Acetate Supplementation as a therapeutic strategy for Canavan disease

描述(申请人提供)：Canavan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，通常在3至10岁之间。目前还没有有效的治疗方法。慢性萎缩症是由天冬氨酸酶(ASPA)基因突变引起的，该酶从大脑中浓缩的代谢物N-乙酰天冬氨酸(NAA)中产生游离醋酸酯。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以合成乙酰辅酶A。由于乙酰辅酶A是髓鞘脂肪合成的关键构件，以及其他关键的发育功能，如通过组蛋白乙酰化进行基因调节，我们推测，在出生后的中枢神经系统髓鞘形成过程中，不能酶降解NAA导致少突胶质细胞醋酸盐缺乏，导致少突胶质细胞死亡和髓鞘脂合成缺陷。我们使用震颤大鼠CD模型验证了在出生后髓鞘形成期间补充醋酸盐将改善与ASPA缺乏相关的严重表型的假设。从出生后7d开始给震颤大鼠注射疏水性醋酸甘油三乙酯(GTA)，断奶后继续在食物和水中给药。在运动性能方面观察到了显著的改善。此外，与镉相关的特征性脑空泡化通过治疗而略有减少。运动能力的改善与空泡化的减少呈正相关。我们的中心假设仍然是，在中枢神经系统发育的关键时期，无法分解NAA会导致脑醋酸酯(乙酰辅酶A)缺乏，从而损害髓鞘形成和脑发育的其他方面。目前，我们的醋酸盐补充疗法在CD的动物模型中仅被证明部分有效。我们计划单独和联合测试更多的醋酸盐/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实现相加或协同效应。具体目标1是确定测试化合物增加大脑中乙酰辅酶A的时间进程和剂量反应，并随后使用最佳剂量和剂量计划确定测试化合物及其组合在我们的CD体内模型中的有效性。具体目标2是确定慢性给药治疗的长期安全性，以便尽快为临床试验准备该方法。拟议研究的重要性在于，CD目前没有治疗方法，仍然是一种对受影响家庭具有毁灭性的致命疾病。醋酸盐替代疗法是一种简单的生化方法，安全、廉价、方便地用于CD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.