Acetate Supplementation as a therapeutic strategy for Canavan disease

描述（由申请人提供）：卡纳万病（CD）是一种罕见的神经系统疾病，由遗传缺陷引起，表现为进行性神经退行性疾病，导致瘫痪和死亡，通常发生在3至10岁之间。目前还没有有效的治疗方法。CD是由天冬氨酸酰化酶（ASPA）基因突变引起的，该酶从浓缩的脑代谢物n -乙酰天冬氨酸（NAA）中产生游离乙酸。NAA在神经元中合成，而ASPA在少突胶质细胞中表达，有证据表明神经元将NAA转移到少突胶质细胞中合成乙酰辅酶a。由于乙酰辅酶a是髓磷脂脂合成和其他关键发育功能（如通过组蛋白乙酰化进行基因调控）的关键组成部分，我们假设在出生后中枢神经系统髓鞘形成过程中，不能酶解分解NAA导致少突胶质细胞醋酸缺乏，导致少突胶质细胞死亡和髓磷脂脂合成缺陷。我们利用震颤大鼠的CD模型，验证了在出生后髓鞘形成期间补充膳食醋酸盐可以改善与ASPA缺乏症相关的严重表型的假设。从出生后7天开始给震颤大鼠服用三乙酸甘油（GTA），一种疏水醋酸来源，断奶后继续在食物和水中给药。运动表现明显改善。此外，与乳糜泻相关的特征性脑空泡化在治疗过程中略有减少。运动表现的改善与空泡化的减少正相关。我们的中心假设仍然是，在中枢神经系统发育的关键时期，NAA的无法分解导致脑醋酸盐（乙酰辅酶a）缺乏，损害髓鞘形成和大脑发育的其他方面。目前，我们的醋酸盐补充疗法已被证明在CD动物模型中仅部分有效。我们计划测试额外的醋酸/乙酰辅酶a来源，以进一步改善结果。我们已经确定了五种这样的测试化合物。这些化合物通过不同的生化机制增加乙酰辅酶a。因此，我们很可能在联合研究中获得加性或协同效应。具体目的1是确定测试化合物增加脑乙酰辅酶a的时间过程和剂量反应，并随后确定测试化合物及其组合在我们的体内CD模型中使用最佳剂量和给药方案的功效。具体目标2是确定长期给药治疗的长期安全性，以便尽快进行临床试验的准备工作。拟议的研究的重要性在于，乳糜泻目前没有治疗方法，仍然是一种致命的疾病，对受影响的家庭来说是毁灭性的。醋酸盐替代疗法是一种简单的生化方法，安全、廉价、方便用于乳糜泻婴儿。临床前研究表明，GTA用于婴儿是安全的，但治疗仍需进一步改进和优化。

DESCRIPTION (provided by applicant): Canavan disease (CD) is a rare neurological disease resulting from genetic defects that manifest as a progressive neurodegenerative disease leading to paralysis and death, usually between 3 and 10 years of age. There is no effective treatment at the present time. CD is caused by mutations in the gene for the enzyme aspartoacylase (ASPA), which produces free acetate from the concentrated brain metabolite N-acetylaspartate (NAA). NAA is synthesized in neurons, but ASPA is expressed in oligodendrocytes, and evidence indicates that neurons transfer NAA to oligodendrocytes for acetyl CoA synthesis. Because acetyl CoA is a key building block for myelin lipid synthesis, and other critical developmental functions such as gene regulation through histone acetylation, we postulated that the inability to enzymatically catabolize NAA leads to an acetate deficiency in oligodendrocytes during postnatal CNS myelination, resulting in oligodendrocyte death and defective myelin lipid synthesis. We tested the hypothesis that dietary acetate supplementation during postnatal myelination would ameliorate the severe phenotype associated with ASPA deficiency using the tremor rat model of CD. Glyceryl-triacetate (GTA), a hydrophobic acetate source, was administered to tremor rats starting 7 days after birth, and administration was continued in food and water after weaning. Significant improvements were observed in motor performance. Further, the characteristic brain vacuolation associated with CD was modestly reduced by the treatment. The improvements in motor performance were positively correlated with the decreased vacuolation. Our central hypothesis continues to be that the inability to catabolize NAA leads to a brain acetate (acetyl CoA) deficiency during a critical period of CNS development, impairing myelination and other aspects of brain development. Currently, our acetate supplementation therapy has proved only partially effective in animal models of CD. We plan to test additional acetate/acetyl CoA sources alone and in combination to improve outcomes further. We have already identified five such test compounds. These compounds increase acetyl CoA by different biochemical mechanisms. Therefore, we are likely to achieve additive or synergetic effects in combination studies. Specific Aim 1 is to determine the time course and dose response of the test compounds to increase acetyl CoA in brain and subsequently determine efficacy of the test compounds and their combinations in our in vivo model of CD using optimal dose and dosing schedules. Specific Aim 2 is to determine the long term safety of the treatment with chronic administration in order to proceed as quickly as possible to prepare the method for clinical trials. Importance of the proposed studies lies in the fact that CD has no current treatment and remains a fatal disease which is devastating to the affected families. Acetate replacement therapy is a simple biochemical approach, which is safe, inexpensive and convenient for use in CD infants. Preclinical studies have shown that GTA is safe to use in infants, but the treatment still requires further improvements and optimization.