Antioxidant-enriched diet does not delay the progression of age-related hearing loss

Abstract

Oxidative stress has been linked to noise- and drug-induced as well as age-related hearing loss. Antioxidants can attenuate the decline of cochlear structure and function after exposure to noise or drugs, but it is debated as to whether they can protect from age-related hearing loss. In a long-term longitudinal study, 10-month old female CBA/J mice were placed on either a control or antioxidant-enriched diet and monitored through 24 months of age. Supplementation with vitamins A, C, and E, L-carnitine and α-lipoic acid significantly increased the antioxidant capacity of inner ear tissues. However, by 24 months of age, the magnitude of hearing loss was equal in both groups. Likewise, there were no significant differences in hair cell loss or degeneration of spiral ganglion cells. We conclude that dietary manipulations can alter cochlear antioxidant capacity but do not ameliorate age-related sensorineural hearing loss in the CBA/J mouse.

Current concepts in age-related hearing loss: Epidemiology and mechanistic pathways

“…When C57BL/6 mice were fed with control diet or diet containing one of 17 antioxidant compounds (acetyl- l -carnitine, α-lipoic acid, carotene, carnosine, coenzyme Q10, curcumin, tocopherol, EGCG, gallic acid, lutein, lycopene, melatonin, poanthocyanidin, quercetin, resveratrol, and tannic acid), AHL was nearly completely prevented by α-lipoic acid and coenzyme Q 10 and partially by N -acetyl- l -cysteine, but not by other compounds (Someya et al, 2009). In CBA/J mice, antioxidant-enriched diet containing vitamins A, C, and E, l -carnitine, and α-lipoic acid given from 10 months through 24 months of age significantly increased the antioxidant capacity of the inner ear tissues but did not ameliorate AHL or loss of the hair cells and spiral ganglion cells (Sha et al, 2012). These findings indicate that supplementation with certain antioxidants can slow AHL in animals but that the effects depends on many factors, including the type and dosage of anti-oxidant compounds, timing and duration of the treatment, species, and strains.…”

Antioxidants and Their Effect on Stress-Induced Pathology in the Inner Ear

“…The authors have examined their fi ndings with exceptional candor. In view of several past studies (some mentioned here as well as those from their own 2010 report) that did show a benefi t from such intervention, the concluding remarks point to that while the authors are not refuting the broad benefi ts of an antioxidant-rich diet on the aging organism, for normally maintained animals (i.e., those with no prior defi ciencies), supplementation was not proven to be effective (Willot and Schacht 2010 ;Sha et al 2012 ). Spankovich and Le Prell have recently made the important analysis of the topic by looking at human subjects in a cross-sectional study utilizing a "healthy eating" index and hearing data in adults with ages between 20 and 69.…”

“…In another interesting study, Heman-Ackah et al have shown that a combination diet with six different antioxidants fed to C57BL/6 mice modeled to have presbycusis, ABR thresholds were decreased compared with controls with a strong statistical effect (Heman-Ackah et al 2010 ). These fi nding have been tempered by the fi ndings from Dr. Schacht's laboratory (Sha et al 2012 ) where CBA/J mice were monitored from young to through 24 months of age with an intervention group maintained on an antioxidant diet (vitamins A, C, and E as well as L -carnitine and α-lipoic acid). These experiments did not show any differences in hearing thresholds between animals that received the supplementation and those who did not.…”

Cellular Mechanisms of Age-Related Hearing Loss

“…Moreover, in C57BL/6 mice supplemented with the mitochondrial antioxidants α-lipoic acid and coenzyme Q 10 , a reversal in ARHL was demonstrated, with lower hair cell and SGN cell death (Someya et al 2009 ). However, 15-, 18-, or 24-month-old Fischer 344 rats treated with L -carnitine with different methods of administration did not show improvement in progression of ARHL , and 10-month-old CBA/J mice supplemented with an antioxidant-enriched diet composed of α-lipoic acid, vitamin A, vitamin C, vitamin E, and L -carnitine showed no delay in the onset of presbycusis or loss of hair cells or SGN at 24 months of age (Sha et al 2012 ). Additional discussion of therapeutics administered to animal subjects is found in Chap.…”