OGT Orchestrates Intestinal Epithelial Homeostasis and Repair through Coordinated mTORC1 Activity

O‑GlcNAc transferase (OGT) mediates O‑GlcNAcylation, a nutrient‑sensitive post‑translational modification that integrates metabolic and signaling cues in diverse biological contexts. However, its role in intestinal stem cell (ISC) homeostasis and epithelial regeneration remains poorly understood. Here, we show that OGT is essential for maintaining intestinal epithelial integrity and regenerative capacity. Inducible deletion of Ogt in Lgr5⁺ crypt base columnar ISCs using Olfm4‑CreER led to crypt hyperplasia, expansion of transit‑amplifying cells, and depletion of the Lgr5⁺ ISC pool, accompanied by Paneth cell dysfunction and impaired epithelial regeneration following X‑ray irradiation. Mechanistically, OGT loss elevated proteasome activity, resulting in increased intracellular free amino acids and subsequent mTORC1 hyperactivation. Conversely, low‑dose rapamycin treatment in OGT‑deficient mice markedly attenuated mTORC1 hyperactivation and substantially improved epithelial regeneration after irradiation. Consistently, OGT‑deficient organoids exhibited heightened sensitivity to irradiation, which was alleviated by rapamycin. Furthermore, pharmacological elevation of O‑GlcNAcylation using the OGA inhibitor Thiamet‑G protected high‑fat diet‑fed mice from irradiation‑induced intestinal damage and promoted epithelial repair. Collectively, our findings establish OGT‑mediated O‑GlcNAcylation as a critical regulator of ISC function and mucosal repair through metabolic control of mTORC1 activity, and suggest that enhancing O‑GlcNAc signaling may represent a therapeutic strategy for radiation‑induced intestinal injury.