Coenzyme A Regulation of Metabolism

描述（由申请人提供）：本提案是一个不断发展的项目的延伸，研究泛酸激酶（PanK）调节辅酶A （CoA）生物合成对中间代谢控制的重要性。上一个资助期完成的目标定义了PanK亚型的调控特性和组织特异性分布，创建了一个敲除小鼠模型，用于揭示增加CoA水平在空腹代谢中的关键重要性，采用化学生物学方法鉴定小分子PanK抑制剂，并鉴定酰基肉碱为PanK激活剂。这些结果完善了我们的总体想法，即改变细胞内辅酶a浓度对于重编程代谢是必不可少的。过去，细胞内CoA被认为超过了完全支持CoA依赖性生物化学所需的水平，乙酰辅酶a通过对PanK活性的反馈控制来缓冲细胞内CoA的含量。这种观点是不正确的。我们的研究结果表明，CoA的供应是动态调节的，CoA含量的调节失败直接影响代谢网络的燃料利用。这一未被认识到的调控方面对于理解中间代谢的营养重编程至关重要。Aim #1的实验将确定调整CoA水平在肌肉从进食代谢到禁食代谢的转变中的作用。这部分研究的结果对于理解肌肉中能量生成对CoA含量的依赖至关重要。在人类中，低血清胰岛素水平与PANK1基因多态性之间存在关联。我们的Pank1/敲除小鼠的突出表型是较低的血清葡萄糖，甘油三酯和胰岛素水平。在Aim #2中，我们将使用我们的Pank1/小鼠模型来定义胰岛素水平降低的潜在代谢基础，并确定肌肉是否是这些动物中葡萄糖耐量增加的主要部位。CoA及其硫酯是浓度依赖的底物和中间代谢关键控制点的变构调节剂，表明通过抑制PanK对CoA水平的药理学操纵可以重编程代谢。我们用PanK抑制剂降低小鼠肝脏CoA和血清葡萄糖的实验验证了这一想法。在Aim #3中，我们将使用该抑制剂降低总CoA含量，从药理学上重新编程肝脏代谢，以抑制饮食引起的肥胖中的糖异生，并确定肝脏CoA的升高是否足以增加葡萄糖的产生。这种重新编程中间代谢的原始方法将确定辅酶a在肝脏糖异生中的作用，并提供对导致人类脂质和葡萄糖稳态紊乱的因素的见解。

DESCRIPTION (provided by applicant): This proposal is an extension of an evolving program investigating the importance of pantothenate kinase (PanK) regulation of coenzyme A (CoA) biosynthesis to the control of intermediary metabolism. The accomplished aims of the last grant period defined the regulatory properties and tissue-specific distribution of the PanK isoforms, generated a knockout mouse model that was used to reveal the critical importance of increasing CoA levels in fasting metabolism, employed a chemical biology approach to identify small molecule PanK inhibitors, and identified acyl-carnitine as a PanK activator. These results have refined our overall idea that altering the intracellular CoA concentration is essential for reprogramming metabolism. In the past, intracellular CoA has been considered to be in excess of what is needed to fully support CoA-dependent biochemistry, with acetyl-CoA exerting feedback control over PanK activity to buffer the cellular CoA content. This view is not correct. Our results show that the CoA supply is dynamically regulated and the failure to modulate CoA content directly impacts fuel utilization by the metabolic network. This unappreciated aspect of regulation is central to understanding the nutritional reprogramming of intermediary metabolism. The experiments in Aim #1 will determine the role of adjusting CoA levels in the transition of muscle from fed to fasting metabolism. The results from this part of the study will be of central importance to understanding the dependence of energy generation in muscle on CoA content. In humans, there is an association between low serum insulin levels and polymorphisms in the PANK1 gene. Prominent phenotypes of our Pank1/ knockout mouse are lower serum glucose, triglycerides and insulin levels. In Aim #2, we will use our Pank1/ mouse model to define the underlying metabolic basis for reduced insulin levels and to determine if muscle is the primary site for increased glucose tolerance in these animals. CoA and its thioesters are concentration- dependent substrates and allosteric regulators of key control points in intermediary metabolism, suggesting that the pharmacological manipulation of CoA levels via PanK inhibition could reprogram metabolism. This idea was validated by our experiments with a PanK inhibitor that lowers hepatic CoA and serum glucose in mice. In Aim #3, we will use this inhibitor to reduce total CoA content to pharmacologically reprogram hepatic metabolism to suppress gluconeogenesis in diet-induced obesity, and determine if the elevation of hepatic CoA is sufficient to increase glucose production. This original approach to reprogramming intermediary metabolism will define the role of CoA in hepatic gluconeogenesis and provide insight into the factors that give rise to human disorders of lipid and glucose homeostasis. PUBLIC HEALTH RELEVANCE: Obesity-associated insulin resistance and hyperglycemia define a metabolic syndrome (type 2 diabetes) that constitutes a large and ever growing medical problem affecting the United States population. The need for more suitable therapeutics to treat this syndrome has focused considerable attention on clearly understanding the normal regulation of intermediary metabolism and the imbalances associated with metabolic syndrome. This research will define the role of pantothenate kinase and coenzyme A in the regulation of intermediary metabolism and its effect on glucose and insulin homeostasis.