SUN-LB101 NRF2 Represses Obesity-Associated Adipose Tissue Inflammation in Mice

Abstract

Obesity is associated with type 2 diabetes, cardiovascular disease and increased incidence of cancer. Chronic inflammation, mainly emanating from adipose tissue, has been proposed to be one of the links between obesity and these pathologies. Thus, identification of new targets against obesity and especially obesity-induced inflammation is needed urgently. Transcription factor Nrf2 (NF-E2-related-factor-2) plays a central role in cytoprotective responses to oxidative and electrophilic stresses and also exerts anti-inflammatory effects in rodent models of inflammation. However, whether activation of Nrf2 signaling pathway influences obesity-associated inflammation in adipose tissue is not well established. To this end, we generated mice with systemic activation of the Nrf2 pathway (Keap1flox/–), as well as mouse models with tissue-specific Nrf2 pathway activation: adipocyte-specific (Fabp4Cre::Keap1flox/ flox) and myeloid cell-specific (LymCre::Keap1flox/ flox). These mice were exposed to a high-fat diet (HFD) 60% kcal fat regimen for 6-weeks or crossed into the db/db background. Keap1flox/– mice showed a dramatic decrease of the numbers of F4/80-positive macrophages in white adipose tissue (WAT). Interestingly, both Fabp4Cre::Keap1flox/ flox and LymCre::Keap1flox/ flox mice showed suppression of F4/80-positive macrophages in WAT as well, suggesting enhanced Nrf2 signaling in either adipocytes or myeloid cells might contribute to anti-inflammatory effects in WAT under the stress of HFD. Transcript levels of inflammatory markers, especially macrophage F4/80 and Cd68 and the chemokine Ccl2 were decreased in the WAT from Keap1flox/– mice on the standard diet and also in the WAT of Keap1flox/– mice in the db/db background. Pharmacological activation of the Nrf2 pathway by treatment with CDDO-Im also suppressed Ccl2 expression in WAT of HFD fed mice and db/db mice. As CCL2 is a key mediator of macrophage accumulation in adipose tissue, we further studied the potential effect of Nrf2 on the transcriptional regulation of Ccl2 using 3T3-L1 preadipocyte and RAW264.7 macrophage cell lines. Treatment of both lines with the small molecule inducer of Nrf2, diethyl maleate significantly suppressed LPS-induced expression of Ccl2. Analysis using luciferase reporter assay revealed that a Nrf2 binding site in the Ccl2 5’ flanking region from -235 to +85 contributed to gene silencing of Ccl2 by activation of Nrf2. Our findings suggest that the druggable Nrf2 pathway may be an effective target to combat obesity-associated inflammation in adipose tissue and its’ concomitant metabolic disorders. Supported by AMED BINDS JP19am0101001 (MY), 19H05649 (MY), 16KK0195 (AU), NIH R35 CA197222 (TWK), JSPS OT 290125 (YY).