Metabolism of lactose-[13C]ureide and lactose-[15N,15N]ureide in normal adults consuming a diet marginally adequate in protein.
Oral lactose-ureide is resistant to human digestive enzymes, but is fermented by the colonic microflora. Nine normal adults consuming a diet which provided 36 g of protein/day were given oral doses of lactose-[(13)C]ureide and lactose-[(15)N,(15)N]ureide. The appearance on breath of (13)CO(2) derived from lactose-[(13)C]ureide was followed for 48 h. The fate of (15)N derived from lactose-[(15)N, (15)N]ureide was determined by measuring the recovery of (15)N in stools and urine in various forms. About 80% of the label given as lactose-[(13)C]ureide was recovered on the breath, and about 80% of label given as lactose-[(15)N,(15)N]ureide was not recovered in stool, indicating that 80% of the dose was completely fermented. At least 5% of the labelled urea was absorbed and excreted as the intact molecule. Of the (15)N derived from lactose-[(15)N, (15)N]ureide and available for further metabolic interaction, 67% was retained and 33% was excreted in urine. The time taken for [(15)N,(15)N]urea to appear in urine was similar for all subjects, but the appearance of either (13)CO(2) on the breath or [(15)N, (14)N]urea in urine varied. It is concluded that the hydrolysis of the sugar-urea bond may reflect oro-caecal transit time, but that other factors related to colonic bacterial metabolism determine the duration and extent of hydrolysis of urea by urease enzymes. Lactose-ureide can be used to probe the metabolic activity of the colonic microflora in normal individuals.
Jackson
A A
AA
Institute of Human Nutrition, University of Southampton, Clinical Nutrition and Metabolism Unit, Level C (113) West Wing, Southampton General Hospital, Tremona Road, Southampton SO16 6YD, U.K. iohn@soton.ac.uk
Bundy
R
R
Hounslow
A
A
Murphy
J L
JL
Wootton
S A
SA
D000328:Adult; D001419:Bacteria / Q000378:metabolism; D001944:Breath Tests; D002247:Carbon Isotopes; D003106:Colon / Q000378:metabolism* / Q000382:microbiology; D004044:Dietary Proteins / Q000008:administration & dosage*; D005260:Female; D005285:Fermentation; D006801:Humans; D007785:Lactose; D008297:Male; D009584:Nitrogen / Q000378:metabolism; D009587:Nitrogen Isotopes; D014508:Urea
D002247:Carbon Isotopes; D004044:Dietary Proteins; D009587:Nitrogen Isotopes; D014508:Urea; D007785:Lactose; D009584:Nitrogen