Kudinoside-D, a triterpenoid saponin derived from Ilex kudingcha suppresses adipogenesis through modulation of the AMPK pathway in 3T3-L1 adipocytes

The leaves of Ilex Kudingcha, locally named "Kudingcha" in China, has been traditionally applied for treating obesity. Studies have demonstrated that the ethanol extract of Ilex kudingcha have anti-adipogenic effects. However, the constituent which was responsible for its anti-obesity and its underlying molecular mechanism has not yet been elucidated. This research explored the anti-obesity effect of kudinoside-D which was a main natural component of triterpenoid saponin from the ethanol extract of Ilex kudingcha, on lipid accumulation and the potential mechanism of action of adipogenesis in 3T3-L1 adipocytes. The adipocytes were treated with various concentrations of kudinoside D (0 to 40μM) during differentiation. The image-based Oil Red O staining analyses revealed that KD-D, dose dependently reduced cytoplasmic lipid droplet in 3T3-L1 adipocytes with the IC₅₀ is 59.49μM. Meanwhile, major adipogenic transcription factor Peroxisome Proliferator-activated Receptor γ (PPARγ), CCAAT/enhancer binding protein-α (C/EBPα) and sterol regulatory element-binding protein 1c (SREBP-1c) were significantly repressed as well as their target genes. The phosphorylation of AMP-activated protein kinase (AMPK) and its downstream target phosphorylated-acetyl CoA carboxylase (ACC) expression were also increased. In addition, the inhibitory effects of KD-D on the expressions of PPARγ and C/EBPα were weakened when cells were cotreated with AMPK Inhibitor Compound C. These results indicated KD-D exerts anti-adipogenic effects through modulation of adipogenic transcription factors via AMPK signaling pathway. And the current findings demonstrated that KD-D was a potential therapeutic candidate for alleviating obesity and hyperlipidemia.