Aucubin, a naturally occurring iridoid glycoside inhibits TNF-α-induced inflammatory responses through suppression of NF-κB activation in 3T3-L1 adipocytes

• Aucubin inhibits TNF-α-induced production of atherogenic adipokines in adipocytes.
• These effects of aucubin result from suppression of NF-κB activation pathway.
• The mechanism explains effects of aucubin on obesity-related inflammatory responses.

Obesity is closely associated with a state of chronic, low-grade inflammation characterized by abnormal cytokine production and activation of inflammatory signaling pathways in adipose tissue. Tumor necrosis factor (TNF)-α is chronically elevated in adipose tissues of obese rodents and humans. Increased levels of TNF-α are implicated in the induction of atherogenic adipokines, such as plasminogen activator inhibitor (PAI)-1, adipose-tissue-derived monocyte chemoattractant protein (MCP)-1, and interleukin (IL)-6. Aucubin, an iridoid glycoside existing in medicinal plants, has been reported to show an anti-inflammatory activity by suppression of TNF-α production in murine macrophages. The present study is aimed to investigate the effects of aucubin on TNF-α-induced atherogenic changes of the adipokines in differentiated 3T3-L1 cells. Aucubin significantly inhibited TNF-α-induced secretion and mRNA synthesis of the atherogenic adipokines including PAI-1, MCP-1, and IL-6. Further investigation of the molecular mechanism revealed that pretreatment with aucubin suppressed extracellular signal-regulated kinase (ERK) activation, inhibitory kappa Bα (IκBα) degradation, and subsequent nuclear factor kappa B (NF-κB) activation. These findings suggest that aucubin may improve obesity-induced atherosclerosis by attenuating TNF-α-induced inflammatory responses.