An Antioxidant Found in Cheese May Prevent Hearing Loss

One of the authors (DH) of this blog article has a confession to make: I don’t like cheese. In fact, I hate it, and always have. I don’t know why, but there is no type of cheese that I find tolerable. So, when I recently heard that a nutrient found in several types of cheese, particularly parmesan, has shown great potential to minimize hearing loss from many causes, I wondered if I should learn to like it.

The nutrient is D-methionine, an amino acid which has strong antioxidant properties. As an “essential” amino acid, humans are not able to produce this protein building block, so any D- methionine we use must be ingested. In addition to cheese, high concentrations of D- methionine are found in Brazil nuts and lean beef. Among other roles, D-methionine is important to cartilage creation, and a deficiency can lead to inflammation of the liver, anemia, and greying of hair.

Unlike many other amino acids, D-methionine is reversibly oxidized and serves as an effective free radical scavenger. It has therefore been actively considered in recent years as a compound to reduce reactive oxygen species that can cause hearing loss (Rewerska et al., 2013). A colleague of Dr. Turner’s at Southern Illinois University School of Medicine, Kathleen Campbell, PhD, has been one of the most active researchers in the effectiveness of D-methionine in minimizing hearing loss, and a sampling of her research shows the potential of this amino acid to protect hearing from several well-known causes of auditory damage:

  • Aminoglycoside ototoxicity: For 23 days, eight groups of guinea pigs were given the same daily dose of kanamycin, an antibiotic that like other aminoglycosides is known to cause ototoxicity. In addition, one group was given saline as a control, and each of the ​other groups was administered a specific daily dose of D-methionine. ABR and cytocochleograms showed that significant otoprotection was provided by D-methionine at several doses, with maximum protection at 300 mg/kg/day (Campbell et al., 2016).

  • Noise-induced hearing loss: Three groups of chinchillas were administered the same dose of D-methionine (200 mg/kg/day) for 2, 2.5, or 3 days prior to noise exposure. A fourth group received saline. All chinchillas were exposed to noise, and after 21 days, ABRs showed significant reduction in threshold shifts for guinea pigs receiving D- methionine for 3 days compared to controls. Cytocochleograms at 21 days showed significant reduction in outer hair cell loss in this same group of animals (Claussen et al., ​2013).

  • Cisplatin ototoxicity: An in vitro study of auditory cortex cells in cortical networks exposed to cisplatin, a chemotherapeutic agent with significant potential to cause ​ ototoxicity, showed pre-treatment with D-methionine prevented or delayed cell death with low or high concentrations of cisplatin, respectively (Gopal et al., 2012).

While the ability of D-methionine to reduce hearing loss in humans remains to be determined, the prospect of using a common food nutrient for otoprotection is very appealing. It is possible

that cheese consumption could help to protect hearing. I don’t believe that I can be persuaded to eat cheese, but I have heard that Brazil nuts are very tasty…

References Rewerska, A., Pawelczyk, M., Rajkowska, E., Politanski, P., & Sliwinska-Kowalska, M. (2013). Evaluating D-methionine dose to attenuate oxidative stress-mediated hearing loss following overexposure to noise. Eur Arch Otorhinolaryngol 270(4), 1513-1520.

Campbell, K.C., Martin, S.M., Meech, R.P., Hargrove, T.L., Verhulst, S.J., & Fox, D.J. (2016). D- methionine (D-met) significantly reduces kanamycin-induced ototoxicity in pigmented guinea pigs. Int J Audiol 55(5), 273-278.

Claussen, A.D., Fox, D.J., Yu, X.C., Meech, R.P., Verhulst, S.J., Hargrove, T.L. & Campbell, K.C. (2013). D-methionine pre-loading reduces both noise-induced permanent threshold shift and outer hair cell loss in the chinchilla. Int J Audiol 52(12), 801-807.

Gopal, K.V., Wu, C., Shrestha, B., Campbell, K.C., Moore, E.J., & Gross, G.W. (2012). d- Methionine protects against cisplatin-induced neurotoxicity in cortical networks. Neurotoxicol Teratol 34(5), 495-504.

Authors David Hicks, M.D.: Dr. Hicks directs business development at Turner Scientific, and has significant training and experience in clinical treatment of ear disorders. Contact: dhicks@turnerscientific.com

Jeremy Turner, Ph.D.: Dr. Turner is the founder and Chief Scientific Officer at Turner Scientific. He completed his Ph.D. in auditory neuroscience, and has more than 22 years’ experience in preclinical hearing loss, tinnitus, and ototoxicity research. Contact: jturner@turnerscientific.com

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