Oncostatin M inhibits adipogenesis through the RAS/ERK and STAT5 signaling pathways

Abstract

Adipocytes play a key role in energy homeostasis and several cytokines have been shown to regulate adipogenesis. While the interleukin (IL)-6 family of cytokines was previously reported to be involved in adipogenesis, roles of this family in adipogenesis and their mechanisms of action are not fully understood. Here we show that among the IL-6 family, oncostatin M (OSM) most strongly inhibits adipogenesis of 3T3-L1 cells and mouse embryonic fibroblasts (MEFs). We also demonstrate that OSM inhibits adipogenesis through the Ras/extracellular signal-regulated kinase(ERK) and signal transducer and activator of transcription (STAT) 5 signaling pathways. In addition, OSM inhibits the early phase of the differentiation without affecting cell proliferation throughout adipogenesis including mitotic clonal expansion. CCAAT/enhancer-binding protein (C/EBP) α, C/EBPβ, and peroxisome proliferator-activated receptor (PPAR) γ are known to be required for adipogenesis. Expression of C/EBPα and PPARγ was almost completely abrogated by OSM. In contrast, neither the mRNA nor protein level of C/EBPβ was affected by OSM. Forced expression of C/EBPβ induced differentiation in the presence of troglitazone, and OSM inhibited this C/EBPβ-induced differentiation. Taken together, our results indicate that OSM inhibits the onset of terminal differentiation of adipocytes through the Ras/ERK and STAT5 signaling pathways by possibly regulating C/EBPβ activity. © 2006 by The American Society for Biochemistry and Molecular Biology, Inc.