Impairment of the intestinal epithelium barrier through alteration of proliferation and differentiation balance in alcohol use disorder

BACKGROUND Alcohol use disorder (AUD) profoundly affects human health, yet its direct impact on the intestinal epithelium and stem cell niche remains insufficiently understood. AIM To characterize alcohol-induced alterations in intestinal epithelial morphology, proliferation, differentiation, and barrier-related functions in AUD patients. METHODS Duodenal biopsies from healthy and AUD patients were analyzed for epithelial architecture, proliferation, differentiation activity, and lineage composition using histological, immunofluorescence, proteomic, and transcriptomic approaches. Findings were complemented by studies in human-derived enteroids exposed to 40- or 70-mM ethanol to assess its direct effects on epithelial proliferation and signaling pathways. RESULTS A subset of AUD patients exhibited marked epithelial remodeling, including increased crypt depth, shortened villi, and expanded proliferation in the crypt base and transit-amplifying zone. Ki67+ cells and OLFM4+ stem-like compartment were increased, with CD44 identified as a potential driver of crypt-base proliferation. Moreover, a higher number of Ki67+ crypts co-expressed the enteroendocrine cells marker CHGA+ and the stem cell marker OLFM4. Ki67+ Kruppel-like factor 4+ cells were elevated in transit-amplifying zone, correlating with higher MUC2, MUC5AC, and anterior gradient-2 expression, alongside reduced antimicrobial peptides DEFA5, DEFA6, and REG3A. Nutrient absorption markers MTTP, FABP2, and SLC1A5 were dysregulated. Ethanol-exposed enteroids showed increased Ki67+ cells and cyclin B1 mRNA without changes in CD44 or Axin2 indicating a proliferative effect independent of canonical Wnt signaling. CONCLUSION Heavy alcohol consumption induces profound alterations in intestinal epithelial morphology, stem cell niche dynamics, and functional barrier properties. Together, these findings suggest that ethanol disturbs the intestinal proliferation-differentiation balance.