Familial hypercholesterolemia: the lipids or the genes?

Does Genotype Affect the Efficacy of PCSK9 Inhibitors in the Treatment of Familial Hypercholesterolemia?

PURPOSE OF REVIEW

This review discusses whether patients' genotype affects the efficacy of PCSK9 inhibitors in treating familial hypercholesterolemia and how this might influence clinical management.

RECENT FINDINGS

Currently, available evidence consistently demonstrates and is in good agreement that, in general, the LDL-C-lowering effect of PCSK9 inhibitors is similar across genotypes, except for compound heterozygous and homozygous familial hypercholesterolemia (FH). However, it remains to be seen whether the comparable therapeutic effect in lowering LDL-C level also leads to a comparable degree of cardiovascular risk reduction with different genotypes. Generally, the level of LDL-C reduction following PCSK9 inhibitor treatment is similar within different genotypes. Hence, genotype is a less reliable predictor for further LDL-C level reduction on PCSK9 inhibitor therapy, and attention should be given to other external influences, especially for heterozygous FH.

Genotype-phenotype correlation in a large cohort of pediatric patients with heterozygous and homozygous familial hypercholesterolemia

BACKGROUND

Familial hypercholesterolemia (FH) is a genetic disorder characterized by elevated low-density lipoprotein cholesterol (LDL-C) levels and premature cardiovascular disease (CVD). Both the heterozygous form and the very severe homozygous form can be diagnosed by genetic testing and by clinical criteria. Genetic testing can discern FH in a form caused by complete absence of the LDL-receptors, the negative variant and a form leading to reduced activity of the LDL receptors, the defective variant. The aim of this study is to provide more insight in the genotype-phenotype correlation in children and adolescents diagnosed with heterozygous FH (HeFH) and with homozygous FH (HoFH), specifically in relation to the clinical and therapeutic consequences of the negative and defective variant of FH.

METHODS AND RESULTS

Data of 5904 children with a tentative diagnosis of FH referred to our center for genetic testing were collected. A lipid-profile was present in 3494 children, who became the study cohort. In this large cohort of children, which includes 2714 HeFH and 41 HoFH patients, it is shown that receptor negative variants are associated with significant higher LDL-C levels in HeFH patients than receptor defective variants (6.0 versus 4.9 mmol/L; p  < 0.001). A negative/negative variant is associated with a significant higher LDL-C level jn HoFH patients than a negative/defective variant, which in itself has a higher LDL-C level than a defective/defective variant. Significantly more premature CVD is present in close relatives of children with HeFH with negative variants compared to close relatives of HeFH children with defective variants (75% vs 59%; p  < 0.001).

CONCLUSIONS

Performing genetic testing and identifying the type of underlying genetic variant is of added value in order to distinguish between pediatric patients with higher risks of premature CVD and to identify those that will benefit most from new types of lipid-lowering therapies. Since in children the phenotype of FH is less affected by environmental factors, the study substantiates the genotype-phenotype correlation in this large pediatric population.

Clinical applications of polygenic risk score for coronary artery disease through the life course

Coronary artery disease (CAD) remains a leading cause of morbidity and mortality worldwide, highlighting the limitations of current primary and secondary prevention frameworks. In this review, we detail how the polygenic risk score for CAD can improve our current preventive and treatment frameworks across three clinical applications that span the life course: (i) identification and treatment of people at increased risk early in the life course prior to the onset of clinical risk factors, (ii) improving the precision around risk estimation in middle age, and (ii) guiding treatment decisions and enabling more efficient clinical trials even after the onset of CAD. We end by summarizing the efforts needed as we head towards more widespread use of polygenic risk score for CAD in clinical practice.

Advances for pediatricians in 2022: allergy, anesthesiology, cardiology, dermatology, endocrinology, gastroenterology, genetics, global health, infectious diseases, metabolism, neonatology, neurology, oncology, pulmonology

The last year saw intensive efforts to advance knowledge in pediatric medicine. This review highlights important publications that have been issued in the Italian Journal of Pediatrics in 2022. We have chosen papers in the fields of allergy, anesthesiology, cardiology, dermatology, endocrinology, gastroenterology, genetics, global health, infectious diseases, metabolism, neonatology, neurology, oncology, pulmonology. Novel valuable developments in epidemiology, pathophysiology, prevention, diagnosis and treatment that can rapidly change the approach to diseases in childhood have been included and discussed.

Detecting Familial hypercholesterolemia in children and adolescents: potential and challenges

Background

It is now well established that atherosclerosis begins in childhood and evolves through adolescence and young adulthood, ultimately resulting in myocardial infarction and stroke in adults.

Main test

Childhood is a critical phase during which atherosclerosis may begin to develop; in the presence of familial hypercholesterolemia, lifelong elevation of Low Density Lipoprotein cholesterol levels greatly accelerates atherosclerosis. These concepts, which have been largely developed from epidemiologic evidence, have not always been simple to implement in the paediatric clinical practice.

The purpose of this article is to briefly review but also to highlight the rationale, the motivation and the methods in the process of identifying children and adolescents with familial hypercholesterolemia, an often hidden but very important genetic disease.

The Role of Registers in Increasing Knowledge and Improving Management of Children and Adolescents Affected by Familial Hypercholesterolemia: the LIPIGEN Pediatric Group

Pathology registers can be a useful tool to overcome obstacles in the identification and management of familial hypercholesterolemia since childhood. In 2018, the LIPIGEN pediatric group was constituted within the Italian LIPIGEN study to focus on FH subjects under 18 years. This work aimed at discussing its recent progress and early outcomes. Demographic, biochemical, and genetic baseline characteristics were collected, with an in-depth analysis of the genetic defects. The analysis was carried out on 1,602 children and adolescents (mean age at baseline 9.9 ± 4.0 years), and almost the whole cohort underwent the genetic test (93.3%). Overall, the untreated mean value of LDL-C was 220.0 ± 97.2 mg/dl, with an increasing gradient from subjects with a negative (N = 317; mean untreated LDL-C = 159.9 ± 47.7 mg/dl), inconclusive (N = 125; mean untreated LDL-C = 166.4 ± 56.5 mg/dl), or positive (N = 1,053; mean untreated LDL-C = 246.5 ± 102.1 mg/dl) genetic diagnosis of FH. In the latter group, the LDL-C values presented a great variability based on the number and the biological impact of involved causative variants. The LIPIGEN pediatric group represents one of the largest cohorts of children with FH, allowing the deepening of the characterization of their baseline and genetic features, providing the basis for further longitudinal investigations for complete details.

Clinical characterization of familial hypercholesterolemia due to an amish founder mutation in Apolipoprotein B

Background

Familial hypercholesterolemia (FH) due to a founder variant in Apolipoprotein B (ApoB^R3500Q) is reported in 12% of the Pennsylvania Amish community. By studying a cohort of ApoB^R3500Q heterozygotes and homozygotes, we aimed to characterize the biochemical and cardiac imaging features in children and young adults with a common genetic background and similar lifestyle.

Methods

We employed advanced lipid profile testing, carotid intima media thickness (CIMT), pulse wave velocity (PWV), and peripheral artery tonometry (PAT) to assess atherosclerosis in a cohort of Amish ApoB^R3500Q heterozygotes (n = 13), homozygotes (n = 3), and their unaffected, age-matched siblings (n = 9). ApoB^R3500Q homozygotes were not included in statistical comparisons.

Results

LDL cholesterol (LDL-C) was significantly elevated among ApoB^R3500Q heterozygotes compared to sibling controls, though several ApoB^R3500Q heterozygotes had LDL-C levels in the normal range. LDL particles (LDL-P), small, dense LDL particles, and ApoB were also significantly elevated among subjects with ApoB^R3500Q. Despite these differences in serum lipids and particles, CIMT and PWV were not significantly different between ApoB^R3500Q heterozygotes and controls in age-adjusted analysis.

Conclusions

We provide a detailed description of the serum lipids, atherosclerotic plaque burden, vascular stiffness, and endothelial function among children and young adults with FH due to heterozygous ApoB^R3500Q. Fasting LDL-C was lower than what is seen with other forms of FH, and even normal in several ApoB^R3500Q heterozygotes, emphasizing the importance of cascade genetic testing among related individuals for diagnosis. We found increased number of LDL particles among ApoB^R3500Q heterozygotes but an absence of detectable atherosclerosis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12872-022-02539-3.

Genetic Polymorphisms in a Familial Hypercholesterolemia Population from North-Eastern Europe

(1) Background: Familial hypercholesterolemia (FH) is one of the most prevalent inherited metabolic disorders. The purpose of the study was to investigate the role in cardiovascular disease (CVD) of PAI-1, ACE, ApoB-100, MTHFR A1298C, and C677T. (2) Methods: From a group of 1499 patients, we included 52 patients diagnosed with FH phenotype and 17 patients in a control group. (3) Results: Most of the FH patients had multiple comorbidities compared to the control group, such as atherosclerosis (48.1% vs. 17.6%), atherosclerotic cardiovascular disease (ASCVD 32.7% vs. 11.8%), and metabolic syndrome (MetS, 40.4% vs. 11.8%). In total, 66.7% of the FH patients had PAI-1 4G/5G genotype and MetS. Between 4G/5G and 4G/4G, a statistically significant difference was observed (p = 0.013). FH patients with ApoB R3500Q polymorphism were correlated with ASCVD (p = 0.031). Both MTHFR C677T and A1298C polymorphisms had a significant correlation with gender, alcohol consumption, and smoking status. ACE polymorphism was associated with ATS in FH patients, statistically significant differences being observed between heterozygous and homozygous D genotype (p = 0.036) as well as between heterozygous and homozygous I genotype (p = 0.021). (4) Conclusions: A link between these polymorphisms was demonstrated in the FH group for ATS, ASCVD, and MetS.

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.

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

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

Pharmacogenomics Variability of Lipid-Lowering Therapies in Familial Hypercholesterolemia

The exponential expansion of genomic data coupled with the lack of appropriate clinical categorization of the variants is posing a major challenge to conventional medications for many common and rare diseases. To narrow this gap and achieve the goals of personalized medicine, a collaborative effort should be made to characterize the genomic variants functionally and clinically with a massive global genomic sequencing of "healthy" subjects from several ethnicities. Familial-based clustered diseases with homogenous genetic backgrounds are amongst the most beneficial tools to help address this challenge. This review will discuss the diagnosis, management, and clinical monitoring of familial hypercholesterolemia patients from a wide angle to cover both the genetic mutations underlying the phenotype, and the pharmacogenomic traits unveiled by the conventional and novel therapeutic approaches. Achieving a drug-related interactive genomic map will potentially benefit populations at risk across the globe who suffer from dyslipidemia.

Limited-Variant Screening vs Comprehensive Genetic Testing for Familial Hypercholesterolemia Diagnosis

Question

How many clinically significant variants for familial hypercholesterolemia would be missed by limited-variant screening conducted on microarrays?

Findings

In this cross-sectional review of comprehensive genetic test results for individuals with indications for familial hypercholesterolemia, a limited-variant screen was found to have a significantly lower detection rate (8.4%) than the comprehensive diagnostic test (27%).

Meaning

The results of this study suggest that clinically significant findings for familial hypercholesterolemia would be missed for two-thirds of affected individuals if limited-variant screening was used.

Importance

Familial hypercholesterolemia (FH) is the most common inherited cardiovascular disease and carries significant morbidity and mortality risks. Genetic testing can identify affected individuals, but some array-based assays screen only a small subset of known pathogenic variants.

Objective

To identify the number of clinically significant variants associated with FH that would be missed by an array-based, limited-variant screen when compared with next-generation sequencing (NGS)–based comprehensive testing.

Design, Setting, and Participants

This cross-sectional study compared comprehensive genetic test results for clinically significant variants associated with FH with results for a subset of 24 variants screened by a limited-variant array. Data were deidentified next-generation sequencing results from indication-based or proactive gene panels. Individuals receiving next-generation sequencing–based genetic testing, either for an FH indication between November 2015 and June 2020 or as proactive health screening between February 2016 and June 2020 were included. Ancestry was reported by clinicians who could select from preset options or enter free text on the test requisition form.

Main Outcomes and Measures

Number of pathogenic or likely pathogenic (P/LP) variants identified.

Results

This study included 4563 individuals who were referred for FH diagnostic testing and 6482 individuals who received next-generation sequencing of FH-associated genes as part of a proactive genetic test. Among individuals in the indication cohort, the median (interquartile range) age at testing was 49 (32-61) years, 55.4% (2528 of 4563) were female, and 63.6% (2902 of 4563) were self-reported White/Caucasian. In the indication cohort, the positive detection rate would have been 8.4% (382 of 4563) for a limited-variant screen compared with the 27.0% (1230 of 4563) observed with the next-generation sequencing–based comprehensive test. As a result, 68.9% (848 of 1230) of individuals with a P/LP finding in an FH-associated gene would have been missed by the limited screen. The potential for missed findings in the indication cohort varied by ancestry; among individuals with a P/LP finding, 93.7% (59 of 63) of self-reported Black/African American individuals and 84.7% (122 of 144) of Hispanic individuals would have been missed by the limited-variant screen, compared with 33.3% (4 of 12) of Ashkenazi Jewish individuals. In the proactive cohort, the prevalence of clinically significant FH variants was approximately 1:191 per the comprehensive test, and 61.8% (21 of 34) of individuals with an FH-associated P/LP finding would have been missed by a limited-variant screen.

Conclusions and Relevance

Limited-variant screens may falsely reassure the majority of individuals at risk for FH that they do not carry a disease-causing variant, especially individuals of self-reported Black/African American and Hispanic ancestry.

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.

Prevalence of cardiovascular events in genetically confirmed versus unconfirmed familial hypercholesterolaemia

Introduction: Genetic testing for familial hypercholesterolaemia (FH) is not yet established for widespread use internationally to provide diagnostic confirmation, in part due to high cost and resource requirement. We need to establish whether genetic testing is clinically justified in terms of risk stratification and prediction of cardiovascular events. Methods:We performed a single tertiary cardiac centre retrospective evaluation of patients with FH managed within our genetic screening service. We evaluated the prevalence of cardiovascular events in genetically confirmed cases of FH compared to those unconfirmed upon genetic testing, to assess whether gene positivity confers a higher risk phenotype. We also compared the clinical characteristics of the genetically confirmed and unconfirmed group. Results:Amongst adult patients (≥18 years) with genetically confirmed heterozygous FH (n=87), 34% (30/87) had one or more documented CV events. In comparison a lower event rate was observed in adult patients with genetically unconfirmed FH (n=170) with 25% (42/170) experiencing one or more documented CV events. Additional cardiovascular risk factors were more prevalent in the unconfirmed group including hypertension, co-morbidities, higher age and body mass index which may have modified the difference in cardiovascular risk. Conclusion:Genetic testing in FH may be clinically justified and appears to identify a subset of patients with higher risk of cardiovascular events. However, the risk difference is modified by alternative cardiovascular risk factors and co-morbidities which may be more prevalent in genetically unconfirmed FH.

A complicated pregnancy in homozygous familial hypercholesterolaemia treated with lipoprotein apheresis: A case report

BACKGROUND AND AIMS

During pregnancy total cholesterol (TC) and low density lipoprotein cholesterol (LDL-C) levels increase significantly and lipoprotein apheresis (LA) is considered the most effective therapy in homozygous familial hypercholesterolaemia (HoFH) for modulating lipid and lipoprotein levels and reducing maternal and foetal complications.

CLINICAL CASE

A primigravida 28 years old Caucasian female patient, previously diagnosed as to be HoFH, was admitted at our outpatient service at the beginning of pregnancy.

METHODS

The patient was continuously submitted to LA every two weeks without foetal complication. During pregnancy two methods have been utilised: selective apheresis, and later plasma exchange. At 33 weeks gestational age the patient developed progressively hypertension, associated to LDL-C levels increase. Weekly LA was favoured.

RESULTS

At 34 weeks +5 days patient suddenly experienced acute chest pain and abnormal electrocardiogram heart tracing and cardiac enzymes increase. An emergency caesarean section was performed without complications and the foetus was healthy. The patient was immediately transferred to Coronary Intensive Care Unit, where she was diagnosed non-ST elevation myocardial infarction (NSTEMI). Notwithstanding the patient improved in few days and was quickly discharged in fair clinical condition.

CONCLUSIONS

LA is a safe and effective tool in HoFH subjects even in pregnancy. Evidence based guidelines for the management of these patients during pregnancy are still lacking.

Preliminary data of familial hypercholesterolemia (FH) patients in Romania

BACKGROUND AND AIMS

Familial hypercholesterolemia (FH) is one of the most frequent monogenic cholesterol disorders. Its prevalence varies in adults between 1/500-1/217 individuals in the heterozygous form. The objective of this study was to uncover the FH prevalence in Romania to perform an adequate prevention for high risk individuals.

METHODS

We have conducted an epidemiological study between January 2015 and January 2018 by recruiting patients from the CardioPrevent Foundation based on their FH score (taking into account their low density lipoprotein cholesterol (LDLc) levels, clinical characteristics such as premature coronary artery disease (CAD), and their family history of premature cardiovascular disease). We have calculated the probability of FH using the Dutch Lipid Clinic Network (DLCN) criteria and we have included patients with a score over 3 points.

RESULTS

We have enrolled 59 patients, out of whom 61% were females. 8.4% of the patients recruited had a first degree relative with premature coronary artery disease and 5% had a relative with LDLc >190 mg/dl (without statin treatment). 10.16% of the patients had coronary artery disease and 15.25% peripheral vascular disease. 91.52% of the patients had a possible FH, while 6.7% had a probable FH and 1.6% a definite FH diagnosis. Based on this data, the prevalence of FH in Romania is: 1:213.

CONCLUSIONS

To raise the suspicion for FH is easy at the level of the general practitioners, based on the analysis of LDLc levels and premature CAD occurrence. Diagnosis can be further refined using an available online free software.

Screening of common genetic variants in the APOB gene related to familial hypercholesterolemia in a Saudi population: A case-control study

Familial hypercholesterolemia (FH) is a monogenic dominant inherited disorder of lipid metabolism characterized by elevated low-density lipoprotein levels, and is mainly attributable to mutations in low-density lipoprotein receptor (LDLR), apolipoprotein B (APOB), and proportein convertase subtilisin/kexin type 9 (PCSK9) genes. Next-generation and exome sequencing studies have primarily involved genome-wide association analyses, and meta-analyses and next-generation studies examined a few single-nucleotide polymorphisms (rs151009667 and Val2095Glu) in the ApoB gene. The present study was conducted to investigate the association of APOB and patients with FH in a Saudi population.We genotyped 100 patients with FH and 100 controls for 2 polymorphisms in APOB using polymerase chain reaction-restriction fragment length polymorphism, followed by 3% agarose gel electrophoresis. The strength of the association between the genotype and allele frequencies with the risk of developing FH was evaluated. Clinical details and genotype analysis results were recorded.For the rs151009667 polymorphism, 18% of the CT genotypes were observed only in patients with FH. There was a positive association between CT and CC (odds ratio [OR] 45.07 [95% conflict of interest (CI), 2.67-759.1]; P = .0001) and between T and C (OR 87.8 [95% CI, 5.34-144.2]; P < .0001). However, no Val2095Glu mutations were found in patients with FH or controls. There was also no correlation between clinical characteristics and the rs151009667 polymorphism.In conclusion, we confirmed the association between the rs151009667 polymorphism and FH in a Saudi population. The Val2095Glu novel variant did not appear in either patients with FH or controls. Similar studies should be performed in different ethnic populations to rule out the role of this polymorphism in FH.

Spectrum of mutations of familial hypercholesterolemia in the 22 Arab countries

BACKGROUND AND AIMS

Familial hypercholesterolemia (FH) is an inherited genetic disorder of lipid metabolism characterized by a high serum LDL-cholesterol profile and xanthoma formation, and FH increases the risk of premature atherosclerosis and cardiovascular disease (CVD). Mutations in the low-density lipoprotein (LDLR), apolipoprotein B (APOB), proprotein convertase subtilisin/kexin 9 (PCSK9), and LDLRAP1 genes have been associated with FH. Although FH is a major risk for CVD, the disease prevalence and its underlying molecular basis in the 22 Arab countries are still understudied. This study aimed to analyze all peer-reviewed studies related to the prevalence of FH and its causative mutations in the 22 Arab countries.

METHODS

We searched five literature databases (Scopus, Science Direct, Web of Science, PubMed, and Google Scholar) from inception until June 2018, using all possible search terms to capture all of the genetic and prevalence data related to Arab patients with FH.

RESULTS

A total of 5,484 titles and abstracts were identified; 51 studies met our inclusion criteria for the final systematic review. Fifty-one mutations in Arab patients with FH were identified in only eight Arab countries; 47 were identified in the LDLR gene, two in the PCSK9 gene, and two in LDLRAP1 gene. Twenty mutations in the LDLR gene were distinctive to Arab patients. A few studies reported prevalence estimates, ranging from 0.4% to 6.8%.

CONCLUSIONS

This is the first systematic review to dissect the up-to-date status of the genetic epidemiology of Arab patients with FH. It seems that FH is underdiagnosed and that its prevalence is understudied due to the dearth of published information about Arab patients with FH. Therefore, there is a need for well-controlled genetic epidemiological studies on Arab patients with FH.

Intracellular cholesterol accumulation and coenzyme Q10 deficiency in Familial Hypercholesterolemia

Familial Hypercholesterolemia (FH) is an autosomal co-dominant genetic disorder characterized by elevated low-density lipoprotein (LDL) cholesterol levels and increased risk for premature cardiovascular disease. Here, we examined FH pathophysiology in skin fibroblasts derived from FH patients harboring heterozygous mutations in the LDL-receptor. Fibroblasts from FH patients showed a reduced LDL-uptake associated with increased intracellular cholesterol levels and coenzyme Q₁₀ (CoQ₁₀) deficiency, suggesting dysregulation of the mevalonate pathway. Secondary CoQ₁₀ deficiency was associated with mitochondrial depolarization and mitophagy activation in FH fibroblasts. Persistent mitophagy altered autophagy flux and induced inflammasome activation accompanied by increased production of cytokines by mutant cells. All the pathological alterations in FH fibroblasts were also reproduced in a human endothelial cell line by LDL-receptor gene silencing. Both increased intracellular cholesterol and mitochondrial dysfunction in FH fibroblasts were partially restored by CoQ₁₀ supplementation. Dysregulated mevalonate pathway in FH, including increased expression of cholesterogenic enzymes and decreased expression of CoQ₁₀ biosynthetic enzymes, was also corrected by CoQ₁₀ treatment. Reduced CoQ₁₀ content and mitochondrial dysfunction may play an important role in the pathophysiology of early atherosclerosis in FH. The diagnosis of CoQ₁₀ deficiency and mitochondrial impairment in FH patients may also be important to establish early treatment with CoQ₁₀.

ASPECTS OF DETECTING PATIENTS WITH FAMILY HYPERCHOLESTEROLEMIA

The review presents current data regarding the etiology and epidemiology of familial hypercholesterolemia (FH), algorithms for identifying patients with FH using clinical scales, genetic testing, cascade screening. The current tactics of treatment of family hypercholesterolemia, including in children and pregnant women, are given.

Premature Valvular Heart Disease in Homozygous Familial Hypercholesterolemia

Valvular heart disease frequently occurs as a consequence of premature atherosclerosis in individuals with familial hypercholesterolemia (FH). Studies have primarily focused on aortic valve calcification in heterozygous FH, but there is paucity of data on the incidence of valvular disease in homozygous FH. We performed echocardiographic studies in 33 relatively young patients (mean age: 26 years) with homozygous FH (mean LDL of 447 mg/dL, 73% on LDL apheresis) to look for subclinical valvulopathy. Twenty-one patients had evidence of valvulopathy of the aortic or mitral valves, while seven subjects showed notable mitral regurgitation. Older patients were more likely to have aortic valve calcification (>21 versus ≤21 years: 59% versus 12.5%; p = 0.01) despite lower LDL levels at the time of the study (385 versus 513 mg/dL; p = 0.016). Patients with valvulopathy were older and had comparable LDL levels and a lower carotid intima-media thickness. Our data suggests that, in homozygous FH patients, valvulopathy (1) is present across a wide age spectrum and LDL levels and (2) is less likely to be influenced by lipid-lowering treatment. Echocardiographic studies that focused on aortic root thickening and stenosis and regurgitation are thus likely an effective modality for serial follow-up of subclinical valvular heart disease.

A Genome-Wide Association Study Identifies the Genomic Region Associated with Shell Color in Yesso Scallop, Patinopecten yessoensis

The shell color polymorphism widely exists in economic shellfish, which not only results in a better visual perception but also shows great value as an economic trait for breeding. Small numbers of reddish-orange shell Yesso scallops, Patinopecten yessoensis, were found in cultured populations compared to the brown majority. In this study, a genome-wide association study was conducted to understand the genetic basis of shell color. Sixty-six 2b-RAD libraries with equal numbers of reddish-orange and brown shell individuals were constructed and sequenced using the Illumina HiSeq 2000 platform. A total of 322,332,684 high-quality reads were obtained, and the average sequencing depth was 18.4×. One genomic region on chromosome 11 that included 239 single-nucleotide polymorphisms (SNPs) was identified as significantly associated with shell color. After verification by high-resolution melting in another population, two SNPs were selected as specific loci for reddish-orange shell color. These two SNPs could be used to improve the selective breeding progress of true-breeding strains with complete reddish-orange scallops. In addition, within the significantly associated genomic region, candidate genes were identified using marker sequences to search the draft genome of Yesso scallop. Three genes (LDLR, FRIS, and FRIY) with known functions in carotenoid metabolism were identified. Further study using high-performance liquid chromatography proved that the relative level of carotenoids in the reddish-orange shells was 40 times higher than that in the brown shells. These results suggested that the accumulation of carotenoids contributes to the formation of reddish-orange shells.

New Approaches in Detection and Treatment of Familial Hypercholesterolemia

Familial hypercholesterolemia (FH) is an autosomal dominant genetic disorder that clinically leads to increased low density lipoprotein-cholesterol (LDL-C) levels. As a consequence, FH patients are at high risk for cardiovascular disease (CVD). Mutations are found in genes coding for the LDLR, apoB, and PCSK9, although FH cannot be ruled out in the absence of a mutation in one of these genes. It is pivotal to diagnose FH at an early age, since lipid lowering results in a decreased risk of cardiovascular complications especially if initiated early, but unfortunately FH is largely underdiagnosed. While a number of clinical criteria are available, identification of a pathogenic mutation in any of the three aforementioned genes is seen by many as a way to establish a definitive diagnosis of FH. It should be remembered that clinical treatment is based on LDL-C levels and not solely on presence or absence of genetic mutations as LDL-C is what drives risk. Traditionally, mutation detection has been done by means of dideoxy sequencing. However, novel molecular testing methods are gradually being introduced. These next generation sequencing-based methods are likely to be applied on broader scale once their efficacy and effect on cost are being established. Statins are the first-line therapy of choice for FH patients as they have been proven to reduce CVD risk across a range of conditions including hypercholesterolemia (though not specifically tested in FH). However, in a significant proportion of FH patients LDL-C goals are not met, despite the use of maximal statin doses and additional lipid-lowering therapies. This underlines the need for additional therapies, and inhibition of PCSK9 and CETP is among the most promising new therapeutic options. In this review, we aim to provide an overview of the latest information about the definition, diagnosis, screening, and current and novel therapies for FH.

Predictors of cardiovascular events after one year of molecular screening for Familial hypercholesterolemia

BACKGROUND AND AIMS

This study reports the first year follow-up of individuals enrolled in Brazil's genetic cascade screening program for Familial Hypercholesterolemia (FH), Hipercol Brasil. Predictors for the occurrence of cardiovascular (CV) events in individuals screened for FH were studied.

METHODS

This is an open prospective cohort of individuals who were included in a cascade genetic screening program for FH. The first prospective follow-up was carried out one year after patients received their genetic test result. Individuals included in this study were index cases (probands) and relatives with identified (M +) or not genetic mutations (M -). Logistic regression analysis was performed to determine predictive variables for the occurrence of CV events censored at one-year of follow-up.

RESULTS

A total of 818 subjects were included, 47 first CV events were ascertained, with 14 (29.7%) being fatal. For index cases, the only factor independently associated with increased risk of CV events was the presence of corneal arcus (OR: 9.39; 95% CI: 2.46-35.82). There was an inverse association of CV events with higher HDL-cholesterol levels (OR: 0.95; 95% CI: 0.90-0.99). For M+ relatives, risk factors associated with increased CV events risk were diabetes mellitus (OR: 7.97; 95% CI: 2.07-30.66) and tobacco consumption (OR: 3.70; 95% CI: 1.09-12.50).

CONCLUSIONS

A high one-year incidence of CV events was found in this cascade-screening cohort. Predictors of events differed between index cases and relatives and can be useful for the development of preventive efforts in this highly susceptible group of individuals.

The genetics and screening of familial hypercholesterolaemia

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

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

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

Genetic Testing in Hyperlipidemia

Hereditary dyslipidemias are often underdiagnosed and undertreated, yet with significant health implications, most importantly causing preventable premature cardiovascular diseases. The commonly used clinical criteria to diagnose hereditary lipid disorders are specific but are not very sensitive. Genetic testing may be of value in making accurate diagnosis and improving cascade screening of family members, and potentially, in risk assessment and choice of therapy. This review focuses on using genetic testing in the clinical setting for lipid disorders, particularly familial hypercholesterolemia.

Variable expressivity and co-occurrence of LDLR and LDLRAP1 mutations in familial hypercholesterolemia: failure of the dominant and recessive dichotomy

BACKGROUND

The familial inherited genetic disorder of lipoprotein metabolism affects more than 10 million individuals around the world. Lebanon is one of the several endemic areas for familial hypercholesterolemia (FH) with a founder mutation in the low-density lipoprotein cholesterol receptor (LDLR) gene, responsible for most of the cases. We have previously shown that 16% of all familial cases with hypercholesterolemia do not show genotype segregation of LDLR with the underlying phenotype.

METHODS

We used Sanger sequencing to genotype 25 Lebanese families with severe FH for the gene encoding the LDLR-associated protein (LDLRAP1), responsible for the recessive form of the disease starting with the four families that did not show any genotype-phenotype correlation in our previous screening.

RESULTS

We showed that the previously reported p.Q136* variant is linked to the hypercholesterolemia phenotype in the four families. In addition, we showed a variable phenotype between families and between members of the same family. One family exhibits mutations in both LDLR and LDLRAP1 with family members showing differential phenotypes unexplained by the underlying genotypes of the two genes.

CONCLUSION

The p.Q136* variant in LDLRAP1 is yet another founder mutation in Lebanon and coupled with the LDLR p.C681* variant explains all the genetic causes of FH in Lebanon.

Exploring the complete mutational space of the LDL receptor LA5 domain using molecular dynamics: linking SNPs with disease phenotypes in familial hypercholesterolemia

Familial hypercholesterolemia (FH), a genetic disorder with a prevalence of 0.2%, represents a high-risk factor to develop cardiovascular and cerebrovascular diseases. The majority and most severe FH cases are associated to mutations in the receptor for low-density lipoproteins receptor (LDL-r), but the molecular basis explaining the connection between mutation and phenotype is often unknown, which hinders early diagnosis and treatment of the disease. We have used atomistic simulations to explore the complete SNP mutational space (227 mutants) of the LA5 repeat, the key domain for interacting with LDL that is coded in the exon concentrating the highest number of mutations. Four clusters of mutants of different stability have been identified. The majority of the 50 FH known mutations (33) appear distributed in the unstable clusters, i.e. loss of conformational stability explains two-third of FH phenotypes. However, one-third of FH phenotypes (17 mutations) do not destabilize the LR5 repeat. Combining our simulations with available structural data from different laboratories, we have defined a consensus-binding site for the interaction of the LA5 repeat with LDL-r partner proteins and have found that most (16) of the 17 stable FH mutations occur at binding site residues. Thus, LA5-associated FH arises from mutations that cause either the loss of stability or a decrease in domain's-binding affinity. Based on this finding, we propose the likely phenotype of each possible SNP in the LA5 repeat and outline a procedure to make a full computational diagnosis for FH.

Evaluation of plasma cholestane-3β,5α,6β-triol and 7-ketocholesterol in inherited disorders related to cholesterol metabolism

Oxysterols are intermediates of cholesterol metabolism and are generated from cholesterol via either enzymatic or nonenzymatic pathways under oxidative stress conditions. Cholestan-3β,5α,6β-triol (C-triol) and 7-ketocholesterol (7-KC) have been proposed as new biomarkers for the diagnosis of Niemann-Pick type C (NP-C) disease, representing an alternative tool to the invasive and time-consuming method of fibroblast filipin test. To test the efficacy of plasma oxysterol determination for the diagnosis of NP-C, we systematically screened oxysterol levels in patients affected by different inherited disorders related with cholesterol metabolism, which included Niemann-Pick type B (NP-B) disease, lysosomal acid lipase (LAL) deficiency, Smith-Lemli-Opitz syndrome (SLOS), congenital familial hypercholesterolemia (FH), and sitosterolemia (SITO). As expected, NP-C patients showed significant increase of both C-triol and 7-KC. Strong increase of both oxysterols was observed in NP-B and less pronounced in LAL deficiency. In SLOS, only 7-KC was markedly increased, whereas in both FH and in SITO, oxysterol concentrations were normal. Interestingly, in NP-C alone, we observed that plasma oxysterols correlate negatively with patient's age and positively with serum total bilirubin, suggesting the potential relationship between oxysterol levels and hepatic disease status. Our results indicate that oxysterols are reliable and sensitive biomarkers of NP-C.

Genetics of familial hypercholesterolemia

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

Familial hypercholesterolemia: developments in diagnosis and treatment

BACKGROUND

Familial hypercholesterolemia (FH) is a congenital disorder of lipid metabolism characterized by a marked elevation of the plasma concentration of LDL (low-density lipoprotein) cholesterol beginning in childhood and by the early onset of coronary heart disease. It is among the commonest genetic disorders, with an estimated prevalence in Germany of at least 1 per 500 persons.

METHOD

Review of pertinent literature retrieved by a selective search.

RESULTS

FH is underdiagnosed and undertreated in Germany. It is clinically diagnosed on the basis of an elevated LDL cholesterol concentration (>190 mg/dL [4.9 mmol/L]), a family history of hypercholesterolemia, and early coronary heart disease, or the demonstration of xanthomas. The gold standard of diagnosis is the identification of the underlying genetic defect, which is possible in 80% of cases and enables the identification of affected relatives of the index patient. The recommended goals of treatment, based on the results of observational studies, are to lower the LDL cholesterol concentration by at least 50% or to less than 100 mg/dL (2.6 mmol/L) (for children: <135 mg/dL [3.5 mmol/L]). The target value is lower for patients with clinically overt atherosclerosis (<70 mg/dL [1.8 mmol/L]). Statins, combined with a health-promoting lifestyle, are the treatment of choice. Lipoprotein apheresis is used in very severe cases; its therapeutic effects on clinical endpoints and its side effect profile have not yet been documented in randomized controlled trials.

CONCLUSION

Familial hypercholesterolemia is a common disease that can be diagnosed simply and reliably on clinical grounds and by molecular genetic testing. Timely diagnosis and appropriate treatment can lower the risk of atherosclerosis in heterozygous patients to that of the general population.

New therapies targeting apoB metabolism for high-risk patients with inherited dyslipidaemias: what can the clinician expect?

Apolipoprotein B (apoB) has a key role in the assembly and secretion of very low-density lipoprotein (VLDL) from the liver. Plasma apoB concentration affects the number of circulating atherogenic particles, and serves as an independent predictor of the risk of atherosclerotic cardiovascular disease. While statins are the most potent apoB-lowering agents currently prescribed, their efficacy in achieving therapeutic targets for low-density lipoprotein cholesterol (LDL-C) in high-risk patients, such as those with familial hypercholesterolaemia (FH), is limited. Resistance and intolerance to statins also occurs in a significant number of patients, necessitating new types of lipid-lowering therapies. Monoclonal antibodies against proprotein convertase subtilisin/kexin type 9 (PCSK9; AMG 145 and REGN727), a sequence-specific antisense oligonucleotide against apoB mRNA (mipomersen) and a synthetic inhibitor of microsomal triglyceride transfer protein (MTTP; lomitapide) have been tested in phase III clinical trials, particularly in patients with FH. The trials demonstrated the efficacy of these agents in lowering apoB, LDL-C, non-high-density lipoprotein cholesterol and lipoprotein(a) by 32-55 %, 37-66 %, 38-61 % and 22-50 % (AMG 145), 21-68 %, 29-72 %, 16-60 % and 8-36 % (REGN727), 16-71 %, 15-71 %, 12-66 % and 23-49 % (mipomersen) and 24-55 %, 25-51 %, 27-50 % and 15-19 % (lomitapide), respectively. Monoclonal antibodies against PCSK9 have an excellent safety profile and may be indicated not only in heterozygous FH, but also in statin-intolerant patients and those with other inherited dyslipidemias, such as familial combined hyperlipidaemia and familial elevation in Lp(a). Mipomersen and lomitapide increase hepatic fat content and are at present indicated for treating adult patients with homozygous FH alone.

Dietary fats and health: dietary recommendations in the context of scientific evidence

Although early studies showed that saturated fat diets with very low levels of PUFAs increase serum cholesterol, whereas other studies showed high serum cholesterol increased the risk of coronary artery disease (CAD), the evidence of dietary saturated fats increasing CAD or causing premature death was weak. Over the years, data revealed that dietary saturated fatty acids (SFAs) are not associated with CAD and other adverse health effects or at worst are weakly associated in some analyses when other contributing factors may be overlooked. Several recent analyses indicate that SFAs, particularly in dairy products and coconut oil, can improve health. The evidence of ω6 polyunsaturated fatty acids (PUFAs) promoting inflammation and augmenting many diseases continues to grow, whereas ω3 PUFAs seem to counter these adverse effects. The replacement of saturated fats in the diet with carbohydrates, especially sugars, has resulted in increased obesity and its associated health complications. Well-established mechanisms have been proposed for the adverse health effects of some alternative or replacement nutrients, such as simple carbohydrates and PUFAs. The focus on dietary manipulation of serum cholesterol may be moot in view of numerous other factors that increase the risk of heart disease. The adverse health effects that have been associated with saturated fats in the past are most likely due to factors other than SFAs, which are discussed here. This review calls for a rational reevaluation of existing dietary recommendations that focus on minimizing dietary SFAs, for which mechanisms for adverse health effects are lacking.

Acute kidney injury during therapy with an antisense oligonucleotide directed against PCSK9

Antisense oligonucleotides have been explored widely in clinical trials and generally are considered to be nontoxic for the kidney, even at high concentrations. We report a case of toxic acute tubular injury in a healthy 56-year-old female volunteer after a pharmacologically active dose of a locked nucleic acid antisense oligonucleotide was administered. The patient received 3 weekly subcutaneous doses of experimental drug SPC5001, an antisense oligonucleotide directed against PCSK9 (proprotein convertase subtilisin/kexin type 9) that is under investigation as an agent to reduce low-density lipoprotein cholesterol levels. Five days after the last dose, the patient's serum creatinine level increased from 0.81 mg/dL at baseline (corresponding to an estimated glomerular filtration rate [eGFR] of 78 mL/min/1.73 m(2)) to 2.67 mg/dL (eGFR, 20 mL/min/1.73 m(2)), and this increase coincided with the presence of white blood cells, granular casts, and minimal hematuria on urine microscopy. The patient's serum creatinine level peaked at 3.81 mg/dL (eGFR, 13 mL/min/1.73 m(2)) 1 week after the last oligonucleotide dose. Kidney biopsy showed multifocal tubular necrosis and signs of oligonucleotide accumulation. Upon conservative treatment, the patient's serum creatinine level gradually decreased and reached her baseline level 44 days after the last oligonucleotide was administered. The patient recovered fully and kidney function was normal at every follow-up visit.

Pregnancy in a woman with homozygous familial hypercholesterolemia not on low-density lipoprotein apheresis

Pregnancy in women with homozygous familial hypercholesterolemia (FH) has been rarely reported and might pose risks on the mother and her fetus. Although most reported cases remained on low-density lipoprotein (LDL) apheresis, there are no clear guidelines regarding the management of this entity. We report the first case of an uncomplicated pregnancy in a 24-year-old homozygous FH woman who was not maintained on LDL apheresis. FH expresses a wide variability in the phenotype, and management of homozygous FH cases who desire to become pregnant should be individualized based on preconceptional assessment with frequent antenatal follow-up. Decisions on management should be made after weighing the risks versus benefits of LDL apheresis.

Patient accounts of diagnostic testing for familial hypercholesterolaemia: comparing responses to genetic and non-genetic testing methods

Background

Continuing developments in genetic testing technology together with research revealing gene-disease associations have brought closer the potential for genetic screening of populations. A major concern, as with any screening programme, is the response of the patient to the findings of screening, whether the outcome is positive or negative. Such concern is heightened for genetic testing, which it is feared may elicit stronger reactions than non-genetic testing.

Methods

This paper draws on thematic analysis of 113 semi-structured interviews with 39 patients being tested for familial hypercholesterolaemia (FH), an inherited predisposition to early-onset heart disease. It examines the impact of disease risk assessments based on both genetic and non-genetic information, or solely non-genetic information.

Results

The impact of diagnostic testing did not seem to vary according to whether or not genetic information was used. More generally, being given a positive or negative diagnosis of FH had minimal discernible impact on people's lives as they maintained the continuity of their beliefs and behaviour.

Conclusions

The results suggest that concerns about the use of genetic testing in this context are unfounded, a conclusion that echoes findings from studies in this and other health contexts.