Functionality of oligo- and polysaccharides against gastrointestinal epithelial membranes: bioadhesive and mucin-stimulating carbohydrates

Within a screening on bioadhesive carbohydrates against gastrointestinal tissues rhamnogalacturonans with a low degree of esterification and linear oligogalacturonids derived from pectin as well as polygalacturonic acid showed significant bioadhesion against intestinal mucous membranes. Bioadhesion was based on the occurrence of linear, strongly acidic homogalacturonide parts in the polymers. Esterification, branching or non-linear backbone structures reduced the adhesive properties. The bioadhesive effects were concentration-dependent and due to exclusive localization of the polysaccharides on the apical membrane surface of the membranes. The bioadhesive effects were tissue specific: no adhesion occurred on porcine small intestine, while porcine stomach and porcine and human colonic membranes strongly bound the carbohydrates. The bioadhesion was due to an interaction of the acidic polymers with the endogenous mucin via bivalent positive cations as shown by in situ investigations on tissue and by a rheological mucin-galacturonide synergism. The artificial mucin layers provided protective effects on colonic mucous membranes against exogenous toxic agents.

Chito-oligosaccharides (N-Acetyl-D-glucosamintetramer and -pentamer) were found to stimulate the endogenous mucin synthesis from intestinal membranes. This stimulating effect was deduced from colorimetric methods and Western blots of mucins with lectin staining. While colonic and stomach tissue were susceptible for this mucin stimulation, membranes from ileum did not show these effects.