FRI022 The Stress-Response Pathways Of NRF2 And Notch Are Upregulated In The Adipocytes But Not In The Immune Cells Of Obese Subjects Adipose Tissue

Abstract

Abstract Disclosure: D. Chartoumpekis: None. I. Georgakopoulos-Soares: None. Introduction: Obesity is characterized by increased reactive oxygen species (ROS) in adipose tissue. Nrf2 is a transcription factor which regulates antioxidant and cytoprotective genes. ROS react with cysteines of Keap1, the cytoplasmic inhibitor of Nrf2, leading to conformational changes which render Keap1 unable to bind to Nrf2 molecules and lead them to degradation by the proteasome. Thus, Nrf2 accumulates, enters the nucleus and induces the expression of its target genes. Notch signaling is known for its roles in development, cell fate, cell differentiation, apoptosis and proliferation. Notch is a family of intermembrane receptors. The extracellular part of Notch interacts with a ligand of a neighboring cell and triggers two successive proteolytic cleavages by proteases. This permits the release of Notch Intracellular Domain (NICD) to enter the nucleus and induce the expression of target genes. ROS have been recently shown to activate the metalloproteases ADAM 10/17 and facilitate the cleavage of NICD and thus the activation of Notch pathway. A bidirectional transcriptional regulation of Nrf2-Notch has also been described. Hence, both Nrf2 and Notch can be considered as pathways that respond to oxidative stress. Hypothesis: We hypothesized that Nrf2 and Notch pathways are upregulated in the adipose tissue of obese subjects in response to increased ROS levels. Methods: We identified publicly available (series GSE176171) single-cell RNA sequencing data from adipose tissue from humans with BMI<25 kg/m2 (normal weight) or BMI>30 kg/m2 (obese) and from C57BL6 mice fed a high-fat diet (60% kcal fat) or a normal chow diet (6.4% kcal fat) for 13 weeks. R studio read RDS and fetchdata functions were employed to analyze the data in the different cell types of adipose tissue (vascular, immune, mesothelial cells and adipocytes). Results: An at least a 2-fold increase was seen in the RNA levels of several cytoprotective genes (such as NQO1, TXNRD1, GCLC, HMOX1, GSTA4), that are known to be regulated by Nrf2, in adipocytes from obese humans compared to the normal weight ones. Similar changes were found in the murine adipocytes of obese subjects. Interestingly, no significant differences were detected in these gene sets in immune cells from the mouse and human adipose tissue between lean and obese individuals. Notch 1-3 RNA was also found increased at least 2-fold in human adipocytes of obese patients while only Notch3 RNA was increased in adipocytes of obese mice. A common target gene of Notch signaling, Hes1, showed increased expression in both human (2-fold) and murine (4-fold) adipocytes of obese subjects. These changes were not seen in the immune cells of both species. Conclusions: This increased Nrf2 and Notch signaling in adipocytes in the obese state warrants further investigation as it may play roles in the homeostasis and the capacity of the adipose tissue and in the resulting metabolic phenotype. Presentation: Friday, June 16, 2023