MTHFR GENE C677T POLYMORPHISM AND LEVELS OF DNA METHYLTRASFERASES IN SUBCLINICAL HYPOTHYROIDISM.

The aim of our study was to investigate the link between MTHFR gene C677T polymorphism and DNMTs levels in patients with Subclinical Hypothyroidism (SCH). In this study 19 adult patients with subclinical hypothyroidism and 19 healthy controls (mean age 31±5.5 and 33±5.1 years respectively) were recruited. All patients were diagnosed based on serum levels of TSH, FT4, anti-TG and anti-TPO antibodies. Written informed consents were obtained from all study subjects. Genomic DNA was extracted using Quick-DNA Universal Kit (Zymo Research, USA). The MTHFR C677T polymorphism was genotyped by PCR-RFLP method. Levels of DNMT1 and 3a were measured in nuclear extracts of PBMC using DNMTs assay kits (Abcam). Our data indicates that the frequency of genotypes and alleles were different among the patient and the control group. There is a significant increase in CC genotype distribution in the control group when compared to the SCH patient group, while the CT as well as TT genotype distribution were not increased significantly in SCH group versus control group. However the C allele is significantly prevalent in the control group compared to the SCH group, while T allele is prevalent in patients compared to the control group with a statically significant difference. In addition, individuals with TT and CT genotypes and hypothyroidism showed elevated amount of DNMT3a in nuclear extracts of PBMC compared with controls, while no significant difference in DNMT1 levels was observed. This study indicates the MTHFR C677T variant may contribute in alteration of epigenetic regulation such as DNA methylation mediated by DNA methyltransferases in patients with subclinical hypothyroidism and also, carriers of the T allele might have an increasing risk of developing SCH.