Effects of Bifidobacterium BL21 and Lacticaseibacillus LRa05 on gut microbiota in type 2 diabetes mellitus mice

Abstract

Gut dysbiosis causes damage to the intestinal barrier and is associated with type 2 diabetes mellitus (T2DM). We tested the potential protective effects of probiotic BL21 and LRa05 on gut microbiota in type 2 diabetes mellitus mice and determined whether these effects were related to the modulation of gut microbiota.Thirty specific pathogen-free C57BL/6J mice were randomly allocated to three groups-the (CTL) control group, HFD/STZ model (T2DM) group, and HFD/STZ-probiotic intervention (PRO) group-and intragastrically administered strains BL21 and LRa05 for 11 weeks. The administration of strains BL21 and LRa05 significantly regulated blood glucose levels, accompanied by ameliorated oxidative stress in mice. The BL21/LRa05-treated mice were protected from liver, cecal, and colon damage. Microbiota analysis showed that the cecal and fecal microbiota of the mice presented significantly different spatial distributions from one another. Principal coordinate analysis results indicated that both T2DM and the BL21/LRa05 intervention had significant effects on the cecal contents and fecal microbiota structure. In terms of the fecal microbiota, an abundance of Akkermansia and Anaeroplasma was noted in the PRO group. In terms of the cecal content microbiota, enrichment of Akkermansia, Desulfovibrio, Bifidobacterium, Lactobacillus, and Limosilactobacillus was noted in the PRO group. The probiotics BL21 and LRa05 prevent or ameliorate T2DM by regulating the intestinal flora and reducing inflammation and oxidative stress. Our results suggest that BL21 and LRa05 colonize in the cecum. Thus, BL21/LRa05 combined with probiotics having a strong ability to colonize in the colon may achieve better therapeutic effects in T2DM. Our study illustrated the feasibility and benefits of the combined use of probiotics and implied the importance of intervening at multiple intestinal sites in T2DM mice.

Keywords: Gut microbiota; Inflammation; Probiotics; Spatial structure; T2DM.

Fig. 1

Effects of BL21 and LRa05 on glucose homeostasis in T2DM mice. Schematic diagram of test flow (A), fasting blood glucose level during the test (B), and area under the curve of oral glucose tolerance test at week 12 (C) in T2DM mice. Data are presented as mean and standard deviation (SD) in B and C. CTL: control; T2DM: type 2 diabetes mellitus; PRO: BL21 and LRa05 mixture (109 CFU each). *p < 0.05, **p < 0.01 and ***p < 0.001 vs T2DM group

Fig. 2

Representative optical micrographs of livers stained with DHE (A), HE (B), and Masson (C)

Fig. 3

Effect of BL21/LRa05 on serum LPS and inflammatory cytokines in T2DM mice. Different letters indicate significant differences between groups (p < 0.05), box plot represents interquartile range, the line within the box represents median value

Fig. 4

Effects of probiotics on diversity of fecal and cecal content microbiota in T2DM mice. Effect of probiotics on alpha diversity (A) and beta diversity (B) of fecal microbiota in T2DM mice. Effect of probiotics on alpha diversity (C) and beta diversity (D) of cecal content microbiota. Alpha diversity (A and C) was represented by boxplots, and significant differences were represented by lowercase letters, with different letters indicating significant differences between the two groups. PCoA analysis was used to demonstrate beta diversity (B and D) between groups, and adonis analysis was used to evaluate the significance of differences between groups (tables in B and E). Box plot represents interquartile range, the line within the box represents median value

Fig. 5

Composition analysis of microbiota structures at phylum level for fecal (A) and cecal contents (B). Different letters indicate significant differences between groups (p < 0.05). Box plot represents interquartile range, the line within the box represents median value

Fig. 6

Results of Linear discriminant analysis effect size (LEfSe) analysis at genus level. T2DM caused an increases of Escherichia/Shigella, Parabacteroides, Enterococcus in faces samples (A). Compared with the T2DM group, supplementation with BL21/LRa05 increased the relative abundance of some beneficial bacteria, such as Akkermansia, Desulfovibrio, Bifidobacterium, Lactobacillus, and Limosilactobacillus (B). LEfSe analysis calculates the linear discriminant analysis (LDA) score by LDA effect size, which is assessed for each differentially abundant bacterial taxon using LDA

Fig. 7

Representative optical micrographs of cecal and colonic tissues stained with H&E (A) and periodic acid-Schiff (B)

Fig. 8

BL21/LRa05 modulates the gut microbiota to improve the pattern of type 2 diabetes mellitus (T2DM) presumably. Lipopolysaccharide (LPS), Zonula occludens-1 (ZO-1), Tumor Necrosis Factor-alpha (TNF-$\alpha$), Interleukin-1 $\mathrm{\beta }$ (IL-1 $\mathrm{\beta }$), (IL-6), Superoxide Dismutase (SOD), Catalase (CAT), Glutathione (GSH), Protein Kinase A (PKA), Glucose-6-phosphatase (G6Pase), Glucagon (GCG), Phosphoenolpyruvate Carboxykinase (PEPCK)