Govind Tekale
Often linked to health issues, cholesterol plays a crucial role in maintaining strong hearing, especially in the inner ear. According to recent research in PLOS Biology, phytosterols, plant-based substances resembling cholesterol, can enhance hearing in mice. Aging leads to a decline in the sensory cells of our inner ear. The connection between hearing loss in aging and the brain’s cholesterol depletion was explored by Argentinian researchers.
The focus of the study was on the enzyme CYP46A1, which has an inverse relationship with cholesterol presence. Setting the stage to test cholesterol’s role in hearing, the team used the HIV drug efavirenz to induce hearing loss in mice. Over-activation of CYP46A1 in younger mice resulted in hearing loss. However, treating these mice with phytosterols remarkably restored their hearing capabilities.
The findings emphasize the potential of phytosterols as a preventive or therapeutic solution for hearing loss. Cholesterol balance in the inner ear emerges as a groundbreaking strategy to combat hearing deterioration. Available in many pharmacies, phytosterols are primarily used to address cholesterol-related health concerns. During digestion, these compounds compete with cholesterol, leading to a reduction in harmful low-density lipoprotein cholesterol (LDL).
Phytosterols aren’t without risks. They can be harmful to people with a specific genetic condition called sitosterolemia and might lead to artery issues if taken excessively. It’s best for children and pregnant people to avoid them. This study is important because it investigates cholesterol’s function in the inner ear, an area not studied before.
While the results are promising in mice, it’s essential to note that the same might not necessarily apply to humans. Further research is vital, with other scientists needing to validate these findings using different mouse strains. The study also suggests exploring alternative methods for quantifying CYP46A1 in specific cell populations.
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María Eugenia Gomez-Casati and her team fromvarious Argentinian institutions reported the association between age-related hearing loss and decreased inner ear cholesterol. Published on August 24, the research demonstrated that phytosterols could replace lost cholesterol, preventing sensory dysfunction in mice. Outer hair cells (OHCs) in the inner ear amplify sounds by adjusting their length. Aging affects these cells’ ability to respond to sound, leading to hearing loss. The study hypothesized that this hearing loss might be linked to cholesterol depletion in OHCs.
Responsible for breaking down cholesterol, the enzyme CYP46A1 was found in higher amounts in older mice. The researchers established a cause-and-effect relationship by artificially inducing hearing loss in young mice. Since direct cholesterol supplementation to the brain isn’t feasible, the team used phytosterols, which can penetrate the brain. Young mice treated with both the CYP46A1-activating drug and phytosterols showed enhanced OHC functionality.
Given the accessibility of phytosterols in supplements, they might offer a solution against age-related hearing loss. However, it’s crucial to test their effects on older mouse models and humans before drawing definitive conclusions. The study’s authors highlighted that aging leads to cholesterol loss from the inner ear’s sensory cells. An HIV/AIDS treatment was found to replicate this cholesterol loss, impairing the function of outer hair cells. The groundbreaking discovery is that phytosterols can partly reverse these defects.
The research provides the first evidence supporting phytosterols as a potential solution for hearing loss prevention. A growing concern is the role of cholesterol in the nervous system’s functional deterioration, especially in the elderly. Affecting nearly one-third of adults over 65, age-related hearing loss is linked to cognitive decline and dementia risk. Modern society’s noise exposure complicates age-related hearing loss, blending it with acquired auditory stress and ontological diseases. Cholesterol is vital for neural cell membranes, influencing synapse formation, cell interactions, and signaling. Disruption in cholesterol balance has been linked to cognitive dysfunction and neurodegenerative diseases. The study aimed to understand the role of cholesterol in the inner ear’s physiopathology, a topic not covered earlier. The findings underscore the importance of cholesterol balance in the inner ear, presenting a novel strategy to delay or prevent hearing loss.
