Large intestine barrier disturbances can have serious consequences for the health of horses. The loss of mucosal integrity that leads to increased intestinal permeability may result from a local inflammatory immune response following alterations of the microbiota, known as dysbiosis. Therefore, our research aimed to identify noninvasive biomarkers for studying the intestinal permeability and the local inflammatory immune response in horses. Regarding the biomarkers used in other mammalian species, we measured the concentrations of lipopolysaccharides (LPS), reflected by 3-OH C14, C16, and C18 fatty acids, in blood, and fecal secretory immunoglobulin-A (SIgA). These biomarkers were evaluated in two trials including 9 and 12 healthy horses, which developed large intestinal dysbiosis experimentally induced by 5 d of antibiotic administration (trimethoprim sulfadiazine [TMS]) or 5 d of abrupt introduction of high starch levels (barley) into the diet. Horses were either control or supplemented with Lactobacillus acidophilus, Ligilactobacillus salivarius, and Bifidobacterium lactis. Correlations were performed between biomarkers and fecal bacterial diversity, composition, and function. No significant interaction between day and supplementation, or supplementation effect were observed for each biomarker. However, with the dietary stressor, a significant increase in blood concentrations of 3-OH C16 (P = 0.0125) and C14 (P = 0.0252) fatty acids was measured 2 d after the cessation of barley administration. Furthermore, with the antibiotic stressor, blood levels of 3-OH C16 progressively increased (P = 0.0114) from the first day to 2 d after the end of TMS administration. No significant day effect was observed for fecal SIgA concentrations for both stressors. These results indicate that both antibiotic- and diet-induced dysbiosis resulted in a local translocation of LPS 2 d after the cessation of the stressor treatments, suggesting an impairment of intestinal permeability, without detectable local inflammation. Blood LPS and fecal SIgA concentrations were significantly correlated with several bacterial variations in the large intestine, which are features of antibiotic- and diet-induced dysbiosis. These findings support the hypothesis that a relationship exists between dysbiosis and the loss of mucosal integrity in the large intestine of horses.
Keywords: horse; lactic acid bacteria; large intestine; lipopolysaccharides; microbiota; secretory immunoglobulin-A.
Horses can suffer from intestinal barrier disruption leading to permeability associated with local inflammation, which can result in discomfort and even disease. Intestinal barrier disruption may be a consequence of microbiota disturbances in the large intestine. Therefore, this study investigated the use of blood and fecal biomarkers for noninvasively assessing intestinal barrier permeability and inflammatory responses to microbial alterations. Two biomarkers were evaluated in healthy horses that were subjected to antibiotic- and diet-induced large intestine bacterial disturbances. Notably, the blood levels of the biomarkers increased 2 d after the cessation of both treatments, reflecting an abnormal intestinal barrier permeability. By contrast, the levels of fecal biomarker detected did not indicate the presence of inflammation. However, levels of the two biomarkers were significantly correlated with several bacterial variations in the feces, supporting the hypothesis that a relationship exists between microbiota disturbances and intestinal barrier disruption in the large intestine of horses.
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