Iwao Shimaoka

Hypocholesterolemic effect of buckwheat protein extract in rats fed cholesterol enriched diets

Abstract To investigate the effects of buckwheat protein on cholesterol metabolism, we prepared an enriched protein extract from buckwheat flour. The rats were fed a cholesterol-rich semipurified diet containing the buckwheat protein extract, soybean protein or casein as protein source for 3 wks. There was no significant difference in food consumption and growth rate among the rats fed three protein sources. Plasma cholesterol levels were decreased in the rats fed the buckwheat protein extract diet compared to the rats fed the soybean protein or casein diet. Concentrations of hepatic cholesterol were also significantly decreased in the rats fed the buckwheat protein extract diet as compared to the rats fed other protein diets. These results suggest that buckwheat protein is one of the dietary factors available for improvement of cholesterol metabolism.

Feeding of buckwheat protein extract reduces hepatic triglyceride concentration, adipose tissue weight, and hepatic lipogenesis in rats

Abstract The objective of this study was to examine effects of feeding buchwheat protein extract (BWPE) on hepatic and plasma lipids, fat pad weights and activities of enzymes relating to lipid metabolism in tissues of rats. Rats were fed a semipurified diet containing either buckwheat protein extract or casein for 3 weeks. Food consumption and growth rate were unaffected by dietary treatment. Hepatic triglyceride concentration and the weights of epididymal and perirenal fat pad were significantly lower in rats fed BWPE compared with those fed casein diet. BWPE feeding caused lower activities of hepatic glucose-6-phosphate dehydrogenase and fatty acid synthase, but did not affect the activity of hepatic carnitine palmitoyltransferase I. In addition, BWPE caused increases in fecal fat and nitrogen. These results demonstrated that feeding BWPE causes reductions in hepatic triglyceride concentration and fat pad weights, and suggested that these reductions might be ascribed to lower activities of hepatic lipogenic enzymes and to lower digestibility of fat and protein. Furthermore, analysis of plasma free amino acids showed marked increases of glycine and arginine in rats fed BWPE compared with rats fed casein, raising the possibility that these alterations in plasma amino acids lead to reduction in body fat.

Purification of a copper binding peptide from the mushroom Grifola frondosa and its effect on copper absorption

The present studies were undertaken to investigate the effect of a copper binding peptide on copper bioavailability. This peptide was extracted from the fruit bodies of the mushroom, Grifola frondosa, and purified to a single peptide using gel filtration and ion exchange chromatography. The purified copper binding peptide was an acidic peptide of molecular weight 2,240 in which four amino acids (aspartic acid, glutamic acid, serine, and glycine) occupied about 84% of total residues, and possessed specific properties to bind copper or to maintain copper in the soluble state at physiological pH. Molar ratio of the peptide and copper binding was 1.01. This peptide, when added to the mucosal solution in the in vitro experiment using everted intestinal sac of the rat, could significantly increase the amount of copper transported across the intestinal cells, compared with the addition of casein or its digestive peptides. These data suggest that this peptide enhances copper absorption in the small intestinal tract by increasing the amount of soluble copper.

Effects of a copper-binding peptide from the mushroom Grifolafrondosa on intestinal copper absorption

Abstract The effect of a copper-binding peptide, purified previously from the fruit bodies of the mushroom, Grifolafrondosa, on copper absorption was investigated by using portal cannulated rats under unanesthetized and unrestrained conditions. When the copper-binding peptide was infused into the duodenum together with copper, the amount of copper in portal blood was significantly increased compared with the absence of this peptide. Furthermore, the remarkable accumulation of copper in the liver was also observed. These results suggest that the copper-binding peptide enhances copper intestinal absorption and accumulation in the liver.