Polymorphisms in folate metabolism genes are associated with susceptibility to presbycusis

Aim: Presbycusis or age related hearing loss is caused by several extrinsic and intrinsic factors that damage the auditory system. Gene polymorphisms in folate metabolism were found to play an important role in the etiology of presbycusis. The present study aimed to investigate the role of 5,10-methylenetetrahydrofolate reductase (MTHFR), methionine synthase (MTR) and thymidylate synthase (TYMS) gene polymorphisms in the onset of presbycusis in a South Indian population. Main methods: A total of 220 subjects confirmed with presbycusis along with 270 age and sex matched healthy controls visiting MAA ENT Hospitals, Hyderabad, India were enrolled for the study. Genotyping of MTHFR C677T (rs180133) and A1298C (rs1801131), MTR A2756G (rs1805087), TSER (rs1801136) and TS1494indel6 bp (rs16430) was carried out using PCR & PCR-RFLP methods. Key findings: The 'TT' genotype of MTHFR C677T and '152 bp/152 bp' genotype of TS1494indel6 bp showed statistically significant risk for presbycusis while CC genotype of MTHFR A1298C, '2R/2R' genotype of TSER at 3'UTR and 6 bp ins/6 bp ins of TYMS at 5'UTR were found to be protective. The T-A-A haplotype combination of MTHFR C677T, MTHFR A1298C and MTR A2756G as well as 3R-152 bp of TYMS at 5'UTR and 3'UTR were also found to contribute significant risk for the onset of presbycusis. Further, the combination of SNP loci TSER: TS1494indel6 bp exhibited moderate linkage in presbycusis. Significance: The present pilot study identified the significant association of gene variants of MTHFR and TYMS with presbycusis. These findings aid in early diagnosis of hearing loss in the elderly population.