Lunasin functionally enhances LDL uptake via inhibiting PCSK9 and enhancing LDLR expression in vitro and in vivo

// Lili Gu 1 , Yue Wang 1 , Yaqiong Xu 1 , Qinghua Tian 1 , Gaoxin Lei 1 , Cheng Zhao 1 , Zhan Gao 1 , Qin Pan 1 , Wenfeng Zhao 1 , Liu Nong 1 and Shuhua Tan 1 1 State Key Laboratory of Natural Medicines, School of Life Science and Technology, China Pharmaceutical University, Nanjing, 211198, China Correspondence to: Shuhua Tan, email: tanshuhua163@163.com Keywords: lunasin, proprotein convertase subtilisin/kexin type 9, low-density lipoprotein cholesterol, low-density lipoprotein receptor, hepatocyte nuclear factor-1α Received: June 26, 2017 Accepted: August 04, 2017 Published: August 24, 2017 ABSTRACT Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a serine protease which regulates serum low-density lipoprotein cholesterol (LDL-C) levels by promoting the degradation of the hepatic low-density lipoprotein receptor (LDLR), and has become an attractive therapeutic target for cholesterol lowering intervention. Lunasin, a 43-amino acid polypeptide initially isolated from soybean, has been previously proven to possess cholesterol lowering activity. Here we identified the down-regulation of PCSK9 expression by lunasin as one new mechanism that increased cell-surface LDLR level and enhanced LDL uptake in vitro and in vivo . Treatment of HepG2 cells with lunasin inhibited the expression of PCSK9 at mRNA and protein levels in a dose-and-time dependent manner via down-regulating hepatocyte nuclear factor-1α (HNF-1α), thereby contributing to increasing LDLR level and functionally enhancing LDL uptake. ApoE -/- mice receiving lunasin administration by intraperitoneal injection at doses of 0.125~0.5 μmol/kg·day for 4 weeks had significantly lower PCSK9 and higher LDLR levels in hepatic tissue, as well as remarkably reduced total-cholesterol (T-CHO) and LDL-C in blood as compared to mice in vehicle control group. Furthermore, we identified that LDLR expression was up-regulated by lunasin via PI3K/Akt-mediated activation of SREBP-2 in HepG2 cells. Taken together, our findings suggest that lunasin inhibits PCSK9 expression by down-regulating HNF-1α and enhances LDLR expression via PI3K/Akt-mediated activation of SREBP-2 pathway, thereby functionally enhances LDL uptake in HepG2 cells and in ApoE -/- mice.