Accumulation Of Homocysteine Research Articles

Homocysteine in Chronic Kidney Disease.

Hyperhomocysteinemia occurs in chronic- and end-stage kidney disease at the time when dialysis or transplant becomes indispensable for survival. Excessive accumulation of homocysteine (Hcy) aggravates conditions associated with imbalanced homeostasis and cellular redox thereby resulting in severe oxidative stress leading to oxidation of reduced free and protein-bound thiols. Thiol modifications such as N-homocysteinylation, sulfination, cysteinylation, glutathionylation, and sulfhydration control cellular responses that direct complex metabolic pathways. Although cysteinyl modifications are kept low, under Hcy-induced stress, thiol modifications persist thus surpassing cellular proteostasis. Here, we review mechanisms of redox regulation and show how cysteinyl modifications triggered by excess Hcy contribute development and progression of chronic kidney disease. We discuss different signaling events resulting from aberrant cysteinyl modification with a focus on transsulfuration.

Role of copper in regression of cardiac hypertrophy.

Pressure overload causes an accumulation of homocysteine in the heart, which is accompanied by copper depletion through the formation of copper-homocysteine complexes and the excretion of the complexes. Copper supplementation recovers cytochrome c oxidase (CCO) activity and promotes myocardial angiogenesis, along with the regression of cardiac hypertrophy and the recovery of cardiac contractile function. Increased copper availability is responsible for the recovery of CCO activity. Copper promoted expression of angiogenesis factors including vascular endothelial growth factor (VEGF) in endothelial cells is responsible for angiogenesis. VEGF receptor-2 (VEGFR-2) is critical for hypertrophic growth of cardiomyocytes and VEGFR-1 is essential for the regression of cardiomyocyte hypertrophy. Copper, through promoting VEGF production and suppressing VEGFR-2, switches the VEGF signaling pathway from VEGFR-2-dependent to VEGFR-1-dependent, leading to the regression of cardiomyocyte hypertrophy. Copper is also required for hypoxia-inducible factor-1 (HIF-1) transcriptional activity, acting on the interaction between HIF-1 and the hypoxia responsible element and the formation of HIF-1 transcriptional complex by inhibiting the factor inhibiting HIF-1. Therefore, therapeutic targets for copper supplementation-induced regression of cardiac hypertrophy include: (1) the recovery of copper availability for CCO and other critical cellular events; (2) the activation of HIF-1 transcriptional complex leading to the promotion of angiogenesis in the endothelial cells by VEGF and other factors; (3) the activation of VEGFR-1-dependent regression signaling pathway in the cardiomyocytes; and (4) the inhibition of VEGFR-2 through post-translational regulation in the hypertrophic cardiomyocytes. Future studies should focus on target-specific delivery of copper for the development of clinical application.

Folinic acid treatment for schizophrenia associated with folate receptor autoantibodies

BackgroundAuto-antibodies against folate receptor alpha (FRα) at the choroid plexus that block N5-methyltetrahydrofolate (MTHF) transfer to the brain were identified in catatonic schizophrenia. Acoustic hallucinations disappeared following folinic acid treatment. Folate transport to the CNS prevents homocysteine accumulation and delivers one-carbon units for methyl-transfer reactions and synthesis of purines. The guanosine derivative tetrahydrobiopterin acts as common co-factor for the enzymes producing dopamine, serotonin and nitric oxide. MethodsOur study selected patients with schizophrenia unresponsive to conventional treatment. Serum from these patients with normal plasma homocysteine, folate and vitamin B12 was tested for FR autoantibodies of the blocking type on serial samples each week. Spinal fluid was analyzed for MTHF and the metabolites of pterins, dopamine and serotonin. The clinical response to folinic acid treatment was evaluated. ResultsFifteen of 18 patients (83.3%) had positive serum FR auto-antibodies compared to only 1 in 30 controls (3.3%) (χ2=21.6; p<0.0001). FRα antibody titers in patients fluctuated over time varying between negative and high titers, modulating folate flux to the CNS, which explained low CSF folate values in 6 and normal values in 7 patients. The mean±SD for CSF MTHF was diminished compared to previously established controls (t-test: 3.90; p=0.0002).A positive linear correlation existed between CSF MTHF and biopterin levels. CSF dopamine and serotonin metabolites were low or in the lower normal range. Administration of folinic acid (0.3–1mg/kg/day) to 7 participating patients during at least six months resulted in clinical improvement. ConclusionAssessment of FR auto-antibodies in serum is recommended for schizophrenic patients. Clinical negative or positive symptoms are speculated to be influenced by the level and evolution of FRα antibody titers which determine folate flux to the brain with up- or down-regulation of brain folate intermediates linked to metabolic processes affecting homocysteine levels, synthesis of tetrahydrobiopterin and neurotransmitters. Folinic acid intervention appears to stabilize the disease process.

Early methyl donor deficiency alters cAMP signaling pathway and neurosteroidogenesis in the cerebellum of female rat pups.

Early deficiency of the methyl donors folate and vitamin B12 produces hyperhomocysteinemia and cognitive and motor disorders in 21-day-old rat pups from dams fed a diet deficient in methyl donors during gestation and lactation. These disorders are associated with impaired neurogenesis and altered synaptic plasticity in cerebellum. We aimed to investigate whether these disorders could be related to impaired expression of neurosteroidogenesis-associated proteins, key regulator receptors, and some steroid content in the cerebellum. The methyl donor deficiency produced a decreased concentration of folate and vitamin B12, along with accumulation of homocysteine in Purkinje cells in both sexes, whereas the S-adenosylmethionine/S-adenosylhomocysteine ratio was reduced only in females. The transcription level and protein expression of StAR, aromatase, ERα, ERβ, and LH receptors were decreased only in females, with a marked effect in Purkinje cells, as shown by immunohistochemistry. Consistently, reduced levels of estradiol and pregnenolone were measured in cerebellar extracts of females only. The decreased expression levels of the transcriptional factors CREB, phospho-CREB, and SF-1, the lesser increase of cAMP concentration, and the lower level of phospho-PKC in the cerebellum of deficient females suggest that the activation of neurosteroidogenesis via cAMP-mediated signaling pathways associated with LHR activation would be altered. In conclusion, a gestational methyl donor deficiency impairs neurosteroidogenesis in cerebellum in a sex-dependent manner.

Hyperhomocysteinemia is a result, rather than a cause, of depression under chronic stress.

BackgroundAlthough the accumulation of homocysteine (Hcy) has been implicated in the pathogenesis of depression, whether Hcy is directly involved and acts as the primary cause of depressive symptoms remains unclear. The present study was designed to clarify whether increased Hcy plays an important role in stress-induced depression.ResultsWe employed the chronic unpredictable mild stress model (CUMS) of depression for 8 weeks to observe changes in the plasma Hcy level in the development of depression. The results showed that Wistar rats exposed to a series of mild, unpredictable stressors for 4 weeks displayed depression-like symptoms such as anhedonia (decreased sucrose preferences) and a decreased 5-Hydroxy Tryptophan (5-HT) concentration in the hippocampus. At the end of 8 weeks, the plasma Hcy level increased in the CUMS rats. The anti-depressant sertraline could decrease the plasma Hcy level and improve the depression-like symptoms in the CUMS rats. RhBHMT, an Hcy metabolic enzyme, could decrease the plasma Hcy level significantly, although it could not improve the depressive symptoms in the CUMS rats.ConclusionsThe results obtained from the experiments did not support the hypothesis that the increased Hcy concentration mediated the provocation of depression in CUMS rats, and the findings suggested that the increased Hcy concentration in the plasma might be the result of stress-induced depression.

5-Mehtyltetrahydrofolate rescues alcohol-induced neural crest cell migration abnormalities.

BackgroundAlcohol is detrimental to early development. Fetal alcohol spectrum disorders (FASD) due to maternal alcohol abuse results in a series of developmental abnormalities including cranial facial dysmorphology, ocular anomalies, congenital heart defects, microcephaly and intellectual disabilities. Previous studies have been shown that ethanol exposure causes neural crest (NC) apoptosis and perturbation of neural crest migration. However, the underlying mechanism remains elusive. In this report we investigated the fetal effect of alcohol on the process of neural crest development in the Xenopus leavis.ResultsPre-gastrulation exposure of 2-4% alcohol induces apoptosis in Xenopus embryo whereas 1% alcohol specifically impairs neural crest migration without observing discernible apoptosis. Additionally, 1% alcohol treatment considerably increased the phenotype of small head (43.4% ± 4.4%, total embryo n = 234), and 1.5% and 2.0% dramatically augment the deformation to 81.2% ± 6.5% (n = 205) and 91.6% ± 3.0% (n = 235), respectively (P < 0.05). Significant accumulation of Homocysteine was caused by alcohol treatment in embryos and 5-mehtyltetrahydrofolate restores neural crest migration and alleviates homocysteine accumulation, resulting in inhibition of the alcohol-induced neurocristopathies.ConclusionsOur study demonstrates that prenatal alcohol exposure causes neural crest cell migration abnormality and 5-mehtyltetrahydrofolate could be beneficial for treating FASD.

Folate deficiency in rat pups during weaning causes learning and memory deficits.

Folate is essential for fetal development, and its deficiency during gestation causes behavioural deficits in the offspring. The present study investigated its influence during weaning on brain function in the pups of rats that were put on a folate-deficient (FD) diet on postnatal day (PND) 1. Systemic folate deficiency in pups on the FD diet (n 15) was evident from the dramatically lower hepatic folate concentrations (median 23·7, range 8·1-48·4 ng/mg protein) and higher homocysteine concentrations (median 27·7, range 14·7-45·5 pmol/mg protein), respectively, compared with those of pups on the normal diet (ND; n 9) (median 114·5, range 64·5-158·5 ng/mg protein and median 15·5, range 11·6-18·9 pmol/mg protein) on PND 23. Brain folate concentrations although low were similar in pups on the FD diet (median 10·5, range 5·5-24·5 ng/mg protein) and ND (median 11·1, range 7·1-24·2 ng/mg protein). There was a high accumulation of homocysteine in the brain of FD pups, mostly in the hippocampus (median 58·1, range 40·8-99·7 pmol/mg protein) and cerebellum (median 69·1, range 50·8-126·6 pmol/mg protein), indicating metabolic folate deficiency despite normal brain folate concentrations. Developmental deficits or autistic traits were more frequent in the FD group than in the ND group and repetitive self-grooming occurred, on average, three times (range 1-8) v. once (range 0-3) during 5 min, respectively. Long-term memory or spatial learning and set-shifting deficits affected 12 to 62% of rats in the FD group compared with none in the ND group. Post-weaning folic acid supplementation did not correct these deficits. These observations indicate that folate deficiency during weaning affects postnatal development even when gestational folate supply is normal.

The role of surface electrostatics on the stability, function and regulation of human cystathionine β-synthase, a complex multidomain and oligomeric protein

Human cystathionine β-synthase (hCBS) is a key enzyme of sulfur amino acid metabolism, controlling the commitment of homocysteine to the transsulfuration pathway and antioxidant defense. Mutations in hCBS cause inherited homocystinuria (HCU), a rare inborn error of metabolism characterized by accumulation of toxic homocysteine in blood and urine. hCBS is a complex multidomain and oligomeric protein whose activity and stability are independently regulated by the binding of S-adenosyl-methionine (SAM) to two different types of sites at its C-terminal regulatory domain. Here we study the role of surface electrostatics on the complex regulation and stability of hCBS using biophysical and biochemical procedures. We show that the kinetic stability of the catalytic and regulatory domains is significantly affected by the modulation of surface electrostatics through noticeable structural and energetic changes along their denaturation pathways. We also show that surface electrostatics strongly affect SAM binding properties to those sites responsible for either enzyme activation or kinetic stabilization. Our results provide new insight into the regulation of hCBS activity and stability in vivo with implications for understanding HCU as a conformational disease. We also lend experimental support to the role of electrostatic interactions in the recently proposed binding modes of SAM leading to hCBS activation and kinetic stabilization.

MTHFR polymorphisms C677T and A1298C and associations with IVF outcomes in Brazilian women

The aim of this study was to investigate the association between MTHFR gene polymorphisms and IVF outcomes in Brazilian women undergoing assisted reproduction treatment. A prospective study was conducted in the Human Reproduction Department at the ABC University School of Medicine and the Ideia Fertility Institute between December 2010 and April 2012. The patient population was 82 women undergoing assisted reproduction cycles. The MTHFR polymorphisms C677T and A1298C were evaluated and compared with laboratory results and pregnancy rates. The C677T variant was associated with proportions of mature (P=0.006) and immature (P=0.003) oocytes whereas the A1298C variant was associated with number of oocytes retrieved (P=0.044). The polymorphisms, whether alone or in combination, were not associated with normal fertilization, good-quality embryo or clinical pregnancy rates. This study suggests that the number and maturity of oocytes retrieved may be related to the MTHFR polymorphisms C677T and A1298C.It is believed that folate has a crucial function in human reproduction and that folate deficiency can compromise the function of the metabolic pathways it is involved in, leading to an accumulation of homocysteine. The gene MTHFR encodes the 5-MTHFR enzyme, which is involved in folate metabolism, and C677T/A1298C polymorphisms of this gene are related to decreased enzyme activity and consequent changes in homocysteine concentration. Folate deficiency and hyperhomocysteinaemia can also compromise fertility and lead to pregnancy complications by affecting the development of oocytes, preparation of endometrial receptivity, implantation of the embryo and pregnancy. In folliculogenesis, hyperhomocysteinaemia can activate apoptosis, leading to follicular atresia and affecting the maturity of oocytes and the quality of embryos cultured in vitro. This study was performed to investigate the association between MTHFR polymorphisms and IVF outcomes in women undergoing assisted reproduction treatment.

The fat mass and obesity-associated FTO rs9939609 polymorphism is associated with elevated homocysteine levels in patients with multiple sclerosis screened for vascular risk factors

The previously reported link between homocysteine and obesity, both identified as established risk factors for multiple sclerosis (MS), has not previously been studied in relation to the fat mass and obesity-associated (FTO) gene. To investigate the mechanism underlying homocysteine accumulation in MS patients. A total of 114 patients and 195 population-matched controls were analysed for the FTO rs9939609 polymorphism. Homocysteine levels were measured in a subgroup of 60 patients and 87 controls screened for multiple vascular risk factors. After adjustment for potential confounders, the risk-associated FTO rs9939609 A-allele was associated with raised homocysteine levels (p = 0.003) in patients diagnosed with MS, but not in controls. Homocysteine levels correlated positively with body mass index (BMI) (p = 0.045) and total cholesterol levels (p = 0.048). Both homocysteine (p = 0.011) and BMI (p = 0.017) were significantly reduced with higher intake of folate in the diet. Higher BMI also correlated with increased intake of saturated/trans fat (p < 0.01) and low physical activity (p < 0.006). Daily intake of at least five fruits and vegetables had a favourable lowering effect on the Expanded Disability Status Scale (EDSS) (p = 0.035), while smoking increased MS disability (p < 0.001). This study has shown for the first time that having a diagnosis of MS moderates the effect of the FTO rs9939609 polymorphism on homocysteine levels. This is consistent with the role of FTO in demethylation and epigenetic changes. Identification of FTO rs9939609 reinforces the importance of adequate fruit, vegetable and folate and restriction of saturated/trans fat intake in the diet.

Abstract W MP37: A Novel Homocysteine Inhibitor Enhances Neurological Recovery after Cerebral Ischemia in Mice and Non-Human Primates

Background: Hyperhomocyteinemia is associated with cardiovascular and cerebrovascular diseases. Many studies have investigated the deleterious effects of intercellular homocysteine (Hcy) accumulation on vascular and brain tissue. AEB-577 is a potent Hcy synthesis inhibitor based on a non-adenosine analog. We hypothesized that AEB-577 could normalize Hcy content in brain tissue, reduce cytotoxicity of Hcy and ameliorate neurological dysfunction after stroke. Method: Male C57BL/6N mice were subjected to photochemically induced thrombosis, and treated orally with AEB-577 (1, 3, 10 mg/kg) or vehicle 10 minutes after the infarction. Infarct volume was assessed by tetrazolium staining and motor incoordination was evaluated using rota-rod test at 24 hours after infarction. In the second experiment, Hcy content in peri-infarct area was measured at 3 days after infarction by HPLC. In a non-human primate experiment, male cynomolgus monkeys were subjected to permanent middle artery occlusion (pMCAO), and divided into 3 groups based on infarction volume assessed by MRI images 18 hours after the onset. And then, vehicle or AEB-577 (4, 12 mg/body) was orally administered once a day for 84 days. The neurological deficits including paralysis, sensory dysfunction, and deficiencies of consciousness and motility were assessed at 3, 5, 7, 11, 14, 28, 56, 84 days after the onset of MCA occlusion. Plasma Hcy level and brain Hcy content were assessed at 84 days. Result: AEB-577 reduced infarct volume and improved motor deficit compared with vehicle treated mice. Hcy content in peri-infarct area significantly increased. AEB-577 decreased elevated Hcy content to normal level. In the monkey study, AEB-577 treatment starting 24 hours after stroke onset significantly promoted neurological recovery. AEB-577 decreased Hcy level in plasma and brain tissue compared with the placebo group at 84 days after stroke onset. Conclusion: Our results indicate that the novel Hcy synthesis inhibitor, AEB-577, can improve functional recovery after cerebral infarction modulating not only plasma Hcy level also Hcy content in brain tissue.

Gestational methyl donor deficiency alters key proteins involved in neurosteroidogenesis in the olfactory bulbs of newborn female rats and is associated with impaired olfactory performance

Gestational methyl donor deficiency (MDD) leads to growth retardation as well as to cognitive and motor disorders in 21-d-old rat pups. These disorders are related to impaired neurogenesis in the cerebral neurogenic areas. Olfactory bulbs (OB), the main target of neuronal progenitors originating from the subventricular zone, play a critical role during the postnatal period by allowing the pups to identify maternal odour. We hypothesised that growth retardation could result from impaired suckling due to impaired olfactory discrimination through imbalanced apoptosis/neurogenesis in the OB. Since neurosteroidogenesis modulates neurogenesis in OB, in the present study, we investigated whether altered neurosteroidogenesis could explain some these effects. Pups born to dams fed a normal diet (n 24) and a MDD diet (n 27) were subjected to olfactory tests during the lactation and weaning periods (n 24 and 20, respectively). We studied the markers of apoptosis/neurogenesis and the expression levels of the key neurosteroidogenic enzyme aromatase, the cholesterol-transfer protein StAR (steroidogenic acute regulatory protein) and the ERα oestrogen receptor and the content of oestradiol in OB. The 21-d-old MDD female pups displayed lower body weight and impaired olfactory discrimination when compared with the control pups. MDD led to greater homocysteine accumulation and more pronounced apoptosis, along with impaired cell proliferation in the OB of female pups. The expression levels of aromatase, StAR and ERα as well as the content of oestradiol were lower in the OB of the MDD female pups than in those of the control female pups. In conclusion, gestational MDD may alter olfactory discrimination performances by affecting neurogenesis, apoptosis and neurosteroidogenesis in OB in a sex-dependent manner. It may be involved in growth retardation through impaired suckling.

Evolved Cobalamin-Independent Methionine Synthase (MetE) Improves the Acetate and Thermal Tolerance of Escherichia coli

Acetate-mediated growth inhibition of Escherichia coli has been found to be a consequence of the accumulation of homocysteine, the substrate of the cobalamin-independent methionine synthase (MetE) that catalyzes the final step of methionine biosynthesis. To improve the acetate resistance of E. coli, we randomly mutated the MetE enzyme and isolated a mutant enzyme, designated MetE-214 (V39A, R46C, T106I, and K713E), that conferred accelerated growth in the E. coli K-12 WE strain in the presence of acetate. Additionally, replacement of cysteine 645, which is a unique site of oxidation in the MetE protein, with alanine improved acetate tolerance, and introduction of the C645A mutation into the MetE-214 mutant enzyme resulted in the highest growth rate in acetate-treated E. coli cells among three mutant MetE proteins. E. coli WE strains harboring acetate-tolerant MetE mutants were less inhibited by homocysteine in l-isoleucine-enriched medium. Furthermore, the acetate-tolerant MetE mutants stimulated the growth of the host strain at elevated temperatures (44 and 45°C). Unexpectedly, the mutant MetE enzymes displayed a reduced melting temperature (Tm) but an enhanced in vivo stability. Thus, we demonstrate improved E. coli growth in the presence of acetate or at elevated temperatures solely due to mutations in the MetE enzyme. Furthermore, when an E. coli WE strain carrying the MetE mutant was combined with a previously found MetA (homoserine o-succinyltransferase) mutant enzyme, the MetA/MetE strain was found to grow at 45°C, a nonpermissive growth temperature for E. coli in defined medium, with a similar growth rate as if it were supplemented by l-methionine.

Teaching Neuro Images : Methotrexate neurotoxicity

A 13-year-old girl presented with acute-onset right hemiparesis involving the face, arm, and leg equally. She was receiving weekly intrathecal methotrexate (last dose 6 days prior) for recently diagnosed acute lymphocytic leukemia. Brain MRI (figure 1) showed diffusion restriction in the left centrum semiovale with reduced apparent diffusion coefficient. Her hemiparesis resolved within 24 hours, but 2 hours later she developed 12-hour left hemiparesis involving face, upper limb, and dysarthria. Follow-up neurologic examination was normal. Repeat MRI (figure 2) 44 hours after the original MRI showed acute right centrum semiovale changes. The changes that were previously seen on the left side had resolved. As before, all changes noted were localized completely in white matter, nonvascular territory. This was consistent with methotrexate neurotoxicity,1,2 possibly secondary to homocysteine accumulation causing direct endothelial injury.3 The patient resumed intrathecal methotrexate 1 month later as part of her ongoing chemotherapeutic regimen without further incidents.

An X-Linked Cobalamin Disorder Caused by Mutations in Transcriptional Coregulator HCFC1

Derivatives of vitamin B12 (cobalamin) are essential cofactors for enzymes required in intermediary metabolism. Defects in cobalamin metabolism lead to disorders characterized by the accumulation of methylmalonic acid and/or homocysteine in blood and urine. The most common inborn error of cobalamin metabolism, combined methylmalonic acidemia and hyperhomocysteinemia, cblC type, is caused by mutations in MMACHC. However, several individuals with presumed cblC based on cellular and biochemical analysis do not have mutations in MMACHC. We used exome sequencing to identify the genetic basis of an X-linked form of combined methylmalonic acidemia and hyperhomocysteinemia, designated cblX. A missense mutation in a global transcriptional coregulator, HCFC1, was identified in the index case. Additional male subjects were ascertained through two international diagnostic laboratories, and 13/17 had one of five distinct missense mutations affecting three highly conserved amino acids within the HCFC1 kelch domain. A common phenotype of severe neurological symptoms including intractable epilepsy and profound neurocognitive impairment, along with variable biochemical manifestations, was observed in all affected subjects compared to individuals with early-onset cblC. The severe reduction in MMACHC mRNA and protein within subject fibroblast lines suggested a role for HCFC1 in transcriptional regulation of MMACHC, which was further supported by the identification of consensus HCFC1 binding sites in MMACHC. Furthermore, siRNA-mediated knockdown of HCFC1 expression resulted in the coordinate downregulation of MMACHC mRNA. This X-linked disorder demonstrates a distinct disease mechanism by which transcriptional dysregulation leads to an inborn error of metabolism with a complex clinical phenotype.

A forgotten lethal psychosis: a case report

Homocystinuria due to cystathionine β-synthase deficiency is an inborn error of metabolism first described almost 50 years ago, which involves the accumulation of plasma homocysteine and other metabolites. Without early detection and appropriate treatment, common and sometimes lethal consequences include ocular abnormalities, osteoporosis, developmental delays, marfanoid phenotype, vascular disease, and mental retardation. Almost 50% of subjects develop a psychiatric disorder during their life, but only 2.8% present a psychiatric symptom as the initial manifestation. Among this group, psychotic disorders are infrequent. We describe the case of a 17-year-old boy presenting with a first episode psychosis and an unknown homocystinuria due to cystathionine β-synthase deficiency, which led to a lethal outcome.

Genetic variants reducing MTR gene expression increase the risk of congenital heart disease in Han Chinese populations

Elevated homocysteine levels are known to be a risk factor for congenital heart disease (CHD), but the mechanism underlying this effect is unknown. During early embryonic development, homocysteine removal is dictated exclusively by the MTR activity. To examine the role of MTR in CHD risk, we identified genetic variants in MTR and investigated the mechanisms that affect its expression levels and that increase the risk of CHD in Chinese populations. The association between regulatory variants of the MTR gene and CHD was examined in three independent case-control studies in a total of 2340 patients with CHD and 2270 controls. The functional consequences of these variants were demonstrated using dual-luciferase assays, real-time polymerase chain reaction (PCR), electrophoretic mobility shift assays, surface plasma resonance, chromatin immunoprecipitation, and bisulfite sequencing, as well as by a group of predicted microRNAs using a gene reporter system. Two regulatory variants of MTR, -186T>G and +905G>A, were associated with an increased risk of CHD in both the separate and combined case-control studies (-186GG P = 1.32 × 10(-9); +905AA P = 6.35 × 10(-14)). Compared with the major allele, the -186G allele exhibited significantly lower promoter activity, decreased hnRNA and mRNA levels, reduced transcription factor binding affinity, and a more highly methylated promoter. The +905A allele exhibited a statistically stronger binding affinity to functional microRNAs that down regulate MTR expression at the translational level. Both of the minor alleles were correlated with elevated plasma homocysteine concentrations, indicating a genetic component for hyperhomocysteinaemia. Regulatory variants of the MTR gene increase CHD risk by reducing MTR expression and inducing the homocysteine accumulation and elevation.

PM.72 Homocystenemia and Pregnancy a Dangerous Combination

Preeclampsia represents one of the most frequent complications of pregnancy. Damage of the endothelial layer lining the blood vessel wall is thought to play an important role in the pathophysiology...

Methyl Group–Donating Vitamins Elevate 3-O-Methyldopa in Patients With Parkinson Disease

Levodopa (LD)/dopa decarboxylase inhibitor application increases 3-O-methyldopa (3-OMD) concentrations in association with methyl group transfers, which demand for the conversion of methionine to homocysteine. This accompanying reaction is partially reversible by methyl group-donating vitamins. The objective of this study was to investigate of the effect of methyl group-donating vitamins on 3-OMD synthesis in LD-treated patients with Parkinson disease. We determined LD, 3-OMD, and homocysteine plasma concentrations in relation to daily LD dosage administered orally or as duodenal infusion with and without vitamins. Orally LD-treated patients with Parkinson disease had a lower LD dose compared with the ones on an LD infusion, but LD, 3-OMD, and homocysteine bioavailability was not different. The same 3-OMD and homocysteine accumulation despite the applied higher LD dosage during the infusion indicates a limited methylation capacity. Higher 3-OMD concentrations occurred during chronic vitamin supplementation, whereas the other parameters did not vary from the ones before vitamin intake. Vitamin supplementation elevated methylation of LD to 3-OMD. We suggest that, to a certain extent, plasma levels of homocysteine may reflect methyl group donation resources, whereas 3-OMD concentrations may mirror methylation capacity.

Treatment of Inherited Homocystinurias

Inherited homocystinurias, have in common, accumulation of homocysteine with subsequent neurotoxicity; they also encompass two distinctive clinical entities: classical homocystinuria due to cystathionine β-synthase (CBS) deficiency and the rare inborn errors of cobalamin and folate metabolism. In the latter group, remethylation disorders of homocysteine to methionine (chiefly CblC defect and 5,10-methylenetetrahydrofolate reductase [MTHFR] deficiency) are by far the most frequently encountered situations. The natural history of CBS deficiency is relatively well known and described. Similarly, clinical presentations of remethylation defects are becoming better recognized and reported. Conversely, few data are available regarding treatment of these disorders, especially for remethylation defects. In this review, after an overview of the metabolic pathophysiology and the clinical features of inherited homocystinurias due to CBS deficiency, CblC defect, and MTHFR deficiency, we focus on present and prospective therapeutic approaches.