Characteristics of hearing loss in diabetic fat rats

HUANG Guowei; LI Guoqing; YAN Xiaoju; LV Ping; LI Huan; LIU Chen; GUO Weiwei; YANG Shiming; YU Ning

doi:10.3969/j.issn.1672-2922.2016.06.022

Abstract：Objective To study the characteristics of early stage hearing loss in rats with primary diabetes. Methods Zucker diabetic fat (ZDF) rats (7 weeks old) were divided into a diabetes/obesity group (fa/fa, n=10) and a control group (fa/+, n=5). The rats were weighed and fasting blood-glucose tested. Auditory brainstem responses were tested using clicks (Click-ABR) and tone burst (tb-ABR), together with distortion product otoacoustic emissions (DPOAEs), at 1, 2, 4 and 6 month. Results In rats in the diabetes obesity group, 12 hours fasting blood-glucose was within normal range in the first 2 months, but elevated to diabetes diagnosis levels and maintained at a high level after 3 months, while fasting blood-glucose remained in the normal range in control rats. In rats with rapidly rising fasting blood-glucose levels, tb–ABR thresholds at 8000 Hz were higher at 4 months than at 2 months (P<0.05), with wave I latency and I-III interval of Click-ABRs (90 dB SPL) prolonged compared to at 2 months (P<0.05). Interestingly, these animals showed shorter wave I latency and I-III in-tervals after 4 months. Rats in the diabetes/obesity group with slowly rising fasting blood-glucose showed higher tb-ABR thresholds at 8, 16 and 32 kHz at 5 months than at 2 months (P< 0.05), especially at 32 kHz. Hearing levels in control group rats showed no significant change before and after the study (P>0.05). Conclusion There is no obvious change in ABR thresholds in ZDF rats in the early stage (2- 3 months). They begin to show hearing impairment when they are 4-5 months old. The rate of hearing loss in diabetic rats may be associated with the speed of blood glucose raising. Hearing loss at high frequencies in diabetic rats indicates the need to monitor high frequency hearing change in diabetic patients as soon as possible.