Bioscience of Microbiota, Food and Health最新文献

The genus Bifidobacterium comprises beneficial intestinal bacteria that play a crucial role in the regulation of human health. Traditional prebiotics are known to increase intestinal bifidobacteria by supplying a carbon source necessary for their growth. However, intestinal bifidobacteria need not only a carbon source but also a nitrogen source for growth. Moreover, the growth of bifidobacteria is known to be inhibited in a culture medium that does not contain glutamic acid. Based on these reports, we hypothesized that the combined intake of traditional prebiotics and glutamic acid would be beneficial for growth of bifidobacteria in the gut. In this study, we investigated the effects of the combination of galactooligosaccharide (GOS; traditional prebiotic material) and poly-γ-glutamic acid (γ-PGA; source of glutamic acid) and only GOS on the intestinal microbiota and health conditions (including intestinal regulation, mood status, gastrointestinal condition, skin condition, and sleep quality) in a randomized, double-blind, parallel-group comparison trial in healthy subjects. The combined intake of GOS and γ-PGA significantly increased the prevalence of B. longum compared to the intake of GOS alone. A minimum effective dose of 2.0 g GOS and 0.3 g γ-PGA improved defecation and mood status. We revealed the combined effects of GOS and γ-PGA on intestinal microbiota as well as physical condition and concluded that the delivery of glutamic acid to the large intestine with traditional prebiotics is useful as an advanced prebiotic.

The relationships between various diseases and the human gut microbiota (GM) have been revealed. However, the relationships between the human abdominal aortic aneurysm (AAA) and GM remains unknown. The aim of this cross-sectional study was to clarify the association between the human AAA and GM. Stool samples from 30 consecutive patients with AAA before aneurysm repair and those of 30 controls without vascular diseases were analyzed by 16S rRNA gene (V3-4) sequencing using an Illumina MiSeq system and QIIME 2. There was no significant difference in age (75 vs. 75 years) or gender (80% vs. 87% males) between the groups. No significant difference in GM composition was observed in principal coordinate analysis between the two groups, whereas the AAA group showed a significantly lower abundance of Bifidobacterium adolescentis (p<0.01) at the species level than the controls. This study demonstrated that the abundance of B. adolescentis decreased in patients with AAA. This is the first study to show the characteristics of the GM in patients with AAA. Studies are needed to reveal if causal relationships exists between the human AAA and GM.

Angiogenesis is a highly regulated biological event and requires the participation of neutrophils, which are innate immune cells, to initiate the systematic responses. Some strains of lactic acid bacteria (LAB) can be used for probiotics that provide functional modifications in our immune systems. Here, we show that oral administration of Lacticaseibacillus casei ATCC393 promoted inflammatory angiogenesis accompanied by enhanced neutrophil activity. Heat-killed L. casei (HK-LC) administration improved angiogenesis in a murine hind-limb ischemia (HLI) model. The recruitment and activity of neutrophils were enhanced by HK-LC administration under the HLI conditions. Our results provide novel evidence of an immunological contribution of LAB uptake in the prevention of or recovery from cardiovascular diseases.

The present study was conducted to elucidate the dietary effects of canna starch on the immune functions and intestinal luminal environment in mice. The amylose and resistant starch characteristics were determined for six types of starch, including edible canna. Canna starch was found to be higher in amylose and resistant starch compared with the other starches. BALB/c mice were fed 3.16% (low-canna group) and 6.32% (high-canna group) canna starch for 2 weeks, and then intestinal parameters were measured. Fecal IgA and mucin levels were markedly elevated by canna starch intake. IgA levels in serum and spleen lymphocytes were elevated by canna starch intake in the high-canna group, but not in the low-canna group. When the mice were fed canna starch, the cecum weight increased, and the pH in the cecum decreased. The high-canna group had significantly increased levels of Clostridium subcluster XIVa lactic acid, acetic acid, and n-butyric acid in the cecum compared with the control group. These results suggested that canna starch supplementation changed the intestinal microbiota and enhanced the intestinal immune and barrier functions and cecal organic acids in mice.

Dietary calcium supplementation has been shown to be an effective adjunct therapy in an inflammatory bowel disease model. Soluble dietary fiber reduces intestinal pH and is known to enhance calcium absorption. Although many circadian clock regulations of nutrient absorption in the intestinal tract have been reported, the effects of clock regulation on calcium absorption have yet to be understood. In this study, we investigated the timing of efficient calcium intake by measuring urinary calcium excretion in mice. The diurnal variations in channel-forming tight junctions (claudins) were detected in both the jejunum and ileum. Following 2 days of feeding with a Ca²⁺-free diet, Ca²⁺-containing diets with or without soluble fiber (inulin) were fed at specific timings, and urine was subsequently examined every 4 hr. There was an evident increase in urinary calcium concentration when the inulin diet was fed at the beginning of the resting period. The Claudin 2 (Cldn2) expression level also showed a significant day-night change, which seemed to be a mechanism for the increased calcium excretion after inulin intake. This diurnal rhythm and enhanced Cldn2 expression were abolished by disruption of the suprachiasmatic nucleus, the central clock in the hypothalamus. This study suggests that intestinal calcium absorption might be modulated by the circadian clock and that the intake of inulin is more effective at the beginning of the resting period in mice.

Clostridium butyricum TO-A, Enterococcus faecium T-110, and Bacillus subtilis TO-A are sold as oral probiotic preparations and reportedly exhibit many beneficial effects on the health of hosts, including humans and livestock. In this study, we compared the ability of these clinically applied probiotic bacteria with Escherichia coli OP50 in extending the lifespan of Caenorhabditis elegans. To compare the C. elegans lifespan-extending effects of the three bacteria, experiments were performed using a nematode growth medium containing a small amount of trypticase soy agar. The maximum lifespans of worms fed C. butyricum TO-A, E. faecium T-110, or B. subtilis TO-A increased by 11, 12, and 26%, respectively, compared with worms fed E. coli OP50. In addition, we conducted a metabolomic analysis of methanol extracts of B. subtilis TO-A cells, which exhibited the strongest lifespan-extending effect on C. elegans among the probiotic bacteria tested in this study. As a result, 59 candidate substances involved in extending the lifespan of C. elegans were identified in B. subtilis TO-A cells.

Improvements in genome analysis technology using next-generation sequencing have revealed that abnormalities in the composition of the intestinal microbiota are important in numerous diseases. Furthermore, intestinal commensal pathogens that are directly involved in the onset and exacerbation of disease have been identified. Specific control of them is strongly desired. However, antibiotics are not appropriate for the control of intestinal commensal pathogens because they may kill beneficial bacteria as well. The intestinal tract contains many viruses: most are bacteriophages (phages) that infect intestinal bacteria rather than viruses that infect human cells. Phages have very high specificity for their host bacteria. Therefore, phage therapy is considered potentially useful for controlling intestinal commensal pathogens. However, the intestinal tract is a specialized, anaerobic environment, and it is impossible to isolate phages that infect host intestinal bacteria if the bacteria cannot be cultured. Furthermore, genomic analysis methods for intestinal phages have not been well established, so until recently, a complete picture of the intestinal phage has not been clear. In this review, I summarize the importance of next-generation phage therapy based on metagenomic data and describe a novel therapy against Clostridioides difficile developed using such data.