Elevated O-GlcNAcylation enhances pro-inflammatory Th17 function by altering the intracellular lipid microenvironment

Chronic, low-grade inflammation increases the risk for atherosclerosis, cancer, and autoimmunity in diseases such as obesity and diabetes. Levels of CD4⁺ T helper 17 (Th17) cells, which secrete interleukin 17A (IL-17A), are increased in obesity and contribute to the inflammatory milieu; however, the relationship between signaling events triggered by excess nutrient levels and IL-17A-mediated inflammation is unclear. Here, using cytokine, quantitative real-time PCR, immunoprecipitation, and ChIP assays, along with lipidomics and MS-based approaches, we show that increased levels of the nutrient-responsive, post-translational protein modification, <i>O</i>-GlcNAc, are present in naive CD4⁺ T cells from a diet-induced obesity murine model and that elevated <i>O</i>-GlcNAc levels increase IL-17A production. We also found that increased binding of the Th17 master transcription factor RAR-related orphan receptor γ t variant (RORγt) at the <i>IL-17</i> gene promoter and enhancer, as well as significant alterations in the intracellular lipid microenvironment, elevates the production of ligands capable of increasing RORγt transcriptional activity. Importantly, the rate-limiting enzyme of fatty acid biosynthesis, acetyl-CoA carboxylase 1 (ACC1), is <i>O</i>-GlcNAcylated and necessary for production of these RORγt-activating ligands. Our results suggest that increased <i>O</i>-GlcNAcylation of cellular proteins may be a potential link between excess nutrient levels and pathological inflammation.