5-6-7-8-tetrahydrofolic-acid and Folic-Acid-Deficiency

Topics: Brain; Child, Preschool; Chromatography, High Pressure Liquid; Diagnosis, Differential; Folate Receptor 1; Folic Acid; Folic Acid Deficiency; Humans; Infant; Leucovorin; Malnutrition; Tetrahydrofolates

The mechanism by which Vitamin B12 prevents demyelination of nerve tissue is still not known. The evidence indicates that the critical site of B12 function in nerve tissue is in the enzyme, methionine synthase, in a system which requires S-adenosylmethionine. In recent years it has been recognized that S-adenosylmethionine gives rise to the deoxyadenosyl radical which catalyzes many reactions including the rearrangement of lysine to beta-lysine. Evidence is reviewed which suggests that there is an analogy between the two systems and that S-adenosyl methionine may catalyze a rearrangement of homocysteine on methionine synthase giving rise to iso- or beta-methionine. The rearranged product is readily degraded to CH3-SH, providing a mechanism for removing toxic homocysteine.

Topics: 5-Methyltetrahydrofolate-Homocysteine S-Methyltransferase; Animals; Biological Transport; Bone Marrow; Folic Acid; Folic Acid Deficiency; Homocysteine; Humans; Methionine; Methylation; Myelin Sheath; Nerve Tissue; S-Adenosylmethionine; Tetrahydrofolates; Vitamin B 12; Vitamin B 12 Deficiency

Neural tube defects (NTDs) are a group of congenital malformations with worldwide distribution and complex aetio-pathogenesis. Animal studies indicate that there may be four sites of initiation of neural tube closure (NTC). Selective involvement of these sites may lead to defects varying from anencephaly to spina bifida. The NTC involves formation of medial and dorsolateral hinge points, convergent extension and a zipper release process. Proliferation and migration of neuroectodermal cells and its morphological changes brought about by microfilaments and other cytoskeletal proteins mediate NTC. Genetic, nutritional and teratogenic mechanisms have been implicated in the pathogenesis of NTDs. Folate is an important component in one carbon metabolism that provides active moieties for synthesis of nucleic acids and proteins. Several gene defects affecting enzymes and proteins involved in transport and metabolism of folate have been associated with NTDs. It may be possible in future, to identify individuals at higher risk of NTDs by genetic studies. Epidemiological and clinical studies have shown that dietary supplementation or food fortification with folic acid would reduce the incidence of NTDs. The protective effect of folic acid may be by overcoming these metabolic blocks through unidentified mechanisms. Genetic and biochemical studies on foetal cells may supplement currently available prenatal tests to diagnose NTDs. Antiepileptic drugs (AEDs), particularly valproate and carbamazepine have been shown to increase the risk of NTDs by possibly increasing the oxidative stress and deranging the folate metabolism. Accordingly, it is recommended that all women taking AEDs may use 1-5 mg folic acid daily in the pre conception period and through pregnancy.

Topics: Dietary Supplements; Female; Folic Acid; Folic Acid Deficiency; Food, Fortified; Humans; Neural Tube Defects; Pregnancy; Risk Factors; Tetrahydrofolates

Topics: Animals; Antibody Formation; Carcinogens; Choline; Choline Deficiency; Diet; DNA; Folic Acid; Folic Acid Deficiency; Humans; Immunity, Cellular; Lipotropic Agents; Liver; Liver Neoplasms; Methionine; Methylation; Neoplasms; Neoplasms, Experimental; Pharmaceutical Preparations; Risk; Tetrahydrofolates; Vitamin B 12; Vitamin B 12 Deficiency

Formaldehyde is extremely toxic reacting with proteins to crosslinks peptide chains. Formaldehyde is a metabolic product in many enzymatic reactions and the question of how these enzymes are protected from the formaldehyde that is generated has largely remained unanswered. Early experiments from our laboratory showed that two liver mitochondrial enzymes, dimethylglycine dehydrogenase (DMGDH) and sarcosine dehydrogenase (SDH) catalyze oxidative demethylation reactions (sarcosine is a common name for monomethylglycine). The enzymatic products of these enzymes were the demethylated substrates and formaldehyde, produced from the removed methyl group. Both DMGDH and SDH contain FAD and both have tightly bound tetrahydrofolate (THF), a folate coenzyme. THF binds reversibly with formaldehyde to form 5,10-methylene-THF. At that time we showed that purified DMGDH, with tightly bound THF, reacted with formaldehyde generated during the reaction to form 5,10-methylene-THF. This effectively scavenged the formaldehyde to protect the enzyme. Recently, post-translational modifications on histone tails have been shown to be responsible for epigenetic regulation of gene expression. One of these modifications is methylation of lysine residues. The first enzyme discovered to accomplish demethylation of these modified histones was histone lysine demethylase (LSD1). LSD1 specifically removes methyl groups from di- and mono-methylated lysines at position 4 of histone 3. This enzyme contained tightly bound FAD and the products of the reaction were the demethylated lysine residue and formaldehyde. The mechanism of LSD1 demethylation is analogous to the mechanism previously postulated for DMGDH, i.e. oxidation of the N-methyl bond to the methylene imine followed by hydrolysis to generate formaldehyde. This suggested that THF might also be involved in the LSD1 reaction to scavenge the formaldehyde produced. Our hypotheses are that THF is bound to native LSD1 by analogy to DMGDH and SDH and that the bound THF serves to protect the FAD class of histone demethylases from the destructive effects of formaldehyde generation by formation of 5,10-methylene-THF. We present pilot data showing that decreased folate in livers as a result of dietary folate deficiency is associated with increased levels of methylated lysine 4 of histone 3. This can be a result of decreased LSD1 activity resulting from the decreased folate available to scavenge the formaldehyde produced at the active site caused

Topics: Catalytic Domain; DNA Methylation; Epigenesis, Genetic; Escherichia coli; Folic Acid; Folic Acid Deficiency; Histone Demethylases; Histones; Humans; Lysine; Mass Spectrometry; Models, Theoretical; Pilot Projects; Protein Processing, Post-Translational; Sarcosine Dehydrogenase; Tetrahydrofolates

It is now established that the mitochondrial production of formate is a major process in the endogenous generation of folate-linked one-carbon groups. We have developed an in vivo approach involving the constant infusion of [(13)C]formate until isotopic steady state is attained to measure the rate of endogenous formate production in rats fed on either a folate-replete or folate-deficient diet. Formate was produced at a rate of 76 μmol·h(-1)·100 g of body weight(-1) in the folate-replete rats, and this was decreased by 44% in folate-deficient rats. This decreased formate production was confirmed in isolated rat liver mitochondria where formate production from serine, the principal precursor of one-carbon groups, was decreased by 85%, although formate production from sarcosine and dimethylglycine (choline metabolites) was significantly increased. We attribute this unexpected result to the demonstrated production of formaldehyde by sarcosine dehydrogenase and dimethylglycine dehydrogenase from their respective substrates in the absence of tetrahydrofolate and subsequent formation of formate by formaldehyde dehydrogenase. Comparison of formate production with the ingestion of dietary formate precursors (serine, glycine, tryptophan, histidine, methionine, and choline) showed that ∼75% of these precursors were converted to formate, indicating that formate is a significant, although underappreciated end product of choline and amino acid oxidation. Ingestion of a high protein diet did not result in increased production of formate, suggesting a regulation of the conversion of these precursors at the mitochondrial level to formate.

Topics: Animals; Choline; Dimethylglycine Dehydrogenase; Folic Acid; Folic Acid Deficiency; Formaldehyde; Formates; Glycine; Histidine; Liver; Male; Methionine; Mitochondria; Mitochondria, Liver; Oxygen; Rats; Rats, Sprague-Dawley; Sarcosine Dehydrogenase; Serine; Tetrahydrofolates

Folate deficiency is a global health problem related to neural tube defects, cardiovascular disease, dementia, and cancer. Considering that folic acid (FA) supply through industrialized foods is the most successful intervention, limitations exist for its complete implementation worldwide. Biofortification of plant foods, on the other hand, could be implemented in poor areas as a complementary alternative. A biofortified tomato fruit that accumulates high levels of folates was previously developed. In this study, we evaluated short-term folate bioavailability in rats infused with this folate-biofortified fruit. Fruit from tomato segregants hyperaccumulated folates during an extended ripening period, ultimately containing 3.7-fold the recommended dietary allowance in a 100-g portion. Folate-depleted Wistar rats separated in three groups received a single dose of 1 nmol of folate/g body weight in the form of lyophilized biofortified tomato fruit, FA, or synthetic 5-CH3-THF. Folate bioavailability from the biofortified tomato was comparable to that of synthetic 5-CH3-THF, with areas under the curve (AUC(0-∞)) of 2,080 ± 420 and 2,700 ± 220 pmol · h/mL, respectively (P = 0.12). Whereas, FA was less bioavailable with an AUC(0-∞) of 750 ± 10 pmol · h/mL. Fruit-supplemented animals reached maximum levels of circulating folate in plasma at 2 h after administration with a subsequent steady decline, while animals treated with FA and synthetic 5-CH3-THF reached maximum levels at 1 h. Pharmacokinetic parameters revealed that biofortified tomato had slower intestinal absorption than synthetic folate forms. This is the first study that demonstrates the bioavailability of folates from a biofortified plant food, showing its potential to improve folate deficiency.

Topics: Animals; Area Under Curve; Biological Availability; Dietary Supplements; Folic Acid; Folic Acid Deficiency; Food, Fortified; Fruit; Humans; Intestinal Absorption; Male; Rats; Rats, Wistar; Solanum lycopersicum; Tetrahydrofolates; Vitamin B Complex

Topics: Adult; Corneal Diseases; Diet, Vegetarian; Epithelium, Corneal; Female; Folic Acid Deficiency; Humans; Tetrahydrofolates; Vitamin B 12 Deficiency

Periconceptional folate prevents neural tube defects (NTD) by a mechanism which is unclear. The present study found significant changes in the equilibrium of the homocysteine remethylation cycle in NTD affected mothers, possibly involving B12-dependent methionine synthase or 5,10-methylenetetrahydrofolate reductase. Data were consistent with impaired Hcy remethylation leading to poor regeneration of H4PteGlu1, the main intracellular precursor of all folates. This lesion leads to cellular folate deficiency indicated by a significantly lower radioassay RBC folate and 5CH3H4PteGlu4 in affected mothers. The drop in this tetraglutamate is associated with an increase in the abundance of longer chain oligo-gamma-glutamyl folate, again reflecting the underlying folate deficiency. This effect may compromise purine, DNA-thymine, and methionine production, particularly during embryogenesis when folate demand is high. At this time serine hydroxymethyltransferase may play a critical role in conserving H4PteGlu1 for purine synthesis. Many of these depletion effects were corrected with folate supplementation for 1 month.

Topics: Female; Folic Acid; Folic Acid Deficiency; Humans; Pregnancy; Pregnancy Complications; Spinal Dysraphism; Tetrahydrofolates; Vitamin B 12

Topics: Amino Acids; Cells, Cultured; Chemical Phenomena; Chemistry; Culture Media; Folic Acid; Folic Acid Deficiency; Fragile X Syndrome; Histidine; Homocysteine; Humans; Intellectual Disability; Lymphocytes; Sex Chromosome Aberrations; Tetrahydrofolates

Topics: Alcoholism; Animals; Biological Transport; Diet; Ethanol; Folic Acid; Folic Acid Deficiency; Haplorhini; Humans; Intestinal Absorption; Liver; Tetrahydrofolates

The role of vitamin B12 in the folate dependent biosynthesis of thymidine nucleotides is controversial. In an attempt to clarify this, three methods have been used to assess the relative efficacy of vitamin B12 (hydroxocobalamin) and various folate analogues in titrated concentrations at correcting 'de novo' thymidylate synthesis by megaloblastic human marrow cells: (1) The deoxyuridine (dU) suppression test which analyses the reduction in (3H)-thymidine labeling of DNA by unlabeled dU. Marrow cells were also labeled with (6-3H)-dU with assessment of (2) its incorporation into DNA and (3) the accumulation of (6-3H)-deoxyuridine monophosphate (3H-dUMP). The three methods gave similar results. In both, N6-formyl tetrahydrofolate (formyl-FH4) was the most effective agent at correcting thymidylate synthesis in megaloblastic anemia due to vitamin B12 or folate deficiency. Vitamin B12 corrected the lesion in vitamin B12 deficiency but not in folate deficiency. Tetrahydrofolate (FH4) and folic acid were effective in deficiency of vitamin B12 or folate, although in both deficiencies they were less effective than formyl-FH4. Methyl-FH4 was effective in folate deficiency but not in vitamin B12 deficiency. These results confirm the failure of methyl-FH4 utilisation in vitamin B12 deficiency. They suggest that if vitamin B12 is needed in the formylation of FH4, this is a minor role in provision of the correct coenzyme for thymidylate synthesis compared with its major role of provision of FH4 from methyl-FH4.

Topics: Anemia, Macrocytic; Anemia, Megaloblastic; Bone Marrow; Deoxyuridine; DNA; Folic Acid; Folic Acid Deficiency; Humans; Leucovorin; Tetrahydrofolates; Thymine Nucleotides; Vitamin B 12; Vitamin B 12 Deficiency

Folate deficiency may be diagnosed in man by measuring serum folate activity using either a microbiological procedure with L. casei or a radioassay. The microbiological procedure tends to be time consuming and tedious, as compared with the radioassay; nevertheless it allows the accurate determination of each folate derivative that is normally present in serum. The comparison of serum folate levels obtained by the two methods shows an adequate correlation. However, it results from individual samples show that the values obtained by the radioassay are lower than the microbiological ones by 10-30%. The lower results in the radioisotope test may be caused by the presence of high levels of unsaturated endogenous protein binders in serum and/or by the difference in affinity of lactoglobulin - the binding protein used in the test - for folic acid (standard) and 5-methyl FH4 or 10-formil FH4 (serum).

Topics: Biological Assay; Folic Acid; Folic Acid Deficiency; Humans; Lacticaseibacillus casei; Lactoglobulins; Tetrahydrofolates; Tritium