Differential regulation of the biosynthesis of glucose transporters by the PI3-K and MAPK pathways of insulin signaling by treatment with novel compounds from Liriope platyphylla.

The insulin signaling pathway, involving protein kinase B (PKB) and mitogen-activated protein kinase (MAPK), mediates the biological response to insulin and several growth factors and cytokines. To investigate the correlation between glucose transporter (Glut) biosynthesis and the insulin signaling pathway activated by novel compounds of Liriope platyphylla (LP9M80-H), alterations in Glut and key protein expression in the insulin signaling pathway were analyzed in the liver and brain of ICR mice treated with LP9M80-H. An in vitro assay showed that the highest level of insulin concentration was observed in the LP9M80-H-treated group, followed by the LP-H, LP-M, LP-E, and LP9M80-C-treated groups. Therefore, LP9M80-H was selected for use in studying the detailed mechanism of the insulin signaling pathway in animal systems. In an in vivo experiment, LP9M80-H induced a significant increase in glucose levels and a decrease of insulin concentration in the blood of mice, while their body weight remained constant over 5 days. The expression level of Glut-3 was down-regulated in the liver, or maintained at the same level in the brain of LP9MH80-H-treated mice. These changes corresponded to the phosphorylation of the p38 protein rather than to ERK and JNK in the MAPK signaling pathway. In addition, the expression level of Glut-1 increased significantly after LP9MH80-H treatment of both insulin target tissues in mice. Western blot analysis showed that Akt in the PI3-K pathway mainly participated in Glut-1 biosynthesis. Thus, these results suggest the possibility that the LP9M80-H-induced regulation of Glut-1 and Glut-3 biosynthesis may be mediated by the Akt and p38 MAPK signaling of the insulin signaling pathway in the liver and brain of mice.

Gomisin N isolated from Schisandra chinensis significantly induces anti-proliferative and pro-apoptotic effects in hepatic carcinoma.

Lignans isolated from Schisandria chinensis have been prescribed as anti-cancer and anti-hepatitis treatments in Chinese medicine. To investigate the applications of lignans isolated from Schisandria chinensis in hepatic carcinoma therapy, their apoptotic ability was screened using a cell proliferation assay. Compared to the other lignans, gomisin N induced high apoptotic levels in hepatic carcinoma. Cell morphology and flow cytometric analysis demonstrated that this lignan induced cell death at high concentrations, but did not induce any changes at low concentrations. In addition, the expression levels of Bcl-2 and Bax proteins, which are involved in the apoptotic pathway, were markedly increased in only the 320 µM-treated group compared to the vehicle and other concentration groups, while the expression level of p53 protein remained unchanged in this group. These results suggest that gomisin N is an anti-cancer drug candidate capable of inhibiting the proliferation and inducing the apoptosis of human hepatic carcinomas.