Identification of DNA response elements regulating expression of CCAAT/enhancer-binding protein (C/EBP) β and δ and MAP kinase-interacting kinases during early adipogenesis

ABSTRACT

Given the high and increasing prevalence of obesity and associated disorders, such as type-2 diabetes, it is important to understand the mechanisms that regulate lipid storage and the differentiation of fat cells, a process termed adipogenesis. Using the well-established mouse 3T3-L1 in vitro model of adipogenesis, we refine how the induction of two key adipogenic transcription factors, CCAAT/enhancer-binding proteins (C/EBPs) β and δ are regulated during early adipogenesis. We identify, in the gene promoters of Cebpb and Cebpd, the DNA response elements responsible for binding transcription factors that are activated by cAMP or glucocorticoids. We also show that mitogen-activated protein kinase (MAPK)-interacting kinase 2 (MNK2; Mknk2), which plays a distinct role in diet-induced obesity, is induced during early adipogenesis and identify the functional DNA response elements responsible for regulating its expression. Mknk2 expression is maintained in differentiated 3T3-L1 adipocytes and is expressed at high levels across a range of mouse adipose tissue depots. Together, these new insights help to clarify the transcriptional programme of early adipogenesis and identify Mknk2 as one of potentially many genes up-regulated during adipogenesis.

KEYWORDS:

• Adipogenesis
• adipocyte
• cyclic AMP (cAMP)
• cAMP response element‐binding protein (CREB)
• CCAAT/enhancer‐binding protein (C/EBP)
• glucocorticoid
• glucocorticoid receptor
• MAPK-interacting kinase (MNK)

Acknowledgments

The 3T3-L1 fibroblasts used in this study were generously provided by Yeesim Khew-Goodhall from the Centre for Cancer Biology (SA Pathology). We thank Dr Jianling Xie (SAHMRI) for his excellent assistance with aspects of this study and Professor Murray Whitelaw (University of Adelaide) for valuable advice.

Disclosure statement

The authors declare that they have no conflicts of interest with the contents of this article.

Additional information

Funding

This work was supported by funding from the South Australian Health and Medical Research Institute. JEM acknowledges the support received through the provision of an Australian Government Research Training Program Scholarship. PJP is supported by an L2 Future Leader Fellowship from the National Heart Foundation of Australia [FLF102056] and L2 Career Development Fellowship from the National Health and Medical Research Council [CDF1161506].