A prospective study of triglyceride level, low-density lipoprotein particle diameter, and risk of myocardial infarction

Oral stimulation influences postprandial triacylglycerol concentrations in humans: nutrient specificity

OBJECTIVE

To determined whether the nature of the lipid in an oral stimulus modifies postprandial triacylglycerolemia.

METHODS

Sixteen healthy adults (eight male, eight female) participated in six test sessions conducted weekly. The test sessions were administered randomly after overnight fasts and included: ingestion of 50 grams of butter in capsules (to avoid oral stimulation with lipids) and 500 mL of water in 15 minutes followed by oral stimulation with one of the following foods on a cracker: butter, unsaturated fatty acid (UFA) margarine, jelly, UFA margarine + jelly, cracker alone or no oral stimulation. Sensory stimulation entailed masticating and expectorating approximately 5.0 g samples of each stimulus every three minutes for 110 minutes. Blood was drawn immediately after preload ingestion and at minutes 35, 85, 200, 320, and 440 post loading and analyzed for serum triacylglycerol (TAG), insulin and glucose concentrations.

RESULTS

Only the oral samples containing the UFA margarine led to significant elevations of serum TAG concentration compared to baseline (p < 0.05). Maximum change of TAG concentrations were greater following orosensory stimulation with UFA margarine compared to orosensory stimulation with butter, jelly or UFA margarine + jelly. No differences were observed relative to vehicle alone or no orosensory stimulation, but this is due to lower nadir values for these treatments. Insulin and glucose concentrations were not different between treatments.

CONCLUSION

Oral exposure specifically to an unsaturated dietary lipid augments the postprandial rise of TAG, compared to baseline.

Oxidized LDL and HDL: antagonists in atherothrombosis

Increased LDL oxidation is associated with coronary artery disease. The predictive value of circulating oxidized LDL is additive to the Global Risk Assessment Score for cardiovascular risk prediction based on age, gender, total and HDL cholesterol, diabetes, hypertension, and smoking. Circulating oxidized LDL does not originate from extensive metal ion-induced oxidation in the blood but from mild oxidation in the arterial wall by cell-associated lipoxygenase and/or myeloperoxidase. Oxidized LDL induces atherosclerosis by stimulating monocyte infiltration and smooth muscle cell migration and proliferation. It contributes to atherothrombosis by inducing endothelial cell apoptosis, and thus plaque erosion, by impairing the anticoagulant balance in endothelium, stimulating tissue factor production by smooth muscle cells, and inducing apoptosis in macrophages. HDL cholesterol levels are inversely related to risk of coronary artery disease. HDL prevents atherosclerosis by reverting the stimulatory effect of oxidized LDL on monocyte infiltration. The HDL-associated enzyme paraoxonase inhibits the oxidation of LDL. PAF-acetyl hydrolase, which circulates in association with HDL and is produced in the arterial wall by macrophages, degrades bioactive oxidized phospholipids. Both enzymes actively protect hypercholesterolemic mice against atherosclerosis. Oxidized LDL inhibits these enzymes. Thus, oxidized LDL and HDL are indeed antagonists in the development of cardiovascular disease.

Coronary heart disease prediction from lipoprotein cholesterol levels, triglycerides, lipoprotein(a), apolipoproteins A-I and B, and HDL density subfractions: The Atherosclerosis Risk in Communities (ARIC) Study

BACKGROUND

Despite consensus on the need for blood cholesterol reductions to prevent coronary heart disease (CHD), available evidence on optimal cholesterol levels or the added predictive value of additional lipids is sparse.

METHODS AND RESULTS

After 10 years follow-up of 12 339 middle-aged participants free of CHD in the Atherosclerosis Risk in Communities Study (ARIC), 725 CHD events occurred. The lowest incidence was observed in those at the lowest LDL cholesterol (LDL-C) quintile, with medians of 88 mg/dL in women and 95 mg/dL in men, and risk accelerated at higher levels, with relative risks (RRs) for the highest quintile of 2.7 in women and 2.5 in men. LDL-C, HDL-C, lipoprotein(a) [Lp(a)], and in women but not men, triglycerides (TG) were all independent CHD predictors, providing an RR, together with blood pressure, smoking, and diabetes, of 13.5 in women and 4.9 in men. Lp(a) was less significant in blacks than whites. Prediction was not enhanced by HDL-C density subfractions or apolipoproteins (apo) A-I or B. Despite strong univariate associations, apoB did not contribute to risk prediction in subgroups with elevated TG, with lower LDL-C, or with high apoB relative to LDL-C.

CONCLUSIONS

Optimal LDL-C values are <100 mg/dL in both women and men. LDL-C, HDL-C, TG, and Lp(a), without additional apolipoproteins or lipid subfractions, provide substantial CHD prediction, with much higher RR in women than men.

Targeting triglycerides as prognostic indicators and determining lowest values for patient benefit

A number of reports demonstrate the importance of serum triglyceride values in predicting the clinical onset of vascular disease. However, adjustment for measurements highly correlated with triglyceride (TG) levels, such as history of diabetes, body mass index, and high-density lipoprotein cholesterol (HDL-C), lessen if not remove the TG contribution to outcomes. More recently, improved analytic approaches have more persuasively implicated triglycerides as independently relevant to the onset of cardiovascular disease. Elevated TG values are the consequence of larger TG-rich particles, including very low density lipoprotein and atherogenic intermediate particles, which are in turn associated with dense low-density lipoprotein. It has been observed that a reduction in TG concentrations often proceeds in parallel with improved clinical outcomes; however, direct correlation between the two has been elusive. This has been demonstrated in multiple pharmacologic trials. However, an improvement in these relationships has been observed when TG-correlated measurements of intermediate particles, low-density lipoprotein density, and HDL-C have been made. National guidelines for cholesterol treatment have now incorporated a TG greater than 200 mg/dL as a secondary treatment trigger, which targets apolipoprotein B-related particles, represented by non-HDL-C (total cholesterol minus HDL-C), as the suggested goal of therapy.

Effect of niacin and atorvastatin on lipoprotein subclasses in patients with atherogenic dyslipidemia

This study was conducted to determine the efficacy of atorvastatin and niacin on lipoprotein subfractions in patients with atherogenic dyslipidemia. This was a multicenter, randomized, open-label, parallel-design study of patients with total cholesterol >200 mg/dl, triglycerides between 200 and 800 mg/dl, and apolipoprotein B >110 mg/dl. Patients were randomly assigned to atorvastatin 10 mg or immediate release niacin 3,000 mg daily for 12 weeks following a low-fat diet stabilization period. Lipoprotein subclasses were measured by nuclear magnetic resonance spectroscopy. Atorvastatin and niacin both significantly reduced the concentrations of very low-density lipoprotein (VLDL) particles (-31% and -29%, respectively) and small low-density lipoprotein (LDL) particles (-44% and -35%, respectively). Niacin increased the concentration of large LDL (+75%). Atrovastatin reduced the number of LDL particles more than niacin (31% vs 14%). In patients with atherogenic dyslipidemia, both drugs had important effects on lipoprotein subfractions, which contributed to a reduction in coronary heart disease risk. The drugs equally reduced VLDL subclass levels. Niacin shifted the LDL subclass distribution toward the larger particles, more effectively converted patients from LDL phenotype B to phenotype A, and increased levels of the larger and perhaps more cardioprotective high-density lipoprotein particles. In contrast, atorvastatin preferentially lowered the concentration of small LDL particles without increasing levels of large LDL, and more effectively, reduced LDL particle numbers. Atorvastatin had a preferred LDL effect, whereas niacin had a preferred high-density lipoprotein effect.

Do total and high density lipoprotein cholesterol and triglycerides act independently in the prediction of ischemic heart disease? Ten-year follow-up of Caerphilly and Speedwell Cohorts

Several studies have suggested that men with raised plasma triglycerides (TGs) in combination with adverse levels of other lipids may be at special risk of subsequent ischemic heart disease (IHD). We examined the independent and combined effects of plasma lipids at 10 years of follow-up. We measured fasting TGs, total cholesterol (TC), and high density lipoprotein cholesterol (HDLC) in 4362 men (aged 45 to 63 years) from 2 study populations and reexamined them at intervals during a 10-year follow-up. Major IHD events (death from IHD, clinical myocardial infarction, or ECG-defined myocardial infarction) were recorded. Five hundred thirty-three major IHD events occurred. All 3 lipids were strongly and independently predictive of IHD after 10 years of follow-up. Subjects were then divided into 27 groups (ie, 3(3)) by the tertiles of TGs, TC, and HDLC. The number of events observed in each group was compared with that predicted by a logistic regression model, which included terms for the 3 lipids (without interactions) and potential confounding variables. The incidence of IHD was 22.6% in the group with the lipid risk factor combination with the highest expected risk (high TGs, high TC, and low HDLC) and 4.7% in the group with the lowest expected risk (P<0.01). A comparison of the predicted number of events in the 27 groups with the number of events observed showed that a logistic regression provided an adequate fit without the need to incorporate interactions between lipids in the model. Conclusions are as follows: (1) Serum TGs, TC, and HDLC are independently predictive of IHD at 10 years of follow-up. (2) Combinations of adverse levels of the 3 major lipid risk factors have no greater impact on IHD than that expected from their individual contributions in a logistic regression model. There was no evidence that men with low HDL/raised TGs were at significantly greater risk than that predicted from the independent effects of the 2 lipids considered individually.

Low-density lipoprotein particle size, triglyceride-rich lipoproteins, and glucose tolerance in non-diabetic men with essential hypertension

The aim of the study is to investigate serum lipoproteins abnormalities including low-density lipoprotein (LDL) particle size, and their relationship with other cardiovascular risk factors in men with essential hypertension. Plasma glucose and serum insulin levels during oral glucose tolerance test (OGTT), serum lipoprotein(a), apolipoprotein (apo) A-I. apo B. cholesterol and triglycerides in serum and in lipoproteins, and LDL particle diameter were measured in thirty-eight consecutive newly-diagnosed non-diabetic untreated hypertensive men and 38 healthy male controls. Plasma glucose at baseline, 60 and 120 min during OGTT was significantly higher in patients than controls whereas serum insulin levels did not differ between patients and controls. Serum apo B and triglycerides were significantly raised in patients compared with controls (1.08 +/- 0.17 g/L [mean +/- SD] vs 0.97 +/- 0.22 g/L. p < 0.05, and 1.56 +/- 0.90 mmol/L vs 1.15 +/- 0.57 mmol/L, p < 0.05, respectively). Very-low-density lipoprotein (VLDL) triglycerides and LDL-cholesterol were increased in patients compared with controls (0.89 +/- 0.79 mmol/L and 0.54 +/- 0.35 mmol/L, p < 0.05, and 4.08 +/- 0.85 mmol/L and 3.60 +/- 0.92 mmol/L, p < 0.05, respectively) whereas high-density lipoprotein (HDL) cholesterol was lower in patients compared with controls 0.95 +/- 0.22 mmol/L and 1.07 +/- 0.20 mmol/L, p < 0.05). Adjustment for body mass index, abdominal/hip perimeter ratio and area under the glucose curve did not attenuate the relationship between hypertension and VLDL-triglycerides. Six patients and two controls had a mean LDL diameter < or = 25.5 nm and in the former serum triglycerides ranged from 1.86 mmol/L to 2.37 mmol/L. Mean LDL particle diameter in both patients and controls showed an inverse relationship with log-transformed serum triglycerides (r = - 0.51, p < 0.001 and r = - 0.47, p < 0.005, respectively). Among patients, those with serum triglycerides > or = [corrected] 1.58 mmol/L had a lesser mean LDL diameter than those with triglycerides above this threshold (25.78 +/- 0.47 nm vs 26.30 +/- 0.35 nm, p < 0.001). Higher plasma glucose, serum apo B and LDL-cholesterol as well as the decrease in serum HDL-cholesterol in patients with hypertension are consistent with high coronary heart disease risk. Not only mild hypertriglyceridemia but also high-normal serum triglycerides in themselves or as a surrogate of a predominance of small dense LDL particles in plasma convey an additional risk for cardiovascular disease in hypertensive patients even though routine plasma lipids are within or near normal range.

Assessing the role of oestrogen in the prevention of cardiovascular disease

Coronary heart disease remains the leading cause of death in postmenopausal women around the world, and interest is high in discovering the best treatments and methods of prevention for this disease. For many years, it appeared that one such treatment could be oestrogen, because of its beneficial effects on the vascular endothelium and on cholesterol concentrations. However, recent clinical trials have shown no beneficial effect of long-term hormone replacement therapy (HRT) on risk for major cardiovascular events among women with established coronary disease. These surprising findings have led to still further analyses to elucidate plausible explanations. This paper will review the results from recent trials and clinical studies of HRT, as well as ongoing trials that continue to examine the role of oestrogen in the treatment and prevention of cardiovascular disease.

Statin-fibrate combination therapy

BACKGROUND

Precautionary warnings for severe myopathy and rhabdomyolysis from the coadministration of statins and fibrates have been well publicized. However, a recent cerivastatin labeling change made the combined use with fibric acid derivatives a contraindication. Practical recommendations for clinicians who care for patients with refractory mixed hyperlipidemia are needed.

OBJECTIVE

To provide recommendations for clinicians in the treatment of refractory mixed hyperlipidemia.

DATA SOURCES

A comprehensive MEDLINE (1966-July 2000) and bibliographic search was performed.

DATA SYNTHESIS

Thirty-six published clinical trials and 29 case reports involving combination therapy with hydroxymethylglutaryl coenzyme A (HMG-CoA) reductase inhibitors and fibric acid derivatives regarding the occurrence of rhabdomyolysis or myopathy were reviewed. The literature review demonstrated that combination therapy with a statin and fibrate increases the risk of muscle damage, with an incidence of 0.12%. Risk factors that predispose patients to myopathy caused by combination statin-fibrate therapy include increased age, female gender, renal or liver disease, diabetes, hypothyroidism, debilitated status, surgery, trauma, excessive alcohol intake, and heavy exercise.

CONCLUSIONS

Combination therapy with a statin and fibrate offers significant therapeutic advantage for the treatment of severe or refractory mixed hyperlipidemia. Although such a combination does increase the risk of myopathy, with an incidence of approximately 0.12%, this small risk of myopathy rarely outweighs the established morbidity and mortality benefits of achieving lipid goals. Nevertheless, a higher incidence of myopathy has been reported with statin monotherapy. When monotherapy with a statin fails to control mixed hyperlipidemia, combination therapy may be considered. Niacin may be added before a fibrate is considered, as it appears to have less risk of myopathy. Statin-fibrate combination therapy must be undertaken cautiously and only after careful risk-benefit analysis. Patient counseling on the risks and warning signs of myopathy is extremely important.

The effect of isoflavones extracted from red clover (Rimostil) on lipid and bone metabolism

OBJECTIVE

This study was undertaken to evaluate the effects of varying doses of phytoestrogens on lipid and bone metabolism in postmenopausal women.

DESIGN

A novel red clover isoflavone preparation (Rimostil) containing genistein, daidzein, formononetin, and biochanin was administered to 46 postmenopausal women in a double-blind protocol after a single-blind placebo phase and followed by a single-blind washout phase. Patients were randomized to receive either 28.5 mg, 57 mg, or 85.5 mg of phytoestrogens daily for a 6-month period.

RESULTS

At 6 months, the serum high-density lipoprotein cholesterol had risen significantly by 15.7-28.6% with different doses (p = 0.007, p = 0.002, p = 0.027), although the magnitude of the response was independent of the dose used. The serum apolipoprotein B fell significantly by 11.5-17.0% with different doses (p = 0.005, p = 0.043, p = 0.007) and the magnitude of the response was independent of the dose used. The bone mineral density of the proximal radius and ulna rose significantly by 4.1% over 6 months with 57 mg/day (p = 0.002) and by 3.0% with 85.5 mg/day (p = 0.023) of isoflavones. The response with 28.5 mg/day of isoflavones was not significant. There was no significant increase in endometrial thickness with any of the doses of isoflavone used.

CONCLUSION

These results show that the administration of an isoflavone combination extracted from red clover was associated with a significant increase in high-density lipoprotein cholesterol, a significant fall in apolipoprotein B, and a significant increase in the predominantly cortical bone of the proximal radius and ulna after 6 months of treatment. Interpretation of the results is undertaken cautiously because of the absence of a simultaneously studied control group.

Oral exposure to butter, but not fat replacers elevates postprandial triacylglycerol concentration in humans

Oral exposure to dietary fat augments the postprandial triacylglycerol (TAG) concentration. We investigated the TAG response after oral exposure to butter and selected fat replacers. At 2200 h, 17 healthy adults consumed 80 g of almonds and fasted until 0700 h. Safflower oil (50 g in 1-g capsules) was then consumed. Oral stimulation was provided periodically for 2 h as potatoes, potatoes containing butter or one of three fat replacers or no oral stimulation in random order at weekly intervals. Blood was collected at stipulated intervals for 8 h. Oral exposure to butter led to a significantly longer postprandial TAG elevation than the other treatments. The results could not be explained by differential stimulus ingestion, palatability or perceived fat content. There was no significant treatment effect on concentrations of serum oleic acid, apolipoprotein (apo)B-48 or apoB-100, suggesting any oral exposure influence on release of dietary lipid stored in the lacteals or chylomicron and VLDL particle number contributed little to the postprandial TAG rise. In summary, oral exposure to butter elicited a greater postprandial TAG elevation than the tested fat replacers, possibly due to reduced TAG clearance.

Relationship between Triglyceride Concentrations and LDL Size Evaluated by Malondialdehyde-modified LDL

Background: Hypertriglyceridemia is associated with decreased HDL-cholesterol (HDL-C) and increased small dense LDL. In addition, small dense LDL is known to be susceptible to oxidation.

Methods: We measured LDL particle size, using gradient gel electrophoresis, and malondialdehyde-modified LDL (MDA-LDL), using an ELISA, and investigated the association between triglyceride (TG) concentrations, LDL size, and MDA-LDL.

Results: TG concentrations correlated negatively with the predominant LDL size (r = −0.650) and HDL-C concentration (r = −0.556). The relationship between TG concentration and LDL size, evaluated by measuring MDA-LDL, distinguished subgroups derived from four subfractions of TG concentrations and four distribution ranges of LDL size. These experiments indicated that there is a threshold for oxidation susceptibility at an LDL size of 25.5 nm and a TG concentration of 1500 mg/L. To investigate the relationship between LDL size, MDA-LDL concentration, and other lipids (TGs, HDL-C, apolipoprotein B, and total cholesterol), we evaluated them in control subjects and patients with diabetes mellitus or hypertriglyceridemia. When the size range for normal LDL was postulated to be 25.5 ≤ φ (LDL diameter) &lt; 26.5 nm, the MDA-LDL concentration was significantly higher in the subgroups of patients with LDL in the size range 24.5 ≤ φ &lt; 25.5 nm compared with patients with normal LDL. This result also suggests that the threshold is at a LDL size of 25.5 nm.

Conclusion: The threshold for oxidation susceptibility coincided with the point of LDL size separation between the LDL subclass patterns A and B as an atherosclerotic risk.

Fluvastatin lowers atherogenic dense low-density lipoproteins in postmenopausal women with the atherogenic lipoprotein phenotype

BACKGROUND

Although HMG-CoA reductase inhibitors (HMGRIs) are effective lipid-lowering agents, it remains controversial whether these agents also lower dense LDL (dLDL), a predominance of which is considered to contribute to the atherogenicity of the metabolic syndrome.

METHODS AND RESULTS

In a multicenter, double-blind, randomized, placebo-controlled study, we determined the effect of the HMGRI fluvastatin on lipids, apolipoproteins, and LDL subfractions (by equilibrium density gradient ultracentrifugation). A total of 52 postmenopausal women with combined hyperlipidemia and increased dLDL were treated with either fluvastatin 40 mg/d (n=35) or placebo (n=17). After 12 weeks' treatment, significant reductions (P<0.001) in total cholesterol (-19%), IDL cholesterol (-35%), LDL cholesterol (-23%), apolipoprotein B (-21%), and apolipoprotein B in dLDL (-42%) were apparent among fluvastatin recipients. No significant changes in triglycerides or HDL cholesterol were observed. The effect of fluvastatin on dLDL was correlated with baseline values. There was no consistent relationship, however, between the effect of fluvastatin on triglycerides and the decrease in dLDL.

CONCLUSIONS

Fluvastatin lowers total and LDL cholesterol and the concentration of dLDL. This profile may contribute to an antiatherogenic effect for fluvastatin that is greater than expected on the basis of changes in lipids and apolipoproteins.

Smaller LDL particle size in women with polycystic ovary syndrome compared to controls

OBJECTIVE

Women with polycystic ovary syndrome (PCOS) have an increased risk of cardiovascular disease. The contribution of lipid abnormalities to this higher risk, in particular atherogenic modifications of low density lipoprotein (LDL) such as a shift towards smaller LDL, has not been properly explored. We aimed to examine LDL size variation in relation to androgens and other risk factors in women with PCOS.

DESIGN

Comparison of clinical and biochemical measurements in women with PCOS and women with normal ovarian function, of similar age and body mass index (BMI).

PATIENTS

Thirty-one women with PCOS and 27 controls were studied. Patients were recruited from the outpatient endocrine clinic.

MEASUREMENTS

Fasting total cholesterol, triglycerides (TG), high density lipoprotein (HDL), LDL, glucose, insulin, gonadotrophins, androgens, oestradiol, 17 OH progesterone and SHBG were measured. LDL particle diameter was calculated based on distance travelled in polyacrylamide native gels. Recumbent blood pressure was measured automatically.

RESULTS

LDL particle size appeared to be significantly smaller in hyperandrogenic PCOS as compared to regularly cycling women (P = 0006), independent of variations in lipid levels. SHBG was the only independent predictor of LDL size in this population, with a strong correlation, which persisted after adjustment for all confounding variables.

CONCLUSIONS

Our results suggest that androgen excess and mild insulin-resistance (both responsible for lower SHBG) may have an early modifying effect on low density lipoprotein size in polycystic ovary syndrome women. The denser pattern observed in polycystic ovary syndrome women could by itself constitute a higher cardiovascular risk, even in the absence of overt dyslipidaemia, and contribute to the excess risk of cardiovascular disease reported in this syndrome.

Dietary glycemic load assessed by food-frequency questionnaire in relation to plasma high-density-lipoprotein cholesterol and fasting plasma triacylglycerols in postmenopausal women

BACKGROUND

In metabolic studies, both greater carbohydrate intakes and higher glycemic indexes (GIs) raise fasting triacylglycerol concentrations. In epidemiologic studies, dietary glycemic load (GL) is positively associated with risk of coronary artery disease and type 2 diabetes.

OBJECTIVE

We examined both the physiologic relevance of GI and GL and the ability of dietary questionnaires to measure these variables.

DESIGN

In the Nurses' Health Study, we measured plasma triacylglycerol concentrations in fasting blood samples from 185 healthy postmenopausal women and HDL-cholesterol concentrations in an additional 95 nonfasting samples. Dietary carbohydrate, GI, and GL were assessed by use of semiquantitative food-frequency questionnaires. The cross-sectional associations between these 3 variables and plasma triacylglycerol and HDL were assessed, with adjustment for potential confounding factors.

RESULTS

For the lowest and highest quintiles of GL, the multivariate-adjusted geometric mean triacylglycerol concentrations were 0.98 and 1.75 mmol/L (87 and 155 mg/dL; P for trend < 0.001). Both overall GI (P for trend = 0.03) and carbohydrate (P for trend < 0.01) contributed independently to the strong positive association between GL and fasting triacylglycerol concentrations. GL was also inversely associated with HDL-cholesterol concentrations. For the lowest and highest quintiles of GL, the mean HDL-cholesterol concentrations were 1.50 and 1.34 micromol/L (58 and 52 mg/dL; P for trend = 0.03). The relation between GL and fasting triacylglycerol concentrations differed significantly by body mass index (BMI; in kg/m(2)) categories (P < 0.001 for interaction). For the lowest to the highest quintiles of GL, the mean triacylglycerol concentrations were 0.92 and 2.24 mmol/L (81 and 198 mg/dL) in women with BMIs > 25 (P for trend < 0.001) and 1.02 and 1.42 mmol/L (90 and 126 mg/dL) in women with BMIs < or = 25 (P for trend < 0.001).

CONCLUSION

These data support the physiologic relevance of the GL as a potential risk factor for coronary artery disease in free-living women, particularly those prone to insulin resistance. These findings also document the ability of a semiquantitative food-frequency questionnaire to assess dietary GIs and GLs.

Use of surrogate endpoints: a practical necessity in lipid-altering and antiatherosclerosis drug development

Apparently favorable effects of antiatherosclerosis drugs as assessed by changes in surrogate markers of cardiovascular disease risk are frequently relied upon for drug approval and labeling. Surrogates must be biologically plausible and adequately validated but are, by definition, imperfect as predictors of ultimate outcome (i.e., serious morbidity and mortality). Surrogate markers utilized in the study of drugs for the treatment of atherosclerotic cardiovascular disease may be classified as laboratory/biochemical, anatomic/morphologic, and functional. The places for various surrogates in all three categories in the development of lipid altering drugs are discussed.

Types of dietary fat and risk of coronary heart disease: a critical review

During the past several decades, reduction in fat intake has been the main focus of national dietary recommendations to decrease risk of coronary heart disease (CHD). Several lines of evidence. however, have indicated that types of fat have a more important role in determining risk of CHD than total amount of fat in the diet. Metabolic studies have long established that the type of fat, but not total amount of fat, predicts serum cholesterol levels. In addition, results from epidemiologic studies and controlled clinical trials have indicated that replacing saturated fat with unsaturated fat is more effective in lowering risk of CHD than simply reducing total fat consumption. Moreover, prospective cohort studies and secondary prevention trials have provided strong evidence that an increasing intake of n-3 fatty acids from fish or plant sources substantially lowers risk of cardiovascular mortality. In this article, we review evidence from epidemiologic studies and dietary intervention trials addressing the relationship between dietary fat intake and risk of CHD, with a particular emphasis on different major types of fat, n-3 fatty acids and the optimal balance between n-3 and n-6 fatty acids. We also discuss the implications of the available evidence in the context of current dietary recommendations.

Atherogenic lipoprotein phenotype and diet-gene interactions

Studies employing analysis of LDL subclasses have demonstrated heterogeneity of the LDL response to low fat, high carbohydrate diets in healthy nonobese subjects. In individuals with a genetically influenced atherogenic lipoprotein phenotype, characterized by a predominance of small dense LDL (LDL subclass pattern B), lowering of plasma LDL cholesterol levels by diets with < or =24% fat has been found to represent a reduction in numbers of circulating mid-sized and small LDL particles, and hence an expected lowering of cardiovascular disease risk. In contrast, in the majority of healthy individuals with larger LDL (pattern A, found in approximately 70% of men and a larger percentage of women), a significant proportion of the low fat diet-induced reduction in plasma LDL cholesterol is made by depletion of the cholesterol content of LDL particles. This change in LDL composition is accompanied by a shift from larger to smaller LDL particle diameters. Moreover, with progressive reduction of dietary fat and isocaloric substitution of carbohydrate, an increasing number of subjects with pattern A convert to the pattern B phenotype. Studies in families have indicated that susceptibility to induction of pattern B by low fat diets is under genetic influence. Thus, diet-gene interactions affecting LDL subclass patterns may contribute to substantial interindividual variability in the effects of low fat diets on coronary heart disease risk.

Comparative effects of cerivastatin and fenofibrate on the atherogenic lipoprotein phenotype in proteinuric renal disease

Patients with nephrotic-range proteinuria have impaired clearance of triglyceride-rich lipoproteins. This results in the atherogenic lipoprotein phenotype (mild hypertriglyceridemia, low high-density lipoproteins [HDL], and excess small, dense low-density lipoproteins [LDLIII]). Excess remnant lipoproteins (RLP) are linked to hypertriglyceridemia and may contribute to the atherogenicity of nephrotic dyslipidemia. A randomized crossover study compared the effects of a statin (cerivastatin) and a fibrate (fenofibrate) on LDLIII and RLP in 12 patients with nephrotic-range proteinuria. Cerivastatin reduced cholesterol (21%, P: < 0.01), triglyceride (14%, P: < 0.05), LDL cholesterol (LDL-C; 23%, P: < 0.01), total LDL (18%, P: < 0.01), and LDLIII concentration (27% P: < 0.01). %LDLIII, RLP-C, and RLP triglyceride (RLP-TG) were unchanged. Plasma LDLIII reduction with cerivastatin treatment correlated with LDL-C reduction (r(2) = 34%, P: < 0.05). Fenofibrate lowered cholesterol (19%), triglyceride (41%), very low-density lipoprotein cholesterol (52%), LDLIII concentration (49%), RLP-C (35%), and RLP-TG (44%; all P: < 0.01). Fenofibrate also reduced %LDLIII from 60 to 33% (P: < 0.01). HDL-C (19%, P: < 0.01) increased with fenofibrate treatment; LDL-C and total LDL were unchanged. The reduction in LDLIII concentration and RLP-C with fenofibrate treatment correlated with plasma triglyceride reduction (LDLIII r(2) = 67%, P: < 0.001; RLP cholesterol r(2) = 58%, P: < 0.005). Serum creatinine increased with fenofibrate treatment (14%, P: < 0.01); however, creatinine clearance was unchanged. LDLIII concentration was 187 +/- 85 mg/dl after cerivastatin treatment and 133 +/- 95 mg/dl after fenofibrate treatment. Cerivastatin and fenofibrate reduce LDLIII concentration in nephrotic-range proteinuria. However, atherogenic concentrations of LDLIII remain prevalent after either treatment. Fenofibrate but not cerivastatin reduces remnant lipoproteins. The two treatments seem to reduce LDLIII by different mechanisms, suggesting a potential role for combination therapy to optimize lowering of LDLIII and RLP.

Enhanced oxidative susceptibility and reduced antioxidant content of metabolic precursors of small, dense low-density lipoproteins

PURPOSE

Elevated plasma concentrations of low-density lipoproteins (LDL) increase risk for coronary heart disease. However, lipoprotein profiles rich in small, dense LDL particles confer greater risk than those that mainly consist of large, buoyant LDL. This may be due, in part, to the greater oxidative susceptibility of small, dense LDL. In the current studies, we tested whether differences in the oxidative behavior of buoyant and dense LDL arise from differences in their immediate metabolic precursors, intermediate-density lipoproteins.

SUBJECTS AND METHODS

We compared the properties of intermediate-density lipoproteins and buoyant and dense LDL subfractions in 9 subjects with the large, buoyant LDL phenotype versus 6 with the small, dense LDL phenotype. Oxidative susceptibility was evaluated based on conjugated diene formation and parinaric acid oxidation induced by copper. Antioxidants (ubiquinol-10 and alpha-tocopherol) were measured by high-performance liquid chromatography.

RESULTS

Oxidative susceptibility was increased and antioxidant concentrations were decreased with increasing lipoprotein density (intermediate intermediate-density lipoproteins to buoyant LDL to dense LDL). Intermediate-density lipoproteins from subjects with the small, dense LDL phenotype had a greater oxidative susceptibility (by the parinaric acid test) and lower antioxidant concentrations than corresponding particles from subjects with the large, buoyant LDL phenotype.

CONCLUSIONS

Differences in oxidative susceptibility between large, buoyant and small, dense LDL particles are apparent in their lipoprotein precursors. These results suggest that lipoprotein oxidative susceptibility may be metabolically programmed and that intermediate-density lipoproteins may contribute to the increased risk associated with the small, dense LDL phenotype.

Hepatic lipase as a focal point for the development and treatment of coronary artery disease

Recent epidemiological evidence suggests that although lowering low-density lipoprotein (LDL) cholesterol is important in decreasing cardiovascular disease morbidity and mortality, it accounts only for part of the coronary artery disease (CAD) improvement with lipid-lowering therapy. In the last decade, it has become evident that the atherogenicity of LDL particles is associated not only with their plasma levels, but also with their size and density. The presence of small, dense LDL particles is associated with a three fold increase in CAD risk. Hepatic lipase (HL), a key enzyme in the formation of small, dense LDL particles, modulates their phospholipid and triglyceride contents. The higher the HL activity, the smaller, denser, and more atherogenic the resulting lipoprotein particle. It is, therefore, plausible to hypothesize that at least part of the CAD benefits observed in the recent CAD-prevention pharmacological trials, which are not accounted for by the decrease in LDL-C (LDL-cholesterol), might be explained by a pharmacological effect on LDL size and density, possibly mediated by changes in hepatic lipase activity. By studying patients with dyslipidemia and CAD, we have been able to provide strong evidence that regression of coronary atherosclerosis results from at least two independent effects of lipid-lowering therapy on lipoprotein metabolism: the well known one that leads to changes in LDL-C and apo B levels, and a new pathway of HL-mediated improvement in LDL buoyancy. Finally, HL activity and LDL density appear to be significantly affected by the presence of a common C-->T substitution at position -514 with respect to the transcription start site of the HL gene, raising the possibility that the -514 C-->T polymorphism may significantly contribute to differences in individual CAD response to lipid-lowering treatment, as seen in the recent major primary and secondary CAD-prevention clinical trials.

Diet and Syndrome X

Syndrome X is a cluster of abnormalities, associated with resistance to insulin-mediated glucose uptake, that increases risk of coronary heart disease. Increased carbohydrate intake (with reciprocal decreased fat intake) within the boundaries of menus that can be followed in the free-living state have not been shown to decrease insulin resistance directly, by enhancing insulin sensitivity, or indirectly, by producing and maintaining weight loss. Moreover, such diets accentuate the metabolic abnormalities that constitute Syndrome X. Substitution of monounsaturated fat, polyunsaturated fat, or both for saturated fat results in the same reduction in low-density lipoprotein-cholesterol concentration as seen in diets low in fat and high in carbohydrates but without any untoward effects on the various manifestations of Syndrome X. Consequently, substituting unsaturated fat for saturated fat, without increasing intake of dietary protein or carbohydrate, may be useful for patients with hypercholesterolemia, Syndrome X, or both.

Effects of dietary fructose on plasma lipids in healthy subjects

BACKGROUND

About 9% of average dietary energy intake in the United States comes from fructose. Such a high consumption raises concern about the metabolic effects of this sugar.

OBJECTIVE

The objective of this study was to determine the effect of dietary fructose on plasma lipids.

DESIGN

The study was conducted in the General Clinical Research Center at Fairview-University of Minnesota Medical Center. The participants were 24 healthy adult volunteers (12 men and 12 women; 6 of each sex were aged <40 y and 6 of each sex were aged >/=40 y). All subjects received 2 isoenergetic study diets assigned by using a randomized, balanced crossover design. One diet provided 17% of energy as fructose. The other diet was sweetened with glucose and was nearly devoid of fructose. Each diet was fed for 6 wk. Both diets were composed of common foods and contained nearly identical amounts of carbohydrate, protein, fat, fiber, cholesterol, and saturated, monounsaturated, and polyunsaturated fatty acids. All meals were prepared in the metabolic kitchen of the General Clinical Research Center.

RESULTS

The responses to the study diets differed by sex. In men, the fructose diet produced significantly higher fasting, postprandial, and daylong plasma triacylglycerol concentrations than did the glucose diet. The daylong plasma triacylglycerol concentration after 6 wk of the fructose diet was 32% greater in men than the corresponding concentration during the glucose diet (P: < 0.001). The fructose diet had no significant effect on fasting or postprandial plasma triacylglycerol concentrations in women. The fructose diet also had no persistent effect on fasting plasma cholesterol, HDL cholesterol, or LDL cholesterol in either men or women.

CONCLUSIONS

Dietary fructose was associated with increased fasting and postprandial plasma triacylglycerol concentrations in men. Diets high in added fructose may be undesirable, particularly for men. Glucose may be a suitable replacement sugar.

VLDL, apolipoproteins B, CIII, and E, and risk of recurrent coronary events in the Cholesterol and Recurrent Events (CARE) trial

BACKGROUND

Plasma triglyceride concentration has been an inconsistent independent risk factor for coronary heart disease, perhaps because of the metabolic heterogeneity among VLDL particles, the main carriers of triglycerides in plasma.

METHODS AND RESULTS

We conducted a prospective, nested case-control study in the Cholesterol and Recurrent Events (CARE) trial, a randomized placebo-controlled trial of pravastatin in 4159 patients with myocardial infarction and average LDL concentrations at baseline (115 to 174 mg/dL, mean 139 mg/dL). Baseline concentrations of VLDL-apolipoprotein (apo) B (the VLDL particle concentration), VLDL lipids, and apoCIII and apoE in VLDL+LDL and in HDL were compared in patients who had either a myocardial infarction or coronary death (cases, n=418) with those in patients who did not have a cardiovascular event (control subjects, n=370) in 5 years of follow-up. VLDL-cholesterol, VLDL-triglyceride, VLDL-apoB, apoCIII and apoE in VLDL+LDL and apoE in HDL were all interrelated, and each was a univariate predictor of subsequent coronary events. The significant independent predictors were VLDL-apoB (relative risk [RR] 3.2 for highest to lowest quintiles, P:=0.04), apoCIII in VLDL+LDL (RR 2.3, P:=0.04), and apoE in HDL (RR 1.8, P:=0.02). Plasma triglycerides, a univariate predictor of coronary events (RR 1.6, P:=0.03), was not related to coronary events (RR 1.3, P:=0.6) when apoCIII in VLDL+LDL was included in the model, whereas apoCIII remained significant. Adjustment for LDL- and HDL-cholesterol did not affect these results.

CONCLUSIONS

The plasma concentrations of VLDL particles and apoCIII in VLDL and LDL are more specific measures of coronary heart disease risk than plasma triglycerides perhaps because their known metabolic properties link them more closely to atherosclerosis.

Atherogen lipid profile in HIV-1-infected patients with lipodystrophy syndrome

Background: Cases of lipodystrophy syndrome and metabolic disorders have been described since the onset of highly active antiretroviral therapy in HIV-infected patients. The aim of our study was to estimate the prevalence of lipodystrophy (LD) and to define the associated lipid profile of these patients. Methods: The following were determined for each patient: lipid profile (cholesterol and its subfractions, atherogenicity ratios, and triglycerides), blood glucose, and immunovirological markers (CD4(+) cell count and plasma viral load). Patients were classified into two groups on the basis of whether or not they presented with clinical signs of LD. Results: Among 233 HIV-infected patients included in the study, 61 cases (26.1%) of lipodystrophy (LD) were noted. Compared with non-LD patients (NLD), LD patients were older men (P<10(-4)) with a lower CD4(+) lymphocyte cell count (P<0.007) and more often at the AIDS stage (P<10(-3)) (OR=3.2 (95% CI: 1.47-6.2)). Multivariate analysis showed a correlation between LD cases and age (10 years older) (OR=1.78 (95% CI: 1.23-2.57), P<0.002) and the decrease in CD4(+) cell count (100 CD4(+)/mm(3) lower) (OR=1.31 (95% CI: 1.09-1.58), P<0.004). An analysis of lipid subfractions and atherogenicity ratios clearly indicated a proatherogenic lipid profile for the LD patients. Conclusions: The underlying physiopathological mechanism of LD is still unknown. However, the lipid profile of HIV-1-infected patients with a LD syndrome appears to place these patients at an increased risk of progression of atherosclerosis.

Treatment of hypertriglyceridemia by two diets rich either in unsaturated fatty acids or in carbohydrates: effects on lipoprotein subclasses, lipolytic enzymes, lipid transfer proteins, insulin and leptin

BACKGROUND

There is lack of agreement on which dietary regimen is most suitable for treatment of hypertriglyceridemia, especially if high triglyceride concentrations are not due to obesity or alcohol abuse. We compared the effects on blood lipids of a diet high in total and unsaturated fat with a low-fat diet in patients with triglyceride concentrations of > 2.3 mmol/l.

METHODS

Nineteen non-obese male outpatients with triglycerides ranging from 2.30 to 9.94 mmol/l received two consecutive diets for 3 weeks each: first a modified high-fat diet (39% total fat, 8% SFA, 15% monounsaturated fatty acids, 1.6% marine n-3 polyunsaturated fatty acids), and then a low-fat diet (total fat 28%, carbohydrates 54%).

RESULTS

The high-fat diet significantly decreased triglycerides (-63%), total cholesterol (-22%), VLDL cholesterol (-54%), LDL cholesterol ( 16%), total apoC-III (-27%), apoC-III in apoB containing lipoproteins (apoC-III LpB; -31%) and in HDL (apoC-III nonLpB; -29%), apoE in serum (-33%) and apoB-containing lipoproteins (nonHDL-E; -42%), LpA-I (-16%), insulin (-36%), and leptin (-26%) and significantly increased the means of HDL cholesterol (+8%), LDL size (+6%), lipoprotein lipase (LPL, +11%), hepatic lipase (+13%), and lecithin: cholesterol acyltransferase (LCAT, +2%). The subsequent low-fat diet increased triglycerides (+63%), VLDL cholesterol (+19%), apoC-III (+23%), apoC-III LpB (+44%) apoC-III nonLpB (+17%), apoE (+29%) and nonHDL-E (+43%), and decreased HDL cholesterol (-12%), LPL (-3%), and LCAT (-3%). Changes in triglycerides correlated with changes in LPL activity and insulin levels.

CONCLUSIONS

In hypertriglyceridemic patients, a modified diet rich in mono- and n-3 polyunsaturated fatty acids is more effective than a carbohydrate-rich low-fat diet in correcting the atherogenic lipoprotein phenotype.

Different patterns of brisk walking are equally effective in decreasing postprandial lipaemia

OBJECTIVE

To compare the effects of different patterns of brisk walking on day-long plasma triacylglycerol concentrations in sedentary adults.

DESIGN

A three-trial, repeated measures design in which subjects were studied in the fasted state and throughout a day during which they consumed three standardized, mixed meals. On different occasions, subjects undertook no exercise (control), walked briskly for 10 min before each meal (short walks) or walked briskly for 30min before breakfast (long walk).

SUBJECTS

Seven postmenopausal sedentary women and three sedentary men aged between 34 and 66y, with body mass index between 24 and 35 kg/m2.

MEASUREMENTS

Plasma concentrations of triacylglycerol, non-esterified fatty acids, glucose and insulin, metabolic rate and whole-body substrate oxidation in the fasted state and at hourly intervals for 3 h after each meal.

RESULTS

Postprandial plasma triacylglycerol concentrations were lower (P= 0.009) during the walking trials than during the control trial (average values: control 2.08 +/- 0.28 mmol/l; short walks 1.83 +/- 0.22mmol/l; long walk 1.84 +/- 0.22mmol/l (mean+/-s.e.) but did not differ between the two patterns of walking. The difference between control and walking trials increased as successive meals were consumed (interaction of trial x meal P= 0.03). Plasma triacylglycerol concentration increased during the 3 h after breakfast, changed little after lunch and decreased after the evening meal (interaction of meal x time P=0.001). When both walking trials were treated as one condition, walking increased postprandial fat oxidation (average values: control, 0.066 +/- 0.009 g/min;walking 0.074 +/- 0.008 g/min; P < 0.01).

CONCLUSIONS

Thirty minutes of brisk walking, undertaken in one session or accumulated throughout a day, reduces postprandial plasma triacylglycerol concentrations and increases fat oxidation.

Patients with nephrotic-range proteinuria have apolipoprotein C and E deficient VLDL1

BACKGROUND

Impaired very low-density lipoprotein (VLDL) clearance contributes to dyslipidemia in nephrotic-range proteinuria. VLDL can be subdivided into large light VLDL1 (Sf 60 to 400) and smaller, denser VLDL2 (Sf 20 to 60). In nephrotic-range proteinuria, the clearance of VLDL1 is delayed. VLDL1 lipolysis is influenced by apolipoprotein CII (apoCII) and apoCIII, whereas apoE regulates receptor-mediated clearance.

METHODS

To ascertain whether impaired VLDL1 clearance was related to a deficiency in apolipoproteins on VLDL1, we measured VLDL subfraction concentrations and VLDL1 apolipoprotein and lipid compositions in 27 patients with glomerular disease and urinary albumin> 2 g/24 h along with 27 age- and sex-matched controls.

RESULTS

Proteinuric patients had increased plasma VLDL1, VLDL2, apoCII, apoCIII (all P < 0.001), and apoE concentration (P < 0.002). Patients appeared to have smaller VLDL1 particles, as assessed by triglyceride per particle (median + interquartile range, moles per VLDL1 particle): patients, 4.9 (3.0 to 7.9) x103; controls, 7.0 (4.6 to 15.7) x103, P < 0.05, with reduced apoCII, 4.2 (3.1 to 8.2) versus 9.9 (7.4 to 23.2), P < 0.0004; apoCIII, 16.6 (9.1 to 27.2) versus 29.3 (18.5 to 69.4), P < 0.02; and apoE content, 0.17 (0.08 to 0.44) versus 0.48 (0.31 to 1. 31), P < 0.006. The VLDL1 surface free cholesterol to phospholipid results were increased in proteinuric patients (0.55 +/- 0.17 vs. 0. 40 +/- 0.18, P < 0.002, all mean +/- SD). For all patients, VLDL1 apoCII, apoCIII, and apoE contents per particle were related to particle size (apoCII, r2 = 61.5%, P < 0.001; apoCIII, r2 = 75.8%, P < 0.001; apoE, r2 = 58.2%, P < 0.001) and inversely to the free cholesterol to phospholipid ratio (apoCII, r2 = 41.6%, P < 0.001; apoCIII, r2 = 38.8%, P < 0.001; apoE, r2 = 11.7%, P < 0.05). Multivariate analysis suggested that the relative lack of apoCII and apoCIII on patients VLDL1 was related to smaller particle size and increased free cholesterol:phospholipid (FC:PL) ratio. Particle size but not free cholesterol determined the apoE content of VLDL1.

CONCLUSIONS

We postulate that impaired VLDL1 clearance in nephrotic-range proteinuria results from the appearance of particles deficient in apoCII, apoCIII, and apoE. VLDL1 apoC deficiency is associated with the formation of smaller particles with a high FC:PL ratio, and is likely to cause inefficient lipolysis. VLDL1 apoE deficiency is associated with smaller VLDL1 particles but not altered VLDL1 surface lipid content, and may reduce receptor-mediated clearance of this lipoprotein.

Low-density lipoprotein particle size, triglycerides, and high-density lipoprotein cholesterol as risk factors for coronary heart disease in older Japanese-American men

Decreased low-density lipoprotein (LDL) particle size is associated with coronary heart disease (CHD) risk among middle-aged Caucasian populations, and has been consistently correlated with increased plasma levels of triglyceride and decreased levels of high-density lipoprotein (HDL) cholesterol. This study examines whether these risk factors predict CHD among older Japanese-American men. With use of the Honolulu Heart Program Lipoprotein Exam 3 (1980 to 1982) as baseline, and 12-year follow-up for CHD events, a nested, case-control study was designed. One hundred forty-five incident CHD cases were identified and matched to 2 controls each. LDL particle diameter (size) was determined by gradient gel electrophoresis. A 10-angstrom (A) decrease in LDL size at baseline was associated with increased risk of incident CHD (relative risk 1.28, 95% confidence interval 1.01 to 1.63). After adjustment for baseline risk factors, the LDL size association was no longer statistically significant (relative risk 1.13, 95% confidence interval 0.86 to 1.49). When principal components analysis was used to define a composite variable for LDL size, triglycerides, and HDL cholesterol, this component predicted CHD independent of smoking, alcohol consumption, physical activity, body mass index, hypertension, diabetes, and beta-blocker use (p <0.01). Therefore, this prospective analysis of data from older, Japanese-American men demonstrated that decreased LDL size is a univariate predictor of incident CHD, and that a composite risk factor of LDL size, triglyceride, and HDL cholesterol was a risk factor for CHD independent of other risk factors.

Endothelial dysfunction in men with small LDL particles

BACKGROUND

It is unknown whether LDL particle size is, independent of other lipids and lipoproteins, associated with endothelial dysfunction in vivo.

METHODS AND RESULTS

We determined in vivo endothelial function in 34 healthy men by measuring forearm blood flow responses to intrabrachial artery infusions of acetylcholine (ACh, an endothelium-dependent vasodilator) and sodium nitroprusside (an endothelium-independent vasodilator). LDL peak particle size was measured with gradient gel electrophoresis. Men with small LDL particles (LDL diameter </=25.5 nm, n=10) had a 39% lower blood flow response to ACh than men with large LDL particles (LDL diameter >25. 5 nm, n=24, blood flow 6.9+/-3.6 versus 11.4+/-5.1 mL/dL. min, P=0. 006). The groups had comparable LDL cholesterol concentrations (3. 9+/-0.6 versus 3.7+/-1.0 mmol/L, men with small versus large LDL particles), blood pressure, glucose concentrations, and body mass indexes. LDL size (r=0.45, P=0.01) but not HDL cholesterol (r=0.31, P=0.09) or triglycerides (r=-0.19, P=0.30) was significantly correlated with endothelium-dependent vasodilation. Serum triglyceride concentrations and LDL size were inversely correlated (r=-0.44, P=0.01). In multivariate regression analysis, LDL size was the only significant determinant of the ACh-induced increase in blood flow. Sodium nitroprusside-stimulated endothelium-independent vasodilation was similar in both groups.

CONCLUSIONS

Small LDL particles are associated with impaired in vivo endothelial function independent of HDL and LDL cholesterol and triglyceride concentrations. LDL size may therefore mediate adverse effects of hypertriglyceridemia on vascular function.

Preventing, stopping, or reversing coronary artery disease--triglyceride-rich lipoproteins and associated lipoprotein and metabolic abnormalities: the need for recognition and treatment

A substantial number of treated patients with or at high risk for coronary artery disease continue to have fatal and nonfatal coronary artery events in spite of significant reduction of elevated levels of low-density lipoprotein cholesterol. Other lipoprotein abnormalities besides an elevated level of low-density lipoprotein cholesterol contribute to risk of coronary artery disease and coronary artery events, and the predominant abnormalities that appear to explain much of this continued risk are an elevated serum triglyceride level and a low level of high-density lipoprotein cholesterol. Most patients with coronary artery disease have a mixed dyslipidemia with hypertriglyceridemia, which is associated and metabolically intertwined with other atherogenic risk factors, including the presence of triglyceride-rich lipoprotein remnants, low levels of high-density lipoprotein cholesterol, small, dense, low-density lipoprotein particles, postprandial hyperlipidemia, and a prothrombotic state. Aggressive treatment of these patients needs to focus on these other lipoprotein abnormalities as much as on low-density lipoprotein cholesterol. Combination drug therapy will usually be required. Reliable assessment of risk of coronary artery disease from lipoprotein measurements and response to therapy requires inclusion of all atherogenic lipoproteins in laboratory measurements and treatment protocols. At present this may be best accomplished by use of non-high-density lipoprotein cholesterol (total cholesterol minus high-density lipoprotein cholesterol) calculated from standard laboratory lipoprotein values. Ultimately, a more comprehensive assessment of coronary artery disease risk and appropriate therapy may include measurement of lipoprotein subclass distribution including determination of low-density lipoprotein particle concentration and sizes of the various lipoprotein particles.

Cardiovascular disease mortality in familial forms of hypertriglyceridemia: A 20-year prospective study

BACKGROUND

Familial combined hyperlipidemia (FCHL) and familial hypertriglyceridemia (FHTG) are 2 of the most common familial forms of hyperlipidemia. There is a paucity of prospective data concerning the risk of cardiovascular disease (CVD) in such families. The purposes of this study were to estimate 20-year total and CVD mortality risk among relatives in these families and to evaluate plasma triglyceride as a predictor of death.

METHODS AND RESULTS

The study was based on lipid and medical history data from 101 families ascertained in 2 studies conducted in the early 1970s. Vital status and cause of death was determined during 1993 to 1997 for 685 family members, including first-degree relatives of the probands and spouse control subjects. Compared with spouse control subjects, 20-year CVD mortality risk was increased among siblings and offspring in FCHL (relative risk 1.7, P=0.02) after adjustment for baseline covariates. In FHTG families, the relative risk was also 1.7 but was not statistically significant (P=0.39). Baseline triglyceride was associated with increased CVD mortality risk independent of total cholesterol among relatives in FHTG families (relative risk 2.7, P=0.02) but not in FCHL families (relative risk 1.5, P=0.16) after adjustment for baseline covariates.

CONCLUSIONS

This prospective study establishes that relatives in FCHL families are at increased risk for CVD mortality and illustrates the need for effective prevention strategies in this group. Baseline triglyceride level predicted subsequent CVD mortality among relatives in FHTG families, adding to the growing evidence for the importance of hypertriglyceridemia as a risk factor for CVD.

Inheritance of LDL peak particle diameter: results from a segregation analysis in Israeli families

Genetic and environmental determinants of LDL peak particle diameter (LDL-PPD) were investigated in a sample of 80 kindreds residing in kibbutz settlements in Israel. The sample included 182 males and 191 females ages 15-93 years. LDL-PPD levels were first adjusted for variability in sex and age. Commingling analysis demonstrated that a mixture of two normal distributions fit the adjusted LDL-PPD levels better than did a single normal distribution. Complex segregation analysis was first applied to these sex and age adjusted data but was not conclusive. However, when the regression model for sex and age allowed coefficients to be ousiotype (class) specific, the mixed environmental model was rejected while a major Mendelian model was not. These results suggest that the particular genotypes determined by the major gene, which are associated with different phenotypic variances, are likely to be more realistic, and that this analytic approach can contribute to improving our understanding of the genetics of LDL particle size.

Reduced LDL particle size in children consuming a very-low-fat diet is related to parental LDL-subclass patterns

BACKGROUND

A genetically influenced atherogenic lipoprotein phenotype characterized by a predominance of small, dense LDL particles (subclass pattern B) can be induced by low-fat diets in healthy subjects with large LDL particles (pattern A).

OBJECTIVE

The aim of this study was to test whether genetic predisposition to subclass pattern B contributes to susceptibility to induction of this trait by a low-fat diet.

DESIGN

The prevalence of pattern B in children is relatively low compared with that in older individuals, but genetic susceptibility to this trait in offspring can be inferred by its presence in their parents. Plasma lipoproteins were analyzed 10 d after a change from a usual diet to a very-low-fat (10% fat), high-carbohydrate diet in offspring (mean age: 14 y; range: 7-28 y) of 22 families according to parental LDL-subclass patterns when consuming a low-fat diet: AxA mating (9 families with 19 children), AxB mating (5 families with 10 children), and BxB mating (8 families with 21 children).

RESULTS

The very-low-fat, high-carbohydrate diet produced significantly greater decreases in LDL particle size in offspring of BxB parents (f1.gif" BORDER="0"> +/- SE: -0.55 +/- 0.16 nm) and AxB parents (-0.48 +/- 0.19 nm) than in offspring of AxA parents (0.14 +/- 0.20 nm). The number of children expressing pattern B with the 10%-fat diet and the proportion of children converting from pattern A to pattern B was significantly greater in offspring of BxB parents than in those with 1 or 2 pattern A parents.

CONCLUSION

A very-low-fat, high-carbohydrate diet can induce expression of LDL-subclass pattern B in genetically predisposed children with low expression of the trait while consuming their usual diets.

A prospective study of dietary glycemic load, carbohydrate intake, and risk of coronary heart disease in US women

BACKGROUND

Little is known about the effects of the amount and type of carbohydrates on risk of coronary heart disease (CHD).

OBJECTIVE

The objective of this study was to prospectively evaluate the relations of the amount and type of carbohydrates with risk of CHD.

DESIGN

A cohort of 75521 women aged 38-63 y with no previous diagnosis of diabetes mellitus, myocardial infarction, angina, stroke, or other cardiovascular diseases in 1984 was followed for 10 y. Each participant's dietary glycemic load was calculated as a function of glycemic index, carbohydrate content, and frequency of intake of individual foods reported on a validated food-frequency questionnaire at baseline. All dietary variables were updated in 1986 and 1990.

RESULTS

During 10 y of follow-up (729472 person-years), 761 cases of CHD (208 fatal and 553 nonfatal) were documented. Dietary glycemic load was directly associated with risk of CHD after adjustment for age, smoking status, total energy intake, and other coronary disease risk factors. The relative risks from the lowest to highest quintiles of glycemic load were 1.00, 1.01, 1. 25, 1.51, and 1.98 (95% CI: 1.41, 2.77 for the highest quintile; P for trend < 0.0001). Carbohydrate classified by glycemic index, as opposed to its traditional classification as either simple or complex, was a better predictor of CHD risk. The association between dietary glycemic load and CHD risk was most evident among women with body weights above average ¿ie, body mass index (in kg/m(2)) >/= 23.

CONCLUSION

These epidemiologic data suggest that a high dietary glycemic load from refined carbohydrates increases the risk of CHD, independent of known coronary disease risk factors.

Atherogenic lipoprotein phenotype in end-stage renal failure: origin and extent of small dense low-density lipoprotein formation

End-stage renal failure (ESRF) is associated with dyslipidemia and accelerated atherosclerosis. Triglyceride-rich lipoproteins accumulate and qualitative changes take place in low-density lipoprotein (LDL), with a predominance of the small dense LDL phenotype. Increased small dense LDL (LDLIII) is a known risk factor for cardiovascular disease. To assess the extent of LDLIII formation in ESRF and identify factors contributing to LDLIII production, we analyzed LDL subfractions by density-gradient ultracentrifugation, very low-density lipoprotein subfractions, and lipase activity in 75 patients with ESRF (25 hemodialysis [HD], 25 peritoneal dialysis [PD], and 25 predialysis patients) and 40 age- and sex-matched controls. The percentage of LDLIII was increased in all three patient groups compared with controls (PD, 33% +/- 29% [mean +/- SD]; P < 0.005; HD, 30% +/- 22%; P < 0.01; predialysis, 26% +/- 26%; P < 0.01; all versus controls, 14% +/- 10%). Plasma LDLIII concentration was increased only in PD patients (median, 84 mg/dL; interquartile range [IQR], 29 to 160 mg/dL versus controls; median, 31 mg/dL; IQR, 26 to 54 mg/dL). In other patient groups, total LDL level was less, with heterogeneity in LDLIII concentrations. Forty percent of PD patients and 28% of HD and predialysis patients had LDLIII concentrations greater than 100 mg/dL compared with 2.5% of controls (P = 0.002). Plasma triglyceride levels (r(2) = 38.4%; P < 0.001) and hepatic lipase activity (r(2) = 6.7%; P < 0.03) were independent predictors of LDLIII concentration. The strong association between LDLIII concentration and triglyceride level was present in all three patient groups (HD, r(2) = 47.9%; PD, r(2) = 45. 2%; predialysis, r(2) = 25.8%); plasma triglyceride levels greater than 177 mg/dL (2.0 mmol/L) had an 86% specificity and 79% sensitivity for predicting an LDLIII concentration greater than 100 mg/dL. We conclude that the atherogenic lipoprotein phenotype predominates in ESRF, with excess LDLIII particularly prominent in PD patients. Atherogenic levels of LDLIII are found in patients with triglyceride levels greater than 177 mg/dL. This is likely to represent a further cardiovascular risk factor in this population.

Triglyceride, small, dense low-density lipoprotein, and the atherogenic lipoprotein phenotype

This review provides an overview of the recent data evaluating triglyceride and low-density lipoprotein (LDL) size, two highly interrelated, genetically influenced, risk factors for cardiovascular disease (CVD). An examination of new epidemiologic studies continues to demonstrate that plasma triglyceride levels predict CVD. The first prospective study of the familial forms of hypertriglyceridemia has shown that relatives in familial-combined hyperlipidemia families are at increased risk for CVD mortality and that triglyceride levels predicted 20-year, CVD mortality among relatives in familial hypertriglyceridemia families. A meta-analysis of three, large-scale, prospective studies in men, and the first study to examine the correlation of LDL particle size distribution and vascular changes measured by B-mode ultrasound, add to growing evidence that small, dense LDL is atherogenic. Quantitative genetic analysis has recently shown substantial pleiotropic (common) genetic effects on triglyceride and LDL size. At least part of this may be explained by variation at the cholesterol ester transfer protein locus on chromosome 16, possibly through its role in reverse cholesterol transport. Taken together, these data provide new insights into the importance of triglyceride and LDL particle size for understanding genetic susceptibility to cardiovascular disease and its prevention.

Association of cholesteryl ester transfer protein-TaqIB polymorphism with variations in lipoprotein subclasses and coronary heart disease risk: the Framingham study

Cholesteryl ester transfer protein (CETP) facilitates the exchange of triglycerides and cholesteryl esters between lipoprotein particles, a key step in reverse cholesterol transport in humans. Variations at the CETP locus have been shown to be determinants of the levels and activity of CETP and high density lipoprotein (HDL) plasma concentration. The associations of the common CETP polymorphism, TaqIB in intron 1, with lipoprotein levels and particle size distribution, CETP activity, and coronary heart disease (CHD) risk were examined in a population-based sample of 1411 men and 1505 women from the Framingham Offspring Study. The B2 allele frequency was 0.444 in men and 0.433 in women, and its presence was significantly (P<0.05) associated with decreased CETP activity. B1B1 men had lower HDL cholesterol (HDL-C) levels (1.07 mmol/L) compared with B1B2 (1.14 mmol/L) and B2B2 (1.18 mmol/L) men (P<0.001). Likewise, B1B1 women had lower HDL-C levels (1.40 mmol/L) compared with B1B2 (1.46 mmol/L) and B2B2 (1.53 mmol/L) women (P<0.001). In men, the B2 allele was associated with increased particle size for HDL and low density lipoprotein. In women, a similar effect was demonstrated only for HDL particle size. The odds ratio for prevalent CHD associated with the B2 allele was 0.696 (P=0.035) in men. After adjusting for age, body mass index, systolic blood pressure, diabetes, smoking, alcohol consumption, beta-blocker use, total cholesterol, and HDL-C, this odds ratio was 0.735 (P=0.187), suggesting that the protective effect of the B2 allele was due in part to its association with HDL-C levels. No significant protective effects were observed in women. These data demonstrate that variation at the CETP gene locus is a significant determinant of HDL-C levels, CETP activity, and lipoprotein size in this population. Moreover, these effects appear to translate into a lower CHD risk among those men with the B2 allele.

The relationship between physical fitness and coronary risk factor profiles in Japanese women

The purpose of this study was to investigate the relationship between physical fitness and coronary risk factor profiles in Japanese women. The subjects were 1,483 women (ages 30 to 69) who participated in a practical health promotion program. After medical examination, physical fitness was evaluated by conducting a symptom limited maximal exercise test by ergometer to measure maximum oxygen uptake (peakVO(2)) with an expired gas analyzer. The subjects were classified into 3 groups (high fitness, moderate fitness, and low fitness) according to age and physical fitness level. The results showed that the subjects in higher fitness groups had lower levels in: body mass index (BMI), percentage of body fat, waist-hip ratio, resting blood pressure, and atherogenic index, and higher HDL-cholesterol compared to those in lower fitness group. Even after adjustment for the effects of age and BMI, die subjects in the higher fitness groups had better coronary risk factor profiles. These results suggest that among Japanese women a high level of physical fitness is related to favorable coronary risk factor profiles.

Novel risk factors for atherosclerosis

In the past several years, evidence has accumulated that factors other than conventional risk factors may contribute to the development of atherosclerosis. Conventional risk factors predict less than one half of future cardiovascular events. Furthermore, conventional risk factors may not have the same causal effect in different ethnic groups in whom novel risk factors may have a role. These newer risk factors for atherosclerosis include homocysteine, fibrinogen, impaired fibrinolysis, increased platelet reactivity, hypercoagulability, lipoprotein(a), small dense low-density lipoprotein cholesterol, and inflammatory-infectious markers. Identification of other markers associated with an increased risk of atherosclerotic vascular disease may allow better insight into the pathobiology of atherosclerosis and facilitate the development of preventive and therapeutic measures. In this review, we discuss the evidence associating these factors in the pathogenesis of atherosclerosis, the mechanism of risk, and the clinical implications of this knowledge.

Effect of weight loss with reduction of intra-abdominal fat on lipid metabolism in older men

How weight loss improves lipid levels is poorly understood. Cross-sectional studies have suggested that accumulation of fat in intra-abdominal stores (IAF) may lead to abnormal lipid levels, increased hepatic lipase (HL) activity, and smaller low density lipoprotein (LDL) particle size. To determine what effect loss of IAF would have on lipid parameters, 21 healthy older men underwent diet-induced weight loss. During a period of weight stability before and after weight loss, subjects underwent studies of body composition, lipids, measurement of postheparin lipoprotein and HL lipase activities, cholesteryl ester transfer protein activity, and insulin sensitivity (Si). After an average weight loss of 10%, reductions in fat mass, IAF, and abdominal s.c. fat were seen, accompanied by reductions in levels of triglyceride, very low density lipoprotein cholesterol, apolipoprotein B, and HL activity. High density lipoprotein-2 cholesterol and Si increased. In those subjects with pattern B LDL at baseline, LDL particle size increased. Cholesteryl ester transfer protein activity did not change. Changes in IAF and Si correlated with a decrease in HL activity (although not independently of each other). In summary, in men undergoing diet-induced weight loss, only loss of IAF was found to be associated with a reduction in HL, which is associated with beneficial effects on lipid levels.

Association between elevated plasma fibrinogen and the small, dense low-density lipoprotein phenotype among postmenopausal women

A predominance of small, dense low-density lipoprotein (LDL) particles (subclass pattern B) has been associated with a 2- to threefold increase in coronary heart disease risk. Recently, it has been reported that LDL subclass pattern B is associated with hyperfibrinogenemia, which is also a coronary heart disease risk factor. The present study examined the relation between hyperfibrinogenemia and LDL subclass pattern in 258 postmenopausal women. A significant univariate correlation was observed between the concentration of cholesterol carried in small, dense LDL particles and plasma fibrinogen concentration (r = 0.17, p = 0.01). The prevalence of LDL subclass pattern B was 41.9% in the highest fibrinogen tertile, compared with 27.9% and 24.4% in the first and second tertiles, respectively (global chi-square 6.8, p = 0.03). The crude odds ratio (OR) for LDL subclass pattern B among women in the highest fibrinogen tertile, compared with the lower tertiles, was 2.03 (95% confidence interval [CI] 1.18 to 3.51, p = 0.01). After adjustment for age and plasma lipids (log(e) triglycerides, LDL cholesterol, and high-density lipoprotein cholesterol), the OR was 2.14 (95% CI 1.17 to 3.96, p = 0.01). Further adjustment for hematocrit, indicators of carbohydrate homeostasis, body mass index, waist circumference, and several variables related to lifestyle did not attenuate this association (OR 2.56, 95% CI 1.27 to 5.27, p = 0.01). These data suggest that hyperfibrinogenemia and LDL subclass pattern B may be 2 components of a common syndrome and suggest that hyperfibrinogenemia may contribute to the increased coronary heart disease risk associated with LDL subclass pattern B.

Low-density lipoprotein subclass distribution pattern and adiposity-associated dyslipidemia in postmenopausal women

OBJECTIVE

A predominance of small, dense low-density lipoprotein (LDL) particles (subclass pattern B) is associated with increased risk for coronary heart disease and is characterized by elevated triglycerides and depressed high-density lipoprotein (HDL) cholesterol concentrations. The present analysis was undertaken to assess the impact of LDL subclass distribution pattern and adiposity on serum lipids in postmenopausal women.

METHODS

Anthropometric measurements and fasting lipid data were obtained from 254 postmenopausal women 70 years of age or younger, not receiving sex hormone replacement, who were participating in a clinical trial designed to assess the influence of hormone replacement regimens on coronary heart disease risk markers.

RESULTS

The prevalence of LDL subclass pattern B was 32%. Triglyceride levels were higher and HDL cholesterol lower (both p<0.001) in women with pattern B vs. pattern A, but total and LDL cholesterol levels did not differ. LDL subclass pattern contributed independently to the variance in HDL cholesterol (p<0.001) and log(e) triglyceride (p<0.001) concentrations explained by anthropometric variables (waist circumference or body mass index). Compared to women with LDL subclass pattern A and waist circumference below the median value of 83.0 centimeters, those with pattern B and waist > or =83.0 centimeters had markedly lower HDL cholesterol levels [44.0 (41.6-47.4) vs. 57.2 (54.1-60.3) mg/dL, mean (95% CI)] and increased triglyceride concentrations [geometric mean 147.8 (131.6-165.7) vs. 95.4 (88.2-102.5) mg/dL].

CONCLUSIONS

These data suggest that adiposity and LDL subclass distribution pattern are independent determinants of plasma triglyceride and HDL cholesterol concentrations in postmenopausal women.