Cynara cardunculus L. suppresses adipogenesis in 3T3-L1 adipocytes via AMPK signaling pathway activation

Adipose tissue is an important energetic storage organ where adipocytes play a central role in maintaining lipid homeostasis and energy balance, by storing triacylglycerols or releasing free fatty acids in response to changes in energy demands. In presence of obesity, an imbalance between energy requirement and expenditure occurs, with consequent accumulation of energy in the form of lipids in white adipose tissue (WAT) and expansion of total body mass. Recently has been detected the ability of white adipocytes to transform, in response to several stimuli, into a phenotype tending to brown adipose tissue (BAT), through a process called "browning". In this regard some research has shown, in fact, that the activation of the thermogenesis process, via upregulation of the key sensor of energy metabolism AMP-activated protein kinase (AMPK), represents an important target to counteracting obesity and related disorders. Therefore, the objective of this study was to investigate the in vitro beneficial effects of a standardized extract obtained from the leaves of Cynara cardunculus L. (CCLE), rich in chlorogenic acid and luteolin derivates, on adipogenesis inhibition in 3T3-L1 cells through the involvement of the thermogenic process. CCLE at two different concentrations (5 and 10 μg/mL) was added to 3T3-L1 cells during the 10 days of the adipocyte differentiation process. CCLE effects on lipid accumulation were evaluated through Oil Red O staining, whereas the main markers involved in adipogenesis and thermogenesis were assessed via Western blot and real-time PCR techniques. Data showed that CCLE treatment during 3T3-L1 differentiation markedly inhibited lipid accumulation and suppressed the expression of the main markers involved in the adipogenic process (C/EBPβ, PPARγ, FABP4, and FASN). Furthermore, CCLE significantly increased the thermogenic process via the upregulation of pAMPK protein levels, and UCP1 and PGC1α mRNA expression. However, pretreatment with compound C, a specific AMPK inhibitor, prevented the mitotic clonal expansion (MCE) of preadipocytes and abolished the inhibitory effects of CCLE on C/EBPβ and PPARγ expression, thus suggesting that the antiadipogenic effect of the extract is closely related to AMPK signaling pathway activation. Therefore, these results clearly indicate that CCLE extract inhibits adipogenic differentiation in 3T3-L1 cells via activation of the thermogenic process, opening thereby new perspectives for the use of this natural extract for the prevention and management of obesity.