ACAT1-mediated lactylation reprogramming governs immune-stromal crosstalk in ulcerative colitis.

Ulcerative colitis (UC), a chronic inflammatory bowel disorder characterized by progressive colonic inflammation, presents escalating global incidence rates and heightened risk of colorectal carcinogenesis. Despite emerging evidence implicating lactylation - a novel post-translational modification - in diverse biological pathways, its mechanistic involvement in UC pathogenesis remains poorly elucidated. Through integrative analysis of GEO datasets, we systematically identified lactylation-associated signatures in UC using differential expression profiling, weighted gene co-expression network analysis (WGCNA), and protein-protein interaction network reconstruction. Six machine learning algorithms (Gaussian Mixture Model, Support Vector Machine, Random Forest, Gradient Boosting Machine, XGBoost, and LASSO regression) converged to identify ACAT1 as the central lactylation-associated hub gene. Comprehensive immune microenvironment profiling incorporating CIBERSORT deconvolution, single-sample gene set enrichment analysis (ssGSEA), and single-cell RNA sequencing (SEURAT/CellChat) revealed significant myeloid cell heterogeneity between healthy and UC cohorts, with Mendelian randomization analysis confirming causal immune-UC relationships. Clinical correlation analysis demonstrated marked ACAT1 downregulation in active UC phases, showing positive associations with M2 macrophage infiltration and resting mast cells, but inverse correlations with neutrophil activation and dendritic cell maturation. Building on the above signature, we mined the cMAP repository and retrieved sulfasalazine as an ACAT1-directed small molecule; molecular docking was subsequently employed to assess the predicted binding pose and affinity. Mechanistically, ACAT1 overexpression in colonic epithelial cells attenuated lactate accumulation and suppressed lactylation modifications in both in vitro and dextran sulfate sodium-induced murine colitis models. Our findings establish ACAT1 as a master regulator of lactate metabolism and protein lactylation in UC pathogenesis. The developed lactylation subtype stratification system and elucidated immune-stromal interaction network provide novel mechanistic insights, positioning ACAT1 as a potential diagnostic biomarker and therapeutic target for precision UC management.