It has previously been shown that the consumption of probiotics may have beneficial effects not only on peripheral tissues but also on the central nervous system and behavior via the microbiota–gut–brain axis, raising the possibility that treatment with probiotics could be an effective therapeutic strategy for managing neurodegenerative disorders. In this study, we investigated the effects of oral administration of Bifidobacterium breve strain A1 (B. breve A1) on behavior and physiological processes in Alzheimer’s disease (AD) model mice. We found that administration of B. breve A1 to AD mice reversed the impairment of alternation behavior in a Y maze test and the reduced latency time in a passive avoidance test, indicating that it prevented cognitive dysfunction. We also demonstrated that non-viable components of the bacterium or its metabolite acetate partially ameliorated the cognitive decline observed in AD mice. Gene profiling analysis revealed that the consumption of B. breve A1 suppressed the hippocampal expressions of inflammation and immune-reactive genes that are induced by amyloid-β. Together, these findings suggest that B. breve A1 has therapeutic potential for preventing cognitive impairment in AD.

The effects of intravenous infusion of 17 amino acids, each at a dose of 3 mmol/kg over 30 min, on the secretion of insulin, glucagon, and growth hormone (GH) were studied in 6 castrated male sheep. Insulin-like growth factor I (IGF-I) secretion was also studied using eight of the amino acids. Plasma alpha-amino nitrogen reached a peak at 30 min followed by a gradual decrease thereafter. The greatest increase was obtained using aspartic acid and the smallest with methionine, responses to the remaining amino acids lying between these two. Leucine was the most effective amino acid in stimulating insulin secretion but did not produce any increase in glucagon and GH secretion. Alanine, glycine, and serine induced a greater enhancement of both glucagon and insulin secretion than other amino acids. No amino acid was able to specifically stimulate glucagon secretion without also increasing insulin or GH secretion. With regard to insulin and glucagon secretion, amino acids could be divided into groups according to their R groups. Neutral straight-chain amino acids stimulated both insulin and glucagon secretion, with a greater secretory response to shorter C-chain amino acids. Branched-chain amino acids tended to enhance insulin and suppress glucagon secretion. Acidic amino acids caused an increase in GH secretion. Aspartic acid caused the strongest stimulation of GH secretion, exceeding that induced by arginine. No changes in plasma IGF-I were brought about by any of the amino acids tested.

In our previous study, we reported the therapeutic potential of Bifidobacterium breve A1 in preventing cognitive impairment in a mouse model of Alzheimer’s disease and participants with mild cognitive impairment; we suggested that probiotic supplementation is an effective therapeutic strategy for managing cognitive function. Accordingly, we conducted a randomised, double-blind, placebo-controlled trial to assess whether 12-week B. breve A1 supplementation could affect the cognitive function of elderly subjects with memory complaints. We assessed cognitive function using the Japanese version of the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) and Mini-Mental State Examination (MMSE) at baseline and after 12 weeks of probiotic supplementation. A total of 121 participants were randomised and received B. breve A1 capsules or placebo daily for 12 weeks; of these, 117 participants completed the study. At 12 weeks, neuropsychological test scores significantly increased in both groups; no significant intergroup difference was observed in terms of changes in scores from the baseline scores. However, a stratified analysis revealed a significant difference between B. breve A1 and placebo groups in terms of the subscale ‘immediate memory’ of RBANS and MMSE total score in the subjects with low RBANS total score at baseline. No significant differences in terms of blood parameters between the groups or adverse effects caused by B. breve A1 intervention were observed. The results of the present study suggest the safety of B. breve A1 supplementation and its potential in maintaining cognitive function in elderly subjects with memory complaints. However, future large-scale studies on individuals with impaired cognitive function are required to validate the present findings.

The effects of oral administration of bovine lactoferrin (bLF) and its hydrolysate on the lung colonization by colon 26 carcinoma were investigated. At doses of 100 or 300 mg/kg/day for seven successive days, bLFs demonstrated a significant inhibitory effect on experimental metastasis, which indicated effectiveness before and after tumor implantation. Oral administration of bLFs augmented CD4+, CD8+, and asialoGM1+ cells in the spleen and peripheral blood. Their cytotoxic activities against Yac-1 and colon 26 carcinoma were enhanced by bLF. In the small intestinal epithelium, CD4+ and CD8+ cells were markedly increased, and, simultaneously, enhanced production of interleukin-18 (IL-18) was confirmed in the intestinal epithelial cells. In this model, intravenous injection of murine IL-18 showed significant inhibition of the lung colonization by colon 26 carcinoma. These results suggested that inhibition of experimental metastasis by oral administration of bLF and pepsin hydrolysate of bLF might be due to enhanced cellular immunity, presumably mediated by enhanced IL-18 production in the intestinal epithelium.