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

Interactions of several single nucleotide polymorphisms and high body mass index on serum lipid traits

The interactions between single nucleotide polymorphisms (SNPs) and high body mass index (BMI) on serum lipid profiles are limited. This study was undertaken to detect the interactions of 10 SNPs and high BMI on serum lipid traits in an isolated population. A total of 978 normal BMI (< 24 kg/m2) and 751 high BMI (≥ 24 kg/m2) subjects of Bai Ku Yao were randomly selected from our previous stratified randomized cluster samples. Genotypes of rs2066715, rs1044925, low density lipoprotein receptor (LDL-R) Ava||, rs2070895, rs2000813, rs1801133, rs3757354, rs505151, rs2016520, and rs5888 SNPs were determined by polymerase chain reaction and restriction fragment length polymorphism combined with gel electrophoresis, and then confirmed by direct sequencing. The interactions were detected by factorial design covariance analysis. The genotypic and allelic frequencies of rs2070895 and rs505151 were different between normal and high BMI subjects, the genotypic frequency of rs2000813 and allelic frequency of rs3757354 were also different between normal and high BMI subjects (P < 0.01). The levels of total cholesterol (TC), apolipoprotein (Apo) A1 (rs2066715); TC, low-density lipoprotein cholesterol (LDL-C), ApoA1, ApoB, and ApoA1/ApoB (rs2070895); triglyceride (TG), high-density lipoprotein cholesterol (HDL-C), and ApoA1 (rs2000813); TC, HDL-C, LDL-C, ApoA1, and ApoB (rs1801133); HDL-C and ApoA1 (rs3757354) in normal BMI subjects were different among the genotypes (P < 0.01). The levels of LDL-C, ApoB, and ApoA1/ApoB (rs2066715); HDL-C, ApoA1, ApoB, and ApoA1/ApoB (rs2070895); TC, HDL-C, ApoA1, and ApoB (rs2000813); TC, TG, HDL-C, LDL-C, ApoA1, and ApoB (rs1801133); TC, TG, and ApoB (rs3757354); TG (rs505151); TG and ApoA1 and ApoB (rs2016520); and TC, HDL-C, LDL-C, ApoA1, and ApoB (rs5888) in high BMI subjects were also different among the genotypes (P < 0.01). The SNPs of rs2066715 (LDL-C and ApoA1/ApoB); rs2070895 (TC, LDL-C, ApoA1, and ApoB); rs2000813 (ApoB); rs1801133 (TC, TG, and LDL-C); rs3757354 (TC and TG); rs505151 (TG, HDL-C, ApoB, and ApoA1/ApoB); rs2016520 (TG and ApoA1/ApoB); and rs5888 (TG, ApoA1, and ApoB) interacted with high BMI to influence serum lipid levels (P < 0.01). The differences in serum lipid levels between normal and high BMI subjects might partly result from different interactions of several SNPs and high BMI.

Proprotein convertase subtilisin/kexin type 9 gene E670G polymorphism interacts with alcohol consumption to modulate serum lipid levels

BACKGROUND

Both alcohol consumption and the proprotein convertase subtilisin/kexin type 9 (PCSK9) gene polymorphism modulate serum lipid levels, but their interactions on serum lipid profiles are still unknown. The present study was undertaken to detect the interactions of PCSK9 E670G polymorphism and alcohol consumption on serum lipid levels.

METHODS

Genotypes of the PCSK9 E670G in 1352 unrelated subjects (785 non-drinkers and 567 drinkers) were determined by polymerase chain reaction and restriction fragment length polymorphism combined with gel electrophoresis, and then confirmed by direct sequencing. The interactions between PCSK9 E670G genotypes and alcohol consumption on serum lipid parameters were detected by using a factorial design covariance analysis after controlling for potential confounders.

RESULTS

The levels of serum triglyceride, high-density lipoprotein cholesterol, apolipoprotein (Apo) A1, and the ratio of ApoA1 to ApoB were higher in drinkers than in non-drinkers (P < 0.01 for all), whereas the levels of total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C) and ApoB were lower in drinkers than in non-drinkers (P < 0.001 for all). The genotypic and allelic frequencies of PCSK9 E670G were not different between non-drinkers and drinkers (P > 0.05 for each). The subjects with AA genotype in non-drinkers had higher serum LDL-C levels than the subjects with AG genotype, whereas the subjects with AG genotype in drinkers had higher serum TC levels than the subjects with AA genotypes (P < 0.05 for each). The effects of alcohol consumption on TC and LDL-C levels depended upon genotypes, the subjects with AA genotype had lower serum TC and LDL-C levels in drinkers than in non-drinkers.

CONCLUSIONS

Alcohol consumption can modify the effects of the PCSK9 E670G polymorphism on serum TC and LDL-C levels. The subjects with AA genotype of the PCSK9 E670G benefit more from alcohol consumption than the subjects with AG genotype in decreasing serum TC and LDL-C levels.

Several genetic polymorphisms interact with overweight/obesity to influence serum lipid levels

Background

Information about the interactions of single nucleotide polymorphisms (SNPs) and overweight/obesity on serum lipid profiles is still scarce. The present study was undertaken to detect ten SNPs and their interactions with overweight/obesity on serum lipid levels.

Methods

A total of 978 normal weight and 751 overweight/obese subjects of Bai Ku Yao were randomly selected from our previous stratified randomized cluster samples. Normal weight, overweight and obesity were defined as a body mass index (BMI) < 24, 24–28, and > 28 kg/m²; respectively. Serum total cholesterol (TC), triglyceride (TG), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), apolipoprotein (Apo) A1 and ApoB levels were measured. Genotyping of ATP-binding cassette transporter A1 (ABCA-1) V825I, acyl-CoA:cholesterol acyltransferase-1 (ACAT-1) rs1044925, low density lipoprotein receptor (LDL-R) AvaII, hepatic lipase gene (LIPC) -250G>A, endothelial lipase gene (LIPG) 584C>T, methylenetetrahydrofolate reductase (MTHFR) 677C>T, the E3 ubiquitin ligase myosin regulatory light chain-interacting protein (MYLIP) rs3757354, proprotein convertase subtilisin-like kexin type 9 (PCSK9) E670G, peroxisome proliferator-activated receptor delta (PPARD) +294T>C, and Scavenger receptor class B type 1 (SCARB1) rs5888 was performed by polymerase chain reaction and restriction fragment length polymorphism combined with gel electrophoresis, and then confirmed by direct sequencing. The interactions were detected by factorial design covariance analysis.

Results

The genotypic and allelic frequencies of LIPC and PCSK9 were different between normal weight and overweight/obese subjects, the genotypic frequency of LIPG and allelic frequency of MYLIP were also different between normal weight and overweight/obese subjects (P < 0.05-0.001). The levels of TC, ApoA1 (ABCA-1); TC, LDL-C, ApoA1, ApoB and ApoA1/ApoB (LIPC); TG, HDL-C, and ApoA1 (LIPG); TC, HDL-C, LDL-C, ApoA1 and ApoB (MTHFR); HDL-C and ApoA1 (MYLIP) in normal weight subjects were different among the genotypes (P < 0.01-0.001). The levels of LDL-C, ApoB and ApoA1/ApoB (ABCA-1); HDL-C, ApoA1, ApoB and ApoA1/ApoB (LIPC); TC, HDL-C, ApoA1 and ApoB (LIPG); TC, TG, HDL-C, LDL-C, ApoA1 and ApoB (MTHFR); TC, TG and ApoB (MYLIP); TG (PCSK9); TG, ApoA1 and ApoB (PPARD); and TC, HDL-C, LDL-C, ApoA1 and ApoB (SCARB1) in overweight/obese subjects were different among the genotypes (P < 0.01-0.001). The SNPs of ABCA-1 (LDL-C and ApoA1/ApoB); LIPC (TC, LDL-C, ApoA1 and ApoB); LIPG (ApoB); MTHFR (TC, TG and LDL-C); MYLIP (TC and TG); PCSK9 (TG, HDL-C, ApoB and ApoA1/ApoB); PPARD (TG and ApoA1/ApoB); and SCARB1 (TG, ApoA1 and ApoB) interacted with overweight/obesity to influence serum lipid levels (P < 0.05-0.001).

Conclusions

The differences in serum lipid levels between normal weight and overweight/obese subjects might partly result from different genetic polymorphisms and the interactions between several SNPs and overweight/obesity.

An anti-PCSK9 antibody reduces LDL-cholesterol on top of a statin and suppresses hepatocyte SREBP-regulated genes

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a promising therapeutic target for treating coronary heart disease. We report a novel antibody 1B20 that binds to PCSK9 with sub-nanomolar affinity and antagonizes PCSK9 function in-vitro. In CETP/LDLR-hemi mice two successive doses of 1B20, administered 14 days apart at 3 or 10 mpk, induced dose dependent reductions in LDL-cholesterol (≥ 25% for 7-14 days) that correlated well with the extent of PCSK9 occupancy by the antibody. In addition, 1B20 induces increases in total plasma antibody-bound PCSK9 levels and decreases in liver mRNA levels of SREBP-regulated genes PCSK9 and LDLR, with a time course that parallels decreases in plasma LDL-cholesterol (LDL-C). Consistent with this observation in mice, in statin-responsive human primary hepatocytes, 1B20 lowers PCSK9 and LDLR mRNA levels and raises serum steady-state levels of antibody-bound PCSK9. In addition, mRNA levels of several SREBP regulated genes involved in cholesterol and fatty-acid synthesis including ACSS2, FDPS, IDI1, MVD, HMGCR, and CYP51A1 were decreased significantly with antibody treatment of primary human hepatocytes. In rhesus monkeys, subcutaneous (SC) dosing of 1B20 dose-dependently induces robust LDL-C lowering (maximal ~70%), which is correlated with increases in target engagement and total antibody-bound PCSK9 levels. Importantly, a combination of 1B20 and Simvastatin in dyslipidemic rhesus monkeys reduced LDL-C more than either agent alone, consistent with a mechanism of action that predicts additive effects of anti-PCSK9 agents with statins. Our results suggest that antibodies targeting PCSK9 could provide patients powerful LDL lowering efficacy on top of statins, and lower cardiovascular risk.

Most read in cardiovascular genetics on biomarkers, inherited cardiomyopathies and arrhythmias, metabolomics, and genomics

The following articles are being highlighted as part of Circulation: Cardiovascular Genetics' Topic Review series. This series summarizes the most important manuscripts, as selected by the editors, that have been published in Circulation and the Circulation subspecialty journals. The studies included here represent the most-read articles published on the topic of biomarkers, inherited cardiomyopathies and arrhythmias, metabolomics, and genomics in 2009 and 2010.

Premature coronary artery disease and familial hypercholesterolemia: need for early diagnosis and cascade screening in the Indian population

Cardiovascular disease (CVD) is the leading cause of death in India, accounting for 28% of mortality. The average age of onset of CVD is younger (below 55 years) among Indians than in other populations. This may be due to bad lifestyle, genetic factors, or both. Hypertension, smoking, diabetes, and physical inactivity have been identified as modifiable risk factors for heart disease. Hypercholesterolemia is the most common and treatable cause of heart disease. Genetic factors that lead to hypercholesterolemia have not been fully studied in India. Familial Hypercholesterolemia results from mutations in the LDL receptor, ApoB, PCSK9, and ApoE genes. There is an urgent need to screen subjects with premature CAD and their relatives in India for the presence of FH, identify the mutations that lead to high cholesterol, and carry out cascade screening in the at-risk relatives. Those harbouring mutations in the above genes can be treated to lower the cholesterol levels, prevent early CVD, and avoid death. A programme based on these lines has been initiated in Delhi.

Mechanisms and genetic determinants regulating sterol absorption, circulating LDL levels, and sterol elimination: implications for classification and disease risk

This review integrates historical biochemical and modern genetic findings that underpin our understanding of the low-density lipoprotein (LDL) dyslipidemias that bear on human disease. These range from life-threatening conditions of infancy through severe coronary heart disease of young adulthood, to indolent disorders of middle- and old-age. We particularly focus on the biological aspects of those gene mutations and variants that impact on sterol absorption and hepatobiliary excretion via specific membrane transporter systems (NPC1L1, ABCG5/8); the incorporation of dietary sterols (MTP) and of de novo synthesized lipids (HMGCR, TRIB1) into apoB-containing lipoproteins (APOB) and their release into the circulation (ANGPTL3, SARA2, SORT1); and receptor-mediated uptake of LDL and of intestinal and hepatic-derived lipoprotein remnants (LDLR, APOB, APOE, LDLRAP1, PCSK9, IDOL). The insights gained from integrating the wealth of genetic data with biological processes have important implications for the classification of clinical and presymptomatic diagnoses of traditional LDL dyslipidemias, sitosterolemia, and newly emerging phenotypes, as well as their management through both nutritional and pharmaceutical means.

Gene expression variation between African Americans and whites is associated with coronary artery calcification: the multiethnic study of atherosclerosis

Coronary artery calcium (CAC) is a strong indicator of total atherosclerosis burden. Epidemiological data have shown substantial differences in CAC prevalence and severity between African Americans and whites. However, little is known about the molecular mechanisms underlying initiation and progression of CAC. Microarray gene expression profiling of peripheral blood leucocytes was performed from 119 healthy women aged 50 yr or above in the Multi-Ethnic Study of Atherosclerosis cohort; 48 women had CAC score >100 and carotid intima-media thickness (IMT) >1 mm, while 71 had CAC <10 and IMT <0.65 mm. When 17 African Americans were compared with 41 whites in the low-CAC group, 409 differentially expressed genes (false discovery rate <5%) were identified. In addition, 316 differentially expressed genes were identified between the high- and low-CAC groups. A substantial overlap between these two gene lists was observed (148 genes, P < 10(-6)). Furthermore, genes expressed lower in African Americans also tend to express lower in individuals with low CAC (correlation 0.69, P = 0.002). Ontology analysis of the 409 race-associated genes revealed significant enrichment in mobilization of calcium and immune/inflammatory response (P < 10(-9)). Of note, 25 of 30 calcium mobilization genes were involved in immune/inflammatory response (P < 10(-10)). Our data suggest a connection between immune response and vascular calcification and the result provides a potential mechanistic explanation for the lower prevalence and severity of CAC in African Americans compared with whites.

Clinical aspects of PCSK9

Proprotein convertase subtilisin kexin type 9 (PCSK9) is a circulating protein that impairs LDL clearance by promoting the LDL receptor (LDLR) degradation. PCSK9 has emerged as a new pharmacological target for hypercholesterolemia, and different PCSK9 inhibitors are now evaluated in clinical trials. Here, we propose an overview of the clinical perspectives of PCSK9. First, we describe the clinical features of patients with PCSK9 mutations, and how these variations impact the cardiovascular risk. Then, we extensively discuss the potential role of circulating PCSK9 as a new biomarker of lipid metabolism. Indeed, many studies conducted in healthy and type 2 diabetic patients have tested the association of circulating PCSK9 with LDL-cholesterol as well as with multiple metabolic parameters. The overall picture of the clinical relevance of circulating PCSK9 is complicated by the effect of nutritional status and hypolipidemic drugs such as statins, fibrates, ezetimibe on plasma PCSK9 concentrations. Finally, we present a brief overview of the available therapeutic strategies to inhibit PCSK9.

The proprotein convertase subtilisin/kexin type 9 gene E670G polymorphism and serum lipid levels in the Guangxi Bai Ku Yao and Han populations

Background

Proprotein convertase subtilisin-like kexin type 9 (PCSK9) plays a key role in regulating plasma low-density lipoprotein cholesterol (LDL-C) levels. However, the association of E670G (rs505151) polymorphism in the PCSK9 gene and serum lipid levels is inconsistent in several previous studies. The present study was undertaken to detect the association of PCSK9 E670G polymorphism and several environmental factors with serum lipid levels in the Guangxi Bai Ku Yao and Han populations.

Methods

A total of 649 subjects of Bai Ku Yao and 646 participants of Han were randomly selected from our previous samples. Genotypes of the PCSK9 E670G polymorphism were determined via polymerase chain reaction and restriction fragment length polymorphism combined with gel electrophoresis, and then confirmed by direct sequencing.

Results

Serum levels of total cholesterol, high-density lipoprotein cholesterol (HDL-C), LDL-C, and apolipoprotein (Apo) AI were lower in Bai Ku Yao than in Han (P < 0.01 for all). The frequency of G allele was 2.00% in Bai Ku Yao and 4.80% in Han (P < 0.01). There was significant difference in the genotypic and allelic frequencies between Bai Ku Yao and Han (P < 0.01); between normal LDL-C (≤ 3.20 mmol/L) and high LDL-C subgroups (> 3.20 mmol/L, P < 0.01) in Bai Ku Yao; and between normal HDL-C (≥ 0.91 mmol/L) and low HDL-C (< 0.91 mmol/L, P < 0.05), between normal ApoAI (≥ 1.00 g/L) and low ApoAI (< 1.00 g/L, P < 0.05), or between normal ApoAI/ApoB ratio (≥ 1.00) and low ApoAI/ApoB ratio (< 1.00, P < 0.01) subgroups in Han. The G allele carriers in Han had higher serum HDL-C levels and the ratio of ApoAI to ApoB than the G allele noncarriers. The G allele carriers in Han had higher serum HDL-C and ApoAI levels than the G allele noncarriers in males (P < 0.05 for each), whereas the G allele carriers had lower serum ApoB levels and higher the ratio of ApoAI to ApoB than the G allele noncarriers in females (P < 0.05 for all). Serum HDL-C and ApoAI levels in Han were correlated with genotypes (P < 0.05) in males, and serum ApoB levels and the ratio of ApoAI to ApoB were associated with genotypes (P < 0.05) in females.

Conclusions

The PCSK9 E670G polymorphism is mainly associated with some serum lipid parameters in the Han population. The G allele carriers had higher serum HDL-C and ApoAI levels in males, and lower serum ApoB levels and higher the ApoAI/ApoB ratio in females than the G allele noncarriers.

The influence of PCSK9 polymorphisms on serum low-density lipoprotein cholesterol and risk of atherosclerosis

Pro-protein-convertase-subtilisin-kexin-9 (PCSK9) enhances the degradation of the low-density lipoprotein receptor (LDLR) that plays a major role in cholesterol homeostasis. Recent advances have revealed a large number of genetic variants of PCSK9 that may modulate plasma cholesterol levels either positively or negatively, therefore influencing the risk of atherosclerosis. Recognition of these mutants may have clinical implication in assessing severity of disease, prognosis, or response to drug therapy. PCSK9's expression, secretion, and plasma levels maybe modulated by the proprotein convertase furin, by natural inhibitors (annexin-A2), or influenced by lipid-altering agents such as statins, fibrates, ezetimibe, and berberine. It is now a prime target for therapy, prompting the development of various approaches to reduce its LDLR degrading activity, including antibody neutralization, anti-sense oligonucleotides such as phosphorothioates, locked nucleic acids, and RNA interference, and eventually small molecule inhibitors. Which one will be clinically applicable will depend on long-term effects, cost, and ease of administration.

Effects of PCSK9 genetic variants on plasma LDL cholesterol levels and risk of premature myocardial infarction in the Italian population

The R46L variant in the proprotein-convertase subtilisin-kexin type 9 (PCSK9) gene was associated with reduced levels of LDL and total cholesterol and with a lower risk of coronary artery disease. We investigated the association of R46L with myocardial infarction (MI) in 1,880 Italian patients with premature MI and 1,880 controls. A trend toward a protective effect of the L46 allele was observed [odds ratio (OR) = 0.75, 95% confidence interval (CI) = 0.49-1.13; P = 0.17], although the association with MI was not significant. This is probably due to the combined effect of the low frequency of R46L among Italians and of the young age of the analyzed cohort for whom the impact of coronary atherosclerosis is less important. This hypothesis was indirectly confirmed by the significant association found after including 1,056 additional older controls (OR = 0.67, 95% CI = 0.46-0.97; P = 0.036). LDL cholesterol was significantly lower in L46 carriers (116.2 ± 34.7 mg/dl) than in noncarriers (137.4 ± 47.3 mg/dl; P = 0.00022); a similar reduction was observed for total cholesterol (191.7 ± 37.7 vs. 211.7 ± 49 mg/dl; P = 0.00019). Analysis of 23 additional polymorphisms in the PCSK9 region identified another single nucleotide polymorphism (SNP) (rs11206510) associated with cholesterol levels. We confirmed that the L46 allele not only decreases LDL cholesterol but also protects against MI. Moreover, we replicated the association of total and LDL cholesterol with the SNP rs11206510.

Predictive genetic testing for coronary artery disease

Coronary artery disease (CAD) is an inflammatory-metabolic disease in which atherosclerotic plaques cause stenosis of the coronary arteries, leading to acute clinical complications such as myocardial infarction. Since CAD is a multifactorial, polygenic disease with a substantial environmental component, individual risk prediction and stratification is often difficult. Recent technological advances have resulted in substantial progress elucidating the impact of common genetic variation on CAD progression. The discovery of common genetic variants, including the chromosome 9p21.3 locus as the strongest and most highly replicated independent genetic CAD risk factor, has stimulated interest in genetic testing for CAD-associated risk variants. The ultimate goal of genotype-based CAD risk prediction is to improve upon the discrimination and stratification offered by conventional risk factors alone. Genotype-based CAD risk prediction may eventually have clinical utility, but not without intrinsic complexities. Are genotype variables superior predictors of risk compared to a family history of CAD? Is a 10-year risk prediction window ambitious enough for the predictive power of genotype data? This review will outline the current state of genotype-based CAD risk prediction and highlight challenging issues integral to the successful implementation of genetic testing for CAD.