild-type mice, T0901317 increased expression of Abca1 in liver and intestine, which was associated with an approximately 60% rise in HDL. Biliary cholesterol excretion rose 2.7-fold upon treatment, and fecal neutral sterol output was increased by 150-300%. Plasma cholesterol levels also increased in treated Abca1(-/-) mice (+120%), but exclusively in very low density lipoprotein-sized fractions. Despite the absence of HDL, hepatobiliary cholesterol output was stimulated upon LXR activation in Abca1(-/-) mice, leading to a 250% increase in the biliary cholesterol/phospholipid ratio. Most importantly, fecal neutral sterol loss was induced to a similar extent (+300%) by the LXR agonist in DBA/1 wild-type and Abca1(-/-) mice. Expression of Abcg5 and Abcg8, recently implicated in biliary excretion of cholesterol and its intestinal absorption, was induced in T0901317-treated mice. Thus, activation of LXR in mice leads to enhanced hepatobiliary cholesterol secretion and fecal neutral sterol loss independent of (ABCA1-mediated) elevation of HDL and the presence of ABCA1 in liver and intestine.

Topics: Animals; Anticholesteremic Agents; Bile; Biological Transport; Cholesterol; DNA-Binding Proteins; Fatty Liver; Feces; Hydrocarbons, Fluorinated; Lipoproteins, LDL; Lipoproteins, VLDL; Liver; Liver X Receptors; Male; Mice; Mice, Inbred C57BL; Orphan Nuclear Receptors; Receptors, Cytoplasmic and Nuclear; Receptors, Retinoic Acid; Receptors, Thyroid Hormone; Sulfonamides