Aims To evaluate efficacy of Saccharomyces cerevisiae fermentate prebiotic (EH) in protection of intestinal barrier integrity in rats during heat stress, to analyze the impact of heat stress and preventive treatment with EH on the structure of the gut microbiota. Methods and Results Two groups of rats were treated orally with EH or phosphate‐buffered saline for 14 days. On day 15, half of the rats in each group were exposed to heat stress conditions, while control animals were kept at room temperature. Histological and Western blot analyses of the intestine, culture‐based microbiological analysis and high‐throughput 16S rRNA sequencing for the gut microbiota were performed for each rat. Exposure of animals to heat stress conditions resulted in inhibition of tight junction (TJ) proteins expression, decrease of Paneth and goblet cells, decrease of beneficial and increase of pathogenic bacteria. Oral treatment of rats with EH before stress significantly prevents these adverse effects by elevation of the gut beneficial bacteria, particularly butyrate‐producing bacteria. Conclusions Essential effect of EH in protection of intestinal barrier integrity during heat stress is connected with beneficial modulation of the gut microbiota. Significance and Impact of the Study Our results will contribute to the development of new approaches to prevention of heat stress‐related complications.

Aims To characterize efficacy of the Bacillus subtilis BSB3 (BSB3) strain in the prevention of excessive exercise‐induced side effects and in maintaining stability of the gut microbiota. Methods and Results Rats were pretreated by oral gavage with B. subtilis BSB3 (BSB3) or with phosphate‐buffered saline (PBS) twice a day for 2 days, and were either exposed forced treadmill running or remained sedentary. Histological analysis of intestine, immunofluorescence staining of tight junction (TJ) proteins, serum lipopolysaccharide and intestinal fatty acid‐binding protein assay, culture‐based analysis and pyrosequencing for the gut microbiota were performed for each rat. Forced running resulted in a substantial decrease in intestinal villi height and total mucosa thickness, the depletion of Paneth cells, an inhibition of TJ proteins expression. Short‐term treatment of rats with BSB3 before running prevented these adverse effects. Culture‐based analysis of the gut microbiota revealed significant elevation of pathogenic microorganisms only in treadmill‐exercised rats pretreated with PBS. High‐throughput 16S rRNA gene sequencing also revealed an increase in pathobionts in this group. Preventive treatment of animals with BSB3 resulted in predominance of beneficial bacteria. Conclusions BSB3 prevents excessive exercise‐associated complications by beneficial modulation of the gut microbiota. Significance and Impact of the Study Our study shows a new application of beneficial bacteria for prevention the adverse effects of excessive exercise.

Heat stress results in a multitude of biological and physiological responses which can become lethal if not properly managed. It has been shown that heat stress causes significant adverse effects in both human and animals. Different approaches have been proposed to mitigate the adverse effects caused by heat stress, among which are special diet and probiotics. We characterized the effect of the yeast fermentate EpiCor (EH) on the prevention of heat stress-related complications in rats. We found that increasing the body temperature of animals from 37.1±0.2 to 40.6±0.2°C by exposure to heat (45°C for 25min) resulted in significant morphological changes in the intestine. Villi height and total mucosal thickness decreased in heat-stressed rats pre-treated with PBS in comparison with control animals not exposed to the heat. Oral treatment of rats with EH before heat stress prevented the traumatic effects of heat on the intestine. Changes in intestinal morphology of heat-stressed rats, pre-treated with PBS resulted in significant elevation of lipopolysaccharides (LPS) level in the serum of these animals. Pre-treatment with EH was effective in the prevention of LPS release into the bloodstream of heat-stressed rats. Our study revealed that elevation of body temperature also resulted in a significant increase of the concentration of vesicles released by erythrocytes in rats, pre-treated with PBS. This is an indication of a pathological impact of heat on the erythrocyte structure. Treatment of rats with EH completely protected their erythrocytes from this heat-induced pathology. Finally, exposure to heat stress conditions resulted in a significant increase of white blood cells in rats. In the group of animals pre-treated with EH before heat stress, the white blood cell count remained the same as in non-heated controls. These results showed the protective effect of the EH product in the prevention of complications, caused by heat stress.

The intestinal barrier function is crucial in maintaining the host's homeostasis, as it acts as the first protective barrier between the lumenal content and circulation. Disruptions to this protective barrier have been linked to various pathological conditions. Excessive permeability can lead to tissue damage, systemic inflammation, and even organ failure. Studies have shown that the gut microbiota and its metabolites have an essential role in the regulation of the intestinal barrier function. Negative alterations to the gut microbiota, known as dysbiosis, have been shown to be a factor involved for the increased barrier permeability. Thus, restoration of the gut microbiota can provide a novel approach for the prevention of adverse effects caused by the loss of this protective barrier. The main goal of this study was to evaluate the efficacy of a prebiotic and probiotic in maintaining the intestinal barrier integrity during heat stress.Animals were pre‐treated by oral gavage with Bacillus subtilis probiotic strain, a yeast fermentate product having prebiotic properties, or phosphate buffered saline (PBS) prior to exposure to heat stress. Control rats received identical treatments, but without the exposure to stressor. The results demonstrated that heat stress lead to significant changes to the intestinal barrier in the stressed animals pre‐treated with PBS, causing significant decreases in villi height and total mucosal thickness, and reduced expression of tight junction proteins. The level of lipopolysaccharides in serum also significantly increased in those animals. All registered adverse effects were prevented in stressed animals pre‐treated with the probiotic and prebiotic. Analysis of the gut microbiota revealed significant disruption of microbial composition only in the stressed rats pre‐treated with PBS. These results demonstrate the high efficacy of the prebiotic and probiotic in preventing the loss of the intestinal barrier function. We can speculate that the beneficial modulation of the gut microbiota could be a valuable approach for prevention of stress‐related adverse effects.Support or Funding InformationThis work was supported by Auburn University funds.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.