RESUMO
BACKGROUND AND AIMS: Type I hyperlipoproteinemia, also known as familial chylomicronemia syndrome (FCS), is a rare autosomal recessive disorder caused by variants in LPL, APOC2, APOA5, LMF1 or GPIHBP1 genes. The aim of this study was to identify novel variants in the LPL gene causing lipoprotein lipase deficiency and to understand the molecular mechanisms. METHODS AND RESULTS: A total of 3 individuals with severe hypertriglyceridemia and recurrent pancreatitis were selected from the Lipid Clinic at Sahlgrenska University Hospital and LPL was sequenced. In vitro experiments were performed in human embryonic kidney 293T/17 (HEK293T/17) cells transiently transfected with wild type or mutant LPL plasmids. Cell lysates and media were used to analyze LPL synthesis and secretion. Media were used to measure LPL activity. Patient 1 was compound heterozygous for three known variants: c.337T > C (W113R), c.644G > A (G215E) and c.1211T > G (M404R); patient 2 was heterozygous for the known variant c.658A > C (S220R) while patient 3 was homozygous for a novel variant in the exon 5 c.679G > T (V227F). All the LPL variants identified were loss-of-function variants and resulted in a substantial reduction in the secretion of LPL protein. CONCLUSION: We characterized at the molecular level three known and one novel LPL variants causing type I hyperlipoproteinemia showing that all these variants are pathogenic.
Assuntos
Hiperlipoproteinemia Tipo I/genética , Lipase Lipoproteica/genética , Mutação , Adulto , Idoso , Feminino , Predisposição Genética para Doença , Células HEK293 , Heterozigoto , Homozigoto , Humanos , Hiperlipoproteinemia Tipo I/sangue , Hiperlipoproteinemia Tipo I/diagnóstico , Hiperlipoproteinemia Tipo I/enzimologia , Hipertrigliceridemia/sangue , Hipertrigliceridemia/enzimologia , Hipertrigliceridemia/genética , Lipídeos/sangue , Lipase Lipoproteica/metabolismo , Masculino , Pessoa de Meia-Idade , Pancreatite/sangue , Pancreatite/enzimologia , Pancreatite/genética , Fenótipo , Recidiva , TransfecçãoRESUMO
Genetic testing for hypertrophic cardiomyopathy (HCM) became available in Norway in 2003. Here, we describe the results of this testing in probands with HCM referred until the end of 2012. The translated exons of MYBPC3, MYH7, TNNI3, TNNT2, MYL2 and MYL3 were analyzed in two groups of probands. In Group 1, comprising 696 probands above 1 year of age, a mutation was found in 203 patients (29.2%). Of those, 5.9% were carriers of two mutations. Mean age in double mutation carriers, single mutation carriers and mutation negative probands was 44 years (± 19 years), 50 years (± 5 years) and 55 years (± 6 years), respectively. In Group 2, comprising 26 infants below the age of 1, a mutation was found in 15.4%. A total of 120 different mutations were found of which 51 (42.5%) were novel.
Assuntos
Cardiomiopatia Hipertrófica/genética , Testes Genéticos , Sequenciamento de Nucleotídeos em Larga Escala , Sarcômeros/genética , Adulto , Idoso , Cardiomiopatia Hipertrófica/patologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Mutação/genética , Noruega , Linhagem , Sarcômeros/patologiaRESUMO
The aim of this investigation was to identify pathogenic variants of the ryanodine receptor 2 (RYR2) gene in a cohort of persons aged 0-40 years who died of sudden unexpected death syndrome (SUD), including a cohort of infants who died of sudden infant death syndrome (SIDS). We genetically screened 29 of the 105 exons of the RYR2 gene associated with catecholaminergic polymorphic ventricular tachycardia (CPVT) in 74 cases of SUD without reported structural abnormalities of the heart. Cases were selected from the case database at the Institute of Forensic Medicine, and subsequent mutational screening by DNA sequencing was performed to detect variants in DNA samples extracted from blood samples of deceased persons. A total of 7 of the examined 74 cases were heterozygous for a rare sequence variant in the RYR2 gene. We identified five novel missense variants (p.Q486H, p.D1872N, p.G2367R, p.E4213D, and p.H4579Y), one synonymous variant (p.L4767L), and one previously reported missense variant (p.G4315E). Follow-up studies were possible in family members of three probands (p.Q486H, p.D1872N, and p.H4579Y), and clinical examinations were conducted in family members of two of these probands (p.Q486H and p.H4579Y). In conclusion, we identified a higher prevalence of variants in the CPVT-associated gene RYR2 than in a previously reported cohort of SIDS (9.4% vs. 1-2%). Segregation studies show that one variant (p.H4579Y) co-segregates with CPVT and is presumed to be pathogenic.
Assuntos
Morte Súbita/etiologia , Mutação , Canal de Liberação de Cálcio do Receptor de Rianodina/genética , Taquicardia Ventricular/genética , Adolescente , Adulto , Criança , Pré-Escolar , Estudos de Coortes , Éxons , Feminino , Genética Forense , Testes Genéticos , Heterozigoto , Humanos , Lactente , Recém-Nascido , Masculino , Análise de Sequência de DNA , Adulto JovemRESUMO
The LDL receptor (LDLR) plays an essential role in the regulation of plasma (LDL) cholesterol concentrations by virtue of its ability to clear plasma LDL. Down-regulation of the LDLR by proprotein convertase subtilisin/kexin 9 (PCSK9) has recently emerged as a regulatory mechanism that controls plasma LDL cholesterol concentrations. Studies in which PCSK9 is over-expressed in mice, have demonstrated that PCSK9, by enhancing hepatic LDLR degradation, decreases the availability of the LDLR for LDL uptake, resulting in increased plasma LDL cholesterol levels. However, PCSK9 has also recently been shown to mediate down-regulation of surface receptors other than the LDLR, suggesting that it may have much broader roles than initially thought.
Assuntos
Colesterol/genética , Hipercolesterolemia/genética , Fígado/metabolismo , Receptores de LDL/fisiologia , Serina Endopeptidases/fisiologia , Animais , Colesterol/sangue , Regulação para Baixo/genética , Regulação Enzimológica da Expressão Gênica , Homeostase/genética , Humanos , Hipercolesterolemia/sangue , Camundongos , Mutação de Sentido Incorreto/genética , Pró-Proteína Convertase 9 , Pró-Proteína Convertases , Receptores de LDL/genética , Serina Endopeptidases/genéticaRESUMO
OBJECTIVES: To expand our understanding of the structure and function of proprotein convertase subtilisin/kexin type 9 (PCSK9) by studying how naturally occurring mutations in PCSK9 disrupt the function of PCSK9. DESIGN: Mutations in PCSK9 were identified by sequencing of DNA from subjects with hypo- or hypercholesterolemia. The effect of the identified mutations on the autocatalytic cleavage and secretion of PCSK9, as well as the effect on PCSK9-mediated degradation of the low density lipoprotein receptors, were determined in HepG2 or HEK293 cells transiently transfected with mutant PCSK9-containing plasmids. The findings were collated to the clinical characteristics of the subjects possessing these mutations, and the phenotypic effects were analysed in terms of available structural data for PCSK9. RESULTS: Five novel mutations in PCSK9 were identified. Mutation R215H was a gain-of-function mutation which causes hypercholesterolemia. Mutation G236S and N354I were loss-of-function mutations due to failure to exit the endoplasmic reticulum or failure to undergo autocatalytic cleavage, respectively. Mutations A245T and R272Q were most likely normal genetic variants. By comparing the number of patients with gain-of-function mutations in PCSK9 with the number of familial hypercholesterolemia heterozygotes among subjects with hypercholesterolemia, the prevalence of subjects with gain-of-function mutations in PCSK9 in Norway can be estimated to one in 15,000. CONCLUSION: This study has provided novel information about the structural requirements for the normal function of PCSK9. However, more studies are needed to determine the mechanisms by which gain-of-function mutations in PCSK9 cause hypercholesterolemia.
Assuntos
Domínio Catalítico/genética , LDL-Colesterol/metabolismo , Hipercolesterolemia/genética , Mutação/genética , Serina Endopeptidases/genética , Serina Endopeptidases/metabolismo , Adulto , LDL-Colesterol/sangue , LDL-Colesterol/genética , Análise Mutacional de DNA , Feminino , Genes Dominantes , Humanos , Hipercolesterolemia/sangue , Hipercolesterolemia/tratamento farmacológico , Masculino , Noruega , Valor Preditivo dos Testes , Pró-Proteína Convertase 9 , Pró-Proteína Convertases , Resultado do TratamentoRESUMO
We have studied the effect of lovastatin, an inhibitor of the rate-limiting enzyme in cholesterol biosynthesis (3-hydroxy-3-methylglutaryl coenzyme A reductase), alone and in combination with the bile acid sequestrant cholestyramine on lipid parameters in 30 heterozygous patients with familial hypercholesterolemia (FH) during a 20-week open trial. Lovastatin 40 mg bid (twice daily) decreased significantly total serum cholesterol, low density lipoprotein (LDL)-cholesterol, triglycerides and apolipoprotein B by 36%, 45%, 29% and 11%, respectively, while high density lipoprotein (HDL)-cholesterol and apolipoprotein A-I were increased significantly by 16% and 37%, respectively. These data are consistent with a reduction in both the number of LDL particles and in their cholesterol content. Addition of cholestyramine 4 g bid caused a significant further decrease in total serum cholesterol and LDL-cholesterol to a total of 43% and 61%, respectively. The addition of 4 g bid or 8 g bid of cholestyramine caused only minor changes in the other lipid parameters. No effect was found by these drugs on Lp(a) lipoprotein level. We conclude that lovastatin alone or in combination with a small dose of cholestyramine normalizes the lipid profile in most FH heterozygotes.
Assuntos
Apolipoproteínas/sangue , Resina de Colestiramina/administração & dosagem , Hiperlipoproteinemia Tipo II/tratamento farmacológico , Lipídeos/sangue , Lovastatina/administração & dosagem , Adulto , Resina de Colestiramina/efeitos adversos , Resina de Colestiramina/uso terapêutico , Ensaios Clínicos como Assunto , Quimioterapia Combinada , Feminino , Heterozigoto , Humanos , Hiperlipoproteinemia Tipo II/sangue , Hiperlipoproteinemia Tipo II/genética , Lovastatina/efeitos adversos , Lovastatina/uso terapêutico , Masculino , Pessoa de Meia-IdadeRESUMO
DNA from 20 unrelated familial hypercholesterolemia (FH) subjects were studied by analysis of single-strand conformation polymorphisms (SSCP) for mutations in exon 3 of the low density lipoprotein (LDL) receptor gene. Four different SSCP patterns were observed. The underlying mutations were characterized by DNA sequencing. One pattern represented the wild-type sequence. Another pattern represented a C-->G mutation (FH-Svartor) that changes codon 78 into the amber stop codon. The two other patterns represented heterozygosity and homozygosity, respectively, for a G-->A splice donor mutation (FH-Elverum) in intron 3. Based upon two PCR-based assays, the frequencies of FH-Svartor and FH-Elverum among 267 unrelated FH subjects, were 8% and 25%, respectively. FH Svartor was located on a chromosome with haplotype 3 in all five families where haplotype analysis were performed. FH Elverum was located on haplotype 2 in 16 out of 20 families. The two mutations must be considered founder mutations in the Norwegian population, and their existence will be clinically useful in diagnosing FH. The presence of two founder mutations together with previously published data on the prevalence of FH in Norway, indicate that FH may be a more common disease in Norway than previously thought.
Assuntos
Hiperlipoproteinemia Tipo II/genética , Receptores de LDL/genética , Sequência de Bases , Feminino , Humanos , Hiperlipoproteinemia Tipo II/diagnóstico , Masculino , Dados de Sequência Molecular , Noruega , Linhagem , Reação em Cadeia da Polimerase , Polimorfismo Conformacional de Fita Simples , PrevalênciaRESUMO
We have established an improved method for detecting point mutations by semi-automated DNA sequencing of PCR fragments generated from genomic DNA. The method employs magnetic beads to create immobilized single-stranded DNA templates, and the sequencing reaction is performed with Sequenase. This method is superior to sequencing with Taq DNA polymerase because the uniform peak height with Sequenase makes heterozygosity easily detectable as double peaks that are half the normal height. Detection of heterozygosity by this method is illustrated by sequencing a 180-bp fragment of the human apolipoprotein B gene. This fragment contains codon 3500, where a point mutation (3500CGG-->CAG) is found in subjects with the autosomal dominant disease familial defective apolipoprotein B. The nonuniform peak height with Taq DNA polymerase makes it more difficult to detect heterozygosity. This is also illustrated by sequencing a 278-bp fragment of the low-density lipoprotein receptor gene.
Assuntos
Análise Mutacional de DNA/métodos , Mutação Puntual , Análise de Sequência de DNA/métodos , Apolipoproteínas B/genética , Sequência de Bases , Biotecnologia , DNA/genética , DNA Polimerase Dirigida por DNA , Estudos de Avaliação como Assunto , Humanos , Magnetismo , Dados de Sequência Molecular , Reação em Cadeia da Polimerase , Receptores de LDL/genética , Taq PolimeraseRESUMO
We have previously demonstrated that expression of the human apolipoprotein (apo) E gene is controlled by multiple regulatory elements in the promoter [Paik et al. (1988) J. Biol. Chem. 263, 13340-13349; Chang et al. (1990) J. Biol. Chem. 265, 9496-9504]. To extend these studies, we have characterized an element in the apoE gene promoter that spans nucleotides -101 to -89, upstream regulatory element 3 (URE3). Transcription of promoter/marker gene constructs in vitro showed that URE3 modulates gene expression. Gel mobility shift assays of URE3 using human placental nuclear extracts detected a specific binding protein whose activity can be modulated by micromolar amounts of divalent copper and zinc. Competitive binding and gel shift assays with mutant oligonucleotides revealed critical nucleotides within URE3 required for its specific nuclear protein-binding activity. Gel filtration and oligonucleotide affinity chromatography were employed to isolate a URE3-binding protein (URE3BP) from human placental nuclear extracts. Purified URE3BP appears to be a M(r) = 300,000 protein that is composed of four equally-sized basic subunits of M(r) = 67,000. These studies indicate that URE3 is an active regulatory component of the apoE gene.
Assuntos
Apolipoproteínas E/genética , Proteínas de Ligação a DNA/isolamento & purificação , DNA/genética , Placenta/química , Sequências Reguladoras de Ácido Nucleico , Sequência de Bases , Sítios de Ligação , Cloranfenicol O-Acetiltransferase/genética , DNA/análise , DNA/metabolismo , Proteínas de Ligação a DNA/química , Regulação da Expressão Gênica/fisiologia , Células HeLa , Humanos , Dados de Sequência Molecular , Proteínas Recombinantes de Fusão/genética , Transcrição GênicaRESUMO
Conventional statistical methods based upon single restriction fragment length polymorphisms often prove inadequate in studies of genetic variation. Cladistic analysis has been suggested as an alternative, but requires basic assumptions that usually cannot be met. We wanted to test whether it could be a workable approach to apply the genetic algorithm, an artificial intelligence method, to haplotype data. The genetic algorithm creates in-computer artificial 'individuals', all having 'genes' coding for solutions to a problem. The individuals are allowed to compete and 'mate', individuals with genes coding for better solutions mating more often. Genes coding for good solutions survive through generations of the genetic algorithm. At the end of the run, the best solutions can be extracted. We applied the genetic algorithm to data consisting of cholesterol values and haplotypes made up of seven restriction sites at the LDL receptor locus. The persons included were 114 FH (familial hypercholesterolemia) patients and 61 normals. The genetic algorithm found the restriction sites 1 (Sph1 in intron 6), 2 (StuI in exon 8), and 7 (ApaLI site in the 3' flanking region) were associated with high cholesterol levels. As a validity check we used runs of the genetic algorithm applied to 'artificial patients', i.e. artificially generated haplotypes linked to artificially generated cholesterol values. This demonstrated the genetic algorithm consistently found the appropriate haplotype. We conclude that the genetic algorithm may be a useful tool for studying genetic variation.
Assuntos
Algoritmos , Haplótipos , Modelos Genéticos , Receptores de LDL/genética , Inteligência Artificial , Colesterol/sangue , Estudos de Avaliação como Assunto , Feminino , Variação Genética , Humanos , Hiperlipoproteinemia Tipo II/sangue , Hiperlipoproteinemia Tipo II/genética , Masculino , Polimorfismo de Fragmento de RestriçãoRESUMO
The aim of this investigation was to identify and characterise pathogenic mutations in a sudden cardiac death (SCD) cohort suspected of cardiomyopathy in persons aged 0-40 years. The study material for the genetic screening of cardiomyopathies consisted of 41 cases and was selected from the case database at the Institute of Forensic Medicine. Mutational screening by DNA sequencing was performed to detect mutations in DNA samples from deceased persons suspected of suffering from hypertrophic cardiomyopathy (HCM), dilated cardiomyopathy (DCM), and arrhythmogenic right ventricle cardiomyopathy (ARVC). A total of 9 of the examined 41 cases had a rare sequence variant in the MYBPC3, MYH7, LMNA, PKP2 or TMEM43 genes, of which 4 cases (9.8%) were presumed to be pathogenic mutations. The presumed pathogenic mutations were distributed with one case of suspected HCM and DCM (MYH7; p.R442H), one case of suspected DCM (LMNA; p.R471H), and two cases of suspected ARVC (PKP2; p.R79X and LMNA; p.R644C). The presented data adds important information on the genetic elements of SCD in the young, and calls for expert pathological evaluation and molecular autopsy in the post-mortem examination of SCD victims with structural anomalies of the heart.
Assuntos
Cardiomiopatias/diagnóstico , Cardiomiopatias/genética , Morte Súbita Cardíaca/etiologia , Adolescente , Adulto , Miosinas Cardíacas/genética , Proteínas de Transporte/genética , Criança , Feminino , Genética Forense , Testes Genéticos , Humanos , Lamina Tipo A/genética , Masculino , Proteínas de Membrana/genética , Mutação , Cadeias Pesadas de Miosina/genética , Placofilinas/genética , Análise de Sequência de DNA , Adulto JovemRESUMO
Mutations in the KCNQ1, HERG, SCN5A, minK and MiRP1 genes cause long QT syndrome (LQTS), of which there are two forms: the Romano Ward syndrome and the Jervell and Lange-Nielsen syndrome. We have performed DNA sequencing of the LQTS-associated genes in 169 unrelated patients referred for genetic testing with respect to Romano Ward syndrome and in 13 unrelated patients referred for genetic testing with respect to Jervell and Lange-Nielsen syndrome. A total of 37 different mutations in the 5 genes, of which 20 were novel, were identified. Among patients with the most stringent clinical criteria of Romano Ward syndrome, a mutation was identified in 71%. Twelve of the 13 unrelated patients referred for genetic testing with respect to Jervell and Lange-Nielsen syndrome were provided with a molecular genetic diagnosis. Cascade genetic screening of 505 relatives of index patients with molecularly defined LQTS identified 251 mutation carriers. The observed penetrance was 41%. Although caution must be exerted, the prevalence of heterozygotes for mutations in the LQTS-associated genes in Norway could be in the range 1/100-1/300, based on the prevalence of patients with Jervell and Lange-Nielsen syndrome.
Assuntos
Heterozigoto , Síndrome do QT Longo/epidemiologia , Síndrome do QT Longo/genética , Adolescente , Adulto , Criança , Pré-Escolar , Feminino , Humanos , Lactente , Síndrome do QT Longo/patologia , Masculino , Pessoa de Meia-Idade , Biologia Molecular , Mutação/genética , Noruega/epidemiologia , Prevalência , Canal de Liberação de Cálcio do Receptor de Rianodina/genética , Canal de Liberação de Cálcio do Receptor de Rianodina/metabolismoRESUMO
OBJECTIVE: Missense mutations in the proprotein convertase subtilisin/kexin type 9 (PCSK9) gene have been found to cause autosomal dominant hypercholesterolemia. The objective of this study was to investigate possible mechanisms by which mutation D374Y in the PCSK9 gene causes hypercholesterolemia. MATERIAL AND METHODS: Binding and internalization of low-density lipoprotein LDL in Epstein-Barr virus (EBV)-transformed lymphocytes from D374Y heterozygotes were examined. The autocatalytic activity of the D374Y mutant was studied in transiently transfected HEK293 cells. RESULTS: As determined by Western blot analysis of transiently transfected HEK293 cells, the autocatalytic activity of the D374Y mutant was approximately 95% of the wild-type. Levels of PCSK9 mRNA in EBV-transformed lymphocytes from D374Y heterozygotes and normal controls were similar and less than 1/1000 of the level in HepG2 cells. The amount of cell surface LDL receptors (LDLRs) in EBV-transformed lymphocytes from five D374Y heterozygotes was non-significantly increased by 17% compared with the amount in normal controls. LDLR-dependent binding and internalization of LDL in EBV-transformed lymphocytes from D374Y heterozygotes were non-significantly reduced by 11% and 12%, respectively, compared to the corresponding values in normal controls. CONCLUSIONS: LDLR-mediated endocytosis of LDL is not reduced in EBV-transformed lymphocytes from D374Y heterozygotes. Because of the extremely low levels of PCSK9 mRNA in EBV-transformed lymphocytes, it is possible that the LDLR-dependent endocytosis of LDL could be more severely affected in hepatocytes from D374Y heterozygotes than in EBV-transformed lymphocytes.
Assuntos
Heterozigoto , Hiperlipoproteinemia Tipo II/genética , Mutação de Sentido Incorreto/genética , Receptores de LDL/genética , Serina Endopeptidases/genética , Linhagem Celular Transformada , Endocitose , Herpesvirus Humano 4 , Humanos , Lipoproteínas LDL/metabolismo , Linfócitos/metabolismo , Pró-Proteína Convertase 9 , Pró-Proteína Convertases , Receptores de LDL/metabolismo , Serina Endopeptidases/metabolismo , Estatísticas não ParamétricasRESUMO
Familial hypercholesterolemia (FH) is characterized by autosomal dominantly inherited hypercholesterolemia, xanthomas and premature coronary heart disease. The disease is caused by defective cell surface low density lipoprotein (LDL) receptors. This paper reviews the molecular defects underlying defective LDL receptors. Studies of the molecular genetics of FH have provided important information on the structure-function relationship of the LDL receptor. This information may explain the considerable variation in levels of serum cholesterol among FH subjects, and why FH subjects respond differently to lipid lowering drugs. The diagnostic and therapeutic implications of the molecular findings are discussed.
Assuntos
Hiperlipoproteinemia Tipo II/genética , Receptores de LDL/genética , Humanos , Hiperlipoproteinemia Tipo II/etiologia , Hiperlipoproteinemia Tipo II/metabolismo , Biologia Molecular , Mutação , Receptores de LDL/metabolismoRESUMO
Proprotein convertase subtilisin/kexin type 9 (PCSK9) is at a locus for autosomal dominant hypercholesterolemia, and recent data indicate that the PCSK9 gene is involved in cholesterol biosynthesis. Mutations within this gene have previously been found to segregate with hypercholesterolemia. In this study, DNA sequencing of the 12 exons of the PCSK9 gene has been performed in 51 Norwegian subjects with a clinical diagnosis of familial hypercholesterolemia where mutations in the low-density lipoprotein receptor gene and mutation R3500Q in the apolipoprotein B-100 gene had been excluded. Two novel missense mutations were detected in the catalytic subdomain of the PCSK9 gene. Two patients were heterozygotes for D374Y, and one patient was a double heterozygote for D374Y and N157K. D374Y segregated with hypercholesterolemia in the two former families where family members were available for study. Our findings support the notion that mutations in the PCSK9 gene cause autosomal dominant hypercholesterolemia.
Assuntos
Hipercolesterolemia/genética , Mutação , Serina Endopeptidases/genética , Adolescente , Adulto , Criança , Colesterol/sangue , Feminino , Genes Dominantes , Humanos , Masculino , Pessoa de Meia-Idade , Noruega , Pró-Proteína Convertase 9 , Pró-Proteína ConvertasesRESUMO
Familial hypercholesterolemia (FH) is caused by a mutation in the low-density lipoprotein receptor gene and is characterized by hypercholesterolemia, xanthomas, and premature coronary heart disease. Heterozygotes typically have values for total serum cholesterol in the range of 7-15 mmol/l and efficient lipid-lowering drug therapy is available. However, only approximately 20% of patients are diagnosed and less than 10% are being adequately treated. The most cost-effective strategy to diagnose patients with FH is to screen close relatives of patients already diagnosed with FH. This is referred to as cascade genetic screening. This review focuses on organization of a cascade genetic screening program for FH as well as cost-efficiency assessments, health benefits, possible adverse effects, and the screening of children. The author concludes that cascade genetic screening for FH leads to health benefits and is cost-effective without causing psychological or social damage. Accordingly, national cascade genetic screening programs for FH should be part of ordinary health care.
Assuntos
Testes Genéticos , Hiperlipoproteinemia Tipo II/genética , Análise Custo-Benefício , Testes Genéticos/economia , Testes Genéticos/ética , Testes Genéticos/psicologia , Humanos , Hiperlipoproteinemia Tipo II/diagnóstico , Hiperlipoproteinemia Tipo II/epidemiologiaRESUMO
The effect of the alpha 1 adrenoreceptor antagonist doxazosin on low density lipoprotein (LDL) receptor activity, has been studied in cultured skin fibroblasts. Doxazosin at a concentration of 10(-5) M significantly increased the LDL receptor activity. The possible clinical implications of this observation are discussed.
Assuntos
Antagonistas Adrenérgicos alfa/farmacologia , Lipoproteínas LDL/metabolismo , Prazosina/farmacologia , Quinazolinas/farmacologia , Receptores de Superfície Celular/efeitos dos fármacos , Linhagem Celular , Células Cultivadas , Pré-Escolar , Doxazossina , Fibroblastos/metabolismo , Humanos , Hiperlipoproteinemia Tipo II/metabolismo , Prazosina/análogos & derivados , Receptores de Superfície Celular/metabolismo , Receptores de LipoproteínasRESUMO
Serum lipids were studied in hypercholesterolaemic rabbits treated with the selective alpha 1-adrenoreceptor antagonist doxazosin. Hypercholesterolaemia had been induced by cholesterol feeding which raised mean (+/- SEM) total serum cholesterol from 1.4 (+/- 0.1) mmol/l to 84.1 (+/- 3.6) mmol/l. A cross-over design was used to compare the effect of doxazosin with placebo in 20 rabbits of which 16 completed the study. Doxazosin (2 mg/kg) or placebo vehicle was administered subcutaneously once daily for three weeks. Compared with placebo, doxazosin produced an 8.6% greater reduction in total serum cholesterol. This difference did not, however, reach statistical significance.
Assuntos
Antagonistas Adrenérgicos alfa/farmacologia , Hipercolesterolemia/tratamento farmacológico , Lipídeos/sangue , Prazosina/análogos & derivados , Animais , Chinchila , Colesterol/administração & dosagem , Colesterol/sangue , Doxazossina , Avaliação Pré-Clínica de Medicamentos , Feminino , Prazosina/farmacologiaRESUMO
Low density lipoprotein (LDL) receptor activity in fibroblasts decreases with increasing cell concentration. This was found for radioligand assays at 4 degrees C and 37 degrees C. Thus, it seems that it is the binding of 125I-LDL to the LDL receptor which is the step in the LDL receptor pathway that is influenced by differences in cell concentration. The reduced binding of 125I-LDL with increasing cell concentration seems to result from a modification of 125I-LDL by fibroblasts. Binding of 125I-LDL to cell-free plastic tubes was used to study this modification of 125I-LDL. Such studies indicated that direct cell contact was not required for the modification to occur. The rapid modification of 125I-LDL (within 10 min) took place even at 4 degrees C. These findings suggest that substances released from the cell membrane interact with LDL and decrease its binding to the LDL receptor. The higher the cell concentration is, the more modification of LDL takes place. Fibroblast modified LDL has reduced electrophoretic mobility. We conclude that differences in cell concentration influence LDL receptor activity by interfering with the binding of 125I-LDL to the LDL receptors, rather than affecting the receptor number on the cells' surfaces.
Assuntos
Fibroblastos/metabolismo , Receptores de LDL/metabolismo , Contagem de Células , Células Cultivadas , Meios de Cultura , Eletroforese , Humanos , Hipercolesterolemia/metabolismo , Imunoeletroforese Bidimensional , Ensaio Radioligante , Pele/citologiaRESUMO
Patients with familial hypercholesterolaemia have a significantly elevated risk of coronary heart disease. Accordingly, it is of crucial importance to diagnose and treat these patients before they contract premature coronary heart disease. At present, however, only a small proportion of familial hypercholesterolaemia patients are treated adequately. One main reason for this is probably the relatively vague clinical diagnostic criteria applied. We therefore advocate instead the use of molecular genetics to obtain a specific diagnosis by identifying the underlying genetic defect.