Lotus Leaf Ethanol Extract and Nuciferine Suppress Adipocyte Differentiation by Regulating Akt-mTORC1 Signaling in 3T3-L1 Cells

Abstract

Lotus leaf has been reported to exert anti-inflammatory, hypolipidemic, and hepatoprotective effects. However, the effect of lotus leaf on adipocyte differentiation and its action mechanism have not been clarified. In this study, 3T3-L1 preadipocytes were incubated with or without lotus leaf ethanol extract (EEN) for 8 days. Microscopic inspection and Oil Red O staining indicated that EEN treatment significantly reduced adipogenesis in 3T3-L1 cells. EEN also downregulated the protein levels of adipogenic transcription factors including sterol regulatory element binding protein 1 (SREBP1), peroxisome proliferator-activated receptor-gamma (PPARγ), and CCAAT/enhancer binding protein α (C/EBPα), and target genes such as adipocyte binding protein 2 (aP2) and fatty acid synthase (FAS) in a dose-dependent manner. In order to understand whether nuciferine, the primary active component of EEN contributed to the anti-adipogenic activity of EEN, we examined the effect of nuciferine on adipogenesis related gene expression. Nuciferine significantly reduced expression of adipogenic transcription factors and target genes. Notably, nuciferine downregulated the phosphorylation of Akt, mammalian target of rapamycin complex 1 (mTORC1), S6K, and 4EBP1. These results suggest that lotus leaf ethanol extract exerts anti-adipogenic activity, and could be partially mediated through the regulation of the Akt-mTORC1 signaling pathway by nuciferine.