Effects of fat and protein on cholesterol metabolism at the time of estrogen lack

在切除卵巢的6月龄雌性大鼠中，研究了膳食脂肪和蛋白质对卵巢激素缺乏相关的血浆胆固醇浓度升高的影响。以富含油酸的红花油、富含亚油酸的红花油、紫苏油、鱼油、氢化棕榈油、乳脂为日粮脂肪源。以酪蛋白、大米蛋白、大豆蛋白、马铃薯蛋白、小麦蛋白和鳕鱼蛋白作为饲粮蛋白质源。去卵巢大鼠分别饲喂含有试验脂肪和试验蛋白质的AIN93G饲料28 d。鱼油组血浆胆固醇浓度显著低于其他各组，紫苏油组血浆胆固醇浓度有低于其他各组的趋势。α-亚麻酸在体内转化为EPA和DHA，提示鱼紫苏油降低血浆胆固醇浓度的作用可能与EPA和DHA有关。鱼油组和紫苏油组ldl -受体mRNA水平有较低的趋势。CYP7A1 mRNA水平不受饲料脂肪来源的影响。鱼油组、氢化棕榈油组和乳脂组的粪便胆汁酸排泄量高于其他各组。然而，胆汁酸粪便排泄的增加并不一定导致血浆胆固醇的降低。马铃薯蛋白组、大豆蛋白组和鳕鱼蛋白组血浆胆固醇浓度显著低于酪蛋白组，而水稻蛋白组和小麦蛋白组血浆胆固醇浓度不显著低于酪蛋白组。有研究认为，酪蛋白较高的血浆胆固醇浓度可能与酪蛋白的蛋氨酸含量、赖氨酸/精氨酸比和蛋氨酸/甘氨酸比高于其他膳食蛋白质有关。小麦蛋白、大米蛋白、大豆蛋白和马铃薯蛋白中蛋氨酸含量低于酪蛋白，而小麦蛋白、大米蛋白、大豆蛋白和马铃薯蛋白之间差异不显著。鳕鱼蛋白的蛋氨酸含量、赖氨酸/精氨酸比和蛋氨酸/甘氨酸比均低于酪蛋白。低密度脂蛋白受体mRNA和CYP7A1水平不受膳食蛋白质的影响。血浆胆固醇浓度受蛋白质质量的影响，但与氨基酸组成和膳食蛋白质降胆固醇作用的关系有待进一步研究。少

The effects of dietary fat and protein on the ovarian hormone deficiency-associated increase in plasma cholesterol concentration were studied in ovariectomized 6-month-old female rats. Oleic acid-rich safflower oil, linoleic acid-rich safflower oil, perilla oil, fish oil, hydrogenated palm oil, milk fat were used as dietary fat source. Casein, rice protein, soybean protein, potato protein, wheat protein and cod protein were used as dietary protein source. Ovariectomized rats were fed the diets based on AIN93G containing each test fat or protein for 28 days.The plasma cholesterol concentration of the fish oil group was significantly lower than those of other groups, and that of the perilla oil group was a tendency lower than those of other groups. α-linoelenic acid is changed into EPA and DHA in a body, which suggests that the plasma cholesterol concentration lowering effect of fish and perilla oil might depend on EPA and DHA. The level of LDL-receptor mRNA was a tendency lower in fish … More oil and perilla oil groups than in other groups. The level of CYP7A1 mRNA was not affected by dietary fat source. The fecal excretion of bile acid was higher in fish oil, hydrogenated palm oil and milk fat groups than in other groups. However, the increased fecal excretion of bile acid did not necessarily lead to the reduction of plasma cholesterol.The plasma cholesterol concentrations of potato protein, soybean protein and cod protein groups were significantly lower than that of casein group, but those of rice protein and wheat protein were not. I has been suggested that the higher plasma cholesterol concentration of casein might depend on the higher methionine contnt, lysine/arginine ratio and methionine/glycine ratio compared other dietary protein. The content of methionine was lower in wheat protein, rice protein, soybean protein and potato protein than that in casein, however was not significant difference between wheat protein, rice protein, soybean protein and potato protein. The content of methionine, lysine/arginine ratio and methionine/glycine ratio of cod protein was lower than those of casein. The levels of LDL-receptor mRNA and CYP7A1 were not affected by dietary protein. It was clarified that the plasma cholesterol concentration was affected by the quality of the protein, but a further examination is necessary on the relation to the amino acid composition and hypocholesterolemic effect of dietary protein. Less