Digestion of Gluten-Derived Immunogenic Peptides along the Gastrointestinal Tract of the Growing Pig as a Model for the Adult Human Is Enhanced with Simultaneous Consumption of Exogenous Proteases.

Abstract

Background: Digestion of gluten-derived immunogenic peptides along the gastrointestinal tract (GIT) is not well established.

Objectives: This study aimed to map the digestion of gluten-derived immunogenic peptides along the GIT using the growing pig as a human adult model and actinidin as a model exogenous protease.

Methods: Entire male pigs 9 wk of age [n = 54, 19.3 ± 1.9 (mean ± SD) kg bodyweight] were fed whole wheat soda bread either with yellow kiwifruit (0 U protease actinidin activity/mL fresh juice) or green kiwifruit (27.0 U protease actinidin activity/mL fresh juice) for 8 d. Pigs were killed at 0, 20, 60, 120, and 300 min postprandially. Entire gastrointestinal contents were collected to determine the hydrolysis of wheat proteins in the stomach and the presence of immunogenic peptides along the GIT. Polynomial regression analysis was conducted to determine the treatment, time, and their interaction effects.

Results: In the stomach, the mean rate of digestion of wheat proteins was 0.08 ± 0.006% per minute (mean ± standard error), whereas the mean rate of reduction of immunogenic peptides (R5 epitopes) was 3.4 ± 0.1 mg/min. This resulted in a mean rate of 3.2 ± 0.7 mg/min of the R5 epitopes entering the small intestine. At 300 min postprandial, R5 epitopes reached the large intestine. All these values were influenced when the protease actinidin was present in the meal. For instance, actinidin doubled (P < 0.05) the rate of digestion of wheat proteins in the stomach and subsequently reduced the rate of R5 epitopes entering the small intestine (0.6 ± 0.4 mg/min) and the amount released (P < 0.05) into the large intestine.

Conclusions: Digestion of gluten immunogenic peptides is limited along the GIT, but it can be enhanced by a simultaneous intake of proteases.