Cost-effective study of determination methods for low-density lipoprotein by new direct assay compared to Friedewald's formula calculation in hypercholesterolemic subjects

OBJECTIVE

To study the cost effectiveness of determination methods for low-density lipoprotein by new direct assay compared to Friedewald's formula calculation.

DESIGN

descriptive study.

MATERIAL

Fasting serum from 100 subjects with a history of hypercholesterolemia.

METHOD

Specimens were determined for total cholesterol, high-density lipoprotein (HDL) and triglyceride using automated clinical chemistry, as the basic information in calculation of LDL level. Each specimen was also processed by direct LDL assay by the same automation. Correlation of the results from both methods was analyzed. Cost effectiveness analysis was then performed.

RESULTS

The least-squares equation from comparing direct LDL assay to calculation method gave Y = 0.897X + 20.42 (r = 0.996, p < 0.05). According to the present study, the cost per utility of the direct assay method (47.54 baht) was more expensive than the calculation method (29.59 baht).

CONCLUSION

The results from both methods were well related. However, the cost per utility of the calculation method is cheaper, therefore, the authors recommend the use of the calculation method rather than the direct assay for follow-up of LDL level in hypercholesterolemic patients.

High density lipoprotein-cholesterol changes in children with high cholesterol levels at birth

The predictive value of serum lipoprotein concentrations at birth for the same parameters later in life is under debate. A group of 20 children displaying high total cholesterol (TC) levels at birth (group 2) were compared at age 4 years with 18 control children who had presented a normal lipoprotein profile at birth (group 1). There was a significant correlation between TC, low density lipoprotein-cholesterol, high density lipoprotein (HDL)-cholesterol, and apolipoprotein (Apo) A-I levels at age 4 years and at birth. The increases in TC and HDL-cholesterol levels from birth to age 4 years were significantly lower (P < 0.05, P < 0.01, respectively) in group 2 than in the control group and inversely correlated with the concentrations of these parameters at birth. The increases in HDL-cholesterol and Apo A-I levels were higher in males while those of triacylglycerol and Apo B were higher in females (P < 0.05). However, the increases in TC and HDL-cholesterol were higher in controls (P< 0.05). Diets of children of both groups were similar regarding the energy contribution of saturated, monounsaturated and polyunsaturated fatty acids, although children from group 2 ate less fish and omega-3 fatty acids (P < 0.05).

CONCLUSION

the present data suggest for the first time that when high density lipoprotein-cholesterol levels are high at birth, those levels increase less during the first four years of life. Moreover, low density lipoprotein-cholesterol increased about five times as much as high density lipoprotein-cholesterol did in controls and about 15 times as much as in the children with high cholesterol at birth.

Effect of dietary zinc deficiency on rat lipid concentrations

OBJECTIVE

Evaluation of the lipid profile in serum, liver, and testis of rats fed marginal and severe zinc deficient diets.

METHODS

Three groups of rats were treated for 8 weeks with normal diet, marginally zinc deficient diet and severely zinc deficient diet. Lipid concentrations were measured in serum, liver, and testis of these groups.

RESULTS

The concentrations of serum lipids were not significantly altered between marginally zinc deficient diet treated and control rats. However, in rats treated with severely zinc deficient diet, the concentrations of serum total cholesterol, high density lipoprotein cholesterol and phospholipids were significantly increased (P < 0.01) and (P < 0.001), whereas the concentration of triacylglycerol was significantly decreased (P < 0.01). However, low-density lipoprotein cholesterol concentration was non-significantly different from controls. The concentrations of liver total cholesterol, triacylglycerol and phospholipids were significantly decreased (P < 0.001) in rats treated with severely zinc deficient diet. The testicular concentration of total cholesterol was increased but this increase was non-significantly different from controls, whereas the testicular concentrations of triacylglycerol and phospholipids were significantly decreased (P < 0.001) in rats treated with severely zinc deficient diet.

CONCLUSION

These results suggest that a marginally zinc deficient diet does not play a significant role in altering rat lipid concentrations. However, the changes in serum lipid concentrations could be related to those changes in tissue lipid concentrations.

The associations among thoracic aortic atherosclerosis, coronary atherosclerosis and the function of high density lipoprotein

We sought to determine the associations among thoracic aortic atherosclerosis, coronary atherosclerosis and the function of high density lipoprotein (HDL) in a case-control study. The function of HDL can be assessed by the fractional esterification rate of cholesterol in low density lipoprotein (LDL)- and very low density lipoprotein (VLDL)-depleted plasma (FER(HDL)), which reflects a balance of cholesterol uptake by HDL and cholesterol ester (CE) transport in the reverse cholesterol transport (RCT) system in humans. Cases (n=51, age: 64.3+/-8.0 years) and controls (n=51, age: 58.7+/-13.1 years) were defined as subjects with/without angiographically proven coronary artery disease (CAD), respectively and examined for thoracic aortic atherosclerosis (TAA) by transesophageal echocardiography. The severity of TAA was determined by the ratio of average sclerotic areas (ASA) and average sclerotic lengths (ASL). The cases had significantly (P<0.05) higher values of ASA (0.22+/-0.18 vs. 0.10+/-0.11), ASL (0.82+/-0.56 vs. 0.48+/-0.45), ASA/ASL ratio (0.23+/-0.08 vs. 0.17+/-0.09) and FER(HDL) (10.3+/-3.8 vs. 8.3+/-3.5% per hour) and lower HDL-C and apolipoprotein A-I levels than the controls. A receiver operating characteristic (ROC) curve analysis showed that ASA/ASL and FER(HDL) had moderate discriminating ability for CAD and the diagnostic accuracy of ASA/ASL was better than that of FER(HDL) (area under ROC curve: 0.703 and 0.656, respectively). Multivariate logistic regression analysis indicated that ASA/ASL and FER(HDL) were independent indicators for CAD [odds ratio (95% CI): 7.5 (2.4-27), P<0.01 and 4.0 (1.2-15), P<0.05] after adjusting for age, gender and other conventional risk factors, and that a high FER(HDL) value greatly increased the relative risk of CAD associated with a high ASA/ASL. The function of HDL, as assessed by FER(HDL), enhances the ability of TAA to predict CAD.

Effect of rosuvastatin on low-density lipoprotein cholesterol in patients with hypercholesterolemia

Rosuvastatin is a new, synthetic, orally active statin, with marked low-density lipoprotein (LDL) cholesterol-lowering activity. We conducted 2 dose-ranging studies. In the first study, after a 6-week dietary run-in, 142 moderately hypercholesterolemic patients were randomized equally to receive double-blind placebo or rosuvastatin 1, 2.5, 5, 10, 20, or 40 mg or open-label atorvastatin 10 or 80 mg once daily for 6 weeks; in the second study, conducted to extend the rosuvastatin dose range, 64 patients were randomized to double-blind, once-daily placebo or rosuvastatin 40 or 80 mg (1:1:2 ratio) for 6 weeks. Data from both studies were combined for analysis of lipid effects. No statistical comparison of atorvastatin arms with placebo or rosuvastatin was performed. Rosuvastatin was associated with highly significant dose-dependent reductions in LDL cholesterol compared with placebo (p <0.001); decreases ranged from 34% (1 mg) to 65% (80 mg). Linear regression analysis indicated an additional 4.5% LDL cholesterol reduction for each doubling of the rosuvastatin dose. Across the dose range, approximately 90% of LDL cholesterol reduction occurred within the first 2 weeks of treatment. Significant, dose-dependent reductions in total cholesterol and apolipoprotein B with rosuvastatin were also observed (p <0.001). High-density lipoprotein cholesterol increases and triglyceride reductions were consistently observed and statistically significant at some dose levels. All lipid ratios were significantly reduced at all rosuvastatin dose levels (p <0.001). Adverse events were similar across placebo and active treatments. No significant increases in alanine aminotransferase or creatine kinase were seen in any patient. Over 6 weeks, rosuvastatin produced large, rapid, dose-dependent LDL cholesterol reductions and was well tolerated in hypercholesterolemic patients.

A prospective, population-based study of low density lipoprotein particle size as a risk factor for ischemic heart disease in men

BACKGROUND

The current interpretation of the increased risk of ischemic heart disease (IHD) associated with reduced low density lipoprotein (LDL) particle size is based entirely on data derived from relatively small case-control studies, with a lack of evidence from large, prospective, population-based cohort data.

OBJECTIVES

To investigate the association between LDL particle size and incident IHD on the basis of data from the entire population-based, prospective cohort of men from the Quebec Cardiovascular Study.

PATIENTS AND METHODS

Analyses were conducted in a cohort of 2057 men who were all initially free of IHD, and who were followed up over a five-year period, during which 108 first IHD events (myocardial infarction, angina or coronary death) were recorded. LDL particle size was measured by nondenaturing gradient gel electrophoresis.

RESULTS

Cox proportional hazards analysis indicated that the relationship between LDL particle size and the risk of future IHD events was not linear. Men with an LDL particle size less than 256.0 A had a significant 2.2-fold increase in the five-year rate of IHD (P<0.001) compared with men having an LDL particle size greater than 256.0 A. Multivariate and subgroup analyses indicated that small, dense LDL particles predicted the rate of IHD independent of LDL cholesterol, triglycerides, high density lipoprotein (HDL) cholesterol, apolipoprotein B and the total cholesterol to HDL cholesterol ratio. Finally, the magnitude of the increase in IHD risk attributed to lipid risk factors was modulated to a significant extent by variations in LDL particle size.

CONCLUSIONS

The present study provides the first large scale, population-based, prospective evidence supporting the hypothesis that small, dense LDL particles may be associated with an increased risk of IHD. The results also suggest that information on LDL diameter may improve the ability to predict IHD risk accurately over traditional lipid variables.

Reduced myocardial flow reserve relates to increased carotid intima-media thickness in healthy young men

Increased carotid artery wall thickness and lipoprotein oxidation are key early events in atherosclerosis. To test the hypothesis that reduced myocardial flow reserve is a marker of subclinical atherosclerosis, we examined the relationships between flow reserve and carotid artery intima-media thickness (IMT) in young men free from coronary heart disease. Basal and dipyridamole stimulated coronary blood flow was measured using positron emission tomography (PET) in 55 healthy men aged 36+/-4 years. Myocardial flow reserve was calculated as the ratio of stimulated flow to basal flow. The mean carotid artery IMT was measured using high-resolution ultrasound. Oxidised LDL was measured as baseline LDL diene conjugation. Myocardial flow reserve decreased across the quartiles of increasing IMT (P=0.006), and was 5.2+/-1.9 in the lowest quartile for IMT and 3.7+/-1.2 in the highest (P=0.04, I vs. IV quartile). In univariate analysis, oxidised LDL correlated inversely with flow reserve (r=-0.35, P=0.01) and directly with IMT (r=0.51, P<0.001). The association between flow reserve and IMT remained significant (P< or =0.01) in multivariate regression model including age, blood pressure, left ventricular mass, ox-LDL, total cholesterol, HDL-cholesterol and triglycerides as covariates. These data support the concept that reduced myocardial flow reserve reflects subclinical atherosclerosis in asymptomatic subjects, and suggest that increased lipoprotein oxidation is directly related to early structural and functional atherosclerotic vascular changes.

Effect of atherogenic diet on reverse cholesterol transport in vivo in atherosclerosis susceptible (C57BL/6) and resistant (C3H) mice

Mice susceptible (C57BL/6) or resistant (C3H) to atherosclerosis induced by a high cholesterol-cholate containing diet (A-diet) were used to study reverse cholesterol transport (RCT) in vivo as measured by loss of cholesterol from a depot created by injection of cationized LDL into the rectus femoris muscle. Plasma total and HDL-cholesterol (HDL-C), total and HDL phospholipid (HDL-PL) levels in chow fed C3H male and female mice were higher than in C57BL/6 mice. After one month on A-diet, plasma cholesterol more than doubled in both strains and genders. The decrease in HDL-C and HDL-PL was twice as great in C57BL/6 as in C3H female mice, while in male C3H mice there was no decrease. The loss of exogenous cholesterol mass (ECM) after injection of cationized LDL was more rapid in C3H than in C57BL/6 mice. In chow fed mice, ECM retained in muscle on day 12 was 37% in C57BL/6 and 20% in C3H females; in males it was 39% and 18% in C57BL/6 and C3H, respectively. On A-diet, 76% were retained in C57BL/6 and 28% in C3H females; these values were 59% and 28% in C57BL/6 and C3H males. Thus, the slow clearance of ECM (which represents RCT) in C57BL/6 mice on A-diet, that could be related to a marked decrease of HDL-PL, might contribute towards their susceptibility to atherosclerosis.

Randomised controlled trial of use by hypercholesterolaemic patients of a vegetable oil sterol-enriched fat spread

Plant sterols may be a useful additive therapy in the treatment of hypercholesterolaemic patients. The purpose of this study was to determine the effect of a fat spread enriched with vegetable oil sterols on plasma lipid, lipoprotein and apolipoprotein concentrations. A randomised double blind placebo-controlled crossover trial with two consecutive periods of 8 weeks was conducted. 30 patients with heterozygous familial hypercholesterolaemia treated concurrently with an HMG-CoA reductase inhibitor (statin) and 32 patients with type IIa primary hypercholesterolaemia with a total cholesterol concentration >6.5 mmol/l not taking lipid-lowering drug therapy were recruited from a hospital lipid clinic. The active treatment was a fortified fat spread (25 g/day) providing 2.5 g of plant sterols. The control spread was indistinguishable in taste and appearance. Comparison at the end of the two 8-week trial periods showed a statistically significant reduction in total and LDL-cholesterol with use of the fortified spread but the results were confounded by a carry-over effect, which was partly explained by changes in the background diet. Because a carry-over effect was present, further analyses were restricted to the parallel arms of the first treatment period and were conducted on an intention to treat basis. After 4 weeks, LDL-cholesterol had decreased by 0.04 mmol/l ([0.8%] 95% confidence interval -0.44-0.37 NS) in the placebo group and decreased by -0.76 mmol/l ([15.0%] 95% CI -1.03--0.48, P<0.0001) in the active treatment group. After 8 weeks, the corresponding results were 0.0 mmol/l ([0.0%] 95% CI -0.26-0.24 NS) and -0.51 mmol/l ([10.0%] 95% CI -0.73--0.29 P<0.0001). There were no significant changes in apolipoprotein AI or B concentrations in the placebo group, but there was a small but statistically significant increase in apolipoprotein AI and a decrease in apolipoprotein B in the active treatment group. HDL cholesterol and triglyceride concentrations were unchanged. There was no difference in response between patients with statin-treated familial hypercholesterolaemia and patients with type IIa hyperlipoproteinaemia. We conclude that a fortified fat spread enriched with vegetable oil sterols reduces LDL-cholesterol by 10-15% with no difference in response between hypercholesterolaemic patients prescribed statins and those not taking lipid-lowering drug therapy.

Prevention of a first myocardial infarction

Coronary heart disease is the leading cause of morbidity and mortality in men and women in the Western world. We now have significant evidence that prevention of the first coronary event using lifestyle and pharmacologic therapies is paramount. Events are caused by inflamed arteries leading to rupture of atherosclerotic plaques that induce potentially occlusive thrombi. Analysis of event reduction trials has revealed that LDL-C lowering is only one part of the therapy needed to stabilize plaque. HMG-Co-A-reductase inhibitors, fibrates, and statins all have differing mechanisms of action that provide not only lipid but also inflammatory, rheologic, and coagulation benefits. Concentration and sizes of lipoprotein subfractions have emerged as important new tools with small dense LDL particles having more atherogenicity, which has led to an increasing use of aggressive combination therapy for prevention of first myocardial infarction. Proper use of lipid-lowering therapies requires knowledge of drug metabolism drug-drug interactions.

Design and rationale of the ARBITER trial (Arterial Biology for the Investigation of the Treatment Effects of Reducing Cholesterol)--a randomized trial comparing the effects of atorvastatin and pravastatin on carotid artery intima-media thickness

BACKGROUND

As a class, statins are remarkably effective in reducing low-density lipoprotein (LDL) cholesterol, and several of these drugs have now been shown to reduce coronary heart disease morbidity and mortality. However, several important controversies in the use of statins remain to be answered by clinical trials. For example, it is controversial whether marked cholesterol reduction to levels below 100 mg/dL would further reduce the incidence of coronary heart disease. Furthermore, concerns about differences among statins for nonlipid effects has raised the concern that the assumption of a class effect is premature until head-to-head clinical trials are completed.

METHODS

Arterial Biology for the Investigation for the Treatment Effects of Reducing Cholesterol (ARBITER) is a single-center, randomized, active-controlled study comparing the efficacy of high-dose atorvastatin (80 mg/d) and pravastatin (40 mg/d) in patients being treated for either the primary or secondary prevention of coronary heart disease. This trial will enroll up to 200 patients for the primary end point of the mean change in intima-media thickness of the common carotid artery. This effect will be evaluated over a treatment duration of 12 months. Secondary end points include the effects of statin therapy on inflammatory and hemostatic markers (C-reactive protein and fibrinogen).

CONCLUSION

ARBITER will provide important data on the role of marked LDL reduction and the "class effect" theory of statin therapy in cardiovascular medicine.

Cardiac risk factors, medication, and recurrent clinical events after acute coronary disease; a prospective cohort study

AIMS

Systematic data are sparse on clinical outcome after acute coronary disease followed by cardiac rehabilitation therapy. Therefore, our objective was to determine the long-term development of cardiac risk factors, recurrent clinical events, and cardiac medication in patients undergoing routine in hospital cardiac rehabilitation therapy.

METHODS AND RESULTS

In the prospective PIN Study (Post Infarct Care), 2441 consecutive patients (78% men, 60+/-10 years, 22% women, 65+/-10 years) were enrolled in 18 inpatient rehabilitation centres in Germany following myocardial infarction (56%), coronary artery bypass graft (38%) or percutaneous transluminal coronary angioplasty (6%). Cardiac risk factors, pre-specified clinical end-points, and the prescription of cardiac medication were prospectively documented on admission to and at discharge from rehabilitation therapy, and 3, 6 and 12 months later by obtaining information with standardized questionnaires from the patients and their physicians. The cardiac risk factors improved initially during cardiac rehabilitation therapy, but deteriorated within the following 12 months: 39% patients smoked at the beginning vs 5% at the end of in hospital rehabilitation vs 10% at 12 months follow-up (P<0.001). The respective numbers for patients with blood pressure >140 and/or 90 mmHg were 24 vs 8 vs 25% (P<0.01) and with plasma cholesterol >200 mg. dl(-1)57 vs 29 vs 51% (P<0.01). A total of 886 patients experienced one or more recurrent clinical events during the first year, 69% of those within the initial 6 months. At 12 months follow-up, 77% of patients received aspirin, 70% beta-blockers, 62% lipid lowering medication, and 53% angiotensin converting enzyme inhibitors.

CONCLUSION

The present results indicate that the benefit of cardiac rehabilitation therapy following acute coronary events is only partially maintained during the following year. Continuous strategies of medical care need to be developed to improve the long-term outcome in coronary patients.

Analytical and clinical performance of two homogeneous assays for measuring of LDL-cholesterol

A clinical laboratory currently estimates LDL-Cholesterol (LDL-C) concentration using the Friedewald calculation, which requires fasting specimens and is subject to error with increasing triglycerides levels. We evaluated the analytical and clinical performance of the direct LDL-C assay from two companies, Roche Diagnostics (LDL-C(Roche)) and Wako Pure Chemical (LDL-C(Wako)). Both methods meet current guidelines for precision with within-run coefficients of variation less than 3 per cent. The LDL-C(Roche) assay correlated well with the LDL-C from the Friedewald equation (LDL-C(Fried), r = 0.958, y = 0.85x + 17.08 mg/dL, n = 422). The LDL-C(Wako) assay also correlated with the LDL-C(Fried) (r = 0.946, y = 0.86x + 7.81 mg/dL, n = 422). In addition, at the medical decision cutoff points, LDL-C(Roche) assay and LDL-C(Wako) showed positive predictive values of 87.44 per cent and 69.67 per cent respectively. We conclude that the LDL-C(Roche) assay meets the currently established analytical and clinical performance, but LDL-C(Wako) assay meets only analytical performance. Clinical performance needs further evaluation.

Direct method for the measurement of low-density lipoprotein cholesterol levels in patients with chronic renal disease: a comparative assessment

BACKGROUND/AIM

This study was performed to comparatively evaluate the results obtained for low-density lipoprotein (LDL) cholesterol concentrations by either a newly described direct method or the Friedewald equation in subjects with and without chronic renal disease.

METHODS

Fasting plasma was obtained from a total of 169 subjects, 105 with normal renal function (including 53 hyperlipidaemic) and 64 with chronic renal disease (nephrotic syndrome and/or chronic renal failure; including 40 hyperlipidaemic patients), and analyzed for LDL cholesterol using the Friedewald equation and a direct LDL assay method.

RESULTS

The Friedewald equation and the direct LDL cholesterol assay correlated well with each other (r = 0.79-0.90 in all subjects with plasma triglyceride, TG, levels greater than or less than 4.0 mmol/l and with and without chronic renal disease and/or hyperlipidaemia, all p < 0.0001). The values for LDL cholesterol, however, tended to be higher with the direct measurement. This mean difference was trivial in hyperlipidaemic subjects with (8.5%) and without (7.1%) normal renal function (both p < 0.05), but could be clinically significant in those with TG >4.0 mmol/l (mean difference 18%, p < 0.001). Indeed, bias plots confirmed this observation of wider negative bias for Friedewald estimation in these moderately hypertriglyceridaemic subjects.

CONCLUSION

For most routine laboratories the options immediately available for assessment of lipid levels are the Friedewald equation or the direct measurement. The Friedewald equation and the direct assay method for LDL cholesterol are about equally good for assessment of the LDL status in patients with chronic renal disease and plasma TG <4.0 mmol/l. Where there are restraints on laboratory budgets, it would appear appropriate that the more expensive direct assay method be restricted to cases in whom plasma TG >4.0 mmol/l or to patients who, for whatever reason, are unable to produce fasting samples.

Flow-mediated vasoactivity and circulating adhesion molecules in hypertriglyceridemia: association with small, dense LDL cholesterol particles

BACKGROUND

Endothelial dysfunction is considered one of the earliest events in the process of atherosclerosis, and an impaired vasodilatory response has been reported in patients with dyslipidemias. However, the independent association between hypertriglyceridemia and endothelial dysfunction is controversial, and the relation between endothelium-dependent vasodilation and circulating cell adhesion molecules as markers of endothelial dysfunction has not been fully determined.

METHODS

Brachial artery flow mediated vasodilation (FMV) and the soluble forms of vascular cell adhesion molecule-1 (sVCAM-1) and intercellular adhesion molecule-1 (sICAM-1) were determined after overnight fasting in 16 men with hypertriglyceridemia (age 33 +/- 6 years) and in 16 age-matched healthy men with normal triglycerides and cholesterol. Subjects who smoked and those with known cardiovascular disease, diabetes, hypertension, recent or active infections, or any other disease that could affect leukocyte activation were excluded from the study.

RESULTS

Compared with normal subjects, subjects with hypertriglyceridemia showed a higher level of sVCAM-1 and sICAM-1 (both P <.001), a reduced FMV (P <.01), and a smaller LDL particle size (P <.05). FMV had a significant inverse correlation with sVCAM-1 (r = -0.61, P <.001) and sICAM-1 (r = -0.38, P <.03). LDL particle size had a strong, direct association with FMV (r = 0.75, P <.001) and an inverse association with adhesion molecules. By multiple regression analysis, triglycerides (P <.001) and small LDL particle size (P <.002) predicted a reduced FMV.

CONCLUSIONS

Serum level of cell adhesion molecules is increased and FMV is impaired in young healthy men with hypertriglyceridemia compared with age-matched men with normal lipid levels. Small, dense LDL particles may play a role in determining endothelial dysfunction in these subjects.

Soy protein reduces the arterial low-density lipoprotein (LDL) concentration and delivery of LDL cholesterol to the arteries of diabetic and nondiabetic male cynomolgus monkeys

We have previously shown that soy protein consumption improves lipoprotein concentrations and reduces the progression of atherosclerosis in cynomolgus monkeys. The mechanism for these beneficial effects is unclear. The purpose of this study was to determine potential mechanisms for the atheroprotective effects of soy and to determine if these effects extend to diabetic monkeys. We designed an experiment with a 2 x 2 factorial design in which adult male monkeys (N = 23) were fed an atherogenic diet with a protein source of either soy isolate or casein and lactalbumin, and the monkeys were either control or streptozotocin-induced diabetic. Diabetics had significantly increased fasting glucose and glycated hemoglobin (GHb) levels; this relationship was not affected by the type of dietary protein. Diabetics also had increased total (TC) and low-density lipoprotein cholesterol (LDLC) concentrations. However, soy consumption significantly reduced TC and LDLC concentrations in both control and diabetic monkeys. Plasma and arterial LDL metabolism was determined by injecting 125I-LDL at 48 hours and 131I-tyramine cellobiose LDL at 1 hour prior to necropsy. This allowed a determination of the arterial LDL concentration, permeability, and arterial LDL delivery. An increase in the whole-body plasma LDL fractional catabolic rate (FCR) was found with soy. Soy significantly reduced the arterial LDL concentration across all arterial sites by an average of 50%. Soy also significantly reduced the delivery of LDLC to all arterial sites by an average of 40%. While this was primarily due to the lower plasma LDLC concentration, LDL permeability in the carotid bifurcation and internal carotid arteries was also reduced. There was no additional effect of diabetes. These beneficial effects on plasma and arterial LDL metabolism would be expected to reduce atherosclerosis and were found in both control and diabetic monkeys.

Autosomal dominant type IIa hypercholesterolemia: evaluation of the respective contributions of LDLR and APOB gene defects as well as a third major group of defects

Autosomal dominant type IIa hypercholesterolaemia (ADH) is characterised by an elevation of total plasma cholesterol associated with increased LDL particles. Numerous different molecular defects have been identified in the LDL receptor (LDLR) and few specific mutations in the apolipoprotein B (APOB) gene resulting in familial hypercholesterolaemia and familial defective apoB-100 respectively. To estimate the respective contribution of LDLR, APOB and other gene defects in this disease, we studied 33 well characterised French families diagnosed over at least three generations with ADH through the candidate gene approach. An estimation of the proportions performed with the HOMOG3R program showed that an LDLR gene defect was involved in approximately 50% of the families (P = 0.001). On the other hand, the estimated contribution of an APOB gene defect was only 15%. This low estimation of ADH due to an APOB gene defect is further strengthened by the existence of only two probands carrying the APOB (R3500Q) mutation in the sample. More importantly and surprisingly, 35% of the families in the sample were estimated to be linked to neither LDLR nor APOB genes. These data were confirmed by the exclusion of both genes through direct haplotyping in three families. Our results demonstrate that the relative contributions of LDLR and APOB gene defects to the disease are very different. Furthermore, our results also show that genetic heterogeneity is, generally, underestimated in ADH, and that at least three major groups of defects are involved. At this point, the contribution of the recently mapped FH3 gene to ADH cannot be assessed nor its importance in the group of 'non LDLR/non APOB' families.

Factor XIIa and triacylglycerol rich lipoproteins: responses to exercise intervention

OBJECTIVES

(a) To determine if factor XIIa (FXIIa) would be sensitive to change from exercise intervention in a group of previously sedentary/low active middle aged men and women; (b) to investigate further the previously reported relation between FXIIa and triacylglycerol (TAG) rich lipoproteins.

METHODS

Thirty seven men (mean (SD) age 57 (7) years) and 60 women (mean age 54 (7) years) completed the study. Before the intervention, these subjects were randomly allocated to a group of walkers (n = 81) or controls (n = 16). Before and after an 18 week walking intervention, fasted blood samples were collected and analysed for FXIIa, TAG, total cholesterol (TC), low density lipoprotein cholesterol (LDL-C), high density lipoprotein cholesterol (HDL-C), and apolipoprotein (apo) B.

RESULTS

Kruskal-Wallis analysis of data obtained before the intervention showed no significant differences (p>0.4) between the walking and control groups for age, height, body mass, gender, FXIIa, TAG, TC, HDL-C, or apo B, although the women did show significantly lower levels of TAG (p<0.04) and higher HDL-C (p<0.0001) than the men. General linear model analysis of data obtained after the intervention, using the baseline value as a covariate, showed significant reductions (p<0.0001) in FXIIa for the walkers compared with the controls. Pearson product-moment correlations also showed significant relations between the concentrations of FXIIa and TAG, TC, LDL-C, and apo B.

CONCLUSIONS

The findings of this study suggest that FXIIa is sensitive to change from exercise intervention and support previous research showing an association between the concentrations of FXIIa and TAG rich lipoproteins.

Correlation of low-density lipoprotein modification by myeloperoxidase with hypochlorous acid formation

Myeloperoxidase is an enzyme in phagocytes which catalyzes several redox reactions. A major product is hypochlorous acid which appears to be important in inflammatory processes such as atherosclerosis. The aim of this study was to investigate whether the kinetics of low-density lipoprotein modification by the myeloperoxidase/hydrogen peroxide/chloride system in vitro conform to the established kinetics of hypochlorous acid formation and to compare the results with known in vivo data. The absorbance at 234 nm was applied to study the kinetics of the modification of low-density lipoprotein. Variation of the concentration of low-density lipoprotein, hydrogen peroxide, and chloride, respectively, had a biphasic effect on the maximal rate of low-density lipoprotein modification. Increasing the substrates up to certain threshold levels resulted in increased modification, however, further increases caused inhibition of low-density lipoprotein modification. The inhibitory effect of higher low-density lipoprotein concentrations might be relevant, since these concentrations occur in the human aortic intima. Furthermore, a positive correlation was found between the maximal rate of low-density lipoprotein modification and the acidity of the medium. In summary, low-density lipoprotein modification is affected by the myeloperoxidase/hydrogen peroxide/chloride system in a similar manner to hypochlorous acid production. We conclude that myeloperoxidase, which has been detected in atherosclerotic lesions, is able to modify low-density lipoprotein into the form which is taken up by macrophages in an uncontrolled manner.

Consumption of olive oil has opposite effects on plasma total cholesterol and sphingomyelin concentrations in rats

The hypothesis that olive-oil consumption alters plasma sphingomyelin concentrations and hepatic sphingomyelin metabolism was tested. Rats were fed on purified, high-cholesterol diets with either coconut fat or olive-oil (180 g/kg). In accordance with previous work, olive-oil v. coconut-fat consumption significantly elevated hepatic and total plasma cholesterol concentrations. During the course of the experiment, the concentration of plasma sphingomyelin rose in the coconut-fat group and remained constant in the olive-oil group. When compared with the coconut-fat-fed group, the plasma sphingomyelin levels were significantly lower in the olive-oil-fed group after 14 and 21 d of treatment. Dietary olive oil raised the amounts of cholesterol and sphingomyelin in the VLDL density region, and this change was associated with a reduction in the cholesterol and sphingomyelin contents of the LDL and HDL density ranges. Olive-oil consumption reduced the activity of serine palmitoyltransferase, while the activities of phosphatidylcholine:ceramide cholinephosphotransferase and phosphatidylethanolamine:ceramide ethanolaminephosphotransferase were left unchanged. Dietary olive oil also enhanced the activity of acidic sphingomyelinase, but not that of neutral sphingomyelinase. The present data indicate that dietary olive oil v. coconut fat has opposite effects on total plasma cholesterol and sphingomyelin concentrations. The lower plasma sphingomyelin levels observed in olive-oil-fed, as compared with coconut-fat-fed rats, may be explained by a simultaneous elevation and reduction in sphingomyelin catabolism and synthesis respectively, as based on the measured enzyme activities.

Serum, biliary, and fecal cholesterol and plant sterols in colectomized patients before and during consumption of stanol ester margarine

BACKGROUND

Cholesterol metabolic studies are simplified in colectomized patients because of rapid intestinal passage and reduced bacterial action.

OBJECTIVE

Our objective was to study the effect on cholesterol and plant sterol metabolism of feeding a margarine containing stanol ester to 11 colectomized patients.

DESIGN

A margarine containing 2 g stanol was consumed for 7-18 d. Serum, biliary, and fecal lipids were measured before and during consumption of the margarine.

RESULTS

Serum cholesterol concentrations and the ratio of plant sterol to cholesterol decreased after 1 d of consumption of stanol esters (P < 0.05). After 7 d, serum cholesterol decreased by 16% (P < 0.01), cholesterol absorption efficiency decreased by approximately 40%, and fecal output of cholesterol as neutral sterols (but not as bile acids) increased by 36%. Biliary bile acid composition and the molar percentage of biliary cholesterol were unchanged. Increased ratios of cholesterol precursor sterols in serum and bile indicated enhanced cholesterol synthesis during consumption of stanol esters; the percentage absorption of plant sterols and the ratios of plant sterols to cholesterol decreased, whereas serum and biliary plant stanols and their biliary secretion gradually increased. In feces, 95% of cholesterol and 90% of plant stanols were in unesterified form.

CONCLUSIONS

In colectomized patients, effective inhibition of cholesterol absorption and lowering of serum cholesterol concentrations and plant sterol ratios occurs within 1 d of the start of consumption of stanol esters. The composition of major bile lipids is unchanged, indicating that gallstone formation is unlikely. Small amounts of plant stanols are recovered in serum and bile during consumption of stanol esters but effectively are secreted through bile, thereby balancing the intake-induced increase in their absorption.

Genetic factors associated with response of LDL subfractions to change in the nature of dietary fat

A preponderance of dense low density lipoprotein (LDL) particles is associated with an increased risk of coronary heart disease. It has been shown that dense LDL levels can be modified by diet. We investigated the contribution of polymorphisms in the genes for apolipoprotein (apo) B, apo AIV, lipoprotein lipase (LPL) and cholesterol ester transfer protein (CETP) to variation in the changes in plasma concentrations of dense LDL between a high saturated and a high polyunsaturated fatty acid diet. A total of 46 freeliving individuals (19 men and 27 women) completed a crossover trial with two dietary interventions of 4 weeks each, a high saturated fat diet (providing 21% energy from saturated fat and 3% energy from polyunsaturated fat) and a high polyunsaturated fat diet (providing 11% energy as saturated fat and 10% energy as polyunsaturated fat). Overall, the change in dense LDL between the saturated and polyunsaturated fat period was 0.17+/-0.33 mmol/L and this change was similar in men and women. Of the polymorphisms studied only variation in the apo AIV gene causing the substitution of histidine for glutamine at position 360 (Q360H) was associated with significant differences in the change in dense LDL concentration. Apo AIV Q/H individuals (n=6) showed a three-fold greater change in dense LDL cholesterol unadjusted for Lp(a) levels than Q/Q individuals (0.46+/-0.27 versus 0.12+/-0.31 mmol/L, p=0.02). The greater decrease in dense LDL cholesterol with an increase in polyunsaturated fat seen in those with the apo AIV H360 variant, who represent roughly 10% of the general population, suggests that they may benefit most from a PUFA rich lipid lowering diet.

Endothelium-dependent and -independent functions are impaired in patients with coronary heart disease

Endothelium plays a pivotal role in the development of atherosclerosis. Endothelial dysfunction participates in the course of acute coronary event. Using high-resolution ultrasound technique, endothelial dysfunction has been demonstrated in patients with atherosclerosis and risk factors for coronary disease, such as hypertension, diabetes mellitus, hypercholesterolemia and being smokers. In the present study, using this non-invasive method, the endothelial function of the brachial artery of patients with coronary heart disease (CHD) (n = 71) and control subjects (n = 34) was investigated. The results showed that endothelium-dependent and -independent vasodilatation were impaired in patients with CHD (2.61+/-2.91 vs. 8.10+/-7.81%, 17.20+/-7.93 vs. 23.19+/-8.89%, respectively) (P<0.001). Flow-mediated dilation (FMD) was significantly positively correlated with nitroglycerine-induced dilation (P<0.001). On univariate and multivariate analysis, the extent of FMD was significantly correlated with serum HDL-C levels (P<0.01). In conclusion, our study indicates both endothelial and underlying smooth muscle functions were impaired in patients with CHD. Decreased HDL-C levels may impair endothelial function.

Hypercholesterolemia increases coronary endothelial dysfunction, lipid content, and accelerated atherosclerosis after heart transplantation

Hyperlipidemia may increase endothelial damage and promote accelerated atherogenesis in graft coronary vasculopathy. To study the effects of hypercholesterolemia on coronary endothelial dysfunction, intimal hyperplasia, and lipid content, a porcine model of heterotopic heart transplantation, allowing nonacute rejection without immunosuppressive drugs, was used. A high cholesterol diet was fed to donor and recipient swine 1 month before and after transplantation. The endothelial function of coronary arteries of native and transplanted hearts from cholesterol-fed animals was studied in organ chambers 30 days after implantation and compared with endothelial function in arteries from animals fed a normal diet. The total serum cholesterol increased 3-fold in donors and recipients. Endothelium-dependent relaxations to serotonin, to the alpha(2)-adrenergic agonist UK14,304, and to the direct G-protein activator sodium fluoride were decreased significantly in allografted hearts compared with native hearts from both groups. Relaxations to the calcium ionophore A23187 and bradykinin were decreased significantly in allografts from animals fed the high cholesterol diet. The prevalence of intimal hyperplasia was significantly increased in coronary arteries from hypercholesterolemic swine. There was a significant increase in the lipid content of allograft arteries of hypercholesterolemic recipients. Hypercholesterolemia causes a general coronary endothelial dysfunction, increases the prevalence of intimal hyperplasia, and augments the incorporation of lipids in the vascular wall after heart transplantation. Hyperlipidemia accelerates graft coronary atherosclerosis through its effects on the endothelium.

Estrogen and progesterone reduce lipid accumulation in human monocyte-derived macrophages: a sex-specific effect

BACKGROUND

Males have an earlier onset and greater prevalence of clinical atherosclerosis than age-matched females, which is consistent with an atheroprotective effect of the female sex steroids, estrogen and progesterone. We therefore examined the effects of estrogen and progesterone on human foam cell formation, a key early event in atherogenesis.

METHODS AND RESULTS

Monocytes from healthy female and male donors were obtained from white cell concentrates and allowed to differentiate into macrophages over 10 days. These human monocyte-derived macrophages (MDMs) were exposed to either control (0.1% vol/vol ethanol) or estrogen or progesterone treatment on days 3 through 10. Lipid loading was achieved on days 8 through 10 by incubation with acetylated LDL. Lipid from the MDMs was then extracted for analysis of cholesteryl ester (CE) content. 17beta-Estradiol at both physiological (2 nmol/L) and supraphysiological (20 and 200 nmol/L) concentrations produced a significant reduction in macrophage CE content (88+/-3%, 88+/-2%, and 85+/-4%, respectively; P<0.02 compared with control). Physiological and supraphysiological levels of progesterone (2, 10, and 200 nmol/L) produced an even more dramatic reduction in CE content (74+/-9%, 56+/-10%, and 65+/-8%, respectively; P<0.002 compared with control). This effect could be abrogated by coincubation with the progesterone receptor antagonist RU486. Neither estrogen nor progesterone produced a reduction in lipid loading in male-donor-derived MDMs. Detailed lipid trafficking studies demonstrated that both estrogen and progesterone altered macrophage uptake and/or processing of modified LDL.

CONCLUSIONS

Physiological levels of estrogen and progesterone are associated with a female-sex-specific reduction in human macrophage lipid loading, which is consistent with an atheroprotective effect.

The effect of a combined dietary treatment with cholesterol and cholic acid on the lipid metabolism of geese at low or high choline concentrations

A previous study demonstrated that a dietary treatment of young geese with cholesterol and cholic acid raises lipid concentrations in the liver. The present study was carried out to investigate whether such a lipid accumulation caused by those hyperlipidemic compounds can be intensified by low dietary choline concentrations. Therefore, 38 eight-week old geese were divided into four groups of 9 or 10 animals each and received a basal diet poor in choline which consisted predominately of maize and soy protein isolate over a period of 8 weeks. Treatment factors were supplementation of diets with cholesterol and cholic acid (0 vs. 5 g of cholesterol and cholic acid each per kg) and supplementation of choline chloride (0 vs. 1.5 g/kg). Final body weights as well as carcass weights were neither influenced significantly by dietary treatment with cholesterol and cholic acid nor by low dietary choline concentrations. However, feeding diets supplemented with cholesterol and cholic acid markedly increased liver weights (two-fold), hepatic triglyceride (3.7-fold) and cholesterol (12-fold) concentrations and percentages of monounsaturated fatty acids at the expense of saturated and polyunsaturated fatty acids in the liver. In geese fed diets with cholesterol and cholic acid, insufficient choline supply did not intensify, but even slightly reduced hepatic lipid accumulation. Geese fed diets with cholesterol and cholic acid exhibited markedly increased levels of cholesterol, triglycerides and phospholipids in plasma and very low-density lipoproteins, regardless of the choline supply. Muscle tissue of geese fed diets supplemented with cholesterol and cholic acid exhibited also increased concentrations of triglycerides and cholesterol whereas the fatty acid composition of muscle lipids remained unchanged. Among geese without hyperlipidemic treatment, concentrations of triglycerides in plasma and very low-density lipoproteins as well as the concentrations of phosphatidylcholine in liver and muscle tissue were not reduced by low dietary choline concentrations. Therefore, it is suggested that those animals were able to synthesize endogenous sufficient choline.

Distribution of oleoyl-estrone in rat plasma lipoproteins

Pooled adult normal rat plasma was used for the separation of lipoprotein fractions: VLDL, LDL and HDL, from which a total lipids extract was obtained. The presence of fragments with the MW of estrone and oleoyl-estrone in the lipoprotein fractions was analyzed by HPLC-MS. The results show that oleoyl-estrone is the major estrone component in lipoproteins; this molecular species was present in all three lipoprotein lipid extracts. The lipoprotein fractions were used for the analysis of protein and lipid classes: triacylglycerols, total and esterified cholesterol and phospholipids as well as acyl-estrone. About half of the total acyl-estrone was in the HDL fraction and only about 10% in the VLDL fraction. HDLs contained about one molecule in 50 particles, LDLs one molecule per particle and VLDLs 15 molecules per particle, i.e. given their size, the larger lipoproteins contained more oleoyl-estrone than the HDLs. The distribution of this hormone suggests that oleoyl-estrone is lost with other lipids as the lipoproteins shrink. The results presented show that oleoyl-estrone is a molecule found naturally in rat lipoproteins in low concentrations - the lowest in HDLs - that are consistent with its postulated role in the control of body weight.

Evidence that lipoproteins are carriers of bioactive factors

We recently demonstrated that the mitogenic effect of LDL (100 microg/mL) as well as its early intracellular signaling pathway are mediated by a pertussis-toxin (PTX)-sensitive G(i) protein-coupled receptor that is independent from its classical receptor and involves activation of extracellular response kinases (ERK1/2) (also known as p44(mapk)/p42(mapk)). In the present study we examined whether LDL-adherent factors may be responsible for some of the effects of LDL. The term "signaling activity" is used to characterize fractions that cause an increase in intracellular free Ca(2+) concentration or stimulate ERK1/2 and c-fos mRNA expression. LDL, HDL, and VLDL stimulate ERK1/2 with the following order of potency: LDL>HDL>VLDL. After delipidation of LDL with chloroform/methanol/water mixtures a PTX-sensitive signaling activity was found in one fraction arbitrarily called LDL-F. After further analysis of LDL-F compounds by high pressure liquid chromatography, a PTX-sensitive signaling activity was detected only in the fraction with a retention time of 33 minutes (arbitrarily called LDL-F33). Similarly, after separation of sphingosine-1-phosphate (SPP) and sphingosylphosphorylcholine (SPC) by high pressure liquid chromatography, a PTX-sensitive signaling activity was found in the fractions 33 and 33 to 35, respectively. These findings demonstrate that the effects of LDL-F33 are mimicked by similar fractions collected from SPP/SPC, hence suggesting that these LDL-adherent molecules are possibly closely related to SPP/SPC. A PTX-sensitive signaling activity was also detected in HDL and HDL-F33. Therefore, LDL and other lipoproteins may function as carriers for bioactive phospholipids thereby contributing to the development of coronary artery disease. Our findings support a new research concept that may contribute in elucidating cellular mechanisms promoting coronary artery disease.

LDL particle size distribution is associated with carotid intima-media thickness in healthy 50-year-old men

Results of cross-sectional and prospective studies have suggested that small, dense low-density lipoprotein (LDL) particles predispose to coronary heart disease. We investigated the relationships between plasma concentrations of LDL subfractions and intima-media thickness (IMT) of the common carotid artery (CCA), quantified by B-mode ultrasound, in 94 healthy, 50-year-old men, all of whom were homozygous for the apolipoprotein E3 allele. A novel 3% to 7.5% polyacrylamide gradient gel was developed to provide separation of LDL subfractions with high resolution, as was a procedure to quantify plasma concentrations of these LDL subspecies. The LDL particle size distribution pattern obtained by the gradient gel electrophoresis procedure was in good agreement with the one obtained by a well-established, single-spin density gradient ultracentrifugation technique. LDL-II (particle size, 23.5 to 25.0 nm) was the most abundant subfraction, and its plasma concentration correlated closely with the total LDL cholesterol concentration (r=0. 61, P<0.001) but not with CCA IMT (r=-0.13, NS). In contrast, the plasma concentration of the predominant small, dense LDL particle subfraction (LDL-III; particle size, 22.5 to 23.5 nm) correlated strongly with CCA IMT (r=0.42, P<0.001). In multivariate analysis, the plasma concentration of the LDL-III subfraction contributed significantly to the variation in CCA IMT (R(2)=0.19). When plasma triglycerides and LDL cholesterol were forced into the multivariate model, 10% of the variation in CCA IMT was still accounted for by the LDL-III subfraction. In summary, use of a novel and sensitive gradient gel electrophoresis method for evaluation of LDL heterogeneity provided the basis for demonstrating an independent relation between the plasma concentration of small LDL and IMT of the CCA in healthy, middle-aged men.

Complement and atherogenesis: binding of CRP to degraded, nonoxidized LDL enhances complement activation

Complement activation occurs in temporal correlation with the subendothelial deposition of LDL during early atherogenesis, and complement also plays a pathogenetic role in promoting lesion progression. Two lesion components have been identified that may be responsible for complement activation. First, enzymatic degradation of LDL generates a derivative that can spontaneously activate complement, and enzymatically degraded LDL (E-LDL) has been detected in the lesions. Second, C-reactive protein (CRP) colocalizes with complement C5b-9, as evidenced by immunohistological studies of early atherosclerotic lesions, so the possibility exists that this acute phase protein also fulfills a complement-activating function. Here, we report that addition of LDL and CRP to human serum did not result in significant C3 turnover. Addition of E-LDL provoked complement activation, which was markedly enhanced by CRP. Binding of CRP to E-LDL was demonstrated by sucrose flotation experiments. Binding was Ca(2+)-dependent and inhibitable by phosphorylcholine, and the complement-activating property of E-LDL was destroyed by treatment with phospholipase C. These results indicated that CRP binds to phosphorylcholine groups that become exposed in enzymatically degraded LDL particles. Immunohistological studies complemented these findings in showing that CRP colocalizes with E-LDL in early human atherosclerotic lesions. Thus enzymatic, nonoxidative modification of tissue-deposited LDL can be expected to confer CRP-binding capacity onto the molecule. The ensuing enhancement of complement activation may be relevant to the development and progression of the atherosclerotic lesion.

[Thyroid disorders and dyslipidemias]

While overt thyroid disturbances, characterized by symptoms and/or clinical signs with abnormal serum levels of thyroid hormones, are generally associated with perturbations in the lipid profile, the situation is less clear as far as subclinical thyroid disturbances, defined by isolated abnormalities of thyroid stimulating hormone (TSH) levels, are concerned. In severe hyperthyroidism, a decrease of total cholesterol, LDL cholesterol and apoprotein B concentrations is generally observed. These biological parameters are normalized when appropriate antithyroid treatment is given. In profound hypothyroidism, on the contrary, elevated levels of total and LDL cholesterol levels are observed, which decrease after hormonal replacement. In both cases, the changes in serum levels of HDL cholesterol, triglycerides and lipoprotein (a) are less systematic, both before and after treatment. Lipid abnormalities associated with subclinical thyroid disturbances remain controversial. However, two recent meta-analyses have shown higher LDL cholesterol levels in presence of subclinical hypothyroidism and a significant reduction of such lipid abnormality after administration of thyroxine. Furthermore, they demonstrated a higher prevalence of subclinical hypothyroidism in a population with hypercholesterolaemia when compared to a population with normal cholesterol levels. Finally, a significant reduction in both total and LDL cholesterol concentrations has been reported after administration of thyroxine in a small group of hypercholesterolaemic patients with basal TSH levels in the upper range of normal values. In view of the results of the literature, strategies are proposed to help the clinician in the management of patients with overt or subclinical thyroid disturbances, associated with dyslipidaemia.

Autoantibodies against oxidised low-density lipoprotein in patients with obstructive sleep apnoea

Autoantibodies against oxidised low-density lipoprotein (OxLDL-Abs) have been proposed to be an indicator of endothelial dysfunction and a novel tool for finding individuals with a high cardiovascular risk. In a cross-sectional study, OxLDL-Abs were measured in 297 patients with obstructive sleep apnoea (OSA) and 54 controls using an enzyme-linked immunosorbent assay. The autoantibodies were increased in patients with OSA when compared to controls (age, body mass index (BMI) and gender adjusted, p = 0.001). However, within the OSA patients, OxLDL-Abs were not related to smoking, hypertension or BMI, and there was a weak negative correlation (r = -0.16, P = 0.007) between age and levels of OxLDL-Abs. In conclusion, at present the measurement OxLDL-Abs still remains a method for basic research and is not applicable for screening of at-risk patients with OSA.

Comparison of linkage-disequilibrium methods for localization of genes influencing quantitative traits in humans

Linkage disequilibrium has been used to help in the identification of genes predisposing to certain qualitative diseases. Although several linkage-disequilibrium tests have been developed for localization of genes influencing quantitative traits, these tests have not been thoroughly compared with one another. In this report we compare, under a variety of conditions, several different linkage-disequilibrium tests for identification of loci affecting quantitative traits. These tests use either single individuals or parent-child trios. When we compared tests with equal samples, we found that the truncated measured allele (TMA) test was the most powerful. The trait allele frequencies, the stringency of sample ascertainment, the number of marker alleles, and the linked genetic variance affected the power, but the presence of polygenes did not. When there were more than two trait alleles at a locus in the population, power to detect disequilibrium was greatly diminished. The presence of unlinked disequilibrium (D'*) increased the false-positive error rates of disequilibrium tests involving single individuals but did not affect the error rates of tests using family trios. The increase in error rates was affected by the stringency of selection, the trait allele frequency, and the linked genetic variance but not by polygenic factors. In an equilibrium population, the TMA test is most powerful, but, when adjusted for the presence of admixture, Allison test 3 becomes the most powerful whenever D'*>.15.

Identification of megalin/gp330 as a receptor for lipoprotein(a) in vitro

Lipoprotein(a) [Lp(a)] is an atherogenic lipoprotein of unknown physiological function. The mechanism of Lp(a) atherogenicity as well as its catabolic pathways are only incompletely understood at present. In this report, we show that the low density lipoprotein receptor (LDLR) gene family member megalin/glycoprotein (gp) 330 is capable of binding and mediating the cellular uptake and degradation of Lp(a) in vitro. A mouse embryonic yolk sac cell line with native expression of megalin/gp330 but genetically deficient in LDLR-related protein (LRP) and a control cell line carrying a double knockout for both LRP and megalin/gp330 were compared with regard to their ability to bind, internalize, and degrade dioctadecyltetramethylindocarbocyanine perchlorate (DiI)-fluorescence-labeled Lp(a) as well as equimolar amounts of 125I-labeled Lp(a) and LDL. Uptake and degradation of radiolabeled Lp(a) by the megalin/gp330-expressing cells were, on average, 2-fold higher than that of control cells. This difference could be completely abolished by addition of the receptor-associated protein, an inhibitor of ligand binding to megalin/gp330. Mutual suppression of the uptake of 125I-Lp(a) and of 125I-LDL by both unlabeled Lp(a) and LDL suggested that Lp(a) uptake is mediated at least partially by apolipoprotein B100. Binding and uptake of DiI-Lp(a) resulted in strong signals on megalin/gp330-expressing cells versus background only on control cells. In addition, we show that purified megalin/gp330, immobilized on a sensor chip, directly binds Lp(a) in a Ca2+-dependent manner with an affinity similar to that for LDL. We conclude that megalin/gp330 binds Lp(a) in vitro and is capable of mediating its cellular uptake and degradation.

Cholesteryl ester hydroperoxide lability is a key feature of the oxidative susceptibility of small, dense LDL

Abundant evidence has been provided to substantiate the elevated cardiovascular risk associated with small, dense, low density lipoprotein (LDL) particles. The diminished resistance of dense LDL to oxidative stress in both normolipidemic and dyslipidemic subjects is established; nonetheless, the molecular basis of this phenomenon remains indeterminate. We have defined the primary molecular targets of lipid hydroperoxide formation in light, intermediate, and dense subclasses of LDL after copper-mediated oxidation and have compared the relative stabilities of the hydroperoxide derivatives of phospholipids and cholesteryl esters (CEs) as a function of the time course of oxidation. LDL subclasses (LDL1 through LDL5) were isolated from normolipidemic plasma by isopycnic density gradient ultracentrifugation, and their content of polyunsaturated molecular species of phosphatidylcholine (PC) and CE and of lipophilic antioxidants was quantified by reverse-phase high-performance liquid chromatography. The molar ratio of the particle content of polyunsaturated CE and PC species containing linoleate or arachidonate relative to alpha-tocopherol or beta-carotene did not differ significantly between LDL subspecies. Nonetheless, dense LDL contained significantly less polyunsaturated CE species (400 mol per particle) compared with LDL1 through LDL4 (range, approximately 680 to 490 mol per particle). Although the formation of PC-derived hydroperoxides did not vary significantly between LDL subspecies as a function of the time course of copper-mediated oxidation, the abundance of the C18:2 and C20:4 CE hydroperoxides was uniquely deficient in dense LDL (23 and 0.6 mol per particle, respectively, in LDL5; 47 to 58 and 1.9 to 2.3 mol per particle, respectively, in other LDL subclasses) at propagation half-time. When expressed as a lability ratio (mol hydroperoxides formed relative to each 100 mol of substrate consumed) at half-time, the oxidative lability of CE hydroperoxides in dense LDL was significantly elevated (lability ratio <25:100) relative to that in lighter, larger LDL particle subclasses (lability ratio >40:100) throughout the oxidative time course. We conclude that the elevated lability of CE hydroperoxides in dense LDL underlies the diminished oxidative resistance of these particles. Moreover, this phenomenon appears to result not only from the significantly elevated PC to free cholesterol ratio (1.54:1) in dense LDL particles (1.15:1 to 1.25:1 for other LDL subclasses) but also from their unique structural features, including a distinct apoB100 conformation, which may facilitate covalent bond formation between oxidized CE and apoB100.

Effects of estrogenic oral contraceptives on the lipoprotein B particle system defined by apolipoproteins E and C-III content

Apolipoproteins E and C-III are modulators of lipoprotein metabolism that could affect development of atherosclerosis. The prevalence in plasma of apoB-containing particles (LpB) that contain either apoE or apoC-III, both or neither, and the effect of estrogen on these lipoproteins are unknown. The LpB particle system, defined by the presence or absence of apoE or C-III, was studied in 13 normolipidemic women, 7 nonusers and 6 users of oral contraceptives. Fasting plasma was separated by anti-apoE and C-III affinity chromatography and ultracentrifugation into four types of VLDL, IDL, and LDL particles: with apoE but not apoC-III (E+C-), apoC-III but not apoE (E-C+), both (E+C+) or neither (E-C-). The predominant VLDL particles were E-C- (42% in nonusers, 56% in users) and E+C+ (39% in nonusers, 24% in users), suggesting that apoE and apoC-III mainly exist together in VLDL. In IDL, E-C- was the major fraction (74% nonusers, 81% users), and in LDL, it was 99% in both groups. The triglycerides in VLDL and IDL were mainly contained in C+ particles (79% and 66% of the total VLDL and IDL triglycerides, respectively). Within VLDL, IDL, and LDL, E-C- particles had the smallest size and E+C+ or E-C+ the largest. Users had higher concentrations of VLDL E-C- (280%) and IDL E-C- (90%) particles than nonusers. They also had higher free cholesterol and cholesteryl ester concentrations associated with these fractions and with VLDL E-C+. The triglyceride contents of VLDL E-C- particles were lower in users of oral contraceptives than in nonusers. This study demonstrates that the elevated VLDL TG concentrations in users of estrogen-dominant oral contraceptives is mainly caused by an increased concentration of small VLDL particles that have reduced TG content, and that do not have apoE and C-III. These particles may have lower atherogenicity than particles enriched with apoE and C-III.-Khoo, C., H. Campos, H. Judge, and F. M. Sacks. Effects of estrogenic oral contraceptives on the lipoprotein B particle system defined by apolipoproteins E and C-III content.

Markedly high prevalence of coronary risk factors in apparently healthy African-American and white siblings of persons with premature coronary heart disease

Among persons with a family history of premature coronary heart disease (CHD), siblings bear an excess risk of CHD that is as high as 12 times that of the general population. Aggressive, new, national guidelines for CHD risk reduction have focused on high-risk families, yet little is known about actual remediable risk factors in siblings of persons with premature CHD. To determine the magnitude of the problem relative to the general population, we screened 846 unaffected siblings (ages 30 to 59 years) of persons with documented CHD before age 60 years and compared their risk factor values with population reference norms obtained in the Third National Health and Nutrition Examination Survey (NHANES III) and the National Health Interview Survey (NHIS). Mean levels of low-density lipoprotein cholesterol were 0.52 mmol/L (20 mg/dl) higher in siblings; the prevalence of low-density lipoprotein cholesterol > or =4.14 mmol/L (160 mg/dl) was nearly twice that of race, sex, and age-specific values from NHANES III. Levels of high-density lipoprotein cholesterol <0.91 mmol/L (35 mg/dl) were similar between siblings and NHANES III (11% and 12%, respectively). Only 4% of all siblings had triglyceride levels > or =4.52 mmol/L (400 mg/dl). Hypertension prevalence was twice as high among siblings as among the NHANES III. Current smoking was 33.9% in white siblings and 25.5% in the NHIS, whereas smoking in African-Americans was similar to that in the NHIS (31.1% vs 29.2%). A mere 13% to 29% of siblings were without any major remediable risk factors. The overwhelming need for risk factor modification in this easily identifiable high-risk population supports aggressive national guidelines and demonstrates the lack of adequate treatment of apparently healthy siblings of persons with premature CHD.

Dietary soluble fiber lowers plasma LDL cholesterol concentrations by altering lipoprotein metabolism in female guinea pigs

This experiment was designed to evaluate the effects of pectin (PE), guar gum (GG) and psyllium (PSY) intake on VLDL and LDL metabolism in female guinea pigs fed high dietary cholesterol. Guinea pigs were fed a 15 g/100 g fat diet containing 0.25 g/100 g cholesterol with 12.5 g/100 g PE, 12.5 g/100 g GG, 7.5 g/100 g PSY or 12.5 g/100 g cellulose (control diet) for 4 wk. Plasma cholesterol concentrations were 29, 43 and 39% lower in guinea pigs fed PE, GG or PSY, respectively, compared with the control group (P < 0.0001). Plasma apolipoprotein (apo) B concentrations were 16-22% lower in the groups fed soluble fiber compared with the control group (P < 0.01). In contrast, hepatic cholesterol and triglyceride concentrations were not different among the PE, GG, PSY and control groups. No differences in triacylglycerol (TAG) or apo B secretion rates, measured by blocking VLDL catabolism by triton (WR 1339) injection, were observed, whereas plasma LDL apo B fractional catabolic rates (FCR), determined by injection of radiolabeled LDL, were higher in guinea pigs fed GG or PSY than in those from the control group. All sources of dietary soluble fiber reduced LDL apo B flux (P < 0.05). These results suggest that the mechanisms of plasma LDL cholesterol lowering by dietary soluble fiber are distinctive for each fiber source and result in specific alterations in lipoprotein metabolism in female guinea pigs. Differences between male and female guinea pigs in response to these diets are discussed.

The salubrious effects of ascorbic acid on cyclophosphamide instigated lipid abnormalities in fibrosarcoma bearing rats

The combined effect of cyclophosphamide and ascorbic acid on plasma lipids and lipoprotein profiles are important since, ascorbic acid encumbered the lipid abnormalities initiated by cyclophosphamide during cancer chemotherapy. Hence, the study was launched to appraise the salutary role of ascorbic acid in cyclophosphamide administered fibrosarcoma bearing rats. Fibrosarcoma cell line induced rats were treated with cyclophosphamide (10 mg/kg body weight) and ascorbic acid (200 mg/kg body weight) individually and in combination for 28 days. The concentration of plasma lipids and lipoprotein profiles were determined in control and experimental animals. The untreated, as well as cyclophosphamide administered fibrosarcoma bearing rats, divulged significantly increased levels of plasma total cholesterol, triglycerides, phospholipids, VLDL- and LDL-cholesterol, as compared with their respective control animals. In contrast, ester and HDL-cholesterol levels exhibited a marked decrease in these animals. Similar observations were also noticed in liver lipid values, as well. However, these lipid abnormalities were corrected by the co-administration of ascorbic acid. These results suggested, that some clinical entanglement of cyclophosphamide was refrained by co-administration of ascorbic acid in tumor stress condition.

[Combined therapy with cholestyramine and HMG-CoA reductase inhibitors in secondary prevention of coronary disease]

PURPOSE

To evaluate lipid profile changes associated with cholestyramine addition in hypercholesterolemic patients with established coronary heart disease under treatment with HMG-CoA reductase inhibitors that had not achieved the ideal value of LDL-cholesterol.

METHODS

Twenty patients with coronary heart disease, (12 submitted to coronary artery bypass grafts, 3 to coronary angioplasty and 5 maintained under clinical management) with mean age of 60.78 years old, who were under hypolipemic diet and were medicated with lovastatin 20 mg/d or simvastatin 10 mg/d, received cholestyramine, doses ranging from 8 to 16 g/day during 8 weeks, aiming to reduce LDL-cholesterol to values less than 100 mg/dL.

RESULTS

There was a significant reduction of total cholesterol, from initial mean value of 239.52 mg/dL to final mean value of 199.00 mg/dL, with a mean reduction of 16.92%. The mean value of LDL-cholesterol was also reduced significantly from 172.73 mg/dL to 118.26 mg/dL, with a mean reduction of 31.53%. Mean triglyceridemia increased, still within the normal reference values, from 145.05 mg/dL to 162.00 mg/dL, and the mean difference was 11.69%. There was a significant increase of HDL-cholesterol fraction from an initial mean value of 38.00 mg/dL to a final mean value of 48.21 mg/dL, mean difference of 26.87%. Side effects were not frequent, and did not interfere in the duration of the study.

CONCLUSION

The association of cholestyramine to HMG-CoA reductase inhibitors, both in low doses, in patients with primary hypercholesterolemia and high coronary risk is a good therapeutic option that can reach benefits on the lipid profile similar to those obtained when these drugs are used in association or separately in higher doses.

Comparison of efficacy and cost among lipid-lowering agents in patients with primary hypercholesterolemia

OBJECTIVE

To compare efficacy and cost of lipid-lowering agents in patients with primary hypercholesterolemia.

DESIGN

A meta-analysis was conducted to determine estimates of efficacy for lipid-lowering agents. Efficacy was defined as the change in the ratio of total cholesterol:high density lipoprotein (HDL) induced by treatment. This ratio was selected because of its good predictive value for the risk of coronary disease. Lipid-lowering agents were grouped into three categories according to the decrease in the total cholesterol:HDL ratio. Acquisition prices for drugs were obtained from the Quebec provincial drug formulary. An analysis determined which drugs in each category 'purchased' the greatest decrease in ratio for the lowest cost.

SETTING

Clinical trial study centres.

PATIENTS

The population analyzed had a mean baseline total cholesterol:HDL ratio of 7.3, an average age of 50.5 years and mean proportion of men of 62.5%.

INTERVENTIONS

Twelve lipid-lowering therapies at various doses were investigated.

RESULTS

Drugs that were more recently introduced had the greatest effect on the total cholesterol:HDL ratio. A direct dose-effect relationship was not evident, although there was a trend in this direction. In each of the three categories, there was wide range of cost, suggesting that the same effect is available at a broad range of prices. The drugs with the greatest effect on the ratio at the lowest cost were fluvastatin 60 mg/day, fenofibrate (micronized) 200 mg/day and simvastatin 20 mg/day.

CONCLUSION

These results can be useful for clinicians in the selection of agents that achieve a specified goal of therapy at the lowest cost.

Sibling aggregation of low- and high-density lipoprotein cholesterol and apolipoproteins B and A-I levels in black and white children: the Bogalusa Heart Study

OBJECTIVE

To examine sibling aggregation of low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), apolipoprotein (apo) B and apo A-I in white versus black school-aged children.

DESIGN

Study subjects included 790 full sibships representing 1305 sibpairs aged 5 to 17 years from a biracial community.

METHODS

Intraclass correlation coefficients estimated by analyses of covariance were used to examine sibling aggregation of LDL-C, HDL-C, apo B and apo A-I. The influences of obesity and other lifestyle variables on sibpair differences in LDL-C, HDL-C, apo B and apo A-I were evaluated in black and white children by stepwise multiple regression analyses.

RESULTS

Intraclass correlation coefficients for LDL-C and apo B in black children were lower than those in white children (0.17 and 0.11 versus 0.32 and 0.33, respectively, P < 0.05-0.01); no racial difference was found for HDL-C and apo A-I. Intraclass correlation coefficients for LDL-C and HDL-C were similar to that of apo B and apo A-I, respectively and the sibpair differences in LDL-C and HDL-C were correlated with those of apo B and apo A-I, respectively (P < 0.01). Obesity exerted a greater effect on sibpair differences in LDL-C, HDL-C and apo B in black children than in white children.

CONCLUSIONS

These results suggest that the hereditary influence on LDL-C and apo B is more important in white children than in black children, especially for apo B. Further, genetic influence on LDL-C versus apo B, or HDL-C versus apo A-I may be similar.

Effects of soya milk and Bifidobacterium-fermented soya milk on plasma and liver lipids, and faecal steroids in hamsters fed on a cholesterol-free or cholesterol-enriched diet

The effects of freeze-dried soya milk (SM) and Bifidobacterium-fermented soya milk (FSM) on plasma and liver lipids, and faecal steroid excretion were estimated in hamsters fed on a cholesterol-free or cholesterol-enriched diet. Hamsters fed on the cholesterol-free diet containing 300 g FSM/kg had lower levels of plasma VLDL + LDL cholesterol than the animals fed on the control diet. SM in the diet produced a similar pattern without significant differences. In the cholesterol-enriched diet group, SM and FSM decreased the levels of plasma total cholesterol and VLDL + LDL-cholesterol. SM and FSM decreased the plasma triacylglycerol level in both the cholesterol-free and -enriched diet groups. The liver total cholesterol contents in the SM and FSM groups were lower than that in the control group, for hamsters fed on the cholesterol-free diet. The liver triacylglycerol content was not modified by SM or FSM in hamsters fed on either the cholesterol-free or -enriched diet. SM and FSM increased the total bile acid excretion and the proportion of cholesterol entering the cholic acid biosynthesis pathway in both the cholesterol-free and -enriched diet groups. SM and FSM did not affect neutral steroid excretion in the cholesterol-free or -enriched diet group. There was an inverse relationship between VLDL + LDL-cholesterol and faecal bile acid excretion in hamsters fed on the cholesterol-free (r -0.670, P < 0.01) and cholesterol-enriched (r -0.761, P < 0.001) diets respectively. These results indicated that SM had an anti-atherogenic effect, and that this effect was not diminished by prior fermentation.

Dyslipidemia: clinical approaches, evaluation of methods and strategies for standardization

Disorders in lipid metabolism (dyslipidemia) can result to the chronic heart disease. The low density lipoprotein (LDL) is a critical subfraction of total cholesterol present in serum because it is directly linked to coronary heart disease (CHD). The growing awareness of the risks of CHD stipulates the need for more accurate and precise measurement of LDL cholesterol. Current approaches in diagnosing and monitoring CHD is largely dependent on calculated LDL (CLDL) value due to the inherent complexity of ultracentrifugation method. While friedwald's calculated formula may provide comparable values with ultracentrifugation method, it may provide a result which is different. This difference may be of clinical significance. The lipoprotein electrophoresis may be useful in measuring LDL cholesterol, in the diagnosis of type III hyperlipidemia (broad beta band) and when the triglyceride level exceeds 400 mg/dl. The result that compares the CLDL with that obtained by the electrophoresis showed a significant difference (P > or = 0.000) for LDL and insignificant difference (P = 0.068) for high density lipoprotein (HDL) cholesterol.

beta-VLDL hypercholesterolemia relative to LDL hypercholesterolemia is associated with higher levels of oxidized lipoproteins and a more rapid progression of coronary atherosclerosis in rabbits

The accumulation of the oxidized apolipoprotein, apoB-100, containing lipoproteins in the arterial wall and the progression of coronary atherosclerotic lesions in rabbits with beta-VLDL and LDL hypercholesterolemia was compared. In New Zealand White (NZW) rabbits on a 0.125% cholesterol diet, LDL cholesterol levels increased from 14 +/- 1 mg/dL (mean +/- SEM; n = 9) to 170 +/- 34 mg/dL (n = 10, P = .0002). On 0.5% cholesterol, LDL cholesterol levels were similar, but beta-VLDL cholesterol levels increased from 60 +/- 4 mg/dL (n = 10) to 550 +/- 75 mg/dL (n = 8; P < .0001). In Watanabe heritable hyperlipidemic (WHHL) rabbits, LDL cholesterol levels were 2.3-fold higher (n = 13; P < .0001) than in NZW rabbits on 0.5% cholesterol, whereas their beta-VLDL cholesterol levels were 3.7-fold lower (P < .0001), resulting in similar total cholesterol levels. At 2 months, mean intimal areas of lesions in the coronary arteries of NZW rabbits on 0.125% cholesterol were 0.13 +/- 0.045 mm2 (n = 4; mean +/- SEM) and were 5.8-fold, (n = 4; P = .016) and 2.0-fold (n = 6; P = NS versus 0.125% cholesterol and P = .014 versus 0.5% cholesterol) higher in NZW rabbits on 0.5% cholesterol and in WHHL rabbits, respectively. At 5 months, mean intimal areas were 0.47 +/- 0.088 mm2 (n = 6) in NZW rabbits on 0.125% cholesterol and were 4.5-fold (n = 4; P = .0001) and 2.0-fold (n = 7; P = .012 and P = .0019) higher in rabbits on 0.5% cholesterol and in WHHL rabbits, respectively. Levels of oxidized apoB-100 containing lipoproteins (both beta-VLDL and LDL) in the lesions correlated with mean intimal area (r = .88; n = 31; P < .0001) of those lesions and with the plasma levels of total beta-VLDL/LDL (r = .72; P < .0001). Levels of oxidized apoB-100 containing lipoproteins in the arterial wall correlate with progression of hypercholesterolemia-induced coronary atherosclerotic lesions. Plasma levels of beta-VLDL relative to similar increases in LDL result in a more pronounced accumulation of oxidized apoB-100 containing lipoproteins in the arterial wall and in the plasma and a more rapid progression of coronary atherosclerosis.

Physiological basis for long life span

A collection of clinical data is reported on nonagenarians in comparison to an 'average' population of younger age. The results of these clinical data indicated that a vital physiological basis for long life span probably existed. The basis include a better micro-blood-flow state, a better cardiac, immune (nature killer cell activity), adrenocortical, hepatic and renal function, and a higher level of high density lipoprotein cholesterol. It is suggested that the method, including Chinese traditional medicine, to improve the micro-blood-flow, nature killer cell activity, high density lipoprotein cholesterol and vital organ function may be beneficial for life preservation and aging retarding.