The Mechanisms of miR-638/StarD10&nbsp;in HDL&nbsp;Metabolism
Authors: Ye Ping , Wang Xiaona , Han Jie , Cao Ruihua , Bai Yongyi 
Published: January 2021

Abstract
Background: MicroRNA (miRNA) plays an important role in regulation of genes, especially in post-transcriptional level. Many studies had studied the role of miRNAs in the development and progression of cardiovascular disease through miRNA knockout mice models, and chemically synthesized mimics or inhibitors of miRNAs. This study was designed to further investigate the effect of miR-638 on lipid metabolism-related gene expression.Methods: miR-638 mimics and inhibitors were transfected into HepG2 and macrophages. Appropriate concentrations and time points used to treat cells were determined through pre-experiment. Then RT2 Profiler™ PCR Array chips contained 84 human lipoprotein signals and cholesterol metabolism related gene were used to investigate the effect of miR-638 on lipid metabolism. Real-time PCR and Western blot were also used to verify the results. Mice received 2 times tail vein injections of  StarD10 mimics and inhibitors the first week, and the injection continued three weeks with one time foreach week. Total plasma cholesterol, triglyceride, LDL-C and HDL-C levels were obtained at sacrifice; All mice were injected intraperitoneally with H3-cholesterol–labeled and cholesterol -loaded raw 264.7 macrophages (0.5m L /mice). Serum, liver tissues and feces were collected at 24 hour. All samples were analyzed for the appearance of 3H-tracer (as the percentage of the total injected counts). Protein were extracted from liver tissue, and Western-blot was conducted to evaluate lipid metabolism related protein expression. Sacrificed the mice and removed the aortas, aorta plaque and macrophage were investigated by examination of stained sections by H-E staining, Oil-red O staining and CD68+ staining.Results: Transfected miR-638 Mimics in HepG2 cells and macrophages could significantly increase the expression of miR-638. Transfected miR-638 Inhibitors in HepG2 cells could significantly decreased the expression of miR-638. Results showed that transfected miR-638 Mimics in HepG2 cells and macrophages could reduce the RNA and protein expression levels of ATP-binding cassette A-1 (ABCA1), ATP-binding cassette G-1 (ABCG1) and very low density lipoprotein receptor (VLDLR), and transfected miR-638 Inhibitors in HepG2 cells could increase the RNA and protein expression levels of ABCA1 and ABCG1. Compared with the control groups, the levels of LDL-C and TC were decreased lightly, while the level of HDL3-C/HDL-C was increased in the StarD10 mimics group. The amount of 3H-cholesteral in StarD10 mimics group were increased by 62.86% in the plasma, 30.73% in the liver and 52.72% in the feces, respectively. The expression of ABCA1, ABCG1, protein in the liver was higher in StarD10 mimics. The ratio of the plaque area to luminal area of mice in the StarD10 mimics group is slighter smaller than that of the adenovirus control group, but there is no statistical difference (P > 0.05). Compared with mice in the adenovirus control group, mice in the StarD10 mimics group have much lower lipid content (P < 0.01) and macrophage content (P < 0.01) in the plaque. Conclusions: MiR-638/StarD10 could influence the expression levels of genes related to lipid metabolism. MiR-638/StarD10 can influence the blood lipid level, promote reverse transport of cholesterol, and StarD10 can reduce macrophage content and lipid content in the active surface patches in the mice.