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

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posted on 2018-06-29, 10:39 authored by Nobutaka Ohgami, Xiang Li, Ichiro Yajima, Reina Oshino, Kyoko Ohgami, Yoko Kato, Nazmul Ahsan, Anwarul Azim Akhand, Masashi Kato

Purpose: Elevated hearing thresholds from high frequencies are known to be one of the hallmarks of age-related hearing loss. Our recent study 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, we evaluated Mn in non-invasive biological samples as a possible biomarker for hearing loss in humans.

Materials and methods: We determined hearing levels 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.

Results: 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, our experimental study showed a significant correlation between Mn levels in inner ears and nails, but not hair, in mice orally exposed to Mn.

Conclusions: The results provide novel evidence that Mn in toenails is a possible biomarker for hearing loss at high frequencies in humans.

Funding

This study was supported in part by Grants-in-Aid for Scientific Research on Innovative Areas (24108001 and 16H01639), Scientific Research (A) (15H01743 and 15H02588), (B) (16H02962, 17KT0033) and (C) (16K08343) and Grant-in-Aid for Challenging Exploratory Research (26670525) from the Ministry of Education, Culture, Sports, Science and Technology (MEXT), the Japan Health Foundation, the Mitsui & Co., Ltd. Environment Fund, Foundation from Center for Advanced Medical and Clinical Research Nagoya University Hospital, the Mitsubishi Foundation, AEON Environmental Foundation, Nagono Medical Foundation, The Salt Science Research Foundation and Grant for Environmental Research Projects from the Sumitomo Foundation. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

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