Interactions of 5'-UTR thymidylate synthase polymorphism with 677C → T methylene tetrahydrofolate reductase and 66A → G methyltetrahydrofolate homocysteine methyl-transferase reductase polymorphisms determine susceptibility to coronary artery disease.
OBJECTIVE
The current study aimed to address the inconsistencies in association studies, specifically with reference to methylene tetrahydrofolate reductase (MTHFR) C677T polymorphism in the light of gene-gene and gene-nutrient interactions.


METHODS
A case-control study was conducted to analyze four genetic polymorphisms i.e. thymidylate synthase (TYMS) 5'-UTR 28 bp tandem repeat, MTHFR C677T, methyltetrahydrofolate homocysteine methyltransferase (MTR) A2756G, methyltetrahydrofolate homocysteine methyltransferase reductase (MTRR) A66G using PCR-AFLP and PCR-RFLP methods; plasma folate and B12 using AxSYM kits; plasma homocysteine by reverse phase HPLC and nitric oxide using Griess reaction. Fisher's exact test, logistic regression analysis and multifactor dimensionality reduction analysis were used for statistical analysis of genetic parameters. Student's t-test was used for biochemical parameters.


RESULTS
MTHFR C677T and MTRR A66G were found to increase the risk for CAD by 1.61-fold (95% CI: 1.04-2.50) and 1.92-fold (95% CI: 1.29-2.87) whereas TYMS 2R allele was found to reduce the risk for CAD (OR: 0.66, 95% CI: 0.49-0.88) by counteracting MTHFR and MTRR variant alleles. Significant gene-gene interactions were observed among TYMS/MTRR (P < 0.0001), MTR/TYMS/MTRR (P < 0.0001), and MTHFR/MTR/TYMS/MTRR (P < 0.0001). MTHFR was found to increase the risk (OR: 2.36, 95% CI: 1.28-4.37) only in the absence of the TYMS 2R allele, with marked impairment of the remethylation process (P = 0.007). This impairment was predominant when the dietary folate was in the lowest tertile. In subjects with dietary folate intake in the highest tertile, no such impairment was observed.


CONCLUSIONS
Dietary folate status and TYMS 5'-UTR 28bp tandem repeat polymorphism are important effect modifiers of CAD risk associated with genetic variants in remethylating genes.
Vijaya Lakshmi
Sana Venkata
SV
Department of Clinical Pharmacology & Therapeutics, Nizam's Institute of Medical Sciences, Andhra Pradesh, India. vijaykutala@gmail.com
Naushad
Shaik Mahammad
SM
Rupasree
Yedluri
Y
Seshagiri Rao
Damera
D
Kutala
Vijay Kumar
VK
D020121:5' Untranslated Regions; D013766:5-Methyltetrahydrofolate-Homocysteine S-Methyltransferase / Q000235:genetics*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001483:Base Sequence; D003324:Coronary Artery Disease / Q000201:enzymology / Q000235:genetics*; D017931:DNA Primers; D005260:Female; D020022:Genetic Predisposition to Disease; D006801:Humans; D008297:Male; D042965:Methylenetetrahydrofolate Reductase (NADPH2) / Q000235:genetics*; D008875:Middle Aged; D016133:Polymerase Chain Reaction; D011110:Polymorphism, Genetic; D012150:Polymorphism, Restriction Fragment Length; D013940:Thymidylate Synthase / Q000235:genetics*
D020121:5' Untranslated Regions; D017931:DNA Primers; D042965:Methylenetetrahydrofolate Reductase (NADPH2); D013766:5-Methyltetrahydrofolate-Homocysteine S-Methyltransferase; D013940:Thymidylate Synthase