Cold-water immersion reduces intestinal injury induced by exertional heat stroke via regulating gut microbiota in rats

The pathogenesis of Exertional heatstroke (EHS) is multifactorial, with considerable roles played by the gut microbiota and their metabolic by-products. To evaluate whether cold-water immersion (CWI) ameliorates EHS-induced intestinal damage through alterations in the gut microbiome, an EHS model was established in 18 Wistar rats in the present study which were divided into CTRL, EHS, and CWI groups. Observations consisted of pathological alterations, core temperature (Tcore) fluctuations, and measurements of Lactic acid (Lac) and endotoxin Lipopolysaccharide (LPS) levels. Moreover, fecal samples were subjected to metagenomic shotgun sequencing and LC-MS to evaluate microbiota and metabolomic profiles. Rats that became ill from EHS showed a significant reduction of intestinal congestion, edema, and necrosis when treated with CWI. On the other hand, H&E staining histological analysis showed more severe intestinal damage in the EHS group as compared to the CTRL group; however, CWI group showed much less damage. Remarkably, the EHS group had the highest temperatures as compared to the CTRL group, while the CWI group experienced significantly lower temperatures in relation to the EHS group. Besides, the CWI group significantly decreased LPS and Lac levels as compared to the EHS group, closely approaching those of the CTRL group. The microbiome analysis showed that gut bacteria composition in the EHS group was significantly disturbed, characterized with increased predominance of probable pathogens such as Desulfovibrio fairfieldensis, Desulfamplus magnetovallimortis, and Desulfococcus oleovorans (P<0.05). These microbial disturbances were resolved following CWI treatment, restoring the gut microbiota to a state similar to that of the control group. Metabolomic profiling distinguished several key metabolites differentiating the CWI and EHS groups, including inosine, hypoxanthine, guanosine, and taurine (Variable importance in projection > 1, P<0.05). The relationship between these specific metabolites and the gut microbiota underscored their synergistic impact on intestinal health in EHS, illustrating the therapeutic potential of CWI through its modulation of microbial-derived metabolites.