Interactions of hearing loss and diabetes mellitus in the middle age CBA/CaJ mouse model of presbycusis

Abstract

Recently, we characterized the more severe nature of hearing loss in aged Type 2 diabetic human subjects. The current study prospectively assessed hearing abilities in middle age CBA/CaJ mice with Type 1 diabetes mellitus (T1DM) (STZ injection) or Type 2 diabetes mellitus (T2DM) (high fat diet), for a period of 6 months. Blood glucose, body weight and auditory tests (Auditory Brainstem Response-ABR, Distortion Product Otoacoustic Emissions-DPOAE) were evaluated at baseline and every 2 months. Tone and broadband noise-burst responses in the inferior colliculus were obtained at 6 months. Body weights of controls did not change over 6 months (~32g), but there was a significant (~5g) decline in the T1DM, while T2DM exhibited ~10g weight gain. Blood glucose levels significantly increased: 3 fold for T1DM, 1.3 fold for T2DM; with no significant changes in controls. ABR threshold elevations were found for both types of diabetes, but were most pronounced in the T2DM, starting as early as 2 months after induction of diabetes. A decline of mean DPOAE amplitudes was observed in both diabetic groups at high frequencies, and for the T2DM at low frequencies. In contrast to ABR thresholds, tone and noise thresholds in the inferior colliculus were lower for both diabetic groups. Induction of diabetes in middle-aged CBA/CaJ mice promotes amplification of age-related peripheral hearing loss which makes it a suitable model for studying the interaction of age-related hearing loss and diabetes. On the other hand, initial results of effects from very high blood glucose level (T1DM) on the auditory midbrain showed disruption of central inhibition, increased response synchrony or enhanced excitation in the inferior colliculus.

A long-term high-fat diet increases oxidative stress, mitochondrial damage and apoptosis in the inner ear of d-galactose-induced aging rats

“…Animals fed a long-term HFD show increased oxidative stress and dysfunctional mitochondria in many organs (Kartha et al, 2008;Bruce et al, 2009;Yokota et al, 2009;Ballal et al, 2010). Although some studies have shown that a higher fat intake was significantly associated with a reduced auditory function (Evans et al, 2006;Vasilyeva et al, 2009;Gopinath et al, 2011;Spankovich et al, 2011) and treatment with statins and consumption of monounsaturated fats may have a beneficial influence (Syka et al, 2007;Gopinath et al, 2011), the mechanisms of auditory dysfunction and the relationship between HFD and aging in the inner ear still remain obscure.…”

Effects of Ageing and Alloxan- Induced Diabetes Mellitus on the Structure of Inferior Colliculus in male Albino Rats: a Light and Electron Microscopic Study

“…Idiopathic sudden hearing loss was also recorded in patients with type 2 diabetes mellitus (Fukui et al, 2004). Vasilyeva et al (2009) assessed the hearing abilities in middle aged mice with type 1 and type 2 diabetes mellitus for a period of 6 months and observed that induction of diabetes promotes amplification of peripheral hearing loss and affected auditory midbrain resulting in disruption of the central inhibition and enhanced excitation in the inferior colliculus.…”

“…Type 2DM is an age-related disorder affecting up to 20 % of the population over age 60 (American Diabetes Association, 2006). An association between diabetes mellitus and hearing loss was proved in humans and experimental animals (Maia & Campos, 2005;Vasilyeva et al, 2009). Many of the diabetic complications in older people are associated with natural aging, but they appear earlier in diabetic patients (Biessels et al, 2002).…”

Insulin Receptor Substrate 2 (IRS2)-Deficient Mice Show Sensorineural Hearing Loss That Is Delayed by Concomitant Protein Tyrosine Phosphatase 1B (PTP1B) Loss of Function

“…Diabetes might affect the vasculature and neural system of the inner ear, leading to hearing impairment that was manifested in around 50% of the diabetic patients studied (44,45). In addition, genetic, pharmacological and nutritional animal models were used to study the effects of type 2 diabetes on hearing (46,47). Vasilyeva et al (47) reported elevation of ABR thresholds as early as 2 months after induction of type 2 diabetes in CBA/CaJ mice.…”