Konjac glucomannan polysaccharide and inulin oligosaccharide ameliorate dextran sodium sulfate-induced colitis and alterations in fecal microbiota and short-chain fatty acids in C57BL/6J mice

Abstract

Background: Konjac glucomannan polysaccharide (KGM), inulin oligosaccharide (inulin) and their mixture has been shown to modulate the gut-associated lymphoid tissue immunity.

Aims: The present study was mainly to determine effects of a low-level (2% w/w) KGM and inulin and their combination on dextran sodium sulfate (DSS)-induced colitis. We also determine the potential mechanisms mediating these effects of dietary fibers.

Methods: C57BL/6J mice (6 weeks of age, eight per group) were randomly assigned to consume one of the following diets: control (DSS group) or control diet supplemented with 2% (w/w) of KGM (KGM group), 2% (w/w) of inulin oligosaccharide (inulin group) or KGM+Inulin (1%, w/w each (K+I group)) for 29 days, combined with the DSS drinking water (2% w/v) treatment on days 21-26. Another group served as vehicle was fed the control diet and given regular drinking water throughout the study. Fresh feces were collected on days 26-29. Mice were killed on day 30 after fasting. Segments of distal colon were processed for histological procedure. The remaining colonic tissues were processed to determine the colonic gene expressions of cytokines, tight junction proteins and antioxidant enzymes.

Results: The present study indicated that DSS resulted in colonic dysplasia, severe leukocyte infiltration and enhanced gene expressions of pro-inflammatory cytokines. All fiber treatments ameliorated these indices of colitis. DSS treatment reduced the colonic gene expressions of tight junction proteins and antioxidant enzymes, which were ameliorated or normalized with fiber supplementation. In addition, all fiber treatments prevented the DSS-induced alterations in the fecal microbiota and short-chain acid levels.

Conclusion: Supplementation of low-level, 2% (w/w), of KGM polysaccharide, inulin oligosaccharide and K + I reduced the DSS-induced colitis and mucosal barrier dysfunction, which was likely to be mediated by the prebiotic effects.

Keywords: Colitis; Dextran sulfate sodium; Inulin; Konjac glucomannan; Microbiota; Mucosal barrier.

Figure 1

Body weight of vehicle and DSS-treated experimental mice during days 21–29. Mean values with different superscript letter indicated significantly different across groups (P < 0.05).

Figure 2

Histology of the distal colon of vehicle and DSS-induced mice. Histology of the distal colon was observed under a 200× magnification. Scale represents 50 μm.

Figure 3

Gene expressions of cytokines in the distal colon of vehicle and DSS-induced mice. Relative gene expression was normalized using internal housekeeping gene GAPDH and compared to that of the vehicle group according to the 2^−ΔΔCt method. Bars are presented as mean and standard error of means (n 8 per group). Mean values with unlike letters are significantly different across groups as analyzed by one-way ANOVA followed by Tukey’s honestly significant difference test (P < 0.05).

Figure 4

Gene expressions of tight junction proteins in the distal colon of vehicle and DSS-induced mice. Relative gene expression was normalized using internal control gene glyceraldehyde 3-phosphate dehydrogenase (GAPDH) and compared with that of the vehicle group according to the 2^−ΔΔCt method. Bars are presented as mean and standard error of means (n 8 per group). Mean values with unlike letters are significantly different across groups as analyzed by one-way ANOVA followed by Tukey’s honestly significant difference test (P < 0.05).

Figure 5

Gene expressions of glutathione peroxidase (Gpx2), glutathione S-transferase π (Gstp1), catalase and superoxide dismutase (SOD) in the distal colon of vehicle and DSS-induced mice. Relative gene expression was normalized using internal control gene glyceraldehyde 3-phosphate dehydrogenase (GAPDH) and compared to that of the vehicle group according to the 2^−ΔΔCt method. Bars are presented as mean and standard error of means (n 8 per group). Mean values with unlike letters are significantly different across groups as analyzed by one-way ANOVA followed by Tukey’s honestly significant difference test (P < 0.05).

Figure 6

Fecal bacterial concentrations (log₁₀ counts/g feces). Bars are presented as mean and standard error of means (n 8 per group). Mean values with unlike letters are significantly different across groups as analyzed by one-way ANOVA followed by Tukey’s honestly significant difference test (P < 0.05). The fecal total bacterial concentrations were not significantly different across groups.