Cholesterol-Lowering Activity of Various Undigested Fractions of Soybean Protein in Rats

Abstract

The undigested high-molecular-weight fraction (HMF) of soybean protein prepared after exhaustive digestion by microbial proteases significantly decreased serum cholesterol levels to approximately 45% (p less than 0.05) of those observed with the parent protein in rats fed diets containing cholesterol (0.5%) and sodium cholate (0.125%). HMF bound conjugated bile salts in vitro and significantly increased fecal excretion of both neutral and acidic steroids by 65-95% and 80-170% more, respectively (p less than 0.05), than did the intact protein. Extraction of HMF with methanol slightly decreased the activity, but the methanol-soluble fraction was not regarded as a principal determinant. Soybean saponin at the dietary level equivalent to that contained in HMF did not effectively lower serum cholesterol. The activity was not necessarily duplicated even when methanol-treated fractions were recombined. Further degradation of the methanol-extracted HMF by various proteases resulted in loss of activity. HMF obtained after pepsin digestion exerted a potential similar to that of HMF prepared after digestion by microbial proteases.

Hypocholesterolemic and Angiotensin I Converting Enzyme-Inhibiting Activity of Trypsin-Hydrolysed Bovine Casein

“…After 4 h hydrolysis, the 10 kDa permeate showed 50.7% cholesterol-reducing activity, which is significantly (P<0.05) higher than that of the unhydrolysed crude casein. These results are in agreement with the findings of Sugano et al [19] who showed that the hypocholesterolemic peptides of soybean protein had molecular masses of 1-10 kDa. In that case, the hypocholesterolemic properties of the peptides were attributed to the inhibition of cholesterol absorption and increases in the faecal excretion of steroids (Mine & Shahidi [20]).…”

Effects of Dietary Soybean Peptides on Hepatic Production of Ketone Bodies and Secretion of Triglyceride by Perfused Rat Liver

“…Sugano et al has shown that undigested high-molecular-weight peptides might effectively bind bile acids in the intestine and thereby increase fecal excretion of both neutral and acidic steroids, resulting in induction of the hypocholesterolemic effect. [7][8][9][10] Thus, high-molecular fraction in soybean peptides can modulate cholesterol metabolism through the stimulation of fecal steroid excretion.…”

“…[1][2][3][4] The hypocholesterolemic activity of soybean protein as compared with casein is known to be due to suppression of intestinal cholesterol absorption, 5,6) promotion of fecal steroid excretion, [7][8][9][10] increases in the cholesterol removal rate through the LDL receptor, 1,3,4) and so on. 11,12) Soybean protein has also been found to have triglyceride-lowering action.…”

“…It has been reported that soybean peptides also have a hypocholesterolemic effect. [7][8][9][10] This is because the peptides contain a high-molecular-weight (undigested) fraction, which is responsible for the stimulation of fecal steroid excretion, [7][8][9][10] but the effects of soybean peptides containing a low-molecular-weight (digested) fraction on cholesterol metabolism are unclear. Also, no consistent results have been obtained for the effect of soybean peptides on triglyceride metabolism.…”

Efeito do consumo de tremoço (Lupinus albus) e seu isolado protéico no metabolismo do colesterol em hamsters hipercolesterolemizados

“…A dieta contendo a farinha integral de tremoço apresentou a maior redução de colesterol total e colesterol não-HDL, uma possível causa seria justamente a menor digestibilidade dessa proteína presente nessa dieta, provavelmente devido aos outros componentes bioativos presentes no grão integral, como saponinas, fitoesteróis e fibras (MARTINS et al, 2005 SALTER, 1998;FUKUI et al, 2004). Sugano (1990) e Nagaoka et al (1999) relataram que peptídeos hidrofóbicos de alto peso molecular obtidos após hidrólise enzimática de isolado protéico de soja tem um efeito redutor de colesterol semelhante à proteína intacta. Esses peptídeos resistentes às enzimas tripsina e peptidase, conhecidos como fração não digerível, podem ter propriedade similar aquelas da fibra dietética na sua habilidade de se ligar aos ácidos biliares e colesterol, e assim, aumentar a sua excreção fecal.…”