Koda Kento, Kamogashira Teru, Hayashi Ken, Fujimoto Chisato, Iwasaki Shinichi, Yamasoba Tatsuya, Kondo Kenji
Department of Otolaryngology and Head and Neck Surgery, Faculty of Medicine, University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8655, Japan.
Ikebukuro ENT Hayashi Clinic, 2F, Toshima Eco-Musee Town, 2-45-3, Minami-Ikebukuro, Toshima-ku, Tokyo 171-0022, Japan.
Biology (Basel). 2025 Aug 24;14(9):1118. doi: 10.3390/biology14091118.
Mitochondrial substrate switching plays an important role in aging. The substrate metabolic rate is closely related to mitochondrial activity, as mitochondria are the primary site for substrate oxidation and ATP production. Different substrates (glucose, amino acids, and fatty acids) enter the mitochondria through distinct pathways and are metabolized at different rates, depending on the energy demand and cellular conditions. However, it remains unclear how the mitochondrial metabolic rate of these substrates affects auditory cellular function. This study aimed to characterize the substrate-dependent mitochondrial respiratory responses of cochlear cells under varying energy supply conditions and metabolic stress, focusing on glucose, amino acids, and fatty acids as representative energy sources.
The oxygen consumption rate (OCR) was measured after substrate addition using an Agilent Seahorse XF24 Flux Analyzer In-House Ear Institute-Organ of Corti 1 (HEI-OC1) cells, and the maximum OCR (MOCR) was determined as part of the mitochondrial stress test. Statistical analyses were performed using analysis of variance (ANOVA).
The OCR increased significantly after glutamine (L-Gln) or palmitate addition. The MOCR after L-Gln addition was significantly higher than that after glutamic acid, glycine, and phenylalanine addition. The MOCR after pyruvate addition was significantly higher than that after glucose addition. However, there was no significant increase in the MOCR after fatty acid addition.
Glucose is essential for basal metabolism but cannot rapidly meet sudden energy demands. Pyruvate and L-Gln serve as effective substrates for short-term, high-intensity energy demands. Fatty acids increase OCR through mitochondrial uncoupling effects, though their role may be limited in inner ear cells. These findings provide a foundation for exploring metabolic interventions to support cochlear function and hearing health.
线粒体底物转换在衰老过程中起着重要作用。底物代谢率与线粒体活性密切相关，因为线粒体是底物氧化和ATP产生的主要场所。不同的底物（葡萄糖、氨基酸和脂肪酸）通过不同的途径进入线粒体，并根据能量需求和细胞状况以不同的速率进行代谢。然而，这些底物的线粒体代谢率如何影响听觉细胞功能仍不清楚。本研究旨在表征在不同能量供应条件和代谢应激下，耳蜗细胞依赖底物的线粒体呼吸反应，重点关注葡萄糖、氨基酸和脂肪酸作为代表性能量来源。
使用安捷伦Seahorse XF24通量分析仪在内部耳研究所-柯蒂氏器1（HEI-OC1）细胞中添加底物后测量氧消耗率（OCR），并将最大OCR（MOCR）作为线粒体应激测试的一部分进行测定。使用方差分析（ANOVA）进行统计分析。
添加谷氨酰胺（L-Gln）或棕榈酸酯后，OCR显著增加。添加L-Gln后的MOCR显著高于添加谷氨酸、甘氨酸和苯丙氨酸后的MOCR。添加丙酮酸后的MOCR显著高于添加葡萄糖后的MOCR。然而，添加脂肪酸后MOCR没有显著增加。
葡萄糖对基础代谢至关重要，但不能迅速满足突然的能量需求。丙酮酸和L-Gln是短期高强度能量需求的有效底物。脂肪酸通过线粒体解偶联作用增加OCR，尽管它们在内耳细胞中的作用可能有限。这些发现为探索支持耳蜗功能和听力健康的代谢干预措施提供了基础。
