Screening of ABCG5 and ABCG8 Genes for Sitosterolemia in a Familial Hypercholesterolemia Cascade Screening Program.

BACKGROUND: Sitosterolemia is a rare autosomal recessive disorder caused by homozygous or compound heterozygous variants in ABCG5/ABCG8. The disease is characterized by increased plasma plant sterols. Small case series suggest that patients with sitosterolemia have wide phenotypic heterogeneity with great variability on either plasma cholesterol levels or development of atherosclerotic cardiovascular disease. The present study aims to characterize the prevalence and clinical features of sitosterolemia participating in a familial hypercholesterolemia genetic cascade screening program. METHODS: From 443 familial hypercholesterolemia index cases, 260 were negative for familial hypercholesterolemia genes and were sequenced for the ABCG5/8 genes. Clinical and laboratory characteristics of affected individuals were determined. RESULTS: Eight (3.1%) index cases were found to be homozygous or compound heterozygous variant for ABCG5/ABCG8 genes, confirming the genetic diagnosis of sitosterolemia. Screening their relatives led to the identification of 6 additional confirmed sitosterolemia cases (3 homozygous and 3 compound heterozygous variant) and 18 carriers (heterozygous). The mean age of identified sitosterolemia cases (n=14) was 37.2±19.8 years, 50% were females, and 78.6% (all adults) presented either clinical or subclinical atherosclerotic cardiovascular disease. As expected, affected individuals presented elevated plasma plant sterol levels (mean ß-Sitosterol and campesterol, respectively, 160.3±107.1 and 32.0±19.6 µg/mL) and the highest plasma LDL (low-density lipoprotein)-cholesterol was 269.0±120.0 mg/dL (range: 122-521 mg/dL). LDL-cholesterol mean reduction with therapy among cases was 65%. Eighty-three percent (83%) of identified sitosterolemia patients presented hematologic abnormalities. CONCLUSIONS: Testing genes associated with sitosterolemia in the molecular routine workflow of a familial hypercholesterolemia cascade screening program allowed the precise diagnosis of sitosterolemia in a substantial number of patients with varying LDL-C levels and high incidence of early atherosclerotic cardiovascular disease and hematologic abnormalities.

Rastreamento para Hipercolesterolemia Familiar em Pequenos Municípios: A Experiência do Programa HipercolBrasil em 11 Municípios Brasileiros / Screening for Familial Hypercholesterolemia in Small Towns: Experience from 11 Brazilian Towns in the Hipercolbrasil Program

Resumo Fundamento A hipercolesterolemia familiar (HF) é uma doença genética dominante que se caracteriza por níveis sanguíneos elevados de colesterol de lipoproteína de baixa densidade (LDL-C), e está associada à ocorrência de doença cardiovascular precoce. No Brasil, o HipercolBrasil, que é atualmente o maior programa de rastreamento em cascata para HF, já identificou mais de 2.000 indivíduos com variantes genéticas causadoras de HF. A abordagem padrão baseia-se no rastreamento em cascata de casos índices referidos, indivíduos com hipercolesterolemia e suspeita clínica de HF. Objetivos Realizar rastreamento direcionado de 11 pequenos municípios brasileiros com suspeita de alta prevalência de indivíduos com HF. Métodos A seleção dos municípios ocorreu de 3 maneiras: 1) municípios em que houve suspeita de efeito fundador (4 municípios); 2) municípios em uma região com altas taxas de infarto do miocárdio precoce, conforme descrito pelo banco de dados do Sistema Único de Saúde (2 municípios); e 3) municípios geograficamente próximos a outros municípios com alta prevalência de indivíduos com HF (5 municípios). A significância estatística foi considerada como valor p < 0,05. Resultados Foram incluídos 105 casos índices e 409 familiares de primeiro grau. O rendimento dessa abordagem foi de 4,67 familiares por caso índice, o qual é significativamente melhor (p < 0,0001) do que a taxa geral do HipercolBrasil (1,59). Identificamos 36 CIs com variante patogênica ou provavelmente patogênica para HF e 240 familiares de primeiro grau afetados. Conclusão: Nossos dados sugerem que, uma vez detectadas, regiões geográficas específicas justificam uma abordagem direcionada para a identificação de aglomerações de indivíduos com HF.

Abstract Background Familial hypercholesterolemia (FH) is a genetic disease characterized by elevated serum levels of low-density lipoprotein cholesterol (LDL-C), and it is associated with the occurrence of early cardiovascular disease. In Brazil, HipercolBrasil, which is currently the largest FH cascade screening program, has already identified more than 2000 individuals with causal genetic variants for FH. The standard approach is based on cascade screening of referred index cases, individuals with hypercholesterolemia and clinical suspicion of FH. Objectives To perform targeted screening of 11 small Brazilian cities with a suspected high prevalence of people with FH. Methods The selection of cities occurred in 3 ways: 1) cities in which a founder effect was suspected (4 cities); 2) cities in a region with high rates of early myocardial infarction as described by the National Health System database (2 cities); and 3) cities that are geographically close to other cities with a high prevalence of individuals with FH (5 cities). Statistical significance was considered as p value < 0.05. Results One hundred and five index cases and 409 first-degree relatives were enrolled. The yield of such approach of 4.67 relatives per index case was significantly better (p < 0.0001) than the general HipercolBrasil rate (1.59). We identified 36 IC with a pathogenic or likely pathogenic variant for FH and 240 affected first-degree relatives. Conclusion Our data suggest that, once detected, specific geographical regions warrant a target approach for identification of clusters of individuals with FH.

Screening for Familial Hypercholesterolemia in Small Towns: Experience from 11 Brazilian Towns in the Hipercolbrasil Program. / Rastreamento para Hipercolesterolemia Familiar em Pequenos Municípios: A Experiência do Programa HipercolBrasil em 11 Municípios Brasileiros.

BACKGROUND: Familial hypercholesterolemia (FH) is a genetic disease characterized by elevated serum levels of low-density lipoprotein cholesterol (LDL-C), and it is associated with the occurrence of early cardiovascular disease. In Brazil, HipercolBrasil, which is currently the largest FH cascade screening program, has already identified more than 2000 individuals with causal genetic variants for FH. The standard approach is based on cascade screening of referred index cases, individuals with hypercholesterolemia and clinical suspicion of FH. OBJECTIVES: To perform targeted screening of 11 small Brazilian cities with a suspected high prevalence of people with FH. METHODS: The selection of cities occurred in 3 ways: 1) cities in which a founder effect was suspected (4 cities); 2) cities in a region with high rates of early myocardial infarction as described by the National Health System database (2 cities); and 3) cities that are geographically close to other cities with a high prevalence of individuals with FH (5 cities). Statistical significance was considered as p value < 0.05. RESULTS: One hundred and five index cases and 409 first-degree relatives were enrolled. The yield of such approach of 4.67 relatives per index case was significantly better (p < 0.0001) than the general HipercolBrasil rate (1.59). We identified 36 IC with a pathogenic or likely pathogenic variant for FH and 240 affected first-degree relatives. CONCLUSION: Our data suggest that, once detected, specific geographical regions warrant a target approach for identification of clusters of individuals with FH.

FUNDAMENTO: A hipercolesterolemia familiar (HF) é uma doença genética dominante que se caracteriza por níveis sanguíneos elevados de colesterol de lipoproteína de baixa densidade (LDL-C), e está associada à ocorrência de doença cardiovascular precoce. No Brasil, o HipercolBrasil, que é atualmente o maior programa de rastreamento em cascata para HF, já identificou mais de 2.000 indivíduos com variantes genéticas causadoras de HF. A abordagem padrão baseia-se no rastreamento em cascata de casos índices referidos, indivíduos com hipercolesterolemia e suspeita clínica de HF. OBJETIVOS: Realizar rastreamento direcionado de 11 pequenos municípios brasileiros com suspeita de alta prevalência de indivíduos com HF. MÉTODOS: A seleção dos municípios ocorreu de 3 maneiras: 1) municípios em que houve suspeita de efeito fundador (4 municípios); 2) municípios em uma região com altas taxas de infarto do miocárdio precoce, conforme descrito pelo banco de dados do Sistema Único de Saúde (2 municípios); e 3) municípios geograficamente próximos a outros municípios com alta prevalência de indivíduos com HF (5 municípios). A significância estatística foi considerada como valor p < 0,05. RESULTADOS: Foram incluídos 105 casos índices e 409 familiares de primeiro grau. O rendimento dessa abordagem foi de 4,67 familiares por caso índice, o qual é significativamente melhor (p < 0,0001) do que a taxa geral do HipercolBrasil (1,59). Identificamos 36 CIs com variante patogênica ou provavelmente patogênica para HF e 240 familiares de primeiro grau afetados. Conclusão: Nossos dados sugerem que, uma vez detectadas, regiões geográficas específicas justificam uma abordagem direcionada para a identificação de aglomerações de indivíduos com HF.

Polygenic risk score for hypercholesterolemia in a Brazilian familial hypercholesterolemia cohort.

Background and aims: Familial hypercholesterolemia (FH) is a genetic disorder characterized by high levels of LDL-C leading to premature cardiovascular disease (CAD). Only about 40% of individuals with a clinical diagnosis of FH have a causative genetic variant identified, and a proportion of genetically negative cases may have a polygenic cause rather than a still unidentified monogenic cause. This work aims to evaluate and validate the role of a polygenic risk score (PRS) associated with hypercholesterolemia in a Brazilian FH cohort and its clinical implications. Methods: We analyzed a previously derived PRS of 12 and 6 SNPs (Single Nucleotide Polymorphism) in 684 FH individuals (491 mutation-negative [FH/M-], 193 mutation-positive [FH/M+]) and in 1605 controls. Coronary artery calcium (CAC) score was also evaluated. Results: The PRS was independently associated with LDL-C in control individuals (p < 0.001). Within this group, in individuals in the highest quartile of the 12 SNPs PRS, the odds ratio for CAC score >100 was 1.7 (95% CI: 1.01-2.88, p = 0.04) after adjustment for age and sex. Subjects in the FH/M- group had the highest mean score in both 12 and 6 SNPs PRS (38.25 and 27.82, respectively) when compared to the other two groups (p = 2.2 × 10-16). Both scores were also higher in the FH/M+ group (36.48 and 26.26, respectively) when compared to the control group (p < 0.001 for the two scores) but inferior to the FH/M- group. Within FH individuals, the presence of a higher PRS score was not associated with LDL-C levels or with CAD risk. Conclusion: A higher PRS is associated with significantly higher levels of LDL-C and it is independently associated with higher CAC in the Brazilian general population. A polygenic cause can explain a fraction of FH/M- individuals but does not appear to be a modulator of the clinical phenotype among FH individuals, regardless of mutation status.

Genome-Wide Association of Proprotein Convertase Subtilisin/Kexin Type 9 Plasma Levels in the ELSA-Brasil Study.

Pharmacological inhibition of PCSK9 (proprotein convertase subtilisin/kexin type 9) is an established therapeutic option to treat hypercholesterolemia, and plasma PCSK9 levels have been implicated in cardiovascular disease incidence. A number of genetic variants within the PCSK9 gene locus have been shown to modulate PCSK9 levels, but these only explain a very small percentage of the overall PCSK9 interindividual variation. Here we present data on the genetic association structure between PCSK9 levels and genom-wide genetic variation in a healthy sample from the general population. We performed a genome-wide association study of plasma PCSK9 levels in a sample of Brazilian individuals enrolled in the Estudo Longitudinal de Saude do Adulto cohort (n=810). Enrolled individuals were free from cardiovascular disease, diabetes and were not under lipid-lowering medication. Genome-wide genotyping was conducted using the Axiom_PMRA.r3 array, and imputation was performed using the TOPMED multi-ancestry sample panel as reference. Total PCSK9 plasma concentrations were determined using the Quantikine SPC900 ELISA kit. We observed two genome-wide significant loci and seven loci that reached the pre-defined value of p threshold of 1×10-6. Significant variants were near KCNA5 and KCNA1, and LINC00353. Genetic variation at the PCSK9 locus was able to explain approximately 4% of the overall interindividual variations in PCSK9 levels. Colocalization analysis using eQTL data suggested RWDD3, ATXN7L1, KCNA1, and FAM177A1 to be potential mediators of some of the observed associations. Our results suggest that PCSK9 levels may be modulated by trans genetic variation outside of the PCSK9 gene and this may have clinical implications. Understanding both environmental and genetic predictors of PCSK9 levels may help identify new targets for cardiovascular disease treatment and contribute to a better assessment of the benefits of long-term PCSK9 inhibition.

Cascade screening and genetic diagnosis of familial hypercholesterolemia in clusters of the Southeastern region from Brazil.

Familial hypercholesterolemia (FH) is an autosomal dominant genetic disease characterized by high levels of low-density lipoprotein-cholesterol (LDLc), associated to premature cardiovascular disease. The detection of the variants related to FH is important to improve the early diagnosis in probands / index-cases (ICs) and their relatives. We included ICs with FH and their relatives, living in a small region of Minas Gerais state-Brazil, which were classified according to Dutch Lipid Clinic Network Criteria (DLCNC) and submitted to sequencing of genes related to FH (LDLR, APOB, PCSK9, LDLRAP1, LIPA, STAP1, APOE, ABCG5 e ABCG8). In a total of 143 subjects (32 ICs and 111 relatives), eight variants were identified in 91 individuals. From these variants, five were in LDLR [p.(Asp224Asn), p.(Ser854Gly), p.(Cys34Arg), p.(Asp601His), deletion of exon15 in LDLR)], one in APOB [p.(Met499Val)], one in PCSK9 [p.(Arg237Trp)] and one in APOE [p.(Pro28Leu)] genes. The variants were detected in 100% of those subjects classified as definitive, 87% as probable and 69% as possible FH cases based on DLCNC. The LDLc level was higher in individuals with corneal arch and xanthomas or xanthelasmas, as well as in pathogenic or probably pathogenic variants carriers. This study showed higher frequency of LDLR gene variants compared to other genes related to LDL metabolism in individuals with FH in Minas Gerais - Brazil and the presence of FH in relatives without previous diagnosis. Our data reinforce the importance of molecular and clinical evaluation of FH relatives in order to early diagnosis the FH, as well as cardiovascular diseases prevention.