The concept of prebiotics was established more than 30 years ago. While the prebiotic concept has now expanded thus includes non-carbohydrate substances and diverse categories other than foods, fructooligosaccharides (FOS) have still predominantly been used as pebiotics, because the effects of FOS exclusively act through the enrichment of Bifidobacterium and Lactobacillus spp., which have been classified as beneficial intestinal commensals so far. Now the commercially available FOS products are synthetic mixture of several kinds of FOS components including 1-kestose (GF₂), nystose (GF₃) and GF₄. In our previous studies, superiority of 1-kestose to the longer-chain FOS components such as nystose with regard to bifidogenic activity was clearly demonstrated. Recently, a broader range of beneficial bacteria including butyrate-producing indigenous bacteria have been recognized and expected to be new probiotic strains. Among them, resident Faecalibacterium prausnitzii is a butyrate producer with a significant anti-inflammatory effect thus expected to be useful as a next-generation probiotic. However, this bacterium is extremely oxygen-sensitive thus can be difficult to grow industrially. On the other hand, we have clearly demonstrated a significant prebiotic effect of 1-kestose, which is the smallest component of FOS, on F. prausnitzii in the gut of humans. These findings suggest that 1-kestose has impressive potential as a new prebiotic targeting F. prausnitzii, a next-generation probiotic strain, as well as bifidobacteria.

Microbiota in the stomach and application of probiotics to gastroduodenal diseases

The role of calmodulin (CaM) in apoptosis induced by gp160 of human immunodeficiency virus type 1 was investigated with cells undergoing single-cell killing. These cells were found to express, under the control of an inducible promoter, wild-type gp160 or mutant gp160 devoid of various lengths of the carboxyl terminus. Immunoprecipitation accompanied by immunoblotting revealed binding of CaM to wild-type gp160 but not to mutant gp160 bearing a carboxyl terminus with a deletion spanning more than five amino acid residues. A significant coenzyme activity was detected in the CaM bound to gp160 even in the presence of a Ca²⁺chelater, EGTA. The cells forming this gp160-CaM complex exhibited an elevated intracellular Ca²⁺level followed by DNA fragmentation, which is a hallmark of apoptosis, and finally cell killing, while the cells not forming this complex did not show any significant elevation in Ca²⁺level or DNA fragmentation. These results thus indicated that CaM plays a key role in gp160-induced apoptosis.

Background: To clarify the pathological functions of the virulence factors of Helicobacter pylori, a comparative analysis was carried out on the relationship between motility, flagellar gene polymorphism, vacuolating cytotoxin (VT) production and interleukin-8 (IL-8) induction. Methods: Twenty-five strains were examined for restriction fragment length polymorphism (RFLP) of the flagellin gene. Motility was measured using semisolid agar plates. Cytotoxicity was assayed using RK-13 cells. IL-8 secretion was assessed by the enzyme-linked immunosorbent assay (ELISA) methods. Results: H. pylori was classified into four groups according to their flagellar RFLP. No differences were noted in motility or VT production among the four groups, but a significant difference was noted in IL-8 induction. In addition, highly motile strains produced more IL-8. Conclusion: This flagellar genetic polymorphism may be associated with IL-8 induction.

Objective: To describe probiotics including a Lactobacillus gasseri strain LG21 used for the upper gastrointestinal tract, which are considered to act through improvement of indigenous microbiota inhabiting there. Background and design: Because the early definition of probiotics emphasized their effects on improving the intestinal microbial ecology, their effects on the intestinal tract and its immunity have been considered common general benefits associated with probiotics. This conclusion was also based on a body of successful clinical trials whose endpoints were the prevention or treatment of intestinal diseases. In contrast to intestinal microbiota, our understanding of the role of gastric microbiota in human health and physiology remains poor, as the bacterial load in the stomach is considered too small to exert a significant effect due to the highly acidic environment of the human stomach. Therefore, the intervention using probiotics in the stomach is still limited at present.Results:In this article using representative 38 quoted articles, we first describe the gastric microbiota, as the indigenous microbiota in the stomach is thought to be significantly involved in the pathophysiology of this organ, since probiotics exert their beneficial effects through improving the resident microbiota. We then review the present status and future prospects of probiotics for the treatment of upper gastrointestinal diseases by quoting representative published articles, including our basic and clinical data. Conclusions: Probiotics have been demonstrated to suppress Helicobacter pylori in the stomach, and are also expected to improve functional dyspepsia through the correction of dysbiotic gastric microbiota.

INTRODUCTION: Lipopolysaccharides (LPSs) of Gram-negative bacteria (GNB) are highly toxic and induce inflammation. Therefore, we investigated both the LPS activity and composition of GNB in the gastric fluid (GF) to assess the potential toxicity of them accumulated in the stomach. METHODS: GF and saliva samples were obtained from 158 outpatients who were undergoing upper gastrointestinal endoscopy and 36 volunteers using a nasogastric tube. The LPS activity was measured by assay kits including recombinant Factor C or Limulus amebocyte lysate. To assess the bacterial composition in the samples, a 16S ribosomal DNA-based operational taxonomic unit analysis was performed. We focused on the genera representing >0.1% of the whole microbiota. RESULTS: We found a high LPS activity in the GF samples with weak acidity (approximately > pH 4), whereas little/no activity in those with strong acidity (approximately < pH 2). Spearman test also demonstrated a close correlation between pH and LPS in those samples (r = 0.872). The relative abundance of GNB in the saliva showed no significant difference between the subject groups with weak- and strong-acidity GF. In addition, in the subjects whose GF acidity was weak, the GNB abundance in the GF was almost the same as that in the saliva. By contrast, in the subjects whose GF acidity was strong, the GNB abundance in the GF was significantly lower than that in the saliva. DISCUSSION: GNB that have recently moved from the oral cavity might account for the prominent LPS activity in a stomach with weak acidity.