Cinthia E. Jannes

Familial hypercholesterolemia in Brazil: Cascade screening program, clinical and genetic aspects

BACKGROUND There is little knowledge about familial hypercholesterolemia in Brazil. This study presents the first results of genetic cascade screening performed in the city of Sao Paulo. MATERIAL AND METHODS Two-hundred and forty-eight suspected index cases were initially included. DNA was extracted from peripheral blood and the complete coding sequence of low-density lipoprotein receptor, exon 7 of proprotein convertase subtilisin/kexin type 9 gene and part of exon 26 of apolipoprotein B genes were sequenced. Multiplex Ligation-dependent Probe Amplification was performed on cases where a causal mutation was not identified through sequencing. After the identification of a causal mutation screening in first-degree relatives was pursued. RESULTS From 248 index cases, a mutation was found in 125 individuals (50.4%). 394 relatives were included in the cascade screening program and a mutation was identified in 59.4%. Seventy different causal mutations in the low-density lipoprotein receptor gene (97.2%) and 2 in the apolipoprotein B gene (2.8%) were found. No mutations were encountered in the proprotein convertase subtilisin/kexin type 9 gene. Mutations in exons 14 and 4 were the most prevalent and, 10 cases of true homozygotes (8 index cases and 2 relatives) and 1 compound heterozygote were identified. The most frequent mutation found was of Lebanese origin, the p.(Cys681*) mutation in exon 14 (8.5%). CONCLUSION Genetic familial hypercholesterolemia cascade screening is feasible in Brazil and leads to identification of a mutation in approximately half of the index cases with higher rates of success in their relatives.

cAMP promotes the differentiation of neural progenitor cells in vitro via modulation of voltage-gated calcium channels

The molecular mechanisms underlying the differentiation of neural progenitor cells (NPCs) remain poorly understood. In this study we investigated the role of Ca2+ and cAMP (cyclic adenosine monophosphate) in the differentiation of NPCs extracted from the subventricular zone of E14.5 rat embryos. Patch clamp recordings revealed that increasing cAMP-signaling with Forskolin or IBMX (3-isobutyl-1-methylxantine) significantly facilitated neuronal functional maturation. A continuous application of IBMX to the differentiation medium substantially increased the functional expression of voltage-gated Na+ and K+ channels, as well as neuronal firing frequency. Furthermore, we observed an increase in the frequency of spontaneous synaptic currents and in the amplitude of evoked glutamatergic and GABAergic synaptic currents. The most prominent acute effect of applying IBMX was an increase in L-type Ca2+currents. Conversely, blocking L-type channels strongly inhibited dendritic outgrowth and synapse formation even in the presence of IBMX, indicating that voltage-gated Ca2+ influx plays a major role in neuronal differentiation. Finally, we found that nifedipine completely blocks IBMX-induced CREB phosphorylation (cAMP-response-element-binding protein), indicating that the activity of this important transcription factor equally depends on both enhanced cAMP and voltage-gated Ca2+-signaling. Taken together, these data indicate that the up-regulation of voltage-gated L-type Ca2+-channels and early electrical excitability are critical steps in the cAMP-dependent differentiation of SVZ-derived NPCs into functional neurons. To our knowledge, this is the first demonstration of the acute effects of cAMP on voltage-gated Ca+2channels in NPC-derived developing neurons.

Equivalent Neurogenic Potential of Wild-Type and GFP-Labeled Fetal-Derived Neural Progenitor Cells Before and After Transplantation Into the Rodent Hippocampus

Introduction. The hippocampal formation is a specific structure in the brain where neurogenesis occurs throughout adulthood and in which the neuronal cell loss causes various demential states. The main goal of this study was to verify whether fetal neural progenitor cells (NPCs) from transgenic rats expressing green fluorescent protein (GFP) retain the ability to differentiate into neuronal cells and to integrate into the hippocampal circuitry after transplantation. Methods. NPCs were isolated from E14 (gestational age: 14 days postconception) transgenic-Lewis and wild-type Sprague-Dawley rat embryos. Wild-type and transgenic cells were expanded and induced to differentiate into a neuronal lineage in vitro. Immunocytochemical and electrophysiological analysis were performed in both groups. GFP-expressing cells were implanted into the hippocampus and recorded electrophysiologically 3 months thereafter. Immunohistochemical analysis confirmed neuronal differentiation, and the yield of neuronal cells was determined stereologically. Results. NPCs derived from wild-type and transgenic animals are similar regarding their ability to generate neuronal cells in vitro. Neuronal maturity was confirmed by immunocytochemistry and electrophysiology, with demonstration of voltage-gated ionic currents, firing activity, and spontaneous synaptic currents. GFP-NPCs were also able to differentiate into mature neurons after implantation into the hippocampus, where they formed functional synaptic contacts. Conclusions. GFP-transgenic cells represent an important tool in transplantation studies. Herein, we demonstrate their ability to generate functional neurons both in vitro and in vivo conditions. Neurons derived from fetal NPCs were able to integrate into the normal hippocampal circuitry. The high yield of mature neurons generated render these cells important candidates for restorative approaches based on cell therapy.

Clinical and molecular aspects of familial hypercholesterolemia in Ibero-American countries

BACKGROUND There is little information about familial hypercholesterolemia (FH) epidemiology and care in Ibero-American countries. The Ibero-American FH network aims at reducing the gap on diagnosis and treatment of this disease in the region. OBJECTIVE To describe clinical, molecular, and organizational characteristics of FH diagnosis in Argentina, Brazil, Chile, Colombia, Mexico, Portugal, Spain, and Uruguay. METHODS Descriptive analysis of country data related to FH cascade screening, molecular diagnosis, clinical practice guidelines, and patient organization presence in Ibero-America. RESULTS From a conservative estimation of an FH prevalence of 1 of 500 individuals, there should be 1.2 million heterozygous FH individuals in Ibero-America and roughly 27,400 were diagnosed so far. Only Spain, Brazil, Portugal, and Uruguay have active cascade screening programs. The prevalence of cardiovascular disease ranged from 10% to 42% in member countries, and the highest molecular identification rates are seen in Spain, 8.3%, followed by Portugal, 3.8%, and Uruguay with 2.5%. In the 3 countries with more FH patients identified (Spain, Portugal, and Brazil) between 10 and 15 mutations are responsible for 30% to 47% of all FH cases. Spain and Portugal share 5 of the 10 most common mutations (4 in low density lipoprotein receptor [LDLR] and the APOB3527). Spain and Spanish-speaking Latin American countries share 6 of the most common LDLR mutations and the APOB3527. LDL apheresis is available only in Spain and Portugal and not all countries have specific FH diagnostic and treatment guidelines as well as patient organizations. CONCLUSIONS Ibero-American countries share similar mutations and gaps in FH care.

Peripheral arterial disease in heterozygous familial hypercholesterolemia

BACKGROUND Familial hypercholesterolemia is characterized by elevated plasma cholesterol and early coronary arterial disease onset. However, few studies investigated the association of heterozygous familial hypercholesterolemia with peripheral arterial disease. METHODS In a cross sectional study 202 heterozygous familial hypercholesterolemia patients (91% confirmed by molecular diagnosis) were compared to 524 normolipidemic controls. Peripheral arterial disease was diagnosed by ankle-brachial index values ≤0.90. RESULTS Compared with controls, familial hypercholesterolemia patients were older, more often female, with higher rates of hypertension, diabetes, previous coronary disease and higher total cholesterol levels. Smoking (previous and former) was more common among controls. The prevalence of peripheral arterial disease was 17.3 and 2.3% respectively in familial hypercholesterolemia and controls (p < 0.001). Results persisted after matching familial hypercholesterolemia and controls by a propensity score. Regression analyses demonstrated that age (odds ratio- OR = 1.03 95% CI 1.00-1.05, p = 0.033), previous cardiovascular disease (OR = 3.12 CI 95% 1.56-6.25, p = 0.001) and familial hypercholesterolemia diagnosis (OR = 5.55 CI 95% 2.69-11.44, p< 0.001) were independently associated with peripheral arterial disease. Among familial hypercholesterolemia patients, age (OR 1.05, 95% CI 1.02-1.09, p = 0.005), intermittent claudication (OR 6.32, 95% CI 2.60-15.33, p< 0.001) and smoking (OR 2.44, 95% CI 1.08-5.52, p = 0.032) were associated with peripheral arterial disease. CONCLUSIONS Peripheral arterial disease is more frequent in familial hypercholesterolemia than in normolipidemic subjects and it should routine screened in these individuals even if asymptomatic. However, its role as predictor of cardiovascular events needs to be ascertained prospectively.

The MYLIP p.N342S polymorphism is associated with response to lipid-lowering therapy in Brazilian patients with familial hypercholesterolemia

Background A previous study reported that the myosin regulatory light chain interacting protein (MYLIP) might serve as a novel therapeutic class for treating dyslipidemia. It contributes to variations in the levels of circulating low-density lipoprotein cholesterol (LDL-C), promoting the degradation of LDL–LDLR, thus limiting absorption. The effect of genetic variation in the MYLIP gene in a disease scenario characterized by mutations in the LDLR gene has not been previously evaluated. Objective The aim of this study was to assess the effect of the p.N342S variant on the response to lipid-lowering therapy in Brazilian patients with heterozygous familial hypercholesterolemia (FH). Patients and methods A total of 156 patients with heterozygous FH were followed up for 12 months and received lipid-lowering therapy (different doses of atorvastatin with the addition of ezetimibe in over half the patients of each genotype group). Cholesterol data were assessed, and analysis of the MYLIP rs9370867 (p.N342S) genotypes was carried out by melting curve analysis. Results Baseline total cholesterol and baseline LDL-C levels were not different between genotypes. After 1 year of treatment, LDL-C responses (expressed as mg/dl and as %) were significantly different among genotypes (AA: −79±68 and −39±27, GA: −60±79 and −27±32, and GG: −30±83 and −15±38; P=0.02 and 0.005, respectively). In addition, FH patients carrying the AA genotype were more likely to achieve LDL-C levels of less than 130 mg/dl after 1 year of treatment (75.0%) compared with patients with the GG and GA genotypes (34.5 and 34.8%, respectively; P=0.001). Conclusion Our study indicates that MYLIP p.N342S might be a pharmacogenetic marker for lipid-lowering therapy in patients with FH.

ClinVar database of global familial hypercholesterolemia-associated DNA variants

Accurate and consistent variant classification is imperative for incorporation of rapidly developing sequencing technologies into genomic medicine for improved patient care. An essential requirement for achieving standardized and reliable variant interpretation is data sharing, facilitated by a centralized open‐source database. Familial hypercholesterolemia (FH) is an exemplar of the utility of such a resource: it has a high incidence, a favorable prognosis with early intervention and treatment, and cascade screening can be offered to families if a causative variant is identified. ClinVar, an NCBI‐funded resource, has become the primary repository for clinically relevant variants in Mendelian disease, including FH. Here, we present the concerted efforts made by the Clinical Genome Resource, through the FH Variant Curation Expert Panel and global FH community, to increase submission of FH‐associated variants into ClinVar. Variant‐level data was categorized by submitter, variant characteristics, classification method, and available supporting data. To further reform interpretation of FH‐associated variants, areas for improvement in variant submissions were identified; these include a need for more detailed submissions and submission of supporting variant‐level data, both retrospectively and prospectively. Collaborating to provide thorough, reliable evidence‐based variant interpretation will ultimately improve the care of FH patients.

CORONARY ARTERY CALCIFICATION IS SUPERIOR TO CLASSICAL RISK FACTORS AS PREDICTOR OF CARDIOVASCULAR DISEASE IN FAMILIAL HYPERCHOLESTEROLEMIA

There is heterogeneity on the risk of cardiovascular disease (CVD) in Familial hypercholesterolemia (FH). We tested whether coronary artery calcification (CAC) improves CVD risk stratification in FH. 207 consecutive molecularly proven asymptomatic FH patients (36% men, age 49.2±14.1 years,

Predictors of Family Enrollment in a Genetic Cascade Screening Program for Familial Hypercholesterolemia

Background Genetic cascade screening is the most cost-effective method for the identification of individuals with familial hypercholesterolemia (FH), but the best strategies for the enrollment of at-risk individuals in a FH screening program are not fully known. Objective The aim of this study is to identify the best predictors of familial enrollment into genetic screening, using features derived from tested probands. Methods One hundred and eighty-three index-cases (ICs) with a positive genetic result that had relatives screened from 01/2011 to 07/2015 were included. The response variable was the number of relatives for each enrolled IC. All variables in the study were based on ICs’ derived clinical and socioeconomical features. The effect size of predictor variables were obtained through a general linear model using a negative binomial regression link function. Significance was considered with a p < 0.05. Results Mean IC age when enrolling into the program was 50 years old; 78.1% of individuals reported knowledge of relatives with dyslipidemia. Mean baseline LDL-cholesterol level was 316 ± 90 mg/dL. Referral origin through the cascade program website vs. tertiary care, IC LDL-cholesterol and familial history of high LDL-cholesterol levels were independent predictors associated with a higher number of enrolled relatives. Conclusions Our data suggest that FH cascade screening programs can predict family enrollment based on IC features. This information may be useful for devising better and more effective screening approaches for at-risk individuals.