Regulation of the insulin resistance pathways in 3T3-L1 adipocytes by Tangnaikang (a herbal formula)-medicated serum

Type 2 diabetes is an inherited disease characterized by hyperglycemia and insulin resistance (IR) in peripheral tissues such as adipose tissues and skeletal muscles [1]. Although Chinese herbal medicines have been widely used to treat this disease, little is known about the underlying mechanisms, especially their effect on the insulin signal transduction pathways. In this study, we investigated the influence of a Chinese herbal formula, Tangnaikang (containing Prunella vulgaris, Guava leaf, Saururus chinensis, Lingustrum lucidum and Ginseng) on the expression of insulin receptor (InsR) mRNA, insulin receptor substrate-1 (IRS-1) protein, p85 subunit of phosphatidylinositol-3-kinase (PI-3Kp85) protein, glycogen synthase kinase 3 (GSK-3) protein and glucose transporter 4 (GluT-4) mRNA in 3T3-L1 adipocytes [2]. The insulin resistance model was set up by inducing the differentiation of 3T3-L1 preadipocyte into mature adipocyte. At 48h after administration of Tangnaikang-medicated serum, the gene and protein expression of InsR, GluT-4, IRS-1, PI3-Kp85 and PKB/Akt1 αSer473 was determined [3]. We found that Tangnaikang-medicated serum could up-regulate the gene expression of InsR and GluT4, and the protein expression and phosphorylation of PI3-K p85 and PKB/Akt1 αSer473. Our results demonstrate that Tangnaikang-medicated serum can regulate the insulin signal transduction pathways, suggesting that the effectiveness of Tangnaikang may involve the molecular mechanisms that improve IR conditions.

Acknowledgements: This work was funded by Beijing Municipal Science and Technology Commission.

References: 1. Liberman, Z, Eldar Finkelman, H. (2005)J Biol Chem. 280:4422. 2. Shao, J. et al. (2002) Diabetes 51:19. 3. Wang, Y., Watford, M. (2006) Biochim Biophys Acta 11:23.