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Dose-Response Effect of Arabinoxylooligosaccharides on Gastrointestinal Motility and on Colonic Bacterial Metabolism in Healthy Volunteers

Department of Gastrointestinal Research, University Hospital Gasthuisberg (L.C., V.D.P., P.R., K.V.)
Laboratory of Food Chemistry, K.U.Leuven (K.S., W.F.B., C.M.C., J.A.D.), Leuven, BELGIUM

Address correspondence to: Kristin Verbeke, PhD, Department of Gastrointestinal Research-E462, University Hospital Leuven, Herestraat 49, B-3000 Leuven, BELGIUM. E-mail: Kristin.Verbeke{at}uz.kuleuven.be

Objective: Arabinoxylooligosaccharides (AXOS) are non-digestible in the upper gastrointestinal tract and have been shown to exert prebiotic effects in animals. The aim of this study was to characterize the influence of AXOS with an average degree of polymerization of 15 and an average degree of arabinose substitution of 0.26 (AXOS-15-0.26) on gastrointestinal motility and colonic bacterial metabolism in healthy human volunteers.

Methods: Twelve healthy volunteers received five test meals, containing different amounts of AXOS-15-0.26, with one week intervals between each test meal. Breath tests were used to measure gastric emptying rate, oro-cecal transit time (OCTT) and hydrogen excretion. Colonic bacterial metabolism was estimated using the biomarkers lactose-[¹⁵N, ¹⁵N']-ureide (¹⁵N-LU) and p-cresol.

Results: Gastric emptying and OCTT were not influenced by addition of varying amounts of AXOS-15-0.26. Administration of 2.2g or 4.9g AXOS-15-0.26 significantly decreased the urinary ¹⁵N-excretion (respectively p = 0.008 and p = 0.035) as compared to the baseline, whereas fecal ¹⁵N-excretion was significantly increased (respectively p = 0.034 and p = 0.019). This shift from urinary to fecal ¹⁵N-excretion suggests a higher uptake or incorporation by bacteria due to the stimulation of colonic bacterial growth and/or metabolic activity. Furthermore, a significant increase in hydrogen excretion after administration of 2.2g (p = 0.002) and 4.9g (p = 0.004) AXOS-15-0.26 was observed. No influence on urinary p-cresol excretion was observed.

Conclusion: These findings suggest that a minimal dose of 2.2g AXOS-15-0.26 favorably modulates the colonic bacterial metabolism in healthy humans. However, long term studies are required to confirm a possible prebiotic effect.

Key words: arabinoxylooligosaccharides, dose-response study, healthy volunteers, lactose-[¹⁵N, ¹⁵N']-ureide, p-cresol

Abbreviations: AX = arabinoxylans • AXOS = arabinoxylooligosaccharides • AXOS-15-0.26 = AXOS with an average DP of 15 and an average DAS of 0.26 • DP = degree of polymerization • DAS = degree of arabinose substitution • GE = gastric emptying • GE_t1/2 = gastric half emptying time • GC-MS = gas chromatography-mass spectrometry • IQR = interquartile range • ¹³C-LU = lactose-[¹³C]-ureide • ¹⁵N-LU = lactose-[¹⁵N, ¹⁵N']-ureide • OCTT = oro-cecal transit time • ³H-PEG = [³H]-polyethylene glycol • SCFA = short chain fatty acids