The evidence for the antiatherogenicity of high density lipoprotein in man

It has long been recognized that patients with clinical coronary heart disease (CHD) have, on average, higher concentrations of plasma very low density and low density lipoproteins than do healthy subjects. The same studies clearly demonstrated that coronary victims tend also to have low plasma concentrations of high density lipoprotein (HDL). It is only recently, however, that the possible significance of this second observation has been examined. Direct evidence for an inverse relationship between HDL cholesterol concentration and the prevalence of clinical CHD, independent of other plasma lipoproteins, has been provided by the Honolulu Heart and Cooperative Lipoprotein Phenotyping Studies. The Tromsø Heart and Framingham Studies subsequently demonstrated that this relationship precedes the clinical manifestation of coronary disease. More recently, angiographic studies have confirmed that the severity of existing coronary atherosclerosis is inversely related to HDL cholesterol concentration. Other investigations have shown that coronary victims also have low mean concentrations of apolipoproteins AI and AII (the major protein components of HDL), although the reduction of apoAI concentration may be less marked that that of HDL cholesterol, and preliminary findings from Tromsø have suggested that apolipoprotein AI may be less powerful that HDL cholesterol as a predictor of CHD. Such observations have supported the porposal that HDL may exert a protective effect against coronary atherosclerosis. Final comfirmation (or otherwise) of this hypothesis, however, must await the results of carefully controlled animal experiments and of regression studies in patients with angiogrphically defined atherosclerosis.