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PubMed2006

Pro-thrombotic and pro-oxidant effects of diet-induced hyperhomocysteinemia.

Elevated plasma homocysteine levels are associated with the risk of atherosclerosis and arterial and venous thrombosis. We have previously demonstrated that rabbits rendered hyperhomocysteinemic by parenteral administration of homocysteine develop a dysfibrinogenemia that is associated with the formation of fibrin clots that are abnormally resistant to fibrinolysis. We suggested that this acquired dysfibrinogenemia contributes to the thrombotic tendency in hyperhomocysteinemia. However, it was possible that the homocysteine-associated dysfibrinogenemia was an artifact of the parenteral administration model. Therefore, the goals of the current study were to develop a diet-induced model of homocysteinemia in rabbits and determine whether a dysfibrinogenemia and evidence of oxidative stress develop in this model as they do when homocysteine is injected. We found that rabbits fed a diet severely deficient in folate and mildly deficient in choline develop mild hyperhomocysteinemia: 14.8+/-4.0 microM in deficient rabbits compared to 9.0+/-1.7 microM in controls. The deficient rabbits also develop evidence of oxidant stress: increased lipid peroxidation in liver, impaired mitochondrial enzyme activities in liver and elevated caspase-3 levels in plasma. Most importantly, the deficient rabbits also develop a dysfibrinogenemia characterized by increased resistance to fibrinolysis. We believe that this dietary model of homocysteinemia is clinically relevant and reproduces many features associated with hyperhomocysteinemia in previous work using in vitro and in vivo models. Our findings suggest that an acquired dysfibrinogenemia could play a role in the increased risk of atherothrombotic disease in mildly hyperhomocysteinemic human subjects.

Animals↗
PubMed2001

Preventive nutritional supplementation throughout the reproductive life cycle.

Current interest in preventive nutritional supplementation strategies during the reproductive cycle in developed countries focuses mainly on iron and folic acid. Iron deficiency is the most common cause of anaemia. Inadequate iron nutrition is mainly a problem in developing countries but it also seems to affect a large proportion of pregnant women in the industrialised world. There is no chance for diet modification alone to meet iron requirements during pregnancy. However, dietary advice must be provided to increase iron intake and iron bioavailability. The best choice is prescribed supplementation adapted to the individual's needs. Folic acid supplementation during the periconceptional period reduces the occurrence and recurrence of neural tube defects (NTDs). According to the updated edition of American Dietary Reference Intakes, recommended dietary allowance for folate for women of childbearing age varies throughout the reproductive cycle from 400 microg day(-1) of dietary folate equivalents (DFEs) for non-pregnant women, to 600 microg day(-1) DFEs for pregnant women and 500 microg day(-1) DFEs in lactating women. Increasing dietary folate, fortifying staple foods with folic acid or use of folic acid supplements can increase folate intake.

Adolescent↗
PubMed1999

Folate and vitamin B12.

The folates are made up of a pterdine ring attached to a p-aminobenzoate and a polyglutamyl chain. The active form is tetrahydrofolate which can have C1 units enzymically attached. These C1 units (as a formly group) are passed on to enzymes in the purine pathway that insert the C-2 and C-8 into the purine ring. A methylene group (-CH2-) attached to tetrahydrofolate is used to convert the uracil-type pyrimidine base found in RNA into the thymine base found in DNA. A further folate cofactor, i.e. 5-methyltetrahydrofolate, is involved in the remethylation of the homocysteine produced in the methylation cycle back to methionine. After activation to S-adenosylmethionine this acts as a methyl donor for the dozens of different methyltransferases present in all cells. Folate deficiency results in reduction of purine and pyrimidine biosynthesis and consequently DNA biosynthesis and cell division. This process is most easily seen in a reduction of erythrocytes causing anaemia. Reduction in the methylation cycle has multiple effects less easy to identify. One such effect is certainly on the nerve cells, because interruption of the methylation cycle causing neuropathy can also happen in vitamin B12 deficiency due to reduced activity of the vitamin B12-dependent enzyme methionine synthase (EC 2.1.1.13). In vitamin B12 deficiency, blocking of the methylation cycle causes the folate cofactors in the cell to become trapped as 5-methyltetrahydrofolate. This process in turn produces a pseudo folate deficiency in such cells, preventing cell division and giving rise to an anaemia identical to that seen in folate deficiency.

Diet↗
PubMed1996

Folate, vitamin B12, and neuropsychiatric disorders.

Folate and vitamin B12 are required both in the methylation of homocysteine to methionine and in the synthesis of S-adenosylmethionine. S-adenosylmethionine is involved in numerous methylation reactions involving proteins, phospholipids, DNA, and neurotransmitter metabolism. Both folate and vitamin B12 deficiency may cause similar neurologic and psychiatric disturbances including depression, dementia, and a demyelinating myelopathy. A current theory proposes that a defect in methylation processes is central to the biochemical basis of the neuropsychiatry of these vitamin deficiencies. Folate deficiency may specifically affect central monoamine metabolism and aggravate depressive disorders. In addition, the neurotoxic effects of homocysteine may also play a role in the neurologic and psychiatric disturbances that are associated with folate and vitamin B12 deficiency.

Depressive Disorder↗
PubMed2001

Risk of inadequate intakes of vitamins A, B1, B6, C, E, folate, iron and calcium in the Spanish population aged 4 to 18.

A meta-analysis of the most representative Spanish nutrition studies was carried out to identify inadequate intakes of vitamins, A, B1, B6, C, E, folate, iron, and calcium in children aged 4 to 18. Information on vegetable, fruit and fruit juice/beverage intake was also solicited. Data drawn from the selected studies yielded a total of 6540 children and adolescents in eight geographical areas. The sample was stratified by age (children: 4 to 14 years old and adolescents: 13-18 years old) and sex. Inadequate intakes (below two-thirds of the recommended values) were notable in children for vitamin E, vitamin C, and vitamin A and in girls, iron. In adolescents, low intakes were especially marked for vitamin E and vitamin A, and in girls, calcium, folate, and iron. Adolescents consumed more vegetables, fruit juice, and fruit drinks whereas children had higher fruit intakes. Regional differences in consumption were also detected. Strategies for improving nutrient intake in these vulnerable populations are discussed.

Adolescent↗
PubMedDate not supplied

Spina bifida and other neural tube defects.

NTDs, resulting from failure of the neural tube to close during the fourth week of embryogenesis, are the most common severely disabling birth defects in the United States, with a frequency of approximately 1 of every 2000 births. Neural tube malformations involving the spinal cord and vertebral arches are referred to as spina bifida, with severe types of spina bifida involving protrusion of the spinal cord and/or meninges through a defect in the vertebral arch. Depending on the level of the lesion, interruption of the spinal cord at the site of the spina bifida defect causes paralysis of the legs, incontinence of urine and feces, anesthesia of the skin, and abnormalities of the hips, knees, and feet. Two additional abnormalities often seen in children with spina bifida include hydrocephalus and the Arnold-Chiari type II malformation. Despite the physical and particular learning disabilities children with spina bifida must cope with, participation in individualized educational programs can allow these children to develop skills necessary for autonomy in adulthood. Advances in research to uncover the molecular basis of NTDs is enhanced by knowledge of the link between both the environmental and genetic factors involved in the etiology of NTDs. The most recent development in NTD research for disease-causing genes is the discovery of a genetic link to the most well-known environmental cause of neural tube malformation, folate deficiency in pregnant women. Nearly a decade ago, periconceptional folic acid supplementation was proven to decrease both the recurrence and occurrence of NTDs. The study of folate and its association with NTDs is an ongoing endeavor that has led to numerous studies of different genes involved in the folate metabolism pathway, including the most commonly studied thermolabile mutation (C677T) in the MTHFR gene. An additional focus for NTD research involves mouse models that exhibit both naturally occurring NTDs, as well as those created by experimental design. We hope the search for genes involved in the risk and/or development of NTDs will lead to the development of strategies for prevention and treatment. The most recent achievement in treatment of NTDs involves the repair of meningomyelocele through advancements in fetal surgery. Convincing experimental evidence exists that in utero repair preserves neurologic function, as well as resolving the hydrocephalus and Arnold-Chiari malformation that often accompany meningomyelocele defects. However, follow-up is needed to completely evaluate long-term neurologic function and overall improved quality of life. And in the words of Olutoye and Adzick, "until the benefits of fetal [meningomyelocele] repair are carefully elucidated, weighed against maternal and fetal risks, and compared to conventional postnatal therapy, this procedure should be restricted to a few centers that are committed (clinically and experimentally) to investigating these issues."

Animals↗
PubMed1986

Sulphasalazine associated pancytopenia may be caused by acute folate deficiency.

Agranulocytosis and aplastic anaemia associated with sulphasalazine are well recognised, but pancytopenia caused by acute megaloblastic arrest of haemopoiesis while taking sulphasalazine has not previously been described. We report three patients who, after taking sulphasalazine for over two years, suddenly developed severe pancytopenia with gross megaloblastic changes in the marrow. In two patients there was a good response to high dose oral folic acid but the third required folinic acid. The mechanism appears to be acute folate deficiency, and the requirement for folinic acid in one case suggests that the known inhibition of folate metabolism by sulphasalazine also contributes. The syndrome appears to be associated with high dosage and slow acetylator status. The drug has been successfully restarted at reduced dosage with folate supplements in two patients both of whom were slow acetylators. In the third case, whose acetylator status is not known, progression of her disease led to colectomy.

Adolescent↗