title: Growth hormone stimulates adipogenesis of 3T3-L1 cells through activation of the Stat5A/5B-PPARgamma pathway.
abstract: Growth hormone-deficient (GHD) patients show a decreased number of adipocytes, which is normalized by GH replacement, indicating an adipogenic effect of GH. However, the precise mechanisms underlying this effect remain to be clarified. In this study, we investigated the adipogenic effect of GH. GH stimulated MDI (3-isobutyl-1-methylxanthine, dexamethasone, and insulin)-induced adipogenesis of 3T3-L1 cells with early induction of peroxisome proliferator-activated receptors (PPAR)gamma2 expression. This adipogenic effect of GH was suppressed by overexpression of Stat5A mutant (Stat5A-Y694F), a transcriptional suppressor for the GH-Stat5A/5B signaling pathway, with the reduction of PPARgamma2 expression. Next, we investigated the relationship between Stat5A/5B and CCAAT/enhancer binding protein (C/EBP)beta/delta orPPARgamma in 3T3-L1 cells. Stat5A/5B stimulated C/EBPbeta- and C/EBPdelta-induced adipogenesis with enhancement of PPARgamma2 expression. In addition, Stat5A/5B enhanced the transcriptional activity of C/EBPbeta/delta in the PPARgamma gene promoter. Furthermore, Stat5A/5B stimulated PPARgamma-induced adipogenesis and enhanced the transcriptional activity of PPARgamma. These results suggest that the GH-Stat5A/5B signaling pathway stimulates adipogenesis in cooperation with C/EBPbeta/delta and PPARgamma. To completely understand the effect of GH, cDNA microarray analysis was performed to screen genes affected by GH during MDI-induced adipogenesis. Among 4277 genes, 18 and 19 genes were up- and down-regulated respectively. cDNA microarray analysis also indicated the up-regulation of PPARgamma and the modulation of expression of genes coding for growth factors or growth factor receptors, suggesting that GH stimulates adipogenesis in association with the modulation of cell growth. Thus, the GH-Stat5A/B signaling pathway stimulates adipogenesis through two distinct steps. In addition, cDNA microarray data provide us the further insights underlying the adipogenic effect of GH.
authors.affiliation: Department of Pediatrics, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan.
authors.forename: Masanobu
authors.initials: M
authors.lastname: Kawai
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Namba
authors.forename: Sotaro
authors.initials: S
authors.lastname: Mushiake
authors.forename: Yuri
authors.initials: Y
authors.lastname: Etani
authors.forename: Riko
authors.initials: R
authors.lastname: Nishimura
authors.forename: Makoto
authors.initials: M
authors.lastname: Makishima
authors.forename: Keiichi
authors.initials: K
authors.lastname: Ozono
mesh_terms: D041721:3T3-L1 Cells; D050156:Adipogenesis / Q000502:physiology*; D000818:Animals; D013006:Growth Hormone / Q000502:physiology*; D051379:Mice; D008809:Mice, Inbred C3H; D047495:PPAR gamma / Q000378:metabolism*; D050799:STAT5 Transcription Factor / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*
chemical_list: D047495:PPAR gamma; D050799:STAT5 Transcription Factor; C494093:Stat5a protein, mouse; C494096:Stat5b protein, mouse; D013006:Growth Hormone