Nutrients might prevent hearing loss in war zones,
|Colleen Le Prell and Josef Miller. (Photo by Scott Galvin, U-M Photo Services)|
A University study shows that in animal research a combination of high doses of vitamins A, C, and E and magnesium, taken one hour before noise exposure and continued as a once-daily treatment for five days, was very effective at preventing permanent noise-induced hearing loss. The animals had close-range, prolonged exposure to sounds as loud as a jet engine at take-off.
Clinical trials of a hearing-protection tablet or snack bar for people could begin soon, and if successful could be available in as little as two years, says Josef Miller, senior author of the study published online in the journal Free Radical Biology and Medicine. Miller is a professor in the Department of Otolaryngology at the Medical School, and former director of the U-M Health System Kresge Hearing Research Institute, where the study was performed.
Convinced by emerging evidence that nutrients effectively can block one major factor in hearing loss after noise traumainner ear damage caused by excessive free radical activityMiller has launched a startup company OtoMedicine that is developing the vitamin-and-magnesium formulation.
"These agents have been used for many years, but not for hearing loss. We know they're safe, so that opens the door to push ahead with clinical trials with confidence we're not going to do any harm," Miller says.
The formulation built on earlier animal studies showing that single antioxidant vitamins somewhat were effective in preventing hearing loss, and on studies of Israeli soldiers who gained relatively small protective effects when given magnesium many days prior to exposure.
In the U-M study, noise-induced hearing loss was measured in four groups of guinea pigs treated with the antioxidant vitamins A, C and E, magnesium alone, an ACE-magnesium combination, or a placebo. The group given the combined treatments of vitamins and magnesium showed significantly less noise-induced hearing loss than all of the other groups.
The antioxidant vitamins and magnesium used in the study are widely used dietary supplements, not new drugs, and therefore they don't require the extensive safety tests required for new drugs prior to use in clinical trials. The doses to be used in proposed human trials will be within the ranges considered safe according to the Institute of Medicine and federal nutrition guidelines.
If effective, such pre- and post-noise treatments could have far-reaching effects. About 30 million Americans regularly experience hazardous noise levels at work and at home, according to the National Institute on Deafness and Communications Disorders. Hunting, snowmobiling, using machines such as leaf blowers, lawnmowers and power tools, and attending or playing in loud music concerts commonly expose people to dangerous noise levels. Noise levels above 85 decibels damage hearing. About 28 million Americans have some degree of hearing loss. For about a third of them, noise accounts at least in part for their loss.
The study also adds strength to efforts under way in many research centers to learn how these nutrients might be used to treat many illnesses. "Similar combinations have been very effective in preventing macular degeneration, and many of these agents have been used with Alzheimer's and Parkinson's diseases, stroke-like ischemia, and other conditions that involve neural degeneration," says Colleen Le Prell, the study's lead author and a research investigator at the Kresge Hearing Research Institute.
The study was supported with funds from the National Institutes of Health, General Motors Corp./United Automotive Workers Union, and the Ruth and Lynn Townsend Professorship in Communication Disorders.