DX3004-Derived GABA Fermentate Ameliorates Stress-Induced Auditory Dysfunction-Associated Phenotypes Through Modulation of Auditory-Related Molecular Responses and Oxidative Stress in Drosophila melanogaster.

Environmental stress is increasingly recognized as a contributor to auditory dysfunction through disruption of mechanotransduction-related processes and induction of oxidative stress. This study evaluated the protective effects of a γ-aminobutyric acid (GABA)-enriched fermentate (DX3004-GABA), derived from Levilactobacillus brevis DX3004, using a Drosophila melanogaster model of cold stress-induced auditory dysfunction. Auditory-associated phenotypes were assessed by courtship song-induced chaining behavior, and expression of mechanotransduction-related (nan, nompB), ciliary integrity-associated (btv, rempA, ninaC, tilB), and gene expressions related to antioxidant defense (cncC, cat, sod) was analyzed by quantitative real-time polymerase chain reaction. Cold stress markedly impaired chaining behavior, downregulated auditory-related gene expression, and increased both dihydroethidium-reactive and 2',7'-dichlorofluorescein (DCF)-reactive reactive oxygen species (ROS) levels in fly head samples. Supplementation with DX3004-GABA significantly improved auditory dysfunction-associated phenotypes, restored auditory-related gene expression, and reduced ROS accumulation more effectively than purified GABA. In addition, DX3004-GABA enhanced antioxidant defense-associated gene expression, suggesting improved redox regulation. Collectively, these findings indicate that a GABA-enriched fermentate ameliorates cold stress-induced auditory dysfunction-associated phenotypes through coordinated modulation of auditory-related molecular responses and oxidative stress-associated pathways. The enhanced efficacy of DX3004-GABA compared with purified GABA raises the possibility that additional fermentation-derived metabolites contribute to the observed biological activity, highlighting the potential of postbiotic fermentates as functional ingredients for stress-associated conditions.