Cellular mechanisms of dietary therapy for epilepsy

描述(申请人提供)：癫痫影响大约1%的人类人口。对于现有药物无法充分控制癫痫发作的三分之一患者，一种有效的替代方案是高脂肪和极低碳水化合物生酮饮食(KD)的饮食治疗。KD疗效显著，约1/3的患者癫痫发作消失，但严格的饮食方案难以满足。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癫痫药物。在KD上，大脑使用循环酮小体(Kb‘s，尤其是。2羟基丁酸酯和乙酰乙酸酯)作为通常的燃料来源葡萄糖的替代品。燃料来源的这种变化以某种方式产生了一种抗惊厥作用，但其联系尚不清楚。一个很好的候选离子通道是众所周知的对代谢敏感的离子通道，即ATP敏感的K+通道或KATP通道。在脑片上的实验表明，KBS可在相当快的时间尺度(10‘S分钟)引起黑质网状部细胞自发放电的减慢。KATP通道对这一效应很重要。酮体对兴奋性的短期体外效应以及KATP通道在这一效应中的意义，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通道在癫痫中两个重要的大脑回路中如何发挥作用来跟进这一线索，并了解更多关于这些通道可能通过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焦点。酮体对KATP通道和其他靶点的影响，如基因表达，可能是由于代谢变化的近端后果的变化。用于活性氧物种、NADH和ATP的光学探针将被用来了解在不同燃料分子存在的情况下，中枢神经元如何对兴奋做出反应。这些实验将报告在神经元激活过程中新陈代谢如何变化，以及KBS如何影响这一变化，回答有关大脑新陈代谢和功能的基本问题。与公共健康相关：治疗癫痫(一种影响大约1%人口的癫痫障碍)的最佳疗法之一是非常低碳水化合物、高脂肪的生酮饮食。由于这种饮食令人不快且困难，了解它对脑细胞的作用将是有用的，这样就可以设计出更好的药物疗法(或更容易的饮食)。该项目将通过检测啮齿类动物脑片的电活动和代谢变化，研究饮食过程中身体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.