Distinct roles for calories, fasting, and mTOR in a calorie restricted diet

项目总结 随着全球人口老龄化，制定可预防或延缓与年龄相关的干预措施 疾病对促进健康老龄化越来越重要。因此，人们对……有强烈的兴趣 了解卡路里限制(CR)的机制，这是一种提高两人寿命的干预措施 和健康跨度广泛的模式生物，功能。尽管经过了一个世纪的研究，但这种机制 目前尚不清楚哪种CR能促进健康和长寿。一种流行的模型是CR减少了活动 MTOR复合体1(MTORC1)是一种蛋白激酶，是代谢的关键调节因子。遗传和 药物抑制mTORC1信号通路延长寿命，并在模式生物中进行研究 提示上位性交互作用，提示mTORC1在对CR的反应中起关键作用。然而，研究表明 来自其他实验室的研究人员发现，CR和mTORC1抑制对转录组和 代谢组其他组织，以及CR和mTORC1信号的相互作用对代谢，健康， 和长寿还没有在哺乳动物身上进行正式研究。事实上，由于它们的进食模式非常不同， 与随意(AL)对照相比，CR喂养的动物mTORC1信号是否减少甚至还不清楚。 在我们的初步研究中，我们确定在AL和CR FED FED中mTORC1信号相似 动物，并且与喂AL的对照组相比，喂CR的动物mTORC1信号增强 喂食。我们还确定，结构性激活肝脏mTORC1信号不会阻断 CR饮食对代谢的影响。我们还证实，喂食CR的动物既要减少卡路里 摄入量和每日禁食时间延长，因为它们在~2小时内吃光了全部配给的食物， 在一天的其余时间里，它们都会禁食，这与老鼠的正常食物消费模式形成了鲜明对比。在……里面 初步试验采用不同的喂养方案来区分禁食和卡路里摄入的影响， 我们发现，虽然CR的许多代谢益处是由卡路里调节的，但其他一些可能需要禁食。 拟议项目的总体目标是确定mTORC1在哺乳动物中的作用。 对CR的反应以及CR的益处是否通过减少卡路里和/或延长每日禁食时间来调节。我们 将通过以下方式实现目标：1)我们将确定喂CR的动物是否减少了mTORC1 24小时循环过程中的信号，如果需要减少肝脏mTORC1信号 使用转基因小鼠对CR的代谢反应；以及2)我们将利用一种新的实验范式 在卡路里限制范例中剖析禁食和卡路里限制，并纵向评估 在每天禁食和不禁食的情况下减少卡路里摄入量对新陈代谢的健康、脆弱和 小鼠的长寿。总之，拟议的实验将解决长期存在的生物学问题，包括 CR促进新陈代谢健康、健康和长寿的机制，并将提供急需的 深入了解mTORC1在哺乳动物对CR反应中的作用。

PROJECT SUMMARY As the global population ages, developing interventions that can prevent or delay age-associated diseases is of increasing importance to promote healthy aging. As a result, there is intense interest in understanding the mechanisms by which calorie restriction (CR), an intervention which improves both lifespan and healthspan in wide range of model organisms, functions. Despite a century of study, the mechanism by which CR promotes health and longevity is still unknown. One prevailing model is that CR reduces the activity of mTOR Complex 1 (mTORC1), a protein kinase that is a key regulator of metabolism. Genetic and pharmaceutical inhibition of the mTORC1 signaling pathway extends lifespan, and studies in model organisms suggest an epistatic interaction, suggesting a key role for mTORC1 in the response to CR. However, studies from other labs have found that CR and mTORC1 inhibition have distinct effects on the transcriptome and metabolome other tissues, and the interaction of CR and reduced mTORC1 signaling on metabolism, health, and longevity have not been formally investigated in mammals. In fact, due to their very different feeding patterns, it is not even clear that CR-fed animals have a reduction in mTORC1 signaling relative to ad libitum (AL) controls. During our preliminary studies, we determined that mTORC1 signaling is similar in AL and CR fed fasted animals, and that CR-fed animals have elevated mTORC1 signaling as compared to AL-fed controls following feeding. We also determined that constitutively activating hepatic mTORC1 signaling does not block the metabolic effects of a CR diet. We also established that CR-fed animals are subject to both reduced calorie intake and prolonged daily fasting, as they consume their entire allotment of food within a period of ~2 hours, and fast for the remainder of the day, in sharp contrast to the normal food consumption pattern of a mouse. In preliminary experiments using different feeding regiments to separate out the effects of fasting and calorie intake, we have found that while many metabolic benefits of CR are mediated by calories, others may require fasting. The overall objective of the proposed project is to determine the role of mTORC1 in the mammalian response to CR and if the benefits of CR are mediated by a reduction in calories and/or prolonged daily fast. We will accomplish the objective with the following: 1) we will determine if CR-fed animals have reduced mTORC1 signaling over the course of a 24-hour cycle, and if reduced hepatic mTORC1 signaling is required in the metabolic response to CR using genetically modified mice; and 2) We will utilize a novel experimental paradigm to dissect fasting from calorie restriction in a calorie restriction paradigm, and longitudinally assess the effect of reduced caloric intake with and without the imposition of daily fasting on the metabolic health, frailty, and longevity of mice. Together, the proposed experiments will address long-standing biological questions regarding the mechanisms by which CR promotes metabolic health, fitness, and longevity, and will provided much needed insight into the role of mTORC1 in the mammalian response to CR.