Homozygous familial hypercholesterolaemia: new insights and guidance for clinicians to improve detection and clinical management. A position paper from the Consensus Panel on Familial Hypercholesterolaemia of the European Atherosclerosis Society

Beyond the Usual Suspects: Expanding on Mutations and Detection for Familial Hypercholesterolemia

Introduction: Familial hypercholesterolemia (FH) is a highly prevalent condition, predisposing individuals to premature cardiovascular disease and with a genetic basis more complex than initially thought. Advances in molecular technologies have provided novel insights into the role of next-generation-sequencing, the assessment and classification of newly found variants, the complex genotype-phenotype correlation, and the position of FH in the context of other dyslipidaemias.Areas covered: Understanding the scope of genetic determinants of FH has expanded substantially. This article reviews the current literature on the complexity that comes with this incremental knowledge and highlights the added value of genetic testing as an addition to phenotypic diagnosis of FH. Moreover, we discuss the broad genetic basis of FH, with a focus on the three main FH genes, but we also pay attention to polygenic hypercholesterolemia as well as minor and modulator genes involved in FH.Expert opinion: Both the availability and the need for genetic analysis of FH are on the rise as costs of sequencing continue to drop and new therapies require a genetic diagnosis for reimbursement. However, greater use of genetic testing requires more education of healthcare professionals, since molecular technologies will allow for rapid and accurate evaluation of large numbers of detected variants.

The Added Value of Coronary Calcium Score in Predicting Cardiovascular Events in Familial Hypercholesterolemia

OBJECTIVES

This study aimed at investigating the additional contribution of coronary artery calcium (CAC) score to SAFEHEART (Spanish Familial Hypercholesterolemia Cohort Study) risk equation (SAFEHEART-RE) for cardiovascular risk prediction in heterozygous familial hypercholesterolemia (HeFH).

BACKGROUND

Common cardiovascular risk equations are imprecise for HeFH. Because of the high phenotype variability of HeFH, CAC score could help to better stratify the risk of atherosclerotic cardiovascular disease (ASCVD).

METHODS

REFERCHOL (French Registry of Familial Hypercholesterolemia) and SAFEHEART are 2 ongoing national registries on HeFH. We analyzed data from primary prevention HeFH patients undergoing CAC quantification. We used probability-weighted Cox proportional hazards models to estimate HRs. Area under the receiver-operating characteristic curve (AUC) and net reclassification improvement (NRI) were used to compare the incremental contribution of CAC score when added to the SAFEHEART-RE for ASCVD prediction. ASCVD was defined as coronary heart disease, stroke or transient ischemic attack, peripheral artery disease, resuscitated sudden death, and cardiovascular death.

RESULTS

We included 1,624 patients (mean age: 48.5 ± 12.8 years; men: 45.7%) from both registries. After a median follow-up of 2.7 years (interquartile range: 0.4-5.0), ASCVD occurred in 81 subjects. The presence of a CAC score of >100 was associated with an HR of 32.05 (95% CI: 10.08-101.94) of developing ASCVD as compared to a CAC score of 0. Receiving-operating curve analysis showed a good performance of CAC score alone in ASCVD prediction (AUC: 0.860 [95% CI: 0.853-0.869]). The addition of log(CAC + 1) to SAFEHEART-RE resulted in a significantly improved prediction of ASCVD (AUC: 0.884 [95% CI: 0.871-0.894] for SAFEHEART-RE + log(CAC + 1) vs AUC: 0.793 [95% CI: 0.779-0.818] for SAFEHEART-RE; P < 0.001). These results were confirmed also when considering only hard cardiovascular endpoints. The addition of CAC score was associated with an estimated overall net reclassification improvement of 45.4%.

CONCLUSIONS

CAC score proved its use in improving cardiovascular risk stratification and ASCVD prediction in statin-treated HeFH.

Saudi Familial Hypercholesterolemia Patients With Rare LDLR Stop Gain Variant Showed Variable Clinical Phenotype and Resistance to Multiple Drug Regimen

Familial hypercholesterolemia (FH), a well-known lipid disease caused by inherited genetic defects in cholesterol uptake and metabolism is underdiagnosed in many countries including Saudi Arabia. The present study aims to identify the molecular basis of severe clinical manifestations of FH patients from unrelated Saudi consanguineous families. Two Saudi families with multiple FH patients fulfilling the combined FH diagnostic criteria of Simon Broome Register, and the Dutch Lipid Clinic Network (DLCN) were recruited. LipidSeq, a targeted resequencing panel for monogenic dyslipidemias, was used to identify causative pathogenic mutation in these two families and in 92 unrelated FH cases. Twelve FH patients from two unrelated families were sharing a very rare, pathogenic and founder LDLR stop gain mutation i.e., c.2027delG (p.Gly676Alafs^*33) in both the homozygous or heterozygous states, but not in unrelated patients. Based on the variant zygosity, a marked phenotypic heterogeneity in terms of LDL-C levels, clinical presentations and resistance to anti-lipid treatment regimen (ACE inhibitors, β-blockers, ezetimibe, statins) of the FH patients was observed. This loss-of-function mutation is predicted to alter the free energy dynamics of the transcribed RNA, leading to its instability. Protein structural mapping has predicted that this non-sense mutation eliminates key functional domains in LDLR, which are essential for the receptor recycling and LDL particle binding. In conclusion, by combining genetics and structural bioinformatics approaches, this study identified and characterized a very rare FH causative LDLR pathogenic variant determining both clinical presentation and resistance to anti-lipid drug treatment.

Speckle-Tracking Echocardiography for Detecting Subclinical Left Ventricular Dysfunction in Patients With Familial Hypercholesterolemia

Myocardial ischemia and left ventricular dysfunction have been documented in young adults with familial hypercholesterolemia. We investigated whether speckle-tracking echocardiography can be used to detect subclinically impaired global and regional myocardial function in patients with this lipid disorder. This single-center study included 47 patients with familial hypercholesterolemia and 37 healthy control subjects who underwent transthoracic Doppler echocardiography and speckle-tracking echocardiography from January 2003 through December 2016. Conventional echocardiographic and strain parameters in the 2 groups were analyzed and compared. Left ventricular dimensions were significantly larger at end-diastole (P=0.02) and end-systole (P=0.013), left ventricular walls were significantly thicker (P <0.0001), and the early transmitral/early diastolic mitral annular velocity ratio was significantly higher (P=0.006) in the patient group than in the control group. In the patient group, global longitudinal and circumferential strain values were significantly lower (P <0.0001) and global radial strain values significantly higher (P=0.006); all segmental longitudinal strain (P <0.04) and most segmental circumferential strain values (P ≤0.01) were significantly lower; and some segmental radial strains, especially at the apex, were significantly higher (P ≤0.04). However, average longitudinal, circumferential, and radial strains in the different segments of the 3 main coronary artery territories were significantly lower in the patient group (P <0.01). Global longitudinal strain (r=0.561; P=0.001) and global circumferential strain (r=0.565; P <0.0001) were inversely correlated with low-density-lipoprotein cholesterol levels. We conclude that speckle-tracking echocardiography can be used to detect subclinical global and regional systolic abnormalities in patients with familial hypercholesterolemia.

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.

Familial hypercholesterolemia in Southeast and East Asia

Familial hypercholesterolemia (FH) is a relatively common autosomal dominant disorder associated with a significantly increased risk of coronary heart disease (CHD). Most (~85-90%) cases are due to pathogenic variants in the LDL-receptor gene (LDLR), while the remaining are due to pathogenic variants in the apolipoprotein B (APOB) and proprotein convertase subtilisin/kexin type 9 (PCSK9) genes, though the proportion may vary depending on geographic location. Even though at least a quarter of the world's FH population lives in Southeast and East Asia, there are substantial gaps in knowledge regarding the epidemiology of FH due to low awareness, the absence of national screening programs, and limited availability of genetic testing. In this review, we discuss the most recent and relevant information available related to diagnostic criteria, prevalence, awareness, clinical characteristics, genetic epidemiology, and treatment in the FH population of Southeast and East Asia. Increasing awareness and improving the diagnosis and management of FH will reduce the burden of premature CHD in these regions of the world.

Improvement of Definite Diagnosis of Familial Hypercholesterolemia Using an Expanding Genetic Analysis

BACKGROUND

The deeper understanding of the complex hereditary basis of familial hypercholesterolemia (FH) has raised the rationale of genetic testing, which has been underutilized in clinical practice.

OBJECTIVES

The present study aimed to explore the variant spectrum of FH in an expanding manner and compare its diagnostic performance.

METHODS

A total of 169 Chinese individuals (124 index cases and 45 relatives) with clinical definite/probable FH were consecutively enrolled. Next-generation sequencing was performed for genetic analysis of 9 genes associated with hypercholesterolemia (major genes: LDLR, APOB, and PCSK9; minor genes: LDLRAP1, LIPA, STAP1, APOE, ABCG5, and ABCG8) including the evaluations of small-scale variants and large-scale copy number variants (CNVs).

RESULTS

Among the 169 clinical FH patients included, 98 (58.0%) were men. A total of 85 (68.5%) index cases carried FH-associated variants. The proportion of FH caused by small-scale variants in LDLR, APOB, and PCSK9 genes was 62.1% and then increased by 6.5% when other genes and CNVs were further included. Furthermore, the variants in LDLR, APOB, and PCSK9 genes occupied 75% of all FH-associated variants. Of note, there were 8 non-LDLR CNVs detected in the present study.

CONCLUSIONS

LDLR, APOB, and PCSK9 genes should be tested in the initial genetic screening, although variants in minor genes also could explain phenotypic FH, suggesting that an expanding genetic testing may be considered to further explain phenotypic FH.

Integrated analysis of microRNA and mRNA expression profiles in homozygous familial hypercholesterolemia patients and validation of atherosclerosis associated critical regulatory network

Homozygous familial hypercholesterolemia (HoFH) is a rare, life-threatening genetic disorder characterized by an extremely elevated serum level of low-density lipoprotein cholesterol (LDL-C) and accelerated premature atherosclerotic cardiovascular diseases (ASCVD). However, the detailed mechanism of how the pathogenic mutations of HoFH trigger the acceleration of ASCVD is not well understood. Therefore, we performed high-throughput RNA and small RNA sequencing on the peripheral blood RNA samples of six HoFH patients and three healthy controls. The gene and miRNA expression differences were analyzed, and seven miRNAs and six corresponding genes were screened out through regulatory network analysis. Validation through quantitative PCR of genes and miRNAs from 52 HoFH patients and 20 healthy controls revealed that the expression levels of hsa-miR-486-3p, hsa-miR-941, and BIRC5 were significantly upregulated in HoFH, while ID1, PLA2G4C, and CACNA2D2 were downregulated. Spearman correlation analysis found that the levels of ID1, hsa-miR-941, and hsa-miR-486-3p were significantly correlated with additional ASCVD risk factors in HoFH patients. This study represents the first integrated analysis of transcriptome and miRNA expression profiles in patients with HoFH, a rare disease, and as a result, six differentially expressed miRNAs/genes that may be related to atherosclerosis in HoFH are reported. The miRNA-mRNA regulatory network may be the critical regulation mechanism by which ASCVD is accelerated in HoFH.

Cohort Generation and Characterization of Patient-Specific Familial Hypercholesterolemia Induced Pluripotent Stem Cells

Homozygous familial hypercholesterolemia (hoFH) is a rare disorder caused primarily by pathological mutations in the low-density lipoprotein receptor (LDLR), which disrupts LDL-cholesterol (LDL-C) metabolism homeostasis. hoFH patients are at extremely high risk for cardiovascular disease and are resistant to standard therapies. LDLR knockout animals and in vitro cell models overexpressing different mutations have proved useful, but may not fully recapitulate human LDLR mutation biology. We and others have generated induced pluripotent stem cells (iPSC) from hoFH patient's fibroblasts and T cells and demonstrated their ability to recapitulate hoFH biology. In this study, we present the generation and characterization of a cohort of seven hoFH-iPSC lines derived from peripheral blood mononuclear cells (PBMC) collected from four homozygous and three compound heterozygous patients. The hoFH-iPSC cohort demonstrated a wide range of LDLR expression and LDL-C internalization in response to rosuvastatin that correlated with the predicted pathogenicity of the mutation. We were able to confirm that hoFH-iPSC cohort were pluripotent by differentiation toward all three germ layers and specifically to hepatocyte-like cells (HLC), the cell with primary LDL-C metabolic regulatory control, by expression of hepatocyte markers. hoFH patient PBMC-derived iPSC recapitulate the LDLR dysfunction of their specific mutation. They were capable of differentiating to HLC and could be useful for early developmental studies, pharmacology/toxicology, and potentially autologous cell therapy.

Marked plaque regression in homozygous familial hypercholesterolemia

BACKGROUND AND AIMS

Both plasma low-density lipoprotein (LDL) cholesterol levels and risk for premature cardiovascular disease are extremely elevated in patients with homozygous familial hypercholesterolemia (HoFH), despite the use of multiple cholesterol lowering treatments. Given its inborn nature, atherosclerotic plaques are commonly observed in young HoFH patients. Whether intensive lipid lowering strategies result in plaque regression in adolescent patients is unknown.

METHODS

Two HoFH patients with null/null LDLR variants, who participated in the R1500-CL-1629 randomized clinical trial (NCT03399786) evaluating the LDL cholesterol lowering effect of evinacumab (a human antibody directed against ANGPTL3; 15 mg/kg intravenously once monthly), were included in this study. Patients underwent coronary computed tomography angiography (CCTA) before randomization and after 6 months of treatment.

RESULTS

Both patient A (aged 12) and B (aged 16) were treated with a statin, ezetimibe and weekly apheresis. Evinacumab decreased mean pre-apheresis LDL cholesterol levels from 5.51 ± 0.75 and 5.07 ± 1.45 mmol/l to 2.48 ± 0.31 and 2.20 ± 0.13 mmol/l and post-apheresis LDL levels from 1.45 ± 0.26 and 1.37 ± 39 mmol/l to 0.80 ± 0.16 and 0.78 ± 0.13 mmol/l in patient A and B, respectively. Total plaque volumes were reduced by 76% and 85% after 6 months of evinacumab treatment in patient A and B, respectively.

CONCLUSIONS

We describe two severely affected young HoFH patients in whom profound plaque reduction was observed with CCTA after intensive lipid lowering therapy with statins, ezetimibe, LDL apheresis, and evinacumab. This shows that atherosclerotic plaques possess the ability to regress at young age, even in HoFH patients.

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.

LDL cholesterol and atherosclerosis: The evidence

The lipid theory of atherosclerosis dates back more than a century. Despite this, some authors have questioned the relevance of hypercholesterolaemia in its development. Multiple experimental, epidemiological, and clinical evidence underpins this association. Atherosclerotic cardiovascular disease remains as the major cause of mortality in the world. Recent genetic studies of Mendelian randomisation and randomised clinical trials aimed at LDL cholesterol reduction, are summarised in this article. They, unequivocally ratify the aetiological role of LDL cholesterol in the development of atherosclerosis. Thus, LDL cholesterol lowering is the cornerstone of lipid lowering therapy for the reduction of cardiovascular complications of atherosclerosis.

Intraindividual Comparisons to Determine Comparative Effectiveness: Their Relevance for G-BA's Health Technology Assessments

OBJECTIVES

Health technology assessments (HTA) rely on head-to-head comparisons. We searched for intraindividual comparisons (IIC) qualifying as head-to-head design to develop comparative evidence.

METHODS

Gemeinsamer Bundesausschuss (G-BA) appraisals between January 2011 and April 2020 were reviewed for inclusion of IIC. Identified IIC were grouped according to disease characteristics into nonprogressive, progressive, irregular, or symmetrical conditions. Evaluation of IIC by Institut für Qualität und Wirschaftlichkeit im Gesundheitswesen (IQWIG) and acceptance of IIC by G-BA were determined, and criteria for the usage and quality of IIC were developed.

RESULTS

A total of 483 appraisals finalized between January 2011 and April 2020 were reviewed. Eleven appraisals included IIC: nonacog beta (hemophilia B), turoctocog alpha (hemophilia A), emicizumab (2 appraisals: hemophilia A), pasireotide (unresectable pituitary tumor), lomitapid (homozygous familial hypercholesterolemia), glycerol phenylbutyrate (2 appraisals: urea cycle disorders), asfotase alfa (hypophosphatasia), lumacaftor (cystic fibrosis), and larotrectinib (NTRK⁺ solid tumors). All those appraisals related to rare genetic conditions with hemophilia and its bleeding rate are considered mainly a nonprogressive condition. All the other diseases show progressive disease characteristics. None of the identified IIC has been accepted by G-BA. Inconsistencies of before/after study design, lack of clarity on treatments prior to the switch, and different time intervals were among the most commonly cited methodological concerns.

CONCLUSIONS

IICs provide a rare opportunity to determine comparative effectiveness in distinct clinical settings that are not suitable or difficult to randomize into parallel groups. While manufacturers and researchers should aim for highest methodological standards when running an IIC, HTA bodies should accept IIC in distinct settings when determining relative effectiveness.

Persistent hypercholesterolemia in child with homozygous autosomal recessive hypercholesterolemia: A decade of lipid management

Autosomal recessive hypercholesterolemia (ARH) is a rare form of genetic hypercholesterolemia caused by mutations in low density lipoprotein receptor adaptor protein 1 (LDLRAP1). The proband first presented with linear eruptive xanthomas over her ankles, knees and elbows, with low density lipoprotein cholesterol (LDL-C) of 16.0 mmol/L (618.7 mg/dL), at 2.5 years old. Next generation sequencing revealed a novel homozygous mutation in LDLRAP1 exon 5 (c.466delG). In the first year, drug regimens of either cholestyramine or simvastatin, reduced her LDL-C to 10.5 mmol/L (406 mg/dL) and 11.7 mmol/L (452.4 mg/dL), respectively. Combination simvastatin and ezetimibe was the mainstay of therapy from age 5 - 10 years. Her lowest achieved LDL-C was 6.3 mmol/L (243.6 mg/dL). Switching to atorvastatin did not lead to further reduction. Carotid intima-media thickness was 0.47 mm (> 97^th percentile) and 0.32 mm (75 - 95^th percentile) at ages 8 years and 11 years, respectively. Addition of monthly injections of evolocumab for 3 months, led to an increase in LDL-C, from 7.0 mmol/L (270.7 mg/dL) to a range of [(8.4 - 9.1) mmol/L or (324.8 - 351.9) mg/dL]. In this report, a decade-long lipid management is described in a patient with ARH. Residual activity of LDLRAP1 is a likely determinant of her response. Clinical management remains sub-optimal and options for the paediatric population are limited. Novel classes of cholesterol-lowering medications are needed for this ultra-rare and severe hypercholesterolemia.

A case of homozygous familial hypercholesterolemia with an atypical phenotype and delayed clinical symptoms

We describe the casuistry of a homozygous familial hypercholesterolemia female patient with a biallelic missense variant (NM_000527.4:c.1775G>A, p.Gly592Glu) in the LDLR gene, severe hypertriglyceridemia and late manifestation of coronary heart disease not earlier than at the age of 45 years. An atypical phenotype led to a delayed diagnosis.

A meta-analysis of medications directed against PCSK9 in familial hypercholesterolemia

BACKGROUND AND AIMS

Several medications targeting PCSK9 reduce LDL-cholesterol (LDL-C) in heterozygous familial hypercholesterolemia (HeFH). We aimed to assess in patients diagnosed clinically as HeFH, whether LDL-C reduction varied by different therapeutic approaches to PCSK9-targeting or by the underlying genetic variant.

METHODS

We conducted a random-effects meta-analysis of randomised clinical trials assessing PCSK9-targeting therapies, namely alirocumab, evolocumab and inclisiran, in patients with clinically diagnosed HeFH and restricted analyses to those patients in whom genotypic data were available. A search of MEDLINE and Embase identified eligible trials published between inception and June 29, 2020. We included trials of sufficient duration to allow for a stable treatment effect: ~12 weeks for monoclonal antibodies (mAbs) (alirocumab, evolocumab) and ~1 year for small interfering RNA (siRNA) (inclisiran). Single-moderator meta-regression comparing mean percentage LDL-C reduction between mAbs and siRNA as well as PCSK9-targeting therapies between different genotypes was used to assess heterogeneity.

RESULTS

Eight trials of HeFH met our inclusion criteria, including 1887 genotyped patients. Among monogenic HeFH cases (N = 1347) the LDL-C reduction from baseline was 46.12% (95%CI 48.4-43.9) for siRNA and 50.4% (59.3-41.4) for mAbs compared to control, without evidence of significant heterogeneity between treatment (Q_M = 0.32, df = 1, p = 0.57). Irrespective of therapeutic approach to PCSK9-targeting, reductions in LDL-C were generally consistent across genetic variants (LDL-Receptor variants, LDL-Receptor variants of unknown significance, Apolipoprotein B variants, two variants and no variant) (Q_M = 8.3, df = 4, p = 0.08).

CONCLUSIONS

Among patients with HeFH, the LDL-C-lowering effect of PCSK9-targeting medications did not show statistical heterogeneity across different drug-classes and across genetic variants.

Reduced global longitudinal strain at rest and inadequate blood pressure response during exercise treadmill testing in male heterozygous familial hypercholesterolemia patients

Background

Heterozygous familial hypercholesterolemia (heFH) is a genetic disorder leading to premature coronary artery disease (CAD). We hypothesized that the subclinical pathophysiologic consequences of hypercholesterolemia may be detected before the occurrence of clinically overt CAD by stress testing and myocardial strain imaging.

Patients-methods

We evaluated the treadmill tests (ETTs) of 46 heFH men without known arterial hypertension/diabetes mellitus/vasculopathy like CAD and of 39 healthy men matched for age, baseline systolic/diastolic blood pressure (BP) and heart rate (HR), using Bruce protocol. Global longitudinal strain (GLS) of the left ventricle (LV) additionally to ejection fraction was obtained.

Results

heFH men reached a significantly higher peak systolic and diastolic BP compared to controls (p = 0.002 and p < 0.001, respectively). Mean rate pressure product was significantly higher in heFH patients (p = 0.038). Both duration of the ETT and workload in metabolic equivalents was lower in the heFH group (p < 0.001 and p < 0.001, respectively). Baseline to peak rise of systolic and diastolic BP in heFH men was higher (p = 0.008 and p < 0.001 for systolic and diastolic BP, respectively). Furthermore, heFH men had higher rise of HR from baseline to peak, compared to controls; (p = 0.047). GLS in heHF men was slightly decreased (p = 0.014), although the ejection fraction was similar in both groups.

Conclusion

heFH men have a higher rise in systolic/diastolic BP during ETT, which may reflect early, preclinical hypertension. Furthermore, slight impairment of LV GLS is present, despite the absence of apparent myocardial dysfunction in conventional 2D echocardiography.

Homozygous Familial Hypercholesterolemia

Familial hypercholesterolemia (FH) is an inherited disorder with retarded clearance of plasma LDL caused by mutations of the genes involved in the LDL receptor-mediated pathway and most of them exhibit autosomal dominant inheritance. Homozygotes of FH (HoFH) may have plasma LDL-C levels, which are at least twice as high as those of heterozygous FH (HeFH) and therefore four times higher than normal levels. Prevalence of HoFH had been estimated as 1 in 1,000,000 before but more recent genetic analysis surveys predict 1 in 170,000 to 300,000. Since LDL receptor activity is severely impaired, HoFH patients do not or very poorly respond to medications to enhance activity, such as statins, and have a poorer prognosis compared to HeFH. HoFH should therefore be clinically distinguished from HeFH. Thorough family studies and genetic analysis are recommended for their accurate diagnosis.

Fatal cardiovascular complications could develop even in the first decade of life for HoFH, so aggressive lipid-lowering therapy should be initiated as early as possible. Direct removal of plasma LDL by lipoprotein apheresis has been the principal measure for these patients. However, this treatment alone may not achieve stable LDL-C target levels and combination with drugs should be considered. The lipid-lowering effects of statins and PCSK9 inhibitors substantially vary depending on the remaining LDL receptor activity of individual patients. On the other hand, the action an MTP inhibitor is independent of LDL receptor activity, and it is effective in most HoFH cases.

This review summarizes the key clinical issues of HoFH as well as insurance coverage available under the Japanese public healthcare system.

Supravalvular Aortic Stenosis and the Risk of Premature Death Among Patients With Homozygous Familial Hypercholesterolemia

Patients with homozygous familial hypercholesterolemia (HoFH) have a high risk for premature death. Supravalvular aortic stenosis (SVAS) is a common and the feature lesion of the aortic root in HoFH. The relation between SVAS and the risk of premature death in patients with HoFH has not been fully investigated. The present study analysis included 97 HoFH patients with mean age of 14.7 (years) from the Genetic and Imaging of Familial Hypercholesterolemia in Han Nationality Study. During the median (±SD) follow-up 4.0 (±4.0) years, 40 (41.2%) participants had SVAS and 17 (17.5%) participants experienced death. The proportion of premature death in the non-SVAS and SVAS group was 7.0% and 32.5%, respectively. Compared with the non-SVAS group, SVAS group cumulative survival was lower in the HoFH (log-rank test, p <0.001). This result was further confirmed in the multivariable Cox regression models. After adjusting for age, sex, low density lipoprotein cholesterol (LDL_C)-year-score, lipid-lowering drugs, cardiovascular disease, and carotid artery plaque, SVAS was an independent risk factor of premature death in HoFH on the multivariate analysis (hazard ratio 4.45; 95% confidence interval, 1.10 to 18.12; p = 0.037). In conclusion, a significantly increased risk of premature death was observed in HoFH patients with SVAS. Our study emphasized the importance of careful and aggressive management in these patients when appropriate.

Novel therapies for familial hypercholesterolemia

PURPOSE OF REVIEW

Familial hypercholesterolemia is a genetic disorder of defective clearance and subsequent increase in serum LDL cholesterol (LDL-C) with a resultant increased risk of premature atherosclerotic cardiovascular disease. Despite treatment with traditional lipid-lowering therapies (LLT), most patients with familial hypercholesterolemia are unable to achieve target LDL-C. We review current and future novel therapeutic options available for familial hypercholesterolemia.

RECENT FINDINGS

The use of proprotein convertase subtilisin kexin type 9 (PCSK9) inhibitors are effective in lowering LDL-C in patients with familial hypercholesterolemia, with a reduction in LDL-C of 60% in heterozygous familial hypercholesterolemia (HeFH) and up to 35% in homozygous familial hypercholesterolemia (HoFH). Inclisiran, another novel agent, is a small-interfering ribonucleic acid that reduces hepatic production of PCSK9 to provide a prolonged and sustained reduction in LDL-C of nearly 50% in HeFH. However, both agents require LDL receptor (LDLR) activity. Evinacumab, a novel monoclonal antibody against angiopoetin-like 3 (ANGPTL3), reduces LDL-C by 50% independent of LDLR activity.

SUMMARY

Achieving a target LDL-C in familial hypercholesterolemia can be challenging with standard LLT; however, novel therapeutic modalities show remarkable reductions in LDL-C allowing nearly all patients with HeFH and a significant proportion of patients with HoFH to achieve acceptable LDL-C levels.

Role of PCSK9 Inhibitors in Patients with Familial Hypercholesterolemia

Patients with familial hypercholesterolemia (FH) are at high or very high risk for cardiovascular disease. Those with heterozygous FH (HeFH) often do not reach low-density lipoprotein cholesterol (LDL-C) targets with statin and ezetimibe therapy, and those with homozygous FH (HoFH) usually require additional lipid-modifying therapies. Drugs that inhibit proprotein convertase subtilisin/kexin type 9 (PCSK9) offer a novel approach to reduce LDL-C. The monoclonal antibodies, alirocumab and evolocumab, given by subcutaneous injection every 2 or 4 weeks produce reductions in LDL-C of 50% to 60% in patients with HeFH, allowing many of them to achieve their LDL-C goals. Patients with HoFH show a reduced and more variable LDL-C response, which appears to depend on residual LDL receptor activity, and those with receptor-negative mutations may show no response. Inclisiran is a long-acting small interfering RNA therapeutic agent that inhibits the synthesis of PCSK9. Subcutaneous doses of 300 mg can reduce LDL-C by more than 50% for at least 6 months and the responses in HeFH and HoFH patients are similar to those achieved with monoclonal antibodies. These PCSK9 inhibitors are generally well tolerated and they provide a new opportunity for effective treatment for the majority of patients with FH.

The Spectrum of Low-Density Lipoprotein Receptor Mutations in a Large Turkish Cohort of Patients with Familial Hypercholesterolemia

Background: Monogenic hypercholesterolemia with Mendelian inheritance is a heterogeneous group of diseases that are characterized by elevated plasma low-density lipoprotein cholesterol (LDL-C) levels, and the most common form of this disorder is autosomal-dominant familial hypercholesterolemia (FH). Methods: A total of 104 index cases with the clinical diagnosis of FH were included in this study. Low-density lipoprotein receptor (LDLR) was sequenced using the Sanger sequencing method. Results: Pathogenic/likely pathogenic variants were detected in LDLR in 55 of the 104 cases (mutation detection rate = 52.8%). Thirty different variants were detected in LDLR, three of which were novel. The total cholesterol and LDL-C values of the patients in the group of premature termination codon (PTC) mutation carriers were significantly higher than those of the patients in the group of non-PTC mutation carriers. A total of 87 patients (17 pediatric and 70 adult cases) were diagnosed with cascade genetic screening. Statin treatment was recommended to all 87 patients and was accepted and initiated in 70 of these patients. Conclusions: This study is the largest patient cohort that evaluated FH cases in the Turkish population. Herein, we revealed the LDLR mutation spectrum for a Turkish population and compared the cases in the context of genotype-phenotype correlation. Genetic screening of individuals with suspected FH not only helps to establish their diagnosis, but also facilitates early diagnosis and treatment initiation in other family members through cascade screening.

Genetic Risk Assessment for Atherosclerotic Cardiovascular Disease: A Guide for the General Cardiologist

Genetic testing for cardiovascular (CV) disease has had a profound impact on the diagnosis and evaluation of monogenic causes of CV disease, such as hypertrophic and familial cardiomyopathies, long QT syndrome, and familial hypercholesterolemia (FH). The success in genetic testing for monogenic diseases has prompted special interest in utilizing genetic information in the risk assessment of more common diseases such as atherosclerotic cardiovascular disease (ASCVD). Polygenic risk scores (PRS) have been developed to assess the risk of coronary artery disease (CAD) that now include millions of single-nucleotide polymorphisms (SNPs) that have been identified through genome-wide association studies (GWAS). While these PRS have demonstrated a strong association with CAD in large cross-sectional population studies, there remains intense debate regarding the added value that PRS contribute to existing clinical risk prediction models such as the pooled cohort equations (PCEs). In this review, we provide a brief background of genetic testing for monogenic drivers of CV disease and then focus on the recent developments in genetic risk assessment of ASCVD, including the use of PRS. We outline the genetic testing that is currently available to all cardiologists in the clinic and discuss the evolving sphere of specialized cardiovascular genetics programs (CVGPs) that integrate the expertise of cardiologists, geneticists, and genetic counselors. Finally, we review the possible implications that PRS and pharmacogenomic data may soon have on clinical practice in the care for patients with or at risk of developing ASCVD.

Development of Antisense Oligonucleotide Gapmers for the Treatment of Dyslipidemia and Lipodystrophy

Although technological advances in molecular genetics over the last few decades have greatly expedited the identification of mutations in many genetic diseases, the translation of the genetic mechanisms into a clinical setting has been quite challenging, with a minimum number of effective treatments available. The advancements in antisense therapy have revolutionized the field of neuromuscular disorders as well as lipid-mediated diseases. With the approval of splice-switching antisense oligonucleotide (AO) therapy for nusinersen and eteplirsen for the treatment of spinal muscular atrophy (SMA) and Duchenne muscular dystrophy (DMD), several modified AOs are now being evaluated in clinical trials for the treatment of a number of disorders. In order to activate RNase H-mediated cleavage of the target mRNA, as well as to increase the binding affinity and specificity, gapmer AOs are designed that have a PS backbone flanked with the modified AOs on both sides. Mipomersen (trade name Kynamro), a 2'-O-methoxyethyl (MOE) gapmer, was approved by the Food and Drug Administration (FDA) for the treatment of homozygous familial hypercholesterolemia (HoFH) in 2013. Volanesorsen, another 20-mer MOE gapmer has shown to be successful in lowering the levels of triglycerides (TGs) in several lipid disorders and has received conditional approval in the European Union for the treatment of Familial chylomicronemia syndrome (FCS) in May 2019 following successful results from phase II/III clinical trials. This chapter focuses on the clinical applications of gapmer AOs for genetic dyslipidemia and lipodystrophy.

Existing and emerging therapies for the treatment of familial hypercholesterolemia

Familial hypercholesterolemia (FH), an autosomal dominant disorder of LDL metabolism that is characterized by elevated LDL-cholesterol, is commonly encountered in patients with atherosclerotic coronary heart disease. Combinations of cholesterol-lowering therapies are often used to lower LDL-cholesterol in patients with FH; however, current treatment goals for LDL-cholesterol are rarely achieved in patients with homozygous FH (HoFH) and are difficult to achieve in patients with heterozygous FH (HeFH). Therapies that lower LDL-cholesterol through LDL receptor-mediated mechanisms have thus far been largely ineffective in patients with HoFH, particularly in those with negligible (<2%) LDL receptor activity. Among patients with HeFH who were at very high risk for atherosclerotic cardiovascular disease events, combined therapy consisting of a high dose of high-intensity statin, ezetimibe, and proprotein convertase subtilisin Kexin type 9 inhibitor failed to lower LDL-cholesterol to minimal acceptable goals in more than 50%. This article provides a framework for the use of available and emerging treatments that lower LDL-cholesterol in adult patients with HoFH and HeFH. A framework is provided for the use of angiopoietin-like protein 3 inhibitors in the treatment of HoFH and HeFH.

Lipoprotein metabolism in familial hypercholesterolemia

Familial hypercholesterolemia (FH) is one of the most common genetic disorders in humans. It is an extremely atherogenic metabolic disorder characterized by lifelong elevations of circulating LDL-C levels often leading to premature cardiovascular events. In this review, we discuss the clinical phenotypes of heterozygous and homozygous FH, the genetic variants in four genes (LDLR/APOB/PCSK9/LDLRAP1) underpinning the FH phenotype as well as the most recent in vitro experimental approaches used to investigate molecular defects affecting the LDL receptor pathway. In addition, we review perturbations in the metabolism of lipoproteins other than LDL in FH, with a major focus on lipoprotein (a). Finally, we discuss the mode of action and efficacy of many of the currently approved hypocholesterolemic agents used to treat patients with FH, with a special emphasis on the treatment of phenotypically more severe forms of FH.

Proprotein convertase subtilisin/kexin type 9 inhibitor utilization and low-density lipoprotein-cholesterol control in familial hypercholesterolemia

BACKGROUND

Proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors were approved in August 2015 as an adjunct to maximally tolerated statin treatment in those with familial hypercholesterolemia (FH).

OBJECTIVE

To assess PCSK9 inhibitor utilization patterns and cholesterol control in the high-risk FH population.

METHODS

This study was a retrospective analysis of a large administrative database that includes privately insured and Medicare Advantage patients. Individuals with diagnosis codes for FH from October 2016-September 2019 were identified. Differences in PCSK9 inhibitor utilization between various groups were evaluated using multivariable logistic regression.

RESULTS

During the study period, 1:371 people enrolled in medical/pharmacy plans had a diagnosis of FH. While 62.5% (n = 33,649) had medication fills for statins (without PCSK9 inhibitors), only 2.0% (n = 1062) had medication fills for PCSK9 inhibitors (with or without other medications). Compared to men, women were more likely to be untreated (OR 1.23, 95% confidence interval (CI):1.18-1.28, p < 0.01) but more likely to be treated with PCSK9 inhibitors (OR 2.18, 95%CI:1.90-2.49, p < 0.01). Compared to those younger than 55 years of age, older individuals were more likely to be treated (OR 1.64, 95%CI:1.56-1.72, p < 0.01) but less likely to be treated with PCSK9 inhibitors (OR 0.40, 95%CI:0.34-0.47, p < 0.01). Lastly, those with household incomes ≥$40,000 were more likely to be treated with PCSK9 inhibitors than those with lower household incomes (OR 1.69, 95%CI:1.41-2.02, p < 0.01).

CONCLUSION

PCSK9 inhibitor utilization in FH remains low. Significant differences exist based on demographic factors. Female sex, higher household incomes, and younger age were associated with increased PCSK9 inhibitor utilization.

Familial hypercholesterolaemia and COVID-19: A two-hit scenario for endothelial dysfunction amenable to treatment

Patients with familial hypercholesterolemia (FH) are likely at increased risk for COVID-19 complications in the acute phase of the infection, and for a long time thereafter. Because in FH patients the level of low density lipoprotein cholesterol (LDL-C) is elevated from birth and it correlates with the degree of systemic endothelial dysfunction, both heterozygous FH (HeFH) patients and, in particular, homozygous FH (HoFH) patients have a dysfunctional endothelium prone to further damage by the direct viral attack and the hyper-inflammatory reaction typical of severe COVID-19. Evidence to date shows the benefit of statin use in patients with COVID-19. In FH patients, the focus should therefore be on the effective lowering of LDL-C levels, the root cause of the expected excess vulnerability to COVID-19 infection in these patients. Moreover, the ongoing use of statins and other lipid-lowering therapies should be encouraged during the COVID pandemic to mitigate the risk of cardiovascular complications from COVID-19. For the reduction of the excess risk in FH patients with COVID-19, we advocate stringent adherence to the guideline determined LDL-C levels for FH patients, or maybe even to lower levels. Unfortunately, epidemiologic data are lacking on the severity of COVID-19 infections, as well as the number of acute cardiac events that have occurred in FH subjects during the COVID-19 pandemic. Such data need to be urgently gathered to learn how much the risk for, and the severity of COVID-19 in FH are increased.

Genome editing in cardiovascular diseases

Genetic modification at the molecular level in somatic cells, germline, and animal models requires for different purposes, such as introducing desired mutation, deletion of alleles, and insertion of novel genes in the genome. Various genome-editing tools are available to accomplish these alterations, such as zinc finger nucleases (ZFNs), transcription activator-like effector nucleases (TALENs), and clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR associated (Cas) system. CRISPR-Cas system is an emerging technology, which is being used in biological and medical sciences, including in the cardiovascular field. It assists to identify the mechanism of various cardiovascular disease occurrence, such as hypertrophic cardiomyopathy (HCM), dilated cardiomyopathy (DCM), and arrhythmogenic cardiomyopathy (ACM). Furthermore, it has been advantages to edit various genes simultaneously and can also be used to treat and prevent several human diseases. This chapter explores the use of the scientific and therapeutic potential of a CRISPR-Cas system to edit the various cardiovascular disease-associated genes to understand the pathways involved in disease progression and treatment.

LDL Apheresis and Lp (a) Apheresis: A Clinician's Perspective

PURPOSE OF REVIEW

Lipoprotein apheresis is the most effective means of lipid-lowering therapy. However, it's a semi-invasive, time consuming, and chronic therapy with variable adherence. There are still no specific guideline recommendations for the management of patients on lipid apheresis. The purpose of this review is to discuss the clinical indications and major drawbacks of lipid apheresis in the light of recent evidence.

RECENT FINDINGS

Lipoprotein apheresis should be initiated at early ages and performed frequently to receive the expected cardiovascular benefits. However, in clinical practice, most patients experience ineffective apheresis and fail to reach lipid targets. This real-world failure is due to several factors including late diagnosis, delayed referral, and improper frequency of procedures. All these denote that awareness is still low among physicians. Another important factor is the semi-invasive, time consuming nature of the apheresis, leading to high refusal and low adherence rates. Moreover, apheresis decreases quality of life and increases the risk of depression. Mental status is also deteriorated in patients with familial hypercholesterolemia on lipid apheresis. New effective lipid lowering agents are underway with promising cardiovascular results. To overcome the drawbacks, a structured approach, including standardized protocols for lipoprotein apheresis with regular cardiovascular follow-up is warranted. New effective lipid lowering agents with documented cardiovascular benefit, should be integrated into the treatment algorithms of patients on lipoprotein apheresis.

Mutational Spectrum of LDLR and PCSK9 Genes Identified in Iranian Patients With Premature Coronary Artery Disease and Familial Hypercholesterolemia

Familial hypercholesterolemia (FH) is a common, yet underdiagnosed, genetic disorder characterized by lifelong elevated low-density lipoprotein cholesterol levels, which can increase the risk of early-onset coronary artery disease (CAD). In the present study, we screened the nucleotide variations of the LDLR and PCSK9 genes, as well as a part of the APOB gene, in Iranian patients with FH and premature CAD to find the genetic cause of the disorder. Fifteen unrelated individuals with a clinical diagnosis of FH and premature CAD were recruited. Direct DNA sequencing was applied to screen the whole coding exons and exon-intron boundaries of the LDLR and PCSK9 genes and the main parts of their introns, together with exon 26 of the APOB gene. The pathogenicity of the identified mutations was investigated via either segregation analyses in the family or in silico predictive software. Six different point mutations (p.Cys148Tyr, p.Cys216Tyr, p.Cys302Trp, p.Cys338Trp, p.Leu479Gln, and p.G593Afs∗72) in LDLR and a double mutation (p.Asp172His and p.Ala53Val) in both LDLR and PCSK9 genes were identified in seven families with clinically diagnosed FH (43%), whereas no pathogenic mutations were found in eight families with clinically diagnosed FH. This study is the first to identify 1 pathogenic mutation in the LDLR gene (c.1014C > G [p.Cys338Trp]) and to cosegregate it from the affected individual in the family. No mutations were found in the APOB gene, whereas several silent mutations/polymorphisms were identified in the LDLR and PCSK9 genes. Genetic testing and reports on nucleotide alterations in the Iranian population are still limited. Our findings not only further confirm the significant role of FH in the incidence of premature CAD but also enlarge the spectrum of LDLR and PCSK9 variations and exhibit the heterogeneity of FH in Iranians. In patients with no mutation in the examined genes, the disease could be begotten either by a polygenic cause or by gene defects occurring in other related genes and regions not targeted in this study.

FH through the retrospectoscope

After training as a gastroenterologist in the UK, the author became interested in lipidology while he was a research fellow in the USA and switched careers after returning home. Together with Nick Myant, he introduced the use of plasma exchange to treat familial hypercholesterolemia (FH) homozygotes and undertook non-steady state studies of LDL kinetics, which showed that the fractional catabolic rate of LDL remained constant irrespective of pool size. Subsequent steady-state turnover studies showed that FH homozygotes had an almost complete lack of receptor-mediated LDL catabolism, providing in vivo confirmation of the Nobel Prize-winning discovery by Goldstein and Brown that LDL receptor dysfunction was the cause of FH. Further investigation of metabolic defects in FH revealed that a significant proportion of LDL in homozygotes and heterozygotes was produced directly via a VLDL-independent pathway. Management of heterozygous FH has been greatly facilitated by statins and proprotein convertase subtilisin/kexin type 9 inhibitors but remains dependent upon lipoprotein apheresis in homozygotes. In a recent analysis of a large cohort treated with a combination of lipid-lowering measures, survival was markedly enhanced in homozygotes in the lowest quartile of on-treatment serum cholesterol. Emerging therapies could further improve the prognosis of homozygous FH; whereas in heterozygotes, the current need is better detection.

Validity and reliability of an adapted questionnaire measuring knowledge, awareness and practice regarding familial hypercholesterolaemia among primary care physicians in Malaysia

BACKGROUND

Primary care physicians (PCP) play an important role in detecting Familial Hypercholesterolaemia (FH) early. However, knowledge, awareness and practice (KAP) regarding FH among Malaysian PCP are not well established, and there was no validated tool to assess their FH KAP. Thus, the aim of this study was to adapt an FH KAP questionnaire and determine its validity and reliability among Malaysian PCP.

METHODS

This cross-sectional validation study involved Malaysian PCP with ≥ 1-year work experience in the primary care settings. In Phase 1, the original 19-item FH KAP questionnaire underwent content validation and adaptation by 7 experts. The questionnaire was then converted into an online survey instrument and was face validated by 10 PCP. In Phase 2, the adapted questionnaire was disseminated through e-mail to 1500 PCP. Data were collected on their KAP, demography, qualification and work experience. The construct validity was tested using known-groups validation method. The hypothesis was PCP holding postgraduate qualification (PCP-PG-Qual) would have better FH KAP compared with PCP without postgraduate qualification (PCP-noPG-Qual). Internal consistency reliability was calculated using Kuder Richardson formula-20 (KR-20) and test-retest reliability was tested on 26 PCP using kappa statistics.

RESULTS

During content validation and adaptation, 10 items remained unchanged, 8 items were modified, 1 item was moved to demography and 7 items were added. The adapted questionnaire consisted of 25 items (11 knowledge, 5 awareness and 9 practice items). A total of 130 out of 1500 PCP (response rate: 8.7%) completed the questionnaire. The mean percentage knowledge score was found to be significantly higher in PCP-PG-Qual compared with PCP-noPG-Qual (53.5, SD ± 13.9 vs. 35.9, SD ± 11.79), t(128) = 6.90, p < 0.001. The median percentage awareness score was found to be significantly higher in PCP-PG-Qual compared with PCP-noPG-Qual (15.4, IqR ± 23.08 vs. 7.7, IqR ± 15.38), p = 0.030. The mean percentage practice score was significantly higher in PCP-PG-Qual compared with PCP-noPG-Qual (69.2, SD ± 17.62 vs. 54.4, SD ± 19.28), t(128) = 3.79, p < 0.001. KR-20 value was 0.79 (moderate reliability) and average Kappa was 0.796 (substantial agreement).

CONCLUSION

This study has proven that the 25-item adapted FH KAP questionnaire is valid and reliable. It can be used to measure and establish FH KAP among PCP in Malaysia.

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.

Wilemon KA, Patel J, Aguilar-Salinas C, Ahmed CD, Alkhnifsawi M, Almahmeed W, Alonso R, Al-Rasadi K, Badimon L, Bernal LM, Bogsrud MP, Braun LT, Brunham L, Catapano AL, Cillíková K, Corral P, Cuevas R, Defesche JC, Descamps OS, de Ferranti S, Eiselé JL, Elikir G, Folco E, Freiberger T, Fuggetta F, Gaspar IM, Gesztes ÁG, Grošelj U, Hamilton-Craig I, Hanauer-Mader G, Harada-Shiba M, Hastings G, Hovingh GK, Izar MC, Jamison A, Karlsson GN, Kayikçioglu M, Koob S, Koseki M, Lane S, Lima-Martinez MM, López G, Martinez TL, Marais D, Marion L, Mata P, Maurina I, Maxwell D, Mehta R, Mensah GA, Miserez AR, Neely D, Nicholls SJ, Nohara A, Nordestgaard BG, Ose L, Pallidis A, Pang J, Payne J, Peterson AL, Popescu MP, Puri R, Ray KK, Reda A, Sampietro T, Santos RD, Schalkers I, Schreier L, Shapiro MD, Sijbrands E, Soffer D, Stefanutti C, Stoll M, Sy RG, Tamayo ML, Tilney MK, Tokgözoglu L, Tomlinson B, Vallejo-Vaz AJ, Vazquez-Cárdenas A, de Luca PV, Wald DS, Watts GF, Wenger NK, Wolf M, Wood D, Zegerius A, Gaziano TA, Gidding SS. Reducing the Clinical and Public Health Burden of Familial Hypercholesterolemia: A Global Call to Action

Importance

Familial hypercholesterolemia (FH) is an underdiagnosed and undertreated genetic disorder that leads to premature morbidity and mortality due to atherosclerotic cardiovascular disease. Familial hypercholesterolemia affects 1 in 200 to 250 people around the world of every race and ethnicity. The lack of general awareness of FH among the public and medical community has resulted in only 10% of the FH population being diagnosed and adequately treated. The World Health Organization recognized FH as a public health priority in 1998 during a consultation meeting in Geneva, Switzerland. The World Health Organization report highlighted 11 recommendations to address FH worldwide, from diagnosis and treatment to family screening and education. Research since the 1998 report has increased understanding and awareness of FH, particularly in specialty areas, such as cardiology and lipidology. However, in the past 20 years, there has been little progress in implementing the 11 recommendations to prevent premature atherosclerotic cardiovascular disease in an entire generation of families with FH.

Observations

In 2018, the Familial Hypercholesterolemia Foundation and the World Heart Federation convened the international FH community to update the 11 recommendations. Two meetings were held: one at the 2018 FH Foundation Global Summit and the other during the 2018 World Congress of Cardiology and Cardiovascular Health. Each meeting served as a platform for the FH community to examine the original recommendations, assess the gaps, and provide commentary on the revised recommendations. The Global Call to Action on Familial Hypercholesterolemia thus represents individuals with FH, advocacy leaders, scientific experts, policy makers, and the original authors of the 1998 World Health Organization report. Attendees from 40 countries brought perspectives on FH from low-, middle-, and high-income regions. Tables listing country-specific government support for FH care, existing country-specific and international FH scientific statements and guidelines, country-specific and international FH registries, and known FH advocacy organizations around the world were created.

Conclusions and Relevance

By adopting the 9 updated public policy recommendations created for this document, covering awareness; advocacy; screening, testing, and diagnosis; treatment; family-based care; registries; research; and cost and value, individual countries have the opportunity to prevent atherosclerotic heart disease in their citizens carrying a gene associated with FH and, likely, all those with severe hypercholesterolemia as well.

The LDLR, APOB, and PCSK9 Variants of Index Patients with Familial Hypercholesterolemia in Russia

Familial hypercholesterolemia (FH) is a common autosomal codominant disorder, characterized by elevated low-density lipoprotein cholesterol levels causing premature atherosclerotic cardiovascular disease. About 2900 variants of LDLR, APOB, and PCSK9 genes potentially associated with FH have been described earlier. Nevertheless, the genetics of FH in a Russian population is poorly understood. The aim of this study is to present data on the spectrum of LDLR, APOB, and PCSK9 gene variants in a cohort of 595 index Russian patients with FH, as well as an additional systematic analysis of the literature for the period of 1995-2020 on LDLR, APOB and PCSK9 gene variants described in Russian patients with FH. We used targeted and whole genome sequencing to search for variants. Accordingly, when combining our novel data and the data of a systematic literature review, we described 224 variants: 187 variants in LDLR, 14 variants in APOB, and 23 variants in PCSK9. A significant proportion of variants, 81 of 224 (36.1%), were not described earlier in FH patients in other populations and may be specific for Russia. Thus, this study significantly supplements knowledge about the spectrum of variants causing FH in Russia and may contribute to a wider implementation of genetic diagnostics in FH patients in Russia.

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.

Familial hypercholesterolemia in Mexico: Initial insights from the national registry

BACKGROUND

Familial hypercholesterolemia (FH) remains underdiagnosed and undertreated.

OBJECTIVE

Report the results of the first years (2017-2019) of the Mexican FH registry.

METHODS

There are 60 investigators, representing 28 federal states, participating in the registry. The variables included are in accordance with the European Atherosclerosis Society (EAS) FH recommendations.

RESULTS

To date, 709 patients have been registered, only 336 patients with complete data fields are presented. The mean age is 50 (36-62) years and the average time since diagnosis is 4 (IQR: 2-16) years. Genetic testing is recorded in 26.9%. Tendon xanthomas are present in 43.2%. The prevalence of type 2 diabetes is 11.3% and that of premature CAD is 9.8%. Index cases, male gender, hypertension and smoking were associated with premature CAD. The median lipoprotein (a) level is 30.5 (IQR 10.8-80.7) mg/dl. Statins and co-administration with ezetimibe were recorded in 88.1% and 35.7% respectively. A combined treatment target (50% reduction in LDL-C and an LDL-C <100 mg/dl) was achieved by 13.7%. Associated factors were index case (OR 3.6, 95%CI 1.69-8.73, P = .002), combination therapy (OR 2.4, 95%CI 1.23-4.90, P = .011), type 2 diabetes (OR 2.8, 95%CI 1.03-7.59, P = .036) and age (OR 1.023, 95%CI 1.01-1.05, P = .033).

CONCLUSION

The results confirm late diagnosis, a lower than expected prevalence and risk of ASCVD, a higher than expected prevalence of type 2 diabetes and undertreatment, with relatively few patients reaching goals. Recommendations include, the use of combination lipid lowering therapy, control of comorbid conditions and more frequent genetic testing in the future.

Management of Familial Hypercholesterolemia: Current Status and Future Perspectives

Familial hypercholesterolemia (FH) is the most common monogenic disorder associated with premature atherosclerotic cardiovascular disease. Early diagnosis and effective treatment can significantly improve prognosis. Recent advances in the field of lipid metabolism have shed light on the molecular defects in FH and new therapeutic options have emerged. A search of PubMed database up to March 2020 was performed for this review using the following keywords: "familial hypercholesterolemia," "diagnosis," "management," "guideline," "consensus," "genetics," "screening," "lipid lowering agents." The prevalence rate of heterozygous FH is approximately 1 in 200 to 250 and FH is underdiagnosed and undertreated in many parts of the world. Diagnostic criteria have been developed to aid the clinical diagnosis of FH. Genetic testing is now available but not widely used. Cascade screening is recommended to identify affected family members, and the benefits of early interventions are clear. Treatment strategy and target is currently based on low-density lipoprotein (LDL) cholesterol levels as the prognosis of FH largely depends on the magnitude of LDL cholesterol-lowering that can be achieved by lipid-lowering therapies. Statins with or without ezetimibe are the mainstay of treatment and are cost-effective. Addition of newer medications like PCSK9 inhibitors is able to further lower LDL cholesterol levels substantially, but the cost is high. Lipoprotein apheresis is indicated in homozygous FH or severe heterozygous FH patients with inadequate response to cholesterol-lowering therapies. In conclusion, FH is a common, treatable genetic disorder, and although our understanding of this disease has improved, many challenges still remain for its optimal management.

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.

Genetics of Hypercholesterolemia: Comparison Between Familial Hypercholesterolemia and Hypercholesterolemia Nonrelated to LDL Receptor

Severe hypercholesterolemia (HC) is defined as an elevation of total cholesterol (TC) due to the increase in LDL cholesterol (LDL-C) >95th percentile or 190 mg/dl. The high values of LDL-C, especially when it is maintained over time, is considered a risk factor for the development of atherosclerotic cardiovascular disease (ASCVD), mostly expressed as ischemic heart disease (IHD). One of the best characterized forms of severe HC, familial hypercholesterolemia (FH), is caused by the presence of a major variant in one gene (LDLR, APOB, PCSK9, or ApoE), with an autosomal codominant pattern of inheritance, causing an extreme elevation of LDL-C and early IHD. Nevertheless, an important proportion of serious HC cases, denominated polygenic hypercholesterolemia (PH), may be attributed to the small additive effect of a number of single nucleotide variants (SNVs), located along the whole genome. The diagnosis, prevalence, and cardiovascular risk associated with PH has not been fully established at the moment. Cascade screening to detect a specific genetic defect is advised in all first- and second-degree relatives of subjects with FH. Conversely, in the rest of cases of HC, it is only advised to screen high values of LDL-C in first-degree relatives since there is not a consensus for the genetic diagnosis of PH. FH is associated with the highest cardiovascular risk, followed by PH and other forms of HC. Early detection and initiation of high-intensity lipid-lowering treatment is proposed in all subjects with severe HC for the primary prevention of ASCVD, with an objective of LDL-C <100 mg/dl or a decrease of at least 50%. A more aggressive reduction in LDL-C is necessary in HC subjects who associate personal history of ASCVD or other cardiovascular risk factors.

A Rare Double Heterozygous Mutation in Low-Density Lipoprotein Receptor and Apolipoprotein B-100 Genes in a Severely Affected Familial Hypercholesterolaemia Patient

Familial hypercholesterolaemia (FH) is characterized by high plasma low-density lipoprotein cholesterol (LDL-C) levels and premature cardiovascular disease risk. Mutations in the genes that encode proteins involved in LDL uptake and catabolism, including LDL-receptor (LDLR) and apolipoprotein-B (APOB), are known to cause FH. We present the case of a severely affected FH proband with two mutations in two different causing genes and characterize her first-degree blood relatives. The proband was a 54-year-old woman with a severe FH phenotype with treated LDL-C of 8.3 mmol/L, total cholesterol (TC) level of 11.6 mmol/L, peripheral artery disease, early myocardial infarction, aortic stenosis, and carotid artery disease. Exons of the LDLR and APOB genes were amplified by polymerase chain reactions (PCR). PCR products were examined by pyrosequencing and proven by bidirectional DNA sequencing. The proband was heterozygous for both the LDLR c.420G>C (p.Glu140Asp) mutation known to be pathogenic and a rare APOB c.10708C>T (p.His3570Tyr) mutation with unproven pathogenicity. Cascade testing has been performed in her 15 first-degree blood relatives. Her daughter carries only the LDLR c.420 G>C mutation with a TC of 8.4 mmol/L. Her two sisters carry only the APOB c.10708C>T with a TC of 5.7 and 6.2 mmol/L. This case provides evidence that the rare APOB c.10708C>T mutation alone is not pathogenic, but has a synergic effect on LDLR mutation. The finding is important for understanding the genotype-phenotype correlation and highlights the need to consider the presence of additional mutations in FH families where relatives have varying phenotypes.

Advances with lipid-lowering drugs for pediatric patients with familial hypercholesterolemia

INTRODUCTION

Familial hypercholesterolemia (FH) is a frequent genetic disorder characterized by elevated LDL-cholesterol (LDL-C) and early onset of atherosclerosis.

AREAS COVERED

The authors provide an overview of the pediatric FH scenario, with emphasis on the role of statins as the preferred pharmacological therapy, discussing their potential benefits, as well as adverse effects, and the remaining uncertainties about their use in this population. They also comment on other lipid-lowering therapies.

EXPERT OPINION

Statin therapy is recommended after the ages of 8-10 years old for heterozygous FH patients and can reduce LDL-C by 24-50% depending on drug type and dosage. For more severe cases, higher doses and adjuvant therapies like ezetimibe may be necessary and treatment should be started at diagnosis, as is the case of homozygous FH. Statins reduce progression of subclinical vascular disease and may reduce early cardiovascular events. The available evidence indicates safety of statins in children with no apparent harms related to growth, sexual maturation, steroid hormones, glucose levels, cognitive function, or muscle and liver problems, in comparison with placebo. Newer treatments like lomitapide, PCSK9 inhibitors, bempedoic acid and evinacumab need to be adequately evaluated in pediatric FH patients with more severe dyslipidemia.