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

项目摘要 随着全球人口老龄化，制定干预措施，可以预防或延迟与年龄相关的疾病， 疾病对促进健康老龄化越来越重要。因此，有强烈的兴趣， 了解热量限制（CR）的机制，这是一种既能提高寿命， 和健康跨度在广泛的模式生物，功能。尽管经过了世纪的研究， CR促进健康和长寿仍然是未知的。一个流行的模型是，CR减少了活性， mTOR复合物1（mTORC 1）是一种蛋白激酶，是代谢的关键调节因子。遗传和 mTORC 1信号通路的药物抑制可延长寿命， 提示上位相互作用，提示mTORC 1在CR应答中的关键作用。然而研究 来自其他实验室的研究发现，CR和mTORC 1抑制对转录组有不同的影响， 代谢组其他组织，以及CR和减少的mTORC 1信号传导对代谢，健康， 和寿命还没有在哺乳动物中正式研究过。事实上，由于它们的进食方式非常不同， 甚至不清楚CR喂养的动物相对于随意（AL）对照具有mTORC 1信号传导的减少。 在我们的初步研究中，我们确定mTORC 1信号传导在AL和CR中是相似的， 动物，并且与AL喂养的对照相比，CR喂养的动物具有升高的mTORC 1信号传导， 喂食我们还确定，组成性激活肝脏mTORC 1信号传导并不能阻断肝脏mTORC 1的表达。 CR饮食的代谢作用。我们还确定，CR喂养的动物受到降低的卡路里和热量的影响。 摄入量和延长每日禁食，因为他们在约2小时内消耗了全部食物分配， 并且在一天的剩余时间禁食，这与小鼠的正常食物消耗模式形成鲜明对比。在 使用不同的喂养方案来分离禁食和卡路里摄入的影响的初步实验， 我们已经发现，虽然CR的许多代谢益处是由卡路里介导的，但其他益处可能需要禁食。 该项目的总体目标是确定mTORC 1在哺乳动物中的作用。 如果CR的益处是通过减少卡路里和/或延长每日禁食来介导的，则可以评估对CR的反应。我们 1）我们将确定CR喂养的动物是否具有降低的mTORC 1 在24小时周期的过程中，如果需要减少肝脏mTORC 1信号传导， 使用转基因小鼠对CR的代谢反应; 2）我们将利用一种新的实验范式 在热量限制范例中，从热量限制中剖析禁食，并纵向评估 减少热量摄入，每日禁食和不禁食对代谢健康，虚弱， 老鼠的寿命总之，拟议的实验将解决长期存在的生物学问题， CR促进代谢健康，健身和长寿的机制，并将提供急需的 深入了解mTORC 1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.