Studies On The Role Of Caveolin-1in Nonalcoholic Fatty Liver Disease

BackgroundNAFLD is a clinical syndrome without excess alcohol intake and has the pathological characteristics such as hepatic steatosis and lipid accumulation, become the most common liver disease.In recent years, with the improvement of people’s living standards and lifestyle changes,The incidence of this disease is increasing with average25%-30%of the world’s population involvement, and become the most common liver disease. China’s prevalence rate showed an increasing trend. NAFLD included a series of pathological changes from simple fatty liver to nonalcoholic steatohepatitis(NASH), fibrosis and cirrhosis [4].However, the pathogenesis of NAFLD is still unclear.Previous studies have shown that "two hit"[6] that insulin resistance caused peripheral adipose decompose, and hyperinsulinemia is the primary factor of liver steatosis.Some research on the mechanism design of clinical trial results suggest that improving insulin resistance is not valid for all patients with NAFLD.The main reason is "two hit" theory cannot fully explain all mechanism of NAFLD, suggests there are other mechanisms involved in the occurrence of NAFLD.Some research has shown that, Caveolin-1(Caveolin-1) is the main part of membrane caveolae,a specific structure of depression in liver cells,which is related with insulin resistance, Existing research shows that caveolin-1play an important role in maintaining the integrity of the plasma membrane, vesicular transport, and signal transmission[7].In recent years, the role of caveolin-1in lipid metabolism by more and more attention.Frank.et al, observed the mice of caveolin-1unexpression don’t appear fat after high-fat diet. It shows caveolin-1is one of the key gene of obesity induced by high-fat diet [8].Subsequent animal experiments found that lack of caveolin-1expression can prevent atherosclerosis, glucolipid metabolic disorder diseases such as type2diabetes, it suggests that Caveolin-1may play an important role in aggregation in hepatic fatty acid metabolism and triglyceride accumulation in liver cells[9,10].But its role in NAFLD pathogenesis is not clear. Therefore, This article established C57BL/6mice model of NAFLD induced by high fat diet, L02steatosis induced by FFA, to detect serum lipid concentration, Caveolin-1mRNA and protein levels in NAFLD livers of mice and L02steatosis, and its effect on SREBP-1, FASN,ACC, COX-2, to explore the role of Caveolin-1in the formation of NAFLD.ObjectiveThe purpose of this study is to observe the expression of Caveolin-1mRNA and protein in liver tissue of mice and L02cells induced by FFA,then to explore the effects of Caveolin-1in lipid synthesis.Methods1The animal model of NAFLD (experimental group) was established by giving C57BL/6mice with12-weeks high fat diet(HFD method,80.5%of Ordinary feed,2% cholesterol,7%lard,10%of egg yolk powder and0.5%of bile salts), then kill the mice in4weeks,8weeks,12weeks2The vitro cells model of NAFLD is established in this paper with palmitic acid induced normal liver cell line L02cells.the final concentration of palmitic acid and oleic acid mixture was1mM (palmitic acid:oleic acid=1:2), then add1%fetal bovine serum albumin in DMEM medium,after48hours for harvest.Oil red O staining was to observe lipid droplets in cells, and determine the content of the TG in frozen solution.3Real-time fluorescent quantitative PCR primers (SYBR method) was used to extract Caveolin-1mRNA in mice liver tissue and L02cells induced by FFA.then analyze the changes of Caveolin-1mRNA in two groups of mice and L02cells induced by FFA.4Western Blot was performed after total protein extraction from mice liver and L02cells to observe Caveolin-1protein in the treatment group and the control group, further to confirm whether the changes are corresponding with the mRNA changes.5Oil red O staining was done to observe lipid droplets changes after RNA interference and high gene expression in L02cells induced by FFA, and observe the SREBP-1, FASN, ACC, COX-2protein levels between the RNA interference group and high gene expression group in L02cells induced by FFA.Results1Expression of Caveolin-1mRNA and protein level in the HFD mice group were significantly lower than the control.2Expression of Caveolin-1mRNA and protein level in L02cells induced by FFA were significantly lower than the control.3Fatty degeneration and SREBP-1, FASN, ACC, COX-2protein levels were increased after inhibition of Caveolin-1genes in L02cells.On the contrary, Fatty degeneration and SREBP-1, FASN, ACC, COX-2protein levels were decreased after high expression of Caveolin-1genes in L02cells. ConclusionThese results suggest that Caveolin-1may play a certain protection mechanisms in NAFLD development.it may play a role in NAFLD through the facts of SREBP-1, FASN,ACC and COX-2.