Investigating Mechanisms of Acetyl-CoA Sensing and Its Implications in Non-Alcoholic Fatty Liver Disease

项目总结 营养感知(即细胞和有机体感知、报告和响应营养供应的能力) 是对生命和健康至关重要的基本机制，但在以下情况下往往不受监管 疾病。虽然某些营养素的感知机制的发现，如氨基酸和三磷酸腺苷， 对它们对疾病的影响产生了批判性的洞察，其他基本代谢物可能的机制 感觉到的东西仍未被探索。乙酰辅酶A是一种代谢物，在几个分解代谢，合成代谢和 因此，信号通路可能在报告营养供应方面具有独特的地位。事实上，数据 来自我们的实验室和其他人的研究表明，乙酰辅酶A的可用性是可以检测到的。具体地说，我们的实验室之前 研究表明，当ATP-柠檬酸裂解酶(ACLY)缺失或被抑制时，细胞和组织上调乙酰-辅酶A 合成酶短链家族成员2(ACSS2)，以维持乙酰辅酶A的核-胞浆库。 然而，我们对细胞感知乙酰辅酶A的机制以及如何感知的了解非常有限。 当通过ACLY产生乙酰-CoA时，该传感通路随后可以进行适应性反应 妥协了。值得注意的是，一种针对ACLY的肝脏特异性抑制剂目前正处于第三阶段临床试验 治疗高胆固醇血症。尽管这种临床治疗方法和抑制物有可能成为 广泛用于代谢性疾病的个体，对肝脏ACLY缺乏的遗传模型的研究是 缺乏，尤其是没有研究调查ACLY丢失和随后的影响 代谢性肝病如非酒精性脂肪性肝病中ACSS2的代偿性上调 (NAFLD)。根据我的初步数据，我假设甲氧戊酸和胆固醇的敏感性 ACLY丢失途径通过激活SREBP转录因子和ii)介导ACSS2上调 抑制产生脂肪的乙酰辅酶A的产生和激活这一传感机制在 NAFLD的发病机制是通过引起线粒体功能缺陷和脂肪酸氧化。我要测试一下这个 假设，首先(目标1)通过量化胆固醇途径代谢物和评估SREBP 转录活性，使用ACLY缺乏的体外和体内模型。更进一步，我将描述 目的2抑制造脂乙酰辅酶A在体肝脂肪变性模型中的作用。 具体地说，我将研究产生脂肪的乙酰辅酶A产生的缺陷如何改变脂肪酸氧化和 线粒体功能，并确定这些变化是否依赖于 甲氧戊酸途径产物，泛醌。总体而言，我预计这项研究的结果将解决一个重要的问题 乙酰辅酶A感知的机制以及靶向乙酰辅酶A代谢的功能后果 在非酒精性脂肪肝中，有可能影响现有疗法的治疗策略。

PROJECT SUMMARY Nutrient sensing (i.e. the ability of cells and organisms to sense, report on, and respond to nutrient availability) is a fundamental mechanism that is essential to life and health, but often dysregulated in the context of diseases. While the discovery of sensing mechanisms for some nutrients, such as amino acids and ATP, have yielded critical insight into their implications for disease, the mechanisms other essential metabolites may be sensed remains unexplored. Acetyl-CoA is a metabolite at the intersection of several catabolic, anabolic, and signaling pathways, and therefore, may be uniquely positioned to report on nutrient availability. Indeed, data from our lab and others indicates that acetyl-CoA availability is sensed. Specifically, our lab has previously shown that upon deletion or inhibition of ATP-citrate lyase (ACLY), cells and tissues upregulate Acetyl-CoA synthetase short chain family member 2 (ACSS2) in order to maintain nuclear-cytosolic pools of acetyl-CoA. However, we have a very limited understanding of the mechanisms by which cells sense acetyl-CoA and how this sensing pathway can subsequently engage adaptive responses when acetyl-CoA production via ACLY is compromised. Notably, a liver-specific inhibitor against ACLY is currently in phase 3 clinical trials for the treatment of hypercholesterolemia. Despite this clinical therapeutic and the potential for the inhibitor to be widely used in individuals with metabolic diseases, studies with genetic models of hepatic ACLY deficiency are lacking, and in particular, no studies have investigated the implications of ACLY loss and subsequent compensatory ACSS2 upregulation in metabolic liver disease, such as non-alcoholic fatty liver disease (NAFLD). Based on my preliminary data, I hypothesize i) that the sensitivity of the mevalonate and cholesterol pathway to ACLY loss mediates ACSS2 upregulation via activation of SREBP transcription factors and ii) that suppression of lipogenic acetyl-CoA production and activation of this sensing mechanism has implications in the pathogenesis of NAFLD by causing a defect in mitochondrial function and fatty acid oxidation. I will test this hypothesis, first (aim 1) through quantification of cholesterol pathway metabolites and assessment of SREBP transcriptional activity, using both an in vitro and in vivo model of ACLY deficiency. Further, I will characterize (aim 2) the effect of suppressing lipogenic acetyl-CoA production an in vivo model of hepatic steatosis. Specifically, I will investigate how a deficit in lipogenic acetyl-CoA production alters fatty acid oxidation and mitochondrial function, and determine whether these changes are dependent on alterations in levels of the mevalonate pathway product, ubiquinone. Overall, I expect the results of this study to address an essential mechanism in acetyl-CoA sensing, as well as the functional consequences of targeting acetyl-CoA metabolism in NAFLD, with the potential to impact treatment strategies of existing therapeutics.