The metabolic fate of doubly labelled lactose-[13C, 15N]ureide after pre-dosing with different ureides.
BACKGROUND
To date, the measurement of the orocaecal transit time (OCTT) with lactose-[(13)C]ureide usually requires a pre-dosing with the analogous substrate in its unlabelled form.


OBJECTIVE
In this study, the enzyme induction provoked by different unlabelled sugar ureides in OCTT measurements when using doubly labelled lactose-[(13)C, (15)N]ureide (DLLU) was evaluated.


METHODS
Thirteen healthy adults (age: 22-58 years) received 500 mg DLLU together with a standardized breakfast. Expired air, urine and faeces were collected over a period of 14, 48 and 72 h, respectively. After 1 and 2 weeks, the test was repeated after pre-dosing of 3 x 120 mg glucose ureide (GU) and 3 x 200 mg cellobiose ureide (CU), respectively, on the day before study begin. The (13)C- and (15)N-enrichments were measured by isotope ratio mass spectrometry. The OCTT was calculated by the detection of a significant (13)CO(2) increase.


RESULTS
In comparison with the period without pre-dosing (7.8+/-2.2 h), the measured OCTT was significantly lowered either after GU pre-dosing (5.8+/-1.9 h, P=0.033) or CU pre-dosing (6.0+/-2.2 h, P=0.039). The respective renal (13)C- and (15)N-excretions amounted to 24.5 and 45.6, 24.7 and 54.0, and 22.5 and 50.1%, respectively, whereas the faecal (13)C- and (15)N-excretions amounted to 12.1 and 45.8, 4.8 and 21.5, and 9.6 and 39.8%, respectively.


CONCLUSIONS
Pre-dosing with unlabelled GU and CU before the administration of DLLU led to an unequivocal induction of the enzyme activity and resulted in a definitive estimation of the OCTT, clearly demonstrating that glucose-[(13)C]ureide is the matrix of the bacterial degradation in the caecum.
Wutzke
K D
KD
Children's Hospital, University of Rostock, Rostock, Germany. klaus-dieter.wutzke@med.uni-rostock.de
Mix
J
J
D000328:Adult; D001419:Bacteria; D002247:Carbon Isotopes / Q000032:analysis; D002432:Cecum / Q000378:metabolism / Q000382:microbiology; D019422:Dietary Sucrose / Q000378:metabolism*; D005243:Feces / Q000737:chemistry; D005772:Gastrointestinal Transit; D005947:Glucose / Q000378:metabolism*; D006801:Humans; D007785:Lactose / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D009587:Nitrogen Isotopes / Q000032:analysis; D013194:Staining and Labeling / Q000379:methods; D014508:Urea / Q000008:administration & dosage* / Q000378:metabolism*; D014556:Urine / Q000737:chemistry; D055815:Young Adult
D002247:Carbon Isotopes; D019422:Dietary Sucrose; D009587:Nitrogen Isotopes; D014508:Urea; D005947:Glucose; D007785:Lactose