J-shaped mortality relationship for uric acid in CKD

Higher serum uric acid as a risk factor for frailty in older adults: A nationwide population-based study

BACKGROUND

Uric acid (UA), the terminal breakdown product of purine metabolism, possesses contradictory roles, functioning both as an inflammatory mediator and as an antioxidant. Its clinical relevance, particularly in geriatric populations, remains a topic of ongoing debate. Aiming to elucidate whether circulating UA is detrimental or beneficial to human health, we investigate the association between serum UA concentrations and the frailty index-a comprehensive measure of biological aging in a nationally representative cohort of community-dwelling older adults.

METHODS

We conducted a population-based, cross-sectional study utilizing data from the Korea National Health and Nutrition Examination Survey. The sample included 4268 participants aged 65 years and above. A deficit accumulation frailty index (FI) was constructed using 38 items that assess physical, cognitive, psychological, and social domains. Based on the FI, participants were categorized into non-frail (FI ≤ 0.15), pre-frail (0.15 < FI ≤ 0.25), or frail (FI > 0.25). Serum UA levels were quantified through a colorimetric enzymatic assay.

RESULTS

After controlling for confounders such as age, sex, socioeconomic status (including income and education level), lifestyle factors (smoking status), and medical history (hypertension, diabetes, dyslipidemia, stroke, cardiovascular diseases), and body mass index, serum UA levels were observed to be significantly higher in frail participants compared with their non-frail counterparts (P < 0.001). Furthermore, serum UA concentrations demonstrated a positive correlation with the FI (P < 0.001), and the odds ratio for frailty per 1 mg/dL increase in serum UA was 1.22 (P < 0.001). Additionally, older adults in the highest quartile of UA levels exhibited a significantly higher FI and 1.66-fold increased odds of frailty compared with those in the lowest quartile (P = 0.011 and P = 0.005, respectively).

CONCLUSIONS

These findings suggest that elevated circulating UA levels may act as a pro-aging factor rather than an anti-aging one in older adults, highlighting its potential role in accelerating biological aging. The data further support the utility of serum UA as a potential blood-based biomarker for frailty in this demographic, contributing to the expanding evidence on its significance in geriatric health assessments.

Controversies and practical management of patients with gout and chronic kidney disease

Uric acid is a toxin retained with advancing kidney disease. Clinical manifestations of hyperuricemia include gout and systemic inflammation that are associated with increased risk of cardiovascular mortality. As many as one-third of all patients with chronic kidney disease have a history of gout, yet <25% of these patients are effectively treated to target serum urate levels of ≤6 mg/dl. A major reason for ineffective management of gout and hyperuricemia is the complexity in managing these patients, with some medications contraindicated and others requiring special dosing, potential drug interactions, and other factors. Consequently, many nephrologists do not primarily manage gout despite it being a common complication of chronic kidney disease, leaving management to the primary physician or rheumatologist. We believe that kidney specialists should consider gout as a major complication of chronic kidney disease and actively manage it in their patients. Here, we present insights from nephrologists and rheumatologists into a team approach to gout management that includes the nephrologist.

Xanthoceras sorbifolium leaves alleviate hyperuricemic nephropathy by inhibiting the PI3K/AKT signaling pathway to regulate uric acid transport

ETHNOPHARMACOLOGICAL RELEVANCE

In China, Xanthoceras sorbifolium Bunge was first documented as "Wen Guan Hua" in the "Jiu Huang Ben Cao" in 1406 A.D. According to the "National Compilation of Chinese Herbal Medicine," X. sorbifolium leaves are sweet and flat in nature and can dispel wind and dampness, suggesting that their extract can be used to treat rheumatoid arthritis. X. sorbifolium Bunge has also been used to treat arteriosclerosis, hyperlipidemia, hypertension, chronic hepatitis, and rheumatism, complications associated with hyperuricemic nephropathy (HN), a condition characterized by kidney damage resulting from high levels of uric acid (UA) in the blood.

AIM OF THE STUDY

The purpose of this study was to investigate the effects and underlying mechanisms of a 70% ethanol extract from X. sorbifolium leaves (EX) in alleviating HN.

MATERIALS AND METHODS

A mouse model of hyperuricemia was established to initially evaluate the hypouricemic effects and determine the effective dose of EX. Phytochemical analyses were conducted using ultra high-performance liquid chromatography and liquid chromatography-mass spectroscopy. The potential key pathways of EX in the alleviation of HN were inferred using network pharmacology and bioinformatics. An HN rat model was then established, and experiments including biomarker detection, western blotting, reverse transcription quantitative polymerase chain reaction, immunohistochemical and Masson's trichrome staining, and transmission electron microscopy were conducted to evaluate the effect of EX on UA transporter expression in vitro.

RESULTS

Network pharmacology and bioinformatics analyses revealed that the phosphoinositide 3-kinase (PI3K)/AKT signaling pathway was the key pathway for the alleviation of HN progression by EX. EX treatment reduced serum biomarkers in HN rats, downregulated the expression of p-PI3K, p-AKT, glucose transporter 9 (GLUT9), urate transporter 1 (URAT1), Collagen I, matrix metalloproteinase (MMP)-2, and MMP-9, and upregulated the expression of ATP binding cassette subfamily G member 2 (ABCG2) to improve renal interstitial fibrosis in HN rats. A high content of both quercitrin and cynaroside were identified in EX; their administration inhibited the increased expression of GLUT9 and URAT1 in damaged HK-2 cells.

CONCLUSION

Our study provides evidence that EX alleviates HN. The potential mechanism underlying this effect may be the regulation of UA transporters, such as GLUT9 and URAT1, by limiting the activation of the PI3K/AKT signaling pathway to improve renal injury.

Hyperuricemia: An Intriguing Connection to Metabolic Syndrome, Diabetes, Kidney Disease, and Hypertension

PURPOSE OF THE REVIEW

Our review explores the epidemiology, physiology, and clinical data surrounding the connection between hyperuricemia and metabolic syndrome, chronic kidney disease, and hypertension.

RECENT FINDINGS

Compelling physiologic mechanisms have been proposed to explain a causal relationship between hyperuricemia and metabolic syndrome, chronic kidney disease, and hypertension but clinical studies have given mixed results in terms of whether intervening with hyperuricemia using urate-lowering therapy has any beneficial effects for patients with these conditions. Despite the large amount of research already put into this topic, more randomized placebo-controlled trials are needed to more firmly establish whether a cause-effect relationship exists and whether lowering uric acid levels in patients with these conditions is beneficial.

Nonlinearity association between hyperuricemia and all-cause mortality in patients with chronic kidney disease

Controversy surrounds the role of serum uric acid and whether treatment intervention is favorable in retarding the progression of chronic kidney disease (CKD). The association of serum uric acid levels and CKD patient mortality risk needs to be further determined by large sample cohort studies. The National Health and Nutrition Examination Survey participants with CKD from 1998 to 2017 were enrolled in the study. Multivariable Cox regression models were used to reveal the association of serum uric acid concentrations and CKD mortality risks. A total of 9891 CKD patients were enrolled in the study, and 3698 individuals died during the follow-up. Increasing serum uric acid levels are independently relevant to higher mortality risks of CKD patients (HR per SD increase). A restricted cubic spline curve showed a nonlinear association between serum uric acid and CKD mortality risks (p for nonlinearity = 0.046). CKD patients with higher levels of serum uric acid (≥ 5.900 mg/dL) show a significant increase in mortality risks (HR = 1.102, 95% CI 1.043-1.165). Sensitivity analysis demonstrated that the results were stable and robust. High serum uric acid levels (≥ 5.900 mg/dL) may be associated with increased mortality risks in CKD patients.

Age-Related Effect of Uric Acid on Contrast-Induced Acute Kidney Injury of Patients Undergoing Coronary Angiography

Background

The association between uric acid (UA) and contrast-induced acute kidney injury (CI-AKI) following coronary angiography (CAG) has been established. However, whether the association would vary with age remained undetermined.

Methods

We performed the retrospective analysis based on the Cardio-renal Improvement II study, (ClinicalTrials.gov NCT05050877), which enrolled consecutive patients undergoing coronary angiography in 5 teaching hospitals in China from 2007 to 2020. The primary outcome was CI-AKI defined as the rise of serum creatinine (SCr) ≥ 0.5 mg/dL or 25% compared with the baseline value within 48 hours following CAG. The effect of age on the association between uric acid and CI-AKI was assessed by the logistic regression model.

Results

A total of 36,550 patients (mean age 63.08±5.6-year-old, 41.7% men) were included in the study. After adjusting for the confounders, the risk of CI-AKI between each quartile of uric acid was insignificant in the young group. In patients of the middle group, lower UA was associated with a lower risk of CI-AKI while higher UA was associated with a higher risk (Q1 OR: 0.853, 95% CI: 0.734-0.993; Q4 OR: 1.797, 95% CI: 1.547-2.09). In patients of the elder group, lower and higher UA were both associated with a higher risk of CI-AKI (Q1 OR: 1.247, 95% CI: 1.003-1.553; Q4 OR: 1.688, 95% CI: 1.344-2.124). The restricted cubic spline indicated a non-linear association between UA and CI-AKI in middle and elder age groups but a linear association in the young age group.

Conclusion

The association between uric acid and CI-AKI vary in patients of different age. Patients with elder age should maintain a middle level of uric acid while patients with middle age should consider a lower level of uric acid to reduce the risk of CI-AKI. The level of UA was an insignificant risk factor for CI-AKI in young patients.

Inverted U-shaped relationship between coffee consumption and serum uric acid in American chronic kidney disease population

Objective

The objective of this study was to examine the contentious relationship between coffee consumption and serum uric acid (SUA) levels, specifically within American population with chronic kidney disease (CKD).

Methods

A total of 23,381 participants from the 2001-2018 National Health and Nutrition Examination Survey (NHANES) were selected for inclusion in this investigation. Linear regression models and generalized additive models with smooth curve fitting were employed to analyze the association between log coffee consumption and serum uric acid levels. Furthermore, the robustness of the findings was assessed across diverse populations.

Results

The results of the linear regression analysis indicate a positive and marginally statistically significant (p = 0.0307) association between log coffee consumption and SUA, even after controlling for other variables. Furthermore, the generalized additive model revealed a nonlinear relationship characterized by an inverted U-shape between log coffee consumption and SUA. The inflection point, identified as 11.43 g/day, marks the point at which this relationship changes direction. Moreover, this inverted U-shaped relationship was consistently observed across various subgroups, including gender, age (<60 and ≥ 60 years), hypertensive and non-hypertensive individuals, those with and without cardiovascular disease, non-diabetic individuals, and those who consumed coffee with or without caffeine or sugar.

Conclusion

An inverse U-shaped correlation has been observed between log coffee consumption and SUA levels. This finding implies that once coffee consumption surpasses a specific threshold, it promotes a decline in SUA levels.

Untargeted metabolomics reveals dynamic changes in metabolic profiles of rat supraspinatus tendon at three different time points after diabetes induction

Objective

To investigate the dynamic changes of metabolite composition in rat supraspinatus tendons at different stages of diabetes by untargeted metabolomics analysis.

Methods

A total of 80 Sprague-Dawley rats were randomly divided into normal (NG, n = 20) and type 2 diabetes mellitus groups (T2DM, n = 60) and subdivided into three groups according to the duration of diabetes: T2DM-4w, T2DM-12w, and T2DM-24w groups; the duration was calculated from the time point of T2DM rat model establishment. The three comparison groups were set up in this study, T2DM-4w group vs. NG, T2DM-12w group vs. T2DM-4w group, and T2DM-24w group vs. T2DM-12w group. The metabolite profiles of supraspinatus tendon were obtained using tandem mass spectrometry. Metabolomics multivariate statistics were used for metabolic data analysis and differential metabolite (DEM) determination. The intersection of the three comparison groups' DEMs was defined as key metabolites that changed consistently in the supraspinatus tendon after diabetes induction; then, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis was performed.

Results

T2DM-4w group vs. NG, T2DM-12w group vs. T2DM-4w group, and T2DM-24w group vs. T2DM-12w group detected 94 (86 up-regulated and 8 down-regulated), 36 (13 up-regulated and 23 down-regulated) and 86 (24 up-regulated and 62 down-regulated) DEMs, respectively. Seven key metabolites of sustained changes in the supraspinatus tendon following induction of diabetes include D-Lactic acid, xanthine, O-acetyl-L-carnitine, isoleucylproline, propoxycarbazone, uric acid, and cytidine, which are the first identified biomarkers of the supraspinatus tendon as it progresses through the course of diabetes. The results of KEGG pathway enrichment analysis showed that the main pathway of supraspinatus metabolism affected by diabetes (p < 0.05) was purine metabolism. The results of the KEGG metabolic pathway vs. DEMs correlation network graph revealed that uric acid and xanthine play a role in more metabolic pathways.

Conclusion

Untargeted metabolomics revealed the dynamic changes of metabolite composition in rat supraspinatus tendons at different stages of diabetes, and the newly discovered seven metabolites, especially uric acid and xanthine, may provide novel research to elucidate the mechanism of diabetes-induced tendinopathy.

Korean guidelines for the management of gout

Gout is the most common form of arthritis, with the prevalence increasing worldwide. The present treatment guidelines provide recommendations for the appropriate treatment of acute gout, management during the inter-critical period, and prevention of chronic complications. The guidelines were developed based on evidence-based medicine and draft recommendations finalized after expert consensus. These guidelines are designed to provide clinicians with clinical evidence to enable efficient treatment of gout.

Optical monitoring of hemodialysis using noninvasive measurement of uric acid in the dialysate

The aim of this study was to present a methodology for predicting changes in uric acid concentrations in the blood of chronically hemodialyzed patients based on an optical measurement of the intensity of selected wavelengths in the dialysate. Blood samples were taken from the arterial line every 30 min throughout the hemodialysis period, to measure uric acid levels. Simultaneously, optical measurements were made on dialysate flowing from the dialyzer. Uric acid concentration can be measured either directly from the blood or from dialyzer outflow with acceptable error. In addition, both methods reveal any increased dynamics in uric acid concentration in the initial phase of hemodialysis. The wavelength of the light was adjusted for optimal uric acid particle detection. Comparing the uric acid concentration measured in the blood of patients with the intensity of wave absorption in the dialysate, the functional relationship between the uric acid concentration levels was determined. Using the optical method for measuring uric acid concentration in the dialysate, the concentration of uric acid in the blood during hemodialysis can be non-invasively and accurately estimated. This method can be used to assess the adequacy of hemodialysis by computer acquisition of uric acid concentrations determined in on-line dialysate.

An analysis of the associations of high-sensitivity C-reactive protein and uric acid with metabolic syndrome components in Korean adults by sex: a cross-sectional study using the Korea national health and nutrition examination survey 2016-2018

BACKGROUND

Low-grade inflammation plays a role in the pathogenesis of metabolic syndrome (MetS), and measuring levels of inflammatory molecules, such as high-sensitivity C-reactive protein (hs-CRP), may indicate Mets progression. Serum uric acid (SUA) has also been identified as an independent risk factor for MetS. This study aimed to investigate the association between MetS components and levels of serum hs-CRP and SUA using representative and reliable data for the Korean population.

METHODS

This study used the data of the Korea National Health and Nutrition Examination Survey 2016-2018, a cross-sectional and nationally representative survey performed by the Korean Centers for Disease Control and Prevention.

RESULTS

We analysed the data of 13,454 individuals. High hs-CRP levels were observed in 1,164 (8.7%) subjects while 3,296 (24.5%) subjects had high SUA levels. Moreover, hs-CRP was negatively correlated with serum high-density lipoprotein (HDL) (OR, 1.703; 95% CI, 1.431-2.027). When stratified by sex, this trend remained, but the correlation was stronger in women than in men. Furthermore, high SUA levels were significantly associated with hypertension (HTN) (OR, 1.399; 95% CI, 1.210-1.616), hypertriglyceridemia (OR, 1.735; 95% CI, 1.486-2.026), and low HDL (OR, 1.257; 95% CI, 1.106-1.429), but not with diabetes mellitus (DM) (OR, 0.478; 95% CI, 0.382-0.597). When grouped by sex, this trend remained, however, all MetS components were found to be more prevalent in women with high SUA.

CONCLUSIONS

Our findings showed that low HDL was more prevalent in subjects with high hs-CRP, and high SUA levels were observed in subjects with HTN, hypertriglyceridemia, and low HDL. However, the prevalence of high SUA was lower in diabetic subjects.

J-shaped association between uric acid and breast cancer risk: a prospective case-control study

BACKGROUND/AIM

In terms of breast cancer risk, there is no consensus on the effect of uric acid (UA) levels. The aim of our study was to clarify the link between UA and breast cancer risk in a prospective case-control study and to find the UA threshold point.

METHODS

We designed a case-control study with 1050 females (525 newly diagnosed breast cancer patients and 525 controls). We measured the UA levels at baseline and confirmed the incidence of breast cancer through postoperative pathology. We used binary logistic regression to study the association between breast cancer and UA. In addition, we performed restricted cubic splines to evaluate the potential nonlinear links between UA and breast cancer risk. We used threshold effect analysis to identify the UA cut-off point.

RESULTS

After adjusting for multiple confounding factors, we found that compared with the referential level (3.5-4.4 mg/dl), the odds ratio (OR) of breast cancer was 1.946 (95% CI 1.140-3.321) (P < 0.05) in the lowest UA level and 2.245 (95% CI 0.946-5.326) (P > 0.05) in the highest level. Using the restricted cubic bar diagram, we disclosed a J-shaped association between UA and breast cancer risk (P-nonlinear < 0.05) after adjusting for all confounders. In our study, 3.6 mg/dl was found to be the UA threshold which acted as the optimal turning point of the curve. The OR for breast cancer was 0.170 (95% CI 0.056-0.512) to the left and 1.283 (95% CI 1.074-1.532) to the right of 3.6 mg/dl UA (P for log likelihood ratio test < 0.05).

CONCLUSION

We found a J-shaped association between UA and breast cancer risk. Controlling the UA level around the threshold point of 3.6 mg/dl provides a novel insight into breast cancer prevention.

Korean guidelines for the management of gout

Gout is the most common form of arthritis, with the prevalence increasing worldwide. The present treatment guidelines provide recommendations for the appropriate treatment of acute gout, management during the inter-critical period, and prevention of chronic complications. The guidelines were developed based on evidence-based medicine and draft recommendations finalized after expert consensus. These guidelines are designed to provide clinicians with clinical evidence to enable efficient treatment of gout.

Sex differences between serum uric acid levels and cardiovascular outcomes in patients with coronary artery disease after stent implantation

Background

The relationship between elevated serum uric acid (SUA) levels and cardiovascular outcomes after stent implantation remains uncertain. This study sought to evaluate the impact of SUA on 12-month cardiovascular outcomes after stent implantation.

Methods

We performed a retrospective study of patients who successfully underwent stent implantation and enrolled 3,222 patients with coronary artery disease (CAD) from a single center. SUA levels were measured before stent implantation. The patients were divided into six groups (<4, 4-4.9, 5-5.9, 6-6.9, 7-7.9 and ≥ 8 mg/dL) at SUA intervals of 1.0 mg/dL. The incidence of cardiovascular outcomes in the six groups was monitored for 1 year after stent implantation and the hazard ratios were estimated. Hazard ratios (HRs) and 95% confidence intervals (95% CIs) for cardiovascular outcomes were estimated using a Cox proportional hazard regression analysis. The primary endpoint was all-cause death. The secondary endpoint was a composite of all-cause death, myocardial infarction, target vessel revascularization, stent thrombosis and stroke. The follow-up duration was 12 months.

Results

Over the 12-month follow-up period, there were 101 all-cause deaths and 218 MACCE. After adjustment for several parameters, the group with SUA levels of more than or equal to 8 mg/dL had significantly higher hazard ratios in the incidence of all-cause death or MACCE. The group with <4.0 mg/dL had significantly higher hazard ratios in all-cause death only in male patients. In contrast, there were no significant differences observed for cardiovascular outcomes in female patients.

Conclusions

Our study identified a U-shaped association between SUA levels and cardiovascular outcomes during 12-month follow-up for males, but not for females. Further studies are warranted to clarify the sex differences between SUA levels and clinical outcomes.

The significance of follow-up serum uric acid levels in predicting all-cause mortality and cardiovascular mortality in peritoneal dialysis patients

BACKGROUND

This study aimed to analyze the change of serum uric acid (SUA) level post peritoneal dialysis (PD), and the correlation between follow-up SUA and prognosis in patients with PD.

METHODS

A total of 1402 patients with PD were evaluated. We graded SUA levels into four grades at baseline, 6 months, 12 months, 18 months, and 24 months post PD, and then compared all-cause mortality and cardiovascular mortality among patients with different SUA grades at each time point. Kaplan-Meier and Cox proportional-hazards regression models were used in the analysis.

RESULTS

The SUA levels were 7.97 ± 1.79, 7.12 ± 1.48, 7.05 ± 1.33, 7.01 ± 1.30, and 6.93 ± 1.26 mg/dl at baseline, 6, 12, 18, and 24 months, respectively. There was significant difference on all-cause mortality among patients with PD with different graded SUA levels at 6 months post PD (p = 0.010), and the all-cause mortality was lowest in patients with the grade of 5.65 mg/dl ≤ SUA <7.13 mg/dl.

CONCLUSION

SUA level decreased after PD during follow-up. At 6 months post PD, the grade of 5.65 mg/dl ≤ SUA <7.13 mg/dl was appropriate for better patients' survival.

The effect of allopurinol on cardiovascular outcomes in patients with type 2 diabetes: a systematic review

BACKGROUND

Cardiovascular disease (CVD) remains the main cause of death in patients with type 2 diabetes (T2D). Although hyperuricemia has been associated with multiple CV complications, it is not officially recognized as a target parameter for CVD risk reduction.

AIM

To systematically review the literature in order to determine whether treating hyperuricemia with allopurinol in patients with T2D reduces CVD risk.

METHODS

A thorough literature search in the PubMed, CENTRAL, and EMBASE databases from inception to August 2022 was performed. After application of selection criteria, 6 appropriate studies were identified.

RESULTS

Detailed analysis of the data derived indicated that there is an association between allopurinol treatment and CV benefits, resulting in a reduced risk of CVD events and mortality rates. This association can be attributed mainly to the reduction of inflammation and oxidative burden, as well as to the improvement of glycemic and lipid profiles.

CONCLUSIONS

This systematic review provides evidence that allopurinol may reduce CVD risk in patients with T2D. Randomized, placebo-controlled trials should be performed in order to confirm these findings and identify specific subgroups of patients who will benefit most.

Interpretable machine learning prediction of all-cause mortality

Background

Unlike linear models which are traditionally used to study all-cause mortality, complex machine learning models can capture non-linear interrelations and provide opportunities to identify unexplored risk factors. Explainable artificial intelligence can improve prediction accuracy over linear models and reveal great insights into outcomes like mortality. This paper comprehensively analyzes all-cause mortality by explaining complex machine learning models.

Methods

We propose the IMPACT framework that uses XAI technique to explain a state-of-the-art tree ensemble mortality prediction model. We apply IMPACT to understand all-cause mortality for 1-, 3-, 5-, and 10-year follow-up times within the NHANES dataset, which contains 47,261 samples and 151 features.

Results

We show that IMPACT models achieve higher accuracy than linear models and neural networks. Using IMPACT, we identify several overlooked risk factors and interaction effects. Furthermore, we identify relationships between laboratory features and mortality that may suggest adjusting established reference intervals. Finally, we develop highly accurate, efficient and interpretable mortality risk scores that can be used by medical professionals and individuals without medical expertise. We ensure generalizability by performing temporal validation of the mortality risk scores and external validation of important findings with the UK Biobank dataset.

Conclusions

IMPACT's unique strength is the explainable prediction, which provides insights into the complex, non-linear relationships between mortality and features, while maintaining high accuracy. Our explainable risk scores could help individuals improve self-awareness of their health status and help clinicians identify patients with high risk. IMPACT takes a consequential step towards bringing contemporary developments in XAI to epidemiology.

Prevalence of hyperuricemia in patients with severe obesity and the relationship between serum uric acid and severe obesity: A decade retrospective cross-section study in Chinese adults

Objective

Undoubtedly, the relationship between serum uric acid (SUA) and obesity is less data for Chinese patients with obesity. This study aimed to examine the prevalence of hyperuricemia (HUA) and the association between SUA and patients with obesity.

Methods

All participants were categorized as overweight, obesity I, obesity II, and obesity III. In addition, based on SUA concentration, the participants were stratified into four quartiles. The authors used descriptive analysis, independent t-test, ANOVA, correlation analysis, and multiple linear regression models to verify the SUA level and obesity among Chinese adults.

Results

Overall, the estimated prevalence of HUA was 69.8%. In the BMI categories, the prevalence of HUA was 5.1% in overweight, 15.2% in obesity I, 16.9% in obesity II, and 32.5% in obesity III. Correlation analysis shows that SUA is strongly correlated with BMI, waist circumference (WC), and hip circumference (HC). Multiple linear regression analysis shows that high density-lipoprotein cholesterol (HDL-C) is a protective predictor of serum uric acid levels in patients with obesity. Compared with the overweight, obesity I, obesity II, and obesity III were more likely to have higher levels in the SUA levels.

Conclusion

We mainly showed that the serum uric acid levels in Chinese patients with severe obesity declined slightly as age increased.

Lack of xanthine dehydrogenase leads to a remarkable renal decline in a novel hypouricemic rat model

Uric acid (UA) is the final metabolite in purine catabolism in humans. Previous studies have shown that the dysregulation of UA homeostasis is detrimental to cardiovascular and kidney health. The Xdh gene encodes for the Xanthine Oxidoreductase enzyme group, responsible for producing UA. To explore how hypouricemia can lead to kidney damage, we created a rat model with the genetic ablation of the Xdh gene on the Dahl salt-sensitive rat background (SS^Xdh−/−). SS^Xdh−/− rats lacked UA and exhibited impairment in growth and survival. This model showed severe kidney injury with increased interstitial fibrosis, glomerular damage, crystal formation, and an inability to control electrolyte balance. Using a multi-omics approach, we highlighted that lack of Xdh leads to increased oxidative stress, renal cell proliferation, and inflammation. Our data reveal that the absence of Xdh leads to kidney damage and functional decline by the accumulation of purine metabolites in the kidney and increased oxidative stress.

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A novel rat model of hypouricemia was created by the gene ablation of the Xdh gene

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The SS^Xdh-/- rat showed a failure to thrive, kidney injury, and functional decline

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Multi-omics revealed increased inflammation and oxidative stress in SS^Xdh-/- rats

Association between neutrophil gelatinase-associated lipocalin (NGAL) and iron profile in chronic renal disease

NGAL, also known as lipocalin 2, is a stress protein located on the cell surface that is known for its involvement in iron transport. This study is aimed to evaluate the correlation between the iron profile and NGAL concentration in serum among chronic kidney disease patients under dialysis in order to find its diagnostic value with regards to iron deficiency anaemia (IDA). 47 patients under chronic haemodialysis in end-stage renal disease (ESRD) and 15 healthy controls were evaluated to determine the correlation between serum NGAL concentration and IDA characteristics. Our results recorded a significant correlation between IDA (TSAT < 20%) and NGAL serum concentration with a Spearman's coefficient of 0.314. Serum NGAL was also significantly related to serum ferritin, TIBC, uric acid, creatinine and blood sugar whereas, an inverse relationship with albumin, total cholesterol and LDL. Our study reports a positive correlation between IDA and serum NGAL levels in CKD patients.

Serum uric acid levels and diabetic kidney disease in patients with type 2 diabetes mellitus: A dose-response meta-analysis

OBJECTIVE

Our study aimed to assess the existing evidence on whether serum uric acid (SUA) levels are associated with diabetic kidney disease (DKD) in patients with type 2 diabetes mellitus (T2DM).

METHODS

We conducted a systematic search of articles up to October 2021 in Medline, Embase, The Cochrane Library and Web of Science that estimated DKD by SUA levels in patients with T2DM. Pooled relative risks with 95% CI were calculated using random effects models RESULTS: A total of eight cohort studies involving 25,741 T2DM patients were included. Meta-analysis showed that compared the highest with the lowest category of SUA level, the summary risk ratios were 2.04 (95%CI 1.43-2.92, P < 0.001). The linear dose-response analysis revealed that the risk of DKD increased by 24% for each 1 mg/dl increase of SUA. The non-linear dose-response analysis also showed a significant relevance between SUA and the risk of DKD in patients with type 2 diabetes mellitus (P < 0.001).

CONCLUSIONS

Serum uric acid is associated with an increased risk of diabetic kidney disease in patients with type 2 diabetes mellitus. Serum uric acid level could be a good indicator for predicting diabetic kidney disease in patients with type 2 diabetes mellitus.

Cardiovascular risk and mortality in patients with hyperuricemia treated with febuxostat or allopurinol: a retrospective nation-wide cohort study in Austria 2014-2017

Patients with hyperuricemia and gout are at an increased risk for cardiovascular (CV) disease. Inhibition of the xanthine oxidase with allopurinol or febuxostat have become the mainstay for urate lowering therapy. However, it has been suggested that febuxostat increases the risk for CV mortality as compared to allopurinol. The aim of this retrospective cohort study was to assess the CV risk among patients with febuxostat or allopurinol therapy. Patients who initiated urate lowering therapy with febuxostat or allopurinol between 2014 and 2017 were selected from the drug reimbursement database of the Austrian health insurances funds. The primary CV endpoint was a composite of angina pectoris, nonfatal myocardial infarction, nonfatal subarachnoid or cerebral hemorrhage, nonfatal ischemic stroke, or death from any cause. In total, 28.068 patients (62.1% male) with a mean age of 71 years were included. 7.767 initiated febuxostat treatment and 20.301 received allopurinol. The incidence rate per 100 patient-years of the composite primary endpoint was 448 (febuxostat) and 356 (allopurinol) with a corresponding adjusted hazard ratio (HR) of 0.58 (95% CI 0.53–0.63) for allopurinol vs. febuxostat initiators. Similar HR were found for secondary endpoints including all-cause mortality [0.61 (95% CI 0.55–0.68)] and separate analyses of cardiac events [0.48 (95% CI 0.38–0.61)] and ischemic stroke [0.47 (95% CI 0.36–0.61)]. Data from this Austrian population-based study suggests that febuxostat initiators are at an increased risk for nonfatal CV events or death from any cause as compared to those with allopurinol. This is consistent with CV concerns of other trials, which limited the broad therapeutic use of febuxostat.

U-shaped association of uric acid to overall-cause mortality and its impact on clinical management of hyperuricemia

Serum uric acid (SUA) is significantly elevated in obesity, gout, type 2 diabetes mellitus, and the metabolic syndrome and appears to contribute to the renal, cardiovascular and pulmonary comorbidities that are associated with these disorders. Most previous studies have focused on the pathophysiologic effects of high levels of uric acid (hyperuricemia). More recently, research has also shifted to the impact of hypouricemia, with multiple studies showing the potentially damaging effects that can be caused by abnormally low levels of SUA. Along with these observations, recent inconclusive data from human studies evaluating the treatment of hyperuricemia with xanthine oxidoreductase (XOR) inhibitors have added to the debate about the causal role of UA in human disease processes. SUA, which is largely derived from hepatic degradation of purines, appears to exert both systemic pro-inflammatory effects that contribute to disease and protective antioxidant properties. XOR, which catalyzes the terminal two steps of purine degradation, is the major source of both reactive oxygen species (O2.-, H2O2) and UA. This review will summarize the evidence that both elevated and low SUA may be risk factors for renal, cardiovascular and pulmonary comorbidities. It will also discuss the mechanisms through which modulation of either XOR activity or SUA may contribute to vascular redox hemostasis. We will address future research studies to better account for the differential effects of high versus low SUA in the hope that this will identify new evidence-based approaches for the management of hyperuricemia.

The impact of uremic toxins on Alzheimer's disease

Alzheimer's disease (AD) is the most common type of dementia, pathologically characterized by accumulation of senile plaques and neurofibrillary tangles. Chronic kidney disease (CKD) is highly prevalent in elderly population closely associated with occurrence of dementia. Recent epidemiological and experimental studies suggest a potential association of CKD with AD. Both diseases share a panel of identical risk factors, such as type 2 diabetes; and hypertension. However, the relationship between CKD and AD is unclear. Lower clearance of a panel of uremic toxin including cystatin-C, guanidine, and adiponectin due to CKD is implied to contribute to AD pathogenesis. In this review we summarize the current evidence from epidemiological, experimental and clinical studies on the potential contribution of uremic toxins to AD pathogenesis. We describe outstanding questions and propose an outlook on the link between uremic toxins and AD.

Mini Review: Reappraisal of Uric Acid in Chronic Kidney Disease

Hyperuricemia predicts the development of chronic kidney disease (CKD) and metabolic complications, but whether it has a causal role has been controversial. This is especially true given the 2 recently conducted randomized controlled trials that failed to show a benefit of lowering uric acid in type 1 diabetes-associated CKD and subjects with stage 3-4 CKD. While these studies suggest that use of urate-lowering drugs in unselected patients is unlikely to slow the progression of CKD, there are subsets of subjects with CKD where reducing uric acid synthesis may be beneficial. This may be the case in patients with gout, hyperuricemia (especially associated with increased production), and urate crystalluria. Here, we discuss the evidence and propose that future clinical trials targeting these specific subgroups should be performed.

J-shaped Relationship Between Chronic Kidney Disease and Serum Uric Acid Levels: A Cross-sectional Study on the Korean Population

Objective

Both hypouricemia and hyperuricemia are reportedly associated with reduced kidney function This study investigated the association between uric acid levels and the risk of reduced renal function in men and women.

Methods

We conducted a cross-sectional study using data from a government-funded health examinee cohort of a Korean genome and epidemiological study A total of 172,970 participants (58,981 men, 113,989 women) aged 40∼79 years were included A logistic regression test was performed, and the odds ratio (OR) and 95% confidence interval (CI) were calculated to examine the relationship between stratified uric acid levels and the frequency of chronic kidney disease.

Results

As the uric acid level increased, the risk of reduced renal function increased Moreover, for uric acid levels ≤20 mg/dL, the risk of reduced renal function was higher than that of the reference group Among the total, man, and woman groups, a statistically significant association was observed in men (OR 171, 95% CI 0945∼3111, OR 5003, 95% CI 1405∼17809, and OR 1377, 95% CI 0696∼2724, respectively).

Conclusion

The OR of reduced renal function according to uric acid levels formed a J-shaped curve in both genders.

The Association Between Uric Acid and Symmetric Dimethylarginine Levels in the Patients Undergoing Twice-weekly Hemodialysis

Background: Uric acid (UA) levels are associated with increased risk of cardiovascular events and mortality in hemodialysis patients. However, there are still conflicting data on the mechanism of increased risks related to uric acid levels. Objectives: This study assessed the association between uric acid levels and symmetric dimethylarginine (SDMA), as a marker of cardiovascular disease, in the subjects undergoing hemodialysis twice weekly. Methods: This was a cross-sectional study conducted in a tertiary hospital in Jakarta, Indonesia. We included all the adults who underwent hemodialysis twice weekly for at least three months in our hospital. Subjects already on uric acid lowering therapy, pregnant or lactating women and those with a history of malignancy were excluded. Uric acid and SDMA levels were measured at the same time in pre-dialysis venous blood samples. Bivariate analysis was performed using the Mann-Whitney U test or one-way ANOVA. Results: A total of 126 subjects were included. The median level of UA was 8.4 mg/dL (IQR: 2.6, min: 4.1, max: 13.6), and 72 subjects (57.14%) had UA levels of 8 mg/dL or higher. The median SDMA level was 535.5 (312.7) mmol/dL (min: 119.7, max: 1895.5). Subjects with UA levels > 8 mg/dL had significantly higher SDMA levels compared to subjects with UA levels < 8 mg/dL (550.1 (IQR: 357.25) vs 491.35 (IQR: 181.1), P: 0.0475). Conclusions: In twice-weekly hemodialysis patients, UA levels above 8 mg/dL were associated with increased SDMA levels.

Association between serum uric acid level and mortality in China

BACKGROUND

Whether there is an association between serum uric acid (SUA) level and risk of mortality in the general population remains unclear. Based on the China National Survey of Chronic Kidney Disease linked to mortality data, a population-based cohort study was performed to investigate the association between SUA level and all-cause mortality, cardiovascular disease (CVD) mortality, and cancer mortality in China.

METHODS

The survival status of participants in the cross-sectional survey was identified from January 1, 2006 to December 31, 2017. Only 33,268 individuals with complete SUA data among the 47,204 participants were included in the analysis. We determined the rates of all-cause mortality, CVD mortality, and cancer mortality. We used Cox proportional hazards regression models to evaluate the effect of the SUA level on mortality.

RESULTS

During a total of 297,538.4 person-years of follow-up, 1282 deaths occurred. In the Cox proportional hazards regression model, the rate of all-cause mortality, CVD mortality, and cancer mortality had a U-shaped association with SUA levels only in men, whereas no significant associations were detected in women. For all-cause mortality in men, the multivariable-adjusted hazard ratios (HRs) in the first, second, and fourth quartiles compared with the third quartile were 1.31 (95% confidence interval [CI] 1.04-1.67), 1.17 (95% CI 0.92-1.47), and 1.55 (95% CI 1.24-1.93), respectively. For CVD mortality, the corresponding HRs were 1.47 (95% CI 1.00-2.18), 1.17 (95% CI 0.79-1.75), and 1.67 (95% CI 1.16-2.43), respectively. For the cancer mortality rate, only a marginally significant association was detected in the fourth quartile compared with the third quartile with an HR of 1.43 (95% CI 0.99-2.08).

CONCLUSIONS

The association between SUA and mortality differed by sex. We demonstrated a U-shaped association with SUA levels for all-cause and CVD mortalities among men in China.

Uric acid as a cardiorenal mediator: pathogenesis and mechanistic insights

Introduction: The role of serum uric acid as a connector in cardiorenal interactions has been long debated and studied extensively in the past decade. Epidemiological, and clinical data suggest that hyperuricemia may be an independent risk factor as well as a strong predictor of morbidity and mortality in cardiovascular diseases (CVD) and renal diseases. New data suggesting that urate lowering therapies may improve outcomes in cardiovascular diseases have generated interest.Areas Covered: This review attempts to summarize the pathophysiological mechanisms by which hyperuricemia causes cardiorenal dysfunction. It also provides a summary of the recent evidence for urate lowering therapies and the possible underlying mechanisms which lead to cardiovascular benefits. This was a narrative review with essential references or cross references obtained via expert opinion.Expert Opinion: Emphasis on newer drugs that address the cardio-renal metabolic axis and the relation to their effects on uric acid may help further elucidate underlying mechanisms responsible for their cardiovascular and renal benefits. Once these benefits are well established, we will be able to come up with guidelines for targeting hyperuricemia. This can potentially lead to a change in clinical practice and can possibly lead to improved cardiovascular and renal outcomes.

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.

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.

Low serum uric acid levels increase the risk of all-cause death and cardiovascular death in hemodialysis patients

Background

Elevated serum uric acid (SUA) is associated with increased cardiovascular (CV) and all-cause mortality risk in the general population, but the impact of UA on mortality in hemodialysis patients is still controversial. The aim of the study was to explore the relationship between SUA and all-cause mortality and CV mortality in hemodialysis patients.

Methods

This retrospective, observational cohort study included 210 HD patients with a mean age of 56.6 ± 16.6 years. All demographic and laboratory data were recorded at baseline. The Kaplan–Meier method and Cox proportional hazard regression model were used to examine the association between SUA and all-cause mortality and CV mortality in HD patients.

Results

With 420 µmol/L (20th percentile) and 644 µmol/L (80th percentile) as the boundary points, the patients were divided into three groups. After a median follow-up of 49.8 months, 68 (32.4%) all-cause deaths and 34 (16.2%) CV deaths were recorded. The Kaplan–Meier method showed that with a decrease in SUA, all-cause mortality (log rank χ² = 15.61, p = .000), and CV mortality (log rank χ²=14.28, p = .000) increased. Each 100 µmol/L increase in SUA was associated with lower all-cause mortality with an hazard ratio (HR) of 0.792 (0.645–0.972) and lower CV mortality with an HR of 0.683 (0.505–0.924) after adjusting for age, sex, and complications. Compared to the lowest quartile, all-cause mortality [HR 0.351(0.132–0.934), p = .036] and CV mortality [HR 0.112 (0.014–0.925), p = .042] were lower in the highest SUA quartile.

Conclusion

A lower SUA level in HD patients was associated with a higher risk of all-cause mortality and CV mortality. Moreover, higher SUA concentrations may be cardioprotective in HD patients.

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.

Relationship between Serum Uric Acid and Mortality Risk in Hemodialysis Patients: A Multicenter Prospective Cohort Study

BACKGROUND

Several studies have reported that low serum uric acid (SUA) levels are related to increased risk of mortality in maintenance hemodialysis (MHD) patients. However, the possible detrimental effects of high SUA on the mortality risk have not been well examined. Moreover, the possible effect modifiers for the SUA-mortality association have not been fully investigated. To address the aforementioned gap, we aimed to explore the nonlinear relationship between SUA levels and all-cause and cardiovascular disease (CVD) mortality risk, and to examine any possible effect modifiers in MHD patients.

METHODS

We conducted a multicenter, prospective cohort study among 1,018 MHD patients from 8 hemodialysis centers. The primary outcome was all-cause mortality, and the secondary outcomes were CVD mortality and non-CVD mortality.

RESULTS

The mean value for SUA in the total population was 8.5 ± 1.9 mg/dL. The lowest and highest quintiles of SUA were <7.0 and >10.1 mg/dL, respectively. Over a median follow-up of 45.6 months, 343 deaths were recorded, of which 202 (58.9%) were due to CVD. When SUA was assessed as quintiles, a significantly higher risk of all-cause mortality was found in patients in quintile 1 (<7.0 mg/dL; hazard ratio [HR], 1.33; 95% confidence interval [CI]: 1.02-1.73) or quintile 5 (≥10.1 mg/dL; HR, 1.47; 95% CI: 1.09-2.00), compared to those in quintiles 2-4 (7-10.1 mg/dL). Moreover, the U-shaped SUA-mortality association was mainly found in those with lower C-reactive protein levels (<3 compared with ≥3 mg/L; p for interaction = 0.018). Similar trends were found for CVD mortality and non-CVD mortality.

CONCLUSION

There was a U-shaped relationship between SUA levels and the risk of all-cause mortality, CVD mortality, and non-CVD mortality in MHD patients.

Serum Uric Acid and Mortality Risk Among Hemodialysis Patients

INTRODUCTION

Although high serum uric acid (SUA) has been consistently associated with an increased risk of death in the general population and in persons with nondialysis chronic kidney disease (CKD), studies in patients undergoing dialysis are conflicting. It has been postulated that low SUA simply reflects poor nutritional status in dialysis patients. We here characterize the association between SUA and the risk of death in a large dialysis cohort and explore effect modification by underlying nutritional status as reflected by body composition.

METHODS

In this retrospective cohort study, we included 16,057 hemodialysis (HD) patients treated during 2007 to 2016 in NephroCare centers as recorded in the European Clinical Database (EuCliD). The association between SUA, all-cause, and cardiovascular (CV)-related mortality was evaluated with competing risk models and characterized with splines. Effect modification was explored by lean tissue index (LTI) and fat tissue index (FTI).

RESULTS

During a mean of 1.8 years of follow-up, 2791 patients (17.4%) died. We found a multivariable-adjusted U-shaped pattern between SUA and all-cause mortality. Patients with SUA levels of 6.5 mg/dl (387 μmol/l) were at the lowest risk of death (subdistribution hazard ratio = 0.94 [confidence interval {CI} 0.91; 0.96]). The form of association was not meaningfully affected by underlying LTI and FTI.

CONCLUSION

We found a U-shaped pattern between SUA levels and all-cause mortality among HD patients, which was independent of the patients' body composition.

Effect of Synbiotic and Probiotic Supplementation on Serum Levels of Endothelial Cell Adhesion Molecules in Hemodialysis Patients: a Randomized Control Study

The aim of this study was to investigate the effect of synbiotic and probiotic supplementation on serum vascular dysfunction and necrosis markers in hemodialysis (HD) patients. In this randomized, double-blind, placebo-controlled trial, 75 HD patients were randomly assigned to either the synbiotic or probiotic or placebo group. The patients in the synbiotic group received 15 g of prebiotics and 5 g probiotic powder containing Lactobacillus acidophilus strain T16 (IBRC-M10785), Bifidobacterium bifidum strain BIA-6, Bifidobacterium lactis strain BIA-6, Bifidobacterium longum strain LAF-5 (2.7 × 10⁷ CFU/g each) in sachets (n = 25), whereas the probiotic group received 5 g probiotics same to the first group with 15 g of maltodextrin powder in sachets (n = 25) and the placebo group received 20 g of maltodextrin powder in sachets (n = 25) for 12 weeks. At baseline and the end of the study, serum concentrations of soluble intercellular adhesion molecule type 1 (sICAM-1), soluble vascular cell adhesion molecule type 1 (sVCAM-1), cytokeratin 18 (CK-18) as the necrosis marker, uric acid, and phosphate levels were measured. Feces also were collected for microbiota colony counting. Serum ICAM-1 level reduced significantly in the synbiotic group after the intervention period (P = 0.02), and this reduction was significantly different in the synbiotic group in comparison to the placebo group (P = 0.03). Serum levels of VCAM-1 and CK-18 were not significantly different between the groups. However, the reduction in serum levels of VCAM-1 in the synbiotic group was significantly higher in comparison to the placebo group (P = 0.01). Multivariate linear regression analysis revealed that ∆ phosphate was the sole independent determinant of ∆ICAM-1 (P = 0 < 001). The study indicated that synbiotic supplementation reduced serum ICAM-1 level, which is a risk factor for cardiovascular diseases in HD patients, but has no effect on the necrosis marker. Trial registration: www.irct.ir (IRCT2017041233393N1).

Delayed treatment with an autophagy inhibitor 3-MA alleviates the progression of hyperuricemic nephropathy

Autophagy is a cell self-renewal process that relies on the degradation of the cytoplasmic proteins or organelles of lysosomes and is associated with development of numerous diseases. However, the therapeutic effect of autophagy inhibition on hyperuricemic nephropathy (HN) and the underlying mechanisms are still unknown. Here, we investigated the effect of delayed treatment with 3-methyladenine (3-MA), a specific autophagy inhibitor, on the development of HN in a rat model. Administration of 3-MA at 21 days following after uric acid injury protected kidney from hyperuricemic-related injuries, as demonstrated by improving renal dysfunction and architecture damage, blocking Beclin-1 and LC3II/I and decreasing the number of autophagic vacuoles. Late treatment with 3-MA was also effective in attenuating renal fibrosis as evidenced by reducing ECM protein deposition, blocking epithelial-to-mesenchymal transition (EMT) and decreasing the number of renal epithelial cells arrested at the G2/M phase of cell cycle. Injury to the kidney resulted in increased expression of TGFβ receptor I, and phosphorylation of Smad3, 3-MA significantly abrogated all these responses. Moreover, inhibition of autophagy suppressed mitochondrial fission, downregulated the expression of Dynamin-related protein 1 (Drp-1), Cofilin and F-actin, and alleviated cell apoptosis. Finally, 3-MA effectively blocked STAT3 and NF-κB phosphorylation and suppressed infiltration of macrophages and lymphocytes as well as release of multiple profibrogenic cytokines/chemokines in the injured kidney. Taken together, these findings indicate that hyperuricemia-induced autophagy is critically involved in the activation of renal fibroblasts, EMT, mitochondrial fission and apoptosis of tubular epithelial cells and development of renal fibrosis. Thus, this study provides evidence for autophagy inhibitors as the treatment of HN patients.

Hyperuricemia is associated with a lower glomerular filtration rate in pediatric sickle cell disease patients

BACKGROUND

Sickle cell nephropathy (SCN) is a progressive disease that contributes significant morbidity and mortality in sickle cell disease (SCD), yet it remains poorly understood. Hyperuricemia negatively impacts renal function in the non-sickle cell population but is understudied in SCD.

METHODS

We performed a cross-sectional analysis of the first 78 pediatric SCD patients enrolled in a cohort study. The mechanism of development of hyperuricemia (defined, serum uric acid (UA) ≥ 5.5 mg/dL) was characterized as a result of either UA overproduction or inefficient renal excretion by the Simkin index and fractional clearance of urate (FCU) equations. Associations between hyperuricemia and albuminuria or estimated glomerular filtration rate (eGFR) were determined by linear regression.

RESULTS

The prevalence of hyperuricemia in this young population (mean age 11.6 ± 3.77 years) was 34.2%. Only 1 hyperuricemic participant overproduced UA by Simkin index, while 62.5% were inefficient renal excretors of UA (FCU < 4%). Hyperuricemia was associated with a significant decrease in average eGFR, -27 ml/min/1.73m² below normouricemia (mean eGFR 151.6 ± 40.32), p = 0.0122. Notably, the previously accepted association between decline of eGFR with age is significantly modified by hyperuricemia stratification, where hyperuricemia explains 44% of the variance in eGFR by age (R² = 0.44, p = 0.0004) and is nonsignificant in normouricemia (R² = 0.07, p = 0.0775).

CONCLUSION

These findings indicate that hyperuricemia may be associated with early eGFR decline in SCN. This association must be further characterized in prospective cohort studies in SCN, and hyperuricemia must be investigated as a potential therapeutic target for SCN.

Repeated measurements of serum urate and mortality: a prospective cohort study of 152,358 individuals over 8 years of follow-up

BACKGROUND

Longitudinal evidence on change of serum urate level with mortality risk is limited as prior studies have a measurement of serum urate at a single time point. Further, the combined effect of serum urate and systemic inflammation on mortality is unknown.

METHODS

We conducted a prospective cohort study of 152,358 participants (122,045 men and 30,313 women) with repeated measurements of serum urate in 2006, 2008, 2010, and 2012 (107,751 participants had all four measurements of serum urate). We used the Cox proportional hazard model to examine the association between cumulative average and changes in serum urate with mortality. The combined effect of serum urate and systemic inflammation was determined by testing the interaction of serum urate and high-sensitive C-reactive protein (hs-CRP) in relation to mortality risk.

RESULTS

During a median follow-up of 8.7 (interquartile range 6.3-9.2) years, we identified 7564 all-cause deaths, 1763 CVD deaths, 1706 cancer deaths, and 1572 other deaths. We observed U-shaped relationships of cumulative average serum urate with all-cause mortality, cardiovascular mortality, and other mortalities. Compared with participants with stable serum urate, those with greater increases in serum urate had a 1.7-fold elevated mortality (hazard ratio (HR) = 1.66, 95% confidence interval (CI) = 1.49-1.84), and those with decreased serum urate had a 2-fold elevated mortality risk (HR = 2.14, 95% CI 1.93-2.37). Participants with both hyperuricemia and hs-CRP had 1.6 times higher mortality, compared with those with low serum urate and hs-CRP levels (HR = 1.56, 95% CI 1.37-1.76).

CONCLUSIONS

We observed a U-shaped relationship of long-term cumulative average serum urate with all-cause mortality, cardiovascular mortality, and other mortalities. Compared with participants with relatively stable serum urate levels, a greater increase or decrease in serum urate was associated with elevated mortality. Participants with both hyperuricemia and high systemic inflammation had the greatest mortality risk compared with those with low serum urate and low hs-CRP levels.

Comparative cardiovascular risk of allopurinol versus febuxostat in patients with gout: a nation-wide cohort study

OBJECTIVE

To compare cardiovascular (CV) risk among gout patients initiating allopurinol vs febuxostat.

METHODS

Using 2002-2015 Korean National Health Insurance Service data for the entire Korean population, we conducted a cohort study on gout patients initiating allopurinol or febuxostat. The primary outcome was a composite CV end point of myocardial infarction, stroke/transient ischaemic attack, or coronary revascularization. Secondary outcomes were individual components of the primary outcome, and all-cause mortality. We used propensity score-matching with a 4:1 ratio for allopurinol and febuxostat initiators to control for confounding. Competing risk analyses were done for non-fatal outcomes accounting for deaths.

RESULTS

We included 39 640 allopurinol initiators propensity score-matched on 9910 febuxostat initiators. The mean age was 59.1 years and 78.4% were male. The incidence rate per 100 person-years for the primary outcome was 1.89 for allopurinol and 1.84 for febuxostat initiators. The corresponding hazard ratio comparing allopurinol vs febuxostat initiators was 1.09 (95% CI: 0.90, 1.32). No significant difference was found for the secondary outcomes, including all-cause mortality (hazard ratio 0.96; 95% CI: 0.79, 1.16). Subgroup analyses limited to those at high CV risk and to equipotent-dose initiators (i.e. allopurinol ⩾300 mg/day vs febuxostat ⩾40 mg/day) showed similar results.

CONCLUSION

Overall, this large Korean population-based study suggests no difference in the risk of non-fatal CV events and all-cause mortality between allopurinol and febuxostat initiators. These findings are consistent with the recent US Medicare population study, although the current study population consisted of younger Asians.

Effects of uric acid dysregulation on the kidney

Recently, research has redirected its interests in uric acid (UA) from gout, an inflammatory disease in joints, to groups of closely interrelated pathologies associated with cardiovascular and kidney dysfunction. Many epidemiological, clinical, and experimental studies have shown that UA may play a role in the pathophysiology of the cardiorenal syndrome continuum; however, it is still unclear if it is a risk factor or a causal role. Hyperuricemia has been well studied in the past two decades, revealing mechanistic insights into UA homeostasis. Likewise, some epidemiological and experimental evidence suggests that hypouricemia can lead to cardiorenal pathologies. The goal of this review is to highlight why studying both hyperuricemia and hypouricemia is warranted as well as to summarize the relevance of UA to kidney function.

Serum Uric Acid Levels and Risk of Intracranial Atherosclerotic Stenosis: A Cross-Sectional Study

Elevated serum uric acid (SUA) has been reported to be associated with an increased risk of cardiovascular diseases, but the role of SUA in intracranial atherosclerosis remains unclear. To investigate the association between SUA and intracranial atherosclerotic stenosis (ICAS), we evaluated 1522 subjects (305 with ICAS, 1217 without ICAS) with magnetic resonance angiography (MRA). Subjects were classified into ten groups according to the deciles of the SUA level. The rate of ICAS reached a minimum in the seventh decile (6.0-6.3 mg/dL; reference group). After adjusting for confounding factors, multivariate logistic regression analysis demonstrated that both low SUA level (≤ 3.8 mg/dL; OR, 2.34; 95% CI, 1.29-4.39; p = 0.006) and high SUA level (≥ 7.8 mg/dL; OR, 2.10; 95% CI, 1.15-3.92; p = 0.017) conferred greater risk for ICAS. In multivariable analysis with a quadratic model which used SUA as a continuous variable, a U-shaped association between SUA and the rate of ICAS was confirmed (α > 0; p < 0.001). The estimated SUA level associated with the lowest rate of ICAS was 6.2 mg/dL. In conclusion, our findings suggest a U-shaped association between ICAS and SUA.

Asymptomatic hyperuricaemia: a silent activator of the innate immune system

Asymptomatic hyperuricaemia affects ~20% of the general population in the USA, with variable rates in other countries. Historically, asymptomatic hyperuricaemia was considered a benign laboratory finding with little clinical importance in the absence of gout or kidney stones. Yet, increasing evidence suggests that asymptomatic hyperuricaemia can predict the development of hypertension, obesity, diabetes mellitus and chronic kidney disease and might contribute to disease by stimulating inflammation. Although urate has been classically viewed as an antioxidant with beneficial effects, new data suggest that both crystalline and soluble urate activate various pro-inflammatory pathways. This Review summarizes what is known about the role of urate in the inflammatory response. Further research is needed to define the role of asymptomatic hyperuricaemia in these pro-inflammatory pathways.

Association of Serum Uric Acid Concentration and Its Change with Cardiovascular Death and All-Cause Mortality

Objective

There is no consensus on the role of abnormal uric acid (UA) levels in the prognosis of patients undergoing hemodialysis. We therefore aimed to investigate the effects of changes in UA concentration on the risk of all-cause death and cardiac death in such patients.

Method

In this retrospective cohort study, patients admitted to two hemodialysis centers performing maintenance hemodialysis (MHD) in Wuhan First Hospital and Fourth Hospital Hemodialysis Center from January 1, 2007, to October 31, 2017, were included.

Results

In all, 325 patients undergoing MHD aged 59.7 ± 14.7 years, including 195 men (60%), were enrolled, with a median follow-up of 37 months. Serum UA (p < 0.001) was significantly higher in the surviving group than in the death group. No significant difference was found in UA variability (p < 0.001) was significantly higher in the surviving group than in the death group. No significant difference was found in UA variability (p < 0.001) was significantly higher in the surviving group than in the death group. No significant difference was found in UA variability (p < 0.001) was significantly higher in the surviving group than in the death group. No significant difference was found in UA variability (p < 0.001) was significantly higher in the surviving group than in the death group. No significant difference was found in UA variability (p < 0.001) was significantly higher in the surviving group than in the death group. No significant difference was found in UA variability (p < 0.001) was significantly higher in the surviving group than in the death group. No significant difference was found in UA variability (p < 0.001) was significantly higher in the surviving group than in the death group. No significant difference was found in UA variability (

Conclusion

Low UA levels were closely related to all-cause mortality in patients undergoing MHD. Although UA levels had no significant effect on cardiac death, they had a good predictive value for long-term prognosis in patients on MHD.

Uric acid and left ventricular hypertrophy: another relationship in hemodialysis patients

Background

The impact of serum uric acid (UA) on morbidity and mortality in hemodialysis (HD) patients is quite controversial in relation to the general population. The aim of this study was to evaluate the association of serum UA with both mortality and left ventricular hypertrophy (LVH) in HD patients.

Methods

This longitudinal study enrolled 225 prevalent HD patients who were classified into three groups according to their follow-up-averaged UA (FA-UA) levels: low FA-UA (FA-UA <400 µmol/L), intermediate/reference FA-UA (FA-UA between 400 and 450 µmol/L) and high FA-UA (FA-UA >450 µmol/L). Echocardiography was performed on a nondialysis day and the presence of LVH was defined based on a left ventricular mass index (LVMI) >131 and >100 g/m² for men and women, respectively. The patients were followed during a 60-month period.

Results

The mean FA-UA level was 425 ± 59 µmol/L (range 294–620). There was a consistent association of higher FA-UA with better nutritional status (higher body mass index, normalized protein catabolic rate, creatinine, albumin and phosphorus), higher hemoglobin, but lower C-reactive protein and LVMI. During the 5-year follow-up, 81 patients died (36%) and the main causes of death were cardiovascular (CV) related (70%). When compared with the reference group, the hazard ratio for all-cause mortality was 1.75 [95% confidence interval (CI) 1.02–2.98; P = 0.041] in the low FA-UA group, but there was no significant association with the high FA-UA group. In contrast, FA-UA did not show an association with CV mortality neither with the lower nor with the high FA-UA group. The unadjusted odds ratio (OR) of LVH risk in the low FA-UA compared with the reference FA-UA group was 3.11 (95% CI 1.38–7.05; P = 0.006), and after adjustment for age, gender, diabetes and CV disease, ORs for LVH persisted significantly only in the low FA-UA group [OR 2.82 (95% CI 1.16–6.88,); P = 0.002].

Conclusions

Low serum UA is a mortality risk factor and is associated with LVH in HD patients. These results are in contrast with the association of UA in the general population and should be the subject of further research.

Comparative Renoprotective Effect of Febuxostat and Allopurinol in Predialysis Stage 5 Chronic Kidney Disease Patients: A Nationwide Database Analysis

Hyperuricemia has been associated with chronic kidney disease (CKD) progression. The antihyperuricemic febuxostat's potential renoprotective effect has been demonstrated in stage 1–3 CKD. Large‐scale studies comparing the renoprotective potential of febuxostat and allopurinol in advanced CKD are lacking. We exclusively selected 6,057 eligible patients with predialysis stage 5 CKD prescribed either febuxostat or allopurinol using the National Health Insurance Research Database in Taiwan during 2012–2015. There were 69.57% of allopurinol users and 42.01% febuxostat users who required long‐term dialysis (P < 0.0001). The adjusted hazard ratio (HR) of 0.65 (95% confidence interval (CI) 0.60–0.70) indicated near 35% lower hazards of long‐term dialysis with febuxostat use. The renal benefit of febuxostat was consistent across most patient subgroups and/or using the propensity score‐matched cohort. The adjusted HR was 0.66 (95% CI, 0.61–0.70) for long‐term dialysis or death. In conclusion, lower risk of progression to dialysis was observed in predialysis stage 5 CKD febuxostat users without compromising survival.

Clinical and pathological features of immunoglobulin A nephropathy patients with nephrotic syndrome

IgA nephropathy (IgAN) is the most common glomerulonephritis worldwide. The classic manifestation of IgAN is episodic hematuria and proteinuria. Nephrotic syndrome (NS) is not very common in IgAN, reported to occur in only 5-10% of IgAN patients. However, the clinical and pathological characteristics and long-term outcomes of patients with NS-IgAN at onset remain unknown. A retrospective study was conducted, enrolling 1165 patients with biopsy-proven IgAN from West China Hospital in 2008-2015. Patients with renal biopsy of minimal change disease with mesangial IgA deposits were excluded. The renal endpoint was defined as 50% decrease in eGFR or progressing into end-stage renal disease (ESRD). A total of 1165 patients were enrolled with average age of 34.58, and 171 (14.7%) patients were presented with NS. Comparing NS and non-NS groups, significance differences were shown in hypertension (HTN), 24-h urine protein, serum albumin, serum creatine, eGFR and uric acid. NS group had severe pathological changes such as endocapillary hypercellularity, tubular atrophy or interstitial fibrosis and crescent, but less segmental glomerulosclerosis or adhesion and global sclerosis. During the average follow-up of 44.27 months, 29.8% (51/171) NS patients and 15.8% (157/994) non-NS patients progressed to the renal endpoint. 5-year renal survival rates were 73.1% and 87.8% (P < 0.001) in NS and non-NS groups, respectively. This study demonstrated that IgAN patients with NS had higher serum creatine, lower eGFR, lower uric acid, more acute lesions and poor prognosis. NS was an independent risk factor for progression to the renal endpoint.

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.

Uric acid regulates NLRP3/IL-1β signaling pathway and further induces vascular endothelial cells injury in early CKD through ROS activation and K+ efflux

BACKGROUND

Chronic kidney disease (CKD) has been considered as a major health problem in the world. Increasing uric acid (UA) could induce vascular endothelial injury, which is closely related to microinflammation, oxidative stress, and disorders of lipids metabolism. However, the specific mechanism that UA induces vascular endothelial cells injury in early CKD remains unknown.

METHODS

Human umbilical vein endothelial cells (HUVECs) were cultured and subjected to different concentrations of UA for different periods. Early CKD rat model with elevated serum UA was established. Western blotting and quantitative real-time PCR (qPCR) were applied for measuring protein and mRNA expression of different cytokines. The animals were sacrificed and blood samples were collected for measurement of creatinine, UA, IL-1β, TNF-α, and ICAM-1. Renal tissues were pathologically examined by periodic acid-Schiff (PAS) or hematoxylin-eosin (HE) staining.

RESULTS

The expression of IL-1β, ICAM-1, NLRP3 complexes, and activation of NLRP3 inflammasome could be induced by UA, but the changes induced by UA were partially reversed by siRNA NLRP3 or caspase 1 inhibitor. Furthermore, we identified that UA regulated the activation of NLRP3 inflammasome by activating ROS and K⁺ efflux. In vivo results showed that UA caused the vascular endothelial injury by activating NLRP3/IL-1β pathway. While allopurinol could reduce UA level and may have protective effects on cardiovascular system.

CONCLUSIONS

UA could regulate NLRP3/IL-1β signaling pathway through ROS activation and K⁺ efflux and further induce vascular endothelial cells injury in early stages of CKD.