Abstract
OBJECTIVE: We hypothesized that intestinal barrier impairment is a key pathophysiological feature in AD and that the degree of baseline barrier dysfunction, reflected by serum D-lactate levels, predicts the clinical response to Washed Microbiota Transplantation (WMT). This study aimed to test these hypotheses by investigating the association between intestinal barrier biomarkers and AD severity, and their correlation with WMT outcomes. METHODS: We compared intestinal barrier biomarkers (D-lactate, endotoxin, and diamine oxidase) between 24 AD patients and 23 healthy donors. Additionally, we evaluated the clinical outcomes of 14 AD patients who underwent WMT therapy. RESULTS: AD patients exhibited significantly elevated intestinal barrier biomarkers compared to healthy donors (p < 0.01). Following WMT, significant improvements were observed in SCORAD, EASI, and NRS scores (p < 0.05). In exploratory, uncorrected analyses, baseline D-lactate levels showed a significant negative correlation with improvements in SCORAD (R = -0.738, p = 0.037) and NRS scores (R = -0.650, p = 0.012), suggesting that higher pre-treatment levels might predict greater symptom relief. Microbiota analysis revealed a increase in Acidaminococcus and decreases in Ruminococcus_gnavus_group, Flavonifractor, and Norank_f_Oscillospiraceae following WMT. CONCLUSION: This study confirms significant intestinal barrier dysfunction in AD and demonstrates the potential clinical efficacy of WMT. The strong, uncorrected correlations suggest that pre-treatment D-lactate level warrants further investigation as a candidate biomarker for predicting WMT response. The clinical benefits occurred alongside a restructuring of the gut microbiota.