Enzyme-treated Ecklonia cava extract inhibits adipogenesis through the downregulation of C/EBPα in 3T3-L1 adipocytes

摘要

In this study, we examined the inhibitory effects of enzyme-treated Ecklonia cava (EEc) extract on the adipogenesis of 3T3-L1 adipocytes. The components of Ecklonia cava (E. cava) were first separated and purified using the digestive enzymes pectinase (Rapidase^® X-Press L) and cellulase (Rohament^® CL). We found that the EEc extract contained three distinct phlorotannins: eckol, dieckol and phlorofucofuroeckol-A. Among the phlorotannins, dieckol was the most abundant in the EEc extract at 16 mg/g. Then we examined the inhibitory effects of EEc extract treatment on differentiation-related transcription factors and on adipogenesis-related gene expression in vitro using 3T3-L1 adipocytes. 3T3-L1 pre-adipocytes were used to determine the concentrations of the EEc extract and Garcinia cambogia (Gar) extract that did not result in cytotoxicity. Glucose utilization and triglyceride (TG) accumulation in the EEc-treated adipocytes were similarly inhibited by 50 µg/ml EEc and 200 µg/ml Gar, and these results were confirmed by Oil Red O staining. Protein expression of adipogenesis differentiation-related transcription factors following treatment with the EEc extract was also examined. Only the expression of CCAAT/enhancer-binding protein (C/EBP)α was decreased, while there was no effect on the expression of C/EBPβ, C/EBPδ, and peroxisome proliferator-activated receptor γ (PPARγ). Treatment with the EEc extract decreased the expression levels of adipogenesis-related genes, in particular sterol regulatory element binding protein-1c (SREBP-1c), adipocyte fatty acid binding protein (A-FABP), fatty acid synthase (FAS) and adiponectin. These results suggest that EEc extract treatment has an inhibitory effect on adipogenesis, specifically by affecting the activation of the C/EBPα signaling pathway and the resulting adipogenesis-related gene expression.