1910-P: SOCS3 Deficiency on a High-Fat Diet Accelerates Systemic Inflammation and Results in Lethal Myeloid Hematopoiesis without Obesity and Adiposity

Abstract

Introduction: Suppressors of cytokine signaling (SOCS) are negative regulators of cytokine signaling; SOCS3 controls myeloid hematopoiesis by suppressing G-CSF. SOCS3 haploinsufficiency attenuates diet-induced obesity by enhanced leptin sensitivity while improving insulin resistance. We established SOCS3 conditional knock-out (KO) mice to elucidate how high fat diets (HFD) affect inflammation and obesity in complete SOCS3 deficiency. Methods: Embryonic lethality of complete SOCS3 deficiency was overcome using a conditional Socs3 allele inactivated by tamoxifen (TAM)-inducible cre-recombinase with SOCS3fl/flRosa26-CreERT2T/+ mice. They were fed HFD (60 kcal% fat) or control chaw (10 kcal% fat) starting at 4 weeks of age and TAM or vehicle administration was done at 8 weeks. Results: Although insulin resistance improved and obesity and fatty liver were not confirmed in SOCS3-KO with HFD (S3HFD), the S3HFD group looked moribund around day 30 post-TAM by systemic inflammation; their mean survival was 62.5 days after TAM. Other groups did not look moribund. Significant granulopoiesis was also observed in S3HFD (peripheral blood neutrophil counts 29301 ± 20581/mm3). This myeloid hematopoiesis occurred in the spleen and not the bone marrow. S3HFD exhibited the progression of various granulocytes from progenitor cells (c-kitint∼highLy6G-) to mature granulocytes (c-kit-Ly6G+).Hematopoietic infiltration was confirmed in the liver in S3HFD with granulocytes, monocytes, and macrophages. Inflammasome-associated genes (IL-1β and Caspase1) were elevated in the liver at day 65 post-TAM in S3HFD. Conclusion: SOCS3 deficiency showed myeloid proliferation under HFD without obesity and adiposity. SOCS3-KO may help in the clarification of the specific mechanism of myeloid proliferation and invasion in HFD-induced inflammation. Disclosure K. Cho: None. T. Ushiki: None. H. Ishiguro: None. T. Katagiri: None. T. Suwabe: None. H. Hirai: None. Y. Nakagawa: None. M. Masuko: None. W. Alexander: None. H. Shimano: None. H. Sone: Research Support; Self; Astellas Pharma Inc., Boehringer Ingelheim Pharmaceuticals, Inc., Daiichi Sankyo Company, Limited, Kowa Pharmaceutical Europe Co. Ltd., Kyowa Hakko Kirin Co., Ltd., Novo Nordisk Inc., Ono Pharmaceutical Co., Ltd., Taisho Pharmaceutical Co., Ltd., Takeda Pharmaceutical Company Limited, Teijin Pharma Limited.