The effects of oral ingestion of a hot water extract of matured fruit of the date palm tree (Phoenix dactylifera L.) on allergic responses were investigated in mite-sensitized mice. Sneezing and nose rubbing events in mice given a date extract-added diet were significantly lower than in those given an extract-free (control) diet. The serum total and mite antigen-specific immunoglobulin (Ig) E levels, and the number of spleen interleukin-4+CD4+, IgE+B220+ and FcεRIα+CD117+ cells was significantly lower in mice given the date extract-added diet than in those given the control diet. Chlorogenic acid, pelargonin and ferulic acid significantly reduced the number of IgE+B220+ cells, while chlorogenic acid and pelargonin significantly decreased the number of FcεRIα+CD117+ cells in mouse spleen cell cultures. These results suggest that some polyphenols in the date may reduce mite-induced allergic symptoms in mice via a decrease in the number of IgE-producing plasma cells and high-affinity IgE receptor-expressing mast cells.

Recent studies have linked Ruminococcus gnavus to inflammatory bowel disease and Fusobacterium nucleatum to various cancers. Agarooligosaccharides (AOS), derived from the acid hydrolysis of agar, have shown significant inhibitory effects on the growth of R. gnavus and F. nucleatum at concentrations of 0.1 and 0.2%, respectively. RNA sequencing and quantitative reverse-transcription PCR analyses revealed the downregulation of fatty acid biosynthesis genes (fab genes) in these bacteria when exposed to 0.1% AOS. Furthermore, AOS treatment altered the fatty acid composition of R. gnavus cell membranes, increasing medium-chain saturated fatty acids (C8, C10) and C18 fatty acids while reducing long-chain fatty acids (C14, C16). In contrast, no significant growth inhibition was observed in several strains of Bifidobacteria and Lactobacillales at AOS concentrations of 0.2 and 2%, respectively. Co-culture experiments with R. gnavus and Bifidobacterium longum in 0.2% AOS resulted in B. longum dominating the population, constituting over 96% post-incubation. In vivo studies using mice demonstrated a significant reduction in the Lachnospiraceae family, to which R. gnavus belongs, following AOS administration. Quantitative PCR also showed lower levels of the nan gene, potentially associated with immune disorders, in the AOS group. These findings suggest that AOS may introduce a novel concept in prebiotics by selectively inhibiting potentially pathogenic bacteria while preserving beneficial bacteria such as Bifidobacteria and Lactobacillales.

The immunomodulatory effect of fermented non-salty soybean powder (NSBP) was investigated in C3H/HeN mice. The number of splenic CD11b⁺, CD49b⁺, and interferon (IFN)-γ⁺CD4⁺ cells increased significantly, while that of interleukin (IL)-4⁺CD4⁺ and CD19⁺ cells decreased significantly in cultures containing NSBP. Similarly, in the spleen and Peyer's patches of mice fed a diet containing NSBP, the number of IL-12⁺CD11b⁺, CD49b⁺, and IFN-γ⁺CD4⁺ cells increased noticeably, whereas the number of splenic IL-4⁺CD4⁺ and CD19b⁺ cells was lower compared to mice fed an NSBP-free diet. Superoxide production by peritoneal macrophages was significantly higher in mice fed an NSBP-containing diet. Both intestinal total IgA and serum total IgG levels declined in mice fed the NSBP-containing diet. Microarray analysis of mRNAs extracted from Peyer's patch cells of mice fed the NSBP-containing diet indicated an increase in the expression of several genes related to cellular immune responses, while the expression of genes related to immunoglobulin production decreased. These results indicate that NSBP stimulates the cellular immune response, but suppresses the acquired humoral immune response in C3H/HeN mice.

Background: Agaro-oligosaccharides (AOS) have been shown to modulate the gut microbiota in in vitro and animal studies; however, human evidence remains scarce. Methods: Herein, we conducted a four-week open-label, single-arm, non-randomized pilot trial in 18 healthy Japanese adults to examine the association of AOS intake at 200 mg/day with gut microbiota composition and bowel condition. Fecal samples collected before and after the intervention were analyzed using QIIME2-based 16S rRNA sequencing, and bowel condition was assessed with the Bristol Stool Form Scale. This study was registered in the UMIN Clinical Trials Registry (UMIN000056992). Results: AOS intake was not associated with significant changes in bowel condition. Gut microbiota analysis showed no significant alterations in overall community structure but revealed taxon-specific trends in the relative abundance of several bacterial taxa. Notably, nominal changes were observed in the abundance of the Ruminococcus gnavus group and Bacteroides uniformis after the intervention. In addition, quantitative PCR analysis showed an increase in 3,6-anhydro-L-galactose cycloisomerase (ACI) gene abundance after the intervention. Conclusions: These findings suggest that, in this exploratory pilot study, AOS intake was associated with a taxon-specific pattern in the gut microbiota. Further randomized controlled studies are needed to clarify the microbiota-related effects of AOS in humans.