Abstract
Objective:To investigate whether single nucleotide polymorphisms (SNPs) in the Mn-superoxide dismutase gene (SOD2) underlie the susceptibility to noise-induced hearing loss (NIHL).Methods:Audiometric data from 2400 Chinese Han workers who exposed to occupational noise were analyzed. DNA samples were collected from the 10% most susceptible and the 10% most resistant individuals, and five SNPs (SOD2 rs2842980, rs5746136, rs2758331, rs4880 and rs5746092) were genotyped by Taqman SNP Genotyping Kits. The SNP main effects and interactions between noise exposure and SNP were analyzed using logistic regression. Haplotypes were analyzed by using Haploview software.Results:The CT genotype of rs4880 (SOD2 V16A SNP) was associated with a higher risk of NIHL (covariates-adjusted OR, 2.18; 95% CI, 1.34–3.54,P= 0.002). Haplotype analysis revealed that the frequency of AGCCG at the five SNP loci was significantly higher in the susceptible group (P= 0.020). With AGCTG as the reference, the OR (95% CI) was 2.63 (1.14, 6.06). The rs4880 polymorphisms imposed larger effects when the carriers were exposed to higher levels of noise, indicating the interaction between SNP and noise exposure.Conclusions:Our results suggest that SOD2 V16A SNP in the mitochondrial targeting sequence is associated with noise induced hearing loss in Chinese workers, and this effect was enhanced by higher levels of noise exposure.
Highlights
Noise induced hearing loss (NIHL), one of the most prevalent occupational hazards in countries with rapidly growing activity like China, is considered a complex disease caused by gene-environment interactions [1]
The minor allele frequency (MAF) for all SNPs in SOD2 were higher than 5%, indicating that those SNPs were frequent in Chinese Han population
Inconsistent genotypic distributions between the susceptible and the resistant group were found for different noise exposure levels, suggesting that SNP genotypic effects on the susceptibility to noise induced hearing loss were dependent on the environmental noise exposure level and cumulative noise exposure (CNE)
Summary
Noise induced hearing loss (NIHL), one of the most prevalent occupational hazards in countries with rapidly growing activity like China, is considered a complex. Konings et al [20] identified significant associations between CAT SNPs/haplotypes and susceptibility to development of NIHL, but that the effect of CAT polymorphisms can only be detected when noise exposure levels are taken into account. Another study of this group suggested that PCDH15 and MYH14 may be related to NIHL susceptibility in Swedish and Polish sample sets [21], further replication in independent sample sets was mandatory. We performed a stratified analysis per the levels of noise exposure in order to identify the potential gene-environmental interactions between noise and the SOD2 gene
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