Papel do TLR-4 na resposta inflamatória e resistência insulínica no tecido adiposo em condição de sobrecarga nutricional crônica

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Igor Otavio Minatel
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Bioactive compounds and food biochemistry
Fabiane Francisqueti
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Obesity is associated with low-grade inflammation, triggered in adipose tissue, which may occur due to an excess of SFA from the diet that can be recognised by Toll-like receptor-4. This condition is involved in the development of components of the metabolic syndrome associated with obesity, especially insulin resistance. The aim of the study was to evaluate the manifestation of the metabolic syndrome and adipose tissue inflammation as a function of the period of time in which rats were submitted to a high-sugar/fat diet (HSF). Male Wistar rats were divided into six groups to receive the control diet (C) or the HSF for 6, 12 or 24 weeks. HSF increased the adiposity index in all HSF groups compared with the C group. HSF was associated with higher plasma TAG, glucose, insulin and leptin levels. Homeostasis model assessment increased in HSF compared with C rats at 24 weeks. Both TNF-α and IL-6 were elevated in the epididymal adipose tissue of HSF rats at 24 weeks compared with HSF at 6 weeks and C at 24 weeks. Only the HSF group at 24 weeks showed increased expression of both Toll-like receptor-4 and NF-κB. More inflammatory cells were found in the HSF group at 24 weeks. We can conclude that the metabolic syndrome occurs independently of the inflammatory response in adipose tissue and that inflammation is associated with hypertrophy of adipocytes, which varies according to duration of exposure to the HSF.
Fabiane Francisqueti
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The prevalence of obesity has increased in the past two decades. This growth has been attributed to changes in dietary habits, especially increased consumption of fats and sugars. It is clear that obesity is a risk factor for cardiovascular disease and insulin resistance, and the inflammatory process favors this context. Aim: To address the inflammatory aspects of obesity and associated metabolic complications. Data Sources: Original data from articles found through search of scientific databases. Summary of findings: Micro hypoxia, reticulum stress, and activation of toll-like receptor 4 are responsible for triggering inflammation in adipose tissue, which is the place where the process begins. Thus, there is an increased production of various adipokines, such as IL-6 and TNF-α, which impair insulin signaling pathway, leading to resistance to hormone, one of the first complications of obesity. From this, with the intensity of stimulation, the condition may worsen triggering type 2 diabetes and other comorbidities. Conclusion: Thus, the elucidation of the roles and mechanisms of the main adipokines lead to a better understanding of the pathogenesis of obesity-related disorders.
Ƴ-oryzanol (Orz), a steryl ferulate extracted from rice bran layer, exerts a wide spectrum of biological activities. In addition to its antioxidant activity, Orz is often associated with cholesterol-lowering, anti-inflammatory, anti-cancer and anti-diabetic effects. In recent years, the usefulness of Orz has been studied for the treatment of metabolic diseases, as it acts to ameliorate insulin activity, cholesterol metabolism, and associated chronic inflammation. Previous studies have shown the direct action of Orz when downregulating the expression of genes that encode proteins related to adiposity (CCAAT/enhancer binding proteins (C/EBPs)), inflammatory responses (nuclear factor kappa-B (NF-κB)), and metabolic syndrome (peroxisome proliferator-activated receptors (PPARs)). It is likely that this wide range of beneficial activities results from a complex network of interactions and signals triggered, and/or inhibited by its antioxidant properties. This review focuses on the significance of Orz in metabolic disorders, which feature remarkable oxidative imbalance, such as impaired glucose metabolism, obesity, and inflammation.