Source: UNIVERSITY OF FLORIDA submitted to NRP
GENETIC EFFECTS ON FOLATE-DEPENDENT ONE-CARBON METABOLISM
Sponsoring Institution
State Agricultural Experiment Station
Project Status
COMPLETE
Funding Source
STATE
Reporting Frequency
Annual
Accession No.
0190064
Grant No.
(N/A)
Cumulative Award Amt.
(N/A)
Proposal No.
(N/A)
Multistate No.
(N/A)
Project Start Date
Apr 1, 2001
Project End Date
Dec 31, 2004
Grant Year
(N/A)
Program Code
[(N/A)]- (N/A)
Recipient Organization
UNIVERSITY OF FLORIDA
G022 MCCARTY HALL
GAINESVILLE,FL 32611
Performing Department
FOOD SCIENCE & HUMAN NUTRITION
Non Technical Summary
Adequate intake of the vitamin folate is essential to health because of the vitamin's role in the metabolism of certain amino acids (building blocks of protein) and nucleotides (building blocks of DNA). It appears that folate requirements in humans might be affected by a person's genetics. This research will provide new information about the consequences of inadequate folate nutrition with respect to the metabolic changes involved. These studies will also yield information about the metabolic effects of common genetic variability as affected by folate nutritional status.
Animal Health Component
20%
Research Effort Categories
Basic
80%
Applied
20%
Developmental
(N/A)
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
70260991010100%
Knowledge Area
702 - Requirements and Function of Nutrients and Other Food Components;

Subject Of Investigation
6099 - People and communities, general/other;

Field Of Science
1010 - Nutrition and metabolism;
Goals / Objectives
The major aim of this project is to learn more about the function of the vitamin folate and improve our understanding of its requirement in humans. The following objectives will evaluate relationships and test hypotheses regarding nutritional and genetic factors influencing the metabolism of homocysteine, an amino acid which is a risk factor in vascular disease: (a) Determine the kinetics by which serine serves as a source of one-carbon units for homocysteine remethylation and nucleotide synthesis and the possible degree of impairment of these processes by low folate status and the common C677T mutation of methylenetetrahydrofolate reductase (MTHFR). (b) Determine the influence of folate status and the C677T mutation of MTHFR on thedistribution of cellular one-carbon units as reflected by folate distributions in red blood cells. (c) Determine the influence of folate status and the C677T mutation on the catabolism of homocysteine. (d) Determine the relative contributions of cytosolic and mitochondrial metabolism in the generation of one-carbon units. (e) Determine the relative significance of serine and glycine as sources of cellular one-carbon units.
Project Methods
One-carbon (C1) metabolism consists of the generation of carbon units for use in cellular processes including DNA synthesis, regeneration of methionine (Met) from homocysteine (Hcy), and methylation of many biological compounds. Conditions that impair one-carbon metabolism (e.g. folate deficiency) are associated with elevation in plasma Hcy and increased risk of vascular disease, certain cancers, and neural tube defects. A common mutation of methylene-tetrahydrofolate reductase (MTHFR), known as the "thermolabile" or C677T mutant, has been associated with elevations in plasma Hcy (especially in low folate status), lower plasma folate, altered distribution of erythrocyte folate, potentially increased risk of vascular disease, and decreased risk of colon cancer. The in vivo metabolic effects of the C677T mutation have not been determined directly. Our overall hypothesis is that the rate of acquisition and generation of methyl groups from serine (primary source of C1 units) is reduced in individuals homozygous for the C677T mutation, and that the genotypic effect is greatest when folate nutriture is inadequate. We also hypothesize that the rate of folate-dependent synthesis of nucleotides (purines and thymidylate) will be reduced in folate deficiency but may be enhanced by the C677T mutation. The proposed studies will determine nutritional and genetic dependence of the flow of C1 units from serine (Ser) to Met and from Ser to nucleotides. This protocol also will allow measurement of the transsulfuration pathway of Hcy catabolism important in disposal of excess Hcy. Protocol: In the main protocol, healthy adequately nourished human subjects (20-30 yr) will be classified by MTHFR genotype, (homozygous control and homozygous mutant). Subjects will be given infusions with 13C-serine as primary precursor initially and following 8-wk dietary depletion of 120 ug/d folate to evaluate the effect of nutritional and genotypic effects on C1 kinetics. Two variations of this study will be conducted to determine the relative roles of mitochondrial and cytosolic routes of C1 generation from serine and the role of the mitochondrial glycine cleavage pathway. In total, these studies will yield new functional data regarding the effects of folate deficiency, and the influence of common polymorphism of MTHFR.

Progress 10/01/05 to 09/30/06

Outputs
All objectives in the study of human one-carbon metabolism and the effects of folate deficiency in this project have been completed. In the final component of this grant, studies using primed, constant infusion of stable isotopic tracers were conducted to investigate selected aspects of human one-carbon metabolism to provide additional insight into key processes and to aid in the interpretation of previous kinetic data. Human subjects (n=4-5) received intravenous infusions of: (a) [2H3]serine, (b) [3-13C]serine, (c) [2-13C]glycine, or (d) [13C5]methionine. Although analysis is still in progress, data acquired thus far indicate the following. Comparison of labeling patterns of methionine and deoxynucleosides from serine infusions support and extend previous findings that one-carbon units are generated via both cytosolic and mitochondrial processes. Similar analyses of labeling derived from glycine infusions indicate that glycine is a significant source of one-carbon units in human metabolism. Data from the methionine infusion indicate that the methionine salvage pathway is negligible relative to other sources of one-carbon units under the conditions of this protocol.

Impacts
This study is providing important new insight into the mechanisms and kinetic relationships of human one-carbon metabolism and folate nutritional status.

Publications

  • Bailey, L.B.& Gregory, J.F. (2006) Folate. Chapter in: Present Knowledge in Nutrition, 9th Ed. (B.A. Bowman and R. M. Russell, eds.). ILSI Press, Washington, D.C, 278-301.
  • Quinlivan, E.P., Hanson, A.D., Gregory, J.F. (2006). The analysis of folate and its metabolic precursors in biological samples. Anal. Biochem. 348:163-184.
  • Reed, M.C., Nijhout, H.F., Neuhouser, M.L., Gregory, J.F., Shane, B., James, S.J., Boynton, A., Ulrich, C.M. (2006) A mathematical model gives insights into nutritional and genetic aspects of folate- mediated one-carbon metabolism. J. Nutr. 136: 2653-2661.
  • Gregory, J.F. (2006). Stable isotopic tracers for studies of folate bioavailability and metabolism: development, principles and applications. Congress Proceedings of the 13th International Symposium on Chemistry & Biology of Pteridines & Folates (in press).


Progress 10/01/04 to 09/30/05

Outputs
All objectives in the study of human one-carbon metabolism and the effects of folate deficiency in this project have been completed. In the final component of this grant, studies using primed, constant infusion of stable isotopic tracers were conducted to investigate selected aspects of human one-carbon metabolism to provide additional insight into key processes and to aid in the interpretation of previous kinetic data. Human subjects (n=4-5) received intravenous infusions of: (a) [2H3]serine, (b) [3-13C]serine, (c) [2-13C]glycine, or (d) [13C5]methionine. Although analysis is still in progress, preliminary data indicate the following. Comparison of labeling patterns of methionine and deoxynucleosides from serine infusions support and extend previous findings that one-carbon units are generated via both cytosolic and mitochondrial processes. Similar analyses of labeling derived from glycine infusions indicate that glycine is a significant source of one-carbon units in human metabolism. Data from the methionine infusion will allow the first direct measurement of one-carbon recycling via the methionine salvage pathway.

Impacts
This research has led to improved experimental methods for the investigation of homocysteine metabolism. Our results have yielded a better understanding of the regulation of homocysteine metabolism and DNA synthesis as affected by folate nutritional status and human genetics.

Publications

  • Davis, S.R., Quinlivan, E.P., Shelnutt, K.P., Ghandour, H., Capdevila, A., Coats, B.S., Wagner, C., Shane, B., Selhub, J., Bailey, L.B., Stacpoole, P.W., Gregory, J.F. 2005. Homocysteine synthesis is elevated but total remethylation is unchanged by the methylenetetrahydrofolate reductase 677C>T polymorphism and by dietary folate restriction in young women. J. Nutr. 135:1045-1050.
  • Wright, A.J.A., Finglas, P.M., Dainty, J.R., Wolfe, C.A., Hart, D.J., Wright, D.M. & Gregory, J.F. 2005. Differential kinetic behavior and distribution for pteroylglutamic acid and reduced folates: a revised hypothesis of the primary site of pteroylglutamate metabolism in humans J. Nutr. 135: 619-623.
  • Gregory, J.F., Quinlivan, E.P., and Davis, S.R. (2005) Integrating the issues of folate bioavailability, intake and metabolism in the era of fortification. Trends in Food Science & Technology 16:229-240.
  • Quinlivan, E P. Davis, S.R. Shelnutt, K. P. Henderson, G.N. Ghandour, H. Shane, B. Selhub, J. Bailey, L. B. Stacpoole, P.W. & Gregory, J. F. 2005. Methylenetetrahydrofolate reductase 677 C>T polymorphism and folate status affect one-carbon incorporation into human DNA deoxynucleosides. J. Nutr. 135:389-396.
  • Davis, S.R., Quinlivan, E.P., Shelnutt, K.P., Maneval, D.R., Ghandour, H., Capdevila, A., Coats, B.S., Wagner, C., Selhub, J., Bailey, L.B., Shuster, J.J., Stacpoole, P.W., Gregory, J.F. 2005. Effects of the MTHFR 677C>T polymorphism and dietary folate restriction on plasma one carbon metabolites and red blood cell folate concentrations and distribution in women. J. Nutr. 135:1040-1044.
  • Quinlivan, E.P., Hanson, A.D., Gregory, J.F. (2005). The analysis of folate and its metabolic precursors in biological samples. Anal. Biochem. (in press)
  • Gregory, J.F. (2005). Stable isotopic tracers for studies of folate bioavailability and metabolism: development, principles and applications. Congress Proceedings of the 13th International Symposium on Chemistry & Biology of Pteridines & Folates (in press).
  • Bailey, L.B.& Gregory, J.F. (2005) Folate. Chapter in: Present Knowledge in Nutrition, 9th Ed. (B.A. Bowman and R. M. Russell, eds.). ILSI Press, Washington, D.C, (in press)


Progress 04/01/01 to 12/31/04

Outputs
OUTPUTS: The results of this research have provided new insight into human one-carbon metabolism and the impact of reduced folate status. This study also led to novel stable isotopic tracer infusion protocols for the study of human in vivo kinetics for one-carbon metabolism and deoxyncleotide synthesis. These studies provided new insight into the metabolic consequences of mildly impaired folate status and its effect on DNA synthesis and homocysteine metabolism. PARTICIPANTS: Jesse F. Gregory, PI (UF) Peter W. Stacpoole and Lynn B. Bailey, co-investigators (UF) Jacob Selhub (Tufts Univ.), Barry Shane (Univ. Cal.-Berkeley) and Conrad Wagner (Vanderbilt), co-investigators Steven R. Davis and Eoin P. Quinlivan, postdoctoral associates PROJECT MODIFICATIONS: none

Impacts
Tracer infusion protocols have been developed and validated for the study of human in vivo kinetics. Our analysis suggests that the rate of one-carbon generation from serine, folate-dependent homocysteine remethylation, and total homocysteine remethylation are signficantly higher than previously reported. In contrast to our hypotheses, these processes were not impaired by marginal folate status. However, homocysteine production (apparently via glycine N-methyltransferase) increased significantly, which apparently was responsible for the resulting hyperhomocysteinemia. Folate deficiency also yielded impaired synthesis of thymidylate, an often limiting building block of DNA. Secondary studies yielded important new information indicating that slycine and serine are important one-carbon sources and that methinine salvage is a limited source of one-carbon units. Overall, these studies have provided new insight into human one-carbon metabolism and its folate-dependence.

Publications

  • Davis, S.R., Stacpoole, P.W., Williamson, J., Quinlivan, E.P., Coats, B.S., Shane, B., Bailey, L.B., Gregory, J.F. 2004. Tracer-derived total and folate-dependent homocysteine remethylation and synthesis rates in humans indicate that serine is the main one-carbon donor. Am. J. Physiol. - Endocrinol. Metab. 286: E272-E279. (erratum 286: E674. 2004). Townsend, J.H., Davis, S.R., Mackey, A.D., Gregory, J.F. 2004. Folate deprivation reduces homocysteine remethylation in a human intestinal epithelial cell culture model: role of serine in one-carbon donation. Am. J. Physiol. - Gastrointest. Liver Physiol. 286: G588-G595. Shelnutt, K.P., Kauwell, G.P.A., Gregory, J.F., Maneval, D.R., Quinlivan, E.P., Theriaque, D.W., Henderson, G.N., Bailey, L.B. 2004. Methylenetetrahydrofolate reductase 677 C-->T polymorphism affects DNA methylation in response to controlled folate intake in young women. J. Nutr. Biochem. 15: 554-560. Gregory, J.F. (2004) Dietary folate in a changing environment: bioavailability, fortifi


Progress 10/01/03 to 09/30/04

Outputs
Marginal deficiency of folate is associated with elevated plasma homocysteine concentration, particular in people who have the T/T genotype of the common 677C>T genetic polymorphism of methylenetetrahydrofolate reductase (MTHFR). This implies that there is a metabolic interaction of the effects of folate nutritional status and this genetic polymorphism. We have undertaken a study with the objective of determining the effect of folate deficiency, MTHFR genotype, and their interaction on the in vivo rate of key reactions of human one-carbon metabolism. This study involved the use of an intravenous infusion with stable isotopically labeled tracers to permit in vivo measurement of the rate of homocysteine remethylation, generation of one-carbon units from serine, purine synthesis and thymidylate synthesis, and protein turnover. Human female subjects (n=10 common genotype C/C and n=10 T/T) participated in this protocol. Rates of in vivo metabolic reactions were determined with this infusion procedure initially (each subject in adequate folate status) then again following a 7-week controlled low-folate diet. Initial analysis has shown that in vivo kinetics can be measured with high precision. Under the conditions of this protocol, the serine 3-carbon provides over 80% of the one-carbon units used to remethylate homocysteine. In addition, subjects with the T/T MTHFR genotype did not exhibit a reduction in serine-dependent remethylation flux nor did they exhibit any reduction in total remethylation flux regardless of folate status. Kinetic data indicated that the marginal elevation in plasma homocysteine was associated with an increase in production of homocysteine. The relative rate of synthesis of thymidylate, purines and methylcytosine was determined by analysis of DNA from isolated peripheral blood monocytes. Subjects with the T/T MTHFR genotype exhibited higher relative rates of thymidylate synthesis. This is consistent with epidemiological evidence that the T/T genotype is protective against certain cancers, possibly by promoting DNA repair processes. Another novel finding was that folate deficiency altered the ratio of rates of adenosine and guanosine synthesis.

Impacts
This research has led to improved experimental methods for the investigation of homocysteine metabolism. Our results have yielded a better understanding of the regulation of homocysteine metabolism and DNA synthesis as affected by folate nutritional status and human genetics.

Publications

  • Townsend, J.H., Davis, S.R., Mackey, A.D., Gregory, J.F. 2004. Folate deprivation reduces homocysteine remethylation in a human intestinal epithelial cell culture model: role of serine in one-carbon donation. Am. J. Physiol. - Gastrointest. Liver Physiol. 286: G588-G595.
  • Shelnutt, K.P., Kauwell, G.P.A., Gregory, J.F., Maneval, D.R., Quinlivan, E.P., Theriaque, D.W., Henderson, G.N., Bailey, L.B. 2004. Methylenetetrahydrofolate reductase 677 C->T polymorphism affects DNA methylation in response to controlled folate intake in young women. J. Nutr. Biochem. 15: 554-560.
  • Quinlivan, E P. Davis, S.R. Shelnutt, K. P. Henderson, G.N. Ghandour, H. Shane, B. Selhub, J. Bailey, L. B. Stacpoole, P.W. & Gregory, J. F. 2004. Methylenetetrahydrofolate reductase 677 C->T polymorphism and folate status affect one-carbon incorporation into human DNA deoxynucleosides. J. Nutr. (in press)
  • Davis, S.R., Stacpoole, P.W., Williamson, J., Quinlivan, E.P., Coats, B.S., Shane, B., Bailey, L.B., Gregory, J.F. 2004. Tracer-derived total and folate-dependent homocysteine remethylation and synthesis rates in humans indicate that serine is the main one-carbon donor. Am. J. Physiol. - Endocrinol. Metab. 286: E272-E279.


Progress 10/01/02 to 10/01/03

Outputs
Marginal deficiency of folate is associated with elevated plasma homocysteine concentration, particular in people who have the T/T genotype of the common C677T genetic polymorphism of methylenetetrahydrofolate reductase (MTHFR). This implies that there is a metabolic interaction of the effects of folate nutritional status and this genetic polymorphism. We have undertaken a study with the objective of determining the effect of folate deficiency, MTHFR genotype, and their interaction on the in vivo rate of key reactions of human one-carbon metabolism. Specifically, this study involved the use of an intravenous infusion with stable isotopically labeled tracers to permit in vivo measurement of the rate of homocysteine remethylation, generation of one-carbon units from serine, purine synthesis and thymidylate synthesis, and protein turnover. Human female subjects (n=10 common genotype C/C and n=10 T/T) participated in this protocol. Rates of in vivo metabolic reactions were determined with this infusion procedure initially (each subject in adequate folate status) then again following a 7-week controlled low-folate diet. Initial analysis has shown that in vivo kinetics can be measured with high precision. Although the analysis of data has not yet been completed, initial findings suggest that serine provides about 45-50% of the carbons used to remethylate homocysteine. In addition, subjects with the T/T MTHFR genotype did not exhibit a reduction in serine-dependent remethylation flux nor did they exhibit any reduction in total remethylation flux regardless of folate status. We are currently examining regulatory processes that might be responsible for these findings. The relative rate of synthesis of thymidylate, purines and methylcytosine was determined by analysis of DNA from isolated peripheral blood monocytes. Subjects with the T/T MTHFR genotype exhibited higher relative rates of thymidylate synthesis. This is consistent with epidemiological evidence that the T/T genotype is protective against certain cancers, possibly by promoting DNA repair processes.

Impacts
This research has led to improved experimental methods for the investigation of homocysteine metabolism. Our results have yielded a better understanding of the regulation of homocysteine metabolism and DNA synthesis as affected by folate nutritional status and human genetics.

Publications

  • Townsend, J.H., Davis, S.R., Mackey, A.D., Gregory, J.F. 2003. Folate deprivation reduces homocysteine remethylation in a human intestinal epithelial cell culture model: role of serine in one-carbon donation. Am. J. Physiol. - Gastrointest. Liver Physiol. (November 13, 2003). 10.1152/ajpgi.00454.2003
  • Davis, S.R., Stacpoole, P.W., Williamson, J., Quinlivan, E.P., Coats, B.S., Shane, B., Bailey, L.B., Gregory, J.F. 2004. Total and folate-dependent homocysteine remethylation and homocysteine synthesis rates in humans using amino acid tracers: importance of serine as a 1-C donor. Am. J. Physiol. - Endocrinol. Metab. 286: E272-E279.
  • Shelnutt, K.P., Kauwell, G.P., Chapman, C.M., Gregory, J.F., Maneval, D.R., Browdy, A.A., Theriaque, D.W., Bailey, L.B. 2003. Folate status response to controlled folate intake is affected by the methylenetetrahydrofolate reductase 677C-->T polymorphism in young women. J. Nutr. 133: 4107-4111.
  • Wright AJA, Finglas PM, Dainty JR, Hart DJ, Wolfe CA, Southon S, Gregory JF. 2003. Single oral doses of 13C forms of pteroylmonoglutamic acid and 5-formyltetrahydrofolic acid elicit differences in short term kinetics of labelled and unlabeled folates in plasma: potential problems in interpretation of folate bioavailability studies. Br. J. Nutr. 90:363-371.
  • Wolfe, J.M., Bailey, L.B., Herrlinger-Garcia, K., Theriaque, D.W., Gregory, J.F., Kauwell, G.P.A. 2003. Folate catabolite excretion is responsive to changes in dietary folate intake in elderly women. Am. J. Clin. Nutr. 77: 919-923.
  • Quinlivan, E.P. & Gregory, J.F. 2003. Effect of food fortification on folic acid intake in the United States. Am. J. Clin. Nutr. 77: 221-225. Sanderson, P., McNulty, H., Mastroiacovo, P., McDowell, I.F.W., Melse-Boonstra, A., Finglas, P.M., Gregory, J.F. (2003) Folate bioavailability: UK Food Standards Agency workshop report. Br. J. Nutr. 90: 473-479.
  • Quinlivan, E.P., Gregory. J.F. The impact of food fortification on folic acid intake in Canada. Can. J. Public Health 94:154, 2003.
  • Quinlivan, E.P., Davis, S.R., Henderson, G.N., Bailey, L.B., Stacpoole, P.W., Shane, B., Gregory, J.F. 2003. Stable-isotopic investigation of 1-C partitioning into purine and thymidylate synthesis in humans: effects of MTHFR 677 C-->T polymorphism and folate status. FASEB J. 17: A276 (abstr. 171.8).
  • Davis, S.R., Quinlivan, E.P., Stacpoole, P.W., Bailey, L.B., Gregory, J.F. 2003. Effect of dietary folate depletion and the 677 C-->T methylenetetrahydrofolate reductase gene polymorphism on homocysteine synthesis in healthy young women. FASEB J. 17: A308 (abstr. 191.4).


Progress 10/01/01 to 10/01/02

Outputs
Marginal deficiency of folate is associated with elevated plasma homocysteine concentration, particular in people who have the T/T genotype of the common C677T genetic polymorphism of methylenetetrahydrofolate reductase (MTHFR). This implies that there is a metabolic interaction of the effects of folate nutritional status and this genetic polymorphism. We have undertaken a study with the objective of determining the effect of folate deficiency, MTHFR genotype, and their interaction on the in vivo rate of key reactions of human one-carbon metabolism. Specifically, this study involves the use of an intravenous infusion with stable isotopically labeled tracers to permit in vivo measurement of the rate of homocysteine remethylation, generation of one-carbon units from serine, purine synthesis and thymidylate synthesis, and protein turnover. Human female subjects (n=10 wild type genotype C/C and n=10 T/T) have been enrolled in this protocol. Rates of in vivo metabolic reactions have been determined by this infusion procedure initially (while each subject is in adequate folate status) then again following a 7-week controlled low-folate diet. Initial analysis has shown that in vivo kinetics can be measured with high precision. Although the analysis of data has not yet been completed, initial findings suggest that serine provides about 45-50% of the carbons used to remethylate homocysteine. In addition, subjects with the T/T MTHFR genotype did not exhibit a reduction in serine-dependent remethylation flux nor did they exhibit any reduction in total remethylation flux regardless of folate status. We also examined the relative rate of synthesis of thymidylate, purines and methylcytosine by analysis of DNA from isolated peripheral blood monocytes. Subjects with the T/T MTHFR genotype exhibited higher relative rates of thymidylate synthesis. This is consistent with epidemiological evidence that the T/T genotype is protective against certain cancers, possibly by promoting DNA repair processes.

Impacts
This work is leading to an improved understanding of the independent effects and interactions of folate nutrition and a common genetic polymorphism on human homocysteine metabolism. A long term outcome will be improved understanding of the nutritional requirement for folate, especially with respect to the effects of genetics on the requirement.

Publications

  • Caudill, M.A., Bailey, L.B. & Gregory, J.F. 2002. Consumption of the folate breakdown product para-aminobenzoylglutamate contributes minimally to urinary folate catabolite excretion in humans: Investigation using [13C5]para-aminobenzoylglutamate. J. Nutr. 132:2613-2616.
  • Chapman, C., Bailey, L.B., Gregory, J.F., Maneval, D., Theriaque, D.W., Pagan, K., and Kauwell, G.P.A. 2002. Effect of C677T methylenetetrahydrofolate reductase polymorphism on folate status response to controlled folate intake in nonpregnant women. FASEB J. 16: A268 (217.13).
  • Davis, S, Stacpoole, P.W., Bailey, L.B., Gregory, J.F. 2002. The effect of dietary folate depletion on homocysteine remethylation kinetics in healthy young women who are unaffected by the C677T mutation of the methylenetetraydrofolate reductase gene. FASEB J. 16: A747 (abstr. 568.7).
  • Bailey, L.B., Duhaney, R., Kauwell, G.P.A., Maneval, D., Hutson, A., Davis, S., Quinlivan, E., Gregory, J.F. 2002. Plasma homocysteine association with vitamin B12 and folate status in young women with combined polymorphisms (C677T/A1298C) of the methylenetetrahydrofolate reductase (MTHFR) gene. FASEB J. 16: A268 (abstr. 217.9).
  • Davis, S.R., Quinlivan, E.P., Stacpoole, P.W., Bailey, L.B., Gregory, J.F. 2002. The effects of folate depletion and the C677T methylenetetrahydrofolate reductase genotype on homocysteine remethylation rates in healthy young females. FASEB Summer Research Conference on Folate, Vitamin B12 and One-Carbon Metabolism, Snowmass Village, CO, Aug. 3-8, 2002.
  • Quinlivan, E.P., Davis, S.R., Henderson, G.N., Bailey, L.B., Stacpoole, P.W., Shane, B., Gregory, J.F. 2002. Stable isotopic investigation of 1C partitioning into thymidylate and purine synthesis in humans: effects of C677T polymorphism and folate status. FASEB Summer Research Conference on Folate, Vitamin B12 and One-Carbon Metabolism, Snowmass Village, CO, Aug. 3-8, 2002.
  • Gregory, J.F. and Quinlivan, E.P. (2002) Kinetics of folate metabolism. Chapter in: Annual Review of Nutrition. (D.B. McCormick, ed.), Annual Reviews, Inc., Palo Alto, CA, Volume 22, pp. 199-220.
  • Bailey, L.B., Duhaney, R.L., Maneval, D.R., Kauwell, G.P.A., Quinlivan, E.P., Davis, S.R., Cuadras, A., Hutson, A.D. & Gregory, J.F. 2002. Vitamin B12 status is inversely associated with plasma homocysteine in young women with C677T and/or A1298C methylenetetrahydrofolate reductase polymorphisms. J. Nutr. 132: 1872-1878.


Progress 10/01/00 to 10/01/01

Outputs
Marginal deficiency of folate is associated with elevated plasma homocysteine concentration, particular in people who have the T/T genotype of the common C677T genetic polymorphism of methylenetetrahydrofolate reductase (MTHFR). This implies that there is a metabolic interaction of the effects of folate nutritional status and this genetic polymorphism. We have undertaken a study with the objective of determining the effect of folate deficiency, MTHFR genotype, and their interaction on the in vivo rate of key reactions of human one-carbon metabolism. Specifically, this study involves the use of an intravenous infusion with stable isotopically labeled tracers to permit in vivo measurement of the rate of homocysteine remethylation, generation of one-carbon units from serine, purine synthesis and thymidylate synthesis, and protein turnover. Human female subjects (n=10 wild type genotype C/C and n=10 T/T) have been enrolled in this protocol. Rates of in vivo metabolic reactions have been determined by this infusion procedure initially (while each subject is in adequate folate status) then again following a 7-week controlled low-folate diet. Initial analysis has shown that in vivo kinetics can be measured with high precision. Conclusions regarding nutritional and genetic effects will require completion of analyses that are in progress.

Impacts
This study will yield new insight into the metabolic consequences of a gene-nutrient interaction that has documented importance to human health. The experimental methods developed for in vivo metabolic studies in this research may also lead to better techniques of nutritional assessment.

Publications

  • Gregory, J.F. (2001). Case study: Folate bioavailability. J. Nutr. 131: 1376S-1382S. (NIH- Office of Dietary Supplements Workshop/Conference on Bioavailability)
  • Bailey, L.B., Moyers, S., and Gregory, J.F. (2001) Folate. Chapter in: Present Knowledge in Nutrition, 8th Ed. (B.A. Bowman and R. M. Russell, eds.). ILSI Press, Washington, D.C, pp. 214-229.
  • Gregory, J.F., Caudill, M.A., Opalko, F.J. and Bailey, L.B. (2001) Kinetics of folate turnover in pregnant women and nonpregnant controls during folic acid supplementation: stable-isotopic labeling of plasma folate, urinary folate and folate catabolites shows subtle effects of pregnancy on turnover of folate pools. J. Nutr. 131:1928-1937.
  • Cuskelly, G.J., Stacpoole, P.W., Williamson, J., Baumgartner, T.G., and Gregory, J.F. (2001) Deficiencies of folate and vitamin B6 exert distinct effects on homocysteine, serine and methionine kinetics. Am. J. Physiol. (Endocrinol. and Metabolism) 281: E1182-E1190.
  • Brockman, T.A., Cuskelly, G.J., Stacpoole, P.W., Williamson, J. and Gregory, J.F. 2001. In vivo kinetics of homocysteine remethylation in adequately nourished, folate-deficient, and vitamin B6-deficient human subjects. FASEB J. 15:A612.