Promoting metabolic health through the reduction of dietary branched chain amino acids

2型糖尿病影响着2900多万美国人(20岁以上成年人的12.3%)。疾病的流行 退伍军人的糖尿病发病率大约是普通人群的两倍，而且还在继续上升。膳食 控制或预防2型糖尿病的干预措施可能是非常有效和负担得起的，但减少了卡路里 事实证明，从长远来看，节食是不可持续的。在不减少热量消耗的情况下制定饮食计划 这反而改变了特定的常量营养素的水平，因此两者都认为更可持续 研究人员和公众。有趣的是，最近对老鼠和人类的研究发现，低蛋白质饮食 摄入量与健康和胰岛素敏感性正相关；然而，生理和分子方面的 低蛋白饮食促进新陈代谢健康的机制尚不完全清楚。 我们最近确定减少饮食中三种支链氨基酸的摄入量(支链氨基酸； 亮氨酸、异亮氨酸和缬氨酸)概括了低蛋白质饮食的许多新陈代谢益处，促进了瘦身。 和血糖控制，即使在先前存在饮食诱导的肥胖和2型糖尿病的小鼠中也是如此。我们的预赛 数据表明，低支链氨基酸饮食部分通过减少肝脏糖异生来促进糖耐量。 并增加肝脏对胰岛素的敏感性，这一效应可能是由AA敏感激酶GCN2介导的。 这里检验的中心假设是，降低一种或多种饮食中支链氨基酸的水平会改变信号 通过氨基酸敏感激酶GCN2或其他介体，导致有利的生理变化 在近亲交配和基因异种小鼠以及人类中促进代谢健康。我们的 长期目标是机械地洞察减少饮食中的支链氨基酸如何促进新陈代谢健康， 确定可能针对药物干预或饮食干预的新干预点 预防和治疗退伍军人肥胖和2型糖尿病的战略和更好的治疗选择。 在这项提案中，我们将确定三种支链氨基酸对#年代谢健康的具体贡献 西方饮食的背景，进行代谢表型分析和定量确定 高胰岛素-正血糖钳夹在体及体外对肝脏支链氨基酸的影响 肝细胞。我们将测试我们的发现是否适用于近交系C57BL/6J小鼠，方法是确定 减少支链氨基酸可促进遗传异质性小鼠的代谢健康。最后，我们将进行一项 双管齐下，从机制上深入了解减少支链氨基酸的分子机制 促进新陈代谢健康。首先，我们将使用缺乏肝脏的遗传性小鼠模型来测试GCN2的作用 GCN2。其次，我们将通过蛋白质组和代谢组学分析确定候选的分子介体 用减少支链氨基酸饮食的小鼠的肝脏，测试这些候选介质在调节 细胞培养系统中肝细胞的葡萄糖代谢。 本提案中描述的创新的临床前研究将极大地促进我们对 特定的饮食支链氨基酸调节小鼠的代谢健康，填补了目前知识的一个重要空白。而当 目前的研究将在小鼠身上进行，所有的问题都与我们目前和 正在努力将我们的初步发现转化为人类，目标是改善预防性和 为肥胖或患有2型糖尿病的退伍军人提供治疗选择。

Type 2 diabetes affects over 29 million Americans (12.3% of adults over the age of 20). The prevalence of diabetes in Veterans is approximately double that in the general population and continues to rise. Dietary interventions to control or prevent type 2 diabetes could be highly effective and affordable, but reduced calorie diets have proven to be unsustainable over the long term. Diet plans without a decrease in caloric consumption that instead alter the level of specific macronutrients have therefore been seen as more sustainable by both researchers and the public. Intriguingly, recent studies in mice and humans have found that low dietary protein intake is positively associated with health and insulin sensitivity; however, the physiological and molecular mechanisms by which a low protein diet promotes metabolic health is not fully understood. We recently determined that decreased dietary intake of the three branched chain amino acids (BCAAs; leucine, isoleucine, and valine) recapitulates many metabolic benefits of a low protein diet, promoting leanness and glycemic control even in mice with pre-existing diet-induced obesity and type 2 diabetes. Our preliminary data suggests that a low BCAA diet promotes glucose tolerance in part by reducing hepatic gluconeogenesis and increasing hepatic insulin sensitivity, an effect that may be mediated by the AA-sensing kinase, GCN2. The central hypothesis examined here is that reducing levels of one or more dietary BCAAs alters signaling through the amino acid-sensing kinase GCN2 or other mediators, leading to favorable physiological changes that promote metabolic health in both inbred and genetically heterogeneous mice as well as in humans. Our long-term goal is to gain mechanistic insight into how reducing dietary BCAAs promotes metabolic health, identifying new points of intervention that may be targeted with pharmaceutical interventions or dietary strategies and enabling better therapeutic options to prevent and treat obesity and type 2 diabetes in Veterans. In this proposal, we will determine the specific contribution of each of the three BCAAs on metabolic health in the context of a Western diet, performing metabolic phenotyping and quantitatively determining the effect of altered BCAAs on the liver in vivo using hyperinsulinemic-euglycemic clamps and ex vivo in primary hepatocytes. We will test if our findings are applicable beyond inbred C57BL/6J mice by determining if reducing BCAAs promotes metabolic health in genetically heterogeneous mice. Finally, we will undertake a two-pronged approach to gain mechanistic insight into the molecular mechanisms by which reduced BCAAs promote metabolic health. First, we will test the role of GCN2 using a genetic mouse model lacking hepatic Gcn2. Second, we will identify candidate molecular mediators by proteomic and metabolomics profiling of the livers of mice fed a reduced BCAA diet, and test the role of these candidate mediators in the regulation of hepatocyte glucose metabolism in a cell culture system. The innovative preclinical studies described in this proposal will significantly advance our understanding of how specific dietary BCAAs regulate metabolic health in mice, filling an important gap in present knowledge. While the present studies will be conducted in mice, all of the questions are directly relevant to our current and ongoing efforts to translate our preliminary findings into humans, with the goal of improving preventative and therapeutic options for Veterans who are obese or who have type 2 diabetes.