title: Pigment epithelium-derived factor suppresses adipogenesis via inhibition of the MAPK/ERK pathway in 3T3-L1 preadipocytes.
abstract: We previously reported that circulating levels of pigment epithelium-derived factor (PEDF), a newly identified adipokine, are increased in patients with type 2 diabetes, correlating with body mass index. However, the role of PEDF in adipogenesis remains elusive. In the present study, we have investigated the effects and mechanisms of PEDF on adipocyte differentiation in 3T3-L1 preadipocytes. Differentiation of 3T3-L1 preadipocytes was induced in the presence or absence of human recombinant PEDF protein. The effects of PEDF on adipogenic gene expression, mitotic clonal expansion (MCE), and MAPK activation were investigated. Physiological concentrations of human PEDF protein inhibited adipocyte differentiation, evidenced by decreased lipid accumulation, downregulation of adipocyte markers, and inhibition of master adipogenic transcription factors such as C/EBP-alpha and PPARgamma. The antiadipogenic effects of PEDF were observed only when PEDF was added to the cells on day 0, but not on day 3 during differentiation, suggesting that PEDF targets some early adipogenic events. Similarly, overexpression of PEDF by adenovirus attenuated adipocyte differentiation. Further studies revealed that PEDF, or U-0126, a specific MAPK/ERK inhibitor, sequentially inhibited the early activation of ERK and MCE. Moreover, PEDF attenuated expression and the phosphorylation of C/EBP-beta at Thr(188), an essential step for transcriptional activation of C/EBP-beta. In addition, PEDF expression was decreased significantly in the first 24 h during adipocyte differentiation, suggesting that downregulation of PEDF may be essential for the initiation of MCE and adipogenesis. We conclude that PEDF inhibits adipogenesis in 3T3-L1 preadipocytes partially because of inhibition of the MAPK/ERK signaling pathway and MCE.
authors.affiliation: Harold Hamm Oklahoma Diabetes Center and Section of Endocrinology and Diabetes, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104, USA.
authors.forename: Min
authors.initials: M
authors.lastname: Wang
authors.forename: Joshua J
authors.initials: JJ
authors.lastname: Wang
authors.forename: Jingming
authors.initials: J
authors.lastname: Li
authors.forename: Kyoungmin
authors.initials: K
authors.lastname: Park
authors.forename: Xiaoxian
authors.initials: X
authors.lastname: Qian
authors.forename: Jian-xing
authors.initials: JX
authors.lastname: Ma
authors.forename: Sarah X
authors.initials: SX
authors.lastname: Zhang
mesh_terms: D041721:3T3-L1 Cells; D017667:Adipocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D050156:Adipogenesis / Q000187:drug effects* / Q000502:physiology; D000273:Adipose Tissue / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D000818:Animals; D001391:Azo Compounds / Q000737:chemistry; D015153:Blotting, Western; D002070:Butadienes / Q000494:pharmacology; D022763:CCAAT-Enhancer-Binding Protein-alpha / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects; D005136:Eye Proteins / Q000494:pharmacology*; D006801:Humans; D020935:MAP Kinase Signaling System / Q000187:drug effects*; D051379:Mice; D008856:Microscopy, Fluorescence; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D009414:Nerve Growth Factors / Q000494:pharmacology*; D009570:Nitriles / Q000494:pharmacology; D047495:PPAR gamma / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D012313:RNA / Q000737:chemistry / Q000235:genetics; D011994:Recombinant Proteins / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015843:Serpins / Q000494:pharmacology*; D000099174:Pigment Epithelium-Derived Factor
chemical_list: D001391:Azo Compounds; D002070:Butadienes; D022763:CCAAT-Enhancer-Binding Protein-alpha; D005136:Eye Proteins; D020929:Mitogen-Activated Protein Kinase Kinases; D009414:Nerve Growth Factors; D009570:Nitriles; D047495:PPAR gamma; D047428:Protein Kinase Inhibitors; D012313:RNA; D011994:Recombinant Proteins; D015843:Serpins; D000099174:Pigment Epithelium-Derived Factor; C113580:U 0126; C011049:oil red O