Nobiletin suppresses adipocyte differentiation of 3T3-L1 cells by an insulin and IBMX mixture induction.

BACKGROUND: Nobiletin is a citrus flavonoid which possesses the flavone structure with six methoxy groups. Although nobiletin has been reported to display anti-inflammatory, anti-tumor, and anti-diabetes activities, its effect on adipocyte differentiation remained unclear. In the present study, we investigated the effect of nobiletin on the differentiation of 3T3-L1 preadipocytes into adipocytes. METHODS: 3T3-L1 preadipocytes were treated with nobiletin under various differentiation conditions. The effect of nobiletin on adipocyte differentiation was evaluated by oil red O staining, real-time RT-PCR, and Western blotting. RESULTS: Nobiletin significantly suppressed the differentiation of 3T3-L1 preadipocytes into adipocytes, upon induction with insulin together with a cAMP elevator such as 3-isobutyl-1-methylxanthine (IBMX), by downregulating the expression of the gene encoding peroxisome proliferator-activated receptor (PPAR) γ2. In addition, nobiletin decreased the phosphorylation of cAMP-response element-binding protein (CREB) and strongly enhanced the phophorylation of signal transducer and activator of transcription (STAT) 5. GENERAL SIGNIFICANCE: Nobiletin has a suppressive effect on the differentiation of preadipocytes into adipocytes when cells were induced with a general differentiation cocktail such as insulin, IBMX, and dexamethasone.