Longitudinal association of PCSK9 sequence variations with low-density lipoprotein cholesterol levels: the Coronary Artery Risk Development in Young Adults Study

Effect of the PCSK9 R46L genetic variant on plasma insulin and glucose levels, risk of diabetes mellitus and cardiovascular disease: A meta-analysis

BACKGROUND AND AIM

The impact of the loss-of-function (LOF) genetic variant PCSK9 R46L on glucose homeostasis and cardiovascular disease (CVD) remains uncertain, despite its established correlation with diminished blood cholesterol levels. This meta-analysis aimed at exploring the effect of the PCSK9 R46L genetic variant on plasma insulin and glucose levels, risk of diabetes mellitus and CVD.

METHODS AND RESULTS

PubMed, Embase, and the Cochrane Library were searched for cohort and case-control studies published until October 1, 2023. The studies should report the association of the PCSK9 R46L genetic variant with one of the following: fasting plasma insulin, blood glucose levels, diabetes mellitus, and CVD risk. A dominant model of the PCSK9 R46L genetic variant was employed to statistical analysis. The meta-analyses were performed for continuous variables with standard mean difference (SMD), categorical variables with odds ratio (OR) using a random-effects model. A total of 17 articles with 20 studies engaging 1,186,861 population were identified and mobilized for these analyses. The overall results indicated that, compared with non-carriers of the PCSK9 R46L genetic variant, carriers of the PCSK9 R46L genetic variant did not increase or decrease the levels of fasting plasma insulin (3 studies with 7277 population; SMD, 0.08; 95% CI, -0.04 to 0.19; P = 0.270), and the levels of fasting plasma glucose (7 studies with 9331 population; SMD, 0.03; 95% CI, -0.08 to 0.13; P = 0.610). However, carriers of the PCSK9 R46L genetic variant indeed had 17% reduction in the risk of CVD (11 studies with 558,263 population; OR, 0.83; 95% CI, 0.71 to 0.98; P = 0.030), and 9% increase in the risk of diabetes mellitus (10 studies with 744,466 population; OR, 1.09; 95% CI, 1.04 to 1.14; P < 0.01). Meta-regression analyses indicated that the increased risk of diabetes mellitus and the reduced risk of CVD were positively correlated with reduction in LDL-C (P = 0.004 and 0.033, respectively).

CONCLUSIONS

PCSK9 R46L genetic variant exhibited an elevated susceptibility to diabetes mellitus alongside a reduced vulnerability to CVD.

Unusual effects of PCSK9 E670G (rs505151) variation in patients with in-stent restenosis: Variable effects on restenosis risk according to concomitant chronic conditions

Recent reports showing that neo-atherosclerosis formation in stented coronary artery is characterized by the accumulation of lipid-laden macrophages within the neointima has strengthened the possibility that elevated low-density lipoprotein (LDL)-cholesterol may be a risk factor for in-stent restenosis (ISR). Protein Convertase Subtilisin/Kexin-9 (PCSK9) protein plays an important role in cholesterol metabolism by degrading of LDL receptors. The gain-of-function E670G (rs505151) mutation of the PCSK9 gene is a well-known genetic risk factor for hypercholesterolemia. This study evaluated for the first time the association of the E670G variation with the serum lipids, PCSK9 levels and concomitant diseases on the ISR risk. The study included 109 ISR, and 82 Non-ISR patients, based on the results of coronary angiography. Genotypes were determined using the real-time PCR and serum PCSK9 levels were measured by ELISA technique. The rare G allele of PCSK9 E670G (p < 0.05), hyperlipidemia (HL) (p < 0.001), and type 2 diabetes (T2DM) (p < 0.01) were associated with increased risk for ISR. In hyperlipidemic conditions, the E670G-G allele was associated with hypercholesterolemia and a higher risk of ISR (p < 0.001), while the E670G-AA genotype has been associated with a high prevalence of T2DM and hypertension. In addition, diabetic ISRs had higher serum PCSK9 levels (p < 0.05) and the E670G-AA genotype was associated with increased levels of diabetes markers. Our results indicated that the unusual effects of both G allele and AA genotype of the PCSK9 E670G variation may be involved in the risk of ISR in association with concomitant metabolic diseases.

New Biological Therapies for Low-Density Lipoprotein Cholesterol

Depressed low-density lipoprotein cholesterol concentration protects against atherosclerotic cardiovascular disease. Natural hypocholesterolemia states can have a monogenic etiology, caused by pathogenic loss of function variants in the PCSK9, ANGPTL3, MTTP, or APOB genes. In this focused review, we discuss development and clinical use of several new therapeutics that inhibit these gene products to target elevated levels of low-density lipoprotein cholesterol. In particular, inhibitors of proprotein convertase subtilisin kexin type 9 (PCSK9) have notably affected clinical practice, followed recently by inhibition of angiopoietin-like 3 (ANGPTL3). Currently used in the clinic are alirocumab and evolocumab, two anti-PCSK9 monoclonal antibodies, inclisiran, a small interfering RNA that prevents PCSK9 translation, evinacumab, an anti-ANGPTL3 monoclonal antibody, and lomitapide, a small-molecule inhibitor of microsomal triglyceride transfer protein. Additional therapies are in preclinical or clinical trial stages of development. These consist of other monoclonal antibodies, antisense oligonucleotides, small-molecule inhibitors, mimetic peptides, adnectins, vaccines, and gene-editing therapies. Vaccines and gene-editing therapies in particular hold great potential to confer active long-term attenuation or provide single-treatment life-long knock-down of PCSK9 or ANGPTL3 activity. Biologic therapies inspired by monogenic hypocholesterolemia states are becoming valuable tools to help protect against atherosclerotic cardiovascular disease.

Relationship between Serum Proprotein Convertase Subtilisin/Kexin Type 9 Concentration and Prevalence of Coronary Artery Calcium in a Community-Based Sample of Japanese Men

AIMS

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a promising new target for reducing low-density lipoprotein cholesterol (LDL-C) and cardiovascular events in high-risk patients. However, the influence of circulating PCSK9 concentration on atherosclerotic plaque formation in the general population remains unknown. We assessed the relationship between serum PCSK9 concentration and coronary artery calcium (CAC) prevalence in the general population.

METHODS

Community-dwelling Japanese men (n=622) aged 46-82 years without a history of cardiovascular disease and lipid-lowering medications were included. Serum PCSK9 concentration and CAC score were measured using the Agatston method, and the multivariable analysis was used to assess their association. CAC was defined as an Agatston score of ＞10. We conducted further analysis stratified by age (＜60, 60-69, and ≥ 70 years).

RESULTS

The average age, LDL-C, and median serum PCSK9 concentration were 68 years, 122 mg/dL, and 240 ng/mL, respectively. After multivariable adjustment for traditional cardiovascular risk factors, no significant association was observed between serum PCSK9 concentration and CAC prevalence (adjusted relative risk [aRR] 1.05, 95% confidence interval [CI] 0.97-1.13). With age stratification, serum PCSK9 concentration was significantly associated with CAC prevalence in men aged ＜60 years (aRR 1.38, 95% CI 1.01-1.88) but not in men aged 60-69 years (aRR 0.96, 95% CI 0.85-1.10) or ≥ 70 years (aRR 1.08, 95% CI 0.99-1.19).

CONCLUSIONS

A higher serum PCSK9 concentration was associated with a higher CAC prevalence in men aged ＜60 years, which was independent of traditional cardiovascular risk factors.

Association study of PCSK9 SNPs (rs505151 & rs562556) and their haplotypes with CVDs in Indian population

BACKGROUND

Cardiovascular disease (CVD) has emerged as the most prevalent cause of death in India. Pro-protein Convertase Subtilisin/Kexin Type 9 (PCSK9) gene has been found to be associated with lipid levels and a biomarker for susceptibility of CVD.

AIM

To study the association of PCSK9 SNPs rs505151 & rs562556 and their haplotypes with CVDs in the Indian population.

SUBJECTS & METHODS

The present study comprised of 102 angiographically proven CVD patients & 100 healthy subjects. To study polymorphism, Polymerase Chain Reaction and Restriction Fragment Length Polymorphism (PCR-RFLP) method was used. Biochemical parameters were analysed by enzymatic methods or automated analysers. Haplotype analysis was done using SHEsis software.

RESULTS

The dominant genetic model with an odds ratio (confidence interval) of 4.71 (2.59 - 8.5), (p value = .0001), shows the risk of CVDs. However, rs562556 (I474V) variant was not found to be associated with clinical parameters and risk of CVDs (p value >.05). Out of four haplotypes, H3 (G-A) was found to be associated with the CVDs (OR- 3.137, p value = .0001).

CONCLUSION

This study concludes that G allele of rs505151 SNP (PCSK9) and the H3 (G-A) haplotype of rs505151 & rs562556 were found to be risk factors for CVDs in the Indian population.

Association of PCSK9 Variants With the Risk of Atherosclerotic Cardiovascular Disease and Variable Responses to PCSK9 Inhibitor Therapy

Genetic polymorphisms or variations, randomly distributed in a population, may cause drug-gene response variations. Investigation into these polymorphisms may identify novel mechanisms contributing to a specific disease process. Such investigation necessitates the use of Mendelian randomization, an analytical method that uses genetic variants as instrumental variables for modifiable risk factors that affect population health.¹ In the past decade, advances in our understanding of genetic polymorphisms have enabled the identification of genetic variants in candidate genes that impact low-density lipoprotein cholesterol (LDL-C) regulating pathways and cardiovascular disease (CVD) outcomes. A specific candidate gene of interest is that of the LDL receptor degrading protein, PCSK9. In fact, loss-of-function genetic variants for the PCSK9 gene are what first highlighted this pathway as a candidate for pharmacologic inhibition. PCSK9 inhibitors (PCSK9i) are a class of cholesterol-lowering medications that provide significant reductions in LDL by inhibiting the degradation of LDL receptors (LDLR). These inhibitors have also been found to reduce production and enhance clearance of lipoprotein A (Lp[a]), an LDL-like particle currently under study as a separate risk factor for atherosclerotic CVD. Here, we discuss the promise of personalized medicine in developing a more efficacious and individualized pharmacogenomics-based approach for the use of PCSK9i that considers genetic variation and targets different patient populations. This review explores the pharmacogenomics of PCSK9i in the context of PCSK9 allele variants related to drug-metabolizing enzymes and responses since more studies are demonstrating that some patients are hyporesponsive or non-responsive to PCSK9i.² In summary, the pharmacogenomics of PCSK9 are a promising therapeutic target and genetic information from prospective randomized clinical trials is warranted to gain a full understanding of the efficacy and cost-effectiveness of such allele and/or gene-guided PCSK9i therapy.

Association between the rs615563 variant of PCSK9 gene and circulating lipids and Type 2 diabetes

Objective

Many different genetic variants of proprotein convertase subtilisin kexin 9 (PCSK9) are related to the serum levels of cholesterol and LDL cholesterol (LDL-C). The rs615563 variant of PCSK9 (a gain-of-function mutation) is associated with increased triglycerides and cholesterol levels, but its association with the incidence of diabetes is not well defined. This study aimed to investigate the relationship between the PCSK9 rs615563 variant with the incidence of type 2 diabetes. The data reported in this study are based on subsamples from a 5-year (2009–2014) cohort study of the adult population (590 subjects) aged 20 years and older. The rs615563 polymorphism was genotyped using polymerase chain reaction (PCR) followed by restriction fragment length polymorphism (RFLP) analysis.

Results

The distribution of PCSK9 rs615563 genotypes was not significantly different between the diabetic and non-diabetic individuals. The incidence of diabetes after five-years of follow-up was not different between the genotypes. Our findings also showed no significant relationship between this polymorphism and serum lipid parameters. The data extracted from our cohort study do not support the findings that the gain-of-function mutations of PCSK9 predispose to the incidence of type 2 diabetes.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13104-021-05723-4.

The role of DNA methylation in syndromic and non-syndromic congenital heart disease

Congenital heart disease (CHD) is a common structural birth defect worldwide, and defects typically occur in the walls and valves of the heart or enlarged blood vessels. Chromosomal abnormalities and genetic mutations only account for a small portion of the pathogenic mechanisms of CHD, and the etiology of most cases remains unknown. The role of epigenetics in various diseases, including CHD, has attracted increased attention. The contributions of DNA methylation, one of the most important epigenetic modifications, to CHD have not been illuminated. Increasing evidence suggests that aberrant DNA methylation is related to CHD. Here, we briefly introduce DNA methylation and CHD and then review the DNA methylation profiles during cardiac development and in CHD, abnormalities in maternal genome-wide DNA methylation patterns are also described. Whole genome methylation profile and important differentially methylated genes identified in recent years are summarized and clustered according to the sample type and methodologies. Finally, we discuss the novel technology for and prospects of CHD-related DNA methylation.

Construction and application of a human scFv phage display library based on Cre‑LoxP recombination for anti‑PCSK9 antibody selection

A large human natural single-chain fragment variable (scFv) phage library was constructed based on Cre-LoxP recombination, and used to successfully identify antibodies against proprotein convertase subtilisin/kexin type 9 (PCSK9). The library was derived from 400 blood samples, 30 bone marrow samples, and 10 cord blood samples from healthy donors. Lymphocytes were isolated from each sample and cDNA was synthesized using reverse transcription-quantitative PCR. Two-step overlap PCR was then used for scFv synthesis using a LoxP peptide as the linker. The scFv gene was inserted into the phagemid vector pDF by enzymatic digestion and ligation, and then transformed into Escherichia coli (E. coli) SS320 to establish a primary antibody library in the form of scFvs. A primary antibody library consisting of 5×10⁷ peripheral blood and umbilical cord blood sources, as well as a primary antibody library of 5×10⁷ bone marrow samples were obtained. By optimizing the recombination conditions, the primary phage library was used to infect E. coliBS1365 strain (which expresses the Cre enzyme), and a human scFv recombinant library with a size of 1×10¹¹ was obtained through Cre-LoxP enzyme-mediated heavy and light chain replacement and recombination. This constructed recombinant library was employed to screen for antibodies against recombinant PCSK9. After four rounds of selection, a fully human antibody (3D2) was identified with a binding affinity of 1.96±1.56ⅹ10⁻¹⁰ M towards PCSK9. In vitro, the PCSK9/low-density lipoprotein receptor (LDLR) pathway of Hep-G2 cells was inhibited by 3D2 treatment, thereby increasing LDL uptake in these cells. In addition, combination treatment with 3D2 and statin was more effective at increasing LDLR levels than treatment with 3D2 or statin alone. Furthermore, 3D2 resulted in a 3-fold increase in hepatic LDLR levels, and lowered total serum cholesterol by up to 61.5% in vivo. Taken together, these results suggest that the constructed human Cre-LoxP scFv phage display library can be used to screen fully human scFv, and that 3D2 may serve as a candidate hypolipidemic therapy.

Dynamic incorporation of multiple in silico functional annotations empowers rare variant association analysis of large whole-genome sequencing studies at scale

Large-scale whole-genome sequencing studies have enabled the analysis of rare variants (RVs) associated with complex phenotypes. Commonly used RV association tests have limited scope to leverage variant functions. We propose STAAR (variant-set test for association using annotation information), a scalable and powerful RV association test method that effectively incorporates both variant categories and multiple complementary annotations using a dynamic weighting scheme. For the latter, we introduce 'annotation principal components', multidimensional summaries of in silico variant annotations. STAAR accounts for population structure and relatedness and is scalable for analyzing very large cohort and biobank whole-genome sequencing studies of continuous and dichotomous traits. We applied STAAR to identify RVs associated with four lipid traits in 12,316 discovery and 17,822 replication samples from the Trans-Omics for Precision Medicine Program. We discovered and replicated new RV associations, including disruptive missense RVs of NPC1L1 and an intergenic region near APOC1P1 associated with low-density lipoprotein cholesterol.

Characterization of LDLR rs5925 and PCSK9 rs505151 genetic variants frequencies in healthy subjects from northern Chile: Influence on plasma lipid levels

Background

Identification and characterization of genetic variants and their effects on human health may allow to establish relationships between genetic background and susceptibility to developing cardiovascular diseases. LDLR and PCSK9 polymorphisms have been associated with higher lipid levels and risk of cardiovascular diseases. Thus, the main aim of this study was to evaluate genotype distribution and relative allelic frequency of LDLR rs5925 (1959C > T) and PCSK9 rs505151 (23968 A > G) genetic variants and their effects on lipid levels of healthy subjects from northern Chile.

Methods

A total of 178 healthy individuals were recruited for this study. The genotyping of rs5925 (LDLR) and rs505151 (PCSK9) polymorphisms was performed by PCR‐RFLP and qPCR, respectively. In addition, glucose and lipid levels were determined and associated with the genetic data.

Results

Genotype distribution for LDLR rs5925 polymorphism was as follows: CC = 19%; CT = 53%; and TT = 28% (HWE: χ² = 0.80; P = .37), and for PCSK9 rs505151 genetic variant was as follows: AA = 93%; AG = 7%; and GG = 0% (HWE: χ² = 0.22; P = .64). The frequency of T (rs5925) and G (rs505151) mutated alleles was 0.55 and 0.03, respectively. Data showed that individuals carrying LDLR mutated allele (T) presented lower values of total cholesterol, triglycerides, and LDL‐cholesterol when compared to CC homozygous genotype (P < .05). Subgroup analysis revealed that women carrying the PCSK9 mutated allele (G) exhibited higher values of total cholesterol, triglycerides, HDL‐C, and LDL‐C when compared to male group carrying the same genotype (P < .05).

Conclusions

The effect of LDLR rs5925 and PCSK9 rs505151 gene polymorphisms on lipid levels is associated with gender among healthy subjects from northern Chile.

Functionally oriented analysis of cardiometabolic traits in a trans-ethnic sample

Interpretation of genetic association results is difficult because signals often lack biological context. To generate hypotheses of the functional genetic etiology of complex cardiometabolic traits, we estimated the genetically determined component of gene expression from common variants using PrediXcan (1) and determined genes with differential predicted expression by trait. PrediXcan imputes tissue-specific expression levels from genetic variation using variant-level effect on gene expression in transcriptome data. To explore the value of imputed genetically regulated gene expression (GReX) models across different ancestral populations, we evaluated imputed expression levels for predictive accuracy genome-wide in RNA sequence data in samples drawn from European-ancestry and African-ancestry populations and identified substantial predictive power using European-derived models in a non-European target population. We then tested the association of GReX on 15 cardiometabolic traits including blood lipid levels, body mass index, height, blood pressure, fasting glucose and insulin, RR interval, fibrinogen level, factor VII level and white blood cell and platelet counts in 15 755 individuals across three ancestry groups, resulting in 20 novel gene-phenotype associations reaching experiment-wide significance across ancestries. In addition, we identified 18 significant novel gene-phenotype associations in our ancestry-specific analyses. Top associations were assessed for additional support via query of S-PrediXcan (2) results derived from publicly available genome-wide association studies summary data. Collectively, these findings illustrate the utility of transcriptome-based imputation models for discovery of cardiometabolic effect genes in a diverse dataset.

Variations of the proprotein convertase subtilisin/kexin type 9 gene in coronary artery disease

Objective

Coronary artery disease (CAD) is the principal cause of mortality and morbidity worldwide. Studies have provided controversial results regarding whether variations in the proprotein convertase subtilisin/kexin type 9 gene (PCSK9) are risk factors for CAD. In this study, we evaluated the risk factors associated with PSCK9 genotypes and CAD in the Taiwanese population.

Methods

A total of 501 patients diagnosed with CAD by angiography and 334 CAD-free controls were recruited. Two single nucleotide polymorphisms of PSCK9 (rs505151 and rs529787) were genotyped.

Results

The prevalence of a positive family history for CAD was significantly higher in individuals carrying the AG + GG genotype of the PSCK9 rs505151 polymorphism. Among CAD patients with a positive family history, the prevalence of diabetes mellitus was significantly higher in those carrying the AG + GG genotype of the PSCK9 rs505151 polymorphism (73.3%) than in those carrying the AA genotype (39.2%).

Conclusion

In CAD patients, the AG genotype of PSCK9 rs505151 is associated with diabetes and a positive family history of CAD.

GWAS and Beyond: Using Omics Approaches to Interpret SNP Associations

PURPOSE OF REVIEW

Neurodegenerative diseases, neuropsychiatric disorders, and related traits have highly complex etiologies but are also highly heritable and identifying the causal genes and biological pathways underlying these traits may advance the development of treatments and preventive strategies. While many genome-wide association studies (GWAS) have successfully identified variants contributing to polygenic neurodegenerative and neuropsychiatric phenotypes including Alzheimer's disease (AD), schizophrenia (SCZ), and bipolar disorder (BPD) amongst others, interpreting the biological roles of significantly-associated variants in the genetic architecture of these traits remains a significant challenge. Here we review several 'omics' approaches which attempt to bridge the gap from associated genetic variants to phenotype by helping define the functional roles of GWAS loci in the development of neuropsychiatric disorders and traits.

RECENT FINDINGS

Several common 'omics' approaches have been applied to examine neuropsychiatric traits, such as nearest-gene mapping, trans-ethnic fine mapping, annotation enrichment analysis, transcriptomic analysis, and pathway analysis, and each of these approaches has strengths and limitations in providing insight into biological mechanisms. One popular emerging method is the examination of tissue-specific genetically-regulated gene expression (GReX), which aggregates the genetic variants' effects at the gene-level. Furthermore, proteomic, metabolomic, and microbiomic studies and phenome-wide association studies will further enhance our understanding of neuropsychiatric traits.

SUMMARY

GWAS has been applied to neuropsychiatric traits for a decade, but our understanding about the biological function of identified variants remains limited. Today, technological advancements have created analytical approaches for integrating transcriptomics, metabolomics, proteomics, pharmacology and toxicology as tools for understanding the functional roles of genetics variants. These data, as well as the broader clinical information provided by electronic health records, can provide additional insight and complement genomic analyses.

C679X loss-of-function PCSK9 variant is associated with lower fasting glucose in black South African adolescents: Birth to Twenty Plus Cohort

Aim

To evaluate the association between loss-of-function (LOF) PCSK9 variants (A433T/rs28362263 and C679X/rs28362286) and biomarkers of cardiometabolic risk, specifically fasting glucose and low density lipoprotein cholesterol (LDL-C) concentrations.

Methods

Our study comprised 757 male and female black South African adolescents (mean age 18.0 ± 0.5 years) who are part of the Birth to Twenty Plus Cohort and had been genotyped for the two above-mentioned variants. Anthropometric measures were completed and fasting plasma glucose and lipid analysis were performed using standard procedures.

Results

The median and interquartile range of fasting glucose and LDL-C for the whole group were 4.60 (4.36–4.88) mmol/L and 1.67 (1.25–2.14) mmol/L, respectively. After adjusting for sex, association between the biomarkers and A443T was not significant. However, C679X carriers displayed 0.30 [95% CI (−0.57, −0.02); p = 0.035] mmol/L lower fasting glucose and 0.50 [95% CI (−0.74, −0.26); p < 0.001) mmol/L lower LDL-C concentrations compared to non-carriers.

Conclusions

Our results indicate for the first that the C679X variants associated with low fasting glucose levels during adolescents as had been known for LDL-C. In view that a similar finding was reported in older black South African adults, therefore, the correlation of lower fasting glucose and LDL-C levels with C679X is observed from an early age to adulthood.

PCSK9 loss-of-function variants and risk of infection and sepsis in the Reasons for Geographic and Racial Differences in Stroke (REGARDS) cohort

BACKGROUND

Elevated proprotein convertase subtilisin/kexin type 9 (PCSK9) levels have been associated with adverse outcomes in patients hospitalized for sepsis. PCSK9 loss-of-function (LOF) variants area associated with lower low-density lipoprotein cholesterol (LDL-C) levels. Decreased LDL-C is a biomarker of acute and chronic infection and sepsis risk. We examined the association between presence of two genetic PCSK9 LOF variants and risk of infection and sepsis in community-dwelling adults.

METHODS

We analyzed data from 10,924 Black participants tested for PCSK9 LOF variants in the REasons for Geographic and Racial Differences in Stroke (REGARDS) cohort. The primary endpoint was hospitalization for a serious infection. Within serious infection hospitalizations, we defined sepsis as ≥2 system inflammatory response syndrome criteria. Using multivariable Cox and logistic regression, we investigated the association between LOF variants and hospitalization for infection and sepsis events, adjusting for sociodemographics, health behaviors, chronic medical conditions and select biomarkers.

RESULTS

Among 10,924 Black participants, PCSK9 LOF variants were present in 244 (2.2%). Serious infection hospitalizations occurred in 779 participants (14 with PCSK9 variants and 765 without). The presence of PCSK9 variants was not associated with infection risk (adjusted HR 0.68; 95% CI: 0.38-1.25). Among participants hospitalized for a serious infection, the presence of PCSK9 variants was not associated with sepsis (adjusted OR 7.31; 95% CI = 0.91-58.7).

CONCLUSIONS

PCSK9 LOF variants are not associated with increased risk of hospitalization for a serious infection. Among those hospitalized for a serious infection, PCSK9 LOF variants was not associated with odds of sepsis.

A novel study to examine the association of PCSK9 rs505151 polymorphism and coronary artery disease in north Indian population

There is a drastic increase in the number of people suffering from coronary artery disease (CAD) worldwide with Indians being no exception. Being a developing country and experiencing a dramatic shift in lifestyle and eating habits, urbanization and industrialization, all these factors have collectively predisposed the Indian population towards CAD and the prevalence data arequite alarming. Genetic studies have disclosed the role of genes in CAD susceptibility and severity. One such gene is proprotein convertase subtilisin/kexin type 9 (PCSK9) which is sought to modulate the cholesterol levels and hence, has implications in CAD. We aim to explore the association of PCSK9 A/G (rs505151) polymorphism and hence, the susceptibility towards CAD in the north Indian population. Five-hundred angiographically confirmed CAD patients and 500 healthy individuals as control were genotyped by polymerase chain reaction-restriction fragment length polymorphism. Statistical analysis revealed a significant association with the G allele with odds ratio (OR)=1.50, 95% confidence interval (CI)=1.22-1.85 and P=0.000. Also, a strong association was observedfor CAD risk with OR=1.590, 95% CI=1.106-2.284 and P=0.012. However, the homozygous GG mutant genotype was found to be completely absent from our population. Analysis of the dominant model also revealed an association with CAD risk. Our work demonstrated for the first time the association of PCSK9 A/G (rs505151) polymorphism with CAD risk in the north Indian population.

C679X loss-of-function PCSK9 variant lowers fasting glucose levels in a black South African population: A longitudinal study

AIMS

To determine the longitudinal association of the loss-of-function (LOF) PCSK9 variants (C679X and A443T), proxies of PCSK9 inhibitor drugs, with LDL-C, fasting glucose and glycated hemoglobin.

METHODS

We conducted a five year, longitudinal study, nested within the Prospective Urban and Rural Epidemiology study, among 737 apparently healthy, male and female black South Africans of the North West province. Genotyping of the C679X and A443T PCSK9 variants was achieved using Taqman assays from Applied Biosystems. Generalized estimating equations were used to determine longitudinal association of the A443T and C679X PCSK9 variants with LDL-C, fasting glucose and glycated hemoglobin.

RESULTS

C679X and A443T variant carriers were associated with significant reductions in LDL-C of -0.98(-1.29, -0.67) mmol/L; p < 0.001) and -0.39(-0.57, -0.20) mmol/L; p < 0.001) respectively, compared to the non-carriers. Only C679X variant was independently associated with reductions in fasting glucose of -0.37 (-0.61, -0.13) mmol/L; p = 0.002) compared to non-carriers. However, the association of the selected variants with glycated hemoglobin were not significant. C679X and A443T carriers were associated with -0.07 (-0.23, 0.09) %; p = 0.400), 0.05 (-0.13, 0.22) %; p = 0.599) of glycated haemoglobin respectively.

CONCLUSION

Our results indicated that carriers of A443T and C679X variants exhibit sustained low LDL-C levels over 5 years and have varied effects on T2D biomarkers compared to non-carriers.

Novel Therapeutic Targets for Managing Dyslipidemia

Atherosclerotic cardiovascular disease (ASCVD) remains the leading cause of morbidity and mortality in developed nations. Therapeutic modulation of dyslipidemia by inhibiting 3'-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase is standard practice throughout the world. However, based on findings from Mendelian studies and genetic sequencing in prospective longitudinal cohorts from around the world, novel therapeutic targets regulating lipid and lipoprotein metabolism, such as apoprotein C3, angiopoietin-like proteins 3 and 4, and lipoprotein(a), have been identified. These targets may provide additional avenues to prevent and treat atherosclerotic disease. We therefore review these novel molecular targets by addressing available Mendelian and observational data, therapeutic agents in development, and early outcomes results.

Ossabaw Pigs With a PCSK9 Gain-of-Function Mutation Develop Accelerated Coronary Atherosclerotic Lesions: A Novel Model for Preclinical Studies

BACKGROUND

Ossabaw pigs are unique miniature swine with genetic predisposition to develop metabolic syndrome and coronary atherosclerosis after extended periods receiving atherogenic diets. We have hypothesized that transgenic Ossabaw swine expressing chimp PCSK9 (proprotein convertase subtilisin-like/kexin type 9) containing the D374Y gain of function would develop familial hypercholesterolemia and coronary artery plaques more rapidly than Landrace swine with the same transgene.

METHODS AND RESULTS

Ossabaw and Landrace PCSK9 gain-of-function founders were generated by Sleeping Beauty transposition and cloning. Histopathologic findings in the Ossabaw founder animal showed more advanced plaques and higher stenosis than in the Landrace founder, underscoring the Ossabaw genetic predisposition to atherosclerosis. We chose to further characterize the Ossabaw PCSK9 gain-of-function animals receiving standard or atherogenic diets in a 6-month longitudinal study using computed tomography, magnetic resonance (MR) imaging, intravascular ultrasound, and optical coherence tomography, followed by pathological analysis of atherosclerosis focused on the coronary arteries. The Ossabaw model was consistently hypercholesterolemic, with or without dietary challenge, and by 6 months had consistent and diffuse fibrofatty or fibroatheromatous plaques with necrosis, overlying fibrous caps, and calcification in up to 10% of coronary plaques.

CONCLUSIONS

The Ossabaw PCSK9 gain-of-function model provides consistent and robust disease development in a time frame that is practical for use in preclinical therapeutic evaluation to drive innovation. Although no animal model perfectly mimics the human condition, this genetic large-animal model is a novel tool for testing therapeutic interventions in the context of developing and advanced coronary artery disease.

PCSK9 Variants, Low-Density Lipoprotein Cholesterol, and Neurocognitive Impairment: Reasons for Geographic and Racial Differences in Stroke Study (REGARDS)

BACKGROUND

Despite concerns about adverse neurocognitive events raised by prior trials, pharmacological PCSK9 (proprotein convertase subtilisin/kexin type-9) inhibition was not associated with neurocognitive effects in a recent phase 3 randomized trial. PCSK9 loss-of-function (LOF) variants that result in lifelong exposure to lower levels of low-density lipoprotein cholesterol can provide information on the potential long-term effects of lower low-density lipoprotein cholesterol on neurocognitive impairment and decline.

METHODS

We investigated the association between PCSK9 LOF variants and neurocognitive impairment and decline among black REGARDS study (Reasons for Geographic and Racial Differences in Stroke) participants with (n=241) and without (n=10 454) C697X or Y142X LOF variants. Neurocognitive tests included the Consortium to Establish a Registry for Alzheimer's Disease (CERAD) battery (Word List Learning, World List Delayed Recall, Semantic Animal Fluency) and Six-Item Screener (SIS) assessments, administered longitudinally during follow-up. Neurocognitive impairment was defined as a score ≥1.5 SD below age, sex, and education-based stratum-specific means on 2 or 3 CERAD assessments or, separately, a score <5 on any SIS assessment at baseline or during follow-up. Neurocognitive decline was assessed using standardized continuous scores on individual neurocognitive tests.

RESULTS

The mean sample age was 64 years (SD, 9), 62% were women, and the prevalence of neurocognitive impairment at any assessment was 6.3% by CERAD and 15.4% by SIS definitions. Adjusted odds ratios for neurocognitive impairment for participants with versus without PCSK9 LOF variants were 1.11 (95% confidence interval [CI], 0.58-2.13) using the CERAD battery and 0.89 (95% CI, 0.61-1.30) using the SIS assessment. Standardized average differences in individual neurocognitive assessment scores over the 5.6-year (range, 0.1-9.1) study period ranged between 0.07 (95% CI, -0.06 to 0.20) and -0.07 (95% CI, -0.18 to 0.05) among participants with versus without PCSK9 LOF variants. Patterns of neurocognitive decline were similar between participants with and without PCSK9 LOF variants (all P>0.10). Odds ratios for neurocognitive impairment per 20 mg/dL low-density lipoprotein cholesterol decrements were 1.02 (95% CI, 0.96-1.08) and 0.99 (95% CI, 0.95-1.02) for the CERAD and SIS definitions of impairment, respectively.

CONCLUSIONS

These results suggest that lifelong exposure to low PCSK9 levels and cumulative exposure to lower levels of low-density lipoprotein cholesterol are not associated with neurocognitive effects in blacks.

PCSK9 Loss-of-Function Variants, Low-Density Lipoprotein Cholesterol, and Risk of Coronary Heart Disease and Stroke: Data From 9 Studies of Blacks and Whites

BACKGROUND

PCSK9 loss-of-function (LOF) variants allow for the examination of the effects of lifetime reduced low-density lipoprotein cholesterol (LDL-C) on cardiovascular events. We examined the association of PCSK9 LOF variants with LDL-C and incident coronary heart disease and stroke through a meta-analysis of data from 8 observational cohorts and 1 randomized trial of statin therapy.

METHODS AND RESULTS

These 9 studies together included 17 459 blacks with 403 (2.3%) having at least 1 Y142X or C679X variant and 31 306 whites with 955 (3.1%) having at least 1 R46L variant. Unadjusted odds ratios for associations between PCSK9 LOF variants and incident coronary heart disease (851 events in blacks and 2662 events in whites) and stroke (523 events in blacks and 1660 events in whites) were calculated using pooled Mantel-Haenszel estimates with continuity correction factors. Pooling results across studies using fixed-effects inverse-variance-weighted models, PCSK9 LOF variants were associated with 35 mg/dL (95% confidence interval [CI], 32-39) lower LDL-C in blacks and 13 mg/dL (95% CI, 11-16) lower LDL-C in whites. PCSK9 LOF variants were associated with a pooled odds ratio for coronary heart disease of 0.51 (95% CI, 0.28-0.92) in blacks and 0.82 (95% CI, 0.63-1.06) in whites. PCSK9 LOF variants were not associated with incident stroke (odds ratio, 0.84; 95% CI, 0.48-1.47 in blacks and odds ratio, 1.06; 95% CI, 0.80-1.41 in whites).

CONCLUSIONS

PCSK9 LOF variants were associated with lower LDL-C and coronary heart disease incidence. PCSK9 LOF variants were not associated with stroke risk.

What is the impact of PCSK9 rs505151 and rs11591147 polymorphisms on serum lipids level and cardiovascular risk: a meta-analysis

Background

PCSK9 rs505151 and rs11591147 polymorphisms are identified as gain- and loss-of-function mutations, respectively. The effects of these polymorphisms on serum lipid levels and cardiovascular risk remain to be elucidated.

Methods

In this meta-analysis, we explored the association of PCSK9 rs505151 and rs11591147 polymorphisms with serum lipid levels and cardiovascular risk by calculating the standardized mean difference (SMD) and odds ratios (OR) with 95% confidence intervals (CI).

Results

Pooled results analyzed under a dominant genetic model indicated that the PCSK9 rs505151 G allele was related to higher levels of triglycerides (SMD: 0.14, 95% CI: 0.02 to 0.26, P = 0.021, I² = 0) and low-density lipoproteins cholesterol (LDL-C) (SMD: 0.17, 95% CI: 0.00 to 0.35, P = 0.046, I² = 75.9%) and increased cardiovascular risk (OR: 1.50, 95% CI: 1.19 to 1.89, P = 0.0006, I² = 48%). The rs11591147 T allele was significantly associated with lower levels of total cholesterol (TC) and LDL-C (TC, SMD: -0.45, 95% CI: -0.57 to −0.32, P = 0.000, I² = 0; LDL-C, SMD: -0.44, 95% CI: -0.55 to −0.33, P = 0.000, I² = 0) and decreased cardiovascular risk (OR: 0.77, 95% CI: 0.60 to 0.98, P = 0.031, I² = 59.9) in Caucasians.

Conclusions

This study indicates that the variant G allele of PCSK9 rs505151 confers increased triglyceride (TG) and LDL-C levels, as well as increased cardiovascular risk. Conversely, the variant T allele of rs11591147 protects carriers from cardiovascular disease susceptibility and lower TC and LDL-C levels in Caucasians. These findings provide useful information for researchers interested in the fields of PCSK9 genetics and cardiovascular risk prediction not only for designing future studies, but also for clinical and public health applications.

Monoclonal Antibodies for Lipid Management

In recent years, biochemical and genetic studies have identified proprotein convertase subtilisin/kexin type 9 (PCSK9) as a major mediator of low-density lipoprotein cholesterol (LDL-c) levels and thereby a potential novel target for reducing risk of coronary heart disease (CHD). These observations led to the development of PCSK9 inhibitors, which lower LDL-c levels more than any other non-invasive lipid-lowering therapy presently available. The PCSK9 inhibitors furthest along in clinical trials are subcutaneously injected monoclonal antibodies. These PCSK9 inhibitors have demonstrated LDL-c-lowering efficacy with acceptable safety in phase III clinical trials and may offer a useful therapy in addition to maximally tolerated HMG-CoA reductase inhibitors (statins) in certain patient groups. Longer-term data are required to ensure sustained efficacy and safety of this new class of medications. This review provides an overview of the biology, genetics, development, and clinical trials of monoclonal antibodies designed to inhibit PCSK9.

Prediction of cardiovascular events with levels of proprotein convertase subtilisin/kexin type 9: A systematic review and meta-analysis

BACKGROUND AND AIMS

Inhibition of proprotein convertase subtilisin/kexin type 9 (PCSK9) reduces atherogenic lipoproteins and could lead to reduction of cardiovascular (CV) events. However, it is unclear whether blood PCSK9 levels predict future CV events. We performed a meta-analysis of all longitudinal studies to determine the ability of PCSK9 levels to predict risk of future CV events.

METHODS

A comprehensive search of electronic databases was conducted up to February 2016. Longitudinal studies that reported events or relative risk (RR) estimates with 95% confidence intervals (CI) were included.

RESULTS

All 9 studies included (12,081 participants, mean follow-up 6.62 years) reported results on total CV events. The pooled RR of total CV events for an increase in baseline PCSK9 by 1 standard deviation (SD) was 1.098 (95% CI, 1.02-1.18), corresponding to a risk increase of 10% (Z = 2.43, p = 0.015). The pooled RR of total CV events for subjects categorized in the highest tertile of baseline PCSK9 was 1.228 (95% CI, 1.035-1.457), corresponding to a risk increase of 23% (Z = 2.35, p = 0.019). When pooled estimates were derived independently for low- and high-CV risk populations, baseline PCSK9 levels predicted total CV events only in apparently healthy subjects (RR = 1.13, 95% CI: 1.050-1.222, Z = 3.21, p = 0.001) and not in populations with established CV or renal disease (RR = 1.09, 95% CI: 0.961-1.23, Z = 1.33, p = 0.182).

CONCLUSIONS

PCSK9 levels are modestly but significantly associated with increased risk of total CV events. These results suggest a predictive role of PCSK9 levels on CV health and support the possible clinical role of PCSK9 inhibitors.

Proprotein convertase subtilisin kexin type 9 and high-density lipoprotein metabolism: experimental animal models and clinical evidence

Proprotein convertase subtilisin kexin type 9 (PCSK9) belongs to the proprotein convertase family. Several studies have demonstrated its involvement in the regulation of low-density lipoprotein (LDL) cholesterol levels by inducing the degradation of the LDL receptor (LDLR). However, experimental, epidemiologic, and pharmacologic data provide important evidence on the role of PCSK9 also on high-density lipoproteins (HDLs). In mice, PCSK9 regulates the HDL cholesterol (HDL-C) levels by the degradation of hepatic LDLR, thus inhibiting the uptake of apolipoprotein (Apo)E-containing HDLs. Several epidemiologic and genetic studies reported positive relationship between PCSK9 and HDL-C levels, likely by reducing the uptake of the ApoE-containing HDL particles. PCSK9 enhances also the degradation of LDLR's closest family members, ApoE receptor 2, very low-density lipoprotein receptor, and LDLR-related protein 1. This feature provides a molecular mechanism by which PCSK9 may affect HDL metabolism. Experimental studies demonstrated that PCSK9 directly interacts with HDL by modulating PCSK9 self-assembly and its binding to the LDLR. Finally, the inhibition of PCSK9 by means of monoclonal antibodies directed to PCSK9 (ie, evolocumab and alirocumab) determines an increase of HDL-C fraction by 7% and 4.2%, respectively. Thus, the understanding of the role of PCSK9 on HDL metabolism needs to be elucidated with a particular focus on the effect of PCSK9 on HDL-mediated reverse cholesterol transport.

The Influence of OLR1 and PCSK9 Gene Polymorphisms on Ischemic Stroke: Evidence from a Meta-Analysis

Both OLR1 and PCSK9 genes are associated with atherosclerosis, cardiovascular disease and ischemic stroke. The overall prevalence of PCSK9 rs505151 and OLR1 rs11053646 variants in ischemic stroke were 0.005 and 0.116, respectively. However, to date, association between these polymorphisms and ischemic stroke remains inconclusive. Therefore, this first meta-analysis was carried out to clarify the presumed influence of these polymorphisms on ischemic stroke. All eligible case-control and cohort studies that met the search terms were retrieved in multiple databases. Demographic and genotyping data were extracted from each study, and the meta-analysis was performed using RevMan 5.3 and Metafor R 3.2.1. The pooled odd ratios (ORs) and 95% confidence intervals (CIs) were calculated using both fixed- and random-effect models. Seven case-control studies encompassing 1897 cases and 2119 controls were critically evaluated. Pooled results from the genetic models indicated that OLR1 rs11053646 dominant (OR = 1.33, 95%  CI:1.11–1.58) and co-dominant models (OR = 1.24, 95%  CI:1.02–1.51) were significantly associated with ischemic stroke. For the PCSK9 rs505151 polymorphism, the OR of co-dominant model (OR = 1.36, 95%  CI:1.01–1.58) was found to be higher among ischemic stroke patients. In conclusion, the current meta-analysis highlighted that variant allele of OLR1 rs11053646 G > C and PCSK9 rs505151 A > G may contribute to the susceptibility risk of ischemic stroke.

The associations between proprotein convertase subtilisin/kexin type 9 E670G polymorphism and the risk of coronary artery disease and serum lipid levels: a meta-analysis

BACKGROUND

Studies had investigated the associations between proprotein convertase subtilisin/kexin type 9 (PCSK9) E670G polymorphism and coronary artery disease (CAD) and lipid levels, but the results were controversial. Thus, we performed this meta-analysis to investigate the association between PCSK9 E670G polymorphism and lipid levels and the susceptibility to CAD.

METHODS

All relevant articles according to the inclusion criteria were retrieved and included in the present meta-analysis. Odds ratios (ORs) with 95 % confidence interval (CI) were used to analyze the strength of the association between PCSK9 E670G polymorphism and the susceptibility to CAD. At the same time, the pooled standardized mean difference (SMD) with 95 % CI was used for the meta-analysis of PCSK9 E670G polymorphism and lipid levels. The publication bias was examined by using Begg's funnel plots and Egger's test.

RESULTS

A total of seventeen studies met the inclusion criteria. For CAD association, the pooled effects indicated that the G allele carriers had higher risk of CAD than non-carriers in dominant genetic model (OR:1.601, 95 % CI: 1.314-1.951, P < 0.001), as well as in allelic genetic model (OR: 1.546, 95 % CI: 1.301-1.838, P < 0.001). When the subgroup analysis stratified by ethnicity and HWE was performed, the positive result existed in most of the subgroups. For lipid levels association, the pooled effects indicated that the G allele carriers had higher TC and LDL-C levels than the non-carriers (for TC, SMD: 0.126, 95 % CI: 0.023-0.229, P = 0.016; for LDL-C, SMD: 0.170, 95 % CI: 0.053-0.287, P = 0.004, respectively). There was no difference in the levels of TG and HDL-C between the G carriers and the non-carriers in the whole population (SMD: 0.031, 95 % CI: -0.048-0.110, P = 0.440; SMD: -0.123, 95 % CI: -0.251-0.006, P = 0.061, respectively). When the studies were stratified by ethnicity and type of study, the G carriers had higher TC levels than the non-carriers (SMD: 0.126, 95 % CI: 0.014-0.238, P = 0.027) in the non-Asian subgroup. The similar results existed in cohort subgroup. The association between PCSK9 E670G polymorphism and LDL-C levels was significant in all subgroups. Meanwhile, the G carriers had higher TG levels than the non-carriers (SMD: 0.113, 95 % CI: 0.012-0.214, P = 0.028) in the case-control subgroup. AG + GG genotypes had lower HDL-C levels than AA genotype in Asian subgroup (SMD: -0.224, 95 % CI: -0.423- -0.025, P = 0.027) and in case-control subgroup (SMD: -0.257, 95 % CI: -0.467--0.048, P = 0.016).

CONCLUSIONS

The present meta-analysis concluded that PCSK9 E670G polymorphism was associated with CAD risk and lipid levels.

Association of Proprotein Convertase Subtilisin/Kexin Type 9 (PCSK9) With Cardiovascular Risk in Primary Prevention

OBJECTIVE

Proprotein convertase subtilisin/kexin type 9 (PCSK9) plays an important role in the modulation of low-density lipoprotein metabolism. This study was conducted to evaluate the relationship between serum PCSK9 concentrations and measures of vascular health, subclinical atherosclerosis, and adverse cardiovascular events. The relationship between traditional risk factors and PCSK9 concentrations was also examined.

APPROACH AND RESULTS

The cohort consisted of 1527 middle-aged men enrolled in the Firefighters and Their Endothelium (FATE) study, who were free of vascular disease and followed up over a mean period of 7.2±1.7 years. Baseline evaluation included assessment of traditional cardiovascular risk factors and measurements of flow-mediated dilation, reactive hyperemic velocity time integral, and carotid intima-media thickness. Biochemical parameters, including serum PCSK9 concentrations, were analyzed to determine predictors of vascular measures and to evaluate the role of PCSK9 in the occurrence of adverse cardiovascular events. Multivariate linear regression analyses indicated that body mass index, insulin, low-density lipoprotein-cholesterol, and triglycerides were independent predictors of PCSK9. Further modeling revealed no correlation between PCSK9 concentration and carotid intima media thickness, flow-mediated dilation, or reactive hyperemic velocity time integral. Analyses indicated no significant association between PCSK9 concentrations and cardiovascular event occurrences.

CONCLUSIONS

Although correlated with low-density lipoprotein-cholesterol, insulin, and triglycerides, PCSK9 was not associated with measures of vascular function or structure. There was also no significant relationship between PCSK9 concentrations and cardiovascular events. Thus, although PCSK9 is an important therapeutic target to reduce circulating low-density lipoprotein-cholesterol concentrations, it is unlikely to be a biomarker of atherosclerotic risk or vascular health.

Living the PCSK9 adventure: from the identification of a new gene in familial hypercholesterolemia towards a potential new class of anticholesterol drugs

A decade after our discovery of the involvement of proprotein convertase subtilisin/kexin type 9 (PCSK9) in cholesterol metabolism through the identification of the first mutations leading to hypercholesterolemia, PCSK9 has become one of the most promising targets in cholesterol and cardiovascular diseases. This challenging work in the genetics of hypercholesterolemia paved the way for a plethora of studies around the world allowing the characterization of PCSK9, its expression, its impact on reducing the abundance of LDL receptor, and the identification of loss-of-function mutations in hypocholesterolemia. We highlight the different steps of this adventure and review the published clinical trials especially those with the anti-PCSK9 antibodies evolocumab (AMG 145) and alirocumab (SAR236553/REGN727), which are in phase III trials. The promising results in lowering LDL cholesterol levels raise hope that the PCSK9 adventure will lead, after the large and long-term ongoing phase III studies evaluating efficacy and safety, to a new anticholesterol pharmacological class.

PCSK9 (Proprotein convertase subtilisin/kexin type 9) inhibitors: past, present, and the future

Reduction in low-density lipoprotein cholesterol (LDL-C), mainly with statins, has decreased the risk of cardiovascular events over the last few decades. However, there are several patient populations that warrant further decrease in LDL-C by additional cholesterol-lowering therapy other than statins. Proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors are a new class of drugs that have been shown to further decrease LDL-C by 50-70% when administered as a monotherapy or on a background therapy with statins. Proprotein convertase subtilisin/kexin type 9 inhibitors are also an excellent example of drug development in which discovery of gene mutations and its clinical effects have rapidly progressed into successful preclinical and clinical studies with multiple Phases 1-3 clinical trials completed or ongoing to date. This review summarizes the rapid evolution of the drug from genetic discovery to identification of targets for the drugs, to animal and human testing, and to large clinical outcomes trials, followed by discussion on foreseeable challenges of PCSK9 inhibitors.

Combined PCSK9 and APOE polymorphisms are genetic risk factors associated with elevated plasma lipid levels in a Thai population

Proprotein convertase subtilisin/kexin type 9 (PCSK9) and apolipoprotein E (ApoE) play a key role in the regulation of lipid metabolism. We aimed to investigate the effects of PCSK9 (R46L, I474V, and E670G) and APOE polymorphisms on lipid levels in a Southern Thai population. A total of 495 participants (307 urban, 188 rural) were recruited for the study. Anthropometric and biochemical variables were evaluated. PCSK9 and APOE polymorphisms were analyzed using PCR-RFLP. The 46L urban male carriers had significantly higher diastolic blood pressure (DBP) and fasting blood sugar compared with non-carriers. In contrast, the 46L urban female carriers had significantly lower total cholesterol (TC) and LDL-C levels compared with non-carriers. The 474V rural female carriers had significantly lower HDL-C levels than non-carriers. The 670G urban female carriers showed significantly higher TC and LDL-C levels compared with non-carriers. APOE4 carriers had increased TC and LDL-C levels relative to APOE3 carriers in the urban males. APOE2 carriers had decreased TC and/or LDL-C levels compared with APOE3 carriers in urban males and females. A significant trend of increased TC and LDL-C levels was observed in non-APOE4-PCSK9 670EE carriers to APOE4-PCSK9 670EG carriers in urban subjects. In summary, R46L, I474V, and E670G may be genetic risk factors for cardiovascular disease (CVD) in urban males, rural females, and urban females, respectively. In contrast, R46L had a favorable lipid profiles that may protect against CVD in urban females. The combination of PCSK9 E670G and APOE polymorphisms may represent an independent factor for the determination of lipid levels.

Both rare and common variants in PCSK9 influence plasma low-density lipoprotein cholesterol level in American Indians

CONTEXT

Elevated LDL cholesterol (LDL-C) is an important risk factor for atherosclerosis and cardiovascular disease. Variants in the proprotein convertase subtilisin/kexin type 9 (PCSK9) gene have been associated not only with plasma LDL-C concentration, but also with ischemic heart disease. Little is known about the genetic architecture of PCSK9 and its influence on LDL-C in American Indians.

OBJECTIVE

We aimed to investigate the genetic architecture in the 1p32 region encompassing PCSK9 and its influence on LDL-C in American Indians.

DESIGN

The Strong Heart Family Study (SHFS) is a family-based genetic study.

PARTICIPANTS

Two thousand four hundred fifty eight American Indians from Arizona, Oklahoma, North Dakota, and South Dakota, who were genotyped by Illumina MetaboChip.

RESULTS

We genotyped 486 SNPs in a 3.9 Mb region at chromosome 1p32 encompassing PCSK9 in 2458 American Indians. We examined the association between these SNPs and LDL-C. For common variants (MAF ≥ 1%), meta-analysis across the three geographic regions showed common variants in PCSK9 were significantly associated with higher LDL-C. The most significant SNP rs12067569 (MAF = 1.7 %, β = 16.9 ± 3.7, P = 5.9 × 10(-6)) was in complete LD (r(2) = 1) with a nearby missense SNP, rs505151 (E670G) (β = 15.0 ± 3.6, P = 3.6 × 10(-5)). For rare variants (MAF < 1%), rs11591147 (R46L, MAF = 0.9%) was associated with lower LDL-C (β = - 31.1 ± 7.1, P = 1.4 × 10(-5)). The mean (SD) of LDL-C was 76.9 (7.8) and 107.4 (1.0) mg/dL for those with and without the R46L mutation, respectively. One person who was homozygous for R46L had LDL-C levels of 11 mg/dL. In one family, 6 out of 8 members carrying the R46L mutation had LDL-C levels below the lower 10% percentile of LDL-C among all study participants.

CONCLUSIONS

Both rare and common variants in PCSK9 influence plasma LDL-C levels in American Indians. Follow-up studies may disclose the influence of these mutations on the risk of CVD and responses to cholesterol-lowering medications.

PCSK9 and its modulation

Proprotein convertase subtilisin/kexin type 9 (PCSK9), a newly-recognized protein, plays a key role in regulating cholesterol homeostasis. PCSK9 reduces hepatic low-density lipoprotein receptors (LDLRs) thereby increasing LDL-cholesterol (LDL-C). Recently, biologic and genetic research proposed several approaches to inhibit or reduce PCSK9 to improve lipid profile and cardiovascular performance in patients with dyslipidemia, particularly hypercholesterolemia. Of note, PCSK9 is a secreted protein under tight control by multiple modulators. Therefore, elucidating the factors that influence PCSK9 would enhance our understanding of PCSK9 and potentially day-to-day management of these patients at high cardiovascular risk. This review will focus on genetic variants, physiologic processes, pharmacologic agents and pathologic conditions related to PCSK9 in order to assess current and future therapeutic strategies targeting this molecule.

Lipid lowering with PCSK9 inhibitors

Statins are the most-effective therapy currently available for lowering the LDL-cholesterol (LDL-C) level and preventing cardiovascular events. Additional therapies are necessary for patients who cannot reach the target LDL-C level when taking the maximum-tolerated dose of a statin. Proprotein convertase subtilisin/kexin type 9 (PCSK9) is an enzyme with an important role in lipoprotein metabolism. Rare gain-of-function mutations in PCSK9 lead to a high LDL-C level and premature coronary heart disease, whereas loss-of-function variants lead to a low LDL-C level and a reduced incidence of coronary heart disease. Furthermore, the PCSK9 level is increased with statin therapy through negative feedback, which promotes LDL-receptor degradation and decreases the efficacy of LDL-C lowering with statins. PCSK9 inhibition is, therefore, a rational therapeutic target, and several approaches are being pursued. In phase I, II, and III trials, inhibition of PCSK9 with monoclonal antibodies has produced an additional 50-60% decrease in the LDL-C level when used in combination with statin therapy, compared with statin monotherapy. In short-term trials, PCSK9 inhibitors were well tolerated and had a low incidence of adverse effects. Ongoing phase III trials will provide information about the long-term safety of these drugs, and their efficacy in preventing cardiovascular events.

Proprotein convertase subtilisin/kexin 9 inhibitors: an emerging lipid-lowering therapy?

Proprotein convertase subtilisin/kexin 9 (PCSK9) is part of the proteinase K subfamily of subtilases and plays a key role in lipid metabolism. It increases degradation of the low-density lipoprotein receptor (LDL-R), modulates cholesterol metabolism and transport, and contributes to the production of apolipoprotein B (apoB) in intestinal cells. Exogenous PCSK9 modifies the activity of 3-hydroxy-3-methylglutaryl-coenzyme A reductase and acyl coenzyme A:cholesterol acyltransferase and enhances secretion of chylomicrons by modulating production of lipids and apoB-48. Statins increase PCSK9 messenger RNA expression and attenuate the capacity to increase LDL-R levels. Therefore, the inhibition of PCSK9 in combination with statins provides a promising approach for lowering low-density lipoprotein cholesterol (LDL-C) concentrations. This review will address new therapeutic strategies targeting PCSK9, including monoclonal antibodies, antisense oligonucleotides, small interfering RNAs, and other small molecule inhibitors. Further studies are still needed to determine the efficacy and safety of the PCSK9 inhibitors not only to decrease LDL-C but also to investigate the potential underlying mechanisms involved and to test whether these compounds actually reduce cardiovascular end points and mortality.

Effect of E670G Polymorphism in PCSK9 Gene on the Risk and Severity of Coronary Heart Disease and Ischemic Stroke in a Tunisian Cohort

The association of E670G (rs505151) polymorphism in PCSK9 gene with an increased risk of coronary artery disease (CAD) and ischemic stroke (IS) was reported in previous studies. We investigated the effect of the E670G (rs505151) on the risk of CAD and IS in a Tunisian cohort. Genotyping of the PCSK9 E670G was performed using polymerase chain reaction (PCR)-based restriction fragment length polymorphism (RFLP) and then confirmed by direct sequencing. The frequency of the 670G allele was significantly higher in the CAD than in the no-CAD subgroup (0.132 vs. 0.068, p = 0.030). As expected, the incidence of E670G was significantly important in IS subgroup than control group (0.122 vs. 0.073, p = 0.032). Furthermore in CAD patients, the 670G carriers showed significantly increased plasma total cholesterol and LDL-cholesterol levels compared to E670 carriers (6.78 [6.47-7.00] vs. 4.92 [4.02-5.46] mmol/l, p < 0.0001 and 4.60 [4.00-5.04] vs. 3.00 [2.22-3.70] mmol/l p = 0.001, respectively). The risk and severity of CAD were significantly increased in 670G carriers between no-CAD subgroup and CAD patients presenting a stenosis ≥50 % in two or three major coronary arteries (0.068 vs. 0.198, p = 0.001, OR = 3.39 [1.55-7.37]). The E670G polymorphism of the PCSK9 gene is mainly associated with a increased risk and severity of CAD and IS in Tunisian cohort.

Current Phase II proprotein convertase subtilisin/kexin 9 inhibitor therapies for dyslipidemia

INTRODUCTION

Reduction of plasma low-density lipoprotein (LDL) cholesterol concentration with statins reduces adverse cardiovascular outcomes. However, lack of efficacy and intolerance of statins in many patients requires alternative treatments. Currently available non-statin alternatives include bile acid sequestrants, the cholesterol absorption inhibitor ezetimibe, niacin-based preparations and fibrates; however, each of these has limitations. Newer agents for LDL cholesterol reduction include the cholesterol ester transfer protein inhibitors, the microsomal triglyceride transfer protein inhibitor lomitapide, the apolipoprotein B antisense oligonucleotide mipomersen and several molecules that inhibit or interfere with proprotein convertase subtilisin/kexin 9 (PCSK9).

AREAS COVERED

Among the various PCSK9 inhibitors, human data are available for monoclonal antibodies against PCSK9 of which the two most advanced are alirocumab (SAR236553/REGN727) and AMG 145. Phase II studies of these agents as monotherapy or in combination with statins have shown reductions of LDL cholesterol by > 70%, with acceptable safety and tolerability so far.

EXPERT OPINION

Despite their biochemical efficacy, clinical efficacy, reflected by reduction of cardiovascular end points, remains to be shown for two leading monoclonal antibodies against PSCK9. Other issues to be evaluated with these agents over the longer term include development of rare adverse effects and potential attenuation of efficacy.

Genome-wide characterization of shared and distinct genetic components that influence blood lipid levels in ethnically diverse human populations

Blood lipid concentrations are heritable risk factors associated with atherosclerosis and cardiovascular diseases. Lipid traits exhibit considerable variation among populations of distinct ancestral origin as well as between individuals within a population. We performed association analyses to identify genetic loci influencing lipid concentrations in African American and Hispanic American women in the Women's Health Initiative SNP Health Association Resource. We validated one African-specific high-density lipoprotein cholesterol locus at CD36 as well as 14 known lipid loci that have been previously implicated in studies of European populations. Moreover, we demonstrate striking similarities in genetic architecture (loci influencing the trait, direction and magnitude of genetic effects, and proportions of phenotypic variation explained) of lipid traits across populations. In particular, we found that a disproportionate fraction of lipid variation in African Americans and Hispanic Americans can be attributed to genomic loci exhibiting statistical evidence of association in Europeans, even though the precise genes and variants remain unknown. At the same time, we found substantial allelic heterogeneity within shared loci, characterized both by population-specific rare variants and variants shared among multiple populations that occur at disparate frequencies. The allelic heterogeneity emphasizes the importance of including diverse populations in future genetic association studies of complex traits such as lipids; furthermore, the overlap in lipid loci across populations of diverse ancestral origin argues that additional knowledge can be gleaned from multiple populations.

Differential effects of PCSK9 loss of function variants on serum lipid and PCSK9 levels in Caucasian and African Canadian populations

OBJECTIVES

Variants of the secreted glycoprotein, proprotein convertase subtilisin/kexin 9 (PCSK9), associate with both hypo- and hyper-cholesterolemic phenotypes. Herein, we carried out full exonic sequencing of PCSK9 documenting the frequency of single and multiple PCSK9 variations and their effects on serum lipoprotein and PCSK9 levels in Caucasian Canadians.

METHODS

The 12 exons of PCSK9 were sequenced in 207 unrelated Caucasian Canadians. Minor allele frequencies of PCSK9 variants were compared amongst LDL cholesterol (LDLC) quintiles. Serum PCSK9 levels were measured by ELISA and lipoproteins by enzymatic methods. Comparisons were made with a Caucasian family cohort (n=51) and first generation African Canadians (n=31).

RESULTS

In Caucasians, but not African Canadians, the c.61_63insCTG (denoted L10Ins) and A53V PCSK9 variations were linked and their frequency was significantly higher among Caucasian Canadians with LDLC levels in the <25th percentile. In both the unrelated and family Caucasian cohorts those carrying the L10A53V PCSK9 variant had significantly lower LDLC without reduction in plasma PCSK9. The I474V PCSK9 variant associated with significantly lower serum PCSK9 and LDLC. A novel PCSK9 variant was identified; E206K. We found that the frequency of multiple PCSK9 variations was higher in first generation African Canadians.

CONCLUSIONS

We showed that the L10A53V and I474V PCSK9 variants were significantly associated with lower LDLC levels in Caucasian Canadians but differed in their effect on serum PCSK9 concentrations, illuminating differences in their mechanism of inaction and indicating that that PCSK9 measurement alone may not always be a good indicator of PCSK9 function.Full exonic sequencing of PCSK9 pointed to factors that may contribute to L10Ins PCSK9 variant loss of function in Canadians of Caucasian but not those of African descent. These included; (1) its tight linkage with the A53V variant in Caucasians and/or (2) for both the L10 and I474V, the combined (and negating) effect of multiple, differing phenotypic PCSK9 variants within individuals of African ancestry for which combinations of PCSK9 variations and their overall frequency was higher. No population studies, to our knowledge, have addressed or accessed the effect of multiple PCSK9 variants on cholesterol profiles. Our results indicate that this should be considered.