Estimation of an optimum intake level of epigallocatechin gallate for suppression of inflammation in type 2 diabetic GK rats

Abstract

Previous studies have suggested that epigallocatechin gallate (EGCG) exerts anti‐oxidative and anti‐inflammatory actions in various tissues, which might be beneficial for reducing risks of development of diabetes. However, it is unknown whether there is an optimum intake level of EGCG. In this study, we have examined the effect of a diet containing various concentrations of EGCG on the expression of inflammation‐related genes in various tissues including visceral adipose tissue and the liver of non‐obese type‐2 diabetes animal model, Goto‐Kakizaki (GK) rats. GK rats at 5 weeks of age were fed a control high‐fat diet (45 energy% as fat) or the high‐fat diet containing 0.1%, 0.2% or 0.5% EGCG for 34 weeks. The mRNA levels of IL‐1β, IL‐18, TNF‐α and resistin were significantly reduced in the adipose tissue of rats fed a diet containing 0.1% EGCG, but not in those fed diets containing 0.2% or more EGCG, as compared with control. The mRNA levels of IL‐1β and IL‐18 in the liver of rats fed a diet containing 0.1% EGCG were also significantly lower than those in the control. These results suggest that there is an optimum range of intake of EGCG, which may suppress the expression of genes involved in inflammation in the adipose tissue and the liver.