Soy protein peptic hydrolysate with bound phospholipids decreases micellarsolubility and cholesterol absorption in rats and Caco-2 cells

This experiment was designed to evaluate the effects of casein, soy protein , soy protein with bound phospholipids (SP), soy protein peptic hydrolysate (SPH) or soy protein peptic hydrolysate with bound phospholipids (SPHP) on the micellar solubility of cholesterol and the taurocholate binding capaci ty in vitro. We also evaluated the effects of various proteins on cholester ol metabolism in rats and Caco-2 cells. SPHP had a significantly greater bi le acid-binding capacity than that of SPH in vitro, Micellar cholesterol so lubility in vitro was significantly lower in the presence of SPHP compared to casein tryptic hydrolysate (CTH). The cholesterol micelles containing SP HP and SPH significantly suppressed cholesterol uptake by Caco-2 cells comp ared to the cholesterol micelles containing CTH. Consistent with these find ings in the in vivo cholesterol absorption study using radioisotopes, fecal excretion of total steroids was significantly greater in rats fed the SPHP diet compared with those fed the casein, soy protein, SP and SPH diets. Se rum:total cholesterol was significantly lower in rats fed SRHP than in thos e fed casein. The concentrations of total lipids and cholesterol in liver w ere significantly lower in the SPHP-fed group compared with all other group s. These results suggest that the suppression of cholesterol absorption by direct interaction between cholesterol-mixed micelles and SPHP in the jejun al epithelia is part of the mechanism underlying the hypocholesterolemic ac tion of SPHP. SPHP may also inhibit the reabsorption of bile acids in the i leum, thus lowering the serum cholesterol level.