Effects of soya-bean protein and casein on serum cholesterol levels in rats

Abstract

I. The effect of the soya-bean protein isolate and casein, both given zoo g/kg diet for 3-4 weeks, on serum cholesterol was compared in male rats.2. Soya-bean protein exerted a hypocholesteraemic effect only in a cholesterol-free low-fat (10 g maize oil/kg) diet, when the lowering action appeared independent of the strain of the rat or the feeding pattern.The results obtained with diets containing cholesterol or higher levels of fats or both showed no definite pattern of response.3. Although the decrease in serum cholesterol appeared greater in a-lipoproteins than in ,&lipoproteins, the proportion of the former to total cholesterol remained almost unchanged. The concentration of serum apo A-1 was significantly lower in rats given the vegetable protein.4. Rats given soya-bean protein excreted significantly more neutral sterols. 5.The serum amino acid pattern did not reflect the difference in dietary protein. Addition of cholesterol to the diets modified the serum aminogarm, the decrease in threonine being most marked in both protein groups.6. This study shows that the hypocholesteraemic action of soya-bean protein is easily modified by the type of diet.

Effect of soybean protein on coprostanol production and cholesterol metabolism in cholesterol-fed rats.

“…In the similar experiment, the hypocholesterolaemic effect of soybean protein was observed in rats, while the proportion of cholesterol to coprostanol in feces was not changed (4,15).…”

“…Many studies were designed about the differences of the amino acid com position (12)(13)(14)(15). The aim of this study is to clarify the effect of soybean protein on the coprostanol production in the intestine and cholesterol metabolism , and there were no reports investigated from this point of view .…”

Comparison of the Mechanisms Proposed to Explain the Hypocholesterolemic Effect of Soybean Protein versus Casein in Experimental Animals

“…Perhaps, the animals fed the low-fat casein diet had a marginal deficiency of polyunsaturated fatty acids, which amplified the protein effect on serum cholesterol. This would explain why the addition of extra corn oil to the diets counteracted the differential cholesterolemic response to feeding soybean protein and casein (2). After feeding rabbits on semipurified diets containing either casein or soybean protein, but carefully balanced for residual fat and cholesterol in the protein preparations, the differential cholesterolemic effect of the proteins became very small (4).…”

“…The amount of fat in the cholesterol-free diet of rats must be as little as 1% (w/w) in order to demonstrate a hypocho lesterolemic effect of soybean protein versus casein (2). It could be suggested (3) that this actually represents a fat effect.…”

Effects of Simultaneous Intake of Soybean Protein and Diacylglycerol on Lipid Profiles and Body Fat Accumulation in Rats

“…Liver lipids were extracted with chloroformmethanol (2:1, v/v), as described by Folch et al 16) The concentrations of lipids in the liver were determined using enzymatic reagent kits (Cholesterol E-Test and Triglyceride E-Test Wako, Osaka, Japan) after drying the lipid extracts and dissolving the lipids with Triton X-100, 17) with minor modifications. Liver phospholipids concentrations were assayed by the method of Nagata et al 18) Extraction of fecal total lipids and assay of fecal bile acids. Fecal total lipids were extracted from lyophilized feces 3 times with ethanol at 70 C for 1 h. 19) The contents of fecal bile acids were assayed enzymatically using hydroxysteroid dehydrogenase, as described elsewhere, 20) with minor modifications.…”