RESUMO
El objetivo del presente trabajo fue estudiar a una joven paciente con manifestaciones hemorrágicas, caracterizar su fibrina plasmática e identificar la posible alteración molecular del fibrinógeno de la paciente y sus familiares directos. Se diagnosticó una disfibrinogenemia en la paciente, su madre y el medio-hermano, ambos asintomáticos. En estos individuos, la formación y lisis de la fibrina plasmática difirieron de los controles. La fase lag prolongada indicó la liberación lenta y defectuosa de los fibrinopéptidos; la pendiente menor que la del control sugirió una polimerización dificultada. La DOMax inferior mostró una fibrina compuesta por fibras delgadas. La fibrinolisis inducida por estreptoquinasa resultó más rápida que la correspondiente control. La secuenciación del ADN reveló una deleción homocigota que condujo a la ausencia de la glicina 14 de la cadena Aa del fibrinógeno (AaGly14del según nomenclatura de http://www.geht.org/databaseang/fibrinogen). La madre y el medio hermano resultaron heterocigotas para la misma mutación. Esta alteración no descripta previamente, que se ha denominado fibrinógeno Jujuy, podría no interaccionar correctamente con el sitio activo de la trombina, provocando que los fibrinopéptidos se hidrolicen y liberen lentamente, originando fibras de fibrina más delgadas y degradables que las del control. Este mecanismo explicaría el sangrado moderado de la paciente.
The aim of this work was to study a young female with moderate bleeding symptoms, to characterize the plasma fibrin and to identify the possible molecular alteration in the fibrinogen of the patient and her family. A dysfibrinogenemia was diagnosed in the patient, the mother and the half-brother, both the latter asymptomatic. Kinetic parameters obtained from fibrin formation and lysis assays of the patient’s plasma samples were significantly different compared to the ones obtained with control plasma. A prolonged lag phase indicated slow and defective fibrinopeptide releases, whereas a minor slope suggested an impaired fibrin assembly. A lower ODMax revealed a fibrin network composed of thinner fibers. Fibrinolysis induced by streptokinase resulted faster than control. DNA sequencing showed a homozygous deletion leading to AaGly14del (according to http://www.geht.org/databaseang/fibrinogen). The mother and the half-brother resulted heterozygous for the same mutation. This previously undescribed alteration was named fibrinogen Jujuy. The mutate fibrinogen might not be correctly fixed to the active site of thrombin resulting in slow cleavage and release of fibrinopeptides, rendering thinner fibers, more susceptible to lysis than control. This mechanism may explain the moderate bleeding symptoms of the patient.
O objetivo do presente trabalho foi estudar uma jovem paciente com manifestações hemorrágicas, caracterizar sua fibrina plasmática e identificar a possível alteração molecular do fibrinogênio da paciente e seus familiares diretos. Foi diagnosticada uma disfibrinogenemia na paciente, sua mãe e o meio-irmão, ambos assintomáticos. Nestes indivíduos, a formação e lise da fibrina plasmática diferiram dos controles. A fase lag prolongada indicou a liberação lenta e defeituosa dos fibrinopeptídeos; a pendente menor que a do controle sugeriu uma polimerização dificultada. A DOMax inferior mostrou uma fibrina composta por fibras delgadas. A fibrinólise induzida por estreptoquinase resultou mais rápida que a correspondente controle. A sequenciação do DNA revelou uma deleção homozigótica que conduziu à ausência da glicina 14 da cadeia Aa do fibrinogênio (AaGly14del conforme nomenclatura de http://www.geht.org/databaseang/fibrinogen). A mãe e o meio irmão resultaram heterozigotos para a mesma mutação. Esta alteração não descrita previamente, que denominamos fibrinogênio Jujuy, poderia não interagir corretamente com o sítio ativo da trombina, provocando que os fibrinopeptídeos se hidrolisem e liberem lentamente, originando fibras de fibrina mais finas e degradáveis que as do controle. Este mecanismo explicaria o sangramento moderado da paciente.
Assuntos
Humanos , Masculino , Feminino , Adulto , Pessoa de Meia-Idade , Fibrinogênio , Fibrinólise , Hemorragia , Coagulação Sanguínea , TrombinaRESUMO
Epidemiologic studies have shown that hyperhomocysteinemia is an independent risk factor for vascular disease. Homocysteine (Hcy) circulates as different species, mostly protein bound, and approximately 1% as its reduced form and the cyclic thioester homocysteine-thiolactone (HTL). Despite the level of plasma thiolactone being markedly low, detrimental effects are related to its high reactivity. HTL reacts with proteins by acylation of free basic amino groups; in particular, the epsilon-amino group of lysine residues forms adducts and induces structural and functional changes in plasma proteins. In order to assess the effects of HTL on plasma fibrin networks, a pool of normal plasma incubated with HTL (100, 500 and 1,000 µmol/L, respectively) was evaluated by global coagulation tests and fibrin formation kinetic assays, and the resulting fibrin was observed by scanning electron microscopy. HTL significantly prolonged global coagulation tests in a concentration-dependent manner with respect to control, and increases were up to 14.5%. Fibrin formation kinetic parameters displayed statistically significant differences between HTL-treated plasma and control in a concentration-dependent way, showing higher lag phase and lower maximum reaction velocity and final network optical density. Electron microscopy analysis of HTL plasma networks revealed a compact architecture, with more branches and shorter fibers than control. We can conclude that HTL induced a slower coagulation process, rendering more tightly packed fibrin clots. Since these features of the networks have been related to impaired fibrinolysis, the N-homocysteinylation reactions would be involved in the prothrombotic effects associated to hyperhomocysteinemia.
Assuntos
Fibrina/metabolismo , Homocisteína/análogos & derivados , Plasma/efeitos dos fármacos , Plasma/metabolismo , Animais , Coagulação Sanguínea/efeitos dos fármacos , Coagulação Sanguínea/fisiologia , Bovinos , Fibrina/química , Homocisteína/farmacologia , Humanos , Plasma/químicaRESUMO
Dermatan sulfate (DS) is well-known for its anticoagulant activity through binding to heparin cofactor II (HCII) to enhance thrombin inhibition. It has also been reported that DS has a profibrinolytic effect. We have evaluated the effects of DS solutions (4-20 µg/mL) on the formation (by kinetic studies), structure (by electron microscopy and compaction assays) and lysis (with urokinase-type plasminogen activator) of plasma fibrin networks. The results showed that DS significantly prolonged the lag phase and decreased the fibrin formation rate and the optical density of the final networks versus control, in a concentration dependent way. DS-associated networks presented a minor network percentage compared with control, composed of lower number of fibers per field, which resulted significantly thinner and longer. Moreover, DS rendered gels more sensible to rupture by centrifugal force and more susceptible to lysis. When fibrin formation kinetic assays were performed with purified fibrinogen instead of plasma, in the absence of HCII, the optical density of final DS-associated networks was statistically lower than control. Therefore, a direct effect of DS on the thickness of fibers was observed. Since in all in vitro assays low DS concentrations were used, it could be postulated that the fibrin features described above are plausible to be found in in vivo thrombi and therefore, DS would contribute to the formation of less thrombogenic clots.
Assuntos
Anticoagulantes/metabolismo , Dermatan Sulfato/fisiologia , Fibrina/fisiologia , Fibrina/ultraestrutura , Animais , Anticoagulantes/fisiologia , Bovinos , Fibrina/metabolismo , Ligação Proteica/fisiologiaRESUMO
Mechanisms involved in the relationship between hyperhomocysteinemia and thrombosis are still unclear. In previous reports we have shown that high homocysteine concentrations led to more compact and branched fibrin networks than controls. These clots showed an impaired lysis associated to their architecture. The aim of this study was to evaluate the effects of homocysteine on permeation of clots obtained from plasma and purified systems. Fibrin gels were prepared with normal plasma incubated with homocysteine and, in the purified systems, with fibrinogen and factor XIII treated with the amino acid. Permeability constants (K(s)) were determined through flow measurements. Linear regression curve between K(s) values and homocysteine levels in the plasmatic assays showed a negative correlation coefficient, r = -0.997 (p = 0.003). K(s) of fibrin gels obtained from purified systems with fibrinogen incubated with homocysteine was (7.07 ± 0.27) × 10(-9) cm(2), control was (11.40 ± 0.37) × 10(-9) cm(2) (n = 3; p < 0.01). K(s) of fibrin gels obtained with factor XIII treated with homocysteine was (1.47 ± 0.17) × 10(-9) cm (2), and control was (3.31 ± 0.31) × 10(-9) cm(2) (n = 3; p<0.01). Plasma incubated with high homocysteine concentrations produced fibrin clots significantly less permeable than controls in a dose dependent manner, and the results showed that fibrinogen and factor XIII were involved in that detrimental effect. These findings might explain the impaired fibrinolysis related to increased homocysteine levels and contribute to understanding the association between the amino acid and thrombosis.
Assuntos
Fibrina/metabolismo , Fibrinólise , Homocisteína/sangue , Hiper-Homocisteinemia/sangue , Fator XIII/metabolismo , Fibrinogênio/metabolismo , Humanos , Modelos Lineares , PermeabilidadeRESUMO
Several studies have associated elevated plasma homocysteine (Hcy) levels with higher risk of thrombosis. In order to evaluate possible changes in fibrin strength and deformability mediated by Hcy, the effect of the amino acid on plasma fibrin clot was studied, measuring the viscoelastic clots response as a function of Hcy concentration added to plasma (final concentrations: 0, 50, 100, 250 and 500 microM). Storage (G') and loss (G'') moduli were significantly higher than control at all Hcy concentrations evaluated in a dose-independent way (G'50 microM Hcy=254+/-10 Pa vs. 178 +/- 30 Pa, p=0.012; G''50 microM Hcy=32+/-1 Pa vs. 24 +/- 2 Pa, p=0.012). The tangent of the phase shift angles tan delta obtained from Hcy-clots with respect to control system proved to be unchanged (tan delta50 microM Hcy=0.130+/-0.007 Pa vs. 0.150 +/- 0.020 Pa, NS). Increases observed in G' and G'' values allowed us to conclude that Hcy action led to the stiffening of the clots formed in a dose independent way. The higher crosslinking of the fibrin network (higher G') contributed both to this structural behavior and to a higher compartmentalization and viscosity of the fluid phase (higher G'') of the gel. The lower deformability of the clots formed after Hcy addition was also detected through deformation sweep assays. These material's characteristics may lead to pathological behavior, increasing the chances of obstruction in the blood vessels.
Assuntos
Coagulação Sanguínea , Fibrina/química , Homocisteína/farmacologia , Coagulação Sanguínea/efeitos dos fármacos , Elasticidade , Humanos , Trombose/etiologiaRESUMO
La proteína S (PS) regula el sistema de coagulación mostrando actividad de cofactor de la Proteína C activada (PCa) con la cual forma un complejo equimolecular. En presencia de iones calcio este complejo inactiva por proteólisis los factores V y VIII activados por trombina. La proteína S plasmática circula 40% libre (fracción que presenta actividad de cofactor de la PCa) y 60% unida al C4-BP (proteína ligante de la fracción C4 del complemento). El objetivo fue comparar el dosaje de PS realizado por método coagulable e inmunoturbidimétrico e investigar cómo las variables preanalíticas afectan los niveles de PS determinados. Se obtuvieron los siguientes resultados: método coagulable: CV intra ensayo: (n=20): 4%, CV interensayo (n=20, 3 días): 3,4%. Método inmunoturbidimétrico: CV intraensayo (n=20): 3,7%.CV Inter. ensayo (n=20,3 días): 4,5%. Existe buena correlación (R2=0,94) entre ambos métodos, cuando la calibración por el método coagulable se realiza en la misma corrida analítica que las muestras. Cuando se realizó el estudio de Bland y Altman los dos métodos mostraron ser comparables en todos los niveles de PS estudiados. No se observaron diferencias significativas entre las muestras determinadas frescas y conservadas a -20 y -80 °C descongeladas solo una vez.
Protein S has an essential anticoagulant function acting as activated Protein C cofactor and forming an equimolecular complex with it. In the presence of calcium this complex regulates the coagulation process inactivating thrombin activated factors V and VIII by proteolysis. In plasma there are two different forms: a) free Protein S which acts as the cofactor of activated protein C (representing about 40% of total Protein S) and b) C4-BP(C4 binding protein) bound protein S which exhibits no activity as cofactor of activated Protein C (representing about 60% of total PS). The objetive was to compare the PS dosage determination by two methods: immunoturbidimetric and clotting, and to investigate how pre-analytical variables affect the results. The following results were obtained: Clotting method: CV intra assay: (n=20): 4%, CV interassay (n=20, 3 days): 3.4%; immunoturbidimetric method CV intra assay (n=20): 3.7%: CV inter assay (n=20.3 days): 4.5%. There is a good correlation (R2 = 0.94) between both methods; when the clotting method is calibrated in batch with the samples. There is significant difference between fresh and frozen ( -20 °C and -80 °C) samples when the latter have been desfrozen only once.
Assuntos
Humanos , Proteína S/análise , Análise de Sequência de Proteína/métodos , Valores de Referência , Proteína C , Controle de Qualidade/métodosRESUMO
INTRODUCTION: Dermatan sulfate (DS) is well-known for its anticoagulant activity through binding to heparin cofactor II to enhance antithrombin action. It has also been suggested that DS has a profibrinolytic effect, although the exact molecular mechanism is as yet unknown. MATERIALS AND METHODS: An in vitro amidolytic method was used to study the effect of high and low molecular weight-DS on the activation of Glu and Lys-plasminogen by tissue and urinary plasminogen activators (t-PA and u-PA). RESULTS: Both high and low molecular weight-DS exhibited a stimulating effect on the activation of plasminogen by PAs. Interestingly, high molecular weight-DS stimulated Glu and Lys-plasminogen activation by t-PA and u-PA in a way and to an extent similar to that in which fibrin(ogen) degradation products (PDF) increased the t-PA assay. Meanwhile low molecular weight-DS had a lower effect. No DS had any effect on plasmin or u-PA amidolytic activity. The facilitation of the conversion of Glu-plasminogen to plasmin in the presence of DS was confirmed by SDS-PAGE; high molecular weight-DS effect was greater than low molecular weight-DS in accordance with the chromogenic assays. Moreover, the combination of PDF and high and low molecular weight-DS, respectively, did not further stimulate t-PA activation of either Glu or Lys-plasminogen suggesting that both substances may compete for the same binding sites. CONCLUSIONS: Through in vitro assays we demonstrated that high and low molecular weight-DS enhance plasminogen activation by u-PA and t-PA, suggesting that the profibrinolytic activity of DS might be via potentiation of plasminogen conversion to plasmin.
Assuntos
Dermatan Sulfato/farmacologia , Fibrinólise/efeitos dos fármacos , Anticoagulantes/metabolismo , Antitrombinas/metabolismo , Dermatan Sulfato/química , Fibrinolisina/metabolismo , Ácido Glutâmico/química , Humanos , Hidrólise , Modelos Químicos , Peso Molecular , Fragmentos de Peptídeos/química , Plasminogênio/química , Ativadores de Plasminogênio/metabolismo , Fatores de Tempo , Ativador de Plasminogênio Tecidual/metabolismo , Ativador de Plasminogênio Tipo Uroquinase/metabolismoRESUMO
BACKGROUND: Hyperhomocysteinemia is considered an independent risk factor for vascular occlusive diseases. To date, there is no general agreement on hyperhomocysteinemia cutoff values. METHODS: To establish a homocysteine cutoff value, we performed a case-control study in 118 patients suffering from venous thrombosis and in 115 healthy subjects. We calculated odds ratios at different cutoff points and considered hyperhomocysteinemia as homocysteine levels above which the risk of venous thrombosis was increased. RESULTS: Initially we used the 97.5th percentiles for fasting homocysteine levels in the control group to calculate odds ratios (95% CI) of 9.5 (2.6-35.3), 3.7 (0.8-17.9) and 4.5 (1.7-123.8) for the total population, women and men, respectively. When individuals with well-known thrombotic risk factors were excluded (selected population), odds ratios were 10.5 (2.7- 41.1), 6.5 (1.3-32.1) and 11.2 (1.2-103.1), respectively, confirming hyperhomocysteinemia as an independent risk factor for venous thrombosis. We did not find any association of venous thrombosis with the homozygous methylenetetrahydrofolate reductase C677T mutation. When the hyperhomocysteinemia cutoff was set at other arbitrary points, odds ratios for the selected population were statistically significant only at >12 micromol/L. CONCLUSIONS: Based on our results, we propose 12 micromol/L as the hyperhomocysteinemia cutoff value.
Assuntos
Homocisteína/sangue , Homocisteína/normas , Hiper-Homocisteinemia/diagnóstico , Trombose Venosa/sangue , Adulto , Estudos de Casos e Controles , Feminino , Humanos , Masculino , Metilenotetra-Hidrofolato Redutase (NADPH2)/genética , Pessoa de Meia-Idade , Razão de Chances , Trombose Venosa/epidemiologia , Trombose Venosa/etiologiaRESUMO
To elucidate some of the links between homocysteine and vascular disease, we have evaluated the effect of the amino acid on the formation (by kinetics studies), structure (by electron microscopy) and lysis of the fibrin network, using tissue-type plasminogen activator (t-PA) and urokinase-type plasminogen activator (u-PA). We have studied whether homocysteine could alter the activity of the components involved in fibrinolysis (by amidolytic and thrombolytic methods). The results showed that homocysteine-associated networks were more compact and branched than controls (52 +/- 6 vs 44 +/- 5 fibers/field, P = 0.008), and were formed by shorter and thicker fibers. This clot proved to be more resistant to fibrinolysis with u-PA than control [lysis time 50%: 257 +/- 16 (homocysteine) vs 187 +/- 6 min (control); P < 0.004], but there were no differences with t-PA. Homocysteine did not affect the biological activities of plasmin, or plasminogen activation by t-PA and u-PA. Defective fibrinolysis with u-PA was therefore associated with homocysteine-fibrin structural alterations rather than the homocysteine effect on the biological activities of the fibrinolytic components evaluated. Results suggest that hyperhomocysteinemic patients could produce tight clots, were more resistant to lysis, and generated a procoagulant environment in situ. We believe that our findings may contribute to understanding the mechanisms involved in the homocysteine harmful effect.
Assuntos
Fibrina/ultraestrutura , Fibrinólise/fisiologia , Homocisteína/metabolismo , Plasma/metabolismo , Coagulação Sanguínea/fisiologia , Fibrina/química , Fibrina/metabolismo , Fibrinolisina/metabolismo , Humanos , Microscopia Eletrônica , Inibidor 1 de Ativador de Plasminogênio/metabolismo , Ativadores de Plasminogênio/química , Ativadores de Plasminogênio/metabolismo , Inativadores de Plasminogênio/metabolismoRESUMO
Aún después de más de 20 años del empleo de heparinas de bajo peso molecular (HBPM), existe considerable controversia acerca de si estos productos son intercambiables. Nuestras condiciones económicas suelen colocar al profesional encargado de la indicación en la incertidumbre entre su particular preferencia -avalada primariamente por documentación bibliográfica y la disponibilidad del producto donde se desempeña. Por las características del mercado farmacéutico de la Argentina, puede darse la situación de no contar con ninguna HBPM, tener la opción entre varias HBPM o inclusive entre dos fuentes diferentes de una misma HBPM, con ambas ya aprobadas por el organismo fiscalizador competente. Con respecto a esta última situación, dado el distinto origen del medicamento, la escasez de estudios clínicos con el producto de más reciente introducción en nuestro país y la imposibilidad de afrontar un estudio comparativo de efectividad con puntos finales clínicos por el elevado número de individuos necesarios, creímos de utilidad comparar entre ambos algunos parámetros del efecto antitrombótico. Para ello, en 40 voluntarios se determinó la acción sobre la heparinemia, el aPTT y el Tiempo de Trombina, a las dos horas de una dosis subcutánea de 40 mg de enoxaparina de dos orígenes diferentes. Hubo una semana de intervalo entre ambas aplicaciones. Con los dos productos se obtuvo similar prolongación de las pruebas realizadas, si bien para demostrar igual efecto antitrombótico, sería conveniente una comparación directa con puntos finales clínicos relevantes
Assuntos
Heparina de Baixo Peso MolecularRESUMO
Aún después de más de 20 años del empleo de heparinas de bajo peso molecular (HBPM), existe considerable controversia acerca de si estos productos son intercambiables. Nuestras condiciones económicas suelen colocar al profesional encargado de la indicación en la incertidumbre entre su particular preferencia -avalada primariamente por documentación bibliográfica y la disponibilidad del producto donde se desempeña. Por las características del mercado farmacéutico de la Argentina, puede darse la situación de no contar con ninguna HBPM, tener la opción entre varias HBPM o inclusive entre dos fuentes diferentes de una misma HBPM, con ambas ya aprobadas por el organismo fiscalizador competente. Con respecto a esta última situación, dado el distinto origen del medicamento, la escasez de estudios clínicos con el producto de más reciente introducción en nuestro país y la imposibilidad de afrontar un estudio comparativo de efectividad con puntos finales clínicos por el elevado número de individuos necesarios, creímos de utilidad comparar entre ambos algunos parámetros del efecto antitrombótico. Para ello, en 40 voluntarios se determinó la acción sobre la heparinemia, el aPTT y el Tiempo de Trombina, a las dos horas de una dosis subcutánea de 40 mg de enoxaparina de dos orígenes diferentes. Hubo una semana de intervalo entre ambas aplicaciones. Con los dos productos se obtuvo similar prolongación de las pruebas realizadas, si bien para demostrar igual efecto antitrombótico, sería conveniente una comparación directa con puntos finales clínicos relevantes(AU)
Assuntos
Heparina de Baixo Peso MolecularRESUMO
On the basis of growing clinical evidence, it is well known that elevated plasma homocysteine (Hcy) levels are associated with higher risk of venous and arterial thrombosis. Several experimental studies have been carried out in order to elucidate the mechanisms involved that still remain unclear. The aim of our study was to evaluate the homocysteine effects on formation and structure of plasmatic fibrin network. We also assayed homocystine and cysteine to determinate possible participation of thiol group in the tested activity. Aliquots of a pool of plasma incubated separately with sulfur compounds were clotting with thrombin. Fibringeneration and fibrin networks were evaluated by kinetic studies and scanning electronic microscopy, respectively. No significant differences were observed on fibrin generation of the substances assayed in comparison to control. The scanning electronic microscopy showed that Hcy-associated networks were different from control, with shorter, thicker and more branched fibers, resulting in a more compact structure and probably more resistant to fibrinolysis. The thiol group would be involved in this effect. Our findings would be a new contribution to elucidate the mechanisms involved in harmful effects associated to hyperhomocysteinemia.
Assuntos
Fibrina/efeitos dos fármacos , Homocisteína/farmacologia , Compostos de Sulfidrila/farmacologia , Coagulação Sanguínea/efeitos dos fármacos , Fibrina/ultraestrutura , Humanos , Cinética , Microscopia Eletrônica de Varredura , Trombina/farmacologia , Trombose/etiologiaRESUMO
Los niveles elevados de fibrógeno (Fbg) plasmático son considerados como un factor de riesgo para eventos trombóticos y enfermedad cardiovascular. El Fbg se cuantifica habitualmente utilizando el método coagulable de Clauss y el de Fbg derivado del tiempo de protrombina. A pesar de ser éste último, simple y económico, ha sido cuestionado en distintos estudios porque sobrestimaría los valores de Fbg. Para evaluar la confiabilidad de éste método, se lo comparó respecto al valor obtenido por el método de Clauss. Se evaluó, además, el efecto de la heparina (0,2 y 0,6 UI/ml) sobre las determinaciones por el método de Fbg derivado. La equivalencia entre ambos métodos se estableció por el test de Bland y Altman y el test de la Mediana. El efecto de la heparina se evaluó por regresión lineal y correlación de Pearson. Se puede concluir que los valores de Fbg por el método de Fbg derivado dentro de los rangos normales correlacionan con los obtenidos con el método de Clauss. Cuando éstos valores superan los 400 mg/dl debería determinarse el Fbg por el método de Clauss u otra metodología. Los valores obtenidos mediante el método de Fbg derivado no se modifican en muestras que contienen heparina en el rango terapéutico
Assuntos
Humanos , Fibrinogênio/sangue , Doenças Cardiovasculares , Técnicas de Laboratório Clínico , Doença das Coronárias , Fibrinogênio , Infarto do Miocárdio , Fatores de Risco , Acidente Vascular CerebralRESUMO
Los niveles elevados de fibrógeno (Fbg) plasmático son considerados como un factor de riesgo para eventos trombóticos y enfermedad cardiovascular. El Fbg se cuantifica habitualmente utilizando el método coagulable de Clauss y el de Fbg derivado del tiempo de protrombina. A pesar de ser éste último, simple y económico, ha sido cuestionado en distintos estudios porque sobrestimaría los valores de Fbg. Para evaluar la confiabilidad de éste método, se lo comparó respecto al valor obtenido por el método de Clauss. Se evaluó, además, el efecto de la heparina (0,2 y 0,6 UI/ml) sobre las determinaciones por el método de Fbg derivado. La equivalencia entre ambos métodos se estableció por el test de Bland y Altman y el test de la Mediana. El efecto de la heparina se evaluó por regresión lineal y correlación de Pearson. Se puede concluir que los valores de Fbg por el método de Fbg derivado dentro de los rangos normales correlacionan con los obtenidos con el método de Clauss. Cuando éstos valores superan los 400 mg/dl debería determinarse el Fbg por el método de Clauss u otra metodología. Los valores obtenidos mediante el método de Fbg derivado no se modifican en muestras que contienen heparina en el rango terapéutico (AU)
Assuntos
Humanos , Estudo Comparativo , Fibrinogênio/sangue , Fatores de Risco , Doenças Cardiovasculares , Fibrinogênio/diagnóstico , Infarto do Miocárdio , Doença das Coronárias , Técnicas de Laboratório Clínico , Acidente Vascular CerebralRESUMO
Homocysteine is a risk factor for cardiovascular disease. Mutations in a key enzyme in homocysteine metabolism, methylenetetrahydrofolate reductase, may contribute to hyperhomocysteinemia and alter folate and cobalamin levels. After starting hemodialysis, 10 mg oral folate daily and 500 micrograms intravenous methylcobalamin once weekly were prescribed to 27 hemodialysis patients (time on hemodialysis > or = 12 months) and two groups were defined: Group A normal; Group B heterozygous. Initial, third and twelfth month measurements of homocysteine, serum folate and vitamin B12 levels were collected and analyzed. Heterozygous state of methylenetetrahydrofolate reductase prevalence was 48% and homozygozity 4%. Hyperhomocysteinemia was present in both groups. Cobalamin final levels were significantly lower in Group B compared to Group A. Homocysteine, serum folate and cobalamin levels at third and twelfth month were significantly different from baseline levels but non-different between them in both groups. In Group B, vitamin B12 at third month was significantly higher than initial, but final measurements were not different from baseline determinations. In conclusion, the heterozygous prevalence of the enzyme in hemodialysis patients is similar to that reported in the general population; hyperhomocysteinemia is frequent in hemodialysis patients and final levels in heterozygous patients are significantly higher than in normal patients. Cobalamin levels are lower in the heterozygous group. After one year of treatment, homocysteine tends to increase, suggesting a secondary resistance phenomenon to vitamin supplementation in heterozygous patients.
Assuntos
Ácido Fólico/sangue , Homocisteína/sangue , Falência Renal Crônica/enzimologia , Oxirredutases atuantes sobre Doadores de Grupo CH-NH/genética , Vitamina B 12/análogos & derivados , Vitamina B 12/sangue , Adulto , Distribuição de Qui-Quadrado , Feminino , Ácido Fólico/uso terapêutico , Heterozigoto , Homocisteína/genética , Humanos , Hiper-Homocisteinemia/prevenção & controle , Falência Renal Crônica/sangue , Falência Renal Crônica/terapia , Masculino , Metilenotetra-Hidrofolato Redutase (NADPH2) , Pessoa de Meia-Idade , Mutação Puntual/genética , Diálise Renal , Estatísticas não Paramétricas , Vitamina B 12/uso terapêuticoRESUMO
BACKGROUND: Currently, total hyperhomocysteinemia (tHHcy) is a well-known condition linked to a higher risk of vascular disease. Prevalence of HHcy increases in elderly persons as the risk associated with it persists. Because factors can be potentially reduced in the elderly, it is important to carry out epidemiologic studies of HHcy. PROCEDURE: Previously we described the prevalence of hypertension control in an elder population; now, in an observational cross-sectional simple blind study, total homocysteine (tHcy) concentration was determined in 196 of 400 patients from the original cohort. RESULTS: Mean Hcy concentration was 13.2 ,amol/L (95% confidence interval 12.4-14.0; range, 5.0 to 48.9); 15.0 ,imol/L for men and 12.3 pAmol/L for women. Mean serum folic acid levels were 4.9 + 3.1 ng/mL (range, 2.0 to 20.0 ng/mL), and vitamin B12 levels were 384.8 314.1 pg/mL (range, 48.0 to 1500.0 pg/mL). Taking into account the reference values established by the Third National Health and Nutrition Examination Survey III study, HHcy was detected in 69.8% of all the subjects evaluated. The study showed that 76.2% of the men and 66.4% of the women had high Hcy levels. CONCLUSIONS: The very high prevalence of tHHcy in the elderly population, and the consequent risks associated with it suggest that although there are no trials that effectively prove the benefit of tHcy decrease, nutritional intervention is still justified.
Assuntos
Hiper-Homocisteinemia/epidemiologia , Distribuição por Idade , Idoso , Idoso de 80 Anos ou mais , Estudos de Coortes , Estudos Transversais , Feminino , Ácido Fólico/sangue , Homocisteína/sangue , Humanos , Hiper-Homocisteinemia/sangue , Masculino , Prevalência , Distribuição por Sexo , Vitamina B 12/sangueRESUMO
Numerosas evidencias científicas indican que una concentración elevada de homocisteína plasmática (hiperhomocisteinemia) sería un factor de riesgo independiente para las enfermedades vasculares oclusivas, tanto o más importante que el colesterol, el tabaquismo o la hipertensión. Surge entonces la necesidad de conocer y determinar los niveles normales de homocisteinemia. En nuestro estudio se analizaron las muestras de 151 individuos (3 a 59 años) aparentemente sanos, obteniéndose un valor de homocisteina total = 12.1 +- 3.6 umol/l (media +- DE). Además se evaluaron los datos registrados para dos grupos etáreos extremos, obteniéndose 6.4 +- 2.6 umol (neonatos) y 13.6 +- 5.9 umol/l (> 60 años). Se encontró que la homocisteinemia se incrementa con la edad, aún en el grupo de 3 a 59 años, y el valor medio es significativamente mayor en los hombres que en las muAssuntos
Homocisteína
, Trombose
RESUMO
Numerosas evidencias científicas indican que una concentración elevada de homocisteína plasmática (hiperhomocisteinemia) sería un factor de riesgo independiente para las enfermedades vasculares oclusivas, tanto o más importante que el colesterol, el tabaquismo o la hipertensión. Surge entonces la necesidad de conocer y determinar los niveles normales de homocisteinemia. En nuestro estudio se analizaron las muestras de 151 individuos (3 a 59 años) aparentemente sanos, obteniéndose un valor de homocisteina total = 12.1 +- 3.6 umol/l (media +- DE). Además se evaluaron los datos registrados para dos grupos etáreos extremos, obteniéndose 6.4 +- 2.6 umol (neonatos) y 13.6 +- 5.9 umol/l (> 60 años). Se encontró que la homocisteinemia se incrementa con la edad, aún en el grupo de 3 a 59 años, y el valor medio es significativamente mayor en los hombres que en las muAssuntos
Homocisteína
, Trombose/prevenção & controle
RESUMO
Homocysteine is a risk factor for cardiovascular disease. Mutations in a key enzyme in homocysteine metabolism, methylenetetrahydrofolate reductase, may contribute to hyperhomocysteinemia and alter folate and cobalamin levels. After starting hemodialysis, 10 mg oral folate daily and 500 micrograms intravenous methylcobalamin once weekly were prescribed to 27 hemodialysis patients (time on hemodialysis > or = 12 months) and two groups were defined: Group A normal; Group B heterozygous. Initial, third and twelfth month measurements of homocysteine, serum folate and vitamin B12 levels were collected and analyzed. Heterozygous state of methylenetetrahydrofolate reductase prevalence was 48
and homozygozity 4
. Hyperhomocysteinemia was present in both groups. Cobalamin final levels were significantly lower in Group B compared to Group A. Homocysteine, serum folate and cobalamin levels at third and twelfth month were significantly different from baseline levels but non-different between them in both groups. In Group B, vitamin B12 at third month was significantly higher than initial, but final measurements were not different from baseline determinations. In conclusion, the heterozygous prevalence of the enzyme in hemodialysis patients is similar to that reported in the general population; hyperhomocysteinemia is frequent in hemodialysis patients and final levels in heterozygous patients are significantly higher than in normal patients. Cobalamin levels are lower in the heterozygous group. After one year of treatment, homocysteine tends to increase, suggesting a secondary resistance phenomenon to vitamin supplementation in heterozygous patients.