Abstract
Lactic acid bacteria (LAB) are the primary genera of the intestinal flora and have many probiotic functions. In the present study, Lactobacillus rhamnosus GG (LGG) ATCC 53103 was used to treat BALB/c mice. After LGG intervention, both low and high LGG doses were shown to improve the observed OTU, Chao1, ACE, and Shannon indices, while the Simpson index decreased, demonstrating that LGG can promote intestinal microbiota abundance and diversity. Furthermore, LGG treatment increased the abundances of intestinal Firmicutes, Bacteroides and Actinomycetes while reducing that of Proteobacteria. In addition to its effect on gut the microbiota, LGG could also regulate the host immune system. In the present study, we showed that LGG could affect the percentage of CD3+ T lymphocytes in the spleens (SPLs), mesenteric lymph nodes (MLNs), Peyer’s patches (PPs) and lamina propria lymphocytes (LPLs) of mice, including total CD3+ T, CD3+CD4+ T, and CD3+CD8+ T lymphocytes. Furthermore, LGG could effectively increase the expression of Th1-type cytokines (IFN-γ) and Th2 cytokines (IL-4) in CD4+ T cells, indicating that the proportion of Th1 and Th2 cells in mice with LGG treatment was in a high equilibrium state compared to the control group. In addition, the IFN-γ/IL-4 ratio was greater than 1 in mice with LGG intervention, suggesting that LGG tends to mediate the Th1 immune response. The results of the present study also showed that LGG upregulated the expression of IL-17 in CD4+ T cells and regulated the percentage of CD4+CD25+Foxp3+ Treg cells in various secondary immunological organs, indicating that LGG may promote the balance of Th-17 and Treg cells.
Highlights
Lactobacillus is the primary genus of the intestinal flora and probiotics of animals, and it is able to ameliorate the imbalance of the intestinal flora and aid in maintaining a number of biological functions of the immune system (Owyang and Wu, 2014)
Lactobacillus rhamnosus GG (LGG) regulate the intestinal flora through the mechanism of “competitive rejection,” where the colonization of pathogens in the intestinal mucosa is hindered by increasing competition for adhesion sites and nutrients, production of antibacterial compounds (Petrova et al, 2016; Tytgat et al, 2016), regulation of gut microbiota homeostasis (Berni Canani et al, 2016), maintaining function of the intestinal barrier (Zhang et al, 2015), as well as modulation of local or systemic immune response (Johansson et al, 2016)
The results showed that after 7 LGG interventions, compared to the control group, the Chao1, ACE, and Shannon indices in the low-dose LGG group (LLGG) group significantly increased, whereas the Simpson index significantly decreased, indicating that the low-dose LGG treatment could promote the richness and diversity of the gut microbiota
Summary
Lactobacillus is the primary genus of the intestinal flora and probiotics of animals, and it is able to ameliorate the imbalance of the intestinal flora and aid in maintaining a number of biological functions of the immune system (Owyang and Wu, 2014). LGG regulate the intestinal flora through the mechanism of “competitive rejection,” where the colonization of pathogens in the intestinal mucosa is hindered by increasing competition for adhesion sites and nutrients, production of antibacterial compounds (Petrova et al, 2016; Tytgat et al, 2016), regulation of gut microbiota homeostasis (Berni Canani et al, 2016), maintaining function of the intestinal barrier (Zhang et al, 2015), as well as modulation of local or systemic immune response (Johansson et al, 2016). LGG granules administration could decrease the number of Clostridium perfringens and increase the Lactobacillus and Bifidobacterium in the intestine of alcoholinduced mice, which suggested LGG granules prevent alcoholinduced intestinal flora disorder, increase Gram-positive bacteria, decrease Gram-negative bacteria that induce LPS accumulation, and reduce fat accumulation and inflammatory response in liver, so as to ameliorate the liver damage (Gu et al, 2020). The high abundance of Bacteroidetes and Alistipes resulted in a high butyrate level in the nude mice treated with LGG to promote butyrate production, protecting against deoxynivalenol exposure in nude mice (Lin et al, 2020)
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