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

以6月龄去卵巢雌性大鼠为模型，研究了膳食脂肪和蛋白质对卵巢激素缺乏所致的血浆胆固醇浓度升高的影响。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、乳脂作为膳食脂肪来源。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为膳食蛋白质来源。以AIN93G为基础饲料喂养去卵巢大鼠28d，鱼油组大鼠的血浆胆固醇浓度显著低于其他组，紫苏油组的血浆胆固醇浓度有降低的趋势。α-亚麻酸在体内转化为EPA和DHA，提示鱼油和紫苏油的降胆固醇作用可能依赖于EPA和DHA。鱼类…低密度脂蛋白受体基因表达水平呈下降趋势石油和紫苏油组比其他组多。日粮脂肪来源不影响CYP7A1基因的表达水平。粪便胆汁酸排泄量鱼油、氢化棕榈油和乳脂组高于其他组。但胆汁酸排泄量的增加并不一定会导致血浆胆固醇的降低，马铃薯蛋白、大豆蛋白和鳕鱼蛋白组的血浆胆固醇浓度显著低于酪蛋白组，而大米蛋白和小麦蛋白组的血浆胆固醇浓度则不显著。作者认为，酪蛋白血浆胆固醇浓度较高可能与其蛋氨酸含量、赖氨酸/精氨酸和蛋氨酸/甘氨酸比值高于其他膳食蛋白有关。小麦蛋白、大米蛋白、大豆蛋白和马铃薯蛋白的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的蛋氨酸含量差异不显著。鳕鱼蛋白的蛋氨酸含量、赖氨酸/精氨酸比值、蛋氨酸/甘氨酸比值均低于酪蛋白。低密度脂蛋白受体和细胞色素P7A1的表达水平不受饲料蛋白的影响。已阐明血浆胆固醇浓度受蛋白质质量的影响，但蛋白质的氨基酸组成与降胆固醇作用的关系还有待进一步研究。较少

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