title: Epigallocatechin gallate improves insulin signaling by decreasing toll-like receptor 4 (TLR4) activity in adipose tissues of high-fat diet rats.
abstract: METHODS
  In this study, we investigated the beneficial effects and the underlying mechanism of epigallocatechin gallate (EGCG) in adipose tissues of rats fed with a high-fat diet (HFD).
  
  
  RESULTS
  Fasting plasma insulin, epididymal fat coefficient and free fatty acids, homeostasis model assessment-insulin resistance index, and the average glucose infusion rate were determined. EGCG significantly decreased free fatty acids, fasting insulin, homeostasis model assessment-insulin resistance index, and epididymal fat coefficient, and increased glucose infusion rate in HFD group. The levels of toll-like receptor 4, TNF receptor associated factor 6, inhibitor-kappa-B kinase β, p-nuclear factor κB, tumor necrosis factor α, and IL-6 in the EGCG group were all significantly lower than the HFD control group. EGCG also decreased the level of phosphorylated insulin receptor substrate 1 and increased phosphoinositide-3-kinase and glucose transporter isoform 4 in the HFD group. Decreased macrophage infiltration was in EGCG group versus HFD group, and the protein level of CD68 in EGCG group was also significantly lower than that of HFD group.
  
  
  CONCLUSIONS
  EGCG attenuated inflammation by decreasing the content of macrophages, interfered the toll-like receptor 4 mediated inflammatory response pathway, thus, improving insulin signaling in adipose tissues.
authors.affiliation: Department of Endocrinology and Metabolism, Institute of Endocrinology, Liaoning Provincial Key Laboratory of Endocrine Diseases, The First Affiliated Hospital of China Medical University, Shenyang, P. R. China.
authors.forename: Suqing
authors.initials: S
authors.lastname: Bao
authors.forename: Yanli
authors.initials: Y
authors.lastname: Cao
authors.forename: Chenling
authors.initials: C
authors.lastname: Fan
authors.forename: Yuxin
authors.initials: Y
authors.lastname: Fan
authors.forename: Shuting
authors.initials: S
authors.lastname: Bai
authors.forename: Weiping
authors.initials: W
authors.lastname: Teng
authors.forename: Zhongyan
authors.initials: Z
authors.lastname: Shan
mesh_terms: D000273:Adipose Tissue / Q000187:drug effects* / Q000378:metabolism*; D000818:Animals; D002392:Catechin / Q000031:analogs & derivatives* / Q000494:pharmacology; D059305:Diet, High-Fat / Q000009:adverse effects*; D007328:Insulin / Q000378:metabolism*; D015850:Interleukin-6 / Q000378:metabolism; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism; D008297:Male; D058539:Phosphatidylinositol 3-Kinase / Q000378:metabolism; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000187:drug effects; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000378:metabolism*
chemical_list: D007328:Insulin; D015850:Interleukin-6; C495347:Tlr4 protein, rat; D051197:Toll-Like Receptor 4; D002392:Catechin; C045651:epigallocatechin gallate; D058539:Phosphatidylinositol 3-Kinase
keywords: Adipose tissue; Epigallocatechin gallate; High-fat diet; Insulin sensitivity; Toll-like receptor 4