No abstract

Prior oral exposure to partially hydrolyzed whey protein prevents epicutaneous sensitization and subsequent allergic response to β-LG in mice.

Intestinal absorption of food proteins is well known, whereas its physiological significance remains to be investigated. Various amounts (1, 10 and 50 mg) of ovalbumin were orally administered to mice and the blood kinetics were subsequently analyzed by two-site ELISA. The blood ovalbumin concentration consistently reached its maximum (7-90 ng/ml) about 20 min after the oral administration and then gradually decreased in a dose-dependent manner. Only intact (45 kDa) and truncated (40 kDa) ovalbumins were always detected in the blood independently of the administration site, intra-stomach or intra-intestine, while various fragments of the protein were observed in the gastrointestinal lumen after the oral administration. Recognition by a specific monoclonal antibody and an acidic shift of its pI value suggested that the 40-kDa truncated ovalbumin was produced by intracellular limited proteolysis at its C-terminus. Such stable absorption and blood kinetics of undigested ovalbumin in normal mice suggest some sort of physiological significance for the intestinal uptake of intact food proteins.

We tested whether increased mucin secretion due to ingestion of insoluble dietary fiber (IDF) affects small intestinal nutrient absorption in rats. Polystyrene foam (PSF) with a true expansion ratio of 54.9 was used as a model for IDF with high bulk-forming properties. In Expt. 1, rats were fed a control diet or diet containing 50 g PSF/kg for 1, 3, 5, or 7 d. Small intestinal mucin fractions were isolated, and O-linked oligosaccharide chains were measured. The luminal mucin content reached a maximum within 5 d after PSF ingestion. In Expt. 2, rats were fed a control diet or diet containing 50 g PSF/kg for 7 d, and then all rats were switched to the control diet for 1, 3, or 5 d. The increased capacity for luminal mucin secretion disappeared within 5 d after ceasing PSF ingestion. In Expt. 3, rats were fed a control diet or diet containing 70 g PSF/kg for 7 d. Glucose (1g/kg) was administered orally after 12 h of food deprivation. The blood glucose concentrations did not differ between the groups. In Expt. 4, rats were fed a control diet or diet containing 90 g PSF/kg for 14 d. At d 7, portal cannulae were installed. A mixed solution of glucose (1g/kg) and ovalbumin (OVA, 250 mg/kg) was orally administered after 12 h of food deprivation, and responses of portal glucose and OVA concentrations were monitored for 120 min. Although luminal mucin contents were almost doubled in the 9% PSF group compared with the control group, neither portal glucose nor OVA concentration differed at any time point. The results suggest that the short-term ingestion of IDF significantly increases the luminal mucin content, but that this does not disturb nutrient absorption.