Glutamine supplementation reduces markers of intestinal permeability during running in the heat in a dose-dependent manner

PURPOSE

To examine the dose-response effects of acute glutamine supplementation on markers of gastrointestinal (GI) permeability, damage and, secondary, subjective symptoms of GI discomfort in response to running in the heat.

METHODS

Ten recreationally active males completed a total of four exercise trials; a placebo trial and three glutamine trials at 0.25, 0.5 and 0.9 g kg-1 of fat-free mass (FFM) consumed 2 h before exercise. Each exercise trial consisted of a 60-min treadmill run at 70% of [Formula: see text] in an environmental chamber set at 30 °C. GI permeability was measured using ratio of lactulose to rhamnose (L:R) in serum. Plasma glutamine and intestinal fatty acid binding protein (I-FABP) concentrations were determined pre and post exercise. Subjective GI symptoms were assessed 45 min and 24 h post-exercise.

RESULTS

Relative to placebo, L:R was likely lower following 0.25 g kg-1 (mean difference: - 0.023; ± 0.021) and 0.5 g kg-1 (- 0.019; ± 0.019) and very likely following 0.9 g kg- 1 (- 0.034; ± 0.024). GI symptoms were typically low and there was no effect of supplementation.

DISCUSSION

Acute oral glutamine consumption attenuates GI permeability relative to placebo even at lower doses of 0.25 g kg-1, although larger doses may be more effective. It remains unclear if this will lead to reductions in GI symptoms. Athletes competing in the heat may, therefore, benefit from acute glutamine supplementation prior to exercise in order to maintain gastrointestinal integrity.

Novel multi-sugar assay for site-specific gastrointestinal permeability analysis: a randomized controlled crossover trial

BACKGROUND & AIMS

Increased gastrointestinal (GI) permeability is an important hallmark of many conditions, potentially leading to antigen exposure and sepsis. Current permeability tests are hampered by analytical limitations. This study aims to compare the accuracy of our multi-sugar (MS) and the classical dual sugar (DS) test for detection of increased GI permeability.

METHODS

Ten volunteers received permeability analysis using MS (1 g sucrose, lactulose, sucralose, erythritol, 0.5 g rhamnose in water) or DS (5 g lactulose, 0.5 g rhamnose), after indomethacin or placebo. Blood and urine were analyzed by isocratic LC-MS.

RESULTS

MS testing revealed significantly elevated urinary lactulose/rhamnose (L/R) ratios after indomethacin, due to enhanced lactulose excretion (P < .01) and unaltered rhamnose excretion. The DS test showed increased L/R ratios, due to increased lactulose excretion and decreased rhamnose excretion (both P < .05). After indomethacin, plasma L/R increased in both assays (P < .05 and P < .01). Urinary and plasma L/R ratios correlated significantly. Indomethacin increased sucrose excretion and 0-1 h sucrose/rhamnose. Colon permeability was unchanged.

CONCLUSIONS

Sensitive permeability analysis is feasible in plasma and urine using MS or DS test. In contrast to the DS test, monosaccharide excretion is not decreased by the MS test. In short, the MS test provides accurate, site-specific information on gastroduodenal, small, and large intestinal permeability. Registered at US National Library of Medicine (http://www.clinicaltrials.gov, NCT00943345).

Absorption of sugars in the Egyptian fruit bat (Rousettus aegyptiacus): a paradox explained

Two decades ago D. J. Keegan reported results on Egyptian fruit bats(Rousettus aegyptiacus, Megachiroptera) that were strangely at odds with the prevailing understanding of how glucose is absorbed in the mammalian intestine. Keegan's in vitro tests for glucose transport against a concentration gradient and with phloridzin inhibition in fruit bat intestine were all negative, although he used several different tissue preparations and had positive control results with laboratory rats. Because glucose absorption by fruit bats is nonetheless efficient, Keegan postulated that the rapid glucose absorption from the fruit bat intestine is not through the enterocytes, but must occur via spaces between the cells. Thus, we hypothesized that absorption of water-soluble compounds that are not actively transported would be extensive in these bats, and would decline with increasing molecular mass in accord with sieve-like paracellular absorption. We did not presume from Keegan's studies that there is no Na+-coupled, mediated sugar transport in these bats, and our study was not designed to rule it out, but rather to quantify the level of possible non-mediated absorption. Using a standard pharmacokinetic technique, we fed,or injected intraperitonealy, the metabolically inert carbohydrates l-rhamnose (molecular mass=164 Da) and cellobiose (molecular mass=342 Da), which are absorbed by paracellular uptake, and 3-O-methyl-d-glucose (3OMd-glucose), a d-glucose analog that is absorbed via both mediated(active) and paracellular uptake. As predicted, the bioavailability of paracellular probes declined with increasing molecular mass (rhamnose,62±4%; cellobiose, 22±4%) and was significantly higher in bats than has been reported for rats and other mammals. In addition, fractional absorption of 3OMd-glucose was high (91±2%). We estimated that Egyptian fruit bats rely on passive, paracellular absorption for the majority of their glucose absorption (at least 55% of 3OMd-glucose absorption), much more than in non-flying mammals.

Dual sugar gut-permeability testing on blood drop in animal models

BACKGROUND

Intestinal permeability is determined by measuring nonmetabolized sugars. In animals, intestinal permeability is determined in urine, using cumbersome and expensive metabolic cages. We developed an HPLC method for determining concentrations of lactulose (L) and L-rhamnose (R) in blood-drop of rabbits and mice, and we compared these results with the procedure based on sugars excreted in urine. We measured the intestinal permeability induced by a fragment (DeltaG) of the zonula occludens toxin which opens the paracellular pathway.

METHODS

The animals received sugar solution and later received the same solution+DeltaG. Five-hour urine collection and timed blood tests were performed after ingestion of sugars. Sugars were measured with HPLC, and the percentage of recovered sugars was expressed as L/R ratio.

RESULTS

At 60 min after administration of sugars, the mean L/R ratio for rabbits and mice was 0.026 and 0.052, respectively. At 60 min after administration of sugars+DeltaG, the mean L/R ratio for rabbits and mice was 0.22 and 0.53. The mean L/R ratio in the urine was 0.023 at basal condition and 0.25 after DeltaG ingestion.

CONCLUSIONS

Testing small serum samples for sugar permeability is effective for monitoring changes in permeability of the gut in animals. This cheap simple method allows us to measure in vivo the biological activity of other molecules which modulate the paracellular pathway.

Intestinal permeability of Irish setter puppies challenged with a controlled oral dose of gluten

A combined test of intestinal permeability using lactulose (L) and rhamnose (R), and absorptive function using xylose (X) and 3-O-methylglucose (G), was carried out at four, six, eight and 16 weeks of age in 22 healthy control and six gluten-sensitive Irish setter (IS) dogs fed a diet containing a controlled dose of gluten from weaning. Comparisons were made with two groups of 12 healthy control dogs of breeds other than IS, one fed the same diet as the setters and the other fed a gluten-free diet. Gluten-sensitive IS showed a rise in permeability (mean [SEM] urinary L/R) from 0.23 (0.07) at four weeks to 0.39 (0.05) at eight weeks, remaining at 0.36 (0.04) at 16 weeks. These results were significantly higher in gluten-sensitive than control IS at six, eight and 16 weeks, compatible with jejunal biopsy lesions characteristic of gluten-sensitive enteropathy demonstrated in affected dogs at 16 weeks. Urinary L/R ratios of control dogs of breeds other than IS peaked at six weeks 0.27 (0.02), and were significantly higher than those of control IS at six and eight weeks, demonstrating differences in permeability between Irish setter dogs and other breeds at this age. There were no significant differences in urinary X/G ratios at six, eight and 16 weeks of age between any of the groups of dogs challenged with gluten. Urinary L/R and X/G ratios were similar in the control dogs of breeds other than IS fed gluten-containing and gluten-free diets. These findings indicate that intestinal permeability testing of puppies during controlled oral gluten challenge provides a practical screening test for gluten sensitivity in Irish setter dogs at an early age.

A blood test for intestinal permeability and function: a new tool for the diagnosis of chronic intestinal disease in dogs

We demonstrate that rhamnose, 3-O-methyl-D-glucose, D-xylose and lactulose may be quantified accurately in blood by HPLC and pulsed amperometric detection, thus enabling studies of intestinal permeability and function to be carried out using plasma samples. Prior to HPLC, the endogenous glucose was enzymatically modified to gluconic acid and the protein precipitated. The precision of the quantification of the sugars in plasma (CV: 2.2-5.7%; 8.7-10.6% at very low concentrations) compared well with the quantification in urine. The results for groups of 8 dogs with small intestinal bacterial overgrowth and 12 dogs with inflammatory bowel disease were shown to be significantly different from a group of 20 normal control dogs (P < 0.001), demonstrating the test's value as a diagnostic tool. The normal ranges in blood 2 h post oral administration were determined to be 0.05-0.17 for the lactulose/rhamnose ratio and 0.45-0.65 for the xylose/3-O-methylglucose ratio. This method may be employed advantageously when the collection of urine in intestinal permeability and function tests is difficult.