Masashi Nagata

Increases in calcium absorption with ingestion of soluble dietary fibre, guar-gum hydrolysate, depend on the caecum in partially nephrectomized and normal rats.

Effects of feeding soluble dietary fibre on apparent Ca absorption and the contribution of the caecum to Ca absorption were examined in five-sixths nephrectomized (NPX) and normal rats with or without caecectomy in four experiments. It is known that Ca absorption is lowered by renal failure. In the first experiment the amounts of femur Ca increased linearly with increasing dietary Ca up to 3.0 g Ca/kg diet in intact rats. Partial nephrectomy decreased apparent Ca absorption in rats fed on diets containing 3-0 and 4.5 g Ca/kg diet. In the NPX groups, Ca absorption in rats fed on the diet containing guar-gum hydrolysate (GGH; 50 g/kg diet; 3.0 g Ca/kg diet) was significantly higher than that in rats fed on a fibre-free diet, and the increase in Ca absorption with GGH feeding was completely abolished by caecectomy. Also, ingestion of GGH increased Ca absorption in normal rats, but not in normal, caecectomized rats. Mg absorption was also increased with GGH feeding and was decreased with caecectomy in NPX and normal rats. In experiments which used caecectomized rats, coprophagy was prevented with an anal cup to avoid re-ingestion of faecal Ca. We conclude that ingestion of the soluble dietary fibre, GGH, increased apparent Ca absorption in NPX and non-NPX rats, and the caecum was responsible for these increases in Ca absorption.

Oral tolerance is not influenced by oral application of oil-emulsified proteins

A 2-week program of feeding protein antigens as an oil-in-water emulsion to naive mice elicited a significant serum IgG antibody response, whereas their aqueous preparations did not at all. The unresponsive immune state that had been developed after feeding aqueous antigen was not disturbed by subsequent oral challenge with the same antigen in the presence of oil. These results suggest that the principle of oral tolerance is a feasible strategy for prophylaxis of hypersensitization to protein antigens, where protein tolerogens, in this case, are to be given without any additives at their first introduction.

Enhancing Effect of Dietary Oil Emulsions on Immune Responses to Protein Antigens Fed to Mice

Repeated intragastric administration of β-lactoglobulin (β-Lg) with emulsified soybean oil elicited an antigen-specific, systemic humoral immune response in different strains of mice. The antibody response was enhanced as the dose of oil was increased and the particle size of emulsions was decreased. Feeding of aqueous β-Lg could induce the antibody response only when emulsified oil was fed almost simultaneously. However, the emulsion-driven humoral immune response was not observed when mice were treated with anti-CD40 ligand antibody or in athymic mice. It is likely that the intestinal coexistence of emulsified oil with dietary antigens modulates the immune system to crucially support B cell response. A practical application of the present results to the prevention of cow’s milk protein sensitization in infants is proposed.

1-Kestose consumption during pregnancy and lactation increases the levels of IgA in the milk of lactating mice.

To examine the effect of dietary supplementation with 1-kestose on the IgA levels in milk, BALB/c mice were fed diets with or without 5% 1-kestose during pregnancy and lactation. The total and specific IgA levels in the milk were measured at 7 and 14 days after delivery. A two-way ANOVA with repeated measures resulted in a significant effect of 1-kestose-supplementation on total IgA concentrations (p < 0.05) and the level of anti-Bacteroides IgA (p < 0.05). A significant positive correlation was found between the mean count of Bacteroides spp. in maternal feces and the total IgA concentration in maternal milk (r = 0.55, p < 0.05), suggesting a potential link between the gut and mammary gland immune system. In conclusion, this study demonstrated the effects of dietary prebiotics on milk IgA production. Graphical Abstract Consumption of 1-kestose, a major component of fructooligosaccharides, by pregnant and lactating mice increased the total IgA concentration in the mouse milk.