O‐GlcNAc Regulates CD4+ T Cell Differentiation

Chronic inflammation is a feature of obesity and enhances the risk of atherosclerosis, cancer, diabetes, and autoimmunity. Specifically, pro‐inflammatory T H 1 and T H 17 CD4+ effector T cells are increased in metabolic diseases. However, a clear molecular mechanism linking metabolic changes with pro‐inflammatory T cells is lacking. We hypothesize that elevated levels of O‐linked β‐N‐acetylglucosamine (O‐GlcNAc), a post‐translational modification of nuclear and cytoplasmic proteins, promotes pro‐inflammatory CD4+ T cell differentiation. Since production of O‐GlcNAc involves input from carbohydrate, amino acid, fatty acid, and nucleic acid metabolism, the modification acts as a general sensor of a cell's nutritional status. To investigate the role of O‐GlcNAc in a setting of metabolic disease, we analyzed O‐GlcNAc levels in CD4+ T cells in mice fed a high fat and cholesterol, “Western” diet. CD4+ T cells from obese mice have elevated O‐GlcNAc levels and are primed to secrete more IL‐17A, the eponymous T H 17 cytokine, and IFNγ, the signature T H 1 cytokine. As an in vitro model, we cultured mouse splenic CD4+ T cells with Thiamet‐G (TMG), a selective inhibitor of the enzyme that removes O‐GlcNAc (O‐GlcNAcase, OGA), before activating the T cell receptor under permissive conditions in which differentiation of all effectors is possible. We find a significant 100% increase in protein and transcript levels of IL‐17A in TMG treated cells. Transcript levels of IFNγ are significantly increased 50%. Importantly, T H 17 cells can adopt a T H 1‐like phenotype in which they secrete both IL‐17 and IFNγ. These dual‐producers are known to be particularly pathogenic in autoimmune diseases. Intracellular cytokine staining shows two‐fold increases in IFNγ+ cells, IL‐17+ cells, and dual‐producing IFNγ+IL‐17+ cells. Acetyl CoA carboxylase 1 (ACC1), the rate limiting enzyme in fatty acid synthesis, is known to enhance generation of T H 17 cells by producing ligands that increase the activity of RORγt, the transcription factor which defines the T H 17 lineage. We discovered that ACC1 is O‐GlcNAcylated. Collectively, our data suggest that elevated O‐GlcNAc levels prime T H 17, T H 1, and T H 1‐like T H 17 CD4+ T cell differentiation by altering ACC1 activity. Further study into the molecular mechanism of how O‐GlcNAcylation promotes pro‐inflammatory T cell differentiation will provide insight into how nutritional excess exacerbates inflammation. Support or Funding Information This research was supported by NIH grant R01DK100595‐01, NIH grant R01DK091277‐03, and a KUMC IRHRM pilot grant.Aberrant O‐GlcNAcylation in CD4+ T cells increases inflammatory IL‐17 production through enhancement of RORγt activity by endogenous fatty acids.