Regulation of Nutrient Sensing and Muscle Wasting by Alcohol

肌肉萎缩是持续酗酒的标志，与之相关的虚弱是最重要的 常见形式的骨骼肌肌病。在过去的4年里，我们使用了遗传、生化和 体内和体外的药理学方法，以产生与 急性酒精中毒(酗酒)和慢性酒精消费损害的机制 基础吸收后条件下肌肉蛋白质合成和拮抗合成代谢反应 氨基酸和生长因子。最初的3个目标仍然有效，在R37的第一阶段进行实验 阐明酒精下调营养信号转导的细胞机制 产生骨骼肌病的mTORC1依赖和独立的转导网络，以及 将这些与荷尔蒙和收缩诱导的调节进行比较。取得了非凡的进展(27 出版物)和研究环境，以成功地培训和F32供资一个员额- 博士生，将继续从事与酒精相关的研究。我们的出版物证明，最初的目标是 虽然我们的新数据也开辟了以前不为人知的探索途径，但已经基本实现。 已经开发出独特的工具，使我们能够识别和探索新的机制，从而 验证特定蛋白质作为治疗靶点。特定的目标1决定了酒精是否会导致改变 在Deptor是基础和亮氨酸刺激的肌肉蛋白质合成减少的原因。这一目标 现在扩展到研究酒精在体内引起的Deptor变化的相对重要性 使用我们新开发的肌肉特异性Deptor基因敲除小鼠的条件。此外，我们的新数据显示 酒精降低了此前未被识别的Redd1与Deptor的结合，这一发现将被扩大 在那里。具体目标2描述了酒精改变mTOR内体转运的机制 损害mTORC1和蛋白质的合成。这一目标将通过评估酒精引起的变化来继续， 在有和没有亮氨酸的情况下，Sestrin2磷酸化和与GATOR2复合体的蛋白质结合。这个 这些实验的目标是确定控制mTORC1拓扑的新组件和修饰剂。 特异性目标3阐明MAP4K3信号的改变是否在一定程度上与酒精诱导有关 减少mTORC1。这些研究将扩展到研究MAP4K3依赖的磷酸化 猛禽，可以通过mTORC1依赖和独立的机制发挥作用。此R37扩展利用 创新的方法，由新试剂的可用性实现，并得到我们强大的跟踪支持 唱片。虽然体外研究允许我们定义细胞机制并优先考虑未来的工作，但最先进的 活体方法使我们能够明确地分配生理重要性--从而填补知识空白。这个 预期结果将有助于营养调控方面的翻译知识，并提供开创性的 对酒精诱发肌肉疾病的临床重要病理学的机械论见解。 相关性(请参阅说明)： 酒精过量，无论是慢性滥用还是急性醉酒，都会给社会和 仍然是一个主要的公共卫生问题。酒精使用障碍不仅与死亡率增加有关， 但也有过早和可预防的健康问题，以及受损的康复。我们的研究重点是 过量酒精损害基础骨骼肌蛋白的细胞和分子机制 合成并产生对营养物质正常有益影响的抵抗力，从而导致 发展为酒精性肌病，是最突出的肌肉疾病之一。

Muscle wasting is a hallmark of sustained alcohol abuse and the associated weakness represents the most common form of skeletal muscle myopathy. Over the past 4 years we have used genetic, biochemical and pharmacological approaches, both in vivo and in vitro, to generate definitive evidence pertaining to the mechanisms by which acute alcohol intoxication (binge drinking) and chronic alcohol consumption impair muscle protein synthesis under basal postabsorptive conditions and antagonize the anabolic response to amino acids and growth factors. The original 3 aims remain valid with experiments in the first phase of the R37 elucidating the cellular mechanisms by which alcohol down-regulates nutritional signals transduced via mTORC1-dependent and -independent transduction networks producing skeletal muscle myopathy, and comparing these to hormone- and contraction-induced regulation. Exceptional progress was made (27 publications) and the research environment leveraged for the successful training and F32 funding of a post- doctoral fellow who will continue in alcohol-related research. Our publications attest that the original aims have been largely achieved; although our new data also open previously unrecognized avenues of exploration. Unique tools have been developed that will permit us to identify and explore novel mechanisms and thereby validate specific proteins as therapeutic targets. Specific Aim 1 determined whether alcohol-induced changes in Deptor are responsible for the decrease in basal and leucine-stimulated muscle protein synthesis. This aim is now extended to investigate the relative importance of alcohol-induced changes in Deptor under in vivo conditions using our newly developed muscle-specific Deptor knockout mouse. Further, our new data reveal alcohol decreases the previously unrecognized binding of REDD1 with Deptor, a finding that will be expanded upon. Specific Aim 2 delineated the mechanism by which alcohol alters mTOR endosomal trafficking thereby impairing mTORC1 and protein synthesis. This aim will be continued by assessing alcohol-induced changes, with and without leucine, on Sestrin2 phosphorylation and binding with proteins of the GATOR2 complex. The goal of these experiments is to identify new components and modifiers governing the topology of mTORC1. Specific Aim 3 elucidated whether altered MAP4K3 signaling is in part responsible for alcohol-induced decreases mTORC1. These studies will be extended to examine the MAP4K3-dependent phosphorylation of Raptor that can function by mTORC1-dependent and -independent mechanisms. This R37 extension exploits innovative approaches, made possible by the availability of novel reagents and supported by our strong track record. While in vitro studies permit us to define cellular mechanisms and prioritize future work, state-of-the-art in vivo approaches permit us to definitively assign physiological importance – thus filling knowledge gaps. The expected outcomes will contribute translational knowledge on nutrient regulation and provide seminal mechanistic insights into the clinically significant pathology of alcohol-induced muscle disease. RELEVANCE (See instructions): Alcohol excess, both chronic abuse and acute intoxication, exacts a staggering economic cost to society and remains a major public health problem. Alcohol use disorder is associated not only with increased mortality, but also with premature and preventable health concerns, and impaired rehabilitation. Our study focuses on the cellular and molecular mechanisms by which excess alcohol impairs basal skeletal muscle protein synthesis and produces a resistance to the normal beneficial effects of nutrients, thereby leading to the development of alcoholic myopathy, one of the most prominent muscle diseases.