Analysis of inner ear potassium recycling genes as potential factors associated with tinnitus

Tinnitus is defined as a perception of sound in the absence of an external acoustic stimulus. Several factors are known to influence 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 influence of genetic factors.

To test the hypothesis that genetic variability in genes of the potassium recycling pathway is associated with increased susceptibility to tinnitus.

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.

Nominally significant 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.

Present findings lend support to the notion of potassium recycling pathway genes as possible risk modifiers 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.