Steroid-Binding Peptides from Dietary Proteins

Abstract

SummaryThe undigested high-molecular weight fraction (HMF) of soybean protein prepared after exhaustive digestion either by microbial proteases or by pepsin exerted a remarkable hypocholester olemic activity compared to the parent protein in rats fed cholesterol-enriched diets. HMF bound in vitro with bile salts and stimulated fecal excretion of both neutral and acidic steroids far more than did soybean protein. Extraction of HMF with methanol slightly decreased the activity, but the methanol soluble fraction was not regarded as a principle determinant. Further degradation of the methanol-extracted HMF by various proteases resulted in loss of activity. Bile acid binding capacity of HMF from other vegetable proteins was lower than that from soybean protein.

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.…”

“…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.…”

“…[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.…”

Dietary Soybean Peptides Containing a Low-Molecular Fraction Can Lower Serum and Liver Triglyceride Levels in Rats

“…Soybean peptides containing high-molecular-weight (undigested) peptide fractions, obtained through the digestion of soybean protein isolate (SPI), are believed to play an important role in the hypocholesterolemic effect of soybean proteins (6)(7)(8)(9). High-molecular-weight soybean peptides are responsible for bile acid-binding, which results in the stimulation of fecal steroid excretion (6)(7)(8)(9).…”

“…The various mechanisms underlying the hypocholesterolemic action of soybean protein include the suppression of intestinal cholesterol absorption, promotion of fecal steroid excretion, and increases in the rate of low-density lipoprotein (LDL) receptor-mediated cholesterol removal (3)(4)(5)(6)(7)(8)(9)(10)(11). Soybean peptides containing high-molecular-weight (undigested) peptide fractions, obtained through the digestion of soybean protein isolate (SPI), are believed to play an important role in the hypocholesterolemic effect of soybean proteins (6)(7)(8)(9). High-molecular-weight soybean peptides are responsible for bile acid-binding, which results in the stimulation of fecal steroid excretion (6)(7)(8)(9).…”