The serum D-xylose test as a useful tool to identify malabsorption in rats with antigen specific gut inflammatory reaction

Abstract

The inappropriate immune response to foods, such as peanut, wheat and milk may be the basis in the pathogenesis of enteropathies like coeliac and Crohn disease, which present small intestinal malabsorption. A number of recent studies have utilized d-xylose absorption as an investigative tool to study small intestinal function in a variety of clinical settings. Thus, the aim of this experimental study was to evaluate the intestinal absorption of D-xylose in an antigen-specific gut inflammatory reaction rat model. Animals of the experimental group were inoculated with peanut protein extract before their exposure to a challenge diet containing exclusively peanut seeds to induce the gut inflammatory reaction caused by peanut allergy. Our results show that systemic inoculation with peanut protein extract renders significantly higher antibody titres (5.085 +/- 0.126 units) (P < 0.0001) than control rats (0.905 +/- 0.053 units) and that the antibody titres correlate positively to an inflammatory alteration of the gut morphology (P < 0.0001). Animals pertaining to the experimental group showed an intestinal absorption of D-xylose lower than control rats (P < 0.0001). We also observed that D-xylose absorption correlates negatively with IgG titres and positively with morphometric parameters (Pearson correlation). In conclusion, the use of serum D-xylose test was useful to identify the presence of small intestinal malabsorption in our antigen specific gut inflammatory reaction rat model.

Figure 1

Total antipeanut IgG antibody titres in experimental and control rats. Left panel, the titration curve of anti-peanut protein of experimental animals (EA 1-5) and control animals (CA 1-5). Right panel, arbitrary units as the result of the mean of the area under the curves for each point of experimental and control animals. Experimental group (EG-submitted to systemic inoculation with crude peanut extract) presented significantly higher (P < 0.0001) IgG antibody titres than control group (CG-inoculated with saline).

Figure 2

Determination of the absorption curve of d-xylose in healthy rats (pilot rats group). (a) Individual absorption curve during the first 4 h after gavage. There are no statistical differences in d-xylose blood levels between animals (P > 0.05). (b) Mean values of the five rats showing a statistical difference (***P < 0.0001) between before and after gavage. There is no significant difference between the first and the third hour, but we observed a d-xylose clearance at the fourth hour. There is a statistical difference when compared the third with the fourth hour (**P < 0.05).

Figure 3

Comparison of mean absorption of d-xylose (mg/ml) in experimental and control rats, expressed as the mean of the first and the third hour bleedings. Experimental animals showed an intestinal absorption of xylose significantly lower (***) than control rats. ***P < 0.0001.

Figure 4

Differences in duodenum analysis between experimental and control animals (200×– HE). (a) Villi from a control rat presenting normal aspects. (b) Villi from an experimental rat presenting alteration of the normal morphology (oedema, congestion and a high leucocyte infiltration).