Background: Depressive disorders represent a rising global health problem with numbers estimated to further increase by 2030. As prevention and therapeutic strategies mainly concentrate on psychotherapeutic interventions and antidepressants, recent studies have examined the potential of targeting the gut microbiome of patients suffering depression. Over the past decade, the gut microbiome, the intestinal barrier and the blood-brain barrier have become focus of investigations on their potential involvement in depressive disorders. To clarify these associations barrier markers may represent a diagnostic tool to indirectly assess barrier function and integrity and help elucidate the complex pathophysiology of depressive disorders. Objectives: This systematic review aims to summarize the current evidence on the biomarkers FABP2, FABP7 and GFAP and their potential associations with depressive disorders and symptom severity. Methods: A systematic literature review, following the PRISMA guidelines, was conducted in September 2024. PubMed, Embase, Web of Science and Google Scholar were searched for studies investigating one of the three biomarkers, FABP2, FABP7, or GFAP, in patients with depressive disorders and in healthy control subjects. The Newcastle-Ottawa Scale for case-control studies was used to evaluate the risk of bias and quality of the included studies. Due to heterogeneity, a narrative synthesis was conducted. Results: This review included cross-sectional and case-control studies. Ten studies met the eligibility criteria and were included in this review. Of these, six studies assessed GFAP concentrations and four studies investigated FABP2 serum levels. No eligible study was found for FABP7. In total, the studies examining FABP2 included 234 individuals with depressive disorder and 166 healthy controls. All included studies investigating GFAP comprised a number of 339 individuals with depressive disorder and 218 healthy controls. The findings for FABP2 were consistent and showed positive associations with depressive disorders, whereas the results for GFAP were inconsistent. Five studies additionally examined potential associations with symptom severity and yielded heterogeneous results. One study investigated FABP2 levels and suicidal behavior and found positive associations. Discussion and Conclusion: The limitations of this review consist in a limited number of studies with overall relatively small sample sizes and a lack of longitudinal studies. The findings of this review revealed a significant research gap for FABP7. Furthermore, the results indicate associations with FABP2 and depressive disorders, highlighting the role of the intestinal barrier in depression. No concrete link between symptom severity and both FABP2 and GFAP were found. The findings for GFAP on potential associations with depression were inconclusive. Further research focusing on subgroups of depressive disorders and specific clinical features seems relevant.
Psychoimmunological Interfaces - A systematic analysis of barrier markers in people with depressive disorders
Meyer, S. N. (Author). 2026
Student thesis: Diploma thesis