No abstract

The effect of genetic factors on the serum levels of some but not all lipids appears to decrease with age. Early rearing environment appears to remain an important factor in relation to levels of total cholesterol later in life, but it has less effect on other serum lipids and apolipoproteins in the elderly.

In a study of 307 white patients who underwent coronary angiography, the relationship of coronary artery disease (CAD) to plasma levels of lipoprotein Lp(a) No. 4, 758-765, 1986. THE ASSOCIATION between coronary artery disease and a plasma lipoprotein migrating on agarose gel or cellulose acetate electrophoresis as a distinct pre-beta, band was reported independently in 1972-1973 from several laboratories.'-3 The activity of the pre-beta, lipoprotein4 was soon discovered to be identical to Lp(a) plasma antigenic activity, discovered by Berg in 1963,5 and results of qualitative assays for Lp(a) likewise were associated with various manifestations of coronary artery disease.4 6 7 Studies using quantitative assays of plasma Lp(a) have tended to confirm an association with coronary artery disease, but thus far statistically significant associations have been reported from these studies only in the context of retrospective subgroup analysis8' 9 or dichotomization of Lp(a) lev-

The Lp(a) lipoprotein is structurally related to low-density lipoprotein but is found in lower plasma concentration. It has been associated with coronary disease in several white populations. To test the generalizability of this association, we measured serum Lp(a) by quantitative immunoelectrophoresis in 303 Hawaiian men of Japanese ancestry with a prior myocardial infarction (MI) and in 408 population-based controls. Mean values were 17.1 and 13.7 mg/dL (0.171 and 0.137 g/L), respectively. Increased risk for MI was shown mainly for men in the upper quartile of the Lp(a) lipoprotein distribution (greater than or equal to 20.1 mg/dL [greater than or equal to 0.201 g/L]). Odds ratios at younger than 60, 60 to 69, and 70 years of age or older were 2.5, 1.6, and 1.2 times those for men in the lower three quartiles, respectively. In a multiple logistic model the association with MI remained significant and was not explained by differences in total cholesterol levels, high-density lipoprotein or low-density lipoprotein cholesterol levels, subscapular skin fold, systolic blood pressure, history of smoking, alcohol consumption, or age. We conclude that Lp(a) is an important attribute that should often be considered when coronary heart disease risk is assessed.

Lipoprotein Lp(a) is an atherogenic subfraction of plasma lipoproteins which has been studied predominantly in white populations. We quantified Lp(a) by electroimmunoassay in plasma from 105 black and 134 white healthy men and women. Results were correlated with clinical variables and plasma levels of lipids, other lipoproteins, and apolipoprotein (apo) B determined by radioimmunoassay. Black subjects had levels of Lp(a) that averaged twice those of whites (p < 0.001). Among blacks, Lp(a) levels showed a bell-shaped frequency distribution, while among whites the distribution was strongly skewed, with the highest frequencies at low levels. Contrary to previously published results, the apo B levels in our study correlated significantly, though weakly, with Lp L ipoprotein Lp(a) is a cholesterol-rich lipoprotein that can be identified by its characteristic Lp(a) antigenic activity in human plasma.12 The apoproteins of lipoprotein Lp(a) include apolipoprotein (apo) B and apo (a), the antigenic determinant.2 Lipoprotein Lp(a) migrates as a distinct prebeta, band on agarose gel electrophoresis 1 and shows an apparent hydrated density in the range of 1.05 to 1.12 g/ml on ultracentrifugation.2 It is identical to the "prebeta," or the "sinking-prebeta" lipoprotein. 34 Catabolic rates and pathways of lipoprotein Lp(a) resemble those of iow density iipoprotein (LDL). 56 Other metabolic aspects are obscure but appear to be distinct from those of LDL 7 - Despite the fact that lipoprotein Lp(a) typically carries less than 15% of the cholesterol in plasma, levels of this lipoprotein are strongly and positively associated with coronary heart disease.3 ' A i a " Plasma levels of apo B also are strongly associated with the risk for coronary heart disease, and in certain situations, apo B appears to impart risk independently of total plasma cholesterol or LDL cholesterol.12 " 15However, there are few prevalence data in which both Lp(a) and apo B have been measured in the same group of individuals. 4 Such data are needed to clarify the interactive roles of Lp(a) and apo B in iipid metabolism and atherogenesis.Further understanding may be gained by measuring these putatively atherogenic entities within population groups that differ in their average risk of cardiovascular disease. As measured at autopsy, blacks showed less propensity for atherosclerosis than whites, 16 -17 and black men have relatively low mortality from coronary heart disease.1819 Thus far, the comparison of atherogenic apolipoprotein levels in black versus white individuals is limited to qualitative Lp(a) determinations;