RESUMEN
BACKGROUND: The importance of unmetabolized folic acid in maternal and fetal blood is not known. OBJECTIVE: We investigated total folate, tetrahydrofolate (THF), 5-methyltetrahydrofolate (5-MTHF), formyl-THF, 5,10-methenylTHF, and folic acid concentrations in women and in umbilical cord blood at delivery. DESIGN: The study included 87 pregnant women and 29 cord blood samples, including 24 mother-infant pairs. We measured serum concentrations of folate forms by using ultraperformance liquid chromatography-tandem mass spectrometry. RESULTS: Pregnant women who received 400 µg folic acid daily (n = 25) had higher total folate (P = 0.041), 5-MTHF (P = 0.049), and formyl-THF (P < 0.001) concentrations and slightly higher THF (P = 0.093) concentrations than did nonsupplemented pregnant women (n = 61). We measured folic acid concentrations >0.20 nmol/L in 38 (44%) pregnant women and in 55% of the cord serum samples, but these measurements were not explained by maternal supplement use. Concentrations of folic acid were nonsignificantly higher in cord blood from supplemented women than in cord blood from nonsupplemented women (P = 0.154). Proportions of folic acid to total folate in cord serum did not differ according to maternal supplement usage (0.54% compared with 0.43% in supplemented and nonsupplemented women, respectively). Concentrations of folic acid did not differ between maternal and cord serum. However, folic acid constituted a significantly lower proportion of total folate in cord serum than in maternal serum. CONCLUSIONS: We detected unmetabolized folic acid in more than one-half of cord blood samples. Folic acid (400 µg/d) supplied during pregnancy is not likely to accumulate in the fetus, in contrast to 5-MTHF and THF, which accumulate in the fetus.
Asunto(s)
Sangre Fetal/química , Ácido Fólico/administración & dosificación , Ácido Fólico/sangre , Formiltetrahidrofolatos/sangre , Recién Nacido/sangre , Embarazo/sangre , Tetrahidrofolatos/sangre , Adulto , Suplementos Dietéticos , Femenino , Humanos , Adulto JovenRESUMEN
The in vitro stability and plasma pharmacokinetics of 5,10-methylenetetrahydrofolic acid (CH2FH4), tetrahydrofolic acid (FH4), 5-methyltetrahydrofolic acid (CH3FH4), and 5-formyltetrahydrofolic acid (5-CHOFH4) were studied in view of their potential usefulness in cancer chemotherapy. Analysis of reduced folates was done on a high-performance liquid chromatography (HPLC) system. The high sensitivity of FH4 and CH2FH4 to oxidation can be circumvented by use of high concentrations of the folates, addition of ascorbate, and by thorough exclusion of atmospheric O2. Intravenous injection of 200 mg FH4 or CH2FH4 resulted in average peak concentrations of 69.2 +/- 3.2 nmol/ml and 46.3 +/- 2.6 nmol/ml, respectively. The plasma concentration curves support the concept that these highly oxygen-sensitive reduced folates can be reliably administered as pharmaceuticals to cancer patients through the use of a suitable air-occlusive system for their preparation and administration.
Asunto(s)
Tetrahidrofolatos/química , Tetrahidrofolatos/farmacocinética , Neoplasias Colorrectales/sangre , Estabilidad de Medicamentos , Femenino , Formiltetrahidrofolatos/sangre , Formiltetrahidrofolatos/química , Formiltetrahidrofolatos/farmacocinética , Humanos , Masculino , Oxidación-Reducción , Tetrahidrofolatos/sangreRESUMEN
A common mutation (C677T) in the gene encoding for methylenetetrahydrofolate reductase (MTHFR) (5-methyltetrahydrofolate:(acceptor) oxidoreductase, EC 1.7.99.5), a key regulatory enzyme in one-carbon metabolism, results in a thermolabile variant of the MTHFR enzyme with reduced activity in vitro. In the present study we used a chromatographic method for folate analysis to test the hypothesis that this mutation would be associated with altered distribution of red blood cell (RBC) folates. An alteration was found as manifested by the presence of formylated tetrahydrofolate polyglutamates in addition to methylated derivatives in the RBCs from homozygous mutant individuals. 5-Methyltetrahydrofolate polyglutamates were the only folate form found in RBCs from individuals with the wild-type genotype. Existence of formylated folates in RBCs only from individuals with the thermolabile MTHFR is consistent with the hypothesis that there is in vivo impairment in the activity of the thermolabile variant of MTHFR and that this impairment results in an altered distribution of RBC folates.
Asunto(s)
Eritrocitos/metabolismo , Formiltetrahidrofolatos/sangre , Variación Genética , Oxidorreductasas actuantes sobre Donantes de Grupo CH-NH/genética , Mutación Puntual , Adulto , Anciano , Femenino , Genotipo , Homocigoto , Humanos , Masculino , Metilenotetrahidrofolato Reductasa (NADPH2) , Persona de Mediana Edad , Modelos QuímicosRESUMEN
The in vitro interaction of the [6S]- and [6R]-stereoisomers of CHO-THFA with human RBCs was investigated in the (therapeutically comparable) concentration range from 1.0 to 12.5 micrograms/ml. Both compounds are bound to RBCs with a kRBC ranging from 0.13 to 0.75 for [6S]-CHO-THFA and from 0.06 to 0.33 for [6R]-CHO-THFA, respectively. The interaction of the [6S]-form with RBCs is about two times higher than of the [6R]-form. Incubation of CHO-THFA with RBCs over 24 h showed an accelerated disappearance from the test solution for [6R]-CHO-THFA with a mean t1/2 of 49.9 h in compare to t1/2 = 58.2 h for the [6S]-enantiomer. The results indicate that RBCs may play a major role for the pharmacokinetics and metabolism of CHO-THFA and may act as an intravasal depot especially for [6S]-CHO-THFA.
Asunto(s)
Eritrocitos/metabolismo , Formiltetrahidrofolatos/sangre , Sitios de Unión , Humanos , Cinética , EstereoisomerismoRESUMEN
Patients with advanced gastric cancer were treated with methotrexate-5-fluorouracil sequential therapy. In order to rescue of methotrexate toxicity on the normal proliferating tissue, leucovorin was administered orally to outpatients. As the comparative study, we examined plasma kinetics following oral administration of leucovorin (15 mg) in 6 patients with gastric cancer (received subtotal gastrectomy) and 5 normal subjects. In the patients, peak plasma concentrations of d-1-formyltetrahydrofolate and its main metabolite 5-methyltetrahydrofolate were found after 2 hrs. (7.35 X 10(-7) M, 3.09 X 10(-7) M), and in normal controls also both after 2 hrs. (1.01 X 10(-6) M, 4.89 X 10(-7) M). The active folate metabolite persisted for more than 6 hrs. at over 1 X 10(-7) M that could rescue normal tissue from methotrexate toxicity after leucovorin oral administration in the patients received subtotal gastrectomy.
Asunto(s)
Gastrectomía , Leucovorina/farmacocinética , Neoplasias Gástricas/sangre , Administración Oral , Adulto , Bioensayo/métodos , Cromatografía Líquida de Alta Presión , Femenino , Formiltetrahidrofolatos/sangre , Gastrectomía/métodos , Humanos , Leucovorina/administración & dosificación , Leucovorina/sangre , Masculino , Persona de Mediana Edad , Neoplasias Gástricas/cirugía , Comprimidos , Tetrahidrofolatos/sangreRESUMEN
In an aseptic microbiological assay of folate compounds and their breakdown compounds, using Lactobacillus casei, Streptococcus faecalis, and Pediococcus cerevisiae, 4a-hydroxy-5methyl-4,5,6,7-tetrahydrofolate and 5-methyl-5,8-dihydrofolate were inactive under all conditions to all three organisms and 5-methyl-5,6-dihydrofolate was inactive unless ascorbate was present in the incubation medium, and then only to L. casei. 5-Methyltetrahydrofolate was active only for L. casei, and activity in purified samples to S. faecalis was due to trace amounts of folic acid. Analysis of S. faecalis values in the serum in normal subjects and in patients with various disorders showed that levels of 10-formyltetrahydrofolate are raised in coeliac disease, leukaemia, rheumatoid arthritis, and schizophrenia. 5-Methyltetrahydrofolate is readily absorbed by normal human subjects and by patients with pernicious anaemia but poorly absorbed by patients with coeliac disease or leukaemia. 5-Methyl-5,6-dihydrofolate was quickly absorbed by normal human subjects, being reflected by a considerably raised level of 5-methyltetrahydrofolate in serum when sodium bicarbonate was given by mouth before the 5-methyl-5,6-dihydrofolate. These higher levels were comparable to those in patients with pernicious anaemia after oral administration of 5-methyl-5,6-dihydrofolate. Oral 5-methyl-5,8-dihydrofolate and 4a-hydroxy-5-methyl-tetrahydrofolate did not appear as microbiologically active folates in the serum. The findings of this study suggest that the availability for biological utilisation of the major dietary folate compounds will depend on the amount of gastric acidity and of ascorbate in the intestinal chyme. Many may be unavailable for metabolic utilization in the body.
Asunto(s)
Ácido Fólico/análogos & derivados , Tetrahidrofolatos/sangre , Anemia Perniciosa/sangre , Artritis Reumatoide/sangre , Bioensayo , Enfermedad Celíaca/sangre , Enterococcus faecalis , Ácido Fólico/sangre , Formiltetrahidrofolatos/sangre , Humanos , Lacticaseibacillus casei , Leucemia/sangre , Pediococcus , Esquizofrenia/sangreRESUMEN
The enzyme 5-formyl tetrahydrofolate cyclodehydrase plays an important role in the conversion of 5-formyl tetrahydrofolate to 5,10-methenyl tetrahydrofolate. A second enzyme, cyclohydrolase, converts 5,10-methenyl tetrahydrofolate to 10-formyl tetrahydrofolate. These folate derivatives play a significant part in the biosynthesis of purines. A method has been devised for the cytochemical demonstration of 5-formyl tetrahydrofolate cyclodehydrase and 5,10-methenyl tetrahydrofolate cyclohydrolase activity which uses 5-formyl tetrahydrofolate or 5,10-methenyl tetrahydrofolate as substrate respectively, blocking possible interferences by other enzymes, and allows the nonenzymatic reduction of nitro-blue tetrazolium by 5,10-methenyl tetrahydrofolate formed by the action of the cyclodehydrase on the substrate 5-formyl tetrahydrofolate, and by 10-formyl tetrahydrofolate formed by the action of cyclohydrolase on the substrate 5,10-methenyl tetrahydrofolate, thus revealing intracellular sites of enzyme activity. The methods appear to show only intracellular localization of the blue formazan deposits of reduced tetrazolium. The distribution of positivity in cells of human blood and bone marrow is described.
Asunto(s)
Aminohidrolasas/metabolismo , Formiltetrahidrofolatos/metabolismo , Ligasas/metabolismo , Tetrahidrofolatos/metabolismo , Aminohidrolasas/antagonistas & inhibidores , Aminohidrolasas/sangre , Médula Ósea/enzimología , Células de la Médula Ósea , Ligasas de Carbono-Nitrógeno , Cloromercuribenzoatos/farmacología , Formiltetrahidrofolatos/sangre , Histocitoquímica , Humanos , Leucovorina , Ligasas/antagonistas & inhibidores , Ligasas/sangre , Metotrexato/farmacologíaRESUMEN
It has been suggested that the megaloblastic anaemia in pernicious anaemia is due to inadequate intracellular concentration of monoglutamyl folates other than methyltetrahydrofolate caused by diminished conversion of methyltetrahydrofolate to tetrahydrofolate (methylfolate trap). To test this, we have increased the concentration of methyltetrahydrofolate in the plasma of six patients with pernicious anaemia by feeding DL-5-formyltetrahydrofolate. The effect of therapy on bone marrow morphology and routine haematologic parameters was measured. Of two patients receiving 800 mug/d of DL-5-formyltetrahydrofolate, one had a significant response; of four receiving 6 mg/d, one converted erythroid maturation to normoblastic, and in two others some improvement was noted in levels of neutrophils, platelets or reticulocytes although marrow morphology remained megaloblastic. Response did not correlate with the degree of elevation of plasma folate. In patients receiving this therapy, slight increase of methylcobalamin in plasma may have occurred (P less than 0.05). These observations support ineffective utilization of methyltetrahydrofolate as the major cause of megaloblastic anaemia in pernicious anaemia, but indicate that the degree and location of block varied in different patients, and in different precursor cells of a single patient.