Dietary arginine affects the insulin signaling pathway, glucose metabolism and lipogenesis in juvenile blunt snout bream Megalobrama amblycephala

Hualiang Liang,Qunlan Zhou,Jun Xie,Linghong Miao,Wenjing Pan,Mingchun Ren,Xianping Ge,Yan Lin,Habte-Michael Habte-Tsion

doi:10.1038/s41598-017-06104-3

Abstract

This study evaluated the mechanisms governing insulin resistance, glucose metabolism and lipogenesis in juvenile fish fed with graded levels of dietary arginine. The results showed that, compared with the control group (0.87%), 2.31% dietary arginine level resulted in the upregulation of the relative gene expression of IRS-1, PI3K and Akt in the insulin signaling pathway, while 2.70% dietary arginine level led to inhibition of these genes. 1.62% dietary arginine level upregulated glycolysis by increasing GK mRNA level; 2.70% dietary arginine level upregulated gluconeogenesis and resulted in high plasma glucose content by increasing PEPCK and G6P mRNA level. Furthermore, 2.70% dietary arginine level significantly lowered GLUT2 and increased PK mRNA levels. 1.62% dietary arginine level significantly upregulated ACC, FAS and G6PDH mRNA levels in the fat synthesis pathway and resulted in high plasma TG content. These results indicate that 1.62% dietary arginine level improves glycolysis and fatty acid synthesis in juvenile blunt snout bream. However, 2.70% dietary arginine level results in high plasma glucose, which could lead to negative feedback of insulin resistance, including inhibition of IRS-1 mRNA levels and activation of gluconeogenesis-related gene expression. This mechanism seems to be different from mammals at the molecular level.

Highlights

We reported that the ribosomal protein S6 kinase 1 (S6K1) was overexpressed in response to high dietary arginine levels[2]; S6K1 overexpression might result in insulin resistance through a negative feedback mechanism[19], thereby affecting glucose metabolism in juvenile blunt snout bream
Insulin receptor substrate (IRS) proteins act as messenger molecule-activated receptors of signaling pathways by interacting with Src homology 2 domains, which is an important step in insulin action[21]
We found that the relative expression of insulin receptor substrate 1 (IRS-1) in the groups fed with dietary arginine levels of 1.96 and 2.31% was significantly upregulated compared with that of the control group

Summary

Introduction

We reported that the ribosomal protein S6 kinase 1 (S6K1) was overexpressed in response to high dietary arginine levels[2]; S6K1 overexpression might result in insulin resistance through a negative feedback mechanism[19], thereby affecting glucose metabolism in juvenile blunt snout bream. This phenomena suggested that dietary arginine levels could affect the insulin signaling pathway. The aim of this study was to investigate the effects of dietary arginine levels on the relative gene expression of the insulin signaling pathway, as well as glucose and lipid metabolism-related signaling molecules in juvenile blunt snout bream

Objectives

Methods

Results

Conclusion