Myocardial Protein Synthesis After Alcohol Intoxication

描述（由申请人提供）：本项目的长期目标是了解酒精消耗诱导酒精性心肌病特征性肌原纤维损伤的机制。酗酒仍然是美国最常见的药物滥用形式。酒精滥用与过早死亡率增加有关，部分原因是酒精诱导的心肌病的发展，这种疾病在大约35%的慢性饮酒过量的人中被诊断出来。导致酒精依赖性心肌功能障碍的机制是多因素的，但心肌蛋白表达的改变似乎是一个中心机制。在本资助期间完成的研究表明，酒精消费在mRNA翻译水平上抑制了心脏蛋白质合成的速率。通过了解mRNA翻译过程中的改变，人们希望能够开发新的策略来对抗与慢性酒精中毒相关的心肌结构和功能的病理性紊乱。我们描绘了蛋白质合成过程中的两个调节步骤，活性eIF 4 E-eIF 4G复合物的形成和延伸过程，其部分地负责在慢性酒精施用期间抑制蛋白质合成，而急性酒精中毒仅影响活性eIF 4 E-eIF 4G复合物的形成。我们假设，通过mTOR的正常信号通路负责维持蛋白质合成中这两个步骤的功能，在对照动物中观察到的速率受到乙醇摄入的严重损害。净效应通过包括收缩蛋白在内的心肌蛋白表达的改变来表现。我们进一步假设，通过急性灌胃或膳食喂养给予酒精的大鼠提供氨基酸可以刺激mTOR，导致蛋白质合成速率加快。即将到来的项目周期的实验设计解决了以下具体目的，以检验以下假设：1）酒精消耗降低mTOR活性，导致4 E-BP 1和S6 K1的去磷酸化，从而通过减少活性eIF 4G-eIF 4 E复合物的形成来限制心肌蛋白质合成; 2）补充氨基酸刺激mTOR活性可逆转酒精对心肌蛋白合成的抑制作用; 3）响应于慢性酒精喂养的蛋白质合成的抑制改变心肌蛋白质表达;和4）mTOR的基因消融导致心肌中的功能和生化紊乱，类似于在慢性酒精摄入中观察到的那些。总体而言，研究设计将建立心肌蛋白质合成减少的机制，以应对酒精滥用。

DESCRIPTION (provided by applicant): The long-term goal of this project is to understand the mechanisms by which alcohol consumption induces myofibrillar damage characteristic of alcoholic heart muscle disease. Alcoholism remains the most common form of drug abuse in the United States. Alcohol abuse is associated with an increased premature mortality partly resulting from the development of an alcohol-induced cardiomyopathy, a condition diagnosed in approximately 35% of whose individuals who chronically consume excessive amounts of alcohol. The mechanisms leading to alcohol-dependent myocardial dysfunction are multifactorial, but altered expression of myocardial proteins appears as a central mechanism. Studies completed during the current funding period established that alcohol consumption inhibits rates of protein synthesis in heart at the level of mRNA translation. By understanding the alterations in the process of mRNA translation it is hoped that new strategies could be developed to combat the pathologic derangements in cardiac muscle structure and function associated with chronic alcoholism. We delineated two regulatory steps in the process of protein synthesis, the formation of an active elF4E-elF4G complex and the process of elongation that are responsible, in part, for the inhibition of protein synthesis during chronic alcohol administration, whereas acute alcohol intoxication only affects the formation of an active elF4E-elF4G complex. We hypothesize that the normal signaling path-way through mTOR responsible for maintaining the functioning of these two steps in protein synthesis at rates observed in control animals is severely compromised by ethanol intake. The net effect is manifested through alterations in the expression of myocardial proteins including contractile proteins. We further hypothesize that provision of amino acids either through acute gavage or meal feeding to rats administered alcohol can stimulate mTOR leading to an acceleration of rates of protein synthesis. The experimental design for the forthcoming project period addresses the following Specific Aims in order to test the hypothesis that: 1) Alcohol consumption reduces mTOR activity resulting in dephosphorylation of 4E-BP1 and S6K1, thereby limiting myocardial protein synthesis by reducing formation of active elF4G-elF4E complex; 2) Stimulating mTOR activity with aminp acid supplementation reverses the alcohol-induced inhibition of myocardial protein synthesis; 3) Inhibition of protein synthesis in response to chronic alcohol feeding shifts myocardial protein expression; and 4) Genetic ablation of mTOR causes functional and biochemical derangements in the myocardium similar to those observed with chronic alcohol intake. Overall, the research design will establish the mechanism by which myocardial protein synthesis is reduced in response to alcohol abuse.