Previous studies have suggested that disruptions or deficiencies in folate metabolism increases, and that folate supplementation may reduce, the risk of cardiovascular disease, neural tube defects (NTDs), and cancer. Much of this effect is associated with the homocysteine (Hcy) lowering ability of folate supplementation. In recent years, the contribution of several enzymes involved in folate metabolism, essential to folate-mediated disease states, have begun to be recognized. A key enzyme is MTHFR, which catalyzes the reduction of 5,10-methylenetetrahyrdrofolate. Current understanding of effects of enzyme variants on the in vivo behavior of folate metabolism is still elementary. A first step in understanding the pharmacogenomics of folate/Hcy metabolism is to quantify the in vivo kinetics of folate pools in the context of MTHFR and other genetic variants. Testing system function is best accomplished using in vivo tracer methodologies that have sufficient analytical precision to detect differential metabolism under normal physiological conditions. 14C-labeled substrates coupled with Accelerator Mass Spectrometry (AMS) detection have the sensitivity and specificity to reveal differential metabolism at true tracer (nearly massless) doses that do not disturb or saturate normal enzymatic processes. Our long-range goal, is to establish the basis for the individual response (metabolic phenotyping) to folic acid in the context of genetic variants under normal and pathological conditions. As our next objective in pursuit of this goal, we propose to determine the in vivo kinetic of folic acid in individuals with respect to two variants of MTHFR (C677T & A1298C), MS A2756G, and methionine synthase reductase (MTRR) A66G. Our central hypothesis is that homozygotes for either MTHFR 677 and 1298 (or compound heterzygotes), MS and MTRR (or compound heterozygotes) display altered kinetic behavior and hence altered distribution of folate pools and forms available for normal metabolism. To accomplish the objectives of this application, we will pursue three specific aims: we will screen and stratify about 400 normal premenopausal women and men for MTHFR and MS and MTRR genotypes. We will determine the in vivo kinetic behavior of a tracer dose of folate in blood, urine, and stool. We will then compare the behavior of folate metabolism (functional endpoint) among the various genotypes.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
2R01DK045939-06
Application #
6544887
Study Section
Nutrition Study Section (NTN)
Program Officer
May, Michael K
Project Start
1997-01-01
Project End
2006-06-30
Budget Start
2002-09-01
Budget End
2003-06-30
Support Year
6
Fiscal Year
2002
Total Cost
$324,844
Indirect Cost
Name
University of California Davis
Department
Nutrition
Type
Schools of Earth Sciences/Natur
DUNS #
094878337
City
Davis
State
CA
Country
United States
Zip Code
95618
Clifford, Andrew J; Rincon, Gonzalo; Owens, Janel E et al. (2013) Single nucleotide polymorphisms in CETP, SLC46A1, SLC19A1, CD36, BCMO1, APOA5, and ABCA1 are significant predictors of plasma HDL in healthy adults. Lipids Health Dis 12:66
Clifford, Andrew J; Chen, Kehui; McWade, Laura et al. (2012) Gender and single nucleotide polymorphisms in MTHFR, BHMT, SPTLC1, CRBP2, CETP, and SCARB1 are significant predictors of plasma homocysteine normalized by RBC folate in healthy adults. J Nutr 142:1764-71
Kim, Seung-Hyun; Chuang, Jennifer C; Kelly, Peter B et al. (2011) Carbon isotopes profiles of human whole blood, plasma, red blood cells, urine and feces for biological/biomedical 14C-accelerator mass spectrometry applications. Anal Chem 83:3312-8
Kim, Seung-Hyun; Kelly, Peter B; Clifford, Andrew J (2010) Calculating radiation exposures during use of (14)C-labeled nutrients, food components, and biopharmaceuticals to quantify metabolic behavior in humans. J Agric Food Chem 58:4632-7
Kim, Seung-Hyun; Kelly, Peter B; Ortalan, Volkan et al. (2010) Quality of graphite target for biological/biomedical/environmental applications of 14C-accelerator mass spectrometry. Anal Chem 82:2243-52
Kim, Seung-Hyun; Kelly, Peter B; Clifford, Andrew J (2009) Accelerator mass spectrometry targets of submilligram carbonaceous samples using the high-throughput Zn reduction method. Anal Chem 81:5949-54
Ho, Charlene C; de Moura, Fabiana F; Kim, Seung-Hyun et al. (2009) A minute dose of 14C-{beta}-carotene is absorbed and converted to retinoids in humans. J Nutr 139:1480-6
Kim, Seung-Hyun; Kelly, Peter B; Clifford, Andrew J (2008) Biological/biomedical accelerator mass spectrometry targets. 1. optimizing the CO2 reduction step using zinc dust. Anal Chem 80:7651-60
Kim, Seung-Hyun; Kelly, Peter B; Clifford, Andrew J (2008) Biological/biomedical accelerator mass spectrometry targets. 2. Physical, morphological, and structural characteristics. Anal Chem 80:7661-9
Owens, Janel E; Holstege, Dirk M; Clifford, Andrew J (2005) Quantitation of total folate in whole blood using LC-MS/MS. J Agric Food Chem 53:7390-4

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