Interferon regulatory factor 7 mediates obesity-associated MCP-1 transcription

Hypertrophy, associated with adipocyte dysfunction, causes increased pro-inflammatory adipokine, and abnormal glucose and lipid metabolism, leading to insulin resistance and obesity-related-health problems. By combining DNA microarray and genomic data analyses to predict DNA binding motifs, we identified the transcription factor Interferon Regulatory Factor 7 (IRF7) as a possible regulator of genes related to adipocyte hypertrophy. To investigate the role of IRF7 in adipocytes, we examined gene expression patterns in 3T3-L1 cells infected with a retrovirus carrying the IRF7 gene and found that enforced IRF7 expression induced the expression of monocyte chemoattractant protein-1 (MCP-1), a key initial adipokine in the chronic inflammation of obesity. CRISPR/Cas9 mediated-suppression of IRF7 significantly reduced MCP-1 mRNA. Luciferase assays, chromatin immunoprecipitation PCR analysis and gel shift assay showed that IRF7 transactivates the MCP-1 gene by binding to its proximal Interferon Stimulation Response Element (ISRE), a putative IRF7 binding motif. IRF7 knockout mice exhibited lower expression of MCP-1 in epidydimal white adipose tissue under high-fat feeding conditions, suggesting the transcription factor is physiologically important for inducing MCP-1. Taken together, our results suggest that IRF7 transactivates MCP-1 mRNA in adipocytes, and it may be involved in the adipose tissue inflammation associated with obesity.