title: The influence of inulin on the absorption of nitrogen and the production of metabolites of protein fermentation in the colon.
abstract: In the present study, the production and fate of bacterial metabolites in the colon were investigated in a direct way using two substrates labelled with stable isotopes: lactose [(15)N,(15)N]ureide as a source of labelled ammonia and egg proteins intrinsically labelled with [(2)H4]tyrosine as a precursor of [(2)H4]p-cresol. Both ammonia and phenolic compounds are believed to be carcinogenic. Stimulation of carbohydrate fermentation in order to prevent accumulation of these toxic metabolites was induced by inclusion of inulin in a test meal or by addition of inulin to the daily diet, allowing us to distinguish between changes induced by the actual presence of a fermentable carbohydrate and effects caused by a long-term dietary intervention. When a single dose of inulin was administered together with the labelled substrates, a significant increase in faecal (15)N excretion, accompanied by a proportional decrease in urinary (15)N excretion was observed, probably reflecting an enhanced uptake of ammonia for bacterial biosynthesis, since an increased concentration of labelled N in bacterial pellets was found. A statistically significant reduction of urinary [(2)H4]p-cresol excretion was also noted. Upon supplementation of inulin to the daily diet during 4 weeks, however, only a tendency towards decreased urinary excretion of both labelled and unlabelled p-cresol was noted. Further studies are warranted to confirm these results in a larger cohort.
authors.affiliation: Laboratory of Digestion and Absorption, Department of Gastroenterology, University Hospital Gasthuisberg, Catholic University of Leuven, Herestraat 49, 3000 Leuven, Belgium.
authors.forename: Karen P
authors.initials: KP
authors.lastname: Geboes
authors.forename: Gert
authors.initials: G
authors.lastname: De Hertogh
authors.forename: Vicky
authors.initials: V
authors.lastname: De Preter
authors.forename: Anja
authors.initials: A
authors.lastname: Luypaerts
authors.forename: Bert
authors.initials: B
authors.lastname: Bammens
authors.forename: Pieter
authors.initials: P
authors.lastname: Evenepoel
authors.forename: Yvo
authors.initials: Y
authors.lastname: Ghoos
authors.forename: Karel
authors.initials: K
authors.lastname: Geboes
authors.forename: Paul
authors.initials: P
authors.lastname: Rutgeerts
authors.forename: Kristin
authors.initials: K
authors.lastname: Verbeke
mesh_terms: D000328:Adult; D000641:Ammonia / Q000032:analysis / Q000378:metabolism / Q000652:urine; D000704:Analysis of Variance; D003106:Colon / Q000378:metabolism* / Q000382:microbiology; D003408:Cresols / Q000032:analysis / Q000378:metabolism / Q000652:urine; D004040:Dietary Carbohydrates / Q000008:administration & dosage*; D004044:Dietary Proteins / Q000378:metabolism*; D005243:Feces / Q000737:chemistry; D005260:Female; D005285:Fermentation; D006801:Humans; D007408:Intestinal Absorption / Q000187:drug effects; D007444:Inulin / Q000008:administration & dosage*; D007553:Isotope Labeling; D007785:Lactose / Q000378:metabolism; D008297:Male; D009584:Nitrogen / Q000378:metabolism*; D009587:Nitrogen Isotopes; D010865:Pilot Projects; D018709:Statistics, Nonparametric; D014443:Tyrosine / Q000378:metabolism
chemical_list: D003408:Cresols; D004040:Dietary Carbohydrates; D004044:Dietary Proteins; D009587:Nitrogen Isotopes; C032538:4-cresol; D014443:Tyrosine; D000641:Ammonia; D007444:Inulin; D007785:Lactose; D009584:Nitrogen