t0901317 and Insulin-Resistance

Chemerin is associated with insulin resistance and is expressed in the liver. Nonalcoholic fatty liver disease (NAFLD) is related to impaired insulin sensitivity, but studies evaluating hepatic and serum chemerin in NAFLD resulted in discordant data.. Chemerin mRNA was determined in the liver tissue obtained from 33 controls and 76 NAFLD patients. Chemerin serum levels were measured in a different cohort of patients with ultrasound-diagnosed NAFLD and the respective controls. Hepatic stellate cells and hepatocytes were exposed to selected metabolites and nuclear receptor agonists to study the regulation of chemerin. Effect of recombinant chemerin on hepatocyte released proteins was analysed.. Hepatic chemerin expression was not related to BMI, gender, type 2 diabetes and hypertension. Chemerin mRNA did not correlate with steatosis and was negatively associated with inflammation, fibrosis and nonalcoholic steatohepatitis (NASH) score. Patients with NASH had lower chemerin mRNA compared to those with borderline NASH and controls. Factors with a role in NASH mostly did not regulate chemerin in the liver cells. Of note, liver X receptor agonist reduced chemerin protein. Serum chemerin was not changed in NAFLD. Levels positively correlated with age, waist-to-hip ratio, systolic blood pressure, serum FGF21 and lipocalin 2, and negatively with transferrin saturation. Chemerin induced FGF21 in supernatants of primary human hepatocytes. Hepcidin, a major regulator of iron homoeostasis and lipocalin 2, were not regulated by chemerin.. Chemerin mRNA is reduced in the liver of NASH patients, and liver X receptor seems to have a role herein.

Topics: Adult; Aged; Aged, 80 and over; Body Mass Index; Case-Control Studies; Cell Line; Cells, Cultured; Chemokines; Comorbidity; Cytokines; Diabetes Mellitus, Type 2; Female; Fibroblast Growth Factors; Hep G2 Cells; Hepatic Stellate Cells; Hepatocytes; Hepcidins; Humans; Hydrocarbons, Fluorinated; Hypertension; Hypoglycemic Agents; In Vitro Techniques; Insulin Resistance; Intercellular Signaling Peptides and Proteins; Leptin; Lipocalin-2; Liver; Liver X Receptors; Male; Middle Aged; Non-alcoholic Fatty Liver Disease; Real-Time Polymerase Chain Reaction; Receptors, Cytoplasmic and Nuclear; Recombinant Proteins; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Rosiglitazone; Severity of Illness Index; Sulfonamides; Thiazolidinediones; Waist-Hip Ratio; Young Adult

Activation of Liver X receptors (LXRs), key transcriptional regulators of glucose metabolism, normalizes glycemia and improves insulin sensitivity in rodent models with insulin resistance. However, the molecular mechanism is unclear. This study is aimed to elucidate the mechanism of LXRs-mediated liver glucose metabolic regulation in vitro and in vivo. Db/db mice were used as an in vivo model of diabetes; palmitate (PA)-stimulated HepG2 cells were used as an in vitro cell model with impairment of insulin signaling. TO901317 (TO) was chosen as the LXRs agonist. We demonstrated that TO treatment for 14 days potently improved the hepatic glucose metabolism in db/db mice, including fasting blood glucose, fasting insulin level, and HOMA-IR. TO had no effect on the glucose metabolism in normal WT mice. TO-mediated activation of hepatic LXRs led to strong inhibition of ROS production accompanied by inactivation of JNK pathway and re-activation of Akt pathway. TO also suppressed the expression of gluconeogenic genes such as PEPCK and G-6-pase in db/db mice, but not in WT mice. In HepG2 cells, TO almost completely restored PA-induced Akt inactivation, and suppressed PA-stimulated ROS production and JNK activation. Interestingly, basal level of ROS was also inhibited by TO in HepG2 cells. TO significantly inhibited PA-stimulated expressions of gluconeogenic genes. Finally, we found that anti-oxidative genes, such as Nrf2, were up-regulated after LXRs activation by TO. These results strongly support the notion that activation of LXRs is critical in suppression of liver gluconeogenesis and improvement of insulin sensitivity in diabetic individuals. At molecular levels, the mode of action appears to be as fellows: under diabetic condition, ROS production is increased, JNK is activated, and Akt activity is inhibited; TO-mediated LXR activation potently inhibits ROS production, increases anti-oxidative gene expressions, suppresses JNK activation, and restores Akt activity. Our data provide new evidence to support LXRs as promising therapeutic targets for anti-diabetic drug development.

Topics: Animals; Cell Line; Diabetes Mellitus, Type 2; Disease Models, Animal; Gene Expression Regulation; Glucose; Hep G2 Cells; Humans; Hydrocarbons, Fluorinated; Insulin; Insulin Resistance; Lipid Metabolism; Liver; Liver X Receptors; Male; MAP Kinase Signaling System; Mice; Mice, Transgenic; Orphan Nuclear Receptors; Phenotype; Phosphoenolpyruvate Carboxykinase (ATP); Phosphorylation; Proto-Oncogene Proteins c-akt; Reactive Oxygen Species; Sulfonamides

Liver X receptors (LXRs) have been recognized as a promising therapeutic target for atherosclerosis; however, their role in insulin sensitivity is controversial. Adiponectin plays a unique role in maintaining insulin sensitivity. Currently, no systematic experiments elucidating the role of LXR activation in insulin function based on adiponectin signaling have been reported. Here, we investigated the role of LXR activation in insulin resistance based on adiponectin signaling, and possible mechanisms. C57BL/6 mice maintained on a regular chow received the LXR agonist, T0901317 (30 mg/kg.d) for 3 weeks by intraperitoneal injection, and differentiated 3T3-L1 adipocytes were treated with T0901317 or GW3965. T0901317 treatment induced significant insulin resistance in C57BL/6 mice. It decreased adiponectin gene transcription in epididymal fat, as well as serum adiponectin levels. Activity of AMPK, a key mediator of adiponectin signaling, was also decreased, resulting in decreased Glut-4 membrane translocation in epididymal fat. In contrast, adiponectin activity was not changed in the liver of T0901317 treated mice. In vitro, both T0901317 and GW3965 decreased adiponectin expression in adipocytes in a dose-dependent manner, an effect which was diminished by LXRα silencing. ChIP-qPCR studies demonstrated that T0901317 decreased the binding of PPARγ to the PPAR-responsive element (PPRE) of the adiponectin promoter in a dose-dependent manner. Furthermore, T0901317 exerted an antagonistic effect on the expression of adiponectin in adipocytes co-treated with 3 µM Pioglitazone. In luciferase reporter gene assays, T0901317 dose-dependently inhibited PPRE-Luc activity in HEK293 cells co-transfected with LXRα and PPARγ. These results suggest that LXR activation induces insulin resistance with decreased adiponectin signaling in epididymal fat, probably due to negative regulation of PPARγ signaling. These findings indicate that the potential of LXR activation as a therapeutic target for atherosclerosis may be limited by the possibility of exacerbating insulin resistance-related disease.

Topics: 3T3 Cells; Adipocytes; Adiponectin; Adipose Tissue; AMP-Activated Protein Kinases; Animals; Glucose Transporter Type 4; HEK293 Cells; Humans; Hydrocarbons, Fluorinated; Insulin Resistance; Liver X Receptors; Mice; Mice, Inbred C57BL; Orphan Nuclear Receptors; Pioglitazone; PPAR gamma; Response Elements; Signal Transduction; Sulfonamides; Thiazolidinediones

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

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

Estrogen-related receptor α (ERRα) is an orphan nuclear receptor that has been functionally implicated in the regulation of energy homeostasis. Herein is described the development of diaryl ether based thiazolidenediones, which function as selective ligands against this receptor. Series optimization provided several potent analogues that inhibit the recruitment of a coactivator peptide fragment in in vitro biochemical assays (IC(50) < 150 nM) and cellular two-hybrid reporter assays against the ligand binding domain (IC(50) = 1-5 μM). A cocrystal structure of the ligand-binding domain of ERRα with lead compound 29 revealed the presence of a covalent interaction between the protein and ligand, which has been shown to be reversible. In diet-induced murine models of obesity and in an overt diabetic rat model, oral administration of 29 normalized insulin and circulating triglyceride levels, improved insulin sensitivity, and was body weight neutral. This provides the first demonstration of functional activities of an ERRα ligand in metabolic animal models.

Topics: Administration, Oral; Animals; Binding, Competitive; Biological Availability; Crystallography, X-Ray; Diabetes Mellitus; Dogs; ERRalpha Estrogen-Related Receptor; Ethers; Female; Humans; Hypoglycemic Agents; Insulin; Insulin Resistance; Ligands; Macaca fascicularis; Male; Mice; Mice, Knockout; Models, Molecular; Molecular Structure; Obesity; Rats; Rats, Sprague-Dawley; Receptors, Estrogen; Structure-Activity Relationship; Thiazolidinediones; Triglycerides

We compared hepatic expression of genes that regulate lipid biosynthesis and metabolic signaling in liver biopsy specimens from women who were undergoing gastric bypass surgery (GBP) for morbid obesity with that in women undergoing ventral hernia repair who had experienced massive weight loss (MWL) after prior GBP. Comprehensive metabolic profiles of morbidly obese (MO) (22 subjects) and MWL (9 subjects) were also compared. Analyses of gene expression in liver biopsies from MO and MWL were accomplished by Affymetrix microarray, real-time polymerase chain reaction, and Western blotting techniques. After GBP, MWL subjects had lost on average 102 lb as compared with MO subjects. This was accompanied by effective reversal of the dyslipidemia and insulin resistance that were present in MO. As compared with MWL, livers of MO subjects exhibited increased expression of sterol regulatory element binding protein (SREBP)-1c and its downstream lipogenic targets, fatty acid synthase and acetyl-coenzyme A-carboxylase-1. Livers of MO subjects also exhibited enhanced expression of suppressor of cytokine signaling-3 protein and attenuated Janus kinase signal transducer and activator of transcription (JAK/STAT) signaling. Consistent with these findings, we found that the human SREBP-1c promoter was positively regulated by insulin and negatively regulated by STAT3. These data support the hypothesis that suppressor of cytokine signaling-3-mediated attenuation of the STAT signaling pathway and resulting enhanced expression of SREBP-1c, a key regulator of de novo lipid biosynthesis, are mechanistically related to the development of hepatic insulin resistance and dyslipidemia in MO women.

Topics: Adult; Fatty Acids; Female; Gastric Bypass; Gene Expression Regulation; Humans; Hydrocarbons, Fluorinated; Insulin; Insulin Resistance; Lipoproteins, VLDL; Liver; Obesity, Morbid; Polymerase Chain Reaction; Promoter Regions, Genetic; STAT1 Transcription Factor; STAT3 Transcription Factor; Stearoyl-CoA Desaturase; Sterol Regulatory Element Binding Protein 1; Sulfonamides; Suppressor of Cytokine Signaling 3 Protein; Suppressor of Cytokine Signaling Proteins; Triglycerides; Weight Loss

Vascular smooth muscular cells (VSMC) express lipogenic genes. Therefore in situ lipogenesis could provide fatty acids for triglycerides synthesis and cholesterol esterification and contribute to lipid accumulation in arterial wall with aging and during atheroma.. We investigated expression of lipogenic genes in human and rat arterial walls, its regulation in cultured VSMC and determined if it is modified during insulin-resistance and diabetes, situations with increased risk for atheroma.. Zucker obese (ZO) and diabetic (ZDF) rats accumulated more triglycerides in their aortas than their respective control rats, and this triglycerides content increased with age in ZDF and control rats. However the expression in aortas of lipogenic genes, or of genes involved in fatty acids uptake, was not higher in ZDF and ZO rats and did not increase with age. Expression of lipogenesis-related genes was not increased in human arterial wall (carotid endarterectomy) of diabetic compared to non-diabetic patients. In vitro, glucose and adipogenic medium (ADM) stimulated moderately the expression and activity of lipogenesis in VSMC from control rats. LXR agonists, but not PXR agonist, stimulated also lipogenesis in VSMC but not in arterial wall in vivo. Lipogenic genes expression was lower in VSMC from ZO rats and not stimulated by glucose or ADM.. Lipogenic genes are expressed in arterial wall and VSMC; this expression is stimulated (VSMC) by glucose, ADM and LXR agonists. During insulin-resistance and diabetes, this expression is not increased and resists to the actions of glucose and ADM. It is unlikely that this metabolic pathway contribute to lipid accumulation of arterial wall during insulin-resistance and diabetes and thus to the increased risk of atheroma observed in these situations.

Topics: Aged; Animals; Aorta; Atherosclerosis; Carotid Arteries; Cells, Cultured; Culture Media; Diabetes Mellitus, Type 2; Disease Models, Animal; Female; Gene Expression Regulation; Glucose; Humans; Hydrocarbons, Fluorinated; Insulin; Insulin Resistance; Lipogenesis; Liver X Receptors; Male; Middle Aged; Muscle, Smooth, Vascular; Myocytes, Smooth Muscle; Obesity; Orphan Nuclear Receptors; Rats; Rats, Zucker; RNA, Messenger; Sulfonamides; Time Factors; Triglycerides

Adipocytes release a variety of factors which deregulation could provide the basis for complications such as insulin resistance, an early defect on the onset of type 2 diabetes. Such insulin resistance can initially be overcome by compensatory hyperinsulinemia, but the prolonged presence of the hormone can be detrimental for insulin sensitivity.. The objective of the study was to dissect the molecular mechanisms that may regulate hyperinsulinemia-induced insulin resistance in a human liposarcoma cell line and its paracrine interactions with a human rhabdomyosarcoma cell line.. We studied glucose uptake, lipolysis, insulin signaling, and secretion pattern at different days of adipocyte differentiation in the presence of insulin.. Adipocytes differentiated for 14 d gain insulin sensitivity on glucose uptake and inhibition of lipolysis, but prolonged cultures develop an insulin-resistant state characterized by an increase in phosphatase and tensin homolog-deleted on chromosome 10 expression and defects in insulin signaling at the insulin receptor substrate-1/AKT level. The secretion pattern of nonesterified fatty acids, IL-6, adiponectin, leptin, and monocyte chemotactic protein-1 was in keeping with the changes in insulin sensitivity during differentiation. An inverse biphasic response was also observed in human myocytes when they were cultured with various adipocyte-conditioned media, although insulin resistance was detected earlier than in adipocytes. This behavior mimics hyperinsulinemia because insulin action was restored when adipocytes were cultured in the absence of the hormone. Pharmacological treatment of adipocytes with a liver X receptor agonist reestablishes insulin-stimulated glucose uptake, whereas treatment with a peroxisome proliferator-activated receptor-gamma agonist restored the antilipolytic action of insulin.. Hyperinsulinemia deregulates adipocyte secretion pattern, producing insulin resistance in adipocytes and myocytes, a situation that can be ameliorated with nuclear receptor agonists.

Topics: Adipocytes; Cell Differentiation; Cell Line; Chemokine CCL2; DNA-Binding Proteins; Fatty Acids, Nonesterified; Glucose; Humans; Hydrocarbons, Fluorinated; Hyperinsulinism; Insulin Resistance; Interleukin-6; Lipid Metabolism; Liver X Receptors; Muscle Cells; Muscle, Skeletal; Orphan Nuclear Receptors; Receptors, Cytoplasmic and Nuclear; Sulfonamides