(NaturalNews) A chemical precursor to vitamin B3 may help prevent the hearing loss caused by exposure to loud noises, according to a study conducted by researchers from Weill Cornell Medical College and the Gladstone Institutes and published in the journal Cell Metabolism.
"One of the major limitations in managing disorders of the inner ear, including hearing loss, is there are a very limited number of treatments options," said first author Kevin Brown, MD, PhD, who is now at the University of North Carolina. "This discovery identifies a unique pathway and a potential drug therapy to treat noise-induced hearing loss."
The vitamin B3 precursor, known as nicotinamide riboside (NR), increases the activity of a protein that not only protects against hearing loss but may also help prevent a wide variety of age-related disorders.
The study was funded by Weill Cornell, the Gladstone Institutes, the New York State Department of Health Spinal Cord Injury Fund and the National Institutes of Health.
Prevents hearing damage even after noise exposure
The body turns NR not just into vitamin B3 but also into another related compound, nicotinamide adenine dinucleotide (NAD+). In laboratory studies, Brown and co-senior author Samie Jaffrey found that NAD+ could prevent injury in the nerve cells of a part of the ear known as the cochlea. The cochlea is the part of the ear that transmits sound into the spiral ganglion, which then sends the information on to the brain. The hair cells and nerve synapses are particularly vulnerable to damage from loud noise.NAD+ is a highly unstable compound, however, causing the researchers to worry that it would be ineffective in living animals. For that reason, they carried out an animal trial using NR instead. This was made possible by a recent advance by co-author Anthony Sauve, PhD, who developed a new method allowing NR to be synthesized in quantities high enough for animal studies.
"NR gets into cells very readily and can be absorbed when you take it orally," Jaffrey said. "It has all the properties that you would expect in a medicine that could be administered to people."
The researchers exposed mice to NR either before or after exposing them to noises loud enough to cause cochlear damage. They found that regardless of whether it was administered before or after the noise, NR reduced synaptic damage in mice. In addition, mice treated with NR suffered less hearing loss in both the short and the long term. Mice gained the same degree of protection regardless of when the NR was administered.
Same chemical may prevent diseases of aging
NR and NAD+ are both known to increase activity of a protein known as sirtuin 3 (SIRT3), which plays a key role in maintaining healthy functioning of mitochondria, which provide energy to cells. The researchers hypothesized that this effect might underlie the chemicals' protective benefits. In a followup experiment, they found that mice who had their SIRT3 levels artificially increased were just as resistant to noise damage to their cochlea as mice given NR. Similarly, mice who had their SIRT3 gene removed gained no benefit from NR.Because levels of SIRT3 naturally decline with age, the researchers have suggested that lowered levels of this protein might be responsible for some of the effects of aging, and for the development of certain age-related diseases. SIRT3 levels also naturally vary fairly widely between individuals, which may also explain why some people tend to stay healthier as they age.
"The success of this study suggests that targeting SIRT3 using NR could be a viable target for treating all sorts of aging-related disorders--not only hearing loss but also metabolic syndromes like obesity, pulmonary hypertension, and even diabetes," co-senior author Eric Verdin, MD, said.
Sources:
http://gladstoneinstitutes.org
http://science.naturalnews.com
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