Effects Of Tea Extracts On Serum Uric Acid Levels In Hyperuricemic Mice

As a kind of important drinks,tea is closely related to people's life,and has abundant medicinal values.Tea is exhibited various physiological functions,including scavenging free radicals,reducing anti-lipidemic effects and anti-inflammatory.In this paper,the hypouricemic effects of several tea extracts were investigated and the preliminary mechanisms were confirmed.The main studying contents and results of this experiment were as follows:1.In this experiment,we selected roasted green tea,Qimen black tea and Jingwei Fu brick tea as the materials after boiling water extraction to get water extracts of tea and ready to use after concentrated dry;after recrystallization,the purity of caffeine was greater than 95%;the crude EGCG(Epigallocatechin gallate)was purified(purity98.34%);2.Potassium oxonate plus yeast extract were used to build the hyperuricemic model in mice;the mice in tea-treated groups intragastrically were treated with low dose(0.5 g/kg),middle dose(1 g/kg)and high dose(2 g/kg)green tea extracts(GTEs),black tea extracts(BTEs)and dark tea extracts(DTEs),respectively,for consecutive seven days.The results showed that compared with model group,all of them had hypouricemic activities to some extent,while BTEs showed more obvious effects,attained 27.1%;3.Based on above results,BTEs were chosen for further study.Caffeine is a kind of purine alkaloids,which can affect the uric acid metabolism.So we selected decaffeinated black tea extract(D-BTE)and caffeinated black tea extract(BTE)for further animal experiments and the results showed that: D-BTE groups presented more obvious hypouricemic effects than that of BTEs(more than 12.9%);levels of blood urea nitrogen(BUN)and serum creatinine(Cr)of two kinds of black tea extracts were all lower than that of the model group,suggesting it has good protection of kidney.Meanwhile,through exploring influence on the UA levels of normal mice with different doses of caffeine(50,100,and 200 mg/kg),UA levels in normal mice were markedly increased(up to 55.6%);4.Compared with the mice in model group,UA levels were significantly reduced by treated with low(10 mg/kg),medium(20 mg/kg)and high dose EGCG(50 mg/kg)in hyperuricemic mice(reduced by 29.6%,35.2% and 42.6%,respectively);10 mg/kg EGCG in the lower dosage plus positive drug allopurinol(AP,5 mg/kg)had hypouricemic effect(reached 82.8%),which was superior to those drug treated;levels of BUN and Cr of EGCG groups were less than that of model group,showing the certain renal protection.5.After measuring hepatic xanthine oxidase(XOD)and adenosine deaminase(ADA)activities,compared with model group,the results showed that the XOD and ADA activities of high dose of BTE,more than 18.0% and21.1%;EGCG and AP plus EGCG groups were reduced significantly.After measuring renal glucose transporter 9(GLUT9)and urate transporter1(URAT1)m RNA expression levels,the results presented that two kinds of BTEs could significantly lower GLUT9 m RNA expression,middle and high dose of D-BTEs and high dose of BTE could reduce the renal URAT1 m RNA expression significantly.High dose of EGCG significantly lowered GLUT9 m RNA expression,middle and high dose significantly reduced URAT1 m RNA expression.After treated with EGCG plus AP,GLUT9 m RNA expression had no significant effect in kidney,but this could significantly lower URAT1 m RNA expression.Therefore,a certain dose of BTE and EGCG could inhibit XOD and ADA activities to reduce the generation of UA.BTE and EGCG down-regulated GLUT9 and URAT1 m RNA expression and inhibited reabsorption of UA in renal proximal tubule epithelial cells,while AP plus EGCG reduced UA levels mainly through down-regulating URAT1 m RNA expression of inhibiting renal reabsorption of uric acid.6.Through observing renal histologic sectionin in mice,we found that the kidneys of model group and positive medicine group showed different degree of damages.Tissular structures of tea extract groups were returned to normal,which displayed certain kidney protection.On the whole,several kinds of tea extracts showed obvious improving effects in hyperuricemic mice induced by potassium oxonate plus yeast extract,and we discussed their mechanisms of these actions and made reasonable guidance for people's diet.