Unlocking the sound: A popular supplement may combat age-related hearing loss

summary: Researchers have discovered a link between age-related hearing loss and lower inner ear cholesterol. This decrease in cholesterol affects the outer hair cells (OHCs), which are essential for amplifying sounds.

Experiments on mice have indicated that supplementation with phytosterols, which are compounds similar to cholesterol, can replace lost cholesterol and prevent sensory impairment. If applicable to humans, over-the-counter phytosterol supplements may offer a potential solution to combating age-related hearing loss.

Key facts:

  1. Age-related hearing loss may be related to a decrease in cholesterol in the sensory cells of the inner ear.
  2. Cholesterol is vital to the stretch response of OHCs, which amplify sounds.
  3. In mice, plant compounds called phytosterols were effective in replacing lost cholesterol and maintaining OHC function.

source: Plus

Researchers led by María Eugenia Gómez Casati, Institute of Pharmacology, Faculty of Medicine, University of Buenos Aires-CONICET; Mauricio Martin, Mercedes Medical Research Institute; Martin Ferreira (INIMEC-CONICET-UNC), National University of Córdoba in Argentina, reported that age-related hearing loss is associated with lower cholesterol in the inner ear.

Experiments posted on August 24y In Open Access Journal PLoS Biology showed that phytosterol supplementation was able to act in place of the lost cholesterol and prevent sensory dysfunction in mice.

This shows a man using a hearing aid.
Sensory cells in the inner ear called outer hair cells (OHCs) amplify sounds by changing their length. Credit: Neuroscience News

Sensory cells in the inner ear called outer hair cells (OHCs) amplify sounds by changing their length. As we age, these cells lose their ability to stretch in response to sound, which prevents sound amplification and leads to age-related hearing loss.

Because cholesterol is a key player in the response to stretching, and because cholesterol in the brain has recently declined with age, the researchers hypothesized that hearing loss may be related to cholesterol loss in OHCs.

This hypothesis was tested on mice.

First, the researchers measured the amount of CYP46A1 in inner ear OHCs because this enzyme helps break down and recycle cholesterol.

As expected, they found more CYP46A1 in the inner ear of older mice than in younger mice, and thus less cholesterol. Next, they showed cause and effect by inducing hearing loss in young mice, as evidenced by the production of abnormal inner ear cells, by overactivating CYP46A1 with a drug.

Finally, they tested whether increasing cholesterol in the brain could interfere with medication. Since cholesterol itself cannot enter the brain from the blood, the researchers used cholesterol-like plant compounds called phytosterols that can.

Mice given CYP46A1-activating drug and 3 weeks of dietary phytosterols showed improvement in OHC function.

Since phytosterols can be found in many over-the-counter nutritional supplements, they may be a suitable way to combat age-related hearing loss. However, it will be necessary to directly test their effects on hearing loss in old mouse models as well as in humans before more definitive conclusions can be drawn.

The authors add: “In the present work, we show that: 1) aging leads to a loss of cholesterol from sensory cells in the inner ear, and 2) widely used antiretroviral therapy for HIV/AIDS patients reproduces the cholesterol loss observed in individuals.” Elderly and lead to impaired function of the outer hair cells and 3) we found that these deficiencies can be partially reversed by phytosterol supplementation.

“Our findings are very promising because they provide the first evidence of principle supporting phytosterol supplementation as a potential approach for the prevention or treatment of hearing loss.”

About this hearing loss research news

author: Claire Turner
source: Plus
communication: Claire Turner – PLoS
picture: Image credited to Neuroscience News

Original search: open access.
Phytosterols reverse ART-induced hearing loss, with potential effects on cochlear aging.By Sudero AO et al. PLoS Biology

a summary

Phytosterols reverse ART-induced hearing loss, with potential effects on cochlear aging.

Cholesterol contributes to the integrity of the neuronal membrane, supports the assembly and function of membrane proteins, and facilitates proper signal transduction. Extensive evidence has shown that cholesterol imbalances in the central nervous system occur with aging and in the development of neurodegenerative diseases.

In this work, we describe cholesterol homeostasis in the inner ear of young and old mice as a new, unexplored possibility for the prevention and treatment of hearing loss.

Our results show that cholesterol levels in the inner ear decrease during aging, an effect associated with increased expression of cholesterol 24-hydroxylase (CYP46A1), the main enzyme responsible for cholesterol turnover in the brain.

In addition, we show that pharmacological activation of CYP46A1 with the antiretroviral drug efavirenz reduces the cholesterol content of outer hair cells (OHCs), which leads to a decrease in immunolabelling of pristine and leads to an increase in the DPOAEs thresholds. .

Furthermore, dietary supplements containing phytosterols, which are plant sterols with a structure and function similar to cholesterol, were able to rescue the effect of efavirenz administration on auditory function.

Overall, our findings point to the importance of inner ear cholesterol homeostasis as an innovative therapeutic strategy for preventing and/or delaying hearing loss.

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