Effects of Chinese herb ingredients with different properties on OAT4, URAT1 and serum uric acid level in acute hyperuricemia mice / 中草药

Objective To study the effects of Chinese herb ingredients with different properties on transporters (URAT1 and OAT4) involved in renal urate reabsorption and serum uric acid level in acute hyperuricemia mice. Methods The OAT4, URAT1- overexpressed monoclonal cell line (MDCK-hOAT4, HEK293-hURAT1) was constructed. The inhibition effect and the half maximal inhibitory concentration (IC50) of different ingredients to transport activity of OAT4 and URAT1 mediating 14C-uric acid were determined. The effects of protocatechuic, liquiritigenin and isoliquiritigenin on serum uric acid levels in acute hyperuricemia mice were studied by the acute hyperuricemia mice induced by potassium oxonate and xanthine. Results The results indicated that nobiletin,liquiritigenin, isoliquiritigenin, licochalcone A with bitter flavor showed strong inhibition to OAT4. The IC50 of nobiletin, liquiritigenin, isoliquiritigenin, and licochalcone A on OAT4 were 0.556 μmol/L, 18.40 μmol/L, 6.831 μmol/L, and 6.825 μmol/L, respectively. Protocatechuic acid and liquiritigenin showed strong inhibition to URAT1 with IC50 of 7.709 μmol/L and 14.54 μmol/L, respectively. Liquiritigenin can significantly reduce the level of serum uric acid of acute hyperuricemia mice, increase the excretion of uric acid, and reduce the level of serum creatinine and blood urea nitrogen. Conclusion Nobiletin, liquiritigenin, isoliquiritigenin and licochalcone A can inhibit the transport activity of OAT4, while protocatechuic acid and liquiritigenin can inhibit the transport activity of URAT1. Liquiritigenin can significantly reduce the level of serum uric acid in acute hyperuricemia mice and protect kidney, the mechanism of which may be associated with the decreasing reabsorption of uric acid by inhibiting the activity of URAT1 and OAT4.

Effect of Biling Qutong Prescription on SIRT3 Protein Expression and URAT1 mRNA in Skeletal Muscle of Diabetic Gout Rats / 中国实验方剂学杂志

Objective: To observe the effect of phlegm and blood stasis on the expressions of sirtuin 3(SIRT3)protein and urate transporter 1(URAT1) mRNA in skeletal muscle of diabetic rats with gout. Method: The 40 healthy rats, excepting the normal group, the remaining groups were fed with high-fat diet combined with low-dose streptozotocin solution (40 mg·kg-1) once a day, with blood glucose "16.7 mmol·L-1" as the criterion for the diabetes model. After 4 days, the 5% sodium urate solution was injected into the joint cavity once to induce the gout model. After the successful modeling, the Biling group (10 g·kg-1), the indomethacin group (5 mg·kg-1) and the pioglitazone group (10 mg·kg-1) continued to be administered for 21 days. The normal group and the model group were given the same amount of normal saline. The expression of SIRT3 protein in skeletal muscle tissue was determined by Western blot, URAT1 mRNA expression in bone tissue was detected by quantitative real-time fluorescence polymerase chain reaction(Real-time PCR),and blood was collected to measure blood glucose (GLU), blood uric acid (UA) and C-reactive protein (CRP). Result: Compared with the normal group, GLU, UA and CRP in the model group were significantly increased (PPPPPPPPConclusion: Biling Qutong prescription with effects in purging turbidity, detoxifying and dredging collaterals can significantly reduce the content of serum inflammatory factor CRP, significantly increase the protein expression of SIRT3 in skeletal muscle tissue of model rats, lower the content of URAT1 mRNA, reduce the blood glucose and blood uric acid levels in diabetic gout rats, and protect joints.

Antihyperuricemic effect of mangiferin aglycon derivative J99745 by inhibiting xanthine oxidase activity and urate transporter 1 expression in mice

A mangiferin aglycon derivative J99745 has been identified as a potent xanthine oxidase (XOD) inhibitor by previous study. This study aimed to evaluate the hypouricemic effects of J99745 in experimental hyperuricemia mice, and explore the underlying mechanisms. Mice were orally administered 600 mg/kg xanthine once daily for 7 days and intraperitoneally injected 250 mg/kg oxonic acid on the 7th day to induce hyperuricemia. Meanwhile, J99745 (3, 10, and 30 mg/kg), allopurinol (20 mg/kg) or benzbromarone (20 mg/kg) were orally administered to mice for 7 days. On the 7th day, uric acid and creatinine in serum and urine, blood urea nitrogen (BUN), malondialdehyde (MDA) content and XOD activities in serum and liver were determined. Morphological changes in kidney were observed using hematoxylin and eosin (H&E) staining. Hepatic XOD, renal urate transporter 1 (URAT1), glucose transporter type 9 (GLUT9), organic anion transporter 1 (OAT1) and ATP-binding cassette transporter G2 (ABCG2) were detected by Western blot and real time polymerase chain reaction (PCR). The results showed that J99745 at doses of 10 and 30 mg/kg significantly reduced serum urate, and enhanced fractional excretion of uric acid (FEUA). H&E staining confirmed that J99745 provided greater nephroprotective effects than allopurinol and benzbromarone. Moreover, serum and hepatic XOD activities and renal URAT1 expression declined in J99745-treated hyperuricemia mice. In consistence with the ability to inhibit XOD, J99745 lowered serum MDA content in hyperuricemia mice. Our results suggest that J99745 exerts urate-lowering effect by inhibiting XOD activity and URAT1 expression, thus representing a promising candidate as an anti-hyperuricemia agent.

Functional analysis of + 11G ＞ A single nucleotide polymorphisms in intron 3 of human urate transporter 1 gene / 中华内科杂志

Objective We reported previously that single nucleotide polymorphisms SNP) + 11G ＞ A in intron 3 of the human urate transporter 1 (hURAT1) gene are associated with hyperuncaemia in Han Chinese.The aim of the present study was to evaluate the effect of the variants on hURAT1 function.Methods The wild-type,mutant-type hURAT1 and exon 5-null hURAT1 were constructed,and respectively microinjected into the zebrafish embryo yolks.The subcellular localization of different genotypes of hURAT1 was detected by confocal laser scanning microscope.Results Compared with wild type,the mutant recombinant plasmid transcribed two types of mRNA spliceosome,the wild type and the exon 5-null type.The hURAT1 wild type protein was prominent localized on cell membrane,while the mutant type and exon 5-null hURAT1 proteins were distributed uniform in the cytoplasm but not on the cell membrane.Conclusion The hURAT1 variant + 11 G ＞ A resulted in an alternative splicing of hURAT1 mRNA-exon 5-null type.Its protein product exhibited a different subcellular localization compared with that of wild type.

Human urate transporter 1 promoter polymorphisms and hyperuricemia in Chinese Han people / 中华内分泌代谢杂志

ObjectiveTo analyze the association of human urate transporter 1 ( hURAT1 ) gene promoter single-nucleotide polymorphisms(SNPs) with primary hyperuricemia ( HUA ) in Chinese Han people.MethodsA total of 215 patients with HUA and 323 healthy subjects were chosen to be investigated of SNP of hURAT1 promoter by PCR and sequencing.ResultsFive SNPs were identified,including-454A/T,-434T/C,-382C/T,-87C/T,and + 118G/A.Pairwise linkage disequilibrium analysis displayed a high linkage disequilibrium between the five SNPs ( r2 =0.99).In HUA group,the heterozygous genotypos ( AT,CT,CT,CT,AG ) frequencies were significantly lower than those in control group ( P＜0.05 ).Logistic regression analysis showed that the heterozygosis genotypes ( AT,CT,CT,CT,AG) were protective factors of HUA ( OR 0.68-0.75 ).The minor allele ( T,C,T,T,A ) frequencies for both SNPs were significantly different between two groups ( P =0.022,P =0.038 ).ConclusionThese findings indicate that -454A/T,-434T/C,-382C/T,-87C/T,and + 118G/A SNPs of hURAT1 gene promoter area are associated with HUA in Chinese Han population.

Impact of rosiglitazone on uric acid metabolism and its mechanism / 中华内分泌代谢杂志

Objective To observe whether high-level insulin increases serum uric acid level and rosiglitazone improves hyperuricemia, and to explore the mechanism. Methods OLETF rats with spontaneous type 2 diabetes complicated with metabolic syndrome and normal control LETO rats were randomly divided into three groups (n=20 each). The animals were fed with standard chow diet in control group, high-purine diet and adenine administered intragastrically in experimental group, and rosiglitazone in interventional group. Body weight, serum levels of uric acid, insulin, triglyceride ( TG ) , and total cholesterol ( TC ) were measured after 3 weeks. Urate transporter 1 ( URAT1 ) and uric acid transporter (UAT) mRNA expressions in renal cortex were examined. HK-2 cells were incubated with various concentrations of insulin for 24 hours. UAT mRNA expression in HK-2 cells was examined. Results ( 1 ) In control group, the insulin level of OLETF rats was significantly higher than that of LETO rats ( P<0. 05 ), and there was no significant difference in serum uric acid level between OLETF and LETO rats. (2)In experimental groups, the insulin level in OLETF rats was significantly higher than that in LETO rats [(61.83±12.13 vs 36.73±12.73 )μIU/ml ,P<0. 05], and the incidence of hyperuricemia (76.92% vs 36.13%,P<0.01 ) and serum uric acid level[( 327.75 ±45.73 vs 264.40±36.32 ) μmol/L, P<0. 01]in OLETF rats were significantly higher than those in LETO rats. (3) Insulin[(41.3± 10.2 vs 61.8±12. 1 )μIU/ml,P<0. 05]and uric acid[( 198.0±45.4 vs 236.9±29.30 ) μmol/L, P<0. 05]levels in OLETF rats in interventional group were significantly lower than those of OLETF rats in experimental group, meanwhile the amount of urinary uric acid excretion was significantly increased[(5 644±371 vs 4 692±278 ) μ mol/L, P<0. 05]. (4) There was no significant difference in insulin level and the expressions of URAT1 and UAT mRNA in renal cortex between OLETF rats in control group and experimental group. URAT1 mRNA expression of OLETF rats in interventional group was significantly decreased, while UAT mRNA expression was significantly increased. (5)With the increase of insulinconcentration in culture medium, the expression of UAT mRNA expression in HK-2 cells was gradually decreased. Conclusions Rosiglitazone may alleviate hyperinsulinemia-induced hyperuricemia via regulating UAT and URAT1 mRNA expression.

A case of idiopathic renal hypouricemia / 소아과

Idiopathic renal hypouricemia is a disorder characterized by impaired urate handling in the renal tubules. This disease usually produces no symptoms, but hematuria, uric acid nephrolithiasis or acute renal failure may develop. A defect in the SLC22A12 gene, which encodes the human urate transporter, is the known major cause of this disorder. We describe a 10-month-old boy with idiopathic renal hypouricemia. He was diagnosed with transient pseudohypoaldosteronism at admission, but hypouricemia was accidentally found through follow-up study. By gene analysis, his diagnosis was confirmed to idiopathic renal hypouricemia. In addition, we report a mutation in the human urate transporter 1 (hURAT1) gene identified in his family.