Mechanisms linking the Branched-Chain alpha-Keto Acid regulatory network to the pathogenesis of NASH

支链 α-酮酸调节网络与 NASH 发病机制的联系机制

• 批准号: 10628663
• 负责人: Phillip J White
• 金额: $ 44.82万
• 依托单位: DUKE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-04-15 至 2028-01-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10628663
• 关键词: ATP Citrate (pro-S)-Lyase; Acute Liver Failure; Adenoviruses; Animals; Body Weight; Branched-Chain Amino Acids; CD36 Antigens; CD36 gene; Cardiovascular Diseases; Cell Death; Cirrhosis; Deposition; Development; Eating; Enzymes; Etiology; Fibrosis; Follow-Up Studies; Health; Hepatic; Hepatocellular Damage; Hepatocyte; Human; Incidence; Individual; Inflammation; Keto Acids; Link; Lipids; Liver; Liver Failure; Liver diseases; Mediating; Medicine; Metabolic Diseases; Modeling; Molecular; Morbid Obesity; Non-Insulin-Dependent Diabetes Mellitus; Obesity; Oxidoreductase; Pathogenesis; Pathologic; Pathway interactions; Patients; Persons; Phosphoric Monoester Hydrolases; Phosphorylation; Phosphotransferases; Physical activity; Primary carcinoma of the liver cells; Printing; Protein Dephosphorylation; Protein phosphatase; Rattus; Recombinant Proteins; Reporting; Risk; Risk Factors; Serine; Testing; Therapeutic; Thinness; Translations; Triglycerides; United States; Viral hepatitis; Wistar Rats; Work; adenoviral mediated; amino acid metabolism; bariatric surgery; benign state; cohort; global health; inhibitor; insight; lipid biosynthesis; lipid metabolism; mouse model; non-alcoholic fatty liver disease; nonalcoholic steatohepatitis; novel; overexpression; oxidation; pandemic disease; pharmacologic; simple steatosis; small molecule inhibitor; uptake

Non-alcoholic steatohepatitis (NASH) is a major global health concern that continues to rise at an alarming rate driven by the tide of the obesity pandemic. It is well appreciated that NASH significantly raises risk for development of hepatocellular carcinoma, cirrhosis, and acute liver failure as well as type 2 diabetes and cardiovascular disease. However, there are currently no approved therapies for the treatment or reversal of NASH. Our foundational work defining the molecular pathways linking disturbances in branched-chain amino acid (BCAA) metabolism to the etiology of metabolic disease recently identified a novel regulatory node that exerts a powerful influence on hepatic lipid deposition in obese and lean animals. We discovered that the branched-chain α-keto acid dehydrogenase (BCKDH) kinase, BDK that inhibits branched-chain α-keto acid (BCKA) oxidation robustly stimulates de novo lipogenesis (DNL), by phosphorylating the lipogenic enzyme ATP citrate lyase (ACLY) on its activating serine. Likewise, we found that the BCKDH phosphatase, protein phosphatase M1K (PPM1K), that promotes BCKA oxidation, dephosphorylates ACLY on its activating serine. Accordingly, adenoviral mediated overexpression of BDK in liver of lean healthy Wistar rats was found to be sufficient to raise hepatic DNL by 2.5 fold. Whereas, treatment of genetically obese Zucker Fatty rats with the BDK inhibitor, BT-2, or adenovirus expressing recombinant PPM1K lowered circulating BCKA, reduced phosphorylation of ACLY, and remarkably prompted a 40% reduction in liver triglyceride content in these severely obese animals without altering food intake, body weight, adiposity, or physical activity. Subsequent, studies in our lab have identified an additional effect of BT2 to lower expression of the fatty acid transporter, CD36, in liver. Thus, our current working model is that modulation of the hepatic BCKA regulatory network exerts robust effects on lipid content due to its dual effects on CD36-mediated lipid uptake and ACLY-mediated DNL. Beyond these mechanisms, it remains unclear whether the BCKA themselves exert any direct or synergistic effects on hepatic lipid metabolism. Importantly, our recent medRxiv preprint demonstrates that circulating BCKA and liver BDK expression are strongly associated with NASH status in a cohort of 288 bariatric surgery patients with severe obesity that are discordant for NAFLD and NASH. In the current proposal, we will leverage our newly developed mouse models, established molecular/pharmacologic armamentarium, and novel insight to resolve the molecular mechanisms connecting the BCKA regulatory network to the pathogenesis of NASH by completing three specific aims: 1) Characterize the relative contribution of hepatic BDK, PPM1K, and BCKA to NASH progression. 2) Evaluate the therapeutic potential of small molecule inhibitors of BDK for reversing NASH. 3) Define the mechanisms connecting the BCKA regulatory network to hepatic lipid content. The successful completion of the studies outlined in specific aims 1-3 will define the BCKA regulatory network as an important modulator of NASH progression with strong translation relevance for the treatment of NASH in humans.

非酒精性脂肪性肝炎（NASH）是一个主要的全球健康问题，继续以惊人的速度上升 肥胖症流行的趋势所驱动。很好地理解，NASH显著增加了以下风险： 肝细胞癌、肝硬化和急性肝功能衰竭以及2型糖尿病的发展， 心血管疾病然而，目前还没有批准的治疗或逆转 纳什我们的基础工作定义了连接支链氨基中干扰的分子途径 最近，BCAA代谢对代谢性疾病病因学的研究发现了一个新的调节节点， 对肥胖和瘦型动物的肝脏脂质沉积产生强大的影响。我们发现 抑制支链α-酮酸脱氢酶（BCKDH）激酶 （BCKA）氧化通过使脂肪生成酶ATP磷酸化而强烈刺激从头脂肪生成（DNL 柠檬酸裂解酶（ACLY）对其活化丝氨酸的影响。同样，我们发现BCKDH磷酸酶蛋白 磷酸酶M1 K（PPM 1 K）促进BCKA氧化，使其活化丝氨酸上的ACLY去磷酸化。 因此，发现腺病毒介导的BDK在瘦的健康Wistar大鼠肝脏中的过表达， 足以使肝DNL升高2.5倍。然而，用以下药物治疗遗传性肥胖的Zucker Fatty大鼠， BDK抑制剂BT-2或表达重组PPM 1 K的腺病毒降低循环BCKA， 磷酸化的ACLY，并显着促使40%的肝甘油三酯含量减少，在这些 严重肥胖的动物，而不改变食物摄入量，体重，肥胖或体力活动。随后， 我们实验室的研究已经确定了BT 2降低脂肪酸转运蛋白表达的额外作用， CD 36，肝脏。因此，我们目前的工作模型是，调节肝脏BCKA调节网络发挥作用， 由于其对CD 36介导的脂质摄取和ACLY介导的DNL的双重作用，对脂质含量具有稳健的作用。 除了这些机制，目前尚不清楚BCKA本身是否发挥任何直接或协同作用， 对肝脏脂质代谢的影响。重要的是，我们最近的medRxiv预印本表明，循环BCKA 在288例减肥手术患者的队列中， 与NAFLD和NASH不一致的严重肥胖。在目前的提案中，我们将利用我们的 新开发的小鼠模型、已建立的分子/药理学设备以及新的见解 通过以下方式解决将BCKA调节网络与NASH发病机制联系起来的分子机制： 完成三个具体目标：1）表征肝脏BDK、PPM 1 K和BCKA的相对贡献， NASH进展。2)评价BDK小分子抑制剂逆转NASH的治疗潜力。 3)明确BCKA调节网络与肝脏脂质含量之间的联系机制。成功 完成具体目标1-3中概述的研究将把BCKA监管网络确定为一个重要的 NASH进展的调节剂，与人类NASH的治疗具有强翻译相关性。