Effects of water extract and crude polysaccharides from Liriope spicata var. prolifera on InsR/IRS-1/PI3K pathway and glucose metabolism in mice

Aim of the study: The present study was designed to investigate the effects of water extract (WE) and crude polysaccharides (CPs) from the tuberous root of Liriope spicata var. prolifer on the InsR/IRS-1/PI3K pathway and glucose metabolism in type 2 diabetic mice. Materials and methods: WE and CPs were administered orally at different doses (200 and 100 mg/kg body weight) to streptozotocin (STZ)-induced type 2 diabetic male BABL/c mice, respectively. After 4 weeks of administration, immunohistochemistry and western blot were applied to detect the expression levels of insulin receptor-alpha (InsR-alpha), insulin receptor substrate-1 (IRS-1) and phosphatidylinositol 3-kinase (PI3K) in renal tissues of mice. Moreover, the hepatic glycogen content, glucokinase (GK) and glucose-6-phosphatase (G6Pase) activities were measured to investigate the effect of WE and CPs on glucose metabolism. Results: Compared with diabetic control, greater immunostaining for InsR-alpha, IRS-1 and PI3K was present in the tubulointerstitial regions of WE and CPS groups in renal tissues and the expression levels of these three signal molecules from WE and CPs groups were significantly increased; the glycogen content and GK activity from WE and CPs groups in liver were significantly increased, yet the G6Pase activity was significantly lower. Conclusions: It is demonstrated that WE and CPs can ameliorate insulin signaling transduction and glucose metabolism, as a result, lessen IR and hyperglycemia eventually. So, this study has provided more powerful evidences for Liriope spicata var. prolifer to be a potential hypoglycemic agent and insulin sensitizer. Crown Copyright (C) 2009 Published by Elsevier Ireland Ltd. All rights reserved.