Tanaka K, Sugano M
Laboratory of Nutrition, Nagasaki Prefectural Women's Junior College, Japan.
J Nutr Sci Vitaminol (Tokyo). 1989 Aug;35(4):323-32. doi: 10.3177/jnsv.35.323.
The effects of the supplementation of methionine (Met), cystine (Cys), and glycine (Gly) to soybean protein or casein on serum and liver lipid levels were studied in rats. Rats were fed cholesterol-free diets containing 25% soybean protein or casein supplemented with 0.75% Met, 2.5% Gly, or a combination of these two for 4 weeks. The addition of Met to soybean protein caused a significant increase in serum cholesterol and this was slightly ameliorated when Gly was given simultaneously. In rats fed casein diets, serum cholesterol tended to decrease when Gly, or Met and Gly were added. A simultaneous supplementation of Met and Gly to casein resulted in a reduction of hepatic cholesterol. Cystine added at the 0.6% level did not cause demonstrable changes in lipid concentrations except for a drop in serum triglyceride of the casein group. When 2.0% Gly was added to cholesterol-enriched diets containing 20% protein, serum cholesterol decreased significantly only when the protein source was casein and the level attained was comparable to that observed in rats fed soybean protein. Liver cholesterol was also markedly decreased by the addition of Gly to casein. The results suggest a possible role of Gly in the regulation of serum cholesterol levels by dietary protein.
研究了在大鼠中，向大豆蛋白或酪蛋白中添加蛋氨酸（Met）、胱氨酸（Cys）和甘氨酸（Gly）对血清和肝脏脂质水平的影响。给大鼠喂食不含胆固醇的日粮，日粮包含25%的大豆蛋白或酪蛋白，并添加0.75%的Met、2.5%的Gly或这两者的组合，持续4周。向大豆蛋白中添加Met会导致血清胆固醇显著升高，同时添加Gly时这种升高会稍有改善。在喂食酪蛋白日粮的大鼠中，添加Gly、或Met和Gly时，血清胆固醇有降低的趋势。同时向酪蛋白中添加Met和Gly会使肝脏胆固醇减少。添加0.6%的Cys除了使酪蛋白组的血清甘油三酯下降外，未引起脂质浓度的明显变化。当向含20%蛋白质的富含胆固醇的日粮中添加2.0%的Gly时，只有当蛋白质来源为酪蛋白且降低水平与喂食大豆蛋白的大鼠中观察到的水平相当时，血清胆固醇才会显著降低。向酪蛋白中添加Gly也会使肝脏胆固醇显著降低。结果表明Gly在膳食蛋白质对血清胆固醇水平的调节中可能发挥作用。
