Unknown,Transcriptomics,Genomics,Proteomics

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PPAR-alpha dependent regulation of vanin-1 mediates hepatic lipid metabolism.

ABSTRACT: Peroxisome proliferator-activated receptor alpha (PPARÎ±) is a key regulator of hepatic fat oxidation that serves as an energy source during starvation. Vanin-1 has been described as a putative PPARÎ± target gene in liver, but its function in hepatic lipid metabolism is unknown. We investigated the regulation of vanin-1, and total vanin activity, by PPARÎ± in mice and humans. Furthermore, the function of vanin-1 in the development of hepatic steatosis in response to starvation was examined in Vnn1 deficient mice, and in rats treated with an inhibitor of vanin activity. Liver microarray analyses reveals that Vnn1 is the most prominently regulated gene after modulation of PPARÎ± activity. In addition, activation of mouse PPARÎ± regulates hepatic- and plasma vanin activity. In humans, consistent with regulation by PPARÎ±, plasma vanin activity increases in all subjects after prolonged fasting, as well as after treatment with the PPARÎ± agonist fenofibrate. In mice, absence of vanin-1 exacerbates the fasting-induced increase in hepatic triglyceride levels. Similarly, inhibition of vanin activity in rats induces accumulation of hepatic triglycerides upon fasting. Microarray analysis reveal that the absence of vanin-1 associates with gene sets involved in liver steatosis, and reduces pathways involved in oxidative stress and inflammation. We show that hepatic vanin-1 is under extremely sensitive regulation by PPARÎ± and that plasma vanin activity could serve as a readout of changes in PPARÎ± activity in human subjects. In addition, our data propose a role for vanin-1 in regulation of hepatic TG levels during fasting. Livers of wild type and vanin-1 knockout mice that were fed or fasted for 24h were subjected to gene expression analysis

ORGANISM(S): Mus musculus

SUBMITTER: Guido Hooiveld

PROVIDER: E-GEOD-51712 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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PPAR-alpha dependent regulation of vanin-1 mediates hepatic lipid metabolism.

van Diepen Janna A JA Jansen Patrick A PA Ballak Dov B DB Hijmans Anneke A Hooiveld Guido J GJ Rommelaere Samuel S Galland Franck F Naquet Philippe P Rutjes Floris P J T FP Mensink Ronald P RP Schrauwen Patrick P Tack Cees J CJ Netea Mihai G MG Kersten Sander S Schalkwijk Joost J Stienstra Rinke R

Journal of hepatology 20140418 2

<h4>Background & aims</h4>Peroxisome proliferator-activated receptor alpha (PPARα) is a key regulator of hepatic fat oxidation that serves as an energy source during starvation. Vanin-1 has been described as a putative PPARα target gene in liver, but its function in hepatic lipid metabolism is unknown.<h4>Methods</h4>We investigated the regulation of vanin-1, and total vanin activity, by PPARα in mice and humans. Furthermore, the function of vanin-1 in the development of hepatic steatosis in res ...[more]

PMID: 24751833

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Project description:Background: Studies in mice have shown that PPARÎ± is an important regulator of lipid metabolism in liver and a key transcription factor involved in the adaptive response to fasting. However, much less is known about the role of PPARÎ± in human liver. Here we set out to study the function of PPARÎ± in human liver via analysis of whole genome gene regulation in human liver slices treated with the PPARÎ± agonist Wy14643. Results: Quantitative PCR indicated that PPARÎ± is well expressed in human liver and human liver slices and that the classical PPARÎ± targets PLIN2, VLDLR, ANGPTL4, CPT1A and PDK4 are robustly induced by PPARÎ± activation. Transcriptomics analysis indicated that 617 genes were upregulated and 665 genes were downregulated by PPARÎ± activation (q value<0.05). Many genes induced by PPARÎ± activation were involved in lipid metabolism (ACSL5, AGPAT9, FADS1, SLC27A4), xenobiotic metabolism (POR, ABCC2, CYP3A5) or the unfolded protein response, whereas most of the downregulated genes were involved in immune-related pathways. Among the most highly repressed genes upon PPARÎ± activation were several chemokines (e.g. CXCL9-11, CCL8, CX3CL1, CXCL6), interferon Î³-induced genes (e.g. IFITM1, IFIT1, IFIT2, IFIT3) and numerous other immune-related genes (e.g. TLR3, NOS2, and LCN2). Comparative analysis of gene regulation by Wy14643 between human liver slices and primary human hepatocytes showed that down-regulation of gene expression by PPARÎ± is much better captured by liver slices as compared to primary hepatocytes. In particular, PPARÎ± activation markedly suppressed immunity/inflammation-related genes in human liver slices but not in primary hepatocytes. Finally, several putative new target genes of PPARÎ± were identified that were commonly induced by PPARÎ± activation in the two human liver model systems, including TSKU, RHOF, CA12 and VSIG10L. Conclusion: Our manuscript demonstrates the suitability and superiority of human liver slices over primary hepatocytes for studying the functional role of PPARÎ± in human liver. Our data underscore the major role of PPARÎ± in regulation of hepatic lipid and xenobiotic metabolism in human liver and reveal a marked immuno-suppressive/anti-inflammatory effect of PPARÎ± in human liver slices that may be therapeutically relevant for non-alcoholic fatty liver disease. Precision-cut liver slices, prepared from liver biopsies obtained from obese subjects undergoing bariatric surgery, were incubated with the peroxisome proliferator-activated receptor alpha (PPARÎ±) agonist Wy14643 or vehicle for 24hrs, after which gene expression was profiled by array.

Project description:Little is known about the role of the transcription factor PPARÃ?/d in liver. Here we set out to better elucidate the function of PPARÃ?/d in liver by comparing the effect of PPARa and PPARÃ?/d deletion using whole genome transcriptional profiling and analysis of plasma and liver metabolites. In fed state, the number of genes altered by PPARa and PPARÃ?/d deletion was similar, whereas in fasted state the effect of PPARa deletion was much more pronounced, consistent with the pattern of gene expression of PPARa and PPARÃ?/d. Minor overlap was found between PPARa- and PPARÃ?/d-dependent gene regulation in liver. Pathways upregulated by PPARÃ?/d deletion were connected to innate immunity. Pathways downregulated by PPARÃ?/d deletion included lipoprotein metabolism and various pathways related to glucose utilization, which correlated with elevated plasma glucose and triglycerides and reduced plasma cholesterol in PPARÃ?/d-/- mice. Downregulated genes that may underlie these metabolic alterations included Pklr, Fbp1, Apoa4, Vldlr, Lipg, and Pcsk9, which may represent novel PPARÃ?/d target genes. In contrast to PPARa-/- mice, no changes in plasma FFA, plasma Ã?-hydroxybutyrate, liver triglycerides and liver glycogen were observed in PPARÃ?/d-/- mice. Our data indicate a role for PPARÃ?/d in hepatic glucose utilization and lipoprotein metabolism but not in the adaptive response to fasting. Keywords: Analysis of target gene regulation by using microarrays Pure-bred Sv129 PPARÎ± -/- mice and corresponding wildtype mice were used. Male mice (n=4-5 per group) were either fed or fasted for 24 hours. At the end of the experiment, mice were anaesthetized with a mixture of isofluorane (1.5%), nitrous oxide (70%) and oxygen (30%). Blood was collected by orbital puncture, after which the mice were sacrificed by cervical dislocation. Livers were dissected, snap frozen in liquid nitrogen and kept at -80ÂºC until further analysis. For RNA analyses, tissue from the same part of the liver lobe was used.

Project description:Background & Aims: Overnutrition is one of the major causes of non-alcoholic fatty liver disease (NAFLD) and its advanced form non-alcoholic steatohepatitis (NASH). Besides the quantity of consumed calories, distinct dietary components are increasingly recognized as important contributor to the pathogenesis of NASH. We aimed to develop and characterize a hitherto missing murine model which resembles both the pathology and nutritional situation of NASH-patients in Western societies. Methods: We developed a NASH-inducing diet (ND) enriched with sucrose, cholesterol and a high concentration of fats rich in saturated fatty acids in a composition which mimics Western food. C57Bl6/N mice were fed with the ND or control chow for 12 weeks. Biochemical, real-time polymerase chain reaction, Western Blot and immunohistochemical analyses were performed to characterize systemic and hepatic changes induced by ND-feeding. Immunohistochemistry was used to assess c-Jun levels and activation in 110 human NAFLD and control liver specimens applying tissue micro array technology. Results: ND-fed mice showed significant body weight gain, impaired glucose tolerance, elevated fasting blood glucose levels as well as decreased adiponectin and increased leptin serum levels compared to control mice. In the liver, ND-feeding led to marked steatosis, enhanced cholesterol levels, distinct signs of oxidative stress, hepatocellular damage, inflammation, activation of hepatic stellate cells, and beginning fibrosis. Transcriptome-wide hepatic gene expression analysis comparing ND-fed mice and control mice indicated main alterations in lipid metabolism and inflammatory processes. Search for over-represented transcription factor target sites among the differentially expressed genes identified AP-1 as the most likely factor to cause the transcriptional changes in ND-livers. Combining differentially expressed gene and protein-protein interaction network analysis identified c-Jun (a component of the AP-1 complex) as hub in the largest connected deregulated sub-network in ND-livers. In accordance, ND-livers revealed c-Jun-phosphorylation and nuclear translocation. Moreover, hepatic c-Jun RNA and protein expression was enhanced in ND-fed compared to control mice. Also NAFLD-patients showed enhanced hepatic c-Jun levels, which correlated with inflammation, and notably, with the degree of hepatic steatosis. Conclusions: The new dietary mouse-model shows important pathological changes also found in human NASH and indicates c-jun/AP-1 activation as critical regulator of hepatic alterations. Abundance of c-jun in NAFLD likely facilitates development and progression of NASH, and thus, c-jun appears as attractive prognostic and therapeutic target of NAFLD progression. 14-weeks old male C57BL/6N mice were fed with either regular diet or a newly designed NASH-inducing diet for 12 weeks. Hepatic gene expression levels were measured thereafter.

Dataset Information

PPAR-alpha dependent regulation of vanin-1 mediates hepatic lipid metabolism.

Publications

PPAR-alpha dependent regulation of vanin-1 mediates hepatic lipid metabolism.

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