Objectives: The purpose of this study was to determine the genotype/allele frequencies of C677T and A1298C polymorphisms of methylenetetrahydrofolate (MTHFR) gene in Jordanian rheumatoid arthritis (RA) patients. In addition, the association between MTHFR gene C677T and A1298C polymorphisms and response to and toxicity of methotrexate (MTX) was evaluated.
Methods: 159 adult rheumatoid arthritis ent Rheumatology Clinic at The Jordan University Hospital, between December, 2011 and April, 2012 were recruited into the study. Genomic DNA was extracted from leukocytes using Wizard Genomic DNA extraction Kit. The DNA extracts were amplified by polymerase chain reaction (PCR), and the PCR products were subjected to restriction enzymes to identify the C677T and A1298C genotypes. Genotype frequencies were identified and their relationship to some measures of MTX response and toxicity were evaluated.
Results: The 677 TT genotype frequency was higher in RA patients (15.1%) compared to the healthy control group (5.9%) (odds ratio 3.09, 95% confidence interval (CI) 1.39-6.87, p-value=0.0056). No such differences were seen with the A1298C genotypes. The frequencies of 677T and 1298C variant alleles were 0.346 and 0.296, respectively. None of the change-in-disease-activity measurements in MTX-treated patients has a significant association with the various genotypes. There was no significant association between A1298C genotypes and "any MTX toxicity", but there was an association between C677T polymorphism and "any MTX toxicity" (p=0.037). In addition, there was no association between both SNPs and specific MTX adverse effects. However, some haplotypes or combinations of the C677T and A1298C genotypes were associated with certain MTX side effects.
Conclusions: More data from a larger number of RA patients are needed to evaluate the role of pharmacogenetic studies of MTHFR gene in predicting MTX response and toxicity.