Effects of arginine and lysine addition to casein and soya-bean protein on serum lipids, apolipoproteins, insulin and glucagon in rats

Abstract

1. The effect of variation in arginine: lysine on the relative cholesterolaemic effects of dietary soya-bean protein and casein was studied. Male rats received semi-purified diets containing soya-bean protein isolate or casein supplemented respectively with varing amounts of lysine or arginine for 40 d and blood samples were taken after a 5 h fast.2. Neither the addition of arginine to casein nor lysine to soya-bean protein modified the intrinsic effect of these proteins on serum cholesterol.3. Serum triglyceride levels tended to rise with increasing amounts of lysine supplementation. The opposite trend was obtained with arginine supplementation.4. Casein caused an increase in the concentration of serum insulin, but not glucagon. The glucagon level was increased proportionately with increasing amounts of arginine, while the addition of lysine showed no effect. The effects of added amino acids on serum insulin were inconclusive.5. There was a parallel increase in serum apo E and glucagon in response to arginine supplementation, while lysine supplementation increased serum apo E. 6. Thus, arginine:lysine was more effective in regulating serum triglyceride than serum cholesterol. Insulin was associated with different effects of these proteins on serum lipids.

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

“…Dietary soybean protein, when compared with casein, has been shown to lower the insulin: gluca gon ratio in rats (31) and swine (13), but the opposite was seen in gerbils (32). So far there is no coherent metabolic basis for changes in the insulin: glucagon…”

Effect of germinated and heated soybean meals on plasma cholesterol and triglycerides in rats

“…This is not really unexpected since phytosterols have no hypocholesterolemic effect in rats on a cholesterol-free diet (Sugano et al, 1977 (Jenkins et al, 1983) with a soybean protein concentrate in 10% protein diets in rats, and with a soybean protein isolate in 20% protein diets in rats (Sugano et al, 1982). Tsai et al (1987) (Satouchi and Matsushita, 1976;Gargouri et al, 1984;Wang and Huang, 1984;Lairon et al, 1985;Glenn and Chapman, 1987 …”

Metabolism of cholesterol and triglycerides in young pigs fed beef-based, soy-based, or conventional diets

“…These effects were ameliorated by the addition of 1% arginine to the diet. Results reported by Hentius and Dallinga-Thie (1979) , Mokady and Liener (1982), and Sugano et al (1982) , however, refute the lysine to arginine ratio hypothesis. Each of these studies demonstrated that the cholesterolemic effect of the test protein was not altered by the supplementation of lysine or arginine.…”