Research on GPs Inhibition of miRNA-122 Expression and Lipid-lowering Effect Via Regulation of Lipid Metabolism Enzyme Activity / 世界科学技术-中医药现代化

ABSTRACT

This study was aimed to explore whether gypenosides (GPs) can inhibit the expression of miRNA-122 and regulate the lipid metabolism enzyme activity to play a role in lipid-lowering effect. A total of 48 healthy male SD rats were randomly divided into 4 groups, which were the normal control group (C), hyperlipidemic model group (M), simvastatin group (S) and the GPs group (G). All groups were fed with high-fat diets except the normal control group which was fed with normal diets. The GPs, which were dissolved in 0.3% sodium carboxymethyl cellulose (CMC-Na) solution, were given by the intragastric administration. The C group and M group were given 0.3% CMC-Na solution (1 mL/100 g) daily. The G group was given 160 mg·kg-1 of GPs daily. The S group was given 5 mg·kg-1 of simvastatin daily. The experiment was continued for 8 weeks. After the last medication, rats were fasted for 12 hours. Rats were anesthetized with chloral hydrate (7%). Abdominal arterial blood samples were collected to detect the total cholesterol (TC), triglyceride (TG), high density lipoprotein cholesterol (HDL-C) and low density lipoprotein cholesterol (LDL-C). The wet weight of liver was weighed and the liver index was measured. The liver total RNA was extracted to determine the expression of miRNA-122 by the real-time PCR. The homogenates of liver tissues were prepared for the determination of hepatic lipase (HL), lipoprotein lipase (LPL) and HMG-CoA reductase activity. Cholesterol micelle formation experiments were implementedin vitro. The results showed that compared with the normal control group, TC, TG and LDL-C levels of the model group were significantly increased (P< 0.01), while the HDL-C levels in each group were obviously decreased (P< 0.05). Compared with the model group, TC, TG and LDL-C levels of the S group and G group were obviously decreased (P< 0.05), and the HDL-C level was obviously increased (P< 0.05). Compared with the model group, the liver indexes of the S group and G group were obviously decreased (P< 0.05). Compared with the hyperlipidemia model group, the expressions of miRNA-122 of the S group and G group were significantly reduced (P< 0.05). Compared with the hyperlipidemia model group, the activity of HMG-CoA reductase was obviously reduced in the S group and G group (P< 0.05), but the HL and LPL activities were obviously increased (P< 0.05). GPs can inhibit the formation of cholesterol micelles to some extent. It was concluded that GPs can effectively reduce the blood lipid level in hyperlipidemic rats, in order to relieve the hepatic fatty lesions. Its lipid-lowering mechanism was related to its inhibition of miRNA-122 expression and regulation of lipid metabolism enzyme activity, as well as the inhibition on the formation of cholesterol micelles.