Elucidation of novel functions of cholesterol and its metabolites using genetic manipulation in mice

利用小鼠基因操作阐明胆固醇及其代谢物的新功能

基本信息

批准号：
17390266
负责人：
ISHIBASHI Shun
金额：
$ 8.84万
依托单位：
Jichi Medical University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2005
资助国家：
日本
起止时间：
2005 至 2007
项目状态：
已结题

项目摘要

Cholesterol biosynthetic pathway is divided into two pathways: sterol pathway and non-sterol pathway. Then non-sterol pathway supplies various substances such as isoprenoids, dolichol, Haem A and ubiquinones. HMG-CoA reductase (HMGCR) produces mevalonate which is a precursor of both sterol and non-sterol pathways, whereas squalene synthase (SS) produces squalene which contributes only to sterol pathway. In the present study, we used Cre-LoxP system to disrupt genes of HMGCR or SS in a liver-specific manner to dissect out the functions of the respective enzymes in the liver. Liver-specific HMGCR knockout mice (L-HMGCRKO) were lethal at 1 month after the birth due to fulminant hepatic failure. Plasma cholesterol levels were reduced only by 10% and hepatic cholesterol biosynthesis was not reduced. mRNA expression of SREBP2 was induced, while expression of Cyp7A was reduced. The hepatocytes were filled with triglycerides. Liver-specific SS knockout mice (L-SSKO) showed transient hepatomegaly with liver dysfunction. Although hepatic VLDL production rate was reduced, hepatic cholesterol biosynthesis was not reduced at least in in vivo setting. In conclusion, HMGCR is essential for normal liver function and survival, while SS is dispensable. Normal cholesterol biosynthesis in both models suggests the presence of metabolic bypass pathway which produces cholesterol in the absence of these key enzymes in cholesterol biosynthesis.

胆固醇生物合成途径分为两种途径：固醇途径和非固醇途径。然后，非肉酚途径提供各种物质，例如异普尼，多利果醇，Haem A和泛氨基酮。 HMG-COA还原酶（HMGCR）产生甲硅酸盐酸盐，这是固醇和非甲醇途径的前体，而小矛烯合酶（SS）则产生仅对固醇途径贡献的棘孢子。在本研究中，我们使用CRE-LoxP系统以肝特异性方式破坏HMGCR或SS的基因，以剖析肝脏中各个酶的功能。肝脏特异性的HMGCR敲除小鼠（L-HMGCRKO）在出生后1个月因暴发性肝衰竭而致死。血浆胆固醇水平仅降低10％，肝胆固醇生物合成并未降低。诱导SREBP2的mRNA表达，而CYP7A的表达降低。肝细胞充满了甘油三酸酯。肝特异性SS敲除小鼠（L-SSKO）显示出肝功能障碍的瞬时肝肿大。尽管肝VLDL的产生率降低了，但至少在体内环境中，肝胆固醇生物合成并没有降低。总之，HMGCR对于正常的肝功能和生存至关重要，而SS是可分配的。两种模型中的正常胆固醇生物合成都表明存在代谢旁路途径，在胆固醇生物合成中没有这些关键酶的情况下，它会产生胆固醇。