The Effects of Quercetin on High Fat Diet-Induced Inflammation and Oxidative Stress in Brown Adipose Tissue

Abstract

Abstract Objectives Under obesity state, adipose tissue derived inflammatory mediators circulate all over the body and induce low-grade chronic inflammation, which is the main cause for the development of metabolic diseases. Moreover, inflammation-induced reactive oxygen species (ROS) cause oxidative stress, a process in damaging cellular structure and functions. Recently, microRNAs (miRNAs) were found to potentially regulate inflammation and its associated diseases. Brown adipose tissue (BAT) protects against obesity through thermogenic activity to increase energy expenditure. However, high levels of inflammation, ROS generation and aberrant level of miRNAs result in the dysfunction of BAT. Previously, quercetin showed anti-obesity effect through BAT activation. Thus, the purpose of this study was sought to investigate the effect of quercetin on high fat diet (HFD)-induced inflammation and oxidative stress in BAT. Methods C57BL/6 male mice were fed with a HFD or HFD supplemented with 1% quercetin (HFDQ) for 16 weeks. Total RNA was isolated from BAT to measure the expression of target mRNAs such as tumor necrosis factor alpha (TNFa), interleukin (IL) 1b, IL6, inducible nitric oxide synthase (iNOS), cyclooxygenase (COX) 2, NADPH oxidase (NOX) 2, nuclear factor E2-related factor (NRF) 2, superoxide dismutase (SOD) 2, SOD3, and catalase that are involved in regulation of inflammation and oxidative stress, and microRNA (miRNA)-155, a master regulator of inflammation, using a quantitative PCR. Results BAT of HFDQ-fed mice exhibited decreased expression of COX2, TNFa, IL1b, IL6, and iNOS compared to that of HFD-induced obese mice. NOX2 gene encoding an enzyme that generates ROS was also decreased in BAT of HFDQ-fed mice. The genes such as SOD2, SOD3, NRF2, and catalase that are involved in regulation of antioxidant enzymes were significantly increased. As the cognate gene of TNFa, miRNA-155 levels were downregulated. Conclusions Quercetin ameliorates HFD-induced inflammation and oxidative stress in BAT by regulating miRNA-155. Intake of quercetin may improve obese conditions by regulating BAT function through anti-inflammatory and antioxidant effects. Funding Sources This work was supported by USDA.