PPARα suppresses low-intensity-noise-induced body weight gain in mice: the activated HPA axis plays an critical role.

BACKGROUND: As the second most risky environmental pollution, noise imposes threats to human health. Exposure to high-intensity noise causes hearing impairment, psychotic disorders, endocrine modifications. The relationship among low-intensity noise, obesity and lipid-regulating nuclear factor PPARα is not yet clear. METHODS: In this study, male wild-type (WT) and Pparα-null (KO) mice on a high-fat diet (HFD) were exposed to 75 dB noise for 12 weeks to explore the effect of low-intensity noise on obesity development and the role of PPARα. 3T3-L1 cells were treated with dexamethasone (DEX) and sodium oleate (OA) to verify the down-stream effect of hypothalamic-pituitary-adrenal (HPA) axis activation on the adipose tissues. RESULTS: The average body weight gain (BWG) of WT mice on HFD exposed to noise was inhibited, which was not observed in KO mice. The mass and adipocyte size of adipose tissues accounted for the above difference of BWG tendency. In WT mice on HFD, the adrenocorticotropic hormone level was increased by the noise challenge. The aggravation of fatty liver by noise exposure occurred in both mouse lines, and the transport of hepatic redundant lipid to adipose tissues were similar. The lipid metabolism in adipose tissue driven by HPA axis accorded with the BWG inhibition in vivo, validated in 3T3-L1 adipogenic stem cells. CONCLUSION: Chronic exposure to low-intensity noise aggravated fatty liver in both WT and KO mice. BWG inhibition was observed only in WT mice, which covered up the aggravation of fatty liver by noise exposure. PPARα mediates the activation of HPA axis by noise exposure in mice on HFD. Elevated adrenocorticotropic hormone (ACTH) promoted lipid metabolism in adipocytes, which contributed to the disassociation of BWG and fatty liver development in male WT mice. Summary of PPARα suppresses noise-induced body weight gain in mice on high-fat-diet. Chronic exposure to low-intensity noise exposure inhibited BWG by PPARα-dependent activation of the HPA axis.

Fenofibrate reverses liver fibrosis in cholestatic mice induced by alpha-naphthylisothiocyanate.

Cholestatic liver fibrosis occurs in liver injuries accompanied by inflammation, which develops into cirrhosis if not effectively treated in early stage. The aim of the study is to explore the effect of fenofibrate on liver fibrosis in chronic cholestatic mice. In this study, wild-type (WT) and Pparα-null (KO) mice were dosed alpha-naphthylisothiocyanate (ANIT) diet to induce chronic cholestasis. Induced liver fibrosis was determined by pathological biomarkers. Then fenofibrate 25 mg/kg was orally administrated to mice twice/day for 14 days. Serum and liver samples were collected for analysis of biochemistry and fibrosis. In WT mice, cholestatic biomarkers were increased by 5-8-fold and the expression of tissue inhibitors of metalloproteinases 1 (TIMP-1), Monocyte chemoattractant protein 1 (MCP-1), Collagen protein I (Collagen I) was increased by more than 10-fold. Fenofibrate significantly downgraded the biochemical and fibrotic biomarkers. In Western blot analysis, levels of collagenI and alpha-smooth muscle actin (α-SMA) were strongly inhibited by fenofibrate. In KO mice, liver fibrosis was induced successfully, but no improvement after fenofibrate treatment was observed. These data showed low-dose fenofibrate reverses cholestatic liver fibrosis in WT mice but not in KO mice, suggesting the dependence of therapeutic action on peroxisome proliferator-activated receptor alpha (PPARα). The study offers an additional therapeutic strategy for cholestatic liver fibrosis in practice.

Targeted Metabolomics Reveals a Protective Role for Basal PPARα in Cholestasis Induced by α-Naphthylisothiocyanate.

α-Naphthylisothiocyanate (ANIT) is an experimental agent used to induce intrahepatic cholestasis. The Ppara-null mouse line is widely employed to explore the physiological and pathological roles of PPARα. However, little is known about how PPARα influences the hepatotoxicity of ANIT. In the present study, wild-type and Ppara-null mice were orally treated with ANIT to induce cholestasis. The serum metabolome of wild-type mice segregated from that of the Ppara-null mice, driven by changes of bile acid (BA) metabolites. Alkaline phosphatase and total BAs were elevated preferentially in Ppara-null mice, which correlated with changes in Cyp7a1, Cyp8b1, Mrp3, Cyp3a11, Cyp2b10, Ugt1a2, and Ugt1a5 genes and showed cross-talk between basal PPARα and potentially adaptive pathways. Il6, Tnfa, and target genes in the STAT3 pathway ( Socs3, Fga, Fgb, and Fgg) were up-regulated in Ppara-null mice but not in wild-type mice. The JNK pathway was activated in both mouse lines, while NF-κB and STAT3 were activated only in Ppara-null mice. These data suggest protection against cholestasis by basal PPARα involves regulation of BA metabolism and inhibition of NF-κB/STAT3 signaling. Considering studies on the protective effects of both basal and activated PPARα, caution should be exercised when one attempts to draw conclusions in which the PPARα is modified by genetic manipulation, fasting, or activation in pharmacological and toxicological studies.

Dual action of peroxisome proliferator-activated receptor alpha in perfluorodecanoic acid-induced hepatotoxicity.

Perfluorodecanoic acid (PFDA) is widely used in production of many daily necessities based on their surface properties and stability. It was assigned as a Persistent Organic Pollutant in 2009 and became a public concern partly because of its potential for activation of the peroxisome proliferator-activated receptor alpha (PPARα). In this study, wild-type and Ppara-null mice were administered PFDA (80 mg/kg). Blood and liver tissues were collected and subjected to systemic toxicological and mechanistic analysis. UPLC-ESI-QTOFMS-based metabolomics was used to explore the contributing components of the serum metabolome that led to variation between wild-type and Pparα-null mice. Bile acid homeostasis was disrupted, and slight hepatocyte injury in wild-type mice accompanied by adaptive regulation of bile acid synthesis and transport was observed. The serum metabolome in wild-type clustered differently from that in Pparα-null, featured by sharp increases in bile acid components. Differential toxicokinetic tendency was supported by regulation of UDP-glucuronosyltransferases dependent on PPARα, but it did not contribute to the hepatotoxic responses. Increase in Il-10 and activation of the JNK pathway indicated inflammation was induced by disruption of bile acid homeostasis in wild-type mice. Inhibition of p-p65 dependent on PPARα activation by PFDA stopped the inflammatory cascade, as indicated by negative response of Il-6, Tnf-α, and STAT3 signaling. These data suggest disruptive and protective role of PPARα in hepatic responses induced by PFDA.

Species-related exposure of phase II metabolite gemfibrozil 1-O-ß-glucuronide between human and mice: A net induction of mouse P450 activity was revealed.

Gemfibrozil is a fibrate drug used widely for dyslipidemia associated with atherosclerosis. Clinically, both gemfibrozil and its phase II metabolite gemfibrozil 1-O-ß-glucuronide (gem-glu) are involved in drug-drug interaction (DDI). But the DDI risk caused by gem-glu between human and mice has not been compared. In this study, six volunteers were recruited and took a therapeutic dose of gemfibrozil for 3 days for examination of the gemfibrozil and gem-glu level in human. Male mice were fed a gemfibrozil diet (0.75%) for 7 days, following which a cocktail-based inhibitory DDI experiment was performed. Plasma samples and liver tissues from mice were collected for determination of gemfibrozil, gem-glu concentration and cytochrome p450 enzyme (P450) induction analysis. In human, the molar ratio of gem-glu/gemfibrozil was 15% and 10% at the trough concentration and the concentration at 1.5 h after the 6th dose. In contrast, this molar ratio at steady state in mice was 91%, demonstrating a 6- to 9-fold difference compared with that in human. Interestingly, a net induction of P450 activity and in vivo inductive DDI potential in mice was revealed. The P450 activity was not inhibited although the gem-glu concentration was high. These data suggested species difference of relative gem-glu exposure between human and mice, as well as a net inductive DDI potential of gemfibrozil in mouse model.

Gemfibrozil not fenofibrate decreases systemic glucose level via PPARα.

BACKGROUND: Concurrence of high glucose or diabetes in patients with dyslipidemia is presenting major challenges for clinicians. Although sporadically reported, a rational basis for the use of fibrates for the treatment of dyslipidemia with concurrent metabolic syndrome has not been established. METHODS: In this study, wild-type (WT) and Ppara-null (KO) mice were fed a serial gemfibrozil- and fenofibrate-containing diet under the same experimental conditions for 14 days. Glucose level in the blood, glycogen storage in the liver tissues, and the potential toxic responses were assayed. Genes involved in glucose metabolism were determined by quantitative polymerase chain reaction analysis. RESULTS: Both the blood glucose level and the glycogen content in the liver were down-regulated by gemfibrozil but not by fenofibrate in WT mice, in a dose-dependent manner. This decrement did not occur in KO mice for either fibrate agent. Secondary regulation on the transcription of pyruvate kinase, and gluconolactonase were observed following gemfibrozil treatment, which was differential between WT mice and KO mice. CONCLUSIONS: Gemfibrozil, not fenofibrate, down-regulates systemic glucose level and glycogen storage in the liver dependent on PPARα, suggesting its potential value for treatment of dyslipidemia with concurrent diabetes or high glucose levels.

Deglycosylation of liquiritin strongly enhances its inhibitory potential towards UDP-glucuronosyltransferase (UGT) isoforms.

The detailed mechanisms on licorice-drug interaction remain to be unclear. The aim of the present study is to investigate the inhibition of important UGT isoforms by two important ingredients of licorice, liquiritin, and liquiritigenin. The results showed that liquiritigenin exhibited stronger inhibition towards all the tested UGT isoforms than liquiritin. Data fitting using Dixon and Lineweaver-Burk plots demonstrated the competitive inhibition of liquiritigenin towards UGT1A1 and UGT1A9-mediated 4-MU glucuronidation reaction. The inhibition kinetic parameters (Ki ) were calculated to be 9.1 and 3.2 µM for UGT1A1 and UGT1A9, respectively. Substrate-dependent inhibition behaviour was also observed for UGT1A1 in the present study. All these results will be helpful for understanding the deep mechanism of licorice-drug interaction. However, when translating these in vitro parameters into in vivo situations, more complex factors should be considered, such as substrate-dependent inhibition of UGT isoforms, the contribution of UGT1A1 and UGT1A9 towards the metabolism of drugs, and many factors affecting the abundance of ingredients in the licorice.

Metabolism of fenofibrate in beagle dogs: new metabolites identified and metabolic pathways revealed.

Fenofibrate is a prototypical agonist of peroxisome proliferator-activated receptor alpha (PPARalpha) which is well known to be associated with species related carcinogenesis. Important species differences have been reported in its metabolism and elimination pattern. Its new metabolites have been revealed in Cynomolgus monkeys and Sprague-Dawley rats. However in beagle dogs, several polar metabolites of fenofibrate have not been identified yet. In this study, beagle dogs were orally dosed with fenofibrate mixed with feeds. Urine and plasma samples were collected and subject to LC-MS/MS by comparison with authentic compounds and confirmed using an API 4000 Q-TRAP system. In vitro cultured primary hepatocytes were used to reveal metabolic pathways and confirm the data in vivo. Seven new metabolites of fenofibrate in dogs were identified, and their metabolic pathways were revealed. Fenofibrate in beagle dogs was found to be more prone to be metabolized into other secondary metabolites than fenofibric acid, compared with that in rats.

Down-regulation of hepatic CLOCK by PPARα is involved in inhibition of NAFLD.

This work aimed to investigate the role of nuclear factor peroxisome proliferator-activated receptor α (PPARα) in modification of circadian clock and their relevance to development of nonalcoholic fatty liver disease (NAFLD). Both male wild-type (WT) and Pparα-null (KO) mice treated with high-fat diet (HFD) were used to explore the effect of PPARα and lipid diet on the circadian rhythm. WT, KO, and PPARα-humanized (hPPARα) mice were treated with PPARα agonist fenofibrate to reveal the hPPARα dependence of circadian locomotor output cycles kaput (CLOCK) down-regulation. The mouse model and hepatocyte experiments were designed to verify the action of PPARα in down-regulating CLOCK and lipid accumulation in vivo and in vitro. Strongest NAFLD developed in mice fed 45%HFD, and it was inhibited in WT mice. The activity rhythm of WT mice was found to be different from that of the KO mice on normal diet and HFD. The core circadian factor CLOCK was down-regulated by HFD in both WT and KO mice in the liver, not in the hypothalamus. More interestingly, hepatic CLOCK was down-regulated by basal PPARα and activated PPARα in dose dependence of fenofibrate. Accordingly, CLOCK down-regulation dependent of PPARα activity was involved in inhibition of lipid metabolism in hepatocytes. Down-regulation of hepatic CLOCK by basal PPARα contributes to tolerance against development of NAFLD. Inhibition of CLOCK by activated PPARα is involved in inhibition of NAFLD by PPARα agonists. KEY MESSAGES: • PPARα inhibited NAFLD development induced by HFD. • PPARα mediated modifications of circadian rhythm and the hepatic circadian factor CLOCK in NAFLD models. • Down-regulation of hepatic CLOCK by basal PPARα contributed to tolerance against development of NAFLD. • Inhibition of CLOCK by activated PPARα was involved in therapeutic actions against fatty liver diseases by PPARα agonists.

Hepatocytic AP-1 and STAT3 contribute to chemotaxis in alphanaphthylisothiocyanate-induced cholestatic liver injury.

The development of cholestatic liver injury (CLI) involves inflammation, but the dominant pathway mediating the chemotaxis is not yet established. This work explored key signaling pathway mediating chemotaxis in CLI and the role of Kupffer cells in the inflammatory liver injury. Probe inhibitors T-5224 (100 mg/kg) for AP-1 and C188-9 (100 mg/kg) for STAT3 were used to validate key inflammatory pathways in alpha-naphthylisothiocyanate (ANIT, 100 mg/kg)-induced CLI. Two doses of GdCl3 (10 mg/kg and 40 mg/kg) were used to delete Kupffer cells and explore their role in CLI. Serum and liver samples were collected for biochemical and mechanism analysis. The liver injury in ANIT-treated mice were significantly increased supported by biochemical and histopathological changes, and neutrophils gathering around the necrotic loci. Inhibitor treatments down-regulated liver injury biomarkers except the level of total bile acid. The chemokine Ccl2 increased by 170-fold and to a less degree Cxcl2 by 45-fold after the ANIT treatment. p-c-Jun and p-STAT3 were activated in the group A but inhibited by the inhibitors in western blot analysis. The immunofluorescence results showed AP-1 not STAT3 responded to inhibitors in ANIT-induced CLI. With or without GdCl3, there was no significant difference in liver injury among the CLI groups. In necrotic loci in CLI, CXCL2 colocalized with hepatocyte biomarker Albumin, not with the F4/80 in Kupffer cells. Conclusively, AP-1 played a more critical role in the inflammation cascade than STAT3 in ANIT-induced CLI. Hepatocytes, not the Kupffer cells released chemotactic factors mediating the chemotaxis in CLI.

Validation of visualized transgenic zebrafish as a high throughput model to assay bradycardia related cardio toxicity risk candidates.

Drug-induced QT prolongation usually leads to torsade de pointes (TdP), thus for drugs in the early phase of development this risk should be evaluated. In the present study, we demonstrated a visualized transgenic zebrafish as an in vivo high-throughput model to assay the risk of drug-induced QT prolongation. Zebrafish larvae 48 h post-fertilization expressing green fluorescent protein in myocardium were incubated with compounds reported to induce QT prolongation or block the human ether-a-go-go-related gene (hERG) K⁺ current. The compounds sotalol, indapaminde, erythromycin, ofoxacin, levofloxacin, sparfloxacin and roxithromycin were additionally administrated by microinjection into the larvae yolk sac. The ventricle heart rate was recorded using the automatic monitoring system after incubation or microinjection. As a result, 14 out of 16 compounds inducing dog QT prolongation caused bradycardia in zebrafish. A similar result was observed with 21 out of 26 compounds which block hERG current. Among the 30 compounds which induced human QT prolongation, 25 caused bradycardia in this model. Thus, the risk of compounds causing bradycardia in this transgenic zebrafish correlated with that causing QT prolongation and hERG K⁺ current blockage in established models. The tendency that high logP values lead to high risk of QT prolongation in this model was indicated, and non-sensitivity of this model to antibacterial agents was revealed. These data suggest application of this transgenic zebrafish as a high-throughput model to screen QT prolongation-related cardio toxicity of the drug candidates.

Biphasic regulation of intracellular calcium by gemfibrozil contributes to inhibiting L6 myoblast differentiation: implications for clinical myotoxicity.

Gemfibrozil is the most myotoxic fibrate drug commonly used for dyslipidemia, but the mechanism is poorly understood. The current study revealed that gemfibrozil inhibits myoblast differentiation through the regulation of intracellular calcium ([Ca(2+)]i) as revealed in L6 myoblasts by use of laser scan confocal microscopy and flow cytometry using Fluo-4 AM as a probe. Gemfibrozil at 20-400 µM, could regulate [Ca(2+)]i in L6 cells in a biphasic manner, and sustained reduction was observed when the concentration reached 200 µM. Inhibition of L6 differentiation by gemfibrozil was concentration-dependent with maximal effect noted between 200 and 400 µM, as indicated by creatine kinase activities and the differentiation index, respectively. In differentiating L6 myoblasts, gemfibrozil at concentrations below 400 µM led to no significant signs of apoptosis or cytotoxicity, whereas differentiation, inhibited by 200 µM gemfibrozil, was only partially recovered. A good correlation was noted between gemfibrozil concentrations that regulate [Ca(2+)]i and inhibit L6 myoblasts differentiation, and both are within the range of total serum concentrations found in the clinic. These data suggest a potential pharmacodynamic effect of gemfibrozil on myogenesis as a warning sign, in addition to the complex pharmacokinetic interactions. It is also noteworthy that mobilization of [Ca(2+)]i by gemfibrozil may trigger complex biological responses besides myocyte differentiation. Information revealed in this study explores the mechanism of gemfibrozil-induced myotoxicity through the regulation of intracellular calcium.

Therapeutic action against chronic cholestatic liver injury by low-dose fenofibrate involves anti-chemotaxis via JNK-AP1-CCL2/CXCL2 signaling.

BACKGROUND: Fenofibrate was reported to be beneficial for cholestasis in combination with ursodeoxycholic acid. However, its therapeutic action as single therapy for chronic cholestasis and the underlying mechanism are not known. METHODS: In the present study, wild-type (WT) mice were administered a 0.05% ANIT diet to mimic chronic cholestatic liver injury. Mice were dosed fenofibrate 25 mg/kg twice every day for 10 days to investigate the therapeutic action of fenofibrate on chronic cholestatic liver injury. Ppara-null (KO) mice were used to explore PPARα's role in the therapeutic outcome. RESULTS: Fenofibrate, administered at 25 mg/kg twice daily, substantially reversed ANIT-induced chronic cholestatic liver injury shown by biochemical and pathological end points. The modifications of bile acid metabolism were found to be adaptive responses. The JNK-AP1-CCL2/CXCL2 axis was activated in all the mice administered ANIT which developed chronic cholestatic liver injury. But it was substantially decreased by fenofibrate in WT mice rather than that in KO mice. CONCLUSIONS: Low-dose fenofibrate reversed chronic cholestatic liver injury in mice. The therapeutic action was dependent on PPARα activation and occurred by inhibiting chemotaxis via the JNK-AP1-CCL2/CXCL2 signaling. These data provided an exciting basis for optimization of therapeutic fenofibrate regimen in the clinic. Additionally, they suggested anti-chemotaxis of low-dose fenofibrate in single therapy to treat cholestatic liver diseases.

Inhibition of inflammation by SP600125 in cholestatic liver injury is dependent on the administration­based exposure profile.

SP600125 is a classic inhibitor of c­Jun­N­terminal kinase (JNK) that is widely used in numerous medicinal studies, but its administration regimen has yet to be optimized. In the present study, intraperitoneal (i.p.) and intragastric (i.g.) injections of 15 mg/kg SP600125 was performed in mice to compare the inhibitory effect against JNK signalling in cholestasis induced by α­naphthylisothiocyanate (ANIT). SP600125 at a dose of 15 mg/kg administered by i.p. substantially decreased ANIT­induced liver injury as observed by biochemical and histopathological examinations. The adaptation of bile acid synthesis was inhibited in the A­SP­i.p. group compared with that in the A­SP­i.g. group, as indicated by the expression analysis of CYP7A1 and CYP8B1. The transcription of the pro­inflammatory factors IL­6, IL­1ß, ICAM­1 and IL­10 supported the differential toxic responses. Western blot analysis revealed that JNK signalling activated by ANIT was inhibited more markedly in the A­SP­i.p. group than in the A­SP­i.g. group. The peak concentration and the AUC0­24 of SP600125 in the A­SP­i.p. group were 5­fold and 1.56­fold higher, respectively, compared with those in the A­SP­i.g. group. These data indicated that i.p. administration of SP600125 produced a high plasma exposure profile, which directly determined its efficacy of blocking the JNK signalling. This effect of SP600125 on the JNK pathway may provide an optimized design for future in vivo investigations.

Cholestatic models induced by lithocholic acid and α­naphthylisothiocyanate: Different etiological mechanisms for liver injury but shared JNK/STAT3 signaling.

α­naphthylisothiocyanate (ANIT) is used to induce intrahepatic cholestasis and it is frequently used for investigations into the disease mechanism. The lithocholic acid (LCA) cholestatic model has also been extensively used in various studies; however, to the best of our knowledge, a comparative study determining the hepatotoxic mechanisms induced by these two models has not been previously conducted. In the present study, ICR mice were treated with ANIT or LCA to induce cholestatic liver injury. Biochemical analysis was used to determine the serum. Alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP) and total bile acid (TBA) levels, and histopathological assessment was used to examine the liver tissue. Metabolomic analysis was used for the serum biomarker identification. Reverse transcription­quantitative PCR analysis and western blotting were used to analyze the inflammation biomarkers. The serum metabolome of the ANIT group clustered away from of the LCA group, which was demonstrated by the different modifications of the BA components. ALP level was found to be preferentially increased in the ANIT group from 24 to 48 h. Total BA levels was only increased in the ANIT group at 24 h. In contrast, AST and ALT activity levels were preferentially increased in the LCA group. The bile ducts in the hepatic tissues of the ANIT group were observed to be severely dilated, whereas the presence of edematous hepatocytes around the necrotic lesions and neutrophil infiltration were identified in the LCA group. The expression levels of cholesterol 7α­hydroxylase and sterol 12α­hydroxylase genes were significantly downregulated in the ANIT group compared with the LCA group, where a stronger adaptation of BA metabolism was supported by major differences in the concentration of the BA components. Despite the aforementioned etiological differences in the cholestasis induced by each treatment, the activation of the JNK/STAT3 signaling pathway was similar between the two cholestatic models. In conclusion, these data suggested that the liver injury induced by ANIT may be cholestatic, while the liver injury caused in the LCA model may be hepatocellular. Moreover, the downstream cholestatic liver injury in both models was indicated to be mediated by the JNK/STAT3 signaling pathway.

PPARα mediates night neon light-induced weight gain: role of lipid homeostasis.

Rationale: Light pollution leads to high risk of obesity but the underlying mechanism is not known except for the influence of altered circadian rhythm. Peroxisome proliferator-activated receptor α (PPARα) regulates lipid metabolism, but its role in circadian-related obesity is not clear. Methods: Wild-type (WT) and Ppara-null (KO) mice on a high-fat diet (HFD) were treated with neon light at night for 6 weeks. Body weights were recorded and diet consumption measured. The hypothalamus, liver, adipose and serum were collected for mechanism experimentation. Results: WT mice on a HFD and exposed to night neon light gained about 19% body weight more than the WT control mice without light exposure and KO control mice on a HFD and exposed to night neon light. The increase in adipose tissue weight and adipocyte size led to the differences in body weights. Biochemical analysis suggested increased hepatic lipid accumulated and increased transport of lipid from the liver to peripheral tissues in the WT mice that gained weight under neon light exposure. Unlike KO mice, the expression of genes involved in lipid metabolism and the circadian factor circadian locomotor output cycles kaput (CLOCK) in both liver and adipose tissues were elevated in WT mice under neon light exposure. Conclusions: PPARα mediated weight gain of HFD-treated mice exposed to night neon light. More lipids were synthesized in the liver and transported to peripheral tissue leading to adaptive metabolism and lipid deposition in the adipose tissue. These data revealed an important mechanism of obesity induced by artificial light pollution where PPARα was implicated.

[Preparation of chitosan/hydroxyapatite membrane and its effect on cell culture].

Compound membranes of chitosan/hydroxyapatite were prepared by blending. The physical performance showed that the air-water contact angles decreased from chitosan's 103 degrees to chitosan/hydroxyapatite's 57 and the water adsorption rate increased slightly. When immersed into culture medium, the materials adsorbed Ca2+, and low crystalline hydroxyapatite deposited on the surface of the membranes. Chitosan/hydroxyapatite compound membranes could enhance the attachment and proliferation of mescenchymal stem cells (MSCs). After 12 days' induction on the materials, the alkaline phosphatase (ALP) activity value of MSCs on the compound membrane was 10.1, being much higher than 1.6 on chitosan membrane (P<0.01). All these results indicate that chitosan does not have very good affinity for MSCs, but the biocompatibility of chitosan can be apparently enhanced after mixing with hydroxyapatite. The compound membrane stimulates MSCs to differentiate into osteoblasts and it may be a good potential material for bone substitution.

Basal PPARα inhibits bile acid metabolism adaptation in chronic cholestatic model induced by α-naphthylisothiocyanate.

Cholestasis is one of the most challenging diseases to be treated in current hepatology. However little is known about the adaptation difference and the underlying mechanism between acute and chronic cholestasis. In this study, wild-type and Pparα-null mice were orally administered diet containing 0.05% ANIT to induce chronic cholestasis. Biochemistry, histopathology and serum metabolome analysis exhibited the similar toxic phenotype between wild-type and Pparα-null mice. Bile acid metabolism was strongly adapted in Pparα-null mice but not in wild-type mice. The Shp and Fxr mRNA was found to be doubled in cholestatic Pparα-null mice compared with the control group. Western blot confirmed the up-regulated expression of FXR in Pparα-null mice treated with ANIT. Inflammation was found to be stronger in Pparα-null mice than those in wild-type mice in chronic cholestasis. These data chain indicated that bile acid metabolism and inflammation signaling were different between wild-type and Pparα-null mice developing chronic cholestasis, although their toxic phenotypes could not be discriminated. So basal PPARα cross-talked with FXR and inhibited bile acid metabolism adaptation in chronic cholestasis.

PPARα-independent action against metabolic syndrome development by fibrates is mediated by inhibition of STAT3 signalling.

OBJECTIVES: Metabolic syndrome (MS) is the concurrence of at least three of five medical conditions: obesity, high blood pressure, insulin resistance, high serum triglyceride (TG) and low serum high-density lipoprotein levels. While fibrates are used to treat disorders other than the lowering serum TG, the mechanism by which fibrates decrease MS has not been established. METHODS: In this study, wild-type and Ppara-null mice fed a medium-fat diet (MFD) were administered gemfibrozil and fenofibrate for 3 months respectively, to explore the effect and action mechanism. KEY FINDINGS: In Ppara-null mice, MFD treatment increased body weight, adipose tissue, serum TG and impaired glucose tolerance. These phenotypes were attenuated in two groups treated with gemfibrozil and fenofibrate. The STAT3 pathway was activated in adipose and hepatic tissues in positive control, and inhibited in groups treated with gemfibrozil and fenofibrate. The above phenotypes and inflammation were not observed in any wild-type group. In 3T3-L1 adipogenic stem cells treated with high glucose, STAT3 knockdown greatly decreased the number of lipid droplets. CONCLUSIONS: Low dose of clinical fibrates was effective against MS development independent of PPARα, and this action was mediated by STAT3 signalling inhibition in adipose tissue and, to a lesser extent, in hepatic tissues.

Peroxisome Proliferator-Activated Receptor α Activation Suppresses Cytochrome P450 Induction Potential in Mice Treated with Gemfibrozil.

Gemfibrozil, a peroxisome proliferator-activated receptor α (PPARα) agonist, is widely used for hypertriglyceridaemia and mixed hyperlipidaemia. Drug-drug interaction of gemfibrozil and other PPARα agonists has been reported. However, the role of PPARα in cytochrome P450 (CYP) induction by fibrates is not well known. In this study, wild-type mice were first fed gemfibrozil-containing diets (0.375%, 0.75% and 1.5%) for 14 days to establish a dose-response relationship for CYP induction. Then, wild-type mice and Pparα-null mice were treated with a 0.75% gemfibrozil-containing diet for 7 days. CYP3a, CYP2b and CYP2c were induced in a dose-dependent manner by gemfibrozil. In Pparα-null mice, their mRNA level, protein level and activity were induced more than those in wild-type mice. So, gemfibrozil induced CYP, and this action was inhibited by activated PPARα. These data suggested that the induction potential of CYPs was suppressed by activated PPARα, showing a potential role of this receptor in drug-drug interactions and metabolic diseases treated with fibrates.