Hyperhomocysteinemia as a risk factor for venous thrombosis

A Case of Systemic Lupus Erythematosus without Antiphospholipid Syndrome Causing Superior Vena Cava Syndrome

Systemic lupus erythematosus (SLE) is an autoimmune disease with multisystem involvement. Superior vena cava (SVC) syndrome is mainly caused by malignant tumors such as lung carcinoma, lymphoma, and metastatic tumors. We report a 20-year-old woman who was admitted with features of SVC syndrome secondary to SVC thrombus. Further evaluation confirmed the diagnosis of SLE without associated antiphospholipid syndrome (APS). The patient was treated with heparin with oral anticoagulant, steroids, and hydroxychloroquine. Complete resolution of thrombus was documented within a few weeks. SVC thrombosis as an initial presenting feature of SLE without associated APS has not been reported so far in the literature.

Homocysteine inhibits the viability and migration ability of human umbilical vein endothelial cells by downregulating the expression of vascular endothelial growth factor

The current study aimed to explore the effect of homocysteine (Hcy) on the viability and migration ability of human umbilical vein endothelial cells (HUVECs), as well as to examine the underlying mechanism. The association between the expression level of Hcy and lower extremity deep vein thrombosis (DVT) was detected in clinical samples collected from patients. In addition, the effect of Hcy on the viability and migration ability of HUVECs was detected by cell counting kit-8 and Transwell assays, respectively, while vascular endothelial growth factor (VEGF) expression was measured in order to verify the effect of Hcy on VEGF. The results indicated that the serum Hcy levels in DVT patients were significantly increased. In vitro experiments also confirmed that Hcy was able to significantly inhibit the viability and migration ability of HUVECs, and downregulate the expression of VEGF in these cells. Furthermore, the inhibitory effect of Hcy on HUVEC viability and migration ability was achieved by downregulating the expression of VEGF using small interfering RNA transfection. In conclusion, Hcy inhibited the viability and migration ability of HUVECs by downregulating the expression of VEGF. This may underlie the high incidence of DVT in patients with hyperhomocysteinemia.

Thrombosis in systemic lupus erythematosus: a review article

Thrombosis is a well-known clinical entity in systemic lupus erythematosus (SLE), and it is multifactorial. The most important risk factor is the presence of antiphospholipid antibodies (APLAs). However, approximately 40% of adults with SLE who are negative for APL A are diagnosed with thrombosis, indicating the importance of other risk factors. Thus, the thrombosis risk factors should be evaluated extensively and regularly and treated aggressively in every patient with systemic lupus erythematosus.

Inherited Thrombophilia: Key Points for Genetic Counseling

With the evolution of medical genetics to focus on highly prevalent, multifactorial conditions, it is inevitable that genetic counselors will be called upon to participate in the evaluation and counseling of individuals with inherited thrombophilia. The purpose of this review is to educate the genetic counselor on key issues related to risk assessment and genetic counseling for hereditary thrombophilia. The information contained in this document is derived from an extensive review of the literature, as well as the author's personal expertise. Upon completion of this review, the genetic counselor will be able to: a) describe inherited and acquired risk factors for thrombosis, b) collect and interpret personal and family histories to assess risk related to hereditary thrombophilia, c) discuss the potential advantages and disadvantages of thrombophilia testing, including psychosocial aspects and implications for medical management, and d) identify educational and support resources for patients and families.

Does the oxidation of methionine in thrombomodulin contribute to the hypercoaguable state of smokers and diabetics?

The leading cause of premature death in smokers is cardiovascular disease. Diabetics also suffer from increased cardiovascular disease. This results, in part, from the hypercoagulable state associated with these conditions. However, the molecular cause(s) of the elevated risk of cardiovascular disease and the prothrombotic state of smokers and diabetics remain unknown. It is well known that oxidative stress is increased in both conditions. In smokers, it is established that oxidation of methionine residues takes place in alpha(1)-antitrypsin in lungs and that this leads to emphysema. Thrombomodulin is a key regulator of blood clotting and is found on the endothelium. Oxidation of methionine 388 in thrombomodulin is known to slow the rate at which the thrombomodulin-thrombin complex activates protein C, a protein which, in turn, degrades the factors which activate thrombin and lead to clot formation. In analogy to the cause of emphysema, it is hypothesized that oxidation of this methionine is elevated in smokers relative to non-smokers and, perhaps, in conditions such as diabetes that impose oxidative stress on the body. Evidence for the hypothesis that such an oxidation and concomitant reduction in activated protein C levels would lead to elevated cardiovascular risk is presented.

Thrombophilia in children with venous thromboembolic disease

Venous thromboembolic events (VTEs) in children are usually associated with underlying clinical conditions such as central venous line, cancer and cardiac diseases. The objective of this review is to present the importance of thrombophilia to the occurrence of childhood VTE. The reported prevalence of thrombophilia in children with VTE varies extremely between 10% and 78% in different registries. The variation in the reported prevalence most probably reflects differences in the clinical characteristics of the children studied and differences in study designs. The initial management of children with thrombophilia and VTE is similar to those individuals who do not have a specific inherited thrombophilic risk factor, except in the rare events of homozygous deficiencies of prothrombotic coagulation proteins. The impact of thrombophilic markers on long-term therapy and outcome of children with VTE has not been completely clarified. According to the current guidelines for thrombophilia, all children with VTE should be tested for a full panel of genetic and acquired prothrombotic traits. However, re-evaluation of co-morbid risk factors other than thrombophilic markers and careful consideration of the prognostic value of thrombophilic markers might help to change future attitude from the rigidity of current guidelines to more rational schemes.

Genetic thrombophilia

The genetic thrombophilias are an important cause of venous thrombotic events. Much has been learned about the natural history of these disorders, their genetics, and, to a lesser degree, their treatment. This article provides an overview of the genetics of thrombophilia. Specific information on the factor V Leiden mutation;the prothrombin G20210A mutation; and protein C, proteinS, and antithrombin deficiency is reviewed. Current testing and treatment options for the genetic thrombophilias also are discussed.

Risk factors for catheter-related thrombosis in cancer patients

We investigated the risk factors for venous thrombosis in cancer patients with implantable ports undergoing chemotherapy. One hundred and seventy one ports were placed in a central ("chest ports") and 84 in a peripheral vein ("arm ports"), 181 received prophylactic nadroparin and 10 coumarin. Clinically overt thrombosis was confirmed by ultrasound or angiography. Catheter-related thrombosis incidence without anticoagulants was 28% in arm and 33% in chest ports, but with anticoagulants this was 32% in arm and only 1% in chest ports (odds ratio (OR) 34.8 95% confidence interval (CI) 7.3-165). Left-sided placement compared with right-sided and catheter tip position in the superior vena cava compared with right atrium were associated with a 3.5 respectively 2.6-fold increased risk. Thrombosis was associated with elevated homocysteine levels (OR=3.8, 95% CI 1.3-11.3), but not with factor V Leiden or prothrombin 20210A gene mutations, or high concentration of factor VIII, IX or XI. Prophylaxis with anticoagulants is recommended for chest, but not for arm ports. Determination of plasma homocysteine levels may identify patients at an increased risk for thrombosis.

Effect of Mthfr genotype on diet-induced hyperhomocysteinemia and vascular function in mice

Deficiency of methylenetetrahydrofolate reductase (MTHFR) predisposes to hyperhomocysteinemia and vascular disease. We tested the hypothesis that heterozygous disruption of the Mthfr gene sensitizes mice to diet-induced hyperhomocysteinemia and endothelial dysfunction. Mthfr+/- and Mthfr+/+ mice were fed 1 of 4 diets: control, high methionine (HM), low folate (LF), or high methionine/low folate (HM/LF). Plasma total homocysteine (tHcy) was higher with the LF and HM/LF diets than the control (P < .01) or HM (P < .05) diets, and Mthfr+/- mice had higher tHcy than Mthfr+/+ mice (P < .05). With the control diet, the S-adenosylmethionine (SAM) to S-adenosylhomocysteine (SAH) ratio was lower in the liver and brain of Mthfr+/- mice than Mthfr+/+ mice (P < .05). SAM/SAH ratios decreased further in Mthfr+/+ or Mthfr+/- mice fed LF or LF/HM diets (P < .05). In cerebral arterioles, endothelium-dependent dilation to 1 or 10 μM acetylcholine was markedly and selectively impaired with the HM/LF diet compared with the control diet for both Mthfr+/+ (maximum dilation 5% ± 2% versus 21% ± 4%; P < .01) and Mthfr+/- (6% ± 2% versus 21% ± 3%; P < .01) mice. These findings demonstrate that the Mthfr+/- genotype sensitizes mice to diet-induced hyperhomocysteinemia and that hyperhomocysteinemia alters tissue methylation capacity and impairs endothelial function in cerebral microvessels.

Hyperhomocysteinemia and end-stage renal disease: determinants and association with cardiovascular disease in Tunisian patients

The study reports on plasma total homocysteine (tHcy) levels in Tunisian patients with chronic renal failure (CRF) and those treated with hemodialysis (HD) and renal transplant (RT). The aims of the study were to identify the determinants of tHcy concentration and to test the association between hyperhomocysteinemia and atherothrombotic disease in end-stage renal disease (ESRD). A total of 35 CRF patients on conservative treatment, 50 HD patients, and 30 RT recipients, and 31 age- and sex-matched healthy subjects were included. Plasma tHcy was assessed by a fluorescent-polarizing immunoassay method. Multivariate analysis was applied to identify the main determinants of tHcy concentration and to assess the relationship between hyperhomocysteinemia and cardiovascular disease. Plasma mean tHcy concentration was significantly increased (p < 0.001) in CRF patients (mean +/- SD) (28.9 +/- 9.8 micromol/l), in HD patients (29.4 +/- 11.1 micromol/l), and in RT (19.3 +/- 6.3 micromol/l) patients compared to controls (11.9 +/- 4.1 micromol/l). Multivariate analysis using GLM ANOVA modeling demonstrated that tHcy was significantly higher in males (p = 0.02), and was related to age (p = 0.008), albumin (p = 0.005), vitamin B12 (p = 0.002), folate (p = 0.00001), and creatinine clearance (p = 0.0008). However, tHcy was not associated with C-reactive protein and did not significantly differ between CRF, HD, or RT patients. The upper quartile of tHcy concentration was significantly associated with atherothrombotic cardiovascular disease (unadjusted odds ratio (OR) = 3.09; 95% CI, 1.11-8.61; p = 0.01). This association remained significant after adjusting for sex, age, hypertension, and smoking (multi-adjusted OR = 4.78; 95% CI, 1.92-11.9; p = 0.0008). The mean tHcy concentration was 2 to 3 times higher in ESRD patients than in subjects with normal renal function. This increase could be related to glomerular filtration rate reduction and functional B vitamins deficiency, but was not associated with inflammation. The upper quartile of tHcy concentrations confers 4.78-fold increased independent risk for atherothrombotic events in ESRD patients.

Functional Vitamin B12 Deficiency and Determination of Holotranscobalamin in Populations at Risk

BACKGROUND

The prevalence of a sub-clinical functional vitamin B12 deficiency in the general population is higher than previously expected. Total serum vitamin B12 may not reliably indicate vitamin B12 status. To get more specificity and sensitivity in diagnosing vitamin B12 deficiency, the concept of measuring holotranscobalamin II (holoTC), a sub-fraction of vitamin B12, has aroused great interest. HoloTC as a biologically active vitamin B12 fraction promotes a specific uptake of its vitamin B12 by all cells. In this study we investigated the diagnostic value of storage (holoTC) of vitamin B12 and functional markers (methylmalonic acid (MMA)) of vitamin B12 metabolism in populations who are at risk of vitamin B12 deficiency.

SUBJECTS AND METHODS

Our study included 93 omnivorous German controls, 111 German and Dutch vegetarian subjects, 122 Syrian apparently healthy subjects, 127 elderly Germans and finally 92 German pre-dialysis renal patients. Serum concentrations of homocysteine (Hcy) and MMA were measured by gas chromatography-mass spectrometry, folate and vitamin B12 by chemiluminescence immunoassay, and holoTC by utilizing a RIA test.

RESULTS

High Hcy (>12 micromol/l), high MMA (>271 nmol/l) resp. low holoTC (vitamin B12) in serum were detected in 15%, 8% resp. 13% (1%) of German controls, 36%, 60%, resp. 72% (30%) of vegetarians, 42%, 48% resp. 50% (6%) of Syrians, 75%, 42%, resp. 21% (7%) of elderly subjects and 75%, 67% resp. 4% (2%) of renal patients. The lowest median levels of holoTC were observed in vegetarians, followed by the Syrian subjects (23 and 35 pmol/l, respectively). Renal patients had significantly higher levels of holoTC compared to the German controls (74 vs. 54 pmol/l). In the vitamin B12 range between 156 pmol/l (conventional cut-off level) and 241 pmol/l, both mean concentrations of holoTC and MMA were in the pathological range. HoloTC was the earliest marker for vitamin B12 deficiency followed by MMA. Vitamin B12 deficiency causes folate trapping. A higher folate level is required to keep Hcy normal. The relationship between MMA and holoTC seemed dependent on renal function. In renal patients with a glomerular filtration rate below 36 ml/min, a significantly lower mean level of MMA was detected within the highest tertile of holoTC concentration, compared to the lowest tertile. Thus, in renal patients, a higher serum concentration of circulating holoTC is required to deliver sufficient amounts of holoTC into the cells.

CONCLUSION

Our data support the concept that the measurement of holoTC and MMA provides a better index of cobalamin status than the measurement of total vitamin B12. HoloTC is the most sensitive marker, followed by MMA. The use of holoTC and MMA enables us to differentiate between storage depletion and functional vitamin B12 deficiency. Renal patients have a higher requirement of circulating holoTC. In renal dysfunction, holoTC cannot be used as a marker of vitamin B12 status.

Homocysteine: Chemistry, metabolism and roles in pathophysiology processes

In 1962, 30 years after chemical structure discovery of homocysteine, Carson and Neil reported work in which they described cases of two young people with severe mental retardation and high homocysteinuria. In 1975 McCully emphasized the association between homocysteinuria and thrombus-occlusive vascular changes. Period 1991-98, is the time of very extensive comparative studies, with aim of establishing links between premature coronary artery disease and high homocysteine level in plasma. These results in a whole show that biochemical findings of a mild increase of homocysteine plasma levels in span of 15-45 mmol/L, are independent risk factor for premature coronary artery disease appearance. So far mechanism of direct homociysteine uninfluenced on endothelial vascular vessels cells, or influence of any other factor, which play role in methionine-homocysteine-cysteine path (vitamins B6, B12, folic acid) are not strictly elucidated.

Vegetarian lifestyle and monitoring of vitamin B-12 status

Vegetarians are at risk to develop deficiencies of some essential nutrients, especially vitamin B-12 (cobalamin). Cobalamin occurs in substantial amounts only in foods derived from animals and is essential for one-carbon metabolism and cell division. Low nutritional intake of vitamin B-12 may lead to negative balance and, finally, to functional deficiency when tissue stores of vitamin B-12 are depleted. Early diagnosis of vitamin B-12 deficiency seems to be useful because irreversible neurological damages may be prevented by cobalamin substitution. The search for a specific and sensitive test to diagnose vitamin B-12 deficiency is ongoing. Serum vitamin B-12 measurement is a widely applied standard method. However, the test has poor predictive value. Optimal monitoring of cobalamin status in vegetarians should include the measurement of homocysteine (HCY), methylmalonic acid (MMA), and holotranscobalamin II. Vitamin B-12 deficiency can be divided into four stages. In stages I and II, indicated by a low plasma level of holotranscobalamin II, the plasma and cell stores become depleted. Stage III is characterized by increased levels of HCY and MMA in addition to lowered holotranscobalamin II. In stage IV, clinical signs become recognizable like macroovalocytosis, elevated MCV of erythrocytes or lowered haemoglobin. In our investigations, we have found stage III of vitamin B-12 deficiency in over 60% of vegetarians, thus underlining the importance of cobalamin monitoring in this dietary group.

Magnetic resonance imaging in pediatric stroke

Pediatric stroke is a term that can be used to encompass everything from hypoxic-ischemic injury to the fetal central nervous system, and especially the premature neonate, to bland versus hemorrhagic infarction from arterial or venous causes in the infant and older child. Pediatric stroke is a chronically underrecognized and therefore underdiagnosed problem that may have significant economic implications. The risk factors for stroke in children are numerous and differ from those in adults. However, with adequate workup, the etiology can be identified in about 75% of cases. Cardiac disorders and hemoglobinopathy are the most common causes of ischemic infarction in children, whereas various congenital anomalies of the blood vessels or defects in coagulation or platelet function often are found in children with parenchymal hemorrhage. Magnetic resonance imaging provides a noninvasive method of investigating childhood stroke, aiding in both better diagnosis and management of this problem.

Risk factors for coronary disease: the time for a paradigm shift?

Risk stratification is a key element of clinical management not only in the primary and secondary prevention, but also during the acute stages of cardiovascular disease. The current risk assessment algorithms in primary prevention are based on established risk factors: gender and age, cigarette smoking, the presence of hypertension and diabetes mellitus, and serum concentrations of total cholesterol, low-density lipoprotein (LDL)-cholesterol and high-density lipoprotein-cholesterol. However, many individuals who are assessed as "low risk" on the basis of traditional risk factors, still develop cardiac events. This article addresses current issues relevant to the assessment of cardiovascular risk. It emphasizes the potential importance of disturbed energy supply for atherogenesis, by introducing the concept of fuel transport (chylomicron, VLDL, and remnants) and overflow (LDL) pathways of lipid metabolism. It highlights the present lack of routine methods to monitor the fuel transport pathway. It considers the measurements of serum C-reactive protein and plasma fibrinogen as new additions to the cardiovascular risk factor profiles. Finally, risk stratification based on the traditional and the new risk factors is linked to that based on the markers of acute myocardial damage such as cardiac troponin I or troponin T. It is concluded that the combined use of the markers of myocardial damage and the "new" cardiovascular risk factors is the way ahead for the assessment of cardiovascular risk.