Brevibacillus laterosporus BL1 improves intestinal barrier function and immune homeostasis and modulates gut microbiota in high-fat diet-fed mice.

High-fat diet (HFD)-induced intestinal damage contributes to metabolic dysfunction and systemic inflammation. Brevibacillus laterosporus, a broad-spectrum antimicrobial, has been approved as a microbial feed additive in the breeding industry and may improve intestinal health. This study investigated whether B. laterosporus BL1 enhances intestinal health in HFD-fed mice. C57BL/6 mice were fed an HFD with or without B. laterosporus BL1 supplementation for 8 weeks. The findings showed that B. laterosporus BL1 reduced intestinal morphological damage, enhanced epithelial barrier integrity, and promoted mucosal repair. It also alleviated intestinal inflammation by suppressing innate immune components and pro-inflammatory cytokines. In the ileum, B. laterosporus BL1 downregulated the expression of lipid transport-related molecules. It altered the composition of the intestinal microbiota: the abundance of Faecalibaculum decreased in both the ileum and cecum, and the proportions of ileal norank_f__Erysipelotrichaceae and cecal Lactobacillus increased. The results indicated that B. laterosporus BL1 alleviated intestinal injury in HFD-fed mice by improving intestinal barrier function, enhancing gut immune homeostasis, reducing intestinal lipid transport, and modulating gut microbiota composition. This raises the possibility of using B. laterosporus BL1 as a potential agent to maintain a host-friendly gut environment.