BACKGROUND: Breath tests are currently used to qualitatively assess colonic fermentation; no quantitative estimations are available for healthy subjects. OBJECTIVE: This study describes a stable-isotope-dilution method to measure acetate production quantitatively from colonic bacterial fermentation. DESIGN: Six volunteers received a primed, constant, intravenous infusion of [1-13C]acetate at a rate of 1.01 +/- 0.04 micromol x kg(-1) x min(-1) for 7 h. They ingested 20 g pure lactulose after 1 h of the tracer infusion. Expired air and arterialized venous blood were sampled every 15 min. RESULTS: Before lactulose intake, the breath-hydrogen concentration was 7 +/- 2 ppm and the plasma acetate concentration and isotopic enrichment were 141 +/- 14 micromol/L and 14.8 +/- 1.4 moles percent excess, respectively. Whole-body acetate turnover was 6.0 +/- 0.7 micromol x kg(-1) x min(-1). After lactulose ingestion, maximum breath hydrogen and acetate concentrations reached 63 +/- 15 ppm (P = 0.004) and 313 +/- 25 micromol/L (P = 0.002), respectively, whereas [13C]acetate enrichment decreased to 9.9 +/- 1.3 moles percent excess (P = 0.03). Whole-body acetate turnover increased to 9.8 +/- 1.5 micromol x kg(-1) x min(-1) and later decreased almost to baseline values. Colonic lactulose fermentation yielded 140 +/- 12 mmol acetate over 6 h, representing 86% of the production based on stoichiometric equations. CONCLUSION: This new method provides a quantitative estimate of colonic carbohydrate fermentation via evaluation of acetate production.
BACKGROUND: Breath tests are currently used to qualitatively assess colonic fermentation; no quantitative estimations are available for healthy subjects. OBJECTIVE: This study describes a stable-isotope-dilution method to measure acetate production quantitatively from colonic bacterial fermentation. DESIGN: Six volunteers received a primed, constant, intravenous infusion of [1-13C]acetate at a rate of 1.01 +/- 0.04 micromol x kg(-1) x min(-1) for 7 h. They ingested 20 g pure lactulose after 1 h of the tracer infusion. Expired air and arterialized venous blood were sampled every 15 min. RESULTS: Before lactulose intake, the breath-hydrogen concentration was 7 +/- 2 ppm and the plasma acetate concentration and isotopic enrichment were 141 +/- 14 micromol/L and 14.8 +/- 1.4 moles percent excess, respectively. Whole-body acetate turnover was 6.0 +/- 0.7 micromol x kg(-1) x min(-1). After lactulose ingestion, maximum breath hydrogen and acetate concentrations reached 63 +/- 15 ppm (P = 0.004) and 313 +/- 25 micromol/L (P = 0.002), respectively, whereas [13C]acetate enrichment decreased to 9.9 +/- 1.3 moles percent excess (P = 0.03). Whole-body acetate turnover increased to 9.8 +/- 1.5 micromol x kg(-1) x min(-1) and later decreased almost to baseline values. Colonic lactulose fermentation yielded 140 +/- 12 mmol acetate over 6 h, representing 86% of the production based on stoichiometric equations. CONCLUSION: This new method provides a quantitative estimate of colonic carbohydrate fermentation via evaluation of acetate production.
Authors: Gijs den Besten; Karen van Eunen; Albert K Groen; Koen Venema; Dirk-Jan Reijngoud; Barbara M Bakker Journal: J Lipid Res Date: 2013-07-02 Impact factor: 5.922
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