08-26-2023

Common supplements can combat age-related hearing loss

Earth.com staff writer

Age-related hearing loss is a common ailment that affects millions of people worldwide. Researchers from various institutions in Argentina have recently published a study in the open access journal PLOS Biology, which suggests that common supplements containing phytosterols might help in reducing natural hearing loss associated with aging.

The study was led by María Eugenia Gomez-Casati from the University of Buenos Aires-CONICET, Mauricio Martin from the Institute of Medical Research Mercedes, and Martín Ferreyra from INIMEC-CONICET-UNC, National University of Córdoba.

The results demonstrate the connection between the decrease of cholesterol in the inner ear and sensory dysfunction in mice.

Focus of the study

The inner ear consists of sensory cells called outer hair cells (OHCs) that play a crucial role in amplifying sounds by changing their length.

As individuals age, these cells lose their ability to stretch in response to sound, thereby preventing sound amplification and ultimately leading to age-related hearing loss.

Brain cholesterol

Cholesterol is a key component in the stretch response of OHCs. Recent studies have shown a decrease in brain cholesterol with age, leading the researchers to theorize that hearing loss might be related to the loss of cholesterol in OHCs.

To test this hypothesis, experiments were conducted on mice. The team of researchers began by measuring the levels of CYP46A1, an enzyme involved in breaking down and recycling cholesterol, in the inner ear OHCs of mice.

As anticipated, the experts found higher levels of CYP46A1 in the inner ears of older mice compared to younger ones, resulting in less cholesterol.

How the research was conducted

To establish a cause-and-effect relationship, the researchers induced hearing loss in young mice by over-activating CYP46A1 with a drug, which led to abnormal inner ear-cell output.

Following this, they tested whether increasing cholesterol in the brain could counter the effects of the drug.

Since cholesterol cannot directly enter the brain from the blood, the researchers used plant-based cholesterol-like compounds called phytosterols, which can cross the blood-brain barrier.

What the study revealed

Young mice treated with both the CYP46A1-activating drug and a three-week regimen of dietary phytosterols displayed improved OHC function.

This discovery is particularly promising as phytosterols are present in many over-the-counter supplements, making them a convenient option to combat age-related hearing loss.

Further research is needed

However, the researchers caution that further testing on older mouse models and humans is necessary before more definitive conclusions can be drawn.

Nonetheless, this study represents a significant step forward in understanding the relationship between cholesterol levels in the inner ear and age-related hearing loss, and opens up new avenues for potential treatments.

The study authors noted: “In the present work we show that: 1) aging triggers cholesterol loss from sensory cells of the inner ear, 2) a retroviral treatment widely employed for HIV/AIDS patients reproduces the cholesterol loss observed in aged individuals and leads to impaired outer hair cells’ function and 3) we found that these defects can be partly reversed by phytosterols supplementation.”

“Our findings are very promising because they provide the first proof-of-principle supporting phytosterols supplementation as a possible approach for prevention or treatment of hearing loss

Age-related hearing loss, also known as presbycusis, is a common condition that affects many people as they get older. It usually occurs gradually over time and can affect one or both ears.

This type of hearing loss is a natural part of the aging process and is one of the most common conditions affecting older adults.

Causes

The exact cause of age-related hearing loss is not entirely clear, but it is believed to be a combination of several factors:

Wear and tear

Years of exposure to loud noises can damage the hair cells in the inner ear, which are responsible for transmitting sound to the brain. These hair cells do not regenerate, so their loss is permanent.

Changes in blood flow

As people age, there can be changes in blood flow to the ear, which may affect hearing.

Changes in the structure of the ear

The structure of the ear changes with age, which can also contribute to hearing loss. For example, the eardrum may become less flexible, making it harder for sounds to pass through.