| Background:Hyperuricemia(HUA)is a common metabolic disorder characterized by elevated Serum uric acid(SUA)concentrations.With the increasing incidence in recent years,hyperuricemia is now identified as the fourth largest metabolic disorder after hypertension,hyperglycemia and hyperlipidemia.Diet has been associated with hyperuricemia for centuries.Fruits are rich in minerals,vitamins,dietary fiber,polyphenols and polysaccharides,providing a variety of nutrients needed for the prevention of non-communicable diseases.However,the relationship with hyperuricemia is unclear.ObjectiveIn this study,undergraduate students of Qingdao University were selected as subjects to conduct a large-scale cross-sectional study,aiming to explore the relationship between daily intake of different kinds of fruits and the risk of hyperuricemia,and to clarify whether the main functional components of polyphenols and polysaccharides contained in fruits can reduce serum uric acid concentration in mice with high uric acid through animal experiments and its mechanism.Method1.Cross-sectional study:(1)A cross-sectional study design was adopted to carry out a health examination program for undergraduates in Qingdao University from August 2018 to October 2019.A total of 16,211 undergraduates participated in this program.All volunteers gave written informed consent.(2)Basic information and fruit intake of volunteers were collected by semiquantitative food frequency questionnaire.(3)Physical examination includes basic indicators such as height,weight and blood pressure,and body mass index was calculated.Fasting venous blood of 5 m L was collected from volunteers to detect serum uric acid,triglyceride,total cholesterol,high density lipoprotein cholesterol,etc.(4)To analyze the relationship between fruit intake and the risk of hyperuricemia.2.Animal experiments:(1)Grouping of mice and modeling intervention: After the adaptive feeding,135 mice were randomly divided into 9 groups(n=15),which were control group,model group,allopurinol group(API group,5 mg/kg),resveratrol group(Res group,100 mg/kg),lowdose apple polyphenol group(LAP group,50 mg/kg),high dose apple polyphenol(HAP group,100 mg/kg),inulin group(Inu group,1000 mg/kg),low dose apple polysaccharide group(LAC group,500 mg/kg),high dose apple polysaccharide group(HAC group,1000mg/kg).The control group was fed standard diet,and the other groups were fed high yeast diet.Except the control group,mice in all groups were given potassium oxonate(250mg/kg),adenine(100 mg/kg)and yeast(1 g/kg)intragastric administration for 3 weeks to induce hyperuricemia.One hour after modeling administration,the intervention was administered intragastric according to dosage,and all the modeling reagents and interventions were dissolved in 0.5% CMC-Na solution,respectively.At the same time,mice in the control group were given 0.5% CMC-Na solution of equal volume by intragastric administration.The mice were sacrificed after three consecutive weeks of modeling intervention.(2)Monitoring of basic indicators: the weight,food intake and water intake of mice were recorded weekly.(3)Serum uric acid(UA),serum creatinine(SCR),blood urea nitrogen(BUN)concentrations,serum and liver xanthine oxidase(XOD)activity were measured.(4)The expression level of XOD protein in liver and the protein expression levels of uric acid transporter 1(URAT1),glucose transporter 9(Glut9)and ATP-binding cassette super-family G member 2(ABCG2)in kidney were detected by Western blot.(5)The histopathological changes of mouse liver and kidney were observed under light microscope by HE staining.(6)The m RNA expression levels of XOD and the m RNA expression levels of tumor necrosis factor-α(TNF-α),interleukin 1β(IL-1β)and aspartic proteolytic enzyme(Caspase-1)in liver were detected by reverse transcription polymerase chain reaction(RTPCR).The m RNA expression levels of URAT1,Glut9,ABCG2 and TNF-α,IL-1β and Caspase-1 were detected.(7)Serum metabolomics test was performed to analyze serum metabolites of mice after AP and AC intervention by ultra high performance liquid chromatography/high resolution mass spectrometry(UHPLC-Q-TOF).Results1.Cross-sectional study:(1)The prevalence of hyperuricemia in male volunteers was significantly higher than that in female volunteers(P < 0.001).Serum triglyceride and total cholesterol levels were significantly higher in hyperuricemia patients than in normal volunteer participants(P <0.001),while high density lipoprotein cholesterol(HDL-C)levels were significantly lower in hyperuricemia patients than in normal volunteers(P < 0.001).Patients with hyperuricemia had significantly higher BMI and fasting blood glucose levels than normal volunteers(P < 0.001).(2)After adjusting for gender,BMI,age,blood pressure,blood glucose and lipids,as well as individual fruit intake,only apple intake remained negatively correlated with hyperuricemia(OR=0.86;95%CI: 0.73-0.99,P=0.028),the correlation was not significant for other types of fruit.2.Animal experiments:(1)Within 3 weeks of intervention,the body weight of mice in model group was significantly lower than that in control group(P < 0.05).Compared with the other groups,the body weight in LAP and HAP groups was significantly lower during the intervention period(P < 0.05).At the first and second weeks of intervention,the food intake of mice in model group was lower than that in control group,and the food intake of mice in LAP and HAP groups was significantly lower than that in other groups(P < 0.05).At the third week of intervention,the food intake in LAP and HAP groups was significantly lower than that in control and API groups,and that in LAC and HAC groups was significantly lower than that in model group(P < 0.05).(2)Before modeling,there was no significant difference in serum uric acid concentration among all groups.After one week of intervention,compared with the control group,the serum uric acid concentration in the model group and the intervention group was significantly increased(P < 0.05),except for the API group,there was no significant difference in serum uric acid concentration between the intervention group and the model group.After death,the serum uric acid concentration in the model group and Inu group continued to increase,and was significantly higher than that in the control group(P < 0.05).The uric acid concentration in LAP,HAP,LAC and HAC groups was significantly lower than that in the model group and positive control group(Res group and Inu group)(P <0.05).The uric acid concentration in HAC group was significantly lower than that in LAC group(P < 0.05).The creatinine and urea nitrogen concentrations of mice in model group were significantly higher than those in control group(P < 0.05).After AP and AC intervention,the serum creatinine and urea nitrogen concentrations of mice in other groups were significantly lower than those in model group except that there was no difference between LAP group and model group(P < 0.05).(3)The activity of XOD in serum and liver of mice in model group was significantly higher than that in control group.After AP and AC intervention,the activity of XOD in AP and AC groups was significantly lower than that in model group(P < 0.05),and the activity of XOD in serum in HAC group was lower than that in LAC group(P < 0.05).Compared with the control group,the protein expression level and m RNA level of XOD in the model group were significantly higher(P < 0.05),the protein expression level and m RNA level of XOD in LAP,HAP and HAC groups were significantly lower than those in the model group(P < 0.05),while the liver XOD protein expression level in LAC group was lower than that in the model group but the difference was not significant.(4)The protein expressions of URAT1 and Glut9 in kidney of model group were significantly higher than those of control group(P < 0.05),and the protein expression of ABCG2 was significantly lower than that of model group(P < 0.05).After AP intervention,the expression levels of URAT1 and Glut9 in LAP group and HAP group were significantly lower than those in model group(P < 0.05),and the expression level of Glut9 in HAP group was significantly lower than that in LAP group(P < 0.05).The protein expression of URAT1 in LAC and HAC groups was significantly lower than that in model group(P <0.05),and the protein expression of ABCG2 was significantly higher than that in model group(P < 0.05).The m RNA levels of URAT1 and Glut9 in model group were significantly higher than those in control group(P < 0.05),and the m RNA level of ABCG2 was significantly lower than that in model group(P < 0.05).After AP intervention,the m RNA expressions of URAT1 and Glut9 in the two AP groups were significantly lower than those in the model group(P < 0.05).The URAT1 m RNA level in HAC group was significantly lower than that in model group(P < 0.05),while the ABCG2 m RNA level in LAC and HAC groups was significantly higher than that in model group(P < 0.05).(5)After the mice were killed,the kidney of the control group was dark red crescent shape,while the kidney of the model group was clear beige,and the kidney of HAP and HAC group was dark red.Compared with the control group,AP group and AC group,the renal tubular epithelial cells in the model group showed a large number of vacuolar degeneration,eosinophilic insoluble protein,renal tubular dilatation,and mild inflammatory cell infiltration.In the control group,the hepatic lobule structure was obvious,centered on the central vein and arranged radially to the periphery.Po-induced hyperuricemia mice showed hepatocyte degeneration,loss of hepatic lobule,disordered cell arrangement,loss of hepatic cord structure,inflammatory infiltration,and hepatocyte necrosis.Compared with model group,the structure of hepatic lobule and hepatic cord in AP and AC groups was obvious,and inflammatory infiltration was light.(6)m RNA levels of TNF-α,IL-1β and Caspase-1 in liver and kidney of model group were significantly higher than those of control group(P < 0.05).The m RNA levels of IL-1β,TNF-α and Caspase-1 in liver of mice in AP and AC groups were significantly lower than those in model group(P < 0.05).The m RNA levels of IL-1β in kidney in HAP and LAC groups were significantly lower than those in model group,and the m RNA levels of Caspase-1 and TNF-α in LAP,HAP,LAC and HAC groups were significantly lower than those in model group(P < 0.05).(7)The results of serum metabolomics analysis showed that the concentration of serum uric acid under AP intervention was correlated with serum urea nitrogen(r=0.507,P=0.008),serum deoxyhydroxyproline(r=0.471,P=0.015),serum sphingosinol(r=0.588,P=0.002),serum streptomycin(r=0.623,P=0.001)was positively correlated with serum deoxyceramide(r=-0.413,P=0.036)and serum galactoceramide(r=-0.473,P=0.015).Under AC intervention,serum uric acid concentration was positively correlated with serum urea nitrogen(r=0.392,P=0.036),serum deoxyhydroxyproline(r=0.513,P=0.004),serum sphingosine(r=0.460,P=0.012)and serum streptomycin(r=0.620,P < 0.001)levels.It was negatively correlated with serum caproic acid level(r=-0.477,P=0.009).ConclusionThe prevalence of hyperuricemia was higher in men than in women,and apple intake was negatively correlated with the risk of hyperuricemia.The intervention of apple polyphenol and apple polysaccharide could reduce serum uric acid concentration by inhibiting uric acid synthesis and promoting uric acid excretion,thus ameliorating hyperuricemia. |
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