Effect of Probiotic Bifidobacterium bifidum TMC3115 Supplementation on Psychosocial Stress Using a Sub-Chronic and Mild Social Defeat Stress in Mice.

With the accumulation of knowledge on the relation between psychological stress and gut microbiota, there is growing interest in controlling stress and/or mood disorders via probiotic supplementation. We aimed to examine the effect of probiotic Bifidobacterium bifidum TMC3115 (TMC3115) supplementation using a sub-chronic and mild social defeat stress murine model in this study. TM3115 supplementation maintained body weight gain and alleviated a polydipsia-like symptom induced by the stress. In the analyses of fecal and cecal bacterial profiles, expansions of Proteobacteria in stressed mice and increases in Actinobacteria and Bifidobacterium in mice supplemented with TMC3115 were observed. There was no marked difference in the diversity of cecal bacteria between the tested mice. Elevated serum levels of inflammatory markers such as tumor necrosis factor (TNF)-α and interleukin (IL)-6 were observed in the stressed mice, while TMC3115 only reduced the IL-6 level. These findings suggest that TMC3115 supplementation confers tolerance to psychosocial stress in the host through modulation of the gut microbiota and alleviation of stress-induced inflammatory responses. Furthermore, it may be expected to exert prevention and treatment of disorders related to peripheral IL-6, including depression.

Dietary intake of the citrus flavonoid hesperidin affects stress-resilience and brain kynurenine levels in a subchronic and mild social defeat stress model in mice.

Depressive disorders are partly caused by chronic inflammation through the kynurenine (KYN) pathway. Preventive intervention using anti-inflammatory reagents may be beneficial for alleviating the risk of depression. In this study, we focused on the Japanese local citrus plant, Citrus tumida hort. ex Tanaka (C. tumida; CT), which contains flavonoids such as hesperidin that have anti-inflammatory actions. The dietary intake of 5% immature peels of CT fruits slightly increased stress resilience in a subchronic and mild social defeat (sCSDS) model in mice. Moreover, the dietary intake of 0.1% hesperidin significantly increased stress resilience and suppressed KYN levels in the hippocampus and prefrontal cortex in these mice. In addition, KYN levels in the hippocampus and prefrontal cortex were significantly correlated with the susceptibility to stress. In conclusion, these results suggest that dietary hesperidin increases stress resilience by suppressing the augmentation of KYN signaling under sCSDS.

Effects of non-purified and semi-purified commercial diets on behaviors, plasma corticosterone levels, and cecum microbiome in C57BL/6J mice.

Diverse commercially available feeds are used in animal studies according to the purpose of the studies. We sought to understand the relationship between feed ingredients and their effects on animal physiology and behaviors. Here, we investigated how male laboratory mice (C57BL/6J ("B6") mice) were affected by chronic feeding with two commercially available diets, a non-purified diet (MF) and a semi-purified diet (AIN-93G). In B6 mice, both diets similarly induced spontaneous activities in the home cage and the open field box, anxiety in the elevated plus maze test, and depressive-like behaviors in tail-suspension and forced-swimming tests, and with both diets, similar data were obtained on calorie intake, water intake, body weight gain, and plasma corticosterone levels. By contrast, liver weight was significantly higher in MF-fed B6 mice than in AIN-93G-fed B6 mice. Furthermore, the cecum microbiome was drastically affected by the diets, and, specifically, Allobaculum was the major genus (43.4%) in the cecum microbiota of AIN-93G-fed mice but its abundance was reduced (to 3.8%) in the case of MF-fed mice. Future studies should address whether the differences in diet purity and cecum microbiota influence brain functions and behaviors in B6 mice.