Study On The Role And Mechanism Of Hepatic ChREBP-? In Glycolipid Metabolism

In modern society,with the increasing intake of fructose,the incidence of fructose-related diseases such as nonalcoholic fatty liver,insulin resistance,and hyperlipidemia has also increased year by year.The liver is one of the most important organs for fructose metabolism and the metabolic process of fructose is regulated by many transcription factors,among which ChREBP is a key transcription factor regulating fructose metabolism.There are two subtypes of ChREBP:ChREBP-? and ChREBP-?.ChREBP-? was found in recent years and its expression levels are very low under physiological conditions.It is usually hard to detect ChREBP-? at the protein level.So far,the function of ChREBP-? is still unclear.In order to explore the role and mechanism of hepatic ChREBP-? in regulating glycolipid metabolism,we first generated a Rosa-LSL-ChREBP-? mouse model by introducing a ChREBP-? expression cassette knocked into the Rosa 26 gene locus by gene targeting,the expression of which is blocked in the presence of the Stop sequence flanked with LoxP sites.Then we successfully generated liver-specific ChREBP-? overexpression mice by crossbreeding with Alb-Cre mice,in which Cre-mediated LoxP recombination removed the Stop sequence and allowed ChREBP expression.In addition,we also generated inducible transgenic mice of ChREBP-? by crossbreeding with Mx1-Cre mice,and characterized the biological functions of ChREBP-? in adult liver.The relevant metabolic features of liver-specific ChREBP-? overexpressing mice were observed and analyzed.The main experimental results of my study include:1.We successfully generated two mouse models overexpressing ChREBP-? specifically in the liver,named as LET-? and MET-?,and confirmed both of the two mouse model at genomic DNA,mRNA and protein levels,respectively.Meanwhile,we found that ChREBP-? could negatively regulate ChREBP-? at protein levels in the liver.2.The physiological function of ChREBP-? in the liver was characterized in vivo for the first time.We found that constitutive overexpression of ChREBP-? in the liver led to dysregulated glycolipid metabolism,severe hepatic steatosis,and liver damage.These serious metabolic disorders caused animal death before adulthood.Furthermore,the phenotype of MET-? mice is consistent with that of LET-? mice,which excludes the possibility that the metabolic disorders is due to a developmental defect secondary to ChREBP-?overexpression.3.Overexpression of ChREBP-? in the liver has a great influence on plasma glycolipid metabolism.On the one hand,the blood glucose of both mouse models is significantly decreased,which may be associated with enhanced glucose uptake and glycolysis,improved glucose tolerance(OGTT)and insulin sensitivity(ITT),and the impaired ability of gluconeogenesis.In addition,FGF21,a target gene of ChREBP,was significantly increased both at mRNA levels in the liver and protein levels in the circulation in the transgenic mice,which may mediate the influence of ChREBP-? on plasma glucose metabolism in part.On the other hand,ChREBP-? overexpressed mice have severe fatty liver,and the contents of TG and TC in liver and circulation also increased significantly.Liver DNL-related enzymes like FASN and SCD1 are significantly up-regulated both in RNA and protein levels.The ability of DNL in liver was significantly enhanced.In addition,we found that the expression of PCSK9 was significantly increased by the overexpression of ChREBP-? in liver,suggesting that ChREBP-? regulate liver and circulating lipid metabolism through de novo lipogenesis as well as PCSK9.In summary,we have successfully generated two mouse models specifically overexpressing ChREBP-? in the liver,and systematically analyzed its biological function in vivo,which enriches the knowledge about the regulation of glycolipid metabolism.