Acute L-glutamine supplementation does not improve gastrointestinal permeability, injury or microbial translocation in response to exhaustive high intensity exertional-heat stress

Purpose: Exertional-heat stress adversely distrupts (GI) barrier integrity and, through subsequent microbial translocation (MT), can result in potentially fatal exertional-heat stroke. Acute glutamine (GLN) supplementation is a potential nutritional countermeasure, although the practical value of current supplementation regimens is questionable. Method: Ten males completed two high-intensity exertional-heat stress tests (EHST) involving running in the heat (40 degrees C and 40% relative humidity) at lactate threshold to volitional exhaustion. Participants ingested GLN (0.3 g kg FFM-1) or a non-calorific placebo (PLA) one hour prior to the EHST. Venous blood was drawn pre-, post- and one-hour post-EHST. GI permeability was assessed using a serum dual-sugar absorption test (DSAT) and small intestinal epithelial injury using plasma Intestinal Fatty-Acid Binding Protein (I-FABP). MT was assessed using the Bacteroides/total 16S DNA ratio. Results: Volitional exhaustion occurred after 22:19 +/- 2:22 (minutes: seconds) in both conditions, during which whole-body physiological responses and GI symptoms were not different (p > 0.05). GI permeability (serum DSAT) was greater following GLN (0.043 +/- 0.020) than PLA (0.034 +/- 0.019) ( p = 0.02; d = 0.47), but small intestine epithelial injury (I-FABP) increased comparably ( p = 0.22; eta(2)(p) = 0.16) following the EHST in both trials (GLN Delta = 1.25 +/- 0.63 ng ml(-1); PLA Delta = 0.92 +/- 0.44 ng ml(-1)). GI MT (Bacteroides/total 16S DNA ratio) was unchanged in either condition following the EHST (p = 0.43). Conclusion: Acute low-dose (0.3 g kg(-1) fat free mass) GLN supplementation ingested one hour before high-intesity exertional-heat stress worsened GI permeability, but did not influence either small intestinal epithilial injury or microbial translocation.

Automated summary

The study found that acute low-dose glutamine (GLN) supplementation may worsen intestinal permeability before high-intensity exertional-heat stress, but does not influence small intestinal epithelial injury or microbial translocation.