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Toyoda Y, Takada T, Nakayama A, Shinomiya N, Matsuo H. Biochemical characterization of renal hypouricemia-associated mutations in urate transporter genes using human cells. Hum Cell 2024; 37:1231-1234. [PMID: 38811494 DOI: 10.1007/s13577-024-01079-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2024] [Accepted: 05/13/2024] [Indexed: 05/31/2024]
Affiliation(s)
- Yu Toyoda
- Department of Integrative Physiology and Bio-Nano Medicine, National Defense Medical College, Saitama, Japan
- Department of Pharmacy, The University of Tokyo Hospital, Tokyo, Japan
| | - Tappei Takada
- Department of Pharmacy, The University of Tokyo Hospital, Tokyo, Japan
| | - Akiyoshi Nakayama
- Department of Integrative Physiology and Bio-Nano Medicine, National Defense Medical College, Saitama, Japan
| | - Nariyoshi Shinomiya
- Department of Integrative Physiology and Bio-Nano Medicine, National Defense Medical College, Saitama, Japan
| | - Hirotaka Matsuo
- Department of Integrative Physiology and Bio-Nano Medicine, National Defense Medical College, Saitama, Japan.
- Department of Bioinformation Management, National Defense Medical College Research Institute, Saitama, Japan.
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2
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Shen Z, Xu L, Wu T, Wang H, Wang Q, Ge X, Kong F, Huang G, Pan X. Structural basis for urate recognition and apigenin inhibition of human GLUT9. Nat Commun 2024; 15:5039. [PMID: 38866775 PMCID: PMC11169512 DOI: 10.1038/s41467-024-49420-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2024] [Accepted: 06/03/2024] [Indexed: 06/14/2024] Open
Abstract
Urate, the physiological form of uric acid and a potent antioxidant in serum, plays a pivotal role in scavenging reactive oxygen species. Yet excessive accumulation of urate, known as hyperuricemia, is the primary risk factor for the development of gout. The high-capacity urate transporter GLUT9 represents a promising target for gout treatment. Here, we present cryo-electron microscopy structures of human GLUT9 in complex with urate or its inhibitor apigenin at overall resolutions of 3.5 Å and 3.3 Å, respectively. In both structures, GLUT9 exhibits an inward open conformation, wherein the substrate binding pocket faces the intracellular side. These structures unveil the molecular basis for GLUT9's substrate preference of urate over glucose, and show that apigenin acts as a competitive inhibitor by occupying the substrate binding site. Our findings provide critical information for the development of specific inhibitors targeting GLUT9 as potential therapeutics for gout and hyperuricemia.
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Affiliation(s)
- Zilin Shen
- Beijing Frontier Research Center for Biological Structure, Tsinghua-Peking Joint Center for Life Sciences, State Key Laboratory of Membrane Biology, School of Life Sciences, Tsinghua University, 100084, Beijing, China
| | - Li Xu
- Institute of Bio-Architecture and Bio-Interactions (IBABI), Shenzhen Medical Academy of Research and Translation (SMART), Shenzhen, 518107, Guangdong, China
| | - Tong Wu
- Beijing Frontier Research Center for Biological Structure, Tsinghua-Peking Joint Center for Life Sciences, State Key Laboratory of Membrane Biology, School of Life Sciences, Tsinghua University, 100084, Beijing, China
| | - Huan Wang
- Beijing Frontier Research Center for Biological Structure, Tsinghua-Peking Joint Center for Life Sciences, State Key Laboratory of Membrane Biology, School of Life Sciences, Tsinghua University, 100084, Beijing, China
| | - Qifan Wang
- Beijing Frontier Research Center for Biological Structure, Tsinghua-Peking Joint Center for Life Sciences, State Key Laboratory of Membrane Biology, School of Life Sciences, Tsinghua University, 100084, Beijing, China
| | - Xiaofei Ge
- Beijing Frontier Research Center for Biological Structure, Tsinghua-Peking Joint Center for Life Sciences, State Key Laboratory of Membrane Biology, School of Life Sciences, Tsinghua University, 100084, Beijing, China
| | - Fang Kong
- Beijing Frontier Research Center for Biological Structure, Tsinghua-Peking Joint Center for Life Sciences, State Key Laboratory of Membrane Biology, School of Life Sciences, Tsinghua University, 100084, Beijing, China
| | - Gaoxingyu Huang
- Westlake Laboratory of Life Sciences and Biomedicine, Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, 310024, Zhejiang, China
- Institute of Biology, Westlake Institute for Advanced Study, Hangzhou, 310024, Zhejiang, China
| | - Xiaojing Pan
- Institute of Bio-Architecture and Bio-Interactions (IBABI), Shenzhen Medical Academy of Research and Translation (SMART), Shenzhen, 518107, Guangdong, China.
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Lin CN, Ho CC, Hsieh PC, Hsiao CH, Nfor ON, Liaw YP. Polymorphism rs3733591 of the SLC2A9 gene and metabolic syndrome affect gout risk in Taiwan Biobank subjects. Front Genet 2024; 15:1374405. [PMID: 38689651 PMCID: PMC11058208 DOI: 10.3389/fgene.2024.1374405] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2024] [Accepted: 04/03/2024] [Indexed: 05/02/2024] Open
Abstract
Background Over the past few decades, gout and diseases like metabolic syndrome (MetS) have become more prevalent. Attempts have been made in Taiwan to identify the genes responsible for gout. A few gene loci, among them SLC2A9, have been identified using Taiwan Biobank (TWB) data. We, therefore, examined whether MetS could also account for the association between polymorphism SLC2A9 rs3733591 and gout. Methods The final analysis consisted of 73,558 subjects, of whom 2,709 had gout. To estimate the likelihood of gout occurrence based on rs3733591 and MetS, we used logistic regression models. Results Rs3733591-TC + CC compared to TT genotype was associated with gout (OR, 1.15; 95% CI, 1.06-1.25). Also associated with gout was MetS (OR, 1.21; 95% CI, 1.10-1.33). A significant interaction was seen between rs3733591 and MetS (p-value = 0.039). Using rs3733591-TT/no MetS as the reference group, the ORs (95% CI) for gout was 1.24 (1.11-1.38) for TC + CC/no MetS, 1.35 (1.17-1.56) for TT/MetS, and 1.39 (1.22-1.58) for TC + CC/MetS. However, subgroup analysis defined by sex showed no significant associations in women. Conclusion In summary, metabolic syndrome and SLC2A9 rs3733591 genotypes were interactively associated with gout in Taiwanese men, but not women.
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Affiliation(s)
- Chun-Nan Lin
- Department of Emergency Medicine, Chung-Kang Branch, Cheng Ching Hospital, Taichung, Taiwan
| | - Chien-Chang Ho
- Department of Physical Education, Fu Jen Catholic University, New Taipei, Taiwan
- Research and Development Center for Physical Education, Health, and Information Technology, Fu Jen Catholic University, New Taipei, Taiwan
| | - Pao-Chun Hsieh
- Department of Obstetrics and Gynecology, Chung-Kang Branch, Cheng Ching Hospital, Taichung, Taiwan
| | - Chih-Hsuan Hsiao
- Department of Public Health and Institute of Public Health, Chung Shan Medical University, Taichung, Taiwan
| | - Oswald Ndi Nfor
- Department of Public Health and Institute of Public Health, Chung Shan Medical University, Taichung, Taiwan
| | - Yung-Po Liaw
- Department of Public Health and Institute of Public Health, Chung Shan Medical University, Taichung, Taiwan
- Department of Medical Imaging, Chung Shan Medical University Hospital, Taichung, Taiwan
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4
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Quinlivan R, Murphy E, Pula S, Pain A, Brain H, Scopes G, Gjika F, Ahmadouk N, Manole A, Houlden H. Raised CK and acute kidney injury following intense exercise in three patients with a history of exercise intolerance due to homozygous mutations in SLC2A9. Neuromuscul Disord 2024; 34:49-53. [PMID: 38150892 DOI: 10.1016/j.nmd.2023.11.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Revised: 11/01/2023] [Accepted: 11/27/2023] [Indexed: 12/29/2023]
Abstract
Acute rhabdomyolysis (AR) leading to acute kidney injury has many underlying etiologies, however, when the primary trigger is exercise, the most usual underlying cause is either a genetic muscle disorder or unaccustomed intense exercise in a healthy individual. Three adult men presented with a history of exercise intolerance and episodes of acute renal impairment following intense exercise, thought to be due to AR in the case of two, and dehydration in one. The baseline serum CK was mildly raised between attacks in all three patients and acutely raised during attacks in two of the three patients. Following referral to a specialized neuromuscular centre, further investigation identified very low serum urate (<12 umol/L). In all three men, genetic studies confirmed homozygous mutations in SLC2A9, which encodes for facilitated glucose transporter member 9 (GLUT9), a major regulator of urate homeostasis. Hereditary hypouricaemia should be considered in people presenting with acute kidney injury related to intense exercise. Serum urate evaluation is a useful screening test best undertaken after recovery.
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Affiliation(s)
- Ros Quinlivan
- MRC Centre for Neuromuscular Disease, UCL Institute of Neurology, National Hospital for Neurology and Neurosurgery, London, UK.
| | - Elaine Murphy
- Charles Dent Metabolic Unit, National Hospital for Neurology and Neurosurgery, Queen Square London, UK
| | - Shpresa Pula
- MRC Centre for Neuromuscular Disease, UCL Institute of Neurology, National Hospital for Neurology and Neurosurgery, London, UK
| | - Alexandra Pain
- Department of Acute and General Medicine, Stoke Mandeville Hospital, Mandeville Road, Aylesbury UK
| | - Henrietta Brain
- Department of Acute and General Medicine, Stoke Mandeville Hospital, Mandeville Road, Aylesbury UK
| | - Grace Scopes
- University of Buckingham, Stoke Mandeville, Aylesbury, UK
| | - Frenki Gjika
- University of Buckingham, Stoke Mandeville, Aylesbury, UK
| | - Naim Ahmadouk
- Department of Acute and General Medicine, Stoke Mandeville Hospital, Mandeville Road, Aylesbury UK
| | - Andreea Manole
- Department of neurogenetics, UCL Institute of Neurology, National hospital for Neurology and Neurosurgery, UK
| | - Henry Houlden
- Department of neurogenetics, UCL Institute of Neurology, National hospital for Neurology and Neurosurgery, UK
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5
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Zhou J, Zhang M, Xie Q, Xu N, Li M, Zhang M, Hao C. Recurrent exercise-induced acute kidney injury associated with hypouricemia: a case report and literature review. BMC Nephrol 2023; 24:384. [PMID: 38129773 PMCID: PMC10740252 DOI: 10.1186/s12882-023-03378-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2022] [Accepted: 10/26/2023] [Indexed: 12/23/2023] Open
Abstract
BACKGROUND Hereditary renal hypouricemia (RHUC) is a heterogenous disorder characterized by defective uric acid (UA) reabsorption resulting in hypouricemia and increased fractional excretion of UA. RHUC is an important cause of exercise-induced acute kidney injury (EIAKI), nephrolithiasis and posterior reversible encephalopathy syndrome (PRES). We present here an unusual case of a patient with RHUC who presented with recurrent EIAKI and had two heterozygous mutations in the SLC2A9 gene. CASE PRESENTATION A 43-year old man was admitted to our clinic because of bilateral loin pain, nausea and sleeplessness for 3 days after strenuous exercise. The laboratory results revealed increased levels of blood urea nitrogen (BUN) (15 mmol/l) and serum creatinine (Scr) (450 μmol/l), while the UA level was extremely low at 0.54 mg/dl, and his fractional excretion of urate (FE-UA) was 108%. The patient had an episode of acute kidney injury after playing soccer approximately 20 years ago, and on routine physical examination, his UA was less than 0.50 mg/dl. In view of the marked hypouricemia and high FE-UA, a diagnosis of RHUC was suspected, which led us to perform mutational screening of the SLC22A12 and SLC2A9 genes. DNA sequencing revealed no mutation in SLC22A12 gene, but two heterozygous mutations in the SLC2A9 gene. CONCLUSIONS This is a rare report of a patient with RHUC2 due to the mutation of SLC2A9. And this unique symptom of EIAKI and decreased or normal serum concentrations of UA warrant more attention as an early cue of RHUC.
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Affiliation(s)
- Jie Zhou
- Division of Nephrology, Huashan Hospital, Fudan University, Shanghai, China
- Department of Nephrology, Shuguang Hospital, Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Min Zhang
- Division of Nephrology, Huashan Hospital, Fudan University, Shanghai, China.
| | - Qionghong Xie
- Division of Nephrology, Huashan Hospital, Fudan University, Shanghai, China
| | - Ningxin Xu
- Division of Nephrology, Huashan Hospital, Fudan University, Shanghai, China
| | - Mingxin Li
- Division of Nephrology, Huashan Hospital, Fudan University, Shanghai, China
| | - Ming Zhang
- Division of Nephrology, Huashan Hospital, Fudan University, Shanghai, China
| | - Chuanming Hao
- Division of Nephrology, Huashan Hospital, Fudan University, Shanghai, China
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Perdomo-Ramírez A, Ramos-Trujillo E, Claverie-Martín F. New SLC22A12 (URAT1) Variant Associated with Renal Hypouricemia Identified by Whole-Exome Sequencing Analysis and Bioinformatics Predictions. Genes (Basel) 2023; 14:1823. [PMID: 37761963 PMCID: PMC10530539 DOI: 10.3390/genes14091823] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2023] [Revised: 09/14/2023] [Accepted: 09/18/2023] [Indexed: 09/29/2023] Open
Abstract
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.
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Affiliation(s)
- Ana Perdomo-Ramírez
- Unidad de Investigación, Hospital Universitario Nuestra Señora de Candelaria, 38010 Santa Cruz de Tenerife, Spain; (A.P.-R.); (E.R.-T.)
| | - Elena Ramos-Trujillo
- Unidad de Investigación, Hospital Universitario Nuestra Señora de Candelaria, 38010 Santa Cruz de Tenerife, Spain; (A.P.-R.); (E.R.-T.)
- Departamento de Medicina Física y Farmacología, Facultad de Ciencias de la Salud, Sección Medicina, Universidad de La Laguna, 38071 Santa Cruz de Tenerife, Spain
| | - Félix Claverie-Martín
- Unidad de Investigación, Hospital Universitario Nuestra Señora de Candelaria, 38010 Santa Cruz de Tenerife, Spain; (A.P.-R.); (E.R.-T.)
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Fernando PMS, Gunasekara RASR, Schröder S, Beetz C, Jayawardena A, Jasinge EA. Autosomal Recessive Renal Hypouricemia Type 2 Presenting with Childhood Stroke in a Sri Lankan Child. Lab Med 2023; 54:543-545. [PMID: 36857484 DOI: 10.1093/labmed/lmac165] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/03/2023] Open
Affiliation(s)
- P Mihika S Fernando
- Department of Chemical Pathology, Lady Ridgeway Hospital for Children, Colombo, Sri Lanka
| | | | | | | | - Anura Jayawardena
- Paediatric Unit, Lady Ridgeway Hospital for Children, Colombo, Sri Lanka
| | - Eresha A Jasinge
- Department of Chemical Pathology, Lady Ridgeway Hospital for Children, Colombo, Sri Lanka
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8
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Köksoy AY, Görükmez Ö, Dorum S. Clinical significance of hypouricemia in children and adolescents. Pediatr Nephrol 2023; 38:3017-3025. [PMID: 37000195 DOI: 10.1007/s00467-023-05948-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/16/2022] [Revised: 03/04/2023] [Accepted: 03/06/2023] [Indexed: 04/01/2023]
Abstract
BACKGROUND Although hyperuricemia is a widely studied condition with well-known effects on the kidneys, hypouricemia is usually considered a biochemical abnormality of no clinical significance despite the fact that it can be a sign or major finding of serious metabolic or genetic diseases affecting kidney health. In this study, we aimed to investigate and emphasize the clinical significance of hypouricemia. METHODS Patients were evaluated retrospectively for persistent hypouricemia defined as serum uric acid concentrations of < 2 mg/dL on at least 3 different occasions. According to the blood and urine uric acid (UA) levels, the patients were classified as having hypouricemia due to UA underproduction vs. overexcretion. Demographic, clinical, and genetic characteristics were noted for analysis. RESULTS Fourteen patients (n = 14; M/F 8/6) with persistent hypouricemia were identified. Hypouricemia due to underproduction was the cause of 42.8% of these cases. All of the patients with a uric acid level of 0 mg/dL (n = 4) had hypouricemia due to underproduction. The median serum uric acid level was 0.85 (0-1.6) mg/dL. Isolated hypouricemia and hypouricemia with metabolic acidosis were equally distributed. Among the patients with hypouricemia due to underproduction, the final diagnoses were xanthine dehydrogenase deficiency (n = 5) and alkaptonuria (n = 1). In the overexcretion group, the final diagnoses were nephropathic cystinosis (n = 6), distal renal tubular acidosis (n = 1), and hereditary renal hypouricemia (n = 1). The diagnostic lag was longer for patients with isolated hypouricemia compared to other patients (p = 0.001). CONCLUSIONS Hypouricemia may reflect underlying genetic or metabolic diseases, early diagnosis of which could help preserve kidney function. A higher resolution version of the Graphical abstract is available as Supplementary information.
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Affiliation(s)
- Adem Yasin Köksoy
- Department of Pediatric Nephrology, Van Training and Research Hospital, Van, Turkey.
| | - Özlem Görükmez
- Department of Genetics, Bursa Yüksek İhtisas Training and Research Hospital, Bursa, Turkey
| | - Sevil Dorum
- Department of Metabolism Unit, Bursa Yüksek İhtisas Training and Research Hospital, Bursa, Turkey
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Perdomo-Ramirez A, Cordoba-Lanus E, Trujillo-Frias CJ, Gonzalez-Navasa C, Ramos-Trujillo E, Luis-Yanes MI, Garcia-Nieto V, Claverie-Martin F. Pathogenic Variants of SLC22A12 (URAT1) and SLC2A9 (GLUT9) in Spanish Patients with Renal Hypouricemia: Founder Effect of SLC2A9 Variant c.374C>T; p.(T125M). Int J Mol Sci 2023; 24:ijms24098455. [PMID: 37176161 PMCID: PMC10179447 DOI: 10.3390/ijms24098455] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2023] [Revised: 05/02/2023] [Accepted: 05/03/2023] [Indexed: 05/15/2023] Open
Abstract
Renal hypouricemia (RHUC) is a rare inherited disorder characterized by impaired urate reabsorption in the proximal tubule resulting in low urate serum levels and increased urate excretion. Some patients may present severe complications such as exercise-induced acute renal failure and nephrolithiasis. RHUC is caused by inactivating mutations in the SLC22A12 (RHUC type 1) or SLC2A9 (RHUC type 2) genes, which encode urate transporters URAT1 and GLUT9, respectively. In this study, our goal was to identify mutations associated with twenty-one new cases with RHUC through direct sequencing of SLC22A12 and SLC2A9 coding exons. Additionally, we carried out an SNPs-haplotype analysis to determine whether the rare SLC2A9 variant c.374C>T; p.(T125M), which is recurrent in Spanish families with RHUC type 2, had a common-linked haplotype. Six intragenic informative SNPs were analyzed using PCR amplification from genomic DNA and direct sequencing. Our results showed that ten patients carried the SLC22A12 mutation c.1400C>T; p.(T467M), ten presented the SLC2A9 mutation c.374C>T, and one carried a new SLC2A9 heterozygous mutation, c.593G>A; p.(R198H). Patients carrying the SLC2A9 mutation c.374C>T share a common-linked haplotype, confirming that it emerged due to a founder effect.
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Affiliation(s)
- Ana Perdomo-Ramirez
- Unidad de Investigacion, Hospital Universitario Nuestra Señora de Candelaria, 38010 Santa Cruz de Tenerife, Spain
| | - Elizabeth Cordoba-Lanus
- Unidad de Investigacion, Hospital Universitario Nuestra Señora de Candelaria, 38010 Santa Cruz de Tenerife, Spain
- Instituto Universitario de Enfermedades Tropicales y Salud Publica de Canarias (IUETSPC), Universidad de La Laguna, 38296 Santa Cruz de Tenerife, Spain
| | - Carmen Jane Trujillo-Frias
- Unidad de Investigacion, Hospital Universitario Nuestra Señora de Candelaria, 38010 Santa Cruz de Tenerife, Spain
| | - Carolina Gonzalez-Navasa
- Unidad de Investigacion, Hospital Universitario Nuestra Señora de Candelaria, 38010 Santa Cruz de Tenerife, Spain
- Seccion Medicina, Departamento de Medicina Fisica y Farmacologia, Facultad de Ciencias de la Salud, Universidad de La Laguna, 38200 Santa Cruz de Tenerife, Spain
| | - Elena Ramos-Trujillo
- Unidad de Investigacion, Hospital Universitario Nuestra Señora de Candelaria, 38010 Santa Cruz de Tenerife, Spain
- Seccion Medicina, Departamento de Medicina Fisica y Farmacologia, Facultad de Ciencias de la Salud, Universidad de La Laguna, 38200 Santa Cruz de Tenerife, Spain
| | - Maria Isabel Luis-Yanes
- Unidad de Nefrologia Pediatrica, Hospital Universitario Nuestra Señora de Candelaria, 38010 Santa Cruz de Tenerife, Spain
| | - Victor Garcia-Nieto
- Unidad de Nefrologia Pediatrica, Hospital Universitario Nuestra Señora de Candelaria, 38010 Santa Cruz de Tenerife, Spain
| | - Felix Claverie-Martin
- Unidad de Investigacion, Hospital Universitario Nuestra Señora de Candelaria, 38010 Santa Cruz de Tenerife, Spain
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10
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Cachau R, Shahsavari S, Cho SK. The in-silico evaluation of important GLUT9 residue for uric acid transport based on renal hypouricemia type 2. Chem Biol Interact 2023; 373:110378. [PMID: 36736875 PMCID: PMC10596759 DOI: 10.1016/j.cbi.2023.110378] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2022] [Revised: 01/17/2023] [Accepted: 01/31/2023] [Indexed: 02/04/2023]
Abstract
Uric acid is the end product of purine metabolism. Uric acid transporters in the renal proximal tubule plays a key role in uric acid transport. Functional abnormalities in these transporters could lead to high or low levels of uric acid in the blood plasma, known as hyperuricemia and hypouricemia, respectively. GLUT9 has been reported as a key transporter for uric acid reuptake in renal proximal tubule. GLUT9 mutation is known as causal gene for renal hypouricemia due to defective uric acid uptake, with more severe cases resulting in urolithiasis and exercise induced acute kidney injury (EIAKI). However, the effect of mutation is not fully investigated and hard to predict the change of binding affinity. We comprehensively described the effect of GLUT9 mutation for uric acid transport using molecular dynamics and investigated the specific site for uric acid binding differences. R171C and R380W showed the significant disruption of the structure not affecting transport dynamics whereas L75R, G216R, N333S, and P412R showed the reduced affinity of the extracellular vestibular area towards urate. Interestingly, T125 M showed a significant increase in intracellular binding energy, associated with distorted geometries. We can use this classification to consider the effect mutations by comparing the transport profiles of mutants against those of chemical candidates for transport and providing new perspectives to urate lowering drug discovery using GLUT9.
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Affiliation(s)
- Raul Cachau
- Integrated Data Science Section, Research Technologies Branch, National Institute of Allergies and Infectious Diseases, Bethesda, MD, USA
| | | | - Sung Kweon Cho
- Center for Cancer Research, National Cancer Institute, Frederick, MD, USA; Department of Pharmacology Ajou University, School of Medicine, Suwon, South Korea.
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11
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Toyoda Y, Cho SK, Tasic V, Pavelcová K, Bohatá J, Suzuki H, David VA, Yoon J, Pallaiova A, Šaligová J, Nousome D, Cachau R, Winkler CA, Takada T, Stibůrková B. Identification of a dysfunctional exon-skipping splice variant in GLUT9/ SLC2A9 causal for renal hypouricemia type 2. Front Genet 2023; 13:1048330. [PMID: 36733941 PMCID: PMC9887137 DOI: 10.3389/fgene.2022.1048330] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2022] [Accepted: 12/21/2022] [Indexed: 01/18/2023] Open
Abstract
Renal hypouricemia (RHUC) is a pathological condition characterized by extremely low serum urate and overexcretion of urate in the kidney; this inheritable disorder is classified into type 1 and type 2 based on causative genes encoding physiologically-important urate transporters, URAT1 and GLUT9, respectively; however, research on RHUC type 2 is still behind type 1. We herein describe a typical familial case of RHUC type 2 found in a Slovak family with severe hypouricemia and hyperuricosuria. Via clinico-genetic analyses including whole exome sequencing and in vitro functional assays, we identified an intronic GLUT9 variant, c.1419+1G>A, as the causal mutation that could lead the expression of p.Gly431GlufsTer28, a functionally-null variant resulting from exon 11 skipping. The causal relationship was also confirmed in another unrelated Macedonian family with mild hypouricemia. Accordingly, non-coding regions should be also kept in mind during genetic diagnosis for hypouricemia. Our findings provide a better pathogenic understanding of RHUC and pathophysiological importance of GLUT9.
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Affiliation(s)
- Yu Toyoda
- Department of Pharmacy, The University of Tokyo Hospital, Tokyo, Japan
| | - Sung Kweon Cho
- Molecular Genetics Epidemiology Section, Basic Research Laboratory, National Cancer Institute and Frederick National Laboratory for Cancer Research, Frederick, MD, United States,Department of Pharmacology, Ajou University School of Medicine, Suwon, South Korea
| | - Velibor Tasic
- Faculty of Medicine, University Ss. Cyril and Methodius, Skopje, North Macedonia
| | | | | | - Hiroshi Suzuki
- Department of Pharmacy, The University of Tokyo Hospital, Tokyo, Japan
| | - Victor A. David
- Department of Pharmacy, The University of Tokyo Hospital, Tokyo, Japan
| | - Jaeho Yoon
- Cancer and Developmental Biology Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, MD, United States
| | | | - Jana Šaligová
- Metabolic Clinic, Children’s Faculty Hospital, Košice, Slovakia
| | - Darryl Nousome
- CCR Collaborative Bioinformatics Resource, Center for Cancer Research, National Cancer Institute, Frederick, MD, United States
| | - Raul Cachau
- Integrated Data Science Section, Research Technologies Branch, National Institute of Allergies and Infectious Diseases, Bethesda, MD, United States
| | - Cheryl A. Winkler
- Molecular Genetics Epidemiology Section, Basic Research Laboratory, National Cancer Institute and Frederick National Laboratory for Cancer Research, Frederick, MD, United States
| | - Tappei Takada
- Department of Pharmacy, The University of Tokyo Hospital, Tokyo, Japan
| | - Blanka Stibůrková
- Institute of Rheumatology, Prague, Czechia,Department of Rheumatology, First Faculty of Medicine, Charles University, Prague, Czechia,Department of Pediatrics and Inherited Metabolic Disorders, First Faculty of Medicine, Charles University and General University Hospital, Prague, Czechia,*Correspondence: Blanka Stibůrková,
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12
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Otani N, Ouchi M, Misawa K, Hisatome I, Anzai N. Hypouricemia and Urate Transporters. Biomedicines 2022; 10:biomedicines10030652. [PMID: 35327453 PMCID: PMC8945357 DOI: 10.3390/biomedicines10030652] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2022] [Revised: 03/09/2022] [Accepted: 03/10/2022] [Indexed: 02/07/2023] Open
Abstract
Hypouricemia is recognized as a rare disorder, defined as a serum uric acid level of 2.0 mg/dL or less. Hypouricemia is divided into an overexcretion type and an underproduction type. The former typical disease is xanthinuria, and the latter is renal hypouricemia (RHUC). The frequency of nephrogenic hypouricemia due to a deficiency of URAT1 is high in Japan, accounting for most asymptomatic and persistent cases of hypouricemia. RHUC results in a high risk of exercise-induced acute kidney injury and urolithiasis. It is vital to promote research on RHUC, as this will lead not only to the elucidation of its pathophysiology but also to the development of new treatments for gout and hyperuricemia.
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Affiliation(s)
- Naoyuki Otani
- Department of Clinical Pharmacology and Therapeutics, Faculty of Medicine, Oita University, Yufu 879-5593, Oita, Japan;
| | - Motoshi Ouchi
- Department of Pharmacology and Toxicology, Dokkyo Medical University School of Medicine, Mibu 321-0293, Tochigi, Japan;
| | - Kazuharu Misawa
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama 236-0004, Kanagawa, Japan;
| | - Ichiro Hisatome
- Yonago Medical Center, National Hospital Organization, Yonago 683-0006, Tottori, Japan;
- Department of Genetic Medicine and Regenerative Therapeutics, Institute of Regenerative Medicine and Biofunction, Graduate School of Medical Sciences, Tottori University, Yonago 680-8550, Tottori, Japan
| | - Naohiko Anzai
- Department of Pharmacology, Chiba University Graduate School of Medicine, Chiba 260-8670, Chiba, Japan
- Correspondence:
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13
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Ramdhan RS, Hade NA, Algafari RN. Association of multiple SNPs at slc2a9 exon 8 in gout disease in Iraqi population: A molecular study. Meta Gene 2021. [DOI: 10.1016/j.mgene.2021.100942] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
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14
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Renal Hypouricemia 1: Rare Disorder as Common Disease in Eastern Slovakia Roma Population. Biomedicines 2021; 9:biomedicines9111607. [PMID: 34829836 PMCID: PMC8615432 DOI: 10.3390/biomedicines9111607] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Revised: 10/27/2021] [Accepted: 10/30/2021] [Indexed: 11/17/2022] Open
Abstract
Renal hypouricemia (RHUC) is caused by an inherited defect in the main reabsorption system of uric acid, SLC22A12 (URAT1) and SLC2A9 (GLUT9). RHUC is characterized by a decreased serum uric acid concentration and an increase in its excreted fraction. Patients suffer from hypouricemia, hyperuricosuria, urolithiasis, and even acute kidney injury. We report clinical, biochemical, and genetic findings in a cohort recruited from the Košice region of Slovakia consisting of 27 subjects with hypouricemia and relatives from 11 families, 10 of whom were of Roma ethnicity. We amplified, directly sequenced, and analyzed all coding regions and exon–intron boundaries of the SLC22A12 and SLC2A9 genes. Sequence analysis identified dysfunctional variants c.1245_1253del and c.1400C>T in the SLC22A12 gene, but no other causal allelic variants were found. One heterozygote and one homozygote for c.1245_1253del, nine heterozygotes and one homozygote for c.1400C>T, and two compound heterozygotes for c.1400C>T and c.1245_1253del were found in a total of 14 subjects. Our result confirms the prevalence of dysfunctional URAT1 variants in Roma subjects based on analyses in Slovak, Czech, and Spanish cohorts, and for the first time in a Macedonian Roma cohort. Although RHUC1 is a rare inherited disease, the frequency of URAT1-associated variants indicates that this disease is underdiagnosed. Our findings illustrate that there are common dysfunctional URAT1 allelic variants in the general Roma population that should be routinely considered in clinical practice as part of the diagnosis of Roma patients with hypouricemia and hyperuricosuria exhibiting clinical signs such as urolithiasis, nephrolithiasis, and acute kidney injury.
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15
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Maalouli C, Dahan K, Devresse A, Gillion V. Mutation in the SLC2A9 Gene: A New Family with Familial Renal Hypouricemia Type 2. Case Rep Nephrol 2021; 2021:4751099. [PMID: 34603806 PMCID: PMC8486506 DOI: 10.1155/2021/4751099] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2021] [Accepted: 09/08/2021] [Indexed: 11/18/2022] Open
Abstract
Familial renal hypouricemia is a rare genetic disorder characterized by a defect in renal tubular urate reabsorption. Some patients present with exercise-induced acute kidney injury and nephrolithiasis. Type II is caused by mutations in the SLC2A9 gene. Here, we report the case of a young patient who developed acute kidney injury after exercise secondary to familial renal hypouricemia type II. The same mutation was found in other asymptomatic members of his family. We review the medical literature on this condition. This case highlights the importance of considering uric acid disorders in the work-up of acute kidney injury after exercise.
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Affiliation(s)
- Christian Maalouli
- Division of Nephrology, Cliniques Universitaires Saint-Luc, Université Catholique de Louvain, Brussels, Belgium
| | - Karin Dahan
- Division of Human Genetics, Cliniques Universitaires Saint-Luc, Université Catholique de Louvain, Brussels, Belgium
- Center of Human Genetics, Institut de Pathologie et de Génétique, Charleroi, Belgium
| | - Arnaud Devresse
- Division of Nephrology, Cliniques Universitaires Saint-Luc, Université Catholique de Louvain, Brussels, Belgium
| | - Valentine Gillion
- Division of Nephrology, Cliniques Universitaires Saint-Luc, Université Catholique de Louvain, Brussels, Belgium
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16
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Yoon J, Cachau R, David VA, Thompson M, Jung W, Jee SH, Daar IO, Winkler CA, Cho SK. Characterization of a Compound Heterozygous SLC2A9 Mutation That Causes Hypouricemia. Biomedicines 2021; 9:biomedicines9091172. [PMID: 34572357 PMCID: PMC8471325 DOI: 10.3390/biomedicines9091172] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2021] [Revised: 08/26/2021] [Accepted: 08/28/2021] [Indexed: 11/17/2022] Open
Abstract
Renal hypouricemia is a rare genetic disorder. Hypouricemia can present as renal stones or exercise-induced acute renal failure, but most cases are asymptomatic. Our previous study showed that two recessive variants of SLC22A12 (p.Trp258*, pArg90His) were identified in 90% of the hypouricemia patients from two independent cohorts: the Korean genome and epidemiology study (KoGES) and the Korean Cancer Prevention Study (KCPS-II). In this work, we investigate the genetic causes of hypouricemia in the rest of the 10% of unsolved cases. We found a novel non-synonymous mutation of SLC2A9 (voltage-sensitive uric acid transporter) in the whole-exome sequencing (WES) results. Molecular dynamics prediction suggests that the novel mutation p.Met126Val in SLCA9b (p.Met155Val in SLC2A9a) hinders uric acid transport through a defect of the outward open geometry. Molecular analysis using Xenopus oocytes confirmed that the p.Met126Val mutation significantly reduced uric acid transport but does not affect the SLC2A9 protein expression level. Our results will shed light on a better understanding of SLC2A9-mediated uric acid transport and the development of a uric acid-lowering agent.
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Affiliation(s)
- Jaeho Yoon
- Cancer & Developmental Biology Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, MD 21701, USA; (J.Y.); (I.O.D.)
| | - Raul Cachau
- Advanced Biomedical Computational Science, Frederick National Laboratory for Cancer Research, National Cancer Institute, Frederick, MD 21701, USA;
| | - Victor A. David
- Molecular Genetic Epidemiology Section, Basic Research Laboratory, National Cancer Institute, Frederick, MD 21701, USA; (V.A.D.); (C.A.W.)
| | - Mary Thompson
- Center for Cancer Research, National Cancer Institute, Frederick, MD 21701, USA;
| | - Wooram Jung
- Department of Cancer Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA;
| | - Sun-Ha Jee
- Department of Epidemiology and Health Promotion, Institute for Health Promotion, Graduate School of Public Health, Yonsei University College of Medicine, Seoul 03722, Korea;
| | - Ira O. Daar
- Cancer & Developmental Biology Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, MD 21701, USA; (J.Y.); (I.O.D.)
| | - Cheryl A. Winkler
- Molecular Genetic Epidemiology Section, Basic Research Laboratory, National Cancer Institute, Frederick, MD 21701, USA; (V.A.D.); (C.A.W.)
| | - Sung-Kweon Cho
- Molecular Genetic Epidemiology Section, Basic Research Laboratory, National Cancer Institute, Frederick, MD 21701, USA; (V.A.D.); (C.A.W.)
- Department of Pharmacology, Ajou University School of Medicine, 164, Worldcup-ro, Yeongtong-gu, Suwon 16499, Korea
- Correspondence: or ; Tel.: +82-31-219-4506; Fax: +82-31-219-5069
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17
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Identification of two novel heterozygous SLC2A9 mutations in a Chinese woman and review of literature. Clin Chim Acta 2021; 523:58-64. [PMID: 34499869 DOI: 10.1016/j.cca.2021.09.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2021] [Revised: 07/20/2021] [Accepted: 09/03/2021] [Indexed: 11/23/2022]
Abstract
OBJECTIVE This study is aimed to describe the clinical and genetic characteristics of a Chinese woman diagnosed with renal hypouricemia type 2 (RHUC2). We also summarize the advances in research on RHUC2 by reviewing related literature. METHODS We measured clinical parameters of a 57-year-old female and performed whole-exome sequencing to screen for mutations. Human embryonic kidney 293 cells were transiently transfected with plasmids containing wild-type or mutants. Relative mRNA quantification was determined by real-time quantitative reverse transcription polymerase chain reaction (RT-qPCR). RESULTS This patient was diagnosed with diabetes and coronary heart disease. In addition, a decrease in 24-hour urinary chloride was observed. Two novel heterozygous variants of SLC2A9 (NM_020041.2): c.682-2_682-1insC and c.267C > G (p.Y89X) were identified. The mini-gene splicing assay revealed that c.682-2_682-1insC variant resulted in a frameshift mutation p. E228PfsX23. There was a statistically significant difference in mRNA expression level between the two mutants and the wild-type. CONCLUSIONS These findings strongly suggest that the two novel mutations are the causative agents of RHUC2. In particular, our findings provide further insights into the function of SLC2A9 and mechanisms of the complications.
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18
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Kelly R, Semple D, Harper A. Recurrent Acute Kidney Injury with Severe Loin Pain and Patchy Renal Ischaemia after Anaerobic Exercise without Renal Hypouricaemia in a New Zealand European Male. Case Rep Nephrol Dial 2021; 11:176-182. [PMID: 34327220 PMCID: PMC8299420 DOI: 10.1159/000517114] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2020] [Accepted: 05/07/2021] [Indexed: 12/29/2022] Open
Abstract
Acute kidney injury with severe loin pain and patchy renal ischaemia after anaerobic exercise (ALPE) is a rare clinical syndrome. ALPE has predominantly been described in Japanese and Korean populations to date. Many cases and most recurrent examples are associated with renal hypouricaemia. We describe a 28-year-old New Zealand European male without renal hypouricaemia who developed recurrent ALPE whilst performing elite-level sport. Avoiding elite-level anaerobic exercise was successful at preventing further episodes. This report confirms the first known case of ALPE in a New Zealand European male and raises the possibility that ALPE is an under-recognized condition. Long-term outcomes of recurrent ALPE remain unclear, and preventative strategies should be implemented to preserve renal function. Avoiding intense anaerobic exercise is an effective preventative strategy.
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Affiliation(s)
- Richard Kelly
- Auckland District Health Board, Auckland, New Zealand
| | - David Semple
- Department of Renal Medicine, Auckland District Health Board, Auckland, New Zealand.,School of Medicine, University of Auckland, Auckland, New Zealand
| | - Alana Harper
- Adult Emergency Department, Auckland District Health Board, Auckland, New Zealand.,Auckland Rescue Helicopter Trust, Auckland, New Zealand
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Pavelcova K, Bohata J, Pavlikova M, Bubenikova E, Pavelka K, Stiburkova B. Evaluation of the Influence of Genetic Variants of SLC2A9 (GLUT9) and SLC22A12 (URAT1) on the Development of Hyperuricemia and Gout. J Clin Med 2020; 9:jcm9082510. [PMID: 32759716 PMCID: PMC7465009 DOI: 10.3390/jcm9082510] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Revised: 07/23/2020] [Accepted: 08/01/2020] [Indexed: 02/07/2023] Open
Abstract
Urate transporters, which are located in the kidneys, significantly affect the level of uric acid in the body. We looked at genetic variants of genes encoding the major reabsorption proteins GLUT9 (SLC2A9) and URAT1 (SLC22A12) and their association with hyperuricemia and gout. In a cohort of 250 individuals with primary hyperuricemia and gout, we used direct sequencing to examine the SLC22A12 and SLC2A9 genes. Identified variants were evaluated in relation to clinical data, biochemical parameters, metabolic syndrome criteria, and our previous analysis of the major secretory urate transporter ABCG2. We detected seven nonsynonymous variants of SLC2A9. There were no nonsynonymous variants of SLC22A12. Eleven variants of SLC2A9 and two variants of SLC22A12 were significantly more common in our cohort than in the European population (p = 0), while variants p.V282I and c.1002+78A>G had a low frequency in our cohort (p = 0). Since the association between variants and the level of uric acid was not demonstrated, the influence of variants on the development of hyperuricemia and gout should be evaluated with caution. However, consistent with the findings of other studies, our data suggest that p.V282I and c.1002+78A>G (SLC2A9) reduce the risk of gout, while p.N82N (SLC22A12) increases the risk.
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Affiliation(s)
- Katerina Pavelcova
- Department of Molecular Biology and Immunogenetics, Institute of Rheumatology, 128 50 Prague, Czech Republic; (K.P.); (J.B.); (E.B.); (K.P.)
- Department of Rheumatology, First Faculty of Medicine, Charles University, 128 50 Prague, Czech Republic
| | - Jana Bohata
- Department of Molecular Biology and Immunogenetics, Institute of Rheumatology, 128 50 Prague, Czech Republic; (K.P.); (J.B.); (E.B.); (K.P.)
- Department of Rheumatology, First Faculty of Medicine, Charles University, 128 50 Prague, Czech Republic
| | - Marketa Pavlikova
- Department of Probability and Mathematical Statistics, Faculty of Mathematics and Physics, Charles University, 186 75 Prague, Czech Republic;
| | - Eliska Bubenikova
- Department of Molecular Biology and Immunogenetics, Institute of Rheumatology, 128 50 Prague, Czech Republic; (K.P.); (J.B.); (E.B.); (K.P.)
- Department of Rheumatology, First Faculty of Medicine, Charles University, 128 50 Prague, Czech Republic
| | - Karel Pavelka
- Department of Molecular Biology and Immunogenetics, Institute of Rheumatology, 128 50 Prague, Czech Republic; (K.P.); (J.B.); (E.B.); (K.P.)
| | - Blanka Stiburkova
- Department of Molecular Biology and Immunogenetics, Institute of Rheumatology, 128 50 Prague, Czech Republic; (K.P.); (J.B.); (E.B.); (K.P.)
- Department of Pediatrics and Adolescent Medicine, First Faculty of Medicine, Charles University and General University Hospital in Prague, 120 00 Prague, Czech Republic
- Correspondence: ; Tel.: +420-234-075-319
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20
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Teng L, Zhang Y, Ye L, Lv J, Mao Y, Schneider R, Chen J, Jiang H, Wu J. Donor-derived hypouricemia in irrelevant recipients caused by kidney transplantation. ANNALS OF TRANSLATIONAL MEDICINE 2020; 8:330. [PMID: 32355774 PMCID: PMC7186701 DOI: 10.21037/atm.2020.02.140] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Background Hereditary renal hypouricemia (HRH) is a genetically heterogenetic disease. Patients with HRH are almost asymptomatic; but some may experience exercise-induced acute kidney injury (EAKI) and nephrolithiasis which may bring concerns regarding the risk-benefit ratio as marginal kidney donors. This study examined the pathogenic mutations of hypouricemia in two recipients after receiving kidney transplantation, providing preliminary evidence for the mechanism of hypouricemia. Methods Two participants underwent detailed biochemical examinations. DNA and RNA were extracted from transplant specimens for sequencing. The whole-genome sequencing and polymerase chain reaction (PCR) amplification were performed to confirm the pathogenic genes. Functional effects of mutant proteins were verified by bioinformatics analysis. RNA-sequencing (RNA-seq) was used to study the transcriptome of hypouricemia. Results Both of the recipients had the low serum uric acid (UA) (45–65 µmol/l), high fraction excretion of UA (44% and 75%) and an increase in the UA clearance (35.9 and 73.3 mL/min) with a functioning graft. The sequencing analyses revealed 7 kinds of potential mutational genes in this case, two novel mutations p.R89H and p.L181V in SLC22A12 gene which were revealed by bioinformatics could be pathogenic in nature. Conclusions Two novel mutations of SLC22A12 were identified. Preliminary functional analysis revealed a potential deleterious effect of these mutations in the grafts derived from the donor and sequencing analysis expand the molecular mechanisms of renal hypouricemia.
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Affiliation(s)
- Lisha Teng
- Department of the Kidney Disease Center, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou 310003, China.,Key Laboratory of Kidney Disease Prevention and Control Technology, Hangzhou 310003, China.,The Third-Grade Laboratory under the National State, Administration of Traditional Chinese Medicine, Hangzhou 310000, China
| | - Yanling Zhang
- Department of the Kidney Disease Center, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou 310003, China.,Key Laboratory of Kidney Disease Prevention and Control Technology, Hangzhou 310003, China.,The Third-Grade Laboratory under the National State, Administration of Traditional Chinese Medicine, Hangzhou 310000, China.,Department of Nephrology, The Second Hospital of Shaoxing, Shaoxing 312000, China
| | - Luxi Ye
- Department of the Kidney Disease Center, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou 310003, China.,Key Laboratory of Kidney Disease Prevention and Control Technology, Hangzhou 310003, China.,The Third-Grade Laboratory under the National State, Administration of Traditional Chinese Medicine, Hangzhou 310000, China
| | - Junhao Lv
- Department of the Kidney Disease Center, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou 310003, China.,Key Laboratory of Kidney Disease Prevention and Control Technology, Hangzhou 310003, China.,The Third-Grade Laboratory under the National State, Administration of Traditional Chinese Medicine, Hangzhou 310000, China
| | - Youying Mao
- Nephrology Department, Shanghai Children's Medical Center, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Ronen Schneider
- Division of Nephrology, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA
| | - Jianghua Chen
- Department of the Kidney Disease Center, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou 310003, China.,Key Laboratory of Kidney Disease Prevention and Control Technology, Hangzhou 310003, China.,The Third-Grade Laboratory under the National State, Administration of Traditional Chinese Medicine, Hangzhou 310000, China
| | - Hong Jiang
- Department of the Kidney Disease Center, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou 310003, China.,Key Laboratory of Kidney Disease Prevention and Control Technology, Hangzhou 310003, China.,The Third-Grade Laboratory under the National State, Administration of Traditional Chinese Medicine, Hangzhou 310000, China
| | - Jianyong Wu
- Department of the Kidney Disease Center, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou 310003, China.,Key Laboratory of Kidney Disease Prevention and Control Technology, Hangzhou 310003, China.,The Third-Grade Laboratory under the National State, Administration of Traditional Chinese Medicine, Hangzhou 310000, China
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21
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Shamekhi Amiri F, Rostami Z. Prevalence of inherited changes of uric acid levels in kidney dysfunction including stage 5 D and T: a systematic review. RENAL REPLACEMENT THERAPY 2020. [DOI: 10.1186/s41100-020-0258-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Abstract
Background/aims
Familial juvenile hereditary nephropathy (FJHN) is characterized by hyperuricemia due to severely impaired urinary excretion of urate. Hereditary renal hypouricemia is an inborn error of membrane transport. Because studies of inherited tubulopathy is rare, prevalence and diagnosis of these inherited tubulopathy increase with genetic testing.The aim of this study is to investigate prevalence of clinical features, biochemical profiles, and genetic analysis of patients with changes in serum uric acid levels in inherited tubulopathy.
Main body
The paper has written based on searching PubMed and Google Scholar to identify potentially relevant articles or abstracts. In this retrospective study, a total 65 patients with changes of serum uric acid levels and kidney dysfunction were investigated. Clinical features, laboratory data at initial presentation, management, and outcomes were collected. Forty studies (65 participants) included in this review. The mean ± SD of age of study patients in inherited tubulointerstitial kidney disease was 25.29 ± 14.69 years. Mean ± SD age of patients at time of diagnosis in inherited renal hypouricemia was 18.83 ± 10.59 years. Correlation between exon region in mutated UMOD, SLC22A12, and SLC2A9 genes and serum uric acid levels were assessed and revealed significant statistical correlation between exon region of SLC2A9 mutation and serum uric acid levels. Prevalence of progression to end-stage kidney disease in patients with inherited tubulointerstitial kidney disease and inherited renal hypouricemia were assessed 20% and 2.5%, respectively. There was nephrolithiasis in two patients (2/25, 8%) with inherited renal hypouricemia.
Conclusions
This study shows that UMOD and SLC22A12 gene mutations were responsible for majority of autosomal-dominant tubulointerstitial kidney disease and inherited renal hypouricemia, respectively.
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22
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Wang C, Wang J, Liu S, Liang X, Song Y, Feng L, Zhong L, Guo X. Idiopathic renal hypouricemia: A case report and literature review. Mol Med Rep 2019; 20:5118-5124. [PMID: 31638209 PMCID: PMC6854582 DOI: 10.3892/mmr.2019.10726] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2018] [Accepted: 08/20/2019] [Indexed: 11/06/2022] Open
Abstract
Idiopathic renal hypouricemia is a rare hereditary condition. Type 2 renal hyperuricemia (RHUC2) is caused by a mutation in the SLC2A9 gene, which encodes a high‑capacity glucose and urate transporter, glucose transporter (GLUT)9. RHUC2 predisposes to exercise‑induced acute renal failure (EIARF) and nephrolithiasis, which is caused by a defect in renal tubular urate transport and is characterized by increased clearance of renal uric acid. In the present study a case of a 35‑year‑old Chinese man with EIARF is reported. The patient had isolated renal hypouricemia, with a serum uric acid level of 21 µmol/l and a fractional excretion of uric acid of 200%. The mutational analysis revealed a homozygous mutation (c.857G>A in exon 8) in the SLC2A9 gene. The patient's family members carried the same mutation, but were heterozygous and clinically asymptomatic. In conclusion, to the best of our knowledge, this is the first report of a RHUC2 patient with a GLUT9 mutation, p.W286X, which may be a pathogenic mutation of RHUC2. Further investigation into the functional role of GLUT9 in this novel SLC2A9 mutation is required.
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Affiliation(s)
- Cuiyu Wang
- Department of Nephrology, Shenzhen Hospital, Southern Medical University, Shenzhen, Guangdong 518000, P.R. China
| | - Jin Wang
- Department of Epidemiology, School of Public Health, Sun Yat‑Sen University, Guangzhou Guangdong 510080, P.R. China
| | - Song Liu
- Department of Nephrology, Dalian Liguang Rehabilitation Hospital, Dalian, Liaoning 116000, P.R. China
| | - Xinhua Liang
- Department of Nephrology, Shenzhen Hospital, Southern Medical University, Shenzhen, Guangdong 518000, P.R. China
| | - Yifan Song
- Department of Nephrology, Shenzhen Hospital, Southern Medical University, Shenzhen, Guangdong 518000, P.R. China
| | - Ling Feng
- Department of Nephrology, Shenzhen Hospital, Southern Medical University, Shenzhen, Guangdong 518000, P.R. China
| | - Lanxin Zhong
- Department of Nephrology, Shenzhen Hospital, Southern Medical University, Shenzhen, Guangdong 518000, P.R. China
| | - Xiaohua Guo
- Department of Nephrology, Shenzhen Hospital, Southern Medical University, Shenzhen, Guangdong 518000, P.R. China
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23
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Cha DH, Gee HY, Cachau R, Choi JM, Park D, Jee SH, Ryu S, Kim KK, Won HH, Limou S, Myung W, Winkler CA, Cho SK. Contribution of SLC22A12 on hypouricemia and its clinical significance for screening purposes. Sci Rep 2019; 9:14360. [PMID: 31591475 PMCID: PMC6779878 DOI: 10.1038/s41598-019-50798-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2018] [Accepted: 09/18/2019] [Indexed: 11/09/2022] Open
Abstract
Differentiating between inherited renal hypouricemia and transient hypouricemic status is challenging. Here, we aimed to describe the genetic background of hypouricemia patients using whole-exome sequencing (WES) and assess the feasibility for genetic diagnosis using two founder variants in primary screening. We selected all cases (N = 31) with extreme hypouricemia (<1.3 mg/dl) from a Korean urban cohort of 179,381 subjects without underlying conditions. WES and corresponding downstream analyses were performed for the discovery of rare causal variants for hypouricemia. Two known recessive variants within SLC22A12 (p.Trp258*, pArg90His) were identified in 24 out of 31 subjects (77.4%). In an independent cohort, we identified 50 individuals with hypouricemia and genotyped the p.Trp258* and p.Arg90His variants; 47 of the 50 (94%) hypouricemia cases were explained by only two mutations. Four novel coding variants in SLC22A12, p.Asn136Lys, p.Thr225Lys, p.Arg284Gln, and p.Glu429Lys, were additionally identified. In silico studies predict these as pathogenic variants. This is the first study to show the value of genetic diagnostic screening for hypouricemia in the clinical setting. Screening of just two ethnic-specific variants (p.Trp258* and p.Arg90His) identified 87.7% (71/81) of Korean patients with monogenic hypouricemia. Early genetic identification of constitutive hypouricemia may prevent acute kidney injury by avoidance of dehydration and excessive exercise.
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Affiliation(s)
- Do Hyeon Cha
- Department of Pharmacology, Brain Korea 21 PLUS Project for Medical Sciences, Yonsei University College of Medicine, Seoul, Republic of Korea
| | - Heon Yung Gee
- Department of Pharmacology, Brain Korea 21 PLUS Project for Medical Sciences, Yonsei University College of Medicine, Seoul, Republic of Korea
| | - Raul Cachau
- Advanced Biomedical Computational Science, Frederick National Laboratory for Cancer Research, National Cancer Institute, Frederick, MD, USA
| | - Jong Mun Choi
- Department of Laboratory Medicine, Green Cross, Yongin-si, Gyeonggi-do, Republic of Korea
| | - Daeui Park
- Department of Predictive Toxicology, Korea Institute of Toxicology, Daejeon, Republic of Korea
| | - Sun Ha Jee
- Department of Epidemiology and Health Promotion and Institute for Health Promotion, Graduate School of Public Health, Yonsei University College of Medicine, Seoul, Republic of Korea
| | - Seungho Ryu
- Center for Cohort Studies, Total Healthcare Center, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea
| | - Kyeong Kyu Kim
- Department of Health Sciences and Technology, SAIHST, Sungkyunkwan University, Seoul, Republic of Korea
| | - Hong-Hee Won
- Department of Health Sciences and Technology, SAIHST, Sungkyunkwan University, Seoul, Republic of Korea
| | - Sophie Limou
- Centre de Recherche en Transplantation et Immunologie (CRTI) UMR1064 Inserm, Université de Nantes, Nantes, France.,Institut de Transplantation en Urologie-Néphrologie (ITUN), Nantes University Hospital, Nantes, France.,Ecole Centrale de Nantes, Nantes, France.,Molecular Genetic Epidemiology Section, Basic Science Laboratory, Frederick National Laboratory for Cancer Research, Frederick, MD, USA
| | - Woojae Myung
- Department of Psychiatry, Seoul National University College of Medicine and Bundang Hospital, Seongnam, Korea
| | - Cheryl A Winkler
- Molecular Genetic Epidemiology Section, Basic Science Laboratory, Frederick National Laboratory for Cancer Research, Frederick, MD, USA
| | - Sung Kweon Cho
- Department of Health Sciences and Technology, SAIHST, Sungkyunkwan University, Seoul, Republic of Korea. .,Molecular Genetic Epidemiology Section, Basic Research Laboratory, Center for Cancer Research, National Cancer Institute, 8560 Progress Drive, Frederick, MD 21701, USA.
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Peris Vidal A, Marin Serra J, Lucas Sáez E, Ferrando Monleón S, Claverie-Martin F, Perdomo Ramírez A, Trujillo-Suarez J, Fons Moreno J. Hipouricemia renal hereditaria tipo 1 y 2 en tres niños españoles. Revisión de casos pediátricos publicados. Nefrologia 2019; 39:355-361. [DOI: 10.1016/j.nefro.2018.08.010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2018] [Revised: 07/25/2018] [Accepted: 08/25/2018] [Indexed: 10/27/2022] Open
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Wang Z, Cui T, Ci X, Zhao F, Sun Y, Li Y, Liu R, Wu W, Yi X, Liu C. The effect of polymorphism of uric acid transporters on uric acid transport. J Nephrol 2018; 32:177-187. [DOI: 10.1007/s40620-018-0546-7] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2018] [Accepted: 09/17/2018] [Indexed: 01/09/2023]
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Zhu W, Deng Y, Zhou X. Multiple Membrane Transporters and Some Immune Regulatory Genes are Major Genetic Factors to Gout. Open Rheumatol J 2018; 12:94-113. [PMID: 30123371 PMCID: PMC6062909 DOI: 10.2174/1874312901812010094] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2018] [Revised: 05/30/2018] [Accepted: 06/20/2018] [Indexed: 01/10/2023] Open
Abstract
Gout is a common form of inflammatory arthritis caused by hyperuricemia and the deposition of Monosodium Urate (MSU) crystals. It is also considered as a complex disorder in which multiple genetic factors have been identified in association with its susceptibility and/or clinical outcomes. Major genes that were associated with gout include URAT1, GLUT9, OAT4, NPT1 (SLC17A1), NPT4 (SLC17A3), NPT5 (SLC17A4), MCT9, ABCG2, ABCC4, KCNQ1, PDZK1, NIPAL1, IL1β, IL-8, IL-12B, IL-23R, TNFA, MCP-1/CCL2, NLRP3, PPARGC1B, TLR4, CD14, CARD8, P2X7R, EGF, A1CF, HNF4G and TRIM46, LRP2, GKRP, ADRB3, ADH1B, ALDH2, COMT, MAOA, PRKG2, WDR1, ALPK1, CARMIL (LRRC16A), RFX3, BCAS3, CNIH-2, FAM35A and MYL2-CUX2. The proteins encoded by these genes mainly function in urate transport, inflammation, innate immunity and metabolism. Understanding the functions of gout-associated genes will provide important insights into future studies to explore the pathogenesis of gout, as well as to develop targeted therapies for gout.
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Affiliation(s)
- Weifeng Zhu
- Department of Biochemistry and Molecular Biology, College of Basic Medical Sciences, Nanchang University, Nanchang, China.,Department of Internal Medicine, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Yan Deng
- Department of Internal Medicine, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, TX, USA.,Department of Ophthalmology of Children, The Second Affiliated Hospital of Nanchang University, Nanchang, China
| | - Xiaodong Zhou
- Department of Internal Medicine, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, TX, USA
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Ruiz A, Gautschi I, Schild L, Bonny O. Human Mutations in SLC2A9 (Glut9) Affect Transport Capacity for Urate. Front Physiol 2018; 9:476. [PMID: 29967582 PMCID: PMC6016318 DOI: 10.3389/fphys.2018.00476] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Accepted: 04/16/2018] [Indexed: 01/17/2023] Open
Abstract
SLC2A9 or Glut9 is a voltage sensitive urate transporter, mainly expressed in the kidneys, the liver, and the intestine. Human Glut9 loss-of-function mutations were identified in familial hypouricemia, and several single nucleotide polymorphisms (SNPs) were associated with lower serum urate, further indicating that Glut9 is a major determinant of serum uric acid level. To get insights in Glut9 transport characteristics, we systematically analyzed the function of known human Glut9 mutants using 14C-urate uptake assay and two-electrode voltage clamp (TEVC) in the Xenopus laevis oocyte expression system. Surface expression was assessed by immunostaining and biotinylation. We found decreased urate transport by flux studies for most of the variants. No variant was permissive for glucose transport. We could further differentiate two behaviors among the mutants: those harboring poor overall and cell-surface expression leading to low activity and those fully expressed at the cell surface, but presenting decreased activity. We studied the latter by TEVC and observed, in depolarized conditions, decreased inward currents measured in presence of 400 μM urate, partially reversed in 1 mM urate. In addition, we showed that C210F displays lower transport ability. By contrast, N333S showed decreased urate transport activity and urate affinity, suggesting that it may belong to the urate binding pocket. Systematic analysis of Glut9 mutants confirms Glut9 as putative target for the treatment of hyperuricemia and brings new insights in Glut9 structure – function.
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Affiliation(s)
- Anne Ruiz
- Department of Pharmacology and Toxicology, University of Lausanne, Lausanne, Switzerland
| | - Ivan Gautschi
- Department of Pharmacology and Toxicology, University of Lausanne, Lausanne, Switzerland
| | - Laurent Schild
- Department of Pharmacology and Toxicology, University of Lausanne, Lausanne, Switzerland
| | - Olivier Bonny
- Department of Pharmacology and Toxicology, University of Lausanne, Lausanne, Switzerland.,Service of Nephrology, Department of Medicine, Lausanne University Hospital, Lausanne, Switzerland
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Quan V, Ali O, Pavelcova K, Harris F, Stiburkova B. An Unusual Cause of Exercise-Induced Acute Kidney Injury. Am J Med 2018; 131:e145-e146. [PMID: 29175239 DOI: 10.1016/j.amjmed.2017.10.053] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/29/2017] [Accepted: 10/30/2017] [Indexed: 11/17/2022]
Affiliation(s)
- Virginia Quan
- St Helier University Hospital, Carshalton, United Kingdom.
| | - Omer Ali
- St Helier University Hospital, Carshalton, United Kingdom
| | - Katerina Pavelcova
- Institute of Rheumatology, Prague, Czech Republic; Department of Rheumatology, First Faculty of Medicine, Charles University, Prague, Czech Republic
| | - Fiona Harris
- St Helier University Hospital, Carshalton, United Kingdom
| | - Blanka Stiburkova
- Institute of Rheumatology, Prague, Czech Republic; Institute of Inherited Metabolic Disorders, First Faculty of Medicine, Charles University and General University Hospital in Prague, Czech Republic
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29
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Claverie-Martin F, Trujillo-Suarez J, Gonzalez-Acosta H, Aparicio C, Justa Roldan ML, Stiburkova B, Ichida K, Martín-Gomez MA, Herrero Goñi M, Carrasco Hidalgo-Barquero M, Iñigo V, Enriquez R, Cordoba-Lanus E, Garcia-Nieto VM. URAT1 and GLUT9 mutations in Spanish patients with renal hypouricemia. Clin Chim Acta 2018; 481:83-89. [PMID: 29486147 DOI: 10.1016/j.cca.2018.02.030] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2017] [Revised: 02/22/2018] [Accepted: 02/22/2018] [Indexed: 01/28/2023]
Abstract
BACKGROUND Renal hypouricemia (RHUC), a rare inherited disorder characterized by impaired uric acid (UA) reabsorption in the proximal tubule, is caused by mutations in SLC22A12 or SLC2A9. Most mutations have been identified in Japanese patients, and only a few have been detected in Europeans. METHODS We report clinical, biochemical and genetics findings of fourteen Spanish patients, six Caucasians and eight of Roma ethnia, diagnosed with idiopathic RHUC. Two of the patients presented exercise-induced acute renal failure and another one had several episodes of nephrolithiasis and four of them had progressive deterioration of renal function, while the rest were asymptomatic. RESULTS Molecular analysis revealed SLC22A12 mutations in ten of the patients, and SLC2A9 mutations in the other four. A new heterozygous SLC22A12 missense mutation, c.1427C>A (p.A476D), was identified in two affected members of the same family. The rest of the patients presented homozygous, heterozygous or compound heterozygous mutations that have been previously identified in patients with RHUC; SLC22A12 p.T467M and p.L415_G417del, and SLC2A9 p.T125M. Expression studies in Xenopus oocytes revealed that c.1427C>A reduced UA transport but did not alter the location of URAT1 protein on the plasma membrane. CONCLUSIONS The biochemical and clinical features of our patients together with the genetic analysis results confirmed the diagnosis of RHUC. This is the first report describing SLC22A12 and SLC2A9 mutations in Spanish patients.
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Affiliation(s)
- Felix Claverie-Martin
- Unidad de Investigación, Hospital Nuestra Señora de Candelaria, Santa Cruz de Tenerife, Spain.
| | - Jorge Trujillo-Suarez
- Unidad de Investigación, Hospital Nuestra Señora de Candelaria, Santa Cruz de Tenerife, Spain
| | - Hilaria Gonzalez-Acosta
- Unidad de Investigación, Hospital Nuestra Señora de Candelaria, Santa Cruz de Tenerife, Spain
| | | | | | - Blanka Stiburkova
- Institute of Inherited Metabolic Disorders, Charles University, General University Hospital in Prague, Prague, Czech Republic; Institute of Rheumatology, Prague, Czech Republic
| | - Kimiyoshi Ichida
- Department of Pathophysiology, Tokyo University of Pharmacy and Life Sciences, Tokyo, Japan
| | | | | | | | - Victoria Iñigo
- Unidad de Nefrología, Hospital Son Llàtzer, Palma de Mallorca, Spain
| | | | - Elizabeth Cordoba-Lanus
- Unidad de Investigación, Hospital Nuestra Señora de Candelaria, Santa Cruz de Tenerife, Spain
| | - Victor M Garcia-Nieto
- Unidad de Nefrología Pediatrica, Hospital Nuestra Señora de Candelaria, Santa Cruz de Tenerife, Spain
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Mancikova A, Krylov V, Hurba O, Sebesta I, Nakamura M, Ichida K, Stiburkova B. Functional analysis of novel allelic variants in URAT1 and GLUT9 causing renal hypouricemia type 1 and 2. Clin Exp Nephrol 2015; 20:578-584. [DOI: 10.1007/s10157-015-1186-z] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2015] [Accepted: 10/13/2015] [Indexed: 11/28/2022]
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Hereditary Renal Hypouricemia Type 1 and Autosomal Dominant Polycystic Kidney Disease. Am J Med Sci 2015; 350:268-71. [DOI: 10.1097/maj.0000000000000550] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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32
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High frequency of SLC22A12 variants causing renal hypouricemia 1 in the Czech and Slovak Roma population; simple and rapid detection method by allele-specific polymerase chain reaction. Urolithiasis 2015; 43:441-5. [DOI: 10.1007/s00240-015-0790-4] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2015] [Accepted: 05/19/2015] [Indexed: 10/23/2022]
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Mraz M, Hurba O, Bartl J, Dolezel Z, Marinaki A, Fairbanks L, Stiburkova B. Modern diagnostic approach to hereditary xanthinuria. Urolithiasis 2014; 43:61-7. [PMID: 25370766 DOI: 10.1007/s00240-014-0734-4] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2014] [Accepted: 10/15/2014] [Indexed: 11/25/2022]
Abstract
Hereditary xanthinuria (HX) is a rare inherited disorder caused by a deficiency of xanthine dehydrogenase/oxidase (XDH/XO). Missing XDH/XO activity leads to undetectable levels of uric acid excessively replaced by xanthine in serum/urine. The allopurinol loading test has been traditionally used to differentiate between HX types I and II. Final confirmation of HX has been based on the biopsy finding of the absent XDH/XO activity in the small intestine or liver. We present the clinical, biochemical, ultrasound and molecular genetics findings in three new patients with HX and suggest a simple three-step approach to be used for diagnosis, typing and confirmation of HX. In the first step, the diagnosis of HX is determined by extremely low serum/urinary uric acid excessively replaced by xanthine. Second, HX is typed using urinary metabolomics. Finally, the results are confirmed by molecular genetics. We advocate for this safe and non-invasive diagnostic algorithm instead of the traditional allopurinol loading test and intestinal or liver biopsy used in the past.
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Affiliation(s)
- Martin Mraz
- Department of Nephrology, Birmingham Children's Hospital NHS Foundation Trust, Birmingham, UK
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Hurba O, Mancikova A, Krylov V, Pavlikova M, Pavelka K, Stibůrková B. Complex analysis of urate transporters SLC2A9, SLC22A12 and functional characterization of non-synonymous allelic variants of GLUT9 in the Czech population: no evidence of effect on hyperuricemia and gout. PLoS One 2014; 9:e107902. [PMID: 25268603 PMCID: PMC4182324 DOI: 10.1371/journal.pone.0107902] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2014] [Accepted: 08/18/2014] [Indexed: 11/24/2022] Open
Abstract
Objective Using European descent Czech populations, we performed a study of SLC2A9 and SLC22A12 genes previously identified as being associated with serum uric acid concentrations and gout. This is the first study of the impact of non-synonymous allelic variants on the function of GLUT9 except for patients suffering from renal hypouricemia type 2. Methods The cohort consisted of 250 individuals (150 controls, 54 nonspecific hyperuricemics and 46 primary gout and/or hyperuricemia subjects). We analyzed 13 exons of SLC2A9 (GLUT9 variant 1 and GLUT9 variant 2) and 10 exons of SLC22A12 by PCR amplification and sequenced directly. Allelic variants were prepared and their urate uptake and subcellular localization were studied by Xenopus oocytes expression system. The functional studies were analyzed using the non-parametric Wilcoxon and Kruskall-Wallis tests; the association study used the Fisher exact test and linear regression approach. Results We identified a total of 52 sequence variants (12 unpublished). Eight non-synonymous allelic variants were found only in SLC2A9: rs6820230, rs2276961, rs144196049, rs112404957, rs73225891, rs16890979, rs3733591 and rs2280205. None of these variants showed any significant difference in the expression of GLUT9 and in urate transport. In the association study, eight variants showed a possible association with hyperuricemia. However, seven of these were in introns and the one exon located variant, rs7932775, did not show a statistically significant association with serum uric acid concentration. Conclusion Our results did not confirm any effect of SLC22A12 and SLC2A9 variants on serum uric acid concentration. Our complex approach using association analysis together with functional and immunohistochemical characterization of non-synonymous allelic variants did not show any influence on expression, subcellular localization and urate uptake of GLUT9.
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Affiliation(s)
- Olha Hurba
- Institute of Inherited Metabolic Disorders, First Faculty of Medicine, Charles University in Prague and General University Hospital in Prague, Prague, Czech Republic
| | - Andrea Mancikova
- Charles University in Prague, Faculty of Science, Department of Cell Biology, Prague, Czech Republic
| | - Vladimir Krylov
- Charles University in Prague, Faculty of Science, Department of Cell Biology, Prague, Czech Republic
| | - Marketa Pavlikova
- Institute of Inherited Metabolic Disorders, First Faculty of Medicine, Charles University in Prague and General University Hospital in Prague, Prague, Czech Republic
| | | | - Blanka Stibůrková
- Institute of Inherited Metabolic Disorders, First Faculty of Medicine, Charles University in Prague and General University Hospital in Prague, Prague, Czech Republic
- Institute of Rheumatology, Prague, Czech Republic
- * E-mail:
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Abstract
Uric acid, the end product of purine metabolism, is excreted predominantly by the proximal tubules. Abnormal serum levels of uric acid are due to alterations in production or excretion. Fractional excretion of uric acid is helpful in determining the underlying etiology of hypouricemia or hyperuricemia in children. Abnormalities in the molecular mechanisms that control renal uric acid tubular transport are implicated in various disorders associated with abnormal uric acid levels. Gout is rare in children; yet its presence necessitates evaluation for enzymatic defects in purine metabolism. Well-known effects of uric acid on the kidney include nephrolithiasis and acute kidney injury (AKI) in the setting of tumor lysis. However, recent data suggest that uric acid may be an important factor in the pathogenesis of AKI in general, as well as of chronic kidney disease (CKD) and hypertension. Hence, uric acid may not only be a marker but also a potential therapeutic target in kidney disease. Nonetheless, because of confounders, more studies are needed to clarify the association between uric acid and multifactorial disorders of the kidney.
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36
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Stibůrková B, Pavlíková M, Sokolová J, Kožich V. Metabolic syndrome, alcohol consumption and genetic factors are associated with serum uric acid concentration. PLoS One 2014; 9:e97646. [PMID: 24827988 PMCID: PMC4020828 DOI: 10.1371/journal.pone.0097646] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2014] [Accepted: 04/22/2014] [Indexed: 01/22/2023] Open
Abstract
OBJECTIVE Uric acid is the end product of purine metabolism in humans, and increased serum uric acid concentrations lead to gout. The objective of the current study was to identify factors that are independently associated with serum uric acid concentrations in a cohort of Czech control individuals. METHODS The cohort consisted of 589 healthy subjects aged 18-65 years. We studied the associations between the serum uric acid concentration and the following: (i) demographic, anthropometric and other variables previously reported to be associated with serum uric acid concentrations; (ii) the presence of metabolic syndrome and the levels of metabolic syndrome components; and (iii) selected genetic variants of the MTHFR (c.665C>T, c.1286A>C), SLC2A9 (c.844G>A, c.881G>A) and ABCG2 genes (c.421C>A). A backward model selection procedure was used to build two multiple linear regression models; in the second model, the number of metabolic syndrome criteria that were met replaced the metabolic syndrome-related variables. RESULTS The models had coefficients of determination of 0.59 and 0.53. The serum uric acid concentration strongly correlated with conventional determinants including male sex, and with metabolic syndrome-related variables. In the simplified second model, the serum uric acid concentration positively correlated with the number of metabolic syndrome criteria that were met, and this model retained the explanatory power of the first model. Moderate wine drinking did not increase serum uric acid concentrations, and the urate transporter ABCG2, unlike MTHFR, was a genetic determinant of serum uric acid concentrations. CONCLUSION Metabolic syndrome, moderate wine drinking and the c.421C>A variant in the ABCG gene are independently associated with the serum uric acid concentration. Our model indicates that uric acid should be clinically monitored in persons with metabolic syndrome.
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Affiliation(s)
- Blanka Stibůrková
- Institute of Inherited Metabolic Disorders, First Faculty of Medicine, Charles University in Prague and General University Hospital in Prague, Prague, Czech Republic
| | - Markéta Pavlíková
- Institute of Inherited Metabolic Disorders, First Faculty of Medicine, Charles University in Prague and General University Hospital in Prague, Prague, Czech Republic
| | - Jitka Sokolová
- Institute of Inherited Metabolic Disorders, First Faculty of Medicine, Charles University in Prague and General University Hospital in Prague, Prague, Czech Republic
| | - Viktor Kožich
- Institute of Inherited Metabolic Disorders, First Faculty of Medicine, Charles University in Prague and General University Hospital in Prague, Prague, Czech Republic
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Shen H, Feng C, Jin X, Mao J, Fu H, Gu W, Liu A, Shu Q, Du L. Recurrent exercise-induced acute kidney injury by idiopathic renal hypouricemia with a novel mutation in the SLC2A9 gene and literature review. BMC Pediatr 2014; 14:73. [PMID: 24628802 PMCID: PMC3984694 DOI: 10.1186/1471-2431-14-73] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/25/2013] [Accepted: 03/06/2014] [Indexed: 11/15/2022] Open
Abstract
Background Idiopathic renal hypouricemia (iRHUC) is an autosomal recessive hereditary disorder, characterized by impaired tubular uric acid transport, re-absorption insufficiency and/or the acceleration of secretions. Some patients present with severe complications, such as exercise-induced acute kidney injury (EIAKI) and nephrolithiasis. Case presentation Herein, we report the case of a girl with severe iRHUC (serum urate 0.05 mg/dL, fractional excretion of uric acid 295.99%) associated with recurrent EIAKI, in whom the disease was caused by a homozygous mutation (g.68G > A in exon 3) in the SLC2A9 gene. Her family members (father, mother and brother) carried the same mutation but were heterozygous, without any signs of severe hypouricemia. Conclusions Our findings indicate that iRHUC is a rare disorder but that it should also be considered in patients with EIAKI, especially in those patients who manifest with moderately elevated or normal serum concentrations of uric acid during the acute phase of AKI. Mutational screening of the SLC2A9 gene is necessary for the diagnosis of iRHUC, and homozygous mutations of the SLC2A9 alleles can cause severe hypouricemia. Careful attention should be paid to any signs of hypouricemia during the recovery phase of AKI and long-term follow-up.
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Affiliation(s)
| | | | | | - Jianhua Mao
- Department of Nephrology, The Children's Hospital of Zhejiang University School of Medicine, Hangzhou 310003, Zhejiang Province, China.
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Yood RA, Ottery FD, Irish W, Wolfson M. Effect of pegloticase on renal function in patients with chronic kidney disease: a post hoc subgroup analysis of 2 randomized, placebo-controlled, phase 3 clinical trials. BMC Res Notes 2014; 7:54. [PMID: 24447425 PMCID: PMC3937145 DOI: 10.1186/1756-0500-7-54] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2013] [Accepted: 01/03/2014] [Indexed: 11/11/2022] Open
Abstract
BACKGROUND Pegloticase is approved in the US for treatment of refractory chronic gout. Since chronic kidney disease (CKD) is common in these patients, we conducted a post-hoc analysis of 2 replicate phase 3 trials and the subsequent open-label extension study to determine the effects of pegloticase on renal function in patients with CKD stages 3 and 4, as well as the effects of renal dysfunction on pegloticase efficacy and safety. FINDINGS Patients with renal insufficiency were randomized to pegloticase 8 mg every 2 weeks (n = 42), pegloticase 8 mg every 4 weeks (n = 41), or placebo (n = 20) for 6 months as defined by the study protocols. Renal function was assessed by estimated glomerular filtration rate (eGFR). All patients completing the randomized trials could participate in an open-label extension study for a further 2.5 years. Uric acid response, the primary end point in the trials, was plasma uric acid <6.0 mg/dl for 80% of months 3 and 6.Mean eGFR in both pegloticase dosing cohorts remained constant over the randomized treatment phase and long-term open-label extension study. The number of patients achieving uric acid response was similar across CKD stages (32% stage 1, 23% stage 2, 35% stage 3, and 39% stage 4, respectively, P = 0.3). There was no difference in the pegloticase safety profile based on CKD stage. CONCLUSIONS Pegloticase treatment does not impact eGFR in CKD patients and response to pegloticase is independent of CKD stage. TRIAL REGISTRATION Clinical trial identifier: NCT00325195.
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Affiliation(s)
- Robert A Yood
- Reliant Medical Group, 630 Plantation Street, Worcester, MA 01605, USA
- Reliant Medical Group, 425 North Lake Ave., Worcester, MA 01605, USA
| | - Faith D Ottery
- Savient Pharmaceuticals Inc., 400 Crossing Boulevard, 3rd Floor, Bridgewater, NJ 08807, USA
| | - William Irish
- CTI Clinical Trial and Consulting Services, 8380 Six Forks Road, Suite 203, Raleigh, NC 27615, USA
| | - Marsha Wolfson
- Savient Pharmaceuticals Inc., 400 Crossing Boulevard, 3rd Floor, Bridgewater, NJ 08807, USA
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Jeannin G, Chiarelli N, Gaggiotti M, Ritelli M, Maiorca P, Quinzani S, Verzeletti F, Possenti S, Colombi M, Cancarini G. Recurrent exercise-induced acute renal failure in a young Pakistani man with severe renal hypouricemia and SLC2A9 compound heterozygosity. BMC MEDICAL GENETICS 2014; 15:3. [PMID: 24397858 PMCID: PMC3890613 DOI: 10.1186/1471-2350-15-3] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/03/2013] [Accepted: 12/26/2013] [Indexed: 11/24/2022]
Abstract
Background Familial renal hypouricemia (RHUC) is a hereditary disease characterized by hypouricemia, high renal fractional excretion of uric acid (FE-UA) and can be complicated by acute kidney failure and nephrolithiasis. Loss-of-function mutations in the SLC22A12 gene cause renal hypouricemia type 1 (RHUC1), whereas renal hypouricemia type 2 (RHUC2) is caused by mutations in the SLC2A9 gene. Case presentation We describe a 24-year-old Pakistani man who was admitted twice to our hospital for severe exercise-induced acute renal failure (EIARF), abdominal pain and fever; he had very low serum UA levels (0.2 mg/dl the first time and 0.09 mg/dl the second time) and high FE-UA (200% and 732% respectively), suggestive of RHUC. Mutational analyses of both urate transporters revealed a new compound heterozygosity for two distinct missense mutations in the SLC2A9 gene: p.Arg380Trp, already identified in heterozygosity, and p.Gly216Arg, previously found in homozygosity or compound heterozygosity in some RHUC2 patients. Compared with previously reported patients harbouring these mutations, our proband showed the highest FE-UA levels, suggesting that the combination of p.Arg380Trp and p.Gly216Arg mutations most severely affects the renal handling of UA. Conclusions The clinical and molecular findings from this patient and a review of the literature provide new insights into the genotype-phenotype correlation of this disorder, supporting the evidence of an autosomal recessive inheritance pattern for RHUC2. Further investigations into the functional properties of GLUT9, URAT1 and other urate transporters are required to assess their potential research and clinical implications.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Marina Colombi
- Division of Biology and Genetics, Department of Molecular and Translational Medicine, University of Brescia, Viale Europa 11, 25123 Brescia, Italy.
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Kimura T, Takahashi M, Yan K, Sakurai H. Expression of SLC2A9 isoforms in the kidney and their localization in polarized epithelial cells. PLoS One 2014; 9:e84996. [PMID: 24409316 PMCID: PMC3883675 DOI: 10.1371/journal.pone.0084996] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2013] [Accepted: 11/27/2013] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Many genome-wide association studies pointed out that SLC2A9 gene, which encodes a voltage-driven urate transporter, SLC2A9/GLUT9 (a.k.a. URATv1), as one of the most influential genes for serum urate levels. SLC2A9 is reported to encode two splice variants: SLC2A9-S (512 amino acids) and SLC2A9-L (540 amino acids), only difference being at their N-termini. We investigated isoform-specific localization of SLC2A9 in the human kidney and role of N-terminal amino acids in differential sorting in vitro. METHODOLOGY/PRINCIPAL FINDINGS Isoform specific antibodies against SLC2A9 were developed and human kidney sections were stained. SLC2A9-S was expressed in the apical side of the collecting duct while SLC2A9-L was expressed in the basolateral side of the proximal tubule. GFP fused SLC2A9s were expressed in MDCK cells and intracellular localization was observed. SLC2A9-S was expressed at both apical and basolateral membranes, whereas SLC2A9-L was expressed only at the basolateral membrane. Although SLC2A9-L has a putative di-leucine motif at 33th and 34th leucine, deletion of the motif or replacement of leucine did not affect its subcellular localization. When up to 16 amino acids were removed from the N-terminal of SLC2A9-S or when up to 25 amino acids were removed from the N-terminal of SLC2A9-L, there was no change in their sorting. Deletion of 20 amino acids from SLC2A9-S was not expressed in the cell. More than 30 amino acids deletion from SLC2A9-L resulted in expression at both apical and basolateral membranes as well as in the lysosome. When amino acids from 25th and 30th were changed to alanine in SLC2A9-L, expression pattern was the same as wild-type. CONCLUSIONS/SIGNIFICANCE SLC2A9-L was expressed in the basolateral membrane of kidney proximal tubules in humans and this isoform is likely to responsible for urate reabsorption. N-terminal amino acids unique to each isoform played an important role in protein stability and trafficking.
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Affiliation(s)
- Toru Kimura
- Department of Pharmacology and Toxicology, Kyorin University School of Medicine, Mitaka, Tokyo, Japan
| | - Michi Takahashi
- Department of Pharmacology and Toxicology, Kyorin University School of Medicine, Mitaka, Tokyo, Japan
| | - Kunimasa Yan
- Department of Pediatrics, Kyorin University School of Medicine, Mitaka, Tokyo, Japan
| | - Hiroyuki Sakurai
- Department of Pharmacology and Toxicology, Kyorin University School of Medicine, Mitaka, Tokyo, Japan
- * E-mail:
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Novel allelic variants and evidence for a prevalent mutation in URAT1 causing renal hypouricemia: biochemical, genetics and functional analysis. Eur J Hum Genet 2013; 21:1067-73. [PMID: 23386035 DOI: 10.1038/ejhg.2013.3] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2012] [Revised: 12/14/2012] [Accepted: 01/02/2013] [Indexed: 12/31/2022] Open
Abstract
Renal hypouricemia (RHUC) is a heterogeneous inherited disorder characterized by impaired tubular uric acid (UA) transport with severe complications, such as acute kidney injury (AKI). Type 1 is caused by a loss-of-function mutation in the SLC22A12 gene (URAT1), type 2 in the SLC2A9 gene (GLUT9). This article describes three Czech families with RHUC type 1. The serum UA in the probands was 0.9, 1.1 and 0.5 mg/dl and expressed as an increase in the fractional excretion of UA (48, 43 and 39%). The sequencing analysis of SLC22A12 revealed three novel variants: p.G366R, p.T467M and a deletion p.L415_G417del. A detailed metabolic investigation in proband C for progressive visual failure supported suspicion of neuronal ceroid lipofuscinosis type 7 conditioned by the mutation in the MFSD8 gene. Functional studies showed significantly decreased urate uptake and a mis-localized URAT1 signal in p.G366R, p.L415_G417del and p.T467M. Furthermore, colocalization studies showed accumulation of URAT1 protein in the endoplasmic reticulum. The findings suggest that loss-of-function mutations cause RHUC via loss of UA absorption partly by protein misfolding. However, they do not necessarily lead to AKI and a possible genotype-phenotype correlation was not proposed. Furthermore, results confirm an uneven geographical and ethnic distribution of SLC22A12 variants; the p.L415_G417del mutation predominates in the Roma ethnic group in the Czech Republic.
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Novel URAT1 mutations caused acute renal failure after exercise in two Chinese families with renal hypouricemia. Gene 2013; 512:97-101. [DOI: 10.1016/j.gene.2012.09.115] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2012] [Revised: 09/18/2012] [Accepted: 09/30/2012] [Indexed: 11/22/2022]
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Stiburkova B, Bleyer AJ. Changes in serum urate and urate excretion with age. Adv Chronic Kidney Dis 2012; 19:372-6. [PMID: 23089271 DOI: 10.1053/j.ackd.2012.07.010] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2012] [Revised: 07/18/2012] [Accepted: 07/18/2012] [Indexed: 11/11/2022]
Abstract
A cross-sectional study was performed evaluating serum urate levels and fractional excretion of urate in a group of patients referred for screening for inherited metabolic disorders. From 2003 through 2010, serum urate, serum creatinine, urinary urate, and urinary creatinine levels were obtained as part of a research protocol to identify individuals with inherited metabolic disorders. These values were compared with individuals with uromodulin-associated kidney disease (UAKD). Laboratory studies were evaluated on 1274 individuals. The fractional excretion of urate was very high in infancy (27 ± 21% in males and 29 ± 25% in females). The high fractional excretion declined rapidly over the first several months of life, together with a decline in serum urate levels. The mean fractional excretion was approximately 8% during childhood. It then remained stable in females but decreased in males to 5.9 ± 5.6% in adolescence and 5.3 ± 3.8% in adulthood. Serum urate levels in childhood were influenced by age and kidney function but not gender. In adulthood, serum urate was influenced by age, gender, and estimated glomerular filtration rate. Although patients with UAKD had lower fractional excretions of urate than individuals with normal kidney function, there was considerable overlap.
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