1990-P: STAT1 Knockdown in CD11c+ Cells Prevents Adipose Tissue Inflammation and Metabolic Dysfunction in Mice on High-Fat Diet

Background: Classically activated M1-like CD11c+ macrophages/dendritic cells (MDCs) are increased in obese adipose tissue (AT) and may contribute to AT inflammation and the development of insulin resistance in obesity. STAT1 is a key transcription factor for MDC polarization into M1-like phenotypes. Here, we examined the role of STAT1 in obesity-induced AT MDC polarization and inflammation and insulin resistance in mice. Methods: Mice with specific knockout (KO) of STAT1 in CD11c+ MDCs were generated by crossbreeding STAT1fl/fl and CD11c-Cre mice. CD11c/STAT1 KO and littermate controls were fed high-fat diet (HFD, 16 weeks) to induce obesity and evaluated for immune cells and browning/beige adipogenesis in perigonadal (pAT) and inguinal (iAT) AT and metabolic functions. Results: Compared to control mice, KO mice on HFD had similar body weight. Analyses of AT immune cells revealed that compared to controls, KO mice had a decrease in M1-like proinflammatory polarization but an increase in M2-like polarization of macrophages and reduced CD8+ T cell number in pAT, and significant increases in the proportion of IL-5+ Th2 cells and eosinophils (CD170+) in pAT and iAT (p<0.05). Furthermore, compared to control mice, KO mice showed significantly increased iAT expression of browning markers (Ucp-1, Cidea, and prdm16) and had increased oxygen consumption rate but lower respiratory exchange ratio, indicating higher energy expenditure and increased fat utilization as energy source. Moreover, KO mice, as compared to controls, had significant reductions in triglyceride content in the liver and skeletal muscle and exhibited improved insulin sensitivity and glucose tolerance examined by insulin and glucose tolerance test (p<0.05). Conclusion: STAT1 plays an important role in obesity-induced MDC M1-like polarization and AT inflammation and contributes to insulin resistance and metabolic dysfunctions in obese mice. Disclosure A. Kalathookunnel Antony: None. X. Perrard: None. Z. Lian: None. J. Perrard: None. C.M. Ballantyne: Consultant; Self; Abbott, Akcea Therapeutics, Amarin Corporation, Amgen Inc., AstraZeneca, Boehringer Ingelheim Pharmaceuticals, Inc., Eli Lilly and Company, Esperion, Gilead Sciences, Inc., Matinas BioPharma, Merck & Co., Inc., Novartis Pharmaceuticals Corporation, Novo Nordisk Inc., Regeneron Pharmaceuticals, Roche Diagnostic USA, Sanofi. Research Support; Self; Abbott, Akcea Therapeutics, Amarin Corporation, Amgen Inc., Esperion, Novartis Pharmaceuticals Corporation, Regeneron Pharmaceuticals, Roche Diagnostic USA, Sanofi. Other Relationship; Self; Roche Diagnostic USA. H. Wu: None. Funding American Diabetes Association (1-17-IBS-082 to H.W.)