Increased degradation of lipoprotein(a) in atherosclerotic compared with nonlesioned aortic intima-inner media of rabbits: in vivo evidence that lipoprotein(a) may contribute to foam cell formation

Lipoprotein (a) levels and vulnerable characteristics in nonculprit plaque in patients with acute coronary syndrome

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High Lp(a) level is associated with more TCFA in nonculprit plaque in ACS patients.

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The association was significant among patients with plaque erosion.

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Measurement of Lp(a) may be useful for risk stratification in ACS patients.

Background

High plasma levels of Lp(a) are associated with a worse prognosis in patients with coronary artery disease. The aim of the present study is to clarify the association between high lipoprotein a [Lp(a)] levels and vulnerable characteristics of nonculprit plaques in patients with acute coronary syndrome (ACS).

Methods

A total of 185 consecutive patients with ACS who underwent optical coherence tomography imaging of nonculprit plaques in the culprit vessels were enrolled. Patients were divided into the high Lp(a) group (≥30 mg/dL; 50 nonculprit plaques in 49 patients) or the low Lp(a) group (<30 mg/dL; 139 nonculprit plaques in 136 patients).

Results

The prevalence of thin-cap fibroatheroma (TCFA) was significantly higher in the high Lp(a) group than in the low Lp(a) group (38.0 vs. 21.6%, p = 0.034). Multivariate logistic analysis demonstrated that a high Lp(a) level was independently associated with the prevalence of TCFA (odds ratio, 1.18; 95% confidence interval, 1.01–1.36; p = 0.033). The prevalence of TCFA was significantly higher in the high Lp(a) group than in the low Lp(a) group among patients with plaque erosion (50.0 vs. 9.4%, respectively; p = 0.027), although the difference was not statistically significant between the two groups in patients with plaque rupture.

Conclusions

High Lp(a) levels were associated with a high prevalence of TCFA in nonculprit plaques among patients with ACS, particularly in patients with plaque erosion. The present results may partly explain the pathogenesis of worse clinical outcomes in patients with ACS and a high Lp(a) level as shown in clinical studies.

Characterization of Polyvascular Disease in Heterozygous Familial Hypercholesterolemia: Its Association With Circulating Lipoprotein(a) Levels

Background Heterozygous familial hypercholesterolemia (HeFH) more likely exhibits extensive atherosclerotic disease at multiple vascular beds. Lipoprotein(a) (Lp(a)) is an atherogenic lipoprotein that elevates HeFH-related atherosclerotic cardiovascular disease risks. Whether circulating Lp(a) level associates with polyvascular propagation of atherosclerosis in subjects with HeFH remains uncertain. Methods and Results The current study analyzed 370 subjects with clinically diagnosed HeFH who received evaluation of systemic arteries. Polyvascular disease (polyVD) was defined as more than 2 coexisting atherosclerosis conditions including coronary artery disease, carotid stenosis, or peripheral artery disease. Clinical characteristics and lipid features were analyzed in subjects with HeFH and polyVD; 5.7% of patients with HeFH (21/370) had polyVD. They were more likely to have a clustering of risk factors, tendon (P<0.001) and skin xanthomas (P=0.004), and corneal arcus (P=0.026). Furthermore, an elevated Lp(a) level (P=0.006) and a greater frequency of Lp(a) level ≥50 mg/dL (P<0.001) were observed in subjects with HeFH and polyVD. On multivariable analysis adjusting risk factors and lipid-lowering agents, Lp(a) ≥50 mg/dL (odds ratio [OR], 5.66 [95% CI, 1.68-19.0], P=0.005), age, and family history of premature coronary artery disease independently predicted polyVD in subjects with HeFH. Of note, the prevalence of polyVD rose to 33.3% in patients with HeFH and age >58 years old, family history of premature coronary artery disease, and Lp(a) ≥50 mg/dL (OR, 10.3 [95% CI, 3.12-33.4], P<0.001). Conclusions An increased level of circulating Lp(a) levels predicted concomitance of polyVD in patients with HeFH. The current findings suggest subjects with HeFH and Lp(a) ≥50 mg/dL as a high-risk category who require meticulous screening of systemic vascular beds.

The Predictive Value of Lp(a) for Adverse Cardiovascular Event in ACS Patients With an Achieved LDL-C Target at Follow Up After PCI

Low-density lipoprotein cholesterol (LDL-C) is a traditional and important risk factor for atherosclerotic cardiovascular disease (CVD). Recently, lipoprotein (a) (lp(a)) attracts considerable attention as a residual risk factor for CVD. However, the roles of lp(a) in acute coronary syndrome (ACS) patients with well-controlled LDL-C (≤1.8mmol/L) after percutaneous coronary intervention (PCI) remain unclear. Current study results demonstrated that occurrence of major adverse cardiovascular events (MACE) and recurrent myocardial infarction (MI) increased with the Lp(a) increasing in patients with LDL-C≤1.8mmol/L at 1-month follow-up. In relatively low-risk patients presented with ACS and underwent PCI (LDL-C ≤1.8mmol/L at 1-month follow-up), lp(a) is still independently related to adverse prognosis. Further researches of targeted therapy against lp(a) are warranted.

Association of lipoprotein(a) levels with recurrent events in patients with coronary artery disease

OBJECTIVE

Whether lipoprotein(a) (Lp(a)) is a predictor for recurrent cardiovascular events (RCVEs) in patients with coronary artery disease (CAD) has not been established. This study, hence, aimed to examine the potential impact of Lp(a) on RCVEs in a real-world, large cohort of patients with the first cardiovascular event (CVE).

METHODS

In this multicentre, prospective study, 7562 patients with angiography-diagnosed CAD who had experienced a first CVE were consecutively enrolled. Lp(a) concentrations of all subjects were measured at admission and the participants were categorised according to Lp(a) tertiles. All patients were followed-up for the occurrence of RCVEs including cardiovascular death, non-fatal myocardial infarction and stroke.

RESULTS

During a mean follow-up of 61.45±19.57 months, 680 (9.0%) RCVEs occurred. The results showed that events group had significantly higher Lp(a) levels than non-events group (20.58 vs 14.95 mg/dL, p<0.001). Kaplan-Meier analysis indicated that Lp(a) tertile 2 (p=0.001) and tertile 3 (p<0.001) groups had significantly lower cumulative event-free survival rates compared with tertile 1 group. Moreover, multivariate Cox regression analysis further revealed that Lp(a) was independently associated with RCVEs risk (HR: 2.01, 95% CI: 1.44 to 2.80, p<0.001). Moreover, adding Lp(a) to the SMART risk score model led to a slight but significant improvement in C-statistic (∆C-statistic: 0.018 (95% CI: 0.011 to 0.034), p=0.002), net reclassification (6.8%, 95% CI: 0.5% to 10.9%, p=0.040) and integrated discrimination (0.3%, 95% CI: 0.1% to 0.7%, p<0.001).

CONCLUSIONS

Circulating Lp(a) concentration was indeed a useful predictor for the risk of RCVEs in real-world treated patients with CAD, providing additional information concerning the future clinical application of Lp(a).

Lipoprotein(a) and long-term recurrent infarction after an episode of ST-segment elevation acute myocardial infarction

BACKGROUND

In established ischemic heart disease, the relationship between lipoprotein(a) and new cardiovascular events showed contradictory results. Our aim was to assess the relationship between lipoprotein(a) and very long-term recurrent myocardial infarction (MI) after an index episode of ST-segment elevation acute myocardial infarction (STEMI).

METHODS

We included 435 consecutive STEMI patients discharged from October 2000 to June 2003 in a single teaching center. The relationship between lipoprotein(a) at discharge and recurrent MI was evaluated through negative binomial regression and Cox regression analysis.

RESULTS

The mean age was 65 years (55-74 years), 25.5% were women, 34.7% were diabetic, and 66% had a MI of anterior location. Fibrinolysis, rescue, or primary angioplasty was performed in 215 (49.4%), 19 (4.4%), and 18 (4.1%) patients, respectively. The median lipoprotein(a) was 30.4 mg/dL (12-59.4 mg/dL). After a median follow-up of 9.6 years (4.1-15 years), 180 (41.4%) deaths and 187 MI in 133 (30.6%) patients were recorded. After a multivariate adjustment, the risk gradient of lipoprotein(a) showed a neutral effect along most of the continuum and only extreme higher values identified those at higher risk of recurrent MI (P = 0.020). Those with lipoprotein(a) values >95th percentile (≥135 mg/dL) showed a higher risk of recurrent MI (incidence rate ratio, 2.34; 95% confidence interval, 1.37-4.02; P = 0.002). Lipoprotein(a) was not related to the risk of mortality (P = 0.245).

CONCLUSIONS

After an episode of STEMI, only extreme high values of lipoprotein(a) were associated with an increased risk of long-term recurrent MI.

The different relations of PCSK9 and Lp(a) to the presence and severity of atherosclerotic lesions in patients with familial hypercholesterolemia

BACKGROUND AND AIMS

The relation of lipoprotein (a) [Lp(a)] and proprotein convertase substilisin/kexin type 9 (PCSK9) levels to coronary artery disease (CAD) has been well established in the general population, while little is known about the association between Lp(a) or PCSK9 and atherosclerotic lesions of different artery sites in patients with familial hypercholesterolemia (FH).

METHODS

One hundred and fifty-one patients with verified genotyped heterozygous FH (HeFH) were enrolled. There were available data regarding coronary angiography and carotid ultrasonography in 151 patients and femoral ultrasonography in 55 patients. Coronary and carotid severity was evaluated by Gensini score and Crouse score. PCSK9 and Lp(a) concentrations were determined by ELISA and immunoturbidimetry, respectively. Finally, the correlation of PCSK9 and Lp(a) with the presence and severity of CAD and peripheral artery disease (PAD) was assessed.

RESULTS

The distributions of PCSK9 and Lp(a) were skewed and a close correlation between them in HeFH patients was found. PCSK9 levels were significantly higher in patients with coronary and carotid atherosclerotic lesions compared to their non-atherosclerotic groups, while no difference was found in femoral atherosclerotic lesions groups. Lp(a) levels only differed between patients with or without coronary atherosclerotic lesions. Patients with highest PCSK9 and Lp(a) concentrations had the highest prevalence and severity of atherosclerotic lesions. Multivariate regression analysis showed that PCSK9 was independently associated with CAD and PAD, while Lp(a) was only associated with CAD.

CONCLUSIONS

Circulating PCSK9 concentrations were associated with an increased risk of CAD and PAD, while Lp(a) was only a marker for CAD in HeFH patients.

Vitamin C down-regulate apo(a) expression via Tet2-dependent DNA demethylation in HepG2 cells

Lipoprotein(a)[Lp(a)] is a risk factor for coronary heart diseases. However, the metabolism of this protein remains poorly understood. Efficient and specific drugs that can decrease high plasma levels of Lp(a) have not been developed yet. Vitamin C is responsible for maintaining the catalytic activity of a group of iron and 2-oxoglutarate (2OG)-dependent dioxygenases and induces the generation of 5-hydroxymethylcytosine (5hmC) via Ten-eleven translocation (Tet) dioxygenases. In addition, It has been reported vitamin C deficiency induces atherosclerosis and increases Lp(a) and apo(a) plasma levels in Lp(a)+ mice. However, the mechanism is still unclear. In this study, we investigated the effects of vitamin C on apo(a) expression and the possible molecular mechanism of vitamin C that influences apolipoprotein(a) [apo(a)] biosynthesis in HepG2 cells. Results showed that vitamin C significantly inhibited the expression and secretion levels of apo(a). Vitamin C can also increase ELK1 expression and hydroxymethylation of ELK1 promoter and the globle DNA in HepG2 cells. In addition, the effects of vitamin C inhibiting the apo(a) expression were attenuated by ELK1siRNA and Tet2siRNA. These results suggested vitamin C down-regulate apo(a) expression via Tet2-dependent DNA demethylation in HepG2 cells.

Lipoprotein (a) as a cause of cardiovascular disease: insights from epidemiology, genetics, and biology

Human epidemiologic and genetic evidence using the Mendelian randomization approach in large-scale studies now strongly supports that elevated lipoprotein (a) [Lp(a)] is a causal risk factor for cardiovascular disease, that is, for myocardial infarction, atherosclerotic stenosis, and aortic valve stenosis. The Mendelian randomization approach used to infer causality is generally not affected by confounding and reverse causation, the major problems of observational epidemiology. This approach is particularly valuable to study causality of Lp(a), as single genetic variants exist that explain 27-28% of all variation in plasma Lp(a). The most important genetic variant likely is the kringle IV type 2 (KIV-2) copy number variant, as the apo(a) product of this variant influences fibrinolysis and thereby thrombosis, as opposed to the Lp(a) particle per se. We speculate that the physiological role of KIV-2 in Lp(a) could be through wound healing during childbirth, infections, and injury, a role that, in addition, could lead to more blood clots promoting stenosis of arteries and the aortic valve, and myocardial infarction. Randomized placebo-controlled trials of Lp(a) reduction in individuals with very high concentrations to reduce cardiovascular disease are awaited. Recent genetic evidence documents elevated Lp(a) as a cause of myocardial infarction, atherosclerotic stenosis, and aortic valve stenosis.

New and emerging biomarkers in cardiovascular disease

Cardiovascular disease (CVD) is the most common cause of death and disability worldwide. Therefore, great importance has been placed on the discovery of novel risk factors and metabolic pathways relevant in the prevention and management of CVD. Such research is ongoing and may continue to lead to better risk stratification of individuals and/or the development of new intervention targets and treatment options. This review highlights emerging biomarkers related to lipid metabolism, glycemia, inflammation, and cardiac damage, some of which show promising associations with CVD risk and provide further understanding of the underlying pathophysiology. However, their measurement methodology and assays will require validation and standardization, and it will take time to accumulate evidence of their role in CVD in various population settings in order to fully assess their clinical utility. Several of the novel biomarkers represent intriguing, potentially game-changing targets for therapy.

Novel metabolic biomarkers of cardiovascular disease

Coronary heart disease (CHD) accounts for one in every six deaths in US individuals. Great advances have been made in identifying important risk factors for CHD, such as hypertension, diabetes mellitus, smoking and hypercholesterolaemia, which have led to major developments in therapy. In particular, statins represent one of the greatest successes in the prevention of CHD. While these standard risk factors are important, an obvious opportunity exists to take advantage of ongoing scientific research to better risk-stratify individuals and to identify new treatment targets. In this Review, we summarize ongoing scientific research in a number of metabolic molecules or features, including lipoproteins, homocysteine, calcium metabolism and glycaemic markers. We evaluate the current state of the research and the strength of evidence supporting each emerging biomarker. We also discuss whether the associations with CHD are strong and consistent enough to improve current risk stratification metrics, and whether these markers enhance our understanding of the underlying biology of CHD and thus point towards new treatment options.

Lipoprotein(a) is associated with necrotic core progression of non-culprit coronary lesions in statin-treated patients with angina pectoris

Background

Statin therapy results in regression and stabilization of coronary artery plaques, and reduces the incidence of coronary artery disease. However, statin therapy does not effectively halt the accumulation of necrotic core in all patients. The purpose of the present study was to identify the predictors associated with necrotic core progression during statin therapy.

Methods

Coronary atherosclerosis in non-culprit lesions was evaluated using virtual histology intravascular ultrasound at baseline and 8 months after statin therapy. One hundred nineteen patients were divided into 2 groups based on necrotic core progression or regression during an 8-month follow-up period.

Results

Patients with necrotic core progression had higher serum lipoprotein(a) [Lp(a)] levels than patients with regression at baseline (16 mg/dL vs. 12 mg/dL, p = 0.02) and at the 8-month follow-up (17 mg/dL vs. 10 mg/dL, p = 0.006). Patients with necrotic core progression had a higher fibro-fatty plaque volume (1.28 mm³/mm vs. 0.73 mm³/mm, p = 0.002), and less necrotic core (0.56 mm³/mm vs. 1.04 mm³/mm, p < 0.0001) and dense calcium (0.35 mm³/mm vs. 0.56 mm³/mm, p = 0.006) plaque volumes at baseline than patients with regression. Multivariate logistic regression analysis showed that Lp(a) was a significant independent predictor associated with necrotic core progression during statin therapy (odds ratio [OR]: 3.514; 95% confidence interval [CI]: 1.338-9.228; p = 0.01).

Conclusions

Serum Lp(a) is independently associated with necrotic core progression in statin-treated patients with angina pectoris.

Hyperlipoproteinemia(a): clinical significance and treatment options

Recent epidemiologic and Mendelian randomization studies together have provided evidence that lipoprotein(a) (Lp(a)) plays a causal role in the pathogenesis of atherosclerosis and cardiovascular disease (CVD). The risk association with CVD is weak but seems continuous in shape and without an obvious threshold for Lp(a) levels. A plasma concentration of 60 mg/dl compared to usual levels is associated with an odds ratio for coronary heart disease of about 1.5 after adjustment for other cardiovascular risk factors. Niacin (nicotinic acid) is the pharmacologic means of choice for decreasing elevated Lp(a) levels but the drug is often poorly tolerated due to adverse reactions. Dietary measures, exercise and other lipid-lowering drugs, especially statins, fibrates and ezetimibe, are without effect. In patients with severe progressive cardiovascular disease and very high Lp(a) levels, lipoprotein apheresis may be used to effectively decrease Lp(a) concentrations. The method is expensive and impractical for most patients and its feasibility depends by and large on the healthcare reimbursement system of the respective country. No established treatment, however, selectively reduces Lp(a) without influencing other lipoproteins. Moreover, despite the clear association of hyperlipoproteinemia(a) with cardiovascular risk, no rigorously designed study to date has demonstrated that lowering Lp(a) concentrations has beneficial effects on cardiovascular endpoints. Randomized trials to this effect are urgently needed.

Validation and quantification of genetic determinants of lipoprotein-a levels and predictive value for angiographic coronary artery disease

Lipoprotein(a) (Lp[a]) has gained attention as a heritable coronary artery disease (CAD) risk factor and therapeutic target. Two genetic variants in the LPA gene have been reported to influence Lp(a) levels and increase CAD risk. The aim of this study was to prospectively test these variants for their associations with Lp(a) and CAD risk. Participants (n = 1,400) in the Intermountain Heart Collaborative Study Registry who had Lp(a) cholesterol levels determined at coronary angiography were genotyped for rs3798220 and rs1045587 in LPA. Variants were detected by Taqman polymerase chain reaction. Chi-square and linear and logistic regression tests were used as appropriate among genotypes for Lp(a) and angiographic CAD. Age averaged 63 years; 65% were men; and severe CAD was present in 57%, mild CAD in 12%, and no CAD in 31%. Minor allele frequencies were 0.023 for rs3798220 and 0.090 for rs10455872. In multivariate modeling, only rs10455872 (odds ratio [OR] 2.33, 95% confidence interval [CI] 1.67 to 3.33, p = 1.75 × 10⁻⁹) and rs3798220 (OR 1.99, 95% CI 0.99 to 4.00, p = 0.065) contributed to the prediction of elevated Lp(a) cholesterol. Lp(a) cholesterol was weakly associated with CAD (OR 1.17, 95% CI 1.00 to 1.37, p = 0.055). Rs10455872 strongly predicted prevalent CAD (per allele OR 1.43, 95% CI 1.07 to 1.91, p = 0.0172); the effect size for the rare rs3798220 variant was similar (dominant OR 1.47, 95% CI 0.81 to 2.67, p = 0.20), but power was limited to demonstrate significance. The combined genotype explained only a small percentage (≤4%) of variability in Lp(a) cholesterol and prevalence of angiographic CAD. In conclusion, heritable contributions of LPA rs10455872 and rs3798220 to Lp(a) cholesterol levels and to angiographic CAD were prospectively assessed in this study. The percentage of intersubject variability in Lp(a) cholesterol and the percentage of prevalent CAD explained were small.

Lipoprotein(a) and cardiovascular disease in diabetic patients

Lipoprotein(a) (Lp[a]) is a LDL-like particle consisting of an ApoA moiety linked to one molecule of ApoB(100). Recent data from large-scale prospective studies and genetic association studies provide highly suggestive evidence for a potentially causal role of Lp(a) in affecting risk of cardiovascular disease (CVD) in general populations. Patients with Type 2 diabetes display clustered metabolic abnormalities and elevated risk of CVD. Lower plasma Lp(a) levels were observed in diabetic patients in several recent studies. Epidemiology studies of Lp(a) and CVD risk in diabetic patients generated inconsistent results. We recently found that Lp(a)-related genetic markers did not predict CVD in two diabetic cohorts. The current data suggest that Lp(a) may differentially affect cardiovascular risk in diabetic patients and in the general population. More prospective studies, Mendelian randomization analysis and functional studies are needed to clarify the causal relationship of Lp(a) and CVD in diabetic patients.

Treatment with paroxetine, but not amitriptyline, lowers levels of lipoprotein(a) in patients with major depression

High lipoprotein(a) (Lp(a)) levels constitute a major risk factor for vascular mortality. Major depression also increases the risk of cardiovascular disease. We measured the concentrations of Lp(a) in depressed patients and controls and studied the effects of antidepressant treatment and treatment outcome. Lp(a) levels were analysed at baseline in 35 in-patients with DSM-IV major depression who were then treated in a randomized double-blind manner with amitriptyline (n = 14) or paroxetine (n = 21), as well as in 33 healthy controls. Lp(a) levels were re-assessed after 4 weeks of treatment. We found a significant decrease in Lp(a) in patients treated with paroxetine, but not in those treated with amitriptyline. Our results suggest that antidepressant treatment with paroxetine might contribute to a decrease in vascular mortality risk irrespective of treatment outcome.

Increased lipoprotein(a) is associated with polyvascular disease in patients undergoing coronary artery bypass graft

OBJECTIVE

We sought to identify clinical and biochemical predictors of disease in multiple vascular territories, in patients with established coronary heart disease.

METHODS

A total of 470 patients (329 men, 141 female) who had undergone coronary artery bypass grafting (CABG) were enrolled in this prospective study. Polyvascular disease was defined on the presence of existing symptomatic or asymptomatic carotid artery stenosis and/or peripheral artery disease, which is present in 32.1% of patients (n=151).

RESULTS

Clinical and laboratory features independently associated with the presence of polyvascular disease included age ≥65 years, male sex, hypertension, former or current smoker, low BMI, and high Lp(a). Lp(a) was the only biochemical marker that had an independent association with polyvascular disease (OR=1.01 per 1mg/dl increase; 95% CI, 1.00-1.01). The fourth quartile of Lp(a) has significant associations with the risk of two or more vascular territories involvement (OR=1.866; 95% CI, 1.056-3.297), and three vascular territories involvement (OR=4.240; 95% CI, 1.405-12.798). There was a significant trend towards patients with the highest quartile of Lp(a) that has association with more advanced polyvascular disease (test for trend: p=0.008 for involvement of three vascular territories).

CONCLUSION

High Lp(a) was independently associated with polyvascular disease in patients who undergo CABG, which is suggestive of an indirect evidence of the pathophysiologic function of Lp(a) in polyvascular disease.

Role of biomarkers in predicting CVD risk in the setting of HIV infection?

PURPOSE OF REVIEW

The purpose of this review is to present recent results on biomarkers and risk of cardiovascular disease (CVD) in the general population and to review studies of biomarkers among individuals with HIV infection.

RECENT FINDINGS

Several inflammatory as well as lipid biomarkers are associated with risk of CVD. Biomarkers associated with inflammation such as C-reactive protein and interleukin-6 have been suggested to improve risk stratification among intermediate-risk persons; however, their routine use is not recommended in the general population. Both biomarkers have recently been reported elevated in patients with HIV. Additionally, interleukin-6 and D-dimer have been reported to predict overall mortality among individuals with HIV. However, the utility of other biomarkers to predict CVD among individuals with HIV infection is not clear.

SUMMARY

The risk of CVD is increasing in the HIV-infected population and will increase as this population continues to age. Identification of intermediate-risk individuals using biomarkers will be an important tool for clinicians in the future to be able to treat HIV-infected individuals aggressively. Future studies of biomarkers among individuals with HIV will be needed to help determine the utility of specific markers in predicting CVD risk as well as the mechanism underlying increased CVD risk in the setting of HIV infection.

Lipoprotein(a) and risk of myocardial infarction--genetic epidemiologic evidence of causality

Elevated levels of lipoprotein(a) are associated with an increased risk of myocardial infarction. Our study aimed to test whether genetic data are consistent with this association being causal. Accordingly, we developed a high-throughput realtime PCR assay to genotype for the lipoprotein(a) kringle IV type 2 (KIV-2) repeat polymorphism in the LPA gene in > 40,000 individuals. The LPA KIV-2 genotype associated with plasma levels of lipoprotein(a) (trend p < 0.001), and the LPA KIV-2 genotype associated with risk of myocardial infarction (trend p < 0.001 to 0.03) in a manner consistent with its effect on plasma levels of lipoprotein(a). The association of LPA KIV-2 genotypes raising plasma levels of lipoprotein(a) with increased risk of myocardial infarction strongly supports a causal association of lipoprotein(a) with risk of myocardial infarction.

Lipoprotein(a) accelerates atherosclerosis in uremic mice

Uremic patients have increased plasma lipoprotein(a) [Lp(a)] levels and elevated risk of cardiovascular disease. Lp(a) is a subfraction of LDL, where apolipoprotein(a) [apo(a)] is disulfide bound to apolipoprotein B-100 (apoB). Lp(a) binds oxidized phospholipids (OxPL), and uremia increases lipoprotein-associated OxPL. Thus, Lp(a) may be particularly atherogenic in a uremic setting. We therefore investigated whether transgenic (Tg) expression of human Lp(a) increases atherosclerosis in uremic mice. Moderate uremia was induced by 5/6 nephrectomy (NX) in Tg mice with expression of human apo(a) (n = 19), human apoB-100 (n = 20), or human apo(a) + human apoB [Lp(a)] (n = 15), and in wild-type (WT) controls (n = 21). The uremic mice received a high-fat diet, and aortic atherosclerosis was examined 35 weeks later. LDL-cholesterol was increased in apoB-Tg and Lp(a)-Tg mice, but it was normal in apo(a)-Tg and WT mice. Uremia did not result in increased plasma apo(a) or Lp(a). Mean atherosclerotic plaque area in the aortic root was increased 1.8-fold in apo(a)-Tg (P = 0.025) and 3.3-fold (P = 0.0001) in Lp(a)-Tg mice compared with WT mice. Plasma OxPL, as detected with the E06 antibody, was associated with both apo(a) and Lp(a). In conclusion, expression of apo(a) or Lp(a) increased uremia-induced atherosclerosis. Binding of OxPL on apo(a) and Lp(a) may contribute to the atherogenicity of Lp(a) in uremia.

Lipoprotein(a) and ischemic heart disease--a causal association? A review

The aim of this review is to summarize present evidence of a causal association of lipoprotein(a) with risk of ischemic heart disease (IHD). Evidence for causality includes reproducible associations of a proposed risk factor with risk of disease in epidemiological studies, evidence from in vitro and animal studies in support of pathophysiological effects of the risk factor, and preferably evidence from randomized clinical trials documenting reduced morbidity in response to interventions targeting the risk factor. Elevated and in particular extreme lipoprotein(a) levels have in prospective studies repeatedly been associated with increased risk of IHD, although results from early studies are inconsistent. Data from in vitro and animal studies implicate lipoprotein(a), consisting of a low density lipoprotein particle covalently bound to the plasminogen-like glycoprotein apolipoprotein(a), in both atherosclerosis and thrombosis, including accumulation of lipoprotein(a) in atherosclerotic plaques and attenuation of t-PA mediated plasminogen activation. No randomized clinical trial of the effect of lowering lipoprotein(a) levels on IHD prevention has ever been conducted. Lacking evidence from randomized clinical trials, genetic studies, such as Mendelian randomization studies, can also support claims of causality. Levels of lipoprotein(a) are primarily determined by variation in the LPA gene coding for the apolipoprotein(a) moiety of lipoprotein(a), and genetic epidemiologic studies have documented association of LPA copy number variants, influencing levels of lipoprotein(a), with risk of IHD. In conclusion, results from epidemiologic, in vitro, animal, and genetic epidemiologic studies support a causal association of lipoprotein(a) with risk of IHD, while results from randomized clinical trials are presently lacking.

Lipoprotein(a) concentration and the risk of coronary heart disease, stroke, and nonvascular mortality

CONTEXT

Circulating concentration of lipoprotein(a) (Lp[a]), a large glycoprotein attached to a low-density lipoprotein-like particle, may be associated with risk of coronary heart disease (CHD) and stroke.

OBJECTIVE

To assess the relationship of Lp(a) concentration with risk of major vascular and nonvascular outcomes.

STUDY SELECTION

Long-term prospective studies that recorded Lp(a) concentration and subsequent major vascular morbidity and/or cause-specific mortality published between January 1970 and March 2009 were identified through electronic searches of MEDLINE and other databases, manual searches of reference lists, and discussion with collaborators.

DATA EXTRACTION

Individual records were provided for each of 126,634 participants in 36 prospective studies. During 1.3 million person-years of follow-up, 22,076 first-ever fatal or nonfatal vascular disease outcomes or nonvascular deaths were recorded, including 9336 CHD outcomes, 1903 ischemic strokes, 338 hemorrhagic strokes, 751 unclassified strokes, 1091 other vascular deaths, 8114 nonvascular deaths, and 242 deaths of unknown cause. Within-study regression analyses were adjusted for within-person variation and combined using meta-analysis. Analyses excluded participants with known preexisting CHD or stroke at baseline.

DATA SYNTHESIS

Lipoprotein(a) concentration was weakly correlated with several conventional vascular risk factors and it was highly consistent within individuals over several years. Associations of Lp(a) with CHD risk were broadly continuous in shape. In the 24 cohort studies, the rates of CHD in the top and bottom thirds of baseline Lp(a) distributions, respectively, were 5.6 (95% confidence interval [CI], 5.4-5.9) per 1000 person-years and 4.4 (95% CI, 4.2-4.6) per 1000 person-years. The risk ratio for CHD, adjusted for age and sex only, was 1.16 (95% CI, 1.11-1.22) per 3.5-fold higher usual Lp(a) concentration (ie, per 1 SD), and it was 1.13 (95% CI, 1.09-1.18) following further adjustment for lipids and other conventional risk factors. The corresponding adjusted risk ratios were 1.10 (95% CI, 1.02-1.18) for ischemic stroke, 1.01 (95% CI, 0.98-1.05) for the aggregate of nonvascular mortality, 1.00 (95% CI, 0.97-1.04) for cancer deaths, and 1.00 (95% CI, 0.95-1.06) for nonvascular deaths other than cancer.

CONCLUSION

Under a wide range of circumstances, there are continuous, independent, and modest associations of Lp(a) concentration with risk of CHD and stroke that appear exclusive to vascular outcomes.

Pentanucleotide repeat polymorphism, lipoprotein(a) levels, and risk of ischemic heart disease

CONTEXT

Lipoprotein(a) is a cardiovascular risk factor. Levels of lipoprotein(a) are predominantly determined by apolipoprotein(a) gene variation, including a pentanucleotide repeat promoter polymorphism.

OBJECTIVE

We tested the hypothesis that apolipoprotein(a) pentanucleotide repeat genotype predicts elevated lipoprotein(a) levels and risk of myocardial infarction (MI) and ischemic heart disease (IHD) in the general population.

DESIGN

We used a cohort study of the Danish general population, The Copenhagen City Heart Study, including 10,276 individuals of which 860 and 1,781 developed MI and IHD, respectively, during up to 31 yr of follow-up, and a case-control study including 1,814 IHD patients and 5,076 controls. Follow-up was 100% complete.

RESULTS

Allele frequencies were 0.0018, 0.0018, 0.6750, 0.1596, 0.1465, 0.0146, and 0.0004 for 6, 7, 8, 9, 10, 11, and 12 repeats, respectively. Mean lipoprotein(a) levels were 40, 36, and 27 mg/dl for individuals with 14-15, 16, and 17-22 repeats (sum of repeats on both alleles), respectively (trend, P < 0.001). Cumulative incidence of MI and IHD was increased for individuals with 14-15 vs. at least 16 repeats (log rank, P < 0.001 and P = 0.002). Multifactorially adjusted hazard ratios for 14-15 and 17-22 vs. 16 repeats were 3.1 (95% confidence interval, 1.6-5.8) and 1.0 (0.9-1.2) for MI and 2.2 (1.3-3.6) and 1.0 (0.9-1.1) for IHD. In the case-control study, multifactorially adjusted odds ratios for 14-15 and 17-22 vs. 16 repeats were 2.9 (1.1-7.8) and 0.9 (0.8-1.0) for MI and 2.5 (1.0-6.0) and 0.9 (0.8-1.0) for IHD.

CONCLUSIONS

Apolipoprotein(a) 14-15 pentanucleotide repeats predict elevated levels of lipoprotein(a) and a 3- and 2-fold increased risk of MI and IHD in the general population.

Postprandial effects of dietary trans fatty acids on apolipoprotein(a) and cholesteryl ester transfer

BACKGROUND

The consumption of trans fatty acids adversely affects fasting plasma lipoprotein concentrations.

OBJECTIVE

This study aimed to investigate whether postprandial lipoprotein metabolism is affected by the consumption of trans fatty acids.

DESIGN

In a randomized crossover study, 19 healthy men consumed fatty meals that were identical except that 10% of energy was provided as trans 18:1 acids in the trans meal and as oleic acid in the cis meal.

RESULTS

The meals induced similar responses in plasma lipids. Cholesteryl ester transfer (CET) was activated after consumption of both meals (P < 0.0001); however, it was 28% higher after the trans meal than after the cis meal (280 +/- 129 compared with 219 +/- 116 nmol cholesteryl ester/mL plasma * 6 h; time x diet interaction: P < 0.0001). Plasma apolipoprotein(a) [apo(a)] concentrations remained constant; however, triacylglycerol-rich lipoproteins formed 4 h after ingestion of the trans meal contained a higher concentration of apo(a) than did those formed after ingestion of the cis meal (48.9 +/- 6.6 compared with 39.6 +/- 5.4 U/L; P < 0.02). The change in CET and in the proportion of plasma apo(a) in the triacylglycerol-rich lipoprotein fractions correlated with indexes of alimentary lipemia.

CONCLUSIONS

Consumption of meals high in trans fatty acids results in higher CET and postprandial lipoprotein concentrations enriched in apo(a) than does consumption of meals free of trans fatty acids. This study highlights the importance of double-bond configuration in determining postprandial lipoprotein composition.

The mechanisms of coronary restenosis: insights from experimental models

Since its introduction into clinical practice, more than 20 years ago, percutaneous transluminal coronary angioplasty (PTCA) has proven to be an effective, minimally invasive alternative to coronary artery bypass grafting (CABG). During this time there have been great improvements in the design of balloon catheters, operative procedures and adjuvant drug therapy, and this has resulted in low rates of primary failure and short-term complications. However, the potential benefits of angioplasty are diminished by the high rate of recurrent disease. Up to 40% of patients undergoing angioplasty develop clinically significant restenosis within a year of the procedure. Although the deployment of endovascular stents at the time of angioplasty improves the short-term outcome, 'in-stent' stenosis remains an enduring problem. In order to gain an insight into the mechanisms of restenosis, several experimental models of angioplasty have been developed. These have been used together with the tools provided by recent advances in molecular biology and catheter design to investigate restenosis in detail. It is now possible to deliver highly specific molecular antagonists, such as antisense gene sequences, to the site of injury. The knowledge provided by these studies may ultimately lead to novel forms of intervention. The present review is a synopsis of our current understanding of the pathological mechanisms of restenosis.

Atherogenecity of lipoprotein(a) and oxidized low density lipoprotein: insight from in vivo studies of arterial wall influx, degradation and efflux

The accumulation of atherogenic lipoproteins in the arterial intima is pathognomonic of atherosclerosis. Modification of LDL by covalent linkage of apo(a) (resulting in the formation of Lp(a)) or oxidation probably enhances its atherogenecity. Although the metabolism of LDL in arterial intima has been rather extensively characterized, little has been known about the interaction of Lp(a) and oxidized LDL (ox-LDL) with the arterial wall. The present paper reviews a series of recent in vivo studies of the interaction of Lp(a) and ox-LDL with the arterial wall. The results have identified several factors that affect the accumulation of Lp(a) and ox-LDL in the arterial intima and have provided fresh insight into unique metabolic characteristics of Lp(a) and ox-LDL that may explain the large atherogenic potential of these modified LDL species.

Lipoprotein(a), homocysteine, and remnantlike particles: emerging risk factors

Although lipoprotein(a) [Lp(a)] was first described more than 35 years ago, adequate prospective data have only recently supported Lp(a) as an independent risk factor for coronary heart disease (CHD). In vitro studies suggest that Lp(a) contributes to atherogenesis directly by cholesterol uptake and indirectly by the inhibition of fibrinolysis. In patients with CHD or a significant risk for CHD, Lp(a) should be measured and treated with either niacin or estrogen if the patient has Lp(a) cholesterol levels of more than 10 mg/dL or an Lp(a) mass of more than 30 mg/dL. In addition, homocysteine and remnantlike lipoprotein cholesterol are strongly supported by prospective or population-based prevalence data as independent risk factors for CHD. Homocysteine levels of more than 14 mumol/L should be treated with vitamin supplements of folate, B6, and B12. Remnantlike lipoprotein cholesterol is the product of a novel immunoassay that separates the partially hydrolyzed triglyceride-rich remnant particles. The association of these particles with CHD risk in women may explain the small independent CHD risk that triglycerides have in women in the Framingham Heart Study. A clear therapeutic intervention has not been documented but may include diet, fibric acid derivatives, or hydroxymethylglutamyl coenzyme A reductase inhibitors.

The response-to-retention hypothesis of atherogenesis reinforced

Many lines of evidence indicate that the key initiating event in early atherosclerosis is the subendothelial retention of cholesterol-rich, atherogenic lipoproteins. Once retained, these lipoproteins provoke a cascade of responses that lead to disease in a previously non-lesional artery. We review recent experimental work that has substantially reinforced this hypothesis. Lipoprotein retention has been shown to be a pivotal requirement in the murine model of atherosclerosis: low-density lipoprotein, engineered through site-directed mutagenesis of apolipoprotein-B100 to bind poorly to arterial proteoglycans, causes relatively few lesions in vivo, even during significant hyperlipidemia. In addition, many molecules in the arterial wall that are involved in the retention of atherogenic lipoproteins and in arterial responses to retained material have recently been characterized. Overall, the response-to-retention hypothesis can now be regarded as a central paradigm in our understanding of the pathogenesis of this deadly disease.