Epigallocatechin gallate prevents inflammation by reducing macrophage infiltration and inhibiting tumor necrosis factor-α signaling in the pancreas of rats on a high-fat diet

Abstract

In this study, we hypothesized that epigallocatechin gallate (EGCG) would suppress inflammation in the pancreas, and thus, we investigated the effects that EGCG administration had in the pancreas of rats fed a high-fat diet (HFD). To test our hypothesis, 30 male Sprague-Dawley rats were divided into 2 groups: normal diet (control) group and HFD group. When there was a significant difference in body weight between the 2 groups (P < .05), the HFD group was further divided into 2 subgroups: the HFD group (HFD, n = 10, 16 weeks) and the EGCG group (HFD + 3.2 g/kg EGCG, n = 10, 16 weeks). Metabolite levels and the expression of inflammatory markers (tumor necrosis factor alpha [TNF-α], interleukin 6 [IL-6], and toll-like receptor 4) were measured using standard biochemical techniques. Insulin secretion and pancreatic histology were also evaluated. Epigallocatechin gallate significantly decreased fasting insulin levels as well as the homeostasis model assessment–insulin resistance index. In the HFD group, the average glucose infusion rate and the TNF-α and IL-6 levels increased, whereas toll-like receptor 4 and TNF receptor-associated factor-6 did not. A pathologic analysis of pancreatic tissue revealed an increase in inflammatory TNF-α and infiltrating CD68+ macrophages in the islets of the HFD rats, but rarely is this observed in the in the HFD + EGCG rats. Overall, these data suggest that EGCG suppresses inflammation, partially reverses metabolic abnormalities, and ultimately increases insulin sensitivity in the pancreas of HFD rats.