NEUROPROTECTIVE EFFECTS OF KETONE BODY OXIDATION IN CEREBRAL ISCHEMIA

描述（由申请人提供）：尽管有溶栓和取栓等治疗方法，但卒中是美国发病率和死亡率的主要原因。局灶性缺血性中风发生时，血液供应的大脑的一部分被中断。受影响的脑组织经历能量衰竭，可能导致细胞死亡。当这种中断是暂时的，缺血再灌注序列启动一系列事件，导致坏死和凋亡细胞死亡。大脑对能量衰竭的代谢反应尚不完全清楚，尽管这种反应的一个组成部分是从质膜磷脂中大量释放游离脂肪酸。这些游离脂肪酸氧化可产生酮体。这个项目测试了大脑中局部产生的酮体具有神经保护作用的假设。这一假设扩展了在动物模型中，在生酮饮食中外源性或由肝脏合成的酮体可以保护大脑免受缺血性损伤的观察。无论其来源如何，对缺血的神经保护是否依赖于酮体氧化尚不清楚。酮体氧化需要酮解酶（SCOT）参与酮体转化为乙酰辅酶a进入三羧酸循环。SCOT存在于神经元和星形胶质细胞中。值得注意的是，星形胶质细胞而不是神经元氧化脂肪酸，星形胶质细胞合成酮体可能依赖于SCOT。SCOT在酮体氧化和合成中的作用是可能的，因为它催化的反应接近平衡。局部合成酮体在局灶性缺血中具有神经保护作用的假设需要星形细胞-神经元酮体穿梭。因此，星形胶质细胞会氧化脂肪酸，需要SCOT来合成酮体。然后星形胶质细胞将酮体发送到神经元，然后神经元以SCOT依赖的方式氧化它们。该模型为验证酮体通过其氧化机制保护大脑免受缺血/再灌注损伤的假设提供了一个框架。本项目将通过使用组织学、生化和行为分析，检验短暂性大脑中近端动脉闭塞（tMCAO）对神经元特异性和星形胶质细胞特异性SCOT敲除小鼠的影响，从而验证这一假设。

DESCRIPTION (provided by applicant): Stroke is a leading cause of morbidity and mortality in the US despite the availability of therapies such thrombolysis and thrombectomy. Focal ischemic stroke occurs when the blood supply to a portion of the brain is interrupted. The affected brain tissue experiences energy failure that can cause cell death. When the interruption is temporary, the ischemia reperfusion sequence initiates a cascade of events causing necrotic and apoptotic cell death. The metabolic response of the brain to energy failure is not completely understood, though one component of this response is a massive release of free fatty acids from plasma membrane phospholipids. Oxidation of these free fatty acids could produce ketone bodies. This project tests the hypothesis that locally produced ketone bodies within the brain are neuroprotective. This hypothesis extends the observation that ketone bodies administered exogenously or synthesized by the liver while on a ketogenic diet protect the brain from ischemic damage in animal models. Regardless of their source, whether neuroprotection from ischemia depends on ketone body oxidation is unknown. Ketone body oxidation requires the ketolytic enzyme (SCOT), which participates in the conversion of ketone bodies into acetyl CoA for entry into the tricarboxylic acid cycle. SCOT is present in neurons and astrocytes. Notably, astrocytes but not neurons oxidize fatty acids, and the synthesis of ketone bodies by astrocytes likely depends on SCOT. A role for SCOT in ketone body oxidation and synthesis is possible because the reaction it catalyzes is near equilibrium. The hypothesis that locally synthesized ketone bodies are neuroprotective during focal ischemia requires an astrocyte-neuron ketone body shuttle. Accordingly, astrocytes would oxidize fatty acids and need SCOT to synthesize ketone bodies. The astrocytes would then send the ketone bodies to neurons, which then oxidize them in a SCOT dependent manner. This model provides a framework to test the hypothesis that ketone bodies protect the brain from ischemia / reperfusion damage via a mechanism requiring their oxidation. This project will test this hypothesis by examining the effects of transient proximal middle cerebral artery occlusion (tMCAO) in neuron-specific and astrocyte-specific SCOT knockout mice using histological, biochemical, and behavioral assays.