Mechanisms of Lifespan Modulation by Diet

饮食限制是一种强有力的非遗传饮食操作，迄今已被证明在几乎所有测试的物种中都能延长寿命。我们对DR分子机制的理解主要来自对遗传顺从系统的研究，包括酵母、蠕虫和苍蝇，在这些系统中，DR是通过稀释食物来源或使用降低摄食效率的基因突变来施加的。然而，这些方法的一个主要缺点是，在这些DR范例下确定个人的确切卡路里摄入量仍然存在很大的不确定性，不同于在对啮齿动物等高等生物的研究中的这种能力。为了解决这个问题，我们以前开发了一种替代的饮食模式，饮食剥夺(DD)，并发现与自由喂养(AL)的对照相比，它可以延长线虫的寿命。由于这种方法涉及完全去除食物来源，控制食物摄入量的问题得到了缓解，这一问题阻碍了对过去研究的解释。使用这种明确的方法，我们研究了通过饮食延长寿命所必需的遗传途径。我们已经进行了基因筛查，并发现热休克反应途径对DD反应至关重要。从线虫到人类，热休克反应途径在进化上是保守的。正在准备一份手稿来描述我们的发现。我们目前正在研究这个保守的途径如何在DD条件下调节蠕虫的寿命。揭示这些保守的机制将促进我们对饮食对哺乳动物(包括人类)衰老和长寿的影响的了解。 黑腹果蝇是另一种功能强大的遗传系统，已被广泛用于解决许多基本的生物学问题，包括衰老和饮食限制(DR)。为了进一步研究饮食中的常量营养素对寿命的影响，我们测量了喂食不同比例的常量营养素的果蝇的寿命，包括蛋白质和碳水化合物。此外，为了解决繁殖与寿命之间的关联，我们还测量了果蝇在这些条件下的繁殖。我们发现，饮食结构对寿命和生殖有深远的影响，但不是以协调的方式。本研究结果为进一步研究黑腹鱼的食性调控机制奠定了基础。我们一直在利用公共库存中心可获得的大量苍蝇突变体，并进行基因筛选，以确定哪些基因是DR延长寿命所必需的，识别参与DR的遗传途径将为寿命调控提供洞察。 对啮齿动物的大量研究表明，DR不仅可以延长寿命，还可以延长健康寿命。为了探讨DR对健康寿命的作用机制，我们利用原代细胞培养系统研究了DR的神经保护功能。脂联素是一种30kD的蛋白质，主要由脂肪组织释放到循环中，被认为在外周和中枢神经系统中具有多种功能。我们假设脂联素在介导DR的神经保护中起重要作用。利用原代培养的海马神经元，我们发现脂联素可以保护培养的海马神经元免受海人藻酸(KA)诱导的细胞毒性。我们的数据还表明，AMPK通路参与了脂联素诱导的神经保护。一份描述我们发现的手稿正在接受一份科学期刊的审查。 总而言之，我们在这个项目中解决了与饮食调节寿命相关的几个问题。通过利用线虫独特而健壮的饮食方案，我们正在剖析饮食调节寿命的分子机制。我们正在研究通过限制饮食延长寿命的基因和组织的机制。利用细胞模型，我们正在研究DR有益效应所涉及的信号通路。该项目将使我们能够确定DR延长寿命所需的保守通路，这将对理解人类衰老有价值，更重要的是为人类开发有效的衰老干预策略。

Dietary restriction is a potent non-genetic dietary manipulation that has been shown to extend lifespan in almost all the species tested so far. Our understandings of molecular mechanisms of DR come primarily from studies of genetically amenable systems, including yeast, worms, and flies, where DR has been imposed by either diluting the food source or by using genetic mutations that reduce feeding efficiency. However, a major drawback of these approaches is that it remains substantially uncertain in determining the exact caloric intake of individuals under these DR paradigms, unlike this ability in studies of higher organisms, such as rodents. To address this issue, we previously developed an alternative dietary paradigm, dietary deprivation (DD), and found that it could extend lifespan in C. elegans compared to the control fed ad libitum (AL). Since this regimen involves complete removal of the food source, the problem of controlling food intake, which has hampered interpretation of past studies, is alleviated. Using this unambiguous method, we have investigated the genetic pathways necessary for lifespan extension by diet. We have conducted a genetic screen and have found that the heat shock response pathway is critical for DD response. The heat shock response pathway is evolutionarily conserved from the nematode to humans. A manuscript is under preparation to describe our findings. We are currently investigating how this conserved pathway modulates the lifespan of worms under the DD condition. Uncovering the conserved mechanisms will advance our knowledge on the effects of diet on aging and longevity in mammals, including humans. Drosophila melanogaster is another powerful genetic system that has been utilized extensively to address many basic biological questions including aging and dietary restriction (DR). To further investigate the effects of macronutrients in the diet on lifespan, we have measured lifespan of flies fed diets of various ratios of macronutritions, including protein and carbohydrates. In addition, to address the association of reproduction with lifespan, we have also measured the reproduction of flies in these conditions. We have found that dietary composition has profound effects on lifespan and reproduction but not in a coordinated manner. The results have provided us a foundation to investigate mechanisms of dietary regulation in D. melanogaster. We have been taking advantage of availability of a large number of fly mutants in the public stock centers, and conducting genetic screens to identify which genes are required for lifespan extension by DR. Identification of genetic pathways involved in DR will provide insight on lifespan regulation. Numerous studies in rodents have indicated that DR can extend not only lifespan but also healthspan. To investigate the mechanisms of DR on healthspan, we have employed the primary cell culture system to investigate the neuroprotective function of DR. Adiponectin is a 30 KD protein primarily produced by adipose tissues prior to its release into circulation, and is thought to have multiple functions in the peripheral and central nervous systems. The adiponectin level is significantly induced by DR. We hypothesized that adiponectin plays an important role in mediating the neuroprotection by DR. Using the cultured primary hippocampal cells, we found that adiponectin can protect cultured hippocampal neurons against kainic acid-induced (KA) cytotoxicity. Our data also suggest that the AMPK pathway is involved in adiponectin-induced neuroprotection. A manuscript describing our findings is under review by a scientific journal. In summary, we have addressed several issues related to dietary regulation of lifespan in this project. By utilizing a unique and robust dietary regimen in C. elegans, we are dissecting molecular mechanisms of dietary regulation of lifespan. With D. melanogaster, we are studying mechanisms by which genes and which tissues are critical for lifespan extension by dietary restriction. Using the cellular model, we are investigating the signaling pathways involved in the beneficial effects of DR. This project will allow us identify the conserved pathways required for lifespan extension by DR, which will be valuable for understanding human aging and more importantly for developing efficient aging intervention strategies for humans.