AUTHOR=Austin Thomas T. , Thomas Christian L. , Lewis Clifton , Blockley Alix , Warren Ben 

TITLE=Metabolic decline in an insect ear: correlative or causative for age-related auditory decline?

JOURNAL=Frontiers in Cell and Developmental Biology

VOLUME=Volume 11 - 2023

YEAR=2023

URL=https://www.frontiersin.org/journals/cell-and-developmental-biology/articles/10.3389/fcell.2023.1138392

DOI=10.3389/fcell.2023.1138392

ISSN=2296-634X

ABSTRACT=One leading hypothesis for why we lose our hearing as we age is a decrease in ear metabolism. However, direct measurements of metabolism across a lifespan in any auditory system are lacking. Even if metabolism does decrease with age, the question remains: Is a metabolic decrease a cause of age-related auditory decline or simply correlative? We use an insect, the desert locust, Schistocerca gregaria, as a physiologically versatile model to understand how cellular metabolism correlates with age and impacts on age-related auditory decline. We found that auditory organ metabolism decreases with age. Next, we measured individual auditory organ’s metabolic rate and its sound-evoked nerve activity and found no correlation. To further test for a causative role of metabolic rate in auditory decline, we manipulated metabolism of the auditory organ through diet and cold-rearing but found no difference in sound-evoked nerve activity. We found that although metabolism correlates with age-related auditory decline it is not causative. Finally, we performed RNA-seq on the auditory organs of young and old locusts, and whilst we found enrichment for GO terms associated with metabolism, we also found enrichment for a number of additional ageing GO terms. We hypothesise that age-related hearing loss is dominated by accumulative damage in multiple cell types and multiple processes which outweighs its metabolic decline.