Update and Analysis of the University College London Low Density Lipoprotein Receptor Familial Hypercholesterolemia Database

Model-Informed Dose Selection for a Novel Human Immunoglobulin G4 Derived Monoclonal Antibody Targeting Proprotein Convertase Kwashiorkor Type 9: Insights from Population Pharmacokinetics-Pharmacodynamics and Systems Pharmacology

Monoclonal antibody drugs targeting proprotein convertase kwashiorkor type 9 (PCSK9) have recently demonstrated remarkable success in lipid-lowering therapies. Specifically, antibodies derived from immunoglobulin G1 (IgG1, alirocumab) and IgG2 (evolocumab) have been successfully utilized for this purpose. Recently, a novel recombinant fully human anti-PCSK9 monoclonal antibody, originally derived from IgG4 and designated as SAL003, was developed. This study aimed to explore the pharmacokinetics, efficacy, and safety of SAL003 in both single and multiple administrations. The investigation included both healthy individuals and individuals with hyperlipidemia. To comprehensively grasp the pharmacokinetic (PK) and pharmacodynamic (PD) attributes of SAL003, this study employed population PK-PD (popPK-PD) and mechanistic systems pharmacology (MSP) modeling. These models were employed for predicting low-density lipoprotein cholesterol (LDLc) concentrations and appropriate dosages across diverse potential clinical scenarios. The research results indicated that SAL003 demonstrated comparable pharmacokinetic properties to evolocumab, exhibited notable effectiveness in reducing lipid levels, and was confirmed to be safe and well-tolerated in both healthy individuals and individuals with hyperlipidemia. Notably, SAL003 displayed differing effectiveness between patients and healthy populations. This discrepancy was observed in the popPK-PD model, with a positive population influence on Emax, and the MSP model, indicating elevated PCSK9 clearance and LDLr-related LDLc clearance in the healthy group. Simulation results from the popPK-PD and MSP models indicated a dosage of 140 mg of Q4W and 420 mg of Q8W for phase II/III clinical trials. Reducing the drug dose or extending the dosing intervals may result in treatment failure. Additionally, the simultaneous use of statins led to elevated PCSK9 levels and intensified fluctuations in steady-state LDLc levels during SAL003 treatment.

Genetically modified mice as a tool for the study of human diseases

Modeling a human disease is an essential part of biomedical research. The recent advances in the field of molecular genetics made it possible to obtain genetically modified animals for the study of various diseases. Not only monogenic disorders but also chromosomal and multifactorial disorders can be mimicked in lab animals due to genetic modification. Even human infectious diseases can be studied in genetically modified animals. An animal model of a disease enables the tracking of its pathogenesis and, more importantly, to test new therapies. In the first part of this paper, we review the most common DNA modification technologies and provide key ideas on specific technology choices according to the task at hand. In the second part, we focus on the application of genetically modified mice in studying human diseases.

Genetic and molecular architecture of familial hypercholesterolemia

Atherosclerotic cardiovascular disease is the leading cause of death globally. Despite its important risk of premature atherosclerosis and cardiovascular disease, familial hypercholesterolemia (FH) is still largely underdiagnosed worldwide. It is one of the most frequently inherited diseases due to mutations, for autosomal dominant forms, in either of the LDLR, APOB, and PCSK9 genes or possibly a few mutations in the APOE gene and, for the rare autosomal forms, in the LDLRAP1 gene. The discovery of the genes implicated in the disease has largely helped to improve the diagnosis and treatment of FH from the LDLR by Brown and Goldstein, as well as the introduction of statins, to PCSK9 discovery in FH by Abifadel et al., and the very rapid availability of PCSK9 inhibitors. In the last two decades, major progress has been made in clinical and genetic diagnostic tools and the therapeutic arsenal against FH. Improving prevention, diagnosis, and treatment and making them more accessible to all patients will help reduce the lifelong burden of the disease.

In silico analysis of upstream variants in Brazilian patients with Familial Hypercholesterolemia

Familial hypercholesterolemia (FH) is a prevalent autosomal genetic disease associated with increased risk of early cardiovascular events and death due to chronic exposure to very high levels of low-density lipoprotein cholesterol (LDL-c). Pathogenic variants in the coding regions of LDLR, APOB and PCSK9 account for most FH cases, and variants in non-coding regions maybe involved in FH as well. Variants in the upstream region of LDLR, APOB and PCSK9 were screened by targeted next-generation sequencing and their effects were explored using in silico tools. Twenty-five patients without pathogenic variants in FH-related genes were selected. 3 kb upstream regions of LDLR, APOB and PCSK9 were sequenced using the AmpliSeq (Illumina) and Miseq Reagent Nano Kit v2 (Illumina). Sequencing data were analyzed using variant discovery and functional annotation tools. Potentially regulatory variants were selected by integrating data from public databases, published data and context-dependent regulatory prediction score. Thirty-four single nucleotide variants (SNVs) in upstream regions were identified (6 in LDLR, 15 in APOB, and 13 in PCSK9). Five SNVs were prioritized as potentially regulatory variants (rs934197, rs9282606, rs36218923, rs538300761, g.55038486A>G). APOB rs934197 was previously associated with increased rate of transcription, which in silico analysis suggests that could be due to reducing binding affinity of a transcriptional repressor. Our findings highlight the importance of variant screening outside of coding regions of all relevant genes. Further functional studies are necessary to confirm that prioritized variants could impact gene regulation and contribute to the FH phenotype.

Prevalence of genetically defined familial hypercholesterolemia and the impact on acute myocardial infarction in Taiwanese population: A hospital-based study

Background

Familial hypercholesterolemia (FH) is a common genetic disorder with markedly increased risk of coronary artery diseases (CAD), especially acute myocardial infarction (AMI). However, genetic tests for FH are not always necessary in the current diagnostic criteria of FH, which might lead to underestimation of the prevalence of FH and a lack of awareness of FH-associated CAD and AMI. We aimed to explore the prevalence of genetically defined FH in the hospital-based population and to determine the impact of FH risk variants on CAD and AMI.

Methods

The study participants were recruited between June 24, 2019 and May 12, 2021, at a medical center in Taiwan, in cooperation with the Taiwan Precision Medicine Initiative (TPMI) project. The prevalence of FH was calculated and the effects of FH pathogenic variants on CAD and AMI were analyzed by logistic regression models and shown as ORs and 95% CI.

Results

The prevalence of genetically defined FH was 1.13% in the hospital-based population in Taiwan. Highest LDL and total cholesterol levels were observed in patients with LDLR rs28942084 (LDL 219.4±55.2; total cholesterol 295.8±55.4). There was an approximately 4-fold increased risk of hyperlipidemia in subjects with the LDLR rs769446356 polymorphism (OR, 4.42; 95% CI, 1.92-10.19) and AMI in individuals with the LDLR rs730882109 polymorphism (OR, 3.79; 95% CI, 2.26-6.35), and a 2-fold increased risk of CAD in those with the LDLR rs749038326 polymorphism (OR, 2.14; 95% CI, 1.31-3.50), compared with the groups without pathogenic variants of FH.

Conclusions

The prevalence of genetically defined FH was 1.13% in the hospital-based population in Taiwan, which was higher than the rate observed in individuals with clinically defined FH. The risk of CAD and AMI was increased to varying degrees in subjects with different FH risk alleles. Close monitoring and risk stratification strategy are essential in high-risk patients with FH risk alleles to facilitate early detection and treatments.

An Educational Assessment of Evidence Used for Variant Classification: A Report of the Association for Molecular Pathology

The Association for Molecular Pathology Variant Interpretation Testing Among Laboratories (VITAL) Working Group convened to evaluate the Standards and Guidelines for the Interpretation of Sequence Variants implementation into clinical practice, identify problematic classification rules, and define implementation challenges. Variants and associated clinical information were provided to volunteer respondents. Participant variant classifications were compared with intended consensus-derived classifications of the Working Group. The 24 variant challenges received 1379 responses; 1119 agreed with the intended response (81%; 95% CI, 79% to 83%). Agreement ranged from 44% to 100%, with 16 challenges (67%; 47% to 82%) reaching consensus (≥80% agreement). Participant classifications were also compared to a calculated interpretation of the ACMG Guidelines using the participant-reported criteria as input. The 24 variant challenges had 1368 responses with specific evidence provided and 1121 (82%; 80% to 84%) agreed with the calculated interpretation. Agreement for challenges ranged from 63% to 98%; 15 (63%; 43% to 79%) reaching consensus. Among 81 individual participants, 32 (40%; 30% to 50%) reached agreement with at least 80% of the intended classifications and 42 (52%; 41% to 62%) with the calculated classifications. This study demonstrated that although variant classification remains challenging, published guidelines are being utilized and adapted to improve variant calling consensus. This study identified situations where clarifications are warranted and provides a model for competency assessment.

Assessing accuracy of genotype imputation in the Afrikaner and Brahman cattle breeds of South Africa

Imputation may be used to rescue genomic data from animals that would otherwise be eliminated due to a lower than desired call rate. The aim of this study was to compare the accuracy of genotype imputation for Afrikaner, Brahman, and Brangus cattle of South Africa using within- and multiple-breed reference populations. A total of 373, 309, and 101 Afrikaner, Brahman, and Brangus cattle, respectively, were genotyped using the GeneSeek Genomic Profiler 150 K panel that contained 141,746 markers. Markers with MAF ≤ 0.02 and call rates ≤ 0.95 or that deviated from Hardy Weinberg Equilibrium frequency with a probability of ≤ 0.0001 were excluded from the data as were animals with a call rate ≤ 0.90. The remaining data included 99,086 SNPs and 360 Afrikaner, 75,291 SNPs and 288 animals Brahman, and 97,897 SNPs and 99 Brangus animals. A total of 7986, 7002, and 7000 SNP from 50 Afrikaner and Brahman and 30 Brangus cattle, respectively, were masked and then imputed using BEAGLE v3 and FImpute v2. The within-breed imputation yielded accuracies ranging from 89.9 to 96.6% for the three breeds. The multiple-breed imputation yielded corresponding accuracies from 69.21 to 88.35%. The results showed that population homogeneity and numerical representation for within and across breed strategies, respectively, are crucial components for improving imputation accuracies.

PoLA/CFPiP/PCS/PSLD/PSD/PSH guidelines on diagnosis and therapy of lipid disorders in Poland 2021

In Poland there are still nearly 20 million individuals with hypercholesterolaemia, most of them are unaware of their condition; that is also why only ca. 5% of patients with familial hypercholesterolaemia have been diagnosed; that is why other rare cholesterol metabolism disorders are so rarely diagnosed in Poland. Let us hope that these guidelines, being an effect of work of experts representing 6 main scientific societies, as well as the network of PoLA lipid centers being a part of the EAS lipid centers, certification of lipidologists by PoLA, or the growing number of centers for rare diseases, with a network planned by the Ministry of Health, improvements in coordinated care for patients after myocardial infarction (KOS-Zawał), reimbursement of innovative agents, as well as introduction in Poland of an effective primary prevention program, will make improvement in relation to these unmet needs in diagnostics and treatment of lipid disorders possible.

Genetic testing for familial hypercholesterolemia-past, present, and future

In the early 1980s, the Nobel Prize winning cellular and molecular work of Mike Brown and Joe Goldstein led to the identification of the LDL receptor gene as the first gene where mutations cause the familial hypercholesterolemia (FH) phenotype. We now know that autosomal dominant monogenic FH can be caused by pathogenic variants of three additional genes (APOB/PCSK9/APOE) and that the plasma LDL-C concentration and risk of premature coronary heart disease differs according to the specific locus and associated molecular cause. It is now possible to use next-generation sequencing to sequence all exons of all four genes, processing 96 patient samples in one sequencing run, increasing the speed of test results, and reducing costs. This has resulted in the identification of not only many novel FH-causing variants but also some variants of unknown significance, which require further evidence to classify as pathogenic or benign. The identification of the FH-causing variant in an index case can be used as an unambiguous and rapid test for other family members. An FH-causing variant can be found in 20-40% of patients with the FH phenotype, and we now appreciate that in the majority of patients without a monogenic cause, a polygenic etiology for their phenotype is highly likely. Compared with those with a monogenic cause, these patients have significantly lower risk of future coronary heart disease. The use of these molecular genetic diagnostic methods in the characterization of FH is a prime example of the utility of precision or personalized medicine.

Mouse models of atherosclerosis and their suitability for the study of myocardial infarction

Atherosclerotic plaques impair vascular function and can lead to arterial obstruction and tissue ischaemia. Rupture of an atherosclerotic plaque within a coronary artery can result in an acute myocardial infarction, which is responsible for significant morbidity and mortality worldwide. Prompt reperfusion can salvage some of the ischaemic territory, but ischaemia and reperfusion (IR) still causes substantial injury and is, therefore, a therapeutic target for further infarct limitation. Numerous cardioprotective strategies have been identified that can limit IR injury in animal models, but none have yet been translated effectively to patients. This disconnect prompts an urgent re-examination of the experimental models used to study IR. Since coronary atherosclerosis is the most prevalent morbidity in this patient population, and impairs coronary vessel function, it is potentially a major confounder in cardioprotective studies. Surprisingly, most studies suggest that atherosclerosis does not have a major impact on cardioprotection in mouse models. However, a major limitation of atherosclerotic animal models is that the plaques usually manifest in the aorta and proximal great vessels, and rarely in the coronary vessels. In this review, we examine the commonly used mouse models of atherosclerosis and their effect on coronary artery function and infarct size. We conclude that none of the commonly used strains of mice are ideal for this purpose; however, more recently developed mouse models of atherosclerosis fulfil the requirement for coronary artery lesions, plaque rupture and lipoprotein patterns resembling the human profile, and may enable the identification of therapeutic interventions more applicable in the clinical setting.

Molecular Characterization of Familial Hypercholesterolemia in a North American Cohort

Background

Familial hypercholesterolemia (FH) confers a very high risk of premature cardiovascular disease and is commonly caused by mutations in low-density lipoprotein receptor (LDLR), apolipoprotein B (APOB), or proprotein convertase subtilisin/kexin type 9 (PCSK9) and very rarely in LDLR adaptor protein 1 (LDLRAP1) genes.

Objective

To determine the prevalence of pathogenic mutations in the LDLR, APOB, and PCSK9 in a cohort of subjects who met Simon Broome criteria for FH and compare the clinical characteristics of mutation-positive and mutation-negative subjects.

Methods

Ninety-three men and 107 women aged 19 to 80 years from lipid clinics in the United States and Canada participated. Demographic and historical data were collected, physical examination performed, and serum lipids/lipoproteins analyzed. Targeted sequencing analyses of LDLR and PCSK9 coding regions and exon 26 of APOB were performed followed by detection of LDLR deletions and duplications.

Results

Disease-causing LDLR and APOB variants were identified in 114 and 6 subjects, respectively. Of the 58 LDLR variants, 8 were novel mutations. Compared with mutation-positive subjects, mutation-negative subjects were older (mean 49 years vs 57 years, respectively) and had a higher proportion of African Americans (1% vs 12.5%), higher prevalence of hypertension (21% vs 46%), and higher serum triglycerides (median 86 mg/dL vs 122 mg/dL) levels.

Conclusions

LDLR mutations were the most common cause of heterozygous FH in this North American cohort. A strikingly high proportion of FH subjects (40%) lacked mutations in known culprit genes. Identification of underlying genetic and environmental factors in mutation-negative patients is important to further our understanding of the metabolic basis of FH and other forms of severe hypercholesterolemia.

A Review of PCSK9 Inhibitors and their Effects on Cardiovascular Diseases

BACKGROUND

Cardiovascular diseases remain the leading cause of morbidity and mortality in the world, with elevated Low-Density Lipoprotein-Cholesterol (LDL-C) levels as the major risk factor. Lower levels of LDL-C can effectively reduce the risk of cardiovascular diseases. Proprotein convertase subtilisin/kexin type 9 (PCSK9) plays an important role in regulating the degradation of hepatic LDL receptors that remove LDL-C from the circulation. PCSK9 inhibitors are a new class of agents that are becoming increasingly important in the treatment to reduce LDL-C levels. Two PCSK9 inhibitors, alirocumab and evolocumab, have been approved to treat hypercholesterolemia and are available in the United States and the European Union. Through the inhibition of PCSK9 and increased recycling of LDL receptors, serum LDL-C levels can be significantly reduced.

OBJECTIVE

This review will describe the chemistry, pharmacokinetics, and pharmacodynamics of PCSK9 inhibitors and their clinical effects.

Novel Presentation of Homozygous Familial Hypercholesterolemia With Homozygous Variants in Both LDLR and APOB Genes

This case report describes a 50-year-old-woman from Southeast Asia with extensive atherosclerotic cardiovascular disease, found to have homozygous familial hypercholesterolemia caused by variants of uncertain significance in both the APOB and LDLR genes. Medications were insufficient, and thus LDL apheresis was initiated to further decrease LDL-C. (Level of Difficulty: Beginner.)

Saturation mutagenesis of twenty disease-associated regulatory elements at single base-pair resolution

The majority of common variants associated with common diseases, as well as an unknown proportion of causal mutations for rare diseases, fall in noncoding regions of the genome. Although catalogs of noncoding regulatory elements are steadily improving, we have a limited understanding of the functional effects of mutations within them. Here, we perform saturation mutagenesis in conjunction with massively parallel reporter assays on 20 disease-associated gene promoters and enhancers, generating functional measurements for over 30,000 single nucleotide substitutions and deletions. We find that the density of putative transcription factor binding sites varies widely between regulatory elements, as does the extent to which evolutionary conservation or integrative scores predict functional effects. These data provide a powerful resource for interpreting the pathogenicity of clinically observed mutations in these disease-associated regulatory elements, and comprise a rich dataset for the further development of algorithms that aim to predict the regulatory effects of noncoding mutations.

Spontaneous severe hypercholesterolemia and atherosclerosis lesions in rabbits with deficiency of low-density lipoprotein receptor (LDLR) on exon 7

Rabbits (Oryctolagus cuniculus) have been the very frequently used as animal models in the study of human lipid metabolism and atherosclerosis, because they have similar lipoprotein metabolism to humans. Most of hyperlipidemia and atherosclerosis rabbit models are produced by feeding rabbits a high-cholesterol diet. Gene editing or knockout (KO) offered another means of producing rabbit models for study of the metabolism of lipids and lipoproteins. Even so, apolipoprotein (Apo)E KO rabbits must be fed a high-cholesterol diet to induce hyperlipidemia. In this study, we used the CRISPR/Cas9 system anchored exon 7 of low-density lipoprotein receptor (LDLR) in an attempt to generate KO rabbits. We designed two sgRNA sequences located in E7:g.7055-7074 and E7:g.7102-7124 of rabbit LDLR gene, respectively. Seven LDLR-KO founder rabbits were generated, and all of them contained biallelic modifications. Various mutational LDLR amino acid sequences of the 7 founder rabbits were subjected to tertiary structure modeling with SWISS-MODEL, and results showed that the structure of EGF-A domain of each protein differs from the wild-type. All the founder rabbits spontaneously developed hypercholesterolemia and atherosclerosis on a normal chow (NC) diet. Analysis of their plasma lipids and lipoproteins at the age of 12 weeks revealed that all these KO rabbits exhibited markedly increased levels of plasma TC (the highest of which was 1013.15 mg/dl, 20-fold higher than wild-type rabbits), LDL-C (the highest of which was 730.00 mg/dl, 35-fold higher than wild-type rabbits) and TG accompanied by reduced HDL-C levels. Pathological examinations of a founder rabbit showed prominent aortic atherosclerosis lesions and coronary artery atherosclerosis.In conclusion, we have reported the generation LDLR-KO rabbit model for the study of spontaneous hypercholesterolemia and atherosclerosis on a NC diet. The LDLR-KO rabbits should be a useful rabbit model of human familial hypercholesterolemia (FH) for the simulations of human primary hypercholesterolemia and such models would allow more exact research into cardio-cerebrovascular disease.

From lipoprotein apheresis to proprotein convertase subtilisin/kexin type 9 inhibitors: Impact on low-density lipoprotein cholesterol and C-reactive protein levels in cardiovascular disease patients

In this observational study, we compared the effect of lipoprotein apheresis and evolocumab or alirocumab on levels of lipoprotein cholesterol, triglycerides and inflammatory markers (C reactive protein and interleukin 6) in cardiovascular patients ( n = 9). Patients were monitored during the last year of lipoprotein apheresis followed by six months of treatment with proprotein convertase subtilisin/kexin type 9 inhibitors. The biochemical parameters were determined pre- and post- every apheresis procedure for 12 months and then after one, three and six months of treatment with evolocumab (140 mg every two weeks [Q2W]) or alirocumab (75 mg or 150 mg every two weeks [Q2W]). Lipoprotein apheresis significantly reduced low-density lipoprotein cholesterol levels from 138 ± 32 mg/dl to 46 ± 16 mg/dl ( p < 0.001), with an inter-apheresis level of 114 ± 26 mg/dl. Lipoprotein(a) was also reduced from a median of 42 mg/dl to 17 mg/dl ( p < 0.01). Upon anti-proprotein convertase subtilisin/kexin type 9 therapy, low-density lipoprotein cholesterol levels were similar to post-apheresis (59 ± 25, 41 ± 22 and 42 ± 21mg/dl at one, three and six months, respectively) as well as those of lipoprotein(a) (18 mg/dl). However, an opposite effect was observed on high-density lipoprotein cholesterol levels: –16.0% from pre- to post-apheresis and +34.0% between pre-apheresis and proprotein convertase subtilisin/kexin type 9 inhibitors. Apheresis significantly reduced high-sensitivity C-reactive protein levels (1.5 ± 1.2 mg/l pre-apheresis to 0.6 ± 0.6 mg/l post-apheresis), while no changes were found upon proprotein convertase subtilisin/kexin type 9 mAbs administration. In conclusion, our study demonstrated that, by switching from lipoprotein apheresis to anti-proprotein convertase subtilisin/kexin type 9 therapies, patients reached similar low-density lipoprotein cholesterol and lipoprotein(a) levels, increased those of high-density lipoprotein cholesterol, and showed no changes on high-sensitivity C-reactive protein.

Multimodal lipid-lowering treatment in pediatric patients with homozygous familial hypercholesterolemia-target attainment requires further increase of intensity

BACKGROUND

Familial hypercholesterolemia (FH) causes premature cardiovascular disease (CVD). Lipoprotein apheresis (LA) is recommended as first-line lipid-lowering treatment (LLT) for homozygous (ho) FH.

METHODS

Efficacy of multimodal LLT including lifestyle counseling, drug treatment, and LA was analyzed in 17 pediatric hoFH or compound heterozygous (c-het) FH patients, who commenced chronic LA in Germany before the age of 18.

RESULTS

At time of diagnosis, mean low-density lipoprotein cholesterol (LDL-C) concentration was 19.6 mmol/l (756 mg/dl). Multimodal LLT resulted in 73% reduction of mean LDL-C concentration including a 62% contribution of LA. Only three children (18%) achieved mean LDL-C concentrations below the recommended pediatric target of 3.5 mmol/l (135 mg/dl). In 13 patients (76%) during chronic LA, neither cardiovascular events occurred nor was CVD progression detected clinically or by routine imaging techniques. In four patients (24%), cardiovascular events documented progression of CVD despite weekly LA, including one death due to coronary and cerebrovascular CVD which was not stabilized after commencing LA. Based on the mutational status, only 6 out of the 17 children were candidates for proprotein convertase subtilisin-kexin type 9 (PCSK9) inhibition. Two already responded with further LDL-C decrease by 40%.

CONCLUSIONS

Next to drug therapy, regular LA is an essential component of LLT for approaching LDL-C targets in children with hoFH or c-hetFH, which was successful only in a minority of children. Progression of CVD morbidity and resulting mortality remain unresolved issues. Early and intensified multimodal LLT guided by risk factors beyond LDL-C concentration is needed to improve outcome.

Blood lipid-related low-frequency variants in LDLR and PCSK9 are associated with onset age and risk of myocardial infarction in Japanese

Recent studies have revealed the importance of rare variants in myocardial infarction (MI) susceptibility in European populations. Because genetic architectures vary in different populations, we investigated how they contribute to MI susceptibility in Japanese subjects. We performed targeted sequencing of 36 coronary artery disease risk genes, identified by genome-wide association studies, in 9,956 cases and 8,373 controls. Gene-based association tests identified significant enrichment of rare variants in LDLR and PCSK9 in MI cases. We identified 52 (novel 22) LDLR variants predicted to be damaging. Carriers of these variants showed a higher risk of MI (carriers/non-carriers 89/9867 in cases, 17/8356 controls, OR = 4.4, P = 7.2 × 10⁻¹⁰), higher LDL-cholesterol levels and younger age of onset for MI. With respect to PCSK9, E32K carriers showed higher LDL-cholesterol levels and younger age of onset for MI, whereas R93C carriers had lower LDL-cholesterol levels. A significant correlation between LDL-cholesterol levels and onset age of MI was observed in these variant carriers. In good agreement with previous studies in patients with familial hypercholesterolaemia, our study in the Japanese general population showed that rare variants in LDLR and PCSK9 were associated with the onset age of MI by altering LDL-cholesterol levels.

Detection of Familial Hypercholesterolemia Using Next Generation Sequencing in Two Population-Based Cohorts

We aimed to evaluate the prevalence of familial hypercholesterolaemia (FH) in a subject with hypercholesterolaemia from two population-based cohorts in South Korea. A total of 283 subjects with total cholesterol levels of 290 mg/dL (7.5 mmol/L) or higher were selected from the Namwon and Dong-gu Studies. We used next generation sequencing (NGS) to detect mutations in low-density lipoprotein receptors (LDLR), apolipoprotein B (APOB) and proprotein convertase subtilisin/kexin type 9 (PCSK9) genes. We have confirmed 17 different mutations of the LDLR, APOB and PCSK9 in 23 subjects (8.1%). Eleven LDLR variants and one APOB variant have been previously reported. One LDLR and two PCSK9 rare variants were identified in the variants database, but not in the FH mutation database. Two novel LDLR variants were found, p.Leu680Val, and p.Thr734Phe. No LDLR, APOB or PCSK9 deletions nor insertions were found. When the subjects were restricted to 110 subjects with a total cholesterol ≥310 mg/dL, only 10 variants were found in the 10 subjects (9.1%). These results suggest that given the low prevalence of FH mutations in subjects with high total cholesterol levels, NGS-based testing for a population-based approach to FH detection may not be cost-effective.

Detecting familial hypercholesterolemia by serum lipid profile screening in a hospital setting: Clinical, genetic and atherosclerotic burden profile

BACKGROUND AND AIMS

Familial hypercholesterolemia (FH) is underdiagnosed and public cholesterol screening may be useful to find new subjects. In this study, we aim to investigate the prevalence of FH patients in a hospital screening program and evaluate their atherosclerotic burden using intima-media thickness (IMT).

METHODS AND RESULTS

We screened 1575 lipid profiles and included for genetic analysis adults with a low-density lipoprotein (LDL) cholesterol >190 mg/dL and triglycerides <200 mg/dL and first-degree child relatives with LDL cholesterol >160 mg/dL and triglycerides <200 mg/dL. The diagnosis of FH was presumed by Dutch Lipid Clinic Network (DLCN) criteria and confirmed by the presence of the genetic variant. Mean common carotid intima-media thickness (IMT) was assessed using consensus criteria. After confirming LDL cholesterol value and excluding secondary hypercholesterolemia, 56 subjects with a DLCN ≥4 performed genetic analysis. Of these, 26 had an FH genetic variant. The proportion of patients with a mutation having a DLCN score of 6-8 was 75%; in individuals with a DLCN score >8 it was 100%. Mean IMT was higher in FH patients compared to non FH (0.73 [0.61-0.83] vs 0.71 [0.60-0.75] mm, p < 0.01). Moreover, we detected two mutations not previously described. Finally, simple regression analysis showed a correlation of IMT with LDL cholesterol >190 mg/dL and corneal arcus (p < 0.01 and p < 0.001, respectively).

CONCLUSIONS

A hospital screening was useful to detect FH subjects with increased atherosclerosis. Also, next-generation sequencing was able to detect new FH mutations.

Familial Hypercholesterolaemia Diagnosis and Management

Familial hypercholesterolaemia is the most common monogenic disorder associated with premature coronary artery disease. Mutations are most frequently found in the LDL receptor gene. Clinical criteria can be used to make the diagnosis; however, genetic testing will confirm the disorder and is very useful for cascade screening. Early identification and adequate treatment can improve prognosis, reducing negative clinical cardiovascular outcomes. Patients with familial hypercholesterolaemia are considered at high cardiovascular risk and the treatment target is LDL cholesterol <2.6 mmol/l or at least a 50 % reduction in LDL cholesterol. Patients require intensive treatment with statins and ezetimibe and/or colesevelam. Recently, proprotein convertase subtilisin/kexin type 9 inhibitors have been approved for the management of familial hypercholesterolaemia on top of statins.

Genetic spectrum of low density lipoprotein receptor gene variations in South Indian population

BACKGROUND

Low density lipoprotein receptor (LDLR) is a membrane bound receptor maintaining cholesterol homeostasis along with Apolipoprotein B (APOB), Proprotein Convertase Subtilisin/Kexin type 9 (PCSK9) and other genes of lipid metabolism. Any pathogenic variation in these genes alters the function of the receptor and leads to Familial Hypercholesterolemia (FH) and other cardiovascular diseases.

OBJECTIVE

This study was aimed at screening the LDLR, APOB and PCSK9 genes in Hypercholesterolemic patients to define the genetic spectrum of FH in Indian population.

METHODS

Familial Hypercholesterolemia patients (n=78) of South Indian Tamil population with LDL cholesterol and Total cholesterol levels above 4.9mmol/l and 7.5mmol/l with family history of Myocardial infarction were involved. DNA was isolated by organic extraction method from blood samples and LDLR, APOB and PCSK9 gene exons were amplified using primers that cover exon-intron boundaries. The amplicons were screened using High Resolution Melt (HRM) Analysis and the screened samples were sequenced after purification.

RESULTS

This study reports 20 variations in South Indian population for the first time. In this set of variations 9 are novel variations which are reported for the first time, 11 were reported in other studies also. The in silico analysis for all the variations detected in this study were done to predict the probabilistic effect in pathogenicity of FH.

CONCLUSION

This study adds 9 novel variations and 11 recurrent variations to the spectrum of LDLR gene mutations in Indian population. All these variations are reported for the first time in Indian population. This spectrum of variations was different from the variations of previous Indian reports.

A novel indel variant in LDLR responsible for familial hypercholesterolemia in a Chinese family

Familial hypercholesterolemia (FH) is an inherited disorder characterized by elevation of serum cholesterol bound to low-density lipoprotein. Mutations in LDLR are the major factors responsible for FH. In this study, we recruited a four-generation Chinese family with FH and identified the clinical features of hypercholesterolemia. All affected individuals shared a novel indel mutation (c.1885_1889delinsGATCATCAACC) in exon 13 of LDLR. The mutation segregated with the hypercholesterolemia phenotype in the family. To analyze the function of the indel, we established stable clones of mutant and wild-type LDLR in Hep G2 cells. The mutant LDLR was retained in the endoplasmic reticulum (ER) and failed to glycosylate via the Golgi. Moreover, the membrane LDLR was reduced and lost the ability to take up LDL. Our data also expand the spectrum of known LDLR mutations.

PCSK9 signaling pathways and their potential importance in clinical practice

In the following review, authors described the structure and biochemical pathways of PCSK9, its involvement in LDL metabolism, as well as significances of proprotein convertase subtilisin/kexin type 9 targeted treatment. PCSK9 is a proprotein convertase, which plays a crucial role in LDL receptor metabolism. Transcription and translation of PCSK9 is controlled by different nuclear factors, such as, SREBP and HNF1α. This review focuses on interactions between PCSK9 and LDL receptor, VLDLR, ApoER2, CD36, CD81, and others. The role of PCSK9 in the inflammatory process is presented and its influence on cytokine profile (IL-1, IL-6, IL-10, TNF) in atherosclerotic plaque. Cholesterol metabolism converges also with diabetes by mTORC1 pathways. PCSK9 can be altered by oncologic pathways with utilization of kinases, such as Akt, JNK, and JAK/STAT. Finally, the article shows that blocking PCSK9 has proapoptotic capabilities. Administration of monoclonal antibodies against PCSK9 reduced mortality rate and cardiovascular events in randomized trials. On the other hand, immunogenicity of new drugs may play a crucial role in their efficiency. Bococizumab ended its career following SPIRE-1,2 outcome. PCSK9 inhibitors have enormous potential, which had been reflected by introducing them (as a new class of drugs reducing LDL concentration cholesterol) into New Lipid Guidelines from Rome 2016. Discoveries in drugs development are focused on blocking PCSK9 on different levels. For example, silencing messenger RNA (mRNA of PCSK9) is a new alternative against hypercholesterolemia. Peptides mimicking EGF-A domain of the LDL receptor are gaining significance and hopefully they will soon join others. The significance of PCSK9 has just been uncovered and further data is still required to understand their activity.

The Spectrum of Familial Hypercholesterolemia (FH) in Saudi Arabia: Prime Time for Patient FH Registry

BACKGROUND

Familial hypercholesterolemia (FH) is a life-threatening inherited condition. Untreated patients have the risk to develop raised plasma levels of cholesterol, atherosclerosis and cardiovascular disease (CVD). If diagnosed and treated early in life, the pathological consequences due to atherosclerosis could be avoided and patients with FH can have an anticipated normal life. Mounting evidence suggests that FH is underdiagnosed and undertreated in all populations. The underlying molecular basis of FH is the presence of mutations in one or more genes in the low-density lipoprotein receptor (LDLR), apolipoprotein B (APOB) or proprotein convertase subtilisin/kexin 9 (PCSK9). However, their prevalence is largely unknown in Saudi Arabia but given the high rates of consanguinity, the prevalence appears to be higher. Furthermore, the high prevalence of obesity and diabetes mellitus in Saudi Arabia increases the vascular disease burden in FH cases by adding additional CVD risk factors.

OBJECTIVE

This article explores the spectrum of FH-causing mutations in the highly consanguineous Saudi community, the need for establishing the Saudi FH registry, the challenges in creating gene databases, and cascade screening.

CONCLUSION

The establishment of FH registry and genetic testing should raise awareness not only among healthcare professionals, but the general population as well. It also helps to provide the best treatment regimen in a cost effective manner to this under-recognised population of FH patients.

The use of targeted exome sequencing in genetic diagnosis of young patients with severe hypercholesterolemia

Familial hypercholesterolemia (FH) is an autosomal dominant disorder. Although genetic testing is an important tool for detecting FH-causing mutations in patients, diagnostic methods for young patients with severe hypercholesterolemia are understudied. This study compares the target exome sequencing (TES) technique with the DNA resequencing array technique on young patients with severe hypercholesterolemia. A total of 20 unrelated patients (mean age 14.8 years) with total cholesterol > 10 mmol/L were included. 12 patient samples were processed by DNA resequencing array, 14 patient samples were processed by TES, and 6 patient samples were processed by both methods. Functional characterization of novel mutations was performed by flow cytometry. The mutation detection rate (MDR) of DNA resequencing array was 75%, while the MDR of TES was 100%. A total of 27 different mutations in the LDLR were identified, including 3 novel mutations and 8 mutations with previously unknown pathogenicity. Functional characterization of c.673delA, c.1363delC, p.Leu575Phe and p.Leu582Phe variants found that all of them are pathogenic. Additionally, 7 patients were diagnosed with Heterozygous FH (HeFH) in which lipid levels were significantly higher than common HeFH patients. This data indicates that TES is a very efficient tool for genetic diagnosis in young patients with severe hypercholesterolemia.

The UCL low-density lipoprotein receptor gene variant database: pathogenicity update

Background

Familial hypercholesterolaemia (OMIM 143890) is most frequently caused by variations in the low-density lipoprotein receptor (LDLR) gene. Predicting whether novel variants are pathogenic may not be straightforward, especially for missense and synonymous variants. In 2013, the Association of Clinical Genetic Scientists published guidelines for the classification of variants, with categories 1 and 2 representing clearly not or unlikely pathogenic, respectively, 3 representing variants of unknown significance (VUS), and 4 and 5 representing likely to be or clearly pathogenic, respectively. Here, we update the University College London (UCL) LDLR variant database according to these guidelines.

Methods

PubMed searches and alerts were used to identify novel LDLR variants for inclusion in the database. Standard in silico tools were used to predict potential pathogenicity. Variants were designated as class 4/5 only when the predictions from the different programs were concordant and as class 3 when predictions were discordant.

Results

The updated database (http://www.lovd.nl/LDLR) now includes 2925 curated variants, representing 1707 independent events. All 129 nonsense variants, 337 small frame-shifting and 117/118 large rearrangements were classified as 4 or 5. Of the 795 missense variants, 115 were in classes 1 and 2, 605 in class 4 and 75 in class 3. 111/181 intronic variants, 4/34 synonymous variants and 14/37 promoter variants were assigned to classes 4 or 5. Overall, 112 (7%) of reported variants were class 3.

Conclusions

This study updates the LDLR variant database and identifies a number of reported VUS where additional family and in vitro studies will be required to confirm or refute their pathogenicity.

Child-Parent Familial Hypercholesterolemia Screening in Primary Care

BACKGROUND

Child-parent screening for familial hypercholesterolemia has been proposed to identify persons at high risk for inherited premature cardiovascular disease. We assessed the efficacy and feasibility of such screening in primary care practice.

METHODS

We obtained capillary blood samples to measure cholesterol levels and to test for familial hypercholesterolemia mutations in 10,095 children 1 to 2 years of age during routine immunization visits. Children were considered to have positive screening results for familial hypercholesterolemia if their cholesterol level was elevated and they had either a familial hypercholesterolemia mutation or a repeat elevated cholesterol level 3 months later. A parent of each child with a positive screening result for familial hypercholesterolemia was considered to have a positive screening result for familial hypercholesterolemia if he or she had the same mutation as the child or, if no mutations were identified, had the higher cholesterol level of the two parents.

RESULTS

The use of a prespecified cholesterol cutoff value of 1.53 multiples of the median (MoM, corresponding to a percentile of 99.2) identified 28 children who had positive screening results for familial hypercholesterolemia (0.3% of the 10,095 children; 95% confidence interval [CI], 0.2 to 0.4), including 20 with a familial hypercholesterolemia mutation and 8 with a repeat cholesterol level of at least 1.53 MoM. A total of 17 children who had a cholesterol level of less than 1.53 MoM also had a familial hypercholesterolemia mutation. The overall mutation prevalence was 1 in 273 children (37 in 10,095; 95% CI, 1 in 198 to 1 in 388). The use of an initial cholesterol cutoff value of 1.35 MoM (95th percentile) plus a mutation, or two cholesterol values of at least 1.50 MoM (99th percentile), identified 40 children who had positive screening results for familial hypercholesterolemia (0.4% of the 10,095 children, including 32 children who had a familial hypercholesterolemia mutation and 8 who did not have the mutation) and 40 parents who had positive screening results for familial hypercholesterolemia.

CONCLUSIONS

Child-parent screening was feasible in primary care practices at routine child immunization visits. For every 1000 children screened, 8 persons (4 children and 4 parents) were identified as having positive screening results for familial hypercholesterolemia and were consequently at high risk for cardiovascular disease. (Funded by the Medical Research Council.).

Molecular testing for familial hypercholesterolaemia-associated mutations in a UK-based cohort: development of an NGS-based method and comparison with multiplex polymerase chain reaction and oligonucleotide arrays

Background Detection of disease-associated mutations in patients with familial hypercholesterolaemia is crucial for early interventions to reduce risk of cardiovascular disease. Screening for these mutations represents a methodological challenge since more than 1200 different causal mutations in the low-density lipoprotein receptor has been identified. A number of methodological approaches have been developed for screening by clinical diagnostic laboratories. Methods Using primers targeting, the low-density lipoprotein receptor, apolipoprotein B, and proprotein convertase subtilisin/kexin type 9, we developed a novel Ion Torrent-based targeted re-sequencing method. We validated this in a West Midlands-UK small cohort of 58 patients screened in parallel with other mutation-targeting methods, such as multiplex polymerase chain reaction (Elucigene FH20), oligonucleotide arrays (Randox familial hypercholesterolaemia array) or the Illumina next-generation sequencing platform. Results In this small cohort, the next-generation sequencing method achieved excellent analytical performance characteristics and showed 100% and 89% concordance with the Randox array and the Elucigene FH20 assay. Investigation of the discrepant results identified two cases of mutation misclassification of the Elucigene FH20 multiplex polymerase chain reaction assay. A number of novel mutations not previously reported were also identified by the next-generation sequencing method. Conclusions Ion Torrent-based next-generation sequencing can deliver a suitable alternative for the molecular investigation of familial hypercholesterolaemia patients, especially when comprehensive mutation screening for rare or unknown mutations is required.

Novel Therapies for Familial Hypercholesterolemia

OPINION STATEMENT

Both HeFH and HoFH require dietary and lifestyle modification. Pharmacotherapy of adult HeFH patients is largely driven by the American Heart Association (AHA) algorithm. A high-potency statin is started initially with a goal low-density lipoprotein cholesterol (LDL-C) reduction of >50 %. The LDL-C target is adjusted to <100 or <70 mg/dL in subjects with coronary artery disease (CAD) with ezetimibe being second line. If necessary, a third adjunctive therapy, such as a PSCK9 inhibitor (not yet approved in children) or bile acid-binding resin, can be added. Finally, LDL-C apheresis can be considered in patients with LDL-C >300 mg/dL (or >200 mg/dL with significant CAD, although now approved for LDL-C as low as 160 mg/dL with CAD). Due to the early, severe LDL-C elevation in HoFH patients, concerning natural history, rarity of the condition, and nuances of treatment, all HoFH patients should be treated at a pediatric or adult center with HoFH experience. LDL-C apheresis should be considered as early as 5 years of age. However, apheresis availability and tolerability is limited and pharmacotherapy is required. Generally, the AHA algorithm with reference to the European Atherosclerosis Society Consensus Panel recommendations is reasonable with all patients initiated on high-dose, high-potency statin, ezetimibe, and bile acid-binding resins. In most, additional LDL-C lowering is required with PCSK9 inhibitors and/or lomitapide or mipomersen. Liver transplantation can also be considered at experienced centers as a last resort.

Leveraging human genetics to guide drug target discovery

Identifying appropriate molecular targets is a critical step in drug development. Despite many advantages, the traditional tools of observational epidemiology and cellular or animal models of disease can be misleading in identifying causal pathways likely to lead to successful therapeutics. Here, we review some favorable aspects of human genetics studies that have the potential to accelerate drug target discovery. These include using genetic studies to identify pathways relevant to human disease, leveraging human genetics to discern causal relationships between biomarkers and disease, and studying genetic variation in humans to predict the potential efficacy and safety of inhibitory compounds aimed at molecular targets. We present some examples taken from studies of plasma lipids and coronary artery disease to highlight how human genetics can accelerate therapeutics development.

The genetics and screening of familial hypercholesterolaemia

Familial Hypercholesterolaemia is an autosomal, dominant genetic disorder that leads to elevated blood cholesterol and a dramatically increased risk of atherosclerosis. It is perceived as a rare condition. However it affects 1 in 250 of the population globally, making it an important public health concern. In communities with founder effects, higher disease prevalences are observed.

We discuss the genetic basis of familial hypercholesterolaemia, examining the distribution of variants known to be associated with the condition across the exons of the genes LDLR, ApoB, PCSK9 and LDLRAP1. We also discuss screening programmes for familial hypercholesterolaemia and their cost-effectiveness. Diagnosis typically occurs using one of the Dutch Lipid Clinic Network (DCLN), Simon Broome Register (SBR) or Make Early Diagnosis to Prevent Early Death (MEDPED) criteria, each of which requires a different set of patient data. New cases can be identified by screening the family members of an index case that has been identified as a result of referral to a lipid clinic in a process called cascade screening. Alternatively, universal screening may be used whereby a population is systematically screened.

It is currently significantly more cost effective to identify familial hypercholesterolaemia cases through cascade screening than universal screening. However, the cost of sequencing patient DNA has fallen dramatically in recent years and if the rate of progress continues, this may change.

The genetic spectrum of familial hypercholesterolemia in south-eastern Poland

BACKGROUND

Familial hypercholesterolemia (FH) is a common autosomal dominant disorder with a frequency of 1 in 200 to 500 in most European populations. Mutations in LDLR, APOB and PCSK9 genes are known to cause FH. In this study, we analyzed the genetic spectrum of the disease in the understudied Polish population.

MATERIALS AND METHODS

161 unrelated subjects with a clinical diagnosis of FH from the south-eastern region of Poland were recruited. High resolution melt and direct sequencing of PCR products were used to screen 18 exons of LDLR, a region of exon 26 in the APOB gene and exon 7 of PCSK9. Multiplex ligation-dependent probe amplification (MLPA) was performed to detect gross deletions and insertions in LDLR. Genotypes of six LDL-C raising SNPs were used for a polygenic gene score calculation.

RESULTS

We found 39 different pathogenic mutations in the LDLR gene with 10 of them being novel. 13 (8%) individuals carried the p.Arg3527Gln mutation in APOB, and overall the detection rate was 43.4%. Of the patients where no mutation could be found, 53 (84.1%) had a gene score in the top three quartiles of the healthy comparison group suggesting that they have a polygenic cause for their high cholesterol.

CONCLUSIONS

These results confirm the genetic heterogeneity of FH in Poland, which should be considered when designing a diagnostic strategy in the country. As in the UK, in the majority of patients where no mutation can be found, there is likely to be a polygenic cause of their high cholesterol level.

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

BACKGROUND

Familial hypercholesterolemia (FH) is caused by mutations in the genes encoding low-density lipoprotein receptor (LDLR), apolipoprotein B, or proprotein convertase subtilisin/kexin 9 (PCSK9). However, FH shows variability of the clinical phenotype modified by other genetic variants or environmental factors.

OBJECTIVE

Our objective was to determine the distribution of PCSK9 variants in Japanese FH heterozygotes and to clarify whether those variants and the combination of those variants and LDLR mutations modify the clinical phenotypes.

METHODS

A direct sequence analysis was performed for all 18 exons of LDLR gene and 12 exons of PCSK9 gene in 269 clinically diagnosed FH heterozygotes. The serum lipid levels of the carriers of each variant were compared to those of noncarriers. We also assessed Achilles tendon xanthoma and the prevalence of coronary artery disease (CAD) in the patients aged ≥30 years.

RESULTS

Eleven PCSK9 variants were detected. There were 4 frequent PCSK9 variants: L21_22insL, A53 V, V4I, and E32 K. The PCSK9 L21_22insL and A53 V were in linkage disequilibrium with each other. There were no significant differences in serum lipids levels and the prevalence of CAD at the age of ≥ 30 years between PCSK9 V4I, L21_22insL/A53 V, or E32 K variant carriers and noncarriers without LDLR mutations. In the patients carrying LDLR mutations and aged ≥ 30 years, the additional PCSK9 V4I variant was linked to a significantly increased prevalence of CAD in accord with the elevation of the LDL-cholesterol level.

CONCLUSIONS

The addition of the PCSK9 V4I was suggested to modify the phenotype of patients carrying LDLR mutations by affecting their LDLR metabolism.

Premature coronary heart disease and autosomal dominant hypercholesterolemia: Increased risk in women with LDLR mutations

BACKGROUND

For patients with autosomal dominant hypercholesterolemia (ADH), it remains unclear whether differences exist in the risk of premature coronary heart disease (CHD) between patients with confirmed mutations in low-density lipoprotein receptor (LDLR) vs those without detectable mutations.

OBJECTIVE

This study sought to assess the risk of premature CHD in ADH patients with mutations in LDLR (referred to as familial hypercholesterolemia [FH]) vs those without detectable mutations (unexplained ADH), stratified by sex.

METHODS

Comparative study of premature CHD in a multiethnic cohort of 111 men and 165 women meeting adult Simon-Broome criteria for ADH.

RESULTS

Women with FH (n = 51) had an increased risk of premature CHD compared with unexplained ADH women (n = 111; hazard ratio [HR], 2.74; 95% confidence interval, 1.40-5.34; P = .003) even after adjustment for lipid levels and traditional CHD risk factors (HR, 2.53 [1.10-5.83]; P = .005). Men with FH (n = 42), in contrast, had a similar risk of premature CHD when compared with unexplained ADH men (n = 66; unadjusted: HR, 1.48 [0.84-2.63]; P = .18; adjusted: HR, 1.04 [0.46-2.37]; P = .72). To address whether mutation status provides additional information beyond LDL-cholesterol level, we analyzed premature CHD risk for FH vs unexplained ADH at various percentiles of LDL-cholesterol: the risk ratios were significant for women at 25th percentile (HR, 4.90 [1.69-14.19]) and 50th percentile (HR, 3.44 [1.42-8.32]) but not at 75th percentile (HR, 1.99 [0.95-4.17]), and were not significant for men at any percentile.

CONCLUSIONS

Our findings suggest that genetic confirmation of ADH may be important to identify patient's risk of CHD, especially for female LDLR mutation carriers.

Pharmacogenetics in Central American healthy volunteers: interethnic variability

Ethnicity is one of the major factors involved in interindividual variability to drug response. This study aims to describe the frequency of the most relevant pharmacogenetic biomarkers and metabolic phenotypes in Central American healthy volunteers and to determine its interethnic variability. Twenty-six original research articles on allelic, genotypes or metabolic phenotype frequencies were analyzed, in which a total number of 7611 Central American healthy volunteers were included (6118 were analyzed for genotype and 1799 for metabolic phenotype). No reports were available for population from Belize and Honduras. The CYP2D6*4 and *5 frequencies in Amerindian populations from Costa Rica have shown to be among the highest frequencies so far reported in the world. Furthermore, NAT2*5 and *6 presented higher frequencies in admixed populations than in Amerindians, but, inversely, the NAT2*7 was more frequent in Amerindians compared to an admixed population. Likewise, different patterns of distribution have been shown in HLA-A*02, *03 and HLA-B*07 among Native populations from Latin America. Reports on Central American populations were also found for the CYP2C19, LDLR, CYP2E1, MDR1, G6PD, TP53, CYP1A2, CYP3A4 and CYP3A5 biomarkers, but no data were available for the other 91 pharmacogenetic biomarkers revised in Central American populations. Differences in the frequency of some pharmacogenetic biomarkers and metabolic phenotypes were found, showing interethnic variability within Central American and with other Latin American populations.

The distribution and characteristics of LDL receptor mutations in China: A systematic review

Familial hypercholesterolemia (FH) is a common and serious dominant genetic disease, and its main pathogenic gene is the low-density lipoprotein receptor (LDLR) gene. This study aimed to perform a systematic review of LDLR mutations in China. Using PubMed, Embase, Wanfang (Chinese), the Chinese National Knowledge Infrastructure (Chinese), and the Chinese Biological and Medical database (Chinese), public data were limited to December 2014. The Medical Subject Headings terms and the following key words were used: “familial hypercholesterolemia”, “Chinese”, “China”, “Hong Kong”, and “Taiwan”. A total of 74 studies including 295 probands with 131 LDLR mutations were identified. Most of the mutations were located in exon 4 of LDLR and approximately 60% of the mutations were missense mutations. Thirty new mutations that were not recorded in the LDLR databases were found. In silico analysis revealed that most of the mutations were pathogenic. The primary LDLR mutations were C308Y, H562Y, and A606T, and all of the mutations had functional significance. Prevalence data suggest that there are nearly 3.8 million FH patients in China, although reported numbers are much smaller, suggesting that FH is widely misunderstood. This systematic review provides information that is specific to China for inclusion in the international FH database.

Genetics of familial hypercholesterolemia

Familial hypercholesterolemia (FH) is a genetic disorder characterized by elevated low-density lipoprotein (LDL) cholesterol and premature cardiovascular disease, with a prevalence of approximately 1 in 200-500 for heterozygotes in North America and Europe. Monogenic FH is largely attributed to mutations in the LDLR, APOB, and PCSK9 genes. Differential diagnosis is critical to distinguish FH from conditions with phenotypically similar presentations to ensure appropriate therapeutic management and genetic counseling. Accurate diagnosis requires careful phenotyping based on clinical and biochemical presentation, validated by genetic testing. Recent investigations to discover additional genetic loci associated with extreme hypercholesterolemia using known FH families and population studies have met with limited success. Here, we provide a brief overview of the genetic determinants, differential diagnosis, genetic testing, and counseling of FH genetics.

Profile of evolocumab and its potential in the treatment of hyperlipidemia

Despite the proven efficacy of statins, they often fail to achieve low-density lipoprotein (LDL) cholesterol goals, especially in high-risk patients. Moreover, a large number of subjects cannot tolerate statins or full doses of these drugs, in particular patients with familial hypercholesterolemia. Thus, there is a need for additional effective LDL cholesterol-reducing agents. Evolocumab (AMG145) is a monoclonal antibody inhibiting proprotein convertase subtilisin/kexin type 9 that binds to the liver LDL receptor and prevents it from normal recycling by targeting it for degradation. Phase I, II, and III trials revealed that, on subcutaneous injection, either alone or in combination with statins, evolocumab is able to reduce high LDL cholesterol levels from 54% to 80%, apolipoprotein B100 from 31% to 61%, and lipoprotein(a) from 12% to 36%, in a dose-dependent manner. The incidence of side effects seems to be low and mainly limited to nasopharyngitis, injection site pain, arthralgia, and back pain. Evolocumab is an innovative powerful lipid-lowering drug, additive to statins and/or ezetimibe, with a large therapeutic range associated with a low rate of mild adverse events. If the available data are confirmed in long-term trials with strong outcome measures, evolocumab will become an essential tool in the treatment of a large number of high-risk patients, such as those affected by familial hypercholesterolemia, those who are unable to tolerate an efficacious statin dosage, and those at very high cardiovascular risk and unable to achieve their target LDL cholesterol levels with currently available lipid-lowering therapies.

The MYLIP p.N342S polymorphism is associated with response to lipid-lowering therapy in Brazilian patients with familial hypercholesterolemia

Supplemental Digital Content is available in the text.

Background

A previous study reported that the myosin regulatory light chain interacting protein (MYLIP) might serve as a novel therapeutic class for treating dyslipidemia. It contributes to variations in the levels of circulating low-density lipoprotein cholesterol (LDL-C), promoting the degradation of LDL–LDLR, thus limiting absorption. The effect of genetic variation in the MYLIP gene in a disease scenario characterized by mutations in the LDLR gene has not been previously evaluated.

Objective

The aim of this study was to assess the effect of the p.N342S variant on the response to lipid-lowering therapy in Brazilian patients with heterozygous familial hypercholesterolemia (FH).

Patients and methods

A total of 156 patients with heterozygous FH were followed up for 12 months and received lipid-lowering therapy (different doses of atorvastatin with the addition of ezetimibe in over half the patients of each genotype group). Cholesterol data were assessed, and analysis of the MYLIP rs9370867 (p.N342S) genotypes was carried out by melting curve analysis.

Results

Baseline total cholesterol and baseline LDL-C levels were not different between genotypes. After 1 year of treatment, LDL-C responses (expressed as mg/dl and as %) were significantly different among genotypes (AA: −79±68 and −39±27, GA: −60±79 and −27±32, and GG: −30±83 and −15±38; P=0.02 and 0.005, respectively). In addition, FH patients carrying the AA genotype were more likely to achieve LDL-C levels of less than 130 mg/dl after 1 year of treatment (75.0%) compared with patients with the GG and GA genotypes (34.5 and 34.8%, respectively; P=0.001).

Conclusion

Our study indicates that MYLIP p.N342S might be a pharmacogenetic marker for lipid-lowering therapy in patients with FH.