Fructose Stimulated Colonic Arginine and Proline Metabolism Dysbiosis, Altered Microbiota and Aggravated Intestinal Barrier Dysfunction in DSS-Induced Colitis Rats

Abstract

The dysbiosis of intestinal microbiota and their metabolites is linked to the occurrence and development of metabolic syndrome. Although fructose has been proven to be associated with worsened mucus in the colon, its mechanism remains unclear. In this study, we evaluated the relatively low intake of sucrose and fructose in the experimental colitis of Sprague Dawley rats by investigating the microbiome and metabolome. Results showed that sucrose and fructose significantly reduced body weight, colon length and increased inflammation infiltration in colon. Sucrose and fructose worsen colon functions by inhibiting the expression of tight junction (TJ) protein ZO-1 and increasing the level of lipopolysaccharide neoandrographolide (LPS) in plasma, while fructose was more significant. Furthermore, sucrose and fructose significantly changed the composition of gut microbiota characterized by decreasing Adlercreutzia, Leuconostoc, Lactococcus and Oscillospira and increasing Allobaculum and Holdemania along with reducing histidine, phenylalanine, arginine, glycine, aspartic acid, serine, methionine valine, alanine, lysine, isoleucine, leucine, threonine, tryptophan, tyrosine, proline, citrulline, 4-hydroxyproline and gamma amino butyric acid (GABA). Metabolome results showed that fructose may aggravate experimental colitis symptoms by inducing amino metabolism dysbiosis in the colon. These findings suggested that fructose worsened colitis by manipulating the crosstalk between gut microbiota and their metabolites.

Keywords: arginine and proline metabolism dysbiosis; fructose; metabolome.

Figure 1

The addition of sugar, especially fructose, promoted the symptoms of DSS-induced colitis in rats by decreasing ZO-1 expression and increasing LPS levels. (A) Animal experimental design; (B) body weight of different groups (n = 10); (C) colon length appearance and statistical analysis (n = 6); (D) colon H&E staining (100×); (E) relative expression of ZO-1 (n = 6); (F) LPS level in serum, n = 8. Data represent the following: means ± SEM, * p ˂ 0.05, ** p ˂ 0.01, *** p ˂ 0.001. Different letters indicate a significant difference, p ˂ 0.05.

Figure 2

Fructose induced more oxidative stress and inflammatory levels in serum: (A) malondialdehyde (MDA) level in serum; (B) interleukin-6 (IL-6) level in serum; (C) interleukin-8 (IL-8) level in serum; n = 8. Data represent the following: means ± SEM, * p ˂ 0.05, ** p ˂ 0.01, **** p ˂ 0.0001.

Figure 3

Effects of sucrose and fructose on the overall structure of gut bacteria within different conditions of rats. (A) α-diversity analysis; (B) PCoA score plot of colon contents based on Jaccards. n = 7. Data represent the following: means ± SEM, * p ˂ 0.05.

Figure 4

Alteration of sucrose and fructose on gut bacterial community in rats (n = 7). (A,B) Relative abundance of the fecal microbiota at the phylum and genus level. (C) Cladogram of different groups (LDA > 2). (D) Presentative differential taxa, n = 7. Data represent the following: means ± SEM; different letters indicate significant difference, p ˂ 0.05.

Figure 5

Metabolic profiles of sucrose and fructose in the colon contents of rats. (A,B) PCA score of colon contents in different groups; (C,D) OPLSA-DA permutation: C1. Sac vs. Fru; C2. DssSac vs. DssFru.

Figure 6

Sucrose and fructose alter colonic metabolite profiles. (A) Heatmap of sucrose and fructose’s alteration of metabolites; (B) KEGG annotation analysis of the altered metabolites based on the differences between sucrose and fructose; B1 KEGG annotation barplot of Sac vs. Fru; B2 KEGG annotation barplot of DssSac vs. DssFru. The arginine and proline metabolism pathways are highlighted with red circles in the figure.

Figure 7

Heatmap of Spearman’s correlation between differential taxa and metabolites of rat, * p < 0.05, ** p < 0.01.