Comparison of the Gut Microbiota Disturbance in Rat Models of Irritable Bowel Syndrome Induced by Maternal Separation and Multiple Early-Life Adversity

Abstract

Background: The study aimed to identify the effects of modeling procedures on bacterial communities and to investigate whether different modeling procedures lead to consistent patterns of gut microbiome compositions.

Methods: Two irritable bowel syndrome (IBS) rat models maternal separation (MS) alone and multiple-early-adversity modeling (MAM) were established and the gut microbiome were analyzed using 16S-rRNA-based high-throughput sequencing methods.

Results: Rats from both models exhibited visceral hypersensitivity and the two model groups exhibited differences in the extent of visceral sensitivity and fecal water content. The microbial community structure of the two models exhibited significant differences compared to the controls, while the two model groups also exhibited significant differences between them. Furthermore, microbial community functional predictions suggested that the two models exhibited different abundances of metabolisms and pathways. Several common and distinct characteristic differences were also observed between the two model groups. Alloprevotella were more abundant in both model groups, while Butyricicoccus, Turicibacter, Ruminococcus, and Clostridium_sensu_stricto along with the family it belongs to were less abundant relative to controls. In addition, the abundance of Clostridium_IV, Corynebacterium, Rothia, Elusimicrobium, Romboutsia, Allobaculum, Parasutterella, and their related taxa were specifically associated with MS group, whereas Butyricimonas and Vampirovibrio along with its related taxa were specifically associated with MAM group. Among those, Butyricimonas, Butyricicoccus and Corynebacterium were found to partially mediate early adversity exposure-induced visceral hypersensitivity.

Conclusions: Our results highlight the importance in evaluating gut microbiota characteristics in IBS research while also systematically considering potential modeling procedural differences. The microbial compositional/functional differences identified in this study were suggestive to further investigation of mechanisms of early adversity induced IBS.

Keywords: irritable bowel syndrome; maternal separation; microbiota; multiple early-life adversity; rat; visceral hypersensitivity.

Figure 1

Comparison of visceral hypersensitivity, body weight, and fecal water content in rats of different model groups (n = 7 for each group). (A) Abdominal withdrawal reaction (AWR) scores in response to graded colorectal distension (CRD). (B) Distension threshold values for AWR scores of 2, 3, and 4. (C) Body weight variation of rats (ns, not significant). (D) Fecal water content for rats in the control, MS, and MAM groups.

Figure 2

Bar plots of the gut microbiota compositions of each samples in 3 groups. (A) annotated at phylum level; (B) annotated at genus level.

Figure 3

Alpha diversity values for gut microbial communities among different model group rats.

Figure 4

Beta diversity analysis among and within different model groups. (A) 2D PCoA plots showing differences in the gut microbiota of rats from different model groups based on the unweighted Unifrac distance metric. p = 0.001and r² = 0.21127 in the Adonis test, p = 0.001 and adjusted r² = 0.123634 in db-RDA analysis. (B) 2D PCoA plots showing differences in the gut microbiota of rats from different model groups based on the weighted Unifrac distance metric. p = 0.047 and r² = 0.1743 in the Adonis test. p = 0.048 and adjusted r² = 0.069004 in db-RDA analysis. (C) Comparison of inter-individual variation between and within different model groups based on the unweighted Unifrac distance metric. (D) Comparison of inter-individual variation between and within different model groups based on the weighted Unifrac distance metric.

Figure 5

Linear discriminant effect size (LEfSe) analyses comparing differentially abundant taxa and the KEGG-based ortholog functions and pathways between control and MS group communities and control and MAM group communities. (A, B) The differences in gut microbiota taxa between different model groups. The phylogenic relationship of the taxon with differences were shown in the cladogram. (C, D) Differences of KEGG-based ortholog (KO) inferred functions in gut microbiota between different model groups. (E, F) Differences in KO pathways predicted from gut microbiota compositions between different model groups.