Comparative lipid and lipoprotein metabolism

This review summarizes a number of recent reports in several areas of lipid and lipoprotein metabolism. Absorption of dietary lipids, cholesterol synthesis, and biliary cholesterol metabolism are mentioned only briefly to be complete. Comparative aspects of lipoprotein metabolism, however, are detailed in an effort to integrate the myriad metabolic events which characterize these important lipid transport particles. Where comparative information is known, those aspects of lipoprotein metabolism that may be protective against atherogenesis in certain mammalian species are also described. Efforts to understand atherogenic resistance comparatively in animals lends a better understanding of the metabolic events leading to coronary artery disease in humans. They also provide an important basis for understanding lipid metabolism in numerous veterinary species.     

The Effect of Lecithin Supplementation on the Biochemical Profile and Morphological Changes in the Liver of Rats Fed Different Animal Fats

Sixty-four Wistar rats were divided into 8 equal groups and kept for 36 days in individual boxes. Three of the groups were given full synthetic diets containing various animal fats: beef tallow, pork fat or fish oil. A control group was fed the diets without the fat. The other four groups were fed the same diets with lecithin supplementation. At the end of experiment, sections taken from the liver were stained with haematoxylin–eosin and Sudan III to indicate fat infiltration. Liver enzyme levels, total bilirubin, albumin and two products of lipd metabolism were measured in serum from all the animals. The addition of lecithin to the diets did not influence the level of enzymes in the serum except in rats fed the diet containing beef tallow. A relationship between the type of diet, lecithin supplementation and the total cholesterol concentration in serum was observed. The concentration of HDL-cholesterol was only influenced by lecithin supplementation and that of triglycerides by the type of fat in the diet. The addition of lecithin to the diet was associated with proliferation of Kupffer cells, and an increased number of binuclear cells. Fatty degeneration of hepatocytes was less pronounced in all groups following lecithin supplementation. Lecithin supplementation of the diet did not elicit any pathological lesions and may be considered as a hepatocyte protector. This favourable effect of lecithin was most marked in the group of rats fed the fish oil.     

Lipoprotein electrophoresis differentiation of chylous and nonchylous pleural effusions in dogs and cats and its correlation with pleural effusion triglyceride concentration

Pleural effusions from 23 dogs and 25 cats hospitalized between November 1986 and April 1987 at the Veterinary Hospital of the University of Pennsylvania (VHUP) were classified as chylous (chylomicrons present) or nonchylous (chylomicrons absent) by the presence or absence, respectively, of a chylomicron band on lipoprotein electrophoresis gels of the effusions. Triglyceride concentrations, cholesterol concentrations, and cholesterol/triglyceride (C/T) ratios were compared between the chylous and nonchylous groups in each species. Cholesterol concentrations were not significantly different between chylous and nonchylous effusions in both dogs and cats. Cholesterol/triglyceride ratios of less than 1 were present in all dogs and cats with chylous effusions; however, 12% of dogs with nonchylous effusions and 50% of cats with nonchylous effusions also had a C/T ratio less than 1. Triglyceride concentrations accurately classified all effusions as chylous or nonchylous in both dogs and cats. Pleural effusions with triglyceride concentrations greater than l00 mg/dl were chylous in all cases, whereas, effusions with triglyceride concentrations less than l00 mg/dl were nonchylous in all cases.     

产胆盐水解酶植物乳杆菌降胆固醇作用的研究

采用茚三酮显色法测定了5株具有潜在益生特性的植物乳杆菌的胆盐水解酶(BSH)活性,采用邻苯二甲醛法测定了发酵上清液、菌体洗涤液和菌体破碎液中胆固醇含量,并对二者进行了相关性分析。结果表明,5株菌的BSH比活力为0.0149~0.0299U/mg总蛋白,去除胆固醇能力为37.64~47.88μg/mL。5株乳杆菌BSH活性与菌体洗涤液中胆固醇含量呈显著正相关,推断是菌株BSH水解结合胆盐生成游离胆酸,后者与胆固醇共沉淀,从而达到降胆固醇的效果。上述研究结果为利用益生菌生产具有降胆固醇功效的产品提供了理论依据。     

超声提取—气相色谱法测定油脂中胆固醇

建立了毛细管气相色谱法测定油脂中胆固醇含量的方法,改进了油脂皂化方法以及皂化完成后使用分液漏斗提取胆固醇过程中容易产生乳化、操作复杂且比较耗时的缺点,采用超声波提取胆固醇,优化了样品前处理条件.结果表明,该法在0.002mg/mL～0.500mg/mL范围呈线性(r=0.9997),检出限为20mg/kg,RSD=1.104％,回收率在81.3％～93.8％之间.     

黄酮类化合物影响卵磷脂的研究进展

黄酮类化合物对机体有重要生理功能,能促进机体脂质代谢、提高免疫功能、改善生产性能,是一类具有广阔发展前景的新型饲料添加剂。本文综述了蛋黄卵磷脂在肝脏中合成过程和转运途径,探讨黄酮类化合物能够提高蛋黄卵磷脂含量的可能性。     

苜蓿皂苷对大鼠肝脏及肝脏细胞低密度脂蛋白受体、三磷酸腺苷结合盒转运体mRNA表达的影响

本试验旨在研究苜蓿皂苷对大鼠肝脏及大鼠肝脏细胞(BRL细胞)胆固醇清除和转运途径中关键基因低密度脂蛋白受体(LDLR)、三磷酸腺苷结合盒转运体G5(ABCG5)、三磷酸腺苷结合盒转运体G8(ABCG8)mRNA表达量的影响,从个体和细胞水平初步探讨苜蓿皂苷调控胆固醇清除和转运的分子机制。采用高脂饲粮建立大鼠高脂模型,测定苜蓿皂苷对正常、高脂大鼠血清指标[总胆固醇(TC)、甘油三酯(TG)、高密度脂蛋白胆固醇(HDL-C)、低密度脂蛋白胆固醇(LDL-C)含量]和肝脏LDLR、ABCG5、ABCG8 mRNA表达量的影响;采用高糖DMEM培养液建立BRL细胞脂变模型,测定苜蓿皂苷浓度对BRL细胞活性的影响,测定苜蓿皂苷对正常、脂变细胞LDLR、ABCG5、ABCG8 mRNA表达量的影响。结果表明:1)苜蓿皂苷显著降低高脂大鼠血清中TG、TC和LDL-C的含量(P0.05);2)苜蓿皂苷显著上调正常大鼠肝脏LDLR、ABCG5、ABCG8及高脂大鼠ABCG5、ABCG8 mRNA表达量(P0.05);3)添加200、250μg/m L苜蓿皂苷显著提高了BRL细胞的活性(P0.05);4)苜蓿皂苷显著上调正常BRL细胞LDLR、ABCG5、ABCG8 mRNA表达量(P0.05),而对脂变BRL细胞各基因mRNA表达量无显著影响(P0.05)。结果提示,苜蓿皂苷可通过调控LDLR、ABCG5、ABCG8 mRNA的表达来增加肝细胞内胆固醇的清除和转运,从而降低机体胆固醇的含量。     

Effects of Quercetin on Performance and Lipid Metabolism in Laying Hens

Quercetin has a variety of biological activities. However, its application as a feed additive in poultry production is limited. In this study, the effects of quercetin on performance and lipid metabolism in Hessian laying hens were investigated and the possibility of quercetin to decrease cholesterol in eggs and Low Density Lipoprotein cholesterol(LDL-cholesterol) in laying hens were explored. A total of 240 laying hens at 29-week-old were randomly assigned to four treatments, with six replicates of 10 birds per replicate. The treatments were fed with basal diet supplemented with 0, 0.2, 0.4 and 0.6 g · kg~(-1) quercetin for 8 weeks. Layer performance, lipid concentration in livers, yolks and serum were measured at the end of the experiment. The results showed that laying rate had a quadratic correlation with the level of quercetin(p=0.056) and was maximized by the supplement level of 0.2 g · kg~(-1) diet. When the level of dietary quercetin increased, feed-egg ratio decreased. Crude fat and the total cholesterol of livers decreased by supplementation of quercetin. The total cholesterols of yolks also decreased and had a quadratic correlation with the levels of quercetin(p=0.019). Insulin increased by supplement of quercetin. In conclusion, quercetin improved the performance and reduced egg yolk cholesterol by affecting serum hormone levels.