S. Nagaoka et al., Soy protein peptic hydrolysate with bound phospholipids decreases micellarsolubility and cholesterol absorption in rats and Caco-2 cells, J NUTR, 129(9), 1999, pp. 1725-1730
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.