title: Bowel microbiota moderate host physiological responses to dietary konjac in weanling rats.
abstract: Diets rich in complex carbohydrates that resist digestion in the small bowel can alter large bowel ecology and microbiota biochemistry because the carbohydrates become substrates for bacterial growth and metabolism. Conventional or germ-free weanling rats were fed a control diet or diets containing 1.25, 2.5, or 5% konjac (KJ), a commonly used ingredient in Asian foods, for 28 d. In the absence of bowel microbiota, 5% KJ elicited a significant increase in colonic goblet cell numbers and increased expression of mast cell protease genes and of genes that were overrepresented in the KEGG pathway "Metabolism of xenobiotics by cytochrome P450" relative to the control diet. In contrast, feeding 5% KJ caused few changes in mucosal gene expression in conventional rats. Analysis of the colonic microbiota of conventional rats fed KJ showed modest increases in the proportions of Actinobacteria and Bacteroidetes relative to rats fed the control diet, with a concomitant reduction in Firmicutes, which included a 50% reduction in Lactobacillus abundance. Colonic concentrations of short-chain fatty acids and colonic crypt lengths were increased by feeding KJ. Goblet cell numbers were greater in conventional rats fed KJ relative to the control diet but were lower compared with germ-free animals. Serum metabolite profiles were different in germ-free and conventional rats. Metabolites that differed in concentration included several phospholipids, a bile acid metabolite, and an intermediate product of tryptophan metabolism. Overall, KJ in the diet was potentially damaging to the bowel mucosa and produced a protective response from the host. This response was reduced by the presence of the bowel microbiota, which therefore ameliorated potentially detrimental effects of dietary KJ.
authors.affiliation: Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand. wayne.young@agresearch.co.nz
authors.forename: Wayne
authors.initials: W
authors.lastname: Young
authors.forename: Nicole C
authors.initials: NC
authors.lastname: Roy
authors.forename: Julian
authors.initials: J
authors.lastname: Lee
authors.forename: Blair
authors.initials: B
authors.lastname: Lawley
authors.forename: Don
authors.initials: D
authors.lastname: Otter
authors.forename: Gemma
authors.initials: G
authors.lastname: Henderson
authors.forename: Gerald W
authors.initials: GW
authors.lastname: Tannock
mesh_terms: D039903:Actinobacteria / Q000187:drug effects / Q000254:growth & development; D031056:Amorphophallus / Q000737:chemistry*; D000818:Animals; D041963:Bacteroidetes / Q000187:drug effects / Q000254:growth & development; D001647:Bile Acids and Salts / Q000378:metabolism; D002264:Carboxylic Acids / Q000032:analysis / Q000378:metabolism; D003106:Colon / Q000187:drug effects* / Q000382:microbiology*; D004032:Diet; D004305:Dose-Response Relationship, Drug; D005232:Fatty Acids, Volatile / Q000494:pharmacology; D005856:Germ-Free Life; D008297:Male; D054892:Metagenome; D046228:Microarray Analysis; D028321:Plant Preparations / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D059467:Transcriptome / Q000187:drug effects
chemical_list: D001647:Bile Acids and Salts; D002264:Carboxylic Acids; D005232:Fatty Acids, Volatile; D028321:Plant Preparations