Abstract Body: Introduction: Myeloid cells especially macrophages in adipose tissue (ATMs) are proposed to contribute to the development of insulin resistance in high fat diet (HFD) feeding, particularly in murine models. The receptor for advanced glycation end products (RAGE) is implicated in the pathogenesis of HFD induced obesity and consequent insulin and glucose intolerance in mice. Our previous studies demonstrated that global or adipocyte-specific deletion of Ager (the gene encoding RAGE) protects mice from HFD induced obesity and insulin resistance, and boosts energy expenditure. However, the potential specific roles of RAGE in myeloid cells in HFD-fed mice have yet to be probed.

Methods: To determine RAGE function in myeloid cells, we generated myeloid-specific Ager deleted mice (MDR) by intercrossing Ager floxed mice with Lys2m CRE recombinase mice and performed several physiological analyses upon HFD intervention. We performed single nucleus RNA sequencing (snRNA-seq) analysis in epididymal white adipose tissue (eWAT) of mice fed HFD for 12 weeks to identify intra-cellular crosstalk mechanisms in the development of insulin resistance.

Results: Compared to CRE-control mice, MDR mice displayed greater insulin insensitivity without differences in body mass or composition upon HFD feeding. MDR mice showed higher lipid droplet accumulation and triglyceride content in the liver vs. CRE-control mice. Although the mean adipocyte size was not different between CRE-control and MDR mice, wild type mice (C57BL/6J) that received transplanted eWAT from HFD-fed MDR mice showed greater insulin resistance vs. CRE-control mice upon low fat diet feeding. These phenotypes were rescued by adipocyte-specific deletion of Ager in the transplanted eWAT. The pathway analysis of snRNA-seq in eWAT suggested that toll-like receptor (TLR) signal and lysosome-related genes were upregulated in the cluster of lipids-associated macrophages (LAMs) in MDR vs. CRE-control mice. Moreover, MultiNichenet analysis of snRNA-seq implied that adipocytes regulate TLR signaling in LAMs. Experiments are underway to identify and validate these adipocyte-specific secreted ligands.

Conclusion: Myeloid-specific deletion of Ager attenuates insulin signaling in HFD-fed mice via regulation of intra-cellular communications between macrophages and adipocytes in eWAT. This study unveils a novel adaptive role for RAGE in crosstalk between adipocytes and macrophages that protects from disruption in insulin signaling.