High-density lipoprotein: relations to metabolic parameters and severity of coronary artery disease

Sex-specific association of monocyte count to high-density lipoprotein ratio with SYNTAX score in patients with suspected stable coronary artery disease

Recently, the monocyte count to high-density lipoprotein cholesterol ratio (MHR) was found to be associated with the SYNTAX score in patients with both stable coronary artery disease (CAD) and acute coronary syndrome (ACS). The MHR was significantly higher in male patients. However, the sex-specific association of MHR with SYNTAX score in stable CAD was not well explored. Thus, the present study aimed to investigate the association of MHR and presence and severity of CAD evaluated by coronary angiography and the SYNTAX score in males and females.In total, 873 patients who received selective coronary angiography between March 2017 and July 2018 were included in the present study. Patients were divided into 3 groups according to MHR tertiles. The MHR was calculated by dividing the monocyte count by the high-density lipoprotein cholesterol level. CAD was defined as at least 50% diameter stenosis of a major coronary artery, including the right coronary, left main coronary, left anterior descending, and left circumflex arteries. The SYNTAX score was calculated by 2 experienced interventional cardiologists. SYNTAX score ≥23 was defined as a high SYNTAX score.Males showed a significantly higher MHR (12.2 [8.9-15.5] vs 9.3 [6.2-12.1], P < .001), accompanied by a higher prevalence of CAD (68.1% vs 53.4%, P < .001). Male sex remained an independent predictor of elevated MHR after correction for confounding factors (adjusted odds ratio [OR] 3.102, P = .001). The association between MHR and SYNTAX score was confirmed only in male stable patients with CAD (r = 0.113, P = .036). Multivariate logistic regression analysis showed that MHR was an independent predictor of SYNTAX score ≥23 only in male patients with CAD. The receiver-operating characteristic curve showed a predictive value of MHR for high SYNTAX score only in males.A higher MHR in males and a positive correlation of MHR with SYNTAX score were observed only in male stable patients with CAD. Such an easily obtained index may help interventional cardiologists detect high-risk patients before coronary catheterization, but its application may be restricted to males.

Fasting Lipoprotein Lipase Protein Levels Can Predict a Postmeal Increment of Triglyceride Levels in Fasting Normohypertriglyceridemic Subjects

BACKGROUND

Although a postprandial increment in triglyceride (TG) levels is considered to be a risk factor for atherogenesis, tests (e.g., fat load) to assess postprandial changes in TG levels cannot be easily applied to clinical practice. Therefore, fasting markers that predict postprandial TG states are needed to be developed. One current candidate is lipoprotein lipase (LPL) protein, a molecule that hydrides TGs. This study investigated whether fasting LPL levels could predict postprandial TG levels.

METHODS

A total of 17 subjects (11 men, 6 women, mean age 52 ± 11 years) with normotriglyceridemia during fasting underwent the meal test. Several fasting parameters, including LPL, were measured for the area under the curve of postprandial TGs (AUC-TG).

RESULTS

The subjects' mean fasting TG level was 1.30 mmol/l, and their mean LPL level was 41.6 ng/ml. The subjects' TG levels increased after loading (they peaked after two postprandial hours). Stepwise multiple regression analysis demonstrated that fasting TG levels were a predictor of the AUC-TG. In addition, fasting LPL mass levels were found to be a predictor of the AUC-TG (β = 0.65, P < 0.01), and this relationship was independent of fasting TG levels.

CONCLUSION

Fasting LPL levels may be useful to predict postprandial TG increment in this population.

Relationships among serum lipoprotein lipase mass, visceral fat, and retinal nerve fiber layer thickness

PURPOSE

The purpose of the study was to determine whether there were significant correlations among the serum lipoprotein lipase mass, visceral fat, and the retinal nerve fiber layer (RNFL) thickness.

METHODS

We studied 118 consecutive subjects. Optical coherence tomography (OCT) was used to measure the RNFL thickness. The Pearson correlation coefficient was used to determine the relationships among lipoprotein lipase (LPL) mass, visceral fat area by computed tomography, OCT, and other parameters. We performed a multiple regression analysis to identify independent factors for the RNFL sectors that were the most strongly correlated with the LPL mass and visceral fat area.

RESULTS

The LPL mass was significantly correlated with the nasal RNFL thickness in both eyes (right eye: r = 0.24, p = 0.008, left eye: 0.32, 0.0008) and inferior RNFL thickness in the left eye ( r = 0.23, p = 0.01). The visceral fat area was significantly correlated with the nasal RNFL thickness in both eyes (right eye: r = -0.19, p = 0.04, left eye: -0.30, 0.0008) and the inferior RNFL thickness in the left eye ( r = -0.23, p = 0.01). The subcutaneous fat area was not significantly correlated with any OCT parameters. The multiple regression analysis revealed that age, LPL mass, and visceral fat area were independent contributors to the nasal RNFL thickness in the left eye (age, standard regression coefficient = -0.34 , p = 0.0004; LPL mass, 0.26, 2.49, 0.01; visceral fat area, -0.21, 0.03).

CONCLUSION

A reduction of lipoprotein lipase and accumulation of visceral fat might produce retinal neurodegenerative disorders that decrease the RNFL thickness, especially on the nasal side.

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.

The effect of a combination therapy with myo-inositol and a combined oral contraceptive pill versus a combined oral contraceptive pill alone on metabolic, endocrine, and clinical parameters in polycystic ovary syndrome

AIM

Compare the effects of a combined contraceptive pill (OCP) in combination with myo-inositol (MI) on endocrine, metabolic, and clinical parameters in patients with polycystic ovary syndrome (PCOS).

METHODS

One hundred fifty-five patients with PCOS were enrolled in this prospective, open-label clinical study. Patients were assigned to receive oral treatment with OCP alone (estradiol (EE) 30 μg/gestodene 75 μg) or in combination with myo-inositol 4 g/die, for 12 months.

RESULTS

OCP plus MI therapy resulted in a higher reduction of FG score compared with OCP alone therapy. The combined therapy (OCP plus MI) significantly decreased hyperinsulinaemia, by positively affecting the fasting insulin and glucose levels and homeostasis model assessment-insulin resistance parameters, while no significant changes were observed in the OCP group. Androgens serum levels decreased in both groups, but significantly more in the combined therapy group. The lipid profile was improved in the combined therapy group, by reducing low-density lipoprotein cholesterol levels and enhancing high-density lipoprotein cholesterol levels.

CONCLUSIONS

Our data show that a combination of combined contraceptive pill and MI may be more effective in controlling endocrine, metabolic, and clinical profile in patients with PCOS than OCP alone, and may reduce insulin levels and insulin resistance. Hence, combined treatment may become a more effective long-term therapeutic choice for controlling PCOS symptoms.

Prospective study of coronary heart disease vs. HDL2, HDL3, and other lipoproteins in Gofman's Livermore Cohort

OBJECTIVE

To assess the relationship of lipoprotein subfractions to coronary heart disease (CHD).

METHODS

Prospective 29.1-year follow-up of 1905 men measured for lipoprotein mass concentrations by analytic ultracentrifugation between 1954 and 1957. Vital status was determined for 97.2% of the cohort. Blinded physician medical record and death certificate review confirmed 179 CHD deaths. Follow-up questionnaires identified 182 nonfatal myocardial infarctions and 93 revascularization procedures from 1346 (98.3%) of the surviving cohort and from the next-of-kin of 153 men who died.

RESULTS

When adjusted for age, total incident CHD was inversely related to HDL2-mass (P=0.0001) and HDL3-mass (P=0.02), and concordantly related to LDL-mass (P<10(-11)), IDL-mass (P<10(-7)), and small (P<10(-7)) and large VLDL-mass concentrations (P=0.003). The hazard reduction per mg/dl of HDL was greater for HDL2-mass than HDL3-mass (P=0.04). The lowest quartiles of both HDL2-mass (P=0.007) and HDL3-mass (P=0.001) independently predicted total incident CHD when adjusted for traditional risk factors. Risk for premature CHD (≤65 years old) was significantly greater in men within the lowest HDL2 (P=0.03) and HDL3 quartiles (P=0.04) and having higher LDL-mass concentrations (P=0.001). Serum cholesterol's relationship to incident CHD (P<10(-8)) was accounted for by adjustment for LDL-mass concentrations (adjusted P=0.90).

CONCLUSIONS

Lipoprotein subfractions differ in their relationship to CHD.

Serum lipoprotein lipase mass: clinical significance of its measurement

Lipoprotein lipase (LPL) is a lipolytic enzyme involved in catalyzing hydrolysis of triglycerides (TG) in chylomicrons and very low-density lipoprotein (VLDL) particles. Over the last decade, increasing attention has been paid to the clinical significance of measuring serum LPL protein mass without heparin injection to the study subjects. In earlier studies, this marker was utilized to classify LPL deficient subjects, which is an extremely rare metabolic disorder with a frequency of one in one million. Later, researchers paid more attention to the clinical significance of measuring this parameter in more common metabolic disorders. Studies have shown that pre-heparin plasma or serum LPL mass has significant relationships with serum lipids and lipoproteins, visceral fat area, insulin resistance, and even the development of coronary atherosclerosis in cross-sectional studies, although this might be a metabolic surrogate marker with almost no catalytic activities, which does not appear to be involved in catalyzing hydrolysis of TG in TG-rich lipoproteins. Recently, a prospective study has demonstrated that low serum LPL concentration predicts future coronary events. Taken together, we suggest that pre-heparin LPL mass in plasma or sera provide us with useful and important information on the development of metabolic disorders leading to atherosclerotic disease.

Dietary carbohydrate and cholesterol influence the number of particles and distributions of lipoprotein subfractions in guinea pigs

Guinea pigs (n=10/group) were fed one of three diets: a high carbohydrate (CHO) (42% energy), low cholesterol (0.04%) diet (LChHC), a diet with the same amount of CHO but with 0.25% cholesterol (HChHC) or a diet with 11% of energy from CHO and 0.25% cholesterol (HChLC) for 12 weeks. VLDL- and LDL cholesterol (LDL-C) were higher in the HChLC and HChHC groups than in the LChHC group (P<.0001). Lipoprotein subclasses and size were analyzed by nuclear magnetic resonance. Dietary cholesterol (HChHC and HChLC groups) resulted in larger VLDL particles (71.1+/-6.9, 78.9+/-3.33 nm, respectively) than those in the LChHC group (44.3+/-10.8 nm). In addition, there were higher concentrations of the large VLDL (>60 nm) and the medium VLDL (>35 nm) in the high cholesterol groups (P<.01). Similarly, the concentration of the medium (>8.2 nm) and small HDL (>7.2 nm) was higher in the HChHC and HChLC groups (P<.001). In contrast, CHO restriction affected the concentrations of LDL subfractions. The number of total LDL particles was lower in the HChLC (291.3+/-85.0 nmol/L) than in the HChHC group (467.6+/-113.1 nmol/L), indicating that the cholesterol in LDL was distributed in less particles in the former group. The concentrations of medium LDL (>19.8 nm) (98.4+/-90.8) and small LDL (>18 nm) (29.3+/-24.9 nmol/L) were lower in the HChLC group than in the HChHC group (261.8+/-105.8 and 64.9+/-27.9 nmol/L, respectively). These results indicate that dietary cholesterol increased the atherogenicity of both VLDL and HDL while CHO restriction increased the number of large LDL and decreased the concentrations of the more atherogenic smaller LDL subfractions.

Pre-heparin Lipoprotein Lipase Mass

Lipoprotein lipase (LPL) is a lipolytic enzyme involved in catalyzing the hydrolysis of triglycerides (TG) in chylomicrons and very low-density lipoprotein (VLDL) particles. Over the last decade, the clinical significance of measuring LPL mass without heparin injection has been increasingly studied. In earlier studies, it was shown that this marker was utilized to classify type 1 hyperlipoproteinemia, which is an extremely rare metabolic disorder. Later, researchers paid more attention to the clinical significance of measuring this parameter in more common metabolic disorders. Studies have shown that pre-heparin plasma LPL mass has significant relationships with serum lipid and lipoproteins, visceral fat area, and even a marker for acute inflammation, although this might be a metabolic surrogate marker which does not appear to be involved in catalyzing the hydrolysis of TG in TG-rich lipoproteins. We suggest that pre-heparin LPL mass in plasma or sera provides us with useful and important information on the pathophysiology of metabolic disorders or acute inflammation despite its simplicity from a practical point of view.

Lipoprotein subclasses and particle sizes and their relationship with coronary artery calcification in men and women with and without type 1 diabetes

Type 1 diabetes is associated with increased coronary atherosclerosis, especially in women, even though such patients often have an apparently normal lipid profile. We examined whether lipoprotein particle sizes and subclasses differed between type 1 diabetic subjects (n = 194, age 30-55 years) and age- and sex-matched control subjects (n = 195). We examined whether any abnormalities were of similar magnitude in men and women. The relationship of particle size to electron beam computer tomography-defined coronary artery calcification, a measure of atherosclerosis, was also examined. Proton nuclear magnetic resonance (NMR) spectroscopy was used to quantify VLDL, LDL, and HDL subclass levels and average particle size on fasting samples. LDL size and subclass were similar in diabetic and nondiabetic men. In contrast, in women diabetes was associated with less large and more small LDL and a reduced LDL size (mean difference 0.2 nm; P = 0.0009). This greater effect of diabetes on LDL size in women compared with men was significant (P = 0.007). Diabetes was associated with more large and less small HDL and, to a similar degree in both sexes, a higher HDL size (difference of 0.4 nm in men and 0.3 nm in women; both P < 0.0001). There were no definitive abnormalities in VLDL size. In nondiabetic subjects, lower average HDL particle size, lower LDL size, and higher VLDL size were significantly associated with coronary calcification (P = 0.001, 0.02, and 0.04, respectively). Thus the HDL size differences with diabetes would be expected to be antiatherogenic and the LDL size differences pro-atherogenic. However, there was no clear relationship between particle size and calcification in diabetic subjects. We conclude that in the general population NMR spectroscopy-derived particle size reveals important information about the atherogenicity of lipoprotein profile. Type 1 diabetes is associated with differences in NMR-derived particle size, but their pathogenic significance is unclear.

Mild-to-moderate hypertriglyceridemia in young men is associated with endothelial dysfunction and increased plasma concentrations of asymmetric dimethylarginine

OBJECTIVES

The aim of this study was to investigate endothelial function and common carotid intima-media thickness (IMT) in healthy young men with mild-to-moderate hypertriglyceridemia. Plasma asymmetric dimethylarginine (ADMA), an endogenous nitric oxide synthase inhibitor, was measured to further elucidate the mechanisms involved.

BACKGROUND

Hypertriglyceridemia is a risk factor for coronary heart disease although the mechanisms behind the increased risk remain to be defined. Acute elevation of plasma triglycerides induced by an intravenous fat load is associated with impaired endothelial function. The results of studies examining acute effects induced by a high-fat meal or effects of chronic hypertriglyceridemia on endothelial function are more inconsistent.

METHODS

Flow-mediated vasodilation and nitroglycerin-induced vasodilation of the brachial artery and common carotid IMT were measured noninvasively by ultrasound technique in 15 hypertriglyceridemic (HTG) subjects and 15 matched controls, mean age 34 years. Plasma concentrations of ADMA were measured by high-performance liquid chromatography.

RESULTS

Flow-mediated vasodilation was decreased in the HTG group (p < 0.0001), whereas nitroglycerin-induced vasodilation and carotid IMT did not differ significantly. Asymmetric dimethylarginine concentrations were higher in the HTG group (p < 0.05).

CONCLUSIONS

Hypertriglyceridemia in young men is associated with endothelial dysfunction and increased plasma concentration of ADMA but not with increased IMT of the common carotid artery. The corollary is that chronic hypertriglyceridemia results in endothelial dysfunction, possibly due to increased ADMA concentration, and that endothelial dysfunction might precede increased IMT among the early manifestations of atherosclerosis.

Oral 17beta-estradiol and medroxyprogesterone acetate therapy in postmenopausal women increases HDL particle size

Menopause is accompanied by changes in lipoprotein particles that include an increase in density of low density lipoproteins (LDL) and high density lipoproteins (HDL) particles. The effect of 3 months of oral hormone replacement therapy (HRT) on lipoprotein particle size in postmenopausal women who were randomized to (1) estrogen replacement therapy (ERT) alone (either 17beta-estradiol (1 mg) or conjugated equine estrogens (CEE) (0.625 mg); (2) combination therapy (17beta-estradiol plus medroxyprogesterone acetate (MPA) or CEE plus MPA); and (3) placebo were examined. Lipoprotein subclass concentrations and particle size were quantified by nuclear magnetic resonance spectroscopy (NMR). Combination HRT resulted in significant (P=0.002) increases in HDL particle size as compared with those on placebo formulations or ERT alone. Women assigned to combined HRT had lower concentrations of smaller HDL particles after 3 months (P=0.005) and higher concentrations of larger HDL particles (P=0.02), whereas women assigned to ERT or placebo experienced non-significant changes. In summary, combined HRT increases HDL particle size by altering concentrations of the smallest and largest HDL subspecies.

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.

Hyperalphalipoproteinemia: characterization of a cardioprotective profile associating increased high-density lipoprotein2 levels and decreased hepatic lipase activity

The aim of the present study was to investigate the high-density lipoprotein (HDL) structural characteristics and metabolism in hyperalphalipoproteinemic (HALP) patients (HDL-cholesterol [HDL-C], 92 +/- 14 mg/dL) with combined elevated low-density lipoprotein-cholesterol (LDL-C) levels (LDL-C, 181 +/- 33 mg/dL). Patients were subjected to a complete cardiovascular examination, including ultrasonographic investigation of carotid arteries. Two HALP profiles were identified according to the HDL2/HDL3 ratio. HALP profile A was characterized in 28 patients by increased HDL2/HDL3 ratio, HDL2b, and lipoprotein (Lp)A-I levels compared with normolipidemic subjects, and HALP profile B, including the 12 remaining patients, was characterized by a HDL2/HDL3 ratio within the normal range and by the increase of all HDL subclasses (HDL(2b,2a,3a,3b,3c)), LpA-I, and LpA-I:A-II levels. With regard to the exploration of carotid arteries, in HALP profile A, 20 patients were free from lesions and eight had only intimal wall thickening. In HALP profile B, only one patient was free from lesions, four had intimal wall thickening, and seven displayed plaques, but none had stenosis. Taking into account the number of patients with plaques within each group, HALP profile A was associated with a low prevalence of atherosclerotic lesions, whereas HALP profile B was less cardioprotective (odds ratio, 77.7 [95% confidence interval, 3.7 to 1,569.7]; P < .0001). For both HALP profiles, cholesteryl ester transfer protein (CETP) deficiency was discarded and activities of phospholipid transfer protein (PLTP) and lipoprotein lipase (LPL) were normal. However, hepatic lipase (HL) activity was significantly decreased in HALP profile A, but within the normal range for HALP profile B. In conclusion, an HALP profile A with a low prevalence of atherosclerosis was characterized by an increased HDL2/HDL3 ratio, HDL2b, and LpA-I levels associated with decreased HL activity.

Relation of lipoprotein subclasses as measured by proton nuclear magnetic resonance spectroscopy to coronary artery disease

Although each of the major lipoprotein fractions is composed of various subclasses that may differ in atherogenicity, the importance of this heterogeneity has been difficult to ascertain owing to the labor-intensive nature of subclass measurement methods. We have recently developed a procedure, using proton nuclear magnetic resonance (NMR) spectroscopy, to simultaneously quantify levels of subclasses of very low density (VLDL), low density (LDL), and high density (HDL) lipoproteins; subclass distributions determined with this method agree well with those derived by gradient gel electrophoresis. The objective of the current study of 158 men was to examine whether NMR-derived lipoprotein subclass levels improve the prediction of arteriographically documented coronary artery disease (CAD) when levels of lipids and lipoproteins are known. We found that a global measure of CAD severity was positively associated with levels of large VLDL and small HDL particles and inversely associated with intermediate size HDL particles; these associations were independent of age and standard lipid measurements. At comparable lipid and lipoprotein levels, for example, men with relatively high (higher than the median) levels of either small HDL or large VLDL particles were three to four times more likely to have extensive CAD than were the other men; the 27 men with high levels of both large VLDL and small HDL were 15 times more likely to have extensive CAD than were men with low levels. In contrast, adjustment for levels of triglycerides or HDL cholesterol greatly reduced the relation of small LDL particles to CAD. These findings suggest that large VLDL and small HDL particles may play important roles in the development of occlusive disease and that their measurement, which is not possible with routine lipid testing, may lead to more accurate risk assessment.

Delayed increase in high density lipoprotein-phospholipids after ingestion of a fat load in normolipidemic patients with coronary artery disease

We studied the effect of a single oral fat load, supplemented with retinyl palmitate (RP), on high density lipoprotein (HDL) lipids in six normolipidemic men with coronary artery disease (CAD) and in six age- and lipid-matched controls. All subjects were selected from a study group which underwent the same protocol 2 years earlier. Post-prandial total plasma lipids, plasma RP levels, and HDL lipids were evaluated at 2-h intervals up till 10 h after the meal. In most subjects the post-prandial response of plasma triglyceride (TG) and plasma RP was identical in the first and second tests. Following the fat load, control subjects showed no change in HDL total cholesterol (TC) or HDL cholesteryl ester (CE) and showed an increase in HDL-TG. CAD subjects however showed a decrease in HDL-TC and HDL-CE and an increase in HDL-TG, similar to the increase in control subjects. In control subjects an increase in HDL phospholipid (PL) was apparent between 0 and 8 h after the fat load. By contrast, in CAD subjects the increase in HDL-PL was only found after as long as 6 h. The magnitude of the post-prandial response of HDL-PL measured during the test was significantly lower in the CAD group. The effects of the fat load on HDL free cholesterol (FC) were similar to the changes in HDL-PL. These data support the hypothesis that PL and FC released during the degradation of chylomicrons as surface remnants are taken up by HDL. This process is clearly delayed in normolipidemic CAD subjects compared with controls. The data suggest that differences in the post-prandial response to an oral fat load in normolipidemic CAD patients and control subjects are not confined to the clearance of TG-rich lipoproteins, but also involve a difference in the uptake of chylomicron surface material by HDL.