Study On The Uric Acid-lowering Effect Of Chicory Extract On Intestinal Transporter ABCG

BackgroundHyperuricemia is a kind of metabolic diseases caused by the decrease of uric acid formation or the increase of uric acid excretion.It has been the fourth most common chronic metabolic disease which related with glucolipid metabolic disorders and cardiovascular diseases closely beside diabetes,hypertension and hyperlipemia.Nowadays,western medicines are appearing some side effects in treating hyperuricemia,and they do not show promising effects in hyperuricemia with multi-metabolic disorders.Therefore,it is necessary to observe the therapeutic and preventive effect of traditional Chinese medicine on hyperuricemia.It is commonly accepted that two-thirds of the uric acid is excreted into urine by kidneys,and the remaining third via gut excretion.As a main regulator of uric acid excretion,the kidney plays an important role in uric acid handle.However,intestinal excretion,another important pathway of uric acid flux,has not been studied extensively and its mechanism is still unclear.There is study shown that ATP-binding cassette transporter,sub-family G,member 2(ABCG2,also known as BCRP),is a high-capacity urate secretion transporter.It reported that the decreased expression and dysfunction of ABCG2 is associates with the reduction of intestinal uric acid excretion.Accordingly,ABCG2 may contribute to the intestinal excretion of uric acid as extra-renal elimination pathway.In addition,hyperuricemia patients always have pathological changes in intestines such as intestinal flora disorders,intestinal permeability damages and Lipopolysaccharide increase.At present,there are no drugs targeted at the intestinal pathway of uric acid excretion.Based on the multi-target and multi-channel characteristic of traditional Chinese medicine,the research on the mechanism of action of traditional Chinese medicine on hyperuricemia via intestines has an important academic value.Cichorium intybus L.,commonly known as chicory,is well known as a cholagogic and diuretic agent in Uighur folk medicine.In previous studies,we found chicory could lower serum uric acid effectively.The antihyperuricemic effect of chicory mainly associates with the decreased uric acid formation in the liver and increased uric acid excretion by the kidney.The present investigation is aimed at evaluating the expression of ABCG2 and combines intestinal barrier indexes to explore the potential uricosuric mechanism of chicory via intestinal excretion pathway.HypothesisThere are relationships between expression changes of the intestinal transporter ABCG2 and hyperuricemia induced by the fructose.The intestinal uric acid excretory dysfunction regulated by the abnormal expression of ABCG2 may one of the pathological mechanisms of hyperuricemia induced by the fructose.In addition,the intestinal barrier dysfunction related with the abnormal expression of ABCG2 may associates with hyperuricemia induced by the fructose.Chicory could up-regulate intestinal transporter ABCG2 and promote intestinal uric acid excretion as well as improve intestinal barrier damages to decrease serum uric acid levels.ObjectivesFirstly,to clarify the pathological basis of hyperuricemia induced by fructose by demonstrating the relationship between the intestinal transporter ABCG2 and hyperuricemia via intestinal excretion pathway and observing intestinal barrier indexes related ABCG2.Secondly,to explore the lowering uric acid action of chicory by analyzing influences of the intestinal transporter ABCG2 expressions,intestinal uric acid excretion levels and intestinal barrier indexes.MethodsThis paper contains two parts,the literature review and experimental research.The literature review includes epidemiological and therapeutic studies of hyperuricemia as well as intestinal transporters and intestinal barrier with intestinal uric acid excretion by collecting domestic and foreign literatures.The experimental research takes advantage of various methods,including biochemical examination,high performance liquid chromatography,Immunohistochemistry,western blot and real-time PCR,to explore the pathological basis of hyperuricemia induced by fructose and the therapeutic effect of chicory.ContentsThe first chapter:research between the intestinal transporter ABCG2 and hyperuricemia.Copy hyperuricemia rats by fructose.Observe the protein and gene expressions of ABCG2 in the different parts of the small intestine.Test uric acid levels in feces and the gut lumen.Detect intestinal barrier indexes.The second chapter:Intervention research of chicory on the intestinal transporter ABCG2 in hyperuricemia.Observe the effect of chicory on hyperuricemia rats,including uric acid levels in serum,feces and the gut lumen,the protein and gene expressions of ABCG2,and intestinal barrier indexes.Observe the effect of chicory on ABCG2 expression in Caco-2.Observe the effect of chicory on intestinal barrier indexes in hyperuricemia with intestinal barrier dysfunction model induced by methotrexate and oteracil potassium.ResultsResearch between the intestinal transporter ABCG2 and hyperuricemia:①10%fructose solution can induce hyperuricemia rats model.ABCG2 protein expresses in villus and glands of the small intestine.In intestinal villus,it distributes in the membrane and cytoplasm of intestinal epithelial cells.In intestinal glands,it distributes in the lumen membrane and cytoplasm of cells.Analysis from immunohistochemistry shows that the area and integral optical density of ABCG2 protein in the jejunum and ileum of hyperuricemia rats are more than normal rats.Analysis from real-time PCR also shows that the ABCG2 mRNA expression in the jejunum and ileum of hyperuricemia rats is more than normal rats.②Compared with normal rats,uric acid levels in the face and in the intestinal perfusion fluid of hyperuricemia rats decrease significantly.③ Compared with normal rats,serum levels of diamine oxidase,D-lactate and lipopolysaccharide in hyperuricemia rats increase markedly.There are fewer and smaller goblet cells in hyperuricemia rats.Indistinct intestinal brush border and messily distributed cell nucleus are showed in the jejunum and ileum of hyperuricemia rats.The intestinal flora macrostructure in model rats are changed with the increased coli bacillus and enterococcus facials.Intervention research of chicory on the intestinal transporter ABCG2 in hyperuricemia:① Chicory can decrease the serum uric acid level steadily as well as uric acid in the face and in the intestinal perfusion fluid of hyperuricemia rats.Analysis from molecular biological techniques shows that chicory can increase the protein and gene expression of ABCG2 in the jejunum and ileum of model rats.② Chicory can decrease the dimer protein expression of ABCG2 in the Caco-2 cultured by a high level of uric acid significantly.③ Chicory can decrease serum levels of diamine oxidase,D-lactate and lipopolysaccharide,and increase intestinal goblet cells as well as improve the intestinal flora macrostructure with decreased coli bacillus and enterococcus facials and increased Bifidobacterium in hyperuricemia rats.④ Chicory can decrease the serum lipopolysaccharide level markedly and has a reduced tendency of the serum diamine oxidase level,the serum D-lactate level and the myeloperoxidase level of the small intestine homogenate in hyperuricemia rats with intestinal barrier injuries.Compared with model rats,the bacterial colonies of cecum contents cultured by EC broth from rats treated with chicory decrease significantly,whereas the bacterial colonies of mesenteric lymph nodes from rats treated with chicory has no change.ConclusionsResults of this study confirm and verity the hypothesis,summarizing the following conclusions:① There are pathological relations between decreased expression of the intestinal transporter ABCG2 and hyperuricemia induced by the fructose.The reduced intestinal uric acid excretion regulated by the decreased expression of ABCG2 may one of the pathological mechanisms of hyperuricemia induced by the fructose.② Chicory can up-regulate intestinal transporter ABCG2 and promote intestinal uric acid excretion to decrease serum uric acid levels.The intestinal uric acid excretory dysfunction regulated by the abnormal expression of ABCG2 in hyperuricemia rats induced by fructose and the regulation effect of chicory are associated with the intestinal barrier.The concrete mechanism between them remains the further study.Innovation points:① For the first time to carry out the study about intervention of chicory on hyperuricemia rats induced by fructose by observing intestinal transporter ABCG2 expression via intestinal excretion pathway.And the study demonstrated that chicory can up-regulate intestinal transporter ABCG2 and promote intestinal uric acid excretion to decrease serum uric acid levels.② For the first time to explore effects of chicory on intestinal barrier damages related with the intestinal transporter ABCG2 to lay the foundation for the further study.