Background

Neurodegenerative diseases are incurable disorders caused by progressive neuronal cell death. Retinitis pigmentosa (RP) is a blinding neurodegenerative disease that results in photoreceptor death and progresses to the loss of the entire retinal network. We previously found that proteomic analysis of the adjacent vitreous served as way to indirectly biopsy the retina and identify changes in the retinal proteome.

Methods

We analyzed protein expression in liquid vitreous biopsies from autosomal recessive (ar)RP patients with PDE6A mutations and arRP mice with Pde6ɑ mutations. Proteomic analysis of retina and vitreous samples identified molecular pathways affected at the onset of photoreceptor death. Based on affected molecular pathways, arRP mice were treated with a ketogenic diet or metabolites involved in fatty-acid synthesis, oxidative phosphorylation, and the tricarboxylic acid (TCA) cycle.

Findings

Dietary supplementation of a single metabolite, ɑ-ketoglutarate, increased docosahexaeonic acid levels, provided neuroprotection, and enhanced visual function in arRP mice. A ketogenic diet delayed photoreceptor cell loss, while vitamin B supplementation had a limited effect. Finally, desorption electrospray ionization mass spectrometry imaging (DESI-MSI) on ɑ-ketoglutarate-treated mice revealed restoration of metabolites that correlated with our proteomic findings: uridine, dihydrouridine, and thymidine (pyrimidine and purine metabolism), glutamine and glutamate (glutamine/glutamate conversion), and succinic and aconitic acid (TCA cycle).

Interpretation

This study demonstrates that replenishing TCA cycle metabolites via oral supplementation prolongs retinal function and provides a neuroprotective effect on the photoreceptor cells and inner retinal network.

Funding

NIH grants [R01EY026682, R01EY024665, R01EY025225, R01EY024698, R21AG050437, P30EY026877, 5P30EY019007, R01EY018213, F30EYE027986, T32GM007337, 5P30CA013696], NSF grant CHE-1734082.

中文翻译：

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液体活检蛋白质组学指导的代谢物治疗延迟了视网膜神经变性

背景

神经退行性疾病是由进行性神经元细胞死亡引起的不治之症。色素性视网膜炎（RP）是一种致盲性神经退行性疾病，可导致光感受器死亡并发展为整个视网膜网络的丧失。我们先前发现相邻玻璃体的蛋白质组学分析可作为间接对视网膜进行活检并确定视网膜蛋白质组变化的方法。

方法

我们分析了来自常染色体隐性（AR）RP患者液体玻璃体活检蛋白表达PDE6A突变和ARRP小鼠Pde6ɑ突变。视网膜和玻璃体样品的蛋白质组学分析确定了在光感受器死亡发作时受影响的分子途径。根据受影响的分子途径，使用生酮饮食或涉及脂肪酸合成，氧化磷酸化和三羧酸（TCA）循环的代谢物治疗arRP小鼠。

发现

在arRP小鼠中，膳食补充单一代谢物β-酮戊二酸可增加二十二碳六烯酸水平，提供神经保护作用，并增强视觉功能。生酮饮食延迟了感光细胞的损失，而补充维生素B的作用有限。最后，经β-酮戊二酸处理的小鼠的解吸电喷雾电离质谱成像（DESI-MSI）显示代谢物的恢复与我们的蛋白质组学发现相关：尿苷，二氢尿苷和胸苷（嘧啶和嘌呤代谢），谷氨酰胺和谷氨酸（谷氨酰胺/谷氨酸转化），琥珀酸和乌头酸（TCA循环）。

解释

这项研究表明，通过口服补充来补充TCA循环代谢产物可延长视网膜功能，并对感光细胞和内部视网膜网络提供神经保护作用。

资金

NIH授予[R01EY026682，R01EY024665，R01EY025225，R01EY024698，R21AG050437，P30EY026877、5P30EY019007，R01EY018213，F30EYE027986，T32GM007337、5P30CA013696]，NSF授予CHE-1734082。