Research Suggests Ordinary Supplements Could Mitigate Age-Related Auditory Decline

A team of scientists has uncovered a correlation between the decline in hearing ability due to aging and diminished cholesterol levels in the inner ear. Conducted by María Eugenia Gomez-Casati and her colleagues from the University of Buenos Aires-CONICET’s Institute of Pharmacology, School of Medicine, along with Mauricio Martin from the Institute of Medical Research Mercedes, and Martín Ferreyra from INIMEC-CONICET-UNC, National University of Córdoba, the study suggests that phytosterol supplements could restore lost cholesterol and prevent sensory impairment in mouse models.

Published in the peer-reviewed journal PLOS Biology, the research reveals that the administration of phytosterol supplements successfully substituted for the missing cholesterol, consequently averting sensory malfunctions in mice.

Outer hair cells (OHCs) in the inner ear are responsible for sound amplification and undergo elongation and contraction in response to auditory stimuli. With age, these cells become less flexible, which hampers their sound amplification capabilities and contributes to age-related hearing loss. The researchers posited that this reduced flexibility might be attributable to a cholesterol deficit in the OHCs. This hypothesis was explored through experimentation on mice.

Initial tests involved measuring the concentration of the enzyme CYP46A1 in the inner ear’s OHCs. This enzyme facilitates the breakdown and recycling of cholesterol. It was observed that older mice had higher levels of CYP46A1, and correspondingly, lower cholesterol levels. Subsequently, the researchers induced auditory impairment in younger mice by pharmacologically activating CYP46A1.

The researchers also evaluated the effect of increasing brain cholesterol levels to counteract this induced hearing loss. Given that cholesterol cannot directly penetrate the blood-brain barrier, phytosterols—plant-derived compounds resembling cholesterol—were used. Young mice treated with both the CYP46A1-activating drug and dietary phytosterols for three weeks demonstrated improved OHC functionality.

Phytosterols are commonly available in over-the-counter supplements, potentially offering a practical means of mitigating age-related hearing loss. Nevertheless, it is imperative to validate their efficacy on age-specific mouse models and humans before drawing more definitive conclusions.

In summary, the authors presented evidence indicating that 1) the aging process leads to cholesterol depletion in inner ear sensory cells; 2) the loss of cholesterol can be replicated through retroviral treatment commonly used for HIV/AIDS, leading to impaired OHC functionality; and 3) this dysfunction can be partially reversed through phytosterol supplementation. These findings hold significant promise, as they mark the inaugural evidence supporting the use of phytosterols as a prospective intervention for hearing loss.

The research received financial backing from the Agencia Nacional de Promoción Científica y Técnica (Argentina), with specific grants PICT-2018-00539 to MEGC and PICT-2018-00648 to MGM. Alejandro O. Sodero received support from Pontificia Universidad Católica Argentina. The funders had no influence on the study’s design, data compilation and analysis, the decision to publish, or the preparation of the manuscript.

Frequently Asked Questions (FAQs) about Phytosterol Supplements and Hearing Loss

More about Phytosterol Supplements and Hearing Loss

• PLOS Biology Journal Article
• Agencia Nacional de Promoción Científica y Técnica (Argentina)
• University of Buenos Aires-CONICET’s Institute of Pharmacology
• National University of Córdoba
• Pontificia Universidad Católica Argentina
• Information on Phytosterols
• Understanding Age-Related Hearing Loss
• CYP46A1 Enzyme
• Outer Hair Cells and Hearing