Familial Defective Apolipoprotein Research Articles

Assessing the Attitudes and Perceptions of the Old Order Amish toward Genetic Testing for Familial Defective Apolipoprotein B-100

Through a founder effect, one in eight Lancaster County, PA, Amish harbors the pathogenic APOB variant R3527Q, causing Familial Defective Apolipoprotein B-100 (FDB) that is rare in the general population. Affected individuals are at increased risk for high low density lipoprotein (LDL) cholesterol levels and cardiovascular disease and may benefit from early screening and treatment. A qualitative interview approach was used to investigate the genetic risk perceptions of the Amish and their attitudes towards genetic testing for FDB. The goal was to identify elements necessary for a successful program that would identify high risk individuals in the Lancaster County Amish community and provide them with potentially lifesaving education and interventions. Thirty interviews were conducted. Collected data were analyzed and coded for common themes. Participants perceived a great deal of importance in genetic risk and were aware of the significant impact genetics have on health. Most individuals perceived genetic risk as more significant than family history. Twenty-four of 30 individuals would consider testing; of these, all 24 reported they would take proactive measures to reduce risks if given a positive result. Most would prefer diet modification and natural health remedies, with prescription medication only as a last resort. Several participants stated that most Amish people would be unlikely to test if they were feeling healthy. Cost was the most significant barrier to pursuing testing. Implementing a successful screening program would require community outreach and awareness, risk reduction education and support, and minimal out-of-pocket expenses. The program’s success provides insights into the efficacy of predictive genetic screening for the general population. [Abstract by authors.]

Familial Hypercholesterolemia: Real-World Data of 1236 Patients Attending a Czech Lipid Clinic. A Retrospective Analysis of Experience in More than 50 years. Part II. Clinical Characteristics

Introduction: Patients with familial hypercholesterolemia (FH) are at increased risk of premature atherosclerotic cardiovascular disease (ASCVD). Aim of study: To perform a retrospective analysis of data to assess the effects of individual lipoproteins and other risk factors (RFs) on the development of ASCVD and to compare these parameters in individuals with versus without ASCVD. Patients and methods: Our study group included a total of 1,236 patients with FH (395 men and 841 women with a mean age of 44.8 ± 16.7 years) attending a single lipid clinic. The diagnosis of FH was established using the Dutch Lipid Clinic Network score (DLCN). Among the 1236 FH patients, 1,008 of them [854 suspected with LDL receptor-mediated FH and 154 with familial defective apolipoprotein B-100 (FDB)] were genetically analysed. Their RFs were assessed based on the patients’ clinical characteristics. Results: While patients with ASCVD had higher baseline LDL-C, TC, TG and Lp(a) compared with patients without this diagnosis, this ratio was just the opposite by the follow-up. The highest statistically significant differences were seen in the baseline levels of Lp(a) and, quite surprisingly, TG. Except for Lp(a), the levels of all lipid parameters declined significantly over time. While the incidence of diabetes and arterial hypertension was not higher in our group compared with the general population, these patients were at a more significant risk of ASCVD. Conclusion: Familial hypercholesterolemia is a major RF for the development of ASCVD. While our analysis confirmed the important role of LDL-C, it also corroborated a strong correlation between ASCVD and other lipid parameters, and Lp(a) and TG in particular. Familial hypercholesterolemia is not the only RF and, to reduce cardiovascular risk of their patients, physicians have to search for other potential RFs. Patients diagnosed to have FH benefit from attending a specialized lipid clinic perse.

Familial defective apolipoprotein B-100 – the real world data of the group of patients from the center of preventive cardiology

Background and Aims: Atherosclerotic cardiovascular diseases (ASCVD) play the most important role in mortality of Czech patients. The only one causal risk factor of atherosclerosis is LDL-cholesterol (LDL-C), which is enhanced by genetic predispositions causing defects in LDL receptor, apolipoprotein B or PCSK9 enzyme. The aim of the study was to provide the clinical and laboratory characteristics of 105 patients with the diagnosis of familial defective apolipoprotein B-100 (FDB) from the large cohort of patients (n=1000) with familial hypercholesterolemia (FH). The data was obtained from the real clinical practice at the Center of preventive cardiology (CPC).

PCSK9 inhibitor therapy in homozygous familial defective apolipoprotein B-100 due to APOB R3500Q: A case report

Identification of a patient homozygous for familial defective apolipoprotein B-100(FDB) and successful treatment with PCSK9 inhibition.

Two forms of familial hypercholesterolemia: differences in cardiovascular risk factors, cardiac and extracardiac atherosclerosis

The monogenetic hypercholesterolemias (HC) are associated with a very high risk of premature coronary heart disease (CHD). We sought to assess the influence of the genetic defect and the cardiovascular risk factors on the manifestation of atherosclerotic complications in two forms of genetic HC. Data of patients with genetically defined HC (54 LDL-receptor defective familial hypercholesterolemia (FH) and 54 familial defective apolipoprotein B (FDB)) were analysed retrospectively for cardiac and extracardiac atherosclerosis. Total and LDL-cholesterol were significantly higher in FH men than in FDB men, but not so in women. 41.8% of FH patients had CHD (mean age 41 years), 5.6% of FDB (mean age 52 years). Stenoses (>50% narrowing) of the internal carotid artery were verified in 15% of FH and 4% of FDB patients. Peripheral arterial disease was found in 3 FH and 2 FDB patients. Hypertension and active smoking were allotted almost equally, body weight was normal in most of the patients (BMI ≤ 25 kg/m(2)). Conlusion: Patients with genetic HC suffer from early manifestation of cardiac disease. Patients with FH seem to be affected more often than patients with FDB. Early diagnosis and early and lifelong treatment are essential and, according to the literature, lead to a delay of disease manifestation.

Decreased Bone Mineral Density in Subjects Carrying Familial Defective Apolipoprotein B-100

Although numerous epidemiologic studies have documented associations between osteoporosis and cardiovascular disease, the mechanisms underlying this association remain to be clarified. One hypothesis is that hyperlipidemia may be a common predisposing factor to both atherosclerotic heart disease and bone fragility. To evaluate this, we compared bone mineral density (BMD) between subjects with and without the R3500Q APOB mutation, the cause of familial defective apolipoprotein B-100, which has been previously shown to markedly increase low-density lipoprotein cholesterol (LDL-C). We hypothesized that R3500Q carriers would have lower BMD due to lifetime, elevated LDL-C. This was a a cross-sectional study in the Old Order Amish (OOA) population. The R3500Q APOB mutation is present at a high frequency (∼6% vs <0.5%) in the OOA population due to a founder effect. Therefore, we conducted analysis on 1097 Amish individuals of whom 125 were R3500Q carriers. BMD was measured by dual-energy x-ray absorptiometry. After adjusting for age, age(2), sex, body mass index, and family structure, carriers for the Q risk allele had significantly lower BMD than noncarriers at the femoral neck (P = .037), lumbar spine (P = .035) and whole body (P = .016). Adjusting for LDL-C attenuated the association between R3500Q genotype and BMD but did not completely explain the relationship. Subgroup analyses showed no significant interactions with sex, age, or presence of metabolic syndrome. These results use the unique genetic architecture of the OOA population to provide a novel line of evidence supporting a causal role for elevated LDL-C in lowering BMD.

Molecular Description of Familial Defective APOB-100 in Malaysia

Familial ligand-defective apolipoprotein B-100 is characterized by elevated plasma low-density lipoprotein levels and premature heart disease. This study aims to determine apolipoprotein B gene mutations among Malaysians with clinical diagnoses of familial hypercholesterolemia and to compare the phenotype of patients with apolipoprotein B gene mutations to those with a low-density lipoprotein receptor gene mutation. A group of 164 patients with a clinical diagnosis of familial hypercholesterolemia was analyzed. Amplicons in exon 26 and exon 29 of the apolipoprotein B gene were screened for genetic variants using denaturing gradient high-performance liquid chromatography; 10 variants were identified. Five novel mutations were detected (p.Gln2485Arg, p.Thr3526Ala, p.Glu3666Lys, p.Tyr4343CysfsX221, and p.Arg4297His). Those with familial defective apolipoprotein had a less severe phenotype than those with familial hypercholesterolemia. An apolipoprotein gene defect is present among Malaysian familial hypercholesterolemics. Those with both mutations show a more severe phenotype than those with one gene defect.

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.

First Detection of Hypercholesterolemia Causing ApoB-100 R3527Q Mutation in a Family in Greece

Familial defective apolipoprotein B (FDB) is an autosomal dominant genetic disorder causing hypercholesterolemia in affected patients. It is occurring due to mutation of apoB gene leading to a decreased low density lipoprotein (LDL) particles clearance. The R3527Q mutation is one of the disease’s causative mutations. Data support mutation’s origin 6000-7000 years ago in Central Europe and its prevalence is decreasing in relation to the distance from where initially occurred. Until now, the presence of R3527Q mutation had not been confirmed in Greece. This is the first report of FDB due to R3527Q mutation in a family in Northwest Greece.

Lack of Cardiovascular Disease Among Old Order Amish With Familial Defective Apolipoprotein B—Reply

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Lack of Cardiovascular Disease Among Old Order Amish With Familial Defective Apolipoprotein B

Lack of Cardiovascular Disease Among Old Order Amish With Familial Defective Apolipoprotein B

Familial Defective Apolipoprotein B-100 and Increased Low-Density Lipoprotein Cholesterol and Coronary Artery Calcification in the Old Order Amish

Elevated low-density lipoprotein cholesterol (LDL-C) levels are a major cardiovascular disease risk factor. Genetic factors are an important determinant of LDL-C levels. To identify single nucleotide polymorphisms associated with LDL-C and subclinical coronary atherosclerosis, we performed a genome-wide association study of LDL-C in 841 asymptomatic Amish individuals aged 20 to 80 years, with replication in a second sample of 663 Amish individuals. We also performed scanning for coronary artery calcification (CAC) in 1018 of these individuals. From the initial genome-wide association study, a cluster of single nucleotide polymorphisms in the region of the apolipoprotein B-100 gene (APOB) was strongly associated with LDL-C levels (P < 10(-68)). Additional genotyping revealed the presence of R3500Q, the mutation responsible for familial defective apolipoprotein B-100, which was also strongly associated with LDL-C in the replication sample (P < 10(-36)). The R3500Q carrier frequency, previously reported to be 0.1% to 0.4% in white European individuals, was 12% in the combined sample of 1504 Amish participants, consistent with a founder effect. The mutation was also strongly associated with CAC in both samples (P < 10(-6) in both) and accounted for 26% and 7% of the variation in LDL-C levels and CAC, respectively. Compared with noncarriers, R3500Q carriers on average had LDL-C levels 58 mg/dL higher, a 4.41-fold higher odds (95% confidence interval, 2.69-7.21) of having detectable CAC, and a 9.28-fold higher odds (2.93-29.35) of having extensive CAC (CAC score ≥400). The R3500Q mutation in APOB is a major determinant of LDL-C levels and CAC in the Amish.

A new method for measurement of total plasma PCSK9: clinical applications

The proprotein convertase subtilisin kexin-9 (PCSK9) circulates in plasma as mature and furin-cleaved forms. A polyclonal antibody against human PCSK9 was used to develop an ELISA that measures total plasma PCSK9 rather than only the mature form. A cross-sectional study evaluated plasma levels in normal (n = 254) and hypercholesterolemic (n = 200) subjects treated or untreated with statins or statin plus ezetimibe. In controls, mean plasma PCSK9 (89.5 +/- 31.9 ng/ml) correlated positively with age, total cholesterol, LDL-cholesterol (LDL-C), triglycerides, and fasting glucose. Sequencing PCSK9 from individuals at the extremes of the normal PCSK9 distribution identified a new loss-of-function R434W variant associated with lower levels of circulating PCSK9 and LDL-C. In hypercholesterolemic subjects, PCSK9 levels were higher than in controls (99.3 +/- 31.7 ng/ml, P < 0.04) and increased in proportion to the statin dose, combined or not with ezetimibe. In treated patients (n = 139), those with familial hypercholesterolemia (FH; due to LDL receptor gene mutations) had higher PCSK9 values than non-FH (147.01 +/- 42.5 vs. 127.2 +/- 40.8 ng/ml, P < 0.005), but LDL-C reduction correlated positively with achieved plasma PCSK9 levels to a similar extent in both subsets (r = 0.316, P < 0.02 in FH and r = 0.275, P < 0.009 in non-FH). The detection of circulating PCSK9 in both FH and non-FH subjects means that this assay could be used to monitor response to therapy in a wide range of patients.

Abstract: P847 THE PREVALENCE OF APOLIPOPROTEIN B-100 GENE MUTATIONS IN RUSSIAN FAMILIAL HYPERCHOLESTEROLEMIA PATIENTS

Familial hypercholesterolemia (FH) and familial defective apolipoprotein B-100 (FDB) are relatively common lipid disorders caused by mutations in the low-density lipoprotein receptor (LDLR) and apolipoprotein B (apo B) genes, respectively. Molecular analysis at these loci was performed in eight New Zealand subjects with clinical features of heterozygous FH. Utilization of an in vitro lymphocyte receptor assay demonstrated normal receptor function in four patients, three of whom screened positive for the founder-type apo B mutation, R3500Q, causing FDB. Four patients with reduced LDLR function, consistent with heterozygous FH, revealed three previously documented mutations in exons 3 (W66X), 6 (C292Y) and 7 (G322S) of the LDLR gene and, a novel 2-bp deletion (TC or CT) after nucleotide 1204 (or 1205) in exon 9. The remaining patient was found to be FH/FDB negative after extensive mutation screening using both denaturing gradient gel electrophoresis and heteroduplex-single strand conformation polymorphism analysis. Haplotype analysis at the LDLR and apo B loci finally excluded the likelihood that mutations in these two genes underlie the FH phenotype in the molecularly uncharacterized New Zealand family originating from the United Kingdom. This family represents a valuable source of material for future genetic dissection of autosomal dominant hypercholesterolemia (ADH), shown to be a heterogeneous disease through molecular analysis.

Oft unterschätzte Probleme in der Lipidologie: Verspätung in der Diagnose und Tachyphylaxie in der Therapie

Summary Frequently underestimated problems in lipidology: late diagnosis and tachyphylaxis in treatment ( We report the case of a 44-year-old patient with severe hypercholesterol- aemia, referred to our outpatient clinic . On the basis of the clinical findings we performed a molecular genetic analysis which confirmed the suggested point mutation at amino acid position 3,500 (R3,500Q) in the gene encoding apolipo- protein B-100. The diagnosis of familial defective apolipoprotein B-100 (FDB) was thus molecularly proven. Unfortunately, at the time of diagnosis, a hitherto unknown three-vessel coronary artery disease was already present. ( In addition, this case confronted us with the problem of a potential tachyphy- laxis phenomenon when using atorvastatin. Replacing atorvastatin by rosu- vastatin resulted in a marked and persistent subsequent reduction of the total and LDL-cholesterol concentrations lasting for 40 months at least. ( The frequent problems of late diagnosis in patients with familial forms of hypercholesterolaemia and an insufficient long-term treatment are discussed.

LDLR and ApoB are Major Genetic Causes of Autosomal Dominant Hypercholesterolemia in a Taiwanese Population

Autosomal dominant hypercholesterolemia (ADH) is an autosomal dominant inherited disease characterized by an increase in low-density lipoprotein cholesterol levels and premature coronary heart disease, which can be caused by mutations in genes encoding the low-density lipoprotein receptor (LDLR), apolipoprotein B (APOB) and proprotein convertase subtilisin/kexin type 9 (PCSK9). There is scant information with regard to the role played by each gene in the Taiwanese ADH population, especially the newly discovered PCSK9 gene. We used coupling heteroduplex analysis based on a denaturing high performance liquid chromatography system and DNA sequencing to screen for the LDLR gene, APOB gene and PCSK9 gene in 87 ADH cases recruited from 30 unrelated Taiwanese families. We did not find any mutation-causing variant of the PCSK9 gene in our cases and thus excluded PCSK9 as the major culprit mutation in these families. On the other hand, we identified six previously reported LDLR gene mutations (C107Y, D69N, R385W, W462X, G170X, V408M), two novel LDLR gene mutations (FsG631 and splice junction mutation of intron 10), and one known mutation (R3500W) and one novel missense mutation (T3540M) in the APOB gene that were present in 55 members from 18 ADH families (60%). R3500W, rather than R3500Q, could be the principle mutation responsible for familial defective apolipoprotein B in Taiwanese. The results of our study reveal a characteristic mutation pattern of ADH in Taiwan, mainly in the LDLR and APOB genes. However, PCSK9 gene mutation may not be a major cause of ADH in our study population.

Familial defective apolipoprotein B-100 in Slovakia: Are differences in prevalence of familial defective apolipoprotein B-100 explained by ethnicity?

The objective of this study was to examine frequency of familial defective apo-B-100 (FDB, R3500Q mutation) in probands with the phenotype of familial hypercholesterolemia (FH) and in the general population of 40-year-old subjects in Slovakia and to characterize their lipid and clinical criteria and to compare the frequency of FDB with other populations. We identified 35 patients with FDB among 362 probands with clinical diagnosis of FH and two cases of FDB in the 40-year-old cohort of 2323 subjects from general Slovak population. Probands with FDB differed from those with FH only in plasma triglyceride concentrations (1.84 ± 1.4 mmol/l versus 1.45 ± 0.98 mmol/l, respectively, p < 0.01). Evaluation of personal history of premature atherosclerosis did not show any differences (11.4% in FDB versus 20% in FH, p < 0.16). The FDB patients had similar manifestation of xanthomatosis as the FH patients (17.1% versus 8.25%, p < 0.25). The frequency of FDB of 9.7% found in the FH patients is among the highest of those reported to date. The frequency of R3500Q mutation of 0.09% found in Slovak 40-year-old subjects did not differ significantly from published population molecular data. Our comparison of estimated FDB frequencies with those which were found by DNA analysis demonstrated that estimated frequencies were not only wider in range, but also significantly higher than those which were assessed by the analysis. The definitive answer to the prevalence of FDB and its biochemical and clinical characteristics requires screening of unbiased samples of the general population from different ethnic groups based on molecular genetic methods.

Genetic Heterogeneity of Autosomal Dominant Hypercholesterolemia in Mexico

Familial hypercholesterolemia (FH) and familial defective apolipoprotein B-100 (FDB) are relatively common lipid disorders caused by mutations of the low-density lipoprotein receptor (LDLR) and apolipoprotein B (apoB) genes, respectively. A third locus on chromosome 1p34.1-p32 was recently linked to FH and the responsible gene has been identified [protein convertase subtilisin/kexin type 9 (PCSK9)]. We assessed the contribution of the LDLR, apoB, and PCSK9 genes as cause of FH in Mexico. Forty six unrelated probands, as well as 68 affected and 60 healthy relatives, were included. All index cases were diagnosed as having heterozygous autosomal dominant FH. Seventeen of the 46 index cases had LDLR gene mutations, four of which were novel (Fs92ter108, C268R, Q718X, and Fs736ter743); and only one patient had an apoB mutation (R3500Q). We sequenced the PCSK9 gene in the remainder of the 28 probands with no identified LDLR or APOB gene defects; however, no PCSK9 mutations were found, including one large kindred with positive linkage to the 1p34.1-32 locus (multipoint LOD score of 3.3) and two small pedigrees. Linkage was excluded from these three loci in at least four kindreds suggesting that other yet uncharacterized genes are involved. Our results underline substantial genetic heterogeneity for FH in the Mexican population.

T07-P-004 Phenotype comparison in children with familial defective apolipoprotein B and familial hypercholesterolemia

T07-P-004 Phenotype comparison in children with familial defective apolipoprotein B and familial hypercholesterolemia

Current management of severe homozygous hypercholesterolaemias.

This review focuses on recent advances in the management of patients with homozygous familial hypercholesterolaemia, autosomal recessive hypercholesterolaemia and familial defective apolipoprotein B. Autosomal recessive hypercholesterolaemia has been described as a 'phenocopy' of homozygous familial hypercholesterolaemia. Although the clinical phenotypes are similar, autosomal recessive hypercholesterolaemia seems to be less severe, more variable within a single family, and more responsive to lipid-lowering drug therapy. The cardiovascular complications of premature atherosclerosis are delayed in some individuals and involvement of the aortic root and valve is less common than in homozygous familial hypercholesterolaemia. Apheresis is still the treatment of choice in homozygous familial hypercholesterolaemia and in autosomal recessive hypercholesterolaemia patients in whom maximal drug therapy does not achieve adequate control. In addition to the profound cholesterol-lowering effects of apheresis, other potentially beneficial phenomena have been documented: improved vascular endothelial function and haemorheology, reduction in lipoprotein (a) and procoagulatory status, and a decrease in adhesion molecules and C-reactive protein. Patients with severe homozygous hypercholesterolaemia illustrate the natural history of atherosclerosis within a condensed timeframe. Effective cholesterol-lowering treatment started in early childhood is essential to prevent onset of life-threatening atherosclerotic involvement of the aortic root and valve, and the coronary arteries. Noninvasive methods for regular monitoring of the major sites involved in the atherosclerotic process are necessary in patients with no symptoms or signs of ischaemia. Management of patients with severe homozygous hypercholesterolaemia continues to be a major challenge.