Systemic LPS and Inflammatory Response during Consecutive Days of Exercise in Heat

This investigation studied circulating LPS activity, potential intestinal damage, and the systemic inflammatory response (SIR) during the exercise heat acclimation process. 8 healthy males (Age=24 +/- 3 years) ran in a hot environment on 5 consecutive days until core temperature (T-c) was elevated 2 degrees C above rest. Plasma was obtained pre-, post-, 1h post-, and 3h post-exercise on the 1(st), 3(rd), and 5(th) day of exercise and analyzed for TNF-alpha, IL-6, IL-10, IL-1ra, LPS, and intestinal fatty acid-binding protein (I-FABP). Plasma LPS (1.1EU center dot ml(-1)+/- 0.1 vs. 0.7EU center dot ml(-1)+/- 0.03; P<0.01) and I-FABP (930.7pg center dot ml(-1)+/- 149.0 vs. 640.2pg center dot ml(-1)+/- 125.0; P<0.001) were significantly increased post-exercise each. The SIR remained largely unchanged during the study except for TNF-alpha. Plasma TNF-alpha was significantly lower on Day 5 at 1h (3.2pg center dot ml(-1)+/- 0.6 vs. 4.5pg center dot ml(-1)+/- 0.8; P=0.01) and 3h (3.6pg center dot ml(-1)+/- 0.8 vs. 4.8pg center dot ml(-1)+/- 0.9; P=0.05) post-exercise as compared to Day 1. Findings indicate that adaptations to exercise in the heat resulting in reductions of intestinal damage and plasma LPS activity require longer time periods in moderately trained males.