Effects Of Uridine On Liver Metabolism In Obese And High-fat Diet Mice And Its Regulatory Mechanism

Obesity is one of the important risk factors of type 2 diabetes,nonalcoholic fatty liver disease(NAFLD)and hypertension.In order to find prevention and treatment strategies for obesity and its related health hazards,studies in recent decades have investigated the impact of many nutrients on obesity.Uridine(UR)is an important pyrimidine nucleoside,which closely related to the energy metabolism of the body,and has potential therapeutic effect on obesity.Therefore,this study intends to explore 1)the effects of UR supplementation on liver metabolism in obese mice;2)the effects of UR supplementation on liver lipid accumulation and intestinal microflora in mice fed with high-fat diet;3)the effects of dynamic supplementation of UR on body weight and liver metabolic rhythm of mice fed with high-fat diet;4)the intervention effect of UR on lipid accumulation of liver organs,so as to provide certain basis for the treatment of liver metabolism disorder induced by high fat dietary.The main results are as follows:1)Oral administration of UR inhibited the increase of liver weight,epididymal and intra-abdominal white adipose tissue weight(P < 0.05).UR treatments decreased the total triacylglycerols,cholesterol,and leptin in the serum of obesity mice(P < 0.05).In addition,relative expression of lipid synthesis,metabolism,transport,pyrimidine metabolism,and deve no synthesis genes have been improved in the liver of the obese mice by the addition of UR(P < 0.05).Moreover,metabolomics identified 29 differential metabolites among 3 groups,which mainly enriched in arachidonic acid metabolism and ?-linolenic acid metabolism.The findings demonstrate that UR positively regulated lipid metabolism and reduced body fat content in obese mice.2)UR supplementation significantly reduced the body weight and suppressed the accumulation of subcutaneous,epididymal,and mesenteric white adipose tissue in HFD-fed mice(P < 0.05).Meanwhile,UR also decreased the lipid droplet accumulation in the liver and liver organoids(P < 0.05).In addition,UR supplementation increased bacterial diversity and Bacterioidetes abundance,and decreased the Firmicutes-to-Bacteroidetes ratio in HFD-fed mice significantly(P <0.05).UR promoted the growth of butyrate-producing bacteria of Odoribacter,unidentified-Ruminococcaceae,Intestinimonas,Ruminiclostridium,and unidentifiedLachnospiraceae.A close correlation between several specific bacterial phyla or genera and the levels of white adipose tissue weight,hepatic TC,or hepatic TG genera was revealed through Spearman's correlation analysis.These results demonstrated that UR supplementation could be beneficial by attenuating HFD-induced obesity and nonalcoholic fatty liver disease.3)UR supplementation,independent of the time of administration during the day,significantly reduced body weight gain(P < 0.05).Furthermore,liver weight and ratio showed a strong time dependence(P < 0.001).Additionally,oral administration of UR during daytime or nighttime changed the expression levels of genes involved in the metabolism of UR(SLC29A1,UMPS,UPP,UGT1A1,and DHODH;P < 0.05).Furthermore,UR affected the levels of 10 fatty acids,lipid and glucose gene(FASN,LCAT,PC,PEPCK,GSK3?,and GLUT2;P < 0.05)depending on the timing of administration(P < 0.05).In conclusion,oral supplementation with UR affected the diurnal variations in liver nucleotide and lipid metabolism,which contributed to the weight loss in HFD-fed mice.4)The organoids were successfully cultured from mouse liver by isolation and digestion,and the long-term amplification culture was stable.Uridine(1 m M)and fatty acid(0.6 m M)had no significant effect on the proliferation and total apoptosis of liver organoids(P > 0.05).After 15 days of differentiation culture,the expression of hepatic cell markers increased(P < 0.05),including TBX,HNF4 ?,CYP3a11 and CYP1A2.The number of lipid droplets in hepatocytes increased significantly after treatment with0.6 m M fatty acids for 24 h(P < 0.05).However,1 m M UR significantly inhibited the accumulation of lipid in liver organoids induced by free fatty acid(FFA)(P < 0.05).UR affected the expression of UMPS in liver organoids after FFA treatment(P < 0.05).It suggested that exogenous UR can affect the growth of liver like organs,reduce lipid aggregation and participate in the synthesis of nucleotides.