Piperine Improves Hyperuricemic Nephropathy by Inhibiting URAT1/GLUT9 and the AKT-mTOR Pathway.

Uncontrolled hyperuricemia often leads to the development of hyperuricemic nephropathy (HN), characterized by excessive inflammation and oxidative stress. Piperine, a cinnamic acid alkaloid, possesses various pharmacological activities, such as antioxidant and anti-inflammatory effects. In this study, we intended to investigate the protective effects of piperine on adenine and potassium oxonate-induced HN mice and a uric-acid-induced injury model in renal tubular epithelial cells (mRTECs). We observed that treatment with piperine for 3 weeks significantly reduced serum uric acid levels and reversed kidney function impairment in mice with HN. Piperine (5 µM) alleviated uric acid-induced damage in mRTECs. Moreover, piperine inhibited transporter expression and dose-dependently inhibited the activity of both transporters. The results revealed that piperine regulated the AKT/mTOR signaling pathway both in vivo and in vitro. Overall, piperine inhibits URAT1/GLUT9 and ameliorates HN by inhibiting the AKT/mTOR pathway, making it a promising candidate for patients with HN.

New SLC22A12 (URAT1) Variant Associated with Renal Hypouricemia Identified by Whole-Exome Sequencing Analysis and Bioinformatics Predictions.

Renal hypouricemia (RHUC) is a rare hereditary disorder caused by loss-of-function mutations in the SLC22A12 (RHUC type 1) or SLC2A9 (RHUC type 2) genes, encoding urate transporters URAT1 and GLUT9, respectively, that reabsorb urate in the renal proximal tubule. The characteristics of this disorder are low serum urate levels, high renal fractional excretion of urate, and occasional severe complications such as nephrolithiasis and exercise-induced acute renal failure. In this study, we report two Spanish (Caucasian) siblings and a Pakistani boy with clinical characteristics compatible with RHUC. Whole-exome sequencing (WES) analysis identified two homozygous variants: a novel pathogenic SLC22A12 variant, c.1523G>A; p.(S508N), in the two Caucasian siblings and a previously reported SLC2A9 variant, c.646G>A; p.(G216R), in the Pakistani boy. Our findings suggest that these two mutations cause RHUC through loss of urate reabsorption and extend the SLC22A12 mutation spectrum. In addition, this work further emphasizes the importance of WES analysis in clinical settings.

Effects of polysaccharides-riched Prunus mume fruit juice concentrate on uric acid excretion and gut microbiota in mice with adenine-induced chronic kidney disease.

The present study aimed to determine the effects of polysaccharides-riched Prunus mume fruit juice concentrate (PFC) on uric acid (UA) excretion and the gut microbiota in mice with chronic kidney disease (CKD). C57BL/6 mice were randomly allocated to four groups: two that were fed AIN93M diet, one of which was administered 500 mg/kg PFC, and two that were fed AIN93M diet containing 0.2% adenine, one of which was administered 500 mg/kg PFC. PFC promoted UA excretion, which may have been mediated through increases in the protein expression of ATP-binding cassette transporter G2 (ABCG2), organic anion transporter 1 (OAT1), organic carnitine transporter 2 (OCTN2), and reductions in the protein expression of glucose transporter 9 (GLUT9) and urate transporter 1 (URAT1) in kidneys of CKD mice. ABCG2 expression in the intestine was also increased by PFC administration. Additionally, PFC significantly increased large intestinal short-chain fatty acids (SCFAs) concentrations, and the number of gut microbial species, and reduced the abundance of the genera Bacteroides, Pseudoflavonifractor, Helicobacter, Clostridium_IV and Allobaculum, which have a negative effect on UA excretion. In conclusion, PFC may promote UA excretion in CKD mice by altering the expression of urate transporters and regulating the gut microbiota.

Hyperuricemia during Pregnancy Leads to a Preeclampsia-Like Phenotype in Mice.

Hyperuricemia is a common feature in pregnancies compromised by pre-eclampsia, a pregnancy disease characterized by hypertension and proteinuria. The role of uric acid in the pathogenesis of pre-eclampsia remains largely unclear. The aim of this study was to investigate the effect of elevated uric acid serum levels during pregnancy on maternal blood pressure and neonatal outcome using two different murine knockout models. Non-pregnant liver-specific GLUT9 knockout (LG9KO) mice showed elevated uric acid serum concentrations but no hypertensive blood pressure levels. During pregnancy, however, blood pressure levels of these animals increased in the second and third trimester, and circadian blood pressure dipping was severely altered when compared to non-pregnant LG9KO mice. The impact of hyperuricemia on fetal development was investigated using a systemic GLUT9 knockout (G9KO) mouse model. Fetal hyperuricemia caused distinctive renal tissue injuries and, subsequently an impaired neonatal growth pattern. These findings provide strong evidence that hyperuricemia plays a major role in the pathogenesis of hypertensive pregnancy disorders such as pre-eclampsia. These novel insights may enable the development of preventive and therapeutic strategies for hyperuricemia-related diseases.

Hypouricemic effect of 2,4-dihydroxybenzoic acid methyl ester in hyperuricemic mice through inhibiting XOD and down-regulating URAT1.

In this paper, we reported the hypouricemic effect of 2,4-dihydroxybenzoic acid methyl ester (DAE), a component of Ganoderma applanatum, in hyperuricemic mice through inhibiting XOD and down-regulating URAT1. Computationally, DAE showed a high similarity to allopurinol and depicted a high affinity in docking to XOD. In vitro, DAE exhibited an inhibitory effect against XOD. Importantly, DAE demonstrated a remarkable hypouricemic effect, decreasing serum uric acids (SUAs) of hyperuricemic mice (407 ± 31 µmol/L) to 195 ± 23, 145 ± 33 and 134 ± 16 µmol/L (P < 0.01) at the doses of 20, 40, and 80 mg/kg with a dose-dependent manner and showing efficacies at 54-68 %, which were close to the efficacies of allopurinol (61 %) and benzbromarone (57 %). DAE depicted higher and negatively dose-independent urinary uric acids in comparison with that of the hyperuricemic control, implying DAE exerted an uricosuric effect and also a reduction effect on uric acid production. Unlike toxic allopurinol and benzbromarone, no general toxicity on body weights and no negative influence on liver, kidney, spleen and thymus were observed for DAE. Mechanistically, DAE inhibited XOD activities in vivo. Moreover, DAE up-regulated OAT1 and down-regulated GLUT9, URAT1 and CNT2. Overall, DAE may present a hypouricemic effect through inhibiting XOD and up-regulating OAT1 and down-regulating GLUT9, URAT1 and CNT2. This work provided novel insights into the hypouricemic effect of DAE and G. applanatum.

Glucose Transporter 9 (GLUT9) Plays an Important Role in the Placental Uric Acid Transport System.

BACKGROUND: Hyperuricemia is a common laboratory finding in pregnant women compromised by preeclampsia. A growing body of evidence suggests that uric acid is involved in the pathogenesis of preeclampsia. Glucose transporter 9 (GLUT9) is a high-capacity uric acid transporter. The aim of this study was to investigate the placental uric acid transport system, and to identify the (sub-) cellular localization of GLUT9. METHODS: Specific antibodies against GLUT9a and GLUT9b isoforms were raised, and human villous (placental) tissue was immunohistochemically stained. A systemic GLUT9 knockout (G9KO) mouse model was used to assess the placental uric acid transport capacity by measurements of uric acid serum levels in the fetal and maternal circulation. RESULTS: GLUT9a and GLUT9b co-localized with the villous (apical) membrane, but not with the basal membrane, of the syncytiotrophoblast. Fetal and maternal uric acid serum levels were closely correlated. G9KO fetuses showed substantially higher uric acid serum concentrations than their mothers. CONCLUSIONS: These findings demonstrate that the placenta efficiently maintains uric acid homeostasis, and that GLUT9 plays a key role in the placental uric acid transport system, at least in this murine model. Further studies investigating the role of the placental uric acid transport system in preeclampsia are eagerly needed.

CDER167, a dual inhibitor of URAT1 and GLUT9, is a novel and potent uricosuric candidate for the treatment of hyperuricemia.

Urate transporter 1 (URAT1) and glucose transporter 9 (GLUT9) are important targets for the development of uric acid-lowering drugs. We previously showed that the flexible linkers of URAT1 inhibitors could enhance their potency. In this study we designed and synthesized CDER167, a novel RDEA3710 analogue, by introducing a linker (methylene) between the naphthalene and pyridine rings to increase flexibility, and characterized its pharmacological and pharmacokinetics properties in vitro and in vivo. We showed that CDER167 exerted dual-target inhibitory effects on both URAT1 and GLUT9: CDER167 concentration-dependently inhibited the uptake of [14C]-uric acid in URAT1-expressing HEK293 cells with an IC50 value of 2.08 ± 0.31 µM, which was similar to that of RDEA3170 (its IC50 value was 1.47 ± 0.23 µM). Using site-directed mutagenesis, we demonstrated that CDER167 might interact with URAT1 at S35 and F365. In GLUT9-expressing HEK293T cells, CDER167 concentration-dependently inhibited GLUT9 with an IC50 value of 91.55 ± 15.28 µM, whereas RDEA3170 at 100 µM had no effect on GLUT9. In potassium oxonate-induced hyperuricemic mice, oral administration of CDER167 (10 mg·kg-1 · d-1) for 7 days was more effective in lowering uric acid in blood and significantly promoted uric acid excretion in urine as compared with RDEA3170 (20 mg·kg-1 · d-1) administered. The animal experiment proved the safety of CDER167. In addition, CDER167 displayed better bioavailability than RDEA3170, better metabolic stability and no hERG toxicity at 100 µM. These results suggest that CDER167 deserves further investigation as a candidate antihyperuricemic drug targeting URAT1 and GLUT9.

Genetic and Physiological Effects of Insulin on Human Urate Homeostasis.

Insulin and hyperinsulinemia reduce renal fractional excretion of urate (FeU) and play a key role in the genesis of hyperuricemia and gout, via uncharacterized mechanisms. To explore this association further we studied the effects of genetic variation in insulin-associated pathways on serum urate (SU) levels and the physiological effects of insulin on urate transporters. We found that urate-associated variants in the human insulin (INS), insulin receptor (INSR), and insulin receptor substrate-1 (IRS1) loci associate with the expression of the insulin-like growth factor 2, IRS1, INSR, and ZNF358 genes; additionally, we found genetic interaction between SLC2A9 and the three loci, most evident in women. We also found that insulin stimulates the expression of GLUT9 and increases [14C]-urate uptake in human proximal tubular cells (PTC-05) and HEK293T cells, transport activity that was effectively abrogated by uricosurics or inhibitors of protein tyrosine kinase (PTK), PI3 kinase, MEK/ERK, or p38 MAPK. Heterologous expression of individual urate transporters in Xenopus oocytes revealed that the [14C]-urate transport activities of GLUT9a, GLUT9b, OAT10, OAT3, OAT1, NPT1 and ABCG2 are directly activated by insulin signaling, through PI3 kinase (PI3K)/Akt, MEK/ERK and/or p38 MAPK. Given that the high-capacity urate transporter GLUT9a is the exclusive basolateral exit pathway for reabsorbed urate from the renal proximal tubule into the blood, that insulin stimulates both GLUT9 expression and urate transport activity more than other urate transporters, and that SLC2A9 shows genetic interaction with urate-associated insulin-signaling loci, we postulate that the anti-uricosuric effect of insulin is primarily due to the enhanced expression and activation of GLUT9.

Apigenin ameliorates hyperuricemic nephropathy by inhibiting URAT1 and GLUT9 and relieving renal fibrosis via the Wnt/ß-catenin pathway.

BACKGROUND: Hyperuricemia (HUA) is characterized by abnormal serum uric acid (UA) levels and demonstrated to be involved in renal injury leading to hyperuricemic nephropathy (HN). Apigenin (API), a flavonoid naturally present in tea, berries, fruits, and vegetables, exhibits various biological functions, such as antioxidant and anti-inflammatory activity. PURPOSE: To investigate the effect of API treatment in HN and to reveal its underlying mechanisms. METHODS: The mice with HN were induced by potassium oxonate intraperitoneally and orally administered for two weeks. The effects of API on renal function, inflammation, fibrosis, and uric acid (UA) metabolism in mice with HN were evaluated. The effects of API on urate transporters were further examined in vitro. RESULTS: The mice with HN exhibited abnormal renal urate excretion and renal dysfunction accompanied by increased renal inflammation and fibrosis. In contrast, API reduced the levels of serum UA, serum creatinine (CRE), blood urea nitrogen (BUN) and renal inflammatory factors in mice with HN. Besides, API ameliorated the renal fibrosis via Wnt/ß-catenin pathway suppression. Furthermore, API potently promoted urinary UA excretion and inhibited renal urate transporter 1 (URAT1) and glucose transporter 9 (GLUT9) in mice with HN. In vitro, API competitively inhibited URAT1 and GLUT9 in a dose-dependent manner, with IC50 values of 0.64 ± 0.14 µM and 2.63 ± 0.69 µM, respectively. CONCLUSIONS: API could effectively attenuate HN through co-inhibiting UA reabsorption and Wnt/ß-catenin pathway, and thus it might be a potential therapy to HN.

Fucoidan from Laminaria japonica Inhibits Expression of GLUT9 and URAT1 via PI3K/Akt, JNK and NF-κB Pathways in Uric Acid-Exposed HK-2 Cells.

This work aimed to investigate the effect of fucoidan (FPS) on urate transporters induced by uric acid (UA). The results showed that UA stimulated the expression of glucose transporter 9 (GLUT9) and urate transporter 1 (URAT1) in HK-2 cells, and FPS could reverse the effect. Moreover, UA could activate NF-κB, JNK and PI3K/Akt pathways, but both pathway inhibitors and FPS inhibited the UA-induced activation of these three pathways. These data suggested that FPS effectively inhibited the expression induction of reabsorption transporters URAT1 and GLUT9 by UA, through repressing the activation of NF-κB, JNK and PI3K/Akt signal pathways in HK-2 cells. The in vitro research findings support the in vivo results that FPS reduces serum uric acid content in hyperuricemia mice and rats through inhibiting the expression of URAT1 and GLUT9 in renal tubular epithelial cells. This study provides a theoretical basis for the application of FPS in the treatment of hyperuricemia.

Characterizations of the Urate Transporter, GLUT9, and Its Potent Inhibitors by Patch-Clamp Technique.

Glucose transporter 9 (GLUT9), which transports urate in an electrogenic and voltage-dependent manner, plays an important role in the maintenance of normal blood uric acid/urate levels. In the present study, we established a cell model based on the single-electrode patch-clamp technique for characterization of GLUT9 and explored the inhibitory effects of benzobromarone (BM) and probenecid (PB) on urate-induced currents in mouse GLUT9a (mGLUT9a)-expressing HEK-293T cells. The results showed that uric acid, rather than glucose perfusion, led to a rapid and large outward current by mGLUT9a in dose-, voltage-, and pH-dependent manners. BM prominently and irreversibly inhibited the uric acid-induced currents through mGLUT9a, and PB weakly and reversibly inhibited mGLUT9a. We found that depletion of K+ in the external solution significantly strengthened the blockade of BM on mGLUT9a. In addition, an enhanced inhibitory rate of BM was detected when the pH of the external solution was changed from 7.4 to 5.5, indicating that BM functions optimally in an acidic environment. In conclusion, the combination of the established cell model with patch-clamp techniques first revealed the function properties of GLUT9 inhibitors and may provide potential benefits to the study of GLUT9 inhibitors as antihyperuricemic or antigout agents.

Baicalein alleviates hyperuricemia by promoting uric acid excretion and inhibiting xanthine oxidase.

BACKGROUND: Insufficient renal urate excretion and/or overproduction of uric acid (UA) are the dominant causes of hyperuricemia. Baicalein (BAL) is widely distributed in dietary plants and has extensive biological activities, including antioxidative, anti-inflammatory and antihypertensive activities. PURPOSE: To investigate the anti-hyperuricemic effects of BAL and the underlying mechanisms in vitro and in vivo. METHODS: We investigated the inhibitory effects of BAL on GLUT9 and URAT1 in vitro through electrophysiological experiments and 14C-urate uptake assays. To evaluate the impact of BAL on serum and urine UA, the expression of GLUT9 and URAT1, and the activity of xanthine oxidase (XOD), we developed a mouse hyperuricemia model by potassium oxonate (PO) injection. Molecular docking analysis based on homology modeling was performed to explain the predominant efficacy of BAL compared with the other test compounds. RESULTS: BAL dose-dependently inhibited GLUT9 and URAT1 in a noncompetitive manner with IC50 values of 30.17 ± 8.68 µM and 31.56 ± 1.37 µM, respectively. BAL (200 mg/kg) significantly decreased serum UA and enhanced renal urate excretion in PO-induced hyperuricemic mice. Moreover, the expression of GLUT9 and URAT1 in the kidney was downregulated, and XOD activity in the serum and liver was suppressed. The docking analysis revealed that BAL potently interacted with Trp336, Asp462, Tyr71 and Gln328 of GLUT9 and Ser35 and Phe241 of URAT1. CONCLUSION: These results indicated that BAL exerts potent antihyperuricemic efects through renal UA excretal promotion and serum UA production. Thus, we propose that BAL may be a promising treatment for the prevention of hyperuricemia owing to its multitargeted inhibitory activity.

Chicken serum uric acid level is regulated by glucose transporter 9.

OBJECTIVE: Glucose transporter 9 (GLUT9) is a uric acid transporter that is associated with uric absorption in mice and humans; but it is unknown whether GLUT9 involves in chicken uric acid regulation. This experiment aimed to investigate the chicken GLUT9 expression and serum uric acid (SUA) level. METHODS: Sixty chickens were divided into 4 groups (n = 15): a control group (NC); a sulfonamide-treated group (SD) supplemented with sulfamonomethoxine sodium via drinking water (8 mg/L); a fishmeal group (FM) supplemented with 16% fishmeal in diet; and a uric acid-injection group (IU), where uric acid (250 mg/kg) was intraperitoneally injected once a day. The serum was collected weekly to detect the SUA level. Liver, kidney, jejunum, and ileum tissues were collected to detect the GLUT9 mRNA and protein expression. RESULTS: The results showed in the SD and IU groups, the SUA level increased and GLUT9 expression increased in the liver, but decreased in the kidney, jejunum, and ileum. In the FM group, the SUA level decreased slightly and GLUT9 expression increased in the kidney, but decreased in the liver, jejunum, and ileum. Correlation analysis revealed that liver GLUT9 expression correlated positively, and renal GLUT9 expression correlated negatively with the SUA level. CONCLUSION: These results demonstrate that there may be a feedback regulation of GLUT9 in the chicken liver and kidney to maintain the SUA balance; however, the underlying mechanism needs to be investigated in future studies.

Lycium barbarum polysaccharides protect mice from hyperuricaemia through promoting kidney excretion of uric acid and inhibiting liver xanthine oxidase.

CONTEXT: Lycium barbarum L. (Solanaceae) polysaccharides (LBPs) are important active constituents that have demonstrated kidney protection. OBJECTIVE: This study investigated the effect of LBPs on hyperuricaemia and explored the underlying mechanism in mice. MATERIALS AND METHODS: Thirty-six C57BL/6 mice were randomly divided into the control group, hyperuricaemia group, allopurinol group (5 mg/kg) and three LBP groups (n = 6). The LBP groups were treated orally with LBPs at 50, 100 and 200 mg/kg body weight for 7 days. We examined the levels of serum uric acid (SUA) and urinary uric acid (UUA), as well as xanthine oxidase (XOD) activities. mRNA and protein were quantified by quantitative real-time PCR and Western blotting, respectively. RESULTS: LBPs treatment (100 and 200 mg/kg) significantly reduced the SUA levels to 4.83 and 4.48 mg/dL, and markedly elevated the UUA levels to 4.68 and 5.18 mg/dL (p < 0.05), respectively, while significantly increased the mRNA and protein expression levels of renal organic anti-transporter 1 (OAT1) and organic anti-transporter 3 (OAT3), and markedly decreased the levels of glucose transporter 9 (GLUT9) (p < 0.05). Additionally, the serum XOD activities were reduced to 31.5 and 31.1 mU/mL, and the liver XOD activities were reduced to 80.6 and 75.6 mU/mL after treatment with 100 and 200 mg/kg LBPs (p < 0.01), respectively. DISCUSSION AND CONCLUSIONS: This study demonstrated the potential role of LBPs in reducing the uric acid level in hyperuricemic mice. A border study population should be evaluated. These results are valuable for the development of new anti-hyperuricaemia agents from LBPs.

Epigallocatechin gallate reduces uric acid levels by regulating xanthine oxidase activity and uric acid excretion in vitro and in vivo.

BACKGROUND: This study investigates the effect of epigallocatechin gallate (EGCG) from tea leaves on hyperuricemia and explores the underlying mechanisms in vitro and in vivo. METHODS: The effects of EGCG on proliferation of BRL 3A rat liver cells were evaluated by CCK8 and after stimulation by xanthine the uric acid and xanthine oxidase (XOD) levels were evaluated by a kit; In an in vivo experiment, rats were treated with oxonic acid potassium salt combined with ethylamine pyrimidine to induce high uric acid hematic disease (7 days), The serum uric acid levels and XOD levels were evaluated by a kit, The expressions of OTA1 and GLUT9 were detected by RT-qPCR and Immunohistochemical. RESULTS: EGCG had no effect on proliferation, and significantly reduced serum uric acid levels and inhibited XOD activity (P<0.05). The rat model exhibited a significant rise in blood uric acid levels (54.59 mg/dL), and EGCG significantly reduced the high level of serum uric acid and inhibited XOD activity in the serum and liver tissues (P<0.05). RT-PCR showed that EGCG significantly increased mOAT1 expression in the kidney tissues and reduced mGLUT9 expression (P<0.05). Immunohistochemical results showed that EGCG significantly increased OAT1 expression in the kidney tissues and decreased GLUT9 expression (P<0.05). CONCLUSIONS: These results demonstrate that EGCG has obvious anti-hyperuricemia effects in vitro and in vivo via the inhibition of XOD activity and GLUT9 expression and the promotion of OAT1 expression.

Research Progress of Pathology of Gout and Clinical Treatment with Traditional Chinese and Western Medicine / 中国实验方剂学杂志

With the improvement of people's living standard and the change of dietary structure, the prevalence of gout has increased gradually with the increased intake of protein, sugar and fat. There has been a positive correlation between gout and age, and the age of onset decreased gradually. The inflammation induced by sodium urate crystal is the pathological basis of gout, which activates innate immunity, releases many kinds of inflammatory mediators, such as interleukin(IL)-1β, IL-6 and tumor necrosis factor(TNF)-α, and then causes inflammatory cascade reaction and acute attacks, such as joint redness, swelling and heat pain. There is a spontaneous remission mechanism in gout. For one thing, macrophages reduce the stimulation of monosodium urate(MSU) through phagocytosis of MSU crystals as foreign bodies, for another, differentiated and mature macrophages secrete anti-inflammatory factor transforming growth factor(TGF)-β1, inhibit the expression of inflammatory factors and promote spontaneous relief of acute gout attack. In addition to the activation mechanism of intracellular signaling molecules associated with inflammatory response, the inflammatory mechanism of gout also involves complement activation, cell activation and other pathways. The complications caused by gout, such as cardiovascular system damage and joint destruction, are seriously harmful to human health. At present, western drugs, such as allopurinol and febuxostat, exert an effect in inhibiting xanthine oxidase. Benzimarone has effect in reducing renal absorption of uric acid and promoting uric acid excretion by inhibiting uric acid transporter 1(URAT1) and glucose transporter 9(GLUT9). Even Lesinurad and other medicines in current studies are based on the inhibition of uric acid re-absorption, but with adverse reactions that limit the clinical application. The treatment of gout with traditional Chinese medicine(TCM) has multi-target characteristics, with advantages in reducing uric acid, resisting inflammation and improving joint function and a high safety. It has been gradually popularized and applied in clinical treatment of gout. Therefore, it is a promising research direction to treat gout with TCM and western medicine based on the pathomechanism of gout.

Molecular mechanistic insight into the anti-hyperuricemic effect of Eucommia ulmoides in mice and rats.

CONTEXT: Eucommia ulmoides Oliver (Eucommiaceae) has various medicinal properties. Our previous studies revealed that Eucommia ulmoides has a protective effect on hyperuricaemia. OBJECTIVE: This study investigates the effect of Eucommia ulmoides cortex ethanol extract (EU) on hyperuricaemia and explores the underlying mechanism in Kunming mice and Sprague-Dawley rats. MATERIAL AND METHODS: Sixty mice and sixty rats were divided into normal control, hyperuricaemia, allopurinol (10 mg/kg) and three EU groups. The EU groups received intragastric EU at 80, 160, 320 mg/kg in mice and 100, 200, 400 mg/kg in rats for 7 days. Serum uric acid (SUA) was measured using a kit. mRNA and proteins were quantified by RT-qPCR and immunohistochemical assays (IHC), respectively. RESULTS: The Maximal Tolerable Dose (MTD) of EU administered intragastrically was 18 g/kg in mice. The intermediate (160 mg/kg) and high (320 mg/kg) EU treatment significantly reduced (p < 0.05) SUA levels to 130.16 µmol/L and 109.29 µmol/L, respectively, and markedly elevated the mRNA expression of organic anion transporters 1 (OAT1) and organic anion transporters 3 (OAT3), while significantly deceasing the mRNA levels of glucose transporter 9 (GLUT9) and uric acid transporter 1 (URAT1) in the mouse kidney (p < 0.05). In hyperuricemic rats, high EU (400 mg/kg) significantly reduced SUA levels to 253.85 µmol/L, and increased OAT1 and OAT3 levels, but decreased URAT1 and GLUT9, compared to the hyperuricaemia group (p < 0.05). DISCUSSION AND CONCLUSIONS: This study demonstrated the potential hyperuricaemia ameliorating effect of EU. Specific active ingredients in EU should be evaluated. These results are valuable for the development of antihyperuritic agents from EU.

Hypouricemic Effects of Armillaria mellea on Hyperuricemic Mice Regulated through OAT1 and CNT2.

Ethanol and water extracts of Armillaria mellea were prepared by directly soaking A. mellea in ethanol (AME) at 65[Formula: see text]C, followed by decocting the remains in water (AMW) at 85[Formula: see text]C. Significantly, AME and AMW at 30, 60 and 120[Formula: see text]mg/kg exhibited excellent hypouricemic actions, causing remarkable declines from hyperuricemic control (351[Formula: see text][Formula: see text]mol/L, [Formula: see text]) to 136, 130 and 115[Formula: see text][Formula: see text]mol/L and 250, 188 and 152[Formula: see text][Formula: see text]mol/L in serum uric acid, correspondingly. In contrast to the evident renal toxicity of allopurinol, these preparations showed little impacts. Moreover, they showed some inhibitory effect on XOD (xanthine oxidase) activity. Compared with hyperuricemic control, protein expressions of OAT1 (organic anion transporter 1) were significantly elevated in AME- and AMW-treated mice. The levels of GLUT9 (glucose transporter 9) expression were significantly decreased by AMW. CNT2 (concentrative nucleoside transporter 2), a key target for purine absorption in gastrointestinal tract was involved in this study, and was verified for its innovative role. Both AME and AMW down-regulated CNT2 proteins in the gastrointestinal tract in hyperuricemic mice. As they exhibited considerable inhibitory effects on XOD, we selected XOD as the target for virtual screening by using molecular docking, and four compounds were hit with high ranks. From the analysis, we concluded that hydrogen bond, Pi-Pi and Pi-sigma interactions might play important roles for their orientations and locations in XOD inhibition.

Uric acid transporter and the balance of serum uric acid / 国际药学研究杂志

During the uric acid production, excretion and reabsorption in the liver, kidney and intestine, several uric acid transporter proteins are involved in these processes. A large number of studies have shown that glucose transporter 9 plays an important role in the uric acid transport in the liver, kidney and intestine, and participates in the uric acid reabsorption. The ATP-binding cassette superfamily G member 2 is mainly expressed in the apical membrane of the proximal tubular epithelial cells of the kidney, which is involved in the uric acid secretion. The multidrug resistant protein 4 is expressed in the apical membrane of the renal tubular epithelial cells, which transfers uric acid from the renal tubular epithelial cells into the renal tubular lumen. The urate-anion transporter 1 as well as the organic anion transporters 1 and 3 are all the organic anion transporters belonging to the SLC22 A family of transmembrane transporters, and all participate in the uric acid transport in the kidney, especially the uric acid secretion and excretion. In this review, we summarize the research progress of these uric acid transporters, focusing on their effects on the regulation of the serum uric acid balance.

Saponins extracted from Dioscorea collettii rhizomes regulate the expression of urate transporters in chronic hyperuricemia rats.

OBJECTIVE: The current study aimed to investigate whether the saponins, bioactive component of effects of D. collettii, could reduce the serum uric acid level in a hyperuricemic mouse via regulation of urate transporters. METHODS: Chronic hyperuricemia model was established by combine administration of adenine (100mg/kg) and ethambutol (250mg/kg). In the model group, the serum uric acid (SUA), urine uric acid (UUA) volume, and 24-h UUA values increased significantly, while the uric acid clearance rate (CUr) and creatinine clearance rate (CCr) values decreased. Further, the model groups showed significantly lower expression of organic anion transporter 1 (OAT1) and organic anion transporter 3 (OAT3) and significantly higher expression of renal tubular urate transporter 1 (URAT1), glucose transporter 9 (GLUT9) and URAT1 mRNA than the normal control group. RESULTS: Saponins administration was found to have a dose-dependent effect, as evidenced by the increase in the 24-h UUA, CUr and CCr values; the decrease in SUA; the decrease in the renal expression of URAT1 mRNA and URAT1 and GLUT9 proteins; and the increase in the renal expression of the OAT1 and OAT3 proteins. CONCLUSION: The saponins extracted from D. collettii rhizomes had an obvious anti-hyperuricemic effect through downregulation of the URAT1 mRNA and the URAT1 and GLUT9 proteins and upregulation of the OAT1 and OAT3 proteins.