![[Feedback]](/icons/banner/feedbackACT.gif){kind=icon}
![[For Subscribers]](/icons/banner/subscriberACT.gif){kind=icon}
![[Archive]](/icons/banner/archiveACT.gif){kind=icon}
![[Search]](/icons/banner/searchACT.gif){kind=icon}
![[Contents]](/icons/banner/tocACT.gif){kind=icon}
|
|
|
|
|
||
Vitamin Metabolism and Aging Laboratory, Jean Mayer U.S. Department of Agriculture Human Nutrition Research Center on Aging at Tufts University, Boston, MA 02111;
* Department of Nutritional Sciences, University of California, Berkeley, CA 94720; and
Amino Acid Disorder Laboratory at Massachusetts General Hospital, Charlestown, MA 02129
2To whom correspondence should be addressed. E-mail: jacob.selhub{at}tufts.edu.
Methylenetetrahydrofolate reductase (MTHFR) catalyzes the reduction of 5,10-methylenetetrahydrofolate to 5-methyltetrahydrofolate, the methyl donor for the synthesis of methionine from homocysteine. A common C677T mutation in the MTHFR gene renders the enzyme 
50% less active than the wild-type enzyme as shown in in vitro studies using cell extracts. We developed an immortalized cell culture model to determine whether the lower in vitro activity imparted by the homozygous (T/T) genotype is demonstrated in situ when exposed to adequate and marginal physiologic concentrations of folate and riboflavin. T/T MTHFR activity was compared with that of C/C genotype cell extracts by an in vitro assay and in intact cells by measuring the distribution of folate forms, the accumulation of homocysteine in the medium and the synthesis of methionine from formate and homocysteine. Under adequate nutrient conditions, the in vitro activity of the T/T MTHFR enzyme was approximately half that of the C/C genotype. Similarly, the proportion of 5-methyltetrahydrofolate in cells with the T/T genotype was approximately half that of the cells with wild-type MTHFR. In contrast, homocysteine accumulation in the culture medium was low and not different between genotypes, nor was there a difference in methionine synthetic capacity. Significant differences were observed between genotypes only when the supply of both folate and riboflavin was limited in the medium, which resulted in increased homocysteine accumulation and decreased methionine production in the T/T genotype. These data are consistent with the current understanding of the molecular interaction of the MTHFR mutant with folate substrates and the FAD prosthetic group.
KEY WORDS: • folate • methylenetetrahydrofolate reductase • homocysteine • immortalized cells
This article has been cited by other articles:
|
|
 |
|
  L. Paul, M. Cattaneo, A. D'Angelo, F. Sampietro, I. Fermo, C. Razzari, G. Fontana, N. Eugene, P. F. Jacques, and J. Selhub Telomere Length in Peripheral Blood Mononuclear Cells Is Associated with Folate Status in Men J. Nutr., July 1, 2009; 139(7): 1273 - 1278. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 K. S McCully Homocysteine, vitamins, and vascular disease prevention Am. J. Clinical Nutrition, November 1, 2007; 86(5): 1563S - 1568S. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. R. Davis, E. P. Quinlivan, K. P. Shelnutt, D. R. Maneval, H. Ghandour, A. Capdevila, B. S. Coats, C. Wagner, J. Selhub, L. B. Bailey, et al. The Methylenetetrahydrofolate Reductase 677C->T Polymorphism and Dietary Folate Restriction Affect Plasma One-Carbon Metabolites and Red Blood Cell Folate Concentrations and Distribution in Women J. Nutr., May 1, 2005; 135(5): 1040 - 1044. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 K. Robien, C. M. Ulrich, J. Bigler, Y. Yasui, T. Gooley, B. Bruemmer, J. D. Potter, and J. P. Radich Methylenetetrahydrofolate Reductase Genotype Affects Risk of Relapse after Hematopoietic Cell Transplantation for Chronic Myelogenous Leukemia Clin. Cancer Res., November 15, 2004; 10(22): 7592 - 7598. [Abstract] [Full Text] [PDF]
|
|
