Hongmei Peng

Enterotoxigenic Escherichia coli (ETEC) is one of the primary pathogenic bacteria causing intestinal diseases and diarrhea in young animals. Probiotics can enhance intestinal barrier function and alleviate the occurrence of intestinal diseases and diarrhea by regulating the composition and metabolic products of the gut microbiota. In preliminary studies, we isolated a strain of Lactobacillus reuteri L81 with good probiotic properties from the rectal feces of healthy calves. This strain was found to alleviate weaning diarrhea in calves and improve immune function and antioxidant capacity. However, it remains unclear whether it can mitigate intestinal barrier damage caused by Escherichia coli K99 by regulating the composition of the gut microbiota and its metabolites. Therefore, this study selected 24 male SPF-grade ICR mice aged 4 weeks, randomly divided into 4 groups (n = 6): control group, ETEC group, low-dose Lactobacillus reuteri L81 group (L_L81 group), and high-dose Lactobacillus reuteri L81 group (H_L81 group). From days 1 to 17 of the experiment, the L_L81 and H_L81 groups were gavaged with 0.2 mL of bacterial suspensions at concentrations of 1 × 10⁸ CFU/mL and 1 × 10⁹ CFU/mL daily, respectively, while the control and ETEC groups were given an equal volume of physiological saline. From days 18 to 22, the ETEC, L_L81, and H_L81 groups were infected daily with 0.2 mL of an ETEC K99 bacterial suspension at a concentration of 5 × 10⁹ CFU/mL, whereas the control group continued to receive physiological saline. The results showed that the intervention of Lactobacillus reuteri L81 could regulate the gene expression levels of tight junction proteins in the colon tissue of mice. Moreover, the intervention with H_L81 group could increase the gene expression levels of Claudin-1 and ZO-1 ( P < 0.05) in the colon tissue of mice. The intervention with L_L81 group can inhibit the expression of IL-1β, MyD88, and TLR4 genes in the colon tissue of mice. The analysis of gut microbiota composition revealed that the intervention with Lactobacillus reuteri L81 exhibited a trend toward increasing microbial richness and diversity. It elevated the relative abundances of Lactobacillus, Prevotellaceae_UCG-001, and Gordonibacter in the mouse colon, while reducing the relative abundance of Salmonella. The non-targeted metabolomics analysis indicated that the intervention with Lactobacillus reuteri L81 has regulatory effects on multiple metabolic pathways, including bile secretion, β-alanine metabolism, glutathione metabolism, and arginine and proline metabolism. In conclusion, Lactobacillus reuteri L81 can alleviate intestinal barrier damage induced by ETEC K99 in mice by modulating the composition and metabolites of the gut microbiota.

Activities such as childbirth and breastfeeding can cause severe oxidative stress and inflammatory damage to the mother during early lactation, and can affect animal milk production, and the growth and development of offspring. Trehalose alleviates damage to the body by endowing it with stress resistance. In this study, we used trehalose combined with Lactobacillus plantarum, Bifidobacterium longum, Bacillus subtilis, and Saccharomyces cerevisiae to explore whether dietary intervention can alleviate oxidative stress and inflammatory damage in early lactation and to evaluate the growth ability, acid production ability, antioxidant ability, non-specific adhesion ability, antibacterial ability, and other parameters to determine the optimal combinations and proportions. The results showed that the synbiotics composed of 2.5% trehalose and 1 × 10⁷ cfu/g of Bifidobacterium longum could regulate the gut microbiota, and promote mammary gland development in dams by reducing progesterone (PROG) content in the blood, increasing prolactin (PRL) and insulin-like growth factor-1 (IGF-1) content, enhancing their antioxidant and immune abilities, and effectively increasing the weight and lactation of early lactating dams. In addition, it can also affect the growth of offspring and the development of the intestinal barrier. These results indicate that trehalose synbiotics have great potential in alleviating oxidative stress and inflammatory damage in early lactation.