Genipin Improves The Molecular Mechanism Of Hyperlipidemia Induced By High-fat Diet And Reduces Liver Lipid Accumulation

Recently,we have changed our diet and lifestyle to high calories and sedentary and less exercise with development of society and improvement of living standard,which leads to overwhelmed lipid accumulation and obesity.Excess lipid accumulation in adipose tissue and other organs such as heart,liver and in skeletal muscle can cause lipid toxicity in metabolism,chronic low-grade inflammation and metabolic disorders,increasing the risk of chronic diseases,such as cardiovascular disease,hypertension,dyslipidemia,type 2 diabetes mellitus,nonalcoholic fatty liver disease,cancer and so on.It is urgent to solve this public health problem by raising effective strategy on how to reduce weight and the occurrence of obesity related metabolic disorders.Genipin is an active constituent of gardenia,which is often used as a traditional Chinese medicine treatment for diabetes.However,the effect and molecular mechanism of genipin on over-nutrition-induced hyperlipidemia and hepatic lipid accumulation,are still unknown.In this study,we take high-fat diet(HFD)fed obese mice as research objects to investigate the effect of intra-gastric administration of genipin on over-nutrition-induced obesity and metabolic disorders.We examine body weight and food intake of mice every week and analyze the basal metabolic index according to respiratory quotient(RQ),energy expenditure(EE),oxygen consumption(VO2)and activity detected by metabolic chamber.In addition,we test effect of genipin on lipid metabolism by measuring lipid level in plasma and liver.At the same time,we can observe the effect of genipin on hepatic lipid droplet storage through immune-histochemical experiments.To further explore the molecular mechanism of genipin on lipid metabolism,we examine the expression of genes related to lipid metabolism at mRNA and protein levels in genipin treated mice and primary hepatocytes.Moreover,we conduct oil red O staining experiment and examine triglyceride(TG)concentration in genipin treated primary hepatocytes to confirm effect of genipin on lipid metabolism in functional.We speculate microRNAs(miRNAs)are crucial in response to genipin to regulate lipid metabolism as the important role of miRNAs in the regulation of lipid homeostasis.We predict miRNAs target to genes which regulate lipid metabolism by bioinformatics,verify their function on target genes and expression after treated with genipin.Further,we determine the function sequence via luciferase repoter assay and explore the mediated role of miRNAs in regulating lipid metabolism via transfection with mimic and inhibitor.We found that the body weight of HFD-fed obese mice were reduced in a dose dependent manner,while leave food intake unchanged.In addition,we speculated the lower body weight resulted from aggrandized energy metabolism as VO2,EE and activity were ’enhanced in genipin treated mice.Moreover,genipin reduced lipid concentration in serum and liver and alleviated hyperlipidemia and inhibited hepatic lipid accumulation.At the molecular level,we profiled lipid metabolic gene expression and found that genipin inhibited lipogenesis gene expression specifically in liver tissues.In isolated primary hepatocytes,lipogenesis gene expression upregulated by free fatty acids(FFAs)were also inhibited by genipin in a dose dependent manner.We analyzed miRNAs targeted to Srebp-1c 3’ untranslated regions(UTRs)using bioinformatics and examined their expression in genipin treated cells,only miR-142a-5p can be upregulated.And we found that miR-142a-5p can interact with Srebp-1c 3’ UTR through ACTTTATT to decrease its activity and protein level.In primary hepatocytes transfected with miR-142a-5p inhibitor,genipin did not change the protein expression of SREBP-lc and hepatic lipid accumulation,indicated that miR-142a-5p mediated the inhibitory effects of genipin on SREBP-lc and lipid accumulation.In conclusion,genipin alleviated HFD-induced hyperlipidemia and hepatic lipid accumulation in mice via miR-142a-5p/SREBP-l c axis.Our study focused on genipin’s role in lipid metabolism regulation,especially on the molecular mechanism in inhibiting hepatic lipid accumulation.We followed the main line of miRNA/SREBP-lc axis and further clarified the molecular mechanism of genipin in regulating lipid metabolism,which provided new ideas to solve the hyperlipidemia and hepatic lipid accumulation.