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A class of dietary supplements may hold the key to protecting hearing in aging, according to a recent study
Phytosterol supplements suggest a recent study published in PLOS Biology as a tool to prevent presbyacusis or aging hearing loss. Plant sterols, “plant cholesterols” that have a structure similar to animal cholesterol and are abundant in foods such as sesame, peanuts, tomato, artichoke, sunflower seed, banana, cherries, figs, walnuts and whole grains etc., can replace the deficit that comes with old age.
The sensory cells of hearing (hair cells) in the inner ear, the outer hair cells (OHC) as they are called, act as sound amplifiers, thanks to their ability to move and change their length. As we age, this ability to elongate (polarize) is lost, resulting in the inability to amplify sound and gradual hearing loss. Cholesterol plays a key role in the polarization process. As brain cholesterol declines with age, researchers hypothesized that hearing loss may be related to cholesterol loss in outer hair cells. To test the hypothesis, they performed experiments on mice.
In a first step, they measured the levels of the CYP46A1 enzyme in outer hair cells of the inner ear. It is a special enzyme that is involved in the elimination and in general the cycle of cholesterol in the brain. As expected, the concentration of the enzyme was higher in the ears of the old mice compared to the younger ones, resulting in lower cholesterol levels.
Then, to illuminate the mechanisms responsible, they artificially induced hearing loss in young mice by giving them efavirenz, an antiretroviral drug that activates the CYP46A1 enzyme, and tested whether an increase in cholesterol in the brain could counteract the drug’s effect.
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Since cholesterol cannot cross the blood-brain barrier, the research team chose phytosterols, which can cross it and accumulate in the brain. The young mice that received the antiretroviral drug and combined phytosterol supplements for three weeks saw an improvement in outer hair cell function.
The researchers described their findings as “very promising” for preventing or treating hearing loss, but noted that clinical trials would need to be done before any firmer conclusions can be drawn and before supplements can be recommended to combat or even reverse hearing loss. aging.