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

J.A. van Diepen, P.A. Jansen, D.B. Ballak, A. Hijmans, G.J.E.J. Hooiveld, S. Rommelaere, A.H. Kersten, R. Stienstra

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Abstract

Background & Aims Peroxisome proliferator-activated receptor alpha (PPARa) is a key regulator of hepatic fat oxidation that serves as an energy source during starvation. Vanin-1 has been described as a putative PPARa target gene in liver, but its function in hepatic lipid metabolism is unknown. Methods We investigated the regulation of vanin-1, and total vanin activity, by PPARa 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. Results Liver microarray analyses reveals that Vnn1 is the most prominently regulated gene after modulation of PPARa activity. In addition, activation of mouse PPARa regulates hepatic- and plasma vanin activity. In humans, consistent with regulation by PPARa, plasma vanin activity increases in all subjects after prolonged fasting, as well as after treatment with the PPARa 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. Conclusions We show that hepatic vanin-1 is under extremely sensitive regulation by PPARa and that plasma vanin activity could serve as a readout of changes in PPARa activity in human subjects. In addition, our data propose a role for vanin-1 in regulation of hepatic TG levels during fasting. Abbreviations PPAR, Peroxisome proliferator-activated receptor; RXR, Retinoid X Receptor; VNN1, vanin-1; VNN2, vanin-2; VNN3, vanin-3; WT, wild-type; BMI, body mass index; Pan-AMC, pantothenate-7-amino-4-methylcoumarin; TG, Triglycerides; TC, total cholesterol; FFA, free fatty acids; KLF15, Kruppel-like factor 15; STAT3, signal transducer and activator of transcription 3; SP1, trans-acting transcription factor 1; CBFB, core binding factor beta; XBP1, x-box binding protein 1; NAFLD, non-alcoholic fatty liver disease; Pan-PNa, pantothenate-4-nitroanilide; Abcd2, chemokine (C-C motif) ligand 17; Acadm, acyl-CoA dehydrogenase, medium chain; Acot1, acyl-CoA thioesterase 1; Acot2, acyl-CoA thioesterase 2; Acsl5, acyl-CoA synthetase long-chain family member 5; Ehhadh, enoyl-CoA hydratase/3-hydroxylacyl CoA dehydrogenase; NASH, non-alcoholic steatohepatitis (NASH)
Original languageEnglish
Pages (from-to)366-372
JournalJournal of Hepatology
Volume61
Issue number2
DOIs
Publication statusPublished - 2014

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Keywords

  • high-fat diet
  • gene-expression
  • insulin-resistance
  • null mice
  • liver
  • cysteamine
  • tissue
  • acids
  • hepatocytes
  • fenofibrate

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