Probiotics, as dietary supplements, transmit their major effects through the regulation of gut microbiota. According to a previous study, one possible mechanism of Lactobacillus casei CCFM419 protection against diabetes may involve gut flora. To test this hypothesis, high fat and streptozotocin-induced C57BL/6J mice were fed L. casei CCFM419 at 10⁸, 10⁹, and 10¹⁰ colony forming units (CFU). Compared to untreated mice, 10⁹ CFU of L. casei CCFM419 attenuated several symptoms of diabetes, including fasting blood glucose, postprandial blood glucose, glucose intolerance, and insulin resistance. In addition, this CFU level also decreased the levels of the inflammatory markers tumor necrosis factor-α and interleukin-6 and increased intestinal glucagon-like peptide-1 (GLP-1) levels, which are associated with the production of short chain fatty acids (SCFAs). The 16S rRNA gene sequencing of fecal samples demonstrated that 10⁹ CFU of L. casei CCFM419 dramatically increased the abundance of Bacteroidetes and decreased the proportion of Firmicutes at the phylum level, and enriched Bifidobacterium, Lactobacillus, and SCFA-producing bacteria, including Allobaculum and Bacteroides. These findings suggested that L. casei CCFM419 modified the gut flora-SCFA-inflammation/GLP-1 mechanism to ameliorate type 2 diabetes.

B. longum has been reported to exert an alleviative effect on colitis, but the results also suggested significant differences among strains. Here in this study, we compared the effect of B. longum subsp. longum strains with different properties in EPS production on DSS-induced colitis. To investigate the alleviative effect of a ropy-exopolysaccharide (EPS) producing strain, Bifidobacterium longum subsp. longum YS108R, on experimental colitis, C57BL/6J mice (male, 6–8 weeks old) were randomly assigned to six groups (n = 8): normal control, DSS colitis and four DSS colitis groups orally administered with three B. longum subsp. longum strains (YS108R, C11A10B and HAN4-25) and B. animalis subsp. lactis BB12, respectively, in which YS108R produced ropy-EPS, C11A10B produced non-ropy-EPS, HAN4-25 did not produce EPS and BB12 was set as a positive control. Ropy-EPS producing strain YS108R could alleviate the symptoms and remit inflammation induced by DSS, in which YS108R could decrease the pro-inflammatory cytokine IL-6 and IL-17A levels after DSS challenge (from 102 ± 45.22 to 37.95 ± 20.33 pg mL⁻¹ and from 22.14 ± 5.43 to 12.58 ± 2.74, p < 0.05), but another non-ropy-EPS producing strain C11A10B did not decrease the levels of these pro-inflammatory cytokines. Furthermore, YS108R could maintain the expression levels of genes related to the mucosal barrier, but strain HAN4-25, a non-EPS producer, was not able to maintain the expression levels of these genes after DSS challenge. Analysis of gut microbiota showed that DSS treatment significantly increased the relative abundance of Enterobacteriaceae and Peptostreptococcaceae (0.2623 ± 0.162 and 0.0512 ± 0.0361) and decreased the relative abundance of S24-7 (0.042 ± 0.0326); however, YS108R administration could decrease the relative abundance of Enterobacteriaceae and Peptostreptococcaceae to 0.0848 ± 0.0399 and 0.0032 ± 0.0047 and increase the relative abundance of S24-7 to 0.2625 ± 0.0566 (p < 0.05). The results showed that B. longum subsp. longum YS108R could alleviate DSS-induced colitis by modulating the inflammation related cytokines, maintenance of the normal mucosal barrier and reverting the change of microbiota.

Constipation is one of the most common gastrointestinal complaints worldwide. This study was performed to determine whether Bifidobacterium adolescentis exerts inter-strain differences in alleviating constipation induced by loperamide in BALB/c mice and to analyze the main reasons for these differences. BALB/c mice underwent gavage with B. adolescentis (CCFM 626, 667, and 669) once per day for 17 days. The primary outcome measures included related constipation indicators, and the secondary outcome measures were the basic biological characteristics of the strains, the concentration changes of short-chain fatty acids in feces, and the changes in the fecal flora. B. adolescentis CCFM 669 and 667 relieved constipation symptoms by adhering to intestinal epithelial cells, growing quickly in vitro and increasing the concentrations of propionic and butyric acids. The effect of B. adolescentis on the gut microbiota in mice with constipation was investigated via 16S rRNA metagenomic analysis. The results revealed that the relative abundance of Lactobacillus increased and the amount of Clostridium decreased in the B. adolescentis CCFM 669 and 667 treatment groups. In conclusion, B. adolescentis exhibits strain-specific effects in the alleviation of constipation, mostly due to the strains’ growth rates, adhesive capacity and effects on the gut microbiome and microenvironment.

Evidence linking Faecalibacterium prausnitzii abundance to nonalcoholic fatty liver disease (NAFLD) is accumulating; however, the causal relationship remains obscure. In this study, 12 F. prausnitzii strains were orally administered to high fat diet fed C57BL/6J mice for 12 weeks to evaluate the protective effects of F. prausnitzii on NAFLD. We found that five F. prausnitzii strains, A2-165, LB8, ZF21, PL45, and LC49, significantly restored serum lipid profiles and ameliorated glucose intolerance, adipose tissue dysfunction, hepatic steatosis, inflammation, and oxidative stress in a mouse model of NAFLD. Moreover, two strains, LC49 and LB8, significantly enhanced short-chain fatty acid (SCFA) production and modulated the gut microbiota. Based on the combined analysis of linear discriminant analysis effect size and microbial communities, the core microbiome related to NAFLD comprised Odoribacter, Roseburia, Erysipelatoclostridium, Tyzzerella, Faecalibaculum, Blautia, and Acetatifactor, and the last five genera can be reversed by treatment with the LC49 and LB8 strains. Additionally, the LC49 and LB8 strains enriched Lactobacillus, Ileibacterium, Faecalibacterium, Dubosiella, and Bifidobacterium and downregulated pathways involving carbohydrate metabolism, amino acid metabolism, and fatty acid biosynthesis. Interestingly, LC49 supplementation also upregulated tryptophan metabolism, glutathione metabolism, and valine, leucine, and isoleucine degradation, which might be related to NAFLD prevention. Collectively, F. prausnitzii LC49 and LB8 exerted considerable anti-NAFLD and microbiota-regulating effects, indicating their potential as probiotic agents for NAFLD treatment.