Soy Protein Enhances the Cholesterol-Lowering Effect of Plant Sterol Esters in Cholesterol-Fed Hamsters

Abstract

This study aimed to investigate whether the combination of plant sterol esters (PSE) with soy protein or soy isoflavones may have extra cholesterol-lowering effects. Male hamsters (n=20/group) were fed diets containing (g/100 g diet) (A) 20 casein (control), (B) 0.24 PSE, (C) 20 intact soy protein (replacing casein), (D) 0.02 soy isoflavones, (E) 0.24 PSE plus 20 soy protein (replacing casein), or (F) 0.24 PSE plus 0.02 soy isoflavones, for 5 wk. All diets contained 0.08 g cholesterol/100 g diet. Compared with the control diet, the PSE and soy protein diets significantly lowered the plasma total cholesterol concentration by 13% (P<0.05) and 9% (P<0.05), respectively, whereas the isoflavone diet (D) had no effect. The combination of PSE and soy protein (diet E) decreased plasma total cholesterol by 26% (P<0.05). The decrease in plasma cholesterol concentration was mainly in the non-HDL fraction. In addition, the combination of PSE and soy protein significantly decreased plasma triacylglycerol concentration (37%, P<0.05) and reduced cholesterol accumulation in the liver. The abundance of hepatic LDL-receptors was not influenced by any of the test diets. PSE selectively increased fecal excretion of neutral sterols by 190% (P<0.05), whereas soy protein increased fecal excretion of neutral sterols and bile acids by 66% (P<0.05) and 130% (P<0.05), respectively. The combination of PSE and soy protein increased the fecal excretion of neutral sterols and bile acids compared with PSE and soy protein alone. In conclusion, the combination of PSE and soy protein more dramatically lowers plasma lipids than the individual ingredients.

Phytosterol stearate esters elicit similar responses on plasma lipids and cholesterol absorption but different responses on fecal neutral sterol excretion and hepatic free cholesterol in male Syrian hamsters

“…Whereas stearic acid-enriched phytosterol esters fed to hamsters at 5% of the diet lowered non-HDL cholesterol [6], our 2.5% PSE treatments did not lower plasma total, non-HDL, or HDL cholesterol. In contrast, hamsters fed a much lower amount (0.24% of the diet) of phytosterol esters made with unsaturated fatty acids (canola oil) exhibited reductions in plasma non-HDL cholesterol [30,31]. We recently reported that phytosterol esters containing unsaturated fatty acids (oleate) are hydrolyzed in vitro to a much greater extent than phytosterol esters containing saturated fatty acids [22], suggesting that hydrolysis and liberation of free sterol may be important factors in decreasing cholesterol absorption and/or plasma non-HDL cholesterol concentration.…”

“…When fed PSE at 2.5% of the diet-assuming approximately 5% hydrolysis and the fact that the sterol moiety is 60% of PSE mass-the maximum amount of free phytosterol liberated from hydrolysis would be equivalent to feeding free phytosterol at 0.075% of the diet. In comparison, feeding 0.24% phytosterol esters made with unsaturated fatty acids [30,31], assuming 90% hydrolysis, would be equivalent to feeding free phytosterol at 0.13% of the diet. If cholesterol-lowering efficacy is indeed dependent on the presence of free phytosterol, then our treatment using stearate esters may have had the disadvantage of resisting hydrolysis and limiting the amount of free phytosterol.…”

JNK-Mediated SREBP-2 Processing by Genistein up-regulates LDLR Expression in HepG2 Cells

“…Dietary soy isoflavones, including genistein, have received great attention as anti-atherogenic foods due to their lipid-improving effects [15][16][17][18][19], but in vivo and in vitro findings regarding their total and/or LDL cholesterol-lowering effects have been inconsistent [20][21][22][23][24][25]. Some studies report that dietary supplementation with genistein, a strong bioactive soy isoflavone, lowers total and LDL-cholesterol levels [23,24], while others describe no effect of soy isoflavones on the concentration of LDL-cholesterol even when vascular function is improved [25].…”

Effect of genistein on cholesterol metabolism-related genes in a colon cancer cell line

“…In these connections, soy isoflavones have been reported to have a variety of biological activities including estrogenic [32], antioxidative [19], anti-osteoporotic [1] and anticarcinogenic [18] activities. Furthermore, recent clinical trials [2] and animal studies [4,21,33] also showed that dietary soy proteins or ISF reduce the risk factors for cardiovascular diseases, lowering triglyceride, total and low density lipoprotein (LDL) cholesterol levels and increasing the ratio of HDL/LDL cholesterol. However, the reported beneficial health effects were quite variable in different studies and the lack of understanding in the molecular mechanisms by which lipid metabolism is impacted, may contribute a major part to the discrepancies.…”