Effects of gypenosides on PCSK9 gene expression and blood lipids lowered by simvastatin

AIM: To explore the effect of gypenosides (GPs) on PCSK9 gene expression in hyperlipidemic rat liver and the blood lipids lowered by simvastatin.METHODS: Healthy male SD rats (n=60) were randomized into 5 groups:normal control group, hyperlipidemic model group, simvastatin group, GPs group and GPs combined with simvastatin group (combined group). The rats in all groups were fed high-fat diet except normal control group which were fed with ordinary diet. The rats in control group and hyperlipidemic model group were gavaged with 0.3% CMC-Na every day. The rats in GPs group were gavaged with GPs at 160 mg·kg^-1·d^-1. The rats in simvastatin group were gavaged with simvastatin at 5 mg·kg^-1·d^-1. The rats in combined group were gavaged with GPs and simvastatin. The experiment lasted for 8 weeks. The rats were anesthetized with chloral hydrate, and abdominal arterial blood samples were collected to detect the total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C). The body weight and the wet weight of the livers were measured, and the liver index was calculated. The pathological changes of the livers were observed under microscope with HE staining. The expression of PCSK9 and low-density lipoprotein receptor (LDLR) at mRNA and protein levels was determined by real-time PCR and Western blot. RESULTS: The model of hyperlipidemia rats was established successfully. Compared with model group, the levels of TC, TG and LDL-C in simvastatin group, GPs group and combined group were obviously decreased (P<0.05), and the HDL-C levels were obviously upregulated (P<0.05). Compared with model group, the liver indexes in simvastatin group, GPs group and combined group were obviously decreased (P<0.05). The pathological changes of the liver tissues showed that hepatic adipose appeared in model group, and that in simvastatin group and GPs group had different degrees of relief, especially in combined group. Compared with model group, the mRNA expression levels of PCSK9 and LDLR in simvastatin group were obviously increased, while the mRNA expression levels of PCSK9 in GPs group and combined group were obviously decreased (P<0.05), and the mRNA expression of LDLR in combined group was obviously increased (P<0.05). Compared with model group, the protein expression of PCSK9 and LDLR in simvastatin group was obviously increased, while the protein expression levels of PCSK9 in GPs group and combined group were obviously reduced, and the LDLR protein levels were obviously increased (P<0.05). CONCLUSION: Gypenosides inhibit the expression of PCSK9 and increase the expression of LDLR in the liver. The combination of gypenosides and simvastatin promotes the lipid-lowering effect of simvastatin and attenuates hepatic steatosis, which may be related to inhibiting the expression of PCSK9 in the liver.