Effects of Dietary Fiber on Fecal Concanavalin A-binding Glycoprotein in Rats

Abstract

This study investigates the relationship between the dietary components and quantitative changes in fecal concanavalin A-binding glycoprotein (CBGP) derived from small intestinal epithelia in rats. Although fecal CBGP increased with increasing protein content in the diet, the increase in fecal CBGP due to dietary protein was much smaller than that resulting from the addition of pectin, cellulose or Gobo dietary fiber (GDF) to the diet. The increasing effect of 10% GDF by weight added to a 200/0 casein high-sucrose diet (HSD) on fecal CBGP was the most pronounced without producing any gastrointestinal disorders, whereas that from the addition of pectin to HSD at a level of 5% significantly decreased the intestinal sucrase activity. A similar increase in fecal CBGP was observed when rice bran dietary fiber, carrot dietary fiber, Hiziki or Wakame was added to HSD, but these increasing effects on fecal CBGP were independent of their insoluble-soluble ratio. This and our previous observations suggest that such dietary fiber may prompt the renewal and exfoliation of small intestinal epithelia.In the previous studies,1,2) we suggested the presence of a concanavalin A-binding glycoprotein (CBGP) in the gastrointestinal tract and feces of rats. Afterwards, CBGP could be isolated from the stomach, small intestine, cecum, and feces, and was found to be at a higher level in the small intestine than in the'others 3 ) and to be localized in its luminal surface. We recently found that CBGP could be isolated from both the feces of germ-free rats and of the conventionalized rats, but not from the intestinal microflora.4 ) Therefore, the origin of the fecal CBGP was considered to be the luminal surface, i.e. the epithelium, of the small intestine. On the other hand, it has recently become clear that the mucosa of the small intestine is very sensitive to various nutritional conditions 5 ,6); the rate of cell proliferation and the morphology of the villi are influenced by dietary components, and especially by unabsorbed polysaccharides. Accordingly, quantitative changes in fecal CBGP that reflect changes in the exfoliation and renewal of epithelial cells in the small intestine may serve as a criterion for representing the relationship between ingested food components and the luminal surface of the small intestine. Thus, this present study was undertaken to observe the relationship between quantitative changes in fecal CBGP and dietary fiber intake, and to investigate the effect of dietary components on the renewal of epithelia in the small intestine. Materials and MethodsAnimals and diets. Male rats of the Wi star strain weighing approximately 100 g were obtained from Japan SLC, Shizuoka, Japan. They were individually housed in suspended wire-mesh cages in a room kept at 21 to 23°C, with lighting regulated to automatically provide a 12-h light and dark cycle (lighting-up between 8:00 and 20:00). The rats were fed on a basal diet ad libitum for 7 days before the start of the experiments. The composition of the basal diet (HSD) was a...