Risks for hyperlipidemia

Abstract

The predisposition for the development of hyperlipidemia rests almost equally on genetic and environmental factors and their interplay. Because one of the least understood factors is the duration of exposure to risk, the authors have chosen to review here some of the genetic factors and some of the relatively long-term environmental factors, such as diet and drug therapies, that are known to increase the risk of hyperlipidemia and likely the predisposition to cardiovascular disease.

PIP: Some of the genetic factors and environmental factors such as diet and drug therapies that are known to increase the risk of hyperlipidemia and possibly the predisposition to cardiovascular disease are reviewed. The cholesterol associated with the low-density lipoproteins (LDL), accounting for 60-75% of the plasma levels, is responsible for the powerful and direct relationship which exists between plasma cholesterol and coronary heart disease. Also, the cholesterol that accumulates in atheromatous lesions is derived primarily from plasma LDL. Hyperlipidemia is defined by elevated levels of the plasma levels; the risk for atherosclerosis is associated with the classification types IIa, IIb, III, and possibly IV, a classification system based on phenotypic manifestations of increased lipoprotein fractions. The Lipid Research Clinics Program reports data on plasma lipid and lipoprotein cholesterol distributions of a large-scale screening of white men and women (both with and without sex hormone usage) aged 20-59 years in the US. They found age-related trends for rising triglycerides and cholesterol with differences between the sexes clearly demonstrated. It has been established that normolipemic individuals are not immune to the development of atherosclerosis. The recent focus on the apolipoprotein moieties has revealed a number of normolipemic dyslipoproteinemias associated with tissue lipid infiltration. Multifactorial population studies provide a strong case for the powerful role of the environment, i.e., predominantly dietary intake of total fat, saturated fat, saturated fats, and calories, in hyperlipidemia. According to the Seven Countries Study, populations with higher levels of cholesterol and LDL cholesterol (and increased atherosclerosis) have saturated fat intakes of 10% or more of calories. Migration studies of Japanese populations in Japan and in the US also show the influence of diet. As was shown early on, oral contraceptive (OC) use predisposes to the development of hyperlipidemia. OCs also predispose to other cardiovascular risk factors that, when combined with smoking, bring about a greatly magnified risk for myocardial infarction. Also reviewed in terms of their effect on the lipoprotein profile are antihypertensive therapies, retinoids, and hypolipidemic agents. Regarding genetic predisposition, single-gene mutations in apoproteins, lipoproteins, and some of the enzymes involved in lipoprotein may underlie disorders of hyperlipoproteinemia or hypolipoproteinemia.