Maple Syrup Urine Disease (MSUD) is an autosomal recessive inherited disorder, caused by a deficiency on branched chain α‐ketoacid dehydrogenase complex activity, resulting in accumulation of branched‐chain amino acids (BCAA) (e.g. leucine). The treatment of MSDU patients increases survival time and quality of life. Thus, nowadays there are a crescent number of adolescents and adults with MSUD. Relevant studies have been reported behavioral alterations in these patients, i.e. high risk of chronic neuropsychiatric problems, such as attention deficit disorder, depression and anxiety. Moreover, MSUD is associated to neurotransmitters deficiency. Herein, we aimed to investigate whether the toxicity of leucine is associated to anxiety‐like behavioral, using zebrafish acutely exposed to leucine as experimental model of MSUD. In addition, we evaluated the effects of high levels of leucine in the acetylcholinesterase (AChE) and choline acetyltransferase (ChAT) activities, components of cholinergic neurotransmission system. Young zebrafish were exposed to 2 mM and 5 mM concentration of leucine for 24 h. After that, the animals were submitted to the Novel Tank test, having the brain collected to enzymatic determination. The exposure to both concentrations of leucine caused behavioral and brain cholinergic activity alterations in young zebrafish, indicating an anxiety‐like behavior and cholinergic dysfunction. Therefore, this animal could be considered a promising organism to study the BCAA neurotoxic effects, which could help to a better comprehension of the behavioral and neurochemical alterations present in patients with MSUD.

中文翻译：

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急性暴露于亮氨酸会改变斑马鱼的行为参数和胆碱能活性

枫糖浆尿病 (MSUD) 是一种常染色体隐性遗传疾病，由支链 α-酮酸脱氢酶复合物活性缺陷引起，导致支链氨基酸 (BCAA)（例如亮氨酸）积累。MSDU 患者的治疗增加了生存时间和生活质量。因此，如今患有 MSUD 的青少年和成年人的数量越来越多。相关研究报告了这些患者的行为改变，即慢性神经精神问题的高风险，例如注意力缺陷障碍、抑郁和焦虑。此外，MSUD 与神经递质缺乏有关。在此，我们旨在研究亮氨酸的毒性是否与焦虑样行为有关，使用急性暴露于亮氨酸的斑马鱼作为 MSUD 的实验模型。此外，我们评估了高水平亮氨酸对乙酰胆碱酯酶 (AChE) 和胆碱乙酰转移酶 (ChAT) 活性（胆碱能神经传递系统的组成部分）的影响。年轻的斑马鱼暴露于 2 mM 和 5 mM 浓度的亮氨酸 24 小时。之后，对动物进行新罐试验，收集大脑以进行酶测定。暴露于两种浓度的亮氨酸都会导致年轻斑马鱼的行为和大脑胆碱能活动发生改变，表明出现焦虑样行为和胆碱能功能障碍。因此，这种动物可以被认为是研究 BCAA 神经毒性作用的有希望的生物体，这有助于更好地理解 MSUD 患者存在的行为和神经化学改变。