Allopurinol improves endothelial dysfunction in chronic heart failure

Serum uric acid to eGFR ratio correlates with adverse outcomes in elderly hospitalized for acute heart failure

BACKGROUND

Serum uric acid (SUA) is a known biomarker of severity in acute heart failure (AHF), reflecting the intricate interplay between cardiovascular and metabolic dysfunction. Since SUA can increase in response to worsening kidney function, and subjects with AHF often have cardiorenal syndrome or are on diuretic therapy, we tested whether the ratio of SUA to eGFR might provide prognostic value in elderly hospitalized for AHF.

METHODS

The BOTERO-AHF Study (BOlogna study of Therapies, Epidemiology and Radiodiagnostic Outcomes in Acute Heart Failure patients) included 293 patients admitted for AHF who were consecutively enrolled from January 2020 onwards. We compared the baseline characteristics of participants who had a composite outcome (CO) (n = 203) of death or re-hospitalization for AHF within 12 months from discharge to those without CO (n = 90), and we assessed the prognostic impact of SUA/eGFR for 12-months CO.

RESULTS

SUA/eGFR was significantly higher in participants who experienced a CO within 12 months from discharge for AHF, compared to those who did not experience any CO (17.8 (16.6) vs. 13.7 (12.1) mg/dl/ml/min*100, p = 0.008). SUA/eGFR, and not SUA alone, was associated with an increase in the rate of CO (unadjusted HR 1.011, CI 95% 1.004-1.019, p = 0.003). This association lost significance in participants under treatment with xanthine oxidase inhibitors but remained significant after adjustment for multiple confounders.

CONCLUSION

The SUA/ eGFR ratio provides prognostic value in elderly patients hospitalized for AHF. Future studies may clarify if SUA/eGFR and XOI may represent novel diagnostic and therapeutic approaches for subgroups of patients with AHF.

Impact of hyperuricemia on 5-year clinical outcomes following percutaneous transluminal angioplasty

BACKGROUND

Although the correlation between hyperuricemia and cardiovascular disease (CVD) is well known, there have been limited data regarding the impact of hyperuricemia on long-term clinical outcomes in patients with peripheral arterial disease (PAD) after percutaneous transluminal angioplasty (PTA).

METHODS

A total of 718 patients who underwent PTA for PAD were enrolled. The patients were divided into the hyperuricemia group (N = 168) and the normal group (N = 550). Hyperuricemia was defined as a uric acid level ≥ 7.0 mg/dL in men, and ≥ 6.5 mg/dL in women. The primary endpoint was major adverse cerebral and cardiovascular event (MACCE), including death, myocardial infarction (MI), any coronary revascularization, and stroke, up to 5 years. The secondary endpoint was major adverse limb event (MALE), including any repeated PTA, and target extremity surgery (TES). Inverse probability weighting (IPTW) analysis, derived from the logistic regression model, was performed to adjust potential confounders.

RESULTS

After IPTW matching analysis, compared to the normal group, the hyperuricemia group was not associated with increased MACCE but was associated with an increased incidence of MI (2.6 % vs. 0.5 %, p = 0.001), and coronary revascularization (6.7 % vs. 3.9 %, p = 0.018). Also, the hyperuricemia group was associated with a higher incidence of MALE (45.3 % vs. 28.9 %, p < 0.001), including target extremity revascularization (TER; 25.1 % vs. 15.9 %, p < 0.001), non-TER (11.5 % vs. 5.6 %, p < 0.001), and TES (22.8 % vs. 16.2 %, p = 0.002).

CONCLUSIONS

In the present study, hyperuricemia was associated with worse clinical outcomes in PAD patients following PTA during 5-year clinical follow-up. Further investigations should be made regarding the clinical benefit of controlling hyperuricemia on clinical outcomes.

Antioxidant therapies for obstructive sleep apnea: A systematic review and meta-analysis

PURPOSE

Obstructive sleep apnea (OSA) is a common clinical problem that is associated with adverse cardiovascular outcomes attributed to the oxidative stress due to sympathetic overstimulation. Treatment approaches targeting oxidative stress have been tried by multiple investigators. This systematic review and meta-analysis evaluated the efficacy and safety of such approaches.

METHODS

Pubmed and Embase databases were searched for human studies evaluating the utility of antioxidant therapies in patients with OSA.

RESULTS

A total of six studies (five randomized trials and one case-control study) were included, including 160 patients with OSA using N-acetyl cysteine, vitamin C, carbocysteine, superoxide dismutase, vitamin E, allopurinol, and their combinations. There was a significant improvement in flow-mediated dilatation (FMD) following antioxidants, with the pooled effect being 2.16 % (95% CI 1.65-2.67) using the random-effects model (I2 = 0% and p<0.001). It was also associated with a significant reduction in malondialdehyde levels and an increase in reduced glutathione (GSH) levels. There was also a significant improvement in the Epworth sleepiness scale, oxygen desaturation index, and minimum oxygen saturation during sleep without any significant adverse effects.

CONCLUSION

Antioxidant therapy in patients with OSA is associated with improved endothelial function, reduced oxidative stress, and improved sleep parameters. These results call for future multicentre studies with longer follow-ups to assess the utility of antioxidant therapy in patients with OSA.

Allopurinol and cardiovascular outcomes in patients with ischaemic heart disease: the ALL-HEART RCT and economic evaluation

Background

Allopurinol is a xanthine oxidase inhibitor that lowers serum uric acid and is used to prevent acute gout flares in patients with gout. Observational and small interventional studies have suggested beneficial cardiovascular effects of allopurinol.

Objective

To determine whether allopurinol improves major cardiovascular outcomes in patients with ischaemic heart disease.

Design

Prospective, randomised, open-label, blinded endpoint multicentre clinical trial.

Setting

Four hundred and twenty-four UK primary care practices.

Participants

Aged 60 years and over with ischaemic heart disease but no gout.

Interventions

Participants were randomised (1 : 1) using a central web-based randomisation system to receive allopurinol up to 600 mg daily that was added to usual care or to continue usual care.

Main outcome measures

The primary outcome was the composite of non-fatal myocardial infarction, non-fatal stroke or cardiovascular death. Secondary outcomes were non-fatal myocardial infarction, non-fatal stroke, cardiovascular death, all-cause mortality, hospitalisation for heart failure, hospitalisation for acute coronary syndrome, coronary revascularisation, hospitalisation for acute coronary syndrome or coronary revascularisation, all cardiovascular hospitalisations, quality of life and cost-effectiveness. The hazard ratio (allopurinol vs. usual care) in a Cox proportional hazards model was assessed for superiority in a modified intention-to-treat analysis.

Results

From 7 February 2014 to 2 October 2017, 5937 participants were enrolled and randomised to the allopurinol arm (n = 2979) or the usual care arm (n = 2958). A total of 5721 randomised participants (2853 allopurinol; 2868 usual care) were included in the modified intention-to-treat analysis population (mean age 72.0 years; 75.5% male). There was no difference between the allopurinol and usual care arms in the primary endpoint, 314 (11.0%) participants in the allopurinol arm (2.47 events per 100 patient-years) and 325 (11.3%) in the usual care arm (2.37 events per 100 patient-years), hazard ratio 1.04 (95% confidence interval 0.89 to 1.21); p = 0.65. Two hundred and eighty-eight (10.1%) participants in the allopurinol arm and 303 (10.6%) participants in the usual care arm died, hazard ratio 1.02 (95% confidence interval 0.87 to 1.20); p = 0.77. The pre-specified health economic analysis plan was to perform a 'within trial' cost-utility analysis if there was no statistically significant difference in the primary endpoint, so NHS costs and quality-adjusted life-years were estimated over a 5-year period. The difference in costs between treatment arms was +£115 higher for allopurinol (95% confidence interval £17 to £210) with no difference in quality-adjusted life-years (95% confidence interval -0.061 to +0.060). We conclude that there is no evidence that allopurinol used in line with the study protocol is cost-effective.

Limitations

The results may not be generalisable to younger populations, other ethnic groups or patients with more acute ischaemic heart disease. One thousand six hundred and thirty-seven participants (57.4%) in the allopurinol arm withdrew from randomised treatment, but an on-treatment analysis gave similar results to the main analysis.

Conclusions

The ALL-HEART study showed that treatment with allopurinol 600 mg daily did not improve cardiovascular outcomes compared to usual care in patients with ischaemic heart disease. We conclude that allopurinol should not be recommended for the secondary prevention of cardiovascular events in patients with ischaemic heart disease but no gout.

Future work

The effects of allopurinol on cardiovascular outcomes in patients with ischaemic heart disease and co-existing hyperuricaemia or clinical gout could be explored in future studies.

Trial registration

This trial is registered as EU Clinical Trials Register (EudraCT 2013-003559-39) and ISRCTN (ISRCTN 32017426).

Funding

This award was funded by the National Institute for Health and Care Research (NIHR) Health Technology Assessment programme (NIHR award ref: 11/36/41) and is published in full in Health Technology Assessment; Vol. 28, No. 18. See the NIHR Funding and Awards website for further award information.

Uric acid is a biomarker for heart failure, but not therapeutic target: result from a comprehensive meta-analysis

AIMS

This systematic review and meta-analysis aimed to investigate the association between serum uric acid (SUA) levels and the incidence rate and prognosis of heart failure (HF), as well as the impact of uric acid-lowering treatment on HF patients.

METHODS AND RESULTS

PubMed and Embase were searched for original articles reporting on the association between SUA and HF incidence, adverse outcomes, and the effect of uric acid-lowering treatment in HF patients. Data were pooled using random effects or fixed effects models. Univariable meta-regression analysis assessed the influence of study characteristics on research outcomes. Statistical analyses were conducted using RevMan software and STATA software version 15.0. Eleven studies on HF incidence and 24 studies on adverse outcomes in HF patients were included. Higher SUA levels were associated with an increased risk of HF (RR: 1.81, 95% CI: 1.53-2.16), all-cause mortality (RR: 1.44, 95% CI: 1.25-1.66), cardiac death (RR: 1.56, 95% CI: 1.32-1.84), and HF rehospitalization (RR: 2.07, 95% CI: 1.37-3.13) in HF patients. Uric acid-lowering treatment was found to increase all-cause mortality in HF patients (RR: 1.15, 95% CI: 1.05-1.25).

CONCLUSIONS

Uric acid is an independent predictor of heart failure occurrence and adverse prognosis. Targeting uric acid lowering as a therapeutic intervention does not improve the prognosis of patients with heart failure. It may not be advisable to use traditional urate-lowering drugs in young patients with heart failure, and elderly patients should exercise caution when using them.

Relationship of Serum Uric Acid with Kidney Function Decline Mediated by Systemic Arterial Stiffness: A Retrospective Cohort Study in Japan

Hyperuricemia is associated with kidney function decline (KFD), although whether hyperuricemia directly causes nephrotoxicity or is indirectly mediated by systemic arterial stiffening remains unclear. We examined the detailed relationship of serum uric acid (SUA) with KFD and potential mediation by arterial stiffness. Study population was 27,648 urban residents with an estimated glomerular filtration rate (eGFR) of ≥60 mL/min/1.73 m2 at baseline, and they participated in a median of three consecutive annual health examinations. Arterial stiffness was assessed using cardio-ankle vascular index (CAVI). KFD was defined as a decrease in eGFR to below 60. Multivariate analysis showed an association between baseline SUA and CAVI independent of eGFR. During the study period, 6.6% of participants developed KFD. Stratified analysis revealed a linear relationship between the contribution of CAVI or SUA and KFD. ROC analysis determined a cutoff CAVI of 8.0 (males) or 7.9 (females) and a cutoff SUA of 6.3 (males) or 4.5 mg/dL (females) for predicting KFD. The linkage between SUA and CAVI was associated with a greater increase in the hazard ratio for KFD with an increase in SUA. CAVI showed the mediating effect on the relationship of SUA with KFD after an adjustment for confounders. SUA was associated positively with CAVI-mediated KFD. Further studies should verify whether intensive SUA-lowering treatment prevents KFD via improving vascular function.

Allopurinol Prevents Cirrhosis-Related Complications: A Quadruple Blind Placebo-Controlled Trial

BACKGROUND

Complications associated with liver cirrhosis are various and potentially fatal. The treatment options to counteract hepatic decompensation are limited. Therefore, the study aimed to explore the use of allopurinol in preventing the recurrence of liver cirrhosis-related complications.

METHODS

One hundred patients with hepatic decompensation were randomized into 1:1 ratio to receive either allopurinol 300 mg or placebo tablets once daily for 6 months. The primary endpoint was the incidence of cirrhosis-related complications (overt ascites, spontaneous bacterial peritonitis, variceal bleeding, hepatorenal syndrome, and hepatic encephalopathy).

RESULTS

Six months following treatment, allopurinol reduced the relative risk (RR) of any first complication experienced after enrollment by 56% (hazard ratio [HR] 0.44; 95% confidence interval [CI], 0.27-0.62); P ˂ .001). Allopurinol decreased the RR of overt ascites by 67% (HR 0.33; 95% CI, 0.0098-0.94); P = .039] and reduced the RR of spontaneous bacterial peritonitis by about 75% (HR 0.25; 95% CI, 0.05-0.76; P = .01). Likewise, allopurinol was linked to an 80% reduction in the RR of developing hepatorenal syndrome (HR 0.2; 95% CI, 0.04-0.87; P = .033).

CONCLUSION

Allopurinol significantly decreased the recurrence of overall liver cirrhosis-related complications. Therefore, allopurinol may constitute a promising agent for patients with hepatic decompensation. These positive outcomes could be a result of its ability to reduce bacterial translocation and inflammation.

CLINICALTRIALS

GOV IDENTIFIER

NCT005545670.

Serum uric acid levels and risk of cardiovascular disease in type 2 diabetes: results from a cross-sectional study and Mendelian randomization analysis

Aims

Serum uric acid (SUA) levels have been previously linked to a higher risk of cardiovascular disease (CVD) in individuals with type 2 diabetes (T2D) according to various observational studies. However, whether this association is causally linked or simply influenced by confounding factors is unclear. Therefore, this study utilized Mendelian randomization (MR) analysis to explore the causality between SUA levels and the risk of CVD in individuals with T2D.

Methods

Our study cohort consisted of 5723 participants who were diagnosed with T2D in the National Health and Nutrition Examination Survey (NHANES) from 1999-2018. The study assessed the association between SUA levels and the risk of CVD using a multivariable logistic regression model. To further examine causality between SUA levels and CVD, a two-sample MR study was conducted utilizing genetic data from genome-wide association studies (GWAS) involving over 140,000 individuals. The main MR analysis employed the inverse-variance-weighted (IVW) method. Additionally, several sensitivity analyses were performed to evaluate the robustness and pleiotropy of the results.

Results

In the cross-sectional study, after multivariable adjustment, participants with SUA levels >6.7 mg/dL exhibited odds ratios (ORs) of 1.51 (95% CI: 1.01-2.26, p=0.049) for heart failure, 1.02 (95% CI: 0.69-1.50, p=0.937) for coronary heart disease, 1.36 (95% CI: 0.78-2.38, p=0.285) for angina, and 1.22 (95% CI: 0.80-1.85, p=0.355) for myocardial infarction when compared to participants with SUA levels ≤ 4.6 mg/dL. However, in the IVW analysis, no causality between SUA levels and the risk of heart failure was observed (OR = 1.03, 95% CI: 0.97-1.09, p = 0.293). The secondary analysis yielded similar results (OR = 1.05, 95% CI: 0.96-1.14, p = 0.299). The sensitivity analyses further supported our primary findings.

Conclusion

Based on the MR study, we did not find supporting evidence for a causal association between SUA levels and the risk of heart failure.

Efficacy of Allopurinol in Improving Endothelial Dysfunction: A Systematic Review and Meta-Analysis

INTRODUCTION

Endothelial dysfunction has been implicated in various cardiovascular disorders as the initial pathology. Allopurinol has been shown to improve endothelial dysfunction in patients with gout, but its effect on cardiovascular patients is unclear.

AIMS

We aim to assess allopurinol efficacy in improving endothelial dysfunction overall and in different disease states including but not limited to heart failure, chronic kidney disease, ischemic heart disease METHODS: We conducted a literature search of PubMed, Cochrane's Central Library, and Scopus until December 2022, including randomized controlled trials and double-arm observational studies. The primary outcome measure was endothelial function assessed by change in flow mediated dilation (FMD) RESULTS: Our meta-analysis included 22 studies with a total of 1472 patients. Our pooled analysis shows that allopurinol significantly improved FMD (WMD = 1.46%, 95% CI [0.70, 2.22], p < 0.01) compared to control. However, there was no significant difference between allopurinol and control for endothelial-independent vasodilation measured by forearm blood flow (WMD = 0.10%, 95% CI [- 0.89, 0.69], p = 0.80). Subgroup analysis indicated that the effect of allopurinol on FMD was more significant in diabetic and congestive heart failure patients.

CONCLUSION

While allopurinol may improve endothelial function in various patient populations, further high-quality randomized controlled trials are needed to determine its efficacy in preventing cardiovascular disease exacerbation.

Allopurinol for Secondary Prevention in Patients with Cardiovascular Disease: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

BACKGROUND

The effects of allopurinol in patients with cardiovascular disease are not well defined; therefore, the latest evidence is summarized in this study.

METHODS

PubMed, Embase, Cochrane Library, and ClinicalTrials.gov databases were searched for randomized controlled trials (RCTs) of allopurinol in patients with cardiovascular disease published up to 11 February 2023. The primary outcome was cardiovascular death.

RESULTS

We combined the results of 21 RCTs that included 22,806 patients. Compared to placebo/usual care, allopurinol treatment was not associated with a significant reduction in cardiovascular death (RR 0.60; 95% CI 0.33-1.11) or all-cause death (RR 0.90; 95% CI 0.72-1.12). However, evidence from earlier trials and studies with small sample sizes indicated that allopurinol might confer a protective effect in decreasing cardiovascular death (RR 0.34; 95% CI 0.15-0.76) across patients undergoing coronary artery bypass grafting (CABG) or having acute coronary syndrome (ACS). In comparisons between allopurinol and febuxostat, we observed no difference in cardiovascular death (RR 0.92; 95% CI 0.69-1.24) or all-cause death (RR 1.02; 95% CI 0.75-1.38).

CONCLUSION

Allopurinol could not reduce cardiovascular (CV) death or major adverse CV outcomes significantly in patients with existing cardiovascular diseases. Given the limitations of the original studies, the potential advantages of allopurinol observed in patients undergoing CABG or presenting with ACS necessitate further confirmation through subsequent RCTs. In the comparisons between allopurinol and febuxostat, our analysis failed to uncover any marked superiority of allopurinol in reducing the risk of adverse cardiovascular incidents.

Uric acid plasma levels are associated with C-reactive protein concentrations and the extent of coronary artery lesions in patients with acute coronary syndromes

Many studies have pointed out that inflammation plays a pivotal role in pathophysiology of acute coronary syndromes (ACS) because several inflammatory molecules impair the endothelial functions in the coronary circulation and promote atherothrombotic events. Recently, many clinical/experimental evidences indicate that elevated plasma levels of uric acid (UA) might be considered a risk factor for developing ACS. It has been reported that elevated UA doses impair physiologic functions of endothelial cells, shifting them toward a pro atherothrombotic phenotype. In the present manuscript, we investigated the relationship between UA plasma levels, inflammatory burden, and extension of coronary atherosclerotic disease in patients with ACS. Patients with a clinical presentation of ACS (ST-elevated and non-ST-elevated myocardial infarction) admitted to the Vanvitelli Catheterization Laboratory at Monaldi Hospital in 2019, before the COVID-19 pandemia, were retrospectively analyzed. Biochemical profile, type of ACS presentation, as well as extension of coronary atherosclerosis were assessed. A total of 132 ACS patients were included in the analysis, and grouped into 3 tertiles according to the UA values (UA < 4.72 mg/dl, UA between 4.72 and 6.15 mg/dl, and UA > 6.15 mg/dl). Patients with UA plasma levels ≥ 6.15 mg/dL showed higher levels of C-reactive protein (mean of 5.1 mg/dL) as compared to patients with lower UA plasma levels. Moreover, the former group of patients showed higher levels of cardiac troponin and CPK, and presented more often with multivessel disease and complex coronary stenosis (type C of Ellis classification). Even though monocentric and with limited sample size, the present study shows that plasma levels of UA and hs-CRP are elevated in ACS patients and are associated with a more severe coronary disease, suggesting a potential role of UA in the pathophysiology of acute coronary events.

Xanthine oxidase mediates chronic stress-induced cerebrovascular dysfunction and cognitive impairment

Xanthine oxidase (XO) mediates vascular function. Chronic stress impairs cerebrovascular function and increases the risk of stroke and cognitive decline. Our study determined the role of XO on stress-induced cerebrovascular dysfunction and cognitive decline. We measured middle cerebral artery (MCA) function, free radical formation, and working memory in 6-month-old C57BL/6 mice who underwent 8 weeks of control conditions or unpredictable chronic mild stress (UCMS) with or without febuxostat (50 mg/L), a XO inhibitor. UCMS mice had an impaired MCA dilation to acetylcholine vs. controls (p < 0.0001), and increased total free radical formation, XOR protein levels, and hydrogen peroxide production in the liver compared to controls. UCMS increased hydrogen peroxide production in the brain and cerebrovasculature compared to controls. Working memory, using the y-maze test, was impaired (p < 0.05) in UCMS mice compared to control mice. However, blocking XO using febuxostat prevented the UCMS-induced impaired MCA response, while free radical production and hydrogen peroxide levels were similar to controls in the liver and brain of UCMS mice treated with febuxostat. Further, UCMS + Feb mice did not have a significant reduction in working memory. These data suggest that the cerebrovascular dysfunction associated with chronic stress may be driven by XO, which leads to a reduction in working memory.

Hyperbaric Oxygen Therapy Reduces Oxidative Stress and Inflammation, and Increases Growth Factors Favouring the Healing Process of Diabetic Wounds

Hyperbaric oxygen therapy (HBOT) is the clinical application of oxygen at pressures higher than atmospheric pressure. HBOT has been effectively used to manage diverse clinical pathologies, such as non-healing diabetic ulcers. The aim of the present study was to analyse the effects of HBOT on the plasma oxidative and inflammation biomarkers and growth factors in patients with chronic diabetic wounds. The participants received 20 HBOT sessions (five sessions/week), and blood samples were obtained at sessions 1, 5 and 20, before and 2 h after the HBOT. An additional (control) blood sample was collected 28 days after wound recovery. No significant differences were evident in haematological parameters, whereas the biochemical parameters progressively decreased, which was significant for creatine phosphokinase (CPK) and aspartate aminotransferase (AST). The pro-inflammatory mediators, tumour necrosis factor alpha (TNF-α) and interleukin 1β (IL-1β), progressively decreased throughout the treatments. Biomarkers of oxidative stress--plasma protein levels of catalase, extracellular superoxide dismutase, myeloperoxidase, xanthine oxidase, malondialdehyde (MDA) levels and protein carbonyls--were reduced in accordance with wound healing. Plasma levels of growth factors--platelet-derived growth factor (PDFG), transforming growth factor β (TGF-β) and hypoxia-inducible factor 1-alpha (HIF-1α)-- were increased as a consequence of HBOT and reduced 28 days after complete wound healing, whereas matrix metallopeptidase 9 (MMP9) progressively decreased with the HBOT. In conclusion, HBOT reduced oxidative and pro-inflammatory mediators, and may participate in activating healing, angiogenesis and vascular tone regulation by increasing the release of growth factors.

Purine Metabolism Dysfunctions: Experimental Methods of Detection and Diagnostic Potential

Purines, such as adenine and guanine, perform several important functions in the cell. They are found in nucleic acids; are structural components of some coenzymes, including NADH and coenzyme A; and have a crucial role in the modulation of energy metabolism and signal transduction. Moreover, purines have been shown to play an important role in the physiology of platelets, muscles, and neurotransmission. All cells require a balanced number of purines for growth, proliferation, and survival. Under physiological conditions, enzymes involved in purines metabolism maintain a balanced ratio between their synthesis and degradation in the cell. In humans, the final product of purine catabolism is uric acid, while most other mammals possess the enzyme uricase that converts uric acid to allantoin, which can be easily eliminated with urine. During the last decades, hyperuricemia has been associated with a number of human extra-articular diseases (in particular, the cardiovascular ones) and their clinical severity. In this review, we go through the methods of investigation of purine metabolism dysfunctions, looking at the functionality of xanthine oxidoreductase and the formation of catabolites in urine and saliva. Finally, we discuss how these molecules can be used as markers of oxidative stress.

Prognostic impact of plasma xanthine oxidoreductase activity in patients with heart failure with atrial fibrillation

BACKGROUND

Xanthine oxidoreductase (XOR) is a rate-limiting enzyme for uric acid (UA) production and plays an important role in generating reactive oxygen species (ROS). Overproduction of ROS is reported to contribute to the pathophysiology of atrial fibrillation (AF), however, the prognostic impact of plasma XOR activity in patients with heart failure (HF) with AF is undetermined.

METHODS

We measured plasma XOR activity in 475 HF patients, including those with sinus rhythm (HF-SR, n = 211), and those with AF (HF-AF, n = 264). The type of AF included paroxysmal (n = 128) and persistent (n = 136) AF. All patients were prospectively followed up for a median period of 804 days.

RESULTS

HF-AF patients had significantly higher plasma XOR activity and serum UA levels compared with HF-SR patients. Both plasma XOR activity and serum UA levels were higher in patients with persistent AF than in those with SR and with paroxysmal AF. Multivariate linear regression analysis showed that persistent AF was independently associated with increased XOR activity. During the follow-up period, there were 79 major adverse cardiovascular events (MACEs). HF-AF patients with MACEs had higher plasma XOR activity compared with those without MACEs, while there were no significant differences in serum UA levels. Multivariate Cox proportional analysis showed that high XOR activity was an independent risk factor for MACEs after adjustment for confounding factors. Kaplan-Meier analysis revealed that the high XOR activity group had a higher risk of MACEs than the low XOR activity group. The prediction model was significantly improved by the addition of XOR activity to the basic predictors.

CONCLUSIONS

HF-AF patients had significantly higher plasma XOR activity compared with HF-SR patients. Plasma XOR activity proved to be a reliable indicator for MACEs in HF-AF patients.

Uric Acid Induces a Proatherothrombotic Phenotype in Human Endothelial Cells by Imbalancing the Tissue Factor/Tissue Factor Pathway Inhibitor Pathway

BACKGROUND

 Several evidence show that elevated plasma levels of uric acid (UA) are associated with the increased risk of developing atherothrombotic cardiovascular events. Hyperuricemia is a risk factor for endothelial dysfunction (ED). ED is involved in the pathophysiology of atherothrombosis since dysfunctional cells lose their physiological, antithrombotic properties. We have investigated whether UA might promote ED by modulating the tissue factor (TF)/TF pathway inhibitor (TFPI) balance by finally changing the antithrombotic characteristics of endothelial cells.

METHODS

 Human umbilical vein endothelial cells were incubated with increasing doses of UA (up to 9 mg/dL). TF gene and protein expressions were evaluated by real-time polymerase chain reaction (PCR) and Western blot. Surface expression and procoagulant activity were assessed by FACS (fluorescence activated cell sorting) analysis and coagulation assay. The mRNA and protein levels of TFPI were measured by real-time PCR and Western blot. The roles of inflammasome and nuclear factor-κB (NF-κB) as possible mechanism(s) of action of the UA on TF/TFPI balance were also investigated.

RESULTS

 UA significantly increased TF gene and protein levels, surface expression, and procoagulant activity. In parallel, TFPI levels were significantly reduced. The NF-κB pathways appeared to be involved in modulating these phenomena. Additionally, inflammasome might also play a role.

CONCLUSION

 The present in vitro study shows that one of the mechanisms by which high levels of UA contribute to ED might be the imbalance between TF/TFPI levels in endothelial cells, shifting them to a nonphysiological, prothrombotic phenotype. These UA effects might hypothetically explain, at least in part, the relationship observed between elevated plasma levels of UA and cardiovascular events.

Erectile Dysfunction: Pharmacological Pathways with Understudied Potentials

Erectile dysfunction (ED) is a public health concern worldwide. In the past, it was perceived as a phenomenon attributed to age advancement. However, more individuals are affected every year that do not fall under that age criterion. Epidemiological research revealed that this abnormality has an association with endothelial dysfunction connected to several cardiovascular (CV) risk factors. Currently, ED is interpreted as a clinical marker for future adverse events and not only as a present health issue that negatively affects the quality of life. The management of ED involves lifestyle modifications, therapeutic optimization for comorbid conditions, and pharmacological and psychosexual therapy. Phosphodiesterase type 5 (PDE5) inhibitors are the first-line pharmacological agents to be prescribed for such a condition. Nonetheless, other pharmacological pathways and agents remain underinvestigated or were investigated at some stage. This review aimed to present to future researchers interested in this field with some pharmacological agents that showed favorable effects on a limited number of studies on human subjects or experimental models.

Uric acid effects on glutathione metabolism estimated by induction of glutamate-cysteine ligase, glutathione reductase and glutathione synthetase in mouse J744A.1 macrophage cell line

INTRODUCTION

Elevated plasma levels of uric acid (UA) are considered an independent risk factor for hypertension, diabetes, cardiovascular disease, endothelial and vascular damage, obesity, and metabolic syndrome. Even physiological concentrations of soluble UA have been proved to induce gene expression of macrophage-secreted inflammatory cytokines and stimulate production of reactive oxygen species in mature adipocytes. UA is also described as a powerful endogenous plasma antioxidant, which reveals a paradox of duality for this parameter.

Maternal serum uric acid, creatinine and blood urea levels in the prediction of pre-eclampsia among pregnant women attending ANC and delivery services at Bahir Dar city public hospitals, northwest Ethiopia: A case-control study

Background

Pre-eclampsia (PE) is a metabolic disorder that adversely affects the lives of mother and their infants. Even though, several studies have been conducted on PE, no effective diagnostic and therapeutic agents were developed so far. Hence, this study was designed to evaluate serum uric acid, blood urea and creatinine levels in the prediction of PE.

Methods

A hospital-based case-control study was conducted among pregnant women. A simple random sampling technique was applied to select study participants. The socio-demographic and clinical data were collected using an interview-administered questionnaire. Serum samples were used to determine the maternal uric acid, urea and creatinine levels via an automated chemistry analyzer. Independent sample t-test, Pearson correlation test and receiver operating characteristic (ROC) curve analysis were performed to check the association and diagnostic accuracy of variables to PE.

Results

The mean ages (in years) of the case and control groups were 27.98 ± 5.64 and 27.33 ± 4.45, respectively. The mean serum uric acid and blood urea levels were significantly higher in pre-eclamptic women than in normotensive pregnant women (6.27 ± 0.20 vs 4.43 ± 0.15, and 8.50 ± 3.99 vs 5.67 ± 2.19), respectively but the serum creatinine level is non-significantly increased in cases as compared to controls (0.70 ± 0.05 vs 0.50 ± 0.01). The areas under the ROC curve of serum uric acid, creatinine and blood urea levels were 0.785, 0.735 and 0.764 (sensitivity: 69%, 60.7%, 67.9%; specificity: 73.8%, 75%, 71.4%) with the cutoff points of ≥5.25 mg/dL, ≥0.565 mg/dL and ≥6.5 mg/dL, respectively.

Conclusion

In this study, we observed a significantly higher concentration of serum uric acid and blood urea values in pre-eclampsia as compared with normotensive pregnant women. Therefore, this suggested that serum uric acid; blood urea and creatinine values can be associated with PE. Moreover, serum uric acid, blood urea and creatinine levels could be carefully utilized as a diagnostic marker for PE, but their inclusion in routine diagnostic test to PE requires large-scale multi-center prospective studies that corroborate our findings.

Allopurinol versus usual care in UK patients with ischaemic heart disease (ALL-HEART): a multicentre, prospective, randomised, open-label, blinded-endpoint trial

BACKGROUND

Allopurinol is a urate-lowering therapy used to treat patients with gout. Previous studies have shown that allopurinol has positive effects on several cardiovascular parameters. The ALL-HEART study aimed to determine whether allopurinol therapy improves major cardiovascular outcomes in patients with ischaemic heart disease.

METHODS

ALL-HEART was a multicentre, prospective, randomised, open-label, blinded-endpoint trial done in 18 regional centres in England and Scotland, with patients recruited from 424 primary care practices. Eligible patients were aged 60 years or older, with ischaemic heart disease but no history of gout. Participants were randomly assigned (1:1), using a central web-based randomisation system accessed via a web-based application or an interactive voice response system, to receive oral allopurinol up-titrated to a dose of 600 mg daily (300 mg daily in participants with moderate renal impairment at baseline) or to continue usual care. The primary outcome was the composite cardiovascular endpoint of non-fatal myocardial infarction, non-fatal stroke, or cardiovascular death. The hazard ratio (allopurinol vs usual care) in a Cox proportional hazards model was assessed for superiority in a modified intention-to-treat analysis (excluding randomly assigned patients later found to have met one of the exclusion criteria). The safety analysis population included all patients in the modified intention-to-treat usual care group and those who took at least one dose of randomised medication in the allopurinol group. This study is registered with the EU Clinical Trials Register, EudraCT 2013-003559-39, and ISRCTN, ISRCTN32017426.

FINDINGS

Between Feb 7, 2014, and Oct 2, 2017, 5937 participants were enrolled and then randomly assigned to receive allopurinol or usual care. After exclusion of 216 patients after randomisation, 5721 participants (mean age 72·0 years [SD 6·8], 4321 [75·5%] males, and 5676 [99·2%] white) were included in the modified intention-to-treat population, with 2853 in the allopurinol group and 2868 in the usual care group. Mean follow-up time in the study was 4·8 years (1·5). There was no evidence of a difference between the randomised treatment groups in the rates of the primary endpoint. 314 (11·0%) participants in the allopurinol group (2·47 events per 100 patient-years) and 325 (11·3%) in the usual care group (2·37 events per 100 patient-years) had a primary endpoint (hazard ratio [HR] 1·04 [95% CI 0·89-1·21], p=0·65). 288 (10·1%) participants in the allopurinol group and 303 (10·6%) participants in the usual care group died from any cause (HR 1·02 [95% CI 0·87-1·20], p=0·77).

INTERPRETATION

In this large, randomised clinical trial in patients aged 60 years or older with ischaemic heart disease but no history of gout, there was no difference in the primary outcome of non-fatal myocardial infarction, non-fatal stroke, or cardiovascular death between participants randomised to allopurinol therapy and those randomised to usual care.

FUNDING

UK National Institute for Health and Care Research.

Phytochemical characterization and antimicrobial activity of Nigella sativa seeds

Nigella sativa is one of the medicinal plant species that gained popularity for a wide range of medicinal applications due to its seeds which are rich in phytoconstituents. Continuous scientific investigations on N. sativa seeds are needed to better understand its many medicinal potentials. This will also form a composition-based foundation that support several old and/or new case beneficial histories of its seeds. In this study, the antimicrobial activity of N. sativa seeds was phytochemically characterized and evaluated. Different extracts of N. sativa seeds were obtained by maceration and soxhlet extraction methods using different extraction solvents. The obtained extracts were tested using UV-Vis, FTIR, TLC, and GC-MS techniques. Antimicrobial analysis against pathogenic bacterial strains (E. coli, P. aeruginosa, S. aureus and B. subtilis) was carried out by disc diffusion method using different preparations of N. sativa seeds. The screening analysis revealed the presence of all the tested phytochemicals. FT-IR analysis of N. sativa seeds oil extracted with absolute ethanol revealed functional groups that are associated with active ingredients of medicinal value. The GC-MS chromatograms revealed different chemical constituents whose known bioactivities and/or applications are essential in the management of life-threatening infections. Different extracts of N. sativa seeds showed antimicrobial activity with different efficacy against the tested pathogenic bacterial strains. Therefore, this study shows that extracts of N. sativa seeds contain a variety of chemical components and functional groups linked to their antimicrobial properties, and they might be natural precursors of nutraceuticals.

Hyperuricemia is Associated with the Presence of Metabolically Obese Normal-Weight and Metabolically Healthy Obese Phenotypes

BACKGROUND

It is well-recognized that hyperuricemia is a common abnormality among individuals with metabolic syndrome.

AIMS

The objective of this study was to determine whether hyperuricemia is associated with the metabolically obese normal-weight (MONW) and metabolically healthy obese (MHO) phenotypes.

METHODS

Men and women equal or greater than 18 years of age were enrolled in a cross-sectional study. Normal-weight subjects were allocated into the MONW or healthy normal-weight (HNW) groups; while obese individuals were divided into the MHO and metabolically unhealthy obese (MUO) subgroups. MONW phenotype was defined by body mass index (BMI) <25.0 kg/m² accompanied by at least one cardiovascular risk factor (hyperglycemia, elevated blood pressure, hypertriglyceridemia, and low high-density lipoprotein cholesterol), and MHO phenotype was considered in obese subjects (BMI ≥30 kg/m²) without metabolic abnormalities.

RESULTS

A total of 567 individuals were enrolled; of them, normal-weight subjects were allocated into the MONW (n = 101) and control (n = 72) groups, whereas obese individuals into the MHO (n = 61) and MUO (n = 333) groups. The multiple logistic regression analysis adjusted by age, gender, and body mass index revealed that hyperuricemia is significantly associated with MONW (OR = 5.14; 95% CI: 1.37-19.29) and MHO (OR = 0.34; 95% CI: 0.14-0.82) phenotypes.

CONCLUSION

Results of our study showed that hyperuricemia is associated with both MONW and MHO phenotypes.

Allopurinol Lowers Serum Urate but Does Not Reduce Oxidative Stress in CKD

Xanthine oxidase (XO) contributes to oxidative stress and vascular disease. Hyperuricemia and gout are common in patients with chronic kidney disease (CKD), a population at increased risk of vascular disease. We evaluated effects of allopurinol on serum XO activity and metabolome of CKD patients who had participated in a randomized double-blind clinical trial of allopurinol vs. placebo. XO activity was measured in participants' serum. XO expression in venous endothelial cells was evaluated via immunofluorescence. Gas chromatography mass spectrometry (GC/MS) was utilized for metabolomics analysis. We found that in patients with stage 3 CKD and hyperuricemia, allopurinol lowered serum urate while increasing serum xanthine levels. Allopurinol, however, did not significantly suppress measured serum XO activity. Of note, baseline serum XO activity was low. Additionally, neither baseline serum XO activity nor XO protein expression were associated with measures of vascular dysfunction or with systemic or endothelial biomarkers of oxidative stress. Allopurinol affected several pathways, including pentose phosphate, pyrimidine, and tyrosine metabolism. Our findings suggest that circulating XO does not contribute to vascular disease in CKD patients. In addition to inhibition of XO activity, allopurinol was observed to impact other pathways; the implications of which require further study.

Pharmacological developments in antihypertensive treatment through nitric oxide-cGMP modulation

Treatment of hypertension until now has been directed at inhibition of vasoconstriction, of cardiac contractility and of blood volume regulation. Despite the arsenal of drugs available for this purpose, the control of target blood pressure is still a difficult goal to reach in outpatients. The nitric oxide-cyclic guanosine monophosphate signaling is one of the most important mediators of vasodilation. It might therefore be a potential and most welcome drug target for optimization of the treatment of hypertension. In this chapter we review the problems that can occur in this signaling system, the attempts that have been made to correct these problems, and those that are still under investigation. Recently developed, clinically safe medicines that are currently approved for other applications, such as myocardial infarction, await to be tested for essential systemic hypertension. We conclude that despite many years of research without translation, stimulation of nitric oxide-cyclic guanosine monophosphate is still a viable strategy in the prevention of the health risk posed by chronic hypertension.

Excess comorbidities in gout: the causal paradigm and pleiotropic approaches to care

Gout is a common hyperuricaemic metabolic condition that leads to painful inflammatory arthritis and a high comorbidity burden, especially cardiometabolic-renal (CMR) conditions, including hypertension, myocardial infarction, stroke, obesity, hyperlipidaemia, type 2 diabetes mellitus and chronic kidney disease. Substantial advances have been made in our understanding of the excess CMR burden in gout, ranging from pathogenesis underlying excess CMR comorbidities, inferring causal relationships from Mendelian randomization studies, and potentially discovering urate crystals in coronary arteries using advanced imaging, to clinical trials and observational studies. Despite many studies finding an independent association between blood urate levels and risk of incident CMR events, Mendelian randomization studies have largely found that serum urate is not causal for CMR end points or intermediate risk factors or outcomes (such as kidney function, adiposity, metabolic syndrome, glycaemic traits or blood lipid concentrations). Although limited, randomized controlled trials to date in adults without gout support this conclusion. If imaging studies suggesting that monosodium urate crystals are deposited in coronary plaques in patients with gout are confirmed, it is possible that these crystals might have a role in the inflammatory pathogenesis of increased cardiovascular risk in patients with gout; removing monosodium urate crystals or blocking the inflammatory pathway could reduce this excess risk. Accordingly, data for CMR outcomes with these urate-lowering or anti-inflammatory therapies in patients with gout are needed. In the meantime, highly pleiotropic CMR and urate-lowering benefits of sodium-glucose cotransporter 2 (SGLT2) inhibitors and key lifestyle measures could play an important role in comorbidity care, in conjunction with effective gout care based on target serum urate concentrations according to the latest guidelines.

Serum Uric Acid and Risk of Chronic Heart Failure: A Systematic Review and Meta-Analysis

Objectives: A systematic review and meta-analysis was performed to evaluate the potential prognostic role of serum uric acid (SUA) in patients with chronic heart failure (CHF).

Methods: The Embase, PubMed, Web of Science and Cochrane Library databases were searched up to 5 April 2021 for relevant publications. Random effects model was used to pool data. STATA15.0 software was used to perform meta-analysis. Heterogeneity was assessed using the Cochran Q statistic (significance level of P < 0.10) and I² statistics (significance level of 50%).

Results: Ultimately, 18 publications reporting adverse events in CHF patients were included. The results indicate reveal associations between a high level of SUA and the risk of all-cause mortality (HR 2.24, 95% CI 1.49–3.37), cardiovascular mortality (HR 1.14, 95% CI 1.06–1.23), and the composite of death or cardiac events (HR 1.26, 95% CI 1.01–1.56) in CHF patients. A 1 mg/dL increase in serum uric acid led to 4% (HR 1.04, 95% CI 1.02–1.05) and 9% (HR 1.09, 95% CI 1.03–1.17) increases in the risk of all-cause mortality and the composite endpoint of death or cardiac events in CHF patients, respectively.

Conclusion: Serum uric acid is positively associated with the risk of adverse events in CHF patients. This study protocol has been registered at PROSPERO as CRD42021247084 (https://www.crd.york.ac.uk/PROSPERO).

Systematic Review Registration:https://www.crd.york.ac.uk/PROSPERO.

Association Between Serum Uric Acid and Carotid Intima-Media Thickness in Different Fasting Blood Glucose Patterns: A Case-Control Study

Our objective was to analyze the correlation between serum uric acid (SUA) levels and carotid intima-media thickness (CIMT) and explore the relationship between SUA and carotid atherosclerosis in different glucose metabolism patterns. A total of 614 patients were enrolled in this case-control study, including 406 in the normouricemia group and 208 in the hyperuricemia group. The two groups were each divided into three groups according to fasting blood glucose (FBG) level: normal, impaired fasting glucose (IFG), and diabetes mellitus (DM). CIMT and the CIMT thickening rate in the hyperuricemia group were significantly higher than those in the normouricemia group: 0.17 (0.11-0.24) cm vs. 0.12 (0.08-0.15) cm and 73.56% vs. 51.97% (p < 0.001). Pearson's correlation analysis showed that age, systolic blood pressure (SBP), diastolic blood pressure, FBG, triglyceride, SUA, creatinine, and blood urea nitrogen were positively correlated with CIMT, whereas high-density lipoprotein cholesterol and total cholesterol were negatively correlated with CIMT. Multiple linear regression analysis showed that age, SUA, FBG, and SBP were independent factors that affected CIMT. Furthermore, age and SBP were independent factors in the normouricemia group, and FBG was an independent factor that affected CIMT in the hyperuricemia group (p < 0.05). In the hyperuricemia group, CIMT in the DM group was significantly higher than that in the normal group [0.20 (0.14-0.25)cm vs. 0.15 (0.1-0.25); p < 0.05], and the CIMT thickening rate in the DM group was significantly higher than those in the IFG and normal groups (90.38% vs. 78.38%, 90.38% vs. 65.81%; p < 0.05). The ROC curve analysis showed that uric acid combined with age, SBP, and FBG had the highest area under the curve (AUC) for predicting CIMT thickening [0.855 (95% confidence interval (CI): 0.804-0.906)], followed by uric acid combined with FBG [AUC: 0.767 (95% CI: 0.726-0.808)]. In conclusion, SUA was closely associated with an increase in CIMT in patients with specific FBG metabolic patterns and may be an independent risk factor for carotid atherosclerosis. SUA, especially in combination with other factors (such as age, SBP, FBG), may serve as a specific model to help predict the incidence of CIMT thickening. Clinical Trial Registration: http://www.chictr.org.cn, identifier ChiCTR2000039124.

The association between uric acid and erectile dysfunction: A systematic review and Meta-analysis

The main purpose of this systematic review and meta-analysis was to explore the association between uric acid (UA) and erectile dysfunction (ED). Databases including PubMed, Cochrane Library and Web of Science were retrieved to identify studies published in English up to 31 June 2021. We preregistered this meta-analysis in the PROSPERO (registration number CRD42021267035). Two independent authors extracted the relevant data from all enrolled articles. We evaluated the quality of enrolled studies using the Newcastle-Ottawa Scale (NOS). The standardized mean difference (SMD), as well as the corresponding 95% confidence intervals (95% CIs), was used to assess the difference between ED patients and healthy subjects. A total of five studies were enrolled for our meta-analysis to explore the association of UA with ED. The pooled SMD of the UA level difference between ED patients and healthy subjects was 0.42 (95% CI:0.09, 0.74, p < 0.001). There were no individual data that significantly influenced the pooled SMDs in the sensitivity analysis. There was no evidence of publication bias. This novel meta-analysis confirmed that UA was an independent risk factor for ED, which suggested that the erectile function of patients with elevated uric acid should be evaluated by clinicians.

Effect of Topiroxostat on Brain Natriuretic Peptide Level in Patients with Heart Failure with Preserved Ejection Fraction: A Pilot Study

BACKGROUND

Various optimal medical therapies have been established to treat heart failure (HF) with reduced ejection fraction (HFrEF). Both HFrEF and HF with preserved ejection fraction (HFpEF) are associated with poor outcomes. We investigated the effect of topiroxostat, an oral xanthine oxidoreductase inhibitor, for HFpEF patients with hyperuricemia or gout.

METHODS

In this nonrandomized, open-label, single-arm trial, we administered topiroxostat 40-160 mg/day to HFpEF patients with hyperuricemia or gout to achieve a target uric acid level of 6.0 mg/dL. The primary outcome was rate of change in log-transformed brain natriuretic peptide (BNP) level from baseline to 24 weeks after topiroxostat treatment. The secondary outcomes included amount of change in BNP level, uric acid evaluation values, and oxidative stress marker levels after 24 weeks of topiroxostat treatment. Thirty-six patients were enrolled; three were excluded before study initiation.

RESULTS

Change in log-transformed BNP level was -3.4 ± 8.9% (p = 0.043) after 24 weeks of topiroxostat treatment. The rate of change for the decrease in BNP level was -18.0 (-57.7, 4.0 pg/mL; p = 0.041). Levels of uric acid and 8-hydroxy-2'-deoxyguanosine/creatinine, an oxidative stress marker, also significantly decreased (-2.8 ± 1.6 mg/dL, p < 0.001, and -2.3 ± 3.7 ng/mgCr, p = 0.009, respectively).

CONCLUSIONS

BNP level was significantly lower in HFpEF patients with hyperuricemia or gout after topiroxostat administration; however, the rate of decrease was low. Further trials are needed to confirm our findings.

Increased QT Dispersion and High Risk of Ventricular Arrhythmias is Associated with Hyperuricemia in Individuals with Normal Renal Function

Background and aim: Uric acid elevation has been shown to be an important risk factor for cardiovascular and cerebrobascular disease. QT dispersion (QTd) is a parameter that shows the heterogeneity of ventricular repolarization and can be calculated noninvasively from surface electrocardiography. Increased QTd has been associated with severe arrhythmia and risk of sudden death in many patients and disease groups. In this context, we aimed to investigate the effect of uric acid levels on QTd and the effects of decrease in uric acid levels on QTd.

Methods: A total of 225 patients with normal renal function were included in the study; 133 of these patients were hyperuricemic (>7 mg/dL), and the remaining 72 patients were normouricemic (Group 1). The hyperuricemic patients were randomly divided into 2 groups, one group (n = 67) was given placebo (Group 2) for 4 months, and the remaining 66 patients were given allopurinol 300 mg/day (Group 3).

Results: Hyperuricemic patients had higher hsCRP and QTd and lower eGFR values compared to the normouricemic control group. After 4 months of treatment, 66 patients treated with allopurinol showed a significant decrease in serum uric acid, systolic and diastolic blood pressure, and hsCRP levels, and a significant increase in eGFR. Although the QTd values in the treatment group did not decrease to the same levels as in the normouricemic control group, a statistically significant decrease was found compared to their baseline values. In hyperuricemic control and normouricemic control patients, there were no differences in the levels of uric acid, hsCRP, eGFR, systolic and diastolic blood pressure, and QTd values compared to baseline values.

Conclusions: There was a significant association between elevated serum uric acid and QTd, as well as with inflammatory biomarkers. Also, patients who had received hypouricemic therapy during the follow-up period presented a significant decrease in inflammatory markers as well as QTd. This indicates the beneficial effects of decreasing uric acid levels in decreasing the risk for future major adverse events related to ventricular arrhythmias.

Human and rodent red blood cells do not demonstrate xanthine oxidase activity or XO-catalyzed nitrite reduction to NO

A number of molybdopterin enzymes, including xanthine oxidoreductase (XOR), aldehyde oxidase (AO), sulfite oxidase (SO), and mitochondrial amidoxime reducing component (mARC), have been identified as nitrate and nitrite reductases. Of these enzymes, XOR has been the most extensively studied and reported to be a substantive source of nitric oxide (NO) under inflammatory/hypoxic conditions that limit the catalytic activity of the canonical NOS pathway. It has also been postulated that XOR nitrite reductase activity extends to red blood cell (RBCs) membranes where it has been immunohistochemically identified. These findings, when combined with countervailing reports of XOR activity in RBCs, incentivized our current study to critically evaluate XOR protein abundance/enzymatic activity in/on RBCs from human, mouse, and rat sources. Using various protein concentrations of RBC homogenates for both human and rodent samples, neither XOR protein nor enzymatic activity (xanthine → uric acid) was detectable. In addition, potential loading of RBC-associated glycosaminoglycans (GAGs) by exposing RBC preparations to purified XO before washing did not solicit detectable enzymatic activity (xanthine → uric acid) or alter NO generation profiles. To ensure these observations extended to absence of XOR-mediated contributions to overall RBC-associated nitrite reduction, we examined the nitrite reductase activity of washed and lysed RBC preparations via enhanced chemiluminescence in the presence or absence of the XOR-specific inhibitor febuxostat (Uloric®). Neither addition of inhibitor nor the presence of the XOR substrate xanthine significantly altered the rates of nitrite reduction to NO by RBC preparations from either human or rodent sources confirming the absence of XO enzymatic activity. Furthermore, examination of the influence of the age (young cells vs. old cells) of human RBCs on XO activity also failed to demonstrate detectable XO protein. Combined, these data suggest: 1) that XO does not contribute to nitrite reduction in/on human and rodent erythrocytes, 2) care should be taken to validate immuno-detectable XO by demonstrating enzymatic activity, and 3) XO does not associate with human erythrocytic glycosaminoglycans or participate in nonspecific binding.

Physical Exercise Protects Against Endothelial Dysfunction in Cardiovascular and Metabolic Diseases

Increasing evidence shows that endothelial cells play critical roles in maintaining vascular homeostasis, regulating vascular tone, inhibiting inflammatory response, suppressing lipid leakage, and preventing thrombosis. The damage or injury of endothelial cells induced by physical, chemical, and biological risk factors is a leading contributor to the development of mortal cardiovascular and cerebrovascular diseases. However, the underlying mechanism of endothelial injury remains to be elucidated. Notably, no drugs effectively targeting and mending injured vascular endothelial cells have been approved for clinical practice. There is an urgent need to understand pathways important for repairing injured vasculature that can be targeted with novel therapies. Exercise training-induced protection to endothelial injury has been well documented in clinical trials, and the underlying mechanism has been explored in animal models. This review mainly summarizes the protective effects of exercise on vascular endothelium and the recently identified potential therapeutic targets for endothelial dysfunction.

Xanthine Oxidase-Induced Inflammatory Responses in Respiratory Epithelial Cells: A Review in Immunopathology of COVID-19

Xanthine oxidase (XO) is an enzyme that catalyzes the production of uric acid and superoxide radicals from purine bases: hypoxanthine and xanthine and is also expressed in respiratory epithelial cells. Uric acid, which is also considered a danger associated molecule pattern (DAMP), could trigger a series of inflammatory responses by activating the inflammasome complex path and NF-κB within the endothelial cells and by inducing proinflammatory cytokine release. Concurrently, XO also converts the superoxide radicals into hydroxyl radicals that further induce inflammatory responses. These conditions will ultimately sum up a hyperinflammation condition commonly dubbed as cytokine storm syndrome (CSS). The expression of proinflammatory cytokines and neutrophil chemokines may be reduced by XO inhibitor, as observed in human respiratory syncytial virus (HRSV)-infected A549 cells. Our review emphasizes that XO may have an essential role as an anti-inflammation therapy for respiratory viral infection, including coronavirus disease 2019 (COVID-19).

Redox signaling in heart failure and therapeutic implications

Heart failure is a growing health burden worldwide characterized by alterations in excitation-contraction coupling, cardiac energetic deficit and oxidative stress. While current treatments are mostly limited to antagonization of neuroendocrine activation, more recent data suggest that also targeting metabolism may provide substantial prognostic benefit. However, although in a broad spectrum of preclinical models, oxidative stress plays a causal role for the development and progression of heart failure, no treatment that targets reactive oxygen species (ROS) directly has entered the clinical arena yet. In the heart, ROS derive from various sources, such as NADPH oxidases, xanthine oxidase, uncoupled nitric oxide synthase and mitochondria. While mitochondria are the primary source of ROS in the heart, communication between different ROS sources may be relevant for physiological signalling events as well as pathologically elevated ROS that deteriorate excitation-contraction coupling, induce hypertrophy and/or trigger cell death. Here, we review the sources of ROS in the heart, the modes of pathological activation of ROS formation as well as therapeutic approaches that may target ROS specifically in mitochondria.

Plasma uric acid is related to large arterial stiffness but not to other hemodynamic variables: a study in 606 normotensive and never-medicated hypertensive subjects

Background

Elevated level of plasma uric acid (PUA) has been associated with cardiovascular disease, but whether uric acid is an independent risk factor or merely a marker remains controversial.

Methods

We investigated in a cross-sectional setting the association of PUA with hemodynamics in 606 normotensive and never-medicated hypertensive subjects (295 men, 311 women, age range 19–73 years) without cardiovascular disease or gout. In all except 15 individuals, PUA was within the normal range. Supine hemodynamics were recorded using whole-body impedance cardiography and radial tonometric pulse wave analysis.

Results

The mean concentrations of PUA in age, sex and body mass index adjusted quartiles were 234, 278, 314, and 373 µmol/l, respectively. The highest PUA quartile presented with higher aortic to popliteal pulse wave velocity (PWV) than the lowest quartile (8.7 vs. 8.2 m/s, p = 0.026) in analyses additionally adjusted for plasma concentrations of C-reactive protein, low density lipoprotein cholesterol, triglycerides, and mean aortic blood pressure. No differences in radial and aortic blood pressure, wave reflections, heart rate, cardiac output, and systemic vascular resistance were observed between the quartiles. In linear regression analysis, PUA was an independent explanatory factor for PWV (β = 0.168, p < 0.001, R² of the model 0.591), but not for systolic or diastolic blood pressure. When the regression analysis was performed separately for men and women, PUA was an independent predictor of PWV in both sexes.

Conclusions

PUA concentration was independently and directly associated with large arterial stiffness in individuals without cardiovascular disease and PUA levels predominantly within the normal range. Trial registration ClinicalTrials.gov NCT01742702.

Targeting Xanthine Oxidase by Natural Products as a Therapeutic Approach for Mental Disorders

Mental disorders comprise diverse human pathologies, including depression, bipolar affective disorder, schizophrenia, and dementia that affect millions of people around the world. The causes of mental disorders are unclear, but growing evidence suggests that oxidative stress and the purine/adenosine system play a key role in their development and progression. Xanthine oxidase (XO) is a flavoprotein enzyme essential for the catalysis of the oxidative hydroxylation of purines -hypoxanthine and xanthine- to generate uric acid. As a consequence of the oxidative reaction of XO, reactive oxygen species (ROS) such as superoxide and hydrogen peroxide are produced and, further, contribute to the pathogenesis of mental disorders. Altered XO activity has been associated with free radical-mediated neurotoxicity inducing cell damage and inflammation. Diverse studies reported a direct association between an increased activity of XO and diverse mental diseases including depression or schizophrenia. Small-molecule inhibitors, such as the well-known allopurinol, and dietary flavonoids, can modulate the XO activity and subsequent ROS production. In the present work, we review the available literature on XO inhibition by small molecules and their potential therapeutic application in mental disorders. In addition, we discuss the chemistry and molecular mechanism of XO inhibitors, as well as the use of structure-based and computational methods to design specific inhibitors with the capability of modulating XO activity.

Independent association of serum uric acid levels with arterial stiffness in the absence of established cardiovascular disorders

BACKGROUND

The impact of serum uric acid (SUA) on atherosclerosis has been suspected to be epiphenomenal owing to its close relationship with metabolic abnormalities. The aim of the present study was to evaluate the association between SUA levels and arterial stiffness in the absence of established cardiovascular (CV) disorders.

METHODS

The relationship between SUA levels and brachial-ankle pulse wave velocity (baPWV) was examined in 353 asymptomatic adults (57 ± 8 years, 11.9% men) without established CV disorders defined as systolic blood pressure (BP) ≥140 mmHg or diastolic BP ≥ 90 mmHg; total cholesterol ≥240 mg/dL; low-density lipoprotein cholesterol ≥160 mg/dL; high-density lipoprotein cholesterol <40 mg/dL; fasting glucose ≥126 mg/dL; body mass index ≥25.0 kg/m² ; current smoking; and history of medication for hypertension, diabetes, and dyslipidemia. Subjects were stratified into four groups based on the quartiles of their SUA levels.

RESULTS

Mean baPWV was significantly different in all groups: group I, 1320 ± 195 cm/s; group II, 1336 ± 195 cm/s; group III, 1404 ± 199 cm/s; and group IV, 1483 ± 248 cm/s (P < .001). SUA levels were significantly correlated with baPWV (r = .364) (P < .001). Multivariate linear regression analysis showed that SUA (β: 32.93; 95% confidence interval [CI]: 18.99-54.87), together with age (β: 11.44; 95% CI: 9.36-13.53) and systolic BP (β: 8.98; 95% CI: 6.80-11.16), was significantly associated with baPWV (P < .001).

CONCLUSIONS

High SUA levels have an independent association with increased arterial stiffness even in subjects without established CV disorders.

Hyperuricemia Is Not an Independent Predictor of Erectile Dysfunction

INTRODUCTION

Erectile dysfunction (ED) is strongly associated with physiological and metabolic disturbances, and hyperuricemia has been proposed to predict the onset of ED.

AIM

To investigate if hyperuricemia is an independent predictor for ED when all relevant confounding factors are taken into account.

METHODS

This is a cross-sectional study of men aged between 45 and 70 years. The population was well characterized for established cardiovascular risk factors, metabolic syndrome, as well as kidney function, depression, and socioeconomic factors. Analysis was limited to 254 men with complete data and also serum uric acid (SUA) measurements were available. This included 150 men with and 104 without ED. The presence and severity of ED was evaluated using International Index of Erectile Function-5 questionnaire. Risk of ED by SUA level was calculated using univariate and multivariable-adjusted logistic regression. Effect modification by participant characteristics were evaluated in subgroup analyses.

MAIN OUTCOME MEASURES

The main outcome measures of this study are prevalence and severity of erectile dysfunction.

RESULTS

Patients with ED (59% of the study population) were older than men without ED (59 vs 54 years) and had lower serum testosterone (14.3, 95% CI 11.3-17.3 vs 15.1 nmol/l, 95% CI 12.1-18.8, respectively). Regarding all other variables, the groups were comparable. No significant difference was found for SUA by ED. SUA was not associated with ED risk in univariate or multivariable analysis (multivariable-adjusted OR 1.14, 95% CI 0.59-2.19, P = .7) for SUA level higher than median compared with median or lesser (OR 1.00, 95% CI 0.997-1.006, P = .7 for continuous variable). No subgroup analysis modified the association. After multivariable adjustment age, education level and depression were statistically significant predictors of ED.

CONCLUSIONS

Elevated SUA was not found to be an independent risk factor for ED. Metabolic syndrome, glomerular filtration rate, or cardiovascular risk factors did not modify this result. ED cannot be predicted based on the level of SUA. A Tuokko, T Murtola, P Korhonen, et al. Hyperuricemia Is Not an Independent Predictor of Erectile Dysfunction. Sex Med 2021;9:100319.

Asymptomatic hyperuricemia: is it really asymptomatic?

PURPOSE OF REVIEW

Hyperuricemia is highly prevalent, affecting approximately 38 million individuals in the United States. However, the significance of asymptomatic hyperuricemia - hyperuricemia in the absence of gout - continues to be debated.

RECENT FINDINGS

Asymptomatic hyperuricemia results in monosodium urate crystal deposition in tissues, which may promote chronic inflammation. Intracellularly, hyperuricemia inhibits the master regulator adenosine monophosphate (AMP)-associated protein kinase and may condition innate immune responses through durable epigenetic modifications. At the population level, asymptomatic hyperuricemia is associated with multiple comorbidities, including hypertension, chronic kidney disease, coronary artery disease, and diabetes; limitations of these studies include that most are retrospective and some do not rigorously distinguish between asymptomatic hyperuricemia and gout. Treatment studies suggest that urate lowering may reduce the risk of incidence or progression of some of these comorbidities; unfortunately, many of these treatment studies are small or flawed, and not all study results are consistent.

SUMMARY

Accumulating evidence suggests that asymptomatic hyperuricemia contributes to the comorbidities with which it associates and that proper asymptomatic hyperuricemia treatment may reduce future risk. Additional prospective trials are needed to definitely establish causality and support decision-making as to whether, and which patients with asymptomatic hyperuricemia would warrant urate-lowering treatment.

Clinical Implications of Uric Acid in Heart Failure: A Comprehensive Review

Affecting more than 26 million people worldwide and with rising prevalence, heart failure (HF) represents a major global health problem. Hence, further research is needed in order to abate poor HF outcomes and mitigate significant expenses that burden health care systems. Based on available data, experts agree that there is an urgent need for a cost-effective prognostic biomarker in HF. Although a significant number of biomarkers have already been investigated in this setting, the clinical utility of adding biomarker evaluation to routine HF care still remains ambiguous. Specifically, in this review we focused on uric acid (UA), a purine metabolism detriment whose role as cardiovascular risk factor has been exhaustingly debated for decades. Multiple large population studies indicate that UA is an independent predictor of mortality in acute and chronic HF, making it a significant prognostic factor in both settings. High serum levels have been also associated with an increased incidence of HF, thus expanding the clinical utility of UA. Importantly, emerging data suggests that UA is also implicated in the pathogenesis of HF, which sheds light on UA as a feasible therapeutic target. Although to date clinical studies have not been able to prove the benefits of xanthine oxidase in HF patients, we discuss the putative role of UA and xanthine oxidase in the pathophysiology of HF as a therapeutic target.

Uric acid and cardiovascular disease: A clinical review

Uric acid, the end-product of purine metabolism in humans, is not only a cause of gout, but also may play roles in developing cardiovascular diseases such as hypertension, atrial fibrillation, chronic kidney disease, heart failure, coronary artery disease, and cardiovascular death. Several clinical investigations have reported serum uric acid as a predictive marker for cardiovascular outcomes. Although the causal relationship of hyperuricemia to cardiovascular diseases remains controversial, there has been a growing interest in uric acid because of the increased prevalence of hyperuricemia worldwide. This review article summarizes current evidence concerning the relation between hyperuricemia and cardiovascular diseases.

Uric Acid and Cardiovascular Disease: An Update From Molecular Mechanism to Clinical Perspective

Uric acid (UA) is the end product of purine nucleotide metabolism in the human body. Hyperuricemia is an abnormally high level of UA in the blood and may result in arthritis and gout. The prevalence of hyperuricemia has been increasing globally. Epidemiological studies have shown that UA levels are positively correlated with cardiovascular diseases, including hypertension, atherosclerosis, atrial fibrillation (AF), and heart failure (HF). Hyperuricemia promotes the occurrence and development of cardiovascular diseases by regulating molecular signals, such as inflammatory response, oxidative stress, insulin resistance/diabetes, endoplasmic reticulum stress, and endothelial dysfunction. Despite extensive research, the underlying molecular mechanisms are still unclear. Allopurinol, a xanthine oxidase (XO) inhibitor, has been shown to improve cardiovascular outcomes in patients with HF, coronary heart disease (CHD), type 2 diabetes (T2D), and left ventricular hypertrophy (LVH). Whether febuxostat, another XO inhibitor, can improve cardiovascular outcomes as well as allopurinol remains controversial. Furthermore, it is also not clear whether UA-lowering treatment (ULT) can benefit patients with asymptomatic hyperuricemia. In this review, we focus on the latest cellular and molecular findings of cardiovascular disease associated with hyperuricemia and clinical data about the efficacy of ULT in patients with cardiovascular disease.

Role of endothelial dysfunction in heart failure

Coronary artery disease is a major underlying etiology for heart failure. The role of coronary microvascular disease, and endothelial dysfunction, in the pathophysiology of heart failure is poorly appreciated. Endothelial dysfunction, induced by oxidative stress, contributes to the development of heart failure. Alterations of endothelial function and nitric oxide-cyclic guanosine monophosphate (NO-cGMP) pathway are involved in the pathophysiology of heart failure with both reduced and preserved ejection fraction. Indeed, an altered endothelium dependent vasodilatation, causing repeated episodes of ischemia/reperfusion, can induce a chronic stunned myocardium with systolic dysfunction and an increased diastolic stiffness with diastolic dysfunction. Moreover, the altered NO-cGMP pathway directly affects myocardial homeostasis. Endothelial dysfunction is associated with worse prognosis and higher rate of cardiovascular events. Potential therapeutic strategies targeting the NO-cGMP pathway in patients with HF will be discussed in this review article. Although clinical data are still inconclusive, the NO-cGMP pathway represents a promising target for therapy.

Renal effects of uric acid: hyperuricemia and hypouricemia

The prevalence of chronic kidney disease (CKD) is increasing worldwide. Although hyperuricemia has been associated with CKD in many studies, it remains controversial whether this is the cause or the result of decreased renal function. Recent observational studies of healthy populations and patients with CKD have reported that uric acid (UA) has an independent role in the development or progression of CKD. Experimental studies have shown several potential mechanisms by which hyperuricemia may cause or promote CKD. However, other reports have indicated an association between hypouricemia and CKD. This opposing effect is hypothesized to occur because UA is a major antioxidant in human plasma and is associated with oxidative stress. In this article, we discuss the potential association between UA imbalance and CKD and how they can be treated.

Network Meta-Analysis of Drug Therapies for Lowering Uric Acid and Mortality Risk in Patients with Heart Failure

PURPOSE

This network meta-analysis aimed to assess the current efficacy of decreasing the uric acid (UA) level with drugs to reduce mortality in patients with heart failure (HF).

METHODS

Electronic literature searches using EMBASE and MEDLINE of studies published from 1 Jan 1950 to 26 Dec 2019 were conducted for randomized controlled trials or non-randomized cohort studies that included at least one group of patients who took UA-lowering drugs and with a study outcome of all-cause mortality. A random-effects network meta-analysis was performed within a frequentist framework. Hierarchy of treatments was expressed as the surface under the cumulative ranking curve (SUCRA) value, which is in proportion to mean rank (best is 100%).

RESULTS

Nine studies, which included seven different types of groups, were eligible for analysis. The "untreated uricemia" group in which patients had hyperuricemia but without treatment had a significantly higher risk of mortality than the "no uricemia" group in which patients had no hyperuricemia (relative risk (RR)(95% confidence interval (CI), 1.43 (1.08-1.89)). The "start-allo" group wherein patients started to take allopurinol did not have a significantly lower risk of mortality than the "untreated uricemia" group (RR (95% CI), 0.68 (0.45-1.01)). However, in the "start-allo" group the SUCRA value was comparable to that in the "no uricemia" group (SUCRA: 65.4% for "start-allo"; 64.1% for "no uricemia").

CONCLUSIONS

Results suggested that allopurinol therapy was not associated with a significantly improved prognosis in terms of mortality but could potentially counteract the adverse effects associated with longstanding hyperuricemia in HF patients.

Effect of allopurinol on phosphocreatine recovery and muscle function in older people with impaired physical function: a randomised controlled trial

Background

Allopurinol has vascular antioxidant effects and participates in purinergic signalling within muscle. We tested whether allopurinol could improve skeletal muscle energetics and physical function in older people with impaired physical performance.

Methods

We conducted a randomised, double blind, parallel group, placebo-controlled trial, comparing 20 weeks of allopurinol 600 mg once daily versus placebo. We recruited community-dwelling participants aged 65 and over with baseline 6-min walk distance of <400 m and no contraindications to magnetic resonance imaging scanning. Outcomes were measured at baseline and 20 weeks. The primary outcome was post-exercise phosphocreatine (PCr) recovery rate measured using ³¹P magnetic resonance spectroscopy of the calf. Secondary outcomes included 6-min walk distance, short physical performance battery (SPPB), lean body mass measured by bioimpedance, endothelial function and quality of life.

Results

In total, 124 participants were randomised, mean age 80 (SD 6) years. A total of 59 (48%) were female, baseline 6-min walk distance was 293 m (SD 80 m) and baseline SPPB was 8.5 (SD 2.0). Allopurinol did not significantly improve PCr recovery rate (treatment effect 0.10 units [95% CI, −0.07 to 0.27], P = 0.25). No significant changes were seen in endothelial function, quality of life, lean body mass or SPPB. Allopurinol improved 6-min walk distance (treatment effect 25 m [95% 4–46, P = 0.02]). This was more pronounced in those with high baseline oxidative stress and urate.

Conclusion

Allopurinol improved 6-min walk distance but not PCr recovery rate in older people with impaired physical function. Antioxidant strategies to improve muscle function for older people may need to be targeted at subgroups with high baseline oxidative stress.

Hyperuricaemia and gout in cardiovascular, metabolic and kidney disease

During the last century, there has been an increasing prevalence of hyperuricaemia noted in many populations. While uric acid is usually discussed in the context of gout, hyperuricaemia is also associated with hypertension, chronic kidney disease, hypertriglyceridaemia, obesity, atherosclerotic heart disease, metabolic syndrome, and type 2 diabetes. Here we review the connection between hyperuricaemia and cardiovascular, kidney and metabolic diseases. Contrary to the popular view that uric acid is an inert metabolite of purine metabolism, recent studies suggest serum uric acid may have a variety of pro-inflammatory, pro-oxidative and vasoconstrictive actions that may contribute to cardiometabolic diseases. Hyperuricaemia is a predictive factor for the development of hypertension, metabolic syndrome, type 2 diabetes, coronary artery disease, left ventricular hypertrophy, atrial fibrillation, myocardial infarction, stroke, heart failure and chronic kidney disease. Treatment with uric acid-lowering therapies has also been found to improve outcomes in patients with hypertension and kidney disease, in some but not all studies. In conclusion, uric acid is emerging as a potentially treatable risk factor for cardiometabolic diseases, and more clinical trials investigating the potential benefit of lowering serum uric acid are recommended in individuals with hyperuricaemia with and without deposition and concomitant hypertension, metabolic syndrome or chronic kidney disease.

Randomized, Open-Label, Cross-Over Comparison of the Effects of Benzbromarone and Febuxostat on Endothelial Function in Patients with Hyperuricemia

Uric acid is generated with reactive oxygen species via xanthine oxidase (XO), and hyperuricemia, which is identified as the excess of uric acid in the blood, has been associated with vascular endothelial dysfunction. However, the effects of urate-lowering medicines on endothelial function have not been fully elucidated. Thus this study determined and compared the effects of benzbromarone (urate transporter 1 inhibitor) and febuxostat (XO inhibitor) on endothelial function.This randomized, cross-over, open-label study initially recruited 30 patients with hyperuricemia. They were divided into two groups, treated initially with benzbromarone or febuxostat for three months and then were switched for the next three months. Endothelial function was defined as reactive hyperemia indexes (RHI) determined using Endo-PAT 2000 before and at three and six months after medication using the two agents. Blood levels of asymmetric dimethylarginine (ADMA) and high-molecular-weight (HMW) adiponectin were also compared. We finally analyzed data from 24 patients whose endothelial function was assessed as described above.Our findings show that levels of uric acid significantly decreased, whereas those of HMW adiponectin and the RHI have significantly increased after treatment with benzbromarone. Meanwhile, in patients administered with febuxostat, uric acid levels tended to decrease and RHI significantly decreased. Neither of the two agents altered ADMA levels. The changes in RHI (P = 0.026) and HMW adiponectin levels (P = 0.001) were found to be significantly greater in patients treated with benzbromarone than febuxostat. Changes in the levels of HMW adiponectin and of uric acid were significantly correlated (r = -0.424, P = 0.039).Benzbromarone has increased adiponectin besides reducing uric acid levels, and thus, this might confer more benefits on endothelial function than febuxostat.

Xanthine Oxidoreductase Inhibitors

Xanthine oxidase inhibitors are primarily used in the clinical prevention and treatment of gout associated with hyperuricemia. The archetypal xanthine oxidase inhibitor, Allopurinol has been shown to have other beneficial effects such as a reduction in vascular reactive oxygen species and mechano-energetic uncoupling. This chapter discusses these properties and their relevance to human pathophysiology with a focus on Allopurinol as well as newer xanthine oxidase inhibitors such as Febuxostat and Topiroxostat. Xanthine oxidase (XO) and xanthine dehydrogenase (XDH) are collectively referred to as xanthine oxidoreductase (XOR). XDH is initially synthesised as a 150-kDa protein from which XO is derived, e.g. under conditions of ischemia/hypoxia either reversibly by conformational changes (calcium or SH oxidation) or irreversibly by proteolysis, the latter leading to formation of a 130-kDa form of XO. Both, XO and XDH, catalyse the conversion of hypoxanthine via xanthine to uric acid, the former by using oxygen forming superoxide and hydrogen peroxide and the latter NAD⁺. However, XDH is in principle also able to generate ROS.

Role of sodium glucose co-transporter 2 inhibitors in patients with heart failure: an elusive mechanism

Heart failure (HF) is a major cause of morbidity and mortality worldwide, and the burden of HF continues to rise. There has been an interest in sodium-glucose co-transporter-2 (SGLT2) inhibitors for their role in reducing HF hospitalizations in pivotal trials. Since these agents were approved by the Food and Drug Administration for the management of diabetes mellitus, multiple small trials and analyses have tried to explain the underlying beneficial mechanisms in HF . In this review, we discuss different mechanisms by which SGLT2 inhibitors play hemodynamic, metabolic, and cellular roles in different HF phenotypes. We also address issues pertaining to the safety of these relatively newer agents.KEY MESSAGESSGLT2 inhibitors are associated with a reduction in HF hospitalizations in both diabetics and non-diabetics.The beneficial role of SGLT2 inhibitors in reducing HF hospitalization is observed among participants with established cardiovascular disease/HF and at-risk population.SGLT2 inhibitors pose an important role in renal protection, another mechanism by which these medications can be helpful in HF patients.