Sulfur Amino Acid Metabolism and Regulation of Hepatic Metabolic Flexibility

项目总结 人们越来越认识到非酒精性脂肪性肝炎(NASH)是一种常见的肝病，具有 复杂和不同的根本原因。现在，新的证据表明，调节失调的肝脏硫 氨基酸代谢与晚期人类NASH有关，并导致明显恶化的脂肪变性 以及在遗传小鼠模型中的损伤。然而，在我们对如何 含硫氨基酸代谢改变NASH严重程度，以及控制肝脏含硫氨基酸的机制 正常生理和肝脏疾病中的代谢。这项建议基于我们的发现，即CoA 代谢是肝脏硫氨基酸代谢受损和肝脏脂肪之间的关键缺失环节 在纳什的积累和伤害。我们的目标是建立一种新的致病机制，即肝脏 半胱氨酸(辅酶A合成底物)的可用性对于维持线粒体辅酶A池至 支持脂肪酸氧化。然而，晚期NAFLD中不平衡的含硫氨基酸流量减少 影响辅酶A合成的半胱氨酸可获得性。肝脏辅酶A不足进而限制了肝脏的 适应增加的脂肪酸流入，造成一种称为新陈代谢不灵活的状况，促进 线粒体功能障碍、脂肪变性和氧化应激。从机制上讲，我们已经确定了受损的 甲硫氨酸腺苷转移酶1A(MAT1A)，它驱动上游蛋氨酸循环-跨硫通量 产生半胱氨酸，以及介导下游的半胱氨酸双加氧酶-1(CDO1)的过度激活 半胱氨酸消除，通过导致半胱氨酸输入和输出不平衡而导致这种致病状态 在NAFLD。进一步的研究揭示了胆汁酸、TFEB和FGF15/19信号调节之间有趣的串扰 Mat1a和CDO1在正常生理条件下对肝脏含硫氨基酸和辅酶A代谢的调控 纳什。我们已经开发出新的小鼠模型，使我们能够在 两个关键的监管步骤(MAT1A，CDO1)。在目标1中，我们将使用肝细胞特异性诱导的CDO1 转基因小鼠和肝细胞特异性CDO1基因敲除小鼠研究CDO1表达的变化 胆汁酸下游信号影响肝脏含硫氨基酸、辅酶A和谷胱甘肽代谢的调控 纳什严重程度。在目标2中，我们将使用肝脏特异性MAT1a功能获得和功能丧失的小鼠模型 目的：探讨MAT1A在调节肝脏含硫氨基酸、辅酶A和谷胱甘肽代谢中的意义。 并进一步研究FGF15/19和TFEB如何调节MAT1A驱动的硫通量和CoA代谢。 生理学和纳什。通过确定含硫氨基酸代谢与辅酶A代谢的新致病联系 并描绘了调节肝脏含硫氨基酸和辅酶A代谢的新机制，我们预计 这项研究可能不仅为推动NASH的机制提供新的见解，而且可能会推动该领域的发展 这不仅是研究进展，也是开发未来治疗干预措施的分子基础。

Project summary It is increasingly recognized that non-alcoholic steatohepatitis (NASH) is a prevalent liver disease with complex and heterogenous underlying causes. Now, new evidence suggests that dysregulated hepatic sulfur amino acid metabolism is associated with advanced human NASH and causes markedly worsened steatosis and injury in genetic mouse models. However, significant knowledge gaps exist in our understanding of how sulfur amino acid metabolism modifies NASH severity, and what mechanisms control hepatic sulfur amino acid metabolism in normal physiology and liver diseases. This proposal builds on our discovery that CoA metabolism is a key missing link between impaired hepatic sulfur amino acid metabolism and liver fat accumulation and injury in NASH. We aim to establish a novel pathogenic mechanism whereby hepatic availability of cysteine (a CoA synthesis substrate) is critical in maintaining the mitochondrial CoA pool to support fatty acid oxidation. However, dysregulated sulfur amino acid flux in advanced NAFLD reduces cysteine availability that impairs CoA synthesis. Hepatic CoA insufficiency in turn limits the liver’s ability to adapt to increased fatty acid influx, creating a condition termed metabolic inflexibility that promotes mitochondrial dysfunction, steatosis and oxidative stress. Mechanistically, we have identified that impaired methionine adenosyltransferase 1A (MAT1A), which drives upstream methionine cycle-transsulfuration flux to produce cysteine, and overactivation of cysteine dioxygenase type-1 (CDO1), which mediates downstream cysteine elimination, contribute to such pathogenic condition by causing imbalanced cysteine input and output in NAFLD. Further study revealed intriguing crosstalk of bile acids, TFEB, and FGF15/19 signaling regulation of MAT1A and CDO1 to control hepatic sulfur amino acid and CoA metabolism under normal physiology and NASH. We have developed novel mouse models that allow us to manipulate hepatic sulfur amino acid flux at the two key regulatory steps (MAT1A, CDO1). In Aim 1, we will use hepatocyte-specific inducible CDO1 transgenic mice and hepatocyte-specific CDO1 knockout mice to study how altered CDO1 expression downstream of bile acid signaling impacts hepatic sulfur amino acid, CoA and GSH metabolism to modulate NASH severity. In Aim 2, we will use liver specific MAT1A gain-of-function and loss-of-function mouse models to establish the significance of the MAT1A in regulating hepatic sulfur amino acid, CoA and GSH metabolism, and further investigate how FGF15/19 and TFEB regulate MAT1A-driven sulfur flux and CoA metabolism in physiology and NASH. By defining a new pathogenic link of sulfur amino acid metabolism to CoA metabolism and delineating novel mechanisms regulating hepatic sulfur amino acid and CoA metabolism, we expect that this study may advance the field by providing not only new insights into the mechanisms driving NASH progression but also molecular basis for developing future therapeutic interventions.