Atsushi Yokota

Bio: Atsushi Yokota is an academic researcher from Hokkaido University. The author has contributed to research in topics: Cholic acid & Bile acid. The author has an hindex of 35, co-authored 168 publications receiving 4310 citations. Previous affiliations of Atsushi Yokota include Ajinomoto.

Mechanism of growth inhibition by free bile acids in lactobacilli and bifidobacteria.

Abstract: The effects of the free bile acids (FBAs) cholic acid (CA), deoxycholic acid (DCA), and chenodeoxycholic acid on the bioenergetics and growth of lactobacilli and bifidobacteria were investigated. It was found that these FBAs reduced the internal pH levels of these bacteria with rapid and stepwise kinetics and, at certain concentrations, dissipated ΔpH. The bile acid concentrations that dissipated ΔpH corresponded with the MICs for the selected bacteria. Unlike acetate, propionate, and butyrate, FBAs dissipated the transmembrane electrical potential (ΔΨ). In Bifidobacterium breve JCM 1192, the synthetic proton conductor pentachlorophenol (PCP) dissipated ΔpH with a slow and continuous kinetics at a much lower concentration than FBAs did, suggesting the difference in mode of action between FBAs and true proton conductors. Membrane damage assessed by the fluorescence method and a viability decrease were also observed upon exposure to CA or DCA at the MIC but not to PCP or a short-chain fatty acid mixture. Loss of potassium ion was observed at CA concentrations more than 2 mM (0.4× MIC), while leakage of other cellular components increased at CA concentrations more than 4 mM (0.8× MIC). Additionally, in experiments with membrane phospholipid vesicles extracted from Lactobacillus salivarius subsp. salicinius JCM 1044, CA and DCA at the MIC collapsed the ΔpH with concomitant leakage of intravesicular fluorescent pH probe, while they did not show proton conductance at a lower concentration range (e.g., 0.2× MIC). Taking these observations together, we conclude that FBAs at the MIC disturb membrane integrity and that this effect can lead to leakage of proton (membrane ΔpH and ΔΨ dissipation), potassium ion, and other cellular components and eventually cell death.

Is bile acid a determinant of the gut microbiota on a high-fat diet?

Abstract: Recently, we discovered that bile acid, a main component of bile, is a host factor that regulates the composition of the cecal microbiota in rats. Because bile secretion increases on a high-fat diet and bile acids generally have strong antimicrobial activity, we speculated that bile acids would be a determinant of the gut microbiota in response to a high-fat diet. The observed changes in the rat cecal microbiota triggered by cholic acid (the most abundant bile acid in human biliary bile) administration resemble those found in animals fed high-fat diets. Here, we discuss the rationale for this hypothesis by evaluating reported diet-induced gut microbiota alterations based on the postulate that bile acids worked as an underlying determinant. The identification of host factors determining the gut microbiota greatly contributes to understanding the causal relationships between changes in the gut microbiota and disease development, which remain to be elucidated.

Diet rapidly and reproducibly alters the human gut microbiome

Abstract: Long-term dietary intake influences the structure and activity of the trillions of microorganisms residing in the human gut, but it remains unclear how rapidly and reproducibly the human gut microbiome responds to short-term macronutrient change. Here we show that the short-term consumption of diets composed entirely of animal or plant products alters microbial community structure and overwhelms inter-individual differences in microbial gene expression. The animal-based diet increased the abundance of bile-tolerant microorganisms (Alistipes, Bilophila and Bacteroides) and decreased the levels of Firmicutes that metabolize dietary plant polysaccharides (Roseburia, Eubacterium rectale and Ruminococcus bromii). Microbial activity mirrored differences between herbivorous and carnivorous mammals, reflecting trade-offs between carbohydrate and protein fermentation. Foodborne microbes from both diets transiently colonized the gut, including bacteria, fungi and even viruses. Finally, increases in the abundance and activity of Bilophila wadsworthia on the animal-based diet support a link between dietary fat, bile acids and the outgrowth of microorganisms capable of triggering inflammatory bowel disease. In concert, these results demonstrate that the gut microbiome can rapidly respond to altered diet, potentially facilitating the diversity of human dietary lifestyles.

The gut microbiota, bacterial metabolites and colorectal cancer

Abstract: Accumulating evidence suggests that the human intestinal microbiota contributes to the aetiology of colorectal cancer (CRC), not only via the pro-carcinogenic activities of specific pathogens but also via the influence of the wider microbial community, particularly its metabolome. Recent data have shown that the short-chain fatty acids acetate, propionate and butyrate function in the suppression of inflammation and cancer, whereas other microbial metabolites, such as secondary bile acids, promote carcinogenesis. In this Review, we discuss the relationship between diet, microbial metabolism and CRC and argue that the cumulative effects of microbial metabolites should be considered in order to better predict and prevent cancer progression.

The role of the gut microbiota in nutrition and health

Abstract: The microbial communities that colonize different regions of the human gut influence many aspects of health. In the healthy state, they contribute nutrients and energy to the host via the fermentation of nondigestible dietary components in the large intestine, and a balance is maintained with the host's metabolism and immune system. Negative consequences, however, can include acting as sources of inflammation and infection, involvement in gastrointestinal diseases, and possible contributions to diabetes mellitus and obesity. Major progress has been made in defining some of the dominant members of the microbial community in the healthy large intestine, and in identifying their roles in gut metabolism. Furthermore, it has become clear that diet can have a major influence on microbial community composition both in the short and long term, which should open up new possibilities for health manipulation via diet. Achieving better definition of those dominant commensal bacteria, community profiles and system characteristics that produce stable gut communities beneficial to health is important. The extent of interindividual variation in microbiota composition within the population has also become apparent, and probably influences individual responses to drug administration and dietary manipulation. This Review considers the complex interplay between the gut microbiota, diet and health.