Impact of plasma homocysteine and prothrombin G20210 A on primary antiphospholipid syndrome

An immunogenomic exome landscape of triple positive primary antiphospholipid patients

Primary antiphospholipid syndrome is characterized by thrombosis and autoantibodies directed against phospholipids or associated proteins. The genetic etiology of PAPS remains unknown. We enrolled 21 patients with thromboembolic events associated to lupus anticoagulant, anticardiolipin and anti β2 glycoprotein1 autoantibodies. We performed whole exome sequencing and a systematic variant-based analysis in genes associated with thrombosis, in candidate genes previously associated with APS or inborn errors of immunity. Data were compared to public databases and to a control cohort of 873 non-autoimmune patients. Variants were identified following a state-of-the-art pipeline. Enrichment analysis was performed by comparing with the control cohort. We found an absence of significant HLA bias and genetic heterogeneity in these patients, including when testing combinations of rare variants in genes encoding for proteins involved in thrombosis and of variants in genes linked with inborn errors of immunity. These results provide evidence of genetic heterogeneity in PAPS, even in a homogenous series of triple positive patients. At the individual scale, a combination of variants may participate to the breakdown of B cell tolerance and to the vessel damage.

Methylenetetrahydrofolate Reductase 677T Allele Is a Risk Factor for Arterial Thrombosis in Chinese Han Patients with Antiphospholipid Syndrome

Antiphospholipid syndrome (APS) is a systemic autoimmune disorder characterized by the persistent presence of antiphospholipid antibodies (aPL) and thrombotic or obstetric events. Given the heterogeneity of the clinical manifestations, it is likely that genetic and acquired factors are involved in the pathogenesis of APS. The inherited polymorphisms of the thrombophilic gene, including methylenetetrahydrofolate reductase (MTHFR) C677T, type 1 plasminogen activator inhibitor (PAI-1) 4G/5G, factor V Leiden (FVL) G1691A, prothrombin (PT) G20210A, antithrombin (AT), and fibrinogen (Fg) polymorphisms, were analyzed in 67 aPL(+) patients from the Chinese Han population, including 41 APS patients and 26 persistent aPL carriers. The MTHFR C677T genotypes of 105 healthy controls, and the PAI-1 4G/5G polymorphism of 120 healthy controls, from the Chinese Han population were acquired for this study. Both the MTHFR C677T genotype (χ² = 10.67, p = 0.004) and C/T allele distribution (χ² = 5.92, p = 0.019) between the aPL(+) patients and healthy controls were found to be significantly different. Furthermore, we observed that the patients with at least one T allele had a higher risk of arterial thrombosis (CT vs. CC, OR 11.00, p= 0.025; CT + TT vs. CC, OR 10.27, p = 0.018). The C677T mutation of MTHFR is a risk factor for arterial thrombosis in Chinese Han patients with APS.

Homozygous methylentetrahydrofolate reductase C667T genotype anticipates age at venous thromboembolism by one decade

The aim of the study was to compare age at first venous thromboembolism (VTE), plasma homocysteine and activated partial thromboplastin time ratio (aPTTr) amongst unprovoked VTE patients with the methylentetrahydrofolate reductase (MTHFR) C667T genotypes, and to identify predictors of age at first VTE, of plasma homocysteine and of the aPTTr; to evaluate whether heterozygous or homozygous prothrombin (PT) G20210A mutation lowered the age at first VTE when associated with MTHFR TT. Retrospective cohort study on 259 MTHFR TT, 76 MTHFR TC and 64 MTHFR CC participants with unprovoked VTE; each participant contributed age, sex, age at VTE, history of dyslipidaemia, hypertension, smoking, homocysteine (measured by enzyme immunoassay) and aPTTr (measured by standard coagulation assay). Age at first VTE was lower in MTHFR TT than MTHFR TC and CC (41 ± 14 vs. 50 ± 16 vs. 51 ± 12 years, respectively, P < 0.0001); plasma homocysteine was higher in MTHFR TT than in the other groups (22 ± 21 vs. 12 ± 11.6 vs. 10 ± 3.3 μmol/l, respectively, P = 0.0005) whilst aPTTr was not different. MTHFR TT independently predicted age at first VTE (P = 0.001), plasma homocysteine (P < 0.0001) alongside sex (P = 0.0007), age and smoking (P = 0.03 for both). Compound MTHFR TT with PT GA or AA had no lowering effect on age at first VTE compared with MTHFR TT alone (41 ± 13 vs. 41 ± 14 years). Plasma homocysteine inversely related to aPTTr in the MTHFR TT group (P = 0.003). MTHFR TT anticipates age at first VTE by an average of 10 years compared with MTHFR TC and CC genotypes.

Antiphospholipid syndrome's genetic and epigenetic aspects

Studies on last genetic and epigenetic predisposition to APS are summarized. It is well known that genetic predisposition is in HLA system (DR4 and DRw53) and that lupus anticoagulant (LA) and anticardiolipin antibodies (aCL) are both associated with the same HLA antigens. Other genes, outside the MHC, give their contribution to the development of this autoimmune syndrome, such as IRF5, STAT4 and those related to inherited thrombophilia - factor V Leiden and G20210A prothrombin polymorphisms. Finally, post-transcriptional modifications of anti-beta2GPI antibodies could be implicated too. The most important discovery of last years is that altered microRNAs' expression is linked to autoimmunity, thrombosis, early atherosclerosis, and oxidative stress in APS.

Hyperhomocysteinemia Relates to the Subtype of Antiphospholipid Antibodies in Non-SLE Patients

Abnormal increases of antiphospholipid antibody and plasma homocysteine levels are recently emerging as nonlipidic risk factors for cerebral atherogenesis and thrombosis. Both antiphospholipid antibody and homocysteine share many similar bioeffects in hemostasis, but their interaction is still inconsistent. In this study, we examined the relation between the plasma homocysteine level and lupus anticoagulant, anticardiolipin antibody, and anti-β2-glycoprotein I antibody in patients with noncardiac cerebral ischemia. Systemic lupus erythrematosus patients were excluded. The results showed a higher frequency of moderate hyperhomocysteinemia in patients with an abnormal increase of lupus anticoagulant only. Neither the serum folate and cobalamin levels nor methylenetetrahydrofolate reductase allele mutation contributes to this result. Accordingly, homocysteine interacts with lupus anticoagulant to promote cerebral atherosclerosis and ischemia. The role of vasculopathic or prothrombotic autoantibody generation in response to specific pathological change such as hyperhomocysteinemia warrants further investigation.

Genetic aspects of the antiphospholipid syndrome: An update

Studies on the immunogenetic predisposition to antiphospholipid syndrome (APS) and on other non-genetic and epigenetic factors are summarised and discussed. Family studies suggest a genetic predisposition to APS. It appears that this genetic predisposition is in part accounted for by the HLA system, the most consistent associations being those with DR4 and DRw53. Furthermore, it appears that lupus anticoagulant (LA) and anticardiolipin (aCL) antibodies are both associated with the same HLA antigens. Population studies suggest that HLA genes have a role in conferring susceptibility to develop primary APS, with some differences in different ethnic groups. Other genes, outside the MHC, give their contribution to the development of this autoimmune syndrome, such as IRF5, STAT4 and those related to inherited thrombophilia--factor V Leiden and G20210A prothrombin polymorphisms. Finally, post-transcriptional modifications of anti-beta2GPI antibodies could be implicated too.

Pathophysiology of the antiphospholipid antibody syndrome

Antiphospholipid antibodies (aPL) are associated with the recurrent pregnancy loss and thrombosis that characterizes the antiphospholipid antibody syndrome (APS). Although the ontogeny of these pathogenic antibodies has not been fully elucidated, there is evidence that indicates the involvement of both genetic and environmental factors. The ability of aPL to induce a procoagulant phenotype in APS patients plays a central role in the development of arterial and venous thrombotic manifestations typical of the disease. Inflammation serves as a necessary link between this procoagulant phenotype and actual thrombus development and is an important mediator of the placental injury seen in APS patients with obstetric complications. Recent evidence has indicated a role for abnormal cellular proliferation and differentiation in the pathophysiology of APS, especially in those patients with pregnancy morbidity and other more atypical manifestations that have no identifiable thrombotic cause. The interplay of genetic and environmental factors responsible for aPL development and the mechanisms by which these antibodies produce disease in APS patients is the focus of this review.

Genetics of antiphospholipid syndrome

Antiphospholipid syndrome (APS) is an autoimmune disease characterized by recurrent arterial or venous thrombosis or fetal loss and the presence of antiphospholipid antibodies (aPL). Genetic factors are thought to play a role in the susceptibility to APS. Similar to many other polygenic autoimmune diseases, human leukocyte antigen associations have been reported. The genetics of b(2)-glycoprotein I, one of the most representative target antigens of aPL, has been extensively studied. Additional genetic risk factors for the development of thrombosis in patients with aPL have also been discussed. However, the genes involved in APS have not been identified because antigen specificity of aPL and the pathophysiology of APS are highly heterogeneous and multifactorial. Genome-wide linkage analysis and larger cohort studies would lead to better understanding of the genes that might be involved in APS.

What is antiphospholipid syndrome?

The description of antiphospholipid syndrome (APS) is vascular thrombosis and/or pregnancy morbidity occurring in persons with antiphospholipid antibodies (aPL). However, because of an unclear etiopathogenesis and the heterogeneous nature of aPL and of aPL-related clinical manifestations, a single, unambiguous definition of APS does not exist. In this paper, we describe a structured approach to APS, discuss the controversies, and offer descriptions of APS that include: an autoimmune systemic disease with a spectrum of (mostly thrombotic) clinical manifestations, an overdiagnosed disease when aPL is present but has no proven direct causative role in the clinical manifestations, and a disease of controversies that requires clarification of etiology and mechanisms and risk-stratified controlled clinical studies.

Homocysteine levels in women with antiphospholipid syndrome and normal fertile controls

OBJECTIVE

Recent studies have identified hyperhomocysteinemia as a risk factor for both recurrent pregnancy loss and thrombosis. Antiphospholipid syndrome, an autoimmune disorder, is also characterized by recurrent pregnancy loss and thrombosis. Thus, our purpose was to determine if hyperhomocysteinemia is more common in patients with APS than normal fertile controls.

METHODS

Plasma, sera and whole blood were obtained from two groups of women: (1) 22 with well-characterized antiphospholipid syndrome; and (2) 41 healthy fertile controls. Levels of fasting homocysteine, vitamin B16, vitamin B12, folate and the incidence of the C677/T mutation of the methylene tetrahydrofolate reductase genotype (C677T/MTHFR) were determined.

RESULTS

The proportion of individuals with hyperhomocysteinemia and fasting plasma homocysteine levels were similar in women with APS and controls. Levels of vitamin B6, vitamin B12, folate and the incidence of C677/MTHFR were also similar in the two groups.

CONCLUSION

Hyperhomocyteinemia and the C677T/MTHFR mutation are not common in women with antiphospholipid syndrome. Abnormal homocysteine metabolism is unlikely to play a major role in the pathogenesis of antiphospholipid syndrome.

Antiphospholipid/antiprotein antibodies, hemostasis-related autoantibodies, and plasma homocysteine as risk factors for a first early pregnancy loss: a matched case-control study

Maternal hypercoagulability is a possible cause of miscarriage during the eighth and ninth weeks of pregnancy, when the placenta replaces the yolk sac. We thus examined associations between putative markers of an acquired hypercoagulable state and the risk of first miscarriage. We conducted a case-control study comparing 743 women who miscarried in weeks 8 and 9 with 743 women who underwent a first provoked abortion, matched for age, number of pregnancies, and time elapsed since abortion. Levels of plasma homocysteine and of various antiphospholipid/antiprotein and hemostasis-related autoantibodies were categorized in 4 strata (percentiles 1-80, 81-95, 96-99, 100 among control patients) and analyzed in conditional logistic regression models. Pregnancy loss was independently associated with positive lupus anticoagulant (matched odds ratio [OR], 2.6; 95% confidence interval [CI], 1.1-6.0), high levels of immunoglobulin M (IgM) antibodies against cardiolipin (OR for percentile 100 versus 0-80, 3.5; CI, 1.2-10.1) and against phosphatidylethanolamine (OR, 4.7; CI, 1.9-12.1), high levels of IgG antibodies against annexin V (OR, 3.2; CI, 1.1-9.1) and against tissue-type plasminogen activator (OR, 19.5; CI, 7.9-48.0), and high homocystinemia (OR, 4.1; CI, 1.3-12.5). A first early pregnancy loss is associated with increased levels of several autoantibodies and of homocysteine.

[Heterozygous prothrombin gene mutation G20210A and associated diseases]

PURPOSE

Prothrombin gene mutation G20210A (factor II) is, in frequency, the second genetic polymorphism involved in venous thrombosis. We report a retrospective studies on 38 patients issued from our medical department, all heterozygous for the factor II mutation and a literature review.

METHODS

We have studied 38 patients, all heterozygous for the factor II mutation, selected through a population of 516 tested patients issued from our medical department from 1997 to 2002. The research was performed face with history of thrombotic or obstetrical events, angiopathy or familial screening.

RESULTS

Twenty out of thirty-eight patients have at least one episode of venous thrombosis: superficial thromboses, deep thromboses and/or pulmonary embolism. One case of cerebral thrombophlebitis is observed. Venous thrombotic risk factors are associated in 12 cases (60%). Four out of thirty-eight patients have one episode of arterial thrombosis: cardiovascular, peripheral or cerebral. Arterial thrombotic risk factors are associated in all cases. Median age of the first venous thrombosis is earlier than the one of arterial thrombosis (39.11 versus 49.25 years).

CONCLUSION

Our studies confirms the interest to search the prothrombin gene mutation when faced with a venous thrombotic event (deep vein thrombosis and/or pulmonary embolism) with or without acquired risk factors. Its involvement in thrombotic arterial disease is still a matter of debate. Data concerning its involvement in systemic diseases and angiopathies (thromboangeitis obliterans, Raynaud's phenomenon and migraine) are still needed. Mechanisms of thromboses could be an increase of prothrombin plasma level with high thrombin synthesis.

Anticardiolipin antibody titre and plasma homocysteine level independently predict intima media thickness of carotid arteries in subjects with idiopathic antiphospholipid antibodies

This study evaluated whether IgG anticardiolipin antibody (aCL) titre and traditional risk factors for atherosclerosis bore any relationship to the intima media thickness (IMT) of carotid arteries of patients with idiopathic antiphospholipid antibodies (aPL). IMT was assessed by high-resolution sonography at the common carotid, carotid bifurcation and internal carotid in 42 (13 male, 29 female, mean age 31+/-10 years) aPL subjects, 29 with primary thrombotic antiphospholipid syndrome and 13 with persistence of aPL in the absence of any underlying disorder. In the same subjects the following were measured: plasma fibrinogen (FNG), von Willebrand factor (vWF), plasminogen activator inhibitor (PAI), homocysteine (HC), total cholesterol (CHO), triglycerides (TG), high density and low density lipoprotein (HDL and LDL), platelet numbers and aCL of IgG and IgM isotype. IMT of the internal carotid was greater in males than females (0.48+/-0.03 vs 0.39+/-0.01 mm, P=0.02). IMT of the carotid bifurcation was greater in thrombotic than nonthrombotic subjects (0.50+/-0.02 vs 0.42+/-0.02 mm, P=0.04). By simple regression, IMT of the common carotids correlated with age (P< 0.0001) IgG aCL titre (P=0.001), FNG (P=0.006), LDL (0.01), CHO (0.02) and PAI (P=0.02). IMT of the carotid bifurcation correlated with age (P=0.002), IgG aCL titre (P=0.0002), FNG (P=0.0001), HC (P=0.009), CHO (P=0.02), vWF (P=0.01) and number of thrombotic events (P=0.03). IMT of the internal carotids correlated with age (P=0.002), IgG aCL titre (P=0.0001), FNG (P=0.0008), PAI (P=0.002) and HC (P=0.01). By stepwise multiple regression analysis, IgG aCL titre independently predicted IMT at all carotid segments examined (P always <0.005). In addition, plasma FNG and HC also resulted independent predictors of IMT at the carotid bifurcation (P=0.001 and P<0.0001, respectively) and internal carotid (P=0.03 and P<0.0001, respectively). These data strongly support an atherogenic role for IgG aCL in patients with aPL. Measurement of plasma HC and FNG may help define aPL subjects at higher vascular risk who may require lowering of HC and FNG by vitamin and/or pharmacologic intervention.