Joanna Cosgrove04.01.09
The Sound of Success
Researchers develop a supplement that prevents noise-induced hearing loss.
By Joanna Cosgrove
Online Editor
“Noise-induced hearing loss is a major unmet medical need in this country. It is the second most self-reported occupational injury in the U.S., the cost of which has been estimated at 2% of the Gross National Product,” commented Colleen Le Prell, PhD, a researcher at the University of Florida, and an associate professor in the UF College of Public Health and Health Professions Department of Communicative Disorders. “We have long known that human acquired hearing loss decreases perceived quality of life, however, it is only in the past 10 years or so, since we first learned that oxidative stress plays a significant role in acquired hearing loss, that we have been able to design interventions that reduce acquired hearing loss.”
Research into the mechanisms of NIHL actually began more than 20 years ago with studies of the influence of noise on inner ear blood flow, she said. The focus was expanded to studies of metabolic stress and the formation of free radicals in the 1990s. In 2000, work began on defining an intervention that would reduce NIHL and inner ear cell death, finally revealing a combination of antioxidants and a vasodilator that would yield a real benefit.
Dr. Le Prell and her colleague, Dr. Josef Miller, a professor in the Department of Otolaryngology at the University of Michigan Medical School, a former director of the U of M Health System’s Kresge Hearing Research Institute, and researcher of the mechanisms of hearing impairment for more than 20 years, conducted an animal study during which the animals received treatment one hour before a five-hour exposure to 120 decibel (dB) sound pressure level noise—as loud as a jet engine at take-off at close range—and continued once daily for five days.
The researchers concluded that 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 NIHL.
“Each of the vitamin components scavenges different free radicals. By targeting multiple free radicals, we increase efficacy relative to any one agent,” explained Dr. Le Prell. “In addition, these vitamins are in some cases fat-soluble, so that they can exert their effects in cell membranes, and in other cases water-soluble, allowing them to act in other parts of cells. Thus, the combination acts to protect cells in multiple ways.
“Magnesium is a little bit different from the other ingredients,” she continued. “The inner ear is very different from other tissues. In most parts of the body, blood rushes to the region subjected to trauma. In the inner ear, blood flow is constricted after noise insult, which reduces oxygen availability and increases trauma. Magnesium preserves blood flow to the inner ear after noise exposure.”
Over the last decade, scientists have learned that mitochondria in the ear produce free radicals in response to loud sounds—initially at first, then again in the days following exposure.
According to the researchers, pre-treating with the vitamin/magnesium formula presumably reduces free radicals that “form during and after noise exposure and noise-induced constriction of blood flow to the inner ear,” and may also reduce “neural excitotoxicity, or the damage to auditory neurons that can occur due to over-stimulation.” The post-noise nutrient doses work to scavenge free radicals that continue to form long after the noise exposure ends.
The efficacy of the vitamin-magnesium combination so convinced Drs. Miller and Le Prell that they launched a U of M start-up company called OtoMedicine Inc. The company is currently developing the formulation into what the researchers hope will be a marketable product, which they have already dubbed AuraQuell.
Dr. Le Prell described OtoMedicine as a “life science company” that has a long-term goal of being a leading provider of medicines to prevent and cure hearing loss. “The company was formed with the assistance and support of the University of Michigan Technology Transfer Office with an initial goal of developing commercial products from intellectual property licensed from the University of Michigan,” she said. “U of M provided initial support for the development of the start-up, for the initiation of the ongoing clinical trials, and holds the patent (pending) for AuraQuell; but the company is … otherwise independent of the U of M.”
The current formulation of AuraQuell is a capsule, taken once or twice, prior to entering a noisy environment; however other delivery vehicles—such as a snack bar—are possible. “We hope that human validation of the efficacy of AuraQuell will be demonstrated by the end of 2009 or early 2010; following those data, OtoMedicine would take the product to market...but not before the clinical data demonstrate efficacy,” said Dr. Le Prell.
She said the company expects AuraQuell to be particularly appealing to those who choose not to or are unable to use hearing protection during loud recreational activities, as well as those consumers who use mechanical hearing protection already, but are slowly accruing hearing loss anyway, (i.e., where the hearing protection is inadequate). Examples include military personnel, hunters, construction workers, many in industry and those exposed to high levels of recreational sound (e.g., musicians and concert attendees).