Lipoprotein and apolipoprotein levels in angiographically defined coronary atherosclerosis

High-density lipoprotein subclasses and their relationship to cardiovascular disease

OBJECTIVE

To assess the clinical utility of measuring high-density lipoprotein (HDL) subfractions to assess coronary heart disease (CHD) risk.

METHODS

Literature review of 80 published investigations.

RESULTS

Measurements of HDL2b by gradient gel electrophoresis provided more consistent evidence of CHD risk than measurement of HDL2 cholesterol. Five of the seven studies that compared the extent or progression of atherosclerosis with gradient gel electrophoresis estimates of HDL subclasses (71%) assigned statistical significance to HDL2b. Ten of the 11 case-control comparisons (91%) reported lower HDL2b in cases. In contrast, of the 16 association studies relating HDL2 cholesterol and HDL3 cholesterol to extent of disease, five reported no significant relationships with either subfraction, two reported significant relationships with both HDL2 and HDL3 cholesterol, four reported significant relationships with HDL2 but not HDL3 cholesterol, and five reported relationships with HDL3 but not HDL2 cholesterol. Forty-five percent of the case-control comparisons reported that both HDL2 cholesterol and HDL3 cholesterol were significantly lower in cases than controls, 17% failed to find significance for either subfraction, and the remainder reported significantly lower values in cases for HDL2 cholesterol only (26%) or HDL3 cholesterol only (11%). On average, the case-control differences were similar for HDL2 (-0.12 ± 0.01 mmol/L) and HDL3 cholesterol (-0.10 ± 0.02 mmol/L), although relative to controls, the percent reduction was twice as great for HDL2 (-25.7 ± 2.9%) than HDL3 cholesterol (-12.1 ± 1.5%). Eight prospective studies were identified and four reported that both HDL2 and HDL3 predicted lower risk for CHD, one reported reductions in risk for HDL2 but not HDL3 cholesterol, and three reported reductions in risk for HDL3 but not HDL2 cholesterol. None of the prospective studies show that measurements of HDL cholesterol subfractions improve the identification of persons at risk.

CONCLUSIONS

HDL2 and HDL3 cholesterol do not distinguish cardioprotective differences between HDL subclasses. More extensive characterization of HDL particles by one or two dimensional gel electrophoresis, ion mobility, or ultracentrifugation may provide more specific information about CHD risk than the measurement of HDL cholesterol, HDL3 cholesterol, or HDL2 cholesterol.

Gene expression patterns in peripheral blood correlate with the extent of coronary artery disease

Systemic and local inflammation plays a prominent role in the pathogenesis of atherosclerotic coronary artery disease, but the relationship of whole blood gene expression changes with coronary disease remains unclear. We have investigated whether gene expression patterns in peripheral blood correlate with the severity of coronary disease and whether these patterns correlate with the extent of atherosclerosis in the vascular wall.

Patients were selected according to their coronary artery disease index (CADi), a validated angiographical measure of the extent of coronary atherosclerosis that correlates with outcome. RNA was extracted from blood of 120 patients with at least a stenosis greater than 50% (CADi≥23) and from 121 controls without evidence of coronary stenosis (CADi = 0).

160 individual genes were found to correlate with CADi (rho>0.2, P<0.003). Prominent differential expression was observed especially in genes involved in cell growth, apoptosis and inflammation. Using these 160 genes, a partial least squares multivariate regression model resulted in a highly predictive model (r² = 0.776, P<0.0001). The expression pattern of these 160 genes in aortic tissue also predicted the severity of atherosclerosis in human aortas, showing that peripheral blood gene expression associated with coronary atherosclerosis mirrors gene expression changes in atherosclerotic arteries.

In conclusion, the simultaneous expression pattern of 160 genes in whole blood correlates with the severity of coronary artery disease and mirrors expression changes in the atherosclerotic vascular wall.

Lipo- and apolipoproteins in a population survey subset in MONICA-Israel

Lipo- and apolipoproteins in a population survey subset in MONICA-Israel. A group of 169 healthy men and women selected at random from the population survey of the MONICA-Israel Project were screened for baseline values of serum lipoproteins and apolipoprotein A-I and B concentrations. The apolipoprotein measurements were obtained using a recently developed immunoturbidimetric assay. The study population was subdivided into age groups of 25-44 years and 45-64 years. It was found that women aged 45-64 years had significantly higher levels of apolipoprotein A-I, apolipoprotein B, total cholesterol (TC), LDL cholesterol (LDL-c) and a lower ratio of HDL-cholesterol (HDL-c) to TC (HDL-c%) than did their younger counterparts. These parameters did not differ significantly between younger and older men. The results suggest that the HDL of women over the age of 45 years contains relatively less cholesterol and more protein than the HDL of younger women. Further studies will show to what degree apolipoprotein concentrations, and their relation to lipoproteins will sharpen the assessment of coronary risk.

Evidence of reduced plasma HDL subfractions in patients with cutaneous discoid lupus erythematosus

OBJECTIVES

The aim of the present study was to evaluate the dyslipidemic profile of patients with Cutaneous Discoid Lupus Erythematosus (DLE) with particular emphasis on the levels of High Density Lipoprotein (HDL) Cholesterol and its subfractions, HDL2 and HDL3.

DESIGN AND METHOD

The study involved characterization of the lipid profile of 30 patients with diagnosed DLE (11 male and 19 female) and 34 age- and BMI-matched healthy individuals.

RESULTS

Patients with DLE presented increased serum cholesterol, triglycerides and LDL-Cholesterol levels (P < 0.001, respectively) compared to the control group, while the levels of HDL-Cholesterol (P < 0.001), as well as its subfractions, HDL2 (P < 0.001) and HDL3 (P < 0.02) were markedly decreased. In addition, the ratio of CHOL/HDL was increased in patients with DLE (P < 0.001), whereas a reduction was observed in the ratio of HDL2/HDL3 (P < 0.001) in the same group.

CONCLUSIONS

Our findings suggest that patients with cutaneous discoid lupus erythematosus have an increased risk of atherosclerosis due to the marked dyslipidemia associated with the disease. The reduced levels of HDL subfractions, HDL2 and HDL3, are believed to contribute to the dyslipidemic profile and further provide an important target for therapeutic intervention.

The significance of serum HDL phospholipid levels in angiographically defined coronary artery disease

OBJECTIVES

To evaluate discriminant serum lipid components associated with the presence and extent of coronary artery disease, with particular emphasis on the role of HDL phospholipids as an important predictor for disease severity.

DESIGN AND METHODS

Total serum lipoprotein and phospholipids levels of 157 adult male patients (grouped based on degree of coronary artery occlusion) who underwent coronary angiography were analyzed.

RESULTS

Patients showed elevated triglyceride (P < 0.001) and VLDL (P < 0.001) levels whereas a significant reduction was observed at LDL (P < 0.01), HDL (P < 0.01), and HDL-phospholipids (P < 0.001) concentrations. Correlation with disease progression (from one to three occluded vessels) showed significant rise in levels (P < 0.001) and markedly decreased HDL phospholipids (P < 0.001).

CONCLUSIONS

Triglyceride levels and HDL phospholipids are better indicators of the presence and extent of coronary artery disease compared to the other lipoproteins studied. Furthermore, the HDL phospholipids/Total Cholesterol ratio is proposed as additional information of the degree of coronary artery occlusion.

Are major risk factors for myocardial infarction the major predictors of degree of coronary artery disease in men?

Although numerous cross-sectional studies have reported associations of hypertension, hypercholesterolemia, diabetes, smoking, and/or obesity with the presence of coronary artery disease (CAD), correlations of these risk factors for myocardial infarction (MI) with the degree or progression of CAD have been less consistent. Nevertheless, these risk factors are generally assumed to be major determinants not only of MI, but of the degree of CAD as well. The present study is an attempt to evaluate the relationship of major risk factors for MI to degree of CAD. From 182 men who underwent diagnostic coronary arteriography, the 154 with CAD were selected for study. These 154 patients were divided into 2 groups, those with hypertension, hypercholesterolemia, diabetes, smoking, and/or obesity (n = 121) and those with none of these risk factors (n = 33). The mean degree of CAD in the group with risk factors for MI (44.4%) and in the group without (50.6%) was not significantly different (P =.15); nor was the increase in CAD with age augmented by the presence of these risk factors. On multiple regression analysis, none of these risk factors was associated with degree of CAD. Three other variables that were considered in this study, age, high-density lipoprotein-cholesterol (HDL-C), and free testosterone (FT), did show an independent association with degree of CAD. These findings, together with the findings of previous studies from other laboratories, raise the possibility that in men selected for coronary arteriography, age, HDL-C, and FT may be stronger predictors of degree of CAD than are blood pressure, cholesterol, diabetes, smoking, and body mass index (BMI).

Association of lipids, lipoproteins, apolipoproteins and paraoxonase enzyme activity with premature coronary artery disease

BACKGROUND AND DESIGN

The association of serum apolipoprotein (apo) A-I and apo B concentrations and paraoxonase (PON) enzyme activity with angiographically determined coronary artery disease (CAD) was investigated in Iranian non-diabetic patients with premature CAD and control participants in a sex- and age-matched case-control study.

METHODS

The study population consisted of 59 non-diabetic patients with premature CAD and 55 CAD control participants. Premature CAD was defined as the presence of angiographically proven coronary stenosis (> or =50% involvement) in men and women younger than 55 and 65 years, respectively. Apolipoprotein concentrations were measured by immunoturbidometric assay and paraoxonase/arylesterase activities by spectrophotometric assay of p-nitrophenol/phenol production following addition of paraoxon/phenylacetate to serum.

RESULTS

In CAD patients, increased concentrations of total cholesterol (215 +/- 43 compared with 193 +/- 43, P < 0.001), low-density lipoprotein cholesterol (137 +/- 46 compared with 116 +/- 39, P < 0.05) and apo B (102 +/- 24 compared with 84 +/- 17, P < 0.001) and a decreased ratio of apo A-I/apo B (1.7 +/- 0.4 compared with 2.0 +/- 0.6, P < 0.001) were observed compared to the control group. Other study variables were not significantly different between the two groups. On multiple logistic regression analysis, the only marker for discrimination between the CAD+ group and the CAD- control group was apo B level.

CONCLUSIONS

In Iranian non-diabetic patients with premature CAD, the concentration of apo B is a better marker than traditional lipids in discriminating between CAD+ and CAD- patients. The lack of significant difference in PON activity between CAD patients and control participants supports the concept of interethnic variability in PON activity and gene polymorphism observed in other studies.

Serum levels of high-density lipoprotein phospholipids correlate inversely with severity of angiographically defined coronary artery disease

In an attempt to assess the relationship between lipid abnormalities and severity of coronary artery disease, we measured serum levels of cholesterol (SC), triglycerides (TG), phospholipids (SP), low density lipoprotein cholesterol (LDL-C), very low density lipoprotein cholesterol (VLDL-C), high density lipoprotein cholesterol (HDL-C), and high density lipoprotein phospholipids (HDL-P), in 217 men undergoing diagnostic coronary arteriography. We found significantly higher mean values of HDL-P and HDL-C in men with normal coronaries, but no significant differences in the other measured lipids. While there was no significant difference in HDL-C among patients with one, two or three-vessel disease, there was a negative correlation between HDL-P levels and the severity of the disease. These observations suggest that prospective studies would be of merit to establish the relevance of HDL-P in the development of coronary artery disease.

Plasma lipoprotein particle concentrations in postmenopausal women with unstable coronary artery disease. Analysis of diagnostic accuracy using receiver operating characteristics

BACKGROUND

The contribution of plasma lipids to cardiovascular risk is usually evaluated by measuring plasma concentrations of total cholesterol, triglycerides and HDL cholesterol, and calculating LDL cholesterol concentration. We investigated plasma concentrations of apolipoproteins and lipoprotein particles in women with unstable coronary artery disease (CAD) to evaluate whether these, better than the routine lipid status, could differentiate women with and without coronary atherosclerosis.

METHODS

Blood samples for lipid analyses were collected from 119 angiographically examined postmenopausal 49-79-year-old women with unstable CAD, and from 101 age-matched controls. Mean plasma concentrations were compared and the discriminatory ability of the different variables were tested using receiver operating characteristics (ROC).

RESULTS

At coronary angiography 19% had normal vessels and 81% had coronary atherosclerosis. A disturbed triglyceride metabolism was the most pronounced lipid abnormality in women with unstable CAD and coronary atherosclerosis. ROC showed that none of the evaluated variables had a particularly high discriminatory power regarding unstable CAD or coronary atherosclerosis. The ratio cholesterol/HDL cholesterol was best with an ROC area of 0.79. Furthermore, the newer lipid variables, i.e. lipoprotein particles and apolipoproteins, were no better than the traditional variables.

CONCLUSION

Lipoprotein changes reflecting a disturbed triglyceride metabolism are most pronounced in women with unstable CAD and coronary atherosclerosis. Lipoprotein particles and apolipoproteins alone were no better than lipids and lipoproteins in separating women with from those without coronary atherosclerosis. Our study does not support the measurement of apolipoproteins and lipoprotein particles on the basis of diagnostic accuracy alone.

Upregulated synthesis of both apolipoprotein A-I and apolipoprotein B in familial hyperalphalipoproteinemia and hyperbetalipoproteinemia

A family was identified with vertical transmission through three generations with simultaneous increases of apolipoprotein A-I (apoA-I), apolipoprotein B (apoB), low-density lipoprotein (LDL)-cholesterol, and high-density lipoprotein (HDL)-cholesterol, which we have designated familial hyperalphalipoproteinemia and hyperbetalipoproteinemia (HA/HBL). Affected patients develop xanthomas and coronary artery disease (CAD). HA/HBL apoA-I and LDL-apoB were isolated and characterized. The in vivo kinetics of radiolabeled apoA-I and LDL-apoB were evaluated in two HA/HBL probands and three controls. Structural and metabolic characterization showed normal apoA-I and LDL-apoB. The kinetics of metabolism of HA/HBL apoA-I in the HA/HBL subjects showed that elevated apoA-I levels were solely due to an increased synthesis rate (15.2 to 17.6 mg/kg/d v 11.1 to 11.4 mg/kg/d) with a normal apoA-I residence time in plasma (4.2 to 5.4 days v 5.1 to 5.3 days). The elevation of LDL-apoB levels resulted from both an increased synthetic rate (16.6 to 22.9 mg/kg/d v 12.3 to 13.8 mg/kg/d) and a prolonged residence time (3.3 to 3.8 days v 1.4 to 1.9 days). In addition, we evaluated another HA/HBL proband of an unrelated family with HA/HBL to confirm the kinetic data. LDL-receptor binding studies of HA/HBL fibroblasts showed normal binding, uptake, and degradation of LDL isolated from a normolipemic control. The serum concentration of the cholesterol ester transfer protein (CETP) was normal in the studied probands. An apoB 3500 and apoB 3531 mutant, respectively, was ruled out by polymerase chain reaction (PCR). In conclusion, the site of the molecular defect in HA/HBL subjects may be involved in the coordinate regulation of metabolism for both LDL and HDL.

Apolipoprotein B and AI distributions in the United States, 1988–1991: results of the National Health and Nutrition Examination Survey III (NHANES III)

Serum apolipoproteins (apo) B and AI were measured in a probability sample of the noninstitutionalized US civilian population, ages ≥4 years, which included non-Hispanic whites, non-Hispanic blacks, and Mexican-Americans. Apo B concentrations were the same in males and females, lower in black males than in other males, low in childhood (∼0.80 g/L) and increasing to ∼1.2 g/L in adults, and higher in younger women on hormones. Apo AI was higher in females than males, higher in blacks than in others, remained constant from childhood to adulthood (∼1.35 g/L) in males, but increased with age (∼1.30 g/L to ∼1.55 g/L) in females, and was higher in women taking hormones. These are the first national probability estimates of apo B and apo AI in the US and are referable to the WHO-IFCC First International Reference Materials for apo AI and B.

Dose-response relationships of serum lipid measurements with the extent of coronary stenosis. Strong, independent, and comprehensive. ECAT Angina Pectoris Study Group

Serum lipids, lipoproteins, and more recently apolipoproteins and lipoprotein(a) [Lp(a)] have been shown to be independent risk factors for coronary vessel disease and its prognosis. However, the relationships between serum lipid levels and the extent of coronary artery disease (CAD) have not been consistently shown. Twenty-five hundred male and female patients with suspected angina pectoris were recruited from 18 European medical centers. The independent relations of total cholesterol, triglycerides, HDL cholesterol, LDL cholesterol, apo A-I and B, and Lp(a) with the presence and extent of CAD, as assessed by coronary angiography, were investigated. All of the lipid measures showed strong relations P < .0001) with the presence of CAD, defined by the existence of at least one > or = 50% coronary vessel stenosis. Total cholesterol, LDL cholesterol, apo B, triglycerides, and Lp(a) were substantially higher and HDL cholesterol and apo A-I lower in patients with CAD. The odds ratio of CAD, in the high-risk tertile of each lipid's distribution compared with the low-risk tertile, was in the range 1.5 to 2.3. Each of total cholesterol (or LDL cholesterol or apo B), HDL cholesterol (or apo A), and Lp(a) had an independent effect in predicting the presence of CAD. In addition, all lipids showed a strong association (P = .0006 for triglycerides, P < .0001 otherwise) with the extent of CAD as defined by the number of stenosed coronary vessels.(ABSTRACT TRUNCATED AT 250 WORDS)

Apolipoprotein polymorphisms fail to define risk of coronary artery disease. Results of a prospective, angiographically controlled study

BACKGROUND

Because genetic factors are believed to contribute to the etiology of coronary artery disease (CAD), it has been suggested that DNA polymorphisms at candidate loci might identify individuals at high risk for developing disease. In this regard, apolipoprotein genes represent extremely promising loci because levels of apolipoproteins and their associated lipoproteins represent a major risk factor for CAD, and rare dysfunctional mutations in these genes result in a significant risk for CAD. To date, although some reports indicate that DNA polymorphisms at these loci are associated with increased risk of CAD, other reports have failed to find such associations.

METHODS AND RESULTS

To resolve the question of whether genetic polymorphisms at apolipoprotein loci can be used to identify individuals at increased risk for CAD, we evaluated the distribution of apolipoprotein genetic polymorphisms in a large series of subjects (n = 848) undergoing coronary angiography. Blinded assessment of angiograms was used to discriminate between patients with CAD (> or = 60% stenosis of any major branch, n = 444) and control subjects without disease (< or = 10% stenosis, n = 404). A total of 12 polymorphisms were evaluated at the following loci: apolipoprotein (apo) A-I/C-III/A-IV (five restriction site polymorphisms--Msp I, Pst I, Sst I, Pvu IIa, Pvu IIb), apo B (three restriction site polymorphisms--Xba I, EcoRI, Msp I, plus an insertion/deletion polymorphism), apo A-II (Msp I polymorphism), apo C-II (Taq I polymorphism), and apo E (protein isoforms revealed by DNA analysis). All subjects were of Northern European (primarily Angloscandinavian) descent, and, within each sex, patients and control subjects were of comparable age. All 12 loci were in Hardy-Weinberg equilibrium, with no indication of population heterogeneity. As expected, patients were distinguished from control subjects by their lipid profiles and a higher frequency of known risk factors for CAD. However, analysis by log-linear models indicated that there were no significant associations between apolipoprotein polymorphisms and the risk of CAD (P = .10 to .90). The lack of association was maintained irrespective of whether the analysis was carried out for the entire sample or the contrast was made more stringent by comparing patients most likely to have a genetic component to their disease (ie, young patients with early-onset CAD) with the control subjects least likely to have genetic susceptibility (ie, older control subjects who had ample time to develop CAD).

CONCLUSIONS

Despite the fundamental role of apolipoprotein genes in lipid metabolism, we find no evidence that common genetic polymorphisms of the major apolipoprotein loci have a significant influence on the risk of developing angiographically defined CAD in this representative population. Therefore, at this time we find no support for the hypothesis that mass screening for genetic polymorphisms at candidate loci can reduce the burden of CAD by identifying a substantial proportion of high-risk individuals. Instead, it appears more appropriate to direct attention toward modifying high-risk behaviors to alleviate the consequences of traditional environmental risk factors.

Alterations in the concentration of an apolipoprotein E-containing subfraction of plasma high density lipoprotein in coronary heart disease

The concentrations of high density lipoprotein (HDL) subfractions in 100 healthy male subjects were compared with 100 newly presenting patients with myocardial infarction (MI) within 12 h of the onset of chest pain. A subfraction of HDL enriched in apolipoprotein E (apo E), separated by heparin-Sepharose affinity chromatography, was present in lower concentrations (P < 0.001) in the plasma of the coronary patients than in the control subjects. This finding was confirmed by a lower content (P < 0.02) of apo E, measured by ELISA, in the total HDL fraction isolated from the coronary patients. Gradient gel electrophoresis of the total HDL demonstrated that the coronary patients had a significantly decreased concentration of the large HDL particles, HDL2b, of mean diameter 10.57 nm and a higher concentration of the smaller-sized HDL3, especially HDL3c, of mean diameter 7.62 nm. The coronary patients had a lower concentration of HDL cholesterol than the control subjects, attributable to the HDL2 fraction, with no difference in HDL2a between the two groups. There was no difference in the concentration of plasma cholesterol or triglyceride. The distribution of apo E phenotypes was similar in the two groups. HDL2b produced the highest discriminant power between the two groups, followed by apo E-rich HDL, HDL2 and HDL3c Plasma cholesterol correlated strongly with apo E-rich HDL for control subjects but not for MI survivors. This study demonstrates that the inverse relationship between HDL cholesterol and coronary risk shown in epidemiological studies is attributable to the large, apo E-containing HDL subspecies which under some circumstances are implicated in cholesterol removal by reverse cholesterol transport. This study also suggests that the concentration of the large, apo E-containing HDL may provide a sensitive predictor for subjects at risk of developing coronary heart disease.

Independent associations between plasma lipoprotein subfraction levels and the course of coronary artery disease in the St. Thomas' Atherosclerosis Regression Study (STARS)

Associations between plasma lipoprotein subfractions and changes in coronary artery diseases (CAD) were examined in 74 men who completed the St. Thomas' Atherosclerosis Regression Study (STARS). Plasma lipoproteins were isolated by stepwise, preparative ultracentrifugation at repeated intervals during the 38-month trial. Paired coronary angiograms were quantitatively analyzed by a computerized method. In univariate linear regression analysis, changes in mean absolute width (delta MAWS) and minimum absolute with (delta MinAWS) of coronary segments were significantly correlated with in-trial concentrations of cholesterol in intermediate-density lipoprotein ([IDL] d = 1.006 to 1.019 kg/L), low-density lipoprotein ([LDL2] d = 1.019 to 1.040 kg/L; LDL3, d = 1.040 to 1.063 kg/L), and high-density lipoprotein ([HDL3] d = 1.125 to 1.210 kg/L) subfractions; no significant associations were found with other lipoproteins. IDL, LDL3, and HDL3 cholesterol were then selected for multiple linear regression analysis because these variables were not co-correlated and because they attained a significance of P less than or equal to .1 in univariate regression. In this analysis, only LDL3 cholesterol level was a significant negative predictor (P < .05) of both delta MAWS and delta MinAWS; a positive association between delta MinAWS and HDL3 cholesterol level just failed to reach conventional statistical significance (P = .066). Correlations between changes in coronary luminal dimensions and LDL3 cholesterol level were independent of age, smoking, weight, and blood pressure. Most patients showing regression of coronary atherosclerosis had an LDL3 cholesterol level of less than 1.8 mmol/L. The findings suggest that LDL3 is the plasma lipoprotein subfraction that exerts the single most powerful effect on the course of CAD in middle-aged men with hypercholesterolemia.

Relation of plasma levels and composition of apolipoprotein B-containing lipoproteins to angiographically defined coronary artery disease in young patients with myocardial infarction

BACKGROUND

Hypertriglyceridemia is a common metabolic disturbance in men < 45 years old with myocardial infarction. To further investigate the relation between triglyceride-rich lipoproteins and severity of coronary atherosclerosis in this subset of postinfarction patients, apolipoprotein B-containing lipoproteins of 64 consecutive patients were subfractionated in connection with coronary angiography.

METHODS AND RESULTS

Density-gradient ultracentrifugation of plasma and coronary angiography were performed 4 to 6 months after the myocardial infarction. Global coronary atherosclerosis and the number and severity of distinct stenoses were evaluated by semiquantitative analysis of 15 proximal coronary segments. The majority of the patients (60%) were hypertriglyceridemic and had higher coronary scores than normotriglyceridemic patients. Of the major plasma lipoproteins, triglycerides and cholesterol in the low-density lipoprotein (LDL) fraction were associated with global coronary atherosclerosis, whereas LDL triglycerides and high-density lipoprotein (HDL) cholesterol correlated directly and inversely, respectively, with the coronary stenosis score. Plasma apolipoprotein B correlated with both coronary scores. The plasma concentrations of lipid and protein in the very-low-density lipoprotein (VLDL) subfractions (VLDL1 through VLDL3) and intermediate-density lipoprotein (IDL) did not correlate with either of the coronary scores, whereas the concentration of triglycerides in dense LDL (density > 1.040 kg/L) was strongly associated with both coronary scores. Compositional analysis of the smallest VLDL particles (VLDL3) and IDL revealed a correlation between the number of cholesteryl ester molecules in small VLDL and global coronary atherosclerosis in hypertriglyceridemic patients.

CONCLUSIONS

Global coronary atherosclerosis and distinct stenoses in young postinfarction patients are associated with the number of apolipoprotein B-containing particles in plasma and the concentration of LDL triglyceride. Specifically, dense triglyceride-rich LDL particles and, in hypertriglyceridemic patients, small cholesteryl ester-rich VLDL particles relate to coronary artery disease severity.

Two-dimensional electrophoresis of plasma lipoproteins: recognition of new apo A-I-containing subpopulations

Two-dimensional electrophoresis has been used to resolve 12 distinct apo A-I-containing high-density lipoprotein (HDL) subpopulations in human plasma. The subpopulations were quantitated by 125I-labeled, monospecific antibody and phosphor-imaging. Modification and standardization of the agarose electrophoresis (first dimension) enabled us to recognize new HDL subpopulations. Lipoprotein mobilities in agarose were expressed relative to the mobility of the sample's endogenous albumin. We demonstrated the presence of lipoproteins with mobilities faster than and similar to albumin, as well as subpopulations with mobilities slower than albumin. We refer to these as pre alpha, alpha and pre beta, respectively. Lipoprotein molecular sizes were determined with a non-denaturing polyacrylamide gradient gel electrophoresis (PAGE) (2% to 36%) in the second dimension. Internal standard of 125I-labeled proteins of known molecular size was run simultaneously in each gel permitting accurate size determination. We have demonstrated that ultracentrifugally-isolated lipoproteins are different from the native apo A-I-containing subpopulations. The major difference observed was the loss of pre beta 1 and pre beta 2 particles from the d < 1.21 g/ml fractions to the d > 1.21 g/ml fractions. Possible physiologic and pathologic implications of these findings are also discussed.

Comparison of the plasma levels of apolipoproteins B and A-1, and other risk factors in men and women with premature coronary artery disease

The predictors of premature coronary atherosclerosis were examined in 203 patients (99 men aged less than or equal to 50 years, and 104 women aged less than or equal to 60 years) undergoing elective diagnostic coronary arteriography. Age, cigarette smoking, hypertension, obesity, diabetes, positive family history of premature coronary artery disease (CAD), and plasma levels of total cholesterol, triglyceride, lipoproteins (i.e., very low, intermediate-, low-, and high-density [HDL] lipoproteins and their subfractions [HDL2 and HDL3], and lipoprotein [a]) and apolipoproteins (apoA-1, apoA-2 and apoB, respectively) were examined using univariate analyses and multivariate logistic regression. In men, age (p less than 0.05), smoking (p less than 0.05), and plasma triglyceride (p less than 0.02) and apoA-1 (p less than 0.05) levels were independently associated with CAD. In women, smoking (p less than 0.001) and plasma apoB levels (p less than 0.04) were the strongest variables independently associated with CAD. It is concluded that the "nontraditional" risk factors (plasma apoA-1 and apoB levels) are better predictors of premature CAD than are plasma lipoproteins and that smoking is the strongest of the traditional nonlipid risk factors.

Lipoprotein cholesterol, apolipoprotein A-I and B and lipoprotein (a) abnormalities in men with premature coronary artery disease

The prevalence of abnormalities of lipoprotein cholesterol and apolipoproteins A-I and B and lipoprotein (a) [Lp(a)] was determined in 321 men (mean age 50 +/- 7 years) with angiographically documented coronary artery disease and compared with that in 901 control subjects from the Framingham Offspring Study (mean age 49 +/- 6 years) who were clinically free of coronary artery disease. After correction for sampling in hospital, beta-adrenergic medication use and effects of diet, patients had significantly higher cholesterol levels (224 +/- 53 vs. 214 +/- 36 mg/dl), triglycerides (189 +/- 95 vs. 141 +/- 104 mg/dl), low density lipoprotein (LDL) cholesterol (156 +/- 51 vs. 138 +/- 33 mg/dl), apolipoprotein B (131 +/- 37 vs. 108 +/- 33 mg/dl) and Lp(a) levels (19.9 +/- 19 vs. 14.9 +/- 17.5 mg/dl). They also had significantly lower high density lipoprotein (HDL) cholesterol (36 +/- 11 vs. 45 +/- 12 mg/dl) and apolipoprotein A-I levels (114 +/- 26 vs. 136 +/- 32 mg/dl) (all p less than 0.005). On the basis of Lipid Research Clinic 90th percentile values for triglycerides and LDL cholesterol and 10th percentile values for HDL cholesterol, the most frequent dyslipidemias were low HDL cholesterol alone (19.3% vs. 4.4%), elevated LDL cholesterol (12.1% vs. 9%), hypertriglyceridemia with low HDL cholesterol (9.7% vs. 4.2%), hypertriglyceridemia and elevated LDL cholesterol with low HDL cholesterol (3.4% vs. 0.2%) and Lp(a) excess (15.8% vs. 10%) in patients versus control subjects, respectively (p less than 0.05). Stepwise discriminant analysis indicates that smoking, hypertension, decreased apolipoprotein A-I, increased apolipoprotein B, increased Lp(a) and diabetes are all significant (p less than 0.05) factors in descending order of importance in distinguishing patients with coronary artery disease from normal control subjects. Not applying a correction for beta-adrenergic blocking agents, sampling bias and diet effects leads to a serious underestimation of the prevalence of LDL abnormalities and an overestimation of HDL abnormalities in patients with coronary artery disease. However, 35% of patients had a total cholesterol level less than 200 mg/dl after correction; of those patients, 73% had an HDL cholesterol level less than 35 mg/dl.

Coronary risk factors and the severity of angiographic coronary artery disease in members of high-risk pedigrees

Affected members of early coronary pedigrees in Utah are at markedly increased risk for the development of clinical coronary heart disease (CHD). The relationship between the presence of coronary risk factors and the severity of angiographic coronary artery disease (CAD) in 53 members of high-risk Utah pedigrees was examined. Mean angiographic severity scores were higher in familial hypercholesterolemia or familial low high-density lipoprotein cholesterol (HDL-C) pedigrees than in type III hyperlipidemia or familial combined hyperlipidemia pedigrees. One sibling pair with hyperhomocyst(e)inemia had the highest mean angiographic severity scores. Clinical CHD (p less than 0.0001), increasing low-density lipoprotein cholesterol (LDL-C) (p = 0.0107), and decreasing HDL-C (p = 0.0068) were significant predictors of angiographic CAD severity. There appeared to be an interaction between gender and body mass index but not between gender and serum lipids in the prediction of angiographic CAD severity. Results of the present study in members of high-risk Utah pedigrees are consistent with results from other angiographic studies in non-high-risk persons. Of particular interest is the suggested independent predictive value of low HDL-C for angiographic CAD severity in members of high-risk pedigrees.

Clinical value of apolipoprotein measurement

Low density and very low density lipoproteins contain apolipoprotein B100 which is synthesized in the liver. Chylomicrons have apolipoprotein B48, which consists of part of the apolipoprotein B100 sequence, and which is produced in the gut by the same gene that encodes for apolipoprotein B100. Both apolipoprotein B100 and apolipoprotein B48 are important for the secretion of triglyceride-rich lipoproteins whereas apolipoprotein B100, which can bind to the low density lipoprotein receptor, is also important for low density lipoprotein catabolism. Apolipoprotein (a) has structural homology with plasminogen and exists as a complex with apolipoprotein B100 in lipoprotein (a). Apolipoprotein AI is the main lipoprotein in high density lipoproteins, whilst apolipoprotein E, present in chylomicrons and intermediate density lipoproteins, plays a major role in their catabolism. Serum apolipoprotein B and apolipoprotein AI have potential in the evaluation of coronary risk. Apolipoprotein B may be of particular value in patients with hypertriglyceridaemia and normal low density lipoprotein cholesterol levels. Apolipoprotein (a) has also been reported to be an important indicator of coronary risk, especially in the presence of elevated apolipoprotein B. Lack of standardization and the limited availability of prospective data at present limit the routine use of apolipoprotein B, AI and (a) measurements. The determination of apolipoprotein E phenotypes has proved useful in the diagnosis of remnant (type III) hyperlipoproteinaemia.

Apolipoprotein E phenotypes, serum lipoproteins and apolipoproteins in angiographically assessed coronary heart disease

To determine the influence of the apolipoprotein E polymorphism on the occurrence of coronary artery disease (CAD) and on serum lipids, lipoproteins and apolipoproteins we studied 145 patients with angiographically defined CAD and compared them with 153 control subjects without history or complaints of vascular disease and with 35 subjects without significant stenosis on coronary arteriography. Subjects with hypertension, diabetes mellitus and endocrine or metabolic disorders were excluded. Covariance analysis and logistic regression analysis were performed with adjustment for age, sex, smoking habits and relative body weight. There were no significant differences for the apoE phenotypes on risk of cardiovascular disease. The CAD group had significantly higher mean values of serum cholesterol and triglycerides, very-low-density lipoprotein (VLDL)-cholesterol and VLDL-triglycerides, low-density lipoprotein (LDL)-cholesterol and apoprotein B; they had lower high-density lipoprotein (HDL)-cholesterol and apo A-I. The combination of LDL-cholesterol, apoA-I and VLDL-cholesterol was the best model in predicting cardiovascular disease. ApoE phenotype group E3/E2 had significantly lower values for serum cholesterol, LDL-cholesterol, and apoB and higher levels of apoE in comparison with the phenotype groups E3/E3 and E4/E3. The combination of LDL-cholesterol, cholesterol, apoE and VLDL-triglycerides was the best model in predicting the apoE phenotype. Thus, taking other risk factors into account, the apoE phenotype is not an independent risk factor for CAD; the apoE polymorphism influences lipoprotein levels and possibly, in that way, indirectly also the risk for CAD.

A prospective study of cholesterol, apolipoproteins, and the risk of myocardial infarction

BACKGROUND

The independent contributions of subfractions of high-density lipoprotein (HDL) cholesterol (HDL2 and HDL3) and apolipoproteins in predicting the risk of myocardial infarction are unclear. Prospective data are sparse, but HDL2 is widely believed to be a more important predictor than HDL3.

METHODS

Blood samples were collected at base line from 14,916 men (ages, 40 to 84 years) who were participants in the Physicians' Health Study. After five years of follow-up, plasma samples from 246 men with new myocardial infarction (case subjects) were analyzed together with specimens from 246 men matched to them for age and smoking status who had not had a myocardial infarction.

RESULTS

The levels of total cholesterol and apolipoprotein B-100 were significantly associated with an increased risk of myocardial infarction (data on levels of low-density lipoprotein cholesterol were unavailable). Both HDL cholesterol and HDL2 levels were associated with a substantially decreased risk of myocardial infarction, but the HDL3 level was the strongest predictor; the relative risk was 0.3 (95 percent confidence interval, 0.2 to 0.6) for those in the fifth of the group with the highest HDL3 levels, as compared with the fifth with the lowest levels. The benefit of a higher HDL cholesterol level was most pronounced among those with lower total cholesterol levels. Levels of apolipoprotein A-I and apolipoprotein A-II were also associated with decreased risk. However, the levels of HDL subfractions and apolipoproteins did not add significantly to the value of a multivariate model that included the ratio of total to HDL cholesterol in predicting myocardial infarction, whereas that ratio remained a significant independent predictor of risk. After adjustment for other risk factors, a change of one unit in the ratio of total to HDL cholesterol was associated with a 53 percent change in risk (95 percent confidence interval, 26 percent to 85 percent).

CONCLUSIONS

This study underscores the importance of HDL cholesterol in predicting the risk of myocardial infarction and demonstrates protective effects of both the HDL3 and HDL2 subfractions of HDL cholesterol. We found little or no predictive value for the levels of apolipoproteins A-I, A-II, and B or HDL subfractions after conventional risk factors and the ratio of total to HDL cholesterol were considered.

Serum lipoproteins and apolipoproteins in young normocholesterolaemic, non-diabetic Indian men with myocardial infarction

Serum total cholesterol, triglycerides, high density lipoprotein cholesterol, low density lipoprotein cholesterol, apolipoprotein A-I and apolipoprotein B were evaluated as potential indicators of the risk of coronary artery disease in young (less than 46 years) normocholesterolaemic, non-diabetic men who had previously sustained a myocardial infarction (n = 50) and in healthy age and sex matched controls (n = 122) with a similar socioeconomic background. Significant differences were observed between patients and controls in the mean concentrations of serum total cholesterol, triglycerides, low density lipoprotein cholesterol, high density lipoprotein cholesterol and apolipoprotein B, as well as in the ratios of total cholesterol to high density lipoprotein cholesterol and apolipoprotein A-I to apolipoprotein B. No significant difference was demonstrated in the concentration of apolipoprotein A-I between the two groups. Stepwise discriminant analysis indicated that apolipoprotein B was the best discriminant between patients and controls. The percentage of exact classification was 74% in patients and 66% in controls. When the patients were compared to a subset of controls (n = 50) matched for age and total cholesterol, significant differences were demonstrated only in the mean concentrations of apolipoprotein B. Discriminant analysis confirmed that the best single discriminating variable was apolipoprotein B. The results therefore indicate that in young normocholesterolaemic, non-diabetic Indian men with myocardial infarction, apolipoprotein B is superior to other lipid parameters studied, as a marker for coronary artery disease.

Apolipoprotein A and prognosis after myocardial infarction in non-diabetic men

The implications of apolipoproteins A-I and A-II for the prognosis of 178 non-diabetic men after acute myocardial infarction were studied. During a mean follow-up period of 4 years, one or more "coronary events" (nonfatal myocardial infarction, fatal coronary heart disease, coronary artery bypass graft surgery, deterioration of exercise ECG) were recorded in 37 patients. Serum levels of apolipoproteins A-I and A-II did not discriminate between patients with and without coronary events. This applied to the entire sample as much as to subgroups defined by presence or absence of interventions (coronary artery bypass graft surgery, long-term therapy with beta-blockers or lipid-lowering drugs). We conclude that coronary events in the first years after myocardial infarction cannot be predicted by apolipoprotein A-I or A-II levels.

Familial aggregation of non-insulin dependent diabetes and coronary heart disease are accompanied by different effects on serum lipids, lipoproteins and apolipoproteins

This study was designed to investigate whether the presence of non-insulin-dependent diabetes mellitus (NIDDM) or coronary heart disease (CHD) in probands have different effects on serum lipid, lipoprotein and apolipoprotein concentrations in the first-degree relatives. Altogether 161 probands (114 men, 47 women) and 788 first-degree relatives of these probands (174 brothers, 246 sisters, 180 sons, 188 daughters) were included in the analyses. The presence of NIDDM in the proband was associated with lowered total, LDL and HDL cholesterol and apolipoprotein A1 and elevated total triglyceride levels in the brothers (P less than 0.05) and elevated total and LDL cholesterol levels in the sisters (P less than 0.05). Total LDL and VLDL cholesterol and apolipoprotein B were higher (P less than 0.05) and HDL/total cholesterol ratio and apolipoprotein A1/B ratio lower (P less than 0.05) in the daughters of the nondiabetic and diabetic probands were pooled, CHD in the proband was associated particularly with low apolipoprotein A1/B ratio. In conclusion, (1) the presence of NIDDM in the proband appears to be associated in siblings with more profound lipid and lipoprotein changes (especially low HDL cholesterol and high total triglycerides) than a history of CHD in the proband, (2) a history of CHD in the proband is associated in children with apolipoprotein changes favouring atherosclerosis (low apolipoprotein A1, high apolipoprotein B, low apolipoprotein A1/B ratio). Different effects of a history of NIDDM and CHD in the proband on lipid, lipoprotein and apolipoprotein levels in the first-degree relatives warrants more population-based studies.

Predictive value of lipoprotein (a) and other serum lipoproteins in the angiographic diagnosis of coronary artery disease

To determine the relation among lipids in predicting coronary artery disease (CAD), 213 patients undergoing diagnostic angiography for suspected CAD were prospectively studied. Twenty-one patients had normal coronary arteries and 192 had CAD in 1 to 3 arteries at arteriography with measurements obtained with digital calipers. Lipoproteins were measured and lipoprotein (a) [Lp(a)] was also assayed in a subset of 98 patients with CAD. Statistical analysis was performed using uni- and multivariate techniques to test the association among age, gender, systemic hypertension, diabetes mellitus, cigarette smoking, family history, total cholesterol, triglycerides, high-density lipoprotein (HDL) cholesterol, low-density lipoprotein (LDL) cholesterol, very low density lipoprotein cholesterol, apolipoproteins (apo) A-I and apo B, ratio of apo A-I to apo B, and ratio of HDL cholesterol to total cholesterol, to Lp(a) and to CAD. All factors except gender, systemic hypertension, diabetes mellitus and cigarette smoking were univariate predictors of CAD. Multivariate predictors were, in decreasing order of significance, family history, age, HDL/total cholesterol ratio and apo B. When Lp(a) was included, multivariate predictors were age, family history, apo B and Lp(a), in that order. Lipid parameters alone showed that the HDL/total cholesterol ratio and that Lp(a) provide the best predictive tests for the detection of CAD in this referral population and may ultimately become important screening tests for CAD.

Lipoprotein-related coronary risk factors in patients with angiographically defined coronary artery disease: relation to number of stenosed arteries

To determine whether an index estimating antagonism between low density lipoprotein (LDL) and high density lipoprotein (HDL) would improve separation between groups with and without coronary artherosclerosis, patients undergoing coronary catheterization (35 women and 99 men) were analysed for total cholesterol (TC), HDL cholesterol (HDLc), apolipoprotein A (apo A) and apolipoprotein B (apo B). The subjects were categorized as groups 0, 1, 2 or 3 according to the number of stenosed arteries (greater than 75% areal stenosis). Thirty of the patients showed no significant coronary atherosclerosis (group 0). Serum apo B and TC concentrations were directly related to the number of stenosed vessels, whereas the concentrations of apo A and HDLc were negatively correlated with the number of stenosed arteries. An 'atherogenic Index' (ATH index) calculated as the product of serum concentrations of apo B, and TC minus HDLc divided by the product of apo A and HDLc, proved more satisfactory than individual lipoprotein components for discrimination between subjects with and without stenosis. Accordingly, identification of coronary groups may be improved by using the ATH index.

Correlates of atherosclerosis in coronary arteries of patients undergoing angiographic evaluation

The correlations between lipid and lipoprotein measurements and other risk factors of coronary artery disease were evaluated in 101 men undergoing coronary angiography. Clinically significant disease was present in 75 patients, whereas 24 had no observable lesions and 2 had minimal lesions. Comparisons of individual lipid and lipoprotein levels were nearly all significantly different between patients with and patients without clinically significant disease; however, no single variable could predict the presence of disease among patients. Logistic regression analysis identified five factors: apolipoprotein A-I, apolipoprotein B, diabetes, age, and family history of heart disease, which account for most of the differences between the two patient groups. These results could have important implications for the evaluation and management of patients suspected of having coronary atherosclerosis.

A new method of scoring coronary angiograms to reflect extent of coronary atherosclerosis and improve correlation with major risk factors

We developed a new angiographic score of the extent of coronary disease (extent score), which we compared with conventional stenosis and vessel scores that emphasize the severity of stenosis. Scores were determined in 132 patients (29 women, 103 men with a mean age of 55 +/- 10 years) who underwent elective coronary angiography. Risk factors were more closely related to the extent score than to either the stenosis or vessel scores (Total R2 = 0.35 versus 0.28 (p less than 0.001) and 0.25 (p less than 0.001), respectively). The extent score was more closely related to age (r = 0.30, p less than 0.05), than was either stenosis (r = 0.21 ns) or vessel score (r = 0.26, p less than 0.05). Apolipoprotein B was the strongest predictor of both extent and stenosis scores but was more closely related to the extent score (r = 0.36, p less than 0.05), even after correction for age and gender. This new angiographic score that assesses the extent of coronary disease is simple to perform and correlates better with age and lipoprotein risk factors than conventional scores do.

Serum lipids, lipoproteins and apolipoproteins in black patients with angiographically defined coronary artery disease

The association between angiographically defined coronary artery disease (CAD) and serum lipids, lipoproteins, and apolipoproteins was evaluated in 151 black men and 245 black women. Patients with 70% or greater narrowing of at least one coronary artery or greater than or equal to 50% stenosis of the left main coronary artery (n = 179) were compared to those with lesions of less than 50% stenosis (n = 217) for total cholesterol (TC), low density lipoprotein-cholesterol (LDL-C), high density lipoprotein-cholesterol (HDL-C), LDL-C/HDL-C, triglycerides, apolipoprotein A-I, apolipoprotein B, and apolipoprotein A-I/B. A consistently more atherogenic pattern of lipids, lipoproteins, and apolipoproteins occurred only among the women. Using stepwise selection multiple logistic regression analysis, the ratio of apolipoprotein A-I/B (odds ratio = 0.38, 95% confidence limits 0.24-0.61) was the only statistically significant association of CAD in women, after adjusting for the effects of age, body mass index, and histories of smoking, hypercholesterolemia, hypertension, and diabetes. When stratified by median of total cholesterol, the ratio of apolipoprotein A-I/B was the most strongly associated with the presence of CAD in the lower half of the total cholesterol distribution (less than 208 mg/dl), whereas in the upper half of the total cholesterol distribution the total cholesterol/HDL-C ratio was more strongly associated with CAD. None of the variables studied was associated with CAD in men. These results support other studies suggesting that apolipoproteins may be better predictors of CAD.

Comparison of serum lipid values in variant angina pectoris and fixed coronary artery disease with normal subjects

Lipid and apolipoprotein (apo) levels in patients with variant angina were examined and compared with patients with coronary artery disease (CAD) and normal subjects (control). Cholesterol and triglyceride levels in plasma, lipoprotein fractions and several apolipoproteins were measured in 108 men (90 of whom had undergone coronary angiography): 22 had variant angina, 56 had fixed CAD (effort angina and old myocardial infarction) and 30 were normal subjects. Patients with variant angina showed more severe atherosclerotic lesions than the control group, but less severe lesions than the patients with fixed CAD. In comparison with lipid and apolipoprotein, high density lipoprotein cholesterol, apo AI and apo AII decreased significantly in control, variant angina and fixed CAD groups, respectively. Additionally, stepwise discriminant analysis revealed that apo AI was the best discriminator among the 3 groups or between variant angina or fixed CAD and the control group. Variant angina and fixed CAD patients could be discriminated from the control subjects by an apo AI level of 135 and 126 mg/dl, with 71% (p less than 0.025) and 73% (p less than 0.005) accuracy, respectively. By these criteria 77% of the patients with variant angina and 73% of the patients with fixed CAD were precisely discriminated. Discrimination between variant angina and fixed CAD patients, however, was not practical, even if the best discriminator was used. Thus, the apo AI level is useful in discriminating patients with variant angina and fixed CAD from normal subjects. Therefore, symptomatic patients with low apo AI levels should be aggressively examined.

Apolipoprotein measurements in clinical biochemistry and their utility vis-a-vis conventional assays

Qualitative and quantitative measurements of apolipoproteins such as Apo CII and Apo E, as well as Apo AI and Apo B can aid in the diagnosis of specific lipoprotein metabolic defects. When used in this way, their usefulness will probably remain more or less confined to specialized research centers which have the expertise to perform such analyses and interpret the measurements. In addition, however, Apo AI and Apo B also promise to be useful for the estimation of cardiovascular risk both in individuals and in populations, and both of these apolipoprotein measurements will probably supplement rather than replace conventional lipoprotein measurements. As with the lipoproteins, the usefulness of Apo AI and Apo B measurements will depend on the accuracy and precision with which they can be measured. The current standardization efforts should lead to the development of reference methods for the measurement of total plasma levels of Apo AI and Apo B, the availability of reference materials for these apolipoproteins, and eventually, to the establishment of methods that can specifically measure Apo AI and Apo B in particular lipoprotein subfractions.

High prevalence of hypertriglyceridaemia and apolipoprotein abnormalities in coronary artery disease

Serum lipids and apolipoproteins A-I and B were measured in 174 men aged less than 60 with angiographically confirmed coronary artery disease and in 572 healthy control men. Two thirds of the patients had raised age-corrected values of fasting serum cholesterol and/or triglyceride and/or a low high density lipoprotein (HDL) cholesterol compared with the controls. Eighteen (30%) of the 61 normolipidaemic patients had a concentration of serum apolipoprotein A-I below the 5th percentile of 233 controls. In normolipidaemic patients on beta blockers the relative prevalence of serum low density lipoprotein (LDL)-apolipoprotein B values above the 95th percentile of 339 controls was significantly increased. Discriminant function analysis showed that a raised concentration of serum triglyceride was the best discriminant between patients and controls, with raised LDL-apolipoprotein B and reduced apolipoprotein A-I coming second only to triglyceride in analyses where each was separately compared with all the lipid variables. These associations were highly significant and were independent of other influences, including beta blockade. These findings re-emphasise the importance of hypertriglyceridaemia as a risk factor and confirm that apolipoprotein abnormalities occur frequently in coronary disease, even in normolipidaemic patients.

Genetic factors influencing apolipoprotein AI and AII levels in a kindred with premature coronary heart disease

A single 51-member kindred, ascertained on the basis of a normotriglyceridemic proband with depressed high-density lipoprotein cholesterol (HDL-C) and myocardial infarctions at ages 40 and 42, was studied with respect to quantitative variation in HDL-C and apolipoprotein (apo) AI and AII levels. The results of bivariate segregation analysis suggest that the etiology of depressed HDL-C involves one or possibly two major loci: one has a pleiotropic effect on apo AI and apo AII levels and, possibly another one that affects apo AI levels. Both the major loci were characterized as having a dominant allele leading to depression of the respective trait(s). In addition, analysis of the cosegregation of HDL-C and apo AI levels gave evidence of residual nonfamilial factors common to both traits, leading to a positive covariance between them. This could reflect the role of apo AI in the transformation of nascent HDL-C particles into mature ones via its cofactor activity to lecithin cholesterol acyltransferase. The proposed two-locus model represents one possible etiology for the heterogeneous disorder of hypoalphalipoproteinemia. This analysis of a single pedigree does not completely define the genetic mechanism, but it does illustrate a useful new analytic approach.

Apolipoprotein E polymorphism and atherosclerosis

The apo E locus contributes to determining the variation in plasma cholesterol levels of healthy and diseased populations. It also influences the expression of hyperlipidemia and appears to modulate the susceptibility to atherosclerosis in a complex multifactorial interaction. There is evidence that the presence of apo E2 is protective, whereas that of apo E4 predisposes to coronary artery disease. The burden of proof, however, lies on future, well-designed clinical trials and prospective studies. The study of the biological significance of the apo E polymorphism in humans has emphasized the importance of gene-gene and gene-environment interactions in the pathogenesis of hyperlipidemia and atherosclerosis. The apo E polymorphism involves the coding region of the apo E gene and results in alterations of the gene product which, in turn, either directly or secondarily affect the metabolic fate of the lipoprotein particles. Rapid advances in knowledge over the last decade have provided a metabolic explanation for the observation of the opposite effects of the epsilon 4 and the epsilon 2 alleles on lipoprotein levels. Apo E2 has lower receptor binding affinity which results in delayed clearance of apo E2-bearing lipoprotein particles from plasma. Apo E4 is distributed differently from apo E3 between VLDL and HDL, is degraded more rapidly than apo E3, and may enhance the catabolism of E4-bearing particles, leading to other alterations in lipoprotein metabolism which result in elevated levels of LDL. In view of the significant opposite impacts of the epsilon 4 and the epsilon 2 alleles on plasma LDL cholesterol concentrations, it is evident that determination of the apo E phenotype will become a useful adjunct to the assessment of the cardiovascular risk profile of an individual. In addition, the relationship between the epsilon 2 allele and type III hyperlipoproteinemia provides a valuable model for the study of complex genetic interactions in the pathogenesis of hyperlipidemia. The further study of apo E and its interactions shows great promise for a deeper comprehension of the pathogenesis of atherosclerosis.

Apolipoprotein A-I containing lipoproteins in coronary artery disease

At least 2 main types of lipoprotein particles are identified within HDL. Those which contain apo A-I and apo A-II (LpA-I:A-II) and those which contain apo A-I but not apo A-II (LpA-I). This study was designed to elucidate to what degree the HDL cholesterol decrease observed in coronary artery disease affects these 2 types of lipoprotein particles. Concentrations of LpA-I:A-II and LpA-I were measured in plasma from 100 normolipidemic male subjects with angiographically defined coronary artery disease (CAD(+)) or without CAD (CAD(-)) and from 50 control subjects, matched for age. CAD(+) subjects had significantly lower levels of HDL cholesterol, total apo A-I, and LpA-I than controls. When compared to CAD(-) subjects, only their levels of HDL cholesterol and LpA-I were found lower. In both cases (CAD(+) vs CAD(-) and CAD(+) vs controls), LpA-I levels were decreased while LpA-I:A-II levels were unchanged. Even, when the levels of their total plasma lipids and lipoproteins are normal, atherosclerotic patients are characterized by a different distribution of apo A-I between LpA-I and LpA-I:A-II. These data support the view that LpA-I might represent the "antiatherogenic" fraction of HDL.

The relation of apolipoproteins A-I and B in children to parental myocardial infarction

Clinical studies suggest that serum levels of apolipoproteins A-I and B may be more strongly related to coronary artery disease than are their respective lipoprotein-cholesterol fractions. Therefore, we assessed the association between levels of apolipoprotein B, apolipoprotein A-I, lipids, and lipoprotein cholesterols in children and the reported histories of myocardial infarction in their parents in a survey of 2416 black and white school-age children. As compared with children whose fathers did not report a myocardial infarction, those whose fathers reported having had an infarction (n = 139) had a lower mean level of apolipoprotein A-I (137 vs. 141 mg per deciliter; P = 0.04) and a lower ratio of low-density lipoprotein cholesterol to apolipoprotein B (1.08 vs. 1.11; P = 0.007), along with a higher ratio of apolipoprotein B to apolipoprotein A-I (0.64 vs. 0.61; P = 0.04). These associations existed independently of the children's race, sex, age, and history of obesity, smoking, alcohol intake, and use of oral contraceptives. Children whose mothers reported having had a myocardial infarction (n = 56) had no decrease in the ratio of low-density lipoprotein cholesterol to apolipoprotein B, but they tended to have an elevated ratio of apolipoprotein B to apolipoprotein A-I. In contrast, serum lipoprotein-cholesterol fractions in children were not related to myocardial infarctions in either parent. These results provide further evidence that apolipoproteins are more strongly related to the risk of cardiovascular disease than are lipoprotein-cholesterol fractions.