Analysis of inner ear potassium recycling genes as potential factors associated with tinnitus
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Department of Audiology and Phoniatrics, Nofer Institute of Occupational Medicine, Łódź, Poland
Department of Audiology and Phoniatrics, Nofer Institute of Occupational Medicine, św. Teresy 8, 91-348, Łódź, Poland
Department of Medical Genetics, University of Antwerp, Antwerp, Belgium
Int J Occup Med Environ Health 2012;25(4):356–364
Tinnitus is defi ned as a perception of sound in the absence of an external acoustic stimulus. Several factors are known to infl uence tinnitus, e.g. hearing loss, noise exposure, age, and hypertension. As only certain individuals develop tinnitus in the presence of the above risks and in approximately 50% of cases tinnitus is not attributed to any particular cause, the question arose whether this inter-individual susceptibility to tinnitus could be explained by the infl uence of genetic factors. Objectives: To test the hypothesis that genetic variability in genes of the potassium recycling pathway is associated with increased susceptibility to tinnitus. Materials and Methods: The study group consisted of 626 subjects exposed to occupational noise (128 with tinnitus and 498 without tinnitus). 99 single nucleotide polymorphisms were investigated in 10 genes involved in the potassium recycling pathway in the inner ear, previously selected as putative noise-induced hearing loss (NIHL) candidate genes. Results: Nominally signifi cant associations were obtained for 2 variants in KCNE1 (potassium voltage-gated channel, Isk-related family, member 1) and SLC12A2 (solute carrier family 12, member 2) genes. The first gene contributed to tinnitus that developed independently of hearing loss, while the second one was associated with increased susceptibility to noise-induced hearing loss. Conclusions: Present fi ndings lend support to the notion of potassium recycling pathway genes as possible risk modifi ers of tinnitus in individuals with and without hearing loss. Due to the lack of replication in other independent populations these results should be seen as suggestive.