Disorders Of Folate Metabolism Research Articles

The Significance of Genetically Determined Methylation and Folate Metabolism Disorders in the Pathogenesis of Coronary Artery Disease: A Target for New Therapies?

Methylation is a biochemical process involving the addition of a methyl group (-CH3) to various chemical compounds. It plays a crucial role in maintaining the homeostasis of the endothelium, which lines the interior surface of blood vessels, and has been linked, among other conditions, to coronary artery disease (CAD). Despite significant progress in CAD diagnosis and treatment, intensive research continues into genotypic and phenotypic CAD biomarkers. This review explores the significance of the methylation pathway and folate metabolism in CAD pathogenesis, with a focus on endothelial dysfunction resulting from deficiency in the active form of folate (5-MTHF). We discuss emerging areas of research into CAD biomarkers and factors influencing the methylation process. By highlighting genetically determined methylation disorders, particularly the MTHFR polymorphism, we propose the potential use of the active form of folate (5-MTHF) as a novel CAD biomarker and personalized pharmaceutical for selected patient groups. Our aim is to improve the identification of individuals at high risk of CAD and enhance their prognosis.

Allelic variants of folate metabolism genes among students in Arctic Russia

AIM: To assess the prevalence of allelic variants of folate metabolism genes in Russian and Indian students living in the Arctic region of Russia.
 METHODS: A cross-sectional study was performed on a sample of ethnic Indians, students at the Faculty of General Practitioner of the Northern State Medical University, living in Arkhangelsk and ethnic Russians who were born in Arkhangelsk region. The study included 117 ethnic Indians and 195 Russian participants. A survey of participants and a molecular genetic study of the nucleotide sequence in the genes involved in the exchange of folate by real-time PCR were carried out. A group of ethnic Indians was compared with Russians according to 4 variants of the nucleotide sequence in the genes involved in folate metabolism.
 RESULTS: Statistically significant differences were observed in the frequency distribution of the T allele of the MTHFR gene polymorphism (rs1801133) (p=0.001). Among Russians, the occurrence of the T allele was found to be 26.3%, whereas among Indians, it was only 7.7%. At the same time, no statistically significant differences were found in the distribution of other polymorphic variants of the folate cycle genes between the groups. The mutant allele G of the MTRR gene polymorphism (rs1801394) was the most frequently occurring polymorphism among the participants.
 CONCLUSION: Greater prevalence of the unfavorable allele T of the MTHFR gene (rs1801133) compared to the group of ethnic Indians may suggest an elevated susceptibility to folate metabolism disorders in the Russian population

Фолатный статус у студентов из Индии, обучающихся в г. Архангельске

The harsh climatic conditions of the subarctic regions of Russia, followed by lifestyle and nutritional changes, put a strain on the adaptive self-regulation mechanisms of newcomers. Acclimatization of foreign students coming to these regions, along with a high mental load and significant lifestyle modifications as well as alimentary and behavioural habits, can lead to homeostatic failure, in particular, folate metabolism disorder. It is known that both genetic (alleles determining the characteristics of folate and homocysteine metabolism) and phenotypic (nutritional and behavioural) factors play an important role in regulating folate metabolism. The purpose of this study was to analyse the folate status of ethnic Indians living in a subarctic region of Russia. Materials and methods. A prospective cross-sectional population-based study was conducted on a sample of ethnic Indians (n = 117) studying at Northern State Medical University in the city of Arkhangelsk. An analysis was performed of the relationship between folate levels and the duration of living in the subarctic region of Russia, body mass index, tobacco smoking, alcohol intake and nutritional status. The results of the study showed that folate levels in Indian students living in Arkhangelsk decreased significantly (from 10.0 [9.325; 13.65] ng/ml in the first year to 4.00 [4.00; 6.00] ng/ml in the sixth year of study; р < 0.001). This can be associated with changes in their diet (less vegetables), smoking and alcohol consumption, which are risk factors for impaired homocysteine metabolism and, as a consequence, for adverse vascular events. The significant folate deficiency in Indian students during their residence in subarctic conditions requires taking a number of measures aimed to prevent maladjustment disorders of folate metabolism in foreign students, which include quality of life, health and nutritional status controls as well as maintaining a healthy lifestyle, including giving up bad habits.

Hyperhomocysteinemia in men and women of married couples with reproductive disorders. What is the difference?

Hyperhomocysteinemia (HHcy) is an autosomal recessive inherited metabolic disease caused by variations in folate metabolism genes, characterized by impaired methionine metabolism and accumulation of homocysteine (Hcy) in the blood serum. It was shown that men usually have higher plasma Hcy levels than women, but have not yet assessed the leading factors of these differences, which is important for the development of personalized protocols for the prevention of folate metabolism disorders in couples with reproductive disorders. This study aimed to analyze the effect of intergenic and gene-factor interactions on the risk of developing HHcy in men and women of married couples with reproductive disorders. In our study were involved 206 married Caucasian couples (206 males and 206 females) from central regions of Ukraine with early pregnancy losses in the anamnesis. We found that the incidence of HHcy in men was significantly higher than in women. Gender differences in folic acid and vitamin B12 levels were identified. The best predictors of HHcy in men (MTRR (A66G), MTHFR (C677T), MTR (A2756G), vitamin B12 level) and in women (MTHFR (C677T), MTR (A2756G), vitamin B12 level) were selected by binary logistic regression. There was no significant difference in the distribution of genotypes by the studied gene variants when comparing men and women with HHcy. Our findings demonstrate that there is a gender difference in the development of HHcy. This difference is caused by intergenic interaction and by environmental factors, in particular, nutrition and vitamins consumption.

Shifting landscapes of human MTHFR missense-variant effects

SummaryMost rare clinical missense variants cannot currently be classified as pathogenic or benign. Deficiency in human 5,10-methylenetetrahydrofolate reductase (MTHFR), the most common inherited disorder of folate metabolism, is caused primarily by rare missense variants. Further complicating variant interpretation, variant impacts often depend on environment. An important example of this phenomenon is the MTHFR variant p.Ala222Val (c.665C>T), which is carried by half of all humans and has a phenotypic impact that depends on dietary folate. Here we describe the results of 98,336 variant functional-impact assays, covering nearly all possible MTHFR amino acid substitutions in four folinate environments, each in the presence and absence of p.Ala222Val. The resulting atlas of MTHFR variant effects reveals many complex dependencies on both folinate and p.Ala222Val. MTHFR atlas scores can distinguish pathogenic from benign variants and, among individuals with severe MTHFR deficiency, correlate with age of disease onset. Providing a powerful tool for understanding structure-function relationships, the atlas suggests a role for a disordered loop in retaining cofactor at the active site and identifies variants that enable escape of inhibition by S-adenosylmethionine. Thus, a model based on eight MTHFR variant effect maps illustrates how shifting landscapes of environment- and genetic-background-dependent missense variation can inform our clinical, structural, and functional understanding of MTHFR deficiency.

Biochemical Markers of Folate Metabolism Disorders in Schizophrenia in the Russian Population

Abstract—A range of foreign studies have shown that, in schizophrenia, hyperhomocysteinemia occurs more frequently than in the general population. Hyperhomocysteinemia may be an integrated marker of folate metabolism disorders (as a result of vitamin deficiency and/or genetic predisposition) or involved in the pathogenesis of the disease through several possible molecular mechanisms. In Russia, similar studies have not been conducted. In addition, there are conflicting results of studies on genetic factors involved in folate and homocysteine metabolism in schizophrenia. The aim of this study was to evaluate an association of serum homocysteine, folate, and cobalamin levels with schizophrenia in the Central part of Russia (Nizhny Novgorod region). For this purpose, 50 patients with schizophrenia and 36 healthy volunteers were randomly selected. The levels of homocysteine, folates and cobalamin (B12) were measured in blood serum. The concentration of homocysteine was measured using the Сobas analyzer (Roche Diagnostics) with an enzymatic assay. The content of folate and vitamin B12 was determined by chemiluminescent microparticle immunoassay (Architect, Abbott lab. S.A). It was found that the level of homocysteine was significantly higher in the patients than in the control group (p = 0.0041), and folate levels were significantly lower (p = 0.0072). The level of homocysteine in the patients had a weak negative statistically significant correlation with both folate level (ρ = –0.38; p = 0.0063) and with B12 level (ρ = –0.36; p = 0.0082). Homocysteine level was significantly higher in men than in women in the entire studied population (Z = –2.1068, p = 0.0351), as well as in subgroups of patients (Z = –2.11; p = 0.035) and healthy controls (z = 3.4; p = 0.00067). The data suggest the need for further investigation of hyperhomocysteinemia and other biochemical markers of folate metabolism disorders in schizophrenia in the Russian population and the development of ways to correct them to optimize the treatment of this mental disorder.

The interaction of folate cycle enzyme genes and the risk of extrapyramidal side effects of antipsychotics

Personalized medicine means the selection of therapy for patients, taking into account the assessment of genetic risk factors for side effects. A number of studies show that folate metabolism disorders, including single nucleotide polymorphisms (SNPs) in the genes of folate-metabolizing enzymes, are more frequently detected in schizophrenic patients than in the general population. The role of SNPs of the key folate cycle enzymes in developing the extrapyramidal side effects of antipsychotics has not yet been studied, although there is evidence of their association with other movement disorders.Objective: to analyze the association between the carriage of SNP alleles of MTHFR 677C>T, MTR 2756A>G, and MTRR 66A>G and the severity of extrapyramidal side effects of antipsychotics in patients with schizophrenia.Patients and methods. The investigation included 61 patients with schizophrenia (according to the criteria for ICD-10 Code F20). All the patients took antipsychotics for at least 7 hospital days were examined using real-time polymerase chain reaction (PCR) with allele-specific primers, followed by detection for the carriage of SNP alleles of MTHFR 677C>T, MTR 2756A>G, and MTRR 66A>G. The standardized Simpson–Angus scale (SAS) was used to evaluate the severity of extrapyramidal symptoms; the PCR test results were unknown during their examination.Results and discussion. In the patients carrying a low-functional 677 T allele in the gene of the key folate cycle enzyme MTHFR, the severity of extrapyramidal side effects of antipsychotics was statistically significantly higher than in the carriers of the wild-type genotype: 13.27±5.10 versus 9.84±6.03 SAS scores, respectively (t=-2.40; p=0.020). In addition, the carriage of the wild allele A of SNP in the MTRR 66A>G gene (F=3.83; p=0.0283; pcorr.=0.043) is associated with the severity of extrapyramidal symptoms. There was a direct moderate correlation of the number of risk alleles at two loci with the total SAS score (r=0.51; p=0.00017).Conclusion. The polymorphic allele of MTHFR 677T and the wild allele of MTRR 66A can be regarded as risk alleles for the development of extrapyramidal side effects of antipsychotics.

Methylene Tetrahydrofolate Reductase Deficiency.

5,10-Methylene-tetrahydrofolate reductase (MTHFR) deficiency is a rare, autosomal recessive, metabolic disorder of folate metabolism, which affects homocysteine remethylation. Elevated homocysteine with normal or low methionine level is the key to diagnosis. Early recognition and treatment with betaine, has been shown to improve the survival and neurological outcomes. The authors report five Indian patients from three unrelated families, with MTHFR deficiency to emphasize the importance of early recognition and initiation of specific treatment.

Characteristics and outcomes of patients with formiminoglutamic aciduria detected through newborn screening.

Glutamate formiminotransferase deficiency (FTCD deficiency) or formiminoglutamic aciduria is the second most common of the known inherited disorders of folate metabolism. Initial case reports suggested that patients may have severe intellectual disability and megaloblastic anemia. However, these cases were obtained from screening cohorts of patients with developmental delay. Subsequently, patients with milder clinical phenotypes have been reported. The full phenotypic spectrum of this disorder remains unknown. In many states, FTCD deficiency can be incidentally detected on tandem mass spectrometry-based newborn screening of dried blood spots. In this work, we report the outcomes of infants identified to have FTCD deficiency through newborn screening. During the study period, 18 patients were identified to have FTCD deficiency and were referred and evaluated at one of the two participating metabolic centers. The overall rate of FTCD deficiency detected through the New Jersey screening program over the study time period was 1:58,982. At a mean age of 56 months at last follow-up: 3/18 (16%) had developmental delays requiring individualized education plans, no patients had profound intellectual disability; 4/16 (25%) had mild self-limited anemia, no patients had profound anemia. These data suggest that the majority of individuals with FTCD deficiency detected by newborn screening are asymptomatic.

Cerebral folate deficiency in adults: A heterogeneous potentially treatable condition

ObjectiveTo describe the phenotype and the response to folinic acid supplementation of cerebral folate deficiency (CFD) in adults, a disorder diagnosed on low 5-methyltetrahydro-folate (5MTHF) in cerebrospinal fluid (CSF), which can correspond to a inherited disorder of folate metabolism (IDFM) or to a metabolic consequence of various neurological diseases. MethodsWe conducted a retrospective study on 224 adult patients with neurological symptoms who had a 5MTHF CSF dosage, collecting their neurologic and neuroimaging data. Results69 patients had CFD (CSF 5MTHF level < 41 nmol/L), 25 of them had severe CFD (sCFD; ≤25 nmol/L) with adult onset neurological symptoms in 41%. 56% of sCFD patients had an underlying identified neurologic disorder, mainly mitochondrial diseases, hepatic encephalopathy and primary brain calcifications (no identified IDFM), the others were classified as undiagnosed. sCFD patients presented most frequently pyramidal syndrome (75%), movement disorders (56%), cerebellar syndrome (50%) and intellectual disability (46%). MRI findings mostly showed white matter abnormalities (WMA; 32%) and calcifications (12%), and were normal in 23%. The clinico-radiological phenotype of sCFD patients was not clearly different from non CFD patients in terms of manifestations frequency. However, their neurological picture was more complex with a higher number of combined neurological symptoms (4.7±1.6 vs 3.4±1.7, p = .01). In Magnetic Resonance Spectroscopy (MRS), Choline/Creatine (Cho/Cr) ratio was lower in sCFD patients (n = 7) compared to non-CFD patients (n = 73) (p = .005), with good sensitivity (71%) and excellent specificity (92%). Among twenty-one CFD patients treated with folinic acid, nine had a sustained improvement, all with sCFD but one (50% of sCFD patients improved). In two undiagnosed patients with extremely low 5MTHF CSF values, MRI WMA and low Cho/Cr ratios, folinic acid treatment leaded to a dramatic clinical and radiological improvement. ConclusionCSF 5MTHF dosage should be considered in patients with mitochondrial diseases, primary brain calcifications and unexplained complex neurological disorders especially if associated with WMA, since folinic acid supplementation in patients with sCFD is frequently efficient.

Characteristics and outcomes of patients with formiminoglutamic aciduria detected through newborn screening

Background Glutamate formiminotransferase deficiency (FTCD deficiency) or formiminoglutamic aciduria is the second most common of the known inherited disorders of folate metabolism. Initial case reports suggested that patients may have severe intellectual disability and megaloblastic anemia. However, these cases were obtained from screening cohorts of patients with developmental delay. Subsequently, patients with milder clinical phenotypes have been reported. The full phenotypic spectrum of this disorder remains unknown. Methods In many states, FTCD deficiency can be incidentally detected on tandem mass spectrometry-based newborn screening of dried blood spots. In this work, we report the outcomes of infants identified to have FTCD deficiency through newborn screening. Results During the study period, 18 patients were identified to have FTCD deficiency and were referred and evaluated at one of the two participating metabolic centers. The overall rate of FTCD deficiency detected through the New Jersey screening program over the study time period was 1:58,982. At a mean age of 56 months at last follow-up: 3/18 (16%) had developmental delays requiring individualized education plans, no patients had profound intellectual disability; 4/16 (25%) had mild self-limited anemia, no patients had profound anemia. Conclusions These data suggest that the majority of individuals with FTCD deficiency detected by newborn screening are asymptomatic.

Diagnostic approach to neurotransmitter monoamine disorders: experience from clinical, biochemical, and genetic profiles.

To improve the diagnostic work-up of patients with diverse neurological diseases, we have elaborated specific clinical and CSF neurotransmitter patterns. Neurotransmitter determinations in CSF from 1200 patients revealed abnormal values in 228 (19%) cases. In 54/228 (24%) patients, a final diagnosis was identified. We have reported primary (30/54, 56%) and secondary (24/54, 44%) monoamine neurotransmitter disorders. For primary deficiencies, the most frequently mutated gene was DDC (n=9), and the others included PAH with neuropsychiatric features (n=4), PTS (n=5), QDPR (n=3), SR (n=1), and TH (n=1). We have also identified mutations in SLC6A3, FOXG1 (n=1 of each), MTHFR (n=3), FOLR1, and MTHFD (n=1 of each), for dopamine transporter, neuronal development, and folate metabolism disorders, respectively. For secondary deficiencies, we have identified POLG (n=3), ACSF3 (n=1), NFU1, and SDHD (n=1 of each), playing a role in mitochondrial function. Other mutated genes included: ADAR, RNASEH2B, RNASET2, SLC7A2-IT1 A/B lncRNA, and EXOSC3 involved in nuclear and cytoplasmic metabolism; RanBP2 and CASK implicated in post-traductional and scaffolding modifications; SLC6A19 regulating amino acid transport; MTM1, KCNQ2 (n=2), and ATP1A3 playing a role in nerve cell electrophysiological state. Chromosome abnormalities, del(8)(p23)/dup(12) (p23) (n=1), del(6)(q21) (n=1), dup(17)(p13.3) (n=1), and non-genetic etiologies (n=3) were also identified. We have classified the final 54 diagnoses in 11 distinctive biochemical profiles and described them through 20 clinical features. To identify the specific molecular cause of abnormal NT profiles, (targeted) genomics might be used, to improve diagnosis and allow early treatment of complex and rare neurological genetic diseases.

The Relationship Between Methylation Defects and Different Genetic Disorders: Two Case Reports

5, 10-methylenetetrahydrofolate reductase (MTHFR) is a coding gene, for a key enzyme in methionine-homocysteine and folate metabolism. This pathway has been associated with gene specific DNA hypo and hypermethylation as a result of gene switching on or off.Methylenetetrahydrofolate reductase C677T and A1298C gene polymorphisms are associated with folate metabolism disorders; such as, it results in an impaired DNA methylation and chromosomal abnormalities, gene deficiencies and structural anomalies. Here, we reported two cases of compound heterozygote and homozygote MTHFR gene mutation association with genetical disorders during the pregnancies.

GENETICALLY SPECIFIED DISORDERS OF FOLATE METABOLISM IN NEONATES WITH CRITICAL CONDITIONS

The paper deals with the influence of genetic polymorphisms on the features of folate metabolism and antioxidant protection in newborns with critical conditions in neonatal period. The objective of the study was to examine changes in folate metabolism, antioxidant defense indicators and their relationship with genetic polymorphism to determine the contribution of genetically determined folate metabolism disorders in the development of critical conditions in newborns. To perform the work 45 infants were examined (gestational age 38-40 weeks) with critical conditions of the early neonatal period (the main group) and 30 infants (gestational age 38-40 weeks) with physiological early neonatal period (the comparison group). Examined children were in obstetric and neonatal intensive care units of the Regional Maternity Hospital in Poltava. There were significant differences in the indices of homocysteine, folate and serum glutathione transferase activity in newborns of the examined groups during the first three days of life, with varying strength correlation found. Dynamics of the indices of folate metabolism on the third day of life as compared to the first day was significantly different in the newborns from the main groups and correlated with the indices of antioxidant protection. The peculiarities of the dynamics of folate metabolism indices, characterizing antioxidant and folate dependent metabolic processes in the perinatal period, were determined. The analysis of the intergenic interaction impact on the development of folate metabolism disorders and critical conditions revealed association with polymorphisms of GSTT1, GSTM1, MTHFR, ACE, TNF-a, AT2R1 genes. Synergistic interaction between polymorphic variants of genes GSTT1 and GSTM1, MTHFR and ACE was found. Polymorphic variants of these genes associated with changes in the dynamics of folate metabolism indicators. In the course of the study the best predictive model of intergenic interaction in the development of critical conditions and genetically determined folate metabolism disorders in newborns was found (predictive value - 91.47%). Analysis of unfavorable polymorphic variants in GSTT1, GSTM1, MTHFR, ACE, TNF-a, AT2R1 genes is a perspective one to predict unfavourable early neonatal period in newborns in clinical practice.

Insights into severe 5,10-methylenetetrahydrofolate reductase deficiency: molecular genetic and enzymatic characterization of 76 patients.

5,10-Methylenetetrahydrofolate reductase (MTHFR) deficiency is the most common inherited disorder of folate metabolism and causes severe hyperhomocysteinaemia. To better understand the relationship between mutation and function, we performed molecular genetic analysis of 76 MTHFR deficient patients, followed by extensive enzymatic characterization of fibroblasts from 72 of these. A deleterious mutation was detected on each of the 152 patient alleles, with one allele harboring two mutations. Sixty five different mutations (42 novel) were detected, including a common splicing mutation (c.1542G>A) found in 21 alleles. Using an enzyme assay in the physiological direction, we found residual activity (1.7%-42% of control) in 42 cell lines, of which 28 showed reduced affinity for nicotinamide adenine dinucleotide phosphate (NADPH), one reduced affinity for methylenetetrahydrofolate, five flavin adenine dinucleotide-responsiveness, and 24 abnormal kinetics of S-adenosylmethionine inhibition. Missense mutations causing virtually absent activity were found exclusively in the N-terminal catalytic domain, whereas missense mutations in the C-terminal regulatory domain caused decreased NADPH binding and disturbed inhibition by S-adenosylmethionine. Characterization of patients in this way provides a basis for improved diagnosis using expanded enzymatic criteria, increases understanding of the molecular basis of MTHFR dysfunction, and points to the possible role of cofactor or substrate in the treatment of patients with specific mutations.

Leukoencephalopathies Associated with Disorders of Cobalamin and Folate Metabolism

Disorders of cobalamin and folate intracellular metabolism that result in defective remethylation of homocysteine to methionine are associated with leukodystrophy, whereas disorders of cobalamin transport generally are not. Cobalamin derivatives are needed for only two reactions in man; remethylation of homocysteine to methionine, with methylcobalamin as a cofactor for methionine synthase, and the conversion of methylmalonyl-coenzyme A to succinyl coenzyme A by methylmalonyl-CoA mutase, with adenosylcobalamin as a cofactor. Mutations at various metabolic steps affect the synthesis of adenosylcobalamin (CblA, CblB, and CblD2), methylcobalamin (CblE, CblG, and CblD1), or both of these (CblF, CblD, and CblC). The most common disorder of folate metabolism, 5,10-methylenetetrahydrofolate deficiency, also affects remethylation and presents with leukodystrophy. Pathways of cobalamin and folate metabolism intersect at one site, methionine synthase. Patients with the remethylating disorders present acutely or chronically with significant neurologic, hematologic, vascular, and other symptoms. Circulating levels of cobalamin and folate are usually normal in these disorders, and initial diagnosis is aided by measurement of homocysteine and methylmalonic acid in blood or urine, together with hematologic tests. Current diagnosis is often by newborn screening. These disorders all show autosomal recessive inheritance, and all are treatable, although with variable outcome.

Oral clefts and maternal biomarkers of folate‐dependent one‐carbon metabolism in utah

Maternal folate intake and related biomarkers have been inconsistently associated with a risk of oral clefts. Maternal concentrations of plasma folate (PF) and erythrocyte folate (EF), plasma pyridoxal-5'-phosphate (PLP; active vitamin B(6) ) and total plasma homocysteine (tHcy) were measured in a Utah study with 347 cases and 469 controls. Risk of all clefts combined, including cleft lip with or without cleft palate (CL/P) and cleft palate only (CP), was 65% lower in the highest versus lowest PF quartile (odds ratio [OR], 0.35; 95% confidence interval [CI], 0.23-0.53; p-trend < 0.001). Results remained significant in the subgroups with isolated CL/P and CP (p-trend < 0.001 in each). EF results were similar. In the highest versus lowest PLP quartile, risk of CP with other malformations was lower (OR, 0.25; 95% CI, 0.07-0.95); however, no other associations were significant for PLP or tHcy. Differences in mean biomarker levels between cases and controls widened with an increasing interval between delivery and maternal blood collection. Decreased cleft risk with increasing quartiles of PF, EF, and PLP and decreasing tHcy was more apparent in mothers with a longer versus shorter interval between the index child delivery and blood collection. Low maternal blood folate concentration was associated with an increased risk of clefts, and the differences in mean case and control PF, EF, PLP, and tHcy concentrations widened over time. Additional mechanistic studies are warranted to elucidate whether an acquired or inherited disorder of folate metabolism plays a role in the etiology of clefts.

Dihydrofolate Reductase Deficiency Due to a Homozygous DHFR Mutation Causes Megaloblastic Anemia and Cerebral Folate Deficiency Leading to Severe Neurologic Disease

The importance of intracellular folate metabolism is illustrated by the severity of symptoms and complications caused by inborn disorders of folate metabolism or by folate deficiency. We examined three children of healthy, distantly related parents presenting with megaloblastic anemia and cerebral folate deficiency causing neurologic disease with atypical childhood absence epilepsy. Genome-wide homozygosity mapping revealed a candidate region on chromosome 5 including the dihydrofolate reductase (DHFR) locus. DHFR sequencing revealed a homozygous DHFR mutation, c.458A>T (p.Asp153Val), in all siblings. The patients' folate profile in red blood cells (RBC), plasma, and cerebrospinal fluid (CSF), analyzed by liquid chromatography tandem mass spectrometry, was compatible with DHFR deficiency. DHFR activity and fluorescein-labeled methotrexate (FMTX) binding were severely reduced in EBV-immortalized lymphoblastoid cells of all patients. Heterozygous cells displayed intermediate DHFR activity and FMTX binding. RT-PCR of DHFR mRNA revealed no differences between wild-type and DHFR mutation-carrying cells, whereas protein expression was reduced in cells with the DHFR mutation. Treatment with folinic acid resulted in the resolution of hematological abnormalities, normalization of CSF folate levels, and improvement of neurological symptoms. In conclusion, the homozygous DHFR mutation p.Asp153Val causes DHFR deficiency and leads to a complex hematological and neurological disease that can be successfully treated with folinic acid. DHFR is necessary for maintaining sufficient CSF and RBC folate levels, even in the presence of adequate nutritional folate supply and normal plasma folate.

Is nitrous oxide use appropriate in neurosurgical and neurologically at-risk patients?

To address controversial issues surrounding the use of nitrous oxide as a component of anesthesia in neurosurgical and neurologically at-risk patients. Nitrous oxide has been used as a component of general anesthesia for over 160 years and has contributed to countless apparently uneventful anesthetics in neurologically at-risk patients. Avoidance of nitrous oxide in specific circumstances, such as pre-existing pneumocephalus, during acute venous air embolism, and in patients with disorders of folate metabolism, is warranted. However, various controversies exist regarding the use of this drug in the general neurosurgical population. Specifically, some suggest a possible association between nitrous oxide and the postoperative development of tension pneumocephalus despite lack of data to support this notion. Additionally, data describing alterations of cerebral hemodynamics and metabolism and exacerbation of ischemic neurologic injury by nitrous oxide are inconsistent. Recent data derived from humans having cerebral aneurysm clipping failed to show any long-term adverse effect from the use of nitrous oxide on gross neurologic or cognitive function. Except in a few specific circumstances, there exists no conclusive evidence to support the dogmatic avoidance of nitrous oxide in neurosurgical patients.

Clinical signs and treatment of cerebral folate transport deficiency, a novel inherited disorder of folate metabolism

Background: Folates are essential cofactors for important metabolic pathways such as synthesis of amino acids, DNA and lipophilic substances. The main folate compound 5-methyltetrahydofolate (5MTHF) is actively transported across the blood- cerebrospinal fluid (CSF)-barrier to supply the brain. Cellular uptake of folates is mediated by the proton-coupled intestinal transporter, the reduced folate carrier, and by two GPI-anchored receptors, folate receptor α (FRa) and β (FRa). At least five distinct inherited disorders of folate transport and metabolism are presently. An inherited disorder of folate transport into brain has not been described yet.