Hyperuricemia, Acute and Chronic Kidney Disease, Hypertension, and Cardiovascular Disease: Report of a Scientific Workshop Organized by the National Kidney Foundation

Role of asymptomatic hyperuricemia in the progression of chronic kidney disease and cardiovascular disease

Previous research has investigated whether hyperuricemia serves as an independent risk factor for cardiovascular and renal diseases. Hyperuricemia is defined as an abnormally high level of uric acid (UA; i.e., serum urate level > 6.8 mg/dL). Hyperuricemia has been considered a complication of chronic kidney disease (CKD). However, it seems to play a pathogenic role in the progression of renal diseases. There has been increasing focus on the link between hyperuricemia and CKD. The results of randomized controlled trials have implied independent associations between hyperuricemia and the progression of cardiovascular and renal morbidities. These associations may be mediated by renin-angiotensin system activation, nitric oxide synthase inhibition, and macrovascular/microvascular disease development. There remains controversy regarding the use of serum UA level as an indirect index of renal vascular disease. This literature review focuses on the role of asymptomatic hyperuricemia in the progression of CKD, as well as the association between hyperuricemia and cardiovascular disease. It also provides a general overview of the physiological metabolism of UA.

Insulin resistance surrogates predict hypertension plus hyperuricemia

AIMS/INTRODUCTION

To compare the association of hypertension plus hyperuricemia with four insulin resistance surrogates, including glucose and triglycerides (TyG index), TyG index with body mass index (TyG-BMI), the ratio of triglycerides divided by high-density lipoprotein cholesterol (TG/HDL-C) and metabolic score for insulin resistance (METS-IR).

MATERIALS AND METHODS

Data from a cross-sectional epidemiological study enrolling a representative population sample aged ≥65 years were used to calculate the four indexes. The association with hypertension plus hyperuricemia and insulin resistance surrogates was examined with multivariate logistic regression and receiver operating characteristic.

RESULTS

A total of 4,352 participants were included, including 93 (2.1%) patients with hyperuricemia alone, 2,875 (66.1%) with hypertension alone and 587 (13.5%) with hypertension plus hyperuricemia. Mutivariate logistic regression showed that TyG index, TyG-BMI, TG/HDL-C and METS-IR were all significantly correlated with hyperuricemia, hypertension and hypertension plus hyperuricemia. Compared with the lowest quartile, the odds ratios (OR) of the highest quartile of the four indicators for hypertension plus hyperuricemia were TyG index: OR 6.39 (95% confidence interval [CI] 4.17-9.78); TyG-BMI: OR 8.54 (95% CI 5.58-13.09); TG/HDL-C: OR 7.21 (95% CI 4.72-11.01); METS-IR: OR 9.30 (95% CI 6.00-14.43), respectively. TyG-BMI and METS-IR had moderate discriminative abilities for hypertension plus hyperuricemia and the AUC values were 0.72 (95% CI 0.70-0.74) and 0.73 (95% CI 0.70-0.75).

CONCLUSIONS

The present study suggested that TyG index, TyG-BMI, TG/HDL-C and METS-IR had a significant correlation with hypertension plus hyperuricemia, and TyG-BMI and METS-IR had discriminative abilities for hypertension plus hyperuricemia.

Serum Uric Acid Levels and Their Changes and Risk of Stroke: A 7-Year Prospective Cohort Study in Northwest China

INTRODUCTION

It is not clear whether serum uric acid (SUA) levels and their changes over time are associated with the risk of stroke. A 7-year prospective cohort study in northwest China was conducted to analyze effects of SUA and their changes on the risk of stroke.

METHODS

A total of 23,262 individuals without cardiovascular disease in the Jinchang cohort were followed up for an average of 5.26 years. The Cox proportional hazard model was used to estimate the hazard ratios (HRs) and 95% confidence interval (95% CI) of stroke incidence to SUA and relative changes in SUA. Sensitivity analysis was performed after controlling the effect of renal insufficiency.

RESULTS

Baseline SUA and relative changes in SUA were positively correlated with the incidence of stroke in both males and females (p for overall association <0.0001). Stroke risk increased by 4.6% per 10% increase in the relative change of SUA (HR = 1.046, 95% CI, 1.007-1.086). The fully adjusted regression analysis demonstrated that only the large gain (>30%) in SUA was associated with an increased risk of stroke by 36.5% (95% CI, 1.8-83.0%), compared with the reference group (participants within ±10% changes in SUA). The same trend was observed in people with normal baseline SUA. In the unadjusted model, the risk of stroke associated with elevated SUA was significantly higher in the hyperuricemia group than in the normal SUA group.

CONCLUSION

High initial SUA concentration and an increase in SUA concentration over time would increase the risk of stroke, and this means that there is no safe increase in SUA.

Optimal uric acid levels by febuxostat treatment and cerebral, cardiorenovascular risks: post hoc analysis of a randomised controlled trial

OBJECTIVES

Hyperuricaemia is recognised as an independent risk marker for cardiovascular and renal diseases. However, uric acid is a powerful free-radical scavenger, and the optimal level of serum uric acid (SUA) determining outcomes are unknown. This study explored whether interventional treatments for excessive SUA reduction were harmful and what constituted the optimal lowering of SUA levels for the prevention of events in patients with asymptomatic hyperuricaemia.

METHODS

This was a post hoc analysis of a randomised trial (Febuxostat for Cerebral and CaRdiorenovascular Events PrEvEntion StuDy [FREED]) in which 1070 older patients with asymptomatic hyperuricaemia were enrolled and allocated to febuxostat (n = 537) or non-febuxostat treatment group (n = 533). We assessed the relationship between the end point (withdrawal or study completion) SUA levels and clinical outcomes. Primary end point was defined as a composite of all-cause mortality, cerebral and cardiorenovascular events.

RESULTS

In the febuxostat group, patients achieving SUA levels ≤4 mg/dl (hazard ratio: 2.01 [95% confidence interval: 1.05-3.87]), >4 to ≤ 5 mg/dl (2.12 [1.07-4.20], >6 to ≤ 7 mg/dl (2.42 [1.05-5.60]), and >7 mg/dl (4.73 [2.13-10.5]) had significantly higher risks for a primary composite event than those achieving SUA levels >5 to ≤ 6 mg/dl (p= 0.003 [log-rank test]). This J-shaped relationship applied to patients with renal impairment (p= 0.007 [Gray's test]) and was not significant in the non-febuxostat treatment group (p= 0.212 [log-rank test]).

CONCLUSION

Optimal SUA levels by febuxostat treatment is 5-6 mg/dl for reducing all-cause mortality, cerebral, cardiovascular, and renal events. Excessive SUA reduction may be harmful in older hyperuricaemic populations.

TRIAL REGISTRATION

ClinicalTrial.gov, https://clinicaltrials.gov, NCT01984749.

Retrospective analysis of renal prognosis in elderly coronary artery disease patients complicated with renal insufficiency

Objective and Methods: The aim of this study was to retrospectively analyze the renal prognosis of elderly coronary artery disease (CAD) patients complicated with renal insufficiency.

Results: A total of 307 patients were included. The mean follow-up period was 25±11months. The average age was 79±7 years. In the worsening renal function group, there were higher occurrence rate of heart failure and severe coronary artery stenosis, lower rate of percutaneous coronary intervention, lower medication rate of renin-angiotensin blocker, lower plasma albumin, magnesium and hemoglobulin level. There was no significant difference in the rate of worsening renal function or gastrointestinal bleeding between patients who took anti-platelet agents/statins and those without. Patients with reduced left ventricular ejective fraction had higher rate of worsening renal function, yet lower medication rate of renin-angiotensin blockers, lower plasma albumin and hemoglobulin level. Anemia, malnutrition and worsening cardiac function were risk factors of renal function deterioration and mortality.

Conclusions: In the elderly coronary artery disease patients who had renal insufficiency, antiplatelet agents and statin have non-adverse effects on renal function; lower medication rate of renin-angiotensin blocker were found in patients with either worsening renal function or heart failure. Anemia, malnutrition and worsening cardiac function are risk factors of renal function deterioration and mortality.

The association between vitamin D3 and diabetes in both hyperuricemia and non-hyperuricemia populations

BACKGROUND

Previous studies have shown that hyperuricemia is involved in diabetes, obesity, hypertension, chronic kidney disease, and other diseases. At the same time, studies have shown that vitamin D3 levels in the body are linked to the onset of diabetes. However, there is currently no sufficient evidence to prove whether this connection is affected by the uric acid level. Therefore, we attempted to investigate the association between vitamin D3 content and the occurrence of diabetes in populations with different uric acid levels though the data of NHANES database from 2009 to 2018.

METHOD

Using the NHANES database, we performed a cross-sectional analysis. The participants were chosen based on stringent inclusion and exclusion requirements. This study finally included a total number of 16,735 individuals. Multivariate logistic regression analysis was used to investigate the association between vitamin D3 and diabetes mellitus in hyperuricemia and non-hyperuricemia patients after complete adjustment, and multivariate linear regression analysis was used to illustrate the association between vitamin D3 and uric acid.

RESULT

The results showed that the association between vitamin D3 and diabetes was weakened in hyperuricemia patients (OR 0.95 (0.92,0.98)). An independent association was discovered between vitamin D3 and uric acid (β -0.12 (-0.16, -0.07)) in all groups of population.

CONCLUSIONS

This study shows that vitamin D3 content is associated with the incidence of diabetes in people with high level of uric acid. This study offers a fresh perspective on the elements that influence the etiology of diabetes in hyperuricemia patients.

Bmk9 and Uricase Nanoparticle Complex for the Treatment of Gouty Arthritis and Uric Acid Nephropathy

Uric acid is the final product of purine metabolism, and excessive serum uric acid can cause gouty arthritis and uric acid nephropathy. Therefore, lowering the uric acid level and alleviating inflammation in the body are the key points to treating these diseases. A stable nanosuspension of peptide BmK9 was prepared by the precipitation-ultrasonication method. By combining uricase on the surface of a positively charged carrier, a complex consisting of neutral rod-shaped BmK9 and uricase nanoparticles (Nplex) was formed to achieve the delivery of BmK9 and uricase, respectively. The formulation of Nplex has a diameter of 180 nm and drug loading up to 200%, which releases BmK9 and uricase slowly and steadily in drug release tests in vitro. There was significantly improved pharmacokinetic behavior of the two drugs because Nplex prolonged the half-life and increased tissue accumulation. Histological assessments showed that the dual drug Nplex can reduce the inflammation response in acute gouty arthritis and chronic uric acid nephropathy in vivo. In the macrophage system, there was lower toxicity and increased beneficial effect on inflammation with Nplex than free BmK9 or uricase. Collectively, this novel formulation provides a dual drug delivery system that can treat gouty arthritis and uric acid nephropathy.

Prevalence and related factors of hyperuricaemia in Shanghai adult women of different ages: a multicentre and cross-sectional study

OBJECTIVE

Women in different age phases have different metabolism and hormone levels that influence the production and excretion of uric acid. We aimed to investigate the prevalence and related factors of hyperuricaemia among women in various age phases.

STUDY DESIGN

Observational, cross-sectional study.

SETTING

Data were obtained from women at three health check-up centres in Shanghai.

PARTICIPANTS

Adult women from three health check-up centres were recruited. Exclusion criteria were individuals with pregnancy, cancer, incomplete information. Finally, 11 601 participants were enrolled.

RESULTS

The prevalence rates of hyperuricaemia of total subjects were 11.15% (95% CIs 10.57% to 11.72%). The prevalence of hyperuricaemia in 18-29, 30-39, 40-49, 50-59, 60-69 and ≥70 years old was 6.41% (95% CI 4.97% to 7.86%), 5.63% (4.71% to 6.55%), 6.02% (5.01%% to 7.03%), 11.51% (10.19% to 12.82%), 16.49% (15.03% to 17.95%) and 23.98% (21.56% to 26.40%), respectively. Compared with 18-29 years old, the ORs for hyperuricaemia in other age phases were 0.870 (95% CI 0.647 to 1.170, p=0.357), 0.935 (0.693 to 1.261, p=0.659), 1.898 (1.444 to 2.493, p<0.001), 2.882 (2.216 to 3.748, p<0.001) and 4.602 (3.497 to 6.056, p<0.001), respectively. During the 18-29 years old, the related factors for hyperuricaemia were obesity and dyslipidaemia. During the 30-59 years old, the related factors were obesity, dyslipidaemia, hypertension and chronic kidney disease (CKD). Over the 60 years old, the occurrence of hyperuricaemia was mainly affected by obesity, dyslipidaemia and CKD, while hypertension cannot be an impact factor for hyperuricaemia independently of obesity and dyslipidaemia.

CONCLUSION

After 50 years old, the prevalence of hyperuricaemia in Shanghai women has increased significantly and reaches the peak after 70. Obesity and dyslipidaemia are two main related factors for hyperuricaemia during all ages, while diabetes mellitus and nephrolithiasis have no relationship with hyperuricaemia throughout. CKD is an independent impact factor for hyperuricaemia after 30 years old.

A Non-purine Xanthine Oxidoreductase Inhibitor Reduces Albuminuria in Patients with DKD: A Randomized Controlled Trial

Background

Diabetic kidney disease (DKD) is characterized by albuminuria and reduced renal function. Whether xanthine oxidoreductase inhibitors (XORIs) have a renoprotective effect in DKD patients with type 2 diabetes remains controversial. We conducted a proof-of-concept study to investigate the renal effects of a novel XORI, TMX-049, in patients with DKD and type 2 diabetes.

Methods

This is a multicenter, 12-week, randomized, double-blind, placebo-controlled phase 2a trial conducted at 49 centers across the United States between April 2018 and June 2019. In total, 130 patients with type 2 diabetes, urine albumin-creatinine ratio (UACR) 200 - 3000 mg/g, eGFR ≥30 ml/min per 1.73 m2, and serum uric acid (sUA) 4 - 10 mg/dl were randomized 1:1:1 to TMX-049 200 mg (n=44) or 40 mg (n=44), or placebo (n=42). The primary end point was change in log-transformed UACR at week 12 from baseline. The secondary end points included changes in UACR, eGFR, and sUA from baseline.

Results

The least squares mean differences for changes in log-transformed UACR from baseline to week 12 compared with placebo were -0.43 (95% confidence interval [95% CI], -0.82 to -0.04, P=0.03) for TMX-049 200 mg and -0.05 (95% CI, -0.44 to 0.34, P=0.80) for 40 mg; a 35% reduction in UACR was observed with TMX-049 200 mg (ratio versus placebo, 0.65; 95% CI, 0.44 to 0.96) but not 40 mg (0.95; 95% CI, 0.64 to 1.41). Throughout the treatment period, marked reductions in sUA levels but no changes in eGFR were observed with both TMX-049 doses. TMX-049 was generally well tolerated, although two patients with TMX-049 200 mg developed gout.

Conclusions

TMX-049 200 mg reduced albuminuria at 12 weeks in patients with DKD and type 2 diabetes. TMX-049 may exert a renoprotective effect independent of its sUA-lowering effect.

microRNA-199a downregulation alleviates hyperuricemic nephropathy via the PPARγ/β-catenin axis

Hyperuricemia always develops into hyperuricemic nephropathy (HN). The role of microRNA (miR) in HN is less studied. We aimed to discuss the role of miR-199a in HN. The expression of miR-199a and PPARγ in renal tissues of HN rats was detected. The targeting relation between miR-199a and PPARγ was verified. The contents of SCr, UA, BUN, and mALB, renal injury-relevant biomarkers were detected, and the pathological changes of renal tissue and renal interstitial fibrosis were observed by histological staining. After miR-199a and PPARγ knockdown, the contents of SCr, BUN, and mALB and renal interstitial fibrosis were estimated. Collectively, overexpression of miR-199a aggravated the renal injury in HN rats. By contrast, inhibition of miR-199a weakened renal injury, as evidenced by decreased contents of SCr, UA, BUN, and mALB, and mitigated renal interstitial fibrosis. miR-199a targeted PPARγ. Silencing of PPARγ upregulated the levels of downstream genes of β-catenin and the contents of SCr, UA, BUN, and mALB and deteriorated renal interstitial fibrosis. Moreover, the silencing of PPARγ blocked the alleviative effects of miR-199a inhibitor on the renal injury. Overall, miR-199a targets PPARγ and activates the β-catenin pathway, thus aggravating HN, which might provide a future target for the treatment of HN.

Hyperuricemia, Elevated Body Mass Index, Female Sex, and Albuminuria Increase the Probability of Elevated High-Sensitivity C-Reactive Protein: Results From the National Health and Nutrition Examination Survey 2015-2018

Importance: High uric acid (UA) is hypothesized to worsen kidney and cardiovascular disease morbidity via activation of systemic inflammation. Clinical trials of UA modification report reduction of the inflammatory marker high sensitivity C-reactive protein (hs-CRP) as an outcome measure, but studies have not demonstrated that hyperuricemia independently increases hs-CRP when adjusted for important confounders such as body mass index (BMI), sex, and age. Objective: To identify clinical risk factors for elevated hs-CRP, including but not limited to hyperuricemia, through a cross-sectional analysis of the National Health and Nutrition Examination Survey (NHANES) 2015-2018. Results: In the final multivariate logistic regression model, the exposure with the strongest effect on the odds of elevated hs-CRP was BMI in the fourth quartile, OR = 13.1 (95% CI 6.25-27.42), followed by female sex (OR = 4.9, 95% CI 2.92-8.34), hyperuricemia (OR = 2.2, 95% CI 1.36-3.45), urine albumin creatinine ratio (ACR; OR = 1.5, 95% CI 1.09-2.18), poor overall health (OR = 1.4, 95% CI 1.18-1.58), and interactions between hyperuricemia and sex (OR = 1.4, 95% CI 1.05-1.83), and between BMI and sex (OR = 1.2, 95% CI 1.03-1.47). Notably, chronic kidney disease (CKD) and CKD surrogates were not associated with hs-CRP despite urine ACR maintaining a significant independent effect. Conclusions: In this national population-based study, we demonstrated that hyperuricemia significantly increases the odds of elevated hs-CRP, independent from BMI, female sex, urine ACR, and overall health status. Further study is recommended to better understand the sex difference in this association and the role of albuminuria, but not CKD, in systemic inflammation.

No association between serum uric acid and lumbar spine bone mineral density in US adult males: a cross sectional study

Available evidence linking serum uric acid (SUA) and bone mineral density (BMD) remains controversial, and data on this association are limited among adult men in the general population. Thus, the aim of this study was to evaluate the association of SUA with lumbar spine BMD in US adult males. A cross-sectional study was conducted based on the National Health and Nutrition Examination Survey (NHANES, 1999–2006) database. Multivariate linear regression analyses were employed to assess the association of SUA with lumbar spine BMD, considering complex survey design and sampling weights. Through rigorous eligibility criteria, a total of 6704 individuals were yielded for final data analysis (average age, 40.5 years; 70.6% white). After fully adjusting potential confounders, no associations were detected between SUA and lumbar spine BMD [β (95% confidence interval, CI), − 0.003 (− 0.007, 0.002)]. Additionally, similar results were observed in all stratification analyses, and no interactions were found based on all priori specifications. In brief, our findings did not provide an inspiring clue for the hypothesis that SUA may be beneficial to lumbar spine BMD. Future more prospective studies are needed to further explore the causal relationship of SUA with lumbar spine BMD.

Genetic and Physiological Effects of Insulin on Human Urate Homeostasis

Insulin and hyperinsulinemia reduce renal fractional excretion of urate (FeU) and play a key role in the genesis of hyperuricemia and gout, via uncharacterized mechanisms. To explore this association further we studied the effects of genetic variation in insulin-associated pathways on serum urate (SU) levels and the physiological effects of insulin on urate transporters. We found that urate-associated variants in the human insulin (INS), insulin receptor (INSR), and insulin receptor substrate-1 (IRS1) loci associate with the expression of the insulin-like growth factor 2, IRS1, INSR, and ZNF358 genes; additionally, we found genetic interaction between SLC2A9 and the three loci, most evident in women. We also found that insulin stimulates the expression of GLUT9 and increases [14C]-urate uptake in human proximal tubular cells (PTC-05) and HEK293T cells, transport activity that was effectively abrogated by uricosurics or inhibitors of protein tyrosine kinase (PTK), PI3 kinase, MEK/ERK, or p38 MAPK. Heterologous expression of individual urate transporters in Xenopus oocytes revealed that the [14C]-urate transport activities of GLUT9a, GLUT9b, OAT10, OAT3, OAT1, NPT1 and ABCG2 are directly activated by insulin signaling, through PI3 kinase (PI3K)/Akt, MEK/ERK and/or p38 MAPK. Given that the high-capacity urate transporter GLUT9a is the exclusive basolateral exit pathway for reabsorbed urate from the renal proximal tubule into the blood, that insulin stimulates both GLUT9 expression and urate transport activity more than other urate transporters, and that SLC2A9 shows genetic interaction with urate-associated insulin-signaling loci, we postulate that the anti-uricosuric effect of insulin is primarily due to the enhanced expression and activation of GLUT9.

Mesenchymal stem cells transplantation attenuates hyperuricemic nephropathy in rats

Mesenchymal stem cells (MSCs), due to their multi-directional differentiation, paracrine and immunomodulation potentials, and the capacity of homing to target organ, have been reported to facilitate regeneration and repair of kidney and improve kidney function in acute or chronic kidney injury. The present study was aimed to evaluate whether MSCs could have a protective effect in hyperuricemic nephropathy (HN) and the underlying mechanisms. A rat HN model was established by oral administration of a mixture of potassium oxonate (PO, 1.5 g/kg) and adenine (Ad, 50 mg/kg) daily for 4 weeks. For MSCs treatment, MSCs (3 × 10⁶ cells/kg per week) were injected via tail vein from the 2nd week for 3 times. The results showed that along with the elevated uric acid (UA) in HN rats, creatinine (CREA), blood urea nitrogen (BUN), microalbuminuria (MAU) and 24-hour urinary protein levels were significantly increased comparing with the normal control rats, while decreased after MSCs treatment. Moreover, the mRNA levels of inflammation and fibrosis-related gene were reduced in UA + MSCs group. Consistently, hematoxylin-eosin (HE) staining results showed the destruction of kidney structure and fibrosis were significantly alleviated after MSCs administration. Similarly, in vitro, NRK-52Es cells were treated with high concentration UA (10 mg/dL) in the presence of MSCs, and we found that MSCs co-culture could inhibited UA-induced cell injury, characterized as improvement of cell viability and proliferation, inhibition of apoptosis, inflammation, and fibrosis. Collectively, MSCs treatment could effectively attenuate UA-induced renal injury, and thus it might be a potential therapy to hyperuricemia-related renal diseases.

Peroxiredoxin AhpC1 protects Pseudomonas aeruginosa against the inflammatory oxidative burst and confers virulence

Pseudomonas aeruginosa is an opportunistic bacterium in patients with cystic fibrosis and hospital acquired infections. It presents a plethora of virulence factors and antioxidant enzymes that help to subvert the immune system. In this study, we identified the 2-Cys peroxiredoxin, alkyl-hydroperoxide reductase C1 (AhpC1), as a relevant scavenger of oxidants generated during inflammatory oxidative burst and a mechanism of P. aeruginosa (PA14) escaping from killing. Deletion of AhpC1 led to a higher sensitivity to hypochlorous acid (HOCl, IC₅₀ 3.2 ± 0.3 versus 19.1 ± 0.2 μM), hydrogen peroxide (IC₅₀ 91.2 ± 0.3 versus 496.5 ± 6.4 μM) and the organic peroxide urate hydroperoxide. ΔahpC1 strain was more sensitive to the killing by isolated neutrophils and less virulent in a mice model of infection. All mice intranasally instilled with ΔahpC1 survived as long as they were monitored (15 days), whereas 100% wild-type and ΔahpC1 complemented with ahpC1 gene (ΔahpC1 attB:ahpC1) died within 3 days. A significantly lower number of colonies was detected in the lung and spleen of ΔahpC1-infected mice. Total leucocytes, neutrophils, myeloperoxidase activity, pro-inflammatory cytokines, nitrite production and lipid peroxidation were much lower in lungs or bronchoalveolar liquid of mice infected with ΔahpC1. Purified AhpC neutralized the inflammatory organic peroxide, urate hydroperoxide, at a rate constant of 2.3 ± 0.1 × 10⁶ M^-1s^-1, and only the ΔahpC1 strain was sensitive to this oxidant. Incubation of neutrophils with uric acid, the urate hydroperoxide precursor, impaired neutrophil killing of wild-type but improved the killing of ΔahpC1. Hyperuricemic mice presented higher levels of serum cytokines and succumbed much faster to PA14 infection when compared to normouricemic mice. In summary, ΔahpC1 PA14 presented a lower virulence, which was attributed to a poorer ability to neutralize the oxidants generated by inflammatory oxidative burst, leading to a more efficient killing by the host. The enzyme is particularly relevant in detoxifying the newly reported inflammatory organic peroxide, urate hydroperoxide.

Factors Influencing the Serum Uric Acid in Gout with Cerebral Infarction

Background

Although the relationship between gout and cardiovascular has been well demonstrated, there is little information about the difference between gout with cerebrovascular disease and cardiovascular disease. In this study, the differences between gout with cerebral infarction (gout+CI) and gout with coronary heart disease (gout+CHD) and related factors that affect serum uric acid (sUA) levels in gout+CI were investigated by a cross-sectional study.

Method

The patients from Jiangxi Provincial People's Hospital with gout+CHD, gout+CI, and gout with coronary heart disease and cerebral infarction (gout+CHD+CI) between 2016 and 2020 were included in this study, and the medical record data were collected and analyzed.

Results

We observed significant differences in age, drinking, hypertension, long-term use of diuretics and NSAIDs, sUA, CRE, and blood glucose in patients with gout+CHD and gout+CI. The sUA level was significantly positively correlated with smoking, CRE, and TG in the gout+CI group and was only positively correlated with CRE in the gout+CHD group and the gout+CHD+CI group (p < 0.05). Interestingly, the sUA level was only negatively correlated with the age and gender in the gout+CI group (p < 0.05). After excluding factors with no significant statistical effect, only age, gender, smoking, CRE, and TG were included in the multiple linear regression model. It suggested that smoking, CRE, and TG are positively correlated with the sUA level, while age was negatively correlated with the sUA level.

Conclusions

There are many discrepancies in clinical characteristics between gout+CHD patients and gout+CI patients, especially that the factors that affect UA levels are significantly different. The data also suggested that uric acid-lowering therapy may need to be strengthened in the young gout+CI patients with a history of smoking.

Apigenin ameliorates hyperuricemic nephropathy by inhibiting URAT1 and GLUT9 and relieving renal fibrosis via the Wnt/β-catenin pathway

BACKGROUND

Hyperuricemia (HUA) is characterized by abnormal serum uric acid (UA) levels and demonstrated to be involved in renal injury leading to hyperuricemic nephropathy (HN). Apigenin (API), a flavonoid naturally present in tea, berries, fruits, and vegetables, exhibits various biological functions, such as antioxidant and anti-inflammatory activity.

PURPOSE

To investigate the effect of API treatment in HN and to reveal its underlying mechanisms.

METHODS

The mice with HN were induced by potassium oxonate intraperitoneally and orally administered for two weeks. The effects of API on renal function, inflammation, fibrosis, and uric acid (UA) metabolism in mice with HN were evaluated. The effects of API on urate transporters were further examined in vitro.

RESULTS

The mice with HN exhibited abnormal renal urate excretion and renal dysfunction accompanied by increased renal inflammation and fibrosis. In contrast, API reduced the levels of serum UA, serum creatinine (CRE), blood urea nitrogen (BUN) and renal inflammatory factors in mice with HN. Besides, API ameliorated the renal fibrosis via Wnt/β-catenin pathway suppression. Furthermore, API potently promoted urinary UA excretion and inhibited renal urate transporter 1 (URAT1) and glucose transporter 9 (GLUT9) in mice with HN. In vitro, API competitively inhibited URAT1 and GLUT9 in a dose-dependent manner, with IC₅₀ values of 0.64 ± 0.14 μM and 2.63 ± 0.69 μM, respectively.

CONCLUSIONS

API could effectively attenuate HN through co-inhibiting UA reabsorption and Wnt/β-catenin pathway, and thus it might be a potential therapy to HN.

Management of oxidative stress and inflammation in cardiovascular diseases: mechanisms and challenges

Cardiovascular diseases (CVDs) have diverse physiopathological mechanisms with interconnected oxidative stress and inflammation as one of the common etiologies which result in the onset and development of atherosclerotic plaques. In this review, we illustrate this strong crosstalk between oxidative stress, inflammation, and CVD. Also, mitochondrial functions underlying this crosstalk, and various approaches for the prevention of redox/inflammatory biological impacts will be illustrated. In part, we focus on the laboratory biomarkers and physiological tests for the evaluation of oxidative stress status and inflammatory processes. The impact of a healthy lifestyle on CVD onset and development is displayed as well. Furthermore, the differences in oxidative stress and inflammation are related to genetic susceptibility to cardiovascular diseases and the variability in the assessment of CVDs risk between individuals; Omics technologies for measuring oxidative stress and inflammation will be explored. Finally, we display the oxidative stress-related microRNA and the functions of the redox basis of epigenetic modifications.

Curcumin modulates gut microbiota and improves renal function in rats with uric acid nephropathy

It is well known that the progression of hyperuricemia disease often contributes to renal dysfunction. However, there have been few studies on uric acid nephropathy (UAN), especially its relationship with gut microbiota. UAN is usually accompanied by disordered intestinal flora, and damaged gut barrier, which are closely related to tubulointerstitial fibrosis, and systemic inflammation. In previous studies, it has been confirmed that curcumin could alleviate tubulointerstitial fibrosis, and improve renal function through its antioxidant, anti-apoptotic, and anti-inflammatory efficacies. However, the effects curcumin exerts on intestinal flora in uric acid nephropathy are still unknown. Therefore, we used next-generation sequencing technology to investigate the effects of curcumin on gut microbiota in a rat model of UAN induced by adenine and potassium oxonate, and rats were randomly divided into control, model or curcumin treatment groups. The results demonstrated that, compared to the model group, the treatment group showed decreased serum uric acid (156.80 ± 11.90 μmol/L vs. 325.60 ± 18.65 μmol/L, p < 0.001), serum creatinine (66.20 ± 11.88 μmol/L vs. 182.20 ± 8.87 μmol/L, p < 0.001) and BUN level (13.33 ± 3.16 mmol/L vs. 36.04 ± 6.60 mmol/L, p < 0.001). The treatment group also displayed attenuated renal pathological lesions and metabolic endotoxemia (25.60 ± 5.90 ng/mL vs. 38.40 ± 4.98 ng/mL, p < 0.01), and improved tightly linked proteins expression. Besides, curcumin altered the gut microbiota structure in UAN rats. More specifically, curcumin treatment protected against the overgrowth of opportunistic pathogens in UAN, including Escherichia-Shigella and Bacteroides, and increased the relative abundance of bacteria producing short‐chain fatty acids (SCFAs), such as Lactobacillus and Ruminococcaceae. These results suggest that curcumin could modulate gut microbiota, fortify the intestinal barrier, attenuate metabolic endotoxemia, and consequently protect the renal function in UAN rats.

The Role of ABCG2 in the Pathogenesis of Primary Hyperuricemia and Gout-An Update

Urate homeostasis in humans is a complex and highly heritable process that involves i.e., metabolic urate biosynthesis, renal urate reabsorption, as well as renal and extrarenal urate excretion. Importantly, disturbances in urate excretion are a common cause of hyperuricemia and gout. The majority of urate is eliminated by glomerular filtration in the kidney followed by an, as yet, not fully elucidated interplay of multiple transporters involved in the reabsorption or excretion of urate in the succeeding segments of the nephron. In this context, genome-wide association studies and subsequent functional analyses have identified the ATP-binding cassette (ABC) transporter ABCG2 as an important urate transporter and have highlighted the role of single nucleotide polymorphisms (SNPs) in the pathogenesis of reduced cellular urate efflux, hyperuricemia, and early-onset gout. Recent publications also suggest that ABCG2 is particularly involved in intestinal urate elimination and thus may represent an interesting new target for pharmacotherapeutic intervention in hyperuricemia and gout. In this review, we specifically address the involvement of ABCG2 in renal and extrarenal urate elimination. In addition, we will shed light on newly identified polymorphisms in ABCG2 associated with early-onset gout.

Targeting hepatocyte carbohydrate transport to mimic fasting and calorie restriction

The pervasion of three daily meals and snacks is a relatively new introduction to our shared experience and is coincident with an epidemic rise in obesity and cardiometabolic disorders of overnutrition. The past two decades have yielded convincing evidence regarding the adaptive, protective effects of calorie restriction (CR) and intermittent fasting (IF) against cardiometabolic, neurodegenerative, proteostatic, and inflammatory diseases. Yet, durable adherence to intensive lifestyle changes is rarely attainable. New evidence now demonstrates that restricting carbohydrate entry into the hepatocyte by itself mimics several key signaling responses and physiological outcomes of IF and CR. This discovery raises the intriguing proposition that targeting hepatocyte carbohydrate transport to mimic fasting and caloric restriction can abate cardiometabolic and perhaps other fasting-treatable diseases. Here, we review the metabolic and signaling fates of a hepatocyte carbohydrate, identify evidence to target the key mediators within these pathways, and provide rationale and data to highlight carbohydrate transport as a broad, proximal intervention to block the deleterious sequelae of hepatic glucose and fructose metabolism.

Uric acid can enhance MAPK pathway-mediated proliferation in rat primary vascular smooth muscle cells via controlling of mitochondria and caspase-dependent cell death

Hyperuricemia may be a risk factor for cardiovascular diseases such as hypertension and atherosclerosis, but the mechanisms underlying uric acid-induced pathological conditions remain unknown. In this study, we investigated the effect of short time and long-term administration of increasing uric acid concentrations on cell viability, proliferative and apoptotic pathways in vascular smooth muscle cells (VSMCs). Cell viability/proliferation was determined with WST-1 assay. Expression levels of mitogen-activated protein kinases (MAPKs) (phosphorylated (p)-p38 and p-p44/42 MAPK), extrinsic (caspase 3, caspase 8), and intrinsic (B-cell lymphoma-extra-large (Bcl-xL)) apoptotic pathway proteins were measured by Western blotting. In order to assess the proliferative effects of uric acid incubations on VSMCs, we monitored the proliferative/apoptosis signaling pathways for up to 24 h. Our results indicated that uric acid increases cell viability at time and dose-dependently in VSMCs. Immunoblotting results showed that uric acid treatment elevated the expression level of p-p38 MAPK but did markedly reduce the protein levels of p-p44/42, compared with all the uric acid doses-treated VSMCs, especially at 1 h. Uric acid stimulation increased caspase-3 protein levels and decreased Bcl-xL, but did not alter caspase-8 protein expression at the same dose and time. Furthermore, low uric acid incubations (0-7.5 mg/dL) did not affect any signaling pathways for long time points (6-24 h). In conclusion, our study demonstrates for the first time that VSMCs induced with uric acid can affect cell viability, proliferative, and apoptosis pathways at the widest time and dose range. These findings provide a better understanding of the uric acid effects related to vascular impairments.

Residential greenness associated with lower serum uric acid levels and hyperuricemia prevalence in a large Chinese rural population

BACKGROUND

The association between residential greenness and hyperuricemia remains unclear, especially in developing countries. The current study aimed to explore the associations between residential greenness and both serum uric acid (SUA) levels and hyperuricemia in a Chinese rural population and to examine potential pathways of these associations.

METHODS

In this cross-sectional study, 38,721 rural residents were recruited from the baseline survey of the Henan Rural Cohort study in 2015-2017. Two satellite-derived vegetation indices, i.e., the normalized difference vegetation index (NDVI) and the enhanced vegetation index (EVI), were used to estimate residential greenness. Air pollution was determined by two proxies: particulate matter with aerodynamic diameter ≤ 2.5 μm (PM2.5) and nitrogen dioxide (NO2). Hyperuricemia was defined as SUA levels of >417 μmol/L and > 357 μmol/L for men and women, respectively. Multivariable-adjusted linear regression and logistic regression models were applied to investigate the associations of greenness with SUA and hyperuricemia, and mediation analyses were used to explore possible mechanisms underlying the associations.

RESULTS

An interquartile range (IQR) increase in both EVI and NDVI in the 500 m buffer was significantly associated with reductions in SUA levels of -7.23 μmol/L (95% confidence interval (CI): -8.96, -5.50) and -4.38 μmol/L (95% CI: -5.93, -2.83), respectively. The same increases in EVI500-m and NDVI500-m were associated with 13.8% (95% CI: 5.8%, 21.2%) and 13.0% (95% CI: 5.6%, 19.8%) lower hyperuricemia prevalence, respectively. These associations were stronger in older people (age ≥ 65), men or participants with higher averaged monthly income. The associations were partly mediated by physical activity and BMI, while no mediation effect was observed for air pollution.

CONCLUSIONS

Higher levels of residential greenness were significantly associated with lower SUA levels and hyperuricemia prevalence in the Chinese rural population. BMI and physical activity may play important mediating roles in the associations.

Dapagliflozin Added to Verinurad Plus Febuxostat Further Reduces Serum Uric Acid in Hyperuricemia: The QUARTZ Study

CONTEXT

Combining a sodium-glucose cotransporter 2 inhibitor with a xanthine oxidase inhibitor (XOI) and a urate transporter 1 (URAT1) inhibitor may enhance serum uric acid (sUA) lowering. However, concerns exist regarding high urinary UA (uUA) excretion rates and subsequent crystallization in renal tubules.

OBJECTIVE

To assess whether dapagliflozin added to verinurad, a selective URAT1 inhibitor, and febuxostat, an XOI, increases uUA excretion.

DESIGN

Randomized, placebo-controlled, 2-way crossover study (NCT03316131).

PATIENTS

Adults with asymptomatic hyperuricemia.

INTERVENTIONS

Subjects (N = 36) were randomized to oral once-daily 9 mg verinurad plus 80 mg febuxostat plus 10 mg dapagliflozin for 7 days and 7 days of oral once-daily 9 mg verinurad plus 80 mg febuxostat plus placebo with an intervening 7- to 21-day washout period.

MAIN OUTCOME MEASURE

Difference in peak uUA excretion between groups from baseline to day 7. Secondary outcomes included changes in sUA levels and 24-h uUA excretion.

RESULTS

Both regimens lowered mean peak uUA excretion (least squares mean changes from baseline: -12.9 mg/h [95% confidence interval (CI): -21.0 to -4.7], dapagliflozin; -13.2 mg/h [95% CI -21.3 to -5.0], placebo). sUA concentrations were lower with dapagliflozin (mean treatment difference -62.3 µmol/L [95% CI -82.8 to -41.8]). Dapagliflozin did not impact verinurad pharmacokinetics, its main metabolites, or febuxostat or fasting plasma glucose levels vs verinurad plus febuxostat. There were no clinically relevant changes in safety parameters.

CONCLUSIONS

Dapagliflozin further reduced sUA without influencing uUA excretion, suggesting that its combination with verinurad and febuxostat at the doses tested does not adversely affect kidney function.

CLINICAL TRIAL REGISTRATION NUMBER

NCT03316131.

Different clinical impact of hyperuricemia according to etiologies of chronic kidney disease: Gonryo Study

BACKGROUND

Hyperuricemia is highly prevalent in chronic kidney disease (CKD) patients, but the evidence for a relationship between uric acid (UA) and clinical outcomes in CKD patients is limited and inconsistent. We hypothesized that UA has a different impact on clinical outcomes according to the underlying disease causing CKD.

METHODS

This study prospectively investigated the associations between UA and renal and non-renal outcomes according to the underlying disease causing CKD in 2,797 Japanese patients under the care of nephrologists. The patients were categorized into four groups: primary renal disease (n = 1306), hypertensive nephropathy (n = 467), diabetic nephropathy (n = 275), and other nephropathy (n = 749). The renal outcome was defined as end-stage renal disease (ESRD), and the non-renal outcome was defined as a composite endpoint of cardiovascular events (CVEs) and all-cause mortality.

RESULTS

During a median 4.8-year follow-up, 359 (12.8%) patients reached the renal outcome, and 260 (9.3%) reached the non-renal outcome. In the all-patient analysis, hyperuricemia was not associated with the risks for renal and non-renal outcomes, but in primary renal disease (PRD) and hypertensive renal disease (HTN) patients, hyperuricemia was significantly associated with non-renal outcomes. Per 1 mg/dl higher UA level, multivariable adjusted hazard ratio was 1.248 (95% CI: 1.003 to 1.553) for PRD, and 1.250 (1.035 to 1.510) for HTN. Allopurinol did not reduce the risks for renal and non-renal outcomes, both in all patients and in the subgroup analysis.

CONCLUSIONS

The effect of hyperuricemia on clinical outcomes in CKD patients varies according to the underlying disease causing CKD. Hyperuricemia is an independent risk factor for non-renal outcomes in primary renal disease and hypertensive renal disease patients. Allopurinol did not decrease the risks for renal and non-renal outcomes.

Baseline and change in serum uric acid predict the progression from prehypertension to hypertension: a prospective cohort study

Evidence is lacking about the role of serum uric acid (SUA) in the progression from prehypertension to hypertension. Herein, we aimed to investigate the association of both baseline and dynamic change in SUA with the risk of hypertension developing from prehypertension. The study enrolled 11,488 participants with prehypertension during 2006-2010 from the Kailuan study. Change in SUA was assessed as % change of SUA from 2006 (baseline) to 2010. Participants were categorized into four groups by quartiles of baseline and change in SUA, separately. Multivariable logistic regressions were used to calculation the odds ratio (OR) and 95% confidence interval (CI). During a median follow-up of 7.06 years, 2716 (23.64%) participants developed hypertension from prehypertension. In the multivariable-adjusted model, the OR for hypertension comparing participants in the highest versus the lowest quartile of baseline SUA were 1.18 (95% CI, 1.02-1.36). Increased SUA over time was also associated with elevated risk of hypertension (OR in the highest quartile was 1.41 [95% CI, 1.23-1.62] versus the lowest quartile), especially in those with baseline SUA ≥ median (OR, 1.48; 95% CI, 1.21-1.81). Moreover, the addition of SUA to a conventional risk model had an incremental effect on the predictive value for hypertension (integrated discrimination improvement 0.30%, P < 0.0001; category-free net reclassification improvement 12.36%, P < 0.0001). Both high initial SUA and increased SUA over time can independently predict the progression from prehypertension to hypertension. Strategies aiming at controlling SUA level in prehypertensive subjects may impede the onset of hypertension.

Serum Uric Acid and Mortality in Patients with Chronic Kidney Disease: A Systematic Review and Meta-Analysis

BACKGROUND

Existing studies suggested conflicting relationships between serum uric acid (SUA) and mortality in CKD patients. The present meta-analysis aimed to determine whether SUA can be a predictor for mortality in CKD cohorts.

METHOD

A systematical search was conducted on PubMed, EMBASE, and The Cochrane Library to identify studies reporting the relationship between SUA level and all-cause and cardiovascular mortality in CKD populations. In addition, random-effects models were adopted to calculate the hazard ratios (HRs) and corresponding 95% confidence intervals (CIs).

RESULTS

On the whole, 29 studies were involved. In the present meta-analysis, patients exhibiting the maximum SUA level showed an association with a significantly higher risk for all-cause mortality (HR, 1.30; 95% CI, 1.06-1.59) compared with patients exhibiting the minimum SUA level. As revealed from the meta-analysis of 8 studies, low level of SUA was another predictor for all-cause mortality in patients with CKD (HR, 1.36; 95% CI, 1.20-1.54). No significant relationship was identified between SUA and cardiovascular mortality.

CONCLUSIONS

Higher and lower SUA levels are both associated with significantly increased risk of all-cause mortality in patients with CKD. A appreciate dose of treatment of lowering SUA agents should be confirmed.

Recent evidence on the effect of urate-lowering treatment on the progression of kidney disease

PURPOSE OF REVIEW

Several observational studies have shown that hyperuricemia is associated with chronic kidney disease (CKD) progression and is a potential therapeutic target in people with CKD. This review discusses the results of three recently published placebo-controlled randomized trials evaluating the effect of urate-lowering treatment on the progression of CKD with at least 2 years of follow-up.

RECENT FINDINGS

The Febuxostat versus Placebo Randomized Controlled Trial Regarding Reduced Renal Function in Patients with Hyperuricemia Complicated by Chronic Kidney Disease Stage 3 trial evaluated the effect of febuxostat in 443 patients with stage 3 CKD (mean estimated glomerular filtration rate [eGFR] 45 mL/min/1.73 m2) and asymptomatic hyperuricemia (mean serum urate 7.8 mg/dL). The Controlled trial of slowing of Kidney Disease progression From the Inhibition of Xanthine oxidase and Preventing Early Renal Loss in Diabetes trials respectively evaluated the effect of allopurinol in 369 adults with stage 3 or 4 CKD (mean eGFR 31.7 mL/min/1.73 m2, mean serum urate 8.2 mg/dL) with high progression risk and 530 patients with type 1 diabetes and diabetic kidney disease (mean eGFR 74.7 mL/min/1.73 m2, mean serum urate 6.1 mg/dL). Despite the large and sustained reductions in serum urate levels in all 3 trials, urate-lowering treatment with febuxostat or allopurinol did not result in clinically meaningful improvement in kidney outcomes.

SUMMARY

The results of large and well-designed placebo-controlled trials do not support the use of urate-lowering therapy to slow the progression of CKD.

Managing hyperuricemia and gout in chronic kidney disease: a clinical conundrum

PURPOSE OF REVIEW

There is controversy regarding the impact of hyperuricemia on the progression of chronic kidney disease (CKD), and gout remains sub optimally managed in this population. We discuss the prescribing of drugs for the treatment of gout in patients with CKD.

RECENT FINDINGS

There is a lack of consensus from expert guidelines, and prescribers have concerns regarding the risk of adverse reactions from medicines used to treat gout. These situations appear to contribute to suboptimal management of gout in this cohort. Recent data have challenged the role of urate lowering therapy (ULT) in the management of asymptomatic hyperuricemia in CKD.

SUMMARY

ULT should be commenced in all patients with severe, recurrent disease, tophaceous gout and evidence of joint damage. Most international guidelines recommend a treat-to-target approach for the management of gout. In CKD, ULT should be started at low dose with up titration adjusted to serum urate levels, rather than being based on the creatinine clearance. If patients fail first-line therapy, alternative agents are utilized, the specific agent depending on ease of access, burden of disease and other comorbidities. This approach should be incorporated into routine practice to ensure optimal treatment of gout in CKD. More research is required to investigate whether treatment of asymptomatic hyperuricemia has clinical benefits.

Histone Methyltransferase EZH2: A Potential Therapeutic Target for Kidney Diseases

Enhancer of zeste homolog 2 (EZH2) is a histone-lysine N-methyltransferase enzyme that catalyzes the addition of methyl groups to histone H3 at lysine 27, leading to gene silencing. Mutation or over-expression of EZH2 has been linked to many cancers including renal carcinoma. Recent studies have shown that EZH2 expression and activity are also increased in several animal models of kidney injury, such as acute kidney injury (AKI), renal fibrosis, diabetic nephropathy, lupus nephritis (LN), and renal transplantation rejection. The pharmacological and/or genetic inhibition of EZH2 can alleviate AKI, renal fibrosis, and LN, but potentiate podocyte injury in animal models, suggesting that the functional role of EZH2 varies with renal cell type and disease model. In this article, we summarize the role of EZH2 in the pathology of renal injury and relevant mechanisms and highlight EZH2 as a potential therapeutic target for kidney diseases.

Pharmacologic Targeting of BET Proteins Attenuates Hyperuricemic Nephropathy in Rats

Hyperuricemia is an independent risk factor for renal damage and promotes the progression of chronic kidney disease. In this study, we investigated the effect of I-BET151, a small-molecule inhibitor targeting the bromodomain and extraterminal (BET) proteins, on the development of hyperuricemic nephropathy (HN), and the mechanisms involved. Expression levels of bromodomain-containing protein 2 and 4, but not 3 were increased in the kidney of rats with HN; administration of I-BET151 effectively prevented renal dysfunction, decreased urine microalbumin, and attenuated renal fibrosis as indicated by reduced activation of renal interstitial fibroblasts and expression of fibronectin and collagen I in HN rats. Mechanistic studies show that I-BET151 treatment inhibited transition of renal epithelial cells to a mesenchymal cell type as evidenced by preservation of E-cadherin and reduction of vimentin expression. This was coincident with reduced expression of TGF-β1 and dephosphorylation of Smad3 and ERK1/2. I-BET151 was also effective in inhibiting phosphorylation of NF-κB, expression of multiple cytokines and chemokines, and infiltration of macrophages to the injured kidney. Although there were increased serum levels of uric acid and xanthine oxidase, an enzyme that catalyzes production of uric acid, and decreased expression of renal organic anion transporter 1 and 3 that promote urate excretion in the model of HN, and reduced expression levels of urine uric acid, I-BET151 treatment did not affect these responses. Collectively, our results indicate that I-BET151 alleviates HN by inhibiting epithelial to mesenchymal transition and inflammation in association with blockade of TGF-β, ERK1/2 and NF-κB signaling.

A convenient sampling and noninvasive dried spot method of uric acid in human saliva: Comparison of serum uric acid value and salivary uric acid in healthy volunteers and hyperuricemia patients

Concentration of uric acid (UA) in serum is one of the markers used to diagnose gout and hyperuricemia. However, serum treatment and storage are cumbersome, and wounds are susceptible to infection. Therefore, a new sampling and analysis method using noninvasive biological samples has been developed, called the dried spot method of UA in human saliva (DSM-UHS). Saliva (5 μL) was dropped on filter paper (a spot with a diameter of 5 mm) containing hypoxanthine (IS) (5 μL) and dried at room temperature for 30 min. The filter paper was immersed in 200 μL of lithium carbonate solution and shaken in a block bath shaker for 5 min at 30 °C. Afterward, the extraction was concentrated and reconstituted with 100 μL of lithium carbonate solution analyzed by HPLC-UV. When comparing the concentration of UA in the human saliva of hyperuricemia patients (HPs) and with that of healthy volunteers (HVs), we observed the concentration of UA was higher in the HPs than in the HVs (p < 0.0001). In addition, the results showed a significant linear relationship between the content of UA in saliva and the content of UA in the serum (r = 0.6243). The content of UA in human saliva could indirectly reflect the content of UA in human serum. Then DSM-UHS could be used to determine the content of UA in the saliva of HVs and HPs. This study provides a new research method and strategy for the determination of human UA content and the clinical prewiring of hyperuricemia.

Obesity interacts with hyperuricemia on the severity of non-alcoholic fatty liver disease

Background

A series of evidence revealed that body mass index was an important confounding factor in the research of uric acid and ischemic heart disease/hypertension. The objective of this study was to investigate whether obesity status can modify the association between serum uric acid and the severity of liver damage in NAFLD, and the possible interactive effect of hyperuricemia and obesity.

Methods

We conducted a cross-sectional study in a total of 557 ultrasound diagnosed-NAFLD. The hepatic steatosis and liver fibrosis were quantitatively evaluated by transient elastography. Hyperuricemia was defined as serum uric acid > 420 μmol/L in men, > 360 μmol/L in women and obesity was defined as body mass index ≥ 25 kg/m². The adjusted OR values of hyperuricemia and obesity were analyzed by multivariate logistic regression analysis, and the additive model was used to investigate the possible interactive effect.

Results

Multivariate regression analysis showed that hyperuricemia was associated with serious hepatic steatosis (1.74[1.09–2.79]) and elevated ALT (2.17[1.38–3.41]), but not with advanced fibrosis (1.61[0.91–2.85]). The association was further investigated in different BMI group. Hyperuricemia was associated with higher odds of serious hepatic steatosis (2.02[1.14–3.57]) and elevated ALT (2.27[1.37–3.76]) only in obese NAFLD, not in non-obese subjects. Similarly, patients with hyperuricemia had higher odds of advanced fibrosis in obese subjects (2.17[1.13–4.18]), not in non-obese subjects (0.60[0.14–2.70]). Furthermore, there was an additive interaction between hyperuricemia and obesity on the odds of serious hepatic steatosis (AP: 0.39[0.01–0.77]) and advanced fibrosis. (AP: 0.60[0.26–0.95]).

Conclusions

Hyperuricemia and obesity had a significantly synergistic effect on the hepatic steatosis and fibrosis. Thus, management of uric acid may need to be targeted in obese NAFLD.

The effect of baseline serum uric acid on chronic kidney disease in normotensive, normoglycemic, and non-obese individuals: A health checkup cohort study

Introduction

The independent role of serum uric acid (SUA) on kidney disease is controversial due to its association with metabolic syndrome. The objective of this study was to investigate the association of baseline SUA with development of chronic kidney disease and eGFR decline in normotensive, normoglycemic and non-obese individuals during follow up period.

Materials and methods

We included non-hypertensitive, non-diabetic, and non-obese 13,133 adults with estimated glomerular filtration rate (eGFR) ≥ 60ml/min/1.73m² who had a voluntary health check-up during 2004–2017.

Results

SUA was positively related to adjusted means of systolic blood pressure (SBP), triglyceride, body mass index, and body fat percent. SUA was inversely associated with high density lipoprotein HDL (P for trend ≤0.001). SUA was an independent risk factor for the development of diabetes, hypertension, and obesity. During 45.0 [24.0–76.0] months of median follow up, the highest quartiles of SUA showed significant risks of 30% eGFR decline compared than the lowest quartile (RR:3.701; 95% CI: 1.504–9.108). The highest quartile had a 2.2 fold (95% CI: 1.182–4.177) increase in risk for incident chronic kidney disease (CKD).

Conclusions

SUA is an independent risk factor for the development of diabetes, hypertension, and obesity in the healthy population. High SUA is associated with increased risk of CKD development and eGFR decline in participants with intact renal function.

The gut microbiota as a target to control hyperuricemia pathogenesis: Potential mechanisms and therapeutic strategies

Hyperuricemia (HUA) is a metabolic disorder caused by abnormal uric acid (UA) metabolism, which is a complex physiological process involving multiple organs (liver, kidney, and intestine). Although UA metabolism in the liver and kidneys has been elucidated, only a few studies have focused on the process in the intestine. With our growing knowledge of the effects of gut microorganisms on health, the gut microbiota has been identified as a new target for HUA treatment. In this review, the relationship between HUA and the gut microbiota is elucidated, and anti-hyperuricemia mechanisms targeting the intestine are discussed, such as the promotion of purine and UA catabolism by the gut microbiota, increases in UA excretion by the gut microbiota and its metabolites, regulation of UA absorption or secretion in the intestinal tract by certain transporters, and the intestinal inflammatory response to the gut microbiota. Additionally, probiotics (Bifidobacteria and Lactobacilli) and prebiotics (polyphenols, peptides, and phytochemicals) with UA-lowering effects targeting the intestinal tract are summarized, providing reference and guidance for further research.

U-Shaped Association Between Serum Uric Acid and Short-Term Mortality in Patients With Infective Endocarditis

BACKGROUND

Increased uric acid (UA) levels have been reported to be associated with poor clinical outcomes in several conditions. However, the prognostic value of UA in patients with infective endocarditis (IE) is yet unknown.

METHODS

A total of 1,117 patients with IE were included and divided into two groups according to the current definition of hyperuricemia (UA>420 μmol/L in men and >360 μmol/L in women): hyperuricemia group (n=336) and normouricemia group (n=781). The association between the UA level and short-term outcomes were examined.

RESULTS

The in-hospital mortality was 6.2% (69/1117). Patients with hyperuricemia carried a higher risk of in-hospital death (9.8% vs. 4.6%, p=0.001). Hyperuricemia was not an independent risk factor for in-hospital death (adjusted odds ratio [aOR]=1.92, 95% confidence interval [CI]: 0.92-4.02, p=0.084). A U-shaped relationship was found between the UA level and in-hospital death (p<0.001). The in-hospital mortality was lower in patients with UA in the range 250-400 μmol/L. The aOR of in-hospital death in patients with UA>400 and <250 μmol/L was 3.48 (95% CI: 1.38-8.80, p=0.008) and 3.28 (95%CI: 1.27-8.51, p=0.015), respectively. Furthermore, UA>400 μmol/L (adjusted hazard ratio [aHR]=3.54, 95%CI: 1.77-7.07, p<0.001) and <250 μmol/L (aHR=2.23, 95%CI: 1.03-4.80, p=0.041) were independent risk factors for the 6-month mortality.

CONCLUSION

The previous definition of hyperuricemia was not suitable for risk assessment in patients with IE because of the U-shaped relationship between UA levels and in-hospital death. Low and high levels of UA were predictive of increased short-term mortality in IE patients.

Uric Acid Variability and All-Cause Mortality: A Prospective Cohort Study in Northern China

OBJECTIVES

Uric acid(UA) is related with cardiovascular disease, but the association of UA variability with all-cause mortality is rarely known. This study aimed to investigate the relationship between UA variability and all-cause mortality in Kailuan cohort study in northern China.

DESIGN

Cohort study.

SETTING

Kailuan community hospitals in Tangshan, Hebei province, Northern China.

PARTICIPANTS

A total of 55717 participants from Kailuan Study were enrolled, and our study followed up biennially from 2006 to 2010.

MEASUREMENTS

Clinical records of the participants enrolled were analyzed. UA variation independent of mean (UAVIM) values were calculated and all the participants were quartile grouped into four groups as: Q1(UAVIM<0.68), Q2(0.68≤UAVIM<1.10), Q3(1.10≤UAVIM<1.67) and Q4(UAVIM≥1.67). The endpoint event was all-cause death. Cox regression model was performed to evaluate the hazard ratios(HRs) of all-cause mortality based on UAVIM groups.

RESULTS

During a median follow-up of 6.83 years, 2926 deaths occurred. The accumulated mortality rates were 4.6%, 4.8%, 5.4% and 6.1% in group Q1, Q2, Q3 and Q4 respectively. When adjusted potential confounders, the highest risk for all-cause mortality was in group Q4 and the adjusted HRs and 95% confidence intervals(CIs) of group Q2-Q4 for all-cause death were 1.044(0.937, 1.164), 1.182(1.064, 1.314) and 1.353(1.220, 1.501) compared with group Q1, respectively. Further analysis showed that the risk for all-cause death increased as UAVIM value increased. Sensitive analysis still showed the similar results when excluding participants with hyperuricemia or severe chronic kidney diseases. Sub-group analysis by age, gender, BMI or hypertension history also indicated analogous results.

CONCLUSION

Elevated UAVIM was related with increased all-cause mortality and UAVIM was an independent risk factor for all-cause mortality in the community cohort study.

The Role of Soluble Uric Acid in Modulating Autophagy Flux and Inflammasome Activation during Bacterial Infection in Macrophages

Autophagy is a homeostatic process that regulates and recycles intracellular structures and is a host defense mechanism that facilitates bacterial clearance. Uric acid in plasma is a major antioxidant but in certain conditions acts as an inflammatory danger signal. The aim of this study is to investigate the effect of soluble uric acid on autophagy and the inflammatory responses in macrophages during bacterial infection. Herein, we employed murine RAW264.7 macrophages that express uricase enzyme and human THP-1 cells that are uricase-deficient. Three different strains of Staphylococcus aureus and two different strains of Klebsiella pneumoniae were used to infect macrophages in presence and absence of soluble uric acid. We found that soluble uric acid enhanced autophagy flux in infected macrophages. We observed that IL-1β increased during bacterial infection but decreased when macrophages were co-stimulated with bacteria and uric acid. In contrast to IL-1β, soluble uric acid did not affect TNFα release and there were no dramatic differences when macrophages were infected with S. aureus or K. pneumoniae. In conclusion, uric acid enhances autophagy flux during bacterial infection, consequently reducing inflammasome activation in macrophages. Understanding the effect of uric acid on the interplay between autophagy and inflammation will facilitate therapeutic design.

Link between serum uric acid and pancreatic beta-cell function in drug naïve subjects with type 2 diabetes treated with sitagliptin

Aim: The objective of this study is to investigate the changes of UA with sitagliptin in relation to its glycemic/non-glycemic efficacies.Methods: Drug naïve subjects with T2DM (n = 62) were administered 25-50 mg/day sitagliptin monotherapy for 3 months. The subjects were divided into two subgroups according to the changes in (Δ) UA (above the median [group A, n = 31]: ΔUA = 23.3%, p < 0.00001, and below the median [group B, n = 31]: ΔUA = -0.9%, n.s.). Changes in glycemic/non-glycemic parameters were compared between these two groups, which acted as a control for each other.Results: In the overall subjects, UA significantly increased (10.8%, p < 0.00001). Significant correlations between ΔUA and ΔBMI (R = 0.252), ΔHOMA-B (R = 0.309) or ΔCPR-index (R = 0.258), and significant negative correlations between ΔUA and ΔHbA1c (R = -0.290) or ΔFFA (R = -0.271) were seen. Between group A and group B, some parameters displayed distinct regulatory patterns. HbA1c significantly decreased in both groups (group A: from 9.97% to 7.65%, group B: from 10.41% to 8.85%) with significant inter-group differences (higher reductions in group A, p < 0.05). C-peptide (+10.6%) and BMI (+1.7%) significantly increased, and FFA (-20.5%) decreased in group A. HOMA-R or 20/(C-peptide x FBG) had no changes in either group, while HOMA-B (group A: +85.1%, group B: +38.8%) or CPR-index (group A: +37.7%, group B: +20.5%) increased in both groups with significant inter-group differences (both p < 0.01). TG (-18.8%) significantly decreased, and T-C (-3.5%) and non-HDL-C (-4%) had a tendency to decrease in group B.Conclusions: These results suggest that UA and beta-cell functions/glycemic efficacy are closely linked during sitagliptin therapy. Those with elevated UA had better beta-cell enhancing and glyemic efficacies. Body weights increased and FFA decreased in these populations. By contrast, those without changes in UA had favorable profiles in atherogenic lipids.

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.

[Asymptomatic Hyperuricemia and Risk Of Cardiovascular and Renal Diseases]

Asymptomatic hyperuricemia (HU) is common in the population and significantly contributes to the general cardiovascular risk. Despite extensive study of this condition there is still no conclusive answers to questions about detection of asymptomatic HU and its effect on the risk for development and progression of cardiovascular and kidney diseases. This review summarizes key information about these issues, which has been accumulated by the present time.

Hyperuricemia in Kidney Disease: A Major Risk Factor for Cardiovascular Events, Vascular Calcification, and Renal Damage

Kidney disease, especially when it is associated with a reduction in estimated glomerular filtration rate, can be associated with an increase in serum urate (uric acid), suggesting that hyperuricemia in subjects with kidney disease may be a strictly secondary phenomenon. Mendelian randomization studies that evaluate genetic scores regulating serum urate also generally have not found evidence that serum urate is a causal risk factor in chronic kidney disease. Nevertheless, this is countered by a large number of epidemiologic, experimental, and clinical studies that have suggested a potentially important role for uric acid in kidney disease and cardiovascular disease. Here, we review the topic in detail. Overall, the studies strongly suggest that hyperuricemia does have an important pathogenic role that likely is driven by intracellular urate levels. An exception may be the role of extracellular uric acid in atherosclerosis and vascular calcification. One of the more striking findings on reviewing the literature is that the primary benefit of lowering serum urate in subjects with CKD is not by slowing the progression of renal disease, but rather by reducing the incidence of cardiovascular events and mortality. We recommend large-scale clinical trials to determine if there is a benefit in lowering serum urate in hyperuricemic subjects in acute and chronic kidney disease and in the reduction of cardiovascular morbidity and mortality in subjects with end-stage chronic kidney disease.

Effect of Urate-Lowering Therapy on Cardiovascular and Kidney Outcomes: A Systematic Review and Meta-Analysis

BACKGROUND AND OBJECTIVES

Several clinical practice guidelines noted the potential benefits of urate-lowering therapy on cardiovascular disease and CKD progression; however, the effect of this regimen remains uncertain. In this systematic review, we aimed to evaluate the efficacy of urate-lowering therapy on major adverse cardiovascular events, all-cause mortality, kidney failure events, BP, and GFR.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We systematically searched MEDLINE, Embase, and the Cochrane databases for trials published through July 2020. We included prospective, randomized, controlled trials assessing the effects of urate-lowering therapy for at least 6 months on cardiovascular or kidney outcomes. Relevant information was extracted into a spreadsheet by two authors independently. Treatment effects were summarized using random effects meta-analysis.

RESULTS

We identified 28 trials including a total of 6458 participants with 506 major adverse cardiovascular events and 266 kidney failure events. Overall urate-lowering therapy did not show benefits on major adverse cardiovascular events (risk ratio, 0.93; 95% confidence interval, 0.74 to 1.18) and all-cause mortality (risk ratio, 1.04; 95% confidence interval, 0.78 to 1.39) or kidney failure (risk ratio, 0.97; 95% confidence interval, 0.61 to 1.54). Nevertheless, urate-lowering therapy attenuated the decline in the slope of GFR (weighted mean difference, 1.18 ml/min per 1.73 m² per year; 95% confidence interval, 0.44 to 1.91) and lowered the mean BP (systolic BP: weighted mean difference, -3.45 mm Hg; 95% confidence interval, -6.10 to -0.80; diastolic BP: weighted mean difference, -2.02 mm Hg; 95% confidence interval, -3.25 to -0.78). There was no significant difference (risk ratio, 1.01; 95% confidence interval, 0.94 to 1.08) in the risk of adverse events between the participants receiving urate-lowering therapy and the control group.

CONCLUSIONS

Urate-lowering therapy did not produce benefits on the clinical outcomes, including major adverse cardiovascular events, all-cause mortality, and kidney failure. Thus, there is insufficient evidence to support urate lowering in patients to improve kidney and cardiovascular outcomes.

Recent advances in fructose intake and risk of hyperuricemia

With the widespread popularity of hyperuricemia, it has become a severe threat to human public health. Accumulating evidence suggests that dietary fructose has a close relationship with hyperuricemia, but the role of fructose intake in hyperuricemia remains unclear. Hyperuricemia is characterized by excessive production and deposition of urate crystals. Metabolism of fructose leads to the increased serum concentration of urate. In this review, we depict an update of fructose consumption worldwide and the epidemiology of hyperuricemia and summarize the progress in studying the relationship between fructose intake and the risk of hyperuricemia. This review highlights the metabolic process of fructose in the liver, small intestine, and kidney. Furthermore, we discuss molecular insights on fructose metabolism to reveal the underlying mechanism of fructose metabolism. Additionally, we elaborate on the effect of fructose metabolism on hyperuricemia to deeply understand the pathogenesis of hyperuricemia caused by fructose intake. Fructose consumption has a close correlation with an enhanced risk of developing hyperuricemia. More prospective studies are inevitable to understand the role of fructose intake in the development of hyperuricemia.

Mechanistic Insights of Soluble Uric Acid-related Kidney Disease

Hyperuricemia, defined as the presence of elevated serum uric acid (sUA), could lead to urate deposit in joints, tendons, kidney and other tissues. Hyperuricemia as an independent risk factor was common in patients during the causation and progression of kidney disease. Uric acid is a soluble final product of endogenous and dietary purine metabolism, which is freely filtered in kidney glomeruli where approximately 90% of filtered uric acid is reabsorbed. Considerable studies have demonstrated that soluble uric acid was involved in the pathophysiology of renal arteriolopathy, tubule injury, tubulointerstitial fibrosis, as well as glomerular hypertrophy and glomerulosclerosis. In the review, we summarized the mechanistic insights of soluble uric acid related renal diseases.

Prevalence and associated factors of hyperuricemia among urban adults aged 35-79 years in southwestern China: a community-based cross-sectional study

Hyperuricemia is prevalent throughout the world. However, a well-designed large-scale epidemiological investigation of hyperuricemia in southwestern China is lacking. A regional representative sample of 10,141 participants were included using multistage, stratified sampling in Chengdu and Chongqing from September 2013 to March 2014. Hyperuricemia was defined as the self-reported of the doctor's diagnosis of hyperuricemia, or serum uric acid > 420 μmol/L in men or serum uric acid > 360 μmol/L in women. The overall age- and sex-standardized prevalence of hyperuricemia among adults aged 35-79 years was 13.5%. Compared with women, the prevalence of hyperuricemia in men was higher (17.3% versus 10.0%). Hypertension, hyperlipidemia, overweight or obesity, central obesity were associated with an increased risk for hyperuricemia both in men and in women. Married men and women were not susceptible to hyperuricemia. Current cigarette smoking was an associated risk factor of hyperuricemia only in women. Hyperuricemia has become a major health problem among urban adults aged 35-79 years in southwestern China, and special attention should be paid to men. Comorbidities associated with hyperuricemia and causality worth further investigation.