Influences of Diabetes on Hearing Recovery in Noise-Exposed Mice

BACKGROUND AND OBJECTIVES: Many studies have reported an association between diabetes and hearing loss. However, these reports were mainly abstractive correlations between common hearing loss and the incidence of diabetes. Therefore, we evaluated the impact of diabetes on the occurrence of and recovery from noise-induced hearing loss. MATERIALS AND METHODS: We used 5-week-old C57BLKS/J-m wild type (+/+) and C57BLKS/J-db/db male mice as the control and diabetic groups, respectively. In one set of experiments, the hearing levels of control and diabetic mice were measured weekly for 7 weeks. In a second set of experiments, control and diabetic mice were exposed to broadband white noise of 110 dB SPL for 3 hours; hearing levels were analyzed before and immediately after exposure, 1, 3, and 5 days, and 1, 2, 3, and 4 weeks after the noise exposure. RESULTS: The hearing levels of the control group were better than those of the diabetic group at each weekly revision for 7 weeks at all auditory brainstem response frequencies (4, 8, 16, and 32 kHz). After noise exposure, both groups of mice showed an immediate increase in the hearing level threshold at all frequencies. Subsequent threshold recovery was seen in both groups with no difference in the hearing level recovery rates between the two groups. CONCLUSIONS: Hearing level with aging becomes significantly impaired earlier in diabetic mice but hearing recovery after noise exposure is similar between diabetic and control mice.