Recent research suggests that intestinal microbiota affect the aging process. Glucagon-like peptide 2 (GLP-2), a growth factor found in the intestinal mucosal epithelium, reduces intestinal permeability and affects intestinal microbiota. The relationship between aging, GLP-2, and intestinal microbiota are still not well understood. The current study examined the influence of aging and GLP-2 on the intestinal microbiota of rats. Twelve 3-month old male SD rats were randomly divided into two groups: a young control group (group C) and a young GLP-2 treatment group (group G). Twelve 26-month old male SD rats were randomly divided into two groups: an aged control group (group L) and an aged GLP-2 treatment group (group T). GLP-2 was intraperitoneally injected into rats from group G and group T for 14 days. Plasma GLP-2 concentration was evaluated by ELISA tests. Fresh intestinal stool samples were collected from each group and total fecal bacterial genomic DNA was extracted from the associated rats. The bacterial composition of fecal samples was analyzed by Miseq high-throughput sequencing and comparison with SRA databases. Overall, the diversity of intestinal microbiota significantly decreases with age in SD rats, while GLP-2 has no significant effect on the diversity of intestinal microbiota. Upon aging, there is a reduction in probiotic bacteria and a concomitant increase in pathogenic bacteria in rats. Treatment with GLP-2 results in a significant reduction in the prevalence of pathogenic bacterial genera and an increase in some potential benefit bacteria in aged rats. In addition, treatment with GLP-2 results in an increase in several probiotics and a reduction in the prevalence of pathogenic bacterial genera in young rats.
Table 1 Diversity estimation of the intestinal microbiota in SD rats.
Figure 1 Comparison of diversity indices, Venn diagram, rarefaction curve, PCoA, and plasma concentration of GLP-2 among the 4 groups
Comparison of diversity indices including the Shannon Curve (A) and Shannon Index (B). (C) Venn diagram illustrating overlap between the 4 groups. (D) Rarefaction curve. (E) PCoA was analyzed by unweighted Unifrac. (F) Plasma concentration of GLP-2 among the 4 groups. C denotes group C; G denotes group G; L denotes group L; T denotes group T; young denotes group C and group G; old denotes group L and group T; treat denotes treatment with GLP-2; * denotes P<0.05.
Figure 2 Relative abundance at the phylum level and the genus level in fecal microbiota
(A) Relative abundance at the phylum level in fecal microbiota. (B) Relative abundance at the genus level in fecal microbiota.
Table 2 The relative abundance of microbial phyla in the microbiota of Groups C, G, L and T.
Figure 3 Comparison relative abundance of microbiota at the phylum level among the 4 groups
Relative abundance (at the phylum level) of Bacteroidetes (A), Firmicutes (B), Proteobacteria (C), Verrucomicrobia (D), and Spirochaetae (E) among the 4 groups. C denotes group C; G denotes group G; L denotes group L; T denotes group T; * denotes P<0.05.
Abundance in Group C (%)
Abundance in Group L (%)
Trends in Group L
Table 3 The relative abundance of microbial genera in the microbiota of Group C and Group L.
Figure 4 Comparison relative abundance of microbiota at the genus level among the 4 groups
Relative abundance (at the genus level) of Anaerovibrio (A), Desulfovibrio (B), Helicobacter (C), Intestinimonas (D), Oscillibacter (E), Parasutterella (F), Prevotella (G), Psychrobacter (H), and Treponema (I) among the 4 groups. C denotes group C; G denotes group G; L denotes group L; T denotes group T; * denotes P<0.05.
Figure 5 The linear correlation between plasma concentrations of GLP-2 and relative abundance of microbiota
The linear correlation between plasma concentrations of GLP-2 and relative abundance of Spirochaetae (A), Intestinimonas (B), Desulfovibrio (C), Treponema (D).
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