痛风性关节炎动物模型的研究现状与展望

痛风是由于机体嘌呤代谢紊乱,导致血内尿酸增高和/或肾脏排泄尿酸减少,从而引起尿酸盐在组织沉积的疾病,目前尚未见在实验动物中复制出类似人类的痛风性关节炎模型。通过对目前国内外高尿酸血症及痛风模型复制的方法、机制和应用的研究,分析各自的特点及不足之处,并提出复制更加符合临床的高尿酸血症及痛风性关节炎动物模型的展望与设想。     

血清尿酸对心血管系统及神经退行性病变的影响

尿酸是人体嘌呤代谢的最终产物。高尿酸血症,即血清尿酸水平过高,是引发痛风的主要病因。越来越多的流行病学研究将高尿酸血症与心血管系统疾病和神经退行性病变紧密联系在一起。这些研究表明,炎性反应极有可能是高尿酸水平引发痛风的致病机制。同时,炎性反应与尿酸引起的心血管系统改变息息相关。尿酸钠晶体被认为通过Toll样受体家族诱发炎症反应诱导炎症的发生。此外,可溶性尿酸可以促进自由基的生成,起到促进氧化的作用。本综述总结了近期关于高尿酸血症和心血管系统疾病的流行病学研究,简要回顾了高尿酸血症在神经退行性病变中的作用,并描述了尿酸诱导的炎症产生机制。     

肠道菌群与高尿酸血症及痛风的相关性研究

高尿酸血症以及痛风的发病率持续升高,已经成为一个重大的公共卫生问题。肠道菌群的结构改变或失调可引起机体代谢紊乱,肠道微生态尤其与代谢性疾病的发生发展关系密切。目前研究发现高尿酸血症、痛风患者存在肠道菌群失调,降尿酸治疗后肠道菌群可发生相应改变,并且益生菌制剂具有降尿酸作用。本文概述高尿酸血症及痛风患者的肠道菌群特点,从高嘌呤及高果糖饮食对肠道菌群的影响、肠道参与嘌呤和尿酸的代谢、代谢性内毒素血症以及痛风相关炎症因子等方面探讨肠道菌群与高尿酸血症及痛风的关系,并展望肠道菌群可能成为未来诊治高尿酸血症以及痛风的一种新方法。     

抗高尿酸血症天然产物的药理研究进展

以中药为主的天然产物有效部位或成分通过降低黄嘌呤氧化酶或/和腺苷脱氨酶活性而减少尿酸生成,或者调控表达异常的尿酸盐转运体而促进尿酸的排泄,从而发挥抗高尿酸血症的药理作用。本文综述了抗高尿酸血症的天然产物相关实验研究,阐述了以中药为主的天然产物有效部位或成分治疗高尿酸血症的药理机制,以期为抗高尿酸血症的新药研究和痛风的中医药治疗提供参考。     

高尿酸血症与高血压病相关性的研究进展

尿酸是人体内嘌呤代谢的最终产物,当尿酸生成增多和/或排出减少时,均可引起血中尿酸盐浓度增高。当血尿酸水平男性大于7.0 mg/dl,女性大于6.0 mg/dl称为高尿酸血症。作为嘌呤代谢紊乱所致疾病,高尿酸血症以往仅侧重于痛风性关节炎、痛风石沉积和肾尿酸结石形成等的诊断与治疗。目前新近研究表明:高尿酸血症可能是高血压病的独立危险因素之一且尿酸水平增高通常早于高血压的发生与进展,干预尿酸水平有望成为高血压治疗的新靶点,随着高血压研究的全球化深入,对于尿酸及尿酸水平增高的流行病学、基础学与临床方面的研究也日益备受关注。基于此,本文对尿酸的合成与代谢;高尿酸血症成因及其与高血压的流行病学研究;高尿酸血症通过引发一氧化氮合成水平减低、血管平滑肌细胞生物学行为改变、机体炎症与氧化应激反应及肾素-血管紧张素系统激活等方面所致高血压的发病机制;高尿酸血症干预治疗对于高血压病的转归进行简要综述。     

非综合征型耳聋患者耳聋易感基因突变的检测分析

目的:探究非综合征型耳聋患者耳聋易感基因的携带情况及突变类型,为耳聋患者治疗或遗传咨询提供理论依据。方法:收集821例非综合征型耳聋患者的外周静脉血,提取基因组DNA后,进行4个常见耳聋易感基因GJB2、GJB3、SLC26A4和线粒体12S r RNA的9个突变热点筛查。结果:821例非综合征型耳聋患者中耳聋易感基因筛查阳性375例,阳性率为45.7%,不同性别之间阳性率无明差异(P=0.625)。375例存在耳聋易感基因突变的研究对象中,4个易感基因的9突变热点共检测出447例点突变,其中GJB2基因的有241例点突变(53.9%),以235 del C位点突变率最高;SLC26A4基因的有126例点突变(28.2%),以IVS7-2 AG位点突变为主;线粒体12S r RNA基因的有79例点突变(17.7%),绝大部分为1555 AG位点突变;而GJB3基因仅有1例点突变(0.2%)。375例存在耳聋易感基因突变的研究对象中,304例发生1种突变(81.1%),有70例发生2种突变(18.7%),仅有1例发生3种突变(0.3%)。结论:非综合征型耳聋患者中GJB2基因的235 del C位点以及SLC26A4基因的IVS7-2 AG位点突变率较高,常见耳聋易感基因筛查有助于非综合征型耳聋患者的诊断、干预及治疗。     

痛风病临床诊治及菲牛蛭生物疗法的研究进展

<正>痛风性关节炎是目前最常见的、疼痛最明显的骨关节疾病之一,其已从古代的"王者之病"演变为近代的"疾病之王者"。根据中华医学会风湿病学分会编写的《原发性痛风诊治指南(草案)》提供的资料表明,痛风分为原发性和继发性两大类。痛风痛是由于嘌呤代谢紊乱及(或)尿酸排泄减少所引起的一种晶体性关节炎,临床表现为高尿酸血症和尿尿酸盐结晶沉积所致的特征性急(慢)性关节炎、痛风石形成、     

RUNX3、SLC22A4和PPAR-γ的基因多态性与溃疡性结肠炎的关系

目的:探讨RUNX3(rs2236851,A→G)、SLC22A4(rs3792876,C→T)和PPAR-γ(rs3892175,A→G)基因的单核苷酸多态性(Single Nucleotide Polymorphism,SNP)与溃疡性结肠炎(ulcerative colitis,UC)遗传易感性之间的关系.方法:选取经过临床表现、内镜、病理等方法共同确诊的UC患者81例,健康对照组154例,提取患者的全血基因组DNA,用聚合酶链反应序列特异性引物(PCR-SSP)的方法,检测UC患者、SLC22A4和PPAR-γ的基因型分布,并与健康对照组进行比较.结果:RUNX3的rs2236851位点的多态性与UC紧密相关(P<0.05);而SLC22A4的rs3792876位点与PPAR-γ的rs3892175位点的基因型分布与对照组相比.其差异无统计学意义(P>0.05).结论:RUNX3的rs2236851位点的基因多态性为溃疡性结肠炎的遗传易感因素,而SLC22A4的rs3792876位点与PPAR-γ的rs3892175位点的基因多态性与溃疡性结肠炎的遗传易感性无关.     

高尿酸血症和痛风的表观遗传学研究进展

高尿酸血症和痛风是环境和遗传因素相互作用导致的复杂疾病。近年的研究发现,在复杂疾病中环境因素可通过影响表观遗传修饰的改变,在不改变基因组序列的情况下对基因表达进行调控,从而直接或间接导致疾病的发生发展。表观遗传修饰改变的可逆性和可控性也为疾病早期的预防和治疗提供了新策略。本文对表观遗传学在高尿酸血症和痛风中的研究进展进行综述,以期为高尿酸血症和痛风的诊断与治疗提供借鉴和参考。     

抗痛风中药药效的研究进展

正痛风是一种慢性疾病,是由于人体内嘌呤代谢紊乱,导致血尿酸浓度超过正常上限,尿酸排泄减少,导致尿血结晶过多沉淀而引起[1]。其主要由高尿酸血症和尿酸盐沉积引起反复发作的急、慢性关节炎以及软组织损伤,痛风性肾病,关节畸形等[2]。在临床治疗上,西医常用的药物有秋水仙碱、非甾体类抗炎药、糖皮质激素和促肾上腺皮质激素和IL-1抑制剂等,由于这些药物的不良反应多,临床使用受到限     

Pathogenic GLUT9 Mutations Causing Renal Hypouricemia Type 2 (RHUC2)

Renal hypouricemia (MIM 220150) is an inherited disorder characterized by low serum uric acid levels and has severe complications such as exercise-induced acute renal failure and urolithiasis. We have previously reported that URAT1/SLC22A12 encodes a renal urate-anion exchanger and that its mutations cause renal hypouricemia type 1 (RHUC1). With the large health-examination database of the Japan Maritime Self-Defense Force, we found two missense mutations (R198C and R380W) of GLUT9/SLC2A9 in hypouricemia patients. R198C and R380W occur in highly conserved amino acid motifs in the “sugar transport proteins signatures” that are observed in GLUT family transporters. The corresponding mutations in GLUT1 (R153C and R333W) are known to cause GLUT1 deficiency syndrome because arginine residues in this motif are reportedly important as the determinants of the membrane topology of human GLUT1. Therefore, on the basis of membrane topology, the same may be true of GLUT9. GLUT9 mutants showed markedly reduced urate transport in oocyte expression studies, which would be the result of the loss of positive charges in those conserved amino acid motifs. Together with previous reports on GLUT9 localization, our findings suggest that these GLUT9 mutations cause renal hypouricemia type 2 (RHUC2) by their decreased urate reabsorption on both sides of the renal proximal tubule cells. However, a previously reported GLUT9 mutation, P412R, was unlikely to be pathogenic. These findings also enable us to propose a physiological model of the renal urate reabsorption via GLUT9 and URAT1 and can lead to a promising therapeutic target for gout and related cardiovascular diseases.     

Pathogenic GLUT9 mutations causing renal hypouricemia type 2 (RHUC2)

Renal hypouricemia (MIM 220150) is an inherited disorder characterized by low serum uric acid levels and has severe complications such as exercise-induced acute renal failure and urolithiasis. We have previously reported that URAT1/SLC22A12 encodes a renal urate-anion exchanger and that its mutations cause renal hypouricemia type 1 (RHUC1). With the large health-examination database of the Japan Maritime Self-Defense Force, we found two missense mutations (R198C and R380W) of GLUT9/SLC2A9 in hypouricemia patients. R198C and R380W occur in highly conserved amino acid motifs in the "sugar transport proteins signatures" that are observed in GLUT family transporters. The corresponding mutations in GLUT1 (R153C and R333W) are known to cause GLUT1 deficiency syndrome because arginine residues in this motif are reportedly important as the determinants of the membrane topology of human GLUT1. Therefore, on the basis of membrane topology, the same may be true of GLUT9. GLUT9 mutants showed markedly reduced urate transport in oocyte expression studies, which would be the result of the loss of positive charges in those conserved amino acid motifs. Together with previous reports on GLUT9 localization, our findings suggest that these GLUT9 mutations cause renal hypouricemia type 2 (RHUC2) by their decreased urate reabsorption on both sides of the renal proximal tubule cells. However, a previously reported GLUT9 mutation, P412R, was unlikely to be pathogenic. These findings also enable us to propose a physiological model of the renal urate reabsorption via GLUT9 and URAT1 and can lead to a promising therapeutic target for gout and related cardiovascular diseases.     

Association between intronic SNP in urate-anion exchanger gene, SLC22A12, and serum uric acid levels in Japanese

Serum uric acid levels are maintained by urate synthesis and excretion. URAT1 (coded by SLC22CA12) was recently proposed to be the major absorptive urate transporter protein in the kidney regulating blood urate levels. Because genetic background is known to affect serum urate levels, we hypothesized that genetic variations in SLC22A12 may predispose humans to hyperuricemia and gout. We investigated rs893006 polymorphism (GG, GT and TT) in SLC22A12 in a total of 326 Japanese subjects. Differences in clinical characteristics among the genotype groups were tested by the analysis of variance (ANOVA). In male subjects, mean serum uric acid levels were significantly different among the three genotypes. Levels in the GG genotype subjects were the highest, followed by those with the GT and TT genotypes. However, no differences between the groups were seen in the distributions of creatinine, Fasting plasma glucose (FPG), HbA(1c), total cholesterol, triglyceride, HDL cholesterol levels or BMI. A single nucleotide polymorphism (SNP) in the urate transporter gene SLC22CA12 was found to be associated with elevated serum uric acid levels among Japanese subjects. This SNP may be an independent genetic marker for predicting hyperuricemia.     

Human Sodium Phosphate Transporter 4 (hNPT4/SLC17A3) as a Common Renal Secretory Pathway for Drugs and Urate

The evolutionary loss of hepatic urate oxidase (uricase) has resulted in humans with elevated serum uric acid (urate). Uricase loss may have been beneficial to early primate survival. However, an elevated serum urate has predisposed man to hyperuricemia, a metabolic disturbance leading to gout, hypertension, and various cardiovascular diseases. Human serum urate levels are largely determined by urate reabsorption and secretion in the kidney. Renal urate reabsorption is controlled via two proximal tubular urate transporters: apical URAT1 (SLC22A12) and basolateral URATv1/GLUT9 (SLC2A9). In contrast, the molecular mechanism(s) for renal urate secretion remain unknown. In this report, we demonstrate that an orphan transporter hNPT4 (human sodium phosphate transporter 4; SLC17A3) was a multispecific organic anion efflux transporter expressed in the kidneys and liver. hNPT4 was localized at the apical side of renal tubules and functioned as a voltage-driven urate transporter. Furthermore, loop diuretics, such as furosemide and bumetanide, substantially interacted with hNPT4. Thus, this protein is likely to act as a common secretion route for both drugs and may play an important role in diuretics-induced hyperuricemia. The in vivo role of hNPT4 was suggested by two hyperuricemia patients with missense mutations in SLC17A3. These mutated versions of hNPT4 exhibited reduced urate efflux when they were expressed in Xenopus oocytes. Our findings will complete a model of urate secretion in the renal tubular cell, where intracellular urate taken up via OAT1 and/or OAT3 from the blood exits from the cell into the lumen via hNPT4.     

Mutations in Glucose Transporter 9 Gene SLC2A9 Cause Renal Hypouricemia

Renal hypouricemia is an inherited disorder characterized by impaired renal urate (uric acid) reabsorption and subsequent low serum urate levels, with severe complications such as exercise-induced acute renal failure and nephrolithiasis. We previously identified SLC22A12, also known as URAT1, as a causative gene of renal hypouricemia. However, hypouricemic patients without URAT1 mutations, as well as genome-wide association studies between urate and SLC2A9 (also called GLUT9), imply that GLUT9 could be another causative gene of renal hypouricemia. With a large human database, we identified two loss-of-function heterozygous mutations in GLUT9, which occur in the highly conserved “sugar transport proteins signatures 1/2.” Both mutations result in loss of positive charges, one of which is reported to be an important membrane topology determinant. The oocyte expression study revealed that both GLUT9 isoforms showed high urate transport activities, whereas the mutated GLUT9 isoforms markedly reduced them. Our findings, together with previous reports on GLUT9 localization, suggest that these GLUT9 mutations cause renal hypouricemia by their decreased urate reabsorption on both sides of the renal proximal tubules. These findings also enable us to propose a physiological model of the renal urate reabsorption in which GLUT9 regulates serum urate levels in humans and can be a promising therapeutic target for gout and related cardiovascular diseases.     

Diagnostic Tests for Primary Renal Hypouricemia

Primary renal hypouricemia is a genetic disorder characterized by defective renal uric acid (UA) reabsorption with complications such as nephrolithiasis and exercise-induced acute renal failure. The known causes are: defects in the SLC22A12 gene, encoding the human urate transporter 1 (hURAT1), and also impairment of voltage urate transporter (URATv1), encoded by SLC2A9 (GLUT9) gene. Diagnosis is based on hypouricemia (<119 μmol/L) and increased fractional excretion of UA (>10%). To date, the cases with mutations in hURAT1 gene have been reported in East Asia only. More than 100 Japanese patients have been described. Hypouricemia is sometimes overlooked; therefore, we have set up the flowchart for this disorder. The patients were selected for molecular analysis from 620 Czech hypouricemic patients. Secondary causes of hyperuricosuric hypouricemia were excluded. The estimations of (1) serum UA, (2) excretion fraction of UA, and (3) analysis of hURAT1 and URATv1 genes follow. Three transitions and one deletion (four times) in SLC22A12 gene and one nucleotide insertion in SLC2A9 gene in seven Czech patients were found. Three patients had acute renal failure and urate nephrolithiasis. In addition, five nonsynonymous sequence variants and three nonsynonymous sequence variants in SLC2A9 gene were found in two UK patients suffering from acute renal failure. Our finding of the defects in SLC22A12 and SLC2A9 genes gives further evidence of the causative genes of primary renal hypouricemia and supports their important role in regulation of serum urate levels in humans.     

Diagnostic tests for primary renal hypouricemia

Primary renal hypouricemia is a genetic disorder characterized by defective renal uric acid (UA) reabsorption with complications such as nephrolithiasis and exercise-induced acute renal failure. The known causes are: defects in the SLC22A12 gene, encoding the human urate transporter 1 (hURAT1), and also impairment of voltage urate transporter (URATv1), encoded by SLC2A9 (GLUT9) gene. Diagnosis is based on hypouricemia (<119 μmol/L) and increased fractional excretion of UA (>10%). To date, the cases with mutations in hURAT1 gene have been reported in East Asia only. More than 100 Japanese patients have been described. Hypouricemia is sometimes overlooked; therefore, we have set up the flowchart for this disorder. The patients were selected for molecular analysis from 620 Czech hypouricemic patients. Secondary causes of hyperuricosuric hypouricemia were excluded. The estimations of (1) serum UA, (2) excretion fraction of UA, and (3) analysis of hURAT1 and URATv1 genes follow. Three transitions and one deletion (four times) in SLC22A12 gene and one nucleotide insertion in SLC2A9 gene in seven Czech patients were found. Three patients had acute renal failure and urate nephrolithiasis. In addition, five nonsynonymous sequence variants and three nonsynonymous sequence variants in SLC2A9 gene were found in two UK patients suffering from acute renal failure. Our finding of the defects in SLC22A12 and SLC2A9 genes gives further evidence of the causative genes of primary renal hypouricemia and supports their important role in regulation of serum urate levels in humans.     

Common Polymorphisms Influencing Serum Uric Acid Levels Contribute to Susceptibility to Gout,but Not to Coronary Artery Disease

Background

Recently, a large meta-analysis including over 28,000 participants identified nine different loci with association to serum uric acid (UA) levels. Since elevated serum UA levels potentially cause gout and are a possible risk factor for coronary artery disease (CAD) and myocardial infarction (MI), we performed two large case-control association analyses with participants from the German MI Family Study. In the first study, we assessed the association of the qualitative trait gout and ten single nucleotide polymorphisms (SNP) markers that showed association to UA serum levels. In the second study, the same genetic polymorphisms were analyzed for association with CAD.

Methods and Findings

A total of 683 patients suffering from gout and 1,563 healthy controls from the German MI Family Study were genotyped. Nine SNPs were identified from a recently performed genome-wide meta-analysis on serum UA levels (rs12129861, rs780094, rs734553, rs2231142, rs742132, rs1183201, rs12356193, rs17300741 and rs505802). Additionally, the marker rs6855911 was included which has been associated with gout in our cohort in a previous study. SNPs rs734553 and rs6855911, located in SLC2A9, and SNP rs2231142, known to be a missense polymorphism in ABCG2, were associated with gout (p = 5.6*10⁻⁷, p = 1.1*10⁻⁷, and p = 1.3*10⁻³, respectively). Other SNPs in the genes PDZK1, GCKR, LRRC16A, SLC17A1-SLC17A3, SLC16A9, SLC22A11 and SLC22A12 failed the significance level. None of the ten markers were associated with risk to CAD in our study sample of 1,473 CAD cases and 1,241 CAD-free controls.

Conclusion

SNP markers in SLC2A9 and ABCG2 genes were found to be strongly associated with the phenotype gout. However, not all SNP markers influencing serum UA levels were also directly associated with the clinical manifestation of gout in our study sample. In addition, none of these SNPs showed association with the risk to CAD in the German MI Family Study.     

Apical voltage-driven urate efflux transporter NPT4 in renal proximal tubule

Uric acid (urate) is the end product of purine metabolism in humans. Human kidneys reabsorb a large proportion of filtered urate. This extensive renal reabsorption, together with the fact that humans do not possess uricase that catalyzes the biotransformation of urate into allantoin, results in a higher plasma urate concentration in humans compared to other mammals. A major determinant of plasma urate concentration is renal excretion as a function of the balance between reabsorption and secretion. We previously identified that renal urate absorption in proximal tubular epithelial cells occurs mainly via apical urate/anion exchanger, URAT1/SLC22A12, and by facilitated diffusion along the trans-membrane potential gradient by the basolateral voltage-driven urate efflux transporter, URATv1/SLC2A9/GLUT9. In contrast, the molecular mechanism by which renal urate secretion occurs remains elusive. Recently, we reported a newly characterized human voltage-driven drug efflux transporter, hNPT4/SLC17A3, which functions as a urate exit pathway located at the apical side of renal proximal tubules. This transporter protein has been hypothesized to play an important role with regard to net urate efflux. An in vivo role of hNPT4 is supported by the fact that missense mutations in SLC17A3 present in hyperuricemia patients with urate underexcretion abolished urate efflux capacity in vitro. Herein, we report data demonstrating that loop diuretics and thiazide diuretics substantially interact with hNPT4. These data provide molecular evidence for loop and thiazide-diuretics-induced hyperuricemia. Thus, we propose that hNPT4 is an important transepithelial proximal tubular transporter that transports diuretic drugs and operates functionally with basolateral organic anion transporters 1/3 (OAT1/OAT3).     

Apical Voltage-Driven Urate Efflux Transporter NPT4 in Renal Proximal Tubule

Uric acid (urate) is the end product of purine metabolism in humans. Human kidneys reabsorb a large proportion of filtered urate. This extensive renal reabsorption, together with the fact that humans do not possess uricase that catalyzes the biotransformation of urate into allantoin, results in a higher plasma urate concentration in humans compared to other mammals. A major determinant of plasma urate concentration is renal excretion as a function of the balance between reabsorption and secretion. We previously identified that renal urate absorption in proximal tubular epithelial cells occurs mainly via apical urate/anion exchanger, URAT1/SLC22A12, and by facilitated diffusion along the trans-membrane potential gradient by the basolateral voltage-driven urate efflux transporter, URATv1/SLC2A9/GLUT9. In contrast, the molecular mechanism by which renal urate secretion occurs remains elusive. Recently, we reported a newly characterized human voltage-driven drug efflux transporter, hNPT4/SLC17A3, which functions as a urate exit pathway located at the apical side of renal proximal tubules. This transporter protein has been hypothesized to play an important role with regard to net urate efflux. An in vivo role of hNPT4 is supported by the fact that missense mutations in SLC17A3 present in hyperuricemia patients with urate underexcretion abolished urate efflux capacity in vitro. Herein, we report data demonstrating that loop diuretics and thiazide diuretics substantially interact with hNPT4. These data provide molecular evidence for loop and thiazide-diuretics-induced hyperuricemia. Thus, we propose that hNPT4 is an important transepithelial proximal tubular transporter that transports diuretic drugs and operates functionally with basolateral organic anion transporters 1/3 (OAT1/OAT3).