Proprotein Convertase Subtilisin/kexin Type 9 Variants Research Articles

Is It Ever Wise to Edit Wild-Type Alleles? Engineered CRISPR Alleles Versus Millions of Years of Human Evolution.

The tremendous burden of lipid metabolism diseases, coupled with recent developments in human somatic gene editing, has motivated researchers to propose population-wide somatic gene editing of PCSK9 (proprotein convertase subtilisin/kexin type 9) within the livers of otherwise healthy humans. The best-characterized molecular function of PCSK9 is its ability to regulate plasma LDL (low-density lipoprotein) levels through promoting LDL receptor degradation. Individuals with loss-of-function PCSK9 variants have lower levels of plasma LDL and reduced cardiovascular disease. Gain-of-function variants of PCSK9 are strongly associated with familial hypercholesterolemia. A new therapeutic strategy delivers CRISPR/Cas9 (clustered regularly interspaced short palindromic repeats; CRISPR-associated protein 9) specifically to liver cells to edit the wild-type alleles of PCSK9 with the goal of producing a loss-of-function allele. This direct somatic gene editing approach is being pursued despite the availability of US Food and Drug Administration-approved PCSK9 inhibitors that lower plasma LDL levels. Here, we discuss other characterized functions of PCSK9 including its role in infection and host immunity. We explore important factors that may have contributed to the evolutionary selection of PCSK9 in several vertebrates, including humans. Until such time that more fully understand the multiple biological roles of PCSK9, the ethics of permanently editing the gene locus in healthy, wild-type populations remains highly questionable.

LDLR and PCSK9 3´UTR variants and their putative effects on microRNA molecular interactions in familial hypercholesterolemia: a computational approach.

Familial hypercholesterolemia (FH) is caused by pathogenic variants in low-density lipoprotein (LDL) receptor (LDLR) or its associated genes, including apolipoprotein B (APOB), proprotein convertase subtilisin/kexin type 9 (PCSK9), and LDLR adaptor protein 1 (LDLRAP1). However, approximately 40% of the FH patients clinically diagnosed (based on FH phenotypes) may not carry a causal variant in a FH-related gene. Variants located at 3' untranslated region (UTR) of FH-related genes could elucidate mechanisms involved in FH pathogenesis. This study used a computational approach to assess the effects of 3'UTR variants in FH-related genes on miRNAs molecular interactions and to explore the association of these variants with molecular diagnosis of FH. Exons and regulatory regions of FH-related genes were sequenced in 83 FH patients using an exon-target gene sequencing strategy. In silico prediction tools were used to study the effects of 3´UTR variants on interactions between miRNAs and target mRNAs. Pathogenic variants in FH-related genes (molecular diagnosis) were detected in 44.6% FH patients. Among 59 3'UTR variants identified, LDLR rs5742911 and PCSK9 rs17111557 were associated with molecular diagnosis of FH, whereas LDLR rs7258146 and rs7254521 and LDLRAP1 rs397860393 had an opposite effect (p < 0.05). 3´UTR variants in LDLR (rs5742911, rs7258146, rs7254521) and PCSK9 (rs17111557) disrupt interactions with several miRNAs, and more stable bindings were found with LDLR (miR-4435, miR-509-3 and miR-502) and PCSK9 (miR-4796). LDLR and PCSK9 3´UTR variants disturb miRNA:mRNA interactions that could affect gene expression and are potentially associated with molecular diagnosis of FH.

Advanced progress of the relationship between PCSK9 monoclonal antibodies and hyperglycemic adverse events.

Long-term use of statins had been confirmed to cause an increase in hyperglycemic adverse events (HAEs), whose mechanism has been well understood. Proprotein convertase subtilisin/kexin type 9 (PCSK9) monoclonal antibodies (PCSK9-mAbs), a kind of new lipid-lowering drug, can effectively reduce plasma low-density lipoprotein cholesterol levels in patients with CHD and have been widely used. However, animal experiments, Mendelian randomization studies, clinical researches and Meta-analyses which focused on the relationship between PCSK9-mAbs and HAEs had reached different conclusions, which has attracted great attention from clinicians. The newest FOURIER-OLE randomized controlled trial followed PCSK9-mAbs users for over 8 years, whose results suggested that long-term use of PCSK9-mAbs did not increase the incidence of HAEs. Newest Meta-analyses also indicated that there was no relationship between PCSK9-mAbs and NOD. Meanwhile, genetic polymorphisms and variants related to PCSK9 might have effects on HAEs. According to the results of current studies, there is no significant relationship between PCSK9-mAbs and HAEs. However, longer-term follow-up studies are still needed to confirm it. Although PCSK9 genetic polymorphisms and variants may affect the possible occurrence of HAEs, there is no need to perform relevant genetic testing before applying PCSK9-mAbs.

Association of Rare Protein-Truncating DNA Variants in APOB or PCSK9 With Low-density Lipoprotein Cholesterol Level and Risk of Coronary Heart Disease

Protein-truncating variants (PTVs) in apolipoprotein B (APOB) and proprotein convertase subtilisin/kexin type 9 (PCSK9) are associated with significantly lower low-density lipoprotein (LDL) cholesterol concentrations. The association of these PTVs with coronary heart disease (CHD) warrants further characterization in large, multiracial prospective cohort studies. To evaluate the association of PTVs in APOB and PCSK9 with LDL cholesterol concentrations and CHD risk. This studied included participants from 5 National Heart, Lung, and Blood Institute (NHLBI) studies and the UK Biobank. NHLBI study participants aged 5 to 84 years were recruited between 1971 and 2002 across the US and underwent whole-genome sequencing. UK Biobank participants aged 40 to 69 years were recruited between 2006 and 2010 in the UK and underwent whole-exome sequencing. Data were analyzed from June 2021 to October 2022. PTVs in APOB and PCSK9. Estimated untreated LDL cholesterol levels and CHD. Among 19 073 NHLBI participants (10 598 [55.6%] female; mean [SD] age, 52 [17] years), 139 (0.7%) carried an APOB or PCSK9 PTV, which was associated with 49 mg/dL (95% CI, 43-56) lower estimated untreated LDL cholesterol level. Over a median (IQR) follow-up of 21.5 (13.9-29.4) years, incident CHD was observed in 12 of 139 carriers (8.6%) vs 3029 of 18 934 noncarriers (16.0%), corresponding to an adjusted hazard ratio of 0.51 (95% CI, 0.28-0.89; P = .02). Among 190 464 UK Biobank participants (104 831 [55.0%] female; mean [SD] age, 57 [8] years), 662 (0.4%) carried a PTV, which was associated with 45 mg/dL (95% CI, 42-47) lower estimated untreated LDL cholesterol level. Estimated CHD risk by age 75 years was 3.7% (95% CI, 2.0-5.3) in carriers vs 7.0% (95% CI, 6.9-7.2) in noncarriers, corresponding to an adjusted hazard ratio of 0.51 (95% CI, 0.32-0.81; P = .004). Among 209 537 individuals in this study, 0.4% carried an APOB or PCSK9 PTV that was associated with less exposure to LDL cholesterol and a 49% lower risk of CHD.

Association of PCSK9 Loss-of-Function Variants With Risk of Heart Failure

An animal (mouse) study indicated that deficiency of proprotein convertase subtilisin/kexin type 9 (PCSK9) causes cardiac remodeling and heart failure (HF). Cardiac remodeling after PCSK9-inhibitor treatment is a concern for patients and for development of treatment directed against PCSK9. To determine whether genetic variants in the PCSK9 gene are associated with altered cardiac structure, cardiac function, and HF in humans. This was a nested case-control study within the UK Biobank. Between March 13, 2006, and October 1, 2010, the UK Biobank enrolled 502 480 individuals aged 40 to 69 years. This study focused on a subset of those individuals, who completed cardiac magnetic resonance (CMR) imaging and had available genetic data. Analyses were conducted between November 2, 2021, and October 28, 2022. Carrier status of predicted loss-of-function (pLoF) PCSK9 variants, R46L missense variant, and a genetic risk score (GRS). A total of 11 CMR imaging measurements, generated using a machine learning algorithm, and HF diagnosis. In up to 35 135 individuals with CMR images, 18 252 (52%) were female individuals, and mean (SD) age was 55.0 (7.4) years. No significant association between PCSK9 carrier status and CMR indices were found for left ventricular mass (pLoF: β = -1.01; 95% CI, -2.99 to 0.98; P = .32; R46L: β = -0.18; 95% CI, -0.55 to 0.19; P = .35; GRS: β = -0.19; 95% CI, -0.50 to 0.11; P = .22) and left ventricular ejection fraction (pLoF: β = 0.43; 95% CI, -1.32 to 2.18; P = .63; R46L: β = -0.19; 95% CI, -0.52 to 0.14; P = .26; GRS: β = -0.08; 95% CI, -0.35 to 0.20; P = .58) or HF (pLoF: odds ratio [OR], 1.14; 95% CI, 0.56-2.05; P = .69; R46L: OR, 0.99; 95% CI, 0.90-1.10; P = .91; GRS: OR, 1.04; 95% CI, 0.96-1.13; P = .32). Results of this case-control study suggest that there was no association between PCSK9 genetic variants and altered cardiac structure, cardiac function, or HF in humans.

γGT and PCSK9 variants in subjects with hyper-LDL-cholesterolemia.

Gain-of-function (GOF) variants of proprotein convertase subtilisin/kexin type 9 (PCSK9) gene cause high blood low-density lipoprotein (LDL) cholesterol and PCSK9 levels, which are respectively the markers of cardiovascular disease (CVD). High blood activity of gamma-glutamyl transpeptidase (γGT), a pro-oxidant induced by oxidative conditions, is also a marker of CVD. There may be an association between γGT and PCSK9 variants. We aimed to examine the γGT activity by a GOF variant, p.E32K, of PCSK9 in subjects with hyper-LDL-cholesterolemia, an at-risk state for CVD. This study enrolled 114 subjects (mean age, 59 years; 38 males) with hyper-LDL-cholesterolemia who underwent a genotype assay for identification of p.E32K variant and enzymatic measurement of γGT activity. The relationship between the γGT activity and p.E32K was analyzed. γGT activity was significantly lower (median, 21 IU/L) in subjects with p.E32K (n = 12) than in those without the variant (30 IU/L, P < 0.05). The results remained confirmed by multivariate-adjusted analysis. An inverse association was found between γGT and p.E32K, a GOF variant. Elucidation of the mechanism for their association may help understand the development of CVD by PCSK9 variants.

Genotype-driven NPC1L1 and PCSK9 inhibition and reduced risk of periodontitis.

Epidemiological and pre-clinical studies suggest a chemoprotective role of lipid-lowering agents in periodontitis. We tested the association of genetically proxied inhibition of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR), Niemann-Pick C1-Like 1 (NPC1L1) and proprotein convertase subtilisin/kexin type 9 (PCSK9) with periodontitis. Genetic variants in HMGCR, NCP1L1 and PCSK9 associated with low-density lipoprotein (LDL) cholesterol in a genome-wide association study (GWAS) meta-analysis (N= 188,578) were used to proxy therapeutic inhibition of HMGCR, NPC1L1 and PCSK9. For these genetic variants, associations with periodontitis were obtained from GWAS of 17,353 cases and 28,210 controls in the GeneLifestyle Interactions in Dental Endpoints consortium. Generalized weighted least squares analysis accounted for linkage disequilibrium of genotypes to derive pooled estimates. While genetically proxied HMGCR inhibition equivalent to 1 mmol/L reduction in LDL was not associated with odds of periodontitis (odds ratio [OR]=0.92 [95% confidence interval [CI]: 0.73; 1.16]; p= .4905; false discovery rate [FDR]=0.4905), genetically proxied NPC1L1 (OR=0.53 [95% CI: 0.35; 0.81]; p= .0038; FDR=0.0077) and PCSK9 (OR=0.84 [95% CI: 0.74; 0.95]; p= .0051; FDR=0.0077) inhibition lowered the odds of periodontitis. Genetically proxied inhibition of NCP1L1 and PCSK9 was associated with lower odds of periodontitis.

Polymorphic assessment of proprotein convertase subtilisin/kexin type 9 (PCSK9) variant rs11591147 in coronary artery disease subjects from Pakistan

Background and Aims : Coronary artery disease (CAD) is the narrowing of the lumen of coronary arteries due to deposition of plaque. Extensive research has identified a large number of genetic markers predisposing to CAD. Proprotein convertase subtilisin/kexin type 9 is an enzyme that degrade LDL receptors which results in decreased LDL clearance from blood, however loss of function mutations in its gene do the reverse. One such loss of function PCSK9 variant is rs11591147 also known as G137T or R46L.

Leu22_Leu23 Duplication at the Signal Peptide of PCSK9 Promotes Intracellular Degradation of LDLr and Autosomal Dominant Hypercholesterolemia.

PCSK9 (Proprotein convertase subtilisin/kexin type 9) regulates LDL-C (low-density lipoprotein cholesterol) metabolism by targeting LDLr (LDL receptor) for lysosomal degradation. PCSK9 gain-of-function variants cause autosomal dominant hypercholesterolemia by reducing LDLr levels, the D374Y variant being the most severe, while loss-of-function variants are associated with low LDL-C levels. Gain-of-function and loss-of-function activities have also been attributed to variants occurring in the PCSK9 signal peptide. Among them, L11 is a very rare PCSK9 variant that seems to increase LDL-C values in a moderate way causing mild hypercholesterolemia. Using molecular biology and biophysics methodologies, activities of L8 and L11 variants, both located in the leucine repetition stretch of the signal peptide, have been extensively characterized in vitro. L8 variant is not associated with increased LDLr activity, whereas L11 activity is increased by ≈20% compared with wt PCSK9. The results suggest that the L11 variant reduces LDLr levels intracellularly by a process resulting from impaired cleavage of the signal peptide. This would lead to less efficient LDLr transport to the cell membrane and promote LDLr intracellular degradation. Deletion of a leucine in the signal peptide in L8 variant does not affect PCSK9 activity, whereas the leucine duplication in the L11 variant enhances LDLr intracellular degradation. These findings highlight the importance of deep in vitro characterization of PCSK9 genetic variants to determine pathogenicity and improve clinical diagnosis and therapy of inherited familial hypercholesterolemia disease.

The Influence of Treatment with PCSK9 Inhibitors and Variants in the CRP (rs1800947), TNFA (rs1800629), and IL6 (rs1800795) Genes on the Corresponding Inflammatory Markers in Patients with Very High Lipoprotein(a) Levels.

Chronic inflammation contributes significantly to the development and progression of atherosclerosis. However, the factors that lead to an inflammatory imbalance towards a proinflammatory state are not yet fully understood. The CRP rs1800947, TNFA rs1800629, and IL6 rs1800795 polymorphisms may play a role in the pathogenesis of atherosclerosis and were therefore selected to investigate the influence of genetic variability on the corresponding plasma levels after treatment with a proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitor. A group of 69 patients with stable coronary artery disease after myocardial infarction before the age of 50 years and very high lipoprotein(a) levels were enrolled in the study. All patients received a PCSK9 inhibitor (evolocumab or alirocumab). Genotyping was performed using TaqMan assays (CRP rs1800947, TNFA rs1800629, and IL6 rs1800795). Consistent with previous studies, no significant change in levels of inflammatory biomarkers was observed after 6 months of treatment with PCSK9 inhibitors. We also did not detect any significant association between single nucleotide polymorphisms CRP rs1800947, TNFA rs1800629, and IL6 rs1800795 and plasma levels of high-sensitivity C-reactive protein (hsCRP), tumor necrosis factor-α (TNF-α), or interleukin 6 (IL6), respectively, at enrollment. However, the difference in IL6 levels after treatment with PCSK9 inhibitors was statistically significant (p = 0.050) in patients with IL6-74CC genotype, indicating the possible role of the IL6 rs1800795 polymorphism in modulating inflammation.

Coronary Artery Disease Risk of Familial Hypercholesterolemia Genetic Variants Independent of Clinically Observed Longitudinal Cholesterol Exposure.

Familial hypercholesterolemia (FH) genetic variants confer risk for coronary artery disease independent of LDL-C (low-density lipoprotein cholesterol) when considering a single measurement. In real clinical settings, longitudinal LDL-C data are often available through the electronic health record. It is unknown whether genetic testing for FH variants provides additional risk-stratifying information once longitudinal LDL-C is considered. We used the extensive electronic health record data available through the Million Veteran Program to conduct a nested case-control study. The primary outcome was coronary artery disease, derived from electronic health record codes for acute myocardial infarction and coronary revascularization. Incidence density sampling was used to match case/control exposure windows, defined by the date of the first LDL-C measurement to the date of the first coronary artery disease code of the index case. Adjustments for the first, maximum, or mean LDL-C were analyzed. FH variants in LDLR, APOB, and PCSK9 (Proprotein convertase subtilisin/kexin type 9) were assessed by custom genotype array. In a cohort of 23 091 predominantly prevalent cases at enrollment and 230 910 matched controls, FH variant carriers had an increased risk for coronary artery disease (odds ratio [OR], 1.53 [95% CI, 1.24-1.89]). Adjusting for mean LDL-C led to the greatest attenuation of the risk estimate, but significant risk remained (odds ratio, 1.33 [95% CI, 1.08-1.64]). The degree of attenuation was not affected by the number and the spread of LDL-C measures available. The risk associated with carrying an FH variant cannot be fully captured by the LDL-C data available in the electronic health record, even when considering multiple LDL-C measurements spanning more than a decade.

Abstract 11850: Targeted Next-Generation Sequencing of 36 Lipid-Related Genes in Patients With Clinically Diagnosed Familial Hypercholesterolemia

Background: Familial hypercholesterolemia (FH) is characterized by elevated serum low-density lipoprotein cholesterol (LDL-C) levels and premature coronary artery disease. This condition is considered to be caused by mutations of conventional FH genes such as LDL receptor (LDLR), apolipoprotein B (APOB), and proprotein convertase subtilisin/kexin type 9 (PCSK9). However, it is not fully elucidated whether other lipid-related gene variants may be overlapped in addition to these FH genes. Methods and Results: One hundred twenty-five heterozygous FH (HeFH) patients in Osaka University Hospital and Rinku General Medical Center, who met the clinical FH criteria of Japan Atherosclerosis Society were enrolled. Genomic DNA for each patient was extracted from peripheral blood cells. Targeted exon sequencing was performed to investigate 36 lipid-related genes including conventional FH genes. Among variants with a minor allele frequency of &lt;5% in 1000 Genomes Project of East-Asian population, we have defined pathogenic variants if they fulfilled i) protein truncating variants, ii) damaging missense variants, and iii) ClinVar-registered pathogenic or likely pathogenic variants. Among 125 HeFH patients, we have identified LDLR pathogenic variants in 89 patients (71.2%), PCSK9 variants in 6 patients (4.8%), and APOB variants in 1 patient (0.8%). Among these 96 patients, 37 patients (38.5%) additionally have pathogenic variants of other lipid-related genes, which include apolipoprotein E2 (APOE2) in 3 patients, apolipoprotein E4 (APOE4) in 19 patients, variants of ATP-binding cassette subfamily G member 5 (ABCG5) in 3 patients, apolipoprotein C3 (APOC3) in 1 patient, and CD36 in 11 patients. As for remaining 29 patients without conventional FH gene variants, 17 patients (58.6%) have pathogenic variants of other lipid-related genes, which include APOE4 in 13 patients, apolipoprotein E5 (APOE5) in 1 patient, variants of ABCG5 in 1 patient, and CD36 in 2 patients. Conclusion: Approximately 40% clinically diagnosed HeFH patients have pathogenic variants of other lipid-related genes in addition to those of conventional FH genes. These overlapping variants may affect the atherogenicity of patients and selection of medication.

LDL-cholesterol and PCSK9 in patients with familial hypercholesterolemia: influence of PCSK9 variants under lipid-lowering therapy.

BackgroundFamilial hypercholesterolemia (FH), an autosomal dominant genetic disease with the elevated levels of low‐density lipoprotein (LDL) cholesterol (LDL‐C), increases the risk of coronary artery disease (CAD). The proprotein convertase subtilisin/kexin type 9 (PCSK9) gene is associated with FH. There is a positive relationship between circulating LDL‐C and PCSK9 levels, a potential CAD condition, without lipid‐lowering therapy (LLT); however, we do not know whether their correlation exists in FH patients under LLT.MethodsThis study compared the correlation of PCSK9 variants among patients with FH under LLT (n = 70; mean age, 53 years; male, 63%). LDLR, PCSK9 and APOB variants were analyzed using next‐generation sequencing.ResultsThe LDL‐C and PCSK9 levels in patients with gain‐of‐function (GOF) variants of PCSK9 (n = 7) were mostly similar to those in patients with LDLR variants (n = 17) or variant‐negative patients (n = 46). A significant positive correlation was observed between LDL‐C and PCSK9 levels in patients with GOF variants of PCSK9 (r = 0.79, p = 0.04), but not in patients with LDLR variants or variant‐negative patients.ConclusionThe LDL‐C‐PCSK9 correlation is suggested to be retained in FH patients with GOF variants of PCSK9 even under LLT, and these variants can be used as molecular markers for additional treatment with statins in FH patients.

Substantial PCSK9 inactivation in β-cells does not modify glucose homeostasis or insulin secretion in mice

Proprotein convertase subtilisin/kexin type 9 (PCSK9) plays an important role in cholesterol homeostasis by promoting the degradation of the LDL receptor (LDLR). PCSK9 loss-of-function mutations are associated with increased fasting plasma glucose levels and slightly elevated risk of type 2-diabetes. Considering the known detrimental effects of cholesterol accumulation in β-cell, and the widespread use of PCSK9 inhibitors to treat hypercholesterolemia, it is important to gain insight into the role of pancreatic PCSK9 in glucose homeostasis and β-cell function. We generated the first β-cell-specific KO of PCSK9 (βKO). PCSK9 mRNA and protein expression were reduced by 48% and 78% in βKO islets, respectively, indicating that β-cells constitute a major site of PCSK9 expression. In islets, loss of β-cell PCSK9 resulted in unchanged LDLR protein levels, but reduced LDLR mRNA, indicating that cholesterol internalization is enhanced and that β-cell PCSK9 promotes LDLR degradation. In contrast, whole body PCSK9 KO mice exhibited 2-fold higher LDLR protein levels in islets and a stable expression of cholesterogenic genes. Whole body KO and βKO mice presented normal glucose tolerance, insulin release in response to glucose load and insulin sensitivity. Ex vivo glucose-stimulated insulin secretion in presence or absence of fatty acids was similar in WT and KO islets. Like KO mice, individuals carrying loss-of-function PCSK9 variants may be protected from cholesterol-induced toxicity due to reduced circulating cholesterol levels. Using both whole body KO or βKO models, our data demonstrate that PCSK9 deletion in mouse does not have any toxic effect on β-cell function and glucose homeostasis.

Molecular Genetic Approach and Evaluation of Cardiovascular Events in Patients with Clinical Familial Hypercholesterolemia Phenotype from Romania.

This study identifies the genetic background of familial hypercholesterolemia (FH) patients in Romania and evaluates the association between mutations and cardiovascular events. We performed a prospective observational study of 61 patients with a clinical diagnosis of FH selected based on Dutch Lipid Clinic Network (DLCN) and Simon Broome score between 2017 and 2020. Two techniques were used to identify mutations: multiplex ligation-dependent probe amplification (MLPA) and Sanger sequencing. The mutation rate was 37.7%, i.e., 23 patients with mutations were identified, of which 7 subjects had pathogenic mutations and 16 had polymorphisms. Moreover, 10 variants of the low-density lipoprotein receptor (LDLR) gene were identified in 22 patients, i.e., one variant of the proprotein convertase subtilisin/kexin type 9 (PCSK9) gene in six patients, and one variant of the apolipoprotein B (APOB) gene in three patients. Of the LDLR gene variants, four were LDLR pathogenic mutations (c.81C > G, c.502G > A, c.1618G > A mutations in exon 2, exon 4, exon 11, and exon 13–15 duplication). The PCSK9 and APOB gene variants were benign mutations. The pathogenic LDLR mutations were significant predictors of the new cardiovascular events, and the time interval for new cardiovascular events occurrence was significantly decreased, compared to FH patients without mutations. In total, 12 variants were identified, with four pathogenic variants identified in the LDLR gene, whereas 62.3% of the study population displayed no pathological mutations.

Molecular Characterization of Proprotein Convertase Subtilisin/Kexin Type 9 Gene Mutations in Vietnamese Patients with Hypercholesterolemia

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is an enzyme that plays a key role in regulating the circulating low density lipoprotein cholesterol (LDL-C). Among the PCSK9 variants, while gain-of-function mutations aggravate the degradation of LDL receptors, leading to familial hypercholesterolemia (FH), whereas loss-of-function mutations increase LDL receptor levels, lower LDL levels, and prevent coronary heart disease. The variants of PCSK9 have not been clarified in the Vietnamese pop

Correction to: Novel PCSK9 (Proprotein Convertase Subtilisin Kexin Type 9) Variants in Patients With Familial Hypercholesterolemia From Cape Town.

Correction to: Novel PCSK9 (Proprotein Convertase Subtilisin Kexin Type 9) Variants in Patients With Familial Hypercholesterolemia From Cape Town.

Abstract 12689: Targeted Exon Sequencing of Lipid-related Genes in Patients With Clinically Diagnosed Familial Hypercholesterolemia

Background: Familial hypercholesterolemia (FH) is at high risk of premature coronary artery disease (CAD). Japan Atherosclerosis Society (JAS) has published original criteria for FH. Patients are diagnosed clinical FH if at least 2 of the following criteria are satisfied: i) LDL-C ≥ 180 mg/dL, ii) Tendon/ skin xanthomas, iii) History of FH or premature CAD within 2nd degree blood relatives. Although it is easy to apply these criteria for FH-suspected patients, in fact, we are not sure whether other lipid-related genes may be overlapped in addition to those of conventional FH genes such as LDL receptor (LDLR), apolipoprotein B (APOB), and proprotein convertase subtilisin/kexin type 9 (PCSK9). Methods and Results: Ninety-one heterozygous FH (HeFH) patients in Osaka University Hospital, who met the clinical FH criteria of JAS were enrolled after obtaining informed consent. Genomic DNA for each patient was extracted from peripheral blood cells. Targeted exon sequencing was performed to investigate 36 lipid-related genes including conventional FH genes. We have defined pathogenic variants if they fulfilled i) rare protein truncating variants, ii) rare damaging missense variants, and iii) ClinVar-registered pathogenic or likely pathogenic variants. Among 91 HeFH patients (52.9 ± 14.7 years), 41 patients (45.1%) were males. We have identified LDLR pathogenic variants in 61 patients (67.0%) and PCSK9 variants in 1 patient (1.1%). Among these 62 patients, 22 patients (35.5%) additionally have pathogenic variants of other lipid-related genes, which include apolipoprotein E2 (APOE2) in 1 patient, apolipoprotein E4 (APOE4) in 10 patients, ATP-binding cassette subfamily G member 5 (ABCG5) in 2 patients, apolipoprotein C3 (APOC3) in 1 patient, and CD36 in 10 patients. As for remaining 29 patients without conventional FH gene variants, 13 patients (44.8%) have pathogenic variants of other lipid-related genes, which include APOE4 in 11 patients, apolipoprotein E5 (APOE5) in 1 patient, and variants of ABCG5 in 1 patient. Conclusion: We have identified several variants of lipid-related genes in addition to conventional FH genes in HeFH patients diagnosed according to JAS criteria. These variants may affect the atherogenicity of patients and selection of medication.

PCSK9 rs11591147 R46L loss-of-function variant protects against liver damage in individuals with NAFLD.

The proprotein convertase subtilisin/kexin type 9 (PCSK9) plays a key role in cholesterol homeostasis, and its inhibition represents an effective therapy to lower low-density lipoprotein cholesterol (LDL-C) levels. In this study, we examined the impact of the PCSK9 rs11591147 loss-of-function (LOF) variant on liver damage in a multicenter collection of patients at risk of nonalcoholic steatohepatitis (NASH), in clinical samples and experimental models. We considered 1874 consecutive individuals at risk of NASH as determined by histology. The SNP rs11591147, encoding for the p.R46L variant of PCSK9, was genotyped by TaqMan assays. We also evaluated 1) PCSK9 mRNA hepatic expression in human liver, and 2) the impact of a NASH-inducing diet in mice with hepatic overexpression of human PCSK9. Carriers of PCSK9 rs11591147 had lower circulating LDL-C levels and were protected against nonalcoholic fatty liver disease (NAFLD) (OR: 0.42; 95% CI: 0.22-0.81; P=.01), NASH (OR: 0.48; 95% CI: 0.26-0.87; P=.01) and more severe fibrosis (OR: 0.55; 95% CI: 0.32-0.94; P=.03) independently of clinical, metabolic and genetic confounding factors. PCSK9 hepatic expression was directly correlated with liver steatosis (P=.03). Finally, liver-specific overexpression of human PCSK9 in male mice drives NAFLD and fibrosis upon a dietary challenge. In individuals at risk of NASH, PCSK9 was induced with hepatic fat accumulation and PCSK9 rs11591147 LOF variant was protective against liver steatosis, NASH and fibrosis, suggesting that PCSK9 inhibition may be a new therapeutic strategy to treat NASH.

Cascade Screening for Familial Hypercholesterolemia in South Africa: The Wits FIND-FH Program.

Due to gene founder effects, familial hypercholesterolemia (FH) has a prevalence of ≈1:80 in populations of Afrikaner ancestry and is a major contributor to premature atherosclerotic cardiovascular disease in South Africans of Jewish and Indian descent. No systematic program exists to identify these families. Furthermore, information regarding FH prevalence in Black Africans is sparse. The Wits FIND-FH program was initiated in late 2016 to address these issues. Approach and Results: Based on index subjects with definite or probable FH, first-degree relatives were contacted, informed consent obtained, and targeted medical history, physical examination, and blood samples collected. In patients with likely FH using the Simon Broome criteria, DNA analysis for LDLR (low-density lipoprotein receptor), APOB (apolipoprotein B), PCSK9 (proprotein convertase subtilisin/kexin type 9), and LDLRAP1 (LDLR adaptor protein 1) variants was analyzed by next-generation sequencing. Of the initial 700 subjects screened of whom 295 (42%) were index cases, 479 (68.4%) were clinically diagnosed with probable or definite FH. Genetic analysis confirmed 285 of 479 (59.5%) as having variants consistent with FH. Three subjects met the clinical diagnosis for homozygous FH, but DNA analysis revealed a further 34 patients, including 4 Black African subjects, with ≥2 FH-causing variants. Using phenotype cascade screening, the Wits FIND-FH program has screened an average of 30 subjects monthly of whom 68% had a clinical diagnosis of FH with ≈60% genetically confirmed. The program is identifying a small but growing number of Black South Africans with FH. Interestingly, 37 subjects (7.7%) who underwent DNA testing were found to have ≥2 FH-causing variants.