人参皂苷通过羧酸酯酶调控脂质代谢缓解胆汁淤积性肝损伤的机制研究

Cholestasis is widespread in a variety of liver diseases, and still lacking specific medicines now. Further development of pertinent drugs based on the pathogenesis of cholestasis becomes a hotspot currently. Our previous study found that ginsenoside could significantly alleviate cholestatic liver injury, but also exert other unknown important pharmacological mechanisms in the early stage of cholestasis in addition to its anti-inflammatory and anti-oxidative effects. Domestic and foreign studies have found that lipid metabolism disorder during the initial stage of cholestasis is not only an important reason for liver inflammation and oxidative injury, but also an independent risk factor of disease progression and deterioration. Our preliminary experiments found that ginsenoside could effectively improve the lipid metabolism disorder occurred in the early stage of cholestasis, which was probably related to the reversal of down-expression of hepatic carboxylesterase (CES). However, the underlying regulatory mechanisms and material basis have not been clarified now. Hence, we propose hypothesis that ginsenoside may maitain the lipid homeostasis via up-regulating CES expression, thereby relieving the cholestatic liver injury. This project intends to further confirm the role of ginsenoside in the regulation of CES-mediated lipid metabolism and the remission on hepatic injury in multiple cholestasis animal models. Meanwhile, the mechanism underlying the up-regulation of CES expression via nuclear receptors by ginsenoside will be investigated, and we will further clarify the material basis of ginsenoside by the strategy of serum pharmacology.

胆汁淤积广泛存在于多种肝脏疾病中，且治疗药物匮乏。寻找胆汁淤积发病机制并进一步开发针对药物是目前研究热点之一。本课题组前期发现人参皂苷可显著缓解胆汁淤积性肝损伤，且除抗炎和抗氧化损伤之外，该药尚存在作用于疾病早期的其他未知重要机制。国内外研究发现胆汁淤积早期的脂质代谢紊乱是诱发肝脏炎症和氧化损伤的重要原因，也是疾病发展和恶化的独立危险因素。我们预实验发现人参皂苷可以有效改善胆汁淤积早期的脂质代谢紊乱，这一作用可能与其逆转肝脏羧酸酯酶（CES）下调有关。然而相应的调控机制和物质基础尚不明确。因此我们提出假说：人参皂苷可通过上调CES恢复脂质代谢平衡，进而缓解胆汁淤积性肝损伤。本项目拟在前期基础之上，进一步在多种胆汁淤积动物模型中确证人参皂苷调控CES介导的脂质代谢，从而缓解肝损伤的作用；从核受体调控探讨人参皂苷上调CES的内在机制；同时利用血清药理学手段进一步明确人参皂苷发挥作用的物质基础。

胆汁淤积肝损伤存在许多肝脏疾病，若不及时治疗，会持续加剧肝脏损伤情况，但目前治疗药物单一，且存在一定副作用。胆汁淤积疾病发生的分子机制复杂是限制药物开发的重要原因。本课题组在证实胆汁淤积肝损伤中羧酸酯酶（CES）的表达下调后，发现机体脂质代谢指标发生紊乱。在明确CES在胆汁淤积模型中调节脂质代谢改善胆汁淤积肝损伤的作用下，进一步挖掘调控CES功能的重要核受体，我们筛选出在胆汁淤积肝损伤中变化显著的核受体Nrf2，并且证实了胆汁淤积肝损伤状态下Nrf2是调控CES的“目标核受体”。.此外，我们的研究发现去乙酰化酶Sirt1可以调控核受体Nrf2的表达发挥调节CES的作用，并证明人参皂苷通过调节Sirt1/Nrf2通路恢复脂质代谢与氧化应激水平从而改善胆汁淤积肝损伤。并进一步通过体外血清药理学手段结合分子对接技术，筛选得出Rg1是人参皂苷中治疗胆汁淤积的有效单体成分，并证明Rg1可以调控Sirt1/Nrf2通路调节CES表达水平。.总之，本研究以肝脏脂质代谢调控代谢酶CES为研究起点，发现人参皂苷通过调节CES改善胆汁淤积小鼠脂质代谢水平，从作用CES的核受体以及探究核受体上游调控蛋白的研究思路，发现人参皂苷通过作用Sirt1/Nrf2通路改善胆汁淤积肝损伤情况，并进一步筛选出人参皂苷中有效单体成分Rg1，最终阐述了人参皂苷治疗胆汁淤积肝损伤的分子机制和物质基础，为进一步药物开发和临床应用提供理论基础。