Cham B E
Chem Biol Interact. 1978 Mar;20(3):263-77. doi: 10.1016/0009-2797(78)90105-9.
Lipids, which serve as a source of energy and are an important constituent of cell membrane structure, are readily stored in the body. By definition they are insoluble in water. Specific proteins called apolipoproteins interact with lipids to form soluble lipid-protein complexes called lipoproteins. It is in this form that the major lipids--cholesterol, triglyceride and phospholipid--circulate in plasma. Unesterified fatty acids, another major lipid group, are bound to albumin in the circulation. The plasma lipoproteins are complex macromolecules composed of lipids, apolipoproteins and carbohydrates. The relative proportions of these components differ markedly between lipoprotein classes. Hyperlipidemia is a term used for increased concentrations of plasma cholesterol and/or triglycerides. Any one plasma lipid is present in several types of lipoproteins. Thus, hyperlipidemia implies the presence of hyperlipoproteinemia. The latter has important therapeutic implications. Most of the recent attempts at classification have been directed at the lipoprotein level of plasma lipid organization. Decreased concentrations of lipids in plasma can be achieved by altering the rates of metabolism of lipoproteins. Decrease in lipoprotein synthesis, increased catabolism or impaired release from cells into the blood stream may all result in a decrease of plasma lipids. Drugs which affect one or more of these factors are used to treat hyperlipoproteinemia. In order to elucidate the mechanism of action of hypolipidemic drugs it is necessary to understand the lipoprotein defect at the molecular level. This requires a more detailed knowledge of lipoprotein metabolism than is presently available for most of the hyperlipoproteinemias. This paper will review some of the generally accepted properties of the plasma lipoproteins, describe some difficulties which hamper the understanding of lipoprotein metabolism, and identify possible mechanisms by which drugs may affect lipoprotein metabolism.
脂质作为一种能量来源，是细胞膜结构的重要组成部分，很容易在体内储存。根据定义，它们不溶于水。一种叫做载脂蛋白的特殊蛋白质与脂质相互作用，形成称为脂蛋白的可溶性脂质 - 蛋白质复合物。主要脂质——胆固醇、甘油三酯和磷脂——就是以这种形式在血浆中循环的。另一类主要脂质——未酯化脂肪酸，在循环中与白蛋白结合。血浆脂蛋白是由脂质、载脂蛋白和碳水化合物组成的复杂大分子。这些成分的相对比例在不同的脂蛋白类别之间有显著差异。高脂血症是指血浆胆固醇和/或甘油三酯浓度升高的术语。任何一种血浆脂质都存在于几种类型的脂蛋白中。因此，高脂血症意味着存在高脂蛋白血症。后者具有重要的治疗意义。最近大多数分类尝试都是针对血浆脂质组织的脂蛋白水平。通过改变脂蛋白的代谢速率可以降低血浆中脂质的浓度。脂蛋白合成减少、分解代谢增加或从细胞释放到血流中受损都可能导致血浆脂质减少。影响这些因素中的一个或多个的药物被用于治疗高脂蛋白血症。为了阐明降血脂药物的作用机制，有必要在分子水平上了解脂蛋白缺陷。这需要比目前大多数高脂蛋白血症所掌握的更详细的脂蛋白代谢知识。本文将综述血浆脂蛋白的一些普遍认可的特性，描述一些阻碍理解脂蛋白代谢的困难，并确定药物可能影响脂蛋白代谢的可能机制。
