PILOT STUDIES OF VLDL KINETICS IN HUMANS

要了解脂肪组织脂解和肝脏VLDL-甘油三酯生成之间的动力学关系，需要精确测量FFA流量和VLDL-甘油三酯周转的方法。我们开发了一种用于体外标记极低密度脂蛋白-甘油三酯的技术。该程序包括通过超速离心法分离极低密度脂蛋白颗粒，并在无菌条件下通过超声波掺入[~3H]-三油酸脂。我们发现这种放射性标记的极低密度脂蛋白颗粒在电泳性、胆固醇与甘油三酯的比率和载脂蛋白B100浓度方面与天然极低密度脂蛋白没有区别。用大小排除高效液相色谱法分离单个脂蛋白组分，我们发现含有纯化的VLDL颗粒的样品与全血浆中未经处理的VLDL颗粒洗脱相同。贴标签过程可以在无菌的情况下进行。该方案调查体外标记的极低密度脂蛋白颗粒是否具有与体内生产的极低密度脂蛋白甘油三酯相似的动力学特性。这些研究已经完成。我们证明了使用体内和体外技术分离、纯化和标记人极低密度脂蛋白颗粒是可能的。由于志愿者在GCRC逗留期间难以充分控制饮食，其中两项研究得出的数据不太理想。然而，总的来说，我们在体外和体内标记极低密度脂蛋白的结果都令人满意。已经计划进行更多的研究，以更仔细地评估体外标记的极低密度脂蛋白的代谢。

Understanding the kinetic relationship between adipose tissue lipolysis and hepatic VLDL-triglyceride production requires methods to precisely measure FFA flux and VLDL-triglyceride turnover. We have developed a technique for ex-vivo radiolabeling of VLDL-triglyceride. The procedure involves isolation of VLDL-lipoprotein particles by ultracentrifugation and incorporation of [3H]-triolein by sonication under sterile conditions. We have found such radiolabeled VLDL particles indistinguishable from native VLDL with regard to electrophoretic properties, cholesterol to triglyceride ratio and apo-B 100 concentration. Using size exclusion HPLC to separate individual lipoprotein fractions we have found that samples containing purified VLDL particles elute the same as to unprocessed VLDL particles in whole plasma. The labeling process can be conducted sterilely. This protocol investigates whether ex-vivo labeled VLDL-particles have kinetic properties similar to in-vivo produced VDL-triglycerides. These studies are completed. We demonstrated that it was possible to isolate, purify, and label human VLDL particles using both in vivo and ex vivo techniques. Because of difficulties with adequate control of diet during the volunteer's stay in the GCRC, two of the studies yielded less than ideal data. In general, however, we gained satisfactory results from both ex vivo and in vivo labeled VLDL. Additional studies have been planned to more carefully assess the metabolism of ex vivo labeled VLDL.