Effect of Supplementation of Sulfur-Containing Amino Acids to a Low-Soy Protein Diet Containing Cholesterol on Plasma Cholesterol Levels in Rats Tokik

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1 Effect of Supplementation of Sulfur-Containing Amino Acids to a Low-Soy Protein Diet Containing Cholesterol on Plasma Cholesterol Levels in Rats Tokiko MIZUNO, Hiroko ABE, Ryuji HIRANO and Koji YAMADA Department of Food and Nutrition, Faculty of the Science of Living, Koriyama Women's College, Koriyama 963 Nippon Eiyo Shokuryo Gakkaishi (J. Jpn. Soc. Nutr. Food Sci.) 41, (1988) A study was carried out to examine the effects of the levels of dietary protein and supplemented sulfur-containing amio acids, such as methionine, cystine, cysteine, homo-cystine, S-methyl-L-cysteine, cysteic acid or taurine, on plasma cholesterol levels in growing rats fed a low-soy protein diet containing cholesterol. Hypercholesterolemia was produced by feeding rats a 8.1% soy protein isolate (SPI) diet containing 0.5% cholesterol and 0.25% sodium cholate. An increase in the level of dietary SPI resulted in decreased plasma and liver cholesterol levels and an increase in the level of plasma HDLcholesterol. Supplementation of methionine, cystine, cysteine or homo-cystine had an effect of reducing body weight loss, and at the same time significantly decreasing the plasma cholesterol level. Supplementation of S-methyl-L-cysteine, cysteic acid or taurine had little effect on either the plasma cholesterol level or body weight. Supplementation of methionine to the low-spi diet had little effect on the level of plasma HDL-cholesterol. These results indicate that hypercholesterolemia caused by a low-spi diet containing cholesterol may be due to a deficiency of dietary methionine. (Received March 9, 1988)

2 Table 1. Composition (g/100 g) of experiment dieta) (Exp. I). Chol: cholesterol, SPI: soy protein isolate. a) Protein content 7%.

3 Vol.41 No Table 2. Composition of control diet (Exp. VI). (A) Composition of a control diet. (B) Composition of an amino acid mixture. Table 3. Effects of rice or soy protein isolate on the growth, plasma and liver cholesterol levels in rats (Exp.I). Chol: cholesterol, SPI: soy protein isolate,hdl: high density lipoprotein. Values (means }SE for 5 rats) with different alphabetical superscripts within a line aresignificantly different(p<0.05).

4 Table 4. Effects of dietary soy protein isolate level on the growth, plasma and liver cholesterol levels in rats fed on a diet containing cholesterol and cholic acid (Exp. II) SPI: soy protein isolate, HDL: high density lipoprotein. Values (means +SE for 5 rats) with different alphabetical superscripts within a line aresignificantly different (p<0.05). Table 5. Effects of methionine and threonine on the growth, plasma and liver cholesterollevels in rats fed on a soy protein isolate diet containing cholesterol and cholic acid (Exp.III). HDL: high density lipoprotein. Values (means } SE for 5 rats) with different alphabetical superscripts within a line are significantly different (p<0.05).

5 Vol.41 No Table 6. Effects of cystine, homocystine, S-methyl-L-cysteine, cysteine, cysteic acid and taurine on the growth, plasma and liver cholesterol levels in rats fed on a soy protein isolate diet containing cholesterol and cholic acid (Exps. IV and V). Cys-cys : cystine, Homo-cys-cys: homocystine, SMLC: S-methyl-L-cysteine, Cys: cysteine, Cys A: cysteic acid. Values (means }SE for 5 rats) with different alphabetical superscripts within a column of the same experiment are significantly different (p<0.05) Table 7. Effects of 50% deficiency and 50% excess of methionine in diet on the growth, plasma and liver cholesterol levels in rats fed on a diet containing cholesterol and cholic acid (Exp. VI). HDL: high density lipoprotein. Values (means } SE for 5 rats) with different alphabetical superscripts within a line are significantly different (p<0.05).

Vol.41 No. 6 1988 2) Yokogoshi, H., Yasuda,A., Quazi, S. and Yoshida, A.: Agric. Biol. Chem., 49, 2865 (1985) 3) Carroll, K.K. and Hamilton, R.M.G.: J. Food Sci., 40, 18 (1975) 4) Carroll, K.K.: Fed.

7 Vol.41 No ) Yokogoshi, H., Yasuda,A., Quazi, S. and Yoshida, A.: Agric. Biol. Chem., 49, 2865 (1985) 3) Carroll, K.K. and Hamilton, R.M.G.: J. Food Sci., 40, 18 (1975) 4) Carroll, K.K.: Fed. Proc., 41, 2792 (1982) 5) Park, M.S.C., Kudchodkar, B.J. and Liepa, G.U.: J. Nutr., 117, 30 (1987) 6) Nagata, Y., Ishiwaki, N. and Sugano, M.: J. Nutr., 112, 1614 (1982) 7) Yashiro, A., Oda, S. and Sugano,M.: 115, 1325 (1985) J. Nutr., 8) Iwami, K., Sakakibara, K. and Ibuki,F.: Agric. Biol. Chem., 50, 1217 (1986) 9) Gibney, M.J.: Atherosclerosis, 47, 263 (1983) 10) Huff, M.W. and Carroll, K.K.: J. Nutr., 110, 1676 (1980) 13) Zak, B.: Am. J. Clin., 27, 583 (1958) 14) Folch, J., Lees, M. and Sloane-Stanley, G.H.: J. Biol. Chem., 226, 497 (1957) 15) Fletcher, M.J.: Clin. Chim. Acta, 22, 393 (1968) 17) Nath, N., Harper, A.E. and Elvehjem, CA.: Can. J. Biochem. Physiol., 37, 1375 (1959)

8 18) Fillios, L.C. and Mann, G.V.: Metabolism, 3, Metab., 27, 386 (1983) 16 (1954) 25) Seidel, J.C., Nath, N. and Harper, A.E.: J. Lipid Res., 1, 474 (1960) 20) Sugiyama, K., Kushima, Y. and Muramatsu, K.: Agric. Biol. Chem., 48, 2897 (1984) 21) Sugiyama, K., Kushima, Y. and Muramatsu, K.: Agric. Biol. Chem., 49, 3455 (1985) 22) Renaud, S.: Proc. Soc. Exp. Biol. Med., 121, 452 (1966) 29) Nishida, T., Ueno, A. and Kummerow, F.A.: 23) Itokawa, Y., Inoue, K., Sasagawa, S. and Fujiwara, J. Nutr., 71, 379 (1960) M.: J. Nutr., 103, 88 (1973) 24) Serougne, C. and Rukaj, A.: Ann. Nutr.

Table 1 Components of corn dietary fibers

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