title: Divergent effects of selective peroxisome proliferator-activated receptor-gamma 2 ligands on adipocyte versus osteoblast differentiation.
abstract: PPAR gamma is activated by diverse ligands and regulates the differentiation of many cell types. Based on evidence that activation of PPAR gamma 2 by rosiglitazone stimulates adipogenesis and inhibits osteoblastogenesis in U-33/gamma 2 cells, a model mesenchymal progenitor of adipocytes and osteoblasts, we postulated that the increase in marrow fat and the decrease in osteoblast number that occur during aging are due to increased PPAR gamma 2 activation. Here, we show that the naturally occurring PPAR gamma ligands 9,10-dihydroxyoctadecenoic acid, and 15-deoxy-Delta(12,14)-PGJ(2), also stimulate adipocytes and inhibit osteoblast differentiation of U-33/gamma 2 cells. Strikingly, 9,10-epoxyoctadecenoic acid and the thiazolidine acetamide ligand GW0072 [(+/-)-(2S,5S)-4-(4-(4-carboxyphenyl)butyl)-2-heptyl-4-oxo-5-thaizolidineN,N-dibenzyl-acetamide] prevent osteoblast differentiation, but do not stimulate adipogenesis, whereas 9-hydroxyoctadecadienoic acid stimulates adipogenesis but does not affect osteoblast differentiation. The divergent effects of PPAR gamma 2 ligands on osteoblast and adipocyte differentiation were confirmed in primary murine bone marrow cultures using rosiglitazone and GW0072. These findings indicate that the proadipogenic and antiosteoblastogenic effects of PPAR gamma 2 are mediated by distinct regulatory pathways that can be differentially modulated depending on the nature of the ligand, and they support the idea that increased fatty acid oxidation during aging may inhibit osteoblast differentiation. Moreover, there may be selective PPAR gamma 2 modulators that block the adverse effects of fatty acid oxidation products while retaining beneficial activities such as insulin sensitization.
authors.affiliation: Department of Geriatrics, Reynolds Center on Aging, Division of Endocrinology and Metabolism, Central Arkansas Veterans Healthcare System, University of Arkansas for Medical Sciences, Little Rock, 72205, USA. leckaczernikbeata@uams.edu
authors.forename: Beata
authors.initials: B
authors.lastname: Lecka-Czernik
authors.forename: Elena J
authors.initials: EJ
authors.lastname: Moerman
authors.forename: David F
authors.initials: DF
authors.lastname: Grant
authors.forename: Jürgen M
authors.initials: JM
authors.lastname: Lehmann
authors.forename: Stavros C
authors.initials: SC
authors.lastname: Manolagas
authors.forename: Robert L
authors.initials: RL
authors.lastname: Jilka
mesh_terms: D017667:Adipocytes / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D015152:Blotting, Northern; D001862:Bone Resorption / Q000473:pathology; D002454:Cell Differentiation / Q000187:drug effects; D002460:Cell Line; D005227:Fatty Acids / Q000378:metabolism; D008024:Ligands; D051379:Mice; D010006:Osteoblasts / Q000187:drug effects / Q000502:physiology*; D010084:Oxidation-Reduction; D010641:Phenotype; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism / Q000502:physiology*; D012045:Regulatory Sequences, Nucleic Acid; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013234:Stem Cells / Q000502:physiology; D014157:Transcription Factors / Q000378:metabolism / Q000502:physiology*; D015533:Transcriptional Activation; D014162:Transfection
chemical_list: D005227:Fatty Acids; D008024:Ligands; D018160:Receptors, Cytoplasmic and Nuclear; D014157:Transcription Factors