Coptidis Rhizoma: a comprehensive review of its traditional uses, botany, phytochemistry, pharmacology and toxicology

Wang, Jin; Wang, Lin; Lou, Guan-Hua; Zeng, Hai-Rong; Hu, Ju; Huang, Qin-Wan; Peng, Wei; Yang, Xiang-Bo

Insulin resistance (IR) is a pathological condition in which cells fail to respond to the normal actions of the hormone insulin. IR increases the risk of developing pre-diabetes and type-2 DM. Treatment with berberine at 50 mg/kg/day for 2 weeks was effective against the features of IR syndrome, and could improve levels of IR parameters, such as body weight, hyperglycemia, hyperinsulinemia, hypercholesterolemia, and hypertriglyceridemia . Shen et al. (2012) revealed that berberine could decrease insulin levels in pancreatic islet b-cells via reversible the concentration-dependent inhibition of the INS2 promoter. Increasing the expression of insulin receptor (INSR) is also regarded as a target of berberine to increase insulin sensitivity. This effect is related to a protein kinase C (PKC)-dependent activation of its promoter (Kong WJ et al. 2009 ). In some insulinresistant patients with diabetes, there is a phenomenon of increased INSR dephosphorylation by protein tyrosine phosphatase 1B (PTP1B). Interestingly, berberine can suppress the activation of PTP1B to increase the phosphorylation of INSR . Insulin receptor substrate (IRS) is a key molecule that acts after the insulin receptor and mediates insulin signalling. In insulin signalling, the levels of phosphorylated AKT and IRS were significantly increased by berberine in alloxan-induced diabetic mice (Xie X et al. 2011) . In insulinresistant cells, berberine improved insulin-induced tyrosine-phosphorylation of IRS-1 and the recruitment of p85 to IRS-1, which was related to the inhibition of mTOR (Liu LZ et al. 2010) .