Biomarkers of intestinal permeability and blood-brain barrier permeability in adolescents with major depressive disorder

Background: The etiology in major depressive disorder (MDD) has not been fully understood. Accumulating evidence suggests an association between altered intestinal and blood-brain barrier (BBB) permeability and psychiatric disorders, while its changes in adolescent MDD populations have been received less attention. In this study, our aim was to explore the differences in plasma levels of intestinal and blood-brain barrier permeability markers in adolescents with MDD compared with healthy controls (HCs). Methods: We enrolled MDD (n = 50), and HCs (n = 40) with the age of 13-18 years old. The plasma level of zonulin, I-FABP, LPS, and claudin-5 were quantified. The Hamilton Depression Scale 17 items (HAMD-17) and Hamilton Anxiety Scale 14 items (HAMA-14) were used for symptom assessments. Results: The plasma levels of zonulin, I-FABP, LPS, and claudin-5 in the MDD group were significantly higher than those in the HCs. Plasma I-FABP levels in MDD with moderate to severe anxiety were significantly higher than those in MDD without moderate to severe anxiety and HCs. In addition, these four biomarkers (alone or com-bined) can be used as diagnostic markers for MDD in adolescents. Limitations: The key limitation of this study is the blood measurements at a single time point with a relatively small sample size. Conclusions: These findings advance our understanding of the pathophysiology of intestinal barrier injury, bac-terial translocation, and blood-brain barrier injury involved in adolescents with MDD.