Depression is a disease that accompanies mental and physical symptoms, and psychological stress is strongly involved, causing imbalance in the functioning of the brain, resulting in depressed mood and sleep disorders.It is known that such psychological stress is involved in abnormalities of the intestinal flora, but the mechanism is unknown.

　On the other hand, the research group has found that the antibacterial peptide * called α-defensin secreted by the panelo cells of the small intestine appropriately composes the intestinal flora by the selective bactericidal activity that does not kill the symbiotic bacteria that are resident in the intestine. It was revealed that it was in control.Therefore, we hypothesized that when the amount of α-defensin secretion decreases, the homeostasis of the intestinal flora and its metabolites is disrupted.

　Using mice, the research group first examined the effect of psychological stress on α-defensin secretion.As a result of analyzing the amount of α-defensin in stool, it was found that the amount of secretion was significantly reduced.Analysis of the composition of the intestinal flora and intestinal metabolites also revealed these abnormalities.Furthermore, oral administration of α-defensin to mice to increase the decreased intestinal α-defensin recovered the abnormalities of the intestinal flora and metabolites.

　This time, the relationship between the innate immunity of the intestine and the intestinal flora (gut-brain axis) in depression has been clarified for the first time in the world.In the future, it is expected to develop preventive methods and new treatment methods from the viewpoint of brain-intestinal correlation for such depression.

* A collection of amino acids with bactericidal and antibacterial effects

Paper information:[Scientific Reports] Decrease of α-defensin impairs intestinal metabolite homeostasis via dysbiosis in mouse chronic social defeat stress model