Manganese in toenails is associated with hearing loss at high frequencies in humans

Elevated hearing thresholds from high frequencies are known to be one of the hallmarks of age-related hearing loss. In a recent study, the authors showed accumulation of manganese (Mn) in inner ears resulting in acceleration of age-related hearing loss in mice orally exposed to Mn. However, there is no evidence showing an association between Mn in non-invasive biological samples and hearing loss in humans evaluated by pure tone audiometry (PTA). In this study, the authors evaluated Mn in non-invasive biological samples as a possible biomarker for hearing loss in humans. Hearing levels were determined by PTA and Mn levels in toenails, hair and urine with an inductively coupled plasma mass spectrometer (ICP-MS) in 145 healthy subjects in Bangladesh. Multivariable analyses showed that Mn levels in toenails, but not in hair and urine samples, were significantly associated with hearing loss at 8?kHz and 12?kHz. Moreover, this experimental study showed a significant correlation between Mn levels in inner ears and nails, but not hair, in mice orally exposed to Mn. The results provide novel evidence that Mn in toenails is a possible biomarker for hearing loss at high frequencies in humans.

Authors: Ohgami N, Li X, Yajima I, Oshino R, Ohgami K, Kato Y, Ahsan N, Akhand AA, Kato M. ; Full Source: Biomarkers. 2018 Apr 10:1-7. doi: 10.1080/1354750X.2018.1458153. [Epub ahead of print]

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