Low Density Lipoprotein Receptor Activity Is Modulated by Soybean Globulins in Cell Culture

Abstract

The effects of major storage globulins from soybean on cholesterol homeostasis were investigated in vitro and in vivo systems. The low density lipoprotein (LDL) uptake and degradation was studied both in human skin fibroblasts (HSF) and in a human hepatoma cell line (Hep G2). In Hep G2 cells a dose-dependent increase of both uptake and degradation of 125I-LDL was induced by the 7S globulin, whereas the 11S globulin exerted a lesser effect that was not dose-related. In HSF cells the 11S globulin increased the uptake of 125I-LDL to a greater extent than did 7S globulin; in this cell line, LDL degradation was not stimulated by either of the globulins. Rats fed a casein-cholesterol diet were treated daily with the 11S or 7S globulins for 2 wk. The administration of soybean globulins significantly reduced cholesterolemia (-35 and -34% with 7S and 11S globulins, respectively, vs. controls). Liver membrane preparations from the casein-cholesterol-fed rats showed a nonsignificant increase in the maximal binding of labeled cholesterol-rich lipoprotein fraction (beta-VLDL) to high affinity receptors.

Soybean β-Conglycinin Diet Suppresses Serum Triglyceride Levels in Normal and Genetically Obese Mice by Induction of β-Oxidation, Downregulation of Fatty Acid Synthase, and Inhibition of Triglyceride Absorption

“…The amino acid composition of the -conglycinin diet might be one of the factors, but some specific -conglycinin-derived protein fragment(s) or peptide(s) might play key roles in these multiple events. In this regard, Lovati et al 35,36) showed that soy -conglycinin and peptides derived from it specifically interacted with human hepatoma cells (HepG2) and activated LDL receptor activity. These -conglycinin effects on hepatocytes might represent the putative mechanism of -conglycinin serum TG-lowering effect.…”

Recent Progress in Research and Technology on Soybeans

“…In linear regression analysis, the threshold level of soy intake at which the effects on blood lipids became significant was 25 g. Thus, soy protein represents a safe, viable, and practical nonpharmacologic approach to lowering cholesterol. It is clear that soybean storage proteins possess the hypocholesterolemic effect in themselves, because the plasma total cholesterol of the rats fed casein-cholesterol diets was reduced by 35 and 34% by the administration of purely isolate bconglycinin and glycinin, respectively (Lovati et al, 1992). The exact mechanism of the cholesterol reduction has not been established fully.…”

Nutraceuticals in Dyslipidemia: An Alternative Approach

“…It was noted that the hypocholesterolemic effect of soy protein is mainly due to 7S globulin while 11S is the inactive component. The 7S unit is mainly involved in upregulation of LDL-R [39,40]. The effectiveness of soy protein as proven in various studies reinforces the recommendation to increase soy protein in the diet for cardiovascular protection.…”