Extracts of Rehmanniae radix, Ginseng radix and Scutellariae radix improve glucose-stimulated insulin secretion and β-cell proliferation through IRS2 induction

Abstract

Recent studies have revealed that β-cell dysfunction is an important factor in developing type 2 diabetes. β-cell dysfunction is related to impairment of the insulin/IGF-1 signaling cascade through insulin receptor substrate-2 (IRS2). The induction of IRS2 in β-cells plays an important role in potentiating β-cell function and mass. In this study, we investigated whether herbs used for treating diabetes in Chinese medicine - Galla rhois, Rehmanniae radix, Machilus bark, Ginseng radix, Polygonatum radix, and Scutellariae radix - improved IRS2 induction in rat islets, glucose-stimulated insulin secretion and β-cell survival. R. radix, Ginseng radix and S. radix significantly enhanced glucose-stimulated insulin secretion compared to the control, i.e., by 49, 67 and 58%, respectively. These herbs induced the expression of IRS2, pancreas duodenum homeobox-1 (PDX-1), and glucokinase. The increased level of glucokinase could explain the enhancement of glucose-stimulated insulin secretion with these extracts. Increased PDX-1 expression was associated with β-cell proliferation, which was consistent with the cell viability assay. In conclusion, R. radix, Ginseng radix and S. radix had an insulinotropic action similar to that of exendin-4. © Springer-Verlag 2007.