Hypercholesterolemia Phenotype Research Articles

PCSK9 and Lipid Metabolism: Genetic Variants, Current Therapies, and Cardiovascular Outcomes.

Proprotein convertase subtilisin/kexin type 9 (PCSK9) plays a crucial role in the modulation of lipid metabolism as a critical negative regulator of hepatic low-density lipoprotein receptor (LDLR) levels and circulating low-density lipoprotein (LDL) clearance. Numerous gain-of-function (GOF) mutations in PCSK9 have been identified as causing familial hypercholesterolemia (FH) by reducing LDLR levels, and loss-of-function (LOF) mutations associated with a hypercholesterolemia phenotype protective against atherosclerosis. PCSK9 represents an example of successful translational research resulting in the identification of PCSK9 as a major drug target for a lipid-lowering therapy. To explore the genetic constitution of PCSK9 and its biologic role, in this review, we summarize the current evidence of clinically significant PCSK9 genetic variants involved in lipid metabolism as well as emphasize the importance of PCSK9 inhibition for the improvement of cardiovascular outcomes by conducting a meta-analysis of the available data on the incidence of cardiovascular disease events.

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.

13C-Metabolic flux analysis detected a hyperoxemia-induced reduction of tricarboxylic acid cycle metabolism in granulocytes during two models of porcine acute subdural hematoma and hemorrhagic shock.

Supplementation with increased inspired oxygen fractions has been suggested to alleviate the harmful effects of tissue hypoxia during hemorrhagic shock (HS) and traumatic brain injury. However, the utility of therapeutic hyperoxia in critical care is disputed to this day as controversial evidence is available regarding its efficacy. Furthermore, in contrast to its hypoxic counterpart, the effect of hyperoxia on the metabolism of circulating immune cells remains ambiguous. Both stimulating and detrimental effects are possible; the former by providing necessary oxygen supply, the latter by generation of excessive amounts of reactive oxygen species (ROS). To uncover the potential impact of increased oxygen fractions on circulating immune cells during intensive care, we have performed a 13C-metabolic flux analysis (MFA) on PBMCs and granulocytes isolated from two long-term, resuscitated models of combined acute subdural hematoma (ASDH) and HS in pigs with and without cardiovascular comorbidity. Swine underwent resuscitation after 2 h of ASDH and HS up to a maximum of 48 h after HS. Animals received normoxemia (PaO2 = 80 - 120 mmHg) or targeted hyperoxemia (PaO2 = 200 - 250 mmHg for 24 h after treatment initiation, thereafter PaO2 as in the control group). Blood was drawn at time points T1 = after instrumentation, T2 = 24 h post ASDH and HS, and T3 = 48h post ASDH and HS. PBMCs and granulocytes were isolated from whole blood to perform electron spin resonance spectroscopy, high resolution respirometry and 13C-MFA. For the latter, we utilized a parallel tracer approach with 1,2-13C2 glucose, U-13C glucose, and U-13C glutamine, which covered essential pathways of glucose and glutamine metabolism and supplied redundant data for robust Bayesian estimation. Gas chromatography-mass spectrometry further provided multiple fragments of metabolites which yielded additional labeling information. We obtained precise estimations of the fluxes, their joint credibility intervals, and their relations, and characterized common metabolic patterns with principal component analysis (PCA). 13C-MFA indicated a hyperoxia-mediated reduction in tricarboxylic acid (TCA) cycle activity in circulating granulocytes which encompassed fluxes of glutamine uptake, TCA cycle, and oxaloacetate/aspartate supply for biosynthetic processes. We further detected elevated superoxide levels in the swine strain characterized by a hypercholesterolemic phenotype. PCA revealed cell type-specific behavioral patterns of metabolic adaptation in response to ASDH and HS that acted irrespective of swine strains or treatment group. In a model of resuscitated porcine ASDH and HS, we saw that ventilation with increased inspiratory O2 concentrations (PaO2 = 200 - 250 mmHg for 24 h after treatment initiation) did not impact mitochondrial respiration of PBMCs or granulocytes. However, Bayesian 13C-MFA results indicated a reduction in TCA cycle activity in granulocytes compared to cells exposed to normoxemia in the same time period. This change in metabolism did not seem to affect granulocytes' ability to perform phagocytosis or produce superoxide radicals.

Unraveling the genetic background of individuals with a clinical familial hypercholesterolemia phenotype

Familial hypercholesterolemia (FH) is a common genetic disorder of lipid metabolism caused by pathogenic/likely pathogenic variants in LDLR, APOB, and PCSK9 genes. Variants in FH-phenocopy genes (LDLRAP1, APOE, LIPA, ABCG5, and ABCG8), polygenic hypercholesterolemia, and hyperlipoprotein (a) [Lp(a)] can also mimic a clinical FH phenotype. We aim to present a new diagnostic tool to unravel the genetic background of clinical FH phenotype. Biochemical and genetic study was performed in 1,005 individuals with clinical diagnosis of FH, referred to the Portuguese FH Study. A next-generation sequencing panel, covering eight genes and eight SNPs to determine LDL-C polygenic risk score and LPA genetic score, was validated, and used in this study. FH was genetically confirmed in 417 index cases: 408 heterozygotes and 9 homozygotes. Cascade screening increased the identification to 1,000 FH individuals, including 11 homozygotes. FH-negative individuals (phenotype positive and genotype negative) have Lp(a) >50 mg/dl (30%), high polygenic risk score (16%), other monogenic lipid metabolism disorders (1%), and heterozygous pathogenic variants in FH-phenocopy genes (2%). Heterozygous variants of uncertain significance were identified in primary genes (12%) and phenocopy genes (7%). Overall, 42% of our cohort was genetically confirmed with FH. In the remaining individuals, other causes for high LDL-C were identified in 68%. Hyper-Lp(a) or polygenic hypercholesterolemia may be the cause of the clinical FH phenotype in almost half of FH-negative individuals. A small part has pathogenic variants in ABCG5/ABCG8 in heterozygosity that can cause hypercholesterolemia and should be further investigated. This extended next-generation sequencing panel identifies individuals with FH and FH-phenocopies, allowing to personalize each person’s treatment according to the affected pathway.

Long-Term Mortality in Patients With Severe Hypercholesterolemia Phenotype From a Racial and Ethnically Diverse US Cohort.

Tools for mortality prediction in patients with the severe hypercholesterolemia phenotype (low-density lipoprotein cholesterol ≥190 mg/dL) are limited and restricted to specific racial and ethnic cohorts. We sought to evaluate the predictors of long-term mortality in a large racially and ethnically diverse US patient cohort with low-density lipoprotein cholesterol ≥190 mg/dL. We conducted a retrospective analysis of all patients with a low-density lipoprotein cholesterol ≥190 mg/dL seeking care at Montefiore from 2010 through 2020. Patients <18 years of age or with previous malignancy were excluded. The primary end point was all-cause mortality. Analyses were stratified by age, sex, and race and ethnicity. Patients were stratified by primary and secondary prevention. Cox regression analyses were used to adjust for demographic, clinical, and treatment variables. A total of 18 740 patients were included (37% non-Hispanic Black, 30% Hispanic, 12% non-Hispanic White, and 2% non-Hispanic Asian patients). The mean age was 53.9 years, and median follow-up was 5.2 years. Both high-density lipoprotein cholesterol and body mass index extremes were associated with higher mortality in univariate analyses. In adjusted models, higher low-density lipoprotein cholesterol and triglyceride levels were associated with an increased 9-year mortality risk (adjusted hazard ratio [HR], 1.08 [95% CI, 1.05-1.11] and 1.04 [95% CI, 1.02-1.06] per 20-mg/dL increase, respectively). Clinical factors associated with higher mortality included male sex (adjusted HR, 1.31 [95% CI, 1.08-1.58]), older age (adjusted HR, 1.19 per 5-year increase [95% CI, 1.15-1.23]), hypertension (adjusted HR, 2.01 [95% CI, 1.57-2.57]), chronic kidney disease (adjusted HR, 1.68 [95% CI, 1.36-2.09]), diabetes (adjusted HR, 1.79 [95% CI, 1.50-2.15]), heart failure (adjusted HR, 1.51 [95% CI, 1.16-1.95]), myocardial infarction (adjusted HR, 1.41 [95% CI, 1.05-1.90]), and body mass index <20 kg/m2 (adjusted HR, 3.36 [95% CI, 2.29-4.93]). A significant survival benefit was conferred by lipid-lowering therapy (adjusted HR, 0.57 [95% CI, 0.42-0.77]). In the primary prevention group, high-density lipoprotein cholesterol <40 mg/dL was independently associated with higher mortality (adjusted HR, 1.49 [95% CI, 1.06-2.09]). Temporal trend analyses showed a reduction in statin use over time (P<0.001). In the most recent time period (2019-2020), 56% of patients on primary prevention and 85% of those on secondary prevention were on statin therapy. In a large, diverse cohort of US patients with the severe hypercholesterolemia phenotype, we identified several patient characteristics associated with increased 9-year all-cause mortality and observed a decrease in statin use over time, in particular for primary prevention. Our results support efforts geared toward early recognition and consistent treatment for patients with severe hypercholesterolemia.

Searching for new genes associated with the familial hypercholesterolemia phenotype using whole-genome sequencing and machine learning.

One of the most common congenital metabolic disorders is familial hypercholesterolemia. Familial hypercholesterolemia is a condition caused by a type of genetic defect leading to a decreased rate of removal of low-density lipoproteins from the bloodstream and a pronounced increase in the blood level of total cholesterol. This disease leads to the early development of cardiovascular diseases of atherosclerotic etiology. Familial hypercholesterolemia is a monogenic disease that is predominantly autosomal dominant. Rare pathogenic variants in the LDLR gene are present in 75-85 % of cases with an identified molecular genetic cause of the disease, and variants in other genes (APOB, PCSK9, LDLRAP1, ABCG5, ABCG8, and others) occur at a frequency of < 5 % in this group of patients. A negative result of genetic screening for pathogenic variants in genes of the low-density lipoprotein receptor and its ligands does not rule out a diagnosis of familial hypercholesterolemia. In 20-40 % of cases, molecular genetic testing fails to detect changes in the above genes. The aim of this work was to search for new genes associated with the familial hypercholesterolemia phenotype by modern high-tech methods of sequencing and machine learning. On the basis of a group of patients with familial hypercholesterolemia (enrolled according to the Dutch Lipid Clinic Network Criteria and including cases confirmed by molecular genetic analysis), decision trees were constructed, which made it possible to identify cases in the study population that require additional molecular genetic analysis. Five probands were identified as having the severest familial hypercholesterolemia without pathogenic variants in the studied genes and were analyzed by whole-genome sequencing on the HiSeq 1500 platform (Illumina). The whole-genome sequencing revealed rare variants in three out of five analyzed patients: a heterozygous variant (rs760657350) located in a splicing acceptor site in the PLD1 gene (c.2430-1G>A), a previously undescribed single-nucleotide deletion in the SIDT1 gene [c.2426del (p.Leu809CysfsTer2)], new missense variant c.10313C>G (p.Pro3438Arg) in the LRP1B gene, and single-nucleotide deletion variant rs753876598 [c.165del (p.Ser56AlafsTer11)] in the CETP gene. All these variants were found for the first time in patients with a clinical diagnosis of familial hypercholesterolemia. Variants were identified that may influence the formation of the familial hypercholesterolemia phenotype.

Identification of APOB variants in samples from the Brazilian population with hypercholesterolemic phenotype

Identification of APOB variants in samples from the Brazilian population with hypercholesterolemic phenotype

Comparing heterozygous familial hypercholesterolemia phenotype to genotype in an Irish cohort

Comparing heterozygous familial hypercholesterolemia phenotype to genotype in an Irish cohort

Possible explanations for the common clinical familial hypercholesterolemia phenotypes in the Faroe Islands

The prevalence of clinical familial hypercholesterolemia (FH) is very high in the Faroe Islands, but the possible causes are unknown. We aimed to describe potential genetic causes of FH in the Faroe Islands and to investigate whether levels of lipoprotein(a) and measures of dietary habits were associated with clinical FH in the Faroe Islands. In this case-control study, we identified potential clinical FH cases aged 18-75 years registered within a nationwide clinical laboratory database in the Faroe Islands and invited them for diagnostic evaluation according to clinical FH scoring systems. Controls were identified in the background population. Lipoprotein(a) was measured in plasma, while the fatty acid composition was determined in adipose tissue. The habitual diet of the participants was assessed using a food frequency questionnaire. Genetic testing for FH and polygenic variants was performed in a selection of clinical FH cases. A total of 121 clinical FH cases and 123 age- and sex-matched controls were recruited. We found a very low frequency of monogenic FH (2.5%), but a high level of polygenic FH (63%) in those genetically tested (67%). High levels of plasma lipoprotein(a) were associated with high odds of clinical FH. Clinical FH cases had a lower intake of saturated fatty acids (SFAs) measured by a high fat-score and a lower content of SFAs in adipose tissue compared with controls. The high prevalence of FH in the Faroe Islands may be due to polygenic causes of hypercholesterolemia and to a lesser extent other genetic factors and elevated plasma lipoprotein(a) levels.

Additive Effect of APOE Rare Variants on the Phenotype of Familial Hypercholesterolemia.

Autosomal dominant hypercholesterolemia (ADH) is due to deleterious variants in LDLR, APOB, or PCSK9 genes. Double heterozygote for these genes induces a more severe phenotype. More recently, a new causative variant of heterozygous ADH was identified in APOE. Here we study the phenotype of 21 adult patients, double heterozygotes for rare LDLR and rare APOE variants (LDLR+APOE) in a national wide French cohort. LDLR, APOB, PCSK9, and APOE genes were sequenced in 5743 probands addressed for ADH genotyping. The lipid profile and occurrence of premature atherosclerotic cardiovascular diseases were compared between the LDLR+APOE carriers (n=21) and the carriers of the same LDLR causative variants alone (n=22). The prevalence of LDLR+APOE carriers in this French ADH cohort is 0.4%. Overall, LDL (low-density lipoprotein)-cholesterol concentrations were 23% higher in LDLR+APOE patients than in LDLR patients (9.14±2.51 versus 7.43±1.59 mmol/L, P=0.0221). When only deleterious or probably deleterious variants were considered, the LDL-cholesterol concentrations were 46% higher in LDLR+APOE carriers than in LDLR carriers (10.83±3.45 versus 7.43±1.59 mmol/L, P=0.0270). Two patients exhibited a homozygous familial hypercholesterolemia phenotype (LDL-cholesterol >13 mmol/L). Premature atherosclerotic cardiovascular disease was more common in LDLR+APOE patients than in LDLR carriers (70% versus 30%, P=0.026). Although an incomplete penetrance should be taken into account for APOE variant classification, these results suggest an additive effect of deleterious APOE variants on ADH phenotype highlighting the relevance of APOE sequencing.

Mild hypercholesterolemia impacts achilles sub-tendon mechanical properties in young rats

BackgroundHypercholesterolemia is associated with tendon pathology, but the reasons underpinning this relationship are not well understood. Cholesterol can accumulate in the tendon non-collagenous matrix which may affect both global and local tissue mechanics. Changes to the local strain environment within tendon may have significant implications for mechanosensitive tenocytes. Here, we investigated the association between elevated blood cholesterol and presence of tendon lipids in the Achilles tendon. We expected lipids to be localised in the proteoglycan-rich inter-sub-tendon matrix (ISTM), therefore we also sought to examine the impact of this on the biomechanical and viscoelastic properties of the ISTM.MethodsThe Achilles tendons of 32 young wild-type (SD) and 32 apolipoprotein E knock-out rats (ApoE−/−) were harvested at 15.6 ± 2.3 weeks of age. 32 specimens underwent histological examination to assess the distribution of lipids throughout sub-tendons and ISTM. The remaining specimens were prepared for biomechanical testing, where the ISTM between the gastrocnemius and soleus sub-tendons was subjected to shear load mechanical testing. A sub-set of tests were video recorded to enable a strain analysis.ResultsApoE−/− serum cholesterol was double that of SD rats (mean 2.25 vs. 1.10 mg/ml, p < 0.001) indicating a relatively mild hypercholesterolemia phenotype. Nonetheless, we found histological evidence of esterified lipids in the ISTM and unesterified lipids in the sub-tendons, although the location or intensity of staining was not appreciably different between rat strains. Despite a lack of observable histological differences in lipid content between groups, there were significant differences in the mechanical and viscoelastic behaviour of the Achilles sub-tendon matrix.ConclusionEven slightly elevated cholesterol may result in subtle changes to tendon biomechanical properties and hence injury risk. The young age of our cohort and the mild phenotype of our ApoE−/− rats are likely to have limited our findings and so we also conclude that the ApoE−/− rat model is not well suited for investigating the biomechanical impact of tendon xanthomas on Achilles sub-tendon function.

Women with familial hypercholesterolemia phenotype are undertreated and poorly controlled compared to men

Familial hypercholesterolemia (FH) is an autosomal dominant disease that has a prevalence of approximately 1/250 inhabitants and is the most frequent cause of early coronary heart disease (CHD). We included 1.343.973 women and 1.210.671 men with at least one LDL-c measurement from the Catalan primary care database. We identified 14.699 subjects with Familial hypercholesterolemia-Phenotype (FH-P) based on LDL-c cut-off points by age (7.033 and 919 women, and 5.088 and 1659 men in primary and secondary prevention, respectively). Lipid lower therapy (LLT), medication possession ratio (MPR) as an indicator of adherence, and number of patients that reached their goal on lipid levels were compared by sex. In primary and secondary prevention, 69% and 54% of women (P = 0.001) and 64% and 51% of men (P = 0.001) were on low-to-moderate-potency LLT. Adherence to LLT was reduced in women older than 55 years, especially in secondary prevention (P = 0.03), where the percentage of women and men with LDL-c > 1.81 mmol/L were 99.9% and 98.9%, respectively (P = 0.001). Women with FH-P are less often treated with high-intensity LLT, less adherent to LLT, and have a lower probability of meeting their LDL-c goals than men, especially in secondary prevention.

Impact of variants of uncertain significance of LDL receptor on phenotypes of familial hypercholesterolemia

BackgroundData on the effect of variants of uncertain significance (VUS) of LDL receptor (LDLR) on familial hypercholesterolemia (FH) phenotype is limited. ObjectiveTo investigate the associations between genotypes and phenotypes, including low-density lipoprotein (LDL) cholesterol level and occurrence of major adverse cardiac events (MACEs), in FH patients (N = 1050, male/female = 490/560). MethodsWe retrospectively assessed the data of patients with FH admitted at Kanazawa University Hospital between 1990 and 2020. Based on genotype, the patients were divided into patients without variants, with VUS of LDLR, and with pathogenic variants. Cox proportional hazard model was used to identify the factors associated with MACEs. ResultsThe median follow-up duration was 12.6 years (interquartile range: 9.5–17.9 years). Altogether, 777 patients had FH mutation and 273 had pathogenic mutation, with 92 having VUS. Over the follow-up duration, 175 MACEs were observed. LDL cholesterol level was found to be significantly higher in patients with pathogenic variants (251 mg/dL) than in patients with VUS (225 mg/dL) and without variants (203 mg/dL). Pathogenic variants and VUS are significantly associated with MACEs (hazard ratio [HR] = 1.52, 95% confidence interval [CI] = 1.02–2.02, P = 0.033 and HR = 3.18, 95% CI = 2.00–4.36, P = 1.9 × 10−5, relative to patients without any variants, respectively), independent of classical risk factors. ConclusionVUS of LDLR was significantly associated with poor outcomes in FH patients. Genetic testing is useful for the diagnosis and risk stratification of FH patients.

Effect of Lipoprotein Apheresis on Progression of Carotid Intima-Media Thickness in Patients with Severe Hypercholesterolemia

The extent of intervention effects on carotid intima-media thickness (CIMT) can predict the degree of atherosclerotic cardiovascular risk-reduction. We hypothesized that regular lipoprotein apheresis over the course of 10 years might slow down progression of CIMT in patients with severe hypercholesterolemia. This case series describes 10 Caucasian patients (mean age 60 ± 9 years, 70% female, 80% statin intolerant) with a severe hypercholesterolemia phenotype treated with lipoprotein apheresis between 2005 and 2020 (mean duration, 10 ± 4 years). The median pretreatment low-density lipoprotein cholesterol (LDL-C) level was 214 mg/100 ml (95% confidence interval, 145 to 248), lipoprotein(a) (Lp[a]), 26 mg/100 ml (15 to 109; 40% with Lp(a)>60 mg/100 ml). Three patients were diagnosed with a monogenic cause. The baseline mean CIMT was 850 ± 170 µm, and maximum CIMT was 1,040 ± 220 µm across the age range of 46 to 70 years. Acute effects of lipoprotein apheresis determined as a difference before and immediately after the procedure were estimated as a median of 72 ± 8% and 75 ± 7% reduction in the LDL-C and Lp(a) levels, respectively. Using the imputed trajectories, period-specific on-treatment time-weighted averages for LDL-C and Lp(a) were 141 mg/100 ml (interquartile range, 89 to 152; 38% reduction from the baseline) and 24 mg/100 ml (interquartile range, 12 to 119; 19% reduction from baseline), respectively. The number of patients with CIMT above their "vascular age" decreased from 80% to 30% over the treatment course. In conclusion, an increase in CIMT seen with advanced age and severe hypercholesterolemia was halted with lipoprotein apheresis with an estimated annual rate of change in mean common CIMT of -4 µm/y and maximum CIMT of -3 µm/y.

Prevalence of familial hypercholesterolemia phenotype and ten-year risk of cardiovascular events in a working population in primary prevention: The ICARIA study

Background and aimsWe aimed to assess the prevalence of familial hypercholesterolaemia (FH) and to determine the incidence of cardiovascular events during a 10-year follow up in individuals with FH, compared to unaffected individuals in a working, middle-aged/young population. Methods and results576,724 active workers (36 ± 10 years-old, 70% men) without cardiovascular disease were given regular health check-ups and followed for a median of 8.5 years (i.e., 4,123,927 person-years). The FH phenotype was defined according to validated low-density lipoprotein-cholesterol thresholds, adjusted for age and sex. The primary outcome was a first cardiovascular event, whether fatal or non-fatal. We found that 707 workers (0.12% or 1 in 816 individuals) met the criteria for a heterozygous FH phenotype. During the follow-up, cardiovascular events occurred in 23 of 707 (3.25%) subjects with the FH phenotype and in 3297 of 576,017 (0.57%) subjects without the FH phenotype (p<0.001). The hazard ratio (HR, assessed with a Cox regression model) for the primary outcome was 5.7 (99% CI 3.33–9.78), before adjustments, and 4.7 (99% CI 2.62–8.58) after adjusting for sex, age, smoking, blood pressure, and diabetes. The HRs were significant for both men and women, but the magnitude of the effect was greater for men than for women. ConclusionsOur findings confirmed the high incidence of cardiovascular disease in individuals with untreated FH. We showed that regular health check-ups in an active, and mostly young, working population could contribute to the early identification of FH. Therefore, this approach may provide an opportunity for early treatment.

Prevalence of familial hypercholesterolemia phenotype in working population and incidence of cardiovascular events

Background and Aims: We aimed to determine the prevalence of familial hypercholesterolemia phenotype (FH-P) and the incidence of cardiovascular events with a 10-year follow-up in a working population.

Massive data screening is a second opportunity to improve the management of patients with familial hypercholesterolemia phenotype

IntroductionFamilial Hypercholesterolemia (FH) is an autosomal dominant disease with an estimated prevalence between 1/200–250. It is under-treated and underdiagnosed. Massive data screening can increase the detection of patients with FH. MethodsStudy population: Residents in the health coverage area (N: 195.000 inhabitants) and with at least one determination of cholesterol linked to low-density lipoproteins (LDLC) carried out between January 1, 2010 and December 30, 2019. The highest LDL-C values were selected. Exclusion criteria: nephrotic syndrome, hypothyroidism, Hypothyroid treatment or triglycerides > 400 mg/dL. Seven algorithms suggestive of Familial Hypercholesterolemia Phenotype (HF-P) were analyzed, selecting the most efficient algorithm that could easily be translated into clinical practice. ResultsBased on 6.264.877 assistances and 288.475 patients, after applying the inclusionexclusion criteria, 504.316 tests were included, corresponding to 106.382 adults and 10.509 < 18 years. The selected algorithm presented a prevalence of 0.62%. 840 patients with HF-P were detected, 55.8% being women and 178 < 18 years old, 9.3% had a history of cardiovascular disease (CVD) and 16.4% had died. 65% of the patients in primary prevention had LDL-C values > 130 mg/dL and 83% in secondary prevention values > 70 mg/dL. A ratio of 7.64 (1–18) patients with HF-P per analytical requesting physician was obtained. ConclusionsMassive data screening and patient profiling are effective tools and easily applicable in clinical practice for the detection of patients with FH.

Genetic basis of hypercholesterolemia in adults

We investigated monogenic and polygenic causes of hypercholesterolemia in a population-based cohort, excluding secondary hypercholesterolemia, and using an established framework to identify pathogenic variants. We studied 1682 individuals (50.2 ± 8.6 years, 41.3% males) from southeast Minnesota with primary hypercholesterolemia (low-density lipoprotein cholesterol (LDL-C) ≥155 mg/dl in the absence of identifiable secondary causes). Familial hypercholesterolemia (FH) phenotype was defined as a Dutch Lipid Clinic Network (DLCN) score ≥6. Participants underwent sequencing of LDLR, APOB, and PCSK9, and genotyping of 12 LDL-C-associated single-nucleotide variants to construct a polygenic score (PGS) for LDL-C. The presence of a pathogenic/likely pathogenic variant was considered monogenic etiology and a PGS ≥90th percentile was considered polygenic etiology. The mean LDL-C level was 187.3 ± 32.3 mg/dl and phenotypic FH was present in 8.4% of the cohort. An identifiable genetic etiology was present in 17.1% individuals (monogenic in 1.5% and polygenic in 15.6%). Phenotypic and genetic FH showed poor overlap. Only 26% of those who met the clinical criteria of FH had an identifiable genetic etiology and of those with an identifiable genetic etiology only 12.9% met clinical criteria for FH. Genetic factors explained 7.4% of the variance in LDL-C. In conclusion, in adults with primary hypercholesterolemia, 17.1% had an identifiable genetic etiology and the overlap between phenotypic and genetic FH was modest.

Molecular Genetic Approach and Evaluation of Cardiovascular Events in Patients with Clinical Familial Hypercholesterolemia Phenotype from Romania.

This study identifies the genetic background of familial hypercholesterolemia (FH) patients in Romania and evaluates the association between mutations and cardiovascular events. We performed a prospective observational study of 61 patients with a clinical diagnosis of FH selected based on Dutch Lipid Clinic Network (DLCN) and Simon Broome score between 2017 and 2020. Two techniques were used to identify mutations: multiplex ligation-dependent probe amplification (MLPA) and Sanger sequencing. The mutation rate was 37.7%, i.e., 23 patients with mutations were identified, of which 7 subjects had pathogenic mutations and 16 had polymorphisms. Moreover, 10 variants of the low-density lipoprotein receptor (LDLR) gene were identified in 22 patients, i.e., one variant of the proprotein convertase subtilisin/kexin type 9 (PCSK9) gene in six patients, and one variant of the apolipoprotein B (APOB) gene in three patients. Of the LDLR gene variants, four were LDLR pathogenic mutations (c.81C > G, c.502G > A, c.1618G > A mutations in exon 2, exon 4, exon 11, and exon 13–15 duplication). The PCSK9 and APOB gene variants were benign mutations. The pathogenic LDLR mutations were significant predictors of the new cardiovascular events, and the time interval for new cardiovascular events occurrence was significantly decreased, compared to FH patients without mutations. In total, 12 variants were identified, with four pathogenic variants identified in the LDLR gene, whereas 62.3% of the study population displayed no pathological mutations.

Intronic variant screening with targeted next-generation sequencing reveals first pseudoexon in LDLR in familial hypercholesterolemia

Background and aimsFamilial hypercholesterolemia (FH) is caused by pathogenic variants in LDLR, APOB, or PCSK9 genes (designated FH+). However, a significant number of clinical FH patients do not carry these variants (designated FH-). Here, we investigated whether variants in intronic regions of LDLR attribute to FH by affecting pre-mRNA splicing. MethodsLDLR introns are partly covered in routine sequencing of clinical FH patients using next-generation sequencing. Deep intronic variants, >20 bp from intron-exon boundary, were considered of interest once (a) present in FH- patients (n = 909) with LDL-C >7 mmol/L (severe FH-) or after in silico analysis in patients with LDL-C >5 mmol/L (moderate FH-) and b) absent in FH + patients (control group). cDNA analysis and co-segregation analysis were performed to assess pathogenicity of the identified variants. ResultsThree unique variants were present in the severe FH- group. One of these was the previously described likely pathogenic variant c.2140+103G>T. Three additional variants were selected based on in silico analyses in the moderate FH- group. One of these variants, c.2141-218G>A, was found to result in a pseudo-exon inclusion, producing a premature stop codon. This variant co-segregated with the hypercholesterolemic phenotype. ConclusionsThrough a screening approach, we identified a deep intronic variant causal for FH. This finding indicates that filtering intronic variants in FH- patients for the absence in FH + patients might enrich for true FH-causing variants and suggests that intronic regions of LDLR need to be considered for sequencing in FH- patients.