title: Selective conversion of plasma glucose into CO2 by Saccharomyces cerevisiae for the measurement of 13C abundance by isotope ratio mass spectrometry: proof of principle.
abstract: To study carbohydrate digestion and glucose absorption, time-dependent (13)C enrichment in plasma glucose is measured after oral administration of naturally occurring (13)C-enriched carbohydrates. The isotope enrichment of the administered carbohydrate is low (APE <0.1%) and plasma (13)C glucose measurements are routinely determined with gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS) or liquid chromatography/combustion/isotope ratio mass spectrometry (LC/C/IRMS). In this study, plasma glucose was converted into CO(2) by an in-tube reaction with yeast permitting direct measurement of (13)CO(2) in the headspace. Saccharomyces cerevisiae incubated under anaerobic conditions was able to convert sufficient glucose into CO(2) to produce a consistent CO(2) peak in IRMS with little variation in peak area and precise delta(13)C(PDB) values for corn glucose: -11.40 +/- 0.16 per thousand, potato glucose: -25.17 +/- 0.13 per thousand, and plasma glucose: -26.29 +/- 0.05 per thousand. The measurement showed high linearity (R(2) = 0.999) and selectivity and was not affected by the glucose concentration in the tested range of 5-15 mM. Comparison with GC/C/IRMS showed a good correlation of enrichment data: R(2) > 0.98 for both sources of glucose and plasma samples. Commercially available, instant dried baker's yeast was qualitatively and quantitatively comparable with freshly prepared yeast: R(2) > 0.96, slope 1.03 and 1.08 for glucose solutions and plasma, respectively. Thus, yeast conversion of plasma glucose into CO(2) and (13)C measurement applying a breath (13)CO(2) analyzer is an inexpensive, simple and equally accurate alternative to the more expensive and laborious GC/C/IRMS and LC/C/IRMS measurements.
authors.affiliation: Department of Gastroenterology & Hepatology, Center for Liver, Gastrointestinal & Metabolic Diseases, University Medical Center Groningen, Groningen, The Netherlands.
authors.forename: Krzysztof P
authors.initials: KP
authors.lastname: Rembacz
authors.forename: Klaas Nico
authors.initials: KN
authors.lastname: Faber
authors.forename: Frans
authors.initials: F
authors.lastname: Stellaard
mesh_terms: D001681:Biological Assay / Q000379:methods*; D001774:Blood Chemical Analysis / Q000379:methods; D001786:Blood Glucose / Q000032:analysis* / Q000378:metabolism*; D002245:Carbon Dioxide / Q000032:analysis* / Q000378:metabolism*; D002247:Carbon Isotopes / Q000032:analysis / Q000737:chemistry; D005240:Feasibility Studies; D006801:Humans; D013058:Mass Spectrometry / Q000379:methods*; D012441:Saccharomyces cerevisiae / Q000378:metabolism*
chemical_list: D001786:Blood Glucose; D002247:Carbon Isotopes; D002245:Carbon Dioxide