Effects of Glutamine, Curcumin and Fish Bioactive Peptides Alone or in Combination on Intestinal Permeability in a Chronic-Restraint Stress Model

Abstract

Irritable bowel syndrome (IBS), a multifactorial intestinal disorder, is often associated with a disruption in intestinal permeability as well as an increased expression of pro-inflammatory markers. The aim of this study was to first test the impact of treatment with glutamine (Gln), a food supplement containing natural curcumin extracts and polyunsaturated n-3 fatty acids (Cur); bioactive peptides from a fish protein hydrolysate (Ga); and a probiotic mixture containing Bacillus coagulans, Lactobacillus acidophilus, Lactobacillus gasseri and Lactobacillus helveticus. These compounds were tested alone on a stress-based IBS model, the chronic-restraint stress model (CRS). The combination of Gln, Cur and Ga (GCG) was also tested. Eight-week-old C57Bl/6 male mice were exposed to restraint stress for two hours every day for four days and received different compounds every day one week before and during the CRS procedure. Plasma corticosterone levels were measured as a marker of stress, and colonic permeability was evaluated ex vivo in Ussing chambers. Changes in the gene expression of tight junction proteins (occludin, claudin-1 and ZO 1) and inflammatory cytokines (IL1β, TNFα, CXCL1 and IL10) were assessed using RT-qPCR. The CRS model led to an increase in plasma corticosterone and an increase in colonic permeability compared with unstressed animals. No change in plasma corticosterone concentrations was observed in response to CRS with the different treatments (Gln, Cur, Ga or GCG). Stressed animals treated with Gln, Cur and Ga alone and in combination showed a decrease in colonic permeability when compared to the CRS group, while the probiotic mixture resulted in an opposite response. The Ga treatment induced an increase in the expression of the anti-inflammatory cytokine IL-10, and the GCG treatment was able to decrease the expression of CXCL1, suggesting the synergistic effect of the combined mixture. In conclusion, this study demonstrated that a combined administration of glutamine, a food supplement containing curcumin and polyunsaturated n-3 fatty acids, and bioactive peptides from a fish hydrolysate was able to reduce colonic hyperpermeability and reduce the inflammatory marker CXCL1 in a stress-based model of IBS and could be of interest to patients suffering from IBS.

Keywords: curcumin; fish bioactive peptides; glutamine; intestinal permeability; stress.

Figure 1

Plasma corticosterone levels and colonic permeability in response to acute (ARS) or chronic (CRS) stress models. (a,d): plasma corticosterone levels; (b,e) Lucifer yellow levels; (c,f): Alexa Dextran concentrations measured in Ussing chambers in control vs. ARS or CRS groups, respectively. Data are presented as means ± SEM. n = 8–20 per group. *, p < 0.05, Student’s t-test.

Figure 2

Effect of each selected compound administered individually on plasma corticosterone levels and colonic permeability. Normalized corticosterone levels (a) measured in plasma and Lucifer yellow (b) and Alexa Dextran (c) concentrations measured in Ussing chambers in CRS-vehicle (black bars) vs. CRS-Glutamine (Gln), CRS-Curcuméga^® (Cur) at high and low doses, CRS-Gabolysat^® (Ga) and CRS-Probiotics (Pbs) groups (red bars). n = 8–20 per group. Data are presented as means ± SEM. Data were compared by one-way ANOVA with Dunnett’s post hoc tests; *, p < 0.05 and **, p < 0.01 vs. CRS-vehicle. Dashed line represents the level observed in untreated CRS mice.

Figure 3

Effect of combined selected compounds, glutamine, Curcuméga^® and Gabolysat^® (GCG), on plasma corticosterone levels and colonic permeability. Corticosterone levels (a) measured in plasma and Lucifer yellow (b) and Alexa Dextran (c) concentrations measured in Ussing chambers in the CRS-vehicle (black bars) vs. CRS-GCG group (red bars). n = 10–19 per group. Data are presented as means ± SEM. ***, p < 0.001, Student’s t-test. Dashed line represents the level observed in untreated CRS mice.

Figure 4

Effect of each selected compound administered individually and the GCG mix on colonic tight-junction protein gene expression. (a) Normalized occludin, (b) claudin-1 and (c) ZO-1 gene expression in CRS (black bars) vs. CRS-Glutamine (Gln), CRS-Curcuméga^® (Cur) at high and low doses, CRS-Gabolysat^® (Ga) and CRS-GCG groups (red bars). n = 7–16 per group. Data are presented as means ± SEM. Data were compared by one-way ANOVA with Dunnett’s post hoc tests. Dashed line represents the level observed in untreated CRS mice.

Figure 5

Effect of each selected compound administered individually and the GCG mix on colonic inflammation-related gene expression. (a) Normalized CXCL1, (b) TNFα, (c) IL1β and (d) IL10 gene expression in CRS (black bars) vs. CRS-Glutamine (Gln), CRS-Curcuméga^® (Cur) at high and low doses, CRS-Gabolysat^® (Ga) and CRS-GCG groups (red bars). n = 4–18 per group. Data are presented as means ± SEM. Data were compared by one-way ANOVA with Dunnett’s post hoc tests (a–c) or Kruskal–Wallis with Dunn’s post hoc tests (d). *, p < 0.05 vs. CRS-vehicle. Dashed line represents the level observed in untreated CRS mice.