奶牛酮病肝脂代谢紊乱AMPK信号传导机制

Ketosis of dairy cows is an energy metabolic disease, which is characterized by the pathological basis of negative energy balance, and the biochemical changes of lipid metabolic disorder. The inhibited fat acid metabolism has been demonstrated in liver of ketotic cows, but it is unknown what is the regulating mechanism on lipid metabolism of liver in ketosis. Therefore, it is important to confirm the signaling transition pathway of lipid metabolic disorder for revealing the pathogenesis of ketosis. In vivo and in vitro, the changes of biomarkers in serum and lipid metabolic markers in liver will be determined, especially the expression of key enzyme genes related to lipid metabolism in hepatocyte. And the key molecule changes of AMPK signaling pathway which are responsible for lipid metabolism are determined. Therefore, in this study, the signal transmission mechanism of ketosis in dairy cows could be revealed, and provide valuable theoretical base to reveal the pathogenesis of ketosis and reduce the incidence of ketosis.

酮病是奶牛重要的生产疾病，其病理学基础是能量负平衡，肝脂代谢紊乱是本病发生的关键环节之一。先期研究表明，酮病奶牛肝脂β-氧化能力降低，致使酮体生成和肝脂沉积增加。但还不清楚奶牛酮病肝脂代谢调控的信号传导通路。因此，本项目运用分子生物学和细胞生物学等技术，通过酮病奶牛体内实验和肝细胞体外培养实验，检测肝活体组织和肝细胞脂肪酸转运关键酶、脂肪酸氧化关键酶和脂合成与转运关键酶表达水平的变化；检测肝脏AMPK脂代谢信号通路关键分子的变化，明确奶牛酮病脂代谢紊乱的信号传导机制，为揭示奶牛酮病肝脂代谢紊乱的发生机制和制定针对肝脂代谢障碍的防治措施提供理论基础。

奶牛酮病的病理学基础是能量负平衡，表现为高NEFA和高BHBA血症，且酮病发生时胰岛素水平显著降低，而胰高血糖素却显著升高。这些能量代谢信号的紊乱会引起奶牛肝脏的脂代谢紊乱。AMPK信号通路是肝脏的能量代谢枢纽，控制着肝脂代谢稳态。所以本项目的主要研究内容为探讨酮病奶牛的肝脂代谢状态，明确这些能量代谢信号对肝脏脂代谢的调控机制。先前研究发现，酮病时肝脏AMPK磷酸化水平显著降低，肝脂合成增加，而脂输出和脂氧化作用降低，导致肝脂蓄积。且高浓度的NEFA可抑制AMPK信号通路，促进SREBP-1c和ChREBP及其下游脂合成基因的表达，而抑制PPAR及其下游脂氧化基因的表达，最终引起肝细胞甘油三酯蓄积。高浓度的BHBA也会激活AMPK通路，但是对肝细胞甘油三酯含量影响不大。胰岛素可抑制AMPK信号通路，促进SREBP-1c和ChREBP介导的脂合成作用，抑制PPAR介导的脂氧化作用，促进肝细胞甘油三酯蓄积。而胰高血糖素起到相反的作用。因此本项目旨在明确奶牛酮病的肝脏脂代谢状态，明确酮病奶牛主要代谢刺激信号，高NEFA和BHBA，以及胰岛素和胰高血糖素对奶牛肝细胞脂代谢以及AMPK信号通路的影响。