Guava leaf extracts promote glucose metabolism in SHRSP.Z-Leprfa/Izm rats by improving insulin resistance in skeletal muscle

Xiangyu Guo,Tonghua Liu,Wen Sun,Peifeng Xie,Jingxin Zhou,Ming Gao,Tunhai Xu,Liansha Huang,Ying Duan,Hisae Yoshitomi,Lingling Qin

doi:10.1186/1472-6882-13-52

Abstract

BackgroundMetabolic syndrome (MS) and type 2 diabetes mellitus (T2DM) have been associated with insulin-resistance; however, the effective therapies in improving insulin sensitivity are limited. This study is aimed at investigating the effect of Guava Leaf (GL) extracts on glucose tolerance and insulin resistance in SHRSP.Z-Leprfa/Izm rats (SHRSP/ZF), a model of spontaneously metabolic syndrome.MethodsMale rats at 7 weeks of age were administered with vehicle water or treated by gavage with 2 g/kg GL extracts daily for six weeks, and their body weights, water and food consumption, glucose tolerance, and insulin resistance were measured.ResultsCompared with the controls, treatment with GL extracts did not modulate the amounts of water and food consumption, but significantly reduced the body weights at six weeks post treatment. Treatment with GL extracts did not alter the levels of fasting plasma glucose and insulin, but significantly reduced the levels of plasma glucose at 60 and 120 min post glucose challenge, also reduced the values of AUC and quantitative insulin sensitivity check index (QUICKI) at 42 days post treatment. Furthermore, treatment with GL extracts promoted IRS-1, AKT, PI3Kp85 expression, then IRS-1, AMKP, and AKT308, but not AKT473, phosphorylation, accompanied by increasing the ratios of membrane to total Glut 4 expression and adiponectin receptor 1 transcription in the skeletal muscles.ConclusionsThese data indicated that GL extracts improved glucose metabolism and insulin sensitivity in the skeletal muscles of rats by modulating the insulin-related signaling.

Highlights

Metabolic syndrome (MS) and type 2 diabetes mellitus (T2DM) have been associated with insulin-resistance; the effective therapies in improving insulin sensitivity are limited
Guava Leaf (GL) extracts improve the glucose metabolism but do not affect insulin production in SHRSP/ZF rats To determine whether the GL extracts could affect glucose metabolism, SHRSP/ZF rats were fed with water as the controls or with GL extracts (2 g/kg) in water for six weeks
We found that treatment with GL extracts significantly increased the ratio of membrane to total glucose transporter 4 (GLUT4) expression in the skeletal muscles of SHRSPZF rats

Summary

Introduction

Metabolic syndrome (MS) and type 2 diabetes mellitus (T2DM) have been associated with insulin-resistance; the effective therapies in improving insulin sensitivity are limited. Therapeutic strategies for the intervention of MS and T2DM should center on the improvement of insulin sensitivity. The efficacy of available medicines in improving insulin sensitivity is limited. The skeletal muscles are important for glucose metabolism, in individuals with insulin resistance [3]. The multiple post-receptor intracellular defects, such as activation of the insulinstimulated IRS/PI3K pathway, occur in the skeletal muscles of individuals with insulin resistance [5]. The IRS/PI3K signal pathway in the skeletal muscles is a promising therapeutic target in the effective treatment of MS and T2DM

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