Abstract 11802: IRF2BP2 Regulates Hormone Sensitive Lipase and Lipolysis in Human Adipocytes and in Mice

Abstract

Background: IRF2BP2, a transcriptional co-factor, has emerged as a potential regulator of circulating lipid levels based on several coronary artery disease (CAD) genome-wide association studies (GWAS) studies. However, the role of IRF2BP2 in adipocytes, which regulate fat storage, energy expenditure, and fatty acid release, remains unexplored. Our aim is to investigate the role of IRF2BP2 in adipocyte function regulation. Methods: Human adipocyte stem cells (hASC) were differentiated into adipocytes for in vitro studies. We used the CRISPR system and lentiviral expression constructs to knockout (KO) and overexpress (OE) IRF2BP2. Control, IRF2BP2 KO and IRF2BP2 OE adipocytes were assessed by several methods, including RNA-seq, western blot analysis, and functional assessment of lipolysis and glucose uptake. IRF2BP2 chromatin immunoprecipitation (ChIP)-seq was performed in vitro . Adiponectin-Cre mice were crossed with Irf2bp2 flox/flox mice to generate adipocyte-specific KO (AKO) animals. We evaluated the effect of IRF2BP2 KO on adipose morphology and gene profiles. Circulating fatty acids were assessed in control and AKO mice. Results: IRF2BP2 deletion or OE in hASC-differentiated adipocytes did not affect adipocyte differentiation or glucose uptake. However, triglyceride lipolysis was markedly increased in KO cells. Conversely, IRF2BP2 OE suppressed lipolysis. RNA-seq analysis of control vs. IRF2BP2 KO or OE cells identified the enrichment of lipid catabolic pathways. Notably, IRF2BP2 KO upregulated, whereas IRF2BP2 OE downregulated the mRNA and protein levels of LIPE (i.e. hormone sensitive lipase, or HSL). Further, ChIP-seq analysis demonstrates strong binding of IRF2BP2 to a LIPE enhancer, suggesting direct regulation. In mice, Irf2bp2 AKO increased circulating fatty acids, accompanied by a reduction of adipocyte size. LIPE mRNA and protein expression in adipose tissue was also elevated. Finally, Irf2bp2 AKO induces massive adipose tissue inflammation, evidenced by F4/80 staining and chemotaxis gene markers expression. Conclusions: We established IRF2BP2, as a novel transcriptional regulator of adipocyte lipolysis, through the key lipolytic gene LIPE, which may shed light on deciphering the role of IRF2BP2 in CAD.