title: Colonic transit time is related to bacterial metabolism and mucosal turnover in the gut.
abstract: Little is known about how colonic transit time relates to human colonic metabolism and its importance for host health, although a firm stool consistency, a proxy for a long colonic transit time, has recently been positively associated with gut microbial richness. Here, we show that colonic transit time in humans, assessed using radio-opaque markers, is associated with overall gut microbial composition, diversity and metabolism. We find that a long colonic transit time associates with high microbial richness and is accompanied by a shift in colonic metabolism from carbohydrate fermentation to protein catabolism as reflected by higher urinary levels of potentially deleterious protein-derived metabolites. Additionally, shorter colonic transit time correlates with metabolites possibly reflecting increased renewal of the colonic mucosa. Together, this suggests that a high gut microbial richness does not per se imply a healthy gut microbial ecosystem and points at colonic transit time as a highly important factor to consider in microbiome and metabolomics studies.
authors: National Food Institute, Technical University of Denmark, DK-2860 Søborg, Denmark.
authors: Henrik M
authors: http://orcid.org/0000-0002-2504-8313
authors: HM
authors: Roager
authors: Department of Systems Biology, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark.
authors: Lea B S
authors: LB
authors: Hansen
authors: National Food Institute, Technical University of Denmark, DK-2860 Søborg, Denmark.
authors: Martin I
authors: MI
authors: Bahl
authors: National Food Institute, Technical University of Denmark, DK-2860 Søborg, Denmark.
authors: Henrik L
authors: HL
authors: Frandsen
authors: National Food Institute, Technical University of Denmark, DK-2860 Søborg, Denmark.
authors: Vera
authors: V
authors: Carvalho
authors: The Novo Nordisk Foundation Center for Basic Metabolic Research, Section of Metabolic Genetics, University of Copenhagen, DK-2200 København N, Denmark.
authors: Rikke J
authors: RJ
authors: Gøbel
authors: Department of Systems Biology, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark.
authors: Marlene D
authors: MD
authors: Dalgaard
authors: Department of Systems Biology, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark.
authors: Damian R
authors: http://orcid.org/0000-0002-6555-2557
authors: DR
authors: Plichta
authors: Department of Radiology, Bispebjerg Hospital, DK-2400 København NV, Denmark.
authors: Morten H
authors: MH
authors: Sparholt
authors: The Novo Nordisk Foundation Center for Basic Metabolic Research, Section of Metabolic Genetics, University of Copenhagen, DK-2200 København N, Denmark.
authors: Henrik
authors: http://orcid.org/0000-0003-3090-269X
authors: H
authors: Vestergaard
authors: The Novo Nordisk Foundation Center for Basic Metabolic Research, Section of Metabolic Genetics, University of Copenhagen, DK-2200 København N, Denmark.
authors: Torben
authors: T
authors: Hansen
authors: Department of Systems Biology, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark.
authors: Thomas
authors: T
authors: Sicheritz-Pontén
authors: Department of Systems Biology, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark.
authors: H Bjørn
authors: HB
authors: Nielsen
authors: The Novo Nordisk Foundation Center for Basic Metabolic Research, Section of Metabolic Genetics, University of Copenhagen, DK-2200 København N, Denmark.
authors: Oluf
authors: O
authors: Pedersen
authors: Department of Nutrition, Exercise and Sport, University of Copenhagen, DK-1958 Frederiksberg C, Denmark.
authors: Lotte
authors: L
authors: Lauritzen
authors: Department of Nutrition, Exercise and Sport, University of Copenhagen, DK-1958 Frederiksberg C, Denmark.
authors: Mette
authors: M
authors: Kristensen
authors: Department of Systems Biology, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark.
authors: Ramneek
authors: R
authors: Gupta
authors: National Food Institute, Technical University of Denmark, DK-2860 Søborg, Denmark.
authors: Tine R
authors: http://orcid.org/0000-0002-6399-9574
authors: TR
authors: Licht
mesh_terms: D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000378:metabolism; D050260:Carbohydrate Metabolism; D003106:Colon / Q000378:metabolism; D005243:Feces / Q000382:microbiology; D005260:Female; D005285:Fermentation; D000069196:Gastrointestinal Microbiome; D005772:Gastrointestinal Transit; D006801:Humans; D008297:Male; D008660:Metabolism; D055442:Metabolome; D008875:Middle Aged; D009092:Mucous Membrane / Q000378:metabolism; D011506:Proteins / Q000378:metabolism; D015203:Reproducibility of Results; D055815:Young Adult
chemical_list: D015415:Biomarkers; D011506:Proteins