DIETARY PREVENTION OF CARDIAC MITOCHONDRIAL AGING

她的心脏经历了一些与年龄相关的不利变化，导致功能丧失，最终导致心力衰竭，这是美国65岁以上人群死亡的主要原因。氧化损伤、能量供应丧失和组织萎缩被认为是导致心脏功能障碍的潜在因素，而心脏功能障碍又可能是由线粒体衰退引起的。然而，对于老化心脏中线粒体衰退的程度和性质，以及改善线粒体衰退的膳食补充剂是否能改善心脏功能，人们知之甚少。一些关于线粒体衰变的研究已经使用分离的线粒体进行了，但结果是相互矛盾的，难以解释。这主要是由于一个技术问题：在从衰老组织中分离的过程中，线粒体大量溶解和损伤。我们提出表征和比较线粒体功能的完整新鲜分离的心肌细胞从老年和年轻的大鼠。方法的进步使完整细胞内线粒体功能的分析成为可能，我们现在有初步证据表明，线粒体衰变发生在老年大鼠分离的心肌细胞中。方法的进步使完整细胞内线粒体功能的分析成为可能，我们现在有初步证据表明，线粒体衰变发生在老年大鼠分离的心肌细胞中。因此，本提案中要解决的问题是：A)心肌细胞随年龄增长的线粒体衰变的性质和程度是什么？B)线粒体衰变会影响心脏功能吗？C)喂养老年大鼠乙酰-左旋肉碱（ALCAR）和(R)-硫辛酸（LA）这两种化合物，我们发现它们可以增强分离肝细胞的线粒体功能并抑制线粒体氧化剂，是否也可以改善心肌细胞的线粒体功能？我们提出三个具体目标来研究这些问题：1)表征和比较年轻、成年、成熟和老年大鼠离体心肌细胞的线粒体功能。表征将包括静息细胞和受刺激收缩的肌细胞的耗氧量特征、生物能量和心磷脂含量。其他使用分离心肌细胞或分离灌注心脏的研究将确定线粒体衰变对心脏功能的影响。2)检查线粒体抗氧化剂、氧化剂生成和心肌氧化损伤的年龄相关变化。这些研究不仅有助于确定线粒体衰变对氧化剂产生的影响，而且有助于确定线粒体产生对整个细胞的影响。3)评估饲喂ALCAR和/或LA是否能改善大鼠线粒体功能，降低心肌细胞氧化应激，改善心脏功能。这些实验将测量与具体目标1和2相同的实验终点。因此，这个项目将是我们长期目标的第一步，即确定线粒体衰变在人类心脏衰老病理中的重要性，以及改善线粒体性能的饮食方案是否可以成为治疗衰老心功能障碍的廉价而有效的方法。

Her heart undergoes several adverse age-related changes that lead to loss of performance and ultimately to heart failure, the major cause of death for people over the age of 65 in the U.S. Oxidative damage, loss of energy supply, and tissue atrophy are thought to be underlying factors causing cardiac dysfunction with age, which in turn are likely caused by mitochondrial decay. However, little is known about the extent or nature of mitochondrial decay in the aging heart and whether dietary supplements that ameliorate mitochondrial decline improves cardiac function. Some studies on mitochondrial decay have been performed using isolated mitochondria, but results are conflicting and difficult to interpret. This is primarily due to a technical problem: extensive mitochondrial lysis and damage during isolation from aged tissue. We proposed to characterize and compare mitochondrial function in intact freshly isolated cardiac myocytes from old and young rats. Advances in methodology now make analysis of mitochondrial function within intact cells feasible, and we now have preliminary evidence that mitochondrial decay occurs in isolated cardiac myocytes from old rats. Advances in methodology now make analysis of mitochondrial functions within intact cells feasible, and we now have preliminary evidence that mitochondrial decay occurs is isolated cardiac myocytes from old rats. Thus, the questions to be addressed in this proposal are A) what is the nature and extent of mitochondrial decay in cardiac myocytes with age? B) does mitochondrial decay affect cardiac function? C) does feeding old rats acetyl-L-carnitine (ALCAR) and (R)-lipoic acid (LA), compounds that we showed to enhance mitochondrial function and quench mitochondrial oxidants in isolated hepatocytes, also improve mitochondrial function in cardiac myocytes? We propose to investigate these questions in 3 specific aims: 1) Characterize and compare mitochondrial functions in isolated cardiac myocytes form young, adult, mature and old rats. Characterization will include oxygen consumption characteristics, bioenergics, and cardiolipin content in quiescent cells and in myocytes stimulated to contract. Other studies using isolated cardiac myocytes or isolated perfused hearts will determine the consequences of mitochondrial decay to cardiac performance. 2) Examine age-related changes in mitochondrial antioxidants, oxidant production, and myocardial oxidative damage. These studies will be instrumental in determining not only the impact of mitochondrial decay on oxidant production, but also the effect of mitochondrial production on the cell as a whole. 3) Assess whether feeding rats ALCAR and/or LA improves mitochondrial function, lowers oxidative stress in cardiac myocytes and improves cardiac performance. These experiments will measure the same experimental end-points as in specific aims 1 and 2. This project will thus be the first step in our long term goals of determining the importance of mitochondrial decay in pathologies of the aging human heart and whether dietary regimens that improve mitochondrial performance can be inexpensive yet effective therapies for cardiac dysfunction in aging.