Role of plasma lipoproteins in the pathogenesis of atherosclerotic disease, with special reference to sex hormone effects.

Abstract

Plasma lipoproteins constitute a complex lipid transport system. Very low-density lipoproteins transport triglycerides to peripheral tissues, whereas low-density lipoproteins are the main carriers of cholesterol. Cholesterol transport in low-density lipoprotein enters body cells by way of "low-density lipoprotein receptor pathway" but may also be taken up by macrophages by way of the "scavenger pathway." Excessive influx of cholesterol by way of the "scavenger pathway" may result in deposition of cholesterol in arterial walls and atheroma formation. In a yet incompletely known process of "reverse cholesterol transport," cholesterol is carried away from the tissues to the liver by high-density lipoproteins. The above-mentioned transport processes are regulated by a well-synchronized system that involves several enzymes and lipid transport proteins. Under normal conditions, the lipoprotein system is able to balance the flow of cholesterol and other lipids in both directions between the liver and peripheral tissues. This delicate balance may be disturbed by many factors, including contraceptive steroids. The metabolic steps influenced by administration of contraceptive steroids are summarized.