The Peroxisomal 3-keto-acyl-CoA thiolase B Gene Expression Is under the Dual Control of PPARα and HNF4α in the Liver

PPARα and HNF4α are nuclear receptors that control gene transcription by direct binding to specific nucleotide sequences. Using transgenic mice deficient for either PPARα or HNF4α, we show that the expression of the peroxisomal3-keto-acyl-CoA thiolase B(Thb) is under the dependence of these two transcription factors. Transactivation and gel shift experiments identified a novel PPAR response element within intron 3 of theThbgene, by which PPARα but not HNF4α transactivates. Intriguingly, we found that HNF4α enhanced PPARα/RXRα transactivation from TB PPRE3 in a DNA-binding independent manner. Coimmunoprecipitation assays supported the hypothesis that HNF4α was physically interacting with RXR…

Induction des cytochromes P450 1A1 et 1A2 et d'autres enzymes du métabolisme des xénobiotiques par des caroténoïdes chez le rat et la souris . Implication du récepteur AH.

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Fibrate induction of the adrenoleukodystrophy-related gene (ABCD2)

X-linked adrenoleukodystrophy (X-ALD) is a neurodegenerative disease due to a defect in the ABCD1 (ALD) gene. ABCD1, and the two close homologues ABCD2 (ALDR) and ABCD3 (PMP70), are genes encoding ATP-binding cassette half-transporters of the peroxisomal membrane. As overexpression of the ABCD2 or ABCD3 gene can reverse the biochemical phenotype of X-ALD (reduced beta-oxidation of very-long-chain fatty acids), pharmacological induction of these partially redundant genes may represent a therapeutic approach to X-ALD. We previously reported that the ABCD2 and ABCD3 genes could be strongly induced by fibrates, which are hypolipidaemic drugs and peroxisome-proliferators in rodents. We provide e…

Peroxisome proliferator-activated receptor α (PPARα) activators induce hepatic farnesyl diphosphate synthase gene expression in rodents

Fibrates are hypolipidemic drugs that exert multiple effects on lipid metabolism by activating peroxisome proliferator-activated receptor alpha (PPARalpha) and modulating the expression of many target genes. In order to investigate the link between PPARalpha and cholesterol synthesis, we analysed the effect of fibrates on expression of the farnesyl diphosphate synthase (FPP synthase) gene, known to be regulated by sterol regulatory element-binding proteins (SREBPs), in conjunction with HMG-CoA reductase. In wild-type mice, both fenofibrate and WY 14,643 induced FPP synthase gene expression, an effect impaired in PPARalpha-null mice. A three-fold induction was observed in ciprofibrate-treate…

New molecular aspects of regulation of mitochondrial activity by fenofibrate and fasting

Abstract Fenofibrate and fasting are known to regulate several genes involved in lipid metabolism in a similar way. In this study measuring several mitochondrial enzyme activities, we demonstrate that, in contrast to citrate synthase and complex II, cytochrome c oxidase (COX) is a specific target of these two treatments. In mouse liver organelles, Western blot experiments indicated that mitochondrial levels of p43, a mitochondrial T3 receptor, and mitochondrial peroxisome proliferator activated receptor (mt-PPAR), previously described as a dimeric partner of p43 in the organelle, are increased by both fenofibrate and fasting. In addition, in PPARα-deficient mice, this influence was abolishe…

Dehydroepiandrosterone up-regulates the Adrenoleukodystrophy-related gene (ABCD2) independently of PPAR alpha in rodents

International audience; X-linked adrenoleukodystrophy (X-ALD) is a neurodegenerative disease caused by mutations in the ABCD1 gene, which encodes a peroxisomal ABC transporter, ALDP, supposed to participate in the transport of very long chain fatty acids (VLCFA). The adrenoleukodystrophyrelated protein (ALDRP), which is encoded by the ABCD2 gene, is the closest homolog of ALDP and is considered as a potential therapeutic target since functional redundancy has been demonstrated between the two proteins. Pharmacological induction of Abcd2 by fibrates through the activation of PPARa has been demonstrated in rodent liver. DHEA, the most abundant steroid in human, is described as a PPARa activat…

Effects of peroxisome proliferator-activated receptor alpha activation on pathways contributing to cholesterol homeostasis in rat hepatocytes

International audience; Peroxisome proliferator-activated receptor alpha (PPARa) activation by fibrates controls expression of several genes involved in hepatic cholesterol metabolism. Other genes could be indirectly controlled in response to changes in cellular cholesterol availability. To further understand how fibrates may affect cholesterol synthesis, we investigated in parallel the changes in the metabolic pathways contributing to cholesterol homeostasis in liver. Ciprofibrate increased HMG-CoA reductase and FPP synthase mRNA levels in rat hepatocytes, together with cholesterogenesis from [14C] acetate and [3H] mevalonate. The up-regulation observed in fenofibrate- and WY-14,643-treate…

Tissue-specific Expression of Two Peroxisomal 3-ketoacyl-CoA Thiolase Genes in Wild and PPARα-null Mice and Induction by Fenofibrate

Our laboratory cloned two peroxisomal 3-ketoacyl-CoA thiolase genes in mouse. These genes were named mThA (mouse peroxisomal Thiolase A) and mThB (mouse peroxisomal Thiolase B) by comparison with peroxisomal thiolase genes known in rat (Hijikata et al. 1990, Bodnar & Rachubinski, 1990). In this study, we analysed the tissue expression of the two thiolase genes on wild and on PPARa-null mice.

Molecular cloning, gene structure and expression profile of two mouse peroxisomal 3-ketoacyl-CoA thiolase genes

Abstract Background In rats, two peroxisomal 3-ketoacyl-CoA thiolase genes (A and B) have been cloned, whereas only one thiolase gene is found in humans. The aim of this study was thus to clone the different mouse thiolase genes in order to study both their tissue expression and their associated enzymatic activity. Results In this study, we cloned and characterized two mouse peroxisomal 3-ketoacyl-CoA thiolase genes (termed thiolase A and B). Both thiolase A and B genes contain 12 exons and 11 introns. Using RNA extracted from mouse liver, we cloned the two corresponding cDNAs. Thiolase A and B cDNAs possess an open reading frame of 1272 nucleotides encoding a protein of 424 amino acids. In…

In rats, two peroxisomal 3-ketoacyl-CoA thiolase genes (A and B) have been cloned, whereas only one thiolase gene is found in humans. The aim of this study was thus to clone the different mouse thiolase genes in order to study both their tissue expression and their associated enzymatic activity. In this study, we cloned and characterized two mouse peroxisomal 3-ketoacyl-CoA thiolase genes (termed thiolase A and B). Both thiolase A and B genes contain 12 exons and 11 introns. Using RNA extracted from mouse liver, we cloned the two corresponding cDNAs. Thiolase A and B cDNAs possess an open reading frame of 1272 nucleotides encoding a protein of 424 amino acids. In the coding sequence, the tw…

Ah receptor-dependant CYP1A induction by two carotenoids, canthaxanthin and beta-apo-8'-carotenal, with no affinity for the TCDD binding site

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Pharmacological Induction of Redundant Genes for a Therapy of X-ALD

X-linked adrenoleukodystrophy (X-ALD) is a recessive neurologic disease with an incidence among males of 1/17 000. Since the identification of the X-ALD gene (ABCD1) ten years ago (Mosser et al 1993), no satisfactory therapy has been available. A close homologue (ABCD2) was then cloned and presented as a putative modifier gene that could account for some of the extreme phenotypic variability of X-ALD (Lombard-Platet et al 1996). The inducibility of Abcd2 by the hypolipidemic drug fenofibrate in the liver of rodents (Albet et al 1997), correlated to a partial normalisation of the biochemical phenotype of X-ALD (Netik et al 1999), opened up the way of a pharmacological therapy of X-ALD. The b…