An imaging study on the contribution of glial energy metabolism to the neuroprotective effect of ketone bodies

已知高循环水平的酮体可保护脑组织免受难治性癫痫的侵害，难治性癫痫占该疾病所有临床表现的三分之一。酮体还可以预防葡萄糖转运蛋白缺乏综合征的癫痫发作，对大脑发育很重要。酮体保护作用的细胞和分子机制尚不清楚，已提出各种假说，提出神经元的作用。本项目的目的是研究胶质细胞的能量代谢是否也在保护中发挥作用。来自多个来源的数据，包括我们自己以前的合作努力表明，神经胶质细胞是神经代谢偶联的关键介质，在基础条件下和神经元的需求下从葡萄糖产生乳酸。乳酸反过来又被神经元用作能量燃料，神经元还代谢葡萄糖以保持其氧化还原平衡并避免细胞凋亡。在这种情况下，本项目的主要假设是，酮体，这是有效的氧化底物，允许神经胶质细胞，以减少其氧化的葡萄糖，从而节省糖神经元的使用。我们还将探讨酮体改变神经元对葡萄糖的利用的可能性。为了实现这些目标，我们将利用我们小组开发的新成像技术，其中之一允许使用FRET葡萄糖纳米传感器以高时间分辨率估计单细胞中的糖酵解速率。另一种技术能够使用荧光葡萄糖类似物和多光子显微镜来估计特定细胞类型对组织切片中糖的摄取和代谢的贡献。我们设想，酮体保护机制的理解可能有助于揭示神经系统疾病如癫痫的新治疗靶点。

High circulating levels of ketone bodies are known to protect the brain tissue against intractable epilepsy, which amounts to a third of all clinical presentations of the disease. Ketone bodies also prevent seizures in glucose transporter difficiency syndrome and are important for brain development. The cellular and molecular mechanisms underlying the protective effect of ketone bodies are not clear and various hypothesis have been put forward proposing a role of neurons. The purpose of the present project is to investigate whether energy metabolism in glial cells also play a role in the protection. Data from several sources including our own previous collaborative effort has shown that glial cells are key mediators of neurometabolic coupling, producing lactate from glucose both under basal conditions and upon neuronal demand. Lactate is in turn used as energy fuel by neurons, which in addition metabolize glucose to keep their redox balance and avert apoptosis. In this scenario, the main hypothesis of the present project is that ketone bodies, which are efficient oxidative substrates, allow glial cells to reduce their oxidation of glucose thus sparing the sugar for neuronal usage. We will also explore the possibility that ketone bodies alter the usage of glucose by neurons. To these aims, we will take advantage of new imaging techniques developed by our groups, one of which allows estimation of the glycolytic rate in single cells with high temporal resolution using a FRET glucose nanosensor. The other technique is capable of estimating the contribution of specific cell types to the uptake and metabolism of sugars in tissue slices using fluorescent glucose analogues and multiphoton microscopy. We envisage that a mechanistic understanding of the protection by ketone bodies may help to disclose new therapeutic targets for neurological conditions like epilepsy.