Obesity represents a serious problem in public health that affect both developed and in development countries. It is related to a chronic, low grade inflammation status that predisposes insulin resistance and diabetes mellitus development and, consequently, increases the risk for cardiovascular diseases. In this context, it can be verify that obesity changes the hepatic metabolism by the increase of glucose production and output and by the acute protein syntheses like protein C reative. Moreover, it can be verify that obesity-induced chronic inflammation increases the hepatic expression of kinases, such as inhibitor of ºB (IºB) kinase (IKK) and c-Jun N-terminal kinase (JNK), that contribute to the occurrence of peripheral insulin resistance, since these kinases phosphorylates the serine 307 of insulin receptor substrates (IRS-1). This fact decreases the phosphatidylinositol 3-kinase activity (PI3K) and, consequently, reduces the glucose transport. Yerba Maté (Ilex paraguariensis) contains bioactive compounds, such as cafeic acid, kaempferol, quercetin and 3,5-dicaffeoylquinic acid, which can reduce the genes expression involved in inflammatory response. The present project aims to investigate the effect of Yerba Maté aqueous extract ingestion on proteins involved in the regulation of insulin signaling in the liver of rats fed a high-fat diet. Wistar male rats will be fed a control diet (n= 24) or a high-fat diet (n= 24) during 12 weeks. After this period, 8 animals from each group will be sacrificed, while the remaining animals will be distributed to two groups: one of which will receive, by gavage, Yerba Maté aqueous extract (1 g/kg body weight) for four weeks. Then, all animals will be sacrificed and, by the liver extraction, it will be evaluate JNK, IRS-1 and IKK- ² protein expression (total and phosphorylated). Body composition of animals' carcasses will be analyzed and the blood will be used for the determination of glucose, insulin, total cholesterol, HDL-cholesterol, LDL-cholesterol, VLDL-cholesterol, triacilglicerols, leptin, adiponectin, tumor necrosis factor (TNF)- ±, interleukin (IL)-6, plasminogen activator inhibitor (PAI)-1, monocyte chemotactic protein (MCP)-1 and the enzyme activities of alanin aminotransferase (ALT) and aspartate aminotransferase (AST). Animals will be submitted to an oral glucose tolerance test (OGTT) in the first, tenth and sixteenth experimental protocol week.
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