A systems biology approach to the hepatic role of the oxysterol receptor LXR in the regulation of lipogenesis highlights a cross-talk with PPARα.
The Liver X Receptors (LXRs) α and β and the Peroxisome Proliferator-Activated Receptor α (PPARα) are transcription factors that belong to class II nuclear receptors. They drive the expression of genes involved in hepatic lipid homeostasis and therefore are important targets for the prevention and treatment of nonalcoholic fatty liver disease (NAFLD). LXRs and PPARα are regulated by endogenous ligands, oxysterols and fatty acid derived molecules, respectively. In the liver, pharmacological activation of LXRs leads to the over-expression of genes involved in de novo lipogenesis, while PPARα is critical for fatty acid catabolism in nutrient deprivation. Even if these two nuclear receptors seemed to play opposite parts, recent studies have highlighted that PPARα also influence the expression of genes involved in fatty acids synthesis. In this study, we used pharmacological approaches and genetically engineered mice to investigate the cross-talk between LXRs and PPARα in the regulation of genes responsible for lipogenesis. We first investigated the effect of T0901317 and fenofibrate, two synthetic agonists of LXRs and PPARα, respectively. As expected, T0901317 and fenofibrate induce expression of genes involved LXR-dependent and PPARα-dependent lipogenic responses. Considering such overlapping effect, we then tested whether LXR agonist may influence PPARα driven response and vice versa. We show that the lack of PPARα does not influence the effects of T0901317 on lipogenic genes expression. However, PPARα deficiency prevents the up-regulation of genes involved in ω-hydroxylation that are induced by the LXR agonist. In addition, over-expression of lipogenic genes in response to fenofibrate is decreased in LXR knockout mice as well as the expression of PPARα target genes involved in fatty acid oxidation. Altogether, our work provides in vivo evidence for a central interconnection between nuclear receptors that drive hepatic lipid metabolism in response to oxysterol and fatty acids.
INRA, UMR1331, Toxalim, Research Centre in Food Toxicology, Université de Toulouse, Toulouse, France.
Simon
S
Ducheix
Normand
N
Podechard
Frédéric
F
Lasserre
Arnaud
A
Polizzi
Aurélien
A
Pommier
Stefania
S
Murzilli
Chiara
C
Di Lisio
Simona
S
D'Amore
Justine
J
Bertrand-Michel
Alexandra
A
Montagner
Thierry
T
Pineau
Nicolas
N
Loiseau
Jean-Marc
JM
Lobaccaro
Pascal G P
PG
Martin
Hervé
H
Guillou
D000818:Animals; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics; D000072470:Cytochrome P450 Family 4; D005227:Fatty Acids / Q000378:metabolism; D011345:Fenofibrate / Q000494:pharmacology; D006845:Hydrocarbons, Fluorinated / Q000494:pharmacology; D008024:Ligands; D050155:Lipogenesis / Q000187:drug effects / Q000235:genetics*; D008099:Liver / Q000166:cytology* / Q000378:metabolism*; D000071518:Liver X Receptors; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D020411:Oligonucleotide Array Sequence Analysis; D057093:Orphan Nuclear Receptors / Q000819:agonists / Q000172:deficiency / Q000378:metabolism*; D047493:PPAR alpha / Q000819:agonists / Q000172:deficiency / Q000378:metabolism*; D020033:Protein Isoforms / Q000172:deficiency / Q000378:metabolism; D020239:Receptor Cross-Talk / Q000187:drug effects; D013449:Sulfonamides / Q000494:pharmacology; D049490:Systems Biology; D015533:Transcriptional Activation / Q000187:drug effects; D005466:Fluorocarbons; D000096926:Benzenesulfonamides
D003577:Cytochrome P-450 Enzyme System; D000072470:Cytochrome P450 Family 4; D005227:Fatty Acids; D011345:Fenofibrate; D006845:Hydrocarbons, Fluorinated; D008024:Ligands; D000071518:Liver X Receptors; D057093:Orphan Nuclear Receptors; D047493:PPAR alpha; D020033:Protein Isoforms; D013449:Sulfonamides; C512110:Cyp4a10 protein, mouse; C436963:Cyp4a14 protein, mouse; C423915:T0901317; D005466:Fluorocarbons; D000096926:Benzenesulfonamides