Hyperhomocysteinemia and thrombosis: an overview

Meta-analysis of Factor V Leiden G1691A polymorphism and osteonecrosis of femoral head susceptibility

Testing for genetic risk associations between Factor V Leiden (FVL) and the osteonecrosis of femoral head (ONFH) is common, however, inconsistent results have been previously obtained. To summarize results on the association of FVL mutation polymorphism with ONFH in various populations and to calculate the overall genetic risk factors, we performed a search of electronic databases including PubMed, Elsevier Science Direct, Chinese National Knowledge Infrastructure and the Chinese Biomedical Database to identify published studies correlating the FVL mutation with ONFH. Statistical analysis was performed using Review Manager (RevMan) version 5.0 and Stata statistical software (version 10). We identified 57 titles and included 7 studies comprising 481 cases and 867 controls in this meta-analysis. The groups were pooled, and a significant association between FVL mutation and increased ONFH was found (OR=4.55, 95% CI, 2.75-7.52, P<0.00001). This meta-analysis demonstrated that FVL plays an important role in non-Asian populations. Large sample studies including different ethnic groups and age- and gender-matched groups, as well as multiple gene polymorphism detection should be considered to clarify the association of FVL mutation polymorphism and ONFH susceptibility in the future.

Transsulfuration Is a Significant Source of Sulfur for Glutathione Production in Human Mammary Epithelial Cells

The transsulfuration pathway, through which homocysteine from the methionine cycle provides sulfur for cystathionine formation, which may subsequently be used for glutathione synthesis, has not heretofore been identified as active in mammary cells. Primary human mammary epithelial cells (HMEC's) were labeled with S35-methionine for 24 hours following pretreatment with a vehicle control, the cysteine biosynthesis inhibitor propargylglycine or the gamma-glutamylcysteine synthesis inhibitor buthionine sulfoximine. Cell lysates were prepared and reacted with glutathione-S-transferase and the fluorescent labeling compound monochlorobimane to form a fluorescent glutathione-bimane conjugate. Comparison of fluorographic and autoradiographic images indicated that glutathione had incorporated S35-methionine demonstrating that functional transsulfuration occurs in mammary cells. Pathway inhibitors reduced incorporation by roughly 80%. Measurement of glutathione production in HMEC's treated with and without hydrogen peroxide and/or pathway inhibitors indicates that the transsulfuration pathway plays a significant role in providing cysteine for glutathione production both normally and under conditions of oxidant stress.

Homocysteine and alpha-1 antitrypsin concentration in patients with subclinical hypercortisolemia

PURPOSE

Glucocorticoids have particularly strong impact on the thromboembolic complications. A factor which increases the risk of thrombosis is hyperhomocysteinemia, observed in patients with hypercortisolemia. Proinflammatory factors also affect the haemostatic balance. There has been an extensive research which estimates hemostatic system in patients with Cushing's syndrome. Undoubtedly, much fewer publications are available on thromboembolic complications in patients with Subclinical Cushing's Syndrome (SCS). The purpose of this study was to estimate of homocysteine (HCY) and alpha-1 antitrypsin (α1ATp) concentrations in patients with SCS.

MATERIALS AND METHODS

We studied 35 patients (56.0 ± 15.0 years) with SCS and 33 healthy volunteers (53.3 ± 17.7 years). In all subjects the analysis of HCY and α1ATp concentration in serum was determined with an immunonephelometric method. P-values below 0.05 were considered statistically significant.

RESULTS

A comparison of HCY and α1ATp mean concentrations in patients with SCS and healthy representatives indicated statistically higher values of both analysed parameters in the sera of patients than in the healthy controls (p values were 0.018 and 0.008, respectively). In the patients with SCS a negative correlation between α1ATp and cortisol concentration in overnight dexamethasone test was found (p=0.017, R=-0.40). We did not reveal any statistically significant correlation between the concentrations of HCY and α1ATp, and coagulation parameters such as INR, APTT, fibrinogen concentration in patients with SCS.

CONCLUSIONS

On the basis of the obtained results, a slight increase in the concentration of homocysteine and α1ATp is observed in patients with SCS, which may influence vascular complications.

Sudden sensorineural hearing loss: a vascular cause? Analysis of prothrombotic risk factors in head and neck

OBJECTIVE

This aim of this study was to determine the prevalence of thrombophilic risk factors in sudden sensorineural hearing loss, central retinal vein occlusion, and stroke associated with small vessel disease, with the purpose of investigating and reinforcing the vascular hypothesis in the pathogenesis of sudden sensorineural hearing loss.

DESIGN

Case-control study. Genetic and acquired risk factors of these three groups were compared with healthy controls.

STUDY SAMPLE

Forty-nine, 60, and 101 patients affected respectively by sudden sensorineural hearing loss, central retinal vein occlusion, or stroke associated with small vessel disease, enrolled during a three-year period were compared with 210 healthy controls.

RESULTS

The frequency of hyperhomocysteinemia (homocysteine ≥ 15 μmol/L) was higher in each disease group than in controls. A statically significant, albeit weak, correlation between the MTHFR C677T mutation and hyperhomocysteinemia was found in all three diseases.

CONCLUSIONS

Hyperhomocysteinemia proved to be a risk factor for sudden sensorineural hearing loss. Based on these results, we propose to analyse homocysteine in sudden sensorineural hearing loss patients and, if its values are high, to evaluate the presence of MTHFR C677T mutation.

Higher plasma homocysteine is associated with lower vitamin B6 status in critically ill surgical patients

BACKGROUND

Hyperhomocysteinemia might be at least partially due to compromised B vitamin status in critically ill patients and has been linked with critical illness. This study was conducted to examine the association between plasma homocysteine with B vitamins and clinical outcomes in critically ill surgical patients.

METHODS

Thirty-two patients in the surgical intensive care unit (SICU) were enrolled. Disease severity (Acute Physiology and Chronic Health Evaluation II score), hematological values, serum and erythrocyte folate, serum vitamin B₁₂, plasma, and erythrocyte pyridoxal 5'-phosphate (PLP) were determined within 24 hours of admission and again after 7 days.

RESULTS

The prevalence of hyperhomocysteinemia in the patients was either 46.9% (plasma homocysteine ≥12 µmol/L) or 31.3% (plasma homocysteine ≥15 µmol/L) on day 1 in the SICU and increased to 62.5% (plasma homocysteine ≥12 µmol/L) and 37.5% (plasma homocysteine ≥15 µmol/L) on day 7 after admission to the SICU. Plasma homocysteine, serum folate, and vitamin B₁₂ significantly increased by day 7, whereas plasma and erythrocyte PLP remained constant throughout the study. Plasma homocysteine was not correlated with serum folate and vitamin B₁₂. However, plasma and erythrocyte PLP on day 1 were adversely associated with day 1 levels of plasma homocysteine after adjusting for potential confounders. Plasma homocysteine on day 1 or changes (Δ day 7-day 1) did not show any association with clinical outcomes.

CONCLUSIONS

Lower plasma PLP might be a significant factor for increased plasma homocysteine in critically ill surgical patients. The association between plasma homocysteine and clinical outcomes was not found.

Venous thromboembolism in recipients of antipsychotics: incidence, mechanisms and management

Since chlorpromazine was introduced to the market in the early 1950s, the use of antipsychotic drugs has been associated with venous thromboembolism (VTE) in a number of reports. During the last decade the evidence has been strengthened with large epidemiological studies. Whether all antipsychotics increase the risk for VTE or the risk is confined to certain drugs is still unclear. The aim of this article is to present an updated critical review focusing on the incidence, mechanisms and management of VTE in users of antipsychotics. After searching the databases PubMed and Scopus for relevant articles we identified 12 observational studies, all of which were published after the year 2000. In most of these studies an elevated risk of VTE was observed for antipsychotic drugs, with the highest risk for clozapine, olanzapine and low-potency first-generation antipsychotics. The risk seems to be correlated with dose. The elderly, who mainly use lower doses, do not show an increased risk of VTE to the same extent as younger subjects. The underlying biological mechanisms explaining the association between antipsychotic medication and VTE are to a large extent unknown. Several hypotheses have been proposed, such as body weight gain, sedation, enhanced platelet aggregation, increased levels of antiphospholipid antibodies, hyperprolactinaemia and hyperhomocysteinaemia. The risk of VTE in schizophrenia and other psychotic disorders may also be related to the underlying disease rather than the medication. Very limited evidence exists to guide how cases of VTE in subjects using antipsychotics should be handled. An attempt to compile an algorithm where the patients' individual risk of VTE is assessed and preventive clinical measures are suggested has been published recently. Strong consideration should be given to discontinuation of the offending antipsychotic drug in patients experiencing a VTE, and another antipsychotic drug with a presumably lower risk should be chosen if antipsychotic drug treatment is still indicated. It is essential that physicians and patients are aware that VTE may be an adverse drug reaction to the antipsychotic treatment so the condition is identified early and treated appropriately.

Genetic risk factors for thrombosis in systemic lupus erythematosus

OBJECTIVE

Thrombosis is a serious complication of systemic lupus erythematosus (SLE). We investigated whether genetic variants implicated in thrombosis pathways are associated with thrombosis among 2 ethnically diverse SLE cohorts.

METHODS

Our discovery cohort consisted of 1698 patients with SLE enrolled in the University of California, San Francisco, Lupus Genetics Project and our replication cohort included 1361 patients with SLE enrolled in the PROFILE cohort. Patients fulfilled American College of Rheumatology SLE criteria, and data relevant to thrombosis were available. Thirty-three single nucleotide polymorphisms (SNP) previously shown to be associated with risk of deep venous thrombosis in the general population or implicated in thrombosis pathways were genotyped and tested for association with thrombosis in bivariate allelic analyses. SNP with p < 0.1 in the bivariate analyses were further tested in multivariable logistic regression models adjusted for age, sex, disease duration, antiphospholipid antibody status, smoking, nephritis, and medications.

RESULTS

In the discovery cohort, 23% of patients with SLE experienced a thrombotic event. SNP in the following genes demonstrated association with thrombosis risk overall in the discovery or replication cohorts and were assessed using metaanalytic methods: factor V Leiden (FVL) rs6025 (OR 1.85, p = 0.02) and methylenetetrahydrofolate reductase (MTHFR) rs1801133 (OR 0.75, p = 0.04) in whites, and fibrinogen gamma (FGG) rs2066865 (OR 1.91, p = 0.01) in Hispanic Americans. SNP in these genes showed association with venous thrombosis risk in whites: MTHFR rs1801131 (OR 1.51, p = 0.01), MTHFR rs1801133 (OR 0.70, p = 0.04), FVL rs6025 (OR 2.69, p = 0.002), and FGG rs2066865 (OR 1.49, p = 0.02) in whites. A SNP in FGG rs2066865 (OR 2.19, p = 0.003) demonstrated association with arterial thrombosis risk in Hispanics.

CONCLUSION

Our results implicate specific genetic risk factors for thrombosis in patients with SLE and suggest that genetic risk for thrombosis differs across ethnic groups.

Evaluation of oxidative stress markers and cardiovascular risk factors in Fabry Disease patients

Fabry Disease, an X-linked inborn error of metabolism, is characterized by progressive renal insufficiency, with cardio and cerebrovascular involvement. Homocysteine (Hcy) is considered a risk factor for vascular diseases, but the mechanisms by which it produces cardiovascular damage are still poorly understood. Regarding the vascular involvement in FD patients, the analysis of factors related to thromboembolic events could be useful to improving our understanding of the disease. The aim of this study was to evaluate plasma Hcy and other parameters involved in the methionine cycle, as well as oxidative stress markers. The sample consisted of a group of 10 male FD patients and a control group of 8 healthy individuals, paired by age. Venous blood was collected for Hcy determination, molecular analysis, identification of thiobarbituric acid reactive substances, total glutathione and antioxidant enzymes activity, as well as vitamins quantification. Comparative analysis of FD patients versus the control group indicated hyperhomocysteinemia in 8 of the 10 FD patients, as well as a significant increase in overall glutathione levels and catalase activity. It is inferred that FD patients, apart from activation of the antioxidant system, present increased levels of plasma Hcy, although this is probably unrelated to common alterations in the methionine cycle.

Recurrent venous thromboembolism while on anticoagulant therapy

There has been immense progress in the management of venous thromboembolism in recent years with increased awareness and adequate thromboprophylaxis proving successful in reducing the morbidity and mortality associated with this condition. One of the commonest complications of an initial venous thrombosis is the development of recurrent thrombosis. Unlike in the case of the first clot, the diagnosis and management of the recurrent episode remain a difficult issue. Even more challenging is the clinical situation where a new thrombus develops while the patient is being treated with anticoagulant medication for a previous clot. The clinical approach and management of these patients are complex, and require understanding of the differences in thrombus development in the different clinical circumstances.

Myocardial infarction in a newborn heterozygous for the MTHFR C677T mutation

Neonatal myocardial infarction secondary to congenital heart disease, anomalous coronary artery anatomy, thromboembolism, coagulopathy, birth asphyxia, and unknown causes has been previously reported. We now report an infant who suffered a massive myocardial infarction during birth, requiring extensive resuscitation and aggressive management. A thrombus, the origin of which was not detected on autopsy, was found occluding the proximal left coronary artery several hours after birth. Genetic studies revealed a single copy variant of the MTHFR C677T mutation that we speculate may have predisposed the infant to coronary thrombosis.

Factor V Leiden and thrombosis in patients with inflammatory bowel disease (IBD): a meta-analysis

BACKGROUND

Testing for genetic risks of Factor V Leiden ( FVL ) in inflammatory bowel disease (IBD) patients with thromboembolism (TE) is common, but the safety and utility of such testing need review.

AIM

The aim of the present study was to investigate whether the FVL polymorphisms would be one inherited prothrombotic risk factor that could significantly increase the risk of thrombosis in patients with IBD.

METHODS

We performed an electronic databases search to identify published studies correlating the FVL mutations with four populations including one IBD group with TE complications, one control IBD group without TE complications, one control non-IBD group with TE complications and another healthy control (HC) group. Statistical analysis was performed with Review Manager (RevMan) 5.0. Sub-analysis/sensitivity analysis was also performed.

RESULTS

We identified 112 titles and included 22 studies in this meta-analysis. The odds ratio (OR) of TE in IBD patients with FVL was higher as compared with IBD patients (OR: 4.00; 95%CI: 2.04, 7.87) and HC (OR: 3.19; 95%CI: 1.38, 7.36). There was a 1.25-fold (95%CI: 0.90-1.74) increase in incidence of FVL gene mutation in IBD patients compared with HC. The FVL mutations were not significantly different between IBD patients with thrombosis and non-IBD patients with thrombosis (OR: 0.79; 95%CI: 0.43, 1.47).

CONCLUSION

FVL plays a role in IBD-TE, but to no greater extent than it does in the general population with TE.

Pheochromocytoma presenting with arterial and intracardiac thrombus in a 47-year-old woman: a case report

Introduction

Pheochromocytoma is a rare cause of hypertension but it could have severe consequences if not recognized and treated appropriately. The association of pheochromocytoma and thrombosis is even rarer but significantly increases management complexity, morbidity and mortality. To the best of our knowledge, this is the first report of a patient with pheochromocytoma presenting with left axillary arterial and intracardiac thrombus.

Case presentation

A 47-year-old Caucasian woman with a past medical history of hypertension presented for medical attention with left arm numbness. Doppler ultrasound showed an obstructing thrombus in her left axillary artery. She had symptom resolution after stent placement in her left axillary artery. A subsequent echocardiogram demonstrated a large intracardiac mass and abdominal computed tomography revealed a 7 cm mass between her spleen and left kidney. Labile blood pressure was noted during admission and she had very high levels of plasma and 24-hour urine catecholamines and metanephrines tests. A (123)I- metaiodobenzylguanidine scan showed intense uptake in the left abdominal mass. After adequate alpha blockage with phenoxybenzamine, laparoscopic tumor resection was performed without complications. She had normal metanephrines and complete symptom resolution afterwards. The intracardiac mass also disappeared with anticoagulation. All other endocrine laboratory abnormalities returned to normal after surgery.

Conclusion

Arterial and ventricular thrombosis occurring in patients with pheochromocytoma is rare. A multi-disciplinary approach is necessary in caring for this type of patient. Catecholamines likely contributed to the development of thrombosis in our patient. Early recognition of pheochromocytoma is the key to improving outcome.

C-reactive protein and markers for thrombophilia in patients with chronic plaque psoriasis

Chronic plaque psoriasis is associated to an increased risk of cardiovascular events. The aim of our study is to test patients with psoriasis for common markers of acquired and inherited thrombophilia. A cross-sectional study on 172 patients with psoriasis and 198 controls was carried out. The plasma levels of coagulation protein C, coagulation protein S, homocysteine, folic acid, C-reactive protein (CRP) and fibrinogen as well as activated protein C resistance and antithrombin III activity, were measured. CRP and homocysteine levels were higher in patients with psoriasis than in controls (5.9 ± 7.1 vs 3.1 ± 2.4 mg/L, p=0.0003 and 16.3 ± 12.8 vs 10.4 ± 4.6 umol/L, p=0.0001; mean ± SD) whereas folic acid was lower in psoriatic patients compared to controls (4.3 ± 7.2 vs 12.6 ± 7.9 p=0.006). Levels of coagulation protein C, coagulation protein S, fibrinogen as well as activated protein C resistance, antithrombin III activity were within normal ranges both in cases and controls. In a multivariate regression analysis, psoriasis severity was an independent predictor of higher CRP. In conclusion, high levels of serum CRP and homocysteine were found in patients with psoriasis, related to the severity of the disease. These data suggest that the increased risk of thrombotic cardiovascular events observed in psoriasis patients should be ascribed to an acquired rather than inherited thrombophilic status.

Homocysteine and serum-lipid levels in pulmonary embolism

Pulmonary embolism (PE) is a fatal disease that arises from genetic and environmental factors. There is little evidence for low high-density lipoprotein cholesterol (HDL-C) with hyperhomocysteinemia to lead to PE. Therefore, we evaluated homocysteine levels and lipid profile in PE patients and to display risk for PE. Forty six patients with proven PE and 46 healthy controls were included in the study. Homocysteine and serum lipid levels were calculated and compared in both groups. There were no significant differences between two groups in terms of total cholesterol, triglyceride, and low-density lipoprotein cholesterol. In PE group, HDL-C levels were found significantly lower in comparison to the control group (P = .004). Mean homocysteine levels were significantly higher in PE group than in the control group (P = .001). High-density lipoprotein cholesterol levels were significantly low in which homocysteine levels were high in the PE group. We thought that low HDL-C level with hyperhomocysteinemia is susceptible to PE.

The 844ins68 cystathionine beta-synthase and C677T MTHFR gene polymorphism and the vaso-occlusive event risk in sickle cell disease

INTRODUCTION

Sickle cell disease (SCD) is an inflammatory condition with an increase in the adhesion of sickled erythrocytes, and it is a potential cause of vaso-occlusive episodes, an event related to clinical manifestations, morbidity and mortality. The cystathionine beta-synthase enzyme gene (CBS) and the methylenetetrahydrofolate reductase enzyme gene (MTHFR) are risk factors for thromboembolic disorders. This study evaluated the frequency of the 844ins68 CBS and C677T MTHFR gene polymorphisms and their possibility to be risk factors for vaso-occlusive crises.

MATERIAL AND METHODS

In total 91 blood samples from SCD patients were studied by PCR-RFLP and PCR-allele-specific, for the SCD genotype confirmation and polymorphism identification.

RESULTS

The presence of clinical manifestations related to vaso-occlusive crises were more frequent among patients with the Hb SS genotype (p = 0.007). The CBS enzyme gene was three times more frequent (p = 0.011) among patients with vaso-occlusive complications. The MTHFR gene mutation frequency showed no increased risk for vaso-occlusive crises in SCD patients (p = 0.193). The interaction between the two polymorphisms was evaluated in 12.08% of the SCD patients and doubled the vaso-occlusive disease risk (relative risk: 2.16).

CONCLUSIONS

We conclude that the presence of 844ins68 CBS and C677T MTHFR gene polymorphism was a risk factor for vaso-occlusive episodes in the SCD patients evaluated.

Hyperhomocysteinemia Prevalence Among Patients With Venous Thromboembolism

The aim of this study is to evaluate the plasma total homocysteine level in patients with venous thromboembolism (VTE) and to investigate the effect of different risk factors on plasma levels. Ninety-three-patients with VTE and 37-control participants diagnosed with other than VTE were included in the study. Plasma homocysteine levels and the factors affecting plasma homocysteine levels were evaluated. Plasma homocysteine level was higher among patients with VTE compared to the controls independent from vitamin B12 and folate levels. The prevalence of hyperhomocysteinemia in VTE was 63%. Plasma homocysteine level was higher in patients with PE than deep venous thrombosis (DVT; 23 ± 13.7 vs 16 ± 5.8 μmol/L, P = .018). With regression analysis hyperhomocysteinemia was found to be associated with a 4.8-fold increased risk of VTE. Hyperhomocysteinemia is a common and possibly modifiable risk factor that should be considered when screening patients with VTE. Secondary causes of hyperhomocysteinemia especially vitamin B12 deficiency should be monitored in patients with VTE to prevent recurrences.

Hereditary thrombophilic risk factors for recurrent pregnancy loss

This review summarizes current knowledge about the role of hereditary hypercoagulation factors predisposing to thrombophilia-associated recurrent fetal loss. Thrombophilias are a major cause of adverse pregnancy outcome, playing a role in the etiology of up to 40% of cases worldwide. Hereditary thrombophilic predispositions to recurrent pregnancy wastage include genetic lesions in blood coagulation factors II and V as well as natural anticoagulants antithrombin, protein C, and protein S. Furthermore, methylenetetrahydrofolate reductase gene variants conferring higher thrombophilia risk in combination with these mutations and the newly described annexin A5 gene M2 promoter allele are associated with repeated fetal loss. The review gives a concise description of the molecular defects arising from the genetic changes, of the role these factors play in the timing and definition of fetal loss, and risk estimates from available studies and meta-analysis. This knowledge is instrumental for a more precise assessment of individual risks for repeated fetal loss and should guide therapeutic strategies, where relevant. Since the average childbearing age increases in Western societies, the importance of a timely diagnosis of fetal loss predisposition is increasing.

Rapid multiplexed genotyping for hereditary thrombophilia by SELDI-TOF mass spectrometry

Approximately 50% of patients with venous thromboembolism also present with hereditary predisposition. The most common genetic factors are single nucleotide polymorphisms (SNPs) of factor V Leiden, prothrombin G20210A, and methylenetetrahydrofolate reductase C677T. Genotyping these SNPs helps clinicians to correctly diagnose the disease and properly manage patients. In this study, we report a novel method using surface-enhanced laser desorption and ionization time of flight mass spectrometry to rapidly genotype, in a multiplex fashion, 3 SNPs that predispose patients to thrombosis. First, patient DNA samples were subjected to polymerase chain reaction to amplify and extend the DNA products with masses corresponding to specific genotypes. Polymerase chain reaction products were then applied to Q10 anionic protein chips, undergoing on-chip sample enrichment and clean-up. Finally, the genotypes of the SNPs were determined by surface-enhanced laser desorption and ionization time of flight mass spectrometry. This method offers a rapid turnaround time of less than 5 hours from sample collection to result reporting. The analytical accuracy of each SNP genotyping result has been confirmed by DNA sequencing. In addition, the genotype results produced by this method were validated by comparing them with results obtained by the approved method in the clinical reference laboratory. This novel method is fast, accurate, and reproducible, and thus provides an excellent platform to promote personalized medicine in the management of clotting disorders.

Portal vein thrombosis in Egyptian patients with liver cirrhosis: Role of methylenetetrahydrofolate reductase C677T gene mutation

AIM

The pathogenesis of non-malignant portal vein thrombosis (PVT) in cirrhotic patients is not clearly defined. This case-control study aimed to investigate the role of methylenetetrahydrofolate reductase (MTHFR) C677T gene mutation in the pathogenesis of PVT in Egyptian cirrhotic patients.

METHODS

Plasma homocysteine was measured and MTHFR C677T gene mutation was detected in 76 cirrhotic patients (21 with PVT, 55 without PVT) and 20 healthy controls.

RESULTS

The frequency of CC genotype (wide type) in cirrhotic patients with PVT was lower than controls and cirrhotics without PVT. However, the frequency of TT genotype (homozygous mutation) was elevated in cirrhotic patients with PVT as compared to controls and those without PVT. Cirrhotic patients with PVT had significantly higher homocysteine than those without PVT. Cirrhotic patients with TT genotype are at a significant risk for PVT (odds ratio = 7.7, 95% confidence interval, 1.50-42.81) when compared with CC genotype. Moreover, subjects carrying TT genotype had a higher homocysteine than those carrying CC genotype.

CONCLUSIONS

The TT genotype of MTHFR is associated with an increased risk of PVT in Egyptian cirrhotic patients. Hyperhomocysteinemia could be considered as a relatively new risk factor for PVT in cirrhotic patients and plasma homocysteine should be investigated particularly in patients with PVT of unexplained etiology. The important clinical implication is that the readily available therapy of folate, vitamin B6 and B12 supplementation may reduce homocysteine and prevent further thrombotic complications in cirrhotic patients carrying the TT genotype.

The effect of plasma homocysteine levels on clinical outcomes of patients with acute lung injury/acute respiratory distress syndrome

BACKGROUND

Several reports have shown that homocysteine promotes thrombosis by disturbing the procoagulant-anticoagulant balance, whereas alterations in coagulation and fibrinolysis have been suggested as important pathogenetic and prognostic determinants of mortality in acute lung injury (ALI)/acute respiratory distress syndrome (ARDS). The objective of the study was to evaluate the effect of plasma homocysteine levels on the outcomes of patients with ALI/ARDS.

METHODS

Sixty-nine consecutive ventilated patients with ALI/ARDS were studied. Blood samples were drawn within 3 days of clinical recognition of ARDS. Measurement of plasma homocysteine, vitamin B12, folate, creatinine, protein C and plasminogen-activator inhibitor-1 antigen levels, and genotyping of the methylenetetrahydrofolate reductase gene C677T and A1298C polymorphisms were carried out. The primary outcomes were 28- and 90-day mortality, whereas secondary outcomes included nonpulmonary organ failure-free days, liberation from mechanical ventilation up to day 28, and ventilator-free days during the 28 days after enrollment.

RESULTS

In the multivariable analysis, plasma homocysteine concentration adjusted for age, Acute Physiology and Chronic Health Evaluation II score, methylenetetrahydrofolate reductase C677T and A1298C polymorphisms, and levels of plasminogen-activator inhibitor-1 antigen, protein C, creatinine, vitamin B12, and folate was not found to affect significantly mortality at 28 and 90 days (P = 0.39 and P = 0.83, respectively), days without organ failure besides lungs (P = 0.38), the probability of being free from mechanical ventilation at day 28 (P = 0.63), and days without ventilation assistance (P = 0.73).

CONCLUSION

Our data suggest that increased plasma homocysteine levels, either alone or in synergy with other thrombophilic risk factors, do not seem to adversely affect the prognosis in patients with ALI/ARDS.

Homocysteine inhibits neoangiogenesis in mice through blockade of annexin A2-dependent fibrinolysis

When plasma levels of homocysteine (HC), a thiol amino acid formed upon methionine demethylation, exceed 12 muM, individuals are at increased risk of developing large vessel atherothrombosis and small vessel dysfunction. The annexin A2 complex (termed "A2") is the cell surface coreceptor for plasminogen and TPA and accelerates the catalytic activation of plasmin, the major fibrinolytic agent in mammals. We previously showed that HC prevents A2-mediated, TPA-dependent activation of plasminogen in vitro by disulfide derivatization of the "tail" domain of A2. We also demonstrated that fibrinolysis and angiogenesis are severely impaired in A2-deficient mice. We now report here that, although hyperhomocysteinemic mice had a normal coagulation profile and normal platelet function, fibrin accumulated in their tissues due to reduced perivascular fibrinolytic activity and angiogenesis was impaired. A2 isolated from hyperhomocysteinemic mice failed to fully support TPA-dependent plasmin activation. However, infusion of hyperhomocysteinemic mice with fresh recombinant A2, which localized to neoangiogenic endothelial cells, resulted in normalization of angiogenesis and disappearance of peri- and intravascular fibrin. We therefore conclude that hyperhomocysteinemia impairs postnatal angiogenesis by derivatizing A2, preventing perivascular fibrinolysis, and inhibiting directed endothelial cell migration. These findings provide a mechanistic explanation for microvascular dysfunction and macrovascular occlusion in individuals with hyperhomocysteinemia.

A novel mutation of cystathionine beta-synthase gene in a Thai boy with homocystinuria

The authors reported a 14-year-old boy who presented with multiple organs thrombosis and subluxation of lens. His diagnosis of homocystinuria was delayed owing to the unrecognition of the disease resulting in significant morbidity. The mutation analysis showed one novel mutation that can explain the high level of plasma homocysteine.

The evaluation and management of postnatal thromboses

In the pediatric population, neonates have the highest risk for thromboembolism (TE), most likely due to the frequent use of intravascular catheters. This increased risk is attributed to multiple risk factors. Randomized clinical trials dealing with management of postnatal thromboses do not exist, thus, opinions differ regarding optimal diagnostic and therapeutic interventions. This review begins with an actual case study illustrating the complexity and severity of these types of cases, and then evaluates the neonatal hemostatic system with discussion of the common sites of postnatal thrombosis, perinatal and prothrombotic risk factors, and potential treatment options. A proposed step-wise evaluation of neonates with symptomatic postnatal thromboses will be suggested, as well as future research and registry directions. Owing to the complexity of ischemic perinatal stroke, this topic will not be reviewed.

Factor V Leiden and thrombosis in patients with systemic lupus erythematosus: a meta-analysis

To perform a meta-analysis of the association between the factor V Leiden polymorphism (FVL) and thrombosis among patients with SLE and/or antiphospholipid antibody (aPL) positivity. Included studies recruited patients based on SLE or aPL positive status, confirmed subjects' SLE diagnosis as defined by the American College of Rheumatology, and documented thrombotic events. Excluded studies were non-English or considered only arterial thrombosis. Individual patient data, available from five studies, together with unpublished data from 1210 European-American SLE patients from the UCSF Lupus Genetics Collection genotyped for FVL, were further analyzed. Seventeen studies (n=2090 subjects) were included in the initial meta-analysis. Unadjusted odds ratios (OR) were calculated to assess association of FVL with thrombosis. The OR for association of thrombosis with FVL was 2.88 (95% C.I. 1.98-4.20). In the secondary analysis with our individual patient dataset (n=1447 European-derived individuals), SLE subjects with the FVL polymorphism still had more than two times the odds of thrombosis compared to subjects without this polymorphism, even when adjusting for covariates such as gender, age, and aPL status. SLE and/or aPL positive patients with the FVL variant have more than two times the odds of thrombosis compared to those without this polymorphism.

Contributions of hyperhomocysteinemia to atherosclerosis: Causal relationship and potential mechanisms

Hyperhomocysteinemia (HHcy) is considered an independent risk factor for cardiovascular disease, including ischemic heart disease, stroke, and peripheral vascular disease. Mutations in the enzymes and/or nutritional deficiencies in B vitamins required for homocysteine metabolism can induce HHcy. Studies using genetic- or diet-induced animal models of HHcy have demonstrated a causal relationship between HHcy and accelerated atherosclerosis. Oxidative stress and activation of proinflammatory factors have been proposed to explain the atherogenic effects of HHcy. Recently, HHcy-induced endoplasmic reticulum (ER) stress and the unfolded protein response (UPR) have been found to play a role in HHcy-induced atherogenesis. This review will focus on the cellular mechanisms of HHcy in atherosclerosis from both in vivo and in vitro studies. The contributions of ER stress and the UPR in atherogenesis will be emphasized. Results from recent clinical trials assessing the cardiovascular risk of lowering total plasma homocysteine levels and new findings examining the atherogenic role of HHcy in wild-type C57BL/6J mice will also be discussed. (c) 2009 International Union of Biochemistry and Molecular Biology, Inc.

The evaluation and management of neonatal coagulation disorders

Neonatal hemostatic abnormalities can present diagnostic and therapeutic challenges to the physician. Developmental deficiencies and/or increases of certain coagulation proteins, coupled with acquired or genetic risk factors, can result in a hemorrhagic or thromboembolic emergency. The timely diagnosis of a congenital hemorrhagic or thrombotic disorder can avoid significant long-term sequelae. However, due to the lack of randomized clinical trials addressing the management of neonatal coagulation disorders, treatment strategies are usually empiric and not evidence-based. In this chapter, we will review the neonatal hemostatic system and will discuss the most common types of hemorrhagic and thrombotic disorders. Congenital and acquired risk factors for hemorrhagic and thromboembolic disorders will be presented, as well as current treatment options. Finally, suggested evaluations for neonates with either hemorrhagic or thromboembolic problems will be reviewed.

Homocysteine Measurement by an Enzymatic Method and Potential Role of Homocysteine as a Biomarker in Dogs

In humans, homocysteine (Hcy) is employed to monitor renal, cardiovascular, and other diseases and their complications. The aim of the current study was to define the analytical performances of an enzymatic method not yet validated in dogs for measuring homocysteine, and to assess the possible clinical usefulness of Hcy measurement. Using conventional approaches, the analytical performances were investigated by assessing, imprecision, inaccuracy, and interference of hemoglobin, triglycerides, and bilirubin. The possible clinical usefulness of Hcy determination was assessed by comparing the results of healthy dogs ( n = 8) with those of dogs with heart disease ( n = 10), inflammation ( n = 6), gastrointestinal disorders ( n = 7), neoplasia ( n = 8), renal failure ( n = 4), trauma ( n = 7), and other miscellaneous diseases ( n = 6). Preliminary evaluation of this enzymatic method showed it to be precise at Hcy levels close to or higher than the values in dogs with renal or cardiac disorders that had the highest Hcy levels. By contrast, at low Hcy levels, which were recorded basically in control dogs, the method suffers from high imprecision. The sample of choice is serum. The use of icteric samples should be avoided, while hemoglobin and lipids have only a minor effect on Hcy measurement. In conclusion, the enzymatic method employed in the current study provides useful information in dogs and could be used to monitor cardiac and renal disorders, in which Hcy concentrations are elevated.

Mild hyperhomocysteinemia is associated with increased TAFI levels and reduced plasma fibrinolytic potential

BACKGROUND

Mild hyperhomocysteinemia (HHcy) has been shown to be associated with impaired fibrinolysis, but some aspects of this association are unclear.

OBJECTIVE

Using an in vitro model of physiological relevance, we investigated whether and how HHcy influences plasma fibrinolytic potential.

PATIENTS/METHODS

We studied 176 patients with previous venous thromboembolism, 58 with HHcy, 118 with normal total homocysteine (tHcy) levels (NHcy), at least 3 months after withdrawal of anticoagulant therapy. Plasma fibrinolytic potential was measured as the fibrinolysis time of tissue factor (TF)-induced clots exposed to 15 ng mL(-1) t-PA.

RESULTS

Fibrinolysis time was longer in HHcy than in NHcy patients, but this difference disappeared when the assay was performed in the presence of the TAFIa inhibitor, PTCI. Plasma levels of thrombin activatable fibrinolysis inhibitor (TAFI) and factor VIII (FVIII) were higher in HHcy than NHcy, whereas PAI-1, fibrinogen and endogenous thrombin potential were similar. Using multivariate analysis, plasma tHcy was identified as an independent predictor of fibrinolysis time. Experiments in which native fibrinogen was replaced by purified fibrinogen suggested that alterations of fibrinogen structure did not contribute appreciably to the hypofibrinolysis of HHcy plasma samples. The acute increase of tHcy either in vivo (after an oral methionine load) or in vitro (after incubation of normal plasma with 0.5 mm DL-Hcy) had no effects on fibrinolysis or TAFI levels.

CONCLUSIONS

We describe an enhanced TAFI-related antifibrinolytic activity in mild HHcy, which might account for the reported heightened thrombosis risk; however, it is unknown whether HHcy is causally related to hypofibrinolysis or an associated bystander.

Roles of Oxidants, Nitric Oxide, and Asymmetric Dimethylarginine in Endothelial Function

Vascular endothelium plays a crucial role in ensuring normal function and morphology of blood vessels, and many risk factors of atherosclerosis act via their effects on endothelial cells. However, endothelial dysfunction is induced by very different pathomechanisms. In principle, it is caused by an impaired bioavailability of nitric oxide (NO) due to an inhibited synthesis (eg, by asymmetric dimethylarginine [ADMA]) or increased consumption of formed NO (by reactive oxygen species [ROS]). ROS can be synthesized in the organism (eg, by different enzymes) or can be administered from the environment (eg, by cigarette smoking), whereas ADMA is the subject of endogenous metabolism only. Many studies have elucidated the system of pathomechanisms and targeted some as potential goals for therapeutic interventions. This review demonstrates roles of ROS, NO, ADMA, endothelin, and estrogen in endothelial function and dysfunction focusing on homocysteinemia and diabetes mellitus and provide examples for the medical treatment of endothelial dysfunction.

Anesthetic management of a parturient with hyperhomocysteinemia

High plasma levels of homocysteine are associated with an increased risk for thromboembolic events. Neuraxial anesthesia techniques may be relatively contraindicated in anticoagulated patients, and nitrous oxide may exacerbate the condition by inhibiting the conversion of homocysteine to methionine. We describe the anesthetic implications and management of a patient with hyperhomocysteinemia undergoing an nonemergent cesarean delivery.

Obesity, inflammation, and the potential application of pharmaconutrition

Obesity is an emerging problem worldwide. Hospitalized obese patients often have a worse outcome than patients of normal weight, particularly in the setting of trauma and critical care. Obesity creates a low-grade systemic inflammatory response syndrome (SIRS) that is similar (but on a much smaller scale) to gram-negative sepsis. This process involves up-regulation of systemic immunity, is characterized clinically by insulin resistance and the metabolic syndrome, and puts the patient at increased risk for organ failure, infectious morbidity, and mortality. Through lipotoxicity and cytokine dysregulation, obesity may act to prime the immune system, predisposing to an exaggerated subsequent immune response when a second clinical insult occurs (such as trauma, burns, or myocardial infarction). Specialized nutrition therapy for such patients currently consists of a hypocaloric, high-protein diet. However, this approach does not address the putative pathophysiologic mechanisms of inflammation and altered metabolism associated with obesity. A number of dietary agents such as arginine, fish oil, and carnitine may correct these problems at the molecular level. Pharmaconutrition formulas may provide exciting innovations for the nutrition therapy of the obese patient.