13C abundances of nutrients and the effect of variations in 13C isotopic abundances of test meals formulated for 13CO2 breath tests

Schoeller, Dale A.; Klein, Peter; Watkins, John B.; Heim, T; MacLean, William C.

doi:10.1093/ajcn/33.11.2375

Cited by 220 publications

(154 citation statements)

References 18 publications

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“…Although the LS/MS/MS method allows to measure % 13 C at C 2 cleanly, % 13 C at C 8 also includes that at C 5 [20]. The amount of 13 C at both C 2 and C 8 is included in the denominator because it is unlikely that both positions would be simultaneously enriched by a [ 13 13 C enrichment of human samples [21,22].…”

Section: Measurement Of 13 C Enrichmentmentioning

confidence: 99%

13C enrichment of carbons 2 and 8 of purine by folate-dependent reactions after [13C]formate and [2-13C]glycine dosing in adult humans

2007

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The 10-formyl moiety of 10-formyltetrahydrofolate is the source of carbons at the positions 8 (C 8 ) and 2 (C 2 ) of the purine ring, originating from formate and a few amino acids. Uric acid is the final catabolic product of purines. In adult humans, we independently measured the 13 C enrichment of the C 2 and C 8 positions of urinary uric acid after an oral dose of [ 13 C]sodium formate and that of the C 2 and C 8 plus C 5 positions after [2-13 C]glycine. A liquid-chromatography mass-spectrometric method was used to measure the 13 C enrichment of uric acid in urine which was collected for 3 -4 days. Purine catabolism to uric acid does not alter the positions of carbons in the ring. After the formate dose, the 13 C-enrichment at C 2 was greater that at C 8 , and a circadian rhythm was observed in the enrichment at C 2 . After the glycine dose, the C 8 plus C 5 positions were enriched, whereas no significant enrichment at C 2 was found. These 13 C enrichment patterns are not consistent with previous accepted metabolism. To our knowledge, this is the first study to investigate 13 C enrichment from formate and glycine independently into the C 2 and C 8 positions of purine in the same subjects. Possible mechanisms explaining our findings are discussed. Oral [ 13 C]formate or [2-13 C]glycine dosing and urine collection can be used to study purine biosynthesis in humans.

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Section: Measurement Of 13 C Enrichmentmentioning

confidence: 99%

13C enrichment of carbons 2 and 8 of purine by folate-dependent reactions after [13C]formate and [2-13C]glycine dosing in adult humans

2007

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“…The cumulative percentage 13 C-dose recovery (CPDR) is the product of an assumed CO 2 -production rate (CO 2 PR) of 300 mmol/m 2 /h (Schoeller et al, 1980;Wutzke et al, 1997), the calculated cumulative 13 C-data (Dd 13 C cum ), the isotope ratio of 13 CO 2 standard gas (0.01123) and the body surface area (BSA) in m 2 divided by the 13 C-excess dose (D) in mmol times 10.…”

Section: Study Protocolsmentioning

confidence: 99%

The duration of enzyme induction in orocaecal transit time measurements

Wutzke

Schutt

2007

Eur J Clin Nutr

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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.

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“…The 13 C-exhalation was calculated according to the equations of Schoeller et al (1980);Brösicke (1987); Vantrappen et al (1989); Radke et al (1995); Wutzke et al (1997). The 13 CO 2 -exhalation rate ( 13 CO 2 ER) is the product of an assumed CO 2 -production rate ðV CO2 Þ of 300 mmol/m 2 /h (Schoeller et al, 1980, Wutzke et al, 1997, the calculated cumulative 13 C-data (Dd 13 C cum ), the isotope ratio of 13 CO 2 standard gas (0.01123) and the body surface area (BSA) in m 2 divided by the 13 C-excess dose ( 13 CD) in mmol times 10. 13 CD ¼0:412mmol 13 C=g dlLa1 ðwet weightÞ ¼0:0358mmol 13 C=kg body weight: 13 CO 2 ER ¼V CO2 Á Dd 13 C cum Á ð0:01123Þ Á BSA=10 13 CD:…”

Section: Analytical Techniquesmentioning

confidence: 99%

13C- and 15N-incorporation of doubly stable isotope labelled Lactobacillus johnsonii in humans

Wutzke

Oetjens

2005

Eur J Clin Nutr

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Objective: In the present study, Lactobacillus johnsonii (La1) doubly labelled with 15 N and 13 C (dlLa1) was used to follow the metabolic fate of orally administered dlLa1 in humans. Design: Experimental study. Setting: Research Laboratory, Children's Hospital, University of Rostock. Subjects: A total of 10 healthy adults aged 23-36 y. Intervention: The subjects received 87 mg/kg body weight viable dlLa1 and 10 g raffinose together with breakfast. Expired air samples were taken over 14 h, whereas urine and faeces were collected over 2 days. A blood sample was taken after 2 h. 13 C-and 15 N-enrichments were measured by isotope ratio mass spectrometry (SerCon, UK) and H 2 -concentrations were measured by electrochemical detection (Stimotron, Germany). Results: The orocaecal transit time (OCTT) was reached after 3.7 h. The 13 CO 2 -exhalation amounted to 8.6% of ingested dose. The urinary excretion of 13 C and 15 N was 1.3 and 12.4% of ingested dose, respectively, whereas the faecal excretion was 39.9 and 37.6% of ingested dose, respectively. After 2 h, 13 C-and 15 N-enrichment of fibrinogen amounted to 70 and 90 ppm excess, respectively. Conclusions: In comparison to OCTT of 3.7 h, both stable isotopes appear after 30 min in breath and urine, indicating that dlLa1 is rapidly digested in the small bowel before reaching the caecum. This is confirmed by 13 C-and 15 N-enrichments of blood plasma fractions. The ingestion of dlLa1 led to an excretion of 50% of ingested dose of both stable isotopes.

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13C abundances of nutrients and the effect of variations in 13C isotopic abundances of test meals formulated for 13CO2 breath tests

Cited by 220 publications

References 18 publications

13C enrichment of carbons 2 and 8 of purine by folate-dependent reactions after [13C]formate and [2-13C]glycine dosing in adult humans

13C enrichment of carbons 2 and 8 of purine by folate-dependent reactions after [13C]formate and [2-13C]glycine dosing in adult humans

The duration of enzyme induction in orocaecal transit time measurements

13C- and 15N-incorporation of doubly stable isotope labelled Lactobacillus johnsonii in humans

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