The effect of L-rhamnose on intestinal transit time, short chain fatty acids and appetite regulation: a pilot human study using combined 13CO_2/H_2 breath tests

摘要

Background. The appetite-regulating effects of non-digestible carbohydrates (NDC) have in part previously been attributed to their effects on intestinal transit rates as well as microbial production of short chain fatty acids (SCFA). Increased colonic production of the SCFA propionate has been shown to reduce energy intake and stimulate gut hormone secretion acutely in humans. Objective.We investigated the effect of the propiogenic NDC, L-rhamnose, on gastrointestinal transit times using a combined ~(13)CO_2/H_2 breath test.Wehypothesised that L-rhamnose would increase plasma propionate leading to a reduction in appetite, independent of changes in gastrointestinal transit times. Design.We used a dual ~(13)C-octanoic acid/lactose ~(13)C-ureide breath test combined with breathH2 to measure intestinal transit times following the consumption of 25 g d~(?1) L-rhamnose, compared with inulin and cellulose, in 10 healthy humans in a randomised cross-over design pilot study. Gastric emptying (GE) and oro-caecal transit times (OCTTs) were derived from the breath 13Cdata and compared with breath H_2. Plasma SCFA and peptide YY (PYY) were also measured alongside subjective measures of appetite. Results. L-rhamnose significantly slowed GE rates (by 19.5 min) but there was no difference inOCTT between treatments. However, breath H_2 indicated fermentation of L-rhamnose before it reached the caecum. OCTT was highly correlated with breath H_2 for inulin but not for L-rhamnose or cellulose. L-rhamnose consumption significantly increased plasma propionate and PYY but did not significantly reduce subjective appetite measures. Conclusions. The NDCs tested had a minimal effect on intestinal transit time. Our data suggest that L-rhamnose is partially fermented in the small intestine and that breath H_2 reflects the site of gastrointestinal fermentation and is only a reliable marker of OCTT for certain NDCs (e.g. inulin). Future studies should focus on investigating the appetite-suppressi