Discordance among apoB, non-high-density lipoprotein cholesterol, and triglycerides: implications for cardiovascular prevention

BACKGROUND AND AIMS

Despite growing evidence that apolipoprotein B (apoB) is the most accurate marker of atherosclerotic cardiovascular disease (ASCVD) risk, its adoption in clinical practice has been low. This investigation sought to determine whether low-density lipoprotein cholesterol (LDL-C), non-high-density lipoprotein cholesterol (HDL-C), and triglycerides are sufficient for routine cardiovascular care.

METHODS

A sample of 293 876 UK Biobank adults (age: 40-73 years, 42% men), free of cardiovascular disease, with a median follow-up for new-onset ASCVD of 11 years was included. Distribution of apoB at pre-specified levels of LDL-C, non-HDL-C, and triglycerides was examined graphically, and 10-year ASCVD event rates were compared for high vs. low apoB. Residuals of apoB were constructed after regressing apoB on LDL-C, non-HDL-C, and log-transformed triglycerides and used as predictors in a proportional hazards regression model for new-onset ASCVD adjusted for standard risk factors, including HDL-C.

RESULTS

ApoB was highly correlated with LDL-C and non-HDL-C (Pearson's r = .96, P < .001 for both) but less so with log triglycerides (r = .42, P < .001). However, apoB ranges necessary to capture 95% of all observations at pre-specified levels of LDL-C, non-HDL-C, or triglycerides were wide, spanning 85.8-108.8 md/dL when LDL-C 130 mg/dL, 88.3-112.4 mg/dL when non-HDL-C 160 mg/dL, and 67.8-147.4 md/dL when triglycerides 115 mg/dL. At these levels (±10 mg/dL), 10-year ASCVD rates for apoB above mean + 1 SD vs. below mean - 1 SD were 7.3 vs. 4.0 for LDL-C, 6.4 vs. 4.6 for non-HDL-C, and 7.0 vs. 4.6 for triglycerides (all P < .001). With 19 982 new-onset ASCVD events on follow-up, in the adjusted model, residual apoB remained statistically significant after accounting for LDL-C and HDL-C (hazard ratio 1.06, 95% confidence interval 1.0-1.07), after accounting for non-HDL-C and HDL-C (hazard ratio 1.04, 95% confidence interval 1.03-1.06), and after accounting for triglycerides and HDL-C (hazard ratio 1.13, 95% confidence interval 1.12-1.15). None of the residuals of LDL-C, non-HDL-C, or of log triglycerides remained significant when apoB was included in the model.

CONCLUSIONS

High variability of apoB at individual levels of LDL-C, non-HDL-C, and triglycerides coupled with meaningful differences in 10-year ASCVD rates and significant residual information contained in apoB for prediction of new-onset ASCVD events demonstrate that LDL-C, non-HDL-C, and triglycerides are not adequate proxies for apoB in clinical care.

Validation of the European SCORE2 models in a Canadian primary care cohort

AIMS

Systematic Coronary Risk Evaluation Model 2 (SCORE2) was recently developed to predict atherosclerotic cardiovascular disease (ASCVD) in Europe. Whether these models could be used outside of Europe is not known. The objective of this study was to test the validity of SCORE2 in a large Canadian cohort.

METHODS AND RESULTS

A primary care cohort of persons with routinely collected electronic medical record data from 1 January 2010 to 31 December 2014, in Ontario, Canada, was used for validation. The SCORE2 models for younger persons (YP) were applied to 57 409 individuals aged 40-69 while the models for older persons (OPs) were applied to 9885 individuals 70-89 years of age. Five-year ASCVD predictions from both the uncalibrated and low-risk region recalibrated SCORE2 models were evaluated. The C-statistic for SCORE2-YP was 0.74 in women and 0.69 in men. The uncalibrated SCORE2-YP overestimated risk by 17% in women and underestimated by 2% in men. In contrast, the low-risk region recalibrated model demonstrated worse calibration, overestimating risk by 100% in women and 36% in men. The C-statistic for SCORE2-OP was 0.64 and 0.62 in older women and men, respectively. The uncalibrated SCORE2-OP overestimated risk by more than 100% in both sexes. The low-risk region recalibrated model demonstrated improved calibration but still overestimated risk by 60% in women and 13% in men.

CONCLUSION

The performance of SCORE2 to predict ASCVD risk in Canada varied by age group and depended on whether regional calibration was applied. This underscores the necessity for validation assessment of SCORE2 prior to implementation in new jurisdictions.

Atherothrombotic and thrombolytic biomarkers in incident stroke and atrial fibrillation-related stroke: The Multi-Ethnic Study of Atherosclerosis (MESA)

BACKGROUND AND AIMS

Although several biomarkers have been studied in thromboembolic stroke, measuring the balance between thrombus formation and thrombolysis and data on its role in predicting stroke and atrial fibrillation (AF)-related stroke is limited. We sought to assess atherothrombotic biomarkers grouped into composite factors that reflect thrombotic and thrombolytic potential, and the balance between these factors as it relates to incident stroke or transient ischemic attack (TIA) and stroke/TIA in AF.

METHODS

A Thrombotic Factor, derived from fibrinogen, plasmin-antiplasmin complex, factor VIII, D-dimer, and lipoprotein(a); and a Thrombolytic Factor, derived from plasminogen and oxidized phospholipids on plasminogen, were evaluated at baseline in 5,764 Multi-Ethnic Study of Atherosclerosis (MESA) participants. We evaluated the association between these two factors representative of thrombotic and thrombolytic potential and incident stroke/TIA (n = 402), and AF-related stroke/TIA (n = 82) over a median of 13.9 and 3.7 years, respectively. Cox proportional hazard models adjusted for medication use, cardiovascular risk factors and CHA2DS2-VASc score were utilized. Harrell's C-index was estimated to evaluate model performance.

RESULTS

In models including both factors, Thrombotic Factor was positively while Thrombolytic Factor was inversely associated with incident stroke/TIA and AF-related stroke/TIA. Incorporating these factors along with the CHA2DS2-VASc in adjusted models resulted in a small improvement in risk prediction of incident stroke/TIA and AF-related stroke/TIA compared to models without the factors (C-index from 0.697 to 0.704, and from 0.657 to 0.675, respectively).

CONCLUSIONS

Composite biomarker factors, representative of the balance between thrombotic and thrombolytic propensity, provided an improvement in predicting stroke/TIA beyond CHA2DS2-VASc score.

Large-Scale Proteomics Identifies Novel Biomarkers and Circulating Risk Factors for Aortic Stenosis

BACKGROUND

Limited data exist regarding risk factors for aortic stenosis (AS). The plasma proteome is a promising phenotype for discovery of novel biomarkers and potentially causative mechanisms.

OBJECTIVES

The aim of this study was to discover novel biomarkers with potentially causal associations with AS.

METHODS

We measured 4,877 plasma proteins (SomaScan aptamer-affinity assay) among ARIC (Atherosclerosis Risk In Communities) study participants in mid-life (visit 3 [V3]; n = 11,430; age 60 ± 6 years) and in late-life (V5; n = 4,899; age 76 ± 5 years). We identified proteins cross-sectionally associated with aortic valve (AV) peak velocity (AVmax) and dimensionless index by echocardiography at V5 and with incident AV-related hospitalization after V3 with the use of multivariable linear and Cox proportional hazard regression. We assessed associations of candidate proteins with changes in AVmax over 6 years and with AV calcification with the use of cardiac computed tomography, replicated analysis in an independent sample, performed Mendelian randomization, and evaluated gene expression in explanted human AV tissue.

RESULTS

Fifty-two proteins cross-sectionally were associated with AVmax and dimensionless index at V5 and with risk of incident AV-related hospitalization after V3. Among 3,413 participants in the Cardiovascular Health Study, 6 of those proteins were significantly associated with adjudicated moderate or severe AS, including matrix metalloproteinase 12 (MMP12), complement C1q tumor necrosis factor-related protein 1 (C1QTNF1), and growth differentiation factor-15. MMP12 was also associated with greater increase in AVmax over 6 years, greater degree of AV calcification, and greater expression in calcific compared with normal or fibrotic AV tissue. C1QTNF1 had consistent potential causal effects on both AS and AVmax according to Mendelian randomization analysis.

CONCLUSIONS

These findings identify MMP12 as a potential novel circulating biomarker of AS risk and C1QTNF1 as a new putative target to prevent AS progression.

Major Facilitator Superfamily Domain Containing 5 Inhibition Reduces Lipoprotein(a) Uptake and Calcification in Valvular Heart Disease

BACKGROUND

High circulating levels of Lp(a) (lipoprotein[a]) increase the risk of atherosclerosis and calcific aortic valve disease, affecting millions of patients worldwide. Although atherosclerosis is commonly treated with low-density lipoprotein-targeting therapies, these do not reduce Lp(a) or risk of calcific aortic valve disease, which has no available drug therapies. Targeting Lp(a) production and catabolism may provide therapeutic benefit, but little is known about Lp(a) cellular uptake.

METHODS

Here, unbiased ligand-receptor capture mass spectrometry was used to identify MFSD5 (major facilitator superfamily domain containing 5) as a novel receptor/cofactor involved in Lp(a) uptake.

RESULTS

Reducing MFSD5 expression by a computationally identified small molecule or small interfering RNA suppressed Lp(a) uptake and calcification in primary human valvular endothelial and interstitial cells. MFSD5 variants were associated with aortic stenosis (P=0.027 after multiple hypothesis testing) with evidence suggestive of an interaction with plasma Lp(a) levels.

CONCLUSIONS

MFSD5 knockdown suppressing human valvular cell Lp(a) uptake and calcification, along with meta-analysis of MFSD5 variants associating with aortic stenosis, supports further preclinical assessment of MFSD5 in cardiovascular diseases, the leading cause of death worldwide.

Prevalence of Aortic Valve Calcium and the Long-Term Risk of Incident Severe Aortic Stenosis

BACKGROUND

Aortic valve calcification (AVC) is a principal mechanism underlying aortic stenosis (AS).

OBJECTIVES

This study sought to determine the prevalence of AVC and its association with the long-term risk for severe AS.

METHODS

Noncontrast cardiac computed tomography was performed among 6,814 participants free of known cardiovascular disease at MESA (Multi-Ethnic Study of Atherosclerosis) visit 1. AVC was quantified using the Agatston method, and normative age-, sex-, and race/ethnicity-specific AVC percentiles were derived. The adjudication of severe AS was performed via chart review of all hospital visits and supplemented with visit 6 echocardiographic data. The association between AVC and long-term incident severe AS was evaluated using multivariable Cox HRs.

RESULTS

AVC was present in 913 participants (13.4%). The probability of AVC >0 and AVC scores increased with age and were generally highest among men and White participants. In general, the probability of AVC >0 among women was equivalent to men of the same race/ethnicity who were approximately 10 years younger. Incident adjudicated severe AS occurred in 84 participants over a median follow-up of 16.7 years. Higher AVC scores were exponentially associated with the absolute risk and relative risk of severe AS with adjusted HRs of 12.9 (95% CI: 5.6-29.7), 76.4 (95% CI: 34.3-170.2), and 380.9 (95% CI: 169.7-855.0) for AVC groups 1 to 99, 100 to 299, and ≥300 compared with AVC = 0.

CONCLUSIONS

The probability of AVC >0 varied significantly by age, sex, and race/ethnicity. The risk of severe AS was exponentially higher with higher AVC scores, whereas AVC = 0 was associated with an extremely low long-term risk of severe AS. The measurement of AVC provides clinically relevant information to assess an individual's long-term risk for severe AS.

Development and Validation of the CANHEART Population-Based Laboratory Prediction Models for Atherosclerotic Cardiovascular Disease

BACKGROUND

Prediction of atherosclerotic cardiovascular disease (ASCVD) in primary prevention assessments exclusively with laboratory results may facilitate automated risk reporting and improve uptake of preventive therapies.

OBJECTIVE

To develop and validate sex-specific prediction models for ASCVD using age and routine laboratory tests and compare their performance with that of the pooled cohort equations (PCEs).

DESIGN

Derivation and validation of the CANHEART (Cardiovascular Health in Ambulatory Care Research Team) Lab Models.

SETTING

Population-based cohort study in Ontario, Canada.

PARTICIPANTS

A derivation and internal validation cohort of adults aged 40 to 75 years without cardiovascular disease from April 2009 to December 2015; an external validation cohort of primary care patients from January 2010 to December 2014.

MEASUREMENTS

Age and laboratory predictors measured in the outpatient setting included serum total cholesterol, high-density lipoprotein cholesterol, triglycerides, hemoglobin, mean corpuscular volume, platelets, leukocytes, estimated glomerular filtration rate, and glucose. The ASCVD outcomes were defined as myocardial infarction, stroke, and death from ischemic heart or cerebrovascular disease within 5 years.

RESULTS

Sex-specific models were developed and internally validated in 2 160 497 women and 1 833 147 men. They were well calibrated, with relative differences less than 1% between mean predicted and observed risk for both sexes. The c-statistic was 0.77 in women and 0.71 in men. External validation in 31 697 primary care patients showed a relative difference less than 14% and an absolute difference less than 0.3 percentage points in mean predicted and observed risks for both sexes. The c-statistics for the laboratory models were 0.72 for both sexes and were not statistically significantly different from those for the PCEs in women (change in c-statistic, -0.01 [95% CI, -0.03 to 0.01]) or men (change in c-statistic, -0.01 [CI, -0.04 to 0.02]).

LIMITATION

Medication use was not available at the population level.

CONCLUSION

The CANHEART Lab Models predict ASCVD with similar accuracy to more complex models, such as the PCEs.

PRIMARY FUNDING SOURCE

Canadian Institutes of Health Research.

P2RX7 gene knockout or antagonism reduces angiotensin II-induced hypertension, vascular injury and immune cell activation

OBJECTIVE

Extracellular ATP is elevated in hypertensive mice and humans and may trigger immune activation through the purinergic receptor P2X7 (P2RX7) causing interleukin-1β production and T-cell activation and memory T-cell development. Furthermore, P2RX7 single nucleotide polymorphisms (SNP) are associated with hypertension. We hypothesized that P2RX7 activation contributes to hypertension and cardiovascular injury by promoting immune activation.

METHODS

Male wild-type and P2rx7-/- mice were infused or not with angiotensin II (AngII) for 14 days. A second group of AngII-infused wild-type mice were co-infused with the P2RX7 antagonist AZ10606120 or vehicle. BP was monitored by telemetry. Cardiac and mesenteric artery function and remodeling were assessed using ultrasound and pressure myography, respectively. T cells were profiled in thoracic aorta/perivascular adipose tissue by flow cytometry. Associations between SNPs within 50 kb of P2RX7 transcription, and BP or hypertension were modeled in 384 653 UK Biobank participants.

RESULTS

P2rx7 inactivation attenuated AngII-induced SBP elevation, and mesenteric artery dysfunction and remodeling. This was associated with decreased perivascular infiltration of activated and effector memory T-cell subsets. Surprisingly, P2rx7 knockout exaggerated AngII-induced cardiac dysfunction and remodeling. Treatment with a P2RX7 antagonist reduced BP elevation, preserved mesenteric artery function and reduced activated and effector memory T cell perivascular infiltration without adversely affecting cardiac function and remodeling in AngII-infused mice. Three P2RX7 SNPs were associated with increased odds of DBP elevation.

CONCLUSION

P2RX7 may represent a target for attenuating BP elevation and associated vascular damage by decreasing immune activation.

Is hypertriglyceridemia a reliable indicator of cholesterol-depleted Apo B particles?

OBJECTIVES

Because cholesterol-depleted Apo B particles are thought to be a hallmark of hypertriglyceridemia, American, Canadian and European Lipid Guidelines suggest screening for Apo B only in patients with hypertriglyceridemia. Accordingly, this study examines the relationship of triglycerides to the LDL-C/Apo B and non-HDL-C/Apo B ratios.

METHODS

The study cohort consisted of 6272 NHANES subjects adjusted for a weighted sample size of 150 million subjects without previously diagnosed cardiac disease. Data was reported by LDL-C/Apo B tertiles as weighted frequencies and percent. Sensitivity, specificity, negative predictive and positive predictive values were calculated for triglycerides thresholds of >150 mg/dL and >200 mg/dL. The range of values of Apo B for decisional levels of LDL-C and non-HDL-C were also determined RESULTS: Among patients with triglycerides >200 mg/dL, 75.9% were amongst the lowest LDL-C/Apo B tertile. However, this represents only 7.5% of the total population. Of patients with the lowest LDL-C/Apo B ratio, 59.8% had triglycerides <150 mg/dL. Moreover, there was an inverse relationship between non-HDL-C/Apo B such that elevated triglycerides were associated with the highest tertile of non-HDL-C/Apo B. Finally, the range of values of Apo B for decisional levels of LDL-C and non-HDL-C was determined and is so broad- 30.3-40.6 mg/dl Apo B for different levels of LDL-C and 19.5 to 27.6 mg/dl Apo B for different levels of non-HDL-C- that neither is an adequate clinical surrogate for Apo B.

CONCLUSION

Plasma triglycerides should not be used to restrict the measurement of Apo B since cholesterol-depleted Apo B particles may be present at any level of triglyceride.

Race and Ethnicity With Atherosclerotic Cardiovascular Disease Outcomes Within a Universal Health Care System: Insights From the CARTaGENE Study

BACKGROUND

It remains unclear whether racial and ethnic disparities for atherosclerotic cardiovascular disease (ASCVD) persist within universal health care systems. We aimed to explore long-term ASCVD outcomes within a single-payer health care system with extensive drug coverage in Québec, Canada.

METHODS

CARTaGENE (CaG) is a population-based prospective cohort study of individuals aged 40 to 69 years. We included only participants without previous ASCVD. The primary composite endpoint was time to the first ASCVD event (cardiovascular death, acute coronary syndrome, ischemic stroke-transient ischemic attack, or peripheral arterial vascular event).

RESULTS

The study cohort included 18,880 participants followed for a median of 6.6 years (2009 to 2016). The mean age was 52 years, and 52.4% were female. After further adjustment for socioeconomic and cardiovascular factors, the increase in ASCVD risk for South Asians (SAs) was attenuated (hazard ratio [HR], 1.41; 95% confidence interval [CI], 0.75, 2.67), whereas Black participants' risk was lower (HR, 0.52; 95% CI, 0.29, 0.95) compared with White participants. After similar adjustments, there were no significant differences in ASCVD outcomes among the Middle Eastern, Hispanic, East-Southeast Asian, Indigenous, and mixed race-ethnicities participants and the White participants.

CONCLUSIONS

After adjustment for CV risk factors, the risk of ASCVD was attenuated in the SA CaG participants. Intensive risk-factor modification may mitigate the ASCVD risk of the SAs. Within a universal health care context and comprehensive drug coverage, the ASCVD risk was lower among Black compared with White CaG participants. Future studies are needed to confirm whether universal and liberal access to health care and medications can reduce the rates of ASCVD among the Black population.

Dyslipidemia, inflammation, calcification, and adiposity in aortic stenosis: a genome-wide study

AIMS

Although highly heritable, the genetic etiology of calcific aortic stenosis (AS) remains incompletely understood. The aim of this study was to discover novel genetic contributors to AS and to integrate functional, expression, and cross-phenotype data to identify mechanisms of AS.

METHODS AND RESULTS

A genome-wide meta-analysis of 11.6 million variants in 10 cohorts involving 653 867 European ancestry participants (13 765 cases) was performed. Seventeen loci were associated with AS at P ≤ 5 × 10-8, of which 15 replicated in an independent cohort of 90 828 participants (7111 cases), including CELSR2-SORT1, NLRP6, and SMC2. A genetic risk score comprised of the index variants was associated with AS [odds ratio (OR) per standard deviation, 1.31; 95% confidence interval (CI), 1.26-1.35; P = 2.7 × 10-51] and aortic valve calcium (OR per standard deviation, 1.22; 95% CI, 1.08-1.37; P = 1.4 × 10-3), after adjustment for known risk factors. A phenome-wide association study indicated multiple associations with coronary artery disease, apolipoprotein B, and triglycerides. Mendelian randomization supported a causal role for apolipoprotein B-containing lipoprotein particles in AS (OR per g/L of apolipoprotein B, 3.85; 95% CI, 2.90-5.12; P = 2.1 × 10-20) and replicated previous findings of causality for lipoprotein(a) (OR per natural logarithm, 1.20; 95% CI, 1.17-1.23; P = 4.8 × 10-73) and body mass index (OR per kg/m2, 1.07; 95% CI, 1.05-1.9; P = 1.9 × 10-12). Colocalization analyses using the GTEx database identified a role for differential expression of the genes LPA, SORT1, ACTR2, NOTCH4, IL6R, and FADS.

CONCLUSION

Dyslipidemia, inflammation, calcification, and adiposity play important roles in the etiology of AS, implicating novel treatments and prevention strategies.

Toll-Like Receptor 3 Mediates Aortic Stenosis Through a Conserved Mechanism of Calcification

BACKGROUND

Calcific aortic valve disease (CAVD) is characterized by a phenotypic switch of valvular interstitial cells to bone-forming cells. Toll-like receptors (TLRs) are evolutionarily conserved pattern recognition receptors at the interface between innate immunity and tissue repair. Type I interferons (IFNs) are not only crucial for an adequate antiviral response but also implicated in bone formation. We hypothesized that the accumulation of endogenous TLR3 ligands in the valvular leaflets may promote the generation of osteoblast-like cells through enhanced type I IFN signaling.

METHODS

Human valvular interstitial cells isolated from aortic valves were challenged with mechanical strain or synthetic TLR3 agonists and analyzed for bone formation, gene expression profiles, and IFN signaling pathways. Different inhibitors were used to delineate the engaged signaling pathways. Moreover, we screened a variety of potential lipids and proteoglycans known to accumulate in CAVD lesions as potential TLR3 ligands. Ligand-receptor interactions were characterized by in silico modeling and verified through immunoprecipitation experiments. Biglycan (Bgn), Tlr3, and IFN-α/β receptor alpha chain (Ifnar1)-deficient mice and a specific zebrafish model were used to study the implication of the byglycan (BGN)-TLR3-IFN axis in both CAVD and bone formation in vivo. Two large-scale cohorts (GERA [Genetic Epidemiology Research on Adult Health and Aging], n=55 192 with 3469 aortic stenosis cases; UK Biobank, n=257 231 with 2213 aortic stenosis cases) were examined for genetic variation at genes implicated in BGN-TLR3-IFN signaling associating with CAVD in humans.

RESULTS

Here, we identify TLR3 as a central molecular regulator of calcification in valvular interstitial cells and unravel BGN as a new endogenous agonist of TLR3. Posttranslational BGN maturation by xylosyltransferase 1 (XYLT1) is required for TLR3 activation. Moreover, BGN induces the transdifferentiation of valvular interstitial cells into bone-forming osteoblasts through the TLR3-dependent induction of type I IFNs. It is intriguing that Bgn^-/-, Tlr3^-/-, and Ifnar1^-/- mice are protected against CAVD and display impaired bone formation. Meta-analysis of 2 large-scale cohorts with >300 000 individuals reveals that genetic variation at loci relevant to the XYLT1-BGN-TLR3-interferon-α/β receptor alpha chain (IFNAR) 1 pathway is associated with CAVD in humans.

CONCLUSIONS

This study identifies the BGN-TLR3-IFNAR1 axis as an evolutionarily conserved pathway governing calcification of the aortic valve and reveals a potential therapeutic target to prevent CAVD.

Multiancestry Genome-Wide Association Study of Aortic Stenosis Identifies Multiple Novel Loci in the Million Veteran Program

BACKGROUND

Calcific aortic stenosis (CAS) is the most common valvular heart disease in older adults and has no effective preventive therapies. Genome-wide association studies (GWAS) can identify genes influencing disease and may help prioritize therapeutic targets for CAS.

METHODS

We performed a GWAS and gene association study of 14 451 patients with CAS and 398 544 controls in the Million Veteran Program. Replication was performed in the Million Veteran Program, Penn Medicine Biobank, Mass General Brigham Biobank, BioVU, and BioMe, totaling 12 889 cases and 348 094 controls. Causal genes were prioritized from genome-wide significant variants using polygenic priority score gene localization, expression quantitative trait locus colocalization, and nearest gene methods. CAS genetic architecture was compared with that of atherosclerotic cardiovascular disease. Causal inference for cardiometabolic biomarkers in CAS was performed using Mendelian randomization and genome-wide significant loci were characterized further through phenome-wide association study.

RESULTS

We identified 23 genome-wide significant lead variants in our GWAS representing 17 unique genomic regions. Of the 23 lead variants, 14 were significant in replication, representing 11 unique genomic regions. Five replicated genomic regions were previously known risk loci for CAS (PALMD, TEX41, IL6, LPA, FADS) and 6 were novel (CEP85L, FTO, SLMAP, CELSR2, MECOM, CDAN1). Two novel lead variants were associated in non-White individuals (P<0.05): rs12740374 (CELSR2) in Black and Hispanic individuals and rs1522387 (SLMAP) in Black individuals. Of the 14 replicated lead variants, only 2 (rs10455872 [LPA], rs12740374 [CELSR2]) were also significant in atherosclerotic cardiovascular disease GWAS. In Mendelian randomization, lipoprotein(a) and low-density lipoprotein cholesterol were both associated with CAS, but the association between low-density lipoprotein cholesterol and CAS was attenuated when adjusting for lipoprotein(a). Phenome-wide association study highlighted varying degrees of pleiotropy, including between CAS and obesity at the FTO locus. However, the FTO locus remained associated with CAS after adjusting for body mass index and maintained a significant independent effect on CAS in mediation analysis.

CONCLUSIONS

We performed a multiancestry GWAS in CAS and identified 6 novel genomic regions in the disease. Secondary analyses highlighted the roles of lipid metabolism, inflammation, cellular senescence, and adiposity in the pathobiology of CAS and clarified the shared and differential genetic architectures of CAS with atherosclerotic cardiovascular diseases.

Sortilin enhances fibrosis and calcification in aortic valve disease by inducing interstitial cell heterogeneity

AIMS

Calcific aortic valve disease (CAVD) is the most common valve disease, which consists of a chronic interplay of inflammation, fibrosis, and calcification. In this study, sortilin (SORT1) was identified as a novel key player in the pathophysiology of CAVD, and its role in the transformation of valvular interstitial cells (VICs) into pathological phenotypes is explored.

METHODS AND RESULTS

An aortic valve (AV) wire injury (AVWI) mouse model with sortilin deficiency was used to determine the effects of sortilin on AV stenosis, fibrosis, and calcification. In vitro experiments employed human primary VICs cultured in osteogenic conditions for 7, 14, and 21 days; and processed for imaging, proteomics, and transcriptomics including single-cell RNA-sequencing (scRNA-seq). The AVWI mouse model showed reduced AV fibrosis, calcification, and stenosis in sortilin-deficient mice vs. littermate controls. Protein studies identified the transition of human VICs into a myofibroblast-like phenotype mediated by sortilin. Sortilin loss-of-function decreased in vitro VIC calcification. ScRNA-seq identified 12 differentially expressed cell clusters in human VIC samples, where a novel combined inflammatory myofibroblastic-osteogenic VIC (IMO-VIC) phenotype was detected with increased expression of SORT1, COL1A1, WNT5A, IL-6, and serum amyloid A1. VICs sequenced with sortilin deficiency showed decreased IMO-VIC phenotype.

CONCLUSION

Sortilin promotes CAVD by mediating valvular fibrosis and calcification, and a newly identified phenotype (IMO-VIC). This is the first study to examine the role of sortilin in valvular calcification and it may render it a therapeutic target to inhibit IMO-VIC emergence by simultaneously reducing inflammation, fibrosis, and calcification, the three key pathological processes underlying CAVD.

Interplay of Atherogenic Particle Number and Particle Size and the Risk of Coronary Heart Disease

BACKGROUND

We examined the interplay of apolipoprotein B (apoB) and LDL particle size, approximated by the LDL-cholesterol (LDL-C)/apoB ratio, on the risk of new-onset coronary heart disease (CHD).

METHODS

Participants without cardiovascular disease from the UK Biobank (UKB; n = 308 182), the Women's Health Study (WHS; n = 26 204), and the Framingham Heart Study (FHS; n = 2839) were included. Multivariable Cox models were used to assess the relationship between apoB and LDL-C/apoB ratio and incidence of CHD (14 994 events). Our analyses were adjusted for age, sex (except WHS), HDL-cholesterol (HDL-C), systolic blood pressure, antihypertensive treatment, diabetes, and smoking.

RESULTS

In all 3 studies, there was a strong positive correlation between apoB and LDL-C (correlation coefficients r = 0.80 or higher) and a weak inverse correlation of apoB with LDL-C/apoB ratio (-0.28 ≤ r ≤ -0.14). For all 3 cohorts, CHD risk was higher for higher levels of apoB. Upon multivariable adjustment, the association between apoB and new-onset CHD remained robust and statistically significant in all 3 cohorts with hazard ratios per 1 SD (95% CI): 1.24 (1.22-1.27), 1.33 (1.20-1.47), and 1.24 (1.09-1.42) for UKB, WHS, and FHS, respectively. However, the association between LDL-C/apoB and CHD was statistically significant only in the FHS cohort: 0.78 (0.64-0.94).

CONCLUSIONS

Our analysis confirms that apoB is a strong risk factor for CHD. However, given the null association in 2 of the 3 studies, we cannot confirm that cholesterol-depleted LDL particles are substantially more atherogenic than cholesterol-replete particles. These results lend further support to routine measurement of apoB in clinical care.

Sex Differences in Clopidogrel Effects Among Young Patients With Acute Coronary Syndrome: A Role for Genetics?

Background

Poorer health outcomes experienced by young women with acute coronary syndrome may be related to sex differences in the safety and efficacy of antiplatelet agents, such as clopidogrel. Polymorphisms in drug metabolism enzyme (cytochrome P450 [CYP] family) genes are independent factors for the variability in response to clopidogrel. However, a sex-specific impact of genetics to explain worse clinical outcomes in women has not been explored extensively. Therefore, our objective was to determine whether an interaction of sex with CYP variants occurs among users of clopidogrel, and if so, its impact on 1-year adverse clinical outcomes.

Methods

We used data from a combined cohort of 2272 patients (median age 49 years; 56% female) hospitalized for acute coronary syndrome. We examined interactions between sex and CYP variants among clopidogrel users at admission and discharge to assess associations with 1-year readmission due to cardiac events.

Results

The case-only analysis of 177 participants on clopidogrel at the time of presentation showed that the risk of an atherothrombotic event was greater in female carriers of the CYP2C9∗3 loss-of-function allele (odds ratio = 3.77, 95% confidence interval = 1.54-9.24). The results of the multivariable logistic regression model for users of clopidogrel at discharge (n = 1733) indicated that women had significantly higher risk of atherothrombotic readmissions at 1 year (odds ratio = 1.55, 95% confidence interval = 1.16-2.07), compared to the risk for men, but the loss-of-function alleles, either individually or through a genetic risk score, were not associated with 1-year readmissions.

Conclusion

This study highlights the need for an improved understanding of the role of sex-by-gene interactions in causing sex differences in drug metabolism.

Physiological Bases for the Superiority of Apolipoprotein B Over Low-Density Lipoprotein Cholesterol and Non-High-Density Lipoprotein Cholesterol as a Marker of Cardiovascular Risk

In 2019, the European Society of Cardiology/European Atherosclerosis Society stated that apolipoprotein B (apoB) was a more accurate marker of cardiovascular risk than low-density lipoprotein cholesterol (LDL-C) and non-high-density lipoprotein cholesterol. Since then, the evidence has continued to mount in favor of apoB. This review explicates the physiological mechanisms responsible for the superiority of apoB as a marker of the cardiovascular risk attributable to the atherogenic apoB lipoprotein particles chylomicron remnants, very low-density lipoprotein, and low-density lipoprotein particles. First, the nature and relative numbers of these different apoB particles will be outlined. This will make clear why low-density lipoprotein particles are almost always the major determinants of cardiovascular risk and why the concentrations of triglycerides and LDL-C may obscure this relation. Next, the mechanisms that govern the number of very low-density lipoprotein and low-density lipoprotein particles will be outlined because, except for dysbetalipoproteinemia, the total number of apoB particles determines cardiovascular risk, Then, the mechanisms that govern the cholesterol mass within very low-density lipoprotein and low-density lipoprotein particles will be reviewed because these are responsible for the discordance between the mass of cholesterol within apoB particles, measured either as LDL-C or non-high-density lipoprotein cholesterol, and the number of apoB particles measured as apoB, which creates the superior predictive power of apoB over LDL-C and non-high-density lipoprotein cholesterol. Finally, the major apoB dyslipoproteinemias will be briefly outlined. Our objective is to provide a physiological framework for health care givers to understand why apoB is a more accurate marker of cardiovascular risk than LDL-C or non-high-density lipoprotein cholesterol.

High-Density Lipoprotein and Long-Term Incidence and Progression of Aortic Valve Calcification: The Multi-Ethnic Study of Atherosclerosis

BACKGROUND

Aortic valve calcification (AVC) shares pathological features with atherosclerosis. Lipoprotein components have been detected in aortic valve tissue, including HDL (high-density lipoprotein). HDL measures have inverse associations with cardiovascular disease, but relationships with long-term AVC progression are unclear. We investigated associations of HDL cholesterol, HDL-particle number and size, apoC3-defined HDL subtypes, and, secondarily, CETP (cholesteryl ester transfer protein) mass and activity, with long-term incidence and progression of AVC.

METHODS

We used linear mixed-effects models to evaluate the associations of baseline HDL indices with AVC. AVC was quantified by Agatston scoring of up to 3 serial computed tomography scans over a median of 8.9 (maximum 11.2) years of follow-up in the Multi-Ethnic Study of Atherosclerosis (n=6784).

RESULTS

After adjustment, higher concentrations of HDL-C (high-density lipoprotein cholesterol), HDL-P (HDL particles), large HDL-P, and apoC3-lacking HDL-C were significantly associated with lower incidence/progression of AVC. Neither small or medium HDL-P nor apoC3-containing HDL-C was significantly associated with AVC incidence/progression. When included together, a significant association was observed only for HDL-C, but not for HDL-P. Secondary analyses showed an inverse relationship between CETP mass, but not activity, and AVC incidence/progression. In exploratory assessments, inverse associations for HDL-C, HDL-P, large HDL-P, and apoC3-lacking HDL with AVC incidence/progression were more pronounced for older, male, and White participants. ApoC3-containing HDL-C only showed a positive association with AVC in these subgroups.

CONCLUSIONS

In a multiethnic population, HDL-C, HDL-P, large HDL-P, and apoC3-lacking HDL-C were inversely associated with long-term incidence and progression of AVC. Further investigation of HDL composition and mechanisms could be useful in understanding pathways that slow AVC.

Impact of Outcome Definitions on Cardiovascular Risk Prediction in a Contemporary Primary Prevention Population

BACKGROUND

Estimation of an individual's cardiovascular disease (CVD) risk may enhance risk discussion and treatment decisions. Yet, common cardiovascular outcomes such as heart failure or coronary revascularization are not included in the estimation of atherosclerotic cardiovascular disease (ASCVD) risk. Our objective was to determine the incidence of ASCVD in a contemporary primary prevention population with more than 10 years of follow-up, and how incidence estimates change when incorporating additional cardiovascular endpoints.

METHODS

We used the population-level CANHEART (Cardiovascular Health in Ambulatory Care Research Team) database of all Ontario residents alive January 1, 2008, aged 30-99 years, and with no prior history of cardiovascular disease. Individuals were followed to December 31, 2019 for incident first and recurrent cardiovascular events. ASCVD outcomes were defined by hospitalizations for myocardial infarction, stroke and circulatory death, while global CVD outcomes also included hospitalizations for unstable angina, transient ischemic attacks, peripheral arterial disease, out-of-hospital cardiac arrests, heart failure and coronary revascularization.

RESULTS

Among 7496 165 individuals free of cardiovascular disease, their mean age was 50 years (SD: 13.9 years) and 52.3% were women. After 11 years of follow-up, the rate of an incident ASCVD event was 3.95 per 1000 person-years while the rate of a global CVD event was almost doubled at 6.67 per 1000 person-years. The most common additional first manifestations of CVD were heart failure which accounted for 12.0% of additional events and coronary revascularization which accounted for 12.7%. When considering first and recurrent events, the rate of ASCVD was 5.20 per 1000 person-years while the rate of all global CVD events was more than double at 10.90 per 1000 person-years. This was mainly due to a higher proportion of recurrent heart failure (13.7%) and coronary revascularization (23.2%) events.

CONCLUSIONS

ASCVD accounts for just over half of all preventable first cardiovascular events and even fewer first and recurrent cardiovascular events in contemporary practice. Estimating broader CVD endpoints may enhance risk-discussions with patients and improve informed decision-making.

An adverse lipoprotein phenotype-hypertriglyceridaemic hyperapolipoprotein B-and the long-term risk of type 2 diabetes: a prospective, longitudinal, observational cohort study

BACKGROUND

This study examines the risk of new-onset diabetes in patients with hypertriglyceridaemic hyperapolipoprotein B (high triglycerides, high apolipoprotein B [apoB], low LDL cholesterol to apoB ratio, and low HDL cholesterol). The aim was to establish whether this lipoprotein phenotype identified a substantial group at high risk of developing diabetes over the next 20 years.

METHODS

In this prospective, longitudinal, observational cohort study, we used data from the Framingham Offspring cohort (recruited in Framingham, MA, USA). Participants were aged 40-69 years and free of diabetes and cardiovascular disease at a baseline examination done between April, 1987, and November, 1991, and were followed up until March, 2014. Cox proportional hazards regression with hierarchical adjustment for age and sex, waist circumference, and fasting blood glucose were used to model the relationship between each lipid marker and incident diabetes, as well as the relationship between hypertriglyceridaemic hyperapoB (defined as values greater than sample medians of triglycerides and apoB, and less than medians of HDL cholesterol and LDL cholesterol to apoB ratio) and incident diabetes.

FINDINGS

Of 3446 individuals aged 40-69 years who completed baseline examination, 2515 participants were eligible and included in all analyses. During median 21·1 years (IQR 11·1-23·1) of follow-up, 402 (16·0%) individuals developed diabetes. Age (p=0·032), waist circumference (p<0·0001), fasting blood glucose (p<0·0001), and natural logarithm-transformed triglycerides (p<0·0001) were associated with new-onset diabetes, as were apoB (p=0·0016), LDL cholesterol to apoB ratio (p=0·0018), and HDL cholesterol (p=0·0016) when added to this model. The age and sex-adjusted incidence of diabetes in the hypertriglyceridaemic hyperapoB group was 32·4% (95% CI 27·8-37·7) versus 5·5% (3·5-8·6) in the optimal lipid phenotype group and 15·5% (13·5-17·7) in the mixed lipid phenotype group. The fully adjusted hazard ratio, including glucose and waist circumference, for individuals with hypertriglyceridaemic hyperapoB was 3·30 (95% CI 2·06-5·30; p=0·0008) and for mixed lipid phenotype was 2·17 (1·38-3·40; p<0·0001) compared with those with the optimal lipid phenotype.

INTERPRETATION

Our findings suggest that individuals with hypertriglyceridaemic hyperapoB are at high risk of new-onset diabetes and might benefit from intensive measures to prevent diabetes. The association between this phenotype and incident diabetes is consistent with a pro-diabetic effect due to increased clearance of apoB particles from plasma, which could injure pancreatic islet cells. This mechanism might explain the increased risk of diabetes with statin therapy.

FUNDING

Doggone Foundation.

Key Questions About Familial Hypercholesterolemia: JACC Review Topic of the Week

Familial hypercholesterolemia (FH) is characterized as a monogenic, autosomal dominant disorder, producing severe hypercholesterolemia within families due to causal variants within genes regulating the low-density lipoprotein receptor pathway. Demonstration of a causal variant is widely accepted as evidence of substantially higher cardiovascular risk. However, recent large-scale population studies challenge this characterization of FH, which appears to account for only a minor portion of those with severe hypercholesterolemia. Moreover, a substantial portion of FH variant positive patients do not have marked hypercholesterolemia. These discordances raise doubt as to how FH should be defined and how the concentration of low-density lipoprotein in plasma is regulated in individuals with and without FH. Moreover, review of the evidence suggests the impact of an FH causal variant on cardiovascular risk may be less than previously accepted and that all patients with severe hypercholesterolemia should be prioritized for therapy and family screening.

Atherothrombotic factors and atherosclerotic cardiovascular events: the multi-ethnic study of atherosclerosis

AIMS

Traditional atherosclerotic cardiovascular disease (ASCVD) risk factors fail to address the full spectrum of the complex interplay of atherosclerotic and atherothrombotic factors integral to ASCVD events. This study sought to examine the association between atherothrombotic biomarkers and ASCVD events.

METHODS AND RESULTS

The association between atherothrombotic biomarkers and 877 ASCVD events with and without adjustment for traditional risk factors was evaluated via Cox proportional hazards models and factor analysis in 5789 Multi-Ethnic Study of Atherosclerosis participants over a median follow-up of 14.7 years. Factor analysis accounted for multidimensional relationship and shared variance among study biomarkers, which identified two new variables: a thrombotic factor (Factor 1), principally defined by shared variance in fibrinogen, plasmin-antiplasmin complex, factor VIII, D-dimer, and lipoprotein(a), and a fibrinolytic factor (Factor 2), principally defined by shared variance of plasminogen and oxidized phospholipids on plasminogen. In a model including both factors, the thrombotic factor was associated with the higher risk of ASCVD events [hazard ratio (HR) 1.57, 95% confidence interval (CI) 1.45, 1.70], while the fibrinolytic factor was associated with the lower risk of ASCVD events (HR 0.76, 95% CI 0.70, 0.82), with estimated ASCVD free survival highest for low atherothrombotic Factor 1 and high atherothrombotic Factor 2.

CONCLUSION

Two atherothrombotic factors, one representative of thrombotic propensity and the other representative of fibrinolytic propensity, were significantly and complementarily associated with incident ASCVD events, remained significantly associated with incident ASCVD after controlling for traditional risk factors, and have promise for identifying patients at high ASCVD event risk specifically due to their atherothrombotic profile.

Risk Markers for Limited Coronary Artery Calcium in Persons With Significant Aortic Valve Calcium (From the Multi-ethnic Study of Atherosclerosis)

The early stages of aortic valve calcification (AVC) and coronary artery calcification (CAC) include shared ASCVD risk factors, yet there is considerable heterogeneity between the burden of AVC, and CAC. We sought to identify the markers associated with limited CAC among persons with significant AVC. There were 325 participants from the Multi-Ethnic Study of Atherosclerosis without clinical ASCVD and with AVC ≥100 Agatston units (AU) at Visit 1. Multivariable-adjusted prevalence ratios for limited CAC (0 to 99 AU) were calculated using modified Poisson regression. Participants had a mean age of 72.1 years, median AVC score of 209, and 34% were women. A total of 133 (41%) participants had CAC <100, of whom 46/133 had CAC = 0. Younger age (PR = 1.40, 95% CI: 1.22 to 1.62, per 10-years), female gender (PR = 1.68, 95% CI: 1.28 to 2.20), and low 10-year ASCVD risk (PR = 2.30, 95% CI: 1.85 to 2.85) were most strongly associated with limited CAC. Neither a normal lipoprotein(a) nor normal measures of inflammation were significantly associated with limited CAC. Lower serum phosphate (PR = 1.15, 95% CI: 1.01 to 1.31; per 0.5 mg/dl lower) and calcium-phosphate product (PR = 1.16, 95% CI: 1.02 to 1.34; per SD lower) were associated with an approximately 15% higher prevalence of limited CAC. In conclusion, more than 40% of persons with significant AVC had CAC. Beyond traditional risk factors, lower serum phosphate, and lower calcium-phosphate product were associated with a higher prevalence of limited CAC.

Utility of Genetically Predicted Lp(a) (Lipoprotein [a]) and ApoB Levels for Cardiovascular Risk Assessment

BACKGROUND

Current lipid guidelines suggest measurement of Lp(a) (lipoprotein[a]) and ApoB (apolipoprotein B) for atherosclerotic cardiovascular disease risk assessment. Polygenic risk scores (PRSs) for Lp(a) and ApoB may identify individuals unlikely to have elevated Lp(a) or ApoB and thus reduce such suggested testing.

METHODS

PRSs were developed using least absolute shrinkage and selection operator regression among 273 222 and 356 958 UK Biobank participants of white British ancestry for Lp(a) and ApoB, respectively, and validated in separate sets of 60 771 UK Biobank and 15 050 European Prospective Investigation into Cancer and Nutrition-Norfolk participants. We then assessed the proportion of participants who, based on these PRSs, were unlikely to benefit from Lp(a) or ApoB measurements, according to current lipid guidelines.

RESULTS

In the UK Biobank and European Prospective Investigation into Cancer and Nutrition-Norfolk cohorts, the area under the receiver operating curve for the PRS-predicted Lp(a) and ApoB to identify individuals with elevated Lp(a) and ApoB was at least 0.91 (95% CI, 0.90-0.92) and 0.74 (95% CI, 0.73-0.75), respectively. The Lp(a) PRS and measured Lp(a) showed comparable association with atherosclerotic cardiovascular disease incidence, whereas the ApoB PRS was in general less predictive of atherosclerotic cardiovascular disease risk than measured ApoB. In the context of the European Society of Cardiology/European Atherosclerosis Society lipid guidelines, at a 95% sensitivity to identify individuals with elevated Lp(a) and ApoB levels, at least 54% of Lp(a) and 24% of ApoB testing could be reduced by prescreening with a PRS while maintaining a low false-negative rate.

CONCLUSIONS

A substantial proportion of suggested testing for elevated Lp(a) and a modest proportion of testing for elevated ApoB could potentially be reduced by prescreening individuals with PRSs.

Progress and Research Priorities in Imaging Genomics for Heart and Lung Disease: Summary of an NHLBI Workshop

Imaging genomics is a rapidly evolving field that combines state-of-the-art bioimaging with genomic information to resolve phenotypic heterogeneity associated with genomic variation, improve risk prediction, discover prevention approaches, and enable precision diagnosis and treatment. Contemporary bioimaging methods provide exceptional resolution generating discrete and quantitative high-dimensional phenotypes for genomics investigation. Despite substantial progress in combining high-dimensional bioimaging and genomic data, methods for imaging genomics are evolving. Recognizing the potential impact of imaging genomics on the study of heart and lung disease, the National Heart, Lung, and Blood Institute convened a workshop to review cutting-edge approaches and methodologies in imaging genomics studies, and to establish research priorities for future investigation. This report summarizes the presentations and discussions at the workshop. In particular, we highlight the need for increased availability of imaging genomics data in diverse populations, dedicated focus on less common conditions, and centralization of efforts around specific disease areas.

Clinical reasoning and prevention of cardiovascular disease

All the major lipid prevention guidelines agree that the 10-year risk of a cardiovascular event should be the primary method to select individuals for statin prevention of a cardiovascular event. They also all rely on LDL cholesterol (LDL-C) as the primary metric to monitor lipid lowering therapy. These two principles form the major instruments on which primary prevention of cardiovascular disease is based worldwide. Their application is based on decades of prospective observational studies and large numbers of randomized clinical trials. Their development and application are milestones in medical progress. But are there limits, which were unseen and unintended, that need to be identified and overcome so that cardiovascular prevention can improve? Based on new insights and old knowledge, this Viewpoint will apply Clinical Reasoning, the process by which we integrate all the relevant knowledge, including the knowledge we have gained from physiology, pathology, epidemiology, metabolism, experimental models of disease, and our clinical experience as well as the results of randomized clinical trials to the analysis of a single case to answer these questions. Moreover, this Viewpoint will challenge the universal practice of relating the clinical outcomes of the major successful lipid lowering trials to the decrease in LDL-C and argue that cardiovascular prevention should move from the Risk model to the Causal Benefit model. This Viewpoint will be framed around a single case because, as caregivers, we make decisions case by case and because, as caregivers, the individual is the true object of our concern.

2021 Canadian Cardiovascular Society Guidelines for the Management of Dyslipidemia for the Prevention of Cardiovascular Disease in Adults

The 2021 guidelines primary panel selected clinically relevant questions and produced updated recommendations, on the basis of important new findings that have emerged since the 2016 guidelines. In patients with clinical atherosclerosis, abdominal aortic aneurysm, most patients with diabetes or chronic kidney disease, and those with low-density lipoprotein cholesterol ≥ 5 mmol/L, statin therapy continues to be recommended. We have introduced the concept of lipid/lipoprotein treatment thresholds for intensifying lipid-lowering therapy with nonstatin agents, and have identified the secondary prevention patients who have been shown to derive the largest benefit from intensification of therapy with these agents. For all other patients, we emphasize risk assessment linked to lipid/lipoprotein evaluation to optimize clinical decision-making. Lipoprotein(a) measurement is now recommended once in a patient's lifetime, as part of initial lipid screening to assess cardiovascular risk. For any patient with triglycerides ˃ 1.5 mmol/L, either non-high-density lipoprotein cholesterol or apolipoprotein B are the preferred lipid parameter for screening, rather than low-density lipoprotein cholesterol. We provide updated recommendations regarding the role of coronary artery calcium scoring as a clinical decision tool to aid the decision to initiate statin therapy. There are new recommendations on the preventative care of women with hypertensive disorders of pregnancy. Health behaviour modification, including regular exercise and a heart-healthy diet, remain the cornerstone of cardiovascular disease prevention. These guidelines are intended to provide a platform for meaningful conversation and shared-decision making between patient and care provider, so that individual decisions can be made for risk screening, assessment, and treatment.

Association of FADS1/2 Locus Variants and Polyunsaturated Fatty Acids With Aortic Stenosis

Question

Can genetic analysis identify additional causes of aortic stenosis?

Findings

In this genome-wide association study of 44 703 participants, each copy of a FADS1/2 (fatty acid desaturase) genetic variant was associated with a 13% decrease in the odds of aortic stenosis. Results of a meta-analysis with 7 replication cohorts showed genome-wide significance, with biomarker and mendelian randomization analyses implicating elevated ω-6 fatty acid levels as having a potentially causal association with aortic valve calcium and aortic stenosis.

Meaning

These findings demonstrate that the FADS1/2 locus and fatty acid biosynthesis are associated with aortic stenosis and should be examined further for their potential as therapeutic targets.

Importance

Aortic stenosis (AS) has no approved medical treatment. Identifying etiological pathways for AS could identify pharmacological targets.

Objective

To identify novel genetic loci and pathways associated with AS.

Design, Setting, and Participants

This genome-wide association study used a case-control design to evaluate 44 703 participants (3469 cases of AS) of self-reported European ancestry from the Genetic Epidemiology Research on Adult Health and Aging (GERA) cohort (from January 1, 1996, to December 31, 2015). Replication was performed in 7 other cohorts totaling 256 926 participants (5926 cases of AS), with additional analyses performed in 6942 participants from the Cohorts for Heart and Aging Research in Genomic Epidemiology (CHARGE) Consortium. Follow-up biomarker analyses with aortic valve calcium (AVC) were also performed. Data were analyzed from May 1, 2017, to December 5, 2019.

Exposures

Genetic variants (615 643 variants) and polyunsaturated fatty acids (ω-6 and ω-3) measured in blood samples.

Main Outcomes and Measures

Aortic stenosis and aortic valve replacement defined by electronic health records, surgical records, or echocardiography and the presence of AVC measured by computed tomography.

Results

The mean (SD) age of the 44 703 GERA participants was 69.7 (8.4) years, and 22 019 (49.3%) were men. The rs174547 variant at the FADS1/2 locus was associated with AS (odds ratio [OR] per C allele, 0.88; 95% CI, 0.83-0.93; P = 3.0 × 10⁻⁶), with genome-wide significance after meta-analysis with 7 replication cohorts totaling 312 118 individuals (9395 cases of AS) (OR, 0.91; 95% CI, 0.88-0.94; P = 2.5 × 10⁻⁸). A consistent association with AVC was also observed (OR, 0.91; 95% CI, 0.83-0.99; P = .03). A higher ratio of arachidonic acid to linoleic acid was associated with AVC (OR per SD of the natural logarithm, 1.19; 95% CI, 1.09-1.30; P = 6.6 × 10⁻⁵). In mendelian randomization, increased FADS1 liver expression and arachidonic acid were associated with AS (OR per unit of normalized expression, 1.31 [95% CI, 1.17-1.48; P = 7.4 × 10⁻⁶]; OR per 5–percentage point increase in arachidonic acid for AVC, 1.23 [95% CI, 1.01-1.49; P = .04]; OR per 5–percentage point increase in arachidonic acid for AS, 1.08 [95% CI, 1.04-1.13; P = 4.1 × 10⁻⁴]).

Conclusions and Relevance

Variation at the FADS1/2 locus was associated with AS and AVC. Findings from biomarker measurements and mendelian randomization appear to link ω-6 fatty acid biosynthesis to AS, which may represent a therapeutic target.

Calibration and discrimination of the Framingham Risk Score and the Pooled Cohort Equations

BACKGROUND

Although accurate risk prediction is essential in guiding treatment decisions in primary prevention of atherosclerotic cardiovascular disease, the accuracy of the Framingham Risk Score (recommended by a Canadian guideline) and the Pooled Cohort Equations (recommended by US guidelines) has not been assessed in a large contemporary Canadian population. Our primary objective was to assess the calibration and discrimination of the Framingham Risk Score and Pooled Cohort Equations in Ontario, Canada.

METHODS

We conducted an observational study involving Ontario residents aged 40 to 79 years, without a history of atherosclerotic cardiovascular disease, who underwent cholesterol testing and blood pressure measurement from Jan. 1, 2010, to Dec. 31, 2014. We compared predicted event rates generated by the Framingham Risk Score and the Pooled Cohort Equations with observed event rates at 5 years using linkages from validated administrative databases.

RESULTS

Our study cohort included 84 617 individuals (mean age 56.3 yr, 56.9% female). Over a maximum follow-up period of 5 years, we observed 2162 (2.6%) events according to the outcome definition of the Framingham Risk Score, and 1224 (1.4%) events according to the outcome definition of the Pooled Cohort Equations. The predicted event rate of 5.78% by the Framingham Risk Score and 3.51% by the Pooled Cohort Equations at 5 years overestimated observed event rates by 101% and 115%, respectively. The degree of overestimation differed by age and ethnicity. The C statistics for the Framingham Risk Score (0.74) and Pooled Cohort Equations (0.73) were similar.

INTERPRETATION

The Framingham Risk Score and Pooled Cohort Equations significantly overpredicted the actual risks of atherosclerotic cardiovascular disease events in a large population from Ontario. Our finding suggests the need for further refinement of cardiovascular disease risk prediction scores to suit the characteristics of a multiethnic Canadian population.

Genome-Wide Association Study Highlights APOH as a Novel Locus for Lipoprotein(a) Levels-Brief Report

OBJECTIVE

Lp(a) (lipoprotein[a]) is an independent risk factor for cardiovascular diseases and plasma levels are primarily determined by variation at the LPA locus. We performed a genome-wide association study in the UK Biobank to determine whether additional loci influence Lp(a) levels. Approach and Results: We included 293 274 White British individuals in the discovery analysis. Approximately 93 095 623 variants were tested for association with natural log-transformed Lp(a) levels using linear regression models adjusted for age, sex, genotype batch, and 20 principal components of genetic ancestry. After quality control, 131 independent variants were associated at genome-wide significance (P≤5×10-8). In addition to validating previous associations at LPA, APOE, and CETP, we identified a novel variant at the APOH locus, encoding β2GPI (beta2-glycoprotein I). The APOH variant rs8178824 was associated with increased Lp(a) levels (β [95% CI] [ln nmol/L], 0.064 [0.047-0.081]; P=2.8×10-13) and demonstrated a stronger effect after adjustment for variation at the LPA locus (β [95% CI] [ln nmol/L], 0.089 [0.076-0.10]; P=3.8×10-42). This association was replicated in a meta-analysis of 5465 European-ancestry individuals from the Framingham Offspring Study and Multi-Ethnic Study of Atherosclerosis (β [95% CI] [ln mg/dL], 0.16 [0.044-0.28]; P=0.0071).

CONCLUSIONS

In a large-scale genome-wide association study of Lp(a) levels, we identified APOH as a novel locus for Lp(a) in individuals of European ancestry. Additional studies are needed to determine the precise role of β2GPI in influencing Lp(a) levels as well as its potential as a therapeutic target.

Intersecting Genetics of Frailty and Cardiovascular Disease

OBJECTIVES

To determine the genetic correlates of physical frailty and sarcopenia, focusing on single nucleotide polymorphisms (SNPs) in genome-wide association studies (GWAS), and to explore the genetic overlap of frailty with cardiovascular disease (CVD) and its risk factors.

METHODS

PubMed was systematically searched for GWAS studies investigating the association between SNPs and objective measures of physical frailty or sarcopenia. SNPs were retained if they were associated with one of the phenotypes of interest by a p-value of 5.0x10-8 or less.

RESULTS

Ten studies were included, with a total of 237 SNPs in 181 genes being associated with physical frailty or sarcopenia; as measured by handgrip strength or lean (muscle) mass. These genes were cross-referenced in the GWAS Catalog, and many of them were found to be associated with CVD or metabolic syndrome.

CONCLUSIONS

Evidence from GWAS has shown that frailty is associated with common genetic polymorphisms. Many of these polymorphisms have been implicated in CVD, supporting the hypothesis of a shared pathophysiology between these entities. Future studies are eagerly anticipated to map out the mechanistic links and discover therapeutic targets and novel biomarkers for frailty.

A Patient-Led Referral Strategy for Cardiovascular Screening of Family and Household Members at the Time of Cardiac Intensive Care Unit Admission

Background

Screening relatives of patients with ischemic heart disease can identify over half of the population with poorly controlled cardiovascular (CV) risk factors. Family or household members (FMs) may be highly motivated to undergo CV primary prevention screening at the time of their relative’s admission to the Cardiovascular Intensive Care Unit (CICU).

Methods

Patients aged ≤ 70 years admitted to a tertiary CICU for an acute coronary event were given a letter to refer FMs for CV screening. Interested FMs underwent CV risk-factor assessment and primary prevention counselling. The objectives were to identify FMs with an intermediate or high modified 10-year Framingham risk score (FRS) and to evaluate whether a family-oriented primary prevention strategy improved CV risk.

Results

There were 51 CV probands who referred 101 FMs (62 family, 39 household; mean age: 44.8 ± 15.3; 65 (64.4%) female) for screening. One-third of FMs aged ≥ 30 years (n = 28 of 84; 32.1%) had a new diagnosis of either hypertension, diabetes, or dyslipidemia. Nearly half of FMs (n = 38; 45.2%) had an intermediate or high modified Framingham 10-year CV risk. In FMs aged ≥ 30 years attending the 6-month follow-up (51 of 84; 60.7%), the mean FRS decreased by 4.6% (from 13.2% ± 12.7 to 8.6% ± 10.0, P < 0.001), and 30.4% (7 of 23) of FMs had a low FRS who had initially had an intermediate or high FRS.

Conclusions

A patient-led referral strategy at the time of CICU admission led to a high rate of identification of previously undiagnosed CV risk factors in FMs. Implementing a similar referral program on a larger scale could identify a considerable burden of CV risk.

Genome-wide association meta-analysis in 652,134 participants identifies 9 novel susceptibility loci for aortic stenosis

Background

Aortic stenosis (AS) is the most common form of incident valvular heart disease. While valve replacement is effective, the absence of an approved medical therapy provides no alternatives to patients with contraindications or mild disease. An improved understanding of the genetics of AS could identify targets for pharmacological intervention.

Methods

An inverse variance-weighted, fixed effects meta-analysis of the association of 11,591,806 variants with AS was undertaken using data from 10 European cohorts totalling 652,134 participants (13,758 cases of AS). We queried publicly available datasets to characterize the functional consequences of genome-wide significant variants, conducted a phenome-wide association study to assess their association with other outcomes, and constructed polygenic risk scores to examine their association with AS. We also performed gene- and gene-set enrichment analyses, estimated genetic correlation with cardiovascular traits, and assessed whether five lipid or immunological biomarkers were causally associated with AS using Mendelian randomization.

Results

Eighteen independent variants at 16 loci attained genome-wide significance in the meta-analysis, including variants at all seven previously reported loci. Many of the significant variants were intronic or intergenic, and the phenome-wide association study revealed extensive pleiotropy with apolipoprotein B, C-reactive protein, and other cardiovascular and immunological traits. A weighted polygenic risk score composed of the 18 variants was strongly associated with AS (adjusted OR per SD, 1.38; 95% CI, 1.33 to 1.44; p=4.6×10–57), and improved the discriminatory ability for AS when added to a model that contained clinical risk factors (difference in the area under the curve p=2.0×10–11). Gene-based approaches indicated higher IL6R expression in the blood among AS cases compared to controls (p=3.1×10–6), and the association of LDLR with AS (p=2.3×10–10). Gene set analyses revealed that genes bound by the transcription factor TCF7 or micro-RNAs miR-21, miR-219, miR-491, and miR-19 were differentially expressed in the liver depending on AS status (p≤5.7×10–4), suggesting disease development may be mediated by tissue-specific transcriptional and post-transcriptional regulation. Mendelian randomization supported a causal association of five lipid and immunological biomarkers with AS, including low-density lipoprotein cholesterol (OR per mmol/L, 1.61; 95% CI, 1.48 to 1.75; p=1.3×10–30).

Conclusions

Evidence from large-scale genetic analyses indicate that lipid metabolism, inflammation, and calcification are key contributors to AS.

Funding Acknowledgement

Type of funding source: Public Institution(s). Main funding source(s): Canadian Institutes of Health Research, National Institutes of Health

Primary Prevention Trial Designs Using Coronary Imaging: A National Heart, Lung, and Blood Institute Workshop

Coronary artery calcium (CAC) is considered a useful test for enhancing risk assessment in the primary prevention setting. Clinical trials are under consideration. The National Heart, Lung, and Blood Institute convened a multidisciplinary working group on August 26 to 27, 2019, in Bethesda, Maryland, to review available evidence and consider the appropriateness of conducting further research on coronary artery calcium (CAC) testing, or other coronary imaging studies, as a way of informing decisions for primary preventive treatments for cardiovascular disease. The working group concluded that additional evidence to support current guideline recommendations for use of CAC in middle-age adults is very likely to come from currently ongoing trials in that age group, and a new trial is not likely to be timely or cost effective. The current trials will not, however, address the role of CAC testing in younger adults or older adults, who are also not addressed in existing guidelines, nor will existing trials address the potential benefit of an opportunistic screening strategy made feasible by the application of artificial intelligence. Innovative trial designs for testing the value of CAC across the lifespan were strongly considered and represent important opportunities for additional research, particularly those that leverage existing trials or other real-world data streams including clinical computed tomography scans. Sex and racial/ethnic disparities in cardiovascular disease morbidity and mortality, and inclusion of diverse participants in future CAC trials, particularly those based in the United States, would enhance the potential impact of these studies.

Risks of Incident Cardiovascular Disease Associated With Concomitant Elevations in Lipoprotein(a) and Low-Density Lipoprotein Cholesterol-The Framingham Heart Study

Background

Elevated lipoprotein(a) is a well‐established risk factor for atherosclerotic vascular disease but is not measured in routine clinical care. Screening of high lipoprotein(a) in individuals with moderate elevations of low‐density lipoprotein cholesterol (LDL‐C) may identify individuals at high risk of cardiovascular disease.

Methods and Results

We examined 2606 Framingham Offspring participants (median age, 54 years; 45% men) prospectively with a median follow‐up of 15 years (n=392 incident cardiovascular events). Individuals with higher (≥100 nmol/L) versus lower lipoprotein(a) were divided into groups based on LDL‐C <135 mg/dL versus ≥135 mg/dL. In Cox models, after adjustment for known risk factors, high lipoprotein(a) (≥100 nmol/L) and LDL‐C ≥135 mg/dL were each significant predictors of cardiovascular disease (LDL‐C ≥135 mg/dL: hazard ratio [HR], 1.34; 95% CI, 1.09–1.64; P=0.006; high lipoprotein (a): HR, 1.31; 95% CI, 1.03–1.66; P=0.026). Across the groups of high/low lipoprotein (a) and LDL‐C ≥135 mg/dL or <135 mg/dL, the absolute cardiovascular disease risks at 15 years were 22.6% (high lipoprotein(a)/LDL‐C ≥135 mg/dL, n=248), 17.3% (low lipoprotein(a)/LDL‐C ≥135 mg/dL, n=758), 12.7% (high lipoprotein(a)/LDL‐C <135 mg/dL, n=275) and 11.5% (low lipoprotein(a)/LDL‐C <135 mg/dL, n=1328, reference group). Among individuals with LDL‐C ≥135 mg/dL, those with high lipoprotein(a) had a 43% higher risk (HR, 1.43; 95% CI, 1.05–1.97; P=0.02). Presence of high lipoprotein(a) with moderate LDL‐C levels (135–159 mg/dL) yielded absolute risks equivalent to those with LDL‐C ≥160 mg/dL (23.5%, 95% CI, 17.4%–31.3%; and 20.7%, 95% CI, 16.8%–25.3%, respectively).

Conclusions

Concomitant elevation of LDL‐C ≥135 mg/dL and lipoprotein(a) ≥100 nmol/L is associated with a high absolute risk of incident cardiovascular disease. lipoprotein(a) measurement in individuals with moderate elevations in LDL‐C, who do not otherwise meet criteria for statins, may identify individuals at high cardiovascular risk.

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.

Cost-effectiveness of Low-density Lipoprotein Cholesterol Level-Guided Statin Treatment in Patients With Borderline Cardiovascular Risk

Importance

American College of Cardiology/American Heart Association cholesterol guidelines prioritize primary prevention statin therapy based on 10-year absolute risk (AR10) of atherosclerotic cardiovascular disease (ASCVD). However, given the same AR10, patients with higher levels of low-density lipoprotein cholesterol (LDL-C) experience greater absolute risk reduction from statin therapy.

Objectives

To estimate the cost-effectiveness of expanding preventive statin treatment eligibility from standard care to patients at borderline risk (AR10, 5.0%-7.4%) for ASCVD and with high levels of LDL-C and to estimate cost-effectiveness of statin treatment across ranges of age, sex, AR10, and LDL-C levels.

Design, Setting, and Participants

This study evaluated 100 simulated cohorts, each including 1 million ASCVD-free survey respondents (50% men and 50% women) aged 40 years at baseline. Cohorts were created by probabilistic sampling of the 1999-2014 US National Health and Nutrition Examination Surveys from the perspective of the US health care sector. The CVD Policy Model microsimulation version projected lifetime health and cost outcomes. Probability of first-ever coronary heart disease or stroke event was estimated by analysis of 6 pooled US cohort studies and recalibrated to match contemporary event rates. Other model variables were derived from national surveys, meta-analyses, and published literature. Data were analyzed from May 15, 2018, through June 10, 2019.

Exposures

Four statin treatment strategies were compared: (1) treat all patients with AR10 of at least 7.5%, diabetes, or LDL-C of at least 190 mg/dL (standard care); (2) add treatment for borderline risk and LDL-C levels of 160 to 189 mg/dL; (3) add treatment for borderline risk and LDL-C levels of 130 to 159 mg/dL; and (4) add treatment for remainder of patients with AR10 of at least 5.0%. Statin treatment was also compared with no statin treatment in age, sex, AR10, and LDL-C strata.

Main Outcomes and Measures

Lifetime quality-adjusted life-years (QALYs) and costs (2019 US dollars) were projected and discounted 3.0% annually. The primary outcome was the incremental cost-effectiveness ratio.

Results

In these 100 simulated cohorts, each with 1 million patients aged 40 years at baseline (50% women and 50% men), adding preventive statins to individuals with borderline AR10 and LDL-C levels of 160 to 189 mg/dL would be cost-saving; further treating borderline AR10 and LDL-C levels of 130 to 159 mg/dL would also be cost-saving; and treating all individuals with AR10 of at least 5.0% would be highly cost-effective ($33 558/QALY) and would prevent the most ASCVD events. Within age, AR10, and sex categories, individuals with higher baseline LDL-C levels gained more QALYs from statin therapy. Cost-effectiveness increased with LDL-C level and AR10.

Conclusions and Relevance

In this study, lifetime statin treatment of patients in a hypothetical cohort with borderline ASCVD risk and LDL-C levels of 160 to 189 mg/dL was found to be cost-saving. Results suggest that treating all patients at borderline risk regardless of LDL-C level would likely be highly cost-effective.

Lipoprotein-associated phospholipase A2 activity, genetics and calcific aortic valve stenosis in humans

BACKGROUND

Lipoprotein-associated phospholipase A2 (Lp-PLA2) activity has been shown to predict calcific aortic valve stenosis (CAVS) outcomes. Our objective was to test the association between plasma Lp-PLA2 activity and genetically elevated Lp-PLA2 mass/activity with CAVS in humans.

METHODS AND RESULTS

Lp-PLA2 activity was measured in 890 patients undergoing cardiac surgery, including 476 patients undergoing aortic valve replacement for CAVS and 414 control patients undergoing coronary artery bypass grafting. After multivariable adjustment, Lp-PLA2 activity was positively associated with the presence of CAVS (OR=1.21 (95% CI 1.04 to 1.41) per SD increment). We selected four single nucleotide polymorphisms (SNPs) at the PLA2G7 locus associated with either Lp-PLA2 mass or activity (rs7756935, rs1421368, rs1805017 and rs4498351). Genetic association studies were performed in eight cohorts: Quebec-CAVS (1009 cases/1017 controls), UK Biobank (1350 cases/349 043 controls), European Prospective Investigation into Cancer and Nutrition-Norfolk (504 cases/20 307 controls), Genetic Epidemiology Research on Aging (3469 cases/51 723 controls), Malmö Diet and Cancer Study (682 cases/5963 controls) and three French cohorts (3123 cases/6532 controls), totalling 10 137 CAVS cases and 434 585 controls. A fixed-effect meta-analysis using the inverse-variance weighted method revealed that none of the four SNPs was associated with CAVS (OR=0.99 (95% CI 0.96 to 1.02, p=0.55) for rs7756935, 0.97 (95% CI 0.93 to 1.01, p=0.11) for rs1421368, 1.00 (95% CI 1.00 to 1.01, p=0.29) for rs1805017, and 1.00 (95% CI 0.97 to 1.04, p=0.87) for rs4498351).

CONCLUSIONS

Higher Lp-PLA2 activity is significantly associated with the presence of CAVS and might represent a biomarker of CAVS in patients with heart disease. Results of our genetic association study suggest that Lp-PLA2 is however unlikely to represent a causal risk factor or therapeutic target for CAVS.