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1.
The role of uric acid in mineral bone disorders in chronic kidney disease.
Afsar, B, Sag, AA, Oztosun, C, Kuwabara, M, Cozzolino, M, Covic, A, Kanbay, M
Journal of nephrology. 2019;(5):709-717
Abstract
Increasing survival in the chronic kidney disease (CKD) population exposes the bone to the cumulative detrimental sequelae of CKD, now defined physiologically and histopathologically as chronic kidney disease mineral bone disorder (CKD-BMD). This disorder is increasingly recognized as a "nontraditional" driver of morbidity and mortality and presents an opportunity to improve CKD outcomes via research. However, recent advances in the literature on this topic have not yet been collected into a single review. Therefore, this report aims to discuss the disordered renal-bone axis in CKD-BMD, molecular and hormonal drivers, novel treatment strategies, and forthcoming research in a clinician-directed format. A key novel topic will be the unique impact of uric acid on CKD-BMD, which is poised to apply extensive existing research in the uric acid domain to benefit the CKD-BMD population.
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2.
Dietary Antioxidant Supplements and Uric Acid in Chronic Kidney Disease: A Review.
Roumeliotis, S, Roumeliotis, A, Dounousi, E, Eleftheriadis, T, Liakopoulos, V
Nutrients. 2019;(8)
Abstract
Increased serum levels of uric acid have been associated with the onset and development of chronic kidney disease (CKD), cardiovascular disease, and mortality, through several molecular pathogenetic mechanisms, such as inflammation and oxidative stress. Oxidative stress is present even in the early stages of CKD, progresses parallelly with the deterioration of kidney function, and is even more exacerbated in end-stage renal disease patients undergoing maintenance hemodialysis. Although acting in the plasma as an antioxidant, once uric acid enters the intracellular environment; it behaves as a powerful pro-oxidant. Exogenous intake of antioxidants has been repeatedly shown to prevent inflammation, atherosclerosis and oxidative stress in CKD patients. Moreover, certain antioxidants have been proposed to exert uric acid-lowering properties. This review aims to present the available data regarding the effects of antioxidant supplements on both oxidative stress and uric acid serum levels, in a population particularly susceptible to oxidative damage such as CKD patients.
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3.
Combinational effect of angiotensin receptor blocker and folic acid therapy on uric acid and creatinine level in hyperhomocysteinemia-associated hypertension.
Singh, Y, Samuel, VP, Dahiya, S, Gupta, G, Gillhotra, R, Mishra, A, Singh, M, SreeHarsha, N, Gubbiyappa, SK, Tambuwala, MM, et al
Biotechnology and applied biochemistry. 2019;(5):715-719
Abstract
Homocysteine [HSCH2 CH2 CH(NH2 )COOH] (Hcy) is a sulfur-containing amino acid of 135.18 Da of molecular weight, generated during conversion of methionine to cysteine. If there is a higher accumulation of Hcy in the blood, that is usually above 15 µmol/L, it leads to a condition referred to as hyperhomocysteinemia. A meta-analysis of observational study suggested an elevated concentration of Hcy in blood, which is termed as the risk factors leading to ischemic heart disease and stroke. Further experimental studies stated that Hcy can lead to an increase in the proliferation of vascular smooth muscle cells and functional impairment of endothelial cells. The analyses confirmed some of the predictors for Hcy presence, such as serum uric acid (UA), systolic blood pressure, and hematocrit. However, angiotensin-converting enzyme inhibitors angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs) alone are inadequate for controlling UA and creatinine level, although the addition of folic acid may be beneficial in hypertensive patients who are known to have a high prevalence of elevated Hcy. We hypothesized that combination therapy with an ARB (olmesartan) and folic acid is a promising treatment for lowering the UA and creatinine level in hyperhomocysteinemia-associated hypertension.
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4.
Diagnostic advances in synovial fluid analysis and radiographic identification for crystalline arthritis.
Zell, M, Zhang, D, FitzGerald, J
Current opinion in rheumatology. 2019;(2):134-143
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Abstract
PURPOSE OF REVIEW The present review addresses diagnostic methods for crystalline arthritis including synovial fluid analysis, ultrasound, and dual energy CT scan (DECT). RECENT FINDINGS There are new technologies on the horizon to improve the ease, sensitivity, and specificity of synovial fluid analysis. Raman spectroscopy uses the spectral signature that results from a material's unique energy absorption and scatter for crystal identification. Lens-free microscopy directly images synovial fluid aspirate on to a complementary metal-oxide semiconductor chip, providing a high-resolution, wide field of view (∼20 mm) image. Raman spectroscopy and lens-free microscopy may provide additional benefit over compensated polarized light microscopy synovial fluid analysis by quantifying crystal density in synovial fluid samples. Ultrasound and DECT have good sensitivity and specificity for the identification of monosodium urate (MSU) and calcium pyrophosphate (CPP) crystals. However, both have limitations in patients with recent onset gout and low urate burdens. SUMMARY New technologies promise improved methods for detection of MSU and CPP crystals. At this time, limitations of these technologies do not replace the need for synovial fluid aspiration for confirmation of crystal detection. None of these technologies address the often concomitant indication to rule out infectious arthritis.
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5.
Pharmacological urate-lowering approaches in chronic kidney disease.
Li, X, Liu, J, Ma, L, Fu, P
European journal of medicinal chemistry. 2019;:186-196
Abstract
Chronic kidney disease (CKD) has become a global public health issue and uric acid (UA) remains a major risk factor of CKD. As the main organ for the elimination of UA, kidney owned a group of urate transporters in tubular epithelium. Kidney disease hampered the UA excretion, and the accumulation of serum UA in return harmed the renal function. Commercially, there are three kinds of agents targeting at urate-lowering, xanthine oxidoreductase inhibitor which prevents the production of UA, uricosuric which increases the concentration of UA in urine thus decreasing serum UA level, and uricase which converts UA to allantoin resulting in the dramatic decrement of serum UA. Of note, in patients with CKD, administration of above-mentioned agents, alone or combined, needs special attention. New evidence is emerging for the efficacy of several urate-lowering drugs for the treatment of hyperuricemia in patients with CKD. Besides, loads of novel and promising drug candidates and phytochemicals are in the different phases of research and development. As of today, there is insufficient evidence to recommend the widespread use of UA-lowering therapy to prevent or slow down the progression of CKD. The review summarized the evidence and perspectives about the treatment of hyperuricemia with CKD for medicinal chemist and nephrologist.
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6.
Uric Acid and Cognitive Function in Older Individuals.
Tana, C, Ticinesi, A, Prati, B, Nouvenne, A, Meschi, T
Nutrients. 2018;(8)
Abstract
Hyperuricemia has been recognized as an independent cardiovascular risk factor in epidemiological studies. However, uric acid can also exert beneficial functions due to its antioxidant properties, which may be particularly relevant in the context of neurodegenerative diseases. In this paper, we critically revise the evidence on the relationship between serum uric acid levels and cognitive function in older individuals, focusing on the etiology of cognitive impairment (Alzheimer's disease, Parkinson's dementia, and vascular dementia) and on the interactive connections between uric acid, dementia, and diet. Despite high heterogeneity in the existing studies, due to different characteristics of studied populations and methods of cognitive dysfunction assessment, we conclude that serum uric acid may modulate cognitive function in a different way according to the etiology of dementia. Current studies indeed demonstrate that uric acid may exert neuroprotective actions in Alzheimer's disease and Parkinson's dementia, with hypouricemia representing a risk factor for a quicker disease progression and a possible marker of malnutrition. Conversely, high serum uric acid may negatively influence the disease course in vascular dementia. Further studies are needed to clarify the physio-pathological role of uric acid in different dementia types, and its clinical-prognostic significance.
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7.
Crystal arthritides - gout and calcium pyrophosphate arthritis : Part 2: clinical features, diagnosis and differential diagnostics.
Schlee, S, Bollheimer, LC, Bertsch, T, Sieber, CC, Härle, P
Zeitschrift fur Gerontologie und Geriatrie. 2018;(5):579-584
Abstract
Gout develops in four stages beginning with an asymptomatic increase in blood levels of uric acid. An acute gout attack is an expression of an underlying inflammatory process, which in the course of time is self-limiting. Without therapy monosodium urate crystals remain in the synovial fluid and synovial membrane and trigger more acute attacks. In the course of the disease monosodium urate crystals form deposits (tophi) leading in severe forms to irreversible joint deformities with loss of functionality. In 20% of cases gout leads to involvement of the kidneys. Overproduction of uric acid can cause nephrolithiasis. These stones can be composed of uric acid or calcium phosphate. Another form of kidney disease caused by gout is uric acid nephropathy. This is a form of abacterial chronic inflammatory response with deposition of sodium urate crystals in the medullary interstitium. Acute obstructive nephropathy is relatively rare and characterized by renal failure due to uric acid precipitation in the tubules because of rapid cell lysis that occurs, for example, with chemotherapy. There is a causal interdependence between the occurrence of hyperuricemia and hypertension. Uric acid activates the renin-angiotensin-aldosterone (RAA) system and inhibits nitric oxide (NO) with the possible consequence of a rise in systemic vascular resistance or arteriolar vasculopathy; however, uric acid is also an apparently independent risk factor for atherosclerosis. In contrast to young patients, the diagnosis of an acute gout attack in the elderly can be a challenge for the physician. Polyarticular manifestations and obscure symptoms can make it difficult to differentiate it from rheumatoid arthritis and calcium pyrophosphate deposition disease (CPPD). Aspiration of synovial fluid with visualization of urate crystals using compensated polarized light microscopy is the gold standard for diagnosis of acute gout. Moreover, analysis of synovial fluid enables a distinction from septic arthritis by Gram staining and bacterial culture. Soft tissue ultrasonography is useful to detect affected synovial tissue and monosodium urate crystals within the synovial fluid. Involvement of bone occurs relatively late in the disease so that x‑ray images are not useful in the early stages but might be helpful in differential diagnostics. Dual energy computed tomography (CT) and magnetic resonance imaging (MRI) can be used for certain indications.
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8.
Hyperuricemia and endothelial function: From molecular background to clinical perspectives.
Maruhashi, T, Hisatome, I, Kihara, Y, Higashi, Y
Atherosclerosis. 2018;:226-231
Abstract
Uric acid is the end product of purine metabolism catalyzed by xanthine oxidase in humans. In the process of purine metabolism, reactive oxygen species, including superoxide, are generated concomitantly with uric acid production, which may deteriorate endothelial function through the reaction of superoxide with nitric oxide (NO), leading to decreased NO bioavailability and increased production of peroxynitrite, a reactive oxidant. Therefore, xanthine oxidase may be a therapeutic target in the treatment of endothelial dysfunction. Indeed, clinical studies have shown that endothelial dysfunction is restored by treatment with a xanthine oxidase inhibitor in patients with cardiovascular risk factors. However, it has not been fully determined whether uric acid per se is an independent causal risk factor of endothelial dysfunction in humans. Although experimental studies have indicated that uric acid absorbed into endothelial cells via the activation of uric acid transporters expressed in endothelial cells causes endothelial dysfunction through increased oxidative stress and inflammation, an actual biological effect of uric acid on endothelial function in vivo has not been fully elucidated, in part, because of the difficulty in investigating the effect of uric acid alone on endothelial function due to the close associations of uric acid with other conventional cardiovascular risk factors and the complicated relationship between uric acid and endothelial function attributed to the potent antioxidant properties of uric acid. In this review, we focus on the relationship between uric acid and endothelial function from molecular to clinical perspectives.
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9.
Uric Acid: The Unknown Uremic Toxin.
Treviño-Becerra, A
Contributions to nephrology. 2018;:25-33
Abstract
This review brings together concepts of uric acid metabolism affecting renal parenchyma and its function and the current therapies to reduce hyperuricemia (HyU) and avoid renal disease progression. High uric acid plays an important role in several chronic diseases including kidney diseases such as lithiasis, gout nephropathy, and preeclampsia. In the last 30 years, it has been shown that reducing HyU with low protein and low purine diets in addition to allopurinol creates physiopathological conditions that produce a slight increase in the glomerular filtration rate (GFR). In recent years, in a new era of research in clinical, genetics, pharmacological, and epidemiologic fields, they have been moving forward to support the idea that reduction in HyU could benefit the chronic renal failure (CRF) patients (stage III-IV), thereby avoiding the drop of GFR for undefined mechanisms. There are several clinical trials in progress that show the HyU reducing to very low values and an increased GFR. In a young population, when treating HyU there is a reduction in high blood pressure. There are some reports showing that HyU could play a role in the diabetic nephropathy. Therefore, there have been some speculations that HyU treatment could stop the progression of CRF modifying the natural history of the diseases. So there will be new clinical trials with old and new medication and metabolic procedure to maintain a very low blood levels in the unknown uremic toxin know as uric acid which seems to be the toxin to the damage kidney.
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10.
Change gout: the need for a new approach.
Punzi, L
Minerva medica. 2017;(4):341-349
Abstract
Gout is the most common form of inflammatory arthropathy and is caused by an excess of uric acid in the blood (hyperuricemia). It is a chronic, debilitating condition that gradually increases in severity and affects an increasing number of people. It has a wide spectrum of clinical manifestations and is related to serious kidney and cardiovascular conditions and to an increased risk of mortality. The negative perception of the disease, historically seen as related to a life of dissipation, has led to underestimating its impact and focusing the attention on the short-term treatment of acute attacks rather than on the long-term management of the condition without, consequently, preventing the most serious complications. The most recent scientific evidence and the increasing understanding of the physio-pathologic mechanisms responsible for hyperuricemia and gout reveal a very different reality, in which gout is a condition which is only minimally affected by lifestyle and mainly by increasingly better identified genetic factors. Appropriate doctor training and patient education, catalyzed by the renewed attention to this disease and to new treatment options which overcome the limits of therapies currently available, will help to break down current barriers to allow for its optimal management.