Proprotein convertase subtilisin/kexin 9 V4I variant with LDLR mutations modifies the phenotype of familial hypercholesterolemia

Impact of LDLR polymorphisms on lipid levels and atorvastatin's efficacy in a northern Chinese adult Han cohort with dyslipidemia

BACKGROUND

Dyslipidemia, a significant risk factor for atherosclerotic cardiovascular disease (ASCVD), is influenced by genetic variations, particularly those in the low-density lipoprotein receptor (LDLR) gene. This study aimed to elucidate the effects of LDLR polymorphisms on baseline serum lipid levels and the therapeutic efficacy of atorvastatin in an adult Han population in northern China with dyslipidemia.

METHODS

In this study, 255 Han Chinese adults receiving atorvastatin therapy were examined and followed up. The 3' untranslated region (UTR) of the LDLR gene was sequenced to identify polymorphisms. The associations between gene polymorphisms and serum lipid levels, as well as changes in lipid levels after intervention, were evaluated using the Wilcoxon rank sum test, with a P < 0.05 indicating statistical significance. Assessment of linkage disequilibrium patterns and haplotype structures was conducted utilizing Haploview.

RESULTS

Eleven distinct polymorphisms at LDLR 3' UTR were identified. Seven polymorphisms (rs1433099, rs14158, rs2738466, rs5742911, rs17249057, rs55971831, and rs568219285) were correlated with the baseline serum lipid levels (P < 0.05). In particular, four polymorphisms (rs14158, rs2738466, rs5742911, and rs17249057) were in strong linkage disequilibrium (r2 = 1), and patients with the AGGC haplotype had higher TC and LDL-C levels at baseline. Three polymorphisms (rs1433099, rs2738467, and rs7254521) were correlated with the therapeutic efficacy of atorvastatin (P < 0.05). Furthermore, carriers of the rs2738467 T allele demonstrated a significantly greater reduction in low-density lipoprotein cholesterol (LDL-C) levels post-atorvastatin treatment (P = 0.03), indicating a potentially crucial genetic influence on therapeutic outcomes. Two polymorphisms (rs751672818 and rs566918949) were neither correlated with the baseline serum lipid levels nor atorvastatin's efficacy.

CONCLUSIONS

This research outlined the complex genetic architecture surrounding LDLR 3' UTR polymorphisms and their role in lipid metabolism and the response to atorvastatin treatment in adult Han Chinese patients with dyslipidemia, highlighting the importance of genetic profiling in enhancing tailored therapeutic strategies. Furthermore, this investigation advocates for the integration of genetic testing into the management of dyslipidemia, paving the way for customized therapeutic approaches that could significantly improve patient care.

TRIAL REGISTRATION

This multicenter study was approved by the Ethics Committee of Xiangya Hospital Central South University (ethics number K22144). It was a general ethic. In addition, this study was approved by The First Hospital of Hebei Medical University (ethics number 20220418).

Phenotypic homozygous familial hypercholesterolemia successfully treated with proprotein convertase subtilisin/kexin type 9 inhibitors

Recent data reveal phenotypic HoFH patients may be responsive to PCSK9 inhibitors, challenging prior assumptions. Genetic testing advancements now more accurately forecast patient responses to these therapies, improving treatment strategies.

Impact of providing genetics-based future cardiovascular risk on LDL-C in patients with familial hypercholesterolemia

BACKGROUND

Familial hypercholesterolemia (FH) is an autosomal dominant monogenic disease characterized by high low-density lipoprotein cholesterol (LDL-C) levels. Although carrying causative FH variants is associated with coronary heart disease (CHD), it remains unclear whether disclosing its associated cardiovascular risk affects outcomes in patients with FH.

OBJECTIVE

We aimed to evaluate the efficacy of providing future cardiovascular risk based on genetic testing in addition to a standard FH education program.

METHODS

We conducted a randomized, wait-list controlled, open-label, single-center trial. In the intervention group, we reported a future cardiovascular risk based on the genetic testing adding to standard FH education at week 0. In the wait-list control group, we only disseminated standard FH education according to the guidelines at week 0; they later received a genetic testing-based cardiovascular risk assessment at week 24. The primary endpoint of this study was the plasma LDL-C level at week 24.

RESULTS

Fifty eligible patients with clinically diagnosed FH, without a history of CHD, were allocated to the intervention group (n = 24) or the wait-list control group (n = 26). At week 24, the intervention group had a significantly greater reduction in LDL-C levels than the wait-list control group (mean changes, -13.1 mg/dL vs. 6.6 mg/dL; difference, -19.7 mg/dL; 95% confidence interval, -34 to -5.6; p = 0.009). This interventional effect was consistent with FH causative variant carriers but not with non-carriers.

CONCLUSIONS

In addition to standard FH care, providing future cardiovascular risk based on genetic testing can further reduce plasma LDL-C levels, particularly among FH causal variant carriers.

REGISTRATION

Japan Registry of Clinical Trials (jRCTs04218002). URL: https://jrct.niph.go.jp/latest-detail/jRCTs042180027.

Amplified Risk of Intracranial Artery Stenosis/Occlusion Associated With RNF213 p.R4810K in Familial Hypercholesterolemia

Background

The RNF213 p.R4810K variant is associated with moyamoya disease in East Asian individuals and increases the risk of developing intracranial major artery stenosis/occlusion (ICASO) that affects anterior circulation. Meanwhile, 0.5% to 2.5% of asymptomatic East Asian individuals also carry this variant. As such, additional factors are likely required to develop ICASO in variant carriers. Familial hypercholesterolemia (FH) is a common genetic disorder in Japan that has a significant associated risk of developing premature coronary atherosclerosis; however, the relationship between ICASO and FH remains unknown.

Objectives

This study aimed to determine if FH facilitates RNF213 p.R4810K carriers to develop ICASO.

Methods

We enrolled patients with FH who had undergone brain magnetic resonance angiography at our hospital from May 2005 to March 2020. The RNF213 p.R4810K variant, and LDLR and PCSK9 mutations were genotyped. ICASO lesions in the brain magnetic resonance angiogram were analyzed.

Results

Six RNF213 p.R4810K variant carriers were identified among 167 patients with FH (LDLR, n = 104; PCSK9, n = 22). Five of the carriers (83.3%) exhibited ICASO in the anterior circulation; a significant difference in ICASO frequency was observed between the variant carriers and noncarriers (P = 0.025). The median number of stenotic or occluded arteries in the anterior circulation was also significantly larger in the variant carriers (3 vs 1, P = 0.01); however, did not differ between patients with FH with LDLR and PCSK9 mutations.

Conclusions

Patients with FH exhibit increased prevalence and severity of ICASO associated with RNF213 p.R4810K. Gene mutations for FH may confer an increased risk of ICASO in RNF213 p.R4810K carriers.

Protein structural insights into a rare PCSK9 gain-of-function variant (R496W) causing familial hypercholesterolemia in a Saudi family: whole exome sequencing and computational analysis

Familial hypercholesterolemia (FH) is a globally underdiagnosed genetic condition associated with premature cardiovascular death. The genetic etiology data on Arab FH patients is scarce. Therefore, this study aimed to identify the genetic basis of FH in a Saudi family using whole exome sequencing (WES) and multidimensional bioinformatic analysis. Our WES findings revealed a rare heterozygous gain-of-function variant (R496W) in the exon 9 of the PCSK9 gene as a causal factor for FH in this family. This variant was absent in healthy relatives of the proband and 200 healthy normolipidemic controls from Saudi Arabia. Furthermore, this variant has not been previously reported in various regional and global population genomic variant databases. Interestingly, this variant is classified as "likely pathogenic" (PP5) based on the variant interpretation guidelines of the American College of Medical Genetics (ACMG). Computational functional characterization suggested that this variant could destabilize the native PCSK9 protein and alter its secondary and tertiary structural features. In addition, this variant was predicted to negatively influence its ligand-binding ability with LDLR and Alirocumab antibody molecules. This rare PCSK9 (R496W) variant is likely to expand our understanding of the genetic basis of FH in Saudi Arabia. This study also provides computational structural insights into the genotype-protein phenotype relationship of PCSK9 pathogenic variants and contributes to the development of personalized medicine for FH patients in the future.

Risk factors for cardiovascular events in patients with heterozygous familial hypercholesterolaemia: protocol for a systematic review

INTRODUCTION

Heterozygous familial hypercholesterolaemia (heFH) is the most common monogenic cause of premature atherosclerotic cardiovascular disease. The precise diagnosis of heFH is established by genetic testing. This systematic review will investigate the risk factors that predict cardiovascular events in patients with a genetic diagnosis of heFH.

METHODS AND ANALYSIS

Our literature search will cover publications from database inception until June 2023. We will undertake a search of CINAHL (trial), clinicalKey, Cochrane Library, DynaMed, Embase, Espacenet, Experiments (trial), Fisterra, ÍnDICEs CSIC, LILACS, LISTA, Medline, Micromedex, NEJM Resident 360, OpenDissertations, PEDro, Trip Database, PubPsych, Scopus, TESEO, UpToDate, Web of Science and the grey literature for eligible studies. We will screen the title, abstract and full-text papers for potential inclusion and assess the risk of bias. We will employ the Cochrane tool for randomised controlled trials and non-randomised clinical studies and the Newcastle-Ottawa Scale for assessing the risk of bias in observational studies. We will include full-text peer-reviewed publications, reports of a cohort/registry, case-control and cross-sectional studies, case report/series and surveys related to adults (≥18 years of age) with a genetic diagnostic heFH. The language of the searched studies will be restricted to English or Spanish. The Grading of Recommendations, Assessment, Development and Evaluation approach will be used to assess the quality of the evidence. Based on the data available, the authors will determine whether the data can be pooled in meta-analyses.

ETHICS AND DISSEMINATION

All data will be extracted from published literature. Hence, ethical approval and patient informed consent are not required. The findings of the systematic review will be submitted for publication in a peer-reviewed journal and presentation at international conferences.

PROSPERO REGISTRATION NUMBER

CRD42022304273.

Inclisiran: How Widely and When Should We Use It?

PURPOSE OF REVIEW

Plasma levels of LDL cholesterol (LDL-C) are causally associated with cardiovascular risk. Reducing LDL-C results in a decreased incidence of cardiovascular events, proportionally to the absolute reduction in LDL-C. The inhibition of proprotein convertase subtilisin kexin 9 (PCSK) is a highly effective and safe approach to reducing LDL-C levels. In this review, we discuss the available data on the efficacy and safety of inclisiran, a siRNA targeting PCSK9 and propose a clinical profile for the patients who can benefit the most from this approach.

RECENT FINDINGS

Inclisiran is a small interfering RNA targeting the mRNA of PCSK9 specifically in the liver, owing to the conjugation with triantennary N-acetylgalactosamine. Randomized clinical trials have shown that inclisiran provides robust and durable reductions of PCSK9 and LDL-C levels, with a dosing schedule of once every 6 months after the initial and 3-month doses. These effects are consistent in different categories of patients, including patients with atherosclerotic cardiovascular disease and/or risk equivalent or patients with heterozygous familial hypercholesterolaemia. Ultimately the administration schedule may improve patients' compliance given also the favourable safety profile of the drug. Completion of ongoing outcome clinical trials will provide information on both the expected clinical benefit and the safety of inclisiran administered for longer.

How Can We Identify Very High-Risk Heterozygous Familial Hypercholesterolemia?

Heterozygous familial hypercholesterolemia (HeFH) is a genetic disorder that elevates low-density lipoprotein cholesterol and increases the risk of premature atherosclerotic cardiovascular disease (ASCVD). However, despite their atherogenic lipid profiles, the cardiovascular risk of HeFH varies in each individual. Their variety of phenotypic features suggests the need for better risk stratification to optimize their therapeutic management. The current review summarizes three potential approaches, including (1) definition of familial hypercholesterolemia (FH)-related risk scores, (2) genetic analysis, and (3) biomarkers. The International Atherosclerosis Society has recently proposed a definition of severe FH to identify very high-risk HeFH subjects according to their clinical characteristics. Furthermore, published studies have shown the association of FH-related genetic phenotypes with ASCVD, which indicates the genetic analysis’s potential to evaluate individual cardiovascular risks. Biomarkers reflecting disease activity have been considered to predict the formation of atherosclerosis and the occurrence of ASCVD in HeFH subjects. Incorporating these risk stratifications will be expected to allocate adequate intensity of lipid-lowering therapies in HeFH subjects, which ultimately improves cardiovascular outcomes.

A novel loop-mediated isothermal amplification-based genotyping method and its application for identifying proprotein convertase subtilisin/kexin type 9 variants in familial hypercholesterolemia

BACKGROUND

Proprotein convertase subtilisin/kexin type 9 (PCSK9) plays a key role in regulating low-density lipoprotein levels in plasma. While PCSK9 variants are causatively associated with familial hypercholesterolemia (FH), additional genotyping methods for FH targeting PCSK9 variants are required in a clinical setting. Loop-mediated isothermal amplification (LAMP) is a unique amplification method that amplifies a target gene under isothermal conditions (60-65 °C). However, a robust standardized method has not yet been established for LAMP-based genetic screening tests for genetic diseases, including FH. The present study aimed to develop a novel modification of the LAMP method designed to genotype single nucleotide variants (SNVs) and to apply it for the detection of PCSK9 variants.

METHODS

Using short quenching probes (≤ 10 nucleotides) for the loop structures of LAMP amplicons, accurate detection of SNVs was verified separately for each allele, without any additional procedures, within 3 h. The diagnostic performance of this method in detecting PCSK9 variants was validated in FH patients.

RESULTS

All PCSK9 variants tested via conventional sequencing in FH patients were successfully detected using this novel LAMP method.

CONCLUSIONS

We developed a LAMP-based genotyping method to detect PCSK9 variants in FH. Compared to conventional sequencing, our genotyping method is relatively convenient and time-efficient and is suitable for the screening of FH in clinical settings. Future studies on various genes are also warranted.

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

Background

Familial 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.

Methods

This 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.

Results

The 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.

Conclusion

The 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.

Polygenic risk scores for low-density lipoprotein cholesterol and familial hypercholesterolemia

Familial hypercholesterolemia (FH) is an autosomal dominant monogenic disorder characterized by elevated levels of low-density lipoprotein cholesterol (LDL-C) and an increased risk of premature coronary artery disease (CAD). Recently, it has been shown that a high polygenic risk score (PRS) could be an independent risk factor for CAD in FH patients of European ancestry. However, it is uncertain whether PRS is also useful for risk stratification of FH patients in East Asia. We recruited and genotyped clinically diagnosed FH (CDFH) patients from the Kanazawa University Mendelian Disease FH registry and controls from the Shikamachi Health Improvement Practice genome cohort in Japan. We calculated PRS from 3.6 million variants of each participant (imputed from the 1000 Genome phase 3 Asian dataset) for LDL-C (PRS_LDLC) using a genome-wide association study summary statistic from the BioBank Japan Project. We assessed the association of PRS_LDLC with LDL-C and CAD among and within monogenic FH, mutation negative CDFH, and controls. We tested a total of 1223 participants (376 FH patients, including 173 with monogenic FH and 203 with mutation negative CDFH, and 847 controls) for the analyses. PRS_LDLC was significantly higher in mutation negative CDFH patients than in controls (p = 3.1 × 10^-13). PRS_LDLC was also significantly linked to LDL-C in controls (p trend = 3.6 × 10^-4) but not in FH patients. Moreover, we could not detect any association between PRS_LDLC and CAD in any of the groups. In conclusion, mutation negative CDFH patients demonstrated significantly higher PRS_LDLC than controls. However, PRS_LDLC may have little additional effect on LDL-C and CAD among FH patients.

Patients With LDLR and PCSK9 Gene Variants Experienced Higher Incidence of Cardiovascular Outcomes in Heterozygous Familial Hypercholesterolemia

Background

Patients with familial hypercholesterolemia who harbored both low‐density lipoprotein receptor (LDLR) and PCSK9 (proprotein convertase subtilisin/kexin type 9) gene variants exhibit severe phenotype associated with substantially high levels of low‐density lipoprotein cholesterol. In this study, we investigated the cardiovascular outcomes in patients with both LDLR and PCSK9 gene variants.

Methods and Results

A total of 232 unrelated patients with LDLR and/or PCSK9 gene variants were stratified as follows: patients with LDLR and PCSK9 (LDLR/PCSK9) gene variants, patients with LDLR gene variant, and patients with PCSK9 gene variant. Clinical demographics and the occurrence of primary outcome (nonfatal myocardial infarction) were compared. The observation period of primary outcome started at the time of birth and ended at the time of the first cardiac event or the last visit. Patients with LDLR/PCSK9 gene variants were identified in 6% of study patients. They had higher levels of low‐density lipoprotein cholesterol (P=0.04) than those with LDLR gene variants. On multivariate Cox regression model, they experienced a higher incidence of nonfatal myocardial infarction (hazard ratio, 4.62; 95% CI, 1.66–11.0; P=0.003 versus patients with LDLR gene variant). Of note, risk for nonfatal myocardial infarction was greatest in male patients with LDLR/PCSK9 gene variants compared with those with LDLR gene variant (86% versus 24%; P<0.001).

Conclusions

Patients with LDLR/PCSK9 gene variants were high‐risk genotype associated with atherogenic lipid profiles and worse cardiovascular outcomes. These findings underscore the importance of genetic testing to identify patients with LDLR/PCSK9 gene variants, who require more stringent antiatherosclerotic management.

Proprotein Convertase Subtilisin/Kexin Type 9 Gene Variants in Familial Hypercholesterolemia: A Systematic Review and Meta-Analysis

Proprotein Convertase Subtilisin Kexin type 9 (PCSK9), comprises 12 exons, encoded for an enzyme which plays a critical role in the regulation of circulating low density lipoprotein. The gain-of-function (GOF) mutations aggravate the degradation of LDL receptors, resulting in familial hypercholesterolemia (FH), while loss-of-function (LOF) mutations lead to higher levels of the LDL receptors, lower the levels of LDL cholesterol, and preventing from cardiovascular diseases. It is noted that, previous publications related to the mutations of PCSK9 were not always unification. Therefore, this study aims to present the spectrum and distribution of PCSK9 gene mutations by a meta-analysis. A systematic literature analysis was conducted based on previous studies published by using different keywords. The weighted average frequency of PCSK9 mutation was calculated and accessed by MedCalc®. A total of 32 cohort studies, that included 19,725 familial hypercholesterolemia blood samples, were enrolled in the current study. The analysis results indicated that, based on the random-effect model, the weighted prevalence of PCSK9 mutation was 5.67% (95%CI = 3.68–8.05, p < 0.0001). The prevalence of PCSK9 GOF mutations was 3.57% (95%CI = 1.76–5.97, p < 0.0001) and PCSK9 LOF mutations was 6.05% (95%CI = 3.35–9.47, p < 0.0001). Additionally, the first and the second exon were identified as the hot spot of mutation occurred in PCSK9. Both GOF and LOF mutations have a higher proportion in Asia and Africa compared with other regions. The GOF PCSK9 p.(Glu32Lys) and LOF PCSK9 p.(Leu21dup/tri) were dominant in the Asia region with the proportion as 6.58% (95%CI = 5.77–7.47, p = 0.62) and 16.20% (95%CI = 6.91–28.44, p = 0.0022), respectively. This systematic analysis provided scientific evidence to suggest the mutation of PCSK9 was related to the metabolism of lipoprotein and atherosclerotic cardiovascular disease.

Maternally inherited hypercholesterolemia does not modify the cardiovascular phenotype in familial hypercholesterolemia

BACKGROUND AND AIMS

Familial hypercholesterolemia (FH) is a codominant autosomal disease characterized by a high risk of cardiovascular disease when not in lipid-lowering treatment. However, there is a large variability in the clinical presentation in heterozygous subjects (HeFH). Maternal hypercholesterolemia has been proposed as a cardiometabolic risk factor later in life. Whether this phenotype variability depends on the mother or father origin of hypercholesterolemia is unknown. The objective of this study was to analyze potential differences in anthropometry, superficial lipid deposits, comorbidities, and lipid concentrations depending on the parental origin of hypercholesterolemia within a large group of HeFH.

METHODS

This is a cross-sectional observational, multicenter, nation-wide study in Spain. We recruited adults with HeFH to study clinical differences according to the parental origin. Data on HeFH patients were obtained from the Dyslipidemia Registry of the Spanish Atherosclerosis Society.

RESULTS

HeFH patients were grouped in 1231 HeFH-mother-offspring aged 45.7 (16.3) years and 1174 HeFH-father-offspring aged 44.8 (16.7) years. We did not find any difference in lipid parameters (total cholesterol, triglycerides, LDLc, HDLc, and Lp(a)), nor in the comorbidities studied (cardiovascular disease prevalence, age of onset of cardiovascular disease, obesity, diabetes, and hypertension) between groups. Lipid-lowering treatment did not differ between groups. The prevalence of comorbidities did not show differences when they were studied by age groups.

CONCLUSIONS

Our research with a large group of subjects with HeFH shows that a potential maternal effect is not relevant in FH. However, due to the size of our sample, potential differences between genders cannot be completely ruled out. This implies that severe maternal hypercholesterolemia during pregnancy is not associated with additional risk in the FH affected offspring.

The Digenic Causality in Familial Hypercholesterolemia: Revising the Genotype-Phenotype Correlations of the Disease

Genetically inherited defects in lipoprotein metabolism affect more than 10 million individuals around the globe with preponderance in some parts where consanguinity played a major role in establishing founder mutations. Mutations in four genes have been so far linked to the dominant and recessive form of the disease. Those players encode major proteins implicated in cholesterol regulation, namely, the low-density lipoprotein receptor (LDLR) and its associate protein 1 (LDLRAP1), the proprotein convertase substilin/kexin type 9 (PCSK9), and the apolipoprotein B (APOB). Single mutations or compound mutations in one of these genes are enough to account for a spectrum of mild to severe phenotypes. However, recently several reports have identified digenic mutations in familial cases that do not necessarily reflect a much severe phenotype. Yet, data in the literature supporting this notion are still lacking. Herein, we review all the reported cases of digenic mutations focusing on the biological impact of gene dosage and the potential protective effects of single-nucleotide polymorphisms linked to hypolipidemia. We also highlight the difficulty of establishing phenotype-genotype correlations in digenic familial hypercholesterolemia cases due to the complexity and heterogeneity of the phenotypes and the still faulty in silico pathogenicity scoring system. We finally emphasize the importance of having a whole exome/genome sequencing approach for all familial cases of familial hyperlipidemia to better understand the genetic and clinical course of the disease.

PCSK9 Variants in Familial Hypercholesterolemia: A Comprehensive Synopsis

Autosomal dominant familial hypercholesterolemia (FH) affects approximately 1/250, individuals and potentially leads to elevated blood cholesterol and a significantly increased risk of atherosclerosis. Along with improvements in detection and the increased early diagnosis and treatment, the serious burden of FH on families and society has become increasingly apparent. Since FH is strongly associated with proprotein convertase subtilisin/kexin type 9 (PCSK9), increasing numbers of studies have focused on finding effective diagnostic and therapeutic methods based on PCSK9. At present, as PCSK9 is one of the main pathogenic FH genes, its contribution to FH deserves more explorative research.

Genetic Diagnosis of Familial Hypercholesterolemia in Asia

Familial hypercholesterolemia (FH) is a common genetic disease with an incidence of about 1 in 200-500 individuals. Genetic mutations markedly elevate low-density lipoprotein cholesterol and atherosclerotic cardiovascular disease (ASCVD) in FH patients. With advances in clinical diagnosis and genetic testing, more genetic mutations have been detected, including those in low-density lipoprotein receptor (LDLR), apolipoprotein B (APOB), proprotein convertase subtilisin/kexin type 9 (PCSK9), and so on. Globally, most FH patients remain undiagnosed, untreated, or inappropriately treated. Recently, there was a Global Call to Action by the Global Familial Hypercholesterolemia Community to reduce the health burden of FH. Asia, despite being the most populous continent with half of the global population, has low FH detection rates compared to Western countries. Therefore, we aimed to review the current status of FH genetic diagnosis in Asia to understand the gaps in FH diagnosis and management in this region.

A catalog of the pathogenic mutations of LDL receptor gene in Japanese familial hypercholesterolemia

BACKGROUND

Little data exist on the pathogenic mutations of LDL receptor in Japanese familial hypercholesterolemia (FH).

OBJECTIVE

We aimed to catalog the pathogenic mutations of LDL receptor gene in the 2 major Japanese FH-care centers (Kanazawa University and National Cerebral and Cardiovascular Center Research Institute), where genetic testing of FH has been performed centrally on requests from institutes all over Japan during more than past 2 decades.

METHODS

796 FH subjects from 472 families who had nonsynonymous mutations in LDL receptor gene were included in this study. Genetic mutations were analyzed for mutations by Sanger sequencing as well as by multiplex ligation probe dependent amplification technique for large rearrangements. Pathogenic mutations were defined either as 1) protein truncated variants, 2) registered as pathogenic in ClinVar, or Human Gene Mutation Database (HGMD), or meet the criteria of American College of Medical Genetics and Genomics guideline, or 3) CADD score > 10.

RESULTS

We found 138 different mutations. Among them, 132 mutations were considered as pathogenic, including 19 large rearrangement mutations. However, 6 missense mutations were classified as variants of unknown significance. A single mutation accounted for as much as 41% of the FH subjects recruited from Kanazawa University mainly due to founder gene effect, whereas many singleton mutations were found from National Cerebral and Cardiovascular Center Research Institute located in Osaka.

CONCLUSIONS

We provided the largest catalog of pathogenic mutations of LDL receptor gene in Japanese FH. This could aid to determine the pathogenicity of the LDL receptor genetic mutations not only in Japanese but also in other ethnicities.

Why patients with familial hypercholesterolemia are at high cardiovascular risk? Beyond LDL-C levels

Familial hypercholesterolemia (FH) is a common genetic cause of elevated low-density lipoprotein cholesterol (LDL-C) due to defective clearance of circulating LDL particles. All FH patients are at high risk for premature cardiovascular disease (CVD) events due to their genetically determined lifelong exposure to high LDL-C levels. However, different rates of CVD events have been reported in FH patients, even among those with the same genetic mutations and comparable LDL-C levels. Hence, additional CVD risk modifiers, beyond LDL-C, may contribute to increase CVD risk in the FH population. In this review, we discuss the overall CVD risk burden of the FH population. Additionally, we revise the prognostic impact of several traditional and emerging predictors of CVD risk and we provide an overview of the role of specific tools to stratify CVD risk in FH patients in order to ensure them a more personalized treatment approach.

Impact of LDLR and PCSK9 pathogenic variants in Japanese heterozygous familial hypercholesterolemia patients

BACKGROUND AND AIMS

More than 4970 variants in the low-density lipoprotein receptor (LDLR) gene and 350 variants in the proprotein convertase subtilisin/kexin 9 (PCSK9) gene have been reported in familial hypercholesterolemia (FH) patients. However, the effects of these variants on FH pathophysiology have not been fully clarified. We aimed to update the LDLR and PCSK9 variants in Japanese heterozygous FH (HeFH) patients and annotate their clinical significance for the genetic diagnosis of HeFH.

METHODS

A genetic analysis of the LDLR and PCSK9 genes was performed in 801 clinically diagnosed HeFH patients. The association of the pathogenic variants with the clinical FH phenotype was examined.

RESULTS

Pathogenic variants in the LDLR and PCSK9 genes were found in 46% (n = 296) and 7.8% (n = 51) of unrelated FH patients (n = 650), respectively. The prevalence of Achilles tendon thickness was low (44%) in patients harbouring PCSK9 pathogenic variants. Furthermore, 17% of unrelated FH patients harboured one of five frequent LDLR pathogenic variants: c.1845+2T > C, c.1012T > A: p.(Cys338Ser), c.1297G > C: p.(Asp433His), c.1702C > G: p.(Leu568Val), and c.2431A > T: p.(Lys811*). Patients harbouring the c.1845+2T > C and c.1702C > G: p.(Leu568Val) variants had significantly lower serum LDL-cholesterol levels and higher serum HDL-cholesterol levels, respectively, compared with those harbouring the other LDLR pathogenic variants. The proportion of LDLR pathogenic variants was higher in patients with a younger age of coronary artery disease (CAD) onset and significantly decreased as the age of CAD onset increased.

CONCLUSIONS

This study annotated the clinical significance and characteristics of LDLR and PCSK9 pathogenic variants in Japanese HeFH patients.

Impact of genetic testing on low-density lipoprotein cholesterol in patients with familial hypercholesterolemia (GenTLe-FH): a randomised waiting list controlled open-label study protocol

INTRODUCTION

Familial hypercholesterolemia (FH) is an autosomal-dominant inherited genetic disease. High-throughput sequencing quickly and comprehensively detects causative variants of FH-related genes (LDLR, PCSK9, APOB and LDLRAP1). Although the presence of causative variants in FH-related genes correlates with future cardiovascular events, it remains unclear whether detection of causative gene mutation and disclosure of its associated cardiovascular risk affects outcomes in patients with FH. Therefore, this study intends to evaluate the efficacy of counselling future cardiovascular risk based on genetic testing in addition to standard patients' education programme in patients with FH.

METHODS AND ANALYSIS

A randomised, waiting-list controlled, open-label, single-centre trial will be conducted. We will recruit patients with clinically diagnosed FH without previous history of coronary heart disease from March 2018 to December 2019, and we plan to follow up participants until March 2021. For the intervention group, we will perform genetic counselling and will inform an estimated future cardiovascular risk based on individuals' genetic testing results. The primary endpoint of this study is the plasma low-density lipoprotein cholesterol level at 24 weeks after randomisation. The secondary endpoints assessed at 24 and 48 weeks are as follows: blood test results; smoking status; changes of lipid-lowering agents' regimen and Patients Satisfaction Questionnaire Short Form scores among the four groups divided by the presence of genetic counselling and genetic status of FH.

ETHICS AND DISSEMINATION

This study will be conducted in compliance with the Declaration of Helsinki, the Ethical Guidelines for Medical and Health Research Involving Human Subjects and all other applicable laws and guidelines in Japan. This study protocol was approved by the IRB at Kanazawa University. We will disseminate the final results at international conferences and in a peer-reviewed journal.

TRIAL REGISTRATION NUMBER

UMIN000029375.

Oligogenic familial hypercholesterolemia, LDL cholesterol, and coronary artery disease

BACKGROUND

The genetic background of severe familial hypercholesterolemia (FH) has yet to be determined.

OBJECTIVE

We tested if genetic variants associated with low-density lipoprotein (LDL)-altering autosomal recessive diseases influenced LDL cholesterol levels and the odds for coronary artery disease in patients with high LDL cholesterol.

METHODS

We recruited 500 individuals with elevated LDL cholesterol levels (≥180 mg/dL or ≥140 mg/dL for subjects <15 years). We sequenced the exons of 3 FH genes (LDLR, apolipoprotein B, and proprotein convertase subtilisin/kexin type 9) and 4 LDL-altering accessory genes (ABCG5, ABCG8, APOE, and LDL receptor adaptor protein 1). In addition, 4 single nucleotide polymorphisms associated with polygenic FH in East Asian subjects were genotyped. Oligogenic FH patients were defined as those who harbored damaging variants of both conventional FH genes and LDL-altering accessory genes.

RESULTS

We identified damaging variants of conventional FH genes in 248 participants (50%). We also detected damaging variants in accessory genes in 57 patients (11%) and identified oligogenic FH in 27 of these patients (5%). Polygenic score in the subjects without any FH mutations was significantly higher than those in any other groups. Compared with monogenic FH, oligogenic FH exhibited significantly higher LDL cholesterol (265 mg/dL, 95% confidence interval [CI] 216-312, and 210 mg/dL, 95% CI 189-243; P = .04). Oligogenic FH exhibited higher odds for coronary artery disease when compared with monogenic FH, although it did not reach statistical significance (odds ratio 1.41, 95% CI 0.68-2.21, P = .24).

CONCLUSIONS

Among patients with elevated LDL cholesterol, those with oligogenic FH had higher LDL cholesterol than monogenic FH.

Predicting cardiovascular disease in familial hypercholesterolemia

PURPOSE OF REVIEW

Familial hypercholesterolemia is a frequent genetic disease associated with a high lifetime risk of cardiovascular disease (CVD). Statins are the cornerstone of treatment of familial hypercholesterolemia; however, with the advent of novel LDL-cholesterol lowering therapies, it has become necessary to identify familial hypercholesterolemia subjects presenting a significant residual CVD risk. The aim of this review is to provide an update on the recent literature concerning cardiovascular risk stratification in familial hypercholesterolemia.

RECENT FINDINGS

Recently, several clinical and genetic factors have been shown to be independent predictors of CVD in familial hypercholesterolemia. These include clinical scores such as the Montreal-FH-SCORE, novel protein biomarkers, carotid plaque score and genetic predictors such as genetic risk scores as well as single-nucleotide polymorphisms.

SUMMARY

Although there has been recent progress in cardiovascular risk stratification in familial hypercholesterolemia, there is still a need to further refine our knowledge concerning phenotype modifiers in this disease. Indeed, current known predictors do not explain the entirety of cardiovascular risk. More precise individual risk stratification in familial hypercholesterolemia could help to better tailor the proper therapy for each patient.

Guidelines for Diagnosis and Treatment of Familial Hypercholesterolemia 2017

Statement1. Familial hypercholesterolemia (FH) is an autosomal hereditary disease with the 3 major clinical features of hyper-LDL-cholesterolemia, premature coronary artery disease and tendon and skin xanthomas. As there is a considerably high risk of coronary artery disease (CAD), in addition to early diagnosis and intensive treatment, family screening (cascade screening) is required (Recommendation level A) 2. For a diagnosis of FH, at least 2 of the following criteria should be satisfied:① LDL-C ≥180 mg/dL, ② Tendon/skin xanthomas, ③ History of FH or premature CAD within 2nd degree blood relatives (Recommendation level A) 3. Intensive lipid-lowering therapy is necessary for the treatment of FH. First-line drug should be statins. (Recommendation level A, Evidence level 3) 4. Screening for CAD as well as asymptomatic atherosclerosis should be conducted periodically in FH patients. (Recommendation level A) 5. For homozygous FH, consider LDL apheresis and treatment with PCSK9 inhibitors or MTP inhibitors. (Recommendation level A) 6. For severe forms of heterozygous FH who have resistant to drug therapy, consider PCSK9 inhibitors and LDL apheresis. (Recommendation level A) 7. Refer FH homozygotes as well as heterozygotes who are resistant to drug therapy, who are children or are pregnant or have the desire to bear children to a specialist. (Recommendation level A).

Coronary Artery Plaque Regression by a PCSK9 Antibody and Rosuvastatin in Double-heterozygous Familial Hypercholesterolemia with an LDL Receptor Mutation and a PCSK9 V4I Mutation

The low-density lipoprotein-cholesterol (LDL-C) level of a 38-year-old man diagnosed with acute coronary syndrome was 257 mg/dL. The administration of a proprotein convertase subtilisin-kexin type 9 (PCSK9) antibody in addition to rosuvastatin plus ezetimibe was initiated, reducing his LDL-C level to 37 mg/dL. A genetic analysis revealed both an LDL receptor (LDLR) mutation and a PCSK9 V4I mutation. Nine months after revascularization, intravascular ultrasound revealed plaque regression in the coronary arteries. LDLR/PCSK9 mutation carriers are prone to coronary artery disease. Intensive LDL-C lowering by including PCSK9 antibody was associated with coronary plaque regression, suggesting the expectation of prognosis improvement.

Rare and common variants of APOB and PCSK9 in Korean patients with extremely low low-density lipoprotein-cholesterol levels

Background

Screening of variants, related to lipid metabolism in patients with extreme cholesterol levels, is a tool used to identify targets affecting cardiovascular outcomes. The aim of this study was to examine the prevalence and characteristics of rare and common variants of APOB and PCSK9 in Korean patients with extremely low low-density lipoprotein-cholesterol (LDL-C) levels.

Methods

Among 13,545 participants enrolled in a cardiovascular genome cohort, 22 subjects, whose LDL-C levels without lipid-lowering agents were ≤1 percentile (48 mg/dL) of Korean population, were analyzed. Two target genes, APOB and PCSK9, were sequenced by targeted next-generation sequencing. Prediction of functional effects was conducted using SIFT, PolyPhen-2, and Mutation Taster, and matched against a public database of variants.

Results

Eight rare variants of the two candidate genes (five in APOB and three in PCSK9) were found in nine subjects. Two subjects had more than two different rare variants of either gene (one subject in APOB and another subject in APOB/PCSK9). Conversely, 12 common variants (nine in APOB and three in PCSK9) were discovered in 21 subjects. Among all variants, six in APOB and three in PCSK9 were novel. Several variants previously reported functional, including c.C277T (p.R93C) and c.G2009A (p.G670E) of PCSK9, were found in our population.

Conclusions

Rare variants of APOB or PCSK9 were identified in nine of the 22 study patients with extremely low LDL-C levels, whereas most of them had common variants of the two genes. The common novelty of variants suggested polymorphism of the two genes among them. Our results provide rare genetic information associated with this lipid phenotype in East Asian people.

PCSK9 inhibition in the management of familial hypercholesterolemia

Familial hypercholesterolemia (FH) is a frequent hereditary metabolic disease characterized by high serum low-density lipoprotein (LDL) cholesterol concentration and premature atherosclerotic cardiovascular disease (ASCVD). The discovery of the LDL receptor as one of the causative genes of FH enabled us to understand the pathophysiology of FH and paved the way for developing statins. Similar to LDL receptor, discovery of proprotein convertase subtilisin/kexin type 9 (PCSK9) also created an opportunity for developing its inhibitors. Since PCSK9 degrades LDL receptor protein, inhibiting PCSK9 will be an effective strategy. Evolocumab and alirocumab, anti-PCSK9 antibodies that inhibit binding between PCSK9 and LDL receptors, are now available in Japan. Adding an anti-PCSK9 antibody to standard therapy with statin alone or statin combined with ezetimibe further reduced serum LDL cholesterol levels by around 60% and they significantly decrease cardiovascular event incidence as compared with placebo. Additionally, the strong LDL cholesterol lowering effect of anti-PCSK9 antibody therapies has reportedly enabled the frequency of lipoprotein apheresis to be reduced or to be discontinued. As alternative strategies against PCSK9, antisense oligonucleotide agents that inhibit PCSK9 protein synthesis as well as a small interfering (or short interference) RNA (siRNA) for PCSK9 are also being developed. While relatively high cost can be given as a problem, PCSK9 inhibitors are able to reduce LDL cholesterol dramatically even in FH patients who could not achieve targets until now. To ensure that these drugs are given to the patients who really need them, it is necessary to raise the diagnosis rate and family screening has to be more actively conducted. Finally, it has been reported that PCSK9 is expressed not only in hepatocytes but also in other cells such as epithelial cells in small intestine and vascular smooth muscle cells in atherosclerotic plaque. Further research regarding extra-hepatic pathophysiology of PCSK9 is expected.

Impact of rare variants in autosomal dominant hypercholesterolemia causing genes

PURPOSE OF REVIEW

The systematic analysis of the major candidate genes in autosomal dominant hypercholesterolemia (ADH) and the use of next-generation sequencing (NGS) technology have made possible the discovery of several rare gene variants whose pathogenic effect in most cases remains poorly defined.

RECENT FINDINGS

One major advance in the field has been the adoption of a set of international guidelines for the assignment of pathogenicity to low-density lipoprotein receptor (LDLR) gene variants based on the use of softwares, complemented with data available from literature and public databases. The clinical impact of several novel rare variants in LDLR, APOB, PCSK9, APOE genes have been reported in large studies describing patients with ADH found to be homozygotes/compound heterozygotes, double heterozygotes, or simple heterozygotes. In-vitro functional studies have been conducted to clarify the effect of some rare ApoB variants on LDL binding to LDLR and the impact of a rare ApoE variant on the uptake of VLDL and LDL by hepatocytes.

SUMMARY

The update of the ADH gene variants database and the classification of variants in categories of pathogenicity is a major advance in the understanding the pathophysiology of ADH and in the management of this disorder. The studies of molecularly characterized patients with ADH have emphasized the impact of a specific variant and the variable clinical expression of different genotypes. The functional studies of some variants have increased our understanding of the molecular bases of some forms of ADH.