Elevated uric acid level as a significant predictor of chronic kidney disease: a cohort study with repeated measurements

The relationship between serum uric acid and homocysteine is influenced by kidney function

BACKGROUND AND AIM

Prior research has established a relationship between homocysteine (Hcy) and serum uric acid (SUA) levels; however, the precise mechanisms underlying this association remain unclear. The objective of this research was to explore the correlation between SUA and Hcy and to evaluate the possible role of kidney function as a mediator in the connection between SUA and Hcy.

METHODS AND RESULTS

Consecutive enrollment of 16870 participants aged 20-60 years was conducted at the Third Xiangya Hospital of Central South University. Self-reported health questionnaires were used to gather information on health behaviors and medical backgrounds. Trained personnel performed laboratory examinations using standard methods. A mediation analysis was performed to explore the possible effect of renal function on the association between SUA and Hcy levels. Estimated glomerular filtration rate (eGFR) was used to assess kidney function. Logistic regression analysis showed that SUA levels were positively correlated with Hcy levels and hyperhomocysteinemia (HHcy) risk (p < 0.01). Subgroup analysis showed the robustness of the results. Significant mediation effects of eGFR were found in the relationship between SUA and Hcy, as demonstrated by the subsequent mediation analysis. In the overall study group, the percentage of eGFR mediated in the association between SUA and Hcy was 63.36 %, with 41.59 % and 57.59 % in women and men, respectively.

CONCLUSIONS

SUA was positively correlated with Hcy and HHcy risks, and the effects of SUA on Hcy may be mediated by renal function indicators (eGFR).

Association of serum uric acid with all-cause and cardiovascular mortality in cardiovascular disease patients

The relationship between serum uric acid (SUA) and mortality in patients with cardiovascular disease (CVD) remains controversial. We aimed to explore the relationship between SUA and all-cause mortality (ACM) and cardiovascular mortality (CVM) in adult patients with CVD. This cohort study included 3977 patients with CVD from the National Health and Nutrition Examination Survey (2005-2018). Death outcomes were determined by linking National Death Index (NDI) records through December 31, 2019. We explored the association of SUA with mortality using weighted Cox proportional hazards regression models, subgroup analysis, Kaplan-Meier survival curves, weighted restricted cubic spline (RCS) models, and weighted threshold effect analysis among patients with CVD. During a median follow-up of 68 months (interquartile range, 34-110 months), 1,360 (34.2%) of the 3,977 patients with cardiovascular disease died, of which 536 (13.5%) died of cardiovascular deaths and 824 (20.7%) died of non-cardiovascular deaths. In a multivariable-adjusted model (Model 3), the risk of ACM (HR 1.38, 95% CI 1.16-1.64) and the risk of CVM (HR 1.39, 95% CI 1.04-1.86) for participants in the SUA Q4 group were significantly higher. In patients with CVD, RCS regression analysis revealed a nonlinear association (p < 0.001 for all nonlinearities) between SUA, ACM, and CVM in the overall population and in men. Subgroup analysis showed a nonlinear association between ACM and CVM with SUA in patients with CVD combined with chronic kidney disease (CKD), with thresholds of 5.49 and 5.64, respectively. Time-dependent ROC curves indicated areas under the curve of 0.61, 0.60, 0.58, and 0.55 for 1-, 3-, 5-, and 10-year survival for ACM and 0.69, 0.61, 0.59, and 0.56 for CVM, respectively. We demonstrate that SUA is an independent prognostic factor for the risk of ACM and CVM in patients with CVD, supporting a U-shaped association between SUA and mortality, with thresholds of 5.49 and 5.64, respectively. In patients with CVD combined with CKD, the association of the ACM and the CVM with SUA remains nonlinear.

Postmenopausal status increases the risk of uric acid stones

OBJECTIVE

This study investigated the impact of menopause on stone composition in women with urolithiasis.

STUDY DESIGN

A cross-sectional study was conducted from March 2013 to March 2018. Women with urolithiasis patients were divided into two groups according to their menopause status.

MAIN OUTCOME MEASURES

The clinical demographic characteristics, stone removal, stone composition, and urine chemistry were investigated. Univariate and multivariate survival analyses were performed to identify risk factors for the risk of uric acid stones.

RESULTS

Our study enrolled 1221 female patients with stone diseases, 783 (64.1 %) of whom were postmenopausal (66 patients surgically menopause and 717 patients naturally menopause). Postmenopausal women had higher rates of diabetes and hyperuricemia, a higher serum uric acid level, a higher urinary specific gravity, and a lower estimated glomerular filtration rate. Stone analysis revealed calcium oxalate stones in 66.2 % of the patients, apatite stones in 19.4 %, calcium oxalate and calcium phosphate stones in 7.7 %, uric acid stones in 4.4 %, struvite stones in 2.0 %, and brushite stones in 0.2 %. Postmenopausal women had a higher rate of uric acid stones. Multivariate analysis confirmed that postmenopausal status and hyperuricemia were independent risk factors of uric acid stones. Postmenopausal women required more invasive procedures to remove the stones, and they had lower self-voiding rates.

CONCLUSIONS

Postmenopausal women had higher rates of stone episodes, specifically related to uric acid stones. Given the prevalence and impact of chronic kidney diseases, factors that impede optimal renal function management in women must be identified to provide tailored treatment recommendations.

Gut microbiota dysbiosis in hyperuricaemia promotes renal injury through the activation of NLRP3 inflammasome

BACKGROUND

The prevalence of hyperuricaemia (HUA), a metabolic disorder characterized by elevated levels of uric acid, is on the rise and is frequently associated with renal injury. Gut microbiota and gut-derived uremic toxins are critical mediators in the gut-kidney axis that can cause damage to kidney function. Gut dysbiosis has been implicated in various kidney diseases. However, the role and underlying mechanism of the gut microbiota in HUA-induced renal injury remain unknown.

RESULTS

A HUA rat model was first established by knocking out the uricase (UOX). HUA rats exhibited apparent renal dysfunction, renal tubular injury, fibrosis, NLRP3 inflammasome activation, and impaired intestinal barrier functions. Analysis of 16S rRNA sequencing and functional prediction data revealed an abnormal gut microbiota profile and activation of pathways associated with uremic toxin production. A metabolomic analysis showed evident accumulation of gut-derived uremic toxins in the kidneys of HUA rats. Furthermore, faecal microbiota transplantation (FMT) was performed to confirm the effects of HUA-induced gut dysbiosis on renal injury. Mice recolonized with HUA microbiota exhibited severe renal injury and impaired intestinal barrier functions following renal ischemia/reperfusion (I/R) surgery. Notably, in NLRP3-knockout (NLRP3-/-) I/R mice, the deleterious effects of the HUA microbiota on renal injury and the intestinal barrier were eliminated.

CONCLUSION

Our results demonstrate that HUA-induced gut dysbiosis contributes to the development of renal injury, possibly by promoting the production of gut-derived uremic toxins and subsequently activating the NLRP3 inflammasome. Our data suggest a potential therapeutic strategy for the treatment of renal diseases by targeting the gut microbiota and the NLRP3 inflammasome. Video Abstract.

Analyzing Longitudinal Health Screening Data with Feature Ensemble and Machine Learning Techniques: Investigating Diagnostic Risk Factors of Metabolic Syndrome for Chronic Kidney Disease Stages 3a to 3b

Longitudinal data, while often limited, contain valuable insights into features impacting clinical outcomes. To predict the progression of chronic kidney disease (CKD) in patients with metabolic syndrome, particularly those transitioning from stage 3a to 3b, where data are scarce, utilizing feature ensemble techniques can be advantageous. It can effectively identify crucial risk factors, influencing CKD progression, thereby enhancing model performance. Machine learning (ML) methods have gained popularity due to their ability to perform feature selection and handle complex feature interactions more effectively than traditional approaches. However, different ML methods yield varying feature importance information. This study proposes a multiphase hybrid risk factor evaluation scheme to consider the diverse feature information generated by ML methods. The scheme incorporates variable ensemble rules (VERs) to combine feature importance information, thereby aiding in the identification of important features influencing CKD progression and supporting clinical decision making. In the proposed scheme, we employ six ML models-Lasso, RF, MARS, LightGBM, XGBoost, and CatBoost-each renowned for its distinct feature selection mechanisms and widespread usage in clinical studies. By implementing our proposed scheme, thirteen features affecting CKD progression are identified, and a promising AUC score of 0.883 can be achieved when constructing a model with them.

Exploring multifaceted factors in chronic kidney disease risk: A comprehensive analysis of biochemistry, lifestyle, and inflammation in elderly Chinese individuals

This letter praises a recent article in the World Journal of Clinical Cases (Roles of biochemistry data, lifestyle, and inflammation in identifying abnormal renal function in old Chinese), examining factors affecting abnormal renal function in elderly Chinese using advanced machine learning. It highlights the importance of uric acid, age, hemoglobin, body mass index, sport hours, and systolic blood pressure. The study's holistic approach, integrating lifestyle and inflammation, offers a nuanced understanding of chronic kidney disease risk factors. The letter suggests exploring mechanistic pathways of hyperuricemia, the link between anemia and renal function, and the connection between body mass index and estimated glomerular filtration rate. It advocates investigating physical activity's impact on renal health and the independent effects of blood pressure. The study significantly contributes to chronic kidney disease understanding, proposing avenues for further exploration and interventions. Commendations are extended to the authors and the journal.

Effects of sodium-glucose cotransporter-2 (SGLT-2) inhibitors on serum uric acid levels in patients with chronic kidney disease: a systematic review and network meta-analysis

Elevated serum uric acid levels are an independent predictor of occurrence and development of chronic kidney disease (CKD) and are strongly associated with prognosis. Several clinical trials have demonstrated the benefits of sodium-glucose cotransporter-2 (SGLT-2) inhibitors. To evaluate and rank the effects and safety of various SGLT-2 for serum uric acid levels in patients with CKD. We performed a systematic PubMed, Embase, Scopus, and Web of Science search, including studies published before July 1, 2023. Two researchers independently extracted data on study characteristics and outcomes and assessed study quality using the Cochrane Collaboration's risk of bias tool 2. The gemtc package of R software was used to perform network meta-analysis within a Bayesian framework. The primary outcome was serum uric acid levels, and the secondary outcome was adverse events. Effect sizes are reported as standardized mean differences (SMDs), risk ratio (RR), and 95% CI, respectively. The certainty of evidence was evaluated using Grading of Recommendations, Assessment, Development and Evaluations (GRADE) criteria. Eight RCTs (9367 participants) were included in this meta-analysis. The results of the paired meta-analysis showed that SGLT-2 inhibitors significantly reduced serum uric acid levels in patients with CKD compared with the placebo group (SMD -0.22; 95% CI -0.42 to -0.03; GRADE: low). Pooled analysis of any adverse events reported in the included studies showed similar incidence rates in the SGLT-2 inhibitor and placebo groups (RR: 0.99; 95% CI 0.97 to 1.00; p=0.147; GRADE: high). Subgroup analysis showed a statistically significant difference only for tofogliflozin. Further network meta-analysis showed that dapagliflozin 10 mg and ipragliflozin 50 mg may be the most effective in reducing uric acid levels. SGLT-2 inhibitors significantly reduced serum uric acid levels in patients with CKD, and dapagliflozin 10 mg and ipragliflozin 50 mg may be the optimal dosages. SGLT-2 inhibitors hold great promise as an antidiabetic therapeutic option for patients with CKD who have elevated serum uric acid levels. PROSPERO registration number: CRD42023456581.

The Bidirectional Relationship between Chronic Kidney Disease and Hyperuricemia: Evidence from a Population-Based Prospective Cohort Study

BACKGROUND

Although several studies have examined the association between chronic kidney disease (CKD) and hyperuricemia (HUA), the direction of the association remains unclear. We aimed to investigate whether there was a bidirectional association between them.

METHODS

The present study was conducted in three analyses. Analysis I included 25,433 participants free of HUA at baseline to evaluate the associations between CKD and estimated glomerular filtration rate (eGFR) with incident HUA. Analysis II had 28,422 participants free of CKD at baseline to analyze the relationships between HUA and serum uric acid (sUA) with new-onset CKD. Cox proportional hazards regression models were applied to evaluate the association involved in Analysis I and II. Analysis III included 31,028 participants with complete data and further dissected the bidirectional association between sUA and eGFR using cross-lag models.

RESULTS

New-onset HUA and CKD were observed in the first round of the follow-up study among 1597 and 1212 participants, respectively. A significantly higher risk of HUA was observed in individuals with CKD compared to individuals without CKD (HR = 1.58, 95% CI: 1.28-1.95). The adjusted HRs (95% CIs) of HUA were 3.56 (2.50-5.05) for the participants in the group of eGFR less than 60 mL·min^-1·1.73 m^-2, 1.61 (1.42-1.83) for those in the group of eGFR between 60 and 90 mL·min^-1·1.73 m^-2, and 1.74 (1.42-2.14) for those in the group of eGFR more than 120 mL·min^-1·1.73 m^-2, compared with the group of eGFR between 90 and 120 mL·min^-1·1.73 m^-2. A higher risk of CKD was also observed in individuals with HUA compared to individuals without HUA (HR = 1.28, 95% CI: 1.12-1.47). Compared with the first quintile of sUA, the adjusted HR (95% CI) of CKD was 1.24 (1.01-1.51) for the participants in the fourth quantile. There was a bidirectional relationship between sUA and eGFR, with the path coefficients (ρ₁ = -0.024, p < 0.001) from baseline eGFR to follow-up sUA and the path coefficients (ρ₂ = -0.015, p = 0.002) from baseline sUA to follow-up eGFR.

CONCLUSIONS

The present study indicated that CKD and HUA were closely associated, and there was a bidirectional relationship between sUA and eGFR.

Integration of network pharmacology and intestinal flora to investigate the mechanism of action of Chinese herbal Cichorium intybus formula in attenuating adenine and ethambutol hydrochloride-induced hyperuricemic nephropathy in rats

CONTEXT

Cichorium intybus L. (Asteraceae) formula (CF) has been applied as a folk medicine to treat hyperuricemic nephropathy (HN). However, the exact mechanism remains unclear.

OBJECTIVE

To explore the therapeutic effect and mechanism of CF on HN.

MATERIALS AND METHODS

Through network pharmacological methods, the targets of the active component of CF against HN were obtained. Subsequently, Male Wistar rats were divided into control, HN, allopurinol (50 mg/kg), CF high-dose (8.64 g/kg) and CF low-dose (2.16 g/kg) groups. The HN model was induced via intragastric administration of adenine (100 mg/kg) and ethambutol hydrochloride (250 mg/kg) for 3 weeks. After CF treatment, biochemical indicators including UA, UREA and CREA were measured. Then, HE staining, qRT-PCR and gut microbiota analysis were conducted to further explore the mechanism.

RESULTS

The network pharmacology identified 83 key targets, 6 core genes and 200 signalling pathways involved in the treatment of HN. Compared to the HN group, CF (8.64 g/kg) significantly reduced the levels of UA, UREA and CREA (from 2.4 to 1.57 μMol/L, from 15.87 to 11.05 mMol/L and from 64.83 to 54.83 μMol/L, respectively), and mitigated renal damage. Furthermore, CF inhibited the expression of IL-6, TP53, TNF and JUN. It also altered the composition of gut microbiota, and ameliorated HN by increasing the relative abundance of some probiotics.

CONCLUSIONS

This work elucidated the therapeutic effect and underlying mechanism by which CF protects against HN from the view of the biodiversity of the intestinal flora, thus providing a scientific basis for the usage of CF.

Predictive markers in chronic kidney disease

Chronic kidney disease (CKD) is defined by gradual deterioration of the renal parenchyma and decline of functioning nephrons. CKD is now recognized as a distinct risk factor for cardiovascular disease (CVD). This risk rises in tandem with the decline in kidney function and peaks at the end-stage. It is important to identify individuals with CKD who are at a higher risk of advancing to end-stage renal disease (ESRD) and the beginning of CVD. This will enhance the clinical benefits and so that evidence-based therapy may be started at the initial stages for those individuals. A promising biomarker must represent tissue damage, and be easy to detect using non-invasive methods. Current CKD progression indicators have difficulties in reaching this aim. Hence this review presents an update on markers studied in the last decade, which help in the prediction of CKD progression such as neutrophil gelatinase-associated lipocalin, kidney injury molecule-1, urinary liver-type fatty acid-binding protein, cystatin-C, asymmetric dimethylarginine, symmetric dimethylarginine, endotrophin, methylglyoxal, sclerostin, uric acid, and miRNA-196a. Additional research is needed to determine the predictive usefulness of these indicators in clinical samples for disease development. Their utility as surrogate markers need to be explored further for the early identification of CKD progression.

A systematic review and meta-analysis of the association between uric acid levels and chronic kidney disease

The function of uric acid (UA) in the genesis and evolution of chronic kidney disease (CKD) has motivated numerous studies, but the results remain inconclusive. We sought to conduct a systematic review and meta-analysis of cohort studies aiming to analyze the association of UA levels with the incidence and progression of CKD. Pubmed/Medline, Lilacs/Bireme and Web of Science were searched to identify eligible studies, following the PRISMA protocol. Data were presented for CKD incidence and progression separately. For the meta-analysis, studies with data stratified by subgroups according to serum UA levels were selected. The inverse variance-weighted random effects model was used to generate a combined effect estimate. Meta-regressions were performed to identify the causes of heterogeneity. The Newcastle-Ottawa Scale was used to assess the risk of bias. The publication bias was tested by funnel plot and Egger's test. Eighteen CKD incidence studies (n = 398,663) and six CKD progression studies (n = 13,575) were included. An inverse relationship was observed between UA levels and protection from CKD incidence and progression. Lower UA levels were protective for the risk of CKD incidence (RR 0.65 [95% CI 0.56-0.75]) and progression (RR 0.55 [95% CI 0.44-0.68]). UA seems to be implicated both in the genesis of CKD and its evolution.

Serum uric acid and risk of incident chronic kidney disease: a national cohort study and updated meta-analysis

BACKGROUND

We prospectively examined the association between serum uric acid (SUA) levels and chronic kidney disease (CKD) in China and updated the evidence through a comprehensive meta-analysis of prospective studies worldwide.

METHODS

Our original analyses were based on data from the China Health and Retirement Longitudinal Study. The primary exposure of interest was SUA at baseline, and the main outcome was incident CKD. Logistic regression models were used to examine the association between SUA levels and incident CKD. A meta-analysis was performed to pool our effect estimate and those from other cohort studies.

RESULTS

During a 4-year follow-up, 180 participants developed incident CKD. Participants in the highest SUA quartile were 2.73 times as likely to develop incident CKD compared to those in the lowest quartile (multivariable-adjusted OR, 2.73; 95% CI, 1.65-4.50). Each 1 mg/dL increment in the SUA levels was associated with a 49% increased risk of incident CKD (multivariable-adjusted OR, 1.49; 95% CI, 1.28-1.74). In the meta-analysis of 30 cohort studies (including the current study), pooled relative risks (95% CIs) of incident CKD were 1.15 (1.10-1.21) for SUA each 1 mg/dL increment, 1.22 (1.14-1.30) for the highest versus lowest SUA group, and 1.17 (1.12-1.23) for hyperuricemia versus no hyperuricemia.

CONCLUSIONS

Baseline SUA levels were associated with higher risk of incident CKD in middle-aged and elderly Chinese adults, and this positive association was confirmed in the meta-analysis of multiple cohort studies. Our findings may imply that SUA levels need to be routinely monitored for future CKD risk.

Serum uric acid variability increases the risk of postoperative chronic kidney disease in patients with renal cell carcinoma after radical nephrectomy

OBJECTIVE

Serum uric acid (SUA) level is associated with the progression of chronic kidney disease (CKD). However, little is known about the predictive value of SUA variability for postoperative CKD in patients with renal cell carcinoma after radical nephrectomy. We aimed to investigate the association of SUA variability with postoperative CKD in this population.

METHOD

85 patients with preoperative estimated glomerular filtration rate (eGFR)≥60 ml/min/1.73 m² were enrolled in this single-center retrospective study and followed up for at least 6 months. Intra-individual SUA variability was defined as the standard deviation (SD) of SUA and the patients were stratified into three groups according to the tertiles of SUA SD (the lower, middle and upper tertile). The association of SUA variability with postoperative CKD, defined as an eGFR<60 ml/min/1.73m², was analyzed by Cox proportional hazard models and Kaplan-Meier analyses.

RESULTS

After a median follow-up time of 24(10-43) months, 44(51.7%) patients developed postoperative CKD. Kaplan-Meier curves showed that patients in the lower tertile had a longer CKD-free survival time [median CKD-free survival time 74(52.2-95.8) months] than those in the middle tertile [38(19.2-56.8) months] and upper tertile [21(17.9-24.1) months] (overall generalized Wilcoxon test: P=0.001; lower vs middle tertile: P=0.001; lower vs upper tertile: P<0.001). Adjusted Cox analyses indicated that increasing SUA SD tertiles were associated with a higher risk of postoperative CKD independent of baseline SUA, mean SUA during follow-up and other confounding variables. Compared with patients in the lower tertile, the risk for developing CKD increased by 4.6-fold for patients in the middle tertile and 7.9-fold in the upper tertile, respectively.

CONCLUSION

Increasing SUA variability was associated with an increased risk of postoperative CKD in patients with renal cell carcinoma after radical nephrectomy.

Serum uric acid is associated with incident hip fractures in women and men - Results from a large Austrian population-based cohort study

OBJECTIVES

Serum markers that can be used to estimate the risk of bone fractures are rare, and findings for one candidate marker, uric acid, are heterogeneous. Our aim was to investigate the potential of serum uric acid (SUA) to predict hip fractures occurring in people aged 50 years and over.

STUDY DESIGN

During a medical prevention program over the period 1985-2005 in Vorarlberg, baseline data were collected on SUA levels and covariates (age, BMI, blood pressure, smoking status, diabetes, triglycerides and cholesterol) from 185,397 individuals, of whom 42,488 women and 35,908 men met the inclusion criteria of this population-based cohort study. Information on incident cancer and end-stage kidney disease was acquired from registries.

MAIN OUTCOME MEASURE

Incident hip fracture occurring in participants aged 50 years and over during the observation period 2003-2013.

RESULTS

SUA was associated with a rise in female hip fracture risk by 6% per unit increase (HR 1.06, 95 %-CI 1.01-1.10), and risk in the highest vs. lowest SUA quartile was significantly increased (HR 1.17, 95 %-CI 1.01-1.35), but not at hyperuricemic (>5.7 mg/dl) vs. normouricemic (≤5.7 mg/dl) levels. In men, hip fracture risk rose by 15 % per unit increase (HR 1.15, 95 %-CI 1.08-1.22), and risk was significantly higher in the highest vs. lowest SUA quartile (HR 1.50, 95 %-CI 1.17-1.91) as well as at hyperuricemic (>7.0 mg/dl) vs. normouricemic (≤7.0 mg/dl) levels (HR 1.48, 95 %-CI 1.19-1.84).

CONCLUSIONS

Our results link SUA with increased risk of hip fractures, particularly in men.

Management of Hyperuricemia in Patients with Chronic Kidney Disease: a Focus on Renal Protection

PURPOSE OF REVIEW

In chronic kidney disease (CKD), plasma uric acid levels are increased because of the decrease in glomerular filtration rate. However, in addition to CKD, hyperuricemia is frequently associated with a number of other conditions such as hypertension, type 2 diabetes, obesity, and heart failure, overweight, and cardiovascular disease.

RECENT FINDINGS

It is now becoming increasingly clear that, in many clinical conditions, elevated levels of uric acid have a much greater role beyond just causing gout. The present review will summarize current knowledge on the relation between hyperuricemia, CKD, and existing comorbidities, as well as the mechanisms of uric acid-related renal damage. In addition, the role and evidence for urate-lowering therapy in prevention and cardiovascular protection in CKD patients is discussed with a focus on allopurinol and febuxostat. To date, several clinical studies have provided evidence that urate-lowering therapy may help to prevent and delay the decline of renal function in patients with CKD. Use of a xanthine oxidase inhibitor should be considered in patients who are at high renal risk and/or with declining renal function in the presence of hyperuricemia with and without deposition, although additional studies are warranted to define treatment targets. Notwithstanding, the possibility to delay deterioration of renal function in patients with CKD merits consideration.

Apolipoprotein B Level and the Apolipoprotein B/Apolipoprotein A-I Ratio as a Harbinger of Ischemic Stroke: A Prospective Observation in Taiwan

AIM

Prospective studies indicate that apolipoprotein (apo) measurements predict coronary heart disease risk. However, few population-based follow-up studies have addressed the predictive value of apo measurements in stroke risk. The aims of the present study were to analyze the predictive ability of apo measurements in the risk of ischemic stroke.

METHODS

Serum apo A-I and apo B levels and calculated apo B/apo A-I ratio were measured at baseline in 2002 in a cohort of 4,204 participants who were followed for a mean of 4.61 years for a stroke event.

RESULTS

After adjustment for potential confounders, a significantly stepwise increase in the incidence rate of stroke across quartiles of both apo B and the apo B/apo A-I ratio was evident in both genders and across age-groups. The predictive ability of apo B to detect ischemic stroke was comparable with that of the apo B/apo A-I ratio. Furthermore, both apo B and the apo B/apo A-I ratio were better predictors of the risk of ischemic stroke than total cholesterol (TC), low-density lipoprotein cholesterol, and the TC/high-density lipoprotein cholesterol ratio.

CONCLUSIONS

This cohort study demonstrates that apo B and the apo B/apo A-I ratio were a significant risk predictor of stroke. Furthermore, the predictive ability of apo B and the apo B/apo A-I ratio in stroke risk was better than routine clinical lipid measurements. Thus, measurements of apolipoproteins have superior clinical utility over traditional lipid measurements in identifying subjects at risk for ischemic stroke.

Abnormal metabolism of gut microbiota reveals the possible molecular mechanism of nephropathy induced by hyperuricemia

The progression of hyperuricemia disease is often accompanied by damage to renal function. However, there are few studies on hyperuricemia nephropathy, especially its association with intestinal flora. This study combines metabolomics and gut microbiota diversity analysis to explore metabolic changes using a rat model as well as the changes in intestinal flora composition. The results showed that amino acid metabolism was disturbed with serine, glutamate and glutamine being downregulated whilst glycine, hydroxyproline and alanine being upregulated. The combined glycine, serine and glutamate could predict hyperuricemia nephropathy with an area under the curve of 1.00. Imbalanced intestinal flora was also observed. Flavobacterium, Myroides, Corynebacterium, Alcaligenaceae, Oligella and other conditional pathogens increased significantly in the model group, while Blautia and Roseburia, the short-chain fatty acid producing bacteria, declined greatly. At phylum, family and genus levels, disordered nitrogen circulation in gut microbiota was detected. In the model group, the uric acid decomposition pathway was enhanced with reinforced urea liver-intestine circulation. The results implied that the intestinal flora play a vital role in the pathogenesis of hyperuricemia nephropathy. Hence, modulation of gut microbiota or targeting at metabolic enzymes, i.e., urease, could assist the treatment and prevention of this disease.

Synergistic interaction of hyperuricemia and hypertension on reduced eGFR: insights from a general Chinese population

OBJECTIVES

Hyperuricemia and Hypertension are two independent risk factors of renal function damage. Our research aimed to investigate the synergistic interaction between hyperuricemia and hypertension toward reduced eGFR.

METHODS

Our analyses included 11,694 participants from a cross-sectional population-based Northeast China Rural Cardiovascular Health Study. Interaction was assessed on both multiplicative and additive scales.

RESULTS

The prevalence of reduced estimated glomerular infiltration rate (eGFR) was 2.11% in our population. After adjustment of age, sex, race, education level, family income, current smoking and drinking status, body mass index, total cholesterol, high-density lipoprotein cholesterol, and diabetes, subjects with both hyperuricemia and hypertension suffered from a 11.004 (95% CI: 7.080-17.102) times risk of reduced eGFR than the healthy reference group, greater than that in participants with only hyperuricemia (5.741, 95% CI: 3.045-10.825) or hypertension (1.145, 95% CI: 0.764-1.715). Furthermore, additive interaction between hyperuricemia and hypertension was statistically significant and synergistic (relative excess risk due to interaction: 5.118, 95% CI: 0.611-9.624; the attributable proportion due to interaction: 0.465, 95% CI: 0.151-0.779; Synergy index: 2.047, 95% CI: 1.017-4.120). However, our results revealed no significant interaction on the multiplicative scale.

CONCLUSIONS

Hyperuricemia and hypertension may have a synergistic interaction toward renal function loss in addition to their independent impacts. Our findings may provide a straightforward illustration which is easy for the public to realize the hazard of coexistent hypertension and hyperuricemia on renal injury.

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

AIMS

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Relationship between serum uric acid and clustering of cardiovascular disease risk factors and renal disorders among Shanghai population: a multicentre and cross-sectional study

OBJECTIVES

To estimate the current prevalence of cardiovascular disease risk factors (CRFs) and renal disorders across serum uric acid (SUA) quartiles, and evaluate the relationships between SUA and CRFs and renal diseases in Shanghai population.

STUDY DESIGN

Observational, cross-sectional study.

SETTING

Data were obtained from the physical check-up of local residents at three hospitals in Shanghai.

PARTICIPANTS

Residents were invited to take part in a physical check-up and provided informed consent. Exclusion criteria were diseases that resemble cancer, hepatic disease, and other coexisting illnesses including autoimmune kidney diseases and renal artery stenosis, individuals treated with xanthine oxidase inhibitors, and those with incomplete information. There are 26 768 individuals in our study.

PRIMARY AND SECONDARY OUTCOME MEASURES

Hyperuricaemia was defined as SUA ≥7 mg/dL in men and ≥6 mg/dL in women or taking xanthine oxidase inhibitors. Subjects were divided into gender-specific quartiles. We estimate the prevalence of CRFs and renal disorders across SUA quartiles. The relationships between SUA and CRFs and renal disorders in both genders were evaluated using logistic regression analysis.

RESULTS

There was a significant increase in the prevalence of major CRFs and renal diseases across SUA quartiles in a separate analysis among men and women (all p trend <0.001). After multiple adjustment, hyperuricaemia positively correlated with obesity (male OR=3.165, p<0.001; female OR=3.776, p<0.001), hypertension (male OR=1.341, p<0.001; female OR=1.289, p=0.006), dyslipidaemia (male OR=2.490, p<0.001; female OR=3.614, p<0.001), chronic kidney disease (male OR=7.081, p<0.001; female OR=11.571, p<0.001) and nephrolithiasis (male OR=1.469, p<0.001; female OR=1.242, p=0.041), but negatively correlated with diabetes mellitus (male OR=0.206, p<0.001; female OR=0.524, p<0.001). There was a stronger association between hyperuricaemia and clustered CRFs as well as chronic kidney disease in women than in men.

CONCLUSIONS

In Shanghai population, concomitant with the elevated level of SUA, the prevalence of CRFs and renal diseases was rising. Hyperuricaemia was significantly associated with CRFs and renal disorders, especially in women.

Physiology of Hyperuricemia and Urate-Lowering Treatments

Gout is the most common form of inflammatory arthritis and is a multifactorial disease typically characterized by hyperuricemia and monosodium urate crystal deposition predominantly in, but not limited to, the joints and the urinary tract. The prevalence of gout and hyperuricemia has increased in developed countries over the past two decades and research into the area has become progressively more active. We review the current field of knowledge with emphasis on active areas of hyperuricemia research including the underlying physiology, genetics and epidemiology, with a focus on studies which suggest association of hyperuricemia with common comorbidities including cardiovascular disease, renal insufficiency, metabolic syndrome and diabetes. Finally, we discuss current therapies and emerging drug discovery efforts aimed at delivering an optimized clinical treatment strategy.

Uric acid stones increase the risk of chronic kidney disease

The aim of this study was to compare the clinical characteristics of uric acid stones and their potential risk for chronic kidney disease (CKD). A total of 401 patients (196 with uric acid stone and 205 without) were enrolled from our database of patients with urolithiasis. We analyzed the clinical demographic features, stone location, urine chemistries, and renal function. There was a significant difference (p < 0.001) between the two groups in terms of age, with the higher mean age in the uric acid group. Patients with uric acid stones had much lower pH of urine (p < 0.001) and higher serum uric acid level (p = 0.002). Notably, those with uric acid stones had worse eGFR than those with non-uric acid stones. Multivariate analysis confirmed that age over 60 years (ORs = 9.19; 95% CI 3.5-24.3), female sex (ORs = 4.01; 95% CI 1.8-9.0), hyperuricemia (ORs = 8.47; 95% CI 1.6-43.5), and uric acid stone (OR = 2.86; 95% CI 1.2-6.7) were the independent predictors of poor prognoses in CKD. Therefore, an association exists between uric acid stones and higher prevalence of CKD. Patients with uric acid stones may need close monitoring of renal function during follow-up.

Uric acid upregulates the adiponectin‑adiponectin receptor 1 pathway in renal proximal tubule epithelial cells

Adiponectin (APN) is a protein hormone that is primarily derived from adipocytes. It can also be secreted by renal cells. Hypoadiponectinemia has been documented in patients with hyperuricemia, however, whether soluble uric acid (SUA) regulates the expression of APN and APN receptor 1 (AdipoR1) in renal proximal tubule epithelial cells (PTECs) remains to be elucidated. The present study investigated the expression of APN and AdipoR1 in cultured PTECs that were exposed to SUA through immunofluorescence and western blot analysis. In addition, Sprague-Dawley rats with oxonic acid-induced hyperuricemia (HUA) with or without febuxostat treatment were employed as an animal model to measure 24 h urine protein, serum creatinine, urea nitrogen, uric acid and homeostasis model assessment of insulin resistance. Renal pathology was evaluated using hematoxylin and eosin and immunohistochemical staining. APN and AdipoR1 expression in the renal cortex were evaluated by western blotting. The results demonstrated that, in PTECs, the expression of APN and AdipoR1 was constant and increased upon SUA exposure. Similar observations were made within the proximal renal tubules of rats, and the oxonic acid-induced increases in APN and AdipoR1 were offset by febuxostat treatment. Furthermore, SUA-treated PTECs exhibited an increase in the expression of NLR family pyrin domain-containing (NLRP) 3, which was dose-dependent. NLRP3 expression was also significantly increased in the renal cortex of HUA rats compared with control and febuxostat-treated rats. In conclusion, SUA enhanced the expression of APN and AdipoR1 in PTECs, which was associated with an increase in NLRP3 expression. The APN-AdipoR1 pathway was demonstrated to have an important role in in vitro and in vivo models of renal proximal tubule inflammatory injury. Therefore, this pathway may be a potential therapy target in urate nephropathy.

Uric acid in the pathogenesis of metabolic, renal, and cardiovascular diseases: A review

The association between uric acid (UA) on one side and systemic hypertension (Htn), dyslipidemia, glucose intolerance, overweight, fatty liver, renal disease and cardiovascular disease (CVD) on the other side is well recognized. However, the causal relationship between UA and these different clinical problems is still debatable. The recent years have witnessed hundreds of experimental and clinical trials that favored the opinion that UA is a probable player in the pathogenesis of these disease entities. These studies disclosed the strong association between hyperuricemia and metabolic syndrome (MS), obesity, Htn, type 2 diabetes mellitus (DM), non-alcoholic fatty liver disease, hypertriglyceridemia, acute kidney injury, chronic kidney disease (CKD), coronary heart disease (CHD), heart failure and increased mortality among cardiac and CKD patients. The association between UA and nephrolithiasis or preeclampsia is a non-debatable association. Recent experimental trials have disclosed different changes in enzyme activities induced by UA. Nitric oxide (NO) synthase, adenosine monophosphate kinase (AMPK), adenosine monophosphate dehydrogenase (AMPD), and nicotinamide adenine dinucleotide phosphate (NADPH)-oxidase are affected by UA. These changes in enzymatic activities can lead to the observed biochemical and pathological changes associated with UA. The recent experimental, clinical, interventional, and epidemiologic trials favor the concept of a causative role of UA in the pathogenesis of MS, renal, and CVDs.

Relationship between diurnal blood pressure and renal histopathological changes in white coat hypertension

BACKGROUND

Multiple epidemiological studies have clearly demonstrated the macrovascular risks associated with white coat hypertension (WCH) or sustained hypertension (SH). In patients with WCH, there is no literature available on renal histopathological changes and that on blood pressure pattern and native kidney outcome is scant. We aimed to clarify the relationship between blood pressure variables and pathological features of kidney biopsies in living kidney donors with WCH.

METHODS

This cross-sectional study included living kidney donors with WCH (n = 10) and SH (n = 10), and 20 healthy kidney donors with similar demographic features (control group). Kidney allograft biopsy samples were obtained during transplantation and chronic glomerular, vascular and tubulointertitial changes were semiquantitatively scored according to the Banff classification.

RESULTS

The mean age of the 20 hypertensive subjects (Group 1) and controls (Group 2) was 59.3 ± 8.5 versus 59.6 ± 7.6 years and almost half were female. There was no difference in renal function parameters between the groups; however, kidney histopathology in Group 1 was worse than Group 2 with a chronicity index of 2.80 ± 1.67 versus 1.75 ± 1.16 (p = 0.02). There was no difference between histopathological scores of patients with WCH or SH (chronicity index: 2.60 ± 1.43 vs. 2.70 ± 1.70, p = 0.88). Night-to-day mean arterial pressure (MAP) ratio was significantly associated with chronicity index in patients with WCH. Moreover, WCH patients with non-dipper hypertensive pattern had a worse chronicity index.

CONCLUSIONS

Significant histopathological alterations in the kidney were observed in patients with WCH and SH, and were accentuated in WCH patients with non-dipper blood pressure pattern.

An Invert U-Shaped Curve: Relationship Between Fasting Plasma Glucose and Serum Uric Acid Concentration in a Large Health Check-Up Population in China

There are some published studies focus on the invert U-shaped relationship between fasting plasma glucose (FPG) and serum uric acid (UA), while the threshold value and gender differences of this relationship were still obscure. We aimed to explore the dose-response relation between FPG level and serum UA concentration by conducted this epidemiological research in a large health check-up population in China. A total of 237,703 people were collected from January 2011 to July 2014 in our cross-sectional study; 100,348 subjects age 18 to 89 years and without known diabetes were included for the current analysis. One-way analysis of variance, generalized additive models, and 2-piecewise linear regression model were used. The mean concentration of UA with FPG of <6.1, 6.1 to 6.9, and ≥7.0 mmol/L was 240.9, 260.2, and 259.6 μmol/L in women and 349.0, 360.8, and 331.0 μmol/L in men. An invert U-shape with a threshold FPG of 7.5 (women)/6.5 (men) mmol/L was observed in the regression curve of FPG and UA, even after adjusting for potential confounders. The adjusted regression coefficients were 2.4 (95% confidence interval [CI]: 1.5 to 3.4, P < 0.001) for FPG < 7.5 mmol/L, -3.2 (95% CI: -5.0 to -1.3, P < 0.001) for FPG ≥ 7.5 mmol/L in women; while 0.8 (95% CI: -0.4 to 2.0, P = 0.19) for FPG < 6.5 mmol/L, -7.1 (95% CI: -8.0 to -6.1, P < 0.001) for FPG ≥ 6.5 mmol/L in men. Furthermore, the interaction between different FPG level and sex was significant (P < 0.05). An invert U-shape with a threshold of FPG was existed for serum UA level in Chinese adults age 18 to 89 years without known diabetes, and significant gender differences were found. Future researches should pay more attention to this relationship.

Effect of Non-Alcoholic Fatty Liver Disease on Estimated Glomerular Filtration Rate Could Be Dependent on Age

There is a gap between the association of non-alcoholic fatty liver disease (NAFLD) and renal function in an apparently healthy population. This study aims to assess whether NAFLD is associated with estimated glomerular filtration rate (eGFR) levels and to understand early changes of eGFR in NAFLD. A cross-sectional study was performed among apparently healthy persons who underwent general health screening including laboratory assessments and hepatic ultrasonography from January 2013 to December 2013 at the First Affiliated Hospital of Zhejiang University, College of Medicine, China. This study included 1,193 subjects with a mean age of 48 years. Prevalence of NAFLD was 31.3%. Mean eGFR was significantly lower in NAFLD than in controls (107 ± 19 mL/min/1.73 m(2) vs. 113 ± 23 mL/min/1.73 m(2), P<0.001). Correlation analysis between eGFR and NAFLD related risk factors revealed an inverse correlation between eGFR levels and some NAFLD risk factors (all P<0.01). All subjects were classified into five phases according to age. Average eGFR levels of NAFLD were lower than controls in three phases for subjects with ≤ 50 years of age (all P<0.05), while there were no significant differences on average eGFR levels between NAFLD and controls in two phases for subjects with >50 years of age (Both P>0.05). The eGFR level is significantly associated with NAFLD and its risk factors in an apparently healthy population. Effects of NAFLD on eGFR could be dependent on age.

Gout after living kidney donation: correlations with demographic traits and renal complications

BACKGROUND

The demographic and clinical correlates of gout after living kidney donation are not well described.

METHODS

Using a unique database that integrates national registry identifiers of U.S. living kidney donors (1987-2007) with billing claims from a private health insurer (2000-2007), we identified post-donation gout based on medical diagnosis codes or pharmacy fills for gout therapies. The frequencies and demographic correlates of gout after donation were estimated by Cox regression with left- and right-censoring. We also compared the rates of renal diagnoses among donors with and without gout, matched in the ratio 1:3 by age, sex, and race.

RESULTS

The study sample of 4,650 donors included 13.1% African Americans. By seven years, African Americans were almost twice as likely to develop gout as Caucasian donors (4.4 vs. 2.4%; adjusted hazard ratio, aHR, 1.8; 95% confidence interval (CI) 1.0-3.2). Post-donation gout risk also increased with older age at donation (aHR per year 1.05) and was higher in men (aHR 2.80). Gout rates were similar in donors and age- and sex-matched general non-donors (rate ratio 0.86; 95% CI 0.66-1.13). Compared to matched donors without gout, donors with gout had more frequent renal diagnoses, reaching significance for acute kidney failure (rate ratio 12.5; 95% CI 1.5-107.0), chronic kidney disease (rate ratio 5.0; 95% CI 2.1-11.7), and other disorders of the kidney (rate ratio 2.2; 95% CI 1.2-4.2).

CONCLUSION

Donor subgroups at increased risk of gout include African Americans, older donors, and men. Donors with gout have a higher burden of renal complications after demographic adjustment.