Torsten Henning [Public domain] via Wikimedia CommonsExposure to loud noises can damage the synapses connecting nerves and hair cells in the cochlea of the ear, causing noise-induced hearing loss that can be permanent. Effective strategies to prevent or reverse this damage and the associated hearing loss are lacking. The coenzyme nicotinamide adenine dinucleotide (NAD+) can protect neurons from damage in vitro, but its activity in vivo has proven difficult to test because the compound degrades quickly in serum and is not readily taken up by cells. A group of researchers found a way around that limitation by testing the effects of the NAD+ precursor nicotinamide riboside (NR), which enters cells much more easily than does NAD+. Administration of NR to C57BL/6 mice, which are highly susceptible to noise-induced hearing loss, boosted levels of NAD+ in the cochlea and prevented damage to cochlear synapses after noise exposure (Cell Metab. 20, 1059–1068; 2014). As a result, the NR-treated mice did not develop short- or long-term noise-induced hearing loss.
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