Genetic diagnosis of familial hypercholesterolemia using a DNA-array based platform

Common and rare variants in patients with early onset drusen maculopathy

Early onset drusen maculopathy (EODM) can lead to advanced macular degeneration at a young age, affecting quality of life. However, the genetic causes of EODM are not well studied. We performed whole genome sequencing in 49 EODM patients. Common genetic variants were analysed by calculating genetic risk scores based on 52 age-related macular generation (AMD)-associated variants, and we analysed rare variants in candidate genes to identify potential deleterious variants that might contribute to EODM development. We demonstrate that the 52 AMD-associated variants contributed to EODM, especially variants located in the complement pathway. Furthermore, we identified 26 rare genetic variants predicted to be pathogenic based on in silico prediction tools or based on reported pathogenicity in literature. These variants are located predominantly in the complement and lipid metabolism pathways. Last, evaluation of 18 genes causing inherited retinal dystrophies that can mimic AMD characteristics, revealed 11 potential deleterious variants in eight EODM patients. However, phenotypic characteristics did not point towards a retinal dystrophy in these patients. In conclusion, this study reports new insights into rare variants that are potentially involved in EODM development, and which are relevant for future studies unravelling the aetiology of EODM.

Presence of rare potential pathogenic variants in subjects under 65 years old with very severe or fatal COVID-19

Rare variants affecting host defense against pathogens could be involved in COVID-19 severity and may help explain fatal outcomes in young and middle-aged patients. Our aim was to report the presence of rare genetic variants in certain genes, by using whole exome sequencing, in a selected group of COVID-19 patients under 65 years who required intubation or resulting in death (n = 44). To this end, different etiopathogenic mechanisms were explored using gene prioritization-based analysis in which genes involved in immune response, immunodeficiencies or blood coagulation were studied. We detected 44 different variants of interest, in 29 different patients (66%). Some of these variants were previously described as pathogenic and were located in genes mainly involved in immune response. A network analysis, including the 42 genes with candidate variants, showed three main components, consisting of 25 highly interconnected genes related to immune response and two additional networks composed by genes enriched in carbohydrate metabolism and in DNA metabolism and repair processes. In conclusion, we have detected candidate variants that may potentially influence COVID-19 outcome in our cohort of patients. Further studies are needed to confirm the ultimate role of the genetic variants described in the present study on COVID-19 severity.

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.

Liquid Biopsy of Extracellular Microvesicles Predicts Future Major Ischemic Events in Genetically Characterized Familial Hypercholesterolemia Patients

Objective—

Circulating microvesicles (cMVs) exert regulatory roles in atherothrombosis. Patients with familial hypercholesterolemia (FH) that are at high risk for premature cardiovascular events (CVEs) have previously shown high levels of cMVs related to disease severity. However, much remains unknown about their value as markers of CVE. We sought to investigate the prognostic cMV signature for future major CVE presentation in patients with FH.

Approach and Results—

Liquid biopsies from genetically characterized patients with FH from the SAFEHEART (Spanish Familial Hypercholesterolemia Cohort Study)-cohort without clinical manifestation of disease at entry that were going to suffer a CVE within a mean period of 3.3±2.6 years postsampling (CVE, N=92) and from age/cardiovascular risk factor/treatment-matched patients with FH that did not suffer an event within the same time-period (non-CVE, N=48) were investigated. cMVs were phenotyped by flow cytometry to identify activated parental cells. Patients with CVE had higher number of overall procoagulant annexin V + -cMVs than non-CVE ( P <0.05). Pan-leukocyte-derived and neutrophil-derived cMVs, as well as activated platelet-derived cMVs, were significantly higher in patients with CVE. Baseline number of cMVs derived from lymphocytes, neutrophils, and activated platelets were positively associated with mortality at follow-up ( P <0.05). Patient-risk calculated by classical cardiovascular risk-factor scores did not correlate with cMVs. Inclusion of the cMV signature into the SAFEHEART risk model for patients with FH for the prediction of ischemic events increased the area under the curve from 0.603±0.050 to 0.768±0.042 ( P <0.005).

Conclusions—

Patients with FH who are going to suffer a CVE within a mean period of 3.3 years, despite being treated according to guidelines, have ongoing innate immune cell and platelet activation. The proposed cMV signature is a prognostic marker for accelerated atherosclerosis and clinical event presentation in patients with 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.

Low-density lipoprotein receptor mutational analysis in diagnosis of familial hypercholesterolemia

PURPOSE OF REVIEW

To present up to date evidence on the pathogenicity of low-density lipoprotein receptor (LDLR) variants and to propose a strategy that is suitable for implementation in the clinical work-up of familial hypercholesterolaemia.

RECENT FINDINGS

More than 1800 variants have been described in the LDLR gene of patients with a clinical diagnosis of familial hypercholesterolaemia; however, less than 15% have functional evidence of pathogenicity.

SUMMARY

The spectrum of variants in the LDLR identified in patients with clinical familial hypercholesterolaemia is increasing as novel variants are still being reported. However, over 50% of all LDLR variants need further evidence before they can be confirmed as mutations causing disease. Even with applying the recent American College of Medical Genetics variant classification, a large number of variants are still considered variants of unknown significance. Before obtaining an undisputable confirmation of the effect on the expression and activity of the LDLR, reporting these variants as part of a clinical diagnosis to the patient holds the risk that it might need to be withdrawn in a later stage. An investment should be made to develop functional assays to characterize LDLR variants of unknown significance for a better patient diagnosis and to prevent confusion in the physician's office.

Predicting Cardiovascular Events in Familial Hypercholesterolemia: The SAFEHEART Registry (Spanish Familial Hypercholesterolemia Cohort Study)

BACKGROUND

Although risk factors for atherosclerotic cardiovascular disease (ASCVD) in familial hypercholesterolemia (FH) have been described, models for predicting incident ASCVD have not been reported. Our aim was to use the SAFEHEART registry (Spanish Familial Hypercholesterolemia Cohort Study) to define key risk factors for predicting incident ASCVD in patients with FH.

METHODS

SAFEHEART is a multicenter, nationwide, long-term prospective cohort study of a molecularly defined population with FH with or without previous ASCVD. Analyses to define risk factors and to build a risk prediction equation were developed, and the risk prediction equation was tested for its ability to discriminate patients who experience incident ASCVD from those who did not over time.

RESULTS

We recruited 2404 adult patients with FH who were followed up for a mean of 5.5 years (SD, 3.2 years), during which 12 (0.5%) and 122 (5.1%) suffered fatal and nonfatal incident ASCVD, respectively. Age, male sex, history of previous ASCVD, high blood pressure, increased body mass index, active smoking, and low-density lipoprotein cholesterol and lipoprotein(a) levels were independent predictors of incident ASCVD from which a risk equation with a Harrell C index of 0.85 was derived. The bootstrap resampling (100 randomized samples) of the original set for internal validation showed a degree of overoptimism of 0.003. Individual risk was estimated for each person without an established diagnosis of ASCVD before enrollment in the registry by use of the SAFEHEART risk equation, the modified Framingham risk equation, and the American College of Cardiology/American Heart Association ASCVD Pooled Cohort Risk Equations. The Harrell C index for these models was 0.81, 0.78, and 0.8, respectively, and differences between the SAFEHEART risk equation and the other 2 were significant (P=0.023 and P=0.045).

CONCLUSIONS

The risk of incident ASCVD may be estimated in patients with FH with simple clinical predictors. This finding may improve risk stratification and could be used to guide therapy in patients with FH.

CLINICAL TRIAL REGISTRATION

URL: http://clinicaltrials.gov. Unique identifier: NCT02693548.

Cost-effectiveness of a cascade screening program for the early detection of familial hypercholesterolemia

BACKGROUND

Although familial hypercholesterolemia (FH) confers a high risk of coronary artery disease, most patients are undiagnosed, and little is known about the efficiency of genetic cascade screening programs at national level.

OBJECTIVE

The aim of the study was to estimate the cost-effectiveness of a national genetic cascade screening program in Spain.

METHODS

An economic evaluation was performed using a decision tree analysis. The choice in the decision tree was between implementation of the national program for FH (NPFH) or keeping the usual clinical care. The NPFH detects FH patients through total cholesterol measurement at primary care level and use of genetic testing in index cases and relatives. The payer (National Health System) and social (including the productivity lost) perspectives were considered. The outcome variables were coronary events avoided, deaths avoided, and quality-adjusted life years (QALYs) gained.

RESULTS

From the payer perspective, the application of the NPFH during 1 year prevents 847 coronary events and 203 deaths in the 9000 FH patients cohort during a 10-year follow-up, yielding an extra 767 QALYs, at a cost of €29,608 per QALY gained. From the social perspective, the NPFH is dominant over the control (the cost decreases and the effectiveness increases). The sensitivity analysis confirms the robustness of the findings.

CONCLUSION

The NPFH based on molecular testing is a cost-effective diagnostic and management strategy that supports government expenditure aimed at preventing coronary artery disease in FH patients in Spain. Implementation of such a strategy is likely to be also cost-effective in countries with similar developed healthcare systems.

Attainment of LDL Cholesterol Treatment Goals in Children and Adolescents With Familial Hypercholesterolemia. The SAFEHEART Follow-up Registry

INTRODUCTION AND OBJECTIVES

Little is known about the characteristics of persons with familial hypercholesterolemia (FH) younger than 18 years, the lipid-lowering therapy used in these patients, and the lipid goals reached in real life. Our aim was to evaluate the achievement of low-density lipoprotein cholesterol (LDL-C) treatment goals in FH patients younger than 18 years enrolled in a large national registry.

METHODS

We analyzed patients younger than 18 years enrolled in a large ongoing registry of molecularly-defined patients with FH in Spain. The attainment of guideline-recommended plasma LDL-C goals at entry and follow-up was analyzed in relation to the use of lipid-lowering therapy.

RESULTS

We enrolled 392 individuals younger than 18 years. Of these, 217 were molecularly-diagnosed FH patients and had a complete follow-up. The median follow-up time was 4.69 years (interquartile range, 2.48-6.38 years), 68.2% of FH patients were on statins, and 41.5% patients had LDL-C < 130mg/dL. Statin use was the only predictor of LDL-C goal attainment.

CONCLUSIONS

This study shows that a high proportion of FH patients younger than 18 years have high LDL-C levels and fail to achieve recommended LDL-C targets. Statin use was the only independent predictor of LDL-C goal achievement. No safety concerns were detected during follow-up. These results indicate that many FH patients are not adequately controlled and that there is still room for treatment improvement.

Macrophages of genetically characterized familial hypercholesterolaemia patients show up-regulation of LDL-receptor-related proteins

Familial hypercholesterolaemia (FH) is a major risk for premature coronary heart disease due to severe long‐life exposure to high LDL levels. Accumulation of LDL in the vascular wall triggers atherosclerosis with activation of the innate immunity system. Here, we have investigated (i) gene expression of LDLR and LRPs in peripheral blood cells (PBLs) and in differentiated macrophages of young FH‐patients; and (ii) whether macrophage from FH patients have a differential response when exposed to high levels of atherogenic LDL. PBLs in young heterozygous genetically characterized FH patients have higher expression of LRP5 and LRP6 than age‐matched healthy controls or patients with secondary hypercholesterolaemia. LRP1 levels were similar among groups. In monocyte‐derived macrophages (MACs), LRP5 and LRP1 transcript levels did not differ between FHs and controls in resting conditions, but when exposed to agLDL, FH‐MAC showed a highly significant up‐regulation of LRP5, while LRP1 was unaffected. PBL and MAC cells from FH patients had significantly lower LDLR expression than control cells, independently of the lipid‐lowering therapy. Furthermore, exposure of FH‐MAC to agLDL resulted in a reduced expression of CD163, scavenger receptor with anti‐inflammatory and atheroprotective properties. In summary, our results show for first time that LRPs, active lipid‐internalizing receptors, are up‐regulated in innate immunity cells of young FH patients that have functional LDLR mutations. Additionally, their reduced CD163 expression indicates less atheroprotection. Both mechanisms may play a synergic effect on the onset of premature atherosclerosis in FH patients.

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.

Next-generation-sequencing-based identification of familial hypercholesterolemia-related mutations in subjects with increased LDL-C levels in a latvian population

BACKGROUND

Familial hypercholesterolemia (FH) is one of the commonest monogenic disorders, predominantly inherited as an autosomal dominant trait. When untreated, it results in early coronary heart disease. The vast majority of FH remains undiagnosed in Latvia. The identification and early treatment of affected individuals remain a challenge worldwide. Most cases of FH are caused by mutations in one of four genes, APOB, LDLR, PCSK9, or LDLRAP1. The spectrum of disease-causing variants is very diverse and the variation detection panels usually used in its diagnosis cover only a minority of the disease-causing gene variants. However, DNA-based tests may provide an FH diagnosis for FH patients with no physical symptoms and with no known family history of the disease. Here, we evaluate the use of targeted next-generation sequencing (NGS) to identify cases of FH in a cohort of patients with coronary artery disease (CAD) and individuals with abnormal low-density lipoprotein-cholesterol (LDL-C) levels.

METHODS

We used targeted amplification of the coding regions of LDLR, APOB, PCSK9, and LDLRAP1, followed by NGS, in 42 CAD patients (LDL-C, 4.1-7.2 mmol/L) and 50 individuals from a population-based cohort (LDL-C, 5.1-9.7 mmol/L).

RESULTS

In total, 22 synonymous and 31 nonsynonymous variants, eight variants in close proximity (10 bp) to intron-exon boundaries, and 50 other variants were found. We identified four pathogenic mutations (p.(Arg3527Gln) in APOB, and p.(Gly20Arg), p.(Arg350*), and c.1706-10G > A in LDLR) in seven patients (7.6 %). Three possible pathogenic variants were also found in four patients.

CONCLUSION

NGS-based methods can be used to detect FH in high-risk individuals when they do not meet the defined clinical criteria.

Statins do not increase the risk of developing type 2 diabetes in familial hypercholesterolemia: The SAFEHEART study

BACKGROUND

Familial Hypercholesterolemia (FH) is the most common monogenic disorder that causes premature coronary artery disease (CAD). Our objective was to examine the risk of new onset type 2 diabetes mellitus (T2DM) among FH patients and unaffected relatives in relation to treatment with different statins in the SAFEHEART cohort study.

METHODS

This is a cross-sectional and prospective cohort study in 2558 FH and 1265 unaffected relatives with a mean follow-up of 5.9 years. Several pertinent data, such as age, gender, metabolic syndrome, lipid profile, body mass index (BMI), waist circumference, HOMA-IR, dose, duration and type of statins, were obtained and examined as predictors of incident diabetes.

RESULTS

The new onset diabetes was 1.7% in FH and 0.2% in non FH patients (p=0.001). In multivariate logistic regression, age (OR 1.02, CI 95%: 1.02-1.08), HOMA-IR (OR 1.17, CI 95%: 1.03-1.33), metabolic syndrome (OR 3.3, CI 95%: 1.32-8.28) and specifically plasma glucose, as a component of metabolic syndrome (OR 15.7, CI 95%: 4.70-52.53) were significant predictors of new onset T2DM in the FH group alone. In the adjusted Cox regression model in FH group, age (HR 1.03, CI 95% 1.00-1.06, p=0.031) and metabolic syndrome (HR 4.16, CI 95% 1.58-10.92, p=0.004) remained significant predictors of new onset T2DM.

CONCLUSIONS

Our data do not support the postulated diabetogenic effect associated with high-dose statins use in our cohort of FH patients.

Cost-effectiveness analysis of alternative screening and treatment strategies for heterozygous familial hypercholesterolemia in the United States

BACKGROUND/OBJECTIVES

Familial hypercholesterolemia (FH) is a genetic disorder that leads to premature heart disease or stroke if untreated. Statins are effective for individuals with FH but less than 20% of actual cases are diagnosed in the US and many people are not adherent to treatment. Using new knowledge regarding mutations responsible for FH, some European countries have developed genetic FH screening strategies, many of which have been shown to be cost-effective. This study evaluates the cost-effectiveness of genetic screening and lipid-based screening with statin adherence measures compared to lipid-based screening alone in the US.

METHODS

A decision tree was used to estimate disease detection with the three screening strategies, while a Markov model was used to model disease progression until death, quality-adjusted life years (QALYs) and costs from a US societal perspective.

RESULTS

The results showed that Genetic Screening cost $15,594 for 18.29 QALYs per person and Lipid Screening with adherence measures cost $16,385 for 18.77 QALYs compared with $10,396 for 18.28 QALYs for Lipid Screening alone. The incremental cost-effectiveness ratio (ICER) of Genetic Screening versus Lipid Screening was $519,813/QALY and that of Lipid Screening with adherence measures versus Lipid Screening alone was $12,223/QALY. At a US willingness-to-pay threshold of $150,000/QALY Genetic Screening is not cost-effective compared with Lipid Screening. Sensitivity analyses showed that results were robust to reasonable variations in model parameters.

CONCLUSIONS

Although genetic screening is currently not a cost-effective option in the US, health outcomes for FH individuals could benefit from adherence measures encouraging statin use.

rs11613352 polymorphism (TT genotype) associates with a decrease of triglycerides and an increase of HDL in familial hypercholesterolemia patients

INTRODUCTION AND OBJECTIVES

Recent genome-wide association studies have identified a locus on chromosome 12q13.3 associated with plasma levels of triglyceride and high-density lipoprotein cholesterol, with rs11613352 being the lead single nucleotide polymorphism in this genome-wide association study locus. The aim of the study is to investigate the involvement of rs11613352 in a population with high cardiovascular risk due to familial hypercholesterolemia.

METHODS

The single nucleotide polymorphism was genotyped by Taqman(®) assay in a cohort of 601 unrelated familial hypercholesterolemia patients and its association with plasma triglyceride and high-density lipoprotein cholesterol levels was analyzed by multivariate methods based on linear regression.

RESULTS

Minimal allele frequency was 0.17 and genotype frequencies were 0.69, 0.27, and 0.04 for CC, CT, and TT genotypes, respectively. The polymorphism is associated in a recessive manner (TT genotype) with a decrease in triglyceride levels (P=.002) and with an increase in high-density lipoprotein cholesterol levels (P=.021) after adjusting by age and sex.

CONCLUSIONS

The polymorphism rs11613352 may contribute to modulate the cardiovascular risk by modifying plasma lipid levels in familial hypercholesterolemia patients.

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.

Association of angiotensin converting enzyme gene insertion/deletion polymorphism and familial hypercholesterolemia in the Saudi population

BACKGROUND

The study of the association between genotype and phenotype is of great importance for the prediction of multiple diseases and pathophysiological conditions. The relationship between angiotensin converting enzyme (ACE) Insertion/Deletion (I/D) polymorphism and Familial Hypercholesterolemia (FH) has been not fully investigated in all the ethnicities. In this study we sought to determine the frequency of I/D polymorphism genotypes of ACE gene in Saudi patients with FH.

RESULTS

This is a case-control study carried out purely in Saudi population. Genomic DNA was isolated from 128 subjects who have participated in this study. ACE gene I/D polymorphism was analyzed by polymerase chain reaction in 64 FH cases and 64 healthy controls. There was no statistically significant difference between the groups with respect to genotype distribution. Furthermore, we did not find any significant difference in the frequency of ACE I/D polymorphism in FH subjects when stratified by gender (p = 0.43).

CONCLUSION

Our data suggest that ACE gene I/D polymorphism examined in this study has no role in predicting the occurrence and diagnosis of FH.

The use of next-generation sequencing in clinical diagnosis of familial hypercholesterolemia

Purpose:

Familial hypercholesterolemia is a common Mendelian disorder associated with early-onset coronary heart disease that can be treated by cholesterol-lowering drugs. The majority of cases in the United Kingdom are currently without a molecular diagnosis, which is partly due to the cost and time associated with standard screening techniques. The main purpose of this study was to test the sensitivity and specificity of two next-generation sequencing protocols for genetic diagnosis of familial hypercholesterolemia.

Methods:

Libraries were prepared for next-generation sequencing by two target enrichment protocols; one using the SureSelect Target Enrichment System and the other using the PCR-based Access Array platform.

Results:

In the validation cohort, both protocols showed 100% specificity, whereas the sensitivity for short variant detection was 100% for the SureSelect Target Enrichment and 98% for the Access Array protocol. Large deletions/duplications were only detected using the SureSelect Target Enrichment protocol. In the prospective cohort, the mutation detection rate using the Access Array was highest in patients with clinically definite familial hypercholesterolemia (67%), followed by patients with possible familial hypercholesterolemia (26%).

Conclusion:

We have shown the potential of target enrichment methods combined with next-generation sequencing for molecular diagnosis of familial hypercholesterolemia. Adopting these assays for patients with suspected familial hypercholesterolemia could improve cost-effectiveness and increase the overall number of patients with a molecular diagnosis.

Genet Med 15 12, 948–957.

Genetic polymorphisms in LDLR, APOB, PCSK9 and other lipid related genes associated with familial hypercholesterolemia in Malaysia

Familial hypercholesterolemia (FH) is an autosomal dominant disorder characterized by elevations in total cholesterol (TC) and low density lipoprotein cholesterol (LDLc). Development of FH can result in the increase of risk for premature cardiovascular diseases (CVD). FH is primarily caused by genetic variations in Low Density Lipoprotein Receptor (LDLR), Apolipoprotein B (APOB) or Proprotein Convertase Subtilisin/Kexin type 9 (PCSK9) genes. Although FH has been extensively studied in the Caucasian population, there are limited reports of FH mutations in the Asian population. We investigated the association of previously reported genetic variants that are involved in lipid regulation in our study cohort. A total of 1536 polymorphisms previously implicated in FH were evaluated in 141 consecutive patients with clinical FH (defined by the Dutch Lipid Clinic Network criteria) and 111 unrelated control subjects without FH using high throughput microarray genotyping platform. Fourteen Single Nucleotide Polymorphisms (SNPs) were found to be significantly associated with FH, eleven with increased FH risk and three with decreased FH risk. Of the eleven SNPs associated with an increased risk of FH, only one SNP was found in the LDLR gene, seven in the APOB gene and three in the PCSK9 gene. SNP rs12720762 in APOB gene is associated with the highest risk of FH (odds ratio 14.78, p<0.001). Amongst the FH cases, 108 out of 141 (76.60%) have had at least one significant risk-associated SNP. Our study adds new information and knowledge on the genetic polymorphisms amongst Asians with FH, which may serve as potential markers in risk prediction and disease management.

A DNA microarray for the detection of point mutations and copy number variation causing familial hypercholesterolemia in Europe

To facilitate genetic cascade screening for familial hypercholesterolemia (FH) in Europe, two versions (7 and 9) of a DNA microarray were developed to detect the most frequent point mutations in the low-density lipoprotein receptor (LDLR), apolipoprotein B (APOB), and proprotein convertase subtilisin/kexin 9 (PCSK9) genes. The design of these microarrays is based on LIPOchip, version 4, which detects 191 LDLR and APOB mutations identified in Spanish patients with FH. A major improvement of LIPOchip, versions 7 and 9, is the ability to detect copy number variation (deletions or duplications of entire exons) in LDLR, thus abolishing the need to perform multiplex ligase-dependent probe amplification in patients with FH. The aim of this study was to validate a tool capable of detecting point mutations and copy number variations simultaneously and to evaluate its use and the newly developed software for analysis in clinical practice by reanalysis of several patients with known mutations causing FH. With the help of these validations, several aspects were analyzed, improved, and implemented in a newer version, which was evaluated through an internal validation.

Screening for familial hypercholesterolaemia

Familial hypercholesterolaemia (FH) is an autosomal dominant disorder characterised by increased plasma concentrations of low density lipoprotein (LDL) cholesterol leading to atherosclerosis and premature coronary heart disease (CHD) and death. The clinical diagnosis of FH is based on a personal and family history, physical examination findings and LDL-cholesterol concentrations. FH is primarily caused by mutations in the LDL-receptor gene (LDLR), and less frequently by mutations in genes for APOB and the more recently identified PCSK9. Lifestyle modification and pharmacotherapy can delay or prevent the onset of CHD in FH. It is estimated that only 20% of cases have been diagnosed in Australia and that the majority are inadequately treated. Screening options for FH include population screening (of children or adults), targeted screening of patients with premature CHD and their relatives, or opportunistic screening such as flagging laboratory lipid reports. Cascade screening, a form of targeted screening, is an ethically acceptable, cost-effective strategy for the identification of FH. However, for screening to be successful, medical practitioners need to be aware of the signs and diagnosis of FH and the benefits of early treatment.

Molecular characterization of familial hypercholesterolemia in Spain

Familial hypercholesterolemia (FH), characterized by isolated elevation of plasmatic low-density lipoprotein (LDL) cholesterol and premature coronary heart disease (CHD), is associated with mutations in three major genes: LDL receptor (LDLR), apolipoprotein B (APOB) and proprotein convertase subtilisin/kexin 9 (PCSK9). We have analyzed 5430 Spanish index cases and 2223 relatives since 2004 with LIPOchip(®) genetic diagnostic platform, a microarray for the detection of Spanish common mutations in these three genes, including copy number variation (CNV) in LDLR, followed by sequencing analysis of the coding regions of LDLR and exon 26 of APOB, when the result is negative. Samples were received from hospitals of all around Spain. The preferred clinical criterion to diagnose FH was Dutch Lipid Clinic Network (DLCN) score. Our results show that there is a broad spectrum of mutations in the LDLR gene in Spain since about 400 different mutations were detected, distributed along almost the whole LDLR gene. Mutations in APOB (mainly p.Arg3527Gln) covered 6.5% of positive cases and only one PCSK9 mutation was detected. We found correlation between more severe mutations and the clinical diagnosis but also that 28% of FH patients harboring mutations do not have a definite clinical diagnosis. This study analyzes the mutation spectrum in Spain, remarks the importance of genetic diagnosis of FH patients, as well as the cascade screening, and shows how it is being carried out in Spain.

Functional characterization of splicing and ligand-binding domain variants in the LDL receptor

Familial hypercholesterolemia (FH) is an autosomal dominant disorder mostly caused by mutations in the LDLR gene. Although the detection of functional mutations in the LDLR gene provides an unequivocal diagnosis of the FH condition, there are many variants whose pathogenicity is still unknown. The aims of this study were to set up a rapid method to determine the effect of LDLR mutations, thereby providing an accurate diagnosis of FH, and to functionally characterize six LDLR mutations detected at high frequency by the LIPOchip(®) platform (Progenika Biopharma, Spain) in the Spanish population. LDLR expression and activity were analyzed by one-single-step flow cytometry assay and confocal microscopy. Splicing effects were determined by sequencing reverse transcription polymerase chain reaction products. The analysis of three heterozygous variants with a single point mutation within the low-density lipoprotein binding domain allowed us to classify the c.806G>A variant as nonpathogenic, and c.862G>A and c.895G>A variants as causative of FH. The results obtained for three variants affecting donor splice sites of the LDLR mRNA, c.313+2dupT, c.1186+5G>A, and c.1845+1G>C, demonstrated that these mutations are pathogenic. These results expand our knowledge of mutations responsible for FH, providing an accurate diagnosis and leading to early treatment to reduce the risk of premature cardiovascular events.

Clinical characteristics and evaluation of LDL-cholesterol treatment of the Spanish Familial Hypercholesterolemia Longitudinal Cohort Study (SAFEHEART)

Aim

Familial hypercholesterolemia (FH) patients are at high risk for premature coronary heart disease (CHD). Despite the use of statins, most patients do not achieve an optimal LDL-cholesterol goal. The aims of this study are to describe baseline characteristics and to evaluate Lipid Lowering Therapy (LLT) in FH patients recruited in SAFEHEART.

Methods and Results

A cross-sectional analysis of cases recruited in the Spanish FH cohort at inclusion was performed. Demographic, lifestyle, medical and therapeutic data were collected by specific surveys. Blood samples for lipid profile and DNA were obtained. Genetic test for FH was performed through DNA-microarray. Data from 1852 subjects (47.5% males) over 19 years old were analyzed: 1262 (68.1%, mean age 45.6 years) had genetic diagnosis of FH and 590 (31.9%, mean age 41.3 years) were non-FH. Cardiovascular disease was present in 14% of FH and in 3.2% of non-FH subjects (P < 0.001), and was significantly higher in patients carrying a null mutation compared with those carrying a defective mutation (14.87% vs. 10.6%, respectively, P < 0.05). Prevalence of current smokers was 28.4% in FH subjects. Most FH cases were receiving LLT (84%). Although 51.5% were receiving treatment expected to reduce LDL-c levels at least 50%, only 13.6% were on maximum statin dose combined with ezetimibe. Mean LDL-c level in treated FH cases was 186.5 mg/dl (SD: 65.6) and only 3.4% of patients reached and LDL-c under 100 mg/dl. The best predictor for LDL-c goal attainment was the use of combined therapy with statin and ezetimibe.

Conclusion

Although most of this high risk population is receiving LLT, prevalence of cardiovascular disease and LDL-c levels are still high and far from the optimum LDL-c therapeutic goal. However, LDL-c levels could be reduced by using more intensive LLT such as combined therapy with maximum statin dose and ezetimibe.

Molecular spectrum of autosomal dominant hypercholesterolemia in France

Autosomal Dominant Hypercholesterolemia (ADH), characterized by isolated elevation of plasmatic LDL cholesterol and premature cardiovascular complications, is associated with mutations in 3 major genes: LDLR (LDL receptor), APOB (apolipoprotein B) and PCSK9(proprotein convertase subtilisin-kexin type 9). Through the French ADH Research Network, we collected molecular data from 1358 French probands from eleven different regions in France.Mutations in the LDLR gene were identified in 1003 subjects representing 391 unique events with 46.0% missense, 14.6% frameshift, 13.6% splice, and 11.3% nonsense mutations, 9.7% major rearrangements, 3.8% small in frame deletions/insertions, and 1.0% UTR mutations. Interestingly,175 are novel mutational events and represent 45% of the unique events we identified, highlighting a specificity of the LDLR mutation spectrum in France. Furthermore, mutations in the APOB gene were identified in 89 probands and in the PCSK9 gene in 10 probands. Comparison of available clinical and biochemical data showed a gradient of severity for ADH-causing mutations:FH=PCSK9>FDB>«Others» genes. The respective contribution of each known gene to ADH inthis French cohort is: LDLR 73.9%, APOB 6.6%, PCSK9 0.7%. Finally, in 19.0% of the probands,no mutation was found, thus underscoring the existence of ADH mutations located in still unknown genes.

Current Clinical and Pharmaceutical Applications of Microarrays: From Disease Biomarkers Discovery to Automated Diagnostics

Microarrays used for measuring chromosomal aberrations in genomic DNA and for defining gene expression patterns have become almost routine. A microarray consists of an arrayed series of microscopic spots each containing either DNA or protein molecules known as feature reporters. Advances in microarray fabrication and in feature detection systems, such as high-resolution scanners and their associated software, lead to high-throughput screening of the genome or the transcriptome of a cell or a group of cells in only few days. Despite the potential of high-density microarrays, several problems about data interpretation are still to be solved. In addition, targeted microarrays are shown to be useful tools for rapid and accurate diagnosis of diseases. The aim of this review was to discuss the impact of microarrays on different application levels from the definition of disease biomarkers to pharmaceutical and clinical diagnostics.