Metabolic Dysfunction and Neuroprotection after Pediatric Head Injury

描述(由申请人提供)：这份K08提案描述了一项为期5年的培训计划，旨在发展儿童创伤性脑损伤研究的学术生涯。首席调查员苏珊娜·斯卡菲迪医学博士的总体目标是充分发展必要的科学技能，成为一名专注于治疗儿童创伤性脑损伤的新代谢方法的独立调查员。该培训计划旨在使PI能够应用生化、细胞和分子研究来描述与儿童创伤性脑损伤相关的代谢功能障碍的机制。加里·费斯库姆博士是主要导师，是急性脑损伤后线粒体生物能量学、氧化应激和细胞凋亡方面的专家，曾培训过许多初级教员、博士后研究员和研究生。艾伦·法登是一位临床科学家，在研究脑创伤方面有着丰富的记录；玛丽·麦肯纳博士是一位国际公认的大脑能量代谢和大脑发育方面的专家，并有成功指导的丰富历史。此外，杰出研究人员的咨询监督委员会将提供职业指导和科学支持。马里兰大学医学院为基础科学研究和多学科合作提供了一个极好的环境。培训计划包括具体的教学课程、实用的实验技术、实验设计和数据解释相结合。这项建议的研究计划旨在阐明发育期脑损伤后有氧脑能量代谢的具体变化，并评估可能的神经保护策略。创伤性脑损伤是导致儿童发病率和死亡率的主要原因，但目前尚无特效治疗方法，且有相当数量的颅脑损伤儿童患有终身残疾。脑外伤的特点是抑制脑有氧能量代谢，但脑能量衰竭的潜在机制尚不清楚。我们的发现表明，脑损伤后的能量衰竭是由于特定的线粒体酶损伤，这阻止了通过糖酵解产生的丙酮酸在线粒体中用于能量生产。除了葡萄糖，发育中的大脑还可以利用替代底物，即2-羟基丁酸盐(BHB)和乙酰基-L肉碱(ALCAR)，它们可以绕过丙酮酸代谢的抑制。我们推测：(1)脑创伤后脑组织有氧能量代谢的抑制是由于丙酮酸脱氢酶和星形胶质细胞丙酮酸羧基酶功能障碍所致；(2)药物水平的BHB和ALCAR可维持脑组织氧化能量代谢，抑制细胞死亡。这些假说将使用21-22天未成熟大鼠的创伤性脑损伤皮质撞击受控模型进行验证。测试这些假设所需的特定目标的方法包括使用动物模型、行为测试、定量组织病理学、免疫组织化学、酶活性测量、体外核磁共振波谱、体内最先进的磁共振成像(MRI)和磁共振波谱(MRS)以及与导师合作的其他方法，这些方法将为PI提供广泛的实验室技术经验，这些将极大地促进候选人作为儿科危重护理领域的临床医生/研究员的职业生涯。 公共卫生相关性：脑外伤是美国儿童死亡和长期残疾的主要原因。这些研究旨在确定脑创伤后发育中脑细胞的特异性代谢变化。这些研究还将评估发育中的大脑使用替代底物的自然能力是否可以提供神经保护，如果这些底物在脑损伤后不久以药理剂量给予的话。

DESCRIPTION (provided by applicant): This K08 proposal describes a 5-year training program for the development of an academic career in pediatric traumatic brain injury research. The overall objective for the Principal Investigator (PI), Susanna Scafidi, M.D., is to fully develop the scientific skill-set necessary to become an independent investigator focusing on new metabolic approaches to treating traumatic brain injury in children. The training program is designed to enable the PI to apply biochemical, cellular and molecular investigations to delineate mechanisms of metabolic dysfunction associated with pediatric traumatic brain injury. Gary Fiskum, Ph.D. the primary mentor; is an expert in mitochondrial bioenergetics, oxidative stress, and apoptosis following acute brain injury and has trained numerous junior faculty, postdoctoral fellows and graduate students. Alan Faden is a clinician-scientist with vast track record of studying brain trauma; Mary McKenna, Ph.D. is an internationally recognized expert in brain energy metabolism and brain development, and has a strong history of successful mentorship. In addition, advisory oversight committee of distinguished researchers will provide career guidance and scientific support. The University of Maryland School of Medicine offers a superb environment for basic science research as well as multidisciplinary collaborations. The training program consists of combination of specific didactic coursework, practical experimental techniques, experimental design and data interpretation. The research plan of this proposal is designed to elucidate specific alterations in aerobic brain energy metabolism after brain injury in developing brain and evaluate possible neuroprotective strategies. Traumatic brain injury (TBI) is the leading cause of pediatric morbidity and mortality, yet, there is no specific treatment and a significant number of head-injured children suffer from life-long disabilities. TBI is characterized by inhibition of cerebral aerobic energy metabolism, but the underlying mechanisms for cerebral energy failure are not well understood. Our findings suggest that energy failure post TBI is due to specific mitochondrial enzymes impairment, which precludes pyruvate, generated via glycolysis, from being utilized in the mitochondria for energy production. In addition to glucose, the developing brain can utilize alternative substrates, i.e. 2-hydroxybutyrate (BHB) and acetyl-L-carnitine (ALCAR), that bypass the inhibition of pyruvate metabolism. We hypothesize that (1) inhibition of cerebral aerobic energy metabolism after TBI is due to dysfunction of pyruvate dehydrogenase, astrocytic pyruvate carboxylase and (2) that exposure to pharmacologic levels of BHB and ALCAR will maintain cerebral oxidative energy metabolism and inhibit cell death. These hypotheses will be tested using a controlled cortical impact model of traumatic brain injury in immature 21-22 day old rats. Methods of approach to the Specific Aims needed to test these hypotheses include the use of animal models, behavioral tests, quantitative histopathology, immunohistochemistry, enzyme activity measurements, ex vivo NMR spectroscopy, state of the art in vivo Magnetic resonance imaging (MRI) and Magnetic resonance spectroscopy (MRS) and other methods in collaboration with the mentors will provide the PI with a broad experience in laboratory techniques that will greatly promote the candidate's career as a clinician/investigator in the field of pediatric critical care. PUBLIC HEALTH RELEVANCE: TBI is a leading cause of death and long-term disability in children in United States. The proposed studies aim to determine the cell specific metabolic changes occur after brain trauma in developing brain. The studies will also assess whether the natural capability of developing brain to use alternative substrates for energy may provide neuroprotection if these substrates are administered in pharmacologic doses shortly after TBI.