Effect of Dietary Supplementation with Folate on Choline Deficiency-Induced Hyperhomocysteinemia in Rats

Vitamin B6 deficiency, genome instability and cancer

Vitamin B6 functions as a coenzyme in >140 enzymatic reactions involved in the metabolism of amino acids, carbohydrates, neurotransmitters, and lipids. It comprises a group of three related 3-hydroxy-2-methyl-pyrimidine derivatives: pyridoxine (PN), pyridoxal (PL), pyridoxamine (PM) and their phosphorylated derivatives [pyridoxal 5'-phosphate (PLP) and pyridoxamine 5'-phosphate (PMP)], In the folate metabolism pathway, PLP is a cofactor for the mitochondrial and cytoplasmic isozymes of serine hydroxymethyltransferase (SHMT2 and SHMT1), the P-protein of the glycine cleavage system, cystathionine β-synthase (CBS) and γ-cystathionase, and betaine hydroxymethyltransferase (BHMT), all of which contribute to homocysteine metabolism either through folate- mediated one-carbon metabolism or the transsulfuration pathway. Folate cofactors carry and chemically activate single carbons for the synthesis of purines, thymidylate and methionine. So the evidence indicates that vitamin B6 plays an important role in maintenance of the genome, epigenetic stability and homocysteine metabolism. This article focuses on studies of strand breaks, micronuclei, or chromosomal aberrations regarding protective effects of vitamin B6, and probes whether it is folate-mediated one-carbon metabolism or the transsulfuration pathway for vitamin B6 which plays critical roles in prevention of cancer and cardiovascular disease.

Folic acid fortification ameliorates hyperhomocysteinemia caused by a vitamin B₆-deficient diet supplemented with L-methionine

Vitamin B₆ (B₆) deficiency affects homocysteine metabolism, and this leads to hyperhomocysteinemia. In this study, we examined i) the effects of B₆-deficiency and graduated levels of dietary methionine on homocysteine metabolism, and ii) the effects of fortified folate on homocysteine metabolism. In experiment 1, Wistar male rats were fed a control or a B₆-deficient diet supplemented with L-methionine at a level of 3, 6, or 9 g/kg of diet for 5 weeks. The resulting plasma homocysteine levels in the B₆-deficient groups increased in relation to the increase in dietary methionine level. Next, in experiment 2, rats were fed a control, B₆-deficient, or folate enriched (10 mg pteroylmonoglutamic acid/kg) B₆-deficient diet containing L-methionine at 9 g/kg for 5 weeks. Although the B₆-deficient diet induced hyperhomocysteinemia, folate fortification ameliorated the plasma homocysteine concentration. Overall, our results indicate that folate fortification ameliorates the hyperhomocysteinemia induced by B₆ deficiency and supplemental methionine intake.