Diamine oxidase as a biomarker for depression and disease activity in inflammatory bowel disease: A cross-sectional observational study.

Background: Diamine oxidase (DAO) is secreted by epithelial cells in the intestinal villi, and its serum levels are elevated after intestinal mucosal damage. d-lactate (D-LA) is a gut microbial metabolite that can enter the systemic circulation if intestinal barrier function is impaired. Both DAO and D-LA are serum markers of small bowel mucosal integrity, and can be valuable biomarkers of intestinal barrier damage in inflammatory bowel disease (IBD). Intestinal barrier dysfunction was recently found to contribute to psychological symptoms in IBD patients. However, the correlations among DAO, D-LA, psychological symptoms, and disease activity in IBD remain unexplored.

Aim: To explore the correlations between serum markers of intestinal barrier dysfunction and psychological symptoms in IBD.

Methods: We enrolled of 126 participants in this study. Psychological symptom questionnaires (depression, patient health questionnaire-9; anxiety, generalized anxiety disorder-7; and stress, perceived stress scale) and a quality of life (QOL) questionnaire (IBD questionnaire 32) were collected at the baseline. Serum DAO and D-LA levels were measured to assess intestinal barrier integrity. Receiver operating characteristic (ROC) curves were used to identify candidate markers of psychological symptoms and disease activity in IBD patients. Logistic regression was applied, with DAO as an independent variable for predicting psychological symptoms in IBD.

Results: Serum DAO levels were significantly higher in IBD patients with moderate-to-severe psychological symptoms than in patients with mild or no psychological symptoms. DAO was positively correlated with depression and negatively correlated with QOL in IBD patients. ROC curves revealed that DAO was independently associated with psychological symptoms and clinical activity in patients with IBD. Additionally, logistic regression analysis revealed that each 1-ng/mL increase in DAO levels was significantly associated with an increased risk of psychological symptoms in IBD patients (OR: 1.019, 95%CI: 1.002-1.037). These results highlight the potential of DAO as a novel biomarker for both depression and disease activity in IBD patients.

Conclusion: This study indicates that DAO may be associated with depression and disease activity in IBD patients; however, prospective studies are required to validate its causal relationship.