Familial defective apolipoprotein B-100: a mutation of apolipoprotein B that causes hypercholesterolemia

The singular French PCSK9-p.Ser127Arg gain-of-function variant: A significant player in cholesterol levels from a 775-year-old common ancestor

BACKGROUND AND AIMS

PCSK9 is a key regulator of LDL-cholesterol levels. PCSK9 gain of function variants (GOFVs) cause autosomal dominant hypercholesterolemia (ADH). The first described PCSK9-GOFV, p.Ser127Arg, almost exclusively reported in France, represents 67 % of the PCSK9 French GOFVs due to a founder effect. Few other carriers are reported in South Africa and Norway. This study aims to estimate when the common ancestor lived and to describe a cohort of p.Ser127Arg carriers.

METHODS

Eight families and 14 p.Ser127Arg carriers were genotyped and phenotyped. Haplotypes were constructed using 11 microsatellites around PCSK9 and 6 intragenic single nucleotide polymorphisms (SNPs). To add to the biological analysis, eight additional p.Ser127Arg carriers, 12 carriers of other PCSK9-GOFVs, 93 LDLR loss of function variant (LOFV) carriers and 49 non-carriers subjects were phenotyped.

RESULTS

The most common ancestor of p.Ser127Arg was estimated to have lived 775 years ago [95 % CI: 575-1075]. French Protestants exiled after the revocation of the Edict of Nantes in 1685 AD likely brought the variant to South Africa and Norway. As expected for ADH subjects, carriers of LDLR-LOFV, the p.Ser127Arg, or other PCSK9-GOFVs showed significantly higher LDL-C levels than that of the non-carriers. Interestingly, LDL-C levels are higher for LDLR-LOFVs and for the reduced secreted p.Ser127Arg than for secreted PCSK9-GOFVs, suggesting a greater effect of the p.Ser127Arg. Conversely, HDL-C was significantly lower for LDLR-LOFV and p.Ser127Arg carriers.

CONCLUSIONS

This first report from a large cohort of PCSK9-p.Ser127Arg carriers provides observations suggesting a stronger hypercholesterolemic potential of the mutated pro-PCSK9 compared with the secreted mature protein. This work also provides additional data to support the association between PCSK9 and HDL metabolism, and molecular evidence that this variant appeared in France around 1248 AD (Graphical Abstract = Fig. 1).

The functions of apolipoproteins and lipoproteins in health and disease

Lipoproteins and apolipoproteins are crucial in lipid metabolism, functioning as essential mediators in the transport of cholesterol and triglycerides and being closely related to the pathogenesis of multiple systems, including cardiovascular. Lipoproteins a (Lp(a)), as a unique subclass of lipoproteins, is a low-density lipoprotein(LDL)-like particle with pro-atherosclerotic and pro-inflammatory properties, displaying high heritability. More and more strong evidence points to a possible link between high amounts of Lp(a) and cardiac conditions like atherosclerotic cardiovascular disease (ASCVD) and aortic stenosis (AS), making it a risk factor for heart diseases. In recent years, Lp(a)'s role in other diseases, including neurological disorders and cancer, has been increasingly recognized. Although therapies aimed at low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C) have achieved significant success, elevated Lp(a) levels remain a significant clinical management problem. Despite the limited efficacy of current lipid-lowering therapies, major clinical advances in new Lp(a)-lowering therapies have significantly advanced the field. This review, grounded in the pathophysiology of lipoproteins, seeks to summarize the wide-ranging connections between lipoproteins (such as LDL-C and HDL-C) and various diseases, alongside the latest clinical developments, special emphasis is placed on the pivotal role of Lp(a) in cardiovascular disease, while also examining its future potential and mechanisms in other conditions. Furthermore, this review discusses Lp(a)-lowering therapies and highlights significant recent advances in emerging treatments, advocates for further exploration into Lp(a)'s pathogenic mechanisms and its potential as a therapeutic target, proposing new secondary prevention strategies for high-risk individuals.

Resilient Older Subjects with Heterozygous Familial Hypercholesterolemia, Baseline Differences and Associated Factors

Despite elevated low-density lipoprotein (LDL) cholesterol levels, some older subjects with heterozygous familial hypercholesterolemia (HeFH) do not develop atherosclerotic cardiovascular disease (ACVD) during their lifetime. The factors related to this resilient state have not been fully established. The aim of this study was to evaluate differential characteristics between older HeFH subjects with and without ACVD and factors associated with the presence of ACVD. Subjects were part of the Spanish Atherosclerosis Society Dyslipidemia Registry, and those ≥ 70 years old and with HeFH were included. Baseline characteristics of these subjects with and without ACVD were compared. A multivariate analysis was performed to assess factors associated with the presence of ACVD. A total of 2148 subjects with HeFH were included. Resilient subjects were mostly female, younger and presented fewer comorbidities with respect to the ACVD group. Subjects without ACVD had higher baseline high-density lipoprotein (HDL) cholesterol (55.8 ± 17.1 vs. 47.9 ± 15.4 mg/dL; p < 0.001) and lower lipoprotein(a) [Lp(a)] (53.4 ± 67.9 vs. 66.6 ± 85.6 mg/dL; p < 0.001) levels with respect to those in the ACVD group. Lp(a) and the presence of ≥3 risk factors were associated with the presence of ACVD.

Functional Analysis of 3'UTR Variants at the LDLR and PCSK9 Genes in Patients with Familial Hypercholesterolemia

Familial hypercholesterolemia (FH) is an autosomal dominant disease with an estimated prevalence of 1 in 200-250 individuals. Patients with FH are at increased risk of premature coronary artery disease. Early diagnosis and treatment are essential for improving clinical outcomes. In many cases, however, the genetic diagnosis is not confirmed. At present, routine genetic testing does not analyze the 3'UTR regions of LDLR and PCSK9. However, 3'UTR-single nucleotide variants could be of interest because they can modify the target sequence of miRNAs that regulate the expression of these genes. Our study fully characterizes the 3'UTR regions of LDLR and PCSK9 in 409 patients with a suspected diagnosis of FH using next-generation sequencing. In 30 of the 409 patients, we found 21 variants with an allelic frequency of <1%; 14 of them at 3'UTR-LDLR and 8 at 3'UTR-PCSK9. The variants' pathogenicity was studied in silico; subsequently, a number of the variants were functionally validated using luciferase reporter assays. LDLR:c.∗653G > C showed a 41% decrease in luciferase expression, while PCSK9:c.∗950C > T showed a 41% increase in PCSK9 expression, results that could explain the hypercholesterolemia phenotype. In summary, the genetic analysis of the 3'UTR regions of LDLR and PCSK9 could improve the genetic diagnosis of FH.

Novel LDLR variants affecting low density lipoprotein metabolism identified in familial hypercholesterolemia

BACKGROUND

Familial hypercholesterolemia (FH) is an autosomal dominant disease of lipid metabolism mainly caused by mutations in the low-density lipoprotein receptor (LDLR) gene. Genetic detection of patients with FH help with precise diagnosis and treatment, thus reducing the risk of coronary heart disease (CHD) and other related diseases. The study aimed to identify the causative gene mutations in a Chinese FH family and reveal the pathogenicity and the mechanism of these mutations.

METHODS AND RESULTS

Whole exome sequencing was performed in a patient with severe lipid metabolism dysfunction seeking fertility guidance from a Chinese FH family. Two LDLR variants c.1875 C > G (p.N625K; novel variant) and c.1448G > A (p.W483*) were identified in the family. Wildtype and mutant LDLR constructs were established by the site-direct mutagenesis technique. Functional studies were carried out by cell transfection to evaluate the impact of detected variants on LDLR activity. The two variants were proven to affect LDL uptake and binding, resulting in cholesterol clearance reduction to different degrees. According to The American College of Medical Genetics and Genomics (ACMG) Standards and Guidelines, the W483* variant was classified as "Pathogenic", while the N625K variant as "VUS".

CONCLUSIONS

Our results provide novel experimental evidence of functional alteration by LDLR variants identified in our study and expand the mutational spectrum of LDLR mutation induced FH.

Identification and Functional Analysis of APOB Variants in a Cohort of Hypercholesterolemic Patients

Mutations in APOB are the second most frequent cause of familial hypercholesterolemia (FH). APOB is highly polymorphic, and many variants are benign or of uncertain significance, so functional analysis is necessary to ascertain their pathogenicity. Our aim was to identify and characterize APOB variants in patients with hypercholesterolemia. Index patients (n = 825) with clinically suspected FH were analyzed using next-generation sequencing. In total, 40% of the patients presented a variant in LDLR, APOB, PCSK9 or LDLRAP1, with 12% of the variants in APOB. These variants showed frequencies in the general population lower than 0.5% and were classified as damaging and/or probably damaging by 3 or more predictors of pathogenicity. The variants c.10030A>G;p.(Lys3344Glu) and c.11401T>A;p.(Ser3801Thr) were characterized. The p.(Lys3344Glu) variant co-segregated with high low-density lipoprotein (LDL)-cholesterol in 2 families studied. LDL isolated from apoB p.(Lys3344Glu) heterozygous patients showed reduced ability to compete with fluorescently-labelled LDL for cellular binding and uptake compared with control LDL and was markedly deficient in supporting U937 cell proliferation. LDL that was carrying apoB p.(Ser3801Thr) was not defective in competing with control LDL for cellular binding and uptake. We conclude that the apoB p.(Lys3344Glu) variant is defective in the interaction with the LDL receptor and is causative of FH, whereas the apoB p.(Ser3801Thr) variant is benign.

Cascade screening for familial hypercholesterolemia should be organized at a national level

PURPOSE OF REVIEW

Patients with familial hypercholesterolemia (FH) have a markedly increased risk of premature cardiovascular disease. However, there are effective lipid-lowering therapies available to reduce the risk of cardiovascular disease. This makes it important to diagnose these patients. The most cost-effective strategy to diagnose patients with FH is to perform cascade screening. However, cascade screening as part of ordinary healthcare has not been very successful. Thus, there is a need to implement more efficient cascade screening strategies.

RECENT FINDINGS

Cascade screening for FH should be organized at a national level and should be run by dedicated health personnel such as genetic counsellors. As part of a national organization a national registry of patients with FH needs to be established. Moreover, for cascade screening to be effective, diagnosis of FH must be based on identifying the underlying mutation. There should preferably only be one genetics centre in each country for diagnosing FH, and this genetics centre should be an integrated part of the national cascade screening program.

SUMMARY

Cascade screening for FH is very effective and should be organized at a national level. Even a modest national cascade screening program can result in a large number of patients being identified.

Whole Exome/Genome Sequencing Joint Analysis of a Family with Oligogenic Familial Hypercholesterolemia

Autosomal Dominant Hypercholesterolemia (ADH) is a genetic disorder caused by pathogenic variants in LDLR, APOB, PCSK9 and APOE genes. We sought to identify new candidate genes responsible for the ADH phenotype in patients without pathogenic variants in the known ADH-causing genes by focusing on a French family with affected and non-affected members who presented a high ADH polygenic risk score (wPRS). Linkage analysis, whole exome and whole genome sequencing resulted in the identification of variants p.(Pro398Ala) in CYP7A1, p.(Val1382Phe) in LRP6 and p.(Ser202His) in LDLRAP1. A total of 6 other variants were identified in 6 of 160 unrelated ADH probands: p.(Ala13Val) and p.(Aps347Asn) in CYP7A1; p.(Tyr972Cys), p.(Thr1479Ile) and p.(Ser1612Phe) in LRP6; and p.(Ser202LeufsTer19) in LDLRAP1. All six probands presented a moderate wPRS. Serum analyses of carriers of the p.(Pro398Ala) variant in CYP7A1 showed no differences in the synthesis of bile acids compared to the serums of non-carriers. Functional studies of the four LRP6 mutants in HEK293T cells resulted in contradictory results excluding a major effect of each variant alone. Within the family, none of the heterozygous for only the LDLRAP1 p.(Ser202His) variant presented ADH. Altogether, each variant individually does not result in elevated LDL-C; however, the oligogenic combination of two or three variants reveals the ADH phenotype.

Single Nucleotide Polymorphisms in Apolipoprotein B, Apolipoprotein E, and Methylenetetrahydrofolate Reductase Are Associated With Serum Lipid Levels in Northern Chilean Subjects. A Pilot Study

Characterization of allelic variants is relevant to demonstrate associations among genetic background and susceptibility to develop cardiovascular diseases, which are the main cause of death in Chile. Association of APOB, APOE, and MTHFR polymorphisms with higher lipid levels and the risk of developing hypertension and cardiovascular diseases have been described. Thus, the aim of this study was to assess genotype distribution and relative allelic frequency of ApoB rs693, ApoE rs7412, ApoE rs429358, MTHFR rs1801131, and MTHFR rs1801133 allelic variants and their effects on lipid profile in young healthy men and women from Northern Chile. A group of 193 healthy subjects were enrolled for this study. Genotyping of rs693 (APOB), rs7412 and rs429358 (APOE), and rs1801131 and rs1801133 (MTHFR) polymorphisms were performed by real time PCR. In addition, lipid profiles were determined and associated to genetic data. The genotype distribution was APOB rs693 (CC = 37%, CT = 41%, and TT = 22%), APOE rs7412/rs429358 (E4 = 0.06, E3 = 0.91, and E2 = 0.03), MTHFR rs1801131 (AA = 57%, AC = 30%, and CC = 13%), and MTHFR rs1801133 (CC = 20%, CT = 47%, and TT = 33%). The association of the genetic variants with plasma lipid levels showed that women, but not men, carrying APOB mutated allele (T) and Apo E4 allele presented lower values of total cholesterol when compared with C/C homozygous genotype or E3 allele, respectively (p < 0.05). In addition, a subgroup analysis revealed that ApoB C/C homozygous women exhibited higher values of HDL-C when compared with men carrying identical genotype (p < 0.01). On the other hand, women carrying E4 allele exhibited lower values of triglycerides when compared with male carrying identical genotype (p < 0.05). Finally, women carrying mutate allele (C) for MTHFR rs1801131 showed lower levels of triglycerides when compared with A/A homozygous genotype (p < 0.05) and lower levels of LDL-C for MTHFR rs1801133 in females carrying (T) allele when compared with males carrying identical genotype (p < 0.05). In summary, the present data showed that APOB, APOE, and MTHFR single nucleotide polymorphisms are associated to lipid levels in a gender-dependent manner among healthy subjects from Northern Chile, especially in women.

The importance of cascade genetic screening for diagnosing autosomal dominant hypercholesterolemia: Results from twenty years of a national screening program in Norway

BACKGROUND

The most cost-effective strategy to diagnose patients with autosomal dominant hypercholesterolemia (ADH) is to perform cascade genetic screening.

OBJECTIVE

To present the cascade genetic screening program for ADH in Norway.

METHODS

A national cascade genetic screening program for ADH in Norway has been operating at Unit for Cardiac and Cardiovascular Genetics, Oslo University Hospital for twenty years. This program has been run by just one genetic counsellor. We now present the main findings of this cascade genetic screening program.

RESULTS

After genetic counselling, 8182 at-risk relatives have consented to genetic testing for the mutation that causes ADH in the family. Of these, 3076 (37.6%) relatives have tested positive. Among mutation-positive relatives 31.3% were on lipid-lowering therapy at the time of genetic testing. However, only 9.8% of these relatives had a value for low density lipoprotein (LDL) cholesterol below 2.5 mmol/l (97 mg/dl). At follow-up six months after genetic testing, reductions in the levels of total serum cholesterol and LDL cholesterol of 12% and 17%, respectively were observed. A total of 8811 ADH heterozygotes have been diagnosed in Norway. Thus, the number of patients diagnosed by this modest cascade genetic screening program constitutes 35% of all Norwegian ADH patients provided with a molecular genetic diagnosis.

CONCLUSION

Cascade genetic screening for ADH is very effective and should be organized at a national level. Even a modest cascade genetic screening program with small resources, can result in a large number of patients being identified.

Familial Hypercholesterolemia: Do HDL Play a Role?

Cardiovascular disease (CVD) in heterozygous familial hypercholesterolemia (HeFH), the most frequent monogenic disorder of human metabolism, is largely driven by low-density lipoprotein (LDL) cholesterol concentrations. Since the CVD rate differs considerably in this population, beyond the lifetime LDL cholesterol vascular accumulation, other classical risk factors are involved in the high cardiovascular risk of HeFH. Among other lipoprotein disturbances, alterations in the phenotype and functionality of high-density lipoproteins (HDL) have been described in HeFH patients, contributing to the presence and severity of CVD. In fact, HDL are the first defensive barrier against the burden of high LDL cholesterol levels owing to their contribution to reverse cholesterol transport as well as their antioxidant and anti-inflammatory properties, among others. In this context, the present narrative review aimed to focus on quantitative and qualitative abnormalities in HDL particles in HeFH, encompassing metabolic, genetic and epigenetic aspects.

Patient-Specific Induced Pluripotent Stem Cell-Derived Hepatocyte-Like Cells as a Model to Study Autosomal Recessive Hypercholesterolemia

Autosomal recessive hypercholesterolemia (ARH) is a rare monogenic disorder caused by pathogenic variants in the low-density lipoprotein receptor (LDLR) adaptor protein 1 (LDLRAP1) gene, encoding for the LDLRAP1 protein, which impairs internalization of hepatic LDLR. There are variable responses of ARH patients to treatment and the pathophysiological mechanism(s) for this variability remains unclear. This is in part caused by absence of reliable cellular models to evaluate the effect of LDLRAP1 mutations on the LDLRAP1 protein function and its role in LDLR internalization. Here, we aimed to validate patient-specific induced pluripotent stem cell (iPSC)-derived hepatocyte-like cells (HLCs) as an appropriate tool to model ARH disease. Fibroblasts from an ARH patient carrying the recently reported nonsense mutation, c.649G>T, were reprogrammed into hiPSCs using Sendai viral vectors. In addition, we used clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) to create an LDLRAP1 gene (also known as ARH) knockout in two different human iPSC lines. ARH patient-derived iPSCs, ARH-knockout iPSC lines, and control iPSCs were efficiently differentiated into HLCs. Western blot analysis demonstrated the absence of LDLRAP1 in HLCs derived from patient and knockout iPSCs, and this was associated with a decreased low-density lipoprotein cholesterol (LDL-C) uptake in ARH-mutant/knockout HLCs compared to control HLCs. In conclusion, we determined that the recently described c.649G>T point mutation in LDLRAP1 induces absence of the LDLRAP1 protein, similar to what is seen following LDLRAP1 knockout. This causes a decreased, although not fully absent, LDL-uptake in ARH-mutant/knockout HLCs. As knockout of LDLRAP1 or presence of the c.649G>T point mutation results in absence of LDLRAP1 protein, residual LDL uptake might be regulated by LDLRAP1-independent internalization mechanisms. Patient-specific iPSC-derived HLCs can therefore be a powerful tool to further decipher LDLRAP1 mutations and function of the protein.

ANKS1A genotype predicts cardiovascular events in patients with familial hypercholesterolemia

BACKGROUND

The rs17609940 variant of the ANKS1A gene has been associated with coronary artery disease (CAD) risk in genome-wide association studies (GWAS), but no study has yet replicated this association in familial hypercholesterolemia (FH) population.

OBJECTIVE

The aim of this study is to validate the association between the rs17609940 genotype and incident major adverse cardiovascular events (MACE) in a cohort of genetically-confirmed FH patients.

METHODS

This association study includes 725 genetically-confirmed FH patients with a median observation period of 50 years (33 805 person-years). MACE were defined as either myocardial infarction (MI), stroke, coronary revascularization, hospital admission for unstable angina and cardiovascular disease (CVD) death. The rs17609940 genotype was imputed with an imputation quality of 0.831 following an exome chip genotyping method (Illumina).

RESULTS

The cohort comprised 469 subjects with GG genotype, 218 subjects with CG genotype and 38 subjects with CC genotype. All baseline characteristics were balanced between the three groups. The CC genotype of rs17609940 was associated with a significant lower risk of incident MACE compared to GG and GC carriers in a recessive model (HR 0.30, 95% CI 0.11-0.82, p=0.02). Even after correction for confounding cardiovascular risk factors, the association between the ANKS1A polymorphism and incident MACE remained strongly significant.

CONCLUSIONS

We demonstrated that the rs17609940 SNP of the ANKS1A gene is associated with the risk of incident MACE in FH subjects. The exact mechanism underlying this association remains to be clarified.

Impact of statin therapy on LDL and non-HDL cholesterol levels in subjects with heterozygous familial hypercholesterolaemia

BACKGROUND AND AIMS

Cardiovascular risk in heterozygous familial hypercholesterolaemia (HeFH) is driven by LDL cholesterol levels. Since lipid response to statin therapy presents individual variation, this study aimed to compare mean LDL and non-HDL cholesterol reductions and their variability achieved with different types and doses of the most frequently prescribed statins.

METHODS AND RESULTS

Among primary hypercholesterolaemia cases on the Spanish Arteriosclerosis Society registry, 2894 with probable/definite HeFH and complete information on drug therapy and lipid profile were included. LDL cholesterol reduction ranged from 30.2 ± 17.0% with simvastatin 10 mg to 48.2 ± 14.7% with rosuvastatin 40 mg. After the addition of ezetimibe, an additional 26, 24, 21 and 24% reduction in LDL cholesterol levels was obtained for rosuvastatin, 5, 10, 20 and 40 mg, respectively. Subjects with definite HeFH and a confirmed genetic mutation had a more discrete LDL cholesterol reduction compared to definite HeFH subjects with no genetic mutation. A suboptimal response (<15% or <30% reduction in LDL cholesterol levels, respectively with low-/moderate-intensity and high-intensity statin therapy) was observed in 13.5% and, respectively, 20.3% of the subjects.

CONCLUSION

According to the LDL cholesterol reduction in HeFH patients, the ranking for more to less potent statins was rosuvastatin, atorvastatin and simvastatin; however, at maximum dosage, atorvastatin and rosuvastatin were nearly equivalent. HeFH subjects with positive genetic diagnosis had a lower lipid-lowering response. Approximately 1 in 5 patients on high-intensity statin therapy presented a suboptimal response.

Development and Clinical Applications of Antisense Oligonucleotide Gapmers

DNA-like molecules called antisense oligonucleotides have opened new treatment possibilities for genetic diseases by offering a method of regulating gene expression. Antisense oligonucleotides are often used to suppress the expression of mutated genes which may interfere with essential downstream pathways. Since antisense oligonucleotides have been introduced for clinical use, different chemistries have been developed to further improve efficacy, potency, and safety. One such chemistry is a chimeric structure of a central block of deoxyribonucleotides flanked by sequences of modified nucleotides. Referred to as a gapmer, this chemistry produced promising results in the treatment of genetic diseases. Mipomersen and inotersen are examples of recent FDA-approved antisense oligonucleotide gapmers used for the treatment of familial hypercholesterolemia and hereditary transthyretin amyloidosis, respectively. In addition, volanesorsen was conditionally approved in the EU for the treatment of adult patients with familial chylomicronemia syndrome (FCS) in 2019. Many others are being tested in clinical trials or under preclinical development. This chapter will cover the development of mipomersen and inotersen in clinical trials, along with advancement in gapmer treatments for cancer, triglyceride-elevating genetic diseases, Huntington's disease, myotonic dystrophy, and prion diseases.

Molecular genetic testing for autosomal dominant hypercholesterolemia in 29,449 Norwegian index patients and 14,230 relatives during the years 1993-2020

BACKGROUND AND AIMS

In this study, we present the status regarding molecular genetic testing for mutations in the genes encoding the low density lipoprotein receptor (LDLR), apolipoprotein B (APOB) and proprotein convertase subtilisin/kexin type 9 (PCSK9) as causes of autosomal dominant hypercholesterolemia (ADH) in Norway.

METHODS

We have extracted data from the laboratory information management system at Unit for Cardiac and Cardiovascular Genetics, Oslo University Hospital for the period 1993-2020. This laboratory is the sole laboratory performing molecular genetic testing for ADH in Norway.

RESULTS

A total of 29,449 unrelated hypercholesterolemic patients have been screened for mutations in the LDLR gene, in the APOB gene and in the PCSK9 gene. Of these, 2818 (9.6%) were heterozygotes and 11 were homozygotes or compound heterozygotes. Most of the 264 different mutations identified were found in the LDLR gene. Only two and three mutations were found in the APOB gene or in the PCSK9 gene, respectively. Several founder mutations were identified. After testing of 14,230 family members, a total of 8811 heterozygous patients have been identified. Of these, 94.0% had a mutation in the LDLR gene, 5.4% had a mutation in the APOB gene and 0.6% had a mutation in the PCSK9 gene.

CONCLUSIONS

A large proportion of Norwegian ADH patients have been provided with a molecular genetic diagnosis. Norway is probably only second to the Netherlands in this respect. A molecular genetic diagnosis may form the basis for starting proper preventive measures and for identifying affected family members by cascade genetic screening.

The familial hypercholesterolaemia phenotype: Monogenic familial hypercholesterolaemia, polygenic hypercholesterolaemia and other causes

Familial hypercholesterolaemia (FH) is a monogenic disorder characterised by high low-density lipoprotein cholesterol (LDL-C) concentrations and increased cardiovascular risk. However, in clinically defined FH cohorts worldwide, an FH-causing variant is only found in 40%-50% of the cases. The aim of this work was to characterise the genetic cause of the FH phenotype in Portuguese clinical FH patients. Between 1999 and 2017, 731 index patients (311 children and 420 adults) who met the Simon Broome diagnostic criteria had been referred to our laboratory. LDLR, APOB, PCSK9, APOE, LIPA, LDLRAP1, ABCG5/8 genes were analysed by polymerase chain reaction amplification and Sanger sequencing. The 6-SNP LDL-C genetic risk score (GRS) for polygenic hypercholesterolaemia was validated in the Portuguese population and cases with a GRS over the 25th percentile were considered to have a high likelihood of polygenic hypercholesterolaemia. An FH-causing mutation was found in 39% of patients (94% in LDLR, 5% APOB and 1% PCSK9), while at least 29% have polygenic hypercholesterolaemia and 1% have other lipid disorders. A genetic cause for the FH phenotype was found in 503 patients (69%). All known causes of the FH phenotype should be investigated in FH cohorts to ensure accurate diagnosis and appropriate management.

Montreal-FH-SCORE Predicts Coronary Artery Calcium Score in Patients With Familial Hypercholesterolemia

BACKGROUND

Familial hypercholesterolemia (FH) is a monogenic disease characterized by a high concentration of low-density lipoprotein cholesterol. This population is considered to be at high cardiovascular risk; however, disease evolution remains heterogeneous among individuals. The coronary artery calcium (CAC) score is currently the best predictor of incidental major cardiovascular events in primary prevention in the general population. Few studies have described the CAC score in FH populations.

METHODS

The objective of our study was to determine the predictors of the CAC score in FH patients. We retrospectively studied FH patients followed at the Montreal Clinical Research Institute (IRCM) Lipid Clinic who had a cardiac scan for CAC score, using the Agatston method, between 2013 and 2019.

RESULTS

Final analysis included 62 FH patients. Mean age was 48 ± 14 years old, and 48% were men. Overall, 25 patients had a CAC score of 0 (40%), and 37 patients had a nonzero CAC score (60%). Sex, age, Montreal-FH-SCORE (MFHS), waist circumference, and statin exposure in years were significant predictors (P ≤ 0,05) of a nonzero CAC score in a univariate model. MFHS was the only factor that remained significant in a multivariate model (odds ratio 1.34, 95% confidence interval 1.11-1.61, P = 0.002).

CONCLUSIONS

In conclusion, we found that MFHS, which includes traditional cardiovascular risk factors, was a predictor of a nonzero CAC score in FH patients. This finding suggests that MFHS may play a role in determining the cardiovascular risk and therefore the intensity of treatment in FH patients.

[Clinical case of combined genetic pathology in a patient]

Family hypercholesterolemia (HSX) is a form of genetically deterministic increase in blood lipid levels associated with a high risk of cardiovascular disease, usually at a young age. HSX is a common genetic disease found in the general population in most countries in 1:500 people. Clinically xantomas are found in achilles tendor and wrist flexors, lipoid arc of the cornea, concentration of total cholesterol and low-density lipoproteins is 4.911.6 mmol/l. Gilberts syndrome is a hereditary benign hyperbilirubinium, associated with a decrease in the functional activity of the liver enzyme uridinfosfat-glucuronosil transferase. Clinically, this syndrome appers in intermittent jaundice, which is provoked by physical activity, consumption of alcoholic beverages, insulation and an increase in the level of indirect bilirubin within 20100 micromol/ml. The article presents a rare clinical case of genetic combination of HSC SSC and Gilbert syndrome a young patient has and discusses the elevated bilirubin levels protective role in the atherosclerosis progression in Gilbert syndrome.

Proteostasis Regulation in the Endoplasmic Reticulum: An Emerging Theme in the Molecular Pathology and Therapeutic Management of Familial Hypercholesterolemia

Familial hypercholesterolemia (FH) is an autosomal genetic disease characterized by high serum low-density lipoprotein (LDL) content leading to premature coronary artery disease. The main genetic and molecular causes of FH are mutations in low-density lipoprotein receptor gene (LDLR) resulting in the non-clearance of LDL from the blood by hepatocytes and consequently the formation of plaques. LDLR is synthesized and glycosylated in the endoplasmic reticulum (ER) and then transported to the plasma membrane via Golgi. It is estimated that more than 50% of reported FH-causing mutations in LDLR result in misfolded proteins that are transport-defective and hence retained in ER. ER accumulation of misfolded proteins causes ER-stress and activates unfolded protein response (UPR). UPR aids protein folding, blocks further protein synthesis, and eliminates misfolded proteins via ER-associated degradation (ERAD) to alleviate ER stress. Various studies demonstrated that ER-retained LDLR mutants are subjected to ERAD. Interestingly, chemical chaperones and genetic or pharmacological inhibition of ERAD have been reported to rescue the transport defective mutant LDLR alleles from ERAD and restore their ER-Golgi transport resulting in the expression of functional plasma membrane LDLR. This suggests the possibility of pharmacological modulation of proteostasis in the ER as a therapeutic strategy for FH. In this review, we picture a detailed analysis of UPR and the ERAD processes activated by ER-retained LDLR mutants associated with FH. In addition, we discuss and critically evaluate the potential role of chemical chaperones and ERAD modulators in the therapeutic management of FH.

Optical coherence tomography of retinal and choroidal layers in patients with familial hypercholesterolaemia treated with lipoprotein apheresis

PURPOSE

Detect and quantify morpho-functional alterations of the retina and choroid in patients affected by familial hypercholesterolemia (FH) treated with lipoprotein apheresis (LA) using optic coherence tomography (OCT) and optic coherence tomography-angriography (OCTA).

DESIGN

Observational study.

SUBJECTS

To be diagnosed: A group of 20 patients (40 eyes) being clinically and genetically diagnosed as FH and under treatment (FH-Group)", for at least 2 years, was compared to a control group of 20 healthy subjects (40 eyes), with a normal lipid profile and no ocular disease (CT-Group).

METHODS

Participants were studied with the slit lamp, binocular indirect fundoscopy, OCT and OCTA.

MAIN OUTCOME MEASURES

Best corrected visual acuity (BVCA), spherical equivalent (SE), intraocular pressure (IOP), central macular thickness (CMT), choroidal thickness (CHT), retinal nerve fiber layer in four quadrants (RNFL (Superior = Sup; Inferior = Inf; Nasal = Nas Temporal = Temp), and the mean value across the four quadrants (RNFL G), foveal avascular zone (FAZ) and vascular density (VD).

RESULTS

FH subjects had smaller RNFL superiorly (108 ± 19,38 μm OD/111 ± 16,56 μm OS FH-Group vs 127 ± 7,42 μm OD/129 ± 14,64 μm OS CT-Group; P < 0,001 for both OD and OS) and inferiorly (108 ± 23,58 μm OD/115 ± 17,33 μm OS FH-Group vs 128 ± 18,15 μm OD/133 ± 17,38 μm OS CT-Group; P = 0,002 OD; P = 0,001 OS). G RNFL was consequently smaller (93 ± 12,94 μm OD/94 ± 10,49 μm OS FH-Group vs 101 ± 9,01 μm OD/101 ± 10,20 μm OS CT-Group; P = 0,03 OD; P = 0,02 OS). FH subjects had a larger FAZ (0,31 ± 0,08 mm² OD/0,33 ± 0,10 mm² in OS FH-Group vs 0,21 ± 0,05 mm² OD/0,21 ± 0,07 mm² OS CT-Group; P < 0,001 OD; P = 0,002 OS).

CONCLUSIONS

Early signs of retinal vessel damage in FH patients can be detected and quantified with OCT and OCTA.

Lipid profiling in maternal and fetal circulations in preeclampsia and fetal growth restriction-a prospective case control observational study

Background

While many risk factors for preeclampsia, such as increased body mass index, advanced maternal age, chronic hypertension, diabetes, are now established in clinical practice, maternal lipid profile has not been included in the risk assessment for preeclampsia. We aim to characterize the serum levels of Total Cholesterol (TC), High density lipoprotein (HDL), Low density lipoprotein (LDL), Triglycerides (TG), Apolipoprotein A1, Apolipoprotein B and their ratios TC/HDL and ApoB/ApoA1 in the maternal and fetal circulations of normal pregnancy, preeclampsia (PE), fetal growth restriction (FGR) and PE + FGR.

Methods

A prospective cross-sectional case control study was conducted measuring maternal and fetal lipid levels by enzymatic analysis and immune-turbidimetric enzymatic assays. FGR was defined by elevated umbilical artery Doppler resistance in association with estimated fetal weight < 10%. Kruskal Wallis non-parametric analysis of variance was used to test for homogeneity across the clinical groups for each of the variables, Mann-Whitney tests for pairwise comparisons and Spearman rank correlation were used to quantify gestational age-related changes.

Results

(1) TG levels were elevated in maternal PE and cord blood PE + FGR groups compared to normal pregnancies. (2) A statistically significant elevation of fetal ApoB levels was observed in PE, FGR and PE + FGR compared to normal pregnancies. Apolipoprotein levels A1 and B were not different between maternal groups. (3) TC, HDL, LDL and TC/HDL levels did not show any significant gestational variation or between clinical groups in the maternal or fetal circulation.

Conclusions

Elevation in maternal TG levels may have a role in the pathogenesis of PE. The implications of elevated maternal and fetal TG levels and elevated fetal Apolipoprotein B levels deserves further exploration of their role in long term cardiovascular risk in the mother as well as the offspring.

Behavioural cardiovascular risk factors and prevalence of diabetes in subjects with familial hypercholesterolaemia

A low prevalence of type 2 diabetes mellitus has been reported in familial hypercholesterolaemia. Whether a healthier lifestyle could explain it has not been explored. This cross-sectional study determines the prevalence of lifestyle-related cardiovascular risk factors in heterozygous familial hypercholesterolaemia (HeFH) from the Dyslipidaemia Registry of the Spanish Atherosclerosis Society and in the ENRICA study, a representative sample of the adult Spanish general population, weighted to match the age and sex distribution of the HeFH sample. A total of 2185 HeFH patients and 11,856 individuals from ENRICA were included. HeFH had lower body mass index and fewer of them were smokers than in the reference population. A model adjusted for age, sex and body mass index showed that HeFH more frequently had cardiovascular disease (odds ratio (OR) 23.98; 95% confidence interval (CI) 18.40-31.23) and hypertension (OR 1.20; 95% CI 1.07-1.35), and took anti-hypertensive medication (OR 1.36; 95% CI 1.18-1.56) and anti-diabetic medication (OR 1.25; 95% CI 1.00-1.56), but less frequently were smokers (OR 0.79; 95% CI 0.71-0.89). In a HeFH subsample (n = 513) with complete blood glucose information, those patients without cardiovascular disease showed lower prevalence of smoking and type 2 diabetes mellitus, lower body mass index and glucose, and higher diastolic blood pressure than the Spanish population. The differences in type 2 diabetes mellitus were justified mostly by the difference in body mass index. Body mass index adjustment also showed higher prevalence of hypertension and use of anti-hypertensive drugs in HeFH. In summary, HeFH patients had lower body mass index, which may contribute to explaining the lower prevalence of diabetes, and lower current smoking but higher hypertension.

Plasma proteome profiling of freshwater and seawater life stages of rainbow trout (Oncorhynchus mykiss)

The sea-run phenotype of rainbow trout (Oncorhynchus mykiss), like other anadromous salmonids, present a juvenile stage fully adapted to life in freshwater known as parr. Development in freshwater is followed by the smolt stage, where preadaptations needed for seawater life are developed making fish ready to migrate to the ocean, after which event they become post-smolts. While these three life stages have been studied using a variety of approaches, proteomics has never been used for such purpose. The present study characterised the blood plasma proteome of parr, smolt and post-smolt rainbow trout using a gel electrophoresis liquid chromatography tandem mass spectrometry approach alone or in combination with low-abundant protein enrichment technology (combinatorial peptide ligand library). In total, 1,822 proteins were quantified, 17.95% of them being detected only in plasma post enrichment. Across all life stages, the most abundant proteins were ankyrin-2, DNA primase large subunit, actin, serum albumin, apolipoproteins, hemoglobin subunits, hemopexin-like proteins and complement C3. When comparing the different life stages, 17 proteins involved in mechanisms to cope with hyperosmotic stress and retinal changes, as well as the downregulation of nonessential processes in smolts, were significantly different between parr and smolt samples. On the other hand, 11 proteins related to increased growth in post-smolts, and also related to coping with hyperosmotic stress and to retinal changes, were significantly different between smolt and post-smolt samples. Overall, this study presents a series of proteins with the potential to complement current seawater-readiness assessment tests in rainbow trout, which can be measured non-lethally in an easily accessible biofluid. Furthermore, this study represents a first in-depth characterisation of the rainbow trout blood plasma proteome, having considered three life stages of the fish and used both fractionation alone or in combination with enrichment methods to increase protein detection.

Molecular Characterization of Familial Hypercholesterolemia in a North American Cohort

Background

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

Objective

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

Methods

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

Results

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

Conclusions

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

A new variant (c.1A>G) in LDLRAP1 causing autosomal recessive hypercholesterolemia: Characterization of the defect and response to PCSK9 inhibition

BACKGROUND AND AIMS

Autosomal recessive hypercholesterolemia (ARH) is a rare disorder caused by mutations in LDLRAP1, which impairs internalization of hepatic LDL receptor (LDLR). ARH patients respond relatively well to statins or the combination of statins and Ezetimibe, but scarce and variable data on treatment with PCSK9 inhibitors is available. We aimed to identify and characterize the defect in a hypercholesterolemic patient with premature cardiovascular disease and determine the response to lipid-lowering treatment.

METHODS AND RESULTS

Gene sequencing revealed a homozygous c.1A > G:p.? variant in LDLRAP1. Primary lymphocytes were isolated from the ARH patient, one control and two LDLR-defective subjects, one LDLR:p.(Cys352Ser) heterozygote and one LDLR:p.(Asn825Lys) homozygote. The patient had undetectable full-length ARH protein by Western blotting, but expressed a lower-than-normal molecular weight peptide. LDLR activity was measured by flow cytometry, which showed that LDL binding and uptake were reduced in lymphocytes from the ARH patient as compared to control lymphocytes, but were slightly higher than in those from the LDLR:p.(Cys352Ser) heterozygote. Despite the analogous internalization defect predicted in ARH and homozygous LDLR:p.(Asn825Lys) lymphocytes, LDL uptake was higher in the former than in the latter. LDL-cholesterol levels were markedly reduced by the successive therapy with Atorvastatin and Atorvastatin plus Ezetimibe, and the addition of Evolocumab biweekly decreased LDL-cholesterol by a further 39%.

CONCLUSIONS

The LDLRAP1:c.1A > G variant is associated with the appearance of an N-terminal truncated ARH protein and to reduced, although still significant, LDLR activity in lymphocytes. Residual LDLR activity may be relevant for the substantial response of the patient to Evolocumab.

GWAS Reveal Targets in Vessel Wall Pathways to Treat Coronary Artery Disease

Coronary artery disease (CAD) is the leading cause of mortality worldwide and poses a considerable public health burden. Recent genome-wide association studies (GWAS) have revealed >100 genetic loci associated with CAD susceptibility in humans. While a number of these loci harbor gene targets of currently approved therapies, such as statins and PCSK9 inhibitors, the majority of the annotated genes at these loci encode for proteins involved in vessel wall function with no known drugs available. Importantly many of the associated genes linked to vascular (smooth muscle, endothelial, and macrophage) cell processes are now organized into distinct functional pathways, e.g., vasodilation, growth factor responses, extracellular matrix and plaque remodeling, and inflammation. In this mini-review, we highlight the most recently identified loci that have predicted roles in the vessel wall and provide genetic context for pre-existing therapies as well as new drug targets informed from GWAS. With the development of new modalities to target these pathways, (e.g., antisense oligonucleotides, CRISPR/Cas9, and RNA interference) as well as the computational frameworks to prioritize or reposition therapeutics, there is great opportunity to close the gap from initial genetic discovery to clinical translation for many patients affected by this common disease.

Can modulators of apolipoproteinB biogenesis serve as an alternate target for cholesterol-lowering drugs?

Understanding the molecular defects underlying cardiovascular disease is necessary for the development of therapeutics. The most common method to lower circulating lipids, which reduces the incidence of cardiovascular disease, is statins, but other drugs are now entering the clinic, some of which have been approved. Nevertheless, patients cannot tolerate some of these therapeutics, the drugs are costly, and/or the treatments are approved for only rare forms of disease. Efforts to find alternative treatments have focused on other factors, such as apolipoproteinB (apoB), which transports cholesterol in the blood stream. The levels of apoB are regulated by endoplasmic reticulum (ER) associated degradation as well as by a post ER degradation pathway in model systems, and we suggest that these events provide novel therapeutic targets. We discuss first how cardiovascular disease arises and how cholesterol is regulated, and then summarize the mechanisms of action of existing treatments for cardiovascular disease. We then review the apoB biosynthetic pathway, focusing on steps that might be amenable to therapeutic interventions.

Usefulness of the genetic risk score to identify phenocopies in families with familial hypercholesterolemia?

Familial hypercholesterolemia (FH) is caused by mutations in LDLR (low-density lipoprotein receptor), APOB (apolipoprotein B), PCSK9 (proprotein convertase subtilisin/kexin type 9), or APOE (apolipoprotein E) genes in approximately 80% of the cases. Polygenic forms of hypercholesterolemia may be present among patients clinically diagnosed with FH but with no identified mutation (FH mutation-negative (FH/M-)). To address whether polygenic forms may explain phenocopies in FH families, we calculated a 6-single-nucleotide polymorphism (SNP) genetic risk score (GRS) in all members from five French FH families where a mutation was identified (FH/M+) as well as some phenocopies (FH/M-). In two families, three FH/M- patients present a high GRS suggesting a polygenic hypercholesterolemia for these phenocopies. However, a high GRS is also observed in nine FH/M+ patients and in four unaffected relatives from three families. These observations indicate that the GRS does not seem to be a good diagnostic tool at the individual level. Nevertheless, the GRS seems to be a contributor of the severity of hypercholesterolemia since patients who cumulate a mutation and a high GRS exhibit higher low-density lipoprotein cholesterol levels when compared to patients with only FH (p = 0.054) or only polygenic hypercholesterolemia (p = 0.0039). In conclusion, the GRS can be used as a marker of the severity of hypercholesterolemia but does not seem to be a reliable tool to distinguish phenocopies within FH families.

(Pro)renin Receptor Inhibition Reprograms Hepatic Lipid Metabolism and Protects Mice From Diet-Induced Obesity and Hepatosteatosis

RATIONALE

An elevated level of plasma LDL (low-density lipoprotein) is an established risk factor for cardiovascular disease. Recently, we reported that the (pro)renin receptor ([P]RR) regulates LDL metabolism in vitro via the LDLR (LDL receptor) and SORT1 (sortilin-1), independently of the renin-angiotensin system.

OBJECTIVES

To investigate the physiological role of (P)RR in lipid metabolism in vivo.

METHODS AND RESULTS

We used N-acetylgalactosamine modified antisense oligonucleotides to specifically inhibit hepatic (P)RR expression in C57BL/6 mice and studied the consequences this has on lipid metabolism. In line with our earlier report, hepatic (P)RR silencing increased plasma LDL-C (LDL cholesterol). Unexpectedly, this also resulted in markedly reduced plasma triglycerides in a SORT1-independent manner in C57BL/6 mice fed a normal- or high-fat diet. In LDLR-deficient mice, hepatic (P)RR inhibition reduced both plasma cholesterol and triglycerides, in a diet-independent manner. Mechanistically, we found that (P)RR inhibition decreased protein abundance of ACC (acetyl-CoA carboxylase) and PDH (pyruvate dehydrogenase). This alteration reprograms hepatic metabolism, leading to reduced lipid synthesis and increased fatty acid oxidation. As a result, hepatic (P)RR inhibition attenuated diet-induced obesity and hepatosteatosis.

CONCLUSIONS

Collectively, our study suggests that (P)RR plays a key role in energy homeostasis and regulation of plasma lipids by integrating hepatic glucose and lipid metabolism.

Familial Hypercholesterolaemia in the Era of Genetic Testing

Familial hypercholesterolaemia (FH) is a relatively common autosomal dominant genetic condition leading to premature ischaemic vascular disease and mortality if left untreated. Currently, a universal consensus on the diagnostic criteria of FH does not exist but the diagnosis of FH largely relies on the evaluation of low density lipoprotein-cholesterol (LDL-C) levels, a careful documentation of family history, and the identification of clinical features. Diagnosis based purely on lipid levels remains common but there are several limitations to this method of diagnosis both practically and in the proportion of false-negatives and false-positives detected, resulting in substantial under-diagnosis of FH. In some countries, diagnostic algorithms are supplemented with genetic testing of the index case as well as genetic and lipid testing of relatives of the index case. Such "cascade" screening of families following identification of index cases appears to not only improve the rate of diagnosis but is also cost-effective. Currently, we observe a great variation in the excess mortality among patients with FH, which likely reflects a combination of additional genetic and environmental effects on risk overlaid on the risk associated with FH. Current accepted drug therapies for FH include statins and PSCK9 inhibitors. Further work is required to evaluate the cardiovascular disease risk in patients with genetically diagnosed FH and to determine whether a risk-based approach to the treatment of FH is appropriate.

Polygenic risk score predicts prevalence of cardiovascular disease in patients with familial hypercholesterolemia

BACKGROUND

Although familial hypercholesterolemia (FH) is a severe monogenic disease, it has been shown that clinical risk factors and common genetic variants can modify cardiovascular disease (CVD) risk.

OBJECTIVE

The aim of the study was to evaluate the polygenic contribution to lipid traits and CVD in FH using genetic risk scores (GRSs).

METHODS

Among the 20,434 subjects attending the lipid clinic, we identified and included 725 individuals who carried an FH causing mutation in this retrospective cohort study. We evaluated the association of GRSs for several traits including coronary artery disease (CAD; GRS_CAD) as well as plasma concentrations of low-density lipoprotein cholesterol (LDL-C; GRS_LDL-C), high-density lipoprotein cholesterol (GRS_HDL-C) and triglycerides (GRS_TG).

RESULTS

A total of 32% (n = 231) of FH subjects presented a CVD event before their first visit. Patients in the highest GRS_LDL-C tertile presented an LDL-C 0.4 mmol/L (15.5 mg/dL) higher than the subjects in the lowest tertile (P = .01). The GRS_CAD was strongly associated with CVD events (odds ratio 1.80; 95% confidence interval 1.14-2.85; P = .01) even after adjustment for cardiovascular risk factors. Compared with subjects in the first tertile, those in the third GRS_CAD tertile had a significantly higher prevalence of events (40.9% vs 24.7%, P < .0001) and a significantly higher number of events (average 0.97 vs 0.57 [P = .0001] events per individual).

CONCLUSION

These results indicate that even in the context of a severe monogenic disease such as FH, common genetic variants can significantly modify the disease phenotype. The use of the 192-SNPs GRS_CAD may refine CVD risk prediction in FH patients and this could lead to a more personalized approach to therapy.

Genetic diagnosis of familial hypercholesterolaemia using a rapid biochip array assay for 40 common LDLR, APOB and PCSK9 mutations

BACKGROUND AND AIMS

Familial hypercholesterolaemia (FH) leads to a lifelong increase in plasma LDL levels with subsequent increase in premature vascular disease. Early diagnosis and treatment is the key to effective management of this condition. This research aims to produce a simple and cost effective genetic test which could identify the majority (71%) of mutations causing FH in the UK and Ireland.

METHODS

The Randox Biochip Array Technology was used to detect 40 point mutations in LDLR, APOB and PCSK9 genes, over two 5 × 5 arrays. This technology uses multiplex allele specific PCR and biochip array hybridisation, followed by a chemiluminescence detection system and software for automated mutation calling.

RESULTS

The FH biochip array assay was validated in the Belfast Genetics Laboratory using 199 cascade screening samples previously sequenced for known FH causing family mutations, the overall sensitivity was 98%. The assay was then used for routine testing of 663 patients with possible FH, from clinics across the UK and Ireland. A total of 49 (7.4%) mutation positive individuals were identified, however, for the clinics in England the detection rate was 12.9%. Further analysis of 120 biochip negative patients, using DNA sequencing, did not identify any false negatives.

CONCLUSIONS

The FH biochip array provides a rapid and reliable genetic test for the majority of FH causing point mutations in the UK and Ireland. A total of 32 samples can be run in 3 h. This allows clinics to evaluate additional patients for a possible diagnosis of FH such as patients with high LDL, patients with early onset coronary disease, and patients with relatives known to have FH.

[PCSK9 - "missing link" in familial hypercholesterolemia : New therapeutic options in hypercholesterolemia and coronary artery disease]

Lowering plasma low-density lipoprotein cholesterol (LDL-C) levels to individual therapeutic goals is one of the most effective measures for the prevention of cardiovascular disease. Besides dietary measures, this can be achieved pharmaceutically by inhibition of hepatic cholesterol synthesis with statins or inhibition of intestinal cholesterol absorption (e.g., ezetimibe and bile acid sequestrants). Decisive for lowering LDL is an increased hepatic uptake of circulating LDL via an increase in LDL receptors (LDLR) in hepatic cell membranes. The formation of new LDLR and recirculation of existing LDLR play a decisive role in this process. An important modulator of LDLR is proprotein convertase subtilisin/kexin type 9 (PCSK9). In the last years genetic studies have identified several mutations in the PCSK9 gene leading to a gain of function and carriers of these mutations suffer from autosomal dominant hypercholesterolemia. In contrast, carriers of PCSK9 loss of function mutations show very low plasma LDL-C concentrations and a markedly reduced risk for coronary artery disease. These fundamental discoveries have sparked the development of a completely novel therapeutic approach to treating hypercholesterolemia. At present, inhibition of PCSK9 by monoclonal antibodies presents the most promising therapeutic approach. First human antibodies were recently approved as the first immunotherapeutic agents for the treatment of severe hypercholesterolemia and in patients with statin intolerance. An additional PCSK9 antibody is presently being studied in phase III clinical trials.