Browsing by Author "Alves, A.C."
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- Advantages and versatility of fluorescence-based methodology to characterize the functionality of LDLR and class mutation assignmentPublication . Benito-Vicente, A.; Etxebarria, A.; Alves, A.C.; Bourbon, M.; Martin, C.INTRODUCTION: Familial hypercholesterolemia (FH) is a common autosomal dominant disease with a frequency of 1:500 individuals in its heterozygous form. The genetic basis of FH is mostly mutations within the LDLR gene. Assessing the pathogenicity of LDLR variants is particularly important to give a patient a definitive diagnosis of FH. Current studies of LDLR activity ex vivo are based on the analysis of 125I-labeled lipoproteins or fluorescent-labeled LDL. The main purpose of this study was to compare the effectiveness of these two methods to assess LDLR functionality in order to validate a functional assay to analyse LDLR mutations.
- Advantages and Versatility of Fluorescence-Based Methodology to Characterize the Functionality of LDLR and Class Mutation AssignmentPublication . Etxebarria, A.; Benito-Vicente, A.; Alves, A.C.; Ostolaza, H.; Bourbon, M.; Martin, C.Familial hypercholesterolemia (FH) is a common autosomal codominant disease with a frequency of 1∶500 individuals in its heterozygous form. The genetic basis of FH is most commonly mutations within the LDLR gene. Assessing the pathogenicity of LDLR variants is particularly important to give a patient a definitive diagnosis of FH. Current studies of LDLR activity ex vivo are based on the analysis of 125I-labeled lipoproteins (reference method) or fluorescent-labelled LDL. The main purpose of this study was to compare the effectiveness of these two methods to assess LDLR functionality in order to validate a functional assay to analyse LDLR mutations. LDLR activity of different variants has been studied by flow cytometry using FITC-labelled LDL and compared with studies performed previously with 125I-labeled lipoproteins. Flow cytometry results are in full agreement with the data obtained by the 125I methodology. Additionally confocal microscopy allowed the assignment of different class mutation to the variants assayed. Use of fluorescence yielded similar results than 125I-labeled lipoproteins concerning LDLR activity determination, and also allows class mutation classification. The use of FITC-labelled LDL is easier in handling and disposal, cheaper than radioactivity and can be routinely performed by any group doing LDLR functional validations.
- Analysis of publicly available LDLR, APOB, and PCSK9 variants associated with familial hypercholesterolemia: application of ACMG guidelines and implications for familial hypercholesterolemia diagnosisPublication . Chora, J.R.; Medeiros, A.M.; Alves, A.C.; Bourbon, M.PurposeFamilial hypercholesterolemia (FH) is an autosomal disorder of lipid metabolism presenting with increased cardiovascular risk. Although more than 1,700 variants have been associated with FH, the great majority have not been functionally proved to affect the low-density lipoprotein receptor cycle. We aimed to classify all described variants associated with FH and to establish the proportion of variants that lack evidence to support their pathogenicity.MethodsWe followed American College of Medical Genetics and Genomics (ACMG) guidelines for the classification, and collected information from a variety of databases and individual reports. A worldwide overview of publicly available FH variants was also performed.ResultsA total of 2,104 unique variants were identified as being associated with FH, but only 166 variants have been proven by complete in vitro functional studies to be causative of disease. Additionally, applying the ACMG guidelines, 1,097 variants were considered pathogenic or likely pathogenic. Only seven variants were found in all five continents.ConclusionThe lack of functional evidence for about 85% of all variants found in FH patients can compromise FH diagnosis and patient prognosis. ACMG classification improves variant interpretation, but functional studies are necessary to understand the effect of about 40% of all variants reported. Nevertheless, ACMG guidelines need to be adapted to FH for a better diagnosis.
- Analysis of publicly available LDLR, APOB, and PCSK9 variants associated with familial hypercholesterolemia: application of ACMG guidelines and implications for familial hypercholesterolemia diagnosisPublication . Chora, J.R.; Medeiros, A.M.; Alves, A.C.; Bourbon, M.Familial Hypercholesterolemia (FH): Lipid metabolism autosomal dominant condition; Patients present elevated low-density lipoprotein cholesterol (LDL-C) and total cholesterol (TC) values since birth - elevated cardiovascular risk.
- ApoB/ApoA1 ratio improves clinical criteria sensitivity for the identification of FH childrenPublication . Medeiros, A.M.; Alves, A.C.; Aguiar, P.; Bourbon, M.
- APOB: old gene, new perspective for Familial HypercholesterolaemiaPublication . Alves, A.C.; Etxebarria, A.; Martin, C.; Bourbon, M.Familial hypercholesterolemia (FH) is one of the most common diseases of lipid metabolism, has an autosomal dominant inheritance and was the first genetic disorder of lipid metabolism to be characterized molecularly. FH usually results from inherited defects in the low density lipoprotein receptor (LDLR) gene and is characterised by increased circulating low density lipoprotein (LDL) cholesterol that leads to lipid accumulation in arteries and tendons (xanthomas), causing premature arteriosclerosis and coronary heart disease. Mutations in other genes as the apolipoprotein B (APOB) and proprotein convertase subtilisin/kexin type 9 gene (PCSK9) are rare causes of FH. Until now only a few mutations in exon 26 and 29 have been reported to cause FH, being the APOB3527 the most common. The main aim of this project was to identify and characterize the genetic cause of severe hypercholesterolaemia in individuals with clinical diagnosis of FH, without mutations in LDLR and PCSK9 or in fragments of exon 26 and 29 of APOB routinely screened.
- Caracterização bioquímica e molecular de doentes com hipercolesterolemias genéticasPublication . Alves, A.C.; Medeiros, A.M.; Gomes, A.; Bourbon, M.O colesterol elevado no sangue contribui para o processo arterosclerótico, que está na base das doenças cardiovasculares (DCV). Perturbações no metabolismo lipídico podem dever-se a alterações nos receptores ou seus ligandos, como é o caso da Hipercolesterolemia Familiar (FH). A FH é uma doença autossómica dominante que se caracteriza a nível clínico por níveis elevados de cLDL, levando ao aparecimento prematuro de doenças cardiovasculares. A nível genético esta doença caracteriza-se por mutações em três genes: LDLR, APOB e PCSK9. O objectivo deste estudo foi analisar o perfil bioquímico e molecular de doentes com FH diagnosticada clinicamente e o aparecimento de doença cardiovascular prematura nos doentes referenciados ao Estudo Português de Hipercolesterolemia Familiar (EPFH).
- Cardiovascular risk assessment of dyslipidemic children: analysis of biomarkers for the correct assessment of monogenic dyslipidemiaPublication . Medeiros, A.M.; Alves, A.C.; Aguiar, P.; Bourbon, M.; Estudo Português de Hipercolesterolemia Familiar
- Cardiovascular risk assessment of dyslipidemic children: analysis of biomarkers to identify monogenic dyslipidemiaPublication . Medeiros, A.M.; Alves, A.C.; Aguiar, P; Bourbon, M.; on behalf of the Pediatric Investigators of the Portuguese Familial Hypercholesterolemia StudyThe distinction between a monogenic dyslipidemia and a polygenic/environmental dyslipidemia is important for the cardiovascular risk assessment, counseling, and treatment of these patients. The present work aims to perform the cardiovascular risk assessment of dyslipidemic children to identify useful biomarkers for clinical criteria improvement in clinical settings. Main cardiovascular risk factors were analyzed in a cohort of 237 unrelated children with clinical diagnosis of familial hypercholesterolemia (FH). About 40% carried at least two cardiovascular risk factors and 37.6% had FH, presenting mutations in LDLR and APOB. FH children showed significant elevated atherogenic markers and lower concentration of antiatherogenic particles. Children without a molecular diagnosis of FH had higher levels of TGs, apoC2, apoC3, and higher frequency of BMI and overweight/obesity, suggesting that environmental factors can be the underlying cause of their hypercholesterolem≥ia. An apoB/apoA1 ratio ≥0.68 was identified as the best biomarker (area under the curve = 0.835) to differentiate FH from other dyslipidemias. The inclusion in clinical criteria of a higher cut-off point for LDL cholesterol or an apoB/apoA1 ratio ≥0.68 optimized the criteria sensitivity and specificity. The correct identification, at an early age, of all children at-risk is of great importance so that specific interventions can be implemented. apoB/apoA1 can improve the identification of FH patients.
- Cardiovascular risk assessment of pediatric dyslipidemic patientsPublication . Medeiros, A.M.; Alves, A.C.; Bourbon, M.Identification of young population with high cardiovascular (CV) risk allows early intervention and prevention, delaying or abolishing occurrence of CHD in adult life. Hypercholesterolemia is an important CV risk factor that can be due to environmental or genetic causes. Genetic dyslipidemias, as Familial Hypercholesterolemia (FH), are associated with major risk of CV events.