Investigation of protective effect of metformin in noise-related ototoxicity

Noise-induced hearing loss is one of major causes of hearing loss in the adult population. Reactive oxygen levels increases in cochlea after noise and cochlear blood flow is impaired. The protective effects of many antioxidant treatments were determined in noise-induced hearing loss. Besides being effective and safe diabetes drug metformin has also antioxidant, and neuroprotective effect. This study tested protection of metformin against noise induced ototoxicity as an in vivo controlled experimental animal study. This study was approved by Başkent University Medical and Health Sciences Research Committee and was carried out in animal laboratory of Baskent University. Twenty four rats were included in the study; groups were set as: the first group was exposed to noise, the second group received metformin, the third group was exposed to noise and received metformin, the fourth group control group. After baseline DPOAE and ABR measurements of all rats, metformin group (group 2) and metformin + noise group (group 3) received 300 mg/kg metformin (Glucophage®) treatment dissolved in saline as single dose in a day by using gavage for 10 days. Noise group (group 1) and metformin + noise group (group 3) were exposed to 105 dB SPL white noise for 15 hours at 11th day. DPOAE and ABR measurements of the rats in all groups were repeated at 1st, 7th, 21st days after noise exposure. The rats in 2nd and 3rd groups continued to receive metformin treatment for 31 days until the end of the study. At the first day after noise exposure, ABR thresholds and DPOAE measurements were deteriorated in 1st and 3rd groups, deterioration continued at 7th and 21st days in the first group, deterioration returned to normal at 7th day in the third group. There were no changes in ABR thresholds and DPOAE measurements with metformin treatment in metformin group. As a result, it was found that metformin has therapeutic effect on noise-induced ototoxicity in rats. Metformin can be used as an alternative treatment of noise induced hearing loss.