Probiotics reinforce mucosal degradation of antigens in rats: Implications for therapeutic use of probiotics

Abstract

The effects of probiotics, administered with different diets, i.e., unhydrolyzed or hydrolyzed dietary antigens, on macromolecular degradation in the gut mucosa were studied. Rat pups were divided into five feeding groups at the age of 14 d. In addition to maternal milk, the milk group was gavaged daily with cows' milk and the hydrolysate group with extensively hydrolyzed whey formula, while controls received sterile saline. In addition to these diets, the milk-GG group and the hydrolysate-GG group were given probiotic bacteria, Lactobacillus GG ATCC 53103 (1010 colony-forming units per day). At 21 d, the absorption of macromolecules, horseradish peroxidase and β- lactoglobulin across patch-free jejunal segments was studied in Ussing chambers. The degree of macromolecular degradation was studied by means of HPLC gel filtration. The absorption rate of intact horseradish peroxidase differed among the feeding groups (P = 0.038). This was due to the high median (interquartile range) absorption of intact horseradish peroxidase (ng x h-1 x cm-2) in the milk group [255 (14-1332)] and supplementation with L. GG in the milk-GG group [35 (8-233)] restoring the status to the control level [22 (0-116)]. A parallel effect was seen in the hydrolysate group [100 (9-236)] vs. the hydrolysate-GG group [1 (0-13)]. A gel filtration study confirmed that larger molecules were absorbed across the mucosa in the milk group compared to the other groups. The absorption of degraded horseradish peroxidase differed between the feeding groups (P = 0.005). L. GG had a distinct effect when administered with unhydrolyzed, native protein vs. hydrolyzed protein: it increased absorption of degraded horseradish peroxidase in the milk-GG group [7310 (4763-8228)] vs. the milk group [3726 (2423-5915)], while reducing it in the hydrolysate-GG group [2051 (1463- 2815)] vs. the hydrolysate group [4573 (3759-9620)]. Our results showed that probiotics not only restore aberrant macromolecular transport, but they also have a specific effect on mucosal degradation depending on dietary antigen: adjuvant-like properties (unhydrolyzed antigen) and immunosuppressive-like properties (hydrolyzed antigen). The antigenicity of the diet therefore should be taken into consideration, when introducing novel probiotic functional foods for the management of gastrointestinal disorders.