The outer membrane protein Amuc_1100 of Akkermansia muciniphila alleviates the depression-like behavior of depressed mice induced by chronic stress

Akkermansia muciniphila is a symbiotic intestinal bacterium with a high medicinal value. Amuc_1100 is the outer membrane protein of A. muciniphila and plays an important role in the interaction between A. muciniphila and its host. The objective of this study was to evaluate the antidepressant activity of Amuc_1100 in a chronic unpredictable mild stress (CUMS) model. Amuc_1100 intervention ameliorated CUMS-induced depression-like behavior and CUMS-induced down-regulation of serotonin (5-hydroxytryptamine, or simply, 5-HT) in the serum and colon of mice. Microbial analysis of mouse feces showed that Amuc_1100 could improve the gut microbiota dysregulation induced by CUMS. In addition, Amuc_1100 intervention could also improve the down-regulation of brain-derived neurotrophic factor (BDNF) and inflammation in the hippocampus induced by CUMS. These results suggest that Amuc_1100 has a good antidepressant effect, and the mechanism may be related to the improvement of gut microbiota, the up-regulation of the BDNF level, and the inhibition of the neuroinflammatory response.