Andrographolide inhibits adipogenesis of 3T3-L1 cells by suppressing C/EBPβ expression and activation

Andrographolide, a diterpenoid, is the most abundant terpenoid in Andrographis paniculata, a popular Chinese herbal medicine. Andrographolide displays diverse biological activities including hypoglycemia, hypolipidemia, anti-inflammation, and anti-tumorigenesis. Recent evidence indicates that andrographolide displays anti-obesity property by inhibiting lipogenic gene expression, however, the underlying mechanisms remain to be elucidated. In this study, the effects of andrographolide on transcription factor cascade and mitotic clonal expansion in 3T3-L1 differentiation into adipocyte were determined. Andrographolide dose-dependently (0-15 mu M) inhibited CCAAT/enhancer-binding protein alpha (C/EBP alpha) and C/EBP beta mRNA and protein expression as well as peroxisome proliferator-activated receptor gamma (PPAR gamma) protein level during the adipogenesis of 3T3-L1 cells. Concomitantly, fatty acid synthase and stearoyl-CoA desaturase expression and lipid accumulation were attenuated by andrographolide. Oil-red O staining further showed that the first 48 h after the initiation of differentiation was critical for andrographolide inhibition of adipocyte formation. Andrographolide inhibited the phosphorylation of PKA and the activation of cAMP response element-binding protein (CREB) in response to a differentiation cocktail, which led to attenuated C/EBP beta expression. In addition, ERK and GSK3 beta-dependent C/EBP beta phosphorylation was attenuated by andrographolide. Moreover, andrographolide suppressed cyclin A, cyclin E, and CDK2 expression and impaired the progression of mitotic clonal expansion (MCE) by arresting the cell cycle at the Go/G1 phase. Taken together, these results indicate that andrographolide has a potent anti-obesity action by inhibiting PKA-CREB-mediated C/EBP beta expression as well as C/EBP beta transcriptional activity, which halts MCE progression and attenuates C/EBP alpha and PPAR gamma expression. (C) 2016 Elsevier Inc. All rights reserved.