ABSTRACT
BACKGROUND: Familial chylomicronemia (type I hyperlipidemia) is a rare autosomal recessive disease due mainly to rare variants in the lipoprotein lipase (LPL) gene sequence. Molecular diagnosis of LPL deficiency is now a requirement for the first gene therapy treatment approved in the European Union. Altered coding sequence variants in APOC2, APOA5 or GPIHBP-1 can also cause familial chylomicronemia. Herein, we report the results of our molecular diagnostic activity in this topic, carried out in the setting of a Spanish clinical practice hospital laboratory, which was also extended to some patients who were more likely to have type V hyperlipidemia. METHODS: Samples from twenty-nine unrelated probands with severe hypertriglyceridemia were referred for molecular diagnosis. Samples were first screened for LPL sequence variants by DNA sequencing and, in the absence of alterations, subsequent analysis of APOC2, APOA5, and GPIHBP1 genes was undertaken. Analysis of LPL function in vitro was further studied in two previously uncharacterized LPL sequence variants. RESULTS: Fourteen different, loss-of-function variants were found in the LPL gene: 4 were novel or uncharacterized allelic variants, and of these, 2 were directly shown to affect function. Twenty of 29 probands presented at least one LPL gene allele variant: 8 were homozygous, 9 compound heterozygous and 3 heterozygous. In 13 probands, the finding of two loss-of-function variants supported the diagnosis of LPL deficiency. None of the probands presented sequence variants in the APOC2 gene, whereas 3 presented rare variants within the APOA5 gene. Four of the five patients heterozygous for a common variant in the GPIHBP-1 gene also carried APOA5 sequence variants. CONCLUSIONS: Loss-of-function LPL variants leading to familial chylomicronemia were found in 13 patients, accounting for a significant proportion of the LPL-deficient patients predicted to live in Spain.
Subject(s)
Clinical Laboratory Techniques , Hyperlipidemias/diagnosis , Hyperlipidemias/enzymology , Lipoprotein Lipase/deficiency , Adolescent , Adult , Animals , Apolipoprotein A-V , Apolipoprotein C-II/genetics , Apolipoproteins A/genetics , COS Cells , Child , Child, Preschool , Chlorocebus aethiops , Female , Genetic Variation , Humans , Hyperlipidemias/genetics , Infant , Infant, Newborn , Lipoprotein Lipase/genetics , Male , Middle Aged , Mutagenesis , Receptors, Lipoprotein/genetics , Young AdultABSTRACT
OBJETIVOS: El objetivo de este estudio fue evaluar las alteraciones proteicas de las lipoproteínas de alta densidad (HDL) provocadas por la hiperhomocisteinemia inducida por ingesta de metionina en ratones y su relación con 2 de las propiedades antiaterogénicas más importantes de las HDL. Métodos y resultados La hiperhomocisteinemia inducida por administración de metionina resultó en un aumento (∼ 8 veces) de la concentración plasmática de homocisteína. La hiperhomocisteinemia se correlacionó inversamente con la concentración plasmática de colesterol HDL y del componente proteico principal de las HDL, la apolipoproteína (apo) A- I . El eflujo de colesterol desde macrófagos a las HDL in vivo disminuyó en ratones hiperhomocisteinémicos en comparación con los controles. Sin embargo, el transporte reverso del colesterol desde macrófagos a heces no se observó alterado. Por otro lado, la capacidad de las HDL de ratones hiperhomocisteinémicos de prevenir la modificación oxidativa de las lipoproteínas de baja densidad (LDL) disminuyó, observándose también una reducción en la actividad plasmática de paraoxonasa-1 (PON1) y en la concentración plasmática de apoA- I y con una disminución relativa en la cantidad de apoA- IV (∼ 1,5 veces) en las HDL de ratones hiperhomocisteinémicos comparados con las de los controles. Conclusión La disminución en la protección contra la modificación oxidativa de las LDL por parte de las HDL de ratones hiperhomocisteinémicos se asoció con una disminución de apoA- I , PON1 y apoA- IV
AIM: The aim of this study was to evaluate the proteic changes in high-density lipoproteins(HDL) induced by methionine-induced hyperhomocysteinemia in mice and its relationship with two of their main antiatherogenic properties. METHODS AND RESULTS: The oral administration of methionine resulted in an elevation (∼ 8 times)in the plasma concentration of homocysteine. Hyperhomocysteinemia was inversely correlated with the plasma concentration of HDL cholesterol and its main protein component of HDL, apolipoprotein (apo) A-I, respectively. The cholesterol efflux in vivo from macrophages to HDL was decreased in hyperhomocysteinemic mice compared with the control mice. However, the reverse cholesterol transport from macrophages to feces remained unchanged. On the other hand, the ability of HDL from hyperhomocysteinemic mice to prevent the oxidative modification of low-density lipoproteins (LDL) was found decreased and associated with a concomitant reduction in the plasma activity of paraoxonase-1 (PON1) and the plasma concentration of apoA-I, and with a relative reduction in the apoA-IV content (∼1.5times) in the hyperhomocysteinemic HDL, respectively. Conclusion: The decrease in the ability of HDL from hyperhomocysteinemic mice to prevent LDL from oxidation was associated with a decrease in the apoA-I, PON1 and apoA-IV
Subject(s)
Animals , Mice , Hyperhomocysteinemia/physiopathology , Lipoproteins, HDL/analysis , Proteomics/methods , Atherosclerosis/physiopathology , Disease Models, Animal , Biomarkers/analysisABSTRACT
AIM: The aim of this study was to evaluate the proteic changes in high-density lipoproteins (HDL) induced by methionine-induced hyperhomocysteinemia in mice and its relationship with two of their main antiatherogenic properties. METHODS AND RESULTS: The oral administration of methionine resulted in an elevation (~8 times) in the plasma concentration of homocysteine. Hyperhomocysteinemia was inversely correlated with the plasma concentration of HDL cholesterol and its main protein component of HDL, apolipoprotein (apo) A-I, respectively. The cholesterol efflux in vivo from macrophages to HDL was decreased in hyperhomocysteinemic mice compared with the control mice. However, the reverse cholesterol transport from macrophages to feces remained unchanged. On the other hand, the ability of HDL from hyperhomocysteinemic mice to prevent the oxidative modification of low-density lipoproteins (LDL) was found decreased and associated with a concomitant reduction in the plasma activity of paraoxonase-1 (PON1) and the plasma concentration of apoA-I, and with a relative reduction in the apoA-IV content (~1.5 times) in the hyperhomocysteinemic HDL, respectively. CONCLUSION: The decrease in the ability of HDL from hyperhomocysteinemic mice to prevent LDL from oxidation was associated with a decrease in the apoA-I, PON1 and apoA-IV.
