The effect of oral glutamine supplementation on gut permeability and heat shock protein regulation in runners with a history of gastrointestinal distress
Gastrointestinal (GI) permeability increases during high intensity exercise leading to endotoxin leakage, and a pro-inflammatory immune response. The purpose of this study are to assess whether oral glutamine supplementation (1) reduces exercise induced permeability through up-regulation of the heat shock response resulting in occludin stabilization, and (2) depresses the exercise induced inflammatory response. Methods. Eight human subjects (n=8) participated in baseline (PRE) testing, a glutamine (GLN), and placebo (PLA) supplementation trial in a double blind design. After PRE measurements, subjects ingested .9g/kg fat free mass of glutamine per day or a sugar free lemon placebo drink for seven days with a one-month washout period between trials. A 60-min treadmill run at 70% of maximal oxygen consumption was performed at 30°C in an environmental chamber at the end of each supplementation period. Intestinal permeability was assessed at rest and during each trial through urine concentrations of lactulose and rhamnose. Plasma glutamine, plasma endotoxin, and peripheral blood mononuclear cell levels of heat shock protein 70 (HSP70), and nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor, alpha (IκB-α) were measured pre-exercise, post-exercise, 2hr post-exercise, and 4hr post-exercise. Cultured caco-2 human intestinal epithelial cells supplemented with three concentrations of GLN (0, 4, and 6mmol/L) were exposed to heat stress (41\xbaC) to simulate exercise and control (37\xbaC) conditions. HSP70, heat shock factor 1 (HSF-1), and occludin were measured from each culture. Results: Core temperature was not different between exercise trials (39.40 ± .39 vs. 39.54 ± .22 for PLA vs. GLN, respectively, p>0.05). Resting plasma glutamine levels were significantly higher in the GLN trial versus PLA (1.893 ± 0.245mmol.L vs. 0.8285 ± 0.078 mmol.L, p<0.05). Permeability as the ratio of lactulose to rhamnose was significantly higher in the PLA trial when compared to PRE (.0604 ± .0470 vs. .0218 ±.0084, respectively, p<0.05). Permeability was not statistically different between GLN trial and PRE (.0272 ± .0074 vs. .0218 ± .0084, respectively, p>0.05). PBMC expression of IκB-α and HSP70 were higher at the 4hr post-exercise time point in the GLN trial when compared to the 4hr mark in the PLA (.9839 ± .1587 vs. 1.520 ±.2294 and 2.083 ± .6712 vs. 2.895 ± .8444, p<0.05 for IKB-α and HSP70, respectively). Plasma endotoxin was higher compared to pre-exercise at the 2hr post-exercise in the PLA trial (2.883 ± 0.4310 pg.ml vs. 4.550 ± 0.3350 pg.ml, p<0.05 respectively) and significantly higher when compared to the 2hr post-exercise mark in GLN trial (4.550 ± 0.3350 pg/ml vs. 2.883 ± .4314 pg/ml, p<0.05). Results of cell culture: HSP70 expression in Caco-2 cells was higher in the 6mmol 41\xbaC trial when compared to the 0mmol 41\xbaC trial (1.973 ± 0.163 vs. 1.133 ± 0.064, p<0.05, respectively). HSF-1 was higher in the 4mmol 41 \xbaC and the 6mmol 41\xbaC trials when compared to the 0mmol 41\xbaC (1.649 ± 0.185, 1.785 ± 0.185 vs. 0.6681 ± 0.145, p<0.05). Occludin levels were statistically lower in the 0mmol 41\xbaC when compared to 0mmol 37\xbaC representing de-stabilization of the TJ protein in response to heat stress (0.7434 ± 0.015 ± 1.0000 ± 0.000, p<0.05, respectively). Occludin levels during both 4mmol 41\xbaC and 6mmol 41\xbaC trials were statistically higher when compared to 0mmol 41\xbaC (1.236 ± 0.143 and 1.849 ± 0.143 vs. 0.7434 ± 0.015, p=0.032, p<0.001, respectively) Conclusion: Seven days of oral glutamine supplementation prevents exercise induced intestinal permeability and endotoxin leakage possibly through HSF-1 and HSP70 activation leading to occludin stabilization at the tight junction. In addition, glutamine suppressed the inflammatory response to high intensity exercise through activation of HSP70, reduced IKB-α degradation and possible NFκ-B inhibition.
Gastrointestinal Permeability, Exercise, Heat Shock Proteins
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