Isoquercitrin activates the AMP–activated protein kinase (AMPK) signal pathway in rat H4IIE cells

Jingxin Zhou,Ming Gao,Lingling Qin,Lili Wu,Liansha Huang,Xiangyu Guo,Boxin Zhou,Hisae Yoshitomi,Tonghua Liu,Wen Sun

doi:10.1186/1472-6882-14-42

Abstract

BackgroundIsoquercitrin, a flavonoid compound that is widely distributed in medicinal and dietary plants, possesses many biological activities, including inhibition of adipocyte differentiation. In this study, we investigated the effect of isoquercitrin on lipid accumulation and its molecular mechanisms in rat hepatoma H4IIE cells.MethodsTo investigate the effect of isoquercitrin on lipid accumulation, H4IIE cells were induced by FFA and the total lipid levels were detected by Oil Red O staining. Furthermore, The protein levels of AMPK and acetyl-CoA carboxylase (ACC), the gene expressions of transcriptional factor, lipogenic genes, and adiponectin receptor 1 (AdipoR1) were analyzed by Western blotting and quantitative real-time PCR. To further confirm the pathway of isoquercitrin-mediated hepatic lipid metabolism, H4IIE cells were treated with an AMPK inhibitor and AdipoR1 siRNA.ResultsIsoquercitrin significantly enhances AMPK phosphorylation, downregulates sterol regulatory element binding protein transcription factor 1 (SREBP-1) and fatty acid synthase (FAS) gene expressions. Pretreatment with AMPK inhibitor, significantly decreased the AMPK phosphorylation and increased FAS expression stimulated by isoquercitrin. Isoquercitrin might also upregulate the expression of AdipoR1 dose-dependently via AMPK in the presence of an AMPK inhibitor and AdipoR1 siRNA.ConclusionsIsoquercitrin appears to regulate AMPK activation, thereby enhancing AdipoR1 expression, suppressing SREBP-1 and FAS expressions, and resulting in the regulation of lipid accumulation. These results suggest that isoquercitrin is a novel dietary compound that can be potentially be used to prevent lipid metabolic disorder and nonalcoholic fatty liver disease.

Highlights

Isoquercitrin, a flavonoid compound that is widely distributed in medicinal and dietary plants, possesses many biological activities, including inhibition of adipocyte differentiation
Isoquercitrin inhibits lipid accumulation in free fatty acids (FFAs)-induced H4IIE cells Cells were cultured with different concentrations of isoquercitrin (50, 100, and 200 μM) for 72 h, and cell viability was determined by the MTT assay
AMP-activated protein kinase (AMPK) pathway regulates isoquercitrin-induced reduction of lipid levels in H4IIE cells Because isoquercitrin increased the phosphorylation of AMPK and acetyl-CoA carboxylase (ACC), and reduced the gene expression levels of Sterol regulatory element binding protein 1 (SREBP-1) and fatty acid synthase (FAS) in H4IIE cells, we investigated the critical role of AMPK signaling on isoquercitrin-mediated hepatic fatty acid metabolism using an AMPK inhibitor, compound C

Summary

Introduction

Isoquercitrin, a flavonoid compound that is widely distributed in medicinal and dietary plants, possesses many biological activities, including inhibition of adipocyte differentiation. Its activation results in an increase in fatty acid oxidation and suppression of fatty acid synthesis via inactivation of acetyl-CoA carboxylase (ACC). It inhibits the lipogenic gene expression of fatty acid synthase (FAS) by decreasing the action of transcription factors [1]. Sterol regulatory element binding protein 1 (SREBP-1) is the most important transcription factor regulating the expression of lipogenic enzymes, including ACC and FAS. Many studies have suggested that increased levels of SREBP-1 are closely associated with fatty liver in obese animal models [2]. AMPK plays a key role in fatty acid metabolism in the liver and in whole body lipid metabolism

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