HDL-apoAI gene expression and its kinetics in vivo

本文研究了高密度脂蛋白-载脂蛋白AI（HDL-apo AI）的代谢转换，以了解血浆HDL水平降低和升高的机制。1）我们试图测定正常日本白色家兔（对照）在有或无胆固醇、普罗布考和普伐他汀喂养的情况下HDL-apo AI的动力学参数（转换）。静脉<125>内注射131-标记的HDL，并定期采集血液样品，持续6天。根据载脂蛋白AI比放射性衰变曲线计算动力学参数。结果发现，普伐他汀+Ch组（第1组）的apo AI分解率（FCR）显著低于普伐他汀+普罗布考+Ch组（第2组）（0.546 ± 0.001）。（）0.017 /天vs.0.730（）SY. ±.载脂蛋白AI的合成率（SR），第2组低于第1组（14.76 ± 0.126）SY ± 0.05）。（）1.71 mg/kg/d vs. 11.21（）SY. ±.（）2.38 mg/kg/d，p&lt;0.1）。这些数据表明普伐他汀和普罗布考具有不同的作用 ...更多信息 对含胆固醇饮食中HDL-apo AI动力学的影响。在本实验模型中，普伐他汀与普罗布考合用并不促进HDL代谢，而是减少Apo AI的合成。与对照组相比，普罗布考或普伐他汀处理组兔apo AI mRNA水平无明显变化。2）重组人载脂蛋白AI原（rh-Met-proapo AI）在兔体内的转化率也进行了研究。发现rh-Met-proapo AI的放射性迁移到酸性更强的同种蛋白，在24小时内完全转化。因此，a）原载脂蛋白AI的蛋白水解裂解是细胞外事件，B）来自兔的转化酶对于人原载脂蛋白AI加工是功能性的，和c）将rh-Met-原载脂蛋白AI注射到兔中有助于理解兔中HDL生物合成的早期事件。3）还在纯合Watanabe遗传性高脂血症（WHHL）兔中研究了脂蛋白（a）[Lp（a）]的体内动力学，家族性高胆固醇血症的动物模型，以及脂血正常的日本白色兔（对照）。Lp（a）和LDL的分解代谢率（FCR）分别为1.355 ± 0.001和1.355 ± 0.001。0.189池/日，1.278 SY.（）0.397池/天）显著（p&lt;0.005）小于对照组（2-008（）SY. ±-.）。0.083池/日，2.855 SY.（）0.759池/天）。我们的数据充分表明Lp（a）的清除并不完全依赖于LDL受体，可能是由一些其他机制介导的。4）我们发现了六种类型的apo AI变体。如上所述，将其放射性标记并注射至家兔体内。我们没有发现apo AI变体与天然apo Al（Al_3）动力学相比的特殊途径。少

The metabolic turnover of HDL-apo AI has been studied in order to know the mechanism of low and high plasma HDL levels.1) We attempted here to determine the kinetic parameters (turnover) of HDL apo AI in normal Japanese White (control) rabbits, with or without cholesterol, probucol and pravastatin feeding. ^<125>l-labeled HDL was injected intraveneously and blood samples were taken periodically for 6 days. Kinetic parameters were calculated from the apo AI specific radioactivity decay curves. We found that the apo AI fractional catabolic rates (FCR) in rabbits fed pravastatin with Ch (group 1) were significantly less than those in rabbits fed pravastatin plus probucol with Ch (group 2) (0.546(〕SY.+-.〔)0.017 /day vs. 0.730(〕SY.+-.〔)0.126 /day, p<0.05), while the synthetic rates (SR) of apo AI was lower in group 2 than in group 1 (14.76(〕SY.+-.〔)1.71 mg/kg/day vs. 11.21(〕SY.+-.〔)2.38 mg/kg/day.respectively, p<0.1) . These data indicate that pravastatin and probucol have different effects … More on HDL-apo AI kinetics in a diet which includes cholesterol. The addition of pravastatin to probucol did not enhance HDL metabolism in this expermental models, but rather reduce the synthesis of Apo AI.Total RNA was isolated from rabbit intestine under various conditions as stated above. Compared to findings in control rabbits, probucol or pravastatin treated rabbits showed no changes in mRNA level of apo AI.2) In vivo conversion of recombinant human proapoprotein AI (rh-Met-proapo AI) from E.coli to apo AI was also investigated in rabbits in vivo. It was found that the radioactivity of rh-Met-proapo AI migrated to more acidic isoproteins, the conversion was complete within 24 hours. Thus, a) the proteolytic cleavage of proapo AI is an extracellular event, b) the converting enzyme from rabbits is functional for human proapo AI processing, and c) the injection of rh-Met-proapo AI into rabbits facilities understanding of the early events of HDL biogenesis in rabbits.3) In vivo kinetics of lipoprotein(a) [Lp(a)] were also investigated in homozygous Watanabe heritable hyperlipidemic (WHHL) rabbits, an animal model of familial hypercholesterolemia, and in normolipidemic Japanese White rabbits (controls). The fractional catabolic rates (FCRs) of both Lp(a) and LDL (1.355(〕SY.+-.〔)0.189 pools per day and 1.278(〕SY.+-.〔)0.397 pools per day, respectively) in the WHHL rabbits were significantly (p<0.005) smaller than those in the control rabbits (2-008(〕SY.+-.〔)0.083 pools per day and 2.855(〕SY.+-.〔)0.759 pools per day, respectively) . Our data storongly suggest that Lp(a) clearance is not entirely dependent upon LDL receptors and may be mediated by some other mechanisms.4) We found six types of apo AI variants. They were radiolabeled and injected into rabbits as above. We found no peculiar pathway for apo AI variants compated to the kinetics of native apo Al(Al_3) . Less