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Biomedical subjects

J Zittoun

Publications and source records attributed to J Zittoun.

At least 19 recordsLinked to original sources
PubMed2001

[Biermer's disease].

Pernicious anaemia is an autoimmune atrophic gastritis inducing vitamin B12 deficiency by malabsorption. This disease may be diagnosed in the absence of any anaemia, on a neuropathy or when one or several autoimmune disorders co-exist. Typically, pernicious anaemia is revealed by macrocytic megaloblastic anaemia. Diagnosis is done on low serum vitamin B12, raised serum homocysteine, parietal cell and, intrinsic factor antibodies. Pernicious anaemia should be treated indefinitely by monthly intramuscular hydroxocobalamin. Because of an increased incidence of gastric carcinoma, endoscopy should be evenly performed.

Anemia, Pernicious↗
PubMed2001

Cytotoxic synergism of methioninase in combination with 5-fluorouracil and folinic acid.

Potentiation of the cytotoxic activity of 5-fluorouracil (FUra) by folinic acid (5-HCO-H4folate) is due to elevation of the methylene tetrahydrofolate (CH2-H4folate) level, which increases the stability of the ternary complex of thymidylate synthase (TS), fluorodeoxyuridine monophosphate, and CH2-H4folate that inactivates the TS. Methionine deprivation results in the production of tetrahydrofolate (H4folate) and, subsequently, CH2-H4folate from methyl tetrahydrofolate, as a consequence of the induction of methionine synthesis. We hypothesized that the efficacy of FUra could be augmented by the combination of high-concentration 5-HCO-H4folate and recombinant methioninase (rMETase), a methionine-cleaving enzyme. Studies in vitro were performed with the cell line CCRF-CEM. Cytotoxic synergism of FUra + rMETase and FUra + 5-HCO-H4folate + rMETase was demonstrated with the combination index throughout a broad concentration range of FUra and rMETase. A subcytotoxic concentration of rMETase reduced the IC50 of FUra by a factor of 3.6, and by a factor of 7.5, in the absence and in the presence of 5-HCO-H4folate, respectively. 5-HCO-H4folate increased the intracellular concentrations of CH2-H4folate and H4folate from their baseline levels. Concentrations of folates were not changed by exposure to rMETase. Levels of free TS in cells treated with FUra + 5-HCO-H4folate and with FUra + rMETase were lower than those in cells exposed to FUra alone. The decrease of TS was still more pronounced in cells treated with FUra + 5-HCO-H4folate + rMETase. The synergism described in this study will be a basis for further exploration of combinations of fluoropyrimidines, folates, and rMETase.

Antimetabolites, Antineoplastic↗
PubMed2001

Impact of new mutations in the methylenetetrahydrofolate reductase gene assessed on biochemical phenotypes: a familial study.

Methylenetetrahydrofolate reductase (MTHFR) deficiency was identified in two out of four children born from nonconsanguineous parents. One of the affected children exhibited some clinical findings suggesting cystathionine beta-synthase deficiency; MTHFR activity was extremely reduced. In addition, hyperhomocysteinaemia, hypomethioninaemia, low total folate, especially methylfolate in red blood cells, and a reduced methylfolate/total folate ratio were found. Two mutations not yet reported, one on exon 1 of the gene changing an arginine to stop codon and one other on exon 9 changing an arginine to tryptophan were identified in both children in the compound heterozygous state associated with a common polymorphism, 1298A>C, also in the heterozygous state. The mother, homozygous for the mutation on exon 9 and for the polymorphism 1298A>C on exon 7, was clinically and biochemically normal, with normal folate status, mainly methylfolate levels in red blood cells, although MTHFR activity was moderately decreased. The father, heterozygous for the transition arginine to stop codon and for the common polymorphism 677C>T on exon 4, exhibited major biochemical abnormalities, hyperhomocysteinaemia and low methylfolate levels in red blood cells, but was clinically normal. The unaffected children had a biochemical pattern close to that of their mother and were heterozygous for the mutation on exon 9 and also for the two common polymorphisms, 677C>T and 1298A>C. In the affected children, some biochemical abnormalities, including folate status, especially methylfolate levels, were improved with treatment combining methyltetrahydrofolic acid, hydroxocobalamin, pyridoxine and betaine; however, homocysteine concentrations remained high and methionine concentrations were lowered. The father was treated with folic acid, which partially improved biochemical abnormalities. The impact of these mutations is discussed.

Adult↗
PubMed2001

[Homocystinuria in adulthood].

Homocystinuria is a genetically determined inborn error of the methionine amino acid pathway characterized by increased plasma homocysteine. In its major form, homocystinuria, is due to cystathionine beta synthase deficiency. Treatment of these adulthood patients lead physicians to call up on the skilled advices of pediatricians. But prevention and treatment of age related vascular and osteoporotic complications are still to be evaluated.

Adult↗
PubMed2000

Methylenetetrahydrofolate reductase deficiency in four siblings: a clinical, biochemical, and molecular study of the family.

A diagnosis of methylenetetrahydrofolate reductase (MTHFR) deficiency was made in four sibs at different ages. The first three, including a pair of twins, had retarded psychomotor development, poor social contact, and seizures. Biologically, hyperhomocysteinemia and hypomethioninemia were found associated with low folate levels in serum and red cells, especially undetectable methyltetrahydrofolate in red cells. In the fourth child, prenatal diagnosis was not conclusive because of moderate decrease of enzymatic activity in chorionic villi and trophoblast. The girl was also affected, as shown by hyperhomocysteinemia and low folate levels found several days after birth. A 677C-->T (Ala-->Val) mutation was found in a homozygous state in the four children and in the father. Additionally, a second homozygous mutation, 1081C-->T, changing an arginine to cysteine also was identified in all of the children, whereas the distantly consanguineous parents were heterozygous. This amino acid substitution affecting an arginine residue in a sequence located at the end of catalytic domain seems critical for the function of the enzyme. The difficulty of prenatal diagnosis is discussed given the variability found in enzymatic activity and in the clinical phenotypes.

Adolescent↗
PubMed1999

Haemolytic uraemic syndrome and pulmonary hypertension in a patient with methionine synthase deficiency.

An 18-month-old girl presented with macrocytic megaloblastic anaemia followed by haemolytic uraemic syndrome. Metabolic investigations led to the identification of an inborn error of cobalamin metabolism consisting of defective methylcobalamin biosynthesis, probably cobalamin G, since methionine synthase activity was decreased under standard reducing conditions. Despite treatment, pulmonary hypertension progressively developed and responded to oxygen therapy. Renal involvement evolved to terminal failure and haemodialysis, while pulmonary hypertension was controlled by oxygen therapy. Such clinical manifestations have never been reported in association with a defect of methylcobalamin and thus of methionine biosynthesis. A congenital abnormality of cobalamin metabolism was suspected then confirmed in the presence of typical haematological features associated with unusual clinical manifestations such as progressive renal failure and pulmonary hypertension.

5-Methyltetrahydrofolate-Homocysteine S-Methyltran↗
PubMed1999

Modern clinical testing strategies in cobalamin and folate deficiency.

Folate or cobalamin deficiencies are usually detected by hematologic abnormalities, such as a macrocytic megaloblastic anemia, or often milder signs, such as hypersegmented neutrophils. In fact, these vitamin deficiencies may be associated with clinical conditions in which anemia and/or macrocytosis are absent, such as neuropsychiatric disorders and inborn errors of folate or cobalamin metabolism. A battery of sensitive tests, including blood vitamin levels, serum methylmaIonic acid and homocysteine assays, and the deoxyuridine suppression test in the bone marrow, allows for early detection of vitamin deficiency. Additional tests may be included to identify the causes of deficiency, such as the Schilling test using crystalline cyanocobalamin, or a modified Schilling test for showing food cobalamin malabsorption. Strategies for diagnosing a vitamin deficiency differ according to the hematologic and clinical presentations. The deleterious effects (aside from anemia) that arise from cobalamin or folate deficiency and include neurological complications, increased risk of vascular disease due to hyperhomocysteinemia, and increased risk of some types of cancer related to folate deficiency, underscore the importance of making an early diagnosis and instituting treatment with the appropriate vitamin in preventing permanent damage.

Deoxyuridine↗
PubMed1998

Remethylation defects: guidelines for clinical diagnosis and treatment.

The main remethylation defects include disorders which all have defective methionine synthesis in common. Methylenetetrahydrofolate reductase deficiency impairs methyltetrahydrofolate synthesis, defects in cytosolic reduction of hydroxocobalamin (CblC/D) impair the synthesis of both methyl- and adenosyl cobalamin and deficiencies of methionine synthase (CblE/G) are associated with defective methyl cobalamin synthesis. The clinical presentation is characterized by acute neurological distress in early infancy. In childhood, patients present with progressive encephalopathy with an end-stage which has many signs in common with the adult onset form. In fact, both have more or less severe signs of subacute degeneration of the cord. Cobalamin defective patients must be treated with parenteral supplementation of hydroxocobalamin (1-2 mg per dose). Some methylenetetrahydrofolate patients could be folate responsive and must have a high-dosage folate trial. In addition, oral betaine supplementation (2-9 g per day depending on age) appears an effective means to prevent further neurological deterioration.

5-Methyltetrahydrofolate-Homocysteine S-Methyltran↗
PubMed1998

Plasma homocysteine levels related to interactions between folate status and methylenetetrahydrofolate reductase: a study in 52 healthy subjects.

Hyperhomocysteinemia, a risk factor for vascular disease, is related to vitamin B12, vitamin B6, and especially folate deficiency, or to genetic factors such as mutations in methylenetetrahydrofolate reductase (MTHFR), an enzyme involved in the remethylation pathway of homocysteine to methionine. Recently, a C677 --> T mutation identified in the MTHFR gene was found to be frequently associated with decreased MTHFR activity and an elevated plasma homocysteine concentration. Since hyperhomocysteinemia seems to be determined by both genetic and environmental factors, we studied the interactions between MTHFR (phenotype and genotype) and folate status, including methyltetrahydrofolate (methylTHF), the product of MTHFR, on the homocysteine concentration in 52 healthy subjects, (28 women and 24 men; mean age, 32.7 years). MTHFR activity seems to be dependent on folate status, as shown by a lower activity in folate-deficient subjects and a return to normal values after supplementation with folic acid, and also by a decreased enzymatic activity on phytohemagglutinin (PHA)-stimulated lymphocytes grown in a folic acid-deficient medium. Conversely, the C677 --> T mutation seems to influence folate metabolism. Subjects who were homozygous for this mutation (+/+) had significantly higher plasma homocysteine and lower plasma folate and total and methylfolate levels in red blood cells (RBCs) than heterozygous (+/-) and normal (-/-) subjects. The ratio of RBC methylfolate to RBC total folate was, respectively, 0.27 in +/+, 0.66 in +/-, and 0.71 in -/-. This mutation seems to have an impact on methylTHF generation. These data illustrate the interactions between nutritional and genetic factors.

Adult↗
PubMed1998

[Hemolysis and schizocytosis, malabsorption and the "folate trap": unusual semiological peculiarities associated with vitamin B12 deficiency].

INTRODUCTION: Hemolysis and red cell fragmentation accompanying vitamin B12 deficiency may misdirect the diagnosis. Signs of malabsorption and abnormalities related to folic acid metabolism characterized by discrepancies between folic acid normal serum levels and erythrocytic folic acid levels may also exist. EXEGESIS: We report the occurrence of hemolysis and red cell fragmentation mimicking microangiopathic hemolytic anemia, malabsorption and folic acid deficiency in the course of vitamin B12 deficiency. Appropriate replacement therapy corrected all abnormalities. CONCLUSION: An association between hemolysis, malabsorption and folic acid deficiency should lead physicians to search for signs of vitamin B12 deficiency.

Adult↗
PubMed1998

Reliability of biochemical parameters used in prenatal diagnosis of combined methylmalonic aciduria and homocystinuria.

Prenatal diagnosis for combined methylmalonic aciduria and homocystinuria was performed in five at-risk pregnancies by determination of methylmalonic acid (MMA) and total homocysteine (Hcy) in amniotic fluid supernatant. The incorporation rate of [14C] propionate (+/- OHCbl) and the synthesis of cobalamin derivatives in cultured amniocytes were investigated as well as the [14C] MTHF incorporation rate in intact chorion biopsy. Our experience showed that total Hcy and MMA were clearly elevated in amniotic fluid of affected fetuses. Both the study of [14C] propionate incorporation and that of cobalamin synthesis in cultured amniocytes are useful to confirm the results of metabolite determination. The incorporation of [14C] MTHF in intact chorion biopsy seems not to be a reliable diagnostic method.

Amino Acid Metabolism, Inborn Errors↗
PubMed1995

Congenital errors of folate metabolism.

Congenital errors of folate metabolism can be related either to defective transport of folate through various cells or to defective intracellular utilization of folate due to some enzyme deficiencies. Defective transport of folate across the intestine and the blood-brain barrier was reported in the condition 'Congenital Malabsorption of Folate'. This disease is characterized by a severe megaloblastic anaemia of early appearance associated with mental retardation. Anaemia is folate-responsive, but neurological symptoms are only poorly improved because of the inability to maintain adequate levels of folate in the CSF. A familial defect of cellular uptake was described in a family with a high frequency of aplastic anaemia or leukaemia. An isolated defect in folate transport into CSF was identified in a patient suffering from a cerebellar syndrome and pyramidal tract dysfunction. Among enzyme deficiencies, some are well documented, others still putative. Methylenetetrahydrofolate reductase deficiency is the most common. The main clinical findings are neurological signs (mental retardation, seizures, rarely schizophrenic syndromes) or vascular disease, without any haematological abnormality. Low levels of folate in serum, red blood cells and CSF associated with homocystinuria are constant. Methionine synthase deficiency is characterized by a megaloblastic anaemia occurring early in life that is more or less folate-responsive and associated with mental retardation. Glutamate formiminotransferase-cyclodeaminase deficiency is responsible for massive excretion of formiminoglutamic acid but megaloblastic anaemia is not constant. The clinical findings are a more or less severe mental or physical retardation. Dihydrofolate reductase deficiency was reported in three children presenting with a megaloblastic anaemia a few days or weeks after birth, which responded to folinic acid. The possible relationship between congenital disorders such as neural tube defects or dihydropteridine reductase deficiency and disturbances of folate metabolism are discussed. Neurological symptoms present in most of these congenital disorders highlight the role of folate in the central nervous system.

Female↗