For Familial Hypercholesterolemia Patients Research Articles

Abstract 16434: 104-Week Safety and Effectiveness of Low-Density Lipoprotein Cholesterol-Lowering Therapy With Evolocumab in Patients With Familial Hypercholesterolemia/Hypercholesterolemia in Japan: Results of Post-Marketing Surveillance

Introduction: Evolocumab is the first monoclonal antibody against proprotein convertase subtilisin/kexin type 9 approved in Japan for familial hypercholesterolemia (FH) and hypercholesterolemia (HC). Aims: This study assessed the 104-week safety and effectiveness of low-density lipoprotein cholesterol (LDL-C)-lowering therapy with evolocumab in patients with FH (homo/heterozygous) and HC in a real-world setting in Japan. Methods: Overall, 3721 and 2792 patients (108 and 91 homozygous FH, 2007 and 1613 heterozygous FH, 1606 and 1088 HC) from 668 clinical sites comprised the safety and effectiveness analysis sets, respectively. Primary safety endpoints: incidence (%) and number of patients with adverse drug reactions and serious adverse events. Effectiveness endpoints: % change in LDL-C from baseline at Week 12 (n=2386, primary endpoint) and Weeks 4-104 (secondary endpoint). Results: Mean age: 63.2 years; female: 33.8%. The mean±SD follow-up duration was 545.5±218.8 days. Adverse drug reaction subject incidence was 5.2%. Serious adverse event subject incidence was 8.9% (330/3721). The adverse event incidences of myocardial infarction and stroke were 0.6% (n=23/3721) and 0.6% (n=21/3721; 0.3% ischemic stroke [n=12]/0.2% hemorrhagic stroke [n=9]), respectively. Table 1 shows adverse events by lowest achieved LDL-C levels. The mean±SD % change in LDL-C from baseline to Weeks 12 and 104 were –45.7%±28.2% (n=84) and –50.9±21.1% (n=48) in homozygous FH patients ( P <0.001 vs baseline; two-sided paired t -test), –56.0%±28.9% (n=1440) and –54.5±28.3% (n=905) in heterozygous FH patients ( P <0.001), and –63.3%±23.7% (n=862) and –60.8±28.1% (n=352) in HC patients ( P <0.001), respectively. Conclusions: There were no trends between the lowest achieved LDL-C levels and adverse events in Japanese patients. Evolocumab was well tolerated and sustained LDL-C reduction in patients with FH and HC in a real-world clinical setting in Japan.

Referral rate, profile and degree of control of patients with familial hypercholesterolemia: data from a single lipid unit from a Mediterranean area

BackgroundThe challenging rigorous management of hypercholesterolemia promotes referral to specialized units. This study explored the need, based on referral rate and cardiovascular (CV) risk factor control in patients evaluated for familial hypercholesterolemia (FH), for a lipid unit (LU).MethodsOver a four-year period, 340 referrals to our unit were analyzed to establish the lipid disorder referral rate. Moreover, 118 patients referred for potential FH during the period 2010–2018 (52.4 ± 13.9 years, 47.5% male, Caucasian, 26.3% obese, 33.1% smokers and 51.7% with some glycaemic alteration) were investigated. The Dutch Lipid Clinic Network (DLCN) score, type and dose of lipid-lowering drugs, lipid profile including lipoprotein (a) (Lp(a)) and the presence of plaques with carotid ultrasound (CU) were recorded.ResultsLipids represented 6.2% of referrals (38 patient-years) requiring a 2–3 h weekly monographic outpatient consultation. The potential FH sample displayed a DLCN score ≥ 6 in 78% and modifiable CV risk factors in 51%. Only 22% achieved tight disease control despite intensive treatment. The statin-ezetimibe combination treatment group achieved better goals (73.0% vs. 45.5%, P = 0.003), and the rosuvastatin group had a higher proportion of prediabetes (60.9% vs. 39.1%, P = 0.037). Neither CU plaque presence nor Lp(a) > 50 mg/dL was linked with established CV disease patients, but higher Lp(a) concentrations were detected between them (102.5 (26.3–145.8) vs. 25.0 (13.0–52.0) mg/dL, P = 0.012).ConclusionsThe referral rate, degree of control, and proportion of modifiable CV risk factors in FH patients demonstrate the need for LU in our area as well as optimize control and treatment.

Preliminary results from REALITY: a nation-wide study of a database with 1.8 million real-life patients to study atherosclerotic cardiovascular disease and familial hypercholesterolemia in Spain

Abstract Introduction Ischemic heart disease and stroke are the leading causes of premature death worldwide. Atherosclerotic cardiovascular disease (ASCVD) is the main determining factor for these and other life-threatening pathologies, such as peripheral artery disease (PAD). LDL-lowering therapies are the gold standard to prevent ASCVD. These treatments are also used for familial hypercholesterolemia (FH), a genetic disorder manifesting with high LDL levels. It is crucial to evaluate the management and level of LDL control in “real-life” patients with ASCVD and FH, but so far very few large-scale studies have focussed on these issues. REALITY is an observational retrospective study of ASCVD and FH in Spain. Purpose The goals of REALITY included the analysis of the demographic and clinical characteristics, comorbidities, and concomitant medication of patients with ASCVD and/or FH by a multidisciplinary group of experts. The lipid-lowering therapies used in Spain were assessed, and patient LDL levels were evaluated according to treatment intensity during the two-year follow-up period. Methods Electronic medical records were retrieved from the BIG-PAC® database that includes anonymized data of patients from seven health areas in Spain. The study population included patients presenting a new or recurrent episode of ASCVD (n=26,976) or a new diagnosis of FH (n=572) during the recruitment period (from 01/01/2017 to 31/12/2018). The index date was defined as the date of the event/diagnosis, and a 2-year follow-up was established. Results The average age was 69.9±11.5 for ASCVD patients and 60.1±12 for FH patients (59.4% and 48.6% males, respectively). The average Charlson index was 2.2±1.6 in ASCVD and 1.2±1.4 in FH. The comorbidities most frequently observed in ASCVD vs. FH were hypercholesterolaemia (55% vs. 100%), arterial hypertension (65% vs. 54%), diabetes mellitus (31% vs. 29%) and obesity (31% vs. 21%). Around 25% and 6% of patients with ASCVD and FH, respectively, presented CV events in the follow-up. During the 24-month period, the highest rate of ischemic heart disease was observed in patients with LDL levels of 55–69 mg/dL, whereas LDL levels below 55 mg/dL were associated with the highest incidence of PAD. The highest lipid biochemical reductions in ASCVD vs. FH were observed in total cholesterol (−52±17.4 vs. −53.5±21.3 mg/dL), triglycerides (−53±7.9 vs. −54.2±8.8 mg/dL) and LDL (−27.4±10.4 vs. −29±12.3 mg/dL). HDL levels showed an average increase of 8.5±2 vs. 9.3±2.5 mg/dL. Treatment intensity correlated with reduction of LDL levels in all ASCVD disease subgroups and FH patients (Table 1). Conclusions The results of REALITY provide an estimated clinical picture of ASCVD and FH in Spain. The impact of therapeutical approaches on LDL levels and the prevention of CV events were evaluated by a multidisciplinary group of experts. The findings of the study will help lower the burden of ASCVD and FH in Spain. Funding Acknowledgement Type of funding sources: Private company. Main funding source(s): REALITY study was sponsored by Novartis. Statistical analysis of the BIG-PAC® database was performed by Atrys Health. Medical writing and editing were provided by Medical Science Consulting. All funded by Novartis.

Genetic Variant ABCC1 rs45511401 Is Associated with Increased Response to Statins in Patients with Familial Hypercholesterolemia.

Statins are the first-line treatment for familial hypercholesterolemia (FH), but response is highly variable due to genetic and nongenetic factors. Here, we explored the association between response and genetic variability in 114 Brazilian adult FH patients. Specifically, a panel of 84 genes was analyzed by exon-targeted gene sequencing (ETGS), and the functional impact of variants in pharmacokinetic (PK) genes was assessed using an array of functionality prediction methods. Low-density lipoprotein cholesterol (LDL-c) response to statins (reduction ≥ 50%) and statin-related adverse event (SRAE) risk were assessed in carriers of deleterious variants in PK-related genes using multivariate linear regression analyses. Fifty-eight (50.8%) FH patients responded to statins, and 24 (21.0%) had SRAE. Results of the multivariate regression analysis revealed that ABCC1 rs45511401 significantly increased LDL-c reduction after statin treatment (p < 0.05). In silico analysis of the amino-acid change using molecular docking showed that ABCC1 rs45511401 possibly impairs statin efflux. Deleterious variants in PK genes were not associated with an increased risk of SRAE. In conclusion, the deleterious variant ABCC1 rs45511401 enhanced LDL-c response in Brazilian FH patients. As such, this variant might be a promising candidate for the individualization of statin therapy.

Agreement between the various familial hypercholesterolaemia diagnostic criteria in Malaysian population

Background and Aims: Aim: Diagnostic tools for familial hypercholesterolemia (FH), including the Dutch Lipid Clinic Criteria (DLCC), British Simon Broome (SB) and the US Make Early Diagnosis to Prevent Early Deaths (US MEDPED) criteria, are used to identify FH patients. However, their diagnostic outcomes may not be in agreement with each other. Furthermore, the agreement between those criteria is unclear in the Asian population. This study aimed to investigate the agreement between these criteria in an Asian population.

Successful Genetic Screening and Creating Awareness of Familial Hypercholesterolemia and Other Heritable Dyslipidemias in the Netherlands.

The genetic screening program for familial hypercholesterolemia (FH) in the Netherlands, which was embraced by the Dutch Ministry of Health from 1994 to 2014, has led to twenty years of identification of at least 1500 FH cases per year. Although funding by the government was terminated in 2014, the approach had proven its effectiveness and had built the foundation for the development of more sophisticated diagnostic tools, clinical collaborations, and new molecular-based treatments for FH patients. As such, the community was driven to continue the program, insurance companies were convinced to collaborate, and multiple approaches were launched to find new index cases with FH. Additionally, the screening was extended, now also including other heritable dyslipidemias. For this purpose, a diagnostic next-generation sequencing (NGS) panel was developed, which not only comprised the culprit LDLR, APOB, and PCSK9 genes, but also 24 other genes that are causally associated with genetic dyslipidemias. Moreover, the NGS technique enabled further optimization by including pharmacogenomic genes in the panel. Using such a panel, more patients that are prone to cardiovascular diseases are being identified nowadays and receive more personalized treatment. Moreover, the NGS output teaches us more and more about the dyslipidemic landscape that is less straightforward than we originally thought. Still, continuous progress is being made that underlines the strength of genetics in dyslipidemia, such as discovery of alternative genomic pathogenic mechanisms of disease development and polygenic contribution.

Pharmacogenomics of statins and familial hypercholesterolemia.

To collect evidence on statin pharmacogenomics, and review what is known in this field for familial hypercholesterolemia (FH) patients. There are well-known associations between specific single nucleotide polymorphisms involved in statin transport and metabolism and either adverse effects or altered lipid-lowering efficacy. However, the applicability of this knowledge is uncertain, especially in high-risk populations. There are alternative approaches to study plasma concentrations of statins and new insights on why some association studies fail to be replicated. Statin therapy recommendations are not always followed in primary and secondary prevention and, even when followed, patients often fail to reach therapeutic target values. Considering the stringent 2019 European Atherosclerosis Society and European Society of Cardiology recommended target lipid levels, as well as the persistently high cost for alternative lipid-lowering therapies such as PCSK9 inhibitors, the variability in low-density lipoprotein cholesterol reductions on statin therapy is still an important factor that needs to be addressed to ensure better cardiovascular disease risk management, especially for FH patients, who have not been well studied historically in this context.

Effect of Lipoprotein(a) on the Diagnosis of Familial Hypercholesterolemia: Does It Make a Difference in the Clinic?

Diagnostic tools for familial hypercholesterolemia (FH) rely on estimation of LDL cholesterol concentration. However, routine measurement or calculation of LDL cholesterol concentration using the Friedewald equation contains a cholesterol contribution from lipoprotein(a) [Lp(a)]. We investigated whether Lp(a) influences the phenotypic diagnosis of FH by commonly used clinical criteria. A cohort of 907 adult index patients attending a clinic were studied. The Dutch Lipid Clinic Network (DLCN) and Simon Broome (SB) diagnostic criteria were estimated before and after adjusting LDL cholesterol concentration for the cholesterol content (30%) of Lp(a). Diagnostic reclassification rates and area under the ROC (AUROC) curves in predicting an FH mutation were also compared. Seventy-four patients defined by DLCN criteria (8.2%) and 207 patients defined by SB criteria (22.8%) were reclassified to "unlikely" FH after adjusting LDL cholesterol for Lp(a) cholesterol. The proportion of FH patients defined by DLCN (probable/definite) and SB (possible/definite) criteria decreased significantly in patients with increased Lp(a) (>0.5 g/L; n = 330) after Lp(a) cholesterol adjustment (P < 0.01). The overall reclassification rate was significantly higher in patients with Lp(a) concentration >1.0 g/L (P < 0.001). The AUROC curve for LDL cholesterol concentration ≥191 mg/dL (≥5.0 mmol/L), DLCN criteria, and SB criteria in predicting an FH mutation increased significantly after adjustment (P < 0.001). There was no significant difference in AUROC curve before and after Lp(a) cholesterol adjustment at an LDL cholesterol concentration ≥251 mg/dL (≥6.5 mmol/L). Adjusting LDL cholesterol concentration for Lp(a) cholesterol improves the diagnostic accuracy of DLCN and SB criteria, especially with Lp(a) >1.0 g/L and LDL cholesterol <251 mg/dL (<6.5 mmol/L). Lp(a) should be measured in all patients suspected of having FH.

Drugs that Mimic the Effect of Gene Mutations for the Prevention or the Treatment of Atherosclerotic Disease: From PCSK9 Inhibition to ANGPTL3 Inactivation.

Drugs mimicking natural beneficial mutations, including that for familial hypercholesterolemia (FH), might represent the future of hypolipidemic drug treatment. The aim of this review is to review the properties and the effects of these drugs, which are either already commercially available or are in the process to be approved for the treatment of dyslipidemia. More than a decade ago, it was accidentally discovered that proprotein convertase subtilisin/kexin type 9 (PCSK9) loss-of-function mutations resulted in marked lifelong reduction of LDL-C and the incidence of cardiovascular disease (CVD). This provided the idea for a human anti-PCSK9 antibody. Along with dozens of phase II and III studies demonstrating unprecedented reductions in LDL-C levels, two large clinical trials established the substantial benefits of evolocumab and alirocumab on cardiovascular morbidity and mortality, on top of standard treatment. Evolocumab and alirocumab are now approved and used in clinical practice for the treatment of FH, statin intolerance, and high risk patients not achieving LDL-C targets. Anti RNA, small molecules, peptides and also protein fragments against PCSK9 are in phase 1 trials. Angiopoietin-like protein 3 (ANGPTL3) regulates lipid metabolism increasing triglycerides (TGs), remnants, and LDL-C. In a huge study, ANGPTL3 deficiency due to gene(s) loss-of-function was associated with substantial reductions in circulating TGs, LDL-C, and CVD. Evinacumab, an ANGPTL3 antibody, caused a dose-dependent reduction in fasting TG levels of up to 76% and LDL-C of up to 23% and CVD risk by 41%. There is also antisense oligonucleotide and micro-RNA- 27b (miR-27b) against ANGPTL3. Two naturally occurring mutations in apo3 gene, A23T and K58E, reduce TGs and CVD risk. A monoclonal antibody targeting apoC-III has the same effect. Mimicking the beneficial naturally happening mutations in lipid metabolism pathways with biological drugs is probably the future of hypolipidemic drug treatment.

The impact of LDLR function on fibroblast growth factor 21 levels.

Fibroblast growth factor 21 (FGF21) has been described to have beneficial effects on glucose and lipid metabolism, and FGF21 analogs are currently evaluated in phase 1 trials. However, the complete spectrum of effects and regulators of FGF21 is yet partly elucidated. Recent studies have shown that FGF21 plays a role in transmembrane cholesterol transport. We set out to examine the association between FGF21 and LDLR mediated transmembrane cholesterol transport, by comparing FGF21 levels in patients with genetically impaired LDLR function and unaffected relatives. Secondly, we explored whether the severity of the LDLR mutation was associated with FGF21 levels. We performed a cross-sectional study in carriers of an LDLR mutation and their unaffected relatives. Subjects were eligible if they participated in the Dutch national screening program for familial hypercholesterolemia (FH), were 18-55 years old, and were carrier of a pathogenic LDLR mutation with an untreated LDL-C level below the 75(th) or above the 90(th) percentile of the general population, or did not carry an FH mutation. The outcome measure was the level of FGF21, which was assessed using ELISA. We included 224 carriers of an LDLR mutation and 148 unaffected relatives. FGF21 levels were lower in LDLR mutation carriers compared to unaffected relatives (median [interquartile range]: 96.92 [60.80-174.05] versus 136.98 [77.34-219.47] pg/mL, respectively; p=0.08), but after adjusting for potential confounders, there was no association between LDLR mutations and FGF21 levels (p=0.70). Neither, did we find a relationship between the severity of LDLR mutations and FGF21 levels (p=0.51, after adjustment for potential confounders). We showed that levels of FGF21 are not different in patients with and without LDLR mutations, which suggests that decreased LDLR expression does not have a negative effect on FGF21 levels. Given the potential beneficial effects of FGF21 analogs on lipids and lipoproteins in a phase 1 study, we deem this of great interest for future treatment options for FH patients.

EFFECT OF LDL-APHERESIS ON HDL-C FUNCTIONALITY

The Lipoprotein-apheresis (LA) devices used in North America for Familial Hypercholesterolemia (FH) reduce LDL-C (− 80%) by binding positive charged apolipoprotein B (apoB) to a negative charged environment. FH patients also have low HDL-C levels, and despite their negative charge, HDL-C is

Discriminative Ability of LDL-Cholesterol to Identify Patients With Familial Hypercholesterolemia

Background— Screening for familial hypercholesterolemia (FH) within affected families is often based on cutoff values for low-density lipoprotein cholesterol (LDL-C). However, the diagnostic accuracy of LDL-C levels is influenced by the magnitude of the LDL-C overlap between FH patients and unaffected relatives. The purpose of the current study was to assess to what extent this overlap is influenced by the severity of specific FH mutations. Methods and Results— Individuals were eligible if they underwent family screening for FH between 2003 and 2010. The entire cohort was then compared with those who were investigated for the presence of the most severe mutations (class 1). The area under the receiver operating characteristics curve and the sensitivity of the 90th percentile of LDL-C were calculated for both cohorts. We included 26 406 individuals, of whom 9169 (35%) carried an FH-causing mutation. In the entire cohort at baseline, mean LDL-C was 4.63±1.44 mmol/L for FH carriers (n=5372) and 2.96±0.96 mmol/L for unaffected relatives (n=15 148); P &lt;0.001. The corresponding operating characteristics curve (95% CI) was 86.6% (85.9%–87.2%), and the cutoff level of LDL-C above the 90th percentile showed a sensitivity of 68.5%. The operating characteristics curve and sensitivity significantly improved when the 5933 individuals tested for class 1 mutations were assessed separately; 96.2% (95.3%–97.1%) and 91.3%, respectively. Conclusions— In summary, the overlap in terms of LDL-C levels between those with molecularly proven FH and unaffected relatives is to a large extent because of the high prevalence of modestly severe LDL-receptor mutations in the Netherlands.

5-Lipoxygenase activating protein (ALOX5AP) gene variants associate with the presence of xanthomas in familial hypercholesterolemia

BackgroundTendon xanthomas are characteristic for familial hypercholesterolemia (FH), and are associated with a higher risk of coronary heart disease (CHD). They often present with local inflammation. Inflammation may therefore be involved in their pathogenesis, as it is in the pathogenesis of CHD. A key role in the inflammatory pathway is played by the 5-lipoxygenase activating protein (ALOX5AP), which is known to influence the risk of CHD in FH. To test our hypothesis that ALOX5AP contributes to the development of xanthomas, we studied whether variants in the ALOX5AP gene influence the risk of xanthomas. MethodsWe examined 945 patients with genetically confirmed heterozygous FH to determine whether they had tendon xanthomas. We genotyped seven polymorphisms in the ALOX5AP gene and constructed haplotypes of these polymorphisms. ResultsThe A allele of the rs9551963 polymorphism was associated with an increased risk of xanthomas (OR 1.52, 95% CI 1.11–2.07, p=0.01), while the A allele of rs17222842 was protective (OR 0.62, 95% CI 0.43–0.90, p=0.01). These two polymorphisms fully explained the risk estimates of all haplotypes. Individual haplotypes, however, were not significantly associated with xanthomas. ConclusionVariants in the ALOX5AP gene are associated with the presence of xanthomas in FH patients. This result supports our hypothesis that inflammation is a pathogenetic factor of xanthomas.

Update of the molecular basis of familial hypercholesterolemia in The Netherlands

Autosomal-dominant hypercholesterolemia (ADH) has been identified as a major risk factor for coronary vascular disease (CVD) and is associated with mutations in the low-density lipoprotein receptor (LDLR) and the apolipoprotein B (APOB) gene. Since 1991 DNA samples from clinically diagnosed ADH patients have been routinely analyzed for the presence of LDLR and APOB gene mutations. As of 2001, 1,641 index patients (164 index patients per year) had been identified, while from 2001 onward a more sensitive, high-throughput system was used, resulting in the identification of 1,177 new index patients (average=294 index patients per year). Of these 1,177 index cases, 131 different causative genetic variants in the LDLR gene and six different causative mutations in the APOB gene were new for the Dutch population. Of these 131 mutations, 83 LDLR and four APOB gene mutations had not been reported before. The inclusion of all 2,818 index cases into the national screening program for familial hypercholesterolemia (FH) resulted in the identification of 7,079 relatives who carried a mutation that causes ADH. Screening of the LDLR and APOB genes in clinically diagnosed FH patients resulted in approximately 77% of the patients being identified as carriers of a causative mutation. The population of patients with ADH was divided into three genetically distinct groups: carriers of an LDLR mutation (FH), carriers of an APOB mutation (FDB), and non-LDLR/non-APOB patients (FH3). No differences were found with regard to untreated cholesterol levels, response to therapy, and onset of CVD. However, all groups were at an increased risk for CVD. Therefore, to ultimately identify all individuals with ADH, the identification of new genes and mutations in the genes that cause ADH is of crucial importance for the ongoing national program to identify patients with ADH by genetic cascade screening.

The molecular basis of familial hypercholesterolemia in The Netherlands.

Mutations in the low-density lipoprotein (LDL) receptor gene are responsible for familial hypercholesterolemia (FH). At present, more than 600 mutations in this gene are known to underlie FH. However, the array of mutations varies considerably in different populations. Therefore, the delineation of essentially all LDL-receptor gene mutations in a population is a prerequisite for the implementation of nation-wide genetic testing for FH. In the Netherlands, mutation analysis by denaturing gradient gel electrophoresis and sequencing in 1641 clinically diagnosed FH patients resulted in the characterization of 159 different LDL-receptor gene defects. The nine most common mutations were responsible for 66.5% of our FH index cases. Of these, four mutations occurred with relatively high frequencies in specific parts of the Netherlands. The remaining mutations were only encountered in single FH patients, comprising 22.2% of the patient cohort analyzed. Subsequent genetic testing of relatives of the index cases within the national FH screening program resulted in the identification of 5,531 FH patients in total. The analysis for LDL-receptor mutations is a continuing effort to update the LDL-receptor mutation catalogue. Subsequently, with the newly generated index cases, the screening program can be extended and continued to identify and treat FH patients as early as possible and reduce cardiovascular morbidity and mortality in these patients at high risk.

A suggestion for familial hypercholesterolemia (FH) heterozygosity clinical diagnosis based on epidemiological observations in a large Italian population

We selected 247 subjects from 29 large familial hypercholesterolemia (FH) kindreds from 550 probable FH subjects in Emilia Romagna (Italy) on the basis of LDL-cholesterol plasmatic levels and family trees, in order to define the best diagnostic criteria for heterozygous patients. Familial hypercholesterolemia is a monogenic disease of cholesterol metabolism inherited as an autosomal dominant trait and characterised by early cardiovascular disease. A low xanthomas and xanthelasmas prevalence was found (8.6%); coronary heart disease (CHD) death occurs very frequently in heterozygous males (72% of all deaths; mean age at death 52 years), while in females the primary cause of death was thrombotic stroke (55%; mean age 69 years). Total cholesterol (TC) mean values were 389.8 (m) and 373.3 mg/dl (f) for FH trait carriers, and 223.3 (m) and 228.8 (f) for healthy relatives. No age-related change in TC was found in heterozygotes, while unaffected relatives of FH families showed mean TC and LDL-C values, and a TC frequency distribution and a TC age-related increasing trend similar to the expected values for the Italian population. The TC frequency distribution curve appeared bimodal, with a mid-point between heterozygous and homozygous FH modal values of 280 mg/dl. To identify the FH patients, the final FH heterozygosity risk was evaluated in an unselected free-living population (from 0.07 to 0.8%, respectively, for TC between 265–274 and 295–304 mg/dl) and in hypercholesterolemic families (31 to 83%, and the same TC classes). Our conclusion is that the clinical picture is rarely pathognomonic, while the FH heterozygosity final risk evaluation and the 280 mg/dl cut-off point can be used to guide the practical clinical diagnosis and to select the patients destined for B-E receptor activity evaluation.

Molecular genetic testing for familial hypercholesterolemia: spectrum of LDL receptor gene mutations in The Netherlands.

Mutations in the LDL receptor are responsible for familial hypercholesterolemia (FH). At present, more than 600 mutations of the LDL receptor gene are known to underlie FH. However, the array of mutations varies considerably in different populations. Therefore, the delineation of essentially all LDL receptor gene mutations in a population represents a prerequisite for the implementation of nation-wide genetic testing for FH. In this study, the frequency and geographical distribution of 13 known mutations were evaluated in a cohort of 1223 FH patients. We identified 358 mutation carriers, representing 29% of the FH cohort. Four mutations (N543H-2393de19, 1359--1G-->A, 313 + 1 G-->A and W23X) occurred with a relatively high frequency, accounting for 22.4% of the entire study cohort. Two of these common FH mutations (N543H-2393de19 and 1359 - 1G-->A) showed a preferential geographic distribution. Second, to further expand the array of LDL receptor gene mutations, we conducted mutation analysis by denaturing gradient gel electrophoresis (DGGE) in 141 children with definite FH. A mutation was identified in 111 patients, involving 16 new single base substitutions and four small deletions and insertions, which brings the number of different FH-causing mutations in our country up to 61. Our data indicate that an estimate of the prevalence of specific mutations, as well as the compilation of a database of all FH-causing mutations in a given country, can facilitate selection of the most appropriate molecular diagnostic approach.

Low density lipoprotein receptor mutations in a selected population of individuals with moderate hypercholesterolemia

To evaluate mutations in the low density lipoprotein receptor (LDL-R) gene in moderate primary hypercholesterolemia, a combination of polymerase chain reaction (PCR), single-strand conformation polymorphism (SSCP) and direct sequencing, was used to screen the LDL-R gene in a selected population of 82 unrelated individuals with moderate elevation of plasma LDL-C [mean 4.55±0.55 mmol/l (176.4±21.6 mg/dl)]. Four subjects (5%) were found to be heterozygotes for missense mutations in the LDL-R gene. These mutations were located in four different exons (exons 6, 7 15 and 17) and all alters highly conserved residues of LDL-R protein. None of these mutations were detected in 79 normocholesterolemic individuals. The mutation in exon 15 (T705I) was previously reported in a compound heterozygote for familial hypercholesterolemia (FH). In the proband carrying the mutation in exon 17 (R793Q), an in vivo LDL turnover study was performed and it demonstrated a reduction of LDL catabolism. These findings demonstrate that mutations in the LDL-R may occur in primary moderate hypercholesterolemia. They also extend the concept that some FH patients may present with a mild phenotype.

Two partial deletion mutations involving the same Alu sequence within intron 8 of the LDL receptor gene in Korean patients with familial hypercholesterolemia.

Twenty-eight unrelated persons heterozygous for familial hypercholesterolemia (FH) were screened to assess the frequency and nature of major structural rearrangements at the low-density lipoprotein (LDL) receptor gene in Korean FH patients. Genomic DNA was analyzed by Southern blot hybridization with probes encompassing exons 1-18 of the LDL receptor gene. Two different deletion mutations (FH29 and FH110) were detected in three FH patients (10.7%). Each of the mutations was characterized by the use of exon-specific probes and detailed restriction mapping mediated by long-PCR (polymerase chain reaction). Mutation FH29 was a 3.83-kb deletion extending from intron 6 to intron 8 and FH110 was a 5.71-kb deletion extending from intron 8 to intron 12. In FH29, the translational reading frame was preserved and the deducible result was a cysteine-rich A and B repeat truncated protein that might be unable to bind LDL but would continue to bind beta-VLDL. FH110 is presumed to be a null allele, since the deletion shifts the reading frame and results in a truncated protein that terminates in exon 13. Sequence analysis revealed that both deletions have occurred between two Alu-repetitive sequences that are in the same orientation. This suggested that in these patients the deletions were caused by an unequal crossing over event following mispairing of two Alu sequences on different chromatids during meiosis. Moreover, in both deletions, the recombinations were related to an Alu sequence in intron 8 and the deletion breakpoints are found within a specific sequence, 27 bp in length. This supports the hypothesis that this region might have some intrinsic instability, and act as one of the important factors in large recombinational rearrangements.

Ten LDL receptor mutants explain one third of familial hypercholesterolemia in a German sample.

Mutational defects in the LDL receptor are responsible for familial hypercholesterolemia (FH); thus far more than 150 mutations have been described. Nevertheless, systematic searches among the Germans have not been conducted. We used single-strand conformational polymorphism and polymerase chain reaction to find mutations in 10 index patients and in 40 other individuals with heterozygous FH. Our screen in the 10 index patients revealed 7 hitherto undescribed mutations. A screen of the 40 additional FH patients disclosed 20 defective of 54 total alleles and allowed specific diagnoses in 88 family members. We also found two families in which the children were markedly affected by FH, but the expected parental expression of the trait was not manifest. This observation suggests a role for additional environmental and genetic influences. Our report represents the first comprehensive effort to identify FH mutations in Germany. We found 10 mutations and these mutations explain 37% of FH cases. Our data may have relevance to expected FH patterns in central Europe.