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Ruth G. Abramson - One of the best experts on this subject based on the ideXlab platform.
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functional analysis and molecular model of the human Urate Transporter channel huat
American Journal of Physiology-renal Physiology, 2002Co-Authors: Edgar Lealpinto, Michael S Lipkowitz, Eleazar B Cohen, Ruth G. AbramsonAbstract:Recombinant protein, designated hUAT, the human homologue of the rat Urate Transporter/channel (UAT), functions as a highly selective Urate channel in lipid bilayers. Functional analysis indicates that hUAT activity, like UAT, is selectively blocked by oxonate from its cytosolic side, whereas pyrazinoate and adenosine selectively block from the channel's extracellular face. Importantly, hUAT is a galectin, a protein with two β-galactoside binding domains that bind lactose. Lactose significantly increased hUAT open probability but only when added to the channel's extracellular side. This effect on open probability was mimicked by glucose, but not ribose, suggesting a role for extracellular glucose in regulating hUAT channel activity. These functional observations support a four-transmembrane-domain structural model of hUAT, as previously predicted from the primary structure of UAT. hUAT and UAT, however, are not functionally identical: hUAT has a significantly lower single-channel conductance and open probability is voltage independent. These differences suggest that evolutionary changes in specific amino acids in these highly homologous proteins are functionally relevant in defining these biophysical properties.
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Functional analysis and molecular model of the human Urate Transporter/channel, hUAT.
American journal of physiology. Renal physiology, 2002Co-Authors: Edgar Leal-pinto, B.e. Cohen, Michael S Lipkowitz, Ruth G. AbramsonAbstract:Recombinant protein, designated hUAT, the human homologue of the rat Urate Transporter/channel (UAT), functions as a highly selective Urate channel in lipid bilayers. Functional analysis indicates that hUAT activity, like UAT, is selectively blocked by oxonate from its cytosolic side, whereas pyrazinoate and adenosine selectively block from the channel's extracellular face. Importantly, hUAT is a galectin, a protein with two β-galactoside binding domains that bind lactose. Lactose significantly increased hUAT open probability but only when added to the channel's extracellular side. This effect on open probability was mimicked by glucose, but not ribose, suggesting a role for extracellular glucose in regulating hUAT channel activity. These functional observations support a four-transmembrane-domain structural model of hUAT, as previously predicted from the primary structure of UAT. hUAT and UAT, however, are not functionally identical: hUAT has a significantly lower single-channel conductance and open probability is voltage independent. These differences suggest that evolutionary changes in specific amino acids in these highly homologous proteins are functionally relevant in defining these biophysical properties.
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galectin 9 is the sugar regulated Urate Transporter channel uat
Glycoconjugate Journal, 2002Co-Authors: Michael S Lipkowitz, Edgar Lealpinto, Eleazar B Cohen, Ruth G. AbramsonAbstract:UAT, also designated galectin 9, is a multifunctional protein that can function as a Urate channel/Transporter, a regulator of thymocyte-epithelial cell interactions, a tumor antigen, an eosinophil chemotactic factor, and a mediator of apoptosis. We review the evidence that UAT is a transmembrane protein that transports Urate, describe our molecular model for this protein, and discuss the evidence from epitope tag and lipid bilayer studies that support this model of the Transporter. The properties of recombinant UAT are compared with those of Urate transport into membrane vesicles derived from proximal tubule cells in rat kidney cortex. In addition, we review channel functions predicted by our molecular model that resulted in the novel finding that the Urate channel activity is regulated by sugars and adenosine. Finally, the presence and possible functions of at least 4 isoforms of UAT and a closely related gene hUAT2 are discussed. Published in 2004.
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Localization and topology of a Urate Transporter/channel, a galectin, in epithelium-derived cells
American journal of physiology. Cell physiology, 2001Co-Authors: Joshua Z. Rappoport, Michael S Lipkowitz, Ruth G. AbramsonAbstract:Recombinant protein produced from a cDNA cloned in our laboratory (UAT) functions in lipid bilayers as a Urate Transporter/channel. Because UAT is a galectin, a family of proteins presumed to be soluble, the localization and topology of UAT were assessed in living cells. UAT was targeted to plasma membrane in multiple epithelium-derived cell lines and, in polarized cells, was targeted to both apical and basolateral membranes. The amino and carboxy termini of UAT were both detected on the cytoplasmic side of plasma membranes, whereas cell surface biotinylation studies demonstrated that UAT is not merely a cytosolic membrane-associated protein but contains at least one extracellular domain. Madin-Darby canine kidney cells were shown both functionally and immunologically to contain an apparent homolog of UAT; however, transfection with UAT did not modify Urate uptake. Because coimmunoprecipitation studies revealed that UAT is capable of forming both homo- and heteromultimers, it is proposed that monomers of endogenous channels are in part replaced by monomers of the protein expressed subsequent to transfection, thereby maintaining constancy of Urate uptake at basal levels.
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localization and topology of a Urate Transporter channel a galectin in epithelium derived cells
American Journal of Physiology-cell Physiology, 2001Co-Authors: Joshua Z. Rappoport, Michael S Lipkowitz, Ruth G. AbramsonAbstract:Recombinant protein produced from a cDNA cloned in our laboratory (UAT) functions in lipid bilayers as a Urate Transporter/channel. Because UAT is a galectin, a family of proteins presumed to be soluble, the localization and topology of UAT were assessed in living cells. UAT was targeted to plasma membrane in multiple epithelium-derived cell lines and, in polarized cells, was targeted to both apical and basolateral membranes. The amino and carboxy termini of UAT were both detected on the cytoplasmic side of plasma membranes, whereas cell surface biotinylation studies demonstrated that UAT is not merely a cytosolic membrane-associated protein but contains at least one extracellular domain. Madin-Darby canine kidney cells were shown both functionally and immunologically to contain an apparent homolog of UAT; however, transfection with UAT did not modify Urate uptake. Because coimmunoprecipitation studies revealed that UAT is capable of forming both homo- and heteromultimers, it is proposed that monomers of endogenous channels are in part replaced by monomers of the protein expressed subsequent to transfection, thereby maintaining constancy of Urate uptake at basal levels.
Makoto Hosoyamada - One of the best experts on this subject based on the ideXlab platform.
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P0169DYSFUNCTION OF ABCG2, Urate Transporter, IS RELATED WITH UROLITHIASIS
Nephrology Dialysis Transplantation, 2020Co-Authors: Yuki Ohashi, Hirotaka Matsuo, Makoto Hosoyamada, Satoshi Yamaguchi, Kimiyoshi IchidaAbstract:Abstract Background and Aims Urolithiasis is one of the rapidly increasing diseases in developed countries. It has been reported that urolithiasis is related with lifestyles, diet, obesity, climate and chronic diseases including hyperuricemia, diabetes mellitus, metabolic syndrome, chronic kidney disease et cetera. Among them, hyperuricemia is the leading cause of urolithiasis. ATP–binding cassette subfamily G member 2 (ABCG2), Urate Transporter, excretes uric acid in the kidney and the intestinal tract and ABCG2 dysfunction increases a risk of hyperuricemia. In this study, we investigated the estimated ABCG2 function by common two dysfunctional variants, Q126X (rs72552713) and Q141K (rs2231142), in patients with urolithiasis, and we evaluated the relation between urolithiasis and ABCG2 dysfunction. Method One hundred and ninety-seven urolithiasis patients without gout (150 males and 47 females) were enrolled. Q126X totally abolishes ABCG2 function, while Q141K reduces its function by about 50%. Since these two SNPs do not link each other and two SNPs do not exist on same chromosome, these two are regarded as independent risks. Namely, based on the genotype of Q126X and Q141K, it can be divided into three categories: a full functional group, a 75% functional group and a ≦50% functional group. Serum uric acid levels and amount of urinary uric acid were measured. Renal uric acid handling of the patients was classified into renal uric acid underexcretion type or renal uric acid overload type based on uric acid clearance and amount of urinary uric acid. Stone composition was analysed, if it had been possible. Results ABCG2 function of the patients was evaluated as follows: 82 patients, ABCG2 full function (41.6%); 78 patients, 75% function (39.6%); 37 patients, ≦50% function (18.8%). 155 patients were classified into renal uric acid underexcretion type, 13 patients were classified into renal uric acid overload type and 2 patients were classified into normal type (27 patients have not had 24-hour urine biochemical test). Stone composition analysis was performed for 136 patients; calcium oxalate stone was identified in 107 patients and uric acid stone in 29 patients. In this study, 58.4 % of the patients with urolithiasis had some ABCG2 dysfunction as against 49.8 % of the healthy individuals previously reported (p=0.0246). In addition, the ratio of subjects with urolithiasis having 50% or less of ABCG2 function was higher than healthy individuals significantly (OR=1.773, p=0.007). The high ratio of ABCG2 dysfunctional patients with urolithiasis suggested that ABCG2 dysfunction is a risk factor for urolithiasis. In the patients with urolithiasis, renal uric acid underexcretion type accounted for about 90% of the patients. This means that this type accelerated urolithiasis as well as hyperuricosuria. Conclusion ABCG2 dysfunction and renal uric acid underexcretion type were suggested to be a risk factor for urolithiasis.
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Insulin stimulates uric acid reabsorption via regulating Urate Transporter 1 and ATP-binding cassette subfamily G member 2
American journal of physiology. Renal physiology, 2017Co-Authors: Daigo Toyoki, Kenichi Ishizawa, Makoto Hosoyamada, Shigeru Shibata, Emiko Kuribayashi-okuma, Shunya UchidaAbstract:Accumulating data indicate that renal uric acid (UA) handling is altered in diabetes and by hypoglycemic agents. In addition, hyperinsulinemia is associated with hyperuricemia and hypouricosuria. However, the underlying mechanisms remain unclear. In this study, we aimed to investigate how diabetes and hypoglycemic agents alter the levels of renal Urate Transporters. In insulin-depleted diabetic rats with streptozotocin treatment, both UA excretion and fractional excretion of UA were increased, suggesting that tubular handling of UA is altered in this model. In the membrane fraction of the kidney, the expression of Urate Transporter 1 (URAT1) was significantly decreased, whereas that of ATP-binding cassette subfamily G member 2 (ABCG2) was increased, consistent with the increased renal UA clearance. Administration of insulin to the diabetic rats decreased UA excretion and alleviated UA Transporter-level changes, while sodium glucose coTransporter 2 inhibitor (SGLT2i) ipragliflozin did not change renal UA handling in this model. To confirm the contribution of insulin in the regulation of Urate Transporters, normal rats received insulin and separately, ipragliflozin. Insulin significantly increased URAT1 and decreased ABCG2 levels, resulting in increased UA reabsorption. In contrast, the SGLT2i did not alter URAT1 or ABCG2 levels, although blood glucose levels were similarly reduced. Furthermore, we found that insulin significantly increased endogenous URAT1 levels in the membrane fraction of NRK-52E cells, the kidney epithelial cell line, demonstrating the direct effects of insulin on renal UA transport mechanisms. These results suggest a previously unrecognized mechanism for the anti-uricosuric effects of insulin and provide novel insights into the renal UA handling in the diabetic state.
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Immunohistochemical and in situ hybridization study of Urate Transporters GLUT9/URATv1, ABCG2, and URAT1 in the murine brain.
Fluids and barriers of the CNS, 2016Co-Authors: Naoko H. Tomioka, Tappei Takada, Hiroshi Suzuki, Shigeru Shibata, Shunya Uchida, Yoshifuru Tamura, Makoto HosoyamadaAbstract:Background Uric acid (UA) is known to exert neuroprotective effects in the brain. However, the mechanism of UA regulation in the brain is not well characterized. In our previous study, we described that the mouse Urate Transporter URAT1 is localized to the cilia and apical surface of ventricular ependymal cells. To further strengthen the hypothesis that UA is transported transcellularly at the ependymal cells, we aimed to assess the distribution of other UA Transporters in the murine brain.
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Urat1-Uox double knockout mice are experimental animal models of renal hypouricemia and exercise-induced acute kidney injury.
Nucleosides nucleotides & nucleic acids, 2016Co-Authors: Makoto Hosoyamada, Naoko H. Tomioka, Takayuki Morisaki, Yu Tsurumi, Hidenori Hirano, Yuko Sekine, Shunya UchidaAbstract:Renal hypouricemia (RHUC) is a hereditary disease characterized by a low level of plasma Urate but with normal urinary Urate excretion. RHUC type 1 is caused by mutations of the Urate Transporter U...
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Ependymal cells of the mouse brain express Urate Transporter 1 (URAT1)
Fluids and barriers of the CNS, 2013Co-Authors: Naoko H. Tomioka, Kimiyoshi Ichida, Makiko Nakamura, Masaru Doshi, Yoshiharu Deguchi, Takayuki Morisaki, Makoto HosoyamadaAbstract:Background Elevated uric acid (UA) is commonly associated with gout and it is also a known cardiovascular disease risk factor. In contrast to such deleterious effects, UA possesses neuroprotective properties in the brain and elucidating the molecular mechanisms involved may have significant value regarding the therapeutic treatment of neurodegenerative disease. However, it is not yet fully established how UA levels are regulated in the brain. In this study, we investigated the distribution of mouse Urate Transporter 1 (URAT1) in the brain. URAT1 is a major reabsorptive Urate Transporter predominantly found in the kidney.
Kimiyoshi Ichida - One of the best experts on this subject based on the ideXlab platform.
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P0169DYSFUNCTION OF ABCG2, Urate Transporter, IS RELATED WITH UROLITHIASIS
Nephrology Dialysis Transplantation, 2020Co-Authors: Yuki Ohashi, Hirotaka Matsuo, Makoto Hosoyamada, Satoshi Yamaguchi, Kimiyoshi IchidaAbstract:Abstract Background and Aims Urolithiasis is one of the rapidly increasing diseases in developed countries. It has been reported that urolithiasis is related with lifestyles, diet, obesity, climate and chronic diseases including hyperuricemia, diabetes mellitus, metabolic syndrome, chronic kidney disease et cetera. Among them, hyperuricemia is the leading cause of urolithiasis. ATP–binding cassette subfamily G member 2 (ABCG2), Urate Transporter, excretes uric acid in the kidney and the intestinal tract and ABCG2 dysfunction increases a risk of hyperuricemia. In this study, we investigated the estimated ABCG2 function by common two dysfunctional variants, Q126X (rs72552713) and Q141K (rs2231142), in patients with urolithiasis, and we evaluated the relation between urolithiasis and ABCG2 dysfunction. Method One hundred and ninety-seven urolithiasis patients without gout (150 males and 47 females) were enrolled. Q126X totally abolishes ABCG2 function, while Q141K reduces its function by about 50%. Since these two SNPs do not link each other and two SNPs do not exist on same chromosome, these two are regarded as independent risks. Namely, based on the genotype of Q126X and Q141K, it can be divided into three categories: a full functional group, a 75% functional group and a ≦50% functional group. Serum uric acid levels and amount of urinary uric acid were measured. Renal uric acid handling of the patients was classified into renal uric acid underexcretion type or renal uric acid overload type based on uric acid clearance and amount of urinary uric acid. Stone composition was analysed, if it had been possible. Results ABCG2 function of the patients was evaluated as follows: 82 patients, ABCG2 full function (41.6%); 78 patients, 75% function (39.6%); 37 patients, ≦50% function (18.8%). 155 patients were classified into renal uric acid underexcretion type, 13 patients were classified into renal uric acid overload type and 2 patients were classified into normal type (27 patients have not had 24-hour urine biochemical test). Stone composition analysis was performed for 136 patients; calcium oxalate stone was identified in 107 patients and uric acid stone in 29 patients. In this study, 58.4 % of the patients with urolithiasis had some ABCG2 dysfunction as against 49.8 % of the healthy individuals previously reported (p=0.0246). In addition, the ratio of subjects with urolithiasis having 50% or less of ABCG2 function was higher than healthy individuals significantly (OR=1.773, p=0.007). The high ratio of ABCG2 dysfunctional patients with urolithiasis suggested that ABCG2 dysfunction is a risk factor for urolithiasis. In the patients with urolithiasis, renal uric acid underexcretion type accounted for about 90% of the patients. This means that this type accelerated urolithiasis as well as hyperuricosuria. Conclusion ABCG2 dysfunction and renal uric acid underexcretion type were suggested to be a risk factor for urolithiasis.
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Investigation of the transport of xanthine dehydrogenase inhibitors by the Urate Transporter ABCG2.
Drug metabolism and pharmacokinetics, 2017Co-Authors: Makiko Nakamura, Yu Toyoda, Kyoko Fujita, Tappei Takada, Hiroshi Hasegawa, Kimiyoshi IchidaAbstract:Abstract Hyperuricemia induces gout and kidney stones and accelerates the progression of renal and cardiovascular diseases. Adenosine 5′-triphosphate-binding cassette subfamily G member 2 (ABCG2) is a Urate Transporter, and common dysfunctional variants of ABCG2, non-functional Q126X (rs72552713) and semi-functional Q141K (rs2231142), are risk factors for hyperuricemia and gout. A recent genome wide association study suggested that allopurinol, a serum uric acid-lowering drug that inhibits xanthine dehydrogenase, is a potent substrate of ABCG2. In this study, we aimed to examine the transport of xanthine dehydrogenase inhibitors via ABCG2. Our results show that ABCG2 transports oxypurinol, an active metabolite of allopurinol, whereas allopurinol and febuxostat, a new xanthine dehydrogenase inhibitor, are not substrates of ABCG2. The amount of oxypurinol transported by ABCG2 vesicles significantly increased in the presence of ATP, compared to that observed with mock vesicles. Since the half-life of oxypurinol is longer than that of allopurinol, the xanthine dehydrogenase-inhibiting effect of allopurinol mainly depends on its metabolite, oxypurinol. Our results indicate that the serum level of oxypurinol would increase in patients with ABCG2 dysfunction.
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Ependymal cells of the mouse brain express Urate Transporter 1 (URAT1)
Fluids and barriers of the CNS, 2013Co-Authors: Naoko H. Tomioka, Kimiyoshi Ichida, Makiko Nakamura, Masaru Doshi, Yoshiharu Deguchi, Takayuki Morisaki, Makoto HosoyamadaAbstract:Background Elevated uric acid (UA) is commonly associated with gout and it is also a known cardiovascular disease risk factor. In contrast to such deleterious effects, UA possesses neuroprotective properties in the brain and elucidating the molecular mechanisms involved may have significant value regarding the therapeutic treatment of neurodegenerative disease. However, it is not yet fully established how UA levels are regulated in the brain. In this study, we investigated the distribution of mouse Urate Transporter 1 (URAT1) in the brain. URAT1 is a major reabsorptive Urate Transporter predominantly found in the kidney.
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Effect of losartan and benzbromarone on the level of human Urate Transporter 1 mRNA.
Arzneimittel-Forschung, 2011Co-Authors: Yora Nindita, Toshihiro Hamada, Kimiyoshi Ichida, Makoto Hosoyamada, Udin Bahrudin, Chisato Iwai, Sunao Urashima, Masanari Kuwabara, Sulistiyati Bayu Utami, Einosuke MizutaAbstract:Both an angiotensin II receptor blocker, losartan (CAS 124750-99-8) and a serum Urate lowering agent, benzbromarone (CAS 3562-84-3) exert a uricosuric action by inhibiting Urate Transporter 1 (URAT1). A recent clinical trial indicated that losartan could reduce the level of serum Urate in hypertensive patients treated with Urate lowering agents, suggesting the different mode of action of losartan from benzbromarone. In the present study, the effect of losartan and benzbromarone on the level of URAT1 mRNA was determined in transfected HEK293 cells. Losartan caused a significant reduction of its mRNA level, whereas it was not affected by benzbromarone. These results indicate that losartan decreases the level of human URAT1 mRNA, which may underlie the uricosuric action of losartan in hypertensive patients treated with serum Urate lowering agents.
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Diagnostic Tests for Primary Renal Hypouricemia
Nucleosides Nucleotides & Nucleic Acids, 2011Co-Authors: I. Sebesta, Blanka Stiburkova, Josef Bartl, Kimiyoshi Ichida, Makoto Hosoyamada, J. Taylor, Anthony M. MarinakiAbstract:Primary renal hypouricemia is a genetic disorder characterized by defective renal uric acid (UA) reabsorption with complications such as nephrolithiasis and exercise-induced acute renal failure. The known causes are: defects in the SLC22A12 gene, encoding the human Urate Transporter 1 (hURAT1), and also impairment of voltage Urate Transporter (URATv1), encoded by SLC2A9 (GLUT9) gene. Diagnosis is based on hypouricemia ( 10%). To date, the cases with mutations in hURAT1 gene have been reported in East Asia only. More than 100 Japanese patients have been described. Hypouricemia is sometimes overlooked; therefore, we have set up the flowchart for this disorder. The patients were selected for molecular analysis from 620 Czech hypouricemic patients. Secondary causes of hyperuricosuric hypouricemia were excluded. The estimations of (1) serum UA, (2) excretion fraction of UA, and (3) analysis of hURAT1 and URATv1 genes follow. Three transitions and one delet...
Hitoshi Endou - One of the best experts on this subject based on the ideXlab platform.
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Interactions of Urate Transporter URAT1 in human kidney with uricosuric drugs.
Nephrology (Carlton Vic.), 2011Co-Authors: Ho Jung Shin, Atsushi Enomoto, Naohiko Anzai, Michio Takeda, Masaaki Fujimura, Hiroki Miyazaki, Hitoshi EndouAbstract:Aim: Hyperuricaemia is a significant factor in a variety of diseases, including gout and cardiovascular diseases. The kidney plays a dominant role in maintaining plasma Urate levels through the excretion process. Human renal Urate Transporter URAT1 is thought to be an essential molecule that mediates the reabsorption of Urate on the apical side of the proximal tubule. In this study the pharmacological characteristics and clinical implications of URAT1 were elucidated. Methods: Madin–Darby canine kidney (MDCK) cells stably expressing URAT1 (MDCK-URAT1) were established and examined the interactions of URAT1 with various drugs such as benzbromarone and its metabolites including 6-hydroxybenzbromarone, angiotensin-converting enzyme inhibitors, non-steroidal anti-inflammatory drugs and Urate transport inhibitors including E3040 and probenecid. Results: MDCK-URAT1 cells exhibited a time- and dose-dependent increase in Urate uptake, with a Km value of 570.7 µmol/L. When an URAT1-green fluorescent protein fusion protein construct was expressed in MDCK cells, the protein was sorted mainly to the apical side of the membrane. The drugs except for captoril dose-dependently inhibited Urate uptake mediated by URAT1, with half maximal inhibitory concentration (IC50) values ranging 0.05–716 µmol/L. Conclusion: Comparing these IC50 values with intratubular concentrations of unbound drugs in humans, it is thought that URAT1 is a target molecule of uricosuric drugs, including 6-hydroxybenzbromarone, probenecid, indomethacin and salicylate, to inhibit Urate reabsorption in vivo. In addition, a cell line that stably expressing URAT1 could be a useful tool for the development of uricosuric drugs.
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Effect of fenofibrate on uric acid metabolism and Urate Transporter 1.
Internal medicine (Tokyo Japan), 2010Co-Authors: Daijiro Uetake, Hitoshi Endou, Kimiyoshi Ichida, Iwao Ohno, Yuichiro Yamaguchi, Hajime Saikawa, Tatsuo HosoyaAbstract:Objective To examine the effects of fenofibrate, an antilipotropic drug, on uric acid metabolism in healthy male subjects and on Urate Transporter 1 (URAT1). Methods Fenofibrate was administered to nine male volunteers at a dose of 300 mg (corresponding to 200 mg of micronized fenofibrate), and the metabolic parameters of uric acid were investigated for more than 12 hours. In addition, the effect of fenofibrate on URAT1-expressing cells was examined. Results After the administration of fenofibrate, the concentration of serum uric acid had significantly decreased from 5.8±0.4 mg/dL to 4.3±0.3 mg/dL at 10 h. Uric acid clearance and the fractional excretion of uric acid increased. Fenofibric acid, a fenofibrate metabolite, inhibited URAT1 to an extent similar to that observed with benzbromarone and losartan. Conclusion Fenofibrate decreased serum uric acid levels by increasing its urinary excretion, most likely through the inhibition of URAT1 by fenofibric acid, its major metabolite.
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Sodium-Hydrogen Exchanger Regulatory Factor-1 Interacts with Mouse Urate Transporter 1 to Regulate Renal Proximal Tubule Uric Acid Transport
Journal of the American Society of Nephrology : JASN, 2007Co-Authors: Rochelle Cunningham, Naohiko Anzai, Marc F. Brazie, Srilatha Kanumuru, Xiaofei E, Rajat S. Biswas, Fengying Wang, Deborah Steplock, James B. Wade, Hitoshi EndouAbstract:Sodium-hydrogen exchanger regulatory factor-1–deficient (NHERF-1 −/− ) mice demonstrate increases in the urinary excretion of phosphate, calcium, and uric acid associated with interstitial deposition of calcium in the papilla of the kidney. These studies examine the role of NHERF-1 in the tubular reabsorption of uric acid and regulation of mouse Urate Transporter 1 (mURAT1), a newly described Transporter that is responsible for the renal tubular reabsorption of uric acid. In primary cultures of mouse renal proximal tubule cells, uric acid uptake was significantly lower in NHERF-1 −/− cells compared with wild-type cells over a large range of uric acid concentrations in the media. Western immunoblotting revealed a 56 ± 6% decrease in the brush border membrane (BBM) expression of mURAT1 in NHERF-1 −/− compared with wild-type control kidneys ( P −/− kidneys and demonstrated mislocalization of mURAT1 to intracellular vesicular structures. Para-aminohippUrate significantly inhibited uric acid uptake in wild-type cells (41 ± 2%) compared with NHERF-1 −/− cells (8.2 ± 3%). Infection of NHERF-1 −/− cells with adenovirus–green fluorescence protein–NHERF-1 resulted in significantly higher rates of uric acid transport (15.4 ± 1.1 pmol/μg protein per 30 min) compared with null cells that were infected with control adenovirus–green fluorescence protein (7.9 ± 0.3) and restoration of the inhibitory effect of para-aminohippUrate (% inhibition 34 ± 4%). These findings indicate that NHERF-1 exerts a significant effect on the renal tubular reabsorption of uric acid in the mouse by modulating the BBM abundance of mURAT1 and possibly other BBM uric acid Transporters.
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Roles of organic anion Transporters (OATs) and a Urate Transporter (URAT1) in the pathophysiology of human disease
Clinical and Experimental Nephrology, 2005Co-Authors: Atsushi Enomoto, Hitoshi EndouAbstract:Renal proximal and distal tubules are highly polarized epithelial cells that carry out the specialized directional transport of various solutes. This renal function, which is essential for homeostasis in the body, is achieved through the close pairing of apical and basolateral carriers expressed in the renal epithelial cells. The family of organic anion Transporters (OATs), which belong to the major facilitator superfamily ( SLC22A ), are expressed in the renal epithelial cells to regulate the excretion and reabsorption of endogenous and exogenous organic anions. We now understand that these OATs are crucial components in the renal handling of drugs and their metabolites, and they are implicated in various clinically important drug interactions, and their adverse reactions. In recent years, the molecular entities of these Transporters have been identified, and their function and regulatory mechanisms have been partially clarified. Workers in this field have identified URAT1 (Urate Transporter 1), a novel member of the OAT family that displays unique and selective substrate specificity compared with other multispecific OATs. In the OAT family, URAT1 is the main transporster responsible for human genetic diseases. In this review, we introduce and discuss some novel aspects of OATs, with special emphasis on URAT1, in the context of their biological significance, functional regulation, and roles in human disease.
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Function and Localization of Urate Transporter 1 in Mouse Kidney
Journal of the American Society of Nephrology : JASN, 2004Co-Authors: Makoto Hosoyamada, Atsushi Enomoto, Tatsuo Hosoya, Kimiyoshi Ichida, Hitoshi EndouAbstract:ABSTRACT. Mouse renal-specific Transporter (RST) cDNA, the amino acid sequence of which has 74% identity with that of human Urate Transporter 1 (hURAT1), is potentially the mouse homologue of hURAT1, the gene responsible for hereditary renal hypouricemia. The aim of this study is to determine the location and characteristics of RST molecule in mouse kidney and investigate Urate transport by RST using the Xenopus oocyte expression system. RST transported 14 C-Urate in a Michaelis-Menten manner. The K m and the V max values of RST-dependent Urate transport were 1213 ± 222 μM and 268.8 ± 38.0 pmol/oocyte per hr, respectively ( n = 3). RST-dependent Urate transport was cis-inhibited significantly by 1 mM probenecid (68.7 ± 9.4%), 50 μM benzbromarone (67.9 ± 6.4%), and 10 mM lactate (50.9 ± 9.5%). However, 1 mM p -aminohippUrate (PAH), 1 mM xanthine, and 1 mM oxonate did not inhibit RST-dependent Urate transport. Substitution of Cl anion with gluconate in the external solution enhanced RST-dependent Urate transport. Pre-injected pyrazinoic acid (PZA) or l-lactate trans-stimulated RST-dependent Urate transport. Using immunohistochemistry for mouse kidney, the brush border or intracellular membrane of proximal tubules was stained by an affinity-purified antibody that recognized mouse URAT1 (mURAT1) expressed on Xenopus oocyte. Using Western blotting, anti-mURAT1 antibody detected 70-kD and 62-kD protein bands. The 70-kD protein was n-glycosylated and was identified as a Triton X-100 insoluble brush border membrane protein. RST mRNA and protein levels were higher in male kidneys than female. RST transported Urate similar to hURAT1 and, therefore, appears to be mURAT1—the mouse homologue of hURAT1.
Takamasa Kayama - One of the best experts on this subject based on the ideXlab platform.
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The association between genotypes of Urate Transporter-1, Serum uric acid, and mortality in the community-based population: the Yamagata (Takahata) Study
Clinical and Experimental Nephrology, 2019Co-Authors: Tsuneo Konta, Kazunobu Ichikawa, Hidenori Sato, Kenichi Ishizawa, Hidetoshi Yamashita, Yoshiyuki Ueno, Masafumi Watanabe, Takamasa KayamaAbstract:Background The Urate Transporter-1 (URAT1) is crucial in developing hyperuricemia via reabsorption of uric acid in renal tubules, and its function is regulated by several single nucleotide polymorphisms (SNPs) within SLC22A12 gene encoding URAT1. This study investigated whether the genetic predisposition of URAT1 is associated with the mortality in general population. Methods This study enrolled 1596 participants (male 45%, mean age 61 years) who registered at local health checkup in Takahata, Japan, and the association between the rs505802 genotypes in SLC22A12 gene and the 7-year mortality, was examined. Results The serum uric acid levels (mean ± SD) at baseline in the subjects with GG and AG + AA genotypes of rs505802 were 5.1 ± 1.3 mg/dL and 5.0 ± 1.5 mg/dL, respectively. Kaplan–Meier analysis revealed that the mortality was nonsignificantly higher in the subjects with GG genotype than in those with AG + AA genotype ( P = 0.09). Cox proportional hazard model adjusted with age, gender, renal function, comorbidities, and other possible confounders, demonstrated that the GG genotype was significantly associated with the mortality [hazard ratio (HR) 2.23, 95% confidence interval (CI) 1.05–4.85, (vs. AG + AA genotype)]. Furthermore, adjustment with serum uric acid levels, along with aforementioned confounders retained the significant association (HR 2.26, 95% CI 1.05–4.85). Conclusions This study revealed that the genetic predisposition of URAT1 was independently associated with mortality in the Japanese community-based population. This association might be due to the mechanism independent of serum uric acid levels.
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The association between genotypes of Urate Transporter-1, Serum uric acid, and mortality in the community-based population: the Yamagata (Takahata) Study.
Clinical and Experimental Nephrology, 2019Co-Authors: Tsuneo Konta, Kazunobu Ichikawa, Hidenori Sato, Kenichi Ishizawa, Hidetoshi Yamashita, Yoshiyuki Ueno, Masafumi Watanabe, Takamasa KayamaAbstract:The Urate Transporter-1 (URAT1) is crucial in developing hyperuricemia via reabsorption of uric acid in renal tubules, and its function is regulated by several single nucleotide polymorphisms (SNPs) within SLC22A12 gene encoding URAT1. This study investigated whether the genetic predisposition of URAT1 is associated with the mortality in general population. This study enrolled 1596 participants (male 45%, mean age 61 years) who registered at local health checkup in Takahata, Japan, and the association between the rs505802 genotypes in SLC22A12 gene and the 7-year mortality, was examined. The serum uric acid levels (mean ± SD) at baseline in the subjects with GG and AG + AA genotypes of rs505802 were 5.1 ± 1.3 mg/dL and 5.0 ± 1.5 mg/dL, respectively. Kaplan–Meier analysis revealed that the mortality was nonsignificantly higher in the subjects with GG genotype than in those with AG + AA genotype (P = 0.09). Cox proportional hazard model adjusted with age, gender, renal function, comorbidities, and other possible confounders, demonstrated that the GG genotype was significantly associated with the mortality [hazard ratio (HR) 2.23, 95% confidence interval (CI) 1.05–4.85, (vs. AG + AA genotype)]. Furthermore, adjustment with serum uric acid levels, along with aforementioned confounders retained the significant association (HR 2.26, 95% CI 1.05–4.85). This study revealed that the genetic predisposition of URAT1 was independently associated with mortality in the Japanese community-based population. This association might be due to the mechanism independent of serum uric acid levels.
