Effects of Liraglutide on Mitigation of Hearing Loss After Repeated Blast Exposures: A Summary of Studies in Animal Model of Chinchilla.

INTRODUCTION: Repeated exposures to blasts during training and combat result in high prevalence of hearing loss and tinnitus among Service members. Liraglutide is a glucagon-like-peptide 1 receptor agonist and an Food and Drug Administration-approved treatment of type 2 diabetes, which has shown neuroprotective function against traumatic brain injury. We have recently conducted a series of studies to investigate the effects of liraglutide on the mitigation of hearing loss after repeated blast exposures at various intensity levels, recovery times, and ear conditions in chinchillas. This article summarizes those studies on functional and histopathological findings. MATERIALS AND METHODS: Experimental results measured from various conditions were compared in this study: Low (3-5 psi, G1) and high (15-25 psi, G2) intensity blasts, number (3 and 6) of repeated blasts, 1 time and recurrent blasts, and ear conditions (open and earplug-protected) during the blasts. Based on the starting time of the liraglutide treatment, chinchillas were divided into pre-blast treatment, post-blast treatment, and blast control groups. The auditory brain stem response (ABR) and the histology of cochlea tissues were examined. RESULTS: The effects of liraglutide treatment varied with the ear conditions. In earplug-protected ears, liraglutide reduced the severity of blast-induced acute damage when given before the blast happened. In open ears, liraglutide facilitated post-injury hearing restoration. G2 blasts induced more severe and permanent damage than G1. Wave I suprathreshold amplitudes indicated that the pre-injury liraglutide treatment mitigated the blast-induced temporary damage to the peripheral auditory system. Histology results suggested that the liraglutide treatment reduced the severity of blast-induced hair cell loss. CONCLUSIONS: Liraglutide treatment reduced the severity of permanent hearing loss and facilitated the restoration of hearing function as indicated by ABR results. The optimal effect could be achieved if administered before the injury occurred. The histopathological evidence indicated liraglutide treatment protected hair cells against blasts.