Monogenic hypercholesterolemia: new insights in pathogenesis and treatment

Therapeutic Gene Editing in Dyslipidemias

Dyslipidemia, characterized by abnormal lipid levels in the blood, significantly escalates the risk of atherosclerotic cardiovascular disease and requires effective treatment strategies. While existing therapies can be effective, long-term adherence is often challenging. There has been an interest in developing enduring and more efficient solutions. In this context, gene editing, particularly clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) technology, emerges as a groundbreaking approach, offering potential long-term control of dyslipidemia by directly modifying gene expression. This review delves into the mechanistic insights of various gene-editing tools. We comprehensively analyze various pre-clinical and clinical studies, evaluating the safety, efficacy, and therapeutic implications of gene editing in dyslipidemia management. Key genetic targets, such as low-density lipoprotein receptor (LDLR), proprotein convertase subtilisin/kexin type 9 (PCSK9), angiopoietin-like protein 3 (ANGPTL3), apolipoprotein C3 (APOC3), and lipoprotein (a) (Lp(a)), known for their pivotal roles in lipid metabolism, are scrutinized. The paper highlights the promising outcomes of gene editing in achieving sustained lipid homeostasis, discusses the challenges and ethical considerations in genome editing, and envisions the future of gene therapy in revolutionizing dyslipidemia treatment and cardiovascular risk reduction.

Evinacumab: Mechanism of action, clinical, and translational science

Homozygous familial hypercholesterolemia (HoFH) is a rare and serious genetic condition characterized by premature cardiovascular disease due to severely elevated low-density lipoprotein cholesterol (LDL-C). HoFH primarily results from loss-of-function (LOF) mutations in the LDL receptor (LDLR), reducing LDL-C clearance such that patients experience severe hypercholesterolemia, exacerbating the risk of developing cardiovascular events. Treatment options such as statins, lomitapide, ezetimibe, proprotein convertase subtilisin/kexin type 9 inhibitors, and apheresis help lower LDL-C; however, many patients with HoFH still fail to reach their target LDL-C levels and many of these lipid-lowering therapies are not indicated for pediatric use. Angiopoietin-like protein 3 (ANGPTL3) has been identified as a target to treat elevated LDL-C by acting as a natural inhibitor of lipoprotein lipase (LPL) and endothelial lipase (EL), enzymes involved in the hydrolysis of the triglyceride and phospholipid content of very low-density lipoproteins. Persons heterozygous for LOF mutations in ANGPTL3 were reported to have lower LDL-C than non-carriers and lower risk of coronary artery disease. Evinacumab is a first-in-class human monoclonal antibody that specifically binds to ANGPTL3 to prevent its inhibition of LPL and EL. In clinical trials, a 15 mg/kg intravenous dose every 4 weeks has shown a mean percent change from baseline in LDL-C of ~50% in adult, adolescent, and pediatric patients with HoFH. This mini review article describes the mechanism of action of evinacumab, evinacumab population PK and PD modeling, and clinical development history of evinacumab for the treatment of HoFH.

Failure of lipid control by PCSK9 inhibitors in compound heterozygous familial hypercholesterolemia complicated with premature myocardial infarction: A case report

Key Clinical Message

A certain level of low-density lipoprotein receptor activity is crucial for the efficacy of PCSK9i. Therapeutic strategies for familial hypercholesterolemia patients should consider drug efficacy, and genetic testing will be helpful.

Abstract

Familial hypercholesterolemia (FH) is a serious autosomal dominant disorder. Managing blood lipids in FH patients poses greater challenges for clinicians. Drug therapy may not always yield satisfactory results, particularly in individuals with low-density lipoprotein receptor (LDLR) negative mutations. Herein, we report a young female harboring an LDLR frameshift mutation. This patient developed xanthomas at 7 months old and underwent several years of treatment involving four classes of lipid-lowering drugs, including PCSK9i. However, the response to drug therapy was limited in this patient and eventually culminated in premature myocardial infarction. The efficacy of PCSK9i depends on the activity of LDLR. The inefficacy of PCSK9i may arise from the extensive mutations which leading to loss of LDLR activity. Therapy plans for these patients should take into account the efficacy of drug therapy. Early genetic testing is crucial for clinicians to make informed decisions regarding therapy options.

Antioxidant and antilipidemic action of ketogenic diet and tomato powder mix in high sugar and fat fed Harwich fruit flies

Numerous studies have demonstrated the role of oxidative stress in metabolic disorders which presents as a major global problem. The antioxidant properties of the tomato fruit and the ketogenic diet has likewise been established by different authors. This study uses a fruit fly model to examine the synergistic effect of a ketogenic diet and tomato powder mix on biochemical alterations induced by the High-Fat Diet (HFD) and the High-Sugar Diet (HSD). Six groups of male fruit flies consisting of fifty flies per vial were administered Normal Diet (ND), High-Fat Diet (HFD), High Sugar Diet (HSD), Ketogenic Diet (KD), Tomato Powder-mix (TP), and HSD + HFD, for ten days. Further treatment of KD and TP was administered to group six vials to constitute groups seven to nine: HSD + HFD + KD, HSD + HFD + TP, and HSD + HFD + KD + TP for another five days. Biochemical parameters of oxidative stress were analyzed in the fly homogenates using standard procedures. There were significant increases (P < 0.05) in the concentration of malondialdehyde, total cholesterol, LDL-Cholesterol, Triglycerides, atherogenic index, nitric oxide, total weight gained, and a significant decrease (p < 0.05) in levels of catalase and HDL-Cholesterol in flies treated with HF and HS diets. Further administration of KD and TP to the flies for five days reversed most of the parameters to near control values. The KD diet combination with TP however gave the best ameliorative changes. The dietary model may therefore be effective as adjuvant therapy for the management of metabolic disorders developed and made progressive by oxidative stress and hyperlipidemia.

New uses for an old remedy: Digoxin as a potential treatment for steatohepatitis and other disorders

Repurposing of the widely available and relatively cheap generic cardiac gly-coside digoxin for non-cardiac indications could have a wide-ranging impact on the global burden of several diseases. Over the past several years, there have been significant advances in the study of digoxin pharmacology and its potential non-cardiac clinical applications, including anti-inflammatory, antineoplastic, metabolic, and antimicrobial use. Digoxin holds promise in the treatment of gastrointestinal disease, including nonalcoholic steatohepatitis and alcohol-associated steatohepatitis as well as in obesity, cancer, and treatment of viral infections, among other conditions. In this review, we provide a summary of the clinical uses of digoxin to date and discuss recent research on its emerging applications.

Familial Hypercholesterolemia Presenting as Cerebral Ischemia and Xanthoma

Familial hypercholesterolemia (FH) is one of the inherited metabolic diseases, demonstrating the low-density lipoprotein receptor (LDLR) abnormality and serum cholesterol level marked elevation. FH has become an extremely high incident cause of occlusive coronary heart disease. However, even though hemorheological disorder caused by hyperlipidemia is a risk factor of ischemic cerebrovascular disease, cerebral infarction caused by FH has not been given much attention. We present a 41-year-old man with a family history of hypercholesterolemia was admitted to our hospital with dizziness, vertigo, slurred speech, and weakness in his left limbs. Head CT scan showed multiple acute cerebral infarction in the right frontal and parietal lobes. He had arcus corneae and less obvious signs of cutaneous xanthomas in the hands and knees. Molecular analysis of the LDLR gene identified heterozygous and missense mutation in exon 12 of the LDLR gene. The final diagnosis was cerebral infarction caused by FH. It is worth noting that cerebral infarction may also occur in patients with FH. Even if the most patients do not have any sign or history of cerebral ischemia, they need more attention to precise examination of the brain.

Statin therapy and lipids-lowering supplements - safe and effective treatment of lipids disturbances in children

INTRODUCTION

There is a significant correlation between elevated LDL cholesterol (LDL-C) levels sustained from childhood and future vascular disease. The study aimed to evaluate the effectiveness and safety of the therapy chosen for children with lipid disorders.

MATERIAL AND METHODS

The study group consisted of 37 children with increased LDL-C (13 boys) aged 8.99 ±4.03 years. After 6 months of behavioral treatment, study group was divided into G1 (n = 24) which continued non-pharmacological treatment supported by dietary supplements and G2 (n = 13) in which statin (5-10 mg/day) was added to non-pharmacological treatment. Analysis included: BMI Z-score, total cholesterol (TCh), LDL-C, HDL cholesterol (HDL-C) and triglycerides (TG) measured at several time points.

RESULTS

The concentrations of TCh and LDL-C before treatment were significantly higher in G2 than in G1 (p < 0.001). Due to the treatment, these differences were no longer noticeable at the last visit. In G1 and G2 concentrations of TCh and LDL-C were reduced significantly, greater reduction after the treatment in TCh and LDL-C was observed in G2 than in G1. Moreover, in G1 we noticed reduction of TG after treatment (p < 0.05). The BMI Z-score did not change significantly through the treatment in both groups. G1 also showed a significant negative correlation between BMI Z-score and HDL-C before and after treatment (r = -0.57, p = 0.009; r = -0.52, p = 0.02). Same relationship was noticed also in G2 after treatment (r = 0.67, p = 0.05).

CONCLUSIONS

In children with dyslipidemia, regardless of its background, statin therapy is the most effective in lowering LDL-C. However, therapy with lipids-lowering supplements seems to be safe and effective.

The Clinical Importance of Differentiating Monogenic Familial Hypercholesterolemia from Polygenic Hypercholesterolemia

PURPOSE OF REVIEW

The current review discusses the importance and significance of differentiating monogenic familial hypercholesterolemia (FH) from polygenic hypercholesterolemia for clinical purpose.

RECENT FINDINGS

Consistent scientific evidence have demonstrated that, compared to polygenic hypercholesterolemia, monogenic FH patients are at significantly higher risk for premature coronary heart disease (CHD). This is despite both disease entities having a comparable low-density-lipoprotein cholesterol (LDLC) level. Monogenic FH also has poorer therapeutic response compared to its polygenic counterpart. However, there are no current available clinical management guidelines that stratify hypercholesterolemia patients based on genotype. Monogenic FH patients are at higher risk for CHD with poorer therapeutic response. Thus, genotype testing should be performed when available. There is also an urgency to develop genotype-based clinical guideline that stratify patients on genotype and not only based on traditionally known cardiovascular risk factors.

Gene Therapy for Cardiovascular Disease: Basic Research and Clinical Prospects

In recent years, the vital role of genetic factors in human diseases have been widely recognized by scholars with the deepening of life science research, accompanied by the rapid development of gene-editing technology. In early years, scientists used homologous recombination technology to establish gene knock-out and gene knock-in animal models, and then appeared the second-generation gene-editing technology zinc-finger nucleases (ZFNs) and transcription activator-like effector nucleases (TALENs) that relied on nucleic acid binding proteins and endonucleases and the third-generation gene-editing technology that functioned through protein-nucleic acids complexes-CRISPR/Cas9 system. This holds another promise for refractory diseases and genetic diseases. Cardiovascular disease (CVD) has always been the focus of clinical and basic research because of its high incidence and high disability rate, which seriously affects the long-term survival and quality of life of patients. Because some inherited cardiovascular diseases do not respond well to drug and surgical treatment, researchers are trying to use rapidly developing genetic techniques to develop initial attempts. However, significant obstacles to clinical application of gene therapy still exists, such as insufficient understanding of the nature of cardiovascular disease, limitations of genetic technology, or ethical concerns. This review mainly introduces the types and mechanisms of gene-editing techniques, ethical concerns of gene therapy, the application of gene therapy in atherosclerosis and inheritable cardiovascular diseases, in-stent restenosis, and delivering systems.

Clinical utility of polygenic risk scores for coronary artery disease

Over the past decade, substantial progress has been made in the discovery of alleles contributing to the risk of coronary artery disease. In addition to providing causal insights into disease, these endeavours have yielded and enabled the refinement of polygenic risk scores. These scores can be used to predict incident coronary artery disease in multiple cohorts and indicate the clinical response to some preventive therapies in post hoc analyses of clinical trials. These observations and the widespread ability to calculate polygenic risk scores from direct-to-consumer and health-care-associated biobanks have raised many questions about responsible clinical adoption. In this Review, we describe technical and downstream considerations for the derivation and validation of polygenic risk scores and current evidence for their efficacy and safety. We discuss the implementation of these scores in clinical medicine for uses including risk prediction and screening algorithms for coronary artery disease, prioritization of patient subgroups that are likely to derive benefit from treatment, and efficient prospective clinical trial designs.

The LDLR c.501C>A is a disease-causing variant in familial hypercholesterolemia

Background

As an autosomal dominant disorder, familial hypercholesterolemia (FH) is mainly attributed to disease-causing variants in the low-density lipoprotein receptor (LDLR) gene. The aim of this study was to explore the molecular mechanism of LDLR c.501C>A variant in FH and assess the efficacy of proprotein convertase subtilisin kexin type 9 (PCSK9) inhibitor treatment for FH patients.

Methods

The whole-exome sequencing was performed on two families to identify disease-causing variants, which were verified by Sanger sequencing. The function of LDLR variant was further explored in HEK293 cells by Western Blot and confocal microscopy. Besides, the therapeutic effects of PCSK9 inhibitor treatment for two probands were assessed for 3 months.

Results

All members of the two families with the LDLR c.501C>A variant showed high levels of LDLC. The relationship between the clinical phenotype and LDLR variants was confirmed in the current study. Both in silico and in vitro analyses showed that LDLR c.501C>A variant decreased LDLR expression and LDL uptake. PCSK9 inhibitor treatment lowered the lipid level in proband 1 by 24.91%. However, the treatment was ineffective for proband 2. A follow-up study revealed that the PCSK9 inhibitor treatment had low ability of lipid-lowering effect in the patients.

Conclusions

LDLR c.501C>A variant might be pathogenic for FH. The PCSK9 inhibitor therapy is not a highly effective option for treatment of FH patients with LDLR c.501C>A variant.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12944-021-01536-3.

The Application of Induced Pluripotent Stem Cells Against Liver Diseases: An Update and a Review

Liver diseases are a major health concern globally, and are associated with poor survival and prognosis of patients. This creates the need for patients to accept the main alternative treatment of liver transplantation to prevent progression to end-stage liver disease. Investigation of the molecular mechanisms underpinning complex liver diseases and their pathology is an emerging goal of stem cell scope. Human induced pluripotent stem cells (hiPSCs) derived from somatic cells are a promising alternative approach to the treatment of liver disease, and a prospective model for studying complex liver diseases. Here, we review hiPSC technology of cell reprogramming and differentiation, and discuss the potential application of hiPSC-derived liver cells, such as hepatocytes and cholangiocytes, in refractory liver-disease modeling and treatment, and drug screening and toxicity testing. We also consider hiPSC safety in clinical applications, based on genomic and epigenetic alterations, tumorigenicity, and immunogenicity.

Familial Hypercholesterolemia in the Arabian Gulf Region: Clinical results of the Gulf FH Registry

BACKGROUND AND AIMS

Familial hypercholesterolemia (FH) is a common autosomal dominant disorder that can result in premature atherosclerotic cardiovascular disease (ASCVD). Limited data are available worldwide about the prevalence and management of FH. Here, we aimed to estimate the prevalence and management of patients with FH in five Arabian Gulf countries (Saudi Arabia, Oman, United Arab Emirates, Kuwait, and Bahrain).

METHODS

The multicentre, multinational Gulf FH registry included adults (≥18 years old) recruited from outpatient clinics in 14 tertiary-care centres across five Arabian Gulf countries over the last five years. The Gulf FH registry had four phases: 1- screening, 2- classification based on the Dutch Lipid Clinic Network, 3- genetic testing, and 4- follow-up.

RESULTS

Among 34,366 screened patient records, 3713 patients had suspected FH (mean age: 49±15 years; 52% women) and 306 patients had definite or probable FH. Thus, the estimated FH prevalence was 0.9% (1:112). Treatments included high-intensity statin therapy (34%), ezetimibe (10%), and proprotein convertase subtilisin/kexin type 9 inhibitors (0.4%). Targets for low-density lipoprotein cholesterol (LDL-C) and non-high-density lipoprotein cholesterol were achieved by 12% and 30%, respectively, of patients at high ASCVD risk, and by 3% and 6%, respectively, of patients at very high ASCVD risk (p <0.001; for both comparisons).

CONCLUSIONS

This snap-shot study was the first to show the high estimated prevalence of FH in the Arabian Gulf region (about 3-fold the estimated prevalence worldwide), and is a "call-to-action" for further confirmation in future population studies. The small proportions of patients that achieved target LDL-C values implied that health care policies need to implement nation-wide screening, raise FH awareness, and improve management strategies for FH.

Homozygous Familial Hypercholesterolemia (HoFH) in Saudi Arabia and Two Cases of Lomitapide Use in a Real-World Setting

Introduction

Homozygous familial hypercholesterolemia (HoFH) is a rare, genetic condition in which mutations in key peptides involved in the low-density lipoprotein receptor (LDL-R) pathway result in markedly elevated levels of circulating LDL-cholesterol (LDL-C). Patients are at high risk of developing early-onset atherosclerotic cardiovascular disease with associated mortality risks. Treatment options are extremely limited, and aspects of society and medical care in Saudi Arabia have the potential to increase incidence and limit treatment pathways in HoFH.

Methods

Along with a brief review of the evidence available on HoFH we describe the treatment of two Saudi Arabian patients with HoFH diagnosed and treated in accordance with local clinical practices and with the microsomal triglyceride transferase protein inhibitor lomitapide.

Results

HoFH in Saudi Arabia is characterized by problems associated with consanguinity, a lack of access to lipoprotein apheresis, and pressures to proceed to liver transplant. Among the case histories, the first patient was commenced on lomitapide therapy, and underwent a dramatic decrease in LDL-C levels from 16.5 to 2.2 mmol/L (87% decrease). This patient had problems with access to lomitapide and cessation of the drug resulted in rebound in LDL-C to 22 mmol/L. The second patient experienced delayed commencement of lomitapide therapy. Despite a 45% decrease in LDL-C levels from 15.3 to 6.9 mmol/L, the patient died the following year at age 26 years from complications subsequent to cardiovascular surgery. Lomitapide was well tolerated in both patients

Discussion

The experience of these two cases highlights the need for prompt, effective, and sustained intervention in HoFH to prevent cardiovascular morbidity and mortality. Lomitapide is an effective therapy for HoFH, and we look forward to improved access to this drug in Saudi Arabia, where there is a chronic unmet medical need in HoFH.

Development of an Implementation Framework for Overcoming Underdiagnoses of Familial Hypercholesterolemia in the USA

Familial hypercholesterolemia (FH) is a genetic condition which causes elevated low-density lipoprotein cholesterol from birth. With a prevalence of 1 in 250 and the availability of effective treatments, the diagnostic rate of <1 to 10% is unacceptably low. Screening for FH is supported by multiple organizations, but it has not been broadly adopted and implemented across the USA. To investigate the implementation of FH screening, key informants were recruited from across the USA for their expertise in FH-related literature, guidelines, public health, and/or advocacy to complete -semistructured interviews guided by implementation science (RE-AIM framework). Sixteen semistructured interviews were analyzed with directed content and thematic analyses, yielding specific barriers and recommendations to improve FH screening. Barriers to FH screening included patient recruitment and participation, equitable access to healthcare, provider discomfort with screening and treating FH, provider burden, lack of public health and legislative support, FH awareness, guideline complexity, facilitation of genetic testing and cascade screening, and lack of coordination between stakeholders. Awareness, engagement, communication, and collaboration between stakeholders is integral to successful FH screening. Individualized plans will be required at national, regional, and institutional levels. FH screening implementation can be achieved through practice facilitation, streamlined screening approaches, electric medical record tools, and consensus guidelines to increase screening adoption and consistent delivery. Reliable funding and established lines of communication between stakeholders can maintain efforts as FH screening progresses.

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.

Genome-scale CRISPR screening for modifiers of cellular LDL uptake

Hypercholesterolemia is a causal and modifiable risk factor for atherosclerotic cardiovascular disease. A critical pathway regulating cholesterol homeostasis involves the receptor-mediated endocytosis of low-density lipoproteins into hepatocytes, mediated by the LDL receptor. We applied genome-scale CRISPR screening to query the genetic determinants of cellular LDL uptake in HuH7 cells cultured under either lipoprotein-rich or lipoprotein-starved conditions. Candidate LDL uptake regulators were validated through the synthesis and secondary screening of a customized library of gRNA at greater depth of coverage. This secondary screen yielded significantly improved performance relative to the primary genome-wide screen, with better discrimination of internal positive controls, no identification of negative controls, and improved concordance between screen hits at both the gene and gRNA level. We then applied our customized gRNA library to orthogonal screens that tested for the specificity of each candidate regulator for LDL versus transferrin endocytosis, the presence or absence of genetic epistasis with LDLR deletion, the impact of each perturbation on LDLR expression and trafficking, and the generalizability of LDL uptake modifiers across multiple cell types. These findings identified several previously unrecognized genes with putative roles in LDL uptake and suggest mechanisms for their functional interaction with LDLR.

Identifying Markers of Cardiovascular Event-Free Survival in Familial Hypercholesterolemia

Familial hypercholesterolemia (FH) is an autosomal dominant trait characterized by elevated low-density lipoprotein-cholesterol (LDL-C) concentrations appearing at birth and is associated with increased risk of premature atherosclerotic cardiovascular disease (CVD). However, in some cases, FH subjects over 70 years of age have surprisingly never experienced any CVD symptoms throughout their entire lives. The objective of this study consists of identifying biological and environmental markers acting as cardioprotective factors and associated with unexpected survival in FH. Upon age and reported cardiovascular events (CVE) stratification, we identified a total of 458 French–Canadian FH subjects with premature reported CVE, and 1297 young adults as well as 24 elderly subjects (≥70 years) who have never reported CVE requiring hospitalization. Logistic regression models were used to depict cardioprotective markers among FH survivors (≥70 years). Regression analyses of the FH cohort showed that female sex (odds ratio (OR) = 12.92 (4.23–39.46); p < 0.0001), high levels of high-density lipoprotein (HDL)-C (OR = 6.76 (2.43–18.79); p = 0.0002) and elevated concentrations of adiponectin (OR = 71.40 (5.20–980.47); p = 0.001) were significant contributory factors in reducing FH-related CVD risk. Notably, female (OR = 11.45 (1.25–105.98); p = 0.031) and high HDL-C (OR = 9.78 (1.75–54.67); p = 0.009) were shown to be significant covariates associated with survival in FH. Non-smoking (OR = 11.73 (4.36–31.56); p < 0.0001) was also identified as an environmental factor associated with CVE-free survival. Based on this configured model of premature CVE occurrence, these results demonstrated that, beyond LDL-C levels, female sex, high HDL-C, elevated adiponectin and non-smoking are important markers that contribute to a reduced risk of CVD and CVE-free survival in FH.

Clinical Applications of Single-Stranded Oligonucleotides: Current Landscape of Approved and In-Development Therapeutics

Single-stranded oligonucleotides have been explored as a therapeutic modality for more than 20 years. Only during the last 5 years have single-stranded oligonucleotides become a modality of choice in the fields of precision medicine and targeted therapeutics. Recently, there have been a number of development efforts involving this modality that have led to treatments for genetic diseases that were once untreatable. This review highlights key applications of single-stranded oligonucleotides that function in a sequence-dependent manner when applied to modulate precursor (pre-)mRNA splicing, gene expression, and immune pathways. These applications have been used to address diseases that range from neurological to muscular to metabolic, as well as to develop vaccines. The wide range of applications denotes the versatility of single-stranded oligonucleotides as a robust therapeutic platform. The focus of this review is centered on approved single-stranded oligonucleotide therapies and the evolution of oligonucleotide therapeutics into novel applications currently in clinical development.

A Case of Premature Triple Vessel Coronary Artery Disease and Valvular Degeneration: A Rare Presentation of Familial Hypercholesterolemia

Familial hypercholesterolemia (FH) is one of the inherited causes of coronary artery disease (CAD) and causes calcific valvular degeneration in rare cases. A 13-year-old boy with multiple xanthomas presented with severe chest pain, shortness of breath, and sweating. He was diagnosed with premature CAD leading to non-ST-elevation myocardial infarction, secondary to early-onset FH [severely raised low-density lipoprotein (LDL) and triglycerides (TG) on lipid profile]. CT angiogram showed triple vessel disease, and echocardiogram revealed tight aortic stenosis. Percutaneous coronary angioplasty was done, and valvuloplasty was planned on the follow-up assessment. Early diagnosis and prompt management could have prevented these complications.

The Gulf Familial Hypercholesterolemia Registry (Gulf FH): Design, Rationale and Preliminary Results

Aim:

To determine the prevalence, genetic characteristics, current management and outcomes of familial hypercholesterolaemia (FH) in the Gulf region.

Methods:

Adult (18-70 years) FH patients were recruited from 9 hospitals and centres across 5 Arabian Gulf countries. The study was divided into 4 phases and included patients from 3 different categories. In phase 1, suspected FH patients (category 1) were collected according to the lipid profile and clinical data obtained through hospital record systems. In phase 2, patients from category 2 (patients with a previous clinical diagnosis of FH) and category 1 were stratified into definitive, probable and possible FH according to the Dutch Lipid Clinic Network criteria. In phase 3, 500 patients with definitive and probable FH from categories 1 and 2 will undergo genetic testing for 4 common FH genes. In phase 4, these 500 patients with another 100 patients from category 3 (patients with previous genetic diagnosis of FH) will be followed for 1 year to evaluate clinical management and cardiovascular outcomes. The Gulf FH cohort was screened from a total of 34,366 patients attending out-patient clinics.

Results:

The final Gulf FH cohort consisted of 3,317 patients (mean age: 47±12 years, 54% females). The number of patients with definitive FH is 203. In this initial phase of the study, the prevalence of (probable and definite) FH is 1/232.

Conclusion:

The prevalence of FH in the adult population of the Arabian Gulf region is high. The Gulf FH registry, a first-of-a-kind multi-national study in the Middle East region, will help in improving underdiagnosis and undertreatment of FH in the region.

Maternal cholesterol levels during gestation: boon or bane for the offspring?

An increase in cholesterol levels is perceived during pregnancy and is considered as a normal adaptive response to the development of the fetus. In some pregnancies, excessive increase in total cholesterol with high levels of Low-Density Lipoprotein leads to maladaptation by the fetus to cholesterol demands, resulting in a pathological condition termed as maternal hypercholesterolemia (MH). MH is considered clinically irrelevant and therefore cholesterol levels are not routinely checked during pregnancy, as a consequence of which there is scarce information on its global prevalence in pregnant women. Studies have reported that MH during pregnancy can cause atherogenesis in adults emphasizing the concept of in utero programming of fetus. Moreover, Gestational Diabetes Mellitus, obesity and Polycystic Ovary Syndrome are potential risk factors which strengthen combined pathologies in placenta and fetuses of mothers with MH. However, lack of conclusive evidence on cholesterol transport and underlying programming demand substantial research to develop population-based life style strategies for women in their childbearing years. The current review focuses on the mechanisms and outcomes of MH from existing epidemiological as well as experimental data and presents a detailed insight on this novel risk factor of cardiovascular diseases.

Clinical and Genetic Characteristics of Familial Hypercholesterolemia at Sultan Qaboos University Hospital in Oman

Objectives

We sought to describe the clinical and genetic characteristics of patients with familial hypercholesterolemia (FH) that presented to the lipid clinic at Sultan Qaboos University Hospital, Muscat, Oman.

Methods

Patients who presented with high low-density lipoprotein cholesterol (LDL-C) levels (> 189.0 mg/dL or 4.9 mmol/L) were recruited to the study. FH was diagnosed according to the Dutch Lipid Clinic Network criteria. Analyses were performed using univariate statistics.

Results

The study enrolled 450 patients with a mean age of 48.0±12.0 years, 56.0% (n = 252) were males and 11.3% (n = 51) were smokers. At admission, the proportion of ‘probable/definite’, ‘possible’, and ‘unlikely’ FH were 27.6% (n = 124), 70.0% (n = 315), and 2.4% (n = 11), respectively. Overall, 26.0% (n = 117) of patients had hypertension, 22.4% (n = 101) had a history of coronary artery disease, and 17.3% (n = 78) had diabetes mellitus. Those with ‘probable/definite’ FH were more likely to be prescribed high-intensity statin therapy (75.8% vs. 54.5%; p < 0.001) and statin ezetimibe combination (50.8% vs. 27.3%; p < 0.001) when compared to the ‘unlikely’ FH cohort. Additionally, those with very high atherosclerotic vascular disease (ASCVD) risk were also associated with high-intensity statin therapy (54.7% vs. 42.7%; p = 0.006) and statin ezetimibe combination (26.4% vs. 17.2%; p = 0.023). Patients with ‘probable/definite’ FH were less likely to achieve their LDL-C goal attainment compared to those with ‘unlikely’ FH (13.0% vs. 57.1%; p < 0.001). Furthermore, those with very high ASCVD risk were less likely to achieve their LDL-C goals compared to the high ASCVD risk cohort (9.6% vs. 32.0%; p < 0.001).

Conclusions

FH patients are underdiagnosed, undertreated, and less likely to attain their LDL-C goals in Oman.

Low Density Lipoprotein Receptor Variants in the Beta-Propeller Subdomain and Their Functional Impact

Background: Pathogenic variants in the low density lipoprotein receptor gene are associated with familial hypercholesterolemia. Some of these variants can result in incorrect folding of the LDLR protein, which is then accumulated inside the cell and cannot fulfill its function to internalize LDL particles. We analyzed the functional impact of 10 LDLR variants localized in the beta-propeller of epidermal growth factor precursor homology domain. The experimental part of the work was complemented by a structural analysis on the basis of 3D LDLR protein structure.

Methods: T-Rex Chinese hamster ovary cells transfected with the human LDLR gene were used for live cell imaging microscopy, flow cytometry, and qRT-PCR analysis.

Results: Our results showed that the analyzed LDLR protein variants can be divided into three groups. (1) The variants buried inside the 3D protein structure expressing proteins accumulated in the endoplasmic reticulum (ER) with no or reduced plasma membrane localization and LDL particle internalization, and associated with an increased gene expression of ER-resident chaperones. (2) The variants localized on the surface of 3D protein structure with slightly reduced LDLR plasma membrane localization and LDL particle internalization, and associated with no increased mRNA level of ER-resident chaperones. (3) The variants localized on the surface of the 3D protein structure but expressing proteins with cell responses similar to the group 1.

Conclusion: All analyzed LDLR variants have been evaluated as pathogenic but with different effects on protein localization and function, and expression of genes associated with ER stress.

Polygenic Scores to Assess Atherosclerotic Cardiovascular Disease Risk: Clinical Perspectives and Basic Implications

An individual's susceptibility to atherosclerotic cardiovascular disease is influenced by numerous clinical and lifestyle factors, motivating the multifaceted approaches currently endorsed for primary and secondary cardiovascular disease prevention. With growing knowledge of the genetic basis of atherosclerotic cardiovascular disease-in particular, coronary artery disease-and its contribution to disease pathogenesis, there is increased interest in understanding the potential clinical utility of a genetic predictor that might further refine the assessment and management of atherosclerotic cardiovascular disease risk. Rapid scientific and technological advances have enabled widespread genotyping efforts and dynamic research in the field of coronary artery disease genetic risk prediction. In this review, we describe how genomic analyses of coronary artery disease have been leveraged to create polygenic risk scores. We then discuss evaluations of the clinical utility of these scores, pertinent mechanistic insights gleaned, and practical considerations relevant to the implementation of polygenic risk scores in the health care 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.

Impaired adult hippocampal neurogenesis in a mouse model of familial hypercholesterolemia: A role for the LDL receptor and cholesterol metabolism in adult neural precursor cells

Objective

In familial hypercholesterolemia (FH), mutations in the low-density lipoprotein (LDL) receptor (LDLr) gene result in increased plasma LDL cholesterol. Clinical and preclinical studies have revealed an association between FH and hippocampus-related memory and mood impairment. We here asked whether hippocampal pathology in FH might be a consequence of compromised adult hippocampal neurogenesis.

Methods

We evaluated hippocampus-dependent behavior and neurogenesis in adult C57BL/6JRj and LDLr^−/− mice. We investigated the effects of elevated cholesterol and the function of LDLr in neural precursor cells (NPC) isolated from adult C57BL/6JRj mice in vitro.

Results

Behavioral tests revealed that adult LDLr^−/− mice showed reduced performance in a dentate gyrus (DG)-dependent metric change task. This phenotype was accompanied by a reduction in cell proliferation and adult neurogenesis in the DG of LDLr^−/− mice, suggesting a potential direct impact of LDLr mutation on NPC. Exposure of NPC to LDL as well as LDLr gene knockdown reduced proliferation and disrupted transcriptional activity of genes involved in endogenous cholesterol synthesis and metabolism. The LDL treatment also induced an increase in intracellular lipid storage. Functional analysis of differentially expressed genes revealed parallel modulation of distinct regulatory networks upon LDL treatment and LDLr knockdown.

Conclusions

Together, these results suggest that high LDL levels and a loss of LDLr function, which are characteristic to individuals with FH, might contribute to a disease-related impairment in adult hippocampal neurogenesis and, consequently, cognitive functions.

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The LDLr −/− mice show impaired hippocampal related behaviour and adult neurogenesis.

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In vitro exposure of NPC to LDL and LDLr knock-down reduces cell proliferation.

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LDL exposure induces lipid storage in NPC.

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In vitro LDL and LDLr knock-down in NPC modulates distinct regulatory networks.

Modelling of atherosclerosis in genetically modified animals

Atherosclerosis is a lipid-driven, chronic inflammatory disease that leads to plaque formation at specific sites of the arterial tree. Being the common cause of many cardiovascular disorders, atherosclerosis makes a tremendous impact on morbidity and mortality rates of cardiovascular diseases (CVDs) in countries with higher income. Animal models of atherosclerosis are utilized as useful tools for studying the aetiology, pathogenesis and complications of atherosclerosis, thus, providing a valuable platform for the efficacy testing of different pharmacological therapies and validation of imaging techniques. To date, a large variety of models is available. Pathophysiological changes can be induced in animals by either an atherogenic diet or genetic manipulations. The discussion of advantages and disadvantages of some murine, rabbit and porcine genetic models currently available for the atherosclerosis research is the scope of the following review.

Exploring the dark genome: implications for precision medicine

The increase in the number of both patients and healthcare practitioners who grew up using the Internet and computers (so-called "digital natives") is likely to impact the practice of precision medicine, and requires novel platforms for data integration and mining, as well as contextualized information retrieval. The "Illuminating the Druggable Genome Knowledge Management Center" (IDG KMC) quantifies data availability from a wide range of chemical, biological, and clinical resources, and has developed platforms that can be used to navigate understudied proteins (the "dark genome"), and their potential contribution to specific pathologies. Using the "Target Importance and Novelty Explorer" (TIN-X) highlights the role of LRRC10 (a dark gene) in dilated cardiomyopathy. Combining mouse and human phenotype data leads to increased strength of evidence, which is discussed for four additional dark genes: SLX4IP and its role in glucose metabolism, the role of HSF2BP in coronary artery disease, the involvement of ELFN1 in attention-deficit hyperactivity disorder and the role of VPS13D in mouse neural tube development and its confirmed role in childhood onset movement disorders. The workflow and tools described here are aimed at guiding further experimental research, particularly within the context of precision medicine.

The Impact of the International Cooperation On Familial Hypercholesterolemia Screening and Treatment: Results from the ScreenPro FH Project

Purpose of Review

Familial hypercholesterolemia (FH) is often perceived and described as underdiagnosed and undertreated, though effective treatment of FH is available. Owing to the mentioned facts, it is ever more imperative to screen and treat FH patients. Subsequent to the identification of patients, the project focuses on the improvement of their prognoses. The ScreenPro FH project was established as a functional international network for the diagnosis, screening, and treatment of FH. Individual countries were assigned goals, e.g., to define the actual situation and available treatment. With “central support,” more centers and countries participated in the project. Subsequently, individual countries reported the results at the beginning and end of the project. Collected data were statistically evaluated.

Recent Findings

The increasing number of patients in databases, from 7500 in 2014 to 25,347 in 2018, demonstrates the improvement in overall effectiveness, as well as an increase in the number of centers from 70 to 252. Before all, LDL-C decreased by 41.5% and total cholesterol by 32.3%. As data from all countries and patients were not available at the time of the analysis, only those results from 10 countries and 5585 patients at the beginning of the project and at the time of writing are included.

Summary

Our data are quite positive. However, our results have only limited validity. Our patients are far from the target levels of LDL-C. The situation can be improved with the introduction of new therapy, PCSK9-i, evolocumab, and alirocumab. International cooperation improved the screening of FH and finally led to an improvement in cardiovascular risk.

Arterial Lymphatics in Atherosclerosis: Old Questions, New Insights, and Remaining Challenges

The lymphatic network is well known for its role in the maintenance of tissue fluid homeostasis, absorption of dietary lipids, trafficking of immune cells, and adaptive immunity. Aberrant lymphatic function has been linked to lymphedema and immune disorders for a long time. Discovery of lymphatic cell markers, novel insights into developmental and postnatal lymphangiogenesis, development of genetic mouse models, and the introduction of new imaging techniques have improved our understanding of lymphatic function in both health and disease, especially in the last decade. Previous studies linked the lymphatic vasculature to atherosclerosis through regulation of immune responses, reverse cholesterol transport, and inflammation. Despite extensive research, many aspects of the lymphatic circulation in atherosclerosis are still unknown and future studies are required to confirm that arterial lymphangiogenesis truly represents a therapeutic target in patients with cardiovascular disease. In this review article, we provide an overview of factors and mechanisms that regulate lymphangiogenesis, summarize recent findings on the role of lymphatics in macrophage reverse cholesterol transport, immune cell trafficking and pathogenesis of atherosclerosis, and present an overview of pharmacological and genetic strategies to modulate lymphatic vessel density in cardiovascular tissue.

Function and Immunogenicity of Gene-corrected iPSC-derived Hepatocyte-Like Cells in Restoring Low Density Lipoprotein Uptake in Homozygous Familial Hypercholesterolemia

Gene correction of induced pluripotent stem cells (iPSCs) has therapeutic potential for treating homozygous familial hypercholesterolemia (HoFH) associated with low-density lipoprotein (LDL) receptor (LDLR) dysfunction. However, few data exist regarding the functional recovery and immunogenicity of LDLR gene-corrected iPSC-derived hepatocyte-like cells (HLCs) obtained from an HoFH patient. Therefore, we generated iPSC-derived HLCs from an HoFH patient harbouring a point mutation (NM_000527.4:c.901 G > T) in exon 6 of LDLR, and examined their function and immunogenicity. From the patient’s iPSCs, one homozygous gene-corrected HoFH-iPSC clone and two heterozygous clones were generated using the CRISPR/Cas9 method. Both types of iPSC-derived HLCs showed recovery of the function of LDL uptake in immunofluorescence staining analysis. Furthermore, these gene-corrected iPSC-derived HLCs showed little immunogenicity against the patient’s peripheral blood mononuclear cells in a cell-mediated cytotoxicity assay. These results demonstrate that LDL uptake of iPSC-derived HLCs from HoFH can be restored by gene correction without the appearance of further immunogenicity, suggesting that gene-corrected iPSC-derived HLCs are applicable to the treatment of HoFH.

Usability of Achilles tendon strain elastography for the diagnosis of coronary artery disease

PURPOSE

There are close relationships between major coronary artery disease (CAD) risk factors and Achilles tendon thickness (AT-T) and AT strain ratio (AT-SR). Our aim was to evaluate the diagnostic importance of AT-T and AT-SR as obtained by ultrasonography (USG) and strain elastography (SE) for predicting CAD.

MATERIALS AND METHODS

One hundred and eighty-four patients scheduled to undergo coronary angiography were included in the study. Achilles tendon USG (B-mode and SE) and laboratory tests were performed on all patients. The patients were divided into two groups, i.e., patients with and without CAD.

RESULTS

The patients with CAD (72.8%) were more likely to be male, exhibited higher frequencies of diabetes mellitus (DM) and hyperlipidemia, exhibited higher levels of basal creatinine and glucose, and had higher AT-T and AT-SR values (p < 0.05 for all). Age, DM, AT-T, and AT-SR independently predicted the probability of CAD in a logistic regression analysis (p < 0.05 for all). Age (each year), DM (presence), AT-T (each 1 mm), and AT-SR (each 0.1) increased the CAD risk by 3.4%, 2.9 times, 47.1%, and 16.0%, respectively. ROC analysis revealed AUCs of 0.665 and 0.730 for the AT-T and AT-SR values, respectively (p < 0.05). The AT-SR cutoff value of 1.2 predicted the presence of CAD with 75.4% sensitivity and 72.7% specificity.

CONCLUSIONS

AT-SR is a simple, inexpensive, noninvasive, reproducible, and objective parameter for the prediction of CAD. We think that AT-SR evaluation should become a part of conventional USG assessments in patients who are at a high risk of CAD.

Mendelian Randomization Studies Promise to Shorten the Journey to FDA Approval

There has been a dearth of new drugs approved for cardiovascular disorders. The cost is prohibitive, averaging to $2.5 billion, and requiring 12.5 years. This is in large part due to the high failure rate, with only 5% approval by the Food and Drug Administration. Despite preclinical studies showing potential safety and efficacy, most fail when they go to clinical trials phase I to III. One cause for failure is the drug target, often discovered to be a biomarker rather than causative for the disease. Mendelian randomization (MR) studies would determine whether the drug target is causative and could save millions of dollars and time, and prevent unnecessary exposure to adverse drug effects. This was demonstrated in 3 clinical trials that were negative with 2 drugs, veraspladib and darapladib. MR studies during the trials showed the targets of secretory and lipoprotein-associated phospholipids A2 are not causative for coronary artery disease and predicted negative results. The requirement for MR studies is a genetic risk variant with altered function, randomized at conception that remains fixed throughout one’s lifetime. It is not confounded by dietary, lifestyle, or socioeconomic factors. It is more sensitive than randomized controlled trials because exposure to the risk factor is fixed for a lifetime. MR studies showed plasma high-density lipoprotein cholesterol is not a causative target of coronary artery disease, and neither is uric acid, C-reactive protein, and others. MR studies are highly sensitive in determining whether drug targets are causative, and are relatively easy, inexpensive, and not time consuming. It is recommended that drug targets undergo MR studies before proceeding to randomized controlled trials.

Neurovascular dysfunction in vascular dementia, Alzheimer's and atherosclerosis

Efficient blood supply to the brain is of paramount importance to its normal functioning and improper blood flow can result in potentially devastating neurological consequences. Cerebral blood flow in response to neural activity is intrinsically regulated by a complex interplay between various cell types within the brain in a relationship termed neurovascular coupling. The breakdown of neurovascular coupling is evident across a wide variety of both neurological and psychiatric disorders including Alzheimer’s disease. Atherosclerosis is a chronic syndrome affecting the integrity and function of major blood vessels including those that supply the brain, and it is therefore hypothesised that atherosclerosis impairs cerebral blood flow and neurovascular coupling leading to cerebrovascular dysfunction. This review will discuss the mechanisms of neurovascular coupling in health and disease and how atherosclerosis can potentially cause cerebrovascular dysfunction that may lead to cognitive decline as well as stroke. Understanding the mechanisms of neurovascular coupling in health and disease may enable us to develop potential therapies to prevent the breakdown of neurovascular coupling in the treatment of vascular brain diseases including vascular dementia, Alzheimer’s disease and stroke.

Genome Editing of Pigs for Agriculture and Biomedicine

Pigs serve as an important agricultural resource and animal model in biomedical studies. Efficient and precise modification of pig genome by using recently developed gene editing tools has significantly broadened the application of pig models in various research areas. The three types of site-specific nucleases, namely, zinc-finger nucleases, transcription activator-like effector nucleases, and clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein, are the main gene editing tools that can efficiently introduce predetermined modifications, including knockouts and knockins, into the pig genome. These modifications can confer desired phenotypes to pigs to improve production traits, such as optimal meat production, enhanced feed digestibility, and disease resistance. Besides, given their genetic, anatomic, and physiologic similarities to humans, pigs can also be modified to model human diseases or to serve as an organ source for xenotransplantation to save human lives. To date, many genetically modified pig models with agricultural or biomedical values have been established by using gene editing tools. These pig models are expected to accelerate research progress in related fields and benefit humans.

Percutaneous Coronary Intervention in Familial Hypercholesterolemia Is Understudied

Familial hypercholesterolemia (FH) is a common heritable condition in which mutations of genes governing cholesterol metabolism result in elevated LDL levels and accelerated atherosclerosis. The treatment of FH focuses on lipid lowering drugs to decrease patients' cholesterol levels and reduce their risk of cardiovascular events. Even with optimal medical therapy, some FH patients will develop coronary atherosclerosis, suffer myocardial infarction, and require revascularization. Yet, the revascularization of FH patients has not been widely studied. Here we review FH, identify unanswered questions in the interventional management of FH patients, and explore barriers and opportunities for answering these questions. Further research is needed in this neglected but important topic in interventional cardiology.

Novel compound heterozygous mutations in low density lipoprotein receptor gene causes a severe phenotype in a Chinese hypercholesterolemia family

Mutations in the low density lipoprotein receptor (LDLR) gene serve a causative role in the pathophysiology of familial hypercholesterolemia (FH), a common autosomal inherited disorder characterized by abnormal lipid metabolism. The aim of the present study was to investigate genetic defects in a Chinese family with FH. Clinical features and family histories were collected, as were the results of various laboratory tests, including determinations of serum lipid concentrations, ultrasonography and angiography results. Potential mutations in LDLR were screened using direct polymerase chain reaction (PCR) sequencing. Multiple sequence alignments, structure and hydrophobicity predictions were performed in silico. Novel compound heterozygote mutations in LDLR of the proband were identified, with a Trp577Term-bearing maternal allele and a Pro685Leu-bearing paternal allele. The proband, a 27-year-old male, had severe and diffuse coronary stenosis and non-ST segment elevation myocardial infarction, as well as multiple skin xanthomas and high serum lipid levels. The allele-dosage-dependent clinical features, including hypercholesterolemia and peripheral arterial atherosclerosis, were observed in the proband and the other heterozygous patients. Therefore, the coexistence of Pro685Leu and Trp577Term mutations in LDLR is a novel compound heterozygosis in Chinese patients and may lead to a severe FH phenotype. The explanation for the existence of compound heterozygous mutations instead of homozygous mutations in this particular family requires further study.

Lipids in Children and Links to Adult Vascular Disease

Atherosclerosis often begins in childhood or adolescence. Post-mortem studies in children have shown the presence of coronary atheroma, and there are hereditary conditions associated with hyperlipidaemia in childhood which lead to premature cardiovascular disease. Detection of hyperlipidaemia early in life can be crucial in the prevention of premature death from atherosclerosis. The circulating lipoproteins are in a constant state of flux, with passage of apolipoproteins and lipids between the various particles. Genetic variants of apolipoproteins can cause both hypercholesterolaemia and hypertriglyceridaemia. Elevated concentrations of lipoprotein(a) predispose to coronary artery disease. Another important molecule in lipid metabolism, proprotein convertase subtilisin/kexin type 9 (PCSK9), plays a crucial role in the removal of low-density lipoprotein (LDL) receptors. Reference intervals for the various lipid subfractions are now available for children, and there are guidelines regarding when to take action regarding paediatric hyperlipidaemia. The most important genetic condition in children which may lead to premature death from coronary heart disease is familial hypercholesterolaemia (FH). FH is best diagnosed and treated early in life. Most cases are due to defects in the LDL receptor. Pharmacotherapy for FH usually involves the statin group of drugs, although newer medications are now available, especially for the treatment of homozygous FH. Statin therapy has been demonstrated to be successful in preventing cardiac events in FH. Secondary dyslipidaemia in childhood can be associated with numerous diseases including diabetes, lifestyle disorders such as obesity, and drugs. Treatment of the underlying condition usually resolves the hyperlipidaemia.

Familial Hypercholesterolemia: New Horizons for Diagnosis and Effective Management

Familial hypercholesterolemia (FH) is a common genetic cause of premature cardiovascular disease (CVD). The reported prevalence rates for both heterozygous FH (HeFH) and homozygous FH (HoFH) vary significantly, and this can be attributed, at least in part, to the variable diagnostic criteria used across different populations. Due to lack of consistent data, new global registries and unified guidelines are being formed, which are expected to advance current knowledge and improve the care of FH patients. This review presents a comprehensive overview of the pathophysiology, epidemiology, manifestations, and pharmacological treatment of FH, whilst summarizing the up-to-date relevant recommendations and guidelines. Ongoing research in FH seems promising and novel therapies are expected to be introduced in clinical practice in order to compliment or even substitute current treatment options, aiming for better lipid-lowering effects, fewer side effects, and improved clinical outcomes.

Validation of LDLr Activity as a Tool to Improve Genetic Diagnosis of Familial Hypercholesterolemia: A Retrospective on Functional Characterization of LDLr Variants

Familial hypercholesterolemia (FH) is an autosomal dominant disorder characterized by high blood-cholesterol levels mostly caused by mutations in the low-density lipoprotein receptor (LDLr). With a prevalence as high as 1/200 in some populations, genetic screening for pathogenic LDLr mutations is a cost-effective approach in families classified as ‘definite’ or ‘probable’ FH and can help to early diagnosis. However, with over 2000 LDLr variants identified, distinguishing pathogenic mutations from benign mutations is a long-standing challenge in the field. In 1998, the World Health Organization (WHO) highlighted the importance of improving the diagnosis and prognosis of FH patients thus, identifying LDLr pathogenic variants is a longstanding challenge to provide an accurate genetic diagnosis and personalized treatments. In recent years, accessible methodologies have been developed to assess LDLr activity in vitro, providing experimental reproducibility between laboratories all over the world that ensures rigorous analysis of all functional studies. In this review we present a broad spectrum of functionally characterized missense LDLr variants identified in patients with FH, which is mandatory for a definite diagnosis of FH.

PCSK9: From Basic Science Discoveries to Clinical Trials

Unknown 15 years ago, PCSK9 (proprotein convertase subtilisin/kexin type 9) is now common parlance among scientists and clinicians interested in prevention and treatment of atherosclerotic cardiovascular disease. What makes this story so special is not its recent discovery nor the fact that it uncovered previously unknown biology but rather that these important scientific insights have been translated into an effective medical therapy in record time. Indeed, the translation of this discovery to novel therapeutic serves as one of the best examples of how genetic insights can be leveraged into intelligent target drug discovery. The PCSK9 saga is unfolding quickly but is far from complete. Here, we review major scientific understandings as they relate to the role of PCSK9 in lipoprotein metabolism and atherosclerotic cardiovascular disease and the impact that therapies designed to inhibit its action are having in the clinical setting.

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.

mTOR drives cerebral blood flow and memory deficits in LDLR-/- mice modeling atherosclerosis and vascular cognitive impairment

We recently showed that mTOR attenuation blocks progression and abrogates established cognitive deficits in Alzheimer's disease (AD) mouse models. These outcomes were associated with the restoration of cerebral blood flow (CBF) and brain vascular density (BVD) resulting from relief of mTOR inhibition of NO release. Recent reports suggested a role of mTOR in atherosclerosis. Because mTOR drives aging and vascular dysfunction is a universal feature of aging, we hypothesized that mTOR may contribute to brain vascular and cognitive dysfunction associated with atherosclerosis. We measured CBF, BVD, cognitive function, markers of inflammation, and parameters of cardiovascular disease in LDLR-/- mice fed maintenance or high-fat diet ± rapamycin. Cardiovascular pathologies were proportional to severity of brain vascular dysfunction. Aortic atheromas were reduced, CBF and BVD were restored, and cognitive dysfunction was attenuated potentially through reduction in systemic and brain inflammation following chronic mTOR attenuation. Our studies suggest that mTOR regulates vascular integrity and function and that mTOR attenuation may restore neurovascular function and cardiovascular health. Together with our previous studies in AD models, our data suggest mTOR-driven vascular damage may be a mechanism shared by age-associated neurological diseases. Therefore, mTOR attenuation may have promise for treatment of cognitive impairment in atherosclerosis.

Hypercholesterolaemia - practical information for non-specialists

Hypercholesterolaemia is amongst the most common conditions encountered in the medical profession. It remains one of the key modifiable cardiovascular risk factors and there have been recent advances in the risk stratification methods and treatment options available. In this review, we provide a background into hypercholesterolaemia for non-specialists and consider the merits of the different risk assessment tools available. We also provide detailed considerations as to: i) when to start treatment, ii) what targets to aim for and iii) the role of low density lipoprotein cholesterol.

Dyslipidemias and Cardiovascular Prevention: Tailoring Treatment According to Lipid Phenotype

PURPOSE OF REVIEW

This study aimed to present the current information on the genetic background of dyslipidemias and provide insights into the complex pathophysiological role of several plasma lipids/lipoproteins in the pathogenesis of atherosclerotic cardiovascular disease. Furthermore, we aim to summarize established therapies and describe the scientific rationale for the development of novel therapeutic strategies.

RECENT FINDINGS

Evidence from genetic studies suggests that besides lowering low-density lipoprotein cholesterol, pharmacological reduction of triglyceride-rich lipoproteins, or lipoprotein(a) will reduce risk for coronary heart disease. Dyslipidemia, in particular hypercholesterolemia, is a common clinical condition and represents an important determinant of atherosclerotic vascular disease. Treatment decisions are currently guided by the causative lipid phenotype and the presence of other risk factors suggesting a very high cardiovascular risk. Therefore, the identification of lipid disorders and the optimal combination of therapeutic strategies provide an outstanding opportunity for reducing the onset and burden of cardiovascular disease.

Diagnostic performance of various familial hypercholesterolaemia diagnostic criteria compared to Dutch lipid clinic criteria in an Asian population

BACKGROUND

Familial hypercholesterolaemia (FH) is a genetic disorder with a high risk of developing premature coronary artery disease that should be diagnosed as early as possible. Several clinical diagnostic criteria for FH are available, with the Dutch Lipid Clinic Criteria (DLCC) being widely used. Information regarding diagnostic performances of the other criteria against the DLCC is scarce. We aimed to examine the diagnostic performance of the Simon-Broom (SB) Register criteria, the US Make Early Diagnosis to Prevent Early Deaths (US MEDPED) and the Japanese FH Management Criteria (JFHMC) compared to the DLCC.

METHODS

Seven hundered fifty five individuals from specialist clinics and community health screenings with LDL-c level ≥ 4.0 mmol/L were selected and diagnosed as FH using the DLCC, the SB Register criteria, the US MEDPED and the JFHMC. The sensitivity, specificity, efficiency, positive and negative predictive values of individuals screened with the SB register criteria, US MEDPED and JFHMC were assessed against the DLCC.

RESULTS

We found the SB register criteria identified more individuals with FH compared to the US MEDPED and the JFHMC (212 vs. 105 vs. 195; p < 0.001) when assessed against the DLCC. The SB Register criteria, the US MEDPED and the JFHMC had low sensitivity (51.1% vs. 25.3% vs. 47.0% respectively). The SB Register criteria showed better diagnostic performance than the other criteria with 98.8% specificity, 28.6% efficiency value, 98.1% and 62.3% for positive and negative predictive values respectively.

CONCLUSION

The SB Register criteria appears to be more useful in identifying positive cases leading to genetic testing compared to the JFHMC and US MEDPED in this Asian population. However, further research looking into a suitable diagnosis criterion with high likelihood of positive genetic findings is required in the Asian population including in Malaysia.

Wnt signaling in cardiovascular disease: opportunities and challenges

PURPOSE OF REVIEW

Cardiometabolic diseases increasingly afflict our aging, dysmetabolic population. Complex signals regulating low-density lipoprotein receptor-related protein (LRP) and frizzled protein family members - the plasma membrane receptors for the cadre of Wnt polypeptide morphogens - contribute to the control of cardiovascular homeostasis.

RECENT FINDINGS

Both canonical (β-catenin-dependent) and noncanonical (β-catenin-independent) Wnt signaling programs control vascular smooth muscle (VSM) cell phenotypic modulation in cardiometabolic disease. LRP6 limits VSM proliferation, reduces arteriosclerotic transcriptional reprogramming, and preserves insulin sensitivity while LRP5 restrains foam cell formation. Adipose, skeletal muscle, macrophages, and VSM have emerged as important sources of circulating Wnt ligands that are dynamically regulated during the prediabetes-diabetes transition with cardiometabolic consequences. Platelets release Dkk1, a LRP5/LRP6 inhibitor that induces endothelial inflammation and the prosclerotic endothelial-mesenchymal transition. By contrast, inhibitory secreted frizzled-related proteins shape the Wnt signaling milieu to limit myocardial inflammation with ischemia-reperfusion injury. VSM sclerostin, an inhibitor of canonical Wnt signaling in bone, restrains remodeling that predisposes to aneurysm formation, and is downregulated in aneurysmal vessels by epigenetic methylation.

SUMMARY

Components of the Wnt signaling cascade represent novel targets for pharmacological intervention in cardiometabolic disease. Conversely, strategies targeting the Wnt signaling cascade for other therapeutic purposes will have cardiovascular consequences that must be delineated to establish clinically useful pharmacokinetic-pharmacodynamic relationships.

Familial Hypercholesterolemia: A Systematic Review of Guidelines on Genetic Testing and Patient Management

BACKGROUND

Familial hypercholesterolemia (FH) is an autosomal-dominant hereditary disorder of lipid metabolism that causes lifelong exposure to increased LDL levels resulting in premature coronary heart disease and, if untreated, death. Recent studies have shown its prevalence to be higher than previously considered, which has important implications for the mortality and morbidity of associated cardiovascular disease (CVD). Several clinical tools are used worldwide to help physicians diagnose FH, but nevertheless most patients remain undetected. This systematic review of guidelines aims to assess the role of genetic testing in the screening, diagnosis, and management of patients affected by heterozygous or homozygous FH and to identify related health-care pathways.

METHODS

We performed a systematic review of the literature; inclusion criteria were English or Italian guidelines focusing on genetic testing. The guidelines were included and evaluated for their content and development process using the Appraisal of Guidelines for Research and Evaluation II instrument.

RESULTS

Ten guidelines were considered eligible, and all were judged to be of good quality, with slight differences among them. The most common indications for performing genetic tests were high levels of cholesterol, or physical findings consistent with lipid disorder, in the subject or in the family history. Subsequent screening of family members was indicated when a mutation had been identified in the index patient. Regarding patient management, the various guidelines agreed that intensive treatment with lipid-lowering medications should begin as quickly as possible and that lifestyle modifications should be an integral part of the therapy.

CONCLUSION

Since the early detection of affected patients is beneficial for effective prevention of CVD, genetic testing is particularly useful for identifying family members via cascade screening and for distinguishing between heterozygous and homozygous individuals, the latter of which require more extreme therapeutic intervention.

Interpreting the Mechanism of APOE (p.Leu167del) Mutation in the Incidence of Familial Hypercholesterolemia; An In-silico Approach

Background:

Apolipoprotein E (APOE) gene is a ligand protein in humans which mediates the metabolism of cholesterol by binding to the low-density lipoprotein receptor (LDLR). P.Leu167del mutation in APOE gene was recently connected with Familial Hypercholesterolemia, a condition associated with premature cardiovascular disease. The consequences of this mutation on the protein structure and its receptor binding capacity remain largely unknown.

Objective:

The current study aims to further decipher the underlying mechanism of this mutation using advanced software-based algorithms. The consequences of disrupting the leucine zipper by this mutation was studied at the structural and functional level of the APOE protein.

Methods:

3D protein modeling for both APOE and LDLR (wild types), along with APOE (p.Leu167del) mutant type were generated using homology modeling template-based alignment. Structural deviation analysis was performed to evaluate the spatial orientation and the stability of the mutant APOE structure. Molecular docking analysis simulating APOE-LDLR protein interaction was carried out, in order to evaluate the impact of the mutation on the binding affinity.

Result:

Structural deviation analysis for APOE mutated model showed low degree of deviance scoring root-mean-square deviation, (RMSD) = 0.322 Å. Whereas Docking simulation revealed an enhanced molecular interaction towards the LDLR with an estimation of +171.03 kJ/mol difference in binding free energy.

Conclusion:

This in-silico study suggests that p.Leu167del is causing the protein APOE to associate strongly with its receptor, LDLR. This gain-of-function is likely hindering the ability of LDLR to be effectively recycled back to the surface of the hepatocytes to clear cholesterol from the circulation therefore leading to FH.