Translational investigation of abnormal fat metabolism in mitochondrial disease

 描述（由申请人提供）： 儿童肥胖是一种日益普遍的公共卫生危机，导致2型糖尿病的全球负担不断增加。肥胖症和糖尿病，在最基本的层面上，代表能量平衡失调。在肥胖症中，能量储存超过了利用。在糖尿病中，可用的能量来源（葡萄糖）使用不当。能量平衡由细胞的线粒体感知和控制。重点研究在能量平衡紊乱中被破坏的关键线粒体途径将提高我们对肥胖内分泌并发症的理解，并可能导致新的治疗方法。为了更好地理解线粒体功能障碍和肥胖相关内分泌疾病的交叉点，一个特别相关的研究群体是患有原发性（遗传性）线粒体疾病的患者，即使在没有明显糖尿病或肥胖的情况下，他们也会出现类似的脂肪代谢紊乱，包括高脂血症和低高密度脂蛋白（HDL）胆固醇。通过拟议的K23指导以患者为导向的研究职业发展奖，我将调查原发性线粒体疾病中脂质代谢紊乱的机制基础和代谢后果。拟议的研究将直接支持我的主要职业目标，因为我走向独立作为一个医生，科学家。这些目标是[1]推进我们对线粒体，能量平衡和代谢在儿科内分泌疾病中的作用的理解，并[2]应用生理学见解来开发合理，有针对性和有效的治疗干预措施，以改善内分泌和代谢疾病患者的健康。这些目标将在K23奖励期间通过追求3个总体培训和职业发展目标来推进：首先，我将获得教学 和技术知识的成功设计和执行在这一领域以病人为导向的研究的关键。在获得该奖项的三年期间，我将在内容领域专家顾问的指导下学习执行有价值的体外和体内表型分析技术。具体而言，稳定同位素的体外利用和“胞质杂交体”细胞系的操作，以及由稳定同位素研究补充的高胰岛素-正常血糖钳夹研究的体内性能将是无价的技能。第二，我将积累新的专业知识，在诊断，评估和原发性线粒体疾病患者的管理。这一人群在所有领域都有大量未满足的临床需求，特别是包括儿科内分泌学。他们进一步提供了一个集中的机会来研究线粒体功能障碍在常见内分泌疾病中的作用。这一目标将通过为线粒体疾病患者提供临床护理并在体外和体内进行 研究调查，以确定其血脂异常的程度和基础。第三，我将过渡到作为调查员的独立性。我将继续工作，并与我的指导委员会的专家成员发展富有成效的多学科合作。我将获得必要的专业知识，通过完成拟议的研究过渡到独立，在国家会议上提出，在同行评审的期刊上发表，并确保随后的R 01资金。执行这个拟议的项目将有助于实现这些目标。这些实验将检验我们的中心假设：[1]在初级呼吸链（RC）受损的情况下，细胞NAD+/NADH氧化还原平衡的改变导致α-酮戊二酸（αKG）衍生柠檬酸盐的从头脂质合成增加和脂肪酸氧化（FAO）能力降低，[2]骨骼肌中脂质的过度积累导致骨骼肌胰岛素抵抗。为了验证这些假设，我们将采用体外和体内方法。我们将使用体外人细胞系模型来测试RC抑制是否通过“反向”柠檬酸循环流定量地增加从头脂肪生成。一种补充的体内方法将寻找（i）原发性RC疾病、高脂血症但无DM的成人中新生脂肪生成增加、肌肉脂质蓄积和胰岛素敏感性降低的证据。我们将把这一组与（ii）适当匹配的健康个体进行比较。为了评估“逆转的”柠檬酸循环通量是否也可能导致“典型的”非糖尿病肥胖个体的高甘油三酯血症，我们还将研究（iii）适当匹配的肥胖个体。将来，我们可以将这些研究的各个方面扩展到儿科人群。该项目利用了CHOP和Penn的许多独特资源。首先，我的主要导师Marni J. Falk博士拥有大量具有明确线粒体疾病遗传诊断的患者，这些患者具有良好的表型，为进行拟议的研究提供了理想的受试者和组织的现成来源。CHOP的线粒体和表观基因组医学中心（CMEM）进一步提供该领域的世界级基础设施。宾夕法尼亚大学糖尿病研究中心（DRC）已经拥有教师和核心专业知识，以确保成功完成详细的代谢表型研究，其中主要教师是comentors。我们在宾夕法尼亚大学高级磁共振成像和光谱学中心（CAMRIS）的合作者开发了代谢成像技术来估计和定位线粒体功能。这项工作将使我建立一个坚实的背景，从追求未来的，独立资助的研究线粒体的作用，能量平衡，代谢在儿科内分泌疾病

 DESCRIPTION (provided by applicant): Pediatric obesity is an increasingly prevalent public health crisis that contributes to the rising global burden of type 2 diabetes. Obesity and diabetes, at the most fundamental level, represent disorders of energy balance. In obesity, energy storage exceeds utilization. In diabetes, available energy sources (glucose) are improperly used. Energy balance is sensed and controlled by the cell's mitochondria. Focused study of key mitochondrial pathways that are disrupted in disorders of energy balance will improve our understanding of endocrine complications of obesity, and may lead to new treatment approaches. A particularly relevant group to study to better understand the intersection of mitochondrial dysfunction and obesity-related endocrine disorders are patients with primary (genetic) mitochondrial diseases, who develop similar profiles of disordered fat metabolism even in the absence of overt diabetes or obesity, including hypertriglyceridemia and low high density lipoprotein (HDL) cholesterol. Through the proposed K23 Mentored Patient-Oriented Research Career Development Award, I will investigate the mechanistic basis and metabolic consequences of disrupted lipid metabolism in primary mitochondrial disease. The proposed studies will directly support my main career goals as I progress towards independence as a physician-scientist. These goals are to [1] advance our understanding of the role of mitochondria, energy balance, and metabolism in pediatric endocrine disease, and to [2] apply physiologic insights to develop rational, targeted, and effective therapeutic interventions to improve the health of patients with endocrine and metabolic diseases. These goals will be advanced during the K23 award period through the pursuit of 3 overarching training and career development objectives: First, I will acquire didactic and technical knowledge critical for the successful design and execution of patient-oriented research in this area. During the three years of the proposed award, I will learn to perform valuable in vitro and in vivo phenotyping techniques under the guidance of content-area expert advisors. Specifically, in vitro utilization of stable isotopes and manipulation of "cybrid" cell lnes, and in vivo performance of hyperinsulinemic-euglycemic clamp studies complemented by stable isotope studies will be invaluable skills. Second, I will accrue new expertise in the diagnosis, evaluation, and management of patients with primary mitochondrial disease. This population has a large, unmet clinical need for better-informed subspecialists in all areas, particularly including Pediatric Endocrinology. They further provide a focused opportunity to study the role of the mitochondrial dysfunction in common endocrine disorders. This goal will be met by providing clinical care for mitochondrial disease patients and performing both in vitro and in vivo research investigations to characterize the extent and basis of their dyslipidemia. Third, I will transition to independence as an investigator. I will continue to work and develop productive multi-disciplinary collaborations with the expert members of my mentoring committee. I will gain necessary expertise to transition to independence through completing of the proposed studies, presenting at national meetings, publishing in peer-reviewed journals, and securing subsequent R01 funding.. Performing this proposed project will help accomplish these goals. These experiments will test our central hypotheses that: [1] altered cellular NAD+/NADH redox balance in the setting of primary respiratory chain (RC) impairment leads to increased de novo lipid synthesis from alpha-ketoglutarate (αKG)- derived citrate and decreased fatty acid oxidation (FAO) capacity and [2] the resulting excess accumulation of lipids in skeletal muscle causes skeletal muscle insulin resistance. To test these hypotheses, we will employ both in vitro and in vivo approaches. We will use in vitro human cell line models to test whether RC inhibition quantifiably increases de novo lipogenesis via "reversed" citric acid cycle flow. A complementary in vivo approach will look for evidence of increased de novo lipogenesis, muscle lipid accumulation, and decreased insulin sensitivity in (i) adults with primary RC disease, with hypertriglyceridemia but without DM. We will compare this group to (ii) appropriately matched healthy individuals. To assess whether "reversed" citric acid cycle flux might also contribute to hypertriglyceridemia in "typical" non-diabetic obese individuals, we will also study (iii) appropriately matched obese individuals. In future, we can extend aspects of these studies to the pediatric population. This project leverages many unique resources at CHOP and Penn. First, my primary mentor, Dr. Marni J. Falk, has a large and well-phenotyped cohort of patients with clear genetic diagnoses of mitochondrial disease that provides a ready source of ideal subjects, and tissues, in which to perform the proposed studies. CHOP's Center for Mitochondrial and Epigenomic Medicine (CMEM) further offers world-class infrastructure in this field. Penn's Diabetes Research Center (DRC) has faculty and core expertise already in place to assure successful completion of detailed metabolic phenotyping studies, where key faculty are comentors. Our collaborators at Penn's Center for Advanced Magnetic Resonance Imaging and Spectroscopy (CAMRIS) have developed metabolic imaging technologies to estimate and localize mitochondrial function. This work will allow me to establish a solid background from which to pursue future, independently-funded studies on the role of mitochondria, energy balance, and metabolism in pediatric endocrine disease