We found a match
Your institution may have rights to this item. Sign in to continue.
- Title
Cellular folate vitamer distribution during and after correction of vitamin B<sub>12</sub> deficiency: a case for the methylfolate trap.
- Authors
Smulders, Y. M.; Smith, D. E. C.; Kok, R. M.; Teerlink, T.; Swinkels, D. W.; Stehouwer, C. D. A.; Jakobs, C.
- Abstract
Haematological sequellae of vitamin B12 deficiency are attributed to disturbed DNA synthesis, but vitamin B12 itself plays no role in DNA biosynthesis. A proposed explanation for this is the methylfolate trap hypothesis. This hypothesis states that B12 deficiency impairs overall folate metabolism because 5-methyltetrahydrofolate (5MTHF) becomes metabolically trapped. This trap results from the fact that 5MTHF can neither be metabolised via the methionine synthase pathway, nor can it be reconverted to its precursor, methylenetetrahydrofolate. Other manifestations of the methylfolate trap include cellular folate loss because of shorter 5MTHF polyglutamate chains and global hypomethylation. The methylfolate trap has never been demonstrated in humans. We describe a patient with B12 deficiency who was homozygous for the common methylenetetrahydrofolate reductase (MTHFR) C677T mutation. We analysed red blood cell (RBC) folate vitamers and global DNA methylation by liquid chromatography (LC) in combination with tandem mass spectrometry, and 5MTHF polyglutamate length by LC-electrochemical detection. Compared to post-B12 supplementation values, homocysteine was higher (52·9 μmol/l vs. 16·8 μmol/l), RBC folate was lower (268·92 nmol/l vs. 501·2 nmol/l), the 5MTHF fraction of RBC folate was much higher (94·5% vs. 67·4%), polyglutamate chain length was shorter (more tetra- and pentaglutamates), and global DNA methylation was 22% lower. This is the first time that virtually all features of the methylfolate trap hypothesis have been demonstrated in a human with vitamin B12 deficiency.
- Subjects
VITAMIN B12 deficiency; BIOSYNTHESIS; MASS spectrometry; METHYLATION; LIQUID chromatography; HOMOCYSTEINE
- Publication
British Journal of Haematology, 2006, Vol 132, Issue 5, p623
- ISSN
0007-1048
- Publication type
Article
- DOI
10.1111/j.1365-2141.2005.05913.x