Human Adipocyte Fatty Acid-Binding Protein(aP2)Gene Promoter-Driven Reporter Assay Discriminates Nonlipogenic Peroxisome Proliferator-Activated Receptor y Ligands

摘要

Peroxisome proliferator-activated receptors(PPARs)regulate storage and catabolism of fats and carbohydrates.PPARy activity increases insulin sensitivity and adipocyte differentiation at the expense of adipogenesis and weight gain.The goal of this study was to 1)clone the promoter of the human adipocyte fatty acid binding protein(aP2)gene,namely fatty acid-binding protein-4,2)characterize its pharmacological regulation,and 3)determine its putative predictability for adipogenesis.Among the selected PPAR agonists,rosiglitazone and pioglitazone displayed the highest maximal efficacy(E_(max))on reporter-gene assays in COS-7 cells cotransfected by either a galactosidase 4-resportse element-based or a human aP2 promoter-based Luc reporter vector,along with either chimeric or full-length human PPAR expression plas-mids.The non-subtype-selective 2-(4-[2-(3-[2,4-difluorophenyl]-1-heptylureido)ethyl]phenoxy)-2-methyl-butyric acid(GW-2331)and the compounds [4-[3-(4-acetyl-3-hydroxy-2-propylphenoxy)-propoxyl]phenoxy]-acetic acid(L-165041),(4-((2S,5S)-5-(2-(bis(phenylmethyl)amino)-2-oxoethyl)-2-heptyl-4-oxo-3-thiazolidi-nyl)butyl)-benzoic acid(GW-0072),and indomethacin behaved as partial agonists relative to pioglitazone in full-length human aP2-PPARy2.Beyond their partial PPARy agonist properties,these compounds elicited a lower maximal up-regulation of mouse aP2 mRNA in 3T3-L1 adipocytes as compared with pioglitazone; these properties paralleled a time-dependent increase in neutral lipids.By contrast,the selective PPARa agonist 2,2-dichloro-12-(4-chlorophenyl)dodecanoic acid(BM-17.0744)neither stimulated the human aP2-PPARa promoter reporter-gene assay,thus demonstrating a specific interaction between PPARy and the aP2 promoter,nor affected lipogenesis in 3T3-L1 cells.Altogether,these data characterized a functional promoter of the human aP2 gene; its in vitro pharmacological regulation in PPARy-mediated reporter-gene assay may represent an interesting complement or an alternative to time-consuming procedures aiming at discriminating PPAR ligands with low lipogenic properties.