Lactose [13C]Ureide as a marker for colonic fermentation and the deconvolution of a complex 13CO2 breath test curve

Objective: In this study, the duration of enzyme induction provoked by unlabelled lactose ureide (LU) in orocaecal transit time (OCTT) measurements with lactose-[ 13 C]ureide ( 13 C-LU) was evaluated. Design: Experimental study. Setting: University of Rostock, Children's Hospital, Research Laboratory. Subjects: Fifteen healthy adults aged 19-54 years. Intervention: One-half gram of 13 C-LU was administered together with a continental breakfast. After 1 week, the test was repeated after pre-dosing of 5 Â 100 mg LU on the day before the study began. The 13 C-LU ingestion was repeated under identical conditions but without pre-dosing 1 and 3 weeks after pre-dosing. Expired air samples were taken over 14 h. 13 CO 2 -enrichment was measured by isotope ratio mass spectrometry (SerCon, Crewe, UK). The OCTT was calculated from the interval between 13 C-LU administration and the detection of a significant and sustained 13 C-rise of 2 delta over baseline in breath. Results: Without pre-dosing, an OCTT of 419782 min was measured. The pre-dosing resulted in higher 13 C-enrichments and caused a significant OCTT shortening of 311799 min (P ¼ 0.028). One and 3 weeks after pre-dosing, the measured OCTT again increased to 4047124 and 3797103 min, respectively. Conclusions: Pre-dosing with LU before pulse labelling with 13 C-LU led to an induction of enzyme activity and resulted in a definitive estimation of the OCTT when using a threshold of 2 delta over baseline. After 1 and 3 weeks, respectively, the OCTT was no longer significantly different to those without pre-dosing, indicating the disappearance of enzyme induction. Therefore, a pre-dosing with LU on the day before 13 C-LU ingestion is essential for OCTT measurements.

Section: Discussionmentioning

confidence: 99%

The duration of enzyme induction in orocaecal transit time measurements

Wutzke

Schutt

2007

“…However, our curve-fitting approach allows a more accurate determination of parameters since calculations are based on the whole data set and are therefore less susceptible to local variations in the data. Data from tests 1 and 3, where no predosing was used, were better modelled (lower RMS) using the sum of two peaks (peak 1+peak 2 ¼ fitted model; Morrison et al, 1998). This is purely a 'mathematical fix' that allows a model of this type to fit the data.…”

Section: Discussionmentioning

confidence: 99%

“…The baseline was included as a variable to allow the model to determine basal 13 CO 2 abundance from the data. Some data sets were better fitted (lower RMS) by the sum of two functions (a two-peak model) rather than one (Morrison et al, 1998). In these cases, the composite model was fitted to the experimental data to find the best fit.…”

Section: Methodsmentioning

confidence: 99%

Gastrointestinal handling of glycosyl [13C]ureides

Morrison

Dodson²,

Preston

et al. 2003

Objectives: Lactose [ 13 C]ureide has been proposed as a noninvasive marker for oro-caecal transit time in adults and children. The present study investigates the handling of lactose [ 13 C]ureide ( 13 C LU) and glucose [ 13 C]ureide ( 13 C GU) by the gastrointestinal tract and describes the metabolic fates of these substrates and describes the extent of tracer excretion by different routes. Study Design and Subjects: Four subjects underwent five studies in which they ingested a test meal plus (1) no substrate, (2) 13 C LU, (3) 13 C GU, (4) 13 C LU after predosing with unlabelled lactose ureide and (5) 13 C LU after predosing with glucose ureide. Subjects were studied at home with at least 1 week between tests and they all completed the study. Breath was analysed for 13 CO 2 recovery and urine was analysed for total 13 C recovery, 13 C urea recovery and 13 C GU recovery. Results: The profiles and extent of tracer recovery in breath and urine were similar when either 13 C GU or 13 C LU was used, suggesting similar handling of these substrates by the gut. 13 C GU was the major 13 C-enriched species recovered in the urine even when 13 C LU was consumed. Predosing with either lactose ureide or glucose ureide increased the rate of appearance of tracer, but did not alter transit times.

“…Since the primary publication in 1995, 13 CO 2 -breath tests for measuring the OCTT preferentially by using 13 C-LU have become generally accepted worldwide (Heine et al, 1995;Ruemmele et al, 1997;Geypens et al, 1999;Jackson et al, 1999;Van den Driessche et al, 2000;Christian et al, 2002;Morrison et al, 1998Morrison et al, , 1999Morrison et al, , 2003Wutzke and Sattinger, 2006;Schneider et al, 2007;Berthold et al, 2009). It is commonly assumed that 13 C-GU and the corresponding glucose ureide hydrolase are the key substance and the key enzyme, respectively, of the enzymatic sugar ureide degradation process that is exclusively initiated by C. innocuum in the human caecum (Mohr et al, 1999;Wutzke and Glasenapp, 2004).…”

Section: Discussionmentioning

confidence: 99%

The metabolic fate of doubly labelled lactose-[13C, 15N]ureide after pre-dosing with different ureides

Wutzke

Mix

2010

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 Â 120 mg glucose ureide (GU) and 3 Â 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 ¼ 0.033) or CU pre-dosing (6.0±2.2 h, P ¼ 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.