The Correlation Between The Single Necleotide Polymorphism Of MTHFR And Outcomes Of Methotrexate In The Treatment Of Rheumatoid Arthritis

Background Methotrexate (MTX) is the most commonly used disease modifying anti-rheumatic drug (DMARD) for rheumatoid arthritis (RA) and other inflammatory autoimmune diseases. It is able to reduce disease activity and delay or stabilize the development of bone erosions. While 45%~65% of the patients experience good clinical response, 10%~30% discontinue this therapy due to adverse effects. Although the precise mechanism of MTX is unknown, it is believed to be related to the inhibition of folate pathway enzymes, such as dihydrofolate reductase (DHFR), methylenetetrahydrofolate reductase (MTHFR) and thymidylate synthase (TYMS). Human MTHFR gene locates on 1p36.3 and the coding region is 1980bp, including 11 exons and 10 introns. To date, several single-nucleotide polymorphism (SNPs) of MTHFR gene have been identified: rs1801133C/T, rs1801131A/C, rs2274976A/G, rs2066462C/T and rs4846051C/T, etc. The most studied two SNPs were rs1801133C/T and rs1801131A/C. Currently, the reports about the associations between these SNPs and MTX related adverse effects (AEs) and clinical responses are controversial. These discrepancies may be related to factors such as race difference, region and latitude, polygenic inheritance, sample size and methods. The aim of this study was, therefore, to determine whether MTHFR rs1801133C/T, rs1801131A/C, rs2274976A/G, rs2066462C/T SNPs are associated with MTX related clinical response and AEs in RA patients of Chinese Han people from Anhui Province. The distribution of the four SNPs in RA patients compared with healthy control group was also investigated. We hope the research may help to support a good method for predicting the MTX related AEs and clinical response.Objectives To investigate the distribution of MTHFR rs1801133C/T, rs1801131A/C, rs2274976A/G, rs2066462C/T SNPs in RA patients and the healthy control group of Chinese Han people from Anhui Province. And also to determine whether the distribution of the four SNPs are associated with MTX related clinical response and AEs in RA patients.Methods One hundred and ten RA patients (joint function: II～III) with active disease according to American College of Rheumatology (ACR) revised criteria were recruited and 180 healthy controls were involved in this study. The RA patients and healthy controls are all the Chinese Han people from Anhui Province. All the RA patients were treated with the low-dose MTX (10-15mg/week) without concomitant other DMARDs. Clinical outcomes and laboratory markers were evaluated at 0, 12, 24 weeks to determine the response of MTX (ACR20) and MTX related AEs. The genotypes of MTHFR rs1801133C/T, rs1801131A/C, rs2274976A/G and rs2066462C/T were detected by Real-time fluorescent quantitative PCR. To compare the distribution difference of the four SNPs between RA group and control group. And to investigate the correlation between the distribution of the four SNPs and MTX related clinical response and AEs in RA patients.Results1. There was no significant difference in allele frequencies of the four SNPs between RA group and the control group (46.43% vs 45.71%, 17.02% vs16.29 %, 9.47% vs 10.11%, 6.84% vs 5.93%, P>0.05).2. Among the RA patients, the allele frequency of rs1801131C in the response group was higher than in the non-response group (20.97% vs 8.06%, p<0.05, OR=3.02, 95%CI: 1.10-8.31). The patient with CC or AC genotype can get better clinical response than the patient with AA genotype.3. The allele frequency of rs1801133T was higher in the group with AEs than the group without AEs (56.38% vs 37.50%, P<0.05, OR=2.15, 95%CI: 1.21-3.85). The patient with CT or TT genotype may have more risk of AEs than the patient with CC genotype.4. The allele frequency of rs2274976A was higher in the group with AEs than the group without AEs (14.89% vs 4.17%, P<0.05, OR=4.02, 95%CI: 1.27-12.72). The patient with AG genotype may have more risk of AEs than the patient with GG genotype.5. The haplotype frequency of T-A was higher in the group with AEs than the group without AEs. And the haplotype frequency of C-G was lower in the group with AEs than the group without AEs. While there was no significant difference in the haplotype frequency of C-A or T-G between the group with AEs and the group without AEs.6. There was no correlation between the allele frequency of rs2066462T and the treatment outcomes of MTX (P>0.05).Conclusion1. There was no significant difference in allele frequencies of the four SNPs between RA group and the control group. Maybe there was no relationship between the four SNPs and the pathogenesy of RA.2. The rs1801131A/C SNP was associated with MTX related clinical response in RA patients. The patient with CC or AC genotype can get better clinical response than the patient with AA genotype.3. The rs1801133C/T and rs2274976A/G SNPs were associated with MTX related AEs in the treatment of RA. The patient with CT or TT genotype of rs1801133C/T may have more risk of AEs than the patient with CC genotype. The haplotype T-A may increase the risk of MTX related AEs, while the haplotype C-G may decrease the risk.4. There was no correlation between the rs2066462C/T SNP and the treatment outcomes of MTX.