Uric acid restores endothelial function in patients with type 1 diabetes and regular smokers

Sex difference in the associations among hyperuricemia with self-reported peptic ulcer disease in a large Taiwanese population study

Background

Hyperuricemia may play a role in various systemic diseases. However, few studies have investigated the relationship between hyperuricemia and the risk of peptic ulcer disease (PUD). Therefore, in this population-based study, we enrolled over 120,000 participants from the Taiwan Biobank (TWB) and examined the risk factors for self-reported PUD. In addition, we investigated sex differences in the association between hyperuricemia and self-reported PUD.

Methods

Data of 121,583 participants were obtained from the TWB. Male participants with a serum uric acid level >7 mg/dl and female participants with a serum uric acid level >6 mg/dl were classified as having hyperuricemia. Details of self-reported PUD were obtained by questionnaire. The association between hyperuricemia and self-reported PUD in the male and female participants was examined using multivariable logistic regression analysis.

Results

The overall prevalence of self-reported PUD was 14.6%, with a higher incidence in males (16.5%) compared to females (13.5%). After multivariable adjustment, male sex [vs. female sex; odds ratio (OR) = 1.139; 95% confidence interval (CI) = 1.084-1.198; p < 0.001], and hyperuricemia (OR = 0.919; 95% CI = 0.879-0.961; p < 0.001) were significantly associated with self-reported PUD. Further, a significant interaction was found between sex and hyperuricemia on self-reported PUD (p = 0.004). Hyperuricemia was associated with a low risk of self-reported PUD in males (OR = 0.890; 95% CI = 0.837-0.947; p < 0.001) but not in females (p = 0.139).

Conclusion

The prevalence of self-reported PUD was higher in the male participants than in the female participants. Hyperuricemia was associated with low prevalence of self-reported PUD in males, but not in females. Further studies are needed to clarify the mechanisms behind these observations and verify the potential protective role of hyperuricemia on the development of self-reported PUD.

Uric Acid Is Not Associated With Cardiovascular Health in Youth With Type 1 Diabetes: SEARCH for Diabetes in Youth Study

CONTEXT

Uric acid's role in cardiovascular health in youth with type 1 diabetes is unknown.

OBJECTIVE

Investigate whether higher uric acid is associated with increased blood pressure (BP) and arterial stiffness over time in adolescents and young adults with type 1 diabetes and if overweight/obesity modifies this relationship.

METHODS

Longitudinal analysis of data from adolescents and young adults with type 1 diabetes from 2 visits (mean follow up 4.6 years) in the SEARCH for Diabetes in Youth multicenter prospective cohort study from 2007 to 2018. Our exposure was uric acid at the first visit and our outcome measures were the change in BP, pulse wave velocity (PWV), and augmentation index between visits. We used multivariable linear mixed-effects models and assessed for effect modification by overweight/obesity.

RESULTS

Of 1744 participants, mean age was 17.6 years, 49.4% were female, 75.9% non-Hispanic White, and 45.4% had a follow-up visit. Mean uric acid was 3.7 mg/dL (SD 1.0). Uric acid was not associated with increased BP, PWV-trunk, or augmentation index over time. Uric acid was marginally associated with PWV-upper extremity (β = .02 m/s/year, 95% CI 0.002 to 0.04). The magnitude of this association did not differ by overweight/obesity status.

CONCLUSION

Among adolescents and young adults with type 1 diabetes, uric acid was not consistently associated with increased BP or arterial stiffness over time. These results support findings from clinical trials in older adults with diabetes showing that lowering uric acid levels does not improve cardiovascular outcomes.

Association Between Serum Uric Acid and Abdominal Aortic Calcification in Adults Aged 40 to 80 years: A Retrospective Cross-Sectional Study

There are numerous causes of abdominal aortic calcification (AAC), among which the relationship between serum uric acid and AAC still needs to be investigated further. The aim of this research was to ascertain whether serum uric acid is correlated with AAC. Our study included 3007 participants. We described the study population characteristics and utilized univariate analysis, stratified analysis, multiple equation regression analysis, smoothed curve fitting, and threshold effects analysis. AAC Total 24 score is used to reflect the range of aortic calcification at each vertebral level. As serum uric acid increased, the AAC Total 24 score first decreased and then increased. The fold point is located when serum uric is at 3.5 mg/dL. After adjusting for 16 covariates, the beta values for the groups with moderate and high serum uric acid levels were 0.34 and 0.53, respectively, compared with the low serum uric acid tertile group (P < .05). Our research indicates a negative correlation between serum acid level and AAC when serum uric acid <3.5 mg/dl, but it is positively correlated with the formation of AAC when serum uric acid >3.5 mg/dl.

Longitudinal changes in high sensitivity C-reactive protein associated with serum uric acid in the Korean Genome and Epidemiology Study

Cross-sectional studies support the role of serum uric acid (SUA) in inflammation, but evidence from cohort studies is scarce. Longitudinal associations between SUA and high-sensitivity C-reactive protein (hs-CRP) were examined in the general population. Data for participants from the Health Examinees-Gem cohort (n = 50,028; 40-69 years; 67% women) who were examined between 2004 and 2013 and followed up until 2016 were analyzed. SUA and hs-CRP were measured at baseline and during follow-up. SUA was evaluated as a continuous variable and was also divided into sex-specific quartiles. Mean hs-CRP levels at follow-up were evaluated using multivariable proportional odds regression, with non-linear smoothed baseline hs-CRP levels serving as a covariate. Selected pathological markers were also examined in relation to hs-CRP. Increased levels of SUA at baseline were related to increased levels of hs-CRP at follow-up [regression coefficient per mg/dL increase in baseline SUA (β) = 0.08, 95% confidence interval (CI), 0.040-0.128]. A dose-response relationship was observed, (P for linear trend = 0.0015). The mean values of hs-CRP were highest among participants with the highest follow-up but lowest baseline SUA levels. Elevated hs-CRP levels at follow up (> 3 mg/L) were positively related to fasting blood glucose levels, triglycerides levels, liver enzymes, and blood pressure, but negatively related to high density lipoprotein cholesterol levels per unit increase in baseline hs-CRP. High SUA levels were associated with high hs-CRP levels, suggesting a potential role of SUA in inflammation. However, additional research is needed to confirm these findings.

Genotype and Phenotype of Renal Hypouricemia: A Single-Center Study from China

BACKGROUND

Renal hypouricemia (RHUC), a rare inherited disorder characterized by impaired uric acid reabsorption and subsequent profound hypouricemia, occurs mainly due to variants in SLC22A12 or SLC2A9. Only anecdotal cases and one small-scale RHUC screening study have been reported in the Chinese population.

METHODS

A total of 19 patients with RHUC from 17 unrelated families were recruited from our center. The medical history, clinical manifestations, biochemical exam, and clinical outcomes were collected. Next-generation sequencing-based targeted gene sequencing or whole exon sequencing was performed.

RESULTS

A total of 22 variants in SLC22A12 or SLC2A9 were found in 19 patients. The variant c.944G>A (p.W315X) in SLC2A9 was identified in three patients. Three variants c.165C>A (p.D55E), c.1549_1555delGAGACCC (p.E517Rfs*17), and c.1483T>C (p.W495R) in SLC22A12 and three variants c.1215+1G>A (splicing variant), c.643A>C (p.T215P), and c.227C>A (p.S76X) in SLC2A9 were novel. A proportion of 10 out of 19 patients presented with exercise-induced acute kidney injury (EIAKI). The renal outcome was favorable. Five patients had nephrolithiasis, in whom three had hypercalciuria.

CONCLUSION

The current study reported six novel variants in SLC22A12 and SLC2A9 genes of Chinese patients with RHUC. The variant c.944G>A (p.W315X) in SLC2A9 may be common in Chinese patients. EIAKI is the main clinical phenotype associated with RHUC in our cohort, with a favorable outcome. Hypercalciuria presented in some RHUC patients is a new finding.

The protective effects of uric acid against myocardial ischemia via the Nrf2 pathway

Uric acid (UA) possesses both pro- and anti-oxidative properties in ischemic heart disease, but the underlying mechanism remains unclear. We aimed to investigate UA's protective effect on myocardial ischemia by examining its effects on ECG Ischemic Alterations (EIA) and H2O2-induced oxidative stress in H9C2 myocardial cells. The incidence of EIA decreased over time and was more prevalent among women than men. A U-shaped relationship was observed between UA levels and EIA incidence, with the third quartile exhibiting a protective association. Addition of 237.9 μmol/L UA improved cellular damage and oxidative stress in H2O2-treated H9C2 cells, as determined by cell viability, LDH release, ROS levels, and total antioxidant capacity assays. UA activated the Nrf2 pathway, evidenced by increased expression of Nrf2, GCLC, and HO-1 proteins. By reversing cell cycle blockage, promoting wound healing ability, improving colony-forming capacity, and increasing angiogenesis in H2O2-treated cells, UA exhibited positive effects on cardiomyocyte growth characteristics. Additionally, use of Nrf2 inhibitor ML385 confirmed the involvement of the Nrf2 pathway by negating UA's effects on oxidatively damaged cardiomyocytes. Our findings suggest that UA induces downstream antioxidant factors to ameliorate oxidative stress by activating the Nrf2 pathway, which could be one of the targets responsible for UA's beneficial effects in myocardial ischemia.

Uric acid en route to gout

Gout and hyperuricemia (HU) have generated immense attention due to increased prevalence. Gout is a multifactorial metabolic and inflammatory disease that occurs when increased uric acid (UA) induce HU resulting in monosodium urate (MSU) crystal deposition in joints. However, gout pathogenesis does not always involve these events and HU does not always cause a gout flare. Treatment with UA-lowering therapeutics may not prevent or reduce the incidence of gout flare or gout-associated comorbidities. UA exhibits both pro- and anti-inflammation functions in gout pathogenesis. HU and gout share mechanistic and metabolic connections at a systematic level, as shown by studies on associated comorbidities. Recent studies on the interplay between UA, HU, MSU and gout as well as the development of HU and gout in association with metabolic syndromes, non-alcoholic fatty liver disease (NAFLD), and cardiovascular, renal and cerebrovascular diseases are discussed. This review examines current and potential therapeutic regimens and illuminates the journey from disrupted UA to gout.

Effect of ApoE ε4 gene polymorphism on the correlation between serum uric acid and left ventricular hypertrophy remodeling in patients with coronary heart disease

Background

Hyperuricemia and dyslipidemia are associated with left ventricular hypertrophy (LVH), while the effect of ApoE gene polymorphism on the correlation between serum uric acid (UA) level and severity of LVH in patients with coronary heart disease (CHD) has not been clarified.

Methods

This was a retrospective observational study of patients with CHD. Patients were divided into groups of ε4 carriers and non-ε4 carriers based on sanger sequencing. The association of ApoE ε4 gene polymorphism, serum UA level, and LVH, determined by cardiac color Doppler ultrasound, was evaluated by multivariate analysis.

Results

A total of 989 CHD patients who underwent ApoE genotyping were enrolled and analyzed. Among them, the frequency of the ApoE ε4 genotype was 17.9% (15.7% for E3/4, 1.1% for E4/4, and 1.1% for E2/4). There were 159 patients with LVH, 262 with end-diastolic LV internal diameter (LVEDD) enlargement, 160 with left ventricular ejection fraction (LVEF) reduction, and 154 with heart failure. Multivariate analysis showed that for every increase of 10 μmol/L in serum UA level, the risk of LVH decreased in ε4 carriers (odds ratio (OR) = 0.94, 95% confidence interval (CI): 0.890-0.992, P = 0.025) and increased in non-ε4 carriers (OR = 1.03, 95% CI: 1.005-1.049, P = 0.016). The risk of LVEDD enlargement tended to decrease in ε4 carriers (OR = 0.98, 95% CI: 0.943-1.023, P = 0.391) and increased in non-ε4 carriers (OR = 1.03, 95% CI: 1.009-1.048, P = 0.003). The risk of LVEF reduction was reduced in ε4 carriers (OR = 0.996, 95% CI: 0.949-1.046, P = 0.872) and increased in non-ε4 carriers (OR = 1.02, 95% CI: 0.994-1.037, P = 0.17). The risk of LVEDD enlargement decreased in ε4 carriers (OR = 0.98, 95% CI: 0.931-1.036, P = 0.508) and increased in non-ε4 carriers (OR = 1.02, 95% CI: 0.998-1.042, P = 0.07).

Conclusion

High serum UA levels decreased the risk of LVH in ApoE ε4 carriers with CHD, while increased the risk of LVH in non-ε4 carriers.

Single and combined effect of bisphenol A with high sucrose diet on the diabetic and renal tubular dysfunction phenotypes in Drosophila melanogaster

In the present study, effect of exposure of bisphenol A (BPA) and combined exposure of BPA + HSD has been investigated on the glucose homeostasis and associated renal complications in Drosophila. Exposure of 1.0 mM BPA alone induced type 2 diabetes like condition (T2D) in adult male D. melanogaster via oxidative stress. Elevated TGF-β signaling was evident by increased expression of baboon (babo) in BPA exposed organism that stimulated the modulation of extracellular matrix (ECM) component collagen IV resulting in the fibrosis of the Malpighian tubules (MTs). Combined exposure of BPA + HSD (high sucrose diet) resulted in the increased magnitude of T2D and MTs dysfunction parameters. Taken together, the study illustrates that BPA has diabetogenic potential in exposed Drosophila that caused adverse effects on their MTs and combined exposure with BPA and HSD could aggravate the renal tubular dysfunction. The study further suggests the use of Drosophila model to study the environmental chemicals induced diabetes mediated renal dysfunction.

Negative Effects of Chronic High Intake of Fructose on Lung Diseases

In the modern diet, excessive fructose intake (>50 g/day) had been driven by the increase, in recent decades, of the consumption of sugar-sweetened beverages. This phenomenon has dramatically increased within the Caribbean and Latin American regions. Epidemiological studies show that chronic high intake of fructose related to sugar-sweetened beverages increases the risk of developing several non-communicable diseases, such as chronic obstructive pulmonary disease and asthma, and may also contribute to the exacerbation of lung diseases, such as COVID-19. Evidence supports several mechanisms—such as dysregulation of the renin−angiotensin system, increased uric acid production, induction of aldose reductase activity, production of advanced glycation end-products, and activation of the mTORC1 pathway—that can be implicated in lung damage. This review addresses how these pathophysiologic and molecular mechanisms may explain the lung damage resulting from high intake of fructose.

Nutraceutical Prevention of Diabetic Complications—Focus on Dicarbonyl and Oxidative Stress

Oxidative and dicarbonyl stress, driven by excess accumulation of glycolytic intermediates in cells that are highly permeable to glucose in the absence of effective insulin activity, appear to be the chief mediators of the complications of diabetes. The most pathogenically significant dicarbonyl stress reflects spontaneous dephosphorylation of glycolytic triose phosphates, giving rise to highly reactive methylglyoxal. This compound can be converted to harmless lactate by the sequential activity of glyoxalase I and II, employing glutathione as a catalyst. The transcription of glyoxalase I, rate-limiting for this process, is promoted by Nrf2, which can be activated by nutraceutical phase 2 inducers such as lipoic acid and sulforaphane. In cells exposed to hyperglycemia, glycine somehow up-regulates Nrf2 activity. Zinc can likewise promote glyoxalase I transcription, via activation of the metal-responsive transcription factor (MTF) that binds to the glyoxalase promoter. Induction of glyoxalase I and metallothionein may explain the protective impact of zinc in rodent models of diabetic complications. With respect to the contribution of oxidative stress to diabetic complications, promoters of mitophagy and mitochondrial biogenesis, UCP2 inducers, inhibitors of NAPDH oxidase, recouplers of eNOS, glutathione precursors, membrane oxidant scavengers, Nrf2 activators, and correction of diabetic thiamine deficiency should help to quell this.

Association between RAC1 gene variation, redox homeostasis and type 2 diabetes mellitus

BACKGROUND

Increased production of reactive oxygen species (ROS) and oxidative stress are known to play a key role in the pathogenesis of type 2 diabetes (T2D); however, the relationship between genes encoding a multi-subunit ROS-generated enzyme NADPH oxidase and disease susceptibility remains unexplored.

AIMS

The present pilot study investigated whether single-nucleotide polymorphisms (SNP) at the RAC1 gene (Rac family small GTPase 1), a molecular switcher of NADPH oxidase, are associated with the risk of T2D, glucose metabolism and redox homeostasis.

MATERIALS & METHODS

DNA samples from 3206 unrelated Russian subjects (1579 T2D patients and 1627 controls) were genotyped for six common SNPs rs4724800, rs7784465, rs10951982, rs10238136, rs836478 and rs9374 of RAC1 using the MassArray-4 system.

RESULTS

SNP rs7784465 was associated with an increased risk of T2D (p = .0003), and significant differences in the RAC1 haplotypes occurred between the cases and controls (p = .005). Seventeen combinations of RAC1 genotypes showed significant associations with T2D risk (FDR <0.05). Associations of RAC1 polymorphisms with T2D were modified by environmental factors such as sedentary lifestyle, psychological stresses, a dietary deficit of fresh fruits/vegetables and increased carbohydrate intake. RAC1 polymorphisms were associated with biochemical parameters in diabetics: rs7784465 (p = .015) and rs836478 (p = .028) with increased glycated haemoglobin, rs836478 (p = .005) with increased fasting blood glucose, oxidized glutathione (p = .012) and uric acid (p = .034). Haplotype rs4724800A-rs7784465C-rs10951982G-rs10238136A-rs836478C-rs9374G was strongly associated with increased levels of hydrogen peroxide (p < .0001).

CONCLUSION

Thus, polymorphisms in the RAC1 gene represent novel genetic markers of type 2 diabetes, and their link with glucose metabolism and disease pathogenesis is associated with the changes in redox homeostasis.

Engineering bioactive nanoparticles to rejuvenate vascular progenitor cells

Fetal exposure to gestational diabetes mellitus (GDM) predisposes children to future health complications including type-2 diabetes mellitus, hypertension, and cardiovascular disease. A key mechanism by which these complications occur is through stress-induced dysfunction of endothelial progenitor cells (EPCs), including endothelial colony-forming cells (ECFCs). Although several approaches have been previously explored to restore endothelial function, their widespread adoption remains tampered by systemic side effects of adjuvant drugs and unintended immune response of gene therapies. Here, we report a strategy to rejuvenate circulating vascular progenitor cells by conjugation of drug-loaded liposomal nanoparticles directly to the surface of GDM-exposed ECFCs (GDM-ECFCs). Bioactive nanoparticles can be robustly conjugated to the surface of ECFCs without altering cell viability and key progenitor phenotypes. Moreover, controlled delivery of therapeutic drugs to GDM-ECFCs is able to normalize transgelin (TAGLN) expression and improve cell migration, which is a critical key step in establishing functional vascular networks. More importantly, sustained pseudo-autocrine stimulation with bioactive nanoparticles is able to improve in vitro and in vivo vasculogenesis of GDM-ECFCs. Collectively, these findings highlight a simple, yet promising strategy to rejuvenate GDM-ECFCs and improve their therapeutic potential. Promising results from this study warrant future investigations on the prospect of the proposed strategy to improve dysfunctional vascular progenitor cells in the context of other chronic diseases, which has broad implications for addressing various cardiovascular complications, as well as advancing tissue repair and regenerative medicine.

Drug-loaded liposomal nanoparticles conjugated to endothelial colony-forming cells can improve the vasculogenic potential of vascular progenitor cells exposed to gestational diabetes mellitus.

Sex-specific relationship between serum uric acid levels and the prevalence of large vessel occlusion in acute ischemic stroke

PURPOSE

Previous studies have found that uric acid (UA) plays a neuroprotective role in ischemic stroke patients. However, the relationship between serum UA of acute ischemic stroke (AIS) and large vessel occlusion (LVO) strokes is unclear.

METHODS

In this retrospective study, 1318 AIS patients were enrolled. All patients underwent imaging examinations to assess the intracranial and carotid vessels. Multivariate logistic regression analysis was conducted to evaluate the relationship between UA levels and the prevalence of LVO.

RESULTS

The 1318 enrolled AIS patients were comprised of 287 LVO and 1031 non-LVO patients. UA levels in males were higher than females (321.04 ± 91.28 vs. 274.43 ± 82.11, p < .001). The association between serum UA levels and LVO was modified by sex (p = .007). When serum UA levels were continuous, after adjusting for related risk factors, higher serum UA levels were still associated with a lower prevalence of LVO in males (odds ratio (OR) 0.997, 95% confidence interval (CI) 0.994-0.999), but not in female subjects (OR 0.998, 95% CI 0.995-1.001). When serum UA levels were divided into tertiles, higher UA levels had a lower risk of LVO than the moderate (p = .006) and lower tertiles of UA levels (p = .010) in males, but not in females (p = .402 and p = .206 for moderate and low tertiles, respectively).

CONCLUSIONS

AIS patients with higher serum UA levels tend to be associated with a lower risk of LVO in males, but not in females.

Protective Effect of Uric Acid on ox-LDL-Induced HUVECs Injury via Keap1-Nrf2-ARE Pathway

Uric acid is an effective antioxidant. Oxidized low-density lipoprotein (ox-LDL) is derived from circulating LDL and promotes atherosclerosis. The Keap1-Nrf2-ARE pathway is a key body pathway involved in protection against internal and external oxidative damages. The role of uric acid on vascular endothelial function damaged by ox-LDL, and its effect on the Keap1-Nrf2-ARE pathway has not been fully explored. HUVECs were treated with different concentrations of uric acid and ox-LDL to explore the effect of uric acid in vitro. Cell phenotype was determined by cytometry and Western blot. Nuclear translocation of Nrf2 was determined by immunofluorescence. Coimmunoprecipitation was used to determine the level of Nrf2 ubiquitination. A microfluidic device was used to mimic the vascular environment in the body, and the level of mRNA levels of inflammatory factors was determined by RT-PCR. The findings of this study show that suitable uric acid can significantly reduce endothelial damage caused by ox-LDL, such as oxidative stress, inflammation, and increased adhesion. In addition, uric acid reduced Nrf2 ubiquitination and increased nuclear translocation of Nrf2 protein, thus activating the Keap1-Nrf2-ARE pathway and playing a protective role. Interestingly, the effects of UA were significantly inhibited by administration of Brusatol, an inhibitor of Nrf2. In summary, suitable concentrations of uric acid can alleviate the oxidative stress level of endothelial cells through Nrf2 nuclear translocation and further protect cells from damage.

Deletion of Mocos Induces Xanthinuria with Obstructive Nephropathy and Major Metabolic Disorders in Mice

Background

Xanthinuria type II is a rare autosomal purine disorder. This recessive defect of purine metabolism remains an under-recognized disorder.

Methods

Mice with targeted disruption of the molybdenum cofactor sulfurase (Mocos) gene were generated to enable an integrated understanding of purine disorders and evaluate pathophysiologic functions of this gene which is found in a large number of pathways and is known to be associated with autism.

Results

Mocos-deficient mice die with 4 weeks of age due to renal failure of distinct obstructive nephropathy with xanthinuria, xanthine deposits, cystic tubular dilation, Tamm-Horsfall (uromodulin) protein (THP) deposits, tubular cell necrosis with neutrophils, and occasionally hydronephrosis with urolithiasis. Obstructive nephropathy is associated with moderate interstitial inflammatory and fibrotic responses, anemia, reduced detoxification systems, and important alterations of the metabolism of purines, amino acids, and phospholipids. Conversely, heterozygous mice expressing reduced MOCOS protein are healthy with no apparent pathology.

Conclusions

Mocos-deficient mice develop a lethal obstructive nephropathy associated with profound metabolic changes. Studying MOCOS functions may provide important clues about the underlying pathogenesis of xanthinuria and other diseases requiring early diagnosis.

The Relationship Between Serum Uric Acid at Different Concentrations of Lipid Indices and the Risk of Myocardial Revascularization in Patients With Acute Coronary Syndrome: A Retrospective Analysis

Objective: Both serum uric acid (SUA) levels and lipid components, such as LDL, HDL, and Lp(a), have been reported to associate with CAD. However, the influence of SUA status at different concentrations of lipid indices for the risk of myocardial revascularization (MRT) in ACS patients is currently unknown.

Methods: We retrospectively analyzed a hospital-based sample of 14,234 ACS patients with no previous history of percutaneous coronary intervention (PCI) or coronary artery bypass graft (CABG) surgery. All patients went for coronary angiography. Binary logistic regression models were performed, and the odds ratios (OR) at 95% confidence interval (CIs) were used to approximate the associated risk of UA and lipid profile for myocardial revascularization, with the lowest quartile/tertile serving as the reference category.

Results: Overall, 8,818 (61.9%) patients undergone MRT out of 14,234 patients. Elevated SUA and HDL were negatively associated with an increased likelihood of MRT during admission (P < 0.001). However, LDL and Lp(a) levels were positively associated with MRT among ACS patients. Furthermore, interaction analyses between SUA and lipid profiles, particularly LDL and Lp(a), compared with those in the lowest quartile of SUA levels, show that patients in higher SUA quartiles grouped by lipid components had a significantly lower chance of undergoing MRT, with the lowest OR (95%CI) for subjects being 0.222 (0.170-0.290), 0.478 (0.374-0.612), and 0.604 (0.468-0.780) in LDL tertiles, being 0.671(0.523-0.862), 0.316(0.242-0.413), and 0.410 (0.310-0.542) in Lp(a) tertiles, respectively. In the three tertiles of HDL levels, the incidence of MRT dropped steadily as SUA levels increased. Also, we further analyzed ACS patients without diabetes. Compared with the first quartile of SUA levels, the risks of MRT were significantly lower in different tertiles of lipids components [LDL, Lp(a), HDL].

Conclusion: An increase in SUA levels may decrease the chance of undergoing MRT in ACS patients, even in those with increased Lp(a) and LDL-c. Elevated serum uric acid may play a protective role during an acute stage of ACS.

Hyperuricemia-induced endothelial insulin resistance: the nitric oxide connection

Hyperuricemia, defined as elevated serum concentrations of uric acid (UA) above 416 µmol L^-1, is related to the development of cardiometabolic disorders, probably via induction of endothelial dysfunction. Hyperuricemia causes endothelial dysfunction via induction of cell apoptosis, oxidative stress, and inflammation; however, it's interfering with insulin signaling and decreased endothelial nitric oxide (NO) availability, resulting in the development of endothelial insulin resistance, which seems to be a major underlying mechanism for hyperuricemia-induced endothelial dysfunction. Here, we elaborate on how hyperuricemia induces endothelial insulin resistance through the disruption of insulin-stimulated endothelial NO synthesis. High UA concentrations decrease insulin-induced NO synthesis within the endothelial cells by interfering with insulin signaling at either the receptor or post-receptor levels (i.e., proximal and distal steps). At the proximal post-receptor level, UA impairs the function of the insulin receptor substrate (IRS) and phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt) in the insulin signaling pathway. At the distal level, high UA concentrations impair endothelial NO synthase (eNOS)-NO system by decreasing eNOS expression and activity as well as by direct inactivation of NO. Clinically, UA-induced endothelial insulin resistance is translated into impaired endothelial function, impaired NO-dependent vasodilation, and the development of systemic insulin resistance. UA-lowering drugs may improve endothelial function in subjects with hyperuricemia.

Association of serum uric acid levels with COVID-19 severity

AIMS

Hyperuricemia has attracted increasing attention. However, limited concern has been paid to the potential dangers of lowering serum uric acid (SUA). We observed lower levels of SUA in patients with COVID-19. Therefore, we aim to explore whether patients with COVID-19 had SUA lower than normal and the relationship of SUA and the severity of COVID-19.

METHODS

This was a case-control study based on 91 cases with COVID-19 and 273 age- and sex-matched healthy control subjects. We first compared SUA levels and uric acid/creatinine (UA/Cr) ratio between patients with COVID-19 and the healthy controls. Then, we examined the association of SUA levels and UA/Cr ratios with COVID-19 severity in COVID-19 cases only, defined according to the fifth edition of China's Diagnosis and Treatment Guidelines of COVID-19.

RESULTS

SUA levels in patients with COVID-19 were 2.59% lower, UA/Cr ratios 6.06% lower at admission compared with healthy controls. In sex stratified analysis, levels of SUA and UA/Cr were lower in male patients with COVID-19 while only level of SUA was lower in female patients with COVID-19. Moreover, SUA and UA/Cr values were 4.27 and 8.23% lower in the severe group than that in the moderate group among male COVID-19 patients. Bivariate and partial correlations analysis showed negative correlations between SUA or UA/Cr ratio and COVID-19 after adjusting for age, sex, BMI and eGFR. A multiple linear regression analysis showed that SARS-CoV-2 infection and male sex were independent risk factors associated with lower SUA levels. Male patients with COVID-19 accompanied by low SUA levels had higher risk of developing severe symptoms than those with high SUA levels (incidence rate ratio: 4.05; 95% CI:1.11, 14.72) at admission. Comparing SUA and UA/Cr ratio at three time points (admission, discharge, and follow-up), we found that male patients experienced severe symptoms had lower SUA and UA/Cr ratio levels comparing to moderate patients, but no significant difference between three time points. On the contrary, female patients had lower SUA and UA/Cr ratio at discharge than those at admission, but no significant difference of SUA and UA/Cr ratio between moderate and severe group.

CONCLUSION

Patients with COVID-19 had SUA and UA/Cr values lower than normal at admission. Male COVID-19 patients with low SUA levels had a significantly higher crude risk of developing severe symptoms than those with high SUA levels. During disease aggravation, the level of SUA gradually decreased until discharge. At the follow-up exam, the level of SUA was similar to the levels at admission.

Uric acid shown to contribute to increased oxidative stress level independent of xanthine oxidoreductase activity in MedCity21 health examination registry

Uric acid has both antioxidant and pro-oxidant properties in vitro by scavenging and production of reactive oxygen species (ROS). This cross-sectional study examined whether uric acid possesses effects on oxidative stress under physiological conditions independent of xanthine oxidoreductase (XOR), which is involved in uric acid and ROS production. Serum uric acid level was measured, while plasma XOR activity was determined using our high-sensitive assay in 192 participants (91 males, 101 females) who underwent health examinations and were not taking an antihyperuricemic agent. For antioxidant potential and oxidative stress level, biological antioxidant potential (BAP) and derivative of reactive oxygen metabolites (d-ROMs) in serum, respectively, were measured. Median uric acid level and plasma XOR activity were 5.6 mg/dL and 26.1 pmol/h/mL, respectively, and BAP and d-ROMs levels were 2112.8 μmol/L and 305.5 Carr U, respectively. Multivariable regression analyses revealed no significant association of serum uric acid level with BAP level, whereas serum uric acid level showed a significant association with d-ROMs level independent of plasma XOR activity (p = 0.045), which was prominent in females (p = 0.036; p for interaction = 0.148). Uric acid might contribute to increased oxidative stress independent of XOR activity by increasing ROS production, without affecting ROS scavenging, especially in females.

Why Does Hyperuricemia Not Necessarily Induce Gout?

Hyperuricemia is a risk factor for gout. It has been well observed that a large proportion of individuals with hyperuricemia have never had a gout flare(s), while some patients with gout can have a normuricemia. This raises a puzzle of the real role of serum uric acid (SUA) in the occurrence of gout flares. As the molecule of uric acid has its dual effects in vivo with antioxidant properties as well as being an inflammatory promoter, it has been placed in a delicate position in balancing metabolisms. Gout seems to be a multifactorial metabolic disease and its pathogenesis should not rely solely on hyperuricemia or monosodium urate (MSU) crystals. This critical review aims to unfold the mechanisms of the SUA role participating in gout development. It also discusses some key elements which are prerequisites for the formation of gout in association with the current therapeutic regime. The compilation should be helpful in precisely fighting for a cure of gout clinically and pharmaceutically.

Elevated serum uric acid and risk of cardiovascular or all-cause mortality in maintenance hemodialysis patients: A meta-analysis

BACKGROUND AND AIMS

Studies have shown inconsistent results about the association between serum uric acid (SUA) levels and mortality in hemodialysis patients. We performed this meta-analysis to determine whether higher SUA values comprised a risk factor of cardiovascular or all-cause mortality in maintenance hemodialysis patients.

METHODS AND RESULTS

Pubmed, Embase and the Cochrane library were searched up to August 31, 2020 for the longitudinal studies that investigated the association between the elevated SUA and cardiovascular or all-cause mortality risk in maintenance hemodialysis patients. Pooled adjusted hazard ratios (HR) and corresponding 95% confidence interval (CI) were calculated using a random-effects model. We included 10 studies with an overall sample of 264,571 patients with hemodialysis in this meta-analysis. Patients with the highest SUA were associated with a decreased risk of cardiovascular mortality (HR = 0.72, 95% CI 0.59-0.87) compared with patients with the lowest SUA after adjustment for potential confounders in a random effects model. Moreover, for each increase of 1 mg/dl of SUA, the overall risks of all-cause and cardiovascular mortality decreased by 6% and 9%, respectively (HR = 0.94, 95% CI 0.90-0.99; HR = 0.91, 95% CI 0.89-0.94).

CONCLUSION

Elevated SUA levels are strongly and independently associated with lower risk of cardiovascular mortality in maintenance hemodialysis patients. More designed studies, especially randomized controlled trials, should be conducted to determine whether high SUA levels is an independent risk factor of all-cause mortality in hemodialysis patients.

Circulating biomarkers of nitric oxide bioactivity and impaired muscle vasoreactivity to exercise in adults with uncomplicated type 1 diabetes

AIMS/HYPOTHESIS

Early compromised endothelial function challenges the ability of individuals with type 1 diabetes to perform normal physical exercise. The exact mechanisms underlying this vascular limitation remain unknown, but may involve either formation or metabolism of nitric oxide (NO), a major vasodilator, whose activity is known to be compromised by oxidative stress.

METHODS

Muscle microvascular reactivity (near-infrared spectroscopy) to an incremental exhaustive bout of exercise was assessed in 22 adults with uncomplicated type 1 diabetes (HbA_1c 64.5 ± 15.7 mmol/mol; 8.0 ± 1.4%) and in 21 healthy individuals (18-40 years of age). NO-related substrates/metabolites were also measured in the blood along with other vasoactive compounds and oxidative stress markers; measurements were taken at rest, at peak exercise and after 15 min of recovery. Demographic characteristics, body composition, smoking status and diet were comparable in both groups.

RESULTS

Maximal oxygen uptake was impaired in individuals with type 1 diabetes compared with in healthy participants (35.6 ± 7.7 vs 39.6 ± 6.8 ml min^-1 kg^-1, p < 0.01) despite comparable levels of habitual physical activity (moderate to vigorous physical activity by accelerometery, 234.9 ± 160.0 vs 280.1 ± 114.9 min/week). Compared with non-diabetic participants, individuals with type 1 diabetes also displayed a blunted exercise-induced vasoreactivity (muscle blood volume at peak exercise as reflected by ∆ total haemoglobin, 2.03 ± 5.82 vs 5.33 ± 5.54 μmol/l; interaction 'exercise' × 'group', p < 0.05); this was accompanied by lower K⁺ concentration (p < 0.05), reduced plasma L-arginine (p < 0.05)-in particular when HbA_1c was high (mean estimation: -4.0, p < 0.05)-and lower plasma urate levels (p < 0.01). Nonetheless, exhaustive exercise did not worsen lipid peroxidation or other oxidative stress biomarkers, and erythrocytic enzymatic antioxidant resources were mobilised to a comparable extent in both groups. Nitrite and total nitrosation products, which are potential alternative NO sources, were similarly unaltered. Graphical abstract CONCLUSIONS/INTERPRETATION: Participants with uncomplicated type 1 diabetes displayed reduced availability of L-arginine, the essential substrate for enzymatic nitric oxide synthesis, as well as lower levels of the major plasma antioxidant, urate. Lower urate levels may reflect a defect in the activity of xanthine oxidase, an enzyme capable of producing NO from nitrite under hypoxic conditions. Thus, both canonical and non-canonical NO production may be reduced. However, neither of these changes exacerbated exercise-induced oxidative stress.

TRIAL REGISTRATION

clinicaltrials.gov NCT02051504.

Serum Uric Acid Levels, but Not rs7442295 Polymorphism of SCL2A9 Gene, Predict Mortality in Clinically Stable Coronary Artery Disease

Serum uric acid (SUA) has been associated with cardiovascular disease, but up to now whether SUA is an independent cardiovascular risk factor or merely a disease-related epiphenomenon remains still controversial. within the framework of the Verona Heart Study, we prospectively followed 703 subjects with angiographically demonstrated and clinically stable coronary artery disease between May 1996 and March 2007. At baseline, SUA levels were measured in all the patients. Genotype data of SCL2A9 rs7442295 polymorphism, which has been associated with SUA by genome-wide association studies, were available for 686 subjects (97.6%). After a median follow-up of 57 months, 116 patients (16.5%) had died, 83 (11.8%) because of cardiovascular causes. Patients with hyperuricemia, defined by SUA levels above the 75th percentile (≥0.41 mmol/L), had an increased total and cardiovascular mortality rate than those with SUA below this threshold level (23.3% vs 14.1%, P = 0.048 and 19.4% vs 9.2%, P = 0.001, respectively, by Kaplan-Meier with Log-Rank test). These associations were confirmed by Cox regression after adjustment for sex, age, other predictors of mortality, coronary revascularization, and drug therapies at discharge (hazard ratio for total mortality 1.87 [1.05-3.34], P = 0.033; hazard ratio for cardiovascular mortality 2.09 [1.03-4.25], P = 0.041). Although associated with SUA levels, rs7442295 polymorphism did not predict total or cardiovascular mortality. our data support that SUA may be a prognostic cardiovascular biomarker, predicting total and cardiovascular mortality in the setting of secondary prevention of coronary artery disease. On the other hand, SCL2A9 gene polymorphism, notwithstanding a clear influence on SUA levels, was not associated with mortality.

Evidence for Urate Uptake Through Monocarboxylate Transporter 9 Expressed in Mammalian Cells and Its Enhancement by Heat Shock

Background: Monocarboxylate transporter 9 (MCT9), an orphan transporter member of the solute carrier family 16 (SLC16), possibly reabsorbs uric acid in the renal tubule and has been suggested by genome-wide association studies to be involved in the development of hyperuricemia and gout. In this study we investigated the mechanisms regulating the expression of human (h) MCT9, its degradation, and physiological functions. Methods and Results: hMCT9-FLAG was stably expressed in HEK293 cells and its degradation, intracellular localization, and urate uptake activities were assessed by pulse-chase analysis, immunofluorescence, and [¹⁴C]-urate uptake experiments, respectively. hMCT9-FLAG was localized on the plasma membrane as well as in the endoplasmic reticulum and Golgi apparatus. The proteasome inhibitors MG132 and lactacystine increased levels of hMCT9-FLAG protein expression with enhanced ubiquitination, prolonged their half-life, and decreased [¹⁴C]-urate uptake. [¹⁴C]-urate uptake was increased by both heat shock (HS) and the HS protein inducer geranylgeranylacetone (GGA). Both HS and GGA restored the [¹⁴C]-urate uptake impaired by MG132. Conclusions: hMCT9 does transport urate and is degraded by a proteasome, inhibition of which reduces hMCT9 expression on the cell membrane and urate uptake. HS enhanced urate uptake through hMCT9.

The Complex Relationship Between Serum Uric Acid, Endothelial Function and Small Vessel Remodeling in Humans

Aims: The relationship between serum uric acid (SUA) and microvascular remodeling in humans remains largely unexplored. We assessed whether SUA provides additional information on the severity of microvascular remodeling than that obtained from the European Heart Score (HS), the patterns of microvascular remodeling associated with changes in SUA levels and the mediation by endothelial function and nitric oxide (NO) availability on this relationship. Methods: A total of 162 patients included in the microvascular dataset of the Italian Society of Hypertension with available information on SUA, media-to-lumen (M/L) ratio, media cross-sectional area (MCSA), endothelial function, NO availability and HS were included in the analysis. The top tertile of M/L ratio and MCSA were used to define severe microvascular remodeling. Results: A U-shaped association was observed between SUA and both M/L ratio and MCSA. Adjustment for HS did not affect these associations. SUA was able to reclassify a significant number of subjects without, and with, severe M/L ratio and MCSA remodeling over the HS alone. The microvascular remodeling associated with SUA levels presented a predominant hypertrophic pattern. SUA was inversely associated with endothelial function and NO availability. Structural equation modeling analysis controlling for the HS suggested that the association of SUA with M/L ratio and MCSA was mediated through changes in endothelial function and NO availability. Conclusions: The addition of SUA to the HS improves the identification of subjects with greater microvascular remodeling. The relationship between SUA and microvascular remodeling is mediated by endothelial function and NO availability.

Uric acid and hypertension: a focused review and practical recommendations

: Uric acid levels are higher in humans than in other mammals. Best known as an extracellular antioxidant, uric acid also increases salt sensitivity, fat storage, and lipogenesis. Xanthine oxidase-related oxidative stress may also induce endothelial dysfunction and renal vasoconstriction. Renal structure abnormalities contribute to salt-sensitive and uric acid-independent hypertension. Maternal hyperuricemia during pregnancy and hyperuricemia early in life are likewise independent risk factors for hypertension. Genetic polymorphism is potentially involved in the activity of xanthine oxidoreductase, but further studies are needed. Xanthine oxidase inhibition consistently decreases blood pressure in younger hypertensive patients, albeit modestly. Hyperuricemia affects one out of five adults as a result of the Western diet, insulin resistance, and renal dysfunction. This review advocates lifestyle changes to maintain uric acid levels within the normal range in young (pre)hypertensive individuals or normotensives with a family history of hypertension, metabolic disorders, or obesity; moreover, antihypertensive medications that increase uric acid levels should be avoided.

The Optimal Range of Serum Uric Acid for Cardiometabolic Diseases: A 5-Year Japanese Cohort Study

The optimal range of serum uric acid (urate) associated with the lowest risk for developing cardiometabolic diseases is unknown in a generally healthy population. This 5-year cohort study is designed to identify the optimal range of serum urate. The data were collected from 13,070 Japanese between ages 30 and 85 at the baseline (2004) from the Center for Preventive Medicine, St. Luke’s International Hospital, Tokyo. We evaluated the number of subjects (and prevalence) of those free of the following conditions: hypertension, diabetes, dyslipidemia, and chronic kidney disease (CKD) over 5 years for each 1 mg/dL of serum urate stratified by sex. Furthermore, the odds ratios (ORs) for remaining free of these conditions were calculated with multiple adjustments. Except for truly hypouricemic subjects, having lower serum urate was an independent factor for predicting the absence of hypertension, dyslipidemia, and CKD, but not diabetes. The OR of each 1 mg/dL serum urate decrease as a protective factor for hypertension, dyslipidemia, and CKD was 1.153 (95% confidence interval, 1.068–1.245), 1.164 (1.077–1.258), and 1.226 (1.152–1.306) in men; 1.306 (1.169–1.459), 1.121 (1.022–1.230), and 1.424 (1.311–1.547) in women, respectively. Moreover, comparing serum urate of 3–5 mg/dL in men and 2–4 mg/dL in women, hypouricemia could be a higher risk for developing hypertension (OR: 4.532; 0.943–21.78) and CKD (OR: 4.052; 1.181–13.90) in women, but not in men. The optimal serum urate range associated with the lowest development of cardiometabolic diseases was less than 5 mg/dL for men and 2–4 mg/dL for women, respectively.

Uric Acid and Arterial Stiffness

Hyperuricemia is usually associated with hypertension, diabetes mellitus, metabolic syndrome and chronic kidney disease. Accumulating data from epidemiological studies indicate an association of increased uric acid (UA) with cardiovascular diseases. Possible pathogenic mechanisms include enhancement of oxidative stress and systemic inflammation caused by hyperuricemia. Arterial stiffness may be one of the possible pathways between hyperuricemia and cardiovascular disease, but a clear relationship between increased UA and vascular alterations has not been confirmed. The review summarizes the epidemiological studies investigating the relationship between UA and arterial stiffness and highlights the results of interventional studies evaluating arterial stiffness parameters in patients treated with UA-lowering drugs.

Early Endothelial Dysfunction in Type 1 Diabetes Is Accompanied by an Impairment of Vascular Smooth Muscle Function: A Meta-Analysis

Background: A large yet heterogeneous body of literature exists suggesting that endothelial dysfunction appears early in type 1 diabetes, due to hyperglycemia-induced oxidative stress. The latter may also affect vascular smooth muscles (VSM) function, a layer albeit less frequently considered in that pathology. This meta-analysis aims at evaluating the extent, and the contributing risk factors, of early endothelial dysfunction, and of the possible concomitant VSM dysfunction, in type 1 diabetes. Methods: PubMed, Web of Sciences, Cochrane Library databases were screened from their respective inceptions until October 2019. We included studies comparing vasodilatory capacity depending or not on endothelium (i.e., endothelial function or VSM function, respectively) in patients with uncomplicated type 1 diabetes and healthy controls. Results: Fifty-eight articles studying endothelium-dependent function, among which 21 studies also assessed VSM, were included. Global analyses revealed an impairment of standardized mean difference (SMD) (Cohen's d) of endothelial function: -0.61 (95% CI: -0.79, -0.44) but also of VSM SMD: -0.32 (95% CI: -0.57, -0.07). The type of stimuli used (i.e., exercise, occlusion-reperfusion, pharmacological substances, heat) did not influence the impairment of the vasodilatory capacity. Endothelial dysfunction appeared more pronounced within macrovascular than microvascular beds. The latter was particularly altered in cases of poor glycemic control [HbA_1c > 67 mmol/mol (8.3%)]. Conclusions: This meta-analysis not only corroborates the presence of an early impairment of endothelial function, even in response to physiological stimuli like exercise, but also highlights a VSM dysfunction in children and adults with type 1 diabetes. Endothelial dysfunction seems to be more pronounced in large than small vessels, fostering the debate on their relative temporal appearance.

Hyperuricemia and Hypertension: Links and Risks

Hyperuricemia has long been recognized to be associated with increased cardiovascular risk, including risk of developing hypertension. Epidemiological findings suggest that the link with hypertension is stronger in children and adolescents. Uric acid acts as a strong antioxidant compound in the extracellular environment but has pro-inflammatory effects within the intracellular setting. A chronic phase of microvascular injury is known to occur after prolonged periods of hyperuricemia. This is proposed to contribute to afferent arteriolopathy and elevation of blood pressure that may become unresponsive to uric acid-lowering therapies over time. Studies have struggled to infer direct causality of hyperuricemia due to a vast number of confounders including body mass index. The aim of this review is to present the available data and highlight the need for large scale prospective randomized controlled trials in this area. At present, there is limited evidence to support a role for uric acid-lowering therapies in helping mitigate the risk of hypertension.

Severe Hypouricemia Impairs Endothelium-Dependent Vasodilatation and Reduces Blood Pressure in Healthy Young Men: A Randomized, Placebo-Controlled, and Crossover Study

Background

Uric acid (UA) is a plasmatic antioxidant that has possible effects on blood pressure. The effects of UA on endothelial function are unclear. We hypothesize that endothelial function is not impaired unless significant UA depletion is achieved through selective xanthine oxidase inhibition with febuxostat and recombinant uricase (rasburicase).

Methods and Results

Microvascular hyperemia, induced by iontophoresis of acetylcholine and sodium nitroprusside, and heating‐induced local hyperemia after iontophoresis of saline and a specific nitric oxide synthase inhibitor were assessed by laser Doppler imaging. Blood pressure and renin‐angiotensin system markers were measured, and arterial stiffness was assessed. CRP (C‐reactive protein), allantoin, chlorotyrosine/tyrosine ratio, homocitrulline/lysine ratio, myeloperoxidase activity, malondialdehyde, and interleukin‐8 were used to characterize inflammation and oxidative stress. Seventeen young healthy men were enrolled in a randomized, double‐blind, placebo‐controlled, 3‐way crossover study. The 3 compared conditions were placebo, febuxostat alone, and febuxostat together with rasburicase. The allantoin (μmol/L)/UA (μmol/L) ratio differed between sessions (P<0.0001). During the febuxostat‐rasburicase session, heating‐induced hyperemia became altered in the presence of nitric oxide synthase inhibition; and systolic blood pressure, angiotensin II, and myeloperoxidase activity decreased (P≤0.03 versus febuxostat). The aldosterone concentration decreased in the febuxostat‐rasburicase group (P=0.01). Malondialdehyde increased when UA concentration decreased (both P<0.01 for febuxostat and febuxostat‐rasburicase versus placebo). Other parameters remained unchanged.

Conclusions

A large and short‐term decrease in UA in humans alters heat‐induced endothelium‐dependent microvascular vasodilation, slightly reduces systolic blood pressure through renin‐angiotensin system activity reduction, and markedly reduces myeloperoxidase activity when compared with moderate UA reduction. A moderate or severe hypouricemia leads to an increase in lipid peroxidation through loss of antioxidant capacity of plasma.

Clinical Trial Registration

URL: http://www.clinicaltrials.gov. Unique identifier: NCT03395977.

Dietary Antioxidant Supplements and Uric Acid in Chronic Kidney Disease: A Review

Increased serum levels of uric acid have been associated with the onset and development of chronic kidney disease (CKD), cardiovascular disease, and mortality, through several molecular pathogenetic mechanisms, such as inflammation and oxidative stress. Oxidative stress is present even in the early stages of CKD, progresses parallelly with the deterioration of kidney function, and is even more exacerbated in end-stage renal disease patients undergoing maintenance hemodialysis. Although acting in the plasma as an antioxidant, once uric acid enters the intracellular environment; it behaves as a powerful pro-oxidant. Exogenous intake of antioxidants has been repeatedly shown to prevent inflammation, atherosclerosis and oxidative stress in CKD patients. Moreover, certain antioxidants have been proposed to exert uric acid-lowering properties. This review aims to present the available data regarding the effects of antioxidant supplements on both oxidative stress and uric acid serum levels, in a population particularly susceptible to oxidative damage such as CKD patients.

Differences in the association between glycemia and uric acid levels in diabetic and non-diabetic populations

AIMS

Our study aimed to investigate the influence of different glycemic statuses and their fasting plasma glucose/2-hour post-load glucose on uric acid level.

METHODS

A total of 14,787 subjects were recruited after excluding subjects with medication for hyperuricemia or diabetes. Fasting plasma glucose (FPG), 2-hour post-load glucose (2hPG), and uric acid (UA) were measured. Then, subjects were divided into normal glucose tolerance (NGT), impaired fasting glucose (IFG), impaired glucose tolerance (IGT), and diabetes.

RESULTS

After adjustment for clinical variables, in NGT group, there was no significant relationship found between UA level and FPG. However, there was a positive association between UA level and 2hPG (β = 0.003, 95% CI: 0.002~0.004). A similar trend was also observed between UA level and 2hPG in IFG group (β = 0.004, 95% CI: 0.000~0.009) and IGT group (β = 0.005, 95% CI: 0.002~0.008), but relationship between UA level and FPG remained insignificant. In diabetes group, UA level was negatively associated with both FPG (β = -0.008, 95% CI: -0.010 ~ -0.007) and 2hPG (β = -0.005, 95% CI: -0.006 ~-0.003).

CONCLUSIONS

In non-diabetic individuals, UA level increased with 2hPG, but not with FPG, and UA level was inversely associated with both FPG and 2hPG in diabetic population.

Decreased uric acid levels in the acute phase of Plasmodium vivax malaria

INTRODUCTION

Uric acid is one of the compounds associated with the inflammatory process in malaria. It acts as an indicator of cellular damage by activating the immune response and inflammatory process.

METHODS

We measured serum concentrations of uric acid in 60 symptomatic patients before and after treatment for malarial infections caused by Plasmodium vivax.

RESULTS

Lower serum concentrations of uric acid were found during the acute phase of P. vivax malaria compared to those in its convalescent phase (p < 0.0001).

CONCLUSIONS

Patients in the acute phase of malaria had lower uric acid levels than those in its convalescent phase.

Trends of Lipophilic, Antioxidant and Hematological Parameters Associated with Conventional and Electronic Smoking Habits in Middle-Age Romanians

It is known that cigarette smoking is correlated with medical associated inquires. New electronic cigarettes are intensively advertised as an alternative to conventional smoking, but only a few studies demonstrate their harmful potential. A cross-sectional study was designed using 150 subjects from Brasov (Romania), divided into three groups: non-smokers (NS = 58), conventional cigarettes smokers (CS = 58) and electronic cigarettes users (ECS = 34). The aim of this study was to determine levels of some plasma lipophilic and hematological components, and the total antioxidant status that could be associated with the smoking status of the subjects. Serum low density lipoproteins (LDL) cholesterol increased significantly for ECS participants versus NS group (18.9% difference) (p < 0.05). Also, the CS group is characterized by an increase of serum LDL cholesterol (7.9% difference vs. NS), but with no significant statistical difference. The variation of median values of serum very low density lipoproteins (VLDL) was in order NS < ECS < CS, with statistical difference between NS and CS groups (34.6% difference; p = 0.023). When comparing the antioxidant status of the three groups, significant differences (p < 0.05) were obtained between NS vs. CS and NS vs. ECS. Similar behavior was identified for CS and ECS. Statistically significant changes (p < 0.0001) for both vitamin A and vitamin E were identified in the blood of NS vs. CS and NS vs. ECS, and also when comparing vitamin A in the blood of the CS group versus the ECS group (p < 0.05). When all groups were compared, the difference in the white blood cell (WBC) was (p = 0.008). A slight increase in the red blood cell (RBC) count was observed, but with no statistical difference between groups. These results indicated that conventional cigarette and e-cigarette usage promotes the production of excess reactive oxygen species, involving different pathways, different antioxidants and bioactive molecules.

Potential Dangers of Serum Urate-Lowering Therapy

In observational studies, high serum urate levels are associated with adverse outcomes, including mortality. However, the hypothesis that urate-lowering may improve nongout outcomes has not been confirmed by placebo-controlled clinical trials. On the contrary, 7 recent placebo-controlled trials of urate-lowering drugs with different mechanisms of action (uricosuric: lesinurad; xanthine oxidase inhibition: febuxostat; uricase: pegloticase) have observed higher mortality or trends to higher mortality in gout patients, with the largest decreases in serum urate. Because all urate-lowering mechanisms were implicated, this raises safety concerns about urate-lowering itself. Far from unexpected, the higher mortality associated with more intense urate-lowering is in line with the U-shaped association of urate with mortality in some observational studies. Urate accounts for most of the antioxidant capacity of plasma, and strategies to increase urate are undergoing clinical trials in neurological disease. Post hoc analysis of recent trials should explore whether the magnitude of urate-lowering is associated with adverse outcomes, and safety trials are needed before guidelines recommend lowering serum urate below certain thresholds.

Composite acute phase glycoproteins with coronary artery calcification depends on metabolic syndrome presence - The Brazilian Longitudinal Study of Adult Health (ELSA-Brasil)

BACKGROUND

Inflammation has been weakly associated with coronary artery calcium (CAC) in the overall population. However, it is currently unknown whether this varies according to the cardio-metabolic profile. We evaluated the association between GlycA, a unique composite biomarker of pro-inflammatory acute phase glycoproteins, high sensitivity C-reactive protein (hsCRP), uric acid, and their composite values (composite inflammation) in the overall population and strata according to cardiovascular risk.

METHODS

This is a cross-sectional study of 3753 Sao Paulo site participants of the ELSA-Brasil cohort that were free of cardiovascular/chronic inflammatory disease and not taking statins or allopurinol. We measured GlycA by nuclear magnetic resonance spectroscopy. For each biomarker quartile (Qs), we ran adjusted logistic and linear regression for CAC>0 and CAC score.

RESULTS

In the overall analysis, the 4th vs. 1st GlycA Q odds ratio (OR) for CAC>0 was 1.53 (95% CI: 1.18, 1.98, p trend<0.001) adjusted for demographics and lifestyle, but null after adding metabolic syndrome (MS) components, OR 1.14 (95% CI: 0.86, 1.51, p trend=0.140). Likewise, for continuous CAC values there was no difference across GlycA Qs in the fully adjusted analysis. Similarly, hsCRP, uric acid, and composite inflammation were not associated with CAC>0 or CAC score. In stratified analysis, GlycA was associated with CAC>0 in No-MS individuals, standardized (SD) OR 1.23 (95% CI: 1.08, 1.40); but not in MS individuals, SD OR 1.01 (95% CI: 0.89, 1.15) (p interaction 0.037). We found similar interaction in stratified analysis for continuous CAC on composite inflammation.

CONCLUSIONS

GlycA and composite inflammation are associated with CAC among low cardiovascular risk individuals (No-MS), but not otherwise. GlycA and composite biomarkers may better represent sources of inflammation apart from visceral obesity and traditional cardiovascular risk factors, which may have relevant effect on CAC accumulation in low cardiovascular risk individuals.

Is increased uric acid a risk factor or a defensive response? The Campania Salute Network

BACKGROUND AND AIMS

Circulating uric acid (UA) is positively associated with body mass index (BMI), blood glucose, blood pressure (BP), markers of inflammation, and altered lipid profile. UA has also anti-oxidative properties which might be beneficial for cardiovascular (CV) system. It is still debated whether or not UA is independently associated with increased CV morbidity and/or mortality.

METHODS AND RESULTS

We studied prognostic impact of UA in 8833 hypertensive adults (mean age 53 ± 12 yrs, 3857 women) from the Campania Salute Network, without prevalent CV disease and more than stage 3 CKD. We calculated standardized UA Z-score, adjusted for age, sex, glomerular filtration rate, and BMI. Low and high UA and UA Z-score quartiles were compared to the 2 middle quartiles assumed to be "normal". Prevalence of obesity and diabetes was higher in low and high than in normal UA Z-score group (all p < 0.001). Systolic BP, left ventricular mass, carotid intima thickness were significantly higher and ejection fraction was reduced in the presence of high UA Z-score (all p < 0.001). Over 33-months average follow-up, incident major CV end-points (MACE) were not significantly different among low, normal and high UA or UA Z-score. In the latter analysis, however, incident MACE tended to be more frequent in the low than the high UA Z-score. Despite the results of multivariable analyses, the effect of less aggressive therapy in low UA Z-score cannot be excluded with certainty.

CONCLUSION

In treated hypertensive patients, high levels of UA normalized for major biological determinants do not independently predict CV outcome. CLINICALTRIALS.

GOV IDENTIFIER

NCT02211365.

Elevated serum uric acid levels are associated with endothelial dysfunction in HIV patients receiving highly-active antiretroviral therapy

BACKGROUND AND AIMS

Elevated serum uric acid (SUA) levels may be associated with endothelial dysfunction. Increased rates of metabolic syndrome (MS) and elevated SUA levels were described in human immunodeficiency virus (HIV) infected patients. We investigated whether SUA levels are associated with endothelial dysfunction in HIV positive patients receiving highly-active antiretroviral therapy (HAART) irrespective of MS.

METHODS

In this cross-sectional study of 250 HIV positive patients receiving stable HAART, we evaluated the relationship between MS, SUA levels and endothelial function. SUA levels and brachial artery flow-mediated dilation (bFMD) were measured. The relationship between logarithmic (LG)-transformed SUA levels and bFMD was evaluated after correction for MS.

RESULTS

MS was detected in 28.4% of patients and elevated SUA levels (≥6 mg/dL) in 25.2%. MS was associated with higher LG-SUA levels (age-, gender- and glomerular filtration rate-adjusted beta = 0.204, p = 0.001). The crude linear association between LG-SUA levels and LG-bFMD (beta = -0.166, p = 0.008) was abolished after correction for MS (beta = -0.089, p = 0.172). When SUA levels were used as a categorical variable (≥6 mg/dL or <6 mg/dL and SUA quartiles, respectively), the association between LG-SUA levels and LG-bFMD remained significant after adjustment for MS (beta = -0.142, p = 0.022 and beta = -0.163, p = 0.010, respectively).

CONCLUSIONS

MS significantly affects SUA levels in HAART-treated HIV infected patients. The negative association between SUA and bFMD is independent of MS only for elevated SUA levels.

Relationship Between Serum Uric Acid and Incident Hypertension in Patients with Type 2 Diabetes

BACKGROUND

Little is known about the relationship between high baseline serum uric acid (SUA) and incident hypertension in patients with type 2 diabetes (T2D).

OBJECTIVES

To evaluate the ability of baseline SUA to predict the incidence of hypertension in non-hypertensive patients with T2D.

METHODS

The association between SUA and mean 20-year incidence of hypertension was examined in 1,666 non-hypertensive patients with T2D from Isfahan Endocrine and Metabolism Research Center outpatient clinics, Iran. The primary outcome was incident hypertension defined as systolic blood pressure (BP) of 140 mmHg or higher and/or diastolic BP 90 mmHg or higher and/or use of antihypertensive medications. The mean (standard error (SE)) age of participants was 49.4 years (0.25 years) with a mean (SE) duration of diabetes of 6.1 years (0.15 years) at initial registration. We used multiple logistic regression to estimate the odds ratio (OR) for the incidence of hypertension across quartiles of SUA, and plotted a receiver operating characteristic (ROC) curve to assess discrimination.

RESULTS

The highest quartile of SUA was not associated with hypertension compared with the lowest quartile in multivariable adjusted models (OR: 1.22, 95% CI: 0.87, 1.73). The area under the ROC curve for SUA was 51.7% (95% CI: 48.9, 54.5).

CONCLUSIONS

High initial SUA levels are not a predictor of incident hypertension in an Iranian T2D population.

Determinants of retinal microvascular features and their relationships in two European populations

Supplemental Digital Content is available in the text

Objectives:

To examine factors influencing retinal vasculature in two environmentally contrasted, cross-sectional studies of adult participants of European descent and to estimate the extent and specificity of genetic contributions to each retinal vasculature feature.

Methods:

Retinal images from 1088 participants in the Orkney Complex Disease Study and 387 in the CROATIA-Korčula study, taken using the same nonmydriatic camera system and graded by the same person, were evaluated. Using general linear models, we estimated the influence of an extensive range of systemic risk factors, calculated retinal traits heritabilities and genetic correlations.

Main results:

Systemic covariates explained little (<4%) of the variation in vessel tortuosity, substantially more (>10%, up to 31.7%) of the variation in vessel width and monofractal dimension. Suggestive not well trodden associations of biological interest included that of urate, tissue plasminogen activator and cardiac PR interval with arteriolar narrowing, that of carotid intima–media thickness with less-tortuous arterioles and of cardiac QT interval with more tortuous venules. The genetic underpinning of tortuosity is largely distinct from that of the other retinal vascular features, whereas that of fractal dimension and vessel width greatly overlaps. The previously recognized influence of ocular axial length on vessel widths was high and can be expected to lead to artefactual genetic associations [genetic correlation with central retinal arteriolar equivalent: −0.53 (standard error 0.11)]. The significant genetic correlation between SBP and central retinal arteriolar equivalent, −0.53 (standard error 0.22) (after adjusting for age, sex and axial length of the eye), augurs more favourably for the discovery of genetic variants relevant to vascular physiology.

Roles of serum uric acid, prolactin levels, and psychosocial factors in oral lichen planus

Free radicals play important roles in the mechanisms underlying lichen planus (LP). Uric acid (UA) is an important anti-oxidant in plasma. Prolactin (PRL) is an immunomodulatory hormone that may promote LP, as has been documented in other autoimmune disorders, such as systemic lupus erythematosus, rheumatoid arthritis, and psoriasis. PRL has multiple immune-stimulatory effects and promotes the development of such autoimmune disorders. Prolactin and uric acid may serve as biomarkers of disease activity in lichen planus. The aim of the present study was to evaluate the roles of depression, stress, and anxiety in LP, as well as serum levels of UA and PRL as potential biomarkers of disease activity and compare these findings with those of the control group. Thirty-nine patients clinically diagnosed with oral LP (study group) and 39 age- and sex-matched controls (control group) were selected in this study. Serum UA and PRL levels were measured. The Depression Anxiety Stress Scale-21 was used for psychometric evaluation of LP patients and controls. Serum UA level was found to be significantly higher in the control group as well as during the remission phase of disease in the study. There was no significant difference in serum PRL levels between cases and controls. Depression and stress scores were higher in the study group.

Impaired arterial responsiveness in untreated gout patients compared with healthy non-gout controls: association with serum urate and C-reactive protein

To determine whether arterial responsiveness is impaired among patients with gout, and whether arterial responsiveness inversely correlates with serum urate and inflammatory measures. This is a cross-sectional study of untreated gout subjects (n = 34) and non-gout healthy controls (n = 64). High-resolution dynamic ultrasound-measured flow-mediated dilation (FMD) and nitroglycerin-mediated dilation (NMD) assessed endothelium-dependent and endothelium-independent arterial responsiveness respectively. Serum urate (sUA) and high-sensitivity C-reactive protein (hsCRP) were measured in the gout group, and correlated with FMD and NMD responses. Both FMD (2.20 ± 0.53 vs 3.56 ± 0.31, p = 0.021) and NMD (16.69 ± 1.54 vs 24.51 ± 0.90, p = 0.00002) were impaired in the gout versus control group. Stratification for individual comorbidities suggested that no single risk factor accounted for impaired FMD/NMD in the gout subjects. However, the degree of association between gout and FMD, but not NMD impairment, was dampened after multivariable adjustment (FMD unadjusted beta = - 1.36 (SE 0.58), p = 0.02; adjusted beta = - 1.16 (SE 0.78), p = 0.14 and NMD unadjusted beta = - 7.68 (SE 1.78), p < 0.0001; adjusted beta = - 5.33 (SE 2.46), p = 0.03). Within the gout group, there was an inverse correlation between FMD and sUA (R = - 0.5, p = 0.003), and between FMD and hsCRP (R = - 0.42, p = 0.017), but not between NMD and sUA or hsCRP. Compared with healthy controls, subjects with gout have reduced arterial function. Individual comorbidities are insufficient to account for differences between gout and control groups, but multiple comorbidities may collectively contribute to impairment in endothelium-dependent arterial responsiveness. Endothelial impairment is also related to sUA and hsCRP, markers of gout severity and inflammation respectively. Studies to determine whether gout therapy may improve arterial responsiveness are warranted.

Uric acid and cardiovascular risk: What genes can say

BACKGROUND

Although the relationship of elevated serum uric acid levels and cardiovascular disease has been established in a great number of studies, the causal relevance of this finding remains ambiguous. An approach to evaluate the causal relevance of biomarkers is to exploit the natural randomised allocation of allelic variation in genes affecting their level, also known as Mendelian randomisation.

AIM

The aim of this paper is to review the current literature regarding serum uric acid levels and cardiovascular and renal disease risk in Mendelian randomisation studies.

METHODS

PubMed and Scopus databases were searched to retrieve Mendelian studies regarding uric acid, hyperuricaemia and cardiovascular risk.

CONCLUSIONS

Genetic evidence based on conventional and novel Mendelian randomisation approaches suggest a modest, if any, causal effect of serum uric acid concentration on the development of cardiovascular disease, suggesting that further study of uric acid genes is needed in order to elucidate the relationship of serum uric acid levels and cardiovascular disease.

Association of plasma free amino acids with hyperuricemia in relation to diabetes mellitus, dyslipidemia, hypertension and metabolic syndrome

Previous studies demonstrated independent contributions of plasma free amino acids (PFAAs) and high uric acid (UA) concentrations to increased risks of lifestyle-related diseases (LSRDs), but the important associations between these factors and LSRDs remain unknown. We quantified PFAAs and UA amongst Japanese subjects without LSRDs (no-LSRD, n = 2805), and with diabetes mellitus (DM, n = 415), dyslipidemia (n = 3207), hypertension (n = 2736) and metabolic syndrome (MetS, n = 717). The concentrations of most amino acids differed significantly between the subjects with and without hyperuricemia (HU) and also between the no-LSRD and LSRD groups (p < 0.05 to 0.001). After adjustment, the logistic regression analyses revealed that lysine in DM, alanine, proline and tyrosine in dyslipidemia, histidine, lysine and ornithine in hypertension, and lysine and tyrosine in MetS demonstrated significant positive associations with HU among the patients with LSRDs only (p < 0.05 to 0.005). By contrast, arginine, asparagine and threonine showed significant inverse associations with HU in the no-LSRD group only (p < 0.05 to 0.01). For the first time, we provide evidence for distinct patterns of association between PFAAs and HU in LSRDs, and postulate the possibility of interplay between PFAAs and UA in their pathophysiology.