These findings suggest that LcS may prevent hypersecretion of cortisol and physical symptoms under stressful conditions, possibly through vagal afferent signaling to the brain and reduced stress reactivity in the PVN.

Stress-induced abdominal dysfunction is an attractive target for probiotics. To investigate the effects of the probiotic Lactobacillus casei strain Shirota on abdominal dysfunction, a double-blind, placebo-controlled trial was conducted with healthy medical students undertaking an authorized nationwide examination for academic advancement. For 8 weeks, until the day before the examination, 23 and 24 subjects consumed an L. casei strain Shirota-fermented milk and a placebo milk daily, respectively. In addition to assessments of abdominal symptoms, psychophysical state, and salivary stress markers, gene expression changes in peripheral blood leukocytes and composition of the gut microbiota were analyzed using DNA microarray analysis and 16S rRNA gene amplicon sequence analysis, respectively, before and after the intervention. Stress-induced increases in a visual analog scale measuring feelings of stress, the total score of abdominal dysfunction, and the number of genes with changes in expression of more than 2-fold in leukocytes were significantly suppressed in the L. casei strain Shirota group compared with those in the placebo group. A significant increase in salivary cortisol levels before the examination was observed only in the placebo group. The administration of L. casei strain Shirota, but not placebo, significantly reduced gastrointestinal symptoms. Moreover, 16S rRNA gene amplicon sequencing demonstrated that the L. casei strain Shirota group had significantly higher numbers of species, a marker of the alpha-diversity index, in their gut microbiota and a significantly lower percentage of Bacteroidaceae than the placebo group. Our findings indicate that the daily consumption of probiotics, such as L. casei strain Shirota, preserves the diversity of the gut microbiota and may relieve stress-associated responses of abdominal dysfunction in healthy subjects exposed to stressful situations. IMPORTANCEA novel clinical trial was conducted with healthy medical students under examination stress conditions. It was demonstrated that the daily consumption of lactic acid bacteria provided health benefits to prevent the onset of stress-associated abdominal symptoms and a good change of gut microbiota in healthy medical students. The gut microbiota, a large, diverse, and dynamic ecosystem that generates cross talk between the gut and host, can communicate with the host by modulating the gut-brain axis, which is a bidirectional neurohumoral communication system between the gut and brain. That is, signals from the brain modify the motor, sensory, and secretory modalities of the gastrointestinal tract; in turn, signals from the gut can affect emotional behavior and stress and pain modulation systems through neural, endocrine, and immune pathways (1-3). Thus, the gut-brain axis has now been expanded to the microbiota-gut-brain axis (3).It is particularly interesting to consider the possibility that probiotics (4), which are live microorganisms, can affect emotion in health and disease by modulating the microbiota-g...

This pilot study investigated the effects of the probiotic Lactobacillus casei strain Shirota (LcS) on psychological, physiological, and physical stress responses in medical students undertaking an authorised nationwide examination for promotion. In a double-blind, placebo-controlled trial, 24 and 23 healthy medical students consumed a fermented milk containing LcS and a placebo milk, respectively, once a day for 8 weeks until the day before the examination. Psychophysical state, salivary cortisol, faecal serotonin, and plasma L-tryptophan were analysed on 5 different sampling days (8 weeks before, 2 weeks before, 1 day before, immediately after, and 2 weeks after the examination). Physical symptoms were also recorded in a diary by subjects during the intervention period for 8 weeks. In association with a significant elevation of anxiety at 1 day before the examination, salivary cortisol and plasma L-tryptophan levels were significantly increased in only the placebo group (P<0.05). Two weeks after the examination, the LcS group had significantly higher faecal serotonin levels (P<0.05) than the placebo group. Moreover, the rate of subjects experiencing common abdominal and cold symptoms and total number of days experiencing these physical symptoms per subject were significantly lower in the LcS group than in the placebo group during the pre-examination period at 5-6 weeks (each P<0.05) and 7-8 weeks (each P<0.01) during the intervention period. Our results suggest that the daily consumption of fermented milk containing LcS may exert beneficial effects preventing the onset of physical symptoms in healthy subjects exposed to stressful situations.

During their migration, cerebellar granule cells switch from a tangential to a radial mode of migration. We have previously demonstrated that this involves the transmembrane semaphorin Sema6A. We show here that plexin-A2 is the receptor that controls Sema6A function in migrating granule cells. In plexin-A2-deficient (Plxna2(-/-)) mice, which were generated by homologous recombination, many granule cells remained in the molecular layer, as we saw in Sema6a mutants. A similar phenotype was observed in mutant mice that were generated by mutagenesis with N-ethyl-N-nitrosourea and had a single amino-acid substitution in the semaphorin domain of plexin-A2. We found that this mutation abolished the ability of Sema6A to bind to plexin-A2. Mouse chimera studies further suggested that plexin-A2 acts in a cell-autonomous manner. We also provide genetic evidence for a ligand-receptor relationship between Sema6A and plexin-A2 in this system. Using time-lapse video microscopy, we found that centrosome-nucleus coupling and coordinated motility were strongly perturbed in Sema6a(-/-) and Plxna2(-/-) granule cells. This suggests that semaphorin-plexin signaling modulates cell migration by controlling centrosome positioning.

The present study examined whether Lactobacillus casei strain Shirota (LcS) improves sleep quality under psychological stress. A double-blind, placebo-controlled trial was conducted in healthy 4 year medical students exposed to academic examination stress. The trial was repeated over two consecutive years in different groups of students, and the data were pooled. For 8 weeks prior to and 3 weeks after a national standardised examination, a total of 48 and 46 subjects received a daily dose of 100 ml of LcS-fermented milk or non-fermented placebo milk, respectively. Study measures included subjective anxiety, overnight single-channel electroencephalography (EEG) recordings, and the Oguri-Shirakawa-Azumi (OSA) sleep inventory scores of subjective sleep quality. Total OSA scores were significantly lower than baseline on the day before the exam and recovered after the exam, indicating a stress-induced decline in sleep quality. There was a significant positive effect of LcS treatment on OSA factors for sleepiness on rising and sleep length. Sleep latency measured by EEG lengthened as the exam approached in the placebo group but was significantly suppressed in the LcS group. The percentage of stage 3 non-REM (N3) sleep decreased in the placebo group as the exam approached, whereas it was maintained in the LcS group throughout the trial. Delta power during the first sleep cycle, measured as an index of sleep intensity, increased as the exam approached in the LcS group and was significantly higher than in the placebo group. These findings suggest that daily consumption of LcS may help to maintain sleep quality during a period of increasing stress. The observed retention of N3 sleep and increased delta power in the LcS group may have contributed to higher perceived sleep satisfaction.