Expression and regulation of cytosolic phosphoenolpyruvate carboxykinase in 3T3-L1 adipocytes.

Animal studies have shown that the gene encoding cytosolic phosphoenolpyruvate carboxykinase (PEPCK) is controlled by unique mechanisms in fat. For example, a unique cis-acting DNA sequence located 1-2 kilobase pairs upstream of the promoter is required for PEPCK gene expression in adipocytes but not in other cell types. Moreover, glucocorticoids repress PEPCK gene transcription in fat whereas these steroids induce the same gene in liver and kidney. An in vitro system of cultured adipocytes would greatly facilitate studies of PEPCK gene regulation in fat cells. In this study, we report that cultured 3T3-L1 cells activate the PEPCK gene upon differentiation from fibroblasts to adipocytes. In addition, we report that cAMP induces and insulin and dexamethasone repress PEPCK mRNA in 3T3-L1 adipocytes. Thus these cells may provide a useful model system for future studies.