Transfer of Apolipoproteins between Plasma Lipoproteins and Exogenous Lipid Particles

作为肠外营养液的人工脂颗粒在进入循环时不含任何载脂蛋白，尽管不含载脂蛋白，但其代谢过程与含有多种载脂蛋白的乳糜粒相似。在已知的载脂蛋白中，载脂蛋白C-II和C-III在调节富含甘油三酯的脂蛋白的水解过程中起重要作用。在体内和体外研究了与静脉输注脂肪乳剂相关的载脂蛋白的修饰。人工脂颗粒进入血浆后立即从高密度脂蛋白中获得载脂蛋白C-II和C-III。预先注射脂肪乳剂不影响载脂蛋白向人工脂颗粒的转移。当开始连续输注脂肪乳剂后，血浆中甘油三酯浓度达到平台期时，C-载脂蛋白在脂蛋白部分的分布也稳定下来。由于在体外，C-载脂蛋白从高密度脂蛋白转移到人工脂颗粒上，人工脂颗粒与C-载脂蛋白有密切的亲和力，而且没有特定的器官负责C-载脂蛋白在人工脂颗粒和血浆脂蛋白之间的转移。载脂蛋白E不能仅仅由于人工脂颗粒对载脂蛋白E的亲和力而从血浆脂蛋白转移到人工脂颗粒。

Artificial lipid particles used as parenteral nutrition solution do not contain any apolipoproteins when they are infused into the circulation.Despite the absence of apolipoproteins, the metabolism of artificial lipid particles is similar to that of chylomicrons which contain various kinds of apolipoproteins. Of the known apolipoproteins, apolipoproteins C-II and C-III are important in regulation of hydrolysis of triglycreride-rich lipoproteins. Modifications of apolipoproteins associated with an intravenous infusion of fat emulsion were investigated, in vivo and in vitro. Artificial lipid particles acquired apolipoproteins C-II and C-III from high-density lipoprotein immediately after their entry into plasma. The transfer of apolipoproteins to artificial lipid particles was not influenced by a prior injection of fat emulsion. When the concentrations of triglycerides in plasma reached a plateau after initiation of a continuous infusion of fat emulsion, the distribution of C apolipoproteins in the lipoprotein fraction also stabilized. Since C apolipoproteins moved to artificial lipid particles from high-density lipoprotein even in vitro, it has become evident that artificial lipid particles have a close affinity for C apolipoproteins, and that no specific organ is responsible for the transfer of C apolipoproteins between artificial lipid particles and plasma lipoproteins.Apolipoprotein E can not be transferred from plasma lipoproteins to artificial lipid particles simply as the result of an affinity of artificial lipid particles for apolipoprotein E.