METABOLISM OF APOA-IV IN HUMANS

载脂蛋白A-IV具有许多与载脂蛋白A-IV相同的结构和功能特性 I，主要存在于高密度脂蛋白中，并被认为在 甘油三酯代谢和胆固醇逆向运输。载脂蛋白A-IV 是一种多态的载脂蛋白，是几种 同工异构体已确定。ApoA-IV-2同工蛋白已被 与更低的甘油三酯和更高的高密度脂蛋白水平有关 共同的载脂蛋白A-IV-1同工蛋白。我们已经证实，两种形式的载脂蛋白A- IV在正常受试者中分解极快，平均 每天超过2池的部分分解代谢率，使载脂蛋白A-IV成为 到目前为止分析的最快分解的载脂蛋白。载脂蛋白A-IV-2 同种蛋白的分解速度比apoA-IV-1慢，这与它的 不同的体外特性。载脂蛋白A-IV血浆水平为正 与血浆甘油三酯水平有关。我们决定使用这两种方法 外源标记的放射性示踪剂和稳定的内源性标记 与载脂蛋白A-IV分解速度明显延迟的同位素相比 正常情况下。因此，较高的载脂蛋白A-IV水平与较高的 甘油三酯是由于载脂蛋白A-IV分解代谢速度的延迟，而不是 而不是增加这种载脂蛋白的合成速度。正在进行的研究 旨在确定含有载脂蛋白B的重要性 载脂蛋白在载脂蛋白A-IV代谢中的研究 载脂蛋白A-IV在高密度脂蛋白缺乏状态。 这些研究对象的年龄在18岁到42岁之间。30%的研究 受试者是女性，其中一人是非裔美国人。

ApoA-IV has many structural and functional properties in common with apoA- I, is found primarily in HDL, and has been proposed to be important in both triglyceride metabolism and reverse cholesterol transport. ApoA-IV is a polymorphic apolipoprotein and the molecular basis of several isoforms has been determined. The apoA-IV-2 isoprotein has been associated with lower triglyceride and higher HDL levels than the most common apoA-IV-1 isoprotein. We have established that both forms of apoA- IV are catabolized extremely rapidly in normal subjects, with a mean fractional catabolic rate of greater than 2 pools/day, making apoa-IV the most rapidly catabolized apolipoprotein analyzed to date. The apoA-IV-2 isoprotein has a slower catabolic rate than apoA-IV-1, consistent with its different in vitro properties. ApoA-IV plasma levels are positively associated with plasma triglyceride levels. We determined using both exogenously-labeled radiotracers and endogenous labeling with stable isotopes that the catabolic rate of apoA-IV was markedly delayed compared with normal. Hence, the higher apoA-IV levels seen with higher levels of triglycerides are due to a delay in the rate of apoA-IV catabolism, rather than an increased synthetic rate of this apolipoprotein. Ongoing studies are directed toward establishing the importance of apoB-containing lipoproteins in apoA-IV metabolism and investigating the metabolism of apoA-IV in HDL deficiency states. These studies included subjects of age 18 to 42 years. 30% of the study subjects were women, and one was African-American.