Differential response of cholesterol and particle measures of atherogenic lipoproteins to LDL-lowering therapy: implications for clinical practice

Individual Variation in the Distribution of Apolipoprotein B Levels Across the Spectrum of LDL-C or Non-HDL-C Levels

Importance

Although apolipoprotein B (apoB) is a superior marker of lipid-related risk compared with low-density lipoprotein cholesterol (LDL-C), few data exist to translate the goals and thresholds from LDL-C to their apoB equivalent. In addition, although current American College of Cardiology/American Heart Association guidelines provide a relative indication for apoB measurement among individuals with hypertriglyceridemia, whether discordance is limited to those subgroups is unknown.

Objectives

To assess the variability in apoB level across the spectrum of LDL-C or non-high-density lipoprotein cholesterol (non-HDL-C) levels and evaluate whether discordance between apoB and LDL-C or non-HDL-C is limited to specifiable subgroups.

Design, Setting, and Participants

This cross-sectional study used data from a nationally representative sample of 12 688 adult participants not using statins in the National Health and Nutrition Examination Survey between 2005 and 2016. Statistical analysis was performed from April 2023 to February 2024.

Main Outcomes and Measures

Quantile regression was used to assess the population distribution of apoB across LDL-C or non-HDL-C levels. Discordance between apoB and LDL-C was the difference between measured apoB and median apoB levels for an individual's LDL-C level. Discordance was evaluated by age, sex, race and ethnicity, obesity, diabetes, triglyceride level, hemoglobin A1c level, body mass index (BMI), statin use, and metabolic health (defined as a BMI between 18.5 and 24.9, triglyceride level <150 mg/dL, and no diabetes).

Results

Among the sample of 12 688 participants (median age, 41.0 years [IQR, 29.0-54.0 years]; 52.9% women) for LDL-C values of 55, 70, 100, and 190 mg/dL, the corresponding population median apoB levels were 49, 60, 80, and 140 mg/dL, respectively. For given levels of LDL-C, a range of apoB values was observed. At an LDL-C level of 100 mg/dL, the 95% population distribution of apoB ranged from 66 mg/dL to 99 mg/dL. ApoB variability was highest for LDL-C values estimated using the Friedewald equation, lower when using Sampson or Martin-Hopkins equations, and lowest for non-HDL-C. Although individuals with metabolic risk factors were more likely to have discordantly high apoB levels (ie, had higher median observed apoB levels relative to what was estimated based on LDL-C), significant variability in apoB levels was observed even among metabolically healthy individuals.

Conclusions and Relevance

This study suggests that even metabolically healthy individuals may have discordantly high apoB levels relative to LDL-C or non-HDL-C levels. The current guideline approach for apoB testing only for those with hypertriglyceridemia appears too narrow. Population percentile data can be used to translate LDL-C goals and thresholds to their apoB equivalent to facilitate clinical adoption.

Apolipoprotein B: Bridging the Gap Between Evidence and Clinical Practice

Despite data suggesting that apolipoprotein B (apoB) measurement outperforms low-density lipoprotein cholesterol level measurement in predicting atherosclerotic cardiovascular disease risk, apoB measurement has not become widely adopted into routine clinical practice. One barrier for use of apoB measurement is lack of consistent guidance for clinicians on how to interpret and apply apoB results in clinical context. Whereas guidelines have often provided clear low-density lipoprotein cholesterol targets or triggers to initiate treatment change, consistent targets for apoB are lacking. In this review, we synthesize existing data regarding the epidemiology of apoB by comparing guideline recommendations regarding use of apoB measurement, describing population percentiles of apoB relative to low-density lipoprotein cholesterol levels, summarizing studies of discordance between low-density lipoprotein cholesterol and apoB levels, and evaluating apoB levels in clinical trials of lipid-lowering therapy to guide potential treatment targets. We propose evidence-guided apoB thresholds for use in cholesterol management and clinical care.

Use of Apolipoprotein B in the Era of Precision Medicine: Time for a Paradigm Change?

Atherosclerotic cardiovascular disease (ASCVD) remains the leading cause of death worldwide and the risk of a major cardiovascular event is highest among those with established disease. Ongoing management of these patients relies on the accurate assessment of their response to any prescribed therapy, and their residual risk, in order to optimize treatment. Recent international guidelines and position statements concur that the plasma concentration of apolipoprotein B (apoB) is the most accurate measure of lipoprotein associated ASCVD risk. This is especially true for the growing number of individuals with diabetes, obesity, or the metabolic syndrome, and those on statin therapy. Most guidelines, however, continue to promote LDL-C as the primary risk marker due to uncertainty as to whether the greater accuracy of apoB is sufficient to warrant a paradigm shift. Recommendations regarding apoB measurement vary, and the information provided on how to interpret apoB results is sometimes insufficient, particularly for non-lipid specialists. Misinformation regarding the reliability of the assays is also frequently repeated despite its equivalent or better standardization than many other diagnostic assays. Thus, demand for apoB testing is relatively low, which means there is little incentive to increase its availability or reduce its cost. In this review, we examine the results of recent clinical outcomes studies and meta-analyses on the relative values of apoB, LDL-C, and non-HDL-C as markers of ASCVD risk. Although there is seemingly minimal difference among these markers when only population-based metrics are considered, it is evident from our analysis that, from a personalized or precision medicine standpoint, many individuals would benefit, at a negligible total cost, if apoB measurement were better integrated into the diagnosis and treatment of ASCVD.

Standardization of Apolipoprotein B, LDL-Cholesterol, and Non-HDL-Cholesterol

Concern continues about whether the measurement of apolipoprotein B (apoB) is adequately standardized, and therefore, whether apoB should be applied widely in clinical care. This concern is misplaced. Our objective is to explain why and what the term "standardization" means. To produce clinically valid results, a test must accurately, precisely, and selectively measure the marker of interest. That is, it must be standardized. Accuracy refers to how closely the result obtained with 1 method corresponds to the result obtained with the standard method, precision to how reproducible the result is on repeated testing, and selectivity to how susceptible the method is to error by inclusion of other classes of lipoprotein particles. Multiple expert groups have determined that the measurement of apoB is adequately standardized for clinical care, and that apoB can be measured inexpensively, using widely available automated methods, more accurately, precisely, and selectively than low-density lipoprotein cholesterol or non-high-density lipoprotein cholesterol. ApoB is a standard superior to low-density lipoprotein cholesterol and high-density lipoprotein cholesterol because it is a defined molecule, whereas the cholesterol markers are the mass of cholesterol within lipoprotein particles defined by their density, not by their molecular structure. Nevertheless, the standardization of apoB is being further improved by the application of mass spectrophotometric methods, whereas the limitations in the standardization and, therefore, the accurate, precise, and selective measurement of low-density lipoprotein cholesterol and high-density lipoprotein cholesterol are unlikely to be overcome. We submit that greater accuracy, precision, and selectivity in measurement is a decisive advantage for apoB in the modern era of intensive lipid-lowering therapies.

Remnant cholesterol and risk of myocardial infarction in patients with coronary artery disease undergoing revascularization

BACKGROUND

Despite substantial reduction in low-density lipoprotein cholesterol (LDL-C), patients develop recurrent cardiovascular events. Remnant cholesterol (RC), the cholesterol content of triglyceride-rich lipoproteins, is a potential contributor to this residual risk.

OBJECTIVES

To investigate the association between RC and risk for myocardial infarction (MI) in patients with coronary artery disease, and examine whether the predictive value of RC is retained beyond non-high-density lipoprotein cholesterol (non-HDL-C).

METHODS

Data on 9451 patients undergoing coronary revascularization in a single center. RC was calculated as total cholesterol minus high-density lipoprotein cholesterol minus LDL-C (estimated using Martin-Hopkins equation). Cox-regression models were used to estimate the association between RC and risk for MI. Discordance analyses were performed to examine the correlation between RC and non-HDL-C (or LDL-C) in relation to MI risk.

RESULTS

Mean age was 65±11 years; 67% presented with acute coronary syndrome. During median follow-up of 9.6 years, 1690 patients developed MI. After multivariable adjustment including lipid-lowering therapies and non-HDL-C, RC was associated with higher MI risk: hazard ratio (95% confidence interval): 1.36 (1.20-1.56) and 1.58 (1.35-1.85) in those with RC levels ≥75th (32.6 mg/dL) and ≥90th (41.8 mg/dL) percentile, compared to RC <50th percentile (25.5 mg/dL). When RC and non-HDL-C (or LDL-C) levels were discordant, the level of RC better reflected the risk for MI.

CONCLUSIONS

Elevated RC is a risk factor for MI independent of lipid-lowering therapies and non-HDL-C, providing further support that RC may serve as a residual cardiovascular risk marker and potential treatment target in patients with coronary artery disease.

Differential association between apolipoprotein B and LDL cholesterol and cerebral atherosclerosis according to pre-stroke statin use

BACKGROUND AND AIMS

To reduce cardiovascular risk, low-density lipoprotein cholesterol (LDL-C) is the primary target of statin treatment, while apolipoprotein B (ApoB) is secondary. We investigated the association between atherosclerotic stenosis and LDL-C or ApoB levels and whether a difference in association exists according to pre-admission statin use in ischemic stroke patients.

METHODS

This retrospective cross-sectional study included consecutive patients with acute ischemic stroke or transient ischemic attack who underwent lipid profile and angiographic testing. Patients were categorized into four groups according to stenosis location: normal, extracranial atherosclerotic stenosis (ECAS), intracranial atherosclerotic stenosis (ICAS), or ECAS + ICAS. Subgroup analyses were performed by pre-admission statin use.

RESULTS

Of the 6338 patients included, 1980 (31.2%) were in the normal group, 718 (11.3%) in the ECAS group, 1845 (29.1%) in the ICAS group, and 1795 (28.3%) in the ECAS + ICAS group. Both LDL-C and ApoB levels were associated with every location of stenosis. A significant interaction was found between pre-admission statin use and LDL-C level (p for interaction <0.05). LDL-C was associated with stenosis only in statin-naïve patients, whereas ApoB was associated with ICAS, with or without ECAS, in both statin-naïve and statin-treated patients. ApoB also showed a consistent association with symptomatic ICAS in both statin-treated and statin-naïve patients, whereas LDL-C did not.

CONCLUSIONS

ApoB was consistently associated with ICAS, particularly symptomatic stenosis, in both statin-naïve and statin-treated patients. The close association between ApoB levels and residual risk in statin-treated patients could be partially explained by these results.

A Translational Tool to Facilitate Use of Apolipoprotein B for Clinical Decision-Making

BACKGROUND

Despite recent large-scale discordance studies showing definitively that atherosclerotic cardiovascular disease (ASCVD) risk correlates better with apolipoprotein B (apoB) than with low-density lipoprotein cholesterol (LDL-C), the latter remains the recommended metric for guiding lipid-lowering treatment decisions in the United States. A major barrier to change, in this regard, is the lack of guideline-recommended apoB treatment targets. We developed a simple method to "translate" apoB values into population-equivalent LDL-C units, allowing apoB-based treatment decisions to be made using LDL-C targets.

METHODS

Sequentially collected, population-based samples underwent standard lipid panel analysis and apoB testing by immunoassay. Those with triglycerides greater than 1000 mg/dl were excluded, leaving a study cohort of 15 153 individuals.

RESULTS

Linear regression of calculated LDL-C values against percentile-equivalent apoB values yielded an equation to convert apoB into percentile-equivalent LDL-C units: [LDL-C equivalents = 1.38(apoB) - 29] (R2 = 0.999). The extent of discordance between LDL-C and apoB was examined in subgroups with similar LDL-C, ranging from very low (55-70 mg/dL) to very high (175-190 mg/dL). Among individuals with very low LDL-C, 40% had discordantly higher apoB, indicating higher ASCVD risk. Of those with very high LDL-C, 49% had discordantly lower apoB. Across the range, a minority of patients (25%-40%) had concordant levels of apoB, confirming that discordance between these biomarkers is highly prevalent. Similar results were found in discordance analysis between apoB and non-high-density lipoprotein cholesterol (HDL-C).

CONCLUSIONS

Providing visibility to discrepancies among LDL-C, non-HDL-C, and apoB should help to facilitate more rapid and widespread adoption of apoB for managing ASCVD risk.

Integrating Advanced Lipid Testing and Biomarkers in Assessment and Treatment

PURPOSE OF REVIEW

Our ability to assess and stratify atherosclerotic disease risk in patients is evolving. Recent advances in advanced lipid testing have created opportunities for clinical application of novel biomarkers.

RECENT FINDINGS

Until recently, LDL-C has served largely as the singular biomarker of ASCVD and guide for decisions in treatment for high-risk groups. There are important evolutions in the measurement of LDL-C but even still, the pathogenesis of atherosclerosis and ASCVD is not solely driven by LDL-C. As atherosclerosis is driven by multiple complex pathways including inflammation, it is important to expand our focus beyond LDL-C and utilize multiple biomarkers in the assessment of this disease process. Non-HDL, ApoB, LDL-P, Lp(a), and hsCRP are unique tools to aid in cardiac risk evaluation, especially in higher risk patients, though not limited to this population. A multifaceted approach to advanced lipid testing with novel biomarkers will enhance comprehensive ASCVD risk assessments.

Apolipoprotein B, Residual Cardiovascular Risk After Acute Coronary Syndrome, and Effects of Alirocumab

BACKGROUND

Apolipoprotein B (apoB) provides an integrated measure of atherogenic risk. Whether apoB levels and apoB lowering hold incremental predictive information on residual risk after acute coronary syndrome beyond that provided by low-density lipoprotein cholesterol is uncertain.

METHODS

The ODYSSEY OUTCOMES trial (Evaluation of Cardiovascular Outcomes After an Acute Coronary Syndrome During Treatment With Alirocumab) compared the proprotein convertase subtilisin/kexin type 9 inhibitor alirocumab with placebo in 18 924 patients with recent acute coronary syndrome and elevated atherogenic lipoproteins despite optimized statin therapy. Primary outcome was major adverse cardiovascular events (MACE; coronary heart disease death, nonfatal myocardial infarction, fatal/nonfatal ischemic stroke, hospitalization for unstable angina). Associations between baseline apoB or apoB at 4 months and MACE were assessed in adjusted Cox proportional hazards and propensity score-matched models.

RESULTS

Median follow-up was 2.8 years. In proportional hazards analysis in the placebo group, MACE incidence increased across increasing baseline apoB strata (3.2 [95% CI, 2.9-3.6], 4.0 [95% CI, 3.6-4.5], and 5.5 [95% CI, 5.0-6.1] events per 100 patient-years in strata <75, 75-<90, ≥90 mg/dL, respectively; P_trend<0.0001) and after adjustment for low-density lipoprotein cholesterol (P_trend=0.035). Higher baseline apoB stratum was associated with greater relative (P_trend<0.0001) and absolute reduction in MACE with alirocumab versus placebo. In the alirocumab group, the incidence of MACE after month 4 decreased monotonically across decreasing achieved apoB strata (4.26 [95% CI, 3.78-4.79], 3.09 [95% CI, 2.69-3.54], and 2.41 [95% CI, 2.11-2.76] events per 100 patient-years in strata ≥50, >35-<50, and ≤35 mg/dL, respectively). Compared with propensity score-matched patients from the placebo group, treatment hazard ratios for alirocumab also decreased monotonically across achieved apoB strata. Achieved apoB was predictive of MACE after adjustment for achieved low-density lipoprotein cholesterol or non-high-density lipoprotein cholesterol but not vice versa.

CONCLUSIONS

In patients with recent acute coronary syndrome and elevated atherogenic lipoproteins, MACE increased across baseline apoB strata. Alirocumab reduced MACE across all strata of baseline apoB, with larger absolute reductions in patients with higher baseline levels. Lower achieved apoB was associated with lower risk of MACE, even after accounting for achieved low-density lipoprotein cholesterol or non-high-density lipoprotein cholesterol, indicating that apoB provides incremental information. Achievement of apoB levels as low as ≤35 mg/dL may reduce lipoprotein-attributable residual risk after acute coronary syndrome.

REGISTRATION

URL: https://www.

CLINICALTRIALS

gov; Unique identifier: NCT01663402.

Concordance of apolipoprotein B concentration with the Friedewald, Martin-Hopkins, and Sampson formulas for calculating LDL cholesterol

Introduction

Two new formulas, the Martin-Hopkins and the Sampson formula, were recently developed to overcome shortcomings of the Friedewald formula for calculating LDL-cholesterol. We aimed to compare the concordance of the two formulas with apolipoprotein B (apoB), a surrogate marker of the number of LDL particles.

Materials and methods

In a study of serum lipid data of 1179 patients who consulted the AZ St-Jan Hospital Bruges for cardiovascular risk assessment, the correlation and concordance of the Friedewald, Martin-Hopkins and Sampson formulas with apoB concentration, measured by immunonephelometry, were determined and compared.

Results

The Martin-Hopkins formula showed significantly higher correlation coefficient than the Friedewald formula with apoB in the entire dataset and in patients with low LDL-cholesterol < 1.8 mmol/L. Both Martin-Hopkins and Sampson formulas yielded > 70% concordance of LDL-cholesterol with regard to treatment group classification based on population-equivalent thresholds of apoB in hypertriglyceridemic patients (2-4.5 mmol/L), with the highest concordance (75.6%) obtained using Martin-Hopkins formula vs. 60.5% with Friedewald formula.

Conclusion

The Martin-Hopkins (and, to a lesser extent, Sampson) formula is more closely associated with the number of LDL particles than Friedewald formula. This, in combination with literature evidence of lesser accuracy of the Friedewald formula, is an argument to switch from Friedewald to a modified, improved formula.

Residual Risk of Coronary Atherosclerotic Heart Disease and Severity of Coronary Atherosclerosis Assessed by ApoB and LDL-C in Participants With Statin Treatment: A Retrospective Cohort Study

BACKGROUND

Low-density lipoprotein cholesterol (LDL-C) is the primary target of lipid-lowering therapy on the management of hypercholesterolemia in the United States and European guidelines, while apolipoprotein B (apoB) is the secondary target. The objective was to determine if elevated levels of apoB is superior to LDL-C in assessing residual risk of coronary atherosclerotic heart disease and severity of coronary atherosclerosis in participants with statin treatment.

METHODS

This study included 131 participants with statin treatment. The generalized linear model and relative risk regression (generalized linear Poisson model with robust error variance) were used to analyze the association of the levels of apoB and LDL-C with the severity of coronary atherosclerosis and residual risk of coronary atherosclerotic heart disease.

RESULTS

Categorizing apoB and LDL-C based on tertiles, higher levels of apoB were significantly associated with the severity of coronary atherosclerosis (P_trend = 0.012), whereas no such associations were found for elevated levels of LDL-C (P_trend = 0.585). After multivariate adjustment, higher levels of apoB were significantly associated with residual risk of coronary atherosclerotic heart disease. When compared with low-level apoB (≤0.66 g/L), the multivariate adjusted RR and 95% CI of intermediate-level apoB (0.67-0.89 g/L) and high-level apoB (≥0.90 g/L) were 1.16 (1.01, 1.33) and 1.31 (1.08, 1.60), respectively (P_trend = 0.011). There was a 45% increased residual risk of coronary atherosclerotic heart disease per unit increment in natural log-transformed apoB (P_trend <0.05). However, higher levels of LDL-C were not significantly associated with residual risk of coronary atherosclerotic heart disease. When compared with low-level LDL-C (≤1.56 mmol/L), the multivariate adjusted RR and 95% CI of intermediate-level LDL-C (1.57-2.30 mmol/L) and high-level LDL-C (≥2.31 mmol/L) were 0.99 (0.84, 1.15) and 1.10 (0.86, 1.42), respectively (P_trend = 0.437). Similar results were observed in the stratified analyses and sensitivity analyses. No significant interactions were detected for both apoB and LDL-C (all P_interaction>0.05).

CONCLUSIONS

Elevated apoB are superior in assessing the residual risk of coronary atherosclerotic heart disease and severity of coronary atherosclerosis in participants with statin treatment.

The Use of Blood Biomarkers in Precision Medicine for the Primary Prevention of Atherosclerotic Cardiovascular Disease: a Review

Introduction

A biomarker is a substance, structure, or process that indicates the presence of a disease, infection, or environmental exposure. Clinically useful biomarkers are measurable, improve diagnostic or prognostic performance, and ultimately aid clinicians in determining the initiation, duration, or magnitude of therapy.

Areas Covered

The purpose of this review is to explore the roles of various blood biomarkers of atherosclerotic cardiovascular disease (ASCVD) and how their use may improve the precision with which clinicians can identify, treat, and ultimately prevent ASCVD. Our review will include lipid biomarkers, markers of cardiac injury and wall stress, markers of inflammation, and a few others.

Expert Opinion

Several biomarkers have recently been highlighted as "risk-enhancing factors" in the 2019 American College of Cardiology/American Heart Association Guideline for the Primary Prevention of ASCVD, which can help guide shared decision-making. These included elevated low-density lipoprotein cholesterol, triglycerides, lipoprotein(a), apolipoprotein B, or high-sensitivity C-reactive protein. However, some other biomarkers mentioned in this review are not commonly used despite showing initial promise as prognostic of ASCVD risk, as it is not clear how treatment decisions should be changed after their measurement among asymptomatic individuals. Future studies should focus on whether biomarker-directed management strategies can improve clinical outcomes.

Prognostic implications of calculated Apo-lipoprotein B in patients with ST-segment elevation myocardial infarction undergoing primary percutaneous coronary intervention: Outcome is tied to lower cut-points

Background

Debates still surround using lipoproteins including Apo‐B in risk assessment, management, and prognosis of patients with coronary artery disease. During an acute ST‐segment elevation myocardial infarction, Apo‐B might help to achieve incremental prognostic information.

Objective

We sought to determine the potential prognostic utility of calculated Apo‐B in a cohort of patients with STEMI undergoing primary PCI.

Methods

A retrospective cohort study was conducted enrolling 2,259 patients with a diagnosis of acute STEMI who underwent primary PCI. Apo‐B was obtained using a valid equation based on initial lipid measurements. High Apo‐B was defined as a level of 65 or higher. Primary endpoint of the study was major adverse cardiovascular events (MACE).

Results

Mean age of the participants was 59.54 years and 77.9% of them were male. After a Median follow up of 15 (6.2) months, high Apo‐B was associated with MACE and the OR (95% CI) was 3.02 (1.07–8.47), p = .036. Odds ratios for prediction of MACE pertaining to LVEF, and smoking were 0.97 (p = .044), and 1.07 (p = .033), respectively. However, High Apo‐B was not able to predict suboptimal TIMI flow. Accordingly, the Odds ratio was 0.56 (0.17–1.87), p = 0.349. The power of High LDL‐C and Non‐HDLC for prediction of MACE were assessed in distinct models. Attained odds ratios were [2.40 (0.90–6.36), p = .077] and [1.80 (0.75–4.35), p = 0.191], respectively.

Conclusion

Calculated Apo‐B appears to be a simple tool applicable for prediction of cardiovascular events in patients with STEMI superior to both Non‐HDLC and LDL‐C.

Apolipoprotein B and Non-HDL Cholesterol Better Reflect Residual Risk Than LDL Cholesterol in Statin-Treated Patients

BACKGROUND

In cholesterol guidelines, low-density lipoprotein (LDL) cholesterol remains the primary target while apolipoprotein B (apoB) and non-high-density lipoprotein (non-HDL) cholesterol are secondary targets.

OBJECTIVES

This study sought to determine if elevated apoB and/or non-HDL cholesterol are superior to elevated LDL cholesterol in identifying statin-treated patients at residual risk of all-cause mortality and myocardial infarction.

METHODS

In total, 13,015 statin-treated patients from the Copenhagen General Population Study were included with 8 years median follow-up. Cox regressions among apoB, non-HDL cholesterol, and LDL cholesterol, respectively, and all-cause mortality or myocardial infarction were examined on continuous scales by restricted cubic splines and by categories of concordant and discordant values defined by medians.

RESULTS

High apoB and non-HDL cholesterol were associated with increased risk of all-cause mortality and myocardial infarction, whereas no such associations were found for high LDL cholesterol. Compared with concordant values below medians, discordant apoB above the median with LDL cholesterol below yielded hazard ratios of 1.21 (95% confidence interval [CI]: 1.07 to 1.36) for all-cause mortality and 1.49 (95% CI: 1.15 to 1.92) for myocardial infarction. Corresponding values for high non-HDL cholesterol with low LDL cholesterol were 1.18 (95% CI: 1.02 to 1.36) and 1.78 (95% CI: 1.35 to 2.34). In contrast, discordant high LDL cholesterol with low apoB or non-HDL cholesterol was not associated with increased risk of all-cause mortality or myocardial infarction. Also, discordant high apoB with low non-HDL cholesterol yielded hazard ratios of 1.21 (95% CI: 1.03 to 1.41) for all-cause mortality and of 0.93 (95% CI: 0.62 to 1.40) for myocardial infarction. Furthermore, dual discordant apoB and non-HDL cholesterol above the medians with LDL cholesterol below presented hazard ratios of 1.23 (95% CI: 1.07 to 1.43) for all-cause mortality and 1.82 (95% CI: 1.37 to 2.42) for myocardial infarction.

CONCLUSIONS

In statin-treated patients, elevated apoB and non-HDL cholesterol, but not LDL cholesterol, are associated with residual risk of all-cause mortality and myocardial infarction. Discordance analysis demonstrates that apoB is a more accurate marker of all-cause mortality risk in statin-treated patients than LDL cholesterol or non-HDL cholesterol, and apoB in addition is a more accurate marker of risk of myocardial infarction than LDL cholesterol.

The familial hypercholesterolaemia phenotype: Monogenic familial hypercholesterolaemia, polygenic hypercholesterolaemia and other causes

Familial hypercholesterolaemia (FH) is a monogenic disorder characterised by high low-density lipoprotein cholesterol (LDL-C) concentrations and increased cardiovascular risk. However, in clinically defined FH cohorts worldwide, an FH-causing variant is only found in 40%-50% of the cases. The aim of this work was to characterise the genetic cause of the FH phenotype in Portuguese clinical FH patients. Between 1999 and 2017, 731 index patients (311 children and 420 adults) who met the Simon Broome diagnostic criteria had been referred to our laboratory. LDLR, APOB, PCSK9, APOE, LIPA, LDLRAP1, ABCG5/8 genes were analysed by polymerase chain reaction amplification and Sanger sequencing. The 6-SNP LDL-C genetic risk score (GRS) for polygenic hypercholesterolaemia was validated in the Portuguese population and cases with a GRS over the 25th percentile were considered to have a high likelihood of polygenic hypercholesterolaemia. An FH-causing mutation was found in 39% of patients (94% in LDLR, 5% APOB and 1% PCSK9), while at least 29% have polygenic hypercholesterolaemia and 1% have other lipid disorders. A genetic cause for the FH phenotype was found in 503 patients (69%). All known causes of the FH phenotype should be investigated in FH cohorts to ensure accurate diagnosis and appropriate management.

Apolipoprotein B Particles and Cardiovascular Disease: A Narrative Review

Importance

The conventional model of atherosclerosis presumes that the mass of cholesterol within very low-density lipoprotein particles, low-density lipoprotein particles, chylomicron, and lipoprotein (a) particles in plasma is the principal determinant of the mass of cholesterol that will be deposited within the arterial wall and will drive atherogenesis. However, each of these particles contains one molecule of apolipoprotein B (apoB) and there is now substantial evidence that apoB more accurately measures the atherogenic risk owing to the apoB lipoproteins than does low-density lipoprotein cholesterol or non-high-density lipoprotein cholesterol.

Observations

Cholesterol can only enter the arterial wall within apoB particles. However, the mass of cholesterol per apoB particle is variable. Therefore, the mass of cholesterol that will be deposited within the arterial wall is determined by the number of apoB particles that are trapped within the arterial wall. The number of apoB particles that enter the arterial wall is determined primarily by the number of apoB particles within the arterial lumen. However, once within the arterial wall, smaller cholesterol-depleted apoB particles have a greater tendency to be trapped than larger cholesterol-enriched apoB particles because they bind more avidly to the glycosaminoglycans within the subintimal space of the arterial wall. Thus, a cholesterol-enriched particle would deposit more cholesterol than a cholesterol-depleted apoB particle whereas more, smaller apoB particles that enter the arterial wall will be trapped than larger apoB particles. The net result is, with the exceptions of the abnormal chylomicron remnants in type III hyperlipoproteinemia and lipoprotein (a), all apoB particles are equally atherogenic.

Conclusions and Relevance

Apolipoprotein B unifies, amplifies, and simplifies the information from the conventional lipid markers as to the atherogenic risk attributable to the apoB lipoproteins.

Non-HDL Cholesterol or apoB: Which to Prefer as a Target for the Prevention of Atherosclerotic Cardiovascular Disease?

PURPOSE OF REVIEW

Guidelines propose using non-HDL cholesterol or apolipoprotein (apo) B as a secondary treatment target to reduce residual cardiovascular risk of LDL-targeted therapies. This review summarizes the strengths, weaknesses, opportunities, and threats (SWOT) of using apoB compared with non-HDL cholesterol.

RECENT FINDINGS

Non-HDL cholesterol, calculated as total-HDL cholesterol, includes the assessment of remnant lipoprotein cholesterol, an additional risk factor independent of LDL cholesterol. ApoB is a direct measure of circulating numbers of atherogenic lipoproteins, and its measurement can be standardized across laboratories worldwide. Discordance analysis of non-HDL cholesterol versus apoB demonstrates that apoB is the more accurate marker of cardiovascular risk. Baseline and on-treatment apoB can identify elevated numbers of small cholesterol-depleted LDL particles that are not reflected by LDL and non-HDL cholesterol. ApoB is superior to non-HDL cholesterol as a secondary target in patients with mild-to-moderate hypertriglyceridemia (175-880 mg/dL), diabetes, obesity or metabolic syndrome, or very low LDL cholesterol < 70 mg/dL. When apoB is not available, non-HDL cholesterol should be used to supplement LDLC.

Lowering Targeted Atherogenic Lipoprotein Cholesterol Goals for Patients at "Extreme" ASCVD Risk

PURPOSE OF REVIEW

To review randomized interventional clinical and imaging trials that support lower targeted atherogenic lipoprotein cholesterol goals in "extreme" and "very high" atherosclerotic cardiovascular disease (ASCVD) risk settings. Major atherosclerotic cardiovascular event (MACE) prevention among the highest risk patients with ASCVD requires aggressive management of global risks, including lowering of the fundamental atherogenic apolipoprotein B-associated lipoprotein cholesterol particles [i.e., triglyceride-rich lipoprotein remnant cholesterol, low-density lipoprotein cholesterol (LDL-C), and lipoprotein(a)]. LDL-C has been the long-time focus of imaging studies and randomized clinical trials (RCTs). The 2004 adult treatment panel (ATP-III) update recognized that the long-standing targeted LDL-C goal of < 100 mg/dL potentially fostered substantial undertreatment of the very highest coronary heart disease (CHD) risk individuals and was lowered to < 70 mg/dL as an "optional" goal for "very high" 10-year CHD [CHD death + myocardial infarction (MI)] risk exceeding 20%. This evidence-based guideline change was supported by the observed benefits demonstrated in the high-risk primary and secondary prevention populations in the Heart Protection Study (HPS), the acute coronary syndrome (ACS) population in the Pravastatin or Atorvastatin Evaluation and Infection Therapy-Thrombolysis in Myocardial Infarction 22 trial (PROVE-IT), and the secondary prevention population in the Reversal of Atherosclerosis with Aggressive Lipid Lowering (REVERSAL) intravascular ultrasound (IVUS) study. Subsequent national and international guidelines maintained a targeted LDL-C goal < 70 mg/dL, or a threshold for management of > 70 mg/dL for patients with CHD, CHD risk equivalency, or ASCVD.

RECENT FINDINGS

Subgroup or meta-analyses of several RCTs, IVUS imaging studies, and the ACS population in IMProved Reduction of Outcomes: Vytorin Efficacy International Trial (IMPROVE-IT) supported the evidence-based 2017 American Association Clinical Endocrinologist (AACE) guideline change establishing a targeted LDL-C goal < 55 mg/dL, non-HDL-C < 80 mg/dl, and apolipoprotein B (apo B) < 70 mg/dL for patients at "Extreme" ASCVD risk, i.e., 10-year 3-point-MACE-composite (CV death, non-fatal MI, or ischemic stroke) risk exceeding 30%. Moreover, with no recognized lower-limit-associated intolerance or safety issues, even more intensive lowering of atherogenic cholesterol levels is supported by the following evidence base: (1) analysis of eight high-intensity statin-based prospective secondary prevention IVUS atheroma volume regression trials; (2) a distribution analysis of on-treatment, ezetimibe and background-statin, of the very low LDL-C levels reached and CVD event risk in the IMPROVE-IT ACS population; (3) the secondary prevention Global Assessment of Pl\aque Regression With a PCSK9 Antibody as Measured by Intravascular Ultrasound (GLAGOV) on background-statin; and (4) the secondary prevention population of Further Cardiovascular Outcomes Research with PCSK9 Inhibition in Subjects with Elevated Risk (FOURIER). By example, in FOURIER, the population on background-statin at a baseline median 92 mg/dL achieved median LDL-C level of 30 mg/dL and non-HDL-C to < 65 mg/dl, and apo B to < 50 mg/dL, and subgroup and post hoc analyses all demonstrated additional ASCVD event reduction benefits as LDL-C was further reduced. The level of ASCVD risk determines the degree, urgency, and persistence in global risk management, including fundamental atherogenic lipoprotein cholesterol particle lowering. "Extreme" risk patients may require extremely low targeted LDL-C, non-HDL-C and apo B goals; such efforts, implied by more recent interventional trials and analyses, are aimed at maximal atheroma plaque regression, stabilization, and MACE event reduction with the aspiration of improved quality lifespan.

ApoB in clinical care: Pro and Con

Whether apoB adds significantly to the assessment of the risk and therapy of the atherogenic dyslipoproteinemias has been vigorously contested over many years. That trapping of apoB lipoprotein particles within the arterial wall is fundamental to the initiation and maturation of atherosclerotic lesions within the arterial wall is now widely accepted. At the same time, the concept that primary prevention should be based on the risk of a cardiovascular event, a measure that integrates the effects of age, sex, blood pressure, lipids and other factors, has also become widely accepted. Within the risk framework, the issue becomes whether apoB adds significantly to the assessment of risk. On the other hand, it can be argued that the risk model undervalues how important a role that LDL and blood pressure play as causes of atherosclerosis and that when considered as causes, the importance of apoB emerges. These are the two sides of the debate that will be presented in the article that follows: one will highlight the pros of measuring apoB, the second the cons. The reader can make up his or her mind which side of the issue they favour.

Which Lipids Should Be Analyzed for Diagnostic Workup and Follow-up of Patients with Hyperlipidemias?

PURPOSE OF REVIEW

To summarize and discuss the clinical use of lipid and apolipoprotein tests in the settings of diagnosis and therapeutic follow-up of hyperlipidemia.

RECENT FINDINGS

The joint consensus panel of the European Atherosclerosis Society (EAS) and the European Federation of Clinical Chemistry and Laboratory Medicine (EFLM) recently produced recommendations on the measurement of atherogenic lipoproteins, taking into account the strengths and weaknesses of analytical and clinical performances of the tests. Total cholesterol, triglycerides, HDL cholesterol, LDL cholesterol, and calculated non-HDL cholesterol (= LDL + remnant cholesterol) constitute the primary lipid panel for hyperlipidemia diagnosis and cardiovascular risk estimation. LDL cholesterol is the primary target of lipid-lowering therapies. Non-HDL cholesterol or apolipoprotein B should be used as secondary therapeutic target in patients with mild-to-moderate hypertriglyceridemia, 2-10 mmol/l (175-880 mg/dl). Lipoprotein (a) is included in LDL cholesterol and should be measured at least once in all patients at cardiovascular risk, including to explain poor response to statin treatment.

Quantifying Atherogenic Lipoproteins: Current and Future Challenges in the Era of Personalized Medicine and Very Low Concentrations of LDL Cholesterol. A Consensus Statement from EAS and EFLM

BACKGROUND

The European Atherosclerosis Society-European Federation of Clinical Chemistry and Laboratory Medicine Consensus Panel aims to provide recommendations to optimize atherogenic lipoprotein quantification for cardiovascular risk management.

CONTENT

We critically examined LDL cholesterol, non-HDL cholesterol, apolipoprotein B (apoB), and LDL particle number assays based on key criteria for medical application of biomarkers. (a) Analytical performance: Discordant LDL cholesterol quantification occurs when LDL cholesterol is measured or calculated with different assays, especially in patients with hypertriglyceridemia >175 mg/dL (2 mmol/L) and low LDL cholesterol concentrations <70 mg/dL (1.8 mmol/L). Increased lipoprotein(a) should be excluded in patients not achieving LDL cholesterol goals with treatment. Non-HDL cholesterol includes the atherogenic risk component of remnant cholesterol and can be calculated in a standard nonfasting lipid panel without additional expense. ApoB more accurately reflects LDL particle number. (b) Clinical performance: LDL cholesterol, non-HDL cholesterol, and apoB are comparable predictors of cardiovascular events in prospective population studies and clinical trials; however, discordance analysis of the markers improves risk prediction by adding remnant cholesterol (included in non-HDL cholesterol) and LDL particle number (with apoB) risk components to LDL cholesterol testing. (c) Clinical and cost-effectiveness: There is no consistent evidence yet that non-HDL cholesterol-, apoB-, or LDL particle-targeted treatment reduces the number of cardiovascular events and healthcare-related costs than treatment targeted to LDL cholesterol.

SUMMARY

Follow-up of pre- and on-treatment (measured or calculated) LDL cholesterol concentration in a patient should ideally be performed with the same documented test method. Non-HDL cholesterol (or apoB) should be the secondary treatment target in patients with mild to moderate hypertriglyceridemia, in whom LDL cholesterol measurement or calculation is less accurate and often less predictive of cardiovascular risk. Laboratories should report non-HDL cholesterol in all standard lipid panels.

Discordance between lipoprotein particle number and cholesterol content: an update

PURPOSE OF REVIEW

The cholesterol content within atherogenic apolipoprotein-B (apoB) containing lipid particles is the center of consensus guidelines and clinicians' focus whenever evaluating a patient's risk for atherosclerotic cardiovascular disease. The pathobiology of atherosclerosis requires the retention of lipoprotein particles within the vascular intima over time followed by maladaptive inflammation resulting in plaque formation and rupture in some. The cholesterol content is widely variable within each particle creating either cholesterol-deplete or cholesterol-enriched particles. This variance in particle cholesterol content varies within and between individuals. Discordance analysis exploits this difference in cholesterol content of particles to demonstrate the differential significance of LDL-cholesterol (LDL-C) and non-HDL-C from measures of lipoprotein particle number in terms of assessing atherosclerotic cardiovascular disease risks.

RECENT FINDINGS

Three studies have added to the growing body of literature of discordance analysis. Despite wide variability of discordance cutoffs, baseline risk of atherosclerotic disease, and populations sampled, the conclusion remains the same: risk of atherosclerotic disease follows apoB lipid particle concentration rather than cholesterol content of lipid particles.

SUMMARY

In addition to traditional lipid fractions, assessments of atherogenic particle number should be strongly considered whenever assessing CVD risk in nontreated and treated individuals. There is a need for clinical trials that focus not only on the reduction in LDL-C but apoB, as well.

Effect of Evolocumab on Lipoprotein Particles

The level of low-density lipoprotein cholesterol (LDL-C) reflects the cholesterol carried mainly by low-density lipoprotein particles (LDL-P). LDL-C, however, does not always correlate with LDL-P because of the variable amounts of cholesterol per particle. Consideration of LDL-P concentrations in addition to LDL-C may help guide therapeutic decisions in a select number of patients. Evolocumab is a fully human monoclonal antibody directed against proprotein convertase subtilisin-kexin type 9 that lowers both LDL-C and cardiovascular events. To evaluate the effect of evolocumab on serum levels and size of lipoprotein particles, we conducted a post hoc subanalysis of 619 patients from the Durable Effect of PCSK9 Antibody Compared with Placebo Study or DESCARTES trial, a 52-week, randomized, double-blind, placebo-controlled, global study of patients with hyperlipidemia. At baseline, mean LDL-P concentration was 1077 nmol/L for the placebo group and 1100 nmol/L for the evolocumab group. In patients receiving evolocumab, week 52 total LDL-P concentration decreased to 610 nmol/L, a treatment difference of 50% versus placebo. Evolocumab also reduced concentrations of medium very low-density lipoprotein particles (VLDL-P), small VLDL-P, and intermediate-density lipoprotein particle: median (Q1, Q3) changes were -15.2% (-48, 48), -29% (-54, 18), and -36% (-70, 22), respectively. Mean (95% confidence interval) % changes in total LDL particle size in the evolocumab group was -1.7 (-2.0, -1.4); % changes in HDL and VLDL particle sizes were 1.1 (0.7, 1.5) and 8.7 (7.0, 10.5), respectively. Changes in total LDL, HDL, and VLDL particle sizes (vs placebo) were all significant (p <0.001). In conclusion, evolocumab significantly lowers atherogenic lipoprotein particles including low-density and remnant lipoproteins.

Statins, PCSK9 inhibitors and cholesterol homeostasis: a view from within the hepatocyte

Statins and PCSK9 inhibitors dramatically lower plasma LDL levels and dramatically increase LDL receptor number within hepatocyte cell membranes. It seems self-evident that total clearance of LDL particles from plasma and total delivery of cholesterol to the liver must increase in consequence. However, based on the results of stable isotope tracer studies, this analysis demonstrates the contrary to be the case. Statins do not change the production rate of LDL particles. Accordingly, at steady state, the clearance rate cannot change. Because LDL particles contain less cholesterol on statin therapy, the delivery of cholesterol to the liver must, therefore, be reduced. PCSK9 inhibitors reduce the production of LDL particles and this further reduces cholesterol delivery to the liver. With both agents, a larger fraction of a smaller pool is removed per unit time. These findings are inconsistent with the conventional model of cholesterol homeostasis within the liver, but are consistent with a new model of regulation, the multi-channel model, which postulates that different lipoprotein particles enter the hepatocyte by different routes and have different metabolic fates within the hepatocyte. The multi-channel model, but not the conventional model, may explain how statins and PCSK9 inhibitors can produce sustained increases in LDL receptor number.

Cost Effectiveness of Achieving Targets of Low-Density Lipoprotein Particle Number Versus Low-Density Lipoprotein Cholesterol Level

A recent analysis of a commercially insured US population found fewer cardiovascular disease (CVD) events in high-risk patients attaining low levels of low-density lipoprotein (LDL), as measured by LDL particle number (LDL-P) versus low LDL cholesterol (LDL-C). Here, we investigated the cost effectiveness of LDL-lowering therapy guided by LDL-P. Patients were selected from the HealthCore Integrated Research Database and followed for 12 to 36 months. Patients who achieved LDL-P <1,000 nmol/l were placed into the LDL-P cohort, whereas those without LDL-P tests, but who achieved LDL-C <100 mg/dl, were placed into the LDL-C cohort. CVD-related costs included all health plan paid amounts related to CVD events or lipid management. Cost effectiveness was assessed through incremental cost-effectiveness ratios, defined as difference in total costs across the cohorts divided by difference in CVD events, measured over follow-up. Each cohort included 2,094, 1,242, and 705 patients over 12-, 24-, and 36-month follow-up. Patients in the LDL-P cohort received more aggressive lipid-lowering therapy and had fewer CVD events during follow-up compared to patients in the LDL-C cohort. This led to greater pharmacy costs and lower medical costs over time. Incremental cost-effectiveness ratio estimates ranged from $23,131 per CVD event avoided at 12 months to $3,439 and -$4,555 at 24- and 36-month follow-up, suggesting a high likelihood that achieving LDL-P <1,000 nmol/l is cost effective. In conclusion, LDL-lowering therapy guided by LDL-P was demonstrated to be cost effective, with greater clinical and economic benefit seen over longer time horizons and with the increased use of generic statins.

Should apolipoprotein B replace LDL cholesterol as therapeutic targets are lowered?

PURPOSE OF REVIEW

The success of LDL cholesterol (LDL-C) as a predictor of atherosclerotic cardiovascular disease and a therapeutic target is indisputable. Apolipoprotein B (apoB) is a more contemporary and physiologically relevant measure of atherogenic lipoproteins. This report summarizes recent comparisons of apoB and LDL-C as biomarkers of cardiovascular risk.

RECENT FINDINGS

Multiple recent reports have found that LDL-C methods perform poorly at low concentrations (<70 mg/dl). Several meta-analyses from randomized controlled trials and large prospective observational studies have found that apoB and LDL-C provide equivalent information on risk of cardiovascular disease. More innovative analyses have asserted that apoB is a superior indicator of actual risk when apoB and LDL-C disagree.

SUMMARY

ApoB is more analytically robust and standardized biomarker than LDL-C. Large population studies have found that apoB is at worst clinically equivalent to LDL-C and likely superior when disagreement exists. Realistically, many obstacles prevent the wide spread adoption of apoB and for now providers and their patients must weigh the costs and benefits of apoB.

CONSENSUS STATEMENT BY THE AMERICAN ASSOCIATION OF CLINICAL ENDOCRINOLOGISTS AND AMERICAN COLLEGE OF ENDOCRINOLOGY ON THE COMPREHENSIVE TYPE 2 DIABETES MANAGEMENT ALGORITHM--2015 EXECUTIVE SUMMARY

This document represents the official position of the American Association of Clinical Endocrinologists and the American College of Endocrinology. Where there were no randomized controlled trials or specific U.S. FDA labeling for issues in clinical practice, the participating clinical experts utilized their judgment and experience. Every effort was made to achieve consensus among the committee members. Position statements are meant to provide guidance, but they are not to be considered prescriptive for any individual patient and cannot replace the judgment of a clinician.

Effect of Switching From Statin Monotherapy to Ezetimibe/Simvastatin Combination Therapy Compared With Other Intensified Lipid-Lowering Strategies on Lipoprotein Subclasses in Diabetic Patients With Symptomatic Cardiovascular Disease

Background

Patients with diabetes mellitus and cardiovascular disease may not achieve adequate low‐density lipoprotein cholesterol (LDL‐C) lowering on statin monotherapy, attributed partly to atherogenic dyslipidemia. More intensive LDL‐C–lowering therapy can be considered for these patients. A previous randomized, controlled study demonstrated greater LDL‐C lowering in diabetic patients with symptomatic cardiovascular disease who switched from simvastatin 20 mg (S20) or atorvastatin 10 mg (A10) to combination ezetimibe/simvastatin 10/20 mg (ES10/20) therapy, compared with statin dose‐doubling (to S40 or A20) or switching to rosuvastatin 10 mg (R10). The effect of these regimens on novel biomarkers of atherogenic dyslipidemia (low‐ and high‐density lipoprotein particle number and lipoprotein‐associated phospholipase A2 [Lp‐PLA₂]) was assessed.

Methods and Results

Treatment effects on low‐ and high‐density lipoprotein particle number (by NMR) and Lp‐PLA₂ (by ELISA) were evaluated using plasma samples available from 358 subjects in the study. Switching to ES10/20 reduced low‐density lipoprotein‐particle number numerically more than did statin dose‐doubling and was comparable with R10 (−133.3, −94.4, and −56.3 nmol/L, respectively; P>0.05). Increases in high‐density lipoprotein particle number were significantly greater with switches to ES10/20 versus statin dose‐doubling (1.5 and −0.5 μmol/L; P<0.05) and comparable with R10 (0.7 μmol/L; P>0.05). Percentages of patients attaining low‐density lipoprotein particle number levels <990 nmol/L were 62.4% for ES10/20, 54.1% for statin dose‐doubling, and 57.0% for R10. Switching to ES10/20 reduced Lp‐PLA₂ activity significantly more than did statin dose‐doubling (−28.0 versus −3.8 nmol/min per mL, P<0.05) and was comparable with R10 (−28.0 versus −18.6 nmol/min per mL; P>0.05); effects on Lp‐PLA₂ concentration were modest.

Conclusions

In diabetic patients with dyslipidemia, switching from statins to combination ES10/20 therapy generally improved lipoprotein subclass profile and Lp‐PLA₂ activity more than did statin dose‐doubling and was comparable with R10, consistent with its lipid effects.

Clinical Trial Registration

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00862251.

Apolipoprotein B improves risk assessment of future coronary heart disease in the Framingham Heart Study beyond LDL-C and non-HDL-C

AIMS

Analyses using conventional statistical methodologies have yielded conflicting results as to whether low-density lipoprotein cholesterol (LDL-C) or non-high-density lipoprotein cholesterol (non-HDL-C) or apolipoprotein B (apoB) is the best marker of the apoB-associated risk of coronary heart disease. The aim of this study was to determine the additional value of apoB beyond LDL-C or non-HDL-C as a predictor of coronary heart disease.

METHODS AND RESULTS

For each patient from the Framingham Offspring Cohort aged 40-75 years (n = 2966), we calculated the extent to which the observed apoB differed from the expected apoB based on their LDL-C or non-HDL-C. We added this difference to a Cox model predicting new onset coronary heart disease over a maximum of 20 years adjusting for standard risk factors plus LDL-C or non-HDL. The difference between observed and expected apoB over LDL-C or non-HDL-C was highly prognostic of future coronary heart disease events: adjusted hazard ratios 1.26 (95% confidence interval: 1.15, 1.37) and 1.20 (1.11, 1.29), respectively, for each standard deviation increase beyond expected apoB levels. When this difference between observed and expected apoB was added to standard coronary heart disease prediction models including LDL-C or non-HDL-C, prediction improved significantly (likelihood ratio test p-values <0.0001) and discrimination c-statistics increased from 0.72 to 0.73. The corresponding relative integrated discrimination improvements were 11% and 8%, respectively.

CONCLUSIONS

apoB improves risk assessment of future coronary heart disease events over and beyond LDL-C or non-HDL-C, which is consistent with coronary risk being more closely related to the number of atherogenic apoB particles than to the mass of cholesterol within them.

Differential Genetic Effects on Statin-Induced Changes Across Low-Density Lipoprotein-Related Measures

BACKGROUND

Statin therapy influences not only low-density lipoprotein (LDL) cholesterol levels but also LDL-related biomarkers, including non-high-density lipoprotein cholesterol (non-HDL-C), apolipoprotein B, total number of LDL particles, and mean LDL particle size. Recent studies have identified many genetic loci influencing circulating lipid levels and statin-induced LDL cholesterol reduction. However, it is unknown how these genetic variants influence statin-induced changes in LDL subfractions and non-HDL-C.

METHODS AND RESULTS

One hundred sixty candidate single-nucleotide polymorphisms for effects on circulating lipid levels or statin-induced LDL-cholesterol lowering were tested for association with response of LDL subfractions and non-HDL-C to rosuvastatin or placebo for 1 year among 7046 participants from the Justification for Use of Statins in Prevention: an Intervention Trial Evaluating Rosuvastatin (JUPITER) trial. Of the 51 single-nucleotide polymorphisms associated with statin response for ≥ 1 of the LDL subfractions or non-HDL-C, 20 single-nucleotide polymorphisms could be clustered according to effects predominantly on LDL particle size, predominantly on LDL particle number, and on apolipoprotein B but not on LDL cholesterol or non-HDL-C.

CONCLUSIONS

These differential associations point to pathways of LDL response to statin therapy and possibly to mechanisms of statin-dependent cardiovascular disease risk reduction.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00239681.

Prioritizing health outcomes in a limited world: writing lipid guidelines

PURPOSE OF REVIEW

Guidelines are increasing in importance as healthcare becomes standardized. This article examines the processes by which the new US American College of Cardiology-American Heart Association and UK National Institute of Health and Care Excellence lipid guidelines came to their conclusions and how the nature of the evidence base and health economics contributed to the recommendations made.

RECENT FINDINGS

The writing of guidelines is becoming a systematic formal process with increasing emphasis on maintaining integrity, minimizing conflicts of interest and using consistent systematic methods to define the evidence base, grade its quality and then make recommendations. These processes are illustrated by showing why new cardiovascular disease risk assessment tools were required, what recommendations could be made about diet and lifestyle, why a fixed-dose drug treatment protocol as opposed to a target-based approach was recommended for the management of patients in secondary prevention, diabetes and primary prevention and how these would impact clinical practice.

SUMMARY

Modern systematic evidence assessment and economic appraisal convincingly favour the use of lipid-lowering drugs especially statins at higher doses than currently prescribed in secondary prevention and at lower risk thresholds in primary care than previously imagined. As long-term adherence to treatment is required patient choice is key to realizing the benefits of these interventions.

Clinical guidelines on hyperlipidaemia: recent developments, future challenges and the need for an Australian review

Large reductions in cardiovascular disease (CVD) mortality have been achieved over the last 50 years in developed countries. The health policies that have contributed so much to this success have largely been coordinated by means of expert guidelines for the management of the classic modifiable risk factors such as blood pressure, diabetes and blood lipids. National and international guidelines for lipid management have demonstrated a high degree of consistency between numerous sets of recommendations. It has been argued that some important components of the consensus that has been established over the past decade have been challenged by the latest guidelines of the American Heart Association - American College of Cardiologists (AHA-ACC). Clinicians can be reassured that continued reliance on extensive scientific evidence has reaffirmed the importance of lipid metabolism as a modifiable risk factor for atherosclerotic cardiovascular disease. On the other hand, the recent AHA-ACC guidelines suggest changes in the strategies by which metabolic risk factors may be modified. This small number of important changes should not be sensationalised because these differences usefully reflect the need for guidelines to evolve to accommodate different contexts and changing perspectives as well as emerging issues and new information for which clinical trial evidence is incomplete. This article will consider the recent policies and responses of national and supranational organisations on topics including components of CVD risk assessment, sources of CVD risk information and re-appraisal of lipid-lowering interventions. Timely review of Australian lipid management guidelines will require consideration of these issues because they are creating a new context within which new guidelines must evolve.

Mipomersen preferentially reduces small low-density lipoprotein particle number in patients with hypercholesterolemia

BACKGROUND

Because of variability in lipoprotein cholesterol content, low-density lipoprotein (LDL) cholesterol frequently underrepresents or overrepresents the number of LDL particles. Mipomersen is an antisense oligonucleotide that reduces hepatic production of apolipoprotein B-100, the sole apolipoprotein of LDL.

OBJECTIVE

To characterize the effects of mipomersen on lipoprotein particle numbers as well as subclass distribution using nuclear magnetic resonance (NMR) spectroscopy.

METHODS

We compared the tertiary results for the direct measurement of LDL particle numbers by NMR among 4 placebo-controlled, phase 3 studies of mipomersen that had similar study designs but different patient populations: homozygous familial hypercholesterolemia (HoFH), severe hypercholesterolemia, heterozygous familial hypercholesterolemia with established coronary artery disease, or hypercholesterolemia with high risk for coronary heart disease (HC-CHD).

RESULTS

HoFH patients had the highest median total LDL particles at baseline compared with HC-CHD patients, who had the lowest. At baseline, the HoFH population uniquely had a greater mean percentage of large LDL particles (placebo, 60.2%; mipomersen, 54.9%) compared with small LDL particles (placebo, 33.1%; mipomersen, 38.9%). In all 4 studies, mipomersen was associated with greater reductions from baseline in the concentrations of small LDL particles compared with those of large LDL particles, and both total LDL particles and small LDL particles were statistically significantly reduced.

CONCLUSIONS

Mipomersen consistently reduced all LDL particle numbers and preferentially reduced the concentration of small LDL particles in all 4 phase 3 studies.

Safety profile of subjects treated to very low low-density lipoprotein cholesterol levels (<30 mg/dl) with rosuvastatin 20 mg daily (from JUPITER)

Recent US guidelines expand the indications for high-intensity statin therapy, yet data on the safety of attaining very low-density lipoprotein cholesterol (LDL-C) levels are scarce. Among 16,304 participants in the Justification for the Use of Statins in Prevention: An Intervention Trial Evaluating Rosuvastatin (JUPITER) with on-treatment LDL-C levels, we identified 767 who did and 7,387 who did not achieve LDL-C <30 mg/dl on rosuvastatin 20 mg daily and 718 participants who did and 7,436 who did not achieve LDL-C reductions of ≥70% on rosuvastatin, and 8,150 allocated to placebo. In participants with an LDL-C <30 mg/dl, we observed an increase in the risk of physician-reported type 2 diabetes with an adjusted hazard ratio (95% confidence interval) of 1.56 (1.09 to 2.23, p = 0.01) and physician-reported hematuria (hazard ratio 2.10 [1.39 to 3.19], p <0.001) compared with rosuvastatin-treated participants with LDL-C ≥30 mg/dl. There was also an increased risk of certain musculoskeletal, hepatobiliary, and psychiatric disorders. No difference in renal failure, cancer, memory impairment, or hemorrhagic stroke was observed, although there were few events in these categories. In rosuvastatin-treated participants, achieving LDL-C reduction ≥70% versus <70% did not appear to be associated with increased risk of hepatobiliary, renal, or urinary disorders. In conclusion, in this post hoc analysis in the JUPITER, achieving LDL-C levels <30 mg/dl with high-intensity statin therapy appeared to be generally well tolerated but associated with certain adverse events, including more physician-reported diabetes, hematuria, hepatobiliary disorders, and insomnia. These data may guide the monitoring of patients on intensive statin therapy and adverse events in trials of therapies that lead to very low LDL-C levels.

Discordance between apolipoprotein B and low-density lipoprotein particle number is associated with insulin resistance in clinical practice

BACKGROUND

Discordance between measures of atherogenic lipoprotein particle number (apolipoprotein B [ApoB] and low-density lipoprotein [LDL] particle number by nuclear magnetic resonance spectroscopy [LDL-PNMR]) is not well understood. Appropriate treatment considerations in such cases are unclear.

OBJECTIVES

To assess discordance between apoB determined by immunoassay and LDL-PNMR in routine clinical practice, and to characterize biomarker profiles and other clinical characteristics of patients identified as discordant.

METHODS

Two retrospective cohorts were evaluated. First, 412,013 patients with laboratory testing performed by Health Diagnostic Laboratory, Inc., as part of routine care; and second, 1411 consecutive patients presenting for risk assessment/reduction at 6 US outpatient clinics. Discordance was quantified as a percentile difference (LDL-PNMR percentile - apoB percentile) and attainment of percentile cutpoints (LDL-PNMR ≥ 1073 nmol/L or apoB ≥ 69 mg/dL). A wide range of cardiovascular risk factors were compared.

RESULTS

ApoB and LDL-PNMR values were highly correlated (R(2) = 0.79), although substantial discordance was observed. Similar numbers of patients were identified as at-risk by LDL-PNMR when apoB levels were < 69 mg/dL (5%-6%) and by apoB values when LDL-PNMR was < 1073 nmol/L (6%-7%). Discordance (LDL-PNMR > apoB) was associated with insulin resistance, smaller LDL particle size, increased systemic inflammation, and low circulating levels of "traditional" lipids, whereas discordance (apoB > LDL-PNMR) was associated with larger LDL particle size, and elevated levels of lipoprotein(a) and lipoprotein-associated phospholipase A2 (Lp-PLA2).

CONCLUSION

Discordance between apoB and LDL-PNMR in routine clinical practice is more widespread than currently recognized and may be associated with insulin resistance.

The "New Deadly Quartet" for cardiovascular disease in the 21st century: obesity, metabolic syndrome, inflammation and climate change: how does statin therapy fit into this equation?

Despite population-based improvements in cardiovascular risk factors, such as blood pressure, cholesterol and smoking, cardiovascular disease still remains the number-one cause of mortality in the United States. In 1989, Kaplan coined the term "Deadly Quartet" to represent a combination of risk factors that included upper body obesity, glucose intolerance, hypertriglyceridemia and hypertension [Kaplan in Arch Int Med 7:1514-1520, 1989]. In 2002, the third report of the National Cholesterol Education Program Adult Treatment Panel (NCEP-ATP III) essentially added low HDL-C criteria and renamed this the "metabolic syndrome." [The National Cholesterol Education Program (NCEP) in JAMA 285:2486-2497, 2001] However, often forgotten was that a pro-inflammatory state and pro-thrombotic state were also considered components of the syndrome, albeit the panel did not find enough evidence at the time to recommend routine screening for these risk factors [The National Cholesterol Education Program (NCEP) in JAMA 285:2486-2497, 2001]. Now over a decade later, it may be time to reconsider this deadly quartet by reevaluating the roles of obesity and subclinical inflammation as they relate to the metabolic syndrome. To complete this new quartet, the addition of increased exposure to elevated levels of particulate matter in the atmosphere may help elucidate why this cardiovascular pandemic continues, despite our concerted efforts. In this article, we will summarize the evidence, focusing on how statin therapy may further impact this new version of the "deadly quartet".

NMR measurement of LDL particle number using the Vantera Clinical Analyzer

BACKGROUND

The Vantera Clinical Analyzer was developed to enable fully-automated, high-throughput nuclear magnetic resonance (NMR) spectroscopy measurements in a clinical laboratory setting. NMR-measured low-density lipoprotein particle number (LDL-P) has been shown to be more strongly associated with cardiovascular disease outcomes than LDL cholesterol (LDL-C) in individuals for whom these alternate measures of LDL are discordant.

OBJECTIVE

The aim of this study was to assess the analytical performance of the LDL-P assay on the Vantera Clinical Analyzer as per Clinical Laboratory Standards Institute (CLSI) guidelines.

RESULTS

Sensitivity and linearity were established within the range of 300-3500 nmol/L. For serum pools containing low, medium and high levels of LDL-P, the inter-assay, intra-assay precision and repeatability gave coefficients of variation (CVs) between 2.6 and 5.8%. The reference interval was determined to be 457-2282 nmol/L and the assay was compatible with multiple specimen collection tubes. Of 30 substances tested, only 2 exhibited the potential for assay interference. Moreover, the LDL-P results from samples run on two NMR platforms, Vantera Clinical Analyzer and NMR Profiler, showed excellent correlation (R(2)=0.96).

CONCLUSIONS

The performance characteristics suggest that the LDL-P assay is suitable for routine testing in the clinical laboratory on the Vantera Clinical Analyzer, the first automated NMR platform that supports NMR-based clinical assays.