Abstract：
The cochlear nucleus receives numerous inputs from auditory and nonauditory systems. This extensive innervation of the cochlear nucleus is involved in sound source localization and the integration of auditory signals with other sensory modalities. The dorsal cochlear nucleus may also have an important role in tinnitus. Although its gross anatomy and function have been extensively studied, the metabolome of the cochlear nucleus remains poorly understood, particularly at different stages of auditory maturity. Here, we present a protocol for untargeted metabolomics analysis of the rat cochlear nucleus, then discuss differences in the metabolome of the rat cochlear nucleus between postnatal day (PD) 14 (hearing onset) and PD60 (hearing maturation). Cochlear nucleus samples collected from rats at PD14 or PD60 were analyzed by liquid chromatography-tandem mass spectrometry (LCMS). In total, 344 metabolites were identified. Principal component analysis and orthogonal partial least-square discriminant analysis showed that the metabolic profiles at these two stages had distinct distribution patterns. Moreover, 91 significantly differential metabolites (62 upregulated and 29 downregulated) were identified at PD60 vs. PD14. N-acetylaspartylglutamic acid (NAAG), γ-aminobutyric acid (GABA), taurine, adenosine monophosphate (AMP), and choline were significantly upregulated at PD60. Pathway enrichment analysis suggested that alanine, aspartate, and glutamate metabolism; glycine, serine, and threonine metabolism; the mammalian target of rapamycin (mTOR) signaling pathway; and the AMP-activated protein kinase (AMPK) signaling pathway may be involved in key developmental events during maturation of the cochlear nucleus. Taken together, the metabolic profiles identified in this study could lead to the identification and understanding of specific key biomarkers and metabolic pathways involved in the maturation of hearing. Moreover, LC-MS-based metabolomics provides an alternative approach for the characterization of auditory maturation and auditory diseases.
摘要：
耳蜗核接收来自听觉和非听觉系统的大量输入。耳蜗核的这种广泛的神经支配涉及声源定位以及听觉信号与其他感觉方式的整合。耳蜗背侧核也可能在耳鸣中起重要作用。虽然它的大体解剖结构和功能已被广泛研究，耳蜗核的代谢组仍然知之甚少，特别是在听觉成熟的不同阶段。这里,我们提出了一种用于大鼠耳蜗核的非靶向代谢组学分析的方案，然后讨论出生后第14天（PD）（听力开始）和PD60（听力成熟）之间大鼠耳蜗核代谢组的差异。通过液相色谱-串联质谱法（LCMS）分析从PD14或PD60的大鼠收集的耳蜗核样品。总的来说,共鉴定出344种代谢物。主成分分析和正交偏最小二乘判别分析表明，这两个阶段的代谢谱具有不同的分布模式。此外，在PD60与PD60时鉴定出91种显着差异的代谢物（62种上调和29种下调）。PD14.N-乙酰天冬氨酰谷氨酸(NAAG),γ-氨基丁酸(GABA),牛磺酸,一磷酸腺苷（AMP），和胆碱在PD60时显著上调。途径富集分析表明，丙氨酸，天冬氨酸,和谷氨酸代谢；甘氨酸，丝氨酸,和苏氨酸代谢；哺乳动物雷帕霉素靶蛋白（mTOR）信号通路；AMP激活的蛋白激酶（AMPK）信号通路可能参与耳蜗核成熟过程中的关键发育事件。一起来看,本研究中确定的代谢谱可能导致识别和理解与听力成熟有关的特定关键生物标志物和代谢途径。此外，基于LC-MS的代谢组学为表征听觉成熟和听觉疾病提供了替代方法。
