Hyperuricemia Induces Lipid Disturbances Mediated By LPCAT3 Upregulation In The Liver

Backgrounds: Uric acid is the end product of purine metabolism in the human body.Fasting serum uric acid levels in men>7.0mg/dl and women>6.0mg/dl are defined as hyperuricemia.The incidence of hyperuricemia is increasing globally.The survey shows that 20.1% of American adults suffer from hyperuricemia on average.At the same time,studies have found that hyperuricemia is closely related to a variety of metabolic diseases,including type II diabetes and metabolic syndrome.High levels of uric acid can promote the occurrence of metabolic diseases.However,there are few direct evidence and mechanism studies related to the laboratory.The previous research of the research group confirmed that hyperuricemia can induce lipid metabolism disorders,but the mechanism of this association is unclear.Because the liver is an organ with strong lipid metabolism,this study chose the liver as the research object.This study aims to investigate the effect of high uric acid in the liver on the development of lipid metabolism and its underlying mechanism.In order to further explore the related effects of high uric acid on lipid metabolism,we conducted a lipidomics study in liver and screened out the key differential metabolic enzyme LPCAT3.LPCAT3 is lysophospholipid acyltransferase 3,which is more expressed in the liver.LPCAT3 participates in the remodeling pathway of glycerophospholipids and affects a variety of cell functions.It is a key factor in determining the composition of membrane phospholipids.At the same time,according to literature reports,sterol regulatory element binding protein(SREBP)is the main regulator of total cholesterol(TC),fatty acids and triglyceride(TG)in the lipid synthesis pathway.Moreover,the phospholipid changes mediated by LPCAT3 are the promoters of SREBP-1c maturation.Therefore,we propose to hypothesize whether LPCAT3 affects SREBP-1c by mediating changes in phospholipids in the hyperuricemia model,thereby affecting the downstream phenotype.Aim: This study illustrates the key regulatory role of LPCAT3 in hyperuricemia models through clinical cases,animal models and in vitro studies.The inner link between high uric acid and cholesterol,triglyceride and other lipid synthesis is explored,which adds an important basis for the link between hyperuricemia and lipid metabolism,and may also provide targets for clinical development of therapeutic drugs.Methods: 1)Blood samples of 100 healthy people and 100 hyperuricemia patients were collected from the First Affiliated Hospital of Anhui Medical University,and blood lipid analysis was performed.2)A mouse model of hyperuricemia was established,and blood biochemical indicators were measured,and the liver tissues of the normal group and the hyperuricemia group were analyzed by high performance liquid chromatography-mass spectrometry(LC-MS).The metabolic pathways and lipid changes in the metabolites concentration were summarized to analyze the lipid profile and key metabolic enzymes of hyperuricemia mice.Western blot(WB)and real-time quantitative PCR(q RT-PCR)were used to measure the changes of the key metabolic enzyme LPCAT3,and the content of LPCAT3 substrate lysophosphatidylcholine(LPC)has also been determined.Then the levels of signal transducer and activator of transcription 3(STAT3)and SREBP-1c in the liver of model mice were detected by WB and q RT-PCR.3)We conducted in vitro experiments to verify the lipid metabolism stimulated by high uric acid using normal liver cells(L02 cells)and liver cancer cells(Hep G2 cells).Simultaneously,the L02 cell line with stable knockdown of LPCAT3 was constructed,and the effect of knockdown of LPCAT3 expression on lipid metabolism under high uric acid stimulation was investigated by WB,q RT-PCR,and immunofluorescence(IF).And the effect of knocking down the expression of LPCAT3 on the nuclear transcription of lipid synthesis pathway related protein SREBP-1c and p-STAT3 were studied.Result: 1)In this study,blood samples from 100 healthy people and 100 patients were collected for analysis.We found that hyperuricemia directly induced the disorder of serum lipid metabolism,including the content of TG,TC,low-density lipoprotein cholesterol(LDL-C)increased,indicating that hyperuricemia can cause lipid metabolism disorders.2)In this study,the mice were fed a high-uric acid diet.After 4 weeks,the serum uric acid in the mice increased significantly,and the TC and TG in the serum and liver of the mice also increased significantly,Oil red O staining showed obvious lipid deposition in the liver of hyperuricemia mice,indicating that lipid metabolism disorders will also appear in hyperuricemia mice.We conducted a lipidomics study using LC-MS and found that 54 lipids were differentially expressed in the liver of hyperuricemia mice,and there were significant changes in phosphatidylcholine(PC) and LPC.Simultaneously,according to pathway analysis,the key enzyme LPCAT3,which mediates the conversion of LPC to PC,was significantly up-regulated in the hyperuricemia group.According to literature reports,it was determined by WB and qRT-PCR analysis that LPCAT3 and SREBP-1c were significantly up-regulated in the liver of hyperuricemia mice.It was also found that high uric acid inhibited p-STAT3 expression in the leptin-related pathway closely related to lipid metabolism.3)L02 cells and HepG2 cells were used to explore the changes of LPCAT3 and SREBP-1c under high uric acid stimulation,it was found that the up-regulation of LPCAT3 mediates p-STAT3 inhibition and activation of SREBP-1c in L02 cells stimulated by high uric acid,consistent with in vivo studies.After constructing the L02 stable transgenic cell line with LPCAT3 knockdown,we found that the expression of SREBP-1c is significantly reduced after LPCAT3 knockdown and the related phenotype are restored,while the expression of p-STAT3 was increased.This indicates that LPCAT3 knockdown can significantly reduce the lipid metabolism disorder induced by uric acid in L02 cells.Conclusion: High uric acid may induce lipid metabolism disorders through LPCAT3-mediated p-STAT3 inhibition and SREBP-1c activation.LPCAT3 may be a key regulator between hyperuricemia and lipid metabolism disorders.