Endocrine Abstracts

Introduction: Methylenetetrahydrofolate reductase (MTHFR) gene C677T polymorphism results in thermolabile, reduced functioning enzyme and predicts hyperhomocisteinemia and altered DNA methylation. On the other hand, several studies indicated a higher plasma homocysteine (Hcy) levels in patients with primary hypothyroidism than in healthy, euthyroid individuals, including some experimental studies that indicated decreased MTHFR activity in hypothyroid patients. We conducted this study to see whether there is an association between MTHFR C677T polymorphism, DNA methylation changes and non-autoimmune hypothyroidism (NAH) in Georgian population.

Materials and methods Study ethical approval was granted by Tbilisi State Medical University ethics committee. Informed written consent was obtained from all participants. Genomic DNA of 93 patients (mean age 51.3 ± 15.17) and 96 healthy controls (mean age 51.6 ± 16.65) were isolated using DNA blood Kit (Qiagen). Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis was used for genotyping MTHFR C677T. DNA samples underwent bisulfite modification (Qiagen) and methylation levels of Alu and LINE-1 were examined by the combined bisulfite restriction analysis-interspersed repetitive sequences (COBRA-IRS).

Results: The present study shows an association of MTHFR C677T polymorphism with NAH as T allele and CT genotype are more prevalent in patients then in control group (OR (CI) 3.75 (1.89 to 7.48), P = 0.0002 and OR(CI) 5.03 (2.87 to 8.83), P < 0.0001 respectively). On the other hand, our results suggest that hypermethylated loci (mCmC) at Alu elements are significantly lower (15%) in study group then in controls (37%) (P < 000.1). As for LINE-1 the hypermethylated loci (mCmC) are also lower in study group (18%) then in controls (27%) (P < 000.1).

Conclusion: The results of this case-control study suggest that the MTHFR C677T variant, was significantly associated with non-autoimmune hypothyroidism in Georgians. Also MTHFR 677TT genotype correlates with hypomethylation of Alu and LINE repetitive sequence in hypothyroid than in euthiroid individuals. All above indicates that C677T polymorphism may predispose development of non-autoimmune hypothyroidism.