Limits...
Comprehensive analysis of PPARalpha-dependent regulation of hepatic lipid metabolism by expression profiling.

Rakhshandehroo M, Sanderson LM, Matilainen M, Stienstra R, Carlberg C, de Groot PJ, Müller M, Kersten S - PPAR Res (2007)

Bottom Line: Using an in silico screening approach, one or more PPAR response elements (PPREs) were identified in each of these genes.Regulation of Pnpla2, Lipe, and Mgll, which are involved in triglyceride hydrolysis, was studied under conditions of elevated hepatic lipids.Our study illustrates the power of transcriptional profiling to uncover novel PPARalpha-regulated genes and pathways in liver.

View Article: PubMed Central - PubMed

Affiliation: Nutrigenomics Consortium, Wageningen Centre for Food Sciences, Wageningen, The Netherlands.

ABSTRACT
PPARalpha is a ligand-activated transcription factor involved in the regulation of nutrient metabolism and inflammation. Although much is already known about the function of PPARalpha in hepatic lipid metabolism, many PPARalpha-dependent pathways and genes have yet to be discovered. In order to obtain an overview of PPARalpha-regulated genes relevant to lipid metabolism, and to probe for novel candidate PPARalpha target genes, livers from several animal studies in which PPARalpha was activated and/or disabled were analyzed by Affymetrix GeneChips. Numerous novel PPARalpha-regulated genes relevant to lipid metabolism were identified. Out of this set of genes, eight genes were singled out for study of PPARalpha-dependent regulation in mouse liver and in mouse, rat, and human primary hepatocytes, including thioredoxin interacting protein (Txnip), electron-transferring-flavoprotein beta polypeptide (Etfb), electron-transferring-flavoprotein dehydrogenase (Etfdh), phosphatidylcholine transfer protein (Pctp), endothelial lipase (EL, Lipg), adipose triglyceride lipase (Pnpla2), hormone-sensitive lipase (HSL, Lipe), and monoglyceride lipase (Mgll). Using an in silico screening approach, one or more PPAR response elements (PPREs) were identified in each of these genes. Regulation of Pnpla2, Lipe, and Mgll, which are involved in triglyceride hydrolysis, was studied under conditions of elevated hepatic lipids. In wild-type mice fed a high fat diet, the decrease in hepatic lipids following treatment with the PPARalpha agonist Wy14643 was paralleled by significant up-regulation of Pnpla2, Lipe, and Mgll, suggesting that induction of triglyceride hydrolysis may contribute to the anti-steatotic role of PPARalpha. Our study illustrates the power of transcriptional profiling to uncover novel PPARalpha-regulated genes and pathways in liver.

No MeSH data available.


Related in: MedlinePlus

Regulation of selected genes involvedin lipid metabolism in primary hepatocytes by Wy14643. (a) Microarray-basedheat map showing relative expression levels of genes calculated using a multichipmodified gamma model for oligonucleotide signal (multi-mgMOS) and a remappedchip description file. Expression levels in the absence of ligand were set at1. (b) Relative induction of expression of selected genes in primaryhepatocytes by Wy14643, as determined by Q-PCR. The primary hepatocytes usedfor Q-PCR and microarray analysis were from independent experiments. Genes werenot included when expression was extremely low (Ct > 30). Error bars representSD. The effect of Wy14643 on gene expression was evaluated by Student  test.*; **.
© Copyright Policy - open-access
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2233741&req=5

fig5: Regulation of selected genes involvedin lipid metabolism in primary hepatocytes by Wy14643. (a) Microarray-basedheat map showing relative expression levels of genes calculated using a multichipmodified gamma model for oligonucleotide signal (multi-mgMOS) and a remappedchip description file. Expression levels in the absence of ligand were set at1. (b) Relative induction of expression of selected genes in primaryhepatocytes by Wy14643, as determined by Q-PCR. The primary hepatocytes usedfor Q-PCR and microarray analysis were from independent experiments. Genes werenot included when expression was extremely low (Ct > 30). Error bars representSD. The effect of Wy14643 on gene expression was evaluated by Student test.*; **.

Mentions: To examine whether the PPAR-dependentregulation of the set of genes shown in Figure 3 was not an indirectconsequence of metabolic perturbations elicited by the experimental challenge,we studied the effect of PPAR activation in primary mouse, rat, and human hepatocytes. Gene expression was first analyzed by microarray (Figure 5(a)), followed by targeted analysis of the selected 8 genes by Q-PCR (Figure 5(b)). Expressionlevels were calculated by applying a multichip modified gamma model foroligonucleotide signal (multi-mgMOS) [22] and a remapped chip description file [23]to allow for parallel analysis of the same gene within different species. Expressionof almost every gene studied was highly upregulated by Wy14643 in mouse and rathepatocytes, compared to a more modest or no induction in human hepatocytes. Forreasons that are not completely clear, in human hepatocytes, data from Q-PCRand microarray did not always perfectly align. Overall, the data indicate thatthe PPAR-dependent regulation observed in vivo can be reproduced in primary hepatocytes. Furthermore, the data suggest thatexpression of 6 genes is governed by PPAR in human as well.


Comprehensive analysis of PPARalpha-dependent regulation of hepatic lipid metabolism by expression profiling.

Rakhshandehroo M, Sanderson LM, Matilainen M, Stienstra R, Carlberg C, de Groot PJ, Müller M, Kersten S - PPAR Res (2007)

Regulation of selected genes involvedin lipid metabolism in primary hepatocytes by Wy14643. (a) Microarray-basedheat map showing relative expression levels of genes calculated using a multichipmodified gamma model for oligonucleotide signal (multi-mgMOS) and a remappedchip description file. Expression levels in the absence of ligand were set at1. (b) Relative induction of expression of selected genes in primaryhepatocytes by Wy14643, as determined by Q-PCR. The primary hepatocytes usedfor Q-PCR and microarray analysis were from independent experiments. Genes werenot included when expression was extremely low (Ct > 30). Error bars representSD. The effect of Wy14643 on gene expression was evaluated by Student  test.*; **.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2233741&req=5

fig5: Regulation of selected genes involvedin lipid metabolism in primary hepatocytes by Wy14643. (a) Microarray-basedheat map showing relative expression levels of genes calculated using a multichipmodified gamma model for oligonucleotide signal (multi-mgMOS) and a remappedchip description file. Expression levels in the absence of ligand were set at1. (b) Relative induction of expression of selected genes in primaryhepatocytes by Wy14643, as determined by Q-PCR. The primary hepatocytes usedfor Q-PCR and microarray analysis were from independent experiments. Genes werenot included when expression was extremely low (Ct > 30). Error bars representSD. The effect of Wy14643 on gene expression was evaluated by Student test.*; **.
Mentions: To examine whether the PPAR-dependentregulation of the set of genes shown in Figure 3 was not an indirectconsequence of metabolic perturbations elicited by the experimental challenge,we studied the effect of PPAR activation in primary mouse, rat, and human hepatocytes. Gene expression was first analyzed by microarray (Figure 5(a)), followed by targeted analysis of the selected 8 genes by Q-PCR (Figure 5(b)). Expressionlevels were calculated by applying a multichip modified gamma model foroligonucleotide signal (multi-mgMOS) [22] and a remapped chip description file [23]to allow for parallel analysis of the same gene within different species. Expressionof almost every gene studied was highly upregulated by Wy14643 in mouse and rathepatocytes, compared to a more modest or no induction in human hepatocytes. Forreasons that are not completely clear, in human hepatocytes, data from Q-PCRand microarray did not always perfectly align. Overall, the data indicate thatthe PPAR-dependent regulation observed in vivo can be reproduced in primary hepatocytes. Furthermore, the data suggest thatexpression of 6 genes is governed by PPAR in human as well.

Bottom Line: Using an in silico screening approach, one or more PPAR response elements (PPREs) were identified in each of these genes.Regulation of Pnpla2, Lipe, and Mgll, which are involved in triglyceride hydrolysis, was studied under conditions of elevated hepatic lipids.Our study illustrates the power of transcriptional profiling to uncover novel PPARalpha-regulated genes and pathways in liver.

View Article: PubMed Central - PubMed

Affiliation: Nutrigenomics Consortium, Wageningen Centre for Food Sciences, Wageningen, The Netherlands.

ABSTRACT
PPARalpha is a ligand-activated transcription factor involved in the regulation of nutrient metabolism and inflammation. Although much is already known about the function of PPARalpha in hepatic lipid metabolism, many PPARalpha-dependent pathways and genes have yet to be discovered. In order to obtain an overview of PPARalpha-regulated genes relevant to lipid metabolism, and to probe for novel candidate PPARalpha target genes, livers from several animal studies in which PPARalpha was activated and/or disabled were analyzed by Affymetrix GeneChips. Numerous novel PPARalpha-regulated genes relevant to lipid metabolism were identified. Out of this set of genes, eight genes were singled out for study of PPARalpha-dependent regulation in mouse liver and in mouse, rat, and human primary hepatocytes, including thioredoxin interacting protein (Txnip), electron-transferring-flavoprotein beta polypeptide (Etfb), electron-transferring-flavoprotein dehydrogenase (Etfdh), phosphatidylcholine transfer protein (Pctp), endothelial lipase (EL, Lipg), adipose triglyceride lipase (Pnpla2), hormone-sensitive lipase (HSL, Lipe), and monoglyceride lipase (Mgll). Using an in silico screening approach, one or more PPAR response elements (PPREs) were identified in each of these genes. Regulation of Pnpla2, Lipe, and Mgll, which are involved in triglyceride hydrolysis, was studied under conditions of elevated hepatic lipids. In wild-type mice fed a high fat diet, the decrease in hepatic lipids following treatment with the PPARalpha agonist Wy14643 was paralleled by significant up-regulation of Pnpla2, Lipe, and Mgll, suggesting that induction of triglyceride hydrolysis may contribute to the anti-steatotic role of PPARalpha. Our study illustrates the power of transcriptional profiling to uncover novel PPARalpha-regulated genes and pathways in liver.

No MeSH data available.


Related in: MedlinePlus