Effects of methionine and cystine on the cholesterol concentrations in the serum and liver of cholesterol-fed chicks
1996
Ueda, H. (Ehime Univ., Matsuyama (Japan). Coll. of Agriculture) | Fukui, W.
experiments were conducted to study of effects of methionine and cystine on the cholesterol concentrations in the serum and liver of chicks fed diets containing 1% cholesterol. Soybean protein isolate (SPI) and casein wee used as protein sources providing 14% and 20% crude protein in diets. Casein was fortified with arginine and glycine. Thus, all experimental diet were deficient in sulfur-containing amino acids. Increasing the dietary protein content decreased serum and liver cholesterol concentrations, irrespective of protein source. The addition of methionine to SPI diets lowered the serum cholesterol concentration, but not the liver cholesterol content. The effect of methionine was not observed in casein-fed chicks. Serum cholesterol concentrations were decreased by the addition of methionine, homocystine, N-acetylmethionine and cystine to the SPI diet containing 14% crude protein. This effect was accompanied by the improved growth rate with the exception of cystine. On the other hand, homoserine, taurine, potassium sulfate and choline chloride did not have a hypocholesterolemic action nor a growth-promoting effect. While adding methionine beyond the requirement had little effect on the serum cholesterol concentration, excess cystine tended to lower them. SPI contains more cystine than casein does. However, feeding SPI diets did not always show a hypocholesterolemic action compared with casein diets. These results indicated that methionine and cystine were not positively involved in the control of serum cholesterol concentrations in chicks
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