Lactobacillus and intestinal diseases: Mechanisms of action and clinical applications

The gut microbial ecosystem, which is a collection of the host-microbiota interactions and the inter-species interplay among bacteria-dominated microbiota, has become a research hotspot due to its contribution to host health in recent years. Lactobacillus, which has worldwide usage in fermented dairy products, has aroused increasing attention and becomes one of the commonly used probiotics given its promising applications in intestinal health and disease, though it occupies a relatively small proportion of the intestinal microbiota. In the review, we first update the current understanding of determinants of Lactobacillus abundance in the intestinal tract. We then review evidence from animal models to human trials that provided insights into Lactobacillus's applications in common intestinal disorders including the Helicobacter pylori infection, colorectal cancer, diarrhea, inflammatory bowel disease, and irritable bowel syndrome. Mechanisms underlying the probiotic role of Lactobacillus are finally discussed in five aspects: microbial interactions, the improvement of intestinal barrier function, the immunoregulation, the anticancer activity, and the metabolic regulation. This review aims to yield a profound understanding of how Lactobacillus will contribute to disease prevention and individualized therapies in future clinical practice, and to inspire novel microbial strategies utilizing both probiotics and their products in the fields of biology and medicine.