title: Cholic acid accumulation and its diminution by short-chain fatty acids in bifidobacteria.
abstract: Cholic acid (CA) transport was investigated in nine intestinal Bifidobacterium strains. Upon energization with glucose, all of the bifidobacteria accumulated CA. The driving force behind CA accumulation was found to be the transmembrane proton gradient (Delta pH, alkaline interior). The levels of accumulated CA generally coincided with the theoretical values, which were calculated by the Henderson-Hasselbalch equation using the measured internal pH values of the bifidobacteria, and a pK(a) value of 6.4 for CA. These results suggest that the mechanism of CA accumulation is based on the diffusion of a hydrophobic weak acid across the bacterial cell membrane, and its dissociation according to the Delta pH value. A mixture of short-chain fatty acids (acetate, propionate and butyrate) at the appropriate colonic concentration (117 mM in total) reduced CA accumulation in Bifidobacterium breve JCM 1192(T). These short-chain fatty acids, which are weak acids, reduced the Delta pH, thereby decreasing CA accumulation in a dose-dependent manner. The bifidobacteria did not alter or modify the CA molecule. The probiotic potential of CA accumulation in vivo is discussed in relation to human bile acid metabolism.
authors.affiliation: Northern Advancement Center for Science & Technology, Kita 7 Nishi 2, Kita-ku, Sapporo 060-0807, Japan.
authors.forename: Peter
authors.initials: P
authors.lastname: Kurdi
authors.affiliation: Snow Brand Milk Products Co., Ltd, 1-1-2, Minamidai, Kawagoe 350-1165, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Tanaka
authors.affiliation: Department of Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, 9751 NN Haren, The Netherlands.
authors.forename: Hendrik W
authors.initials: HW
authors.lastname: van Veen
authors.affiliation: Laboratory of Applied Microbiology, Division of Applied Bioscience, Graduate School of Agriculture, Hokkaido University, Kita 9 Nishi 9, Kita-ku, Sapporo 060-8589, Japan.
authors.forename: Kozo
authors.initials: K
authors.lastname: Asano
authors.affiliation: Laboratory of Applied Microbiology, Division of Applied Bioscience, Graduate School of Agriculture, Hokkaido University, Kita 9 Nishi 9, Kita-ku, Sapporo 060-8589, Japan.
authors.forename: Fusao
authors.initials: F
authors.lastname: Tomita
authors.affiliation: Laboratory of Microbial Resources and Ecology, Division of Applied Bioscience, Graduate School of Agriculture, Hokkaido University, Kita 9 Nishi 9, Kita-ku, Sapporo 060-8589, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Yokota
mesh_terms: D019342:Acetic Acid / Q000494:pharmacology; D001644:Bifidobacterium / Q000187:drug effects* / Q000378:metabolism*; D001647:Bile Acids and Salts / Q000378:metabolism; D001693:Biological Transport, Active / Q000187:drug effects; D020148:Butyric Acid / Q000494:pharmacology; D019826:Cholic Acid / Q000378:metabolism*; D004734:Energy Metabolism; D005232:Fatty Acids, Volatile / Q000378:metabolism* / Q000494:pharmacology*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D011422:Propionates / Q000494:pharmacology
chemical_list: D001647:Bile Acids and Salts; D005232:Fatty Acids, Volatile; D011422:Propionates; D020148:Butyric Acid; D019826:Cholic Acid; C029658:propionic acid; D019342:Acetic Acid