枸杞多糖通过SIRT1干预非酒精性脂肪肝肝细胞脂代谢的作用与机制

SIRT1 is a key regulating molecule of lipid metabolism intracellular. Previous studies reported that lycium barbarum polysaccharides (LBP) can obviously improve non-alcoholic fatty liver disease (NAFLD), and significantly activate SIRT1 expression. Thus our study proposes a hypothesis that LBP mediates hepatic lipid metabolism and improves NAFLD via SIRT1. We use male C57BL/6J mice and HepG2 cells induced by high-fat to build NAFLD model. To SIRT1 as molecular target, using RNAi, western blot, quantitative real-time PCR and radiolabeled enzymes activities measurement, our study firstly confirms that LBP regulates SIRT1 activity and expression by increasing NAD+/NADH in the form of time-dependent and concentration-dependent manner. Further confirms the specific effect and mechanism of LBP on SIRT1 activity involved in the key signaling pathway of SIRT1/AMPK in fatty acid oxidation and de novo synthesis in hepatocytes. We will further explore the molecular pharmacological effects in the treatment process of LBP on NAFLD to provide a forceful theoretical system for the pharmaceutical development of lycium barbarum polysaccharides.

SIRT1 是细胞内脂代谢的关键调节分子。前期工作发现枸杞多糖（LBP）能够明显改善非酒精性脂肪肝（NAFLD），并且伴随着SIRT1分子的显著活化。由此，本课题提出"LBP通过SIRT1分子干预肝细胞脂代谢改善NAFLD"的科学假说。课题利用高脂诱导雄性C57BL/6J小鼠、HepG2细胞株建立NAFLD模型，拟以SIRT1作为分子靶标，采用RNAi、蛋白质免疫印迹、荧光定量PCR、放射性同位素标记酶活测定等技术手段，首先验证LBP是否通过升高NAD+/NADH，以时间依赖、剂量依赖的方式调节SIRT1的基因表达及活性；进而阐明LBP通过SIRT1所涉及的关键信号通路SIRT1/AMPK在肝细胞脂肪酸氧化途径及脂肪酸从头合成途径中产生的具体效应及机制。此课题研究成果将阐明枸杞多糖在治疗NAFLD过程中的分子药理作用机制，为传统中药材枸杞的药用开发提供新的理论依据。

本研究旨在探讨枸杞多糖(Lycium barbarum polysaccharide, LBP)对高脂诱导的非酒精性脂肪肝(NAFLD)的保护作用及其机制。近年研究发现，sirtuin 1 (SIRT1)在调节肝细胞脂质代谢的过程中发挥了重要作用。本项目证实LBP通过提高NAD+/NADH比值上调SIRT1去乙酰化酶活性和蛋白表达。随后，LBP通过sirt1相关信号通路促进LKB1去乙酰化和AMPK磷酸化。研究还发现LBP通过激活体外和体外的SIRT1/LKB1/AMPK通路、乙酰辅酶羧化酶(ACC)磷酸化和脂肪甘油三酯脂肪酶(ATGL)蛋白表达从而降低脂肪酸合成酶(FAS)体内。SIRT1小干扰RNA (siRNA)介导的下调逆转了LBP对ACC、FAS和ATGL的介导作用。此外,枸杞多糖还可上调palmitoyltransferase-1α(CPT-1α)表达。综上所述，我们的研究表明LBP在调节肝脂代谢中起着重要作用，LBP对SIRT1的药理激活可能是NAFLD的预防策略之一。