Abstract
The increasing rate of age-related hearing loss (ARHL), with its subsequent reduction in quality of life and increase in health care costs, requires new therapeutic strategies to reduce and delay its impact. The goal of this study was to determine if ARHL could be reduced in a rat model by administering a combination of antioxidant vitamins A, C, and E acting as free radical scavengers along with Mg++, a known powerful cochlear vasodilator (ACEMg). Toward this goal, young adult, 3 month-old Wistar rats were divided into two groups: one was fed with a diet composed of regular chow (“normal diet,” ND); the other received a diet based on chow enriched in ACEMg (“enhanced diet,” ED). The ED feeding began 10 days before the noise stimulation. Auditory brainstem recordings (ABR) were performed at 0.5, 1, 2, 4, 8, 16, and 32 kHz at 3, 6–8, and 12–14 months of age. No differences were observed at 3 months of age, in both ND and ED animals. At 6–8 and 12–14 months of age there were significant increases in auditory thresholds and a reduction in the wave amplitudes at all frequencies tested, compatible with progressive development of ARHL. However, at 6–8 months threshold shifts in ED rats were significantly lower in low and medium frequencies, and wave amplitudes were significantly larger at all frequencies when compared to ND rats. In the oldest animals, differences in the threshold shift persisted, as well as in the amplitude of the wave II, suggesting a protective effect of ACEMg on auditory function during aging. These findings indicate that oral ACEMg may provide an effective adjuvant therapeutic intervention for the treatment of ARHL, delaying the progression of hearing impairment associated with age.
Highlights
In the three decades the number of people aged 60 or more will rise from 900 million to 2 billion, increasing in global rate from 12 to 22% (World Health Organization, 2017a)
Associated to age-related hearing loss (ARHL) there is a significant reduction in the quality of life at an important humanitarian and socio-economic impact including health care costs (Huang and Tang, 2010; Ciorba et al, 2012; Kidd and Bao, 2012; World Health Organization, 2017b)
Analysis of the Auditory brainstem recordings (ABR) recordings in 3 month-old rats showed that auditory thresholds obtained from animals assigned to ND and ED groups (Figure 1A) were comparable to those reported previously for Wistar rats (Jamesdaniel et al, 2009; Church et al, 2010; Alvarado et al, 2012, 2014, 2016; Pilati et al, 2012; MelgarRojas et al, 2015a)
Summary
In the three decades the number of people aged 60 or more will rise from 900 million to 2 billion, increasing in global rate from 12 to 22% (World Health Organization, 2017a). Associated to ARHL there is a significant reduction in the quality of life at an important humanitarian and socio-economic impact including health care costs (Huang and Tang, 2010; Ciorba et al, 2012; Kidd and Bao, 2012; World Health Organization, 2017b). To date there are no effective medications to cure or prevent ARHL. This is partly due to the fact that the etiopathogenesis of this sensory dysfunction is multifactorial and highly complex and still remains unclear (Huang and Tang, 2010; Fetoni et al, 2011; Yamasoba et al, 2013; Melgar-Rojas et al, 2015b), which limits therapeutic approaches
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