Integrating Mendelian Randomization and Epithelial Barrier Assays Reveals Protective Effects of Acetate and Histidine...

This study aims to evaluate the causal relationship between serum biomarkers and gastroesophageal reflux disease (GERD) using Mendelian Randomization (MR) and validate key findings through in vitro functional assays.

Genome-Wide Association Study (GWAS) data for GERD were sourced from the UK Biobank and QSkin Health Study, including 71,522 GERD cases and 261,079 controls from European populations. Serum biomarker data from 27 biomarkers were obtained from approximately 400,000 UK Biobank participants. MR analysis used inverse-variance weighted method as primary approach, complemented by MR-Egger and weighted median methods. For functional validation, human esophageal epithelial Het-1A cells were treated with methyl-β-cyclodextrin (MβCD) to deplete cholesterol, with or without acetate or histidine supplementation. Barrier function was assessed by transepithelial electrical resistance (TEER) and FITC-dextran permeability.

MR analysis revealed that increased acetate concentrations were associated with a 28% reduced risk of GERD (OR: 0.72, 95% CI: 0.56-0.92, p=0.0089). Histidine showed similar protective effects, reducing GERD risk by 15% (OR: 0.85, 95% CI: 0.72-1.00, p=0.047). Conversely, elevated Cystatin C levels were linked to a 32% increased GERD risk (OR: 1.32, 95% CI: 1.10-1.73, p=0.0105). In vitro validation demonstrated that MβCD-induced cholesterol depletion disrupted epithelial barrier function, reducing TEER by 30% and doubling FITC-dextran flux. Co-treatment with acetate or histidine partially rescued barrier integrity, restoring TEER to ~80% of baseline and reducing dextran permeability by ~35%. Western blotting confirmed that acetate and histidine prevented MβCD-induced loss of ZO-1 and suppressed NF-κB activation.

Integrating MR with barrier-function assays demonstrates that genetically and experimentally reduced cholesterol disrupts esophageal epithelial integrity, whereas acetate and histidine confer measurable protection. These findings provide mechanistic insights into GERD pathogenesis and suggest potential therapeutic targets for patients with cholesterol-related barrier dysfunction.