¿Debemos manejar la hiperuricemia asintomática para proteger al riñón?

Contexto: el ácido úrico es el producto final de la degradación de las purinas en los primates, en condiciones normales es un agente antioxidante endógeno y participa en varias vías fisiológicas, sin embargo, cuando los niveles séricos de urato se incrementan, estos participan en el desarrollo de diversas enfermedades. Desde el siglo XIX se conoce de la asociación entre hiperuricemia y daño renal, aunque ninguna guía de manejo recomienda el uso de fármacos hipouricemiantes en pacientes asintomáticos, en algunos casos especiales, el manejo farmacológico beneficiará a pacientes con hiperuricemia, brindando protección al riñón y disminuyendo el riesgo de desarrollar enfermedad renal terminal. Objetivo: describir la relación entre hiperuricemia y daño renal, y analizar los casos en los que el manejo de esta condición con medicamentos resultará en un beneficio para el riñón de los pacientes. Metodología: revisión de la literatura sobre la participación de la hiperuricemia en el daño renal y análisis de los artículos revisados. Resultados: el manejo de la hiperuricemia asintomática puede proteger el riñón en algunas situaciones específicas. Conclusiones: hay situaciones específicas para la disminución de los niveles séricos de ácido úrico.

Background: Uric acid is the end product of purine degradation in primates, under normal conditions it is an endogenous antioxidant agent and participates in several physiological pathways. However, when serum urate levels are increased, they participate in the development of various diseases. Since the nineteenth century, the association between hyperuricemia and kidney damage has been known. Although no management guideline recommends the use of hypouricemic drugs in asymptomatic patients, in some special cases pharmacological management will benefit patients with hyperuricemia, providing protection to the kidney and decreasing the risk of developing end-stage renal disease. Purpose: To describe the relationship between hyperuricemia and kidney damage, and to analyze the cases in which the management of this condition with medications will result in a benefit for the kidney of patients. Methodology: Review of the literature on the involvement of hyperuricemia in kidney damage, analysis of the reviewed articles. Results: Management of asymptomatic hyperuricemia may protect the kidney in some specific situations. Conclusions: There are specific situations for the decrease of serum uric acid levels.

Xanthine Oxidase Drives Hemolysis and Vascular Malfunction in Sickle Cell Disease.

OBJECTIVE: Chronic hemolysis is a hallmark of sickle cell disease (SCD) and a driver of vasculopathy; however, the mechanisms contributing to hemolysis remain incompletely understood. Although XO (xanthine oxidase) activity has been shown to be elevated in SCD, its role remains unknown. XO binds endothelium and generates oxidants as a byproduct of hypoxanthine and xanthine catabolism. We hypothesized that XO inhibition decreases oxidant production leading to less hemolysis. Approach and Results: Wild-type mice were bone marrow transplanted with control (AA) or sickle (SS) Townes bone marrow. After 12 weeks, mice were treated with 10 mg/kg per day of febuxostat (Uloric), Food and Drug Administration-approved XO inhibitor, for 10 weeks. Hematologic analysis demonstrated increased hematocrit, cellular hemoglobin, and red blood cells, with no change in reticulocyte percentage. Significant decreases in cell-free hemoglobin and increases in haptoglobin suggest XO inhibition decreased hemolysis. Myographic studies demonstrated improved pulmonary vascular dilation and blunted constriction, indicating improved pulmonary vasoreactivity, whereas pulmonary pressure and cardiac function were unaffected. The role of hepatic XO in SCD was evaluated by bone marrow transplanting hepatocyte-specific XO knockout mice with SS Townes bone marrow. However, hepatocyte-specific XO knockout, which results in >50% diminution in circulating XO, did not affect hemolysis levels or vascular function, suggesting hepatocyte-derived elevation of circulating XO is not the driver of hemolysis in SCD. CONCLUSIONS: Ten weeks of febuxostat treatment significantly decreased hemolysis and improved pulmonary vasoreactivity in a mouse model of SCD. Although hepatic XO accounts for >50% of circulating XO, it is not the source of XO driving hemolysis in SCD.

Effect of febuxostat on renal function in patients from South China with CKD3 diabetic nephropathy / Efeito do febuxostat na função renal em pacientes do sul da China com nefropatia diabética com DRC3

ABSTRACT Objective: To investigate the efficacy and safety of febuxostat on renal function in CKD stage 3 diabetic nephropathy patients. Methods: Patients in our hospital with chronic kidney disease (CKD) stage 3 diabetic nephropathy (DN) complicated by high serum uric acid (360 µmol/L) were recruited. Patients were then divided into treatment group and control group according to the random number table method. All the patients received low purine diet, renin-angiotensin-aldosterone system (RAAS) inhibitors, and adequate routine hypoglycemic treatment. Febuxostat was employed only in the treatment group. The levels of blood uric acid (sUA), serum creatinine (Scr), cystatin C (cys-c), eGFR, 24-hour urine protein quantification, albuminuria, and creatinine ratio (ACR) were evaluated in all patients before and after treatment at 4, 8, 12, and 24 week. Results: No difference was found before treatment between the two groups. After treatment at 4, 8, 12, and 24 week, the levels of sUA, SCr, cys-c, and eGFR between the two groups were significant different (P<0.05). There was no difference in 24-hour urine protein quantification, albuminuria, and creatinine ratio between two groups before treatment, and significant differences were observed after treatment. Fifty percent of patients from the treatment group achieved the treatment goal with 20 mg febuxostat at 4 weeks. Tubular markers were also decreased with the treatment. Conclusions: Febuxostat can reduce uric acid and improve renal function effectively in patients with CKD stage 3 diabetic nephropathy, while being well tolerated. However, the conclusion is still uncertain due to the short term of the study.

RESUMO Objetivo: Investigar a eficácia e segurança do febuxostat na função renal em pacientes com DRC estágio 3, com nefropatia diabética. Métodos: Foram recrutados pacientes em nosso hospital com nefropatia diabética (DN) estágio 3 de doença renal crônica (DRC) complicada por ácido úrico sérico alto (360 µmol/L). Os pacientes foram então divididos em grupo de tratamento e grupo controle, de acordo com o método da tabela de números aleatórios. Todos os pacientes receberam dieta pobre em purinas, inibidores do sistema renina-angiotensina-aldosterona (RAAS) e tratamento hipoglicêmico de rotina. O Febuxostat foi empregado apenas no grupo de tratamento. Os níveis de ácido úrico no sangue (AIU), creatinina sérica (Scr), cistatina C (cys-c), TFGe, quantificação de proteínas na urina em 24 horas, razão albumina e creatinina (ACR) foram avaliados em todos os pacientes antes e após o tratamento às 4, 8, 12 e 24 semanas. Resultados: Nenhuma diferença foi encontrada antes do tratamento entre os dois grupos. Após o tratamento nas 4, 8, 12 e 24 semanas, os níveis de sUA, SCr, cys-c e TFGe entre os dois grupos foram significativamente diferentes (P <0,05). Não houve diferença na quantificação de proteínas na urina em 24 horas, albuminúria e razão de creatinina entre dois grupos antes do tratamento, e diferenças significativas foram observadas após o tratamento. Cinquenta por cento dos pacientes do grupo de tratamento atingiram a meta de tratamento com 20 mg de febuxostat em 4 semanas. Marcadores tubulares também foram reduzidos com o tratamento. Conclusões: O Febuxostat pode reduzir o ácido úrico e melhorar a função renal efetivamente em pacientes com nefropatia diabética estágio com DRC no estágio 3, sendo bem tolerado. No entanto, a conclusão ainda é incerta devido ao curto prazo do estudo.

Xanthine oxidase inhibitors and sepsis.

Xanthine oxidase activation occurs in sepsis and results in the generation of uric acid (UrAc) and reactive oxygen species (ROS). We aimed to evaluate the effect of xanthine oxidase inhibitors (XOis) in rats stimulated with lipopolysaccharide (LPS). LPS (10 mg/kg) was administered intraperitoneally (i.p.) immediately after allopurinol (Alo, 2 mg/kg) or febuxostat (Feb, 1 mg/kg) every 24 h for 3 days. To increase UrAc levels, oxonic acid (Oxo) was administered by gavage (750 mg/kg per day) for 5 days. Animals were divided into the following 10 groups (n = 6 each): (1) Control, (2) Alo, (3) Feb, (4) LPS, (5) LPSAlo, (6) LPSFeb, (7) Oxo, (8) OxoLPS, (9) OxoLPSAlo, and (10) OxoLPSFeb. Feb with or without Oxo did not aggravate sepsis. LPS administration (with or without Oxo) significantly decreased the creatinine clearance (ClCr) in LPSAlo (60%, P < 0.01) versus LPS (44%, P < 0.05) and LPSFeb (35%, P < 0.05). Furthermore, a significant increase in mortality was observed with LPSAlo (28/34, 82%) compared to LPS treatment alone (10/16, 63%) and LPSFeb (11/17, 65%, P < 0.05). In addition, increased levels of thiobarbituric acid reactive substances (TBARS), tumor necrosis factor (TNF)-α, interleukin (IL)-6, and IL-10 were observed at 72 h compared to the groups that received LPS and LPSFeb with or without Oxo. In this study, coadministration of Alo in LPS-induced experimental sepsis aggravated septic shock, leading to mortality, renal function impairment, and high ROS and proinflammatory IL levels. In contrast, administration of Feb did not potentiate sepsis, probably because it did not interfere with other metabolic events.

Management of Gout and Hyperuricemia in CKD.

Hyperuricemia and gout, the clinical manifestation of monosodium urate crystal deposition, are common in patients with chronic kidney disease (CKD). Although the presence of CKD poses additional challenges in gout management, effective urate lowering is possible for most patients with CKD. Initial doses of urate-lowering therapy are lower than in the non-CKD population, whereas incremental dose escalation is guided by regular monitoring of serum urate levels to reach the target level of <6mg/dL (or <5mg/dL for patients with tophi). Management of gout flares with presently available agents can be more challenging due to potential nephrotoxicity and/or contraindications in the setting of other common comorbid conditions. At present, asymptomatic hyperuricemia is not an indication for urate-lowering therapy, though emerging data may support a potential renoprotective effect.

Gota: nuevos conceptos patogénicos y nuevos agentes terapéuticos / Gout: New pathogenic concepts and new therapeutic agents

La gota es una artropatía inflamatoria caracterizada por brotes autolimitados de artritis con marcado dolor como consecuencia de los depósitos de cristales de urato monosódico (UMS) en los tejidos articulares y periarticulares. En algunas ocasiones se puede desarrollar una gota tofácea crónica que puede conducir a una importante destrucción articular y por ende una marcada discapacidad. La gota es la causa más común de artritis inflamatoria entre hombres y mujeres post-menopáusicas. Durante los últimos años se han dado pasos importantes en la patogenia de la gota, tanto a nivel de estudios genéticos, como la participación del inflamosoma, comportándose la gota como una enfermedad auto-inflamatoria. Adicionalmente, se han desarrollado nuevos agentes farmacológicos incluyendo anti-IL1 (anakinra, rinolacept y canakinumab) e inhibidores de xantina oxidasa (febuxostat) los cuales han demostrado ser útiles en términos de reducción de las concentraciones séricas de ácido úrico (AU) en pacientes resistentes o con intolerancia a las terapias hipouricemiantes convencionales.

Gout is an inflammatory arthritis characterized by selflimiting but excruciatingly painful acute attacks. These are a consequence of monosodium urate crystal deposition within articular or periarticular tissue. After years of acute intermittent gout, chronic tophaceous gout can develop. Gout is the most frequent cause of inflammatory arthritis in men and postmenopausic women. Several important advances had been developed during last years in terms of pathogenic mechanisms, including genetic and inflammatory aspects such as the participation of inflammosome. In that sense, the gout can follow a course similar than othe autoinflammatory disorders. Additionally, new therapeutic agents had been developed, including anti-IL1 antibodies (anakinra, rinolacept and canakinumab) and xanthine oxidase inhibitors such as febuxostat. Those treatments had demonstrated efficacy in term of lowering serum urate concentrations in refractory patients to conventional treatments.

Gota en el anciano / No presenta

La gota es la artritis crónica más común en el anciano. Puede ser fácilmente diagnosticada por la presencia de cristales de urato monosódico al examen microscópico del líquido articular. Existen algunas diferencias clínicas entre la gota del adulto y la del anciano. El tratamiento es altamente efectivo pero puede ocasionar serias reacciones adversas si no se tiene en cuenta la comorbilidad de este grupo.

Gout is the most common chronic arthritis in older people that can lead to significant and severe disability. It can be easy diagnosed with the presence of crystals of urate monosodic in the articular fluid. The clinical stages of gout include asymptomatic hyperuricemia, intermittent gouty arthritis, intercritical period and chronic tophaceous gout. There are some differences necessary to recognize to avoid errors in the management. Treatment of acute gout involves the use of NSAIDs, colchicine, corticosteroids or corticotropin (adrenocorticotropic hormone). Profilactic treatment includes the use of allopurinol and uricosuric agents; but all of these drugs could cause serious reactions in the elderly.