Abstract

Expression of adipocyte differentiation-related protein (ADFP), residing on the surface of lipid droplets, correlates to hepatic fat storage. In the context of consequences and treatment of metabolic disorders, including hepatic steatosis, it is imperative to gain knowledge about the regulation of the human ADFP gene. The nuclear receptor liver-X-receptor (LXR) is a key regulator of hepatic fatty acid biosynthesis and cholesterol homeostasis as well as a potential drug target. Here, we report that two synthetic LXR ligands differently regulate human ADFP expression. The partial LXR agonist 3-[3-[[[2-chloro-3-(trifluoromethyl)phenyl]methyl](2,2- diphenylethyl)amino]propoxy]benzeneacetic acid hydrochloride (GW3965) significantly induces ADFP expression in human primary hepatocytes, whereas the full agonist N-(2,2,2-trifluoroethyl)-N-[4-[2,2,2-trifluoro-1-hydroxy-1(trifluoromethyl)ethyl]phenyl] benzenesulfonamide (T0901317) does not. Bioinformatics analysis revealed several potential LXR response elements (LXREs) in the human ADFP gene. By using chromatin immunoprecipitation and luciferase reporter assays, we show that LXR, upon stimulation with GW3965, directly regulates human ADFP transcription by binding to LXREs located in the 3′-untranslated and the 5′-flanking regions. The ligand-stimulated LXR recruitment was associated with recruitment of RNA polymerase II and the coactivators cAMP response element-binding protein–binding protein/p300 to the promoter region demonstrating that the identified LXREs are functional and able to induce transcription. Moreover, our results show that sequence identity of the hexamer repeats in DR4 elements is not sufficient to determine whether the element binds LXR or not. The partial agonist GW3965 specifically regulates ADFP gene transcription, and our data prove that the two synthetic LXR agonists, commonly used in experimental research, can differentially regulate gene expression. This has implications for pharmaceutical targeting of LXR.