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High Blood Glucose Levels Affect Auditory Brainstem Responses after Acoustic Overexposure in Rats
Jae-Hun Lee1,2, Sang Hee Ji3, Jae Yun Jung1,2
1Beckman Laser Institute Korea, College of Medicine, Dankook University, Cheonan, Republic of Korea.
Audiology & Neuro-Otology
|March 18, 2021
Summary
Diabetes mellitus (DM) in rats impacts hearing function, increasing auditory nerve responses and synapses. Diabetic rats showed altered hearing recovery and synaptic changes after noise exposure.
Area of Science:
- Oto-neurology
- Endocrinology
- Auditory Neuroscience
Background:
- Diabetes mellitus (DM) is a systemic metabolic disorder characterized by hyperglycemia.
- DM is linked to various pathological changes, including hearing dysfunction.
- Inner hair cell (IHC) synaptic integrity is crucial for auditory signal transmission.
Purpose of the Study:
- To investigate hearing function and IHC synaptic changes in rats with streptozotocin (STZ)-induced diabetes.
- To assess the impact of noise exposure on hearing in diabetic rats.
- To explore the relationship between hyperglycemia and auditory system alterations.
Main Methods:
- Diabetes was induced in rats using streptozotocin (STZ).
- Diabetic rats were exposed to narrow-band noise (105 dB SPL) for 2 hours.
- Hearing function (threshold, auditory brainstem response peak 1 amplitude) and IHC synapses were evaluated at various time points.
Main Results:
- Elevated peak 1 amplitudes at 4 kHz and higher frequencies (16, 32 kHz) were observed in diabetic rats compared to controls.
- Hearing threshold recovery was impaired in diabetic rats following noise exposure.
- Histological analysis revealed increased synaptic density in the 16 kHz region in long-term diabetic rats.
Conclusions:
- Hyperglycemia in DM elevates auditory nerve responses (peak 1 amplitude) without altering hearing thresholds.
- Diabetic rats exhibited reduced resilience to hearing threshold changes and were less vulnerable to peak 1 amplitude and synaptic damage post-noise exposure.
- DM induces distinct changes in auditory function and IHC synaptic structure, potentially offering a protective effect against certain noise-induced auditory damages.
