SUN-638 Macrophage PARP1 Is Critical for Regulating White Adipose Tissue Function and Maintaining Metabolic Homeostasis

Abstract Disclosure: J. Zhu: None. R. Gupte: None. T.S. Nandu: None. W.L. Kraus: W.L. Kraus is co-holder of U.S. Patent 9,599,606 covering the ADP-ribose detection reagent used herein, which has been licensed to and is sold by EMD Millipore.. D. Huang: None. Adipose tissue macrophages play a significant role in maintaining adipose tissue homeostasis, as well as promoting chronic low-grade inflammation during the development of obesity and metabolic dysfunction. PARP1, the dominant PARP family member, catalyzes poly(ADP-ribosyl)ation, an NAD+-dependent post-translational modification of proteins. We have revealed an important role of PARP1 in regulating adipogenesis by using an adipocyte precursor-specific Parp1 knockout mouse model. To further investigate the role of macrophage PARP1 in regulating adipose tissue function and metabolic homeostasis, we generated myeloid lineage cell-specific knockout mice of Parp1 gene by crossing Parp1loxp/loxp mice with LysMCre mice (Parp1 cKOLysMCre). To explore whether macrophage-specific knockout of Parp1 affects adipogenesis, we treated primary preadipocytes isolated from the stromal vascular fraction (SVF) of white adipose tissue with the conditioned medium from LPS-stimulated control or Parp1 cKOLysMCre bone marrow-derived macrophages (BMDMs) throughout a 6-day period of differentiation. Macrophage-specific knockout of Parp1 dramatically decreased LPS-induced pro-inflammatory gene expression in BMDMs. Interestingly, the exposure of preadipocytes to the conditioned medium of Parp1 cKOLysMCre BMDMs promoted adipogenesis. To further investigate the function of macrophage PARP1 in regulating metabolic outcomes, we fed the control or Parp1 cKOLysMCre mice with high fat diet (HFD) for 12 weeks. Parp1 cKOLysMCre mice exhibited significant increases in body weight and adipose tissue mass. We also observed that macrophage-specific knockout of Parp1 led to insulin resistance; however, it did not alter the serum lipid level in mice. We also measured energy expenditure by comprehensive laboratory animal monitoring system (CLAMS). Parp1 cKOLysMCre mice exhibited significant decreases in carbon dioxide production and heat generation. To explore the underlying mechanism, we performed single cell RNA-sequencing for CD45 positive cells sorted from SVF of white adipose tissue, as well as metabolomic analysis for white adipose tissue in HFD-fed mice. Initial single cell RNA-sequencing data demonstrated an increased portion of macrophages among the immune cell populations in Parp1 cKOLysMCre mice compared to the control mice. Metabolomic analysis showed that the metabolites significantly regulated by macrophage PARP1 were enriched in metabolic pathways and glycerophospholipid metabolism. Taken together, our study suggests that Parp1 knockout in macrophages selectively affects the recruitment and pro-inflammatory activation of macrophages, as well as adipocyte differentiation in adipose tissue, which leads to obesity and obesity-related metabolic dysfunction. Presentation: Sunday, July 13, 2025