Project description:A functional interaction between peroxisome proliferator-activated receptor alpha (PPARalpha) and components of the circadian clock has been suggested; however, it remains to be clarified whether those transcriptional factors interact with each other to regulate the expression of their target genes. In this study, we used a ligand of PPARalpha, bezafibrate, to search the PPARalpha-regulated genes that express in a CLOCK-dependent circadian manner. Microarrays analyses using hepatic RNA isolated from bezafibrate treated-wild type, Clock mutant (Clk/Clk), and PPARalpha-null mice revealed that 136 genes are transcriptionally regulated by PPARalpha in a CLOCK-dependent manner. Clk/Clk mutant mice with Jcl:ICR background, wild-type mice with the same strain, and PPARalpha-null mice aged 6-12 weeks were housed under a 12 h light-12 h dark cycle [LD 12:12; lights on at Zeitgeber time (ZT) 0]. For chronic treatment of bezafibrate, mice were provided with either a normal diet or the same diet containing 0.5% w/w bezafibrate for 5 days. A white fluorescent lamp provided light (300 - 500 lux at cage level) during the day. To examine the transient effect of bezafibrate injection on hepatic gene expression, bezafibrate was dissolved in warm (~40 C) sterile corn oil (Sigma) at a concentration of 10 mg/ml and administered intraperitoneally (i.p.) in a single dose of 100 mg/kg body weight at ZT2. To examine the PPARalpha-regulated genes that express in a CLOCK-dependent manner in mice, we performed oligonucleotide microarray analysis at ZT14, when CLOCK/BMAL1 transcriptional activity is maximal, using RNA isolated from wild-type (n = 3), Clock mutant (n = 3), and PPARalpha-null mice (n = 3) treated with bezafibrate for 5 days, and control wild-type mice (n = 3). Livers were collected and frozen in liquid nitrogen. Total RNA (250 ng) was extracted using RNAiso.
Project description:A functional interaction between peroxisome proliferator-activated receptor alpha (PPARalpha) and components of the circadian clock has been suggested; however, it remains to be clarified whether those transcriptional factors interact with each other to regulate the expression of their target genes. In this study, we used a ligand of PPARalpha, bezafibrate, to search the PPARalpha-regulated genes that express in a CLOCK-dependent circadian manner. Microarrays analyses using hepatic RNA isolated from bezafibrate treated-wild type, Clock mutant (Clk/Clk), and PPARalpha-null mice revealed that 136 genes are transcriptionally regulated by PPARalpha in a CLOCK-dependent manner.
Project description:Toxicogenomic Dissection of the Perfluorooctanoic Acid (PFOA) Transcript Profile in Mouse Liver: Evidence for the Involvement of Nuclear Receptors PPARalpha and CAR; We performed a toxicogenomics dissection of the transcript profiles in the mouse liver after exposure to PFOA. We uncovered classes of genes that were regulated independently of PPARalpha. Some of these genes, including those involved in lipid metabolism, may be regulated by PPARbeta/delta or PPARgamma, whereas others, such as those involved in xenobiotic metabolism are likely regulated through CAR. Experiment Overall Design: 129S1/SvlmJ wild-type and PPARalpha-null mice were exposed to 3 mg/kg/day PFOA or water for 7 days. Total RNA was isolated from liver samples and gene expression analyzed using Affymetrix Mouse 430 2.0 GeneChips. Data from 16 samples, with four mice in each of the 4 treatment groups, were analyzed.
Project description:Bezafibrate (BEZ), a pan activator of peroxisome proliferator-activated receptors (PPARs), is generally used to treat hyperlipidemia. Clinical trials on patients suffering from type 2 diabetes indicated that BEZ also has beneficial effects on glucose metabolism, but the underlying mechanisms remain elusive. Much less is known about the function of BEZ in type 1 diabetes. Here, we show that BEZ treatment markedly improves hyperglycemia, glucose and insulin tolerance in streptozotocin (STZ)-treated mice, an insulin-deficient mouse model of type 1 diabetes presenting with very high blood glucose levels. Furthermore, BEZ-treated mice also exhibited improved metabolic flexibility as well as an enhanced mitochondrial mass and function in the liver. Our data demonstrate a beneficial effect of BEZ treatment on STZ mice reducing diabetes and suggest that BEZ ameliorates impaired glucose metabolism possibly via augmented hepatic mitochondrial performance, improved insulin sensitivity and metabolic flexibility. We performed gene expression microarray analysis on liver tissue derived from streptozotocin-treated mice treated with bezafibrate in addition.
Project description:Unlike the PPARalpha agonist W14,643, PFOA is capable of inducing effects independently of PPARa. Genes altered in the PPARalpha-null mouse following exposure to PFOA included those associated with fatty acid metabolism, inflammation, xenobiotic metabolism, and cell cycle progression. The specific signaling pathway(s) responsible for these effects is not readily apparent but it is conceivable that other members of the nuclear receptor superfamily such as PPARbeta/delta and CAR may be involved. Keywords: dose response Wild-type and PPARa-null mice were orally dosed for 7 days with either PFOA (1 or 3 mg/kg), the PPARalpha agonist WY-14,643 (50 mg/kg), or compound vehicle. Gene profiling analysis was conducted on 4 animals per group using Applied Biosystems Mouse Genome Survey Microarrays.
Project description:Role of PPARalpha in the effects of DEHP on the hepatic expression of a selection of mouse genes related to nuclear receptor signaling. Di-(2-ethylhexyl)-phthalate (DEHP), a widely used plasticizer, is detected in consumerâs body fluids. Contamination occurs through environmental and food chain sources. In mouse liver, DEHP activates the peroxisome proliferator-activated receptor alpha (PPARalpha) and regulates the expression of its target genes. Several in vitro investigations support the simultaneous recruitment of additional nuclear receptor pathways. We investigated, in vivo, the hepatic impact of low doses of DEHP on PPARalpha activation, and the putative activation of additional signalling pathways. Wild-type and PPARalpha-deficient mice were exposed to different doses of DEHP. Gene expression profiling delineated the role of PPARalpha and revealed a PPARalpha-independent regulation of several prototypic Constitutive Androstane Receptor (CAR) target genes. This finding demonstrates that CAR also represents a transcriptional regulator sensitive to phthalates. CAR-mediated effects of DEHP provide a new rationale for most endpoints of phthalates toxicity described previously, including endocrine disruption, hepatocarcinogenesis and the metabolic syndrome. Keywords: Treatment effect One-color macroarrays, 6 experimental conditions: Wild type (WT) and PPARalpha-deficient mice (PPAR) were treated with vehicle (Ctrl) or with di-(2-ethylhexyl)-phthalate (DEHP) at 20 mg/kg/day (D20) or 200 mg/kg/day (D200) for 21 days, Biological replicates: 10 for each group, One replicate per array
Project description:Circadian clocks drive 24-h rhythms of physiology and behavior. The circadian clock of hepatocytes has been shown to regulate glucose metabolism, and we were interested if rescuing liver clock function can reverse metabolic impairments in hyperphagic/obese Clock-D19 mutant mice. We compared transcripomte regulation in livers (at Zeitgeber time ZT10) of wild-type (C57BL/6J) and Clock-D19 mice and Clock-D19 mice with genetic rescue of liver clock function using hydrodynamic tail vein injection of a WT-CLOCK expression plasmid
Project description:We analyzed the effect of chronic (14 days) treatment with a selective PPARalpha agonist on liver gene expression in vivo in mice (B6/J). The experiment was done in mice from both sexes. The experiment was done in both wild-type (LWT) and in mice with hepatocyte-restricted deletion of PPARalpha.