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Pathophysiological and genetic factors affecting serum uric acid level.
Hasíková, Lenka ; Závada, Jakub (advisor) ; Hrnčíř, Zbyněk (referee) ; Horák, Pavel (referee)
Introduction: Serum uric acid level (SUA) depends on the balance between its production and excretion. SUA is associated with several transmembrane proteins responsible for reabsorption (mainly URAT1 and GLUT9) and secretion (ABCG2) on the apical and basolateral membranes of the proximal tubules in the kidney, and in the case of ABCG2, it also correlates with its significant excretion through the gastrointestinal tract. Gout is a metabolic disease caused by the deposition of urate crystals in the joints and tissues. Chronic hyperuricemia is a primary risk factor for the development of gout; however, gout patients usually have a lower SUA during an acute gout attack than in the intercritical periods. The exact mechanism of this phenomenon is unknown. It has been speculated that the systemic inflammatory response can explain this discrepancy. The aim of the study is to determine whether treatment with specific inhibitors of the proinflammatory cytokine TNF (TNFi) affects SUA in patients with systemic rheumatic disease (SRD), and whether changes in SUA correlate with changes in selected proinflammatory cytokines or with the biomarker of oxidative stress, allantoin. Another aim is to determine the frequency and effect of allelic variants in the ABCG2 urate transporter gene in patients with primary...
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Identification of basolateral localization motifs of the urate transporter GLUT9 using functional studies.
Pácalová, Eliška ; Krylov, Vladimír (advisor) ; Pavelcová, Kateřina (referee)
The GLUT9 transporter, coded by the SLC2A9 gene, is one of the key proteins enabling the trasnfer of uric acid across the membrane in epithelial cells of the proximal tubule. In humans, this protein is naturally expressed in two variants: long (GLUT9L) and short (GLUT9S), which differ from one another by their N-terminus sequence. Each of these isoforms is localized on a different pole of the epithelial cell. The signal sequence/motif responsible for this difference is presumed to be located in the aforementioned N-terminus domain. Numerous allelic variants influencing the transport properties of the protein have also been described. The first aim of this thesis is to verify the influence of a newly discovered variant, characterized by substituting of valine for leucine in the 114th position (V114L, in the short form its corresponding variant V85L) on the ability to transport uric acid. Second aim is to verify the influence of mutations in selected motifs, which could be responsible for the localization of the protein, thus also changing its transport properties. Two dileucine motifs 12LGL14 and 33LL34 and one tyrosine motif 84YIKA87 were tested. Functional studies using 14 C radiolabeled urate demonstrated significant decrease of transport ability for the V114L/V85L allelic variant in both...
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The effect of urate transporter polymorphisms on uric acid excretion
Mančíková, Andrea ; Krylov, Vladimír (advisor) ; Novotný, Jiří (referee) ; Ježek, Petr (referee)
Uric acid excretion disorders are the most common cause of primary dysuricemia. The kidneys eliminate two-thirds of uric acid production and the other third is eliminated in the gastrointestinal tract. Renal reabsorption and secretion occur through the polarised epithelial cells in the proximal tubules. Uric acid transporters are expressed on these cell membranes. Reabsorption deficiency leads to hypouricemia and elevated fraction excretion associated with urolithiasis, nephrolithiasis or acute renal injury. Decreased uric acid secretion in the kidneys and small intestine leads to hyperuricemia, which develops into gout in 10% of individuals. Genome wide association studies detected a strong effect of SLC22A12 (URAT1), SLC2A9 (GLUT9) reabsorbing transporters and ABCG2 (ABCG2) secreting transporter on uric acid serum concentration variability. This thesis aimed to map out urate transporter allelic variants in a cohort of primary dysuricemia patients and identification of the variants causing defective uric acid excretion. Six non-synonymous variants were described in SLC22A12 (URAT1) and SLC2A9 (GLUT9) genes in hypouricemic individuals, which had not been identified previously in any population studies. Significant decreases in uric acid transport have been demonstrated experimentally in vitro,...
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Pathophysiology of urate transporters in primary gout
Pavelcová, Kateřina ; Stibůrková, Blanka (advisor) ; Doležel, Zdeněk (referee) ; Hrnčíř, Zbyněk (referee)
There are localised proteins (so-called urate transporters) in the renal proximal tubules and in the intestine, which excrete and reabsorb uric acid. Polymorphisms in the genes coding these proteins can result in the disruption of the transport function and development of hyperuricemia and gout. However the serum level of uric acid is also determined by other factors which include the intake of exogenous purines in food, synthesis of endogenous purines and degradation of nucleic acids, but also certain conditions. In 250 patients with primary hyperuricemia and gout we used Sanger sequencing to analyse the exons and adjacent intron regions in ten genes coding urate transporters: ABCG2, ABCC4, SLC2A9, SLC22A12, SLC22A11, SLC22A13, SLC17A1, SLC17A3, SLC22A6 and SLC22A8. We examined a possible connection between the identified genetic variants and primary hyperuricemia and gout based on a comparison of allele frequencies with the European population, according to topological models, according to programs predicting the functional impacts of variants and searches in specialised literature. We also took into account the conclusions of functional studies analysing the impact of nonsynonymous variants in the ABCG2 and SLC2A9 genes. We also focused on the effect of the concomitant occurrence of several...
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The effect of urate transporter polymorphisms on uric acid excretion
Mančíková, Andrea
Uric acid excretion disorders are the most common cause of primary dysuricemia. The kidneys eliminate two-thirds of uric acid production and the other third is eliminated in the gastrointestinal tract. Renal reabsorption and secretion occur through the polarised epithelial cells in the proximal tubules. Uric acid transporters are expressed on these cell membranes. Reabsorption deficiency leads to hypouricemia and elevated fraction excretion associated with urolithiasis, nephrolithiasis or acute renal injury. Decreased uric acid secretion in the kidneys and small intestine leads to hyperuricemia, which develops into gout in 10% of individuals. Genome wide association studies detected a strong effect of SLC22A12 (URAT1), SLC2A9 (GLUT9) reabsorbing transporters and ABCG2 (ABCG2) secreting transporter on uric acid serum concentration variability. This thesis aimed to map out urate transporter allelic variants in a cohort of primary dysuricemia patients and identification of the variants causing defective uric acid excretion. Six non-synonymous variants were described in SLC22A12 (URAT1) and SLC2A9 (GLUT9) genes in hypouricemic individuals, which had not been identified previously in any population studies. Significant decreases in uric acid transport have been demonstrated experimentally in vitro,...
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The effect of urate transporter polymorphisms on uric acid excretion
Mančíková, Andrea ; Krylov, Vladimír (advisor) ; Novotný, Jiří (referee) ; Ježek, Petr (referee)
Uric acid excretion disorders are the most common cause of primary dysuricemia. The kidneys eliminate two-thirds of uric acid production and the other third is eliminated in the gastrointestinal tract. Renal reabsorption and secretion occur through the polarised epithelial cells in the proximal tubules. Uric acid transporters are expressed on these cell membranes. Reabsorption deficiency leads to hypouricemia and elevated fraction excretion associated with urolithiasis, nephrolithiasis or acute renal injury. Decreased uric acid secretion in the kidneys and small intestine leads to hyperuricemia, which develops into gout in 10% of individuals. Genome wide association studies detected a strong effect of SLC22A12 (URAT1), SLC2A9 (GLUT9) reabsorbing transporters and ABCG2 (ABCG2) secreting transporter on uric acid serum concentration variability. This thesis aimed to map out urate transporter allelic variants in a cohort of primary dysuricemia patients and identification of the variants causing defective uric acid excretion. Six non-synonymous variants were described in SLC22A12 (URAT1) and SLC2A9 (GLUT9) genes in hypouricemic individuals, which had not been identified previously in any population studies. Significant decreases in uric acid transport have been demonstrated experimentally in vitro,...
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