Study On The Intestinal Mechanism Of Transcription Factor ChREBP In Maintaining Fructose Tolerance

With the social progress and the improvement of people’s living standards,the prevalence of metabolic diseases is growing exponentially in the world,accompanied by their severe harm to human physical and psychological health and the heavy burden of social health care.Metabolic diseases with their relevant cardiovascular diseases are becoming an increasingly urgent public health problem and the top priority of chronic disease prevention and control.Although the concept of "sugar restriction" has become popular,the so-called "sugar free food" in the market often contains a lot of fructose,which has become a hidden killer of residents’ health.Investigations in epidemiology and prospective reports have demonstrated that over-consumption of fructose may become a significant hazard in the epidemic of metabolic disorders.High fructose corn syrup,which is widely added to sugar-sweetened beverages and desserts because of its low cost and high sweetness,has become the main source of fructose in people’s daily life.ChREBP plays a vital role in fructose metabolism.Global knockout of ChREBP in mice has been found to cause hypothermia and half of the deaths within a week under high-fructose diet,indicating that ChREBP plays a crucial role in maintaining the body’s fructose tolerance.However,what is the key metabolic organ and process in the maintenance of fructose tolerance by ChREBP? How does ChREBP sense fructose changes? What biochemical mechanisms are involved? These scientific questions have not yet been reported.In previous studies,liver is generally considered as the main organ of fructose metabolism in mammals,but recent studies on liver ChREBP have failed to fully explain the phenotype of global ChREBP knockout mice under high-fructose diet.The small intestine is the first site of fructose absorption and a vital processor for its metabolism,while the function of ChREBP in these courses still remains unknown.In order to characterize the function of intestinal ChREBP in fructose metabolism,we modeled the gut-specific ChREBP knockout(Ch GO)mice successfully through the Cre/lox P system,and confirmed the tissue specificity and knockout efficiency of ChREBP knockdown in the gut at m RNA and protein levels respectively.It was found that the defect of intestinal ChREBP could lead to decreased food intake,weight loss and severe flatulence in mice under high-fructose diet,which confirmed the crucial role of intestinal ChREBP in maintaining fructose tolerance.To investigate the precise regulatory process of fructose metabolism by intestinal ChREBP,we applied OGTT,OFTT,fructose absorption experiment and tissue HE staining and focused the involved mechanism on fructose absorption.We analyzed the effect of intestinal ChREBP defect on the expression of genes related to glucolipid metabolism under different dietary conditions and found that Slc2a5 was the target gene of ChREBP by Dual Luciferase Assay and chromatin immunoprecipitation.The upregulation of intestinal Slc2a5 induced by high-fructose diet is dependent on the expression of ChREBP,so the Ch GO mice can’t adapt to high-fructose load by Slc2a5 upregulation and subsequently develop a series of manifestations of fructose intolerance.For the first time,we limited the binding region of ChREBP in Slc2a5 promoter to-236～-86 bp upstream of its transcription initiation site.In summary,our study used the Ch GO mouse model to draw the following conclusions: ChREBP is an essential transcription factor for fructose-induced Slc2a5 gene transcriptional activation in small intestinal epithelial cells,and plays a core role in maintaining fructose tolerance.