7,8-Dihydroxyflavone inhibits adipocyte differentiation via antioxidant activity and induces apoptosis in 3T3-L1 preadipocyte cells

Aims: Anti-obesity effects of a natural plant flavonoid 7,8-dihydroxyflavone (7,8-DHF) were evaluated using 3T3-L1 preadipocyte cells. Main methods: The cell viability was determined using MTT assay. Effects of 7,8-DHF on intracellular lipid droplets and intracellular reactive oxygen species (ROS) were measured using a 2,7-dichlorofluorescein diacetate (DCFDA) assay and Oil Red O staining method, respectively. Apoptotic cell death was monitored by annexin V-FITC/PI double staining and by a TUNEL assay. Antioxidant enzyme mRNA levels and protein expression of adipogenic transcription factors were determined by real-time PCR and Western blotting, respectively. Key findings: Whereas the cell viability of 3T3-L1 preadipocytes was not affected by lower concentrations of 7,8-DHF (<20 mu M), higher concentrations of 7,8-DHF (>20 mu M) induced apoptotic cell death. 7,8-DHF (<20 mu M) significantly reduced the intracellular lipid droplets and the expression of major adipogenic transcription factors, such as CCAAT/enhancer-binding protein-alpha (C/EBP-alpha), C/EBP-beta, and peroxisome proliferator activated receptor-gamma (PPAR-gamma). 7,8-DHF treatment also dose-dependently reduced the intracellular ROS level, attenuated MAPK pathway activation, and increased the expression of antioxidant enzymes, such as Mn-superoxide dismutase (Mn-SOD), catalase (CAT), and heme oxygenase-1 (HO-1). Significance: The results of this study indicated that 7,8-DHF inhibits the adipogenesis of 3T3-L1 preadipocyte cells by down-regulating the expression of adipogenic transcription factors, reduces lipid accumulation, and attenuates ROS accumulation by inducing antioxidant enzymes in differentiated 3T3-L1 cells, suggesting for the first time that 7,8-DHF has an anti-obesity effect in vitro via its anti-oxidant activity. (C) 2015 Elsevier Inc. All rights reserved.