Cellular mechanisms of dietary therapy for epilepsy

描述（由申请人提供）：癫痫影响大约1%的人口。对于三分之一的患者谁不能达到充分的癫痫控制与现有的药物，一个有效的替代方案是饮食治疗与高脂肪和非常低碳水化合物生酮饮食（KD）。KD可能非常有效，约1/3的患者无癫痫发作，但患者难以遵守严格的饮食方案。了解KD仍然神秘的机制将教会我们大脑如何自然地保护自己免受癫痫发作，并允许设计更好的饮食治疗和更好的抗惊厥药物。在KD中，大脑使用循环酮体（KB，特别是2-羟基丁酸和乙酰乙酸）作为通常的燃料来源葡萄糖的替代品。这种燃料来源的变化不知何故产生了抗惊厥作用，但联系仍然未知。一个很好的候选者是一个离子通道，众所周知，其敏感性代谢ATP敏感的K+通道或KATP通道。对脑切片的实验表明，KB可以在相当快的时间尺度（10分钟）上导致黑质网状部细胞自发放电减慢。KATP通道对这种效应很重要。酮体对兴奋性的短期体外效应的证明，以及KATP通道在该效应中的意义，为研究生酮饮食的机制提供了新的途径。我们将通过询问KATP通道在癫痫中重要的两个脑回路中的功能来跟进这一线索，并了解更多关于这些通道可能被酮体代谢激活的可能机制。黑质网状部神经元和海马齿状颗粒细胞将是这项工作的主要重点。酮体对KATP通道和其他靶点（如基因表达）的影响可能是由于代谢变化的近端结果发生变化。活性氧、NADH和ATP的光学探针将用于了解中枢神经元在不同燃料分子存在下如何对激发作出反应。这些实验将报告神经元激活期间代谢如何变化，以及这如何受到KBs的影响，回答有关大脑代谢和功能的基本问题。公共卫生相关性：癫痫（一种影响大约1%人口的癫痫发作疾病）的最佳治疗方法之一是非常低的碳水化合物，高脂肪生酮饮食。因为这种饮食既难吃又难，所以了解它如何作用于脑细胞，以便设计出更好的药物疗法（或更简单的饮食）是有用的。该项目将通过检查啮齿动物脑切片的电活动和代谢变化，研究身体在饮食过程中产生的酮体如何作用于脑细胞，以改变其活动并防止癫痫发作。

DESCRIPTION (provided by applicant): Epilepsy affects roughly 1% of the human population. For the one third of patients who cannot achieve adequate seizure control with existing medications, one effective alternative is dietary treatment with a high fat and very low carbohydrate ketogenic diet (KD). The KD can be remarkably effective, with ~1/3 of patients becoming seizure free, but the strict diet regimen is difficult for patients to comply with. Learning the still mysterious mechanism of the KD would teach us how the brain may naturally protect itself against seizures, and also permit the design of better dietary treatments and better anticonvulsant medications. On the KD, the brain uses circulating ketone bodies (KB's, esp. 2 hydroxybutyrate and acetoacetate) as an alternate to the usual fuel source, glucose. This change in fuel source somehow produces an anticonvulsant action, but the link remains unknown. A good candidate is an ion channel well known for its sensitivity to metabolism the ATP sensitive K+ channel or KATP channel. Experiments on brain slices show that KBs can, on a fairly rapid time scale (10's of minutes) lead to slowing of spontaneous firing in cells of substantia nigra pars reticulata. KATP channels are important for this effect. The demonstration of a short term in vitro effect of ketone bodies on excitability, and the implication of KATP channels in the effect, offer a new avenue for investigating the mechanism of the ketogenic diet. We will follow up on this lead by asking how KATP channels function in two brain circuits important in epilepsy, and to learn more about possible mechanisms by which these channels may become activated with ketone body metabolism. Substantia nigra pars reticulata neurons and hippocampal dentate granule cells will be the main focus of this work. The effects of ketone bodies on KATP channels and other targets, such as gene expression, are likely due to changes in proximal consequences of the metabolic change. Optical probes for reactive oxygen species, for NADH, and for ATP will be used to learn how central neurons respond to excitation in the presence of different fuel molecules. These experiments will report on how metabolism changes during neuronal activation, and how this is affected by KBs, answering fundamental questions about brain metabolism and function. PUBLIC HEALTH RELEVANCE: One of the best treatments for epilepsy (a seizure disorder affecting roughly 1% of the population) is a very low carbohydrate, high fat ketogenic diet. Because the diet is unpalatable and difficult, it would be useful to understand how it acts on brain cells so that better drug therapies (or easier diets) can be designed. This project will study how ketone bodies produced by the body during the diet act on brain cells to change their activity and prevent seizures, by examining electrical activity and metabolic changes in brain slices from rodents.