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.
•Uric acid is the end product of purine metabolism catalyzed by xanthine oxidase.•Reactive oxygen species are concomitantly generated with uric acid production.•Xanthine oxidase may be a therapeutic target of endothelial dysfunction.•Experimental studies have shown that uric acid per se causes endothelial dysfunction.•Biological effect of uric acid on endothelial function in vivo and in a clinical setting is not established.
Serum uric acid (UA) is taken up by endothelial cells and reduces the level of nitric oxide (NO) by inhibiting its production and accelerating its degradation. Cytosolic and plasma xanthine oxidase ...(XO) generates superoxide and also decreases the NO level. Thus, hyperuricemia is associated with impaired endothelial function. Hyperuricemia is often associated with vascular diseases such as chronic kidney disease (CKD) and cardiovascular disease (CVD). It has long been debated whether hyperuricemia is causally related to the development of these diseases. The 2020 American College of Rheumatology Guideline for the Management of Gout (ACR2020) does not recommend pharmacological treatment of hyperuricemia in patients with CKD/CVD. In contrast, the Japanese Guideline on Management of Hyperuricemia and Gout (JGMHG), 3rdedition, recommends pharmacological treatment of hyperuricemia in patients with CKD. In a FREED study on Japanese hyperuricemic patients with CVD, an XO inhibitor, febuxostat, improved the primary composite endpoint of cerebro-cardio-renovascular events, providing a rationale for the use of urate-lowering agents (ULAs). Since a CARES study on American gout patients with CVD treated with febuxostat revealed increased mortality, ACR2020 recommends switching to different ULAs. However, there was no difference in the mortality of Japanese patients between the febuxostat-treated group and the placebo or allopurinol-treated groups in either the FEATHER or FREED studies.
Background:Uric acid (UA) serves as an antioxidant in vascular endothelial cells. UA transporter 1 (URAT1) encoded by SLC22A12 is expressed in the kidney and vessels and its loss of function causes ...hypouricemia. The purpose of this study was to examine whether there is any endothelial dysfunction in patients with hypouricemia.Methods and Results:Twenty-six patients with hypouricemia (<2.5 mg/dl) and 13 healthy control subjects were enrolled. Endothelial function was evaluated using flow-mediated dilation (FMD). mRNA of UA transporters expressed in cultured human umbilical endothelial cells (HUVEC) was detected on RT-PCR. There was a positive correlation between FMD and serum UA in the hypouricemia group. URAT1 loss-of-function mutations were found in the genome of 21 of 26 patients with hypouricemia, and not in the other 5. In the hypouricemia groups, serum UA in homozygous and compound heterozygous patients was significantly lower than in other groups, suggesting that severity of URAT1 dysfunction may influence the severity of hypouricemia. Thirteen of 16 hypouricemia subjects with homozygous and compound heterozygote mutations had SUA <0.8 mg/dl and their FMD was lower than in other groups. HUVEC do not express mRNA of URAT1, suggesting the null role of URAT1 in endothelial function.Conclusions:Depletion of UA due to SLC22A12/URAT1 loss-of-function mutations causes endothelial dysfunction in hypouricemia patients. (Circ J 2015; 79: 1125–1132)
Abstract
Aims
To compare the occurrence of cerebral, cardiovascular, and renal events in patients with hyperuricaemia treated with febuxostat and those treated with conventional therapy with ...lifestyle modification.
Methods and results
This multicentre, prospective, randomized open-label, blinded endpoint study was done in 141 hospitals in Japan. A total of 1070 patients were included in the intention-to-treat population. Elderly patients with hyperuricaemia (serum uric acid >7.0 to ≤9.0 mg/dL) at risk for cerebral, cardiovascular, or renal disease, defined by the presence of hypertension, Type 2 diabetes, renal disease, or history of cerebral or cardiovascular disease, were randomized to febuxostat and non-febuxostat groups and were observed for 36 months. Cerebral, cardiovascular, and renal events and all deaths were defined as the primary composite event. The serum uric acid level at endpoint (withdrawal or completion of the study) in the febuxostat (n = 537) and non-febuxostat groups (n = 533) was 4.50 ± 1.52 and 6.76 ± 1.45 mg/dL, respectively (P < 0.001). The primary composite event rate was significantly lower in the febuxostat group than in non-febuxostat treatment hazard ratio (HR) 0.750, 95% confidence interval (CI) 0.592–0.950; P = 0.017 and the most frequent event was renal impairment (febuxostat group: 16.2%, non-febuxostat group: 20.5%; HR 0.745, 95% CI 0.562–0.987; P = 0.041).
Conclusion
Febuxostat lowers uric acid and delays the progression of renal dysfunction.
Registration
ClinicalTrials.gov (NCT01984749).
Hyperuricemia and Atrial Fibrillation Maharani, Nani; Kuwabara, Masanari; Hisatome, Ichiro
International Heart Journal,
2016, Volume:
57, Issue:
4
Journal Article
Peer reviewed
Open access
The importance of atrial fibrillation (AF) as a cause of mortality and morbidity has prompted research on its pathogenesis and treatment. Recognition of AF risk factors is essential to prevent it and ...reduce the risk of death. Hyperuricemia has been widely accepted to be associated with the incidence of paroxysmal or persistent AF, as well as to the risk of AF in post cardiovascular surgery patients. The possible explanations for this association have been based on their relation with either oxidative stress or inflammation. To investigate the link between hyperuricemia and AF, it is necessary to refer to hyperuricemia-induced atrial remodeling. So far, both ionic channel and structural remodeling caused by hyperuricemia might be plausible explanations for the occurrence of AF. Inhibition of xanthine oxidase and nicotinamide adenine dinucleotide phosphate (NADPH)-oxidase, or the use of antioxidants, along with serum uric acid (SUA) level reduction to prevent inflammation, might be useful. Uric acid transporters (UATs) play a key role in the regulation of intracellular uric acid concentration. Intracellular rather than serum uric acid level is considered more important for the pathogenesis of AF. Identification of UATs expressed in cells is thus important, and targeting UATs might become a potential strategy to reduce the risk of hyperuricemia-induced atrial fibrillation.
Clinical studies have shown hyperuricemia strongly associated with insulin resistance as well as cardiovascular disease. Direct evidence of how high uric acid (HUA) affects insulin resistance in ...cardiomyocytes, but the pathological mechanism of HUA associated with cardiovascular disease remains to be clarified. We aimed to examine the effect of HUA on insulin sensitivity in cardiomyocytes and on insulin resistance in hyperuricemic mouse model. We exposed primary cardiomyocytes and a rat cardiomyocyte cell line, H9c2 cardiomyocytes, to HUA, then quantified glucose uptake with a fluorescent glucose analog, 2-NBDG, after insulin challenge and detected reactive oxygen species (ROS) production. Western blot analysis was used to examine the levels of insulin receptor (IR), phosphorylated insulin receptor substrate 1 (IRS1, Ser307) and phospho-Akt (Ser473). We monitored the impact of HUA on insulin resistance, insulin signaling and IR, phospho-IRS1 (Ser307) and phospho-Akt levels in myocardial tissue of an acute hyperuricemia mouse model established by potassium oxonate treatment. HUA inhibited insulin-induced glucose uptake in H9c2 and primary cardiomyocytes. It increased ROS production; pretreatment with N-acetyl-L-cysteine (NAC), a ROS scavenger, reversed HUA-inhibited glucose uptake induced by insulin. HUA exposure directly increased the phospho-IRS1 (Ser307) response to insulin and inhibited that of phospho-Akt in H9C2 cardiomyocytes, which was blocked by NAC. Furthermore, the acute hyperuricemic mice model showed impaired glucose tolerance and insulin tolerance accompanied by increased phospho-IRS1 (Ser307) and inhibited phospho-Akt response to insulin in myocardial tissues. HUA inhibited insulin signaling and induced insulin resistance in cardiomyocytes in vitro and in vivo, which is a novel potential mechanism of hyperuricemic-related cardiovascular disease.
Background:Although adipose-derived stem cell (ADSC) sheets improve the cardiac function after myocardial infarction (MI), underlying mechanisms remain to be elucidated. The aim of this study was to ...determine the fate of transplanted ADSC sheets and candidate angiogenic factors released from ADSCs for their cardiac protective actions.Methods and Results:MI was induced by ligation of the left anterior descending coronary artery. Sheets of transgenic (Tg)-ADSCs expressing green fluorescence protein (GFP) and luciferase or wild-type (WT)-ADSCs were transplanted 1 week after MI. Both WT- and Tg-ADSC sheets improved cardiac functions evaluated by echocardiography at 3 and 5 weeks after MI. Histological examination at 5 weeks after MI demonstrated that either sheet suppressed fibrosis and increased vasculogenesis. Luciferase signals from Tg-ADSC sheets were detected at 1 and 2 weeks, but not at 4 weeks, after transplantation. RNA sequencing of PKH (yellow-orange fluorescent dye with long aliphatic tails)-labeled Tg-ADSCs identified mRNAs of 4 molecules related to angiogenesis, including those of Esm1 and Stc1 that increased under hypoxia. Administration of Esm1 or Stc1 promoted tube formation by human umbilical vein endothelial cells.Conclusions:ADSC sheets improved cardiac contractile functions after MI by suppressing cardiac fibrosis and enhancing neovascularization. Transplanted ADSCs existed for >2 weeks on MI hearts and produced the angiogenic factors Esm1 and Stc1, which may improve cardiac functions after MI.
High serum uric acid (SUA) is associated with the dyslipidemia, but whether hyperuricemia predicts an increase in serum low-density lipoprotein (LDL) cholesterol is unknown. This study is to evaluate ...whether an elevated SUA predicts the development of high LDL cholesterol as well as hypertriglyceridemia.
This is a retrospective 5-year cohort study of 6476 healthy Japanese adults (age, 45.7 ± 10.1 years; 2.243 men) who underwent health examinations at 2004 and were reevaluated in 2009 at St. Luke's International Hospital, Tokyo, Japan. Subjects were included if at their baseline examination they did not have hypertension, diabetes mellitus, dyslipidemia, chronic kidney disease, or if they were on medication for hyperuricemia and/or gout. The analysis was adjusted for age, body mass index (BMI), smoking and drinking habits, baseline estimated glomerular filtration rate (eGFR), baseline SUA and SUA change over the 5 years.
High baseline SUA was an independent risk for developing high LDL cholesterol both in men (OR: 1.159 per 1 mg/dL increase, 95% CI:1.009–1.331) and women (OR: 1.215, 95% CI:1.061–1.390). Other risk factors included a higher baseline LDL cholesterol, higher BMI, and higher baseline eGFR (the latter two in women only). Increased SUA over 5 years were also independent risks for developing high LDL cholesterol and hypertriglyceridemia, but not for low high-density lipoprotein (HDL) cholesterol.
This is the first study to report that an elevated SUA increases the risk for developing high LDL cholesterol, as well as hypertriglyceridemia. This may shed light into the role of SUA in cardiovascular disease.
•This study clarified the relationship between serum uric acid (SUA) and lipid.•High baseline SUA is an independent risk for developing high LDL cholesterol.•Increased SUA over 5 years is also a risk for developing high LDL cholesterol.•Increased SUA is a risk for hypertriglyceridemia, but not for low HDL cholesterol.•It shows a potential mechanism in which high SUA may cause cardiovascular disease.
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