Effect of Coptidis Rhizoma extracts in a water-based solution on insulin resistance in 3T3-L1 adipocytes

The present study was designed to investigate effects and molecular mechanisms of Coptidis Rhizoma extracts (CRE) on the improvement of insulin resistance induced by tumor necrosis factor-α (TNF-α) in adipocytes. We examined whether CRE administration could directly influence the insulin resistance in 3T3-L1 adipocytes. Potential roles of CRE in glucose consumption, mRNA expression of peroxisome proliferators activated receptor (PPAR-γ), expression of insulin receptor substrate-1 (IRS-1) protein, and phosphorylation of IRS-1 Ser307 were also investigated in the present study. Our data demonstrated that TNF-α significantly reduced levels of glucose consumption and IRS-1 protein expression, while TNF-α increased the phosphorylation of IRS-1 Ser307 in adipocytes 24 h after the challenge, suggesting that TNF-α induced a condition with the occurrence of insulin resistance. Those alterations induced by TNF-α were prevented and the mRNA expression of PPAR-γ was up-regulated by the administration of CRE. Thus, our results indicate that CRE can be used to prevent from the TNF-α-induced insulin resistance through PPAR-γ pathways.