Metabolic signature of 13 C-labeled wheat bran consumption related to gut fermentation in humans: a pilot study

Purpose The aim of this pilot study was to analyze concomitantly the kinetics of production of 13 C-labeled gut-derived metabolites from 13 C-labeled wheat bran in three biological matrices (breath, plasma, stools), in order to assess differential fermentation profiles among subjects. Methods Six healthy women consumed a controlled breakfast containing 13 C-labeled wheat bran biscuits. H 2 , CH 4 and 13 CO 2 , 13 CH 4 24 h-concentrations in breath were measured, respectively, by gas chromatography (GC) and GC-isotope ratio mass spectrometry (GC-IRMS). Plasma and fecal concentrations of 13 C-short-chain fatty acids (linear SCFAs: acetate, propionate, butyrate, valerate; branched SCFAs: isobutyrate, isovalerate) were quantified using GC-combustion-IRMS. Gut microbiota composition was assessed by16S rRNA gene sequencing analysis. Results H 2 and CH 4 24 h-kinetics distinguished two groups in terms of fermentation-related gas excretion: high-CH 4 producers vs low-CH 4 producers (fasting concentrations: 45.3 ± 13.6 ppm vs 6.5 ± 3.6 ppm). Expired 13 CH 4 was enhanced and prolonged in high-CH 4 producers compared to low-CH 4 producers. The proportion of plasma and stool 13 C-butyrate tended to be higher in low-CH 4 producers, and inversely for 13 C-acetate. Plasma branched SCFAs revealed different kinetics of apparition compared to linear SCFAs. Conclusion This pilot study allowed to consider novel procedures for the development of biomarkers revealing dietary fiber-gut microbiota interactions. The non-invasive assessment of exhaled gas following 13 C-labeled fibers ingestion enabled to decipher distinct fermentation profiles: high-CH 4 producers vs low-CH 4 producers. The isotope labeling permits a specific in vivo characterisation of the dietary fiber impact consumption on microbiota metabolite production. Clinical trial registration The study has been registered under the number NCT03717311 at ClinicalTrials.gov on October 24, 2018.