Analysis of the Preventive Effect of Lonicera caerulea Pomace and Its Isolated Components on Colitis in Mice Based on Gut Microbiota and Serum Metabolomics

Abstract

Inflammatory bowel disease (IBD), including relapsing-remitting ulcerative colitis and Crohn's disease, is a non-specific chronic intestinal inflammatory disease. Lonicera caerulea, which is rich in polyphenolic compounds, has been shown to exert antioxidative and anti-inflammatory effects. The research evaluates the dietary impacts of Lonicera caerulea pomace, its polyphenol-rich extract, and fiber-rich residue on colitis symptoms. Colitis was induced with 2.5% DSS (dextran sulfate sodium) aqueous solution after continuous feeding of customized Lonicera caerulea feed for 2.5 weeks. The results indicate that the intake of the polyphenol-rich extract has an effect in preventing colitis in mice, but the effect is less than that by the pomace itself, and the fiber residue alone does not prevent the condition when ingested. The pomace and polyphenol-rich extract have a positive regulatory effect on the gut microbiota of mice with colitis, and the intake of Lonicera caerulea pomace significantly restores 15 metabolites in mice with colitis, significantly improving five metabolic pathways, including steroid biosynthesis, with the regulation of metabolites and metabolic pathways being significantly correlated with the gut microbiota.

Keywords: Lonicera caerulea; anti-inflammatory; gut microbiota; metabolomics; polyphenol.

Figure 1

Experimental scheme and effects of LCP and its fractions on DSS-induced mice colitis symptoms. (A) Experimental scheme. (B) Body weight change. (C) Food intake. (D) Water consumption. (E) Disease activity index. (F) Colon length. (G) Representative images of the mouse colon. Data are presented as mean ± SD (n = 8). * p < 0.05, ** p < 0.01, *** p < 0.001, and “*” marked in the B and E diagrams indicate significant differences compared with the DSS group. “ns” denotes comparisons with no significance. One-way ANOVA with post-hoc Tukey test.

Figure 2

Effects of LCP and its fractions on colon histology and the inflammatory response. (A) Histological examination, scale bars, 20 μm. (B) Histological score. (C) MPO activity in colon tissues. (D) Concentration of TNF-α in serum. Data are presented as mean ± SD (n = 8). * p < 0.05, ** p < 0.01, *** p < 0.001, and “ns” denotes comparisons with no significance. One-way ANOVA with post-hoc Tukey test.

Figure 3

Effect of LCP and its fractions on colonic tight junction proteins in colitis mice. (A) Immunohistochemical staining images, scale bars, 50 μm. (B–D) Mean optical densities of ZO-1, Occludin, and Claudin-1 in colon tissues. Data are presented as mean ± SD (n = 8). * p < 0.05, ** p < 0.01, *** p < 0.001, and “ns” denotes comparisons with no significance. One-way ANOVA with post-hoc Tukey test.

Figure 4

Changes in abundance and diversity of the gut microbiota. (A) Species accumulation curve. (B) Venn diagram. (C) Chao 1 index. (D) Shannon index. (E) Simpson index. (F) PCoA plot of structural changes in the gut microbiota. (G) NMDS plot of structural changes in the gut microbiota. Data are presented as mean ± SD (n = 8). * p < 0.05, ** p < 0.01, *** p < 0.001, and “ns” denotes comparisons with no significance. One-way ANOVA with post-hoc Tukey test.

Figure 5

Phylum-level analysis of the species composition of the gut microbiota. (A) Phylum-level histogram. (B) Heat map. Data are presented as mean ± SD (n = 8).

Figure 6

Species with significant changes at the genus level. Data are presented as mean ± SD (n = 8). * p < 0.05, ** p < 0.01, *** p < 0.001, and “ns” denotes comparisons with no significance. One-way ANOVA with post-hoc Tukey test.

Figure 7

LEfSe analysis of different microbial groups. (A) LDA diagram. (B) LDA cluster diagram.

Figure 8

OPLS-DA scoring chart and model replacement test chart.

Figure 9

Difference abundance score chart. (A) DSS group compared to control group, (B) DSS + LCP group compared to DSS group. A DA score of 1 indicates an upregulated expression trend of all annotated differential metabolites in this pathway, and −1 indicates the opposite.

Figure 10

Spearman’s correlation heat map between the gut microbiota and differential metabolites. * p < 0.05, ** p < 0.01, *** p < 0.001.