HEPATIC SECRETION OF SMALL LIPOPROTEIN IN APOBEC-1?/? MICE - LDL RECEPTOR

本子项目是利用由NIH/NCRR资助的中心赠款提供的资源的众多研究子项目之一。子项目和研究者（PI）可能已经从另一个NIH来源获得了主要资金，因此可以在其他CRISP条目中表示。列出的机构是中心的，不一定是研究者的机构。最近的研究检查了LDL受体（LDLR）在调节小鼠肝脏脂蛋白生成和载脂蛋白B （apoB）分泌中的作用，从体内和体外方法得出了不同的结论。我们在体内和体外都重新研究了这个问题，使用apobec1 -/-小鼠来模拟人类肝脏apoB-100分泌的模式。野生型（WT） C57BL/6、apobec1 -/-、ldlr-/-和[apobec1 -/-、ldlr-/-]小鼠体内肝脏甘油三酯的生成（使用Triton WR-1339）没有变化，而[apobec1 -/-、ldlr-/-]小鼠体内apoB-100的生成（使用[35S]蛋氨酸掺入）增加了bb50倍（2倍）。尽管bbb90 %的新合成载脂蛋白ob漂浮在所有基因型血清的d < 1.006部分中，但快速高效液相色谱分离显示，来自[apobec1 -/-， ldlr-/-]小鼠的新生富甘油三酯颗粒分布在较小的（中等和ldl大小）颗粒中，而不是来自WT， apobec1 - -/-或ldlr-/-小鼠。对来自这些不同基因型的分离肝细胞的研究证实，只有[apobec1 -/-， ldlr-/-]小鼠分泌更小的颗粒，脉冲追踪分析表明，apoB-100的分泌增加，翻译后降解几乎消除。这些结果直接支持了LDLR在体内和体外调节肝脏载脂蛋白100的产生和调节富含甘油三酯的小颗粒的分泌的建议。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Recent studies have examined the role of the LDL receptor (LDLR) in regulating murine hepatic lipoprotein production and apolipoprotein B (apoB) secretion, with divergent conclusions from in vivo versus in vitro approaches. We have re-examined this question, both in vivo and in vitro, using apobec-1-/- mice to model the pattern of human hepatic apoB-100 secretion. Hepatic triglyceride production in vivo (using Triton WR-1339) was unchanged in wild-type (WT) C57BL/6, apobec-1-/-, ldlr-/-, and [apobec-1-/-, ldlr-/-] mice, while apoB-100 production (using [35S]methionine incorporation) was increased >2-fold in [apobec-1-/-, ldlr-/-] mice. Although >90% of newly synthesized apoB floated within the d < 1.006 fraction of serum from all genotypes, fast-performance liquid chromatography separation revealed that nascent triglyceride-rich particles from [apobec-1-/-, ldlr-/-] mice, but not WT, apobec-1-/-, or ldlr-/- mice, distributed into smaller (intermediate and LDL-sized) particles. Studies in isolated hepatocytes from these different genotypes confirmed secretion of smaller particles exclusively from [apobec-1-/-, ldlr-/-] mice, and pulse-chase analysis demonstrated increased secretion of apoB-100 with virtual elimination of posttranslational degradation. These results directly support the suggestion that the LDLR regulates hepatic apoB-100 production and modulates secretion of small, triglyceride-rich particles, both in vivo and in vitro.