Activation of early phase of adipogenesis through Kruppel-like factor KLF9-mediated, enhanced expression of CCAAT/enhancer-binding protein β in 3T3-L1 cells

In this study, we found that Kruppel-like factor (KLF) 9 activate the progression of the early phase of adipocyte differentiation in mouse adipocytic 3T3-L1 cells. KLF9 mRNA was detected in preadipocytes; and its level increased after the initiation of adipocyte differentiation, reached its maximum at 1 h, and gradually decreased thereafter. Functional suppression of KLF9 mRNA by its siRNAs repressed the accumulation of the intracellular lipids with a reduction in the expression of CCAAT/enhancer-binding protein (C/EBP) 13, but not in that of C/EBP delta. In contrast, C/EBP beta and C/EBP delta did not affect the expression of KLF9 in 3T3-L1 cells. A chromatin immunoprecipitation assay revealed that KLF9 bound the KLF binding element at position -874 of the mouse C/EBP beta promoter. Moreover, the ability of KLF9 to bind to this element was enhanced, with a peak at 1-2 h after the initiation of adipogenesis, whose profile well resembled that of the expression of the C/EBP beta gene in 3T3-L1 cells. These results indicate that KLF9 activated the early phase of adipogenesis by enhancing the expression of the C/EBP beta gene in 3T3-L1 cells. (C) 2013 Elsevier B.V. All rights reserved.