Uric acid predicts adverse outcomes in chronic kidney disease: a novel insight from trajectory analyses

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.

Joint association of hyperuricemia and chronic kidney disease with mortality in patients with chronic heart failure

Background

The joint association of hyperuricemia and chronic kidney disease (CKD) with mortality in patients with chronic heart failure (CHF) is not conclusive.

Methods

This retrospective cohort study was conducted in Chinese People's Liberation Army General Hospital, Beijing, China. We included 9,367 patients with CHF, who were hospitalized between January 2011 and June 2019. The definitions of hyperuricemia and CKD were based on laboratory test, medication use, and medical record. We categorized patients with CHF into 4 groups according to the absence (-) or presence (+) of hyperuricemia and CKD. The primary outcomes included in-hospital mortality and long-term mortality. We used multivariate logistic regression and Cox proportional hazards regression to estimate the mortality risk according to the hyperuricemia/CKD groups.

Results

We identified 275 cases of in-hospital mortality and 2,883 cases of long-term mortality in a mean follow-up of 4.81 years. After adjusting for potential confounders, we found that compared with the hyperuricemia-/CKD- group, the risks of in-hospital mortality were higher in the hyperuricemia+/CKD- group (odds ratio [OR], 95% confidence interval [CI]: 1.58 [1.01-2.46]), hyperuricemia-/CKD+ group (OR, 95% CI: 1.67 [1.10-2.55]), and hyperuricemia+/CKD+ group (OR, 95% CI: 2.12 [1.46-3.08]). Similar results were also found in long-term mortality analysis. Compared with the hyperuricemia-/CKD- group, the adjusted hazard ratios and 95% CI for long-term mortality were 1.25 (1.11-1.41) for hyperuricemia+/CKD- group, 1.37 (1.22-1.53) for hyperuricemia-/CKD+ group, and 1.59 (1.43-1.76) for hyperuricemia+/CKD+ group. The results remained robust in the sensitivity analysis.

Conclusions

Hyperuricemia and CKD, both individually and cumulatively, are associated with increased mortality risk in patients with CHF. These results highlighted the importance of the combined control of hyperuricemia and CKD in the management of heart failure.

Longitudinal uric acid has nonlinear association with kidney failure and mortality in chronic kidney disease

We investigated the shape of the relationship between longitudinal uric acid (UA) and the hazard of kidney failure and death in chronic kidney disease (CKD) patients, and attempted to identify thresholds associated with increased hazards. We included CKD stage 3-5 patients from the CKD-REIN cohort with one serum UA measurement at cohort entry. We used cause-specific multivariate Cox models including a spline function of current values of UA (cUA), estimated from a separate linear mixed model. We followed 2781 patients (66% men, median age, 69 years) for a median of 3.2 years with a median of five longitudinal UA measures per patient. The hazard of kidney failure increased with increasing cUA, with a plateau between 6 and 10 mg/dl and a sharp increase above 11 mg/dl. The hazard of death had a U-shape relationship with cUA, with a hazard twice higher for 3 or 11 mg/dl, compared to 5 mg/dl. In CKD patients, our results indicate that UA above 10 mg/dl is a strong risk marker for kidney failure and death and that low UA levels below 5 mg/dl are associated with death before kidney failure.

Therapeutic effects of traditional Chinese medicine on gouty nephropathy: Based on NF-κB signalingpathways

As the final product of purine metabolism, excess serum uric acid (SUA) aggravates the process of some metabolic diseases. SUA causes renal tubule damage, interstitial fibrosis, and glomerular hardening, leading to gouty nephropathy (GN). A growing number of investigations have shown that NF-κB mediated inflammation and oxidative stress have been directly involved in the pathogenesis of GN. Traditional Chinese medicine's treatment methods of GN have amassed a wealth of treatment experience. In this review, we first describe the mechanism of NF-κB signaling pathways in GN. Subsequently, we highlight traditional Chinese medicine that can treat GN through NF-κB pathways. Finally, commenting on promising candidate targets of herbal medicine for GN treatment via suppressing NF-κB signaling pathways was summarized.

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.

Association of poorly controlled HbA1c with increased risk of progression to end-stage kidney disease and all-cause mortality in patients with diabetes and chronic kidney disease

Glycosylated hemoglobin (HbA1c) targets for patients with chronic kidney disease (CKD) and type 2 diabetes remain controversial. To evaluate whether baseline HbA1c and HbA1c trajectories are associated with the risk of end-stage kidney disease (ESKD) and all-cause mortality, we recruited adult patients with CKD and type 2 diabetes from a “Pre-ESKD Program” at a medical center in Taiwan from 2003 to 2017. Group-based trajectory modeling was performed to identify distinct patient groups that contained patients with similar longitudinal HbA1c patterns. Cox proportional hazard models were used to estimate hazard ratios (HRs) of ESKD and mortality associated with baseline HbA1c levels and HbA1c trajectories. In the analysis related to baseline HbA1c (n = 4543), the adjusted HRs [95% confidence interval (CI)] of all-cause mortality were 1.06 (0.95–1.18) and 1.25 (95% CI, 1.07–1.46) in patients with an HbA1c level of 7%–9% (53–75 mmol/mol) and >9% (>75 mmol/mol), respectively, as compared with those with an HbA1c level < 7% (<53 mmol/mol). In the trajectory analysis (n = 2692), three distinct longitudinal HbA1c trajectories were identified: nearly optimal (55.9%), moderate to stable (34.2%), and poor control (9.9%). Compared with the “nearly optimal” HbA1c trajectory group, the “moderate-to-stable” group did not have significantly higher mortality, but the “poorly controlled” group had 35% higher risk of mortality (adjusted HR = 1.35, 95% CI = 1.06–1.71). Neither baseline levels of HbA1c nor trajectories were associated with ESKD risk. In conclusion, in patients with CKD and type 2 diabetes, poor glycemic control was associated with an elevated risk of mortality but not associated with a risk of progression to ESKD.

Dyslipidemia and coronary artery calcium: From association to development of a risk-prediction nomogram

BACKGROUND AND AIMS

The associations between dyslipidemia and coronary artery calcium (CAC) are controversial. We investigated their cross-sectional relationships and developed a predictive scoring system for prognostically significant coronary calcification (PSCC).

METHODS AND RESULTS

This study evaluated the lipid profiles and the CAC score (CACS) measured through multidetector computed tomography (MDCT) among Taiwanese adult patients in a tertiary hospital between 2011 and 2016. Patients with CACS higher than 100 were classified as having PSCC. Dyslipidemia for each lipid component was defined based on the clinical cutoffs or the use of the lipid-lowering agents. Multivariable logistic regression was used to assess the association between dyslipidemia and PSCC and the model performance was assessed using calibration plot, discrimination, and a decision curve analysis. Of the 3586 eligible patients, 364 (10.2%) had PSCC. Increased age, male sex, higher body mass index (BMI), and higher level of triglyceride (TG) were associated with PSCC. The adjusted odds ratios (95% confidence intervals) of PSCC was 1.15 (0.90-1.47) for dyslipidemia defined by total cholesterol (TC) ≥200 mg/dL, 1.06 (0.83-1.35) for low-density-lipoprotein-cholesterol (LDL-C) ≥130 mg/dL, and 1.36 (1.06-1.75) for TG ≥ 200 mg/dL. The positive association between TG ≥ 200 mg/dL and PSCC was not modified by sex. Incorporating hypertriglyceridemia did not significantly improve the predictive performance of the base model comprising of age, sex, BMI, smoking, hypertension, diabetes, estimated glomerular filtration rate, and fasting glucose.

CONCLUSIONS

Hypertriglyceridemia was significantly associated with the prevalent odds of PSCC. Our proposed predictive model may be a useful screening tool for PSCC.

High serum uric acid trajectories are associated with risk of myocardial infarction and all-cause mortality in general Chinese population

Background

Long-term patterns of serum uric acid (SUA) and their association with the risk of myocardial infarction (MI) and mortality are poorly characterized as prior studies measured SUA at a single time point. This study aimed to identify SUA trajectories and determine their associations with incident MI and all-cause mortality.

Methods

We included 85,503 participants who were free of MI in or prior 2012 from the Kailuan study. SUA trajectories during 2006–2012 were identified by group-based trajectory modeling. Cox proportional hazard models were used to assess the association of SUA trajectories with MI and all-cause mortality.

Results

We identified three SUA trajectories during 2006–2012: low-stable (n=44,124, mean SUA: 236–249 μmol/L), moderate-stable (n=34,431, mean SUA: 324–354 μmol/L) and high-stable (n=6,984, mean SUA: 425–463 μmol/L). During a median follow-up of 6.8 years, we documented 817 (0.96%) incident MI and 6498 (7.60%) mortality. Compared with the low-stable group, high-stable group experienced a higher risk of MI (hazard ratio [HR], 1.35; 95% confidence [CI], 1.07–1.71) and all-cause mortality (HR, 1.22; 95% CI, 1.12–1.33). Multiple sensitivity analyses yielded similar results. Additionally, the association of SUA trajectory with MI and all-cause mortality was more pronounced in individuals without a history of hypertension (P-interaction=0.0359) and those aged <60 years (P-interaction<0.0001), respectively.

Conclusions

Higher SUA trajectories were associated with altered risk of MI and all-cause mortality, suggesting that monitoring SUA trajectory may assist in identifying subpopulations at higher risk of MI and all-cause mortality.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13075-022-02812-y.

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.

Predicting the risk of postoperative acute kidney injury: development and assessment of a novel predictive nomogram

OBJECTIVE

This study aimed to establish and internally verify the risk nomogram of postoperative acute kidney injury (AKI) in patients with renal cell carcinoma.

METHODS

We retrospectively collected data from 559 patients with renal cell carcinoma from June 2016 to May 2019 and established a prediction model. Twenty-six clinical variables were examined by least absolute shrinkage and selection operator regression analysis, and variables related to postoperative AKI were determined. The prediction model was established by multiple logistic regression analysis. Decision curve analysis was conducted to evaluate the nomogram.

RESULTS

Independent predictors of postoperative AKI were smoking, hypertension, surgical time, blood glucose, blood uric acid, alanine aminotransferase, estimated glomerular filtration rate, and radical nephrectomy. The C index of the nomogram was 0.825 (0.790-0.860) and 0.814 was still obtained in the internal validation. The nomogram had better clinical benefit when the intervention was decided at the threshold probabilities of >4% and <79% for patients and doctors, respectively.

CONCLUSIONS

This novel postoperative AKI nomogram incorporating smoking, hypertension, the surgical time, blood glucose, blood uric acid, alanine aminotransferase, the estimated glomerular filtration rate, and radical nephrectomy is convenient for facilitating the individual postoperative risk prediction of AKI in patients with renal cell carcinoma.

Prediction of non-responsiveness to pre-dialysis care program in patients with chronic kidney disease: a retrospective cohort analysis

The responsiveness of patients with chronic kidney disease (CKD) to nephrologists’ care is unpredictable. We defined the longitudinal stages (LSs) 1–5 of estimated glomerular filtration rate (eGFR) by group-based trajectory modeling for repeated eGFR measurements of 7135 patients with CKD aged 20–90 years from a 13-year pre-end-stage renal disease (ESRD) care registry. Patients were considered nonresponsive to the pre-dialysis care if they had a more advanced eGFR LS compared with the baseline. Conversely, those with improved or stable eGFR LS were considered responsive. The proportion of patients with CKD stage progression increased with the increase in the baseline CKD stage (stages 1–2: 29.2%; stage 4: 45.8%). The adjusted times to ESRD and all-cause mortality in patients with eGFR LS-5 were 92% (95% confidence interval [CI] 86–96%) and 57% (95% CI 48–65%) shorter, respectively, than in patients with eGFR LS-3A. Among patients with baseline CKD stages 3 and 4, the adjusted times to ESRD and all-cause death in the nonresponsive patients were 39% (95% CI 33–44%) and 20% (95% CI 14–26%) shorter, respectively, than in the responsive patients. Our proposed Renal Care Responsiveness Prediction (RCRP) model performed significantly better than the conventional Kidney Failure Risk Equation in discrimination, calibration, and net benefit according to decision curve analysis. Non-responsiveness to nephrologists’ care is associated with rapid progression to ESRD and all-cause mortality. The RCRP model improves early identification of responsiveness based on variables collected during enrollment in a pre-ESRD program. Urgent attention should be given to characterize the underlying heterogeneous responsiveness to pre-dialysis care.

Gegen Qinlian Decoction Ameliorates Hyperuricemia-Induced Renal Tubular Injury via Blocking the Inflammatory Signaling Pathway

Background: Gegen Qinlian decoction (GGQLD) is a typical traditional Chinese medicine (TCM) prescription documented in Shang Han Lun. Clinically, GGQLD has been utilized to manage the inflammatory symptoms of metabolic diseases and to protect against renal damage in China. In the present study, a hypothesis was proposed that the multi-target solution of GGQLD produced anti-inflammatory effects on ameliorating hyperuricemia (HUA).

Methods: A total of 30 primary HUA patients receiving GGQLD treatment (two doses daily) for 4 weeks were selected. Then, differences in uric acid (UA) levels and expression of peripheral blood mononuclear cells (PBMCs) and urinary exosomes before and after treatment were analyzed. The therapeutic indexes for the active ingredients in GGQLD against HUA were confirmed through pharmacological subnetwork analysis. Besides, the HUA rat model was established through oral gavage of potassium oxonate and treated with oral GGQLD. In addition, proximal tubular epithelial cells (PTECs) were stimulated by UA and intervened with GGQLD for 48 h. Subsequently, RNA-seq, flow cytometry, and confocal immunofluorescence microscopy were further conducted to characterize the differences in UA-mediated inflammation and apoptosis of human renal tubular epithelial cells pre- and post-administration of GGQLD. In the meanwhile, quantitative real-time PCR (qPCR) was carried out to determine gene expression, whereas a western blotting (WB) assay was conducted to measure protein expression.

Results: Our network analysis revealed that GGQLD treated HUA via the anti-inflammatory and antiapoptotic pathways. Additionally, NLPR3 expression significantly decreased in PBMCs and urinary exosomes of HUA patients after GGQLD treatment. In vivo, GGQLD treatment alleviated HUA-induced renal inflammation, which was associated with decreased expression of NLRP3 inflammasomes and apoptosis-related mRNAs. Moreover, GGQLD promoted renal UA excretion by inhibiting the activation of GSDMD-dependent pyroptosis induced by NLRP3 inflammasomes and by reducing apoptosis via the mitochondrial apoptosis signaling pathway in vitro.

Conclusion: This study indicates that GGQLD efficiently reduces inflammatory responses while promoting UA excretion in HUA. Our findings also provide compelling evidence supporting the idea that GGQLD protects against the UA-mediated renal tubular epithelial cell inflammation through the mitochondrial apoptosis signaling pathways. Taken together, these findings have demonstrated a novel therapeutic method for the treatment of HUA.

Dose-response relationship between distinct serum uric acid trajectories and metabolic syndrome risk: A 5-year prospective cohort study

BACKGROUND AND AIMS

Although high serum uric acid (SUA) at baseline has been linked to increased risk for metabolic syndrome (MetS), the association of longitudinal SUA changes with MetS risk is unclear. We aimed to examine the effect of distinct SUA trajectories on new-onset MetS risk by sex in a Chinese cohort.

METHODS AND RESULTS

A total of 2364 women and 2770 men who were free of MetS in 2013 were enrolled in this study and followed up to 2018. Group-based trajectory modeling was applied to identify SUA trajectories. Cox proportional hazards model was used to evaluate the association between SUA trajectory and new-onset MetS. The dose-response relationship between SUA trajectories and MetS risk was examined by treating trajectory groups as a continuous variable. During a median follow-up of 48.0 months, 311 (13.16%) women and 950 (34.30%) men developed MetS. SUA trajectories (2013-2018) were defined as four distinct patterns in both women and men: "low", "moderate", "moderate-high", and "high". Compared with "low" SUA trajectory, the adjusted hazard ratio for incident MetS among participants with "moderate", "moderate-high" and "high" trajectory was in a dose-response manner: 1.75 (95% CI: 1.08-2.82), 1.94 (95% CI: 1.20-3.14), and 3.05 (95% CI: 1.81-5.13), respectively, for women; 1.20 (95% CI: 0.97-1.49), 1.48 (95% CI: 1.19-1.85), and 1.66 (95% CI: 1.25-2.21), respectively, for men.

CONCLUSIONS

Elevated SUA trajectories are associated with increased risk for new-onset MetS in women and men. Monitoring SUA trajectories may assist in identifying subpopulations at higher risk for MetS.

A longitudinal analysis of the relationship between serum uric acid and residual renal function loss in peritoneal dialysis patients

Background

Hyperuricemia occurs frequently in patients with continuous ambulatory peritoneal dialysis (CAPD). This study aimed to evaluate the impact of serum uric acid (UA) over time on residual renal function (RRF) loss in a cohort of patients with CAPD.

Methods

A total of 201 patients who started CAPD therapy between January 1, 2008 and April 30, 2016 were included in this single-center, retrospective cohort study. All patients were followed up until December 31, 2016. The median follow-up time was 23.43 ± 16.60 months. RRF loss was represented as the time to anuria.

Results

Eighty-six patients developed anuria within 5 years. Multivariate Cox regression analysis showed that time-averaged serum UA and peritonitis were independent risk factors for RRF loss, while weekly Kt/V urea was a protective factor. Cox proportional hazard regression models showed that both patients with time-averaged uric acid (TA-UA) < 6.77 mg/dL [hazard ratio (HR) = 1.165, 95% confidence interval (CI) 1.054–1.387; p < 0.05] and those with TA-UA≥ 7.64 mg/dL (HR = 1.184, 95% CI 1.045–2.114; p < 0.05) had a higher risk of RRF than those with TA-UA in the range of 6.77–7.64 mg/dL. Penalized spline smoothing also showed a U-shaped relationship between continuous UA and RRF loss.

Conclusion

The present study demonstrated that both high and low serum UA over time were associated with RRF loss in patients with CAPD.

Effects of losartan and enalapril on serum uric acid and GFR in children with proteinuria

BACKGROUND

Studies have shown that losartan reduces serum uric acid in adults, unlike angiotensin-converting enzyme inhibitors. A previous study demonstrated that losartan and enalapril had comparable effects on proteinuria in children.

METHODS

We conducted a post hoc analysis of results from a prospective trial in which the proteinuria-reducing effects of losartan and enalapril were compared. We have now evaluated (a) the effects of these medications on SUA in 248 children with proteinuria and (b) the correlation between changes in SUA and eGFR.

RESULTS

SUA levels after 36 months were found to be increased when compared to baseline in both losartan and enalapril groups. The mean change in SUA from baseline was significantly different at 12 months between 23 hypertensive patients randomised to losartan (3.69% decrease [95% CI 11.31%, 3.93%]) and 24 randomised to enalapril (12.57% increase [95% CI 3.72%, 21.41%]), p = 0.007. This significant difference remained after 24, 30 and 36 months but was observed in the entire group of 248 patients only at 12 months. There was a statistically significant negative correlation between changes in SUA and changes in eGFR at each time point over 36 months.

CONCLUSIONS

Losartan may have long-term beneficial effects on SUA and eGFR in children with proteinuria.

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.

Serum Uric Acid and Progression of Autosomal Dominant Polycystic Kidney Disease: Results from the HALT PKD Trials

BACKGROUND

Epidemiological studies have suggested that elevated serum uric acid may contribute to the progression of chronic kidney disease. However, no large prospective study has examined whether hyperuricemia is an independent risk factor for the progression of autosomal dominant polycystic kidney disease (ADPKD).

METHODS

We measured uric acid in stored serum samples from the 2-year study visit of 671 participants from the HALT PKD multicenter trials. Participants were categorized according to uric acid tertiles. For Study A (participants aged 15-49 years with preserved kidney function, n=350), we used linear mixed effects models to examine the association between uric acid and repeated measures of height-adjusted total kidney volume (htTKV), the primary outcome for Study A. For Study B (participants aged 18-64 with decreased kidney function, n=321), we used Cox proportional hazards models to assess the hazard for the combined endpoint of 50% loss in estimated glomerular filtration rate (eGFR), end-stage kidney disease (ESKD), or death, the primary outcome for Study B. To assess the association of uric acid with the slope of eGFR decline (secondary outcome of HALT A and B), we used linear mixed effects models for the combined population of Study A and B.

RESULTS

In the unadjusted model, the annual change in htTKV was 2.7% higher in the highest uric acid tertile compared to the lowest (p<0.001), but this difference became insignificant after adjustment for gender. Men had faster TKV growth than women (p<0.001). There was no difference in eGFR decline between the 3 uric acid tertiles. Hazard ratios for the clinical endpoint were 2.9 (95% confidence interval, 1.9-4.4) and 1.8 (1.1-2.8) respectively in the high and medium uric acid groups in unadjusted and partially adjusted models (p<0.001), but the significance was lost after adjustment for baseline eGFR. Results were similar when uric acid was examined as a continuous variable.

CONCLUSION

Elevated serum uric acid is not an independent risk factor for disease progression in ADPKD.

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.

Joint Longitudinal Low Calcium High Phosphorus Trajectory Associates with Accelerated Progression, Acute Coronary Syndrome and Mortality in Chronic Kidney Disease

The effects of long-term disturbance of the mineral metabolism on patients with chronic kidney disease (CKD) are unclear. We investigated whether the longitudinal Ca-P (joint calcium and phosphorus) trajectories are associated with incident end-stage renal disease (ESRD), acute coronary syndrome (ACS), and all-cause mortality in patients with CKD. We conducted a prospective cohort study by using data from a 13-year multidisciplinary pre-ESRD care registry. The final study population consisted of 4,237 CKD patients aged 20–90 years with data gathered from 2003 to 2015. Individuals’ Ca-P trajectories were defined using group-based multi-trajectory modeling into three distinct patterns: reference, moderately abnormal, and severely abnormal. Times to ESRD, ACS, and death were analyzed using multiple Cox regression. Compared with those with a “reference” Ca-P trajectory, the adjusted hazard ratios (aHRs) (95% confidence interval [CI]) for incidental ESRD were 5.92 (4.71–7.44) and 15.20 (11.85–19.50) for “moderately abnormal” and “severely abnormal” Ca-P trajectories, respectively. The corresponding aHRs for ACS were 1.94 (1.49–2.52) and 3.18 (2.30–4.39), and for all-cause mortality, they were 1.88 (1.64–2.16) and 2.46 (2.05–2.96) for “moderately abnormal” and “severely abnormal” Ca-P trajectories, respectively. For outcomes of progression to ESRD, the detrimental effects of abnormal Ca-P trajectories were more substantial in patients with CKD stage 3 than those with CKD stage 4 or 5 (p-value for interaction < 0.001). Future studies should validate reliable longitudinal cut-offs of serum phosphorus and consider the “lowering phosphorus— the lower the better, the earlier the better” approach to phosphorus control in CKD.

Dialysis timing may be deferred toward very late initiation: An observational study

The optimal timing to initiate dialysis among patients with an estimated glomerular filtration rate (eGFR) of <5 mL/min/1.73 m2 is unknown. We hypothesized that dialysis initiation time can be deferred in this population even with high uremic burden. A case-crossover study with case (0-30 days before dialysis initiation [DI]) and control (90-120 days before DI) periods was conducted in 1,079 hemodialysis patients aged 18-90 years at China Medical University Hospital between 2006 and 2015. The uremic burden was quantified based on 7 uremic indicators that reached the predefined threshold in case period, namely hemoglobin, serum albumin, blood urea nitrogen, serum creatinine, potassium, phosphorus, and bicarbonate. Dialysis timing was classified as standard (met 0-2 uremic indicators), late (3-5 indicators), and very late (6-7 indicators). Median eGFR-DI of the 1,079 patients was 3.4 mL/min/1.73 m2 and was 2.7 mL/min/1.73 m2 in patients with very late initiation. The median follow-up duration was 2.42 years. Antibiotics, diuretics, antihypertensive medications, and non-steroidal anti-inflammatory drugs (NSAIDs) were more prevalently used during the case period. The fully adjusted hazards ratios of all-cause mortality for the late and very late groups were 0.97 (95% confidence interval 0.76-1.24) and 0.83 (0.61-1.15) compared with the standard group. It is safe to defer dialysis initiation among patients with chronic kidney disease (CKD) having an eGFR of <5 mL/min/1.73 m2 even when patients having multiple biochemical uremic burdens. Coordinated efforts in acute infection prevention, optimal fluid management, and prevention of accidental exposure to NSAIDs are crucial to prolong the dialysis-free survival.

First-year estimated glomerular filtration rate variability after pre-end-stage renal disease program enrollment and adverse outcomes of chronic kidney disease

BACKGROUND

Scarce evidence associates the first-year estimated glomerular filtration rate (eGFR) variability and longitudinal change scales concomitantly to the risk of developing end-stage renal disease (ESRD), acute coronary syndrome (ACS) and death following pre-ESRD program enrollment in chronic kidney disease (CKD).

METHODS

We conducted a prospective cohort study of 5092 CKD patients receiving multidisciplinary care between 2003 and 2015 with careful ascertainment of ESRD, ACS and death during the follow-up. First-year eGFR variability and longitudinal change scales that were based on all first-year eGFR measurements included coefficient of variation of eGFR (eGFR-CV), percent change (eGFR-PC), absolute difference (eGFR-AD), slope (eGFR-slope) and area under the curve (AUC).

RESULTS

A total of 786 incident ESRD, 292 ACS and 410 death events occurred during the follow-up. In the multiple Cox regression, the fully adjusted hazard ratios (HRs) of progression to ESRD for each unit change in eGFR-CV, eGFR-PC, eGFR-AD, eGFR-slope, eGFR-AUC were 1.03 [95% confidence interval (CI) 1.02-1.04], 1.04 (1.03-1.04), 1.16 (1.14-1.18), 1.16 (1.14-1.17) and 1.04 (1.03-1.04), respectively. The adjusted HRs for incident ESRD comparing the extreme with the reference quartiles of eGFR-CV, eGFR-PC, eGFR-AD, eGFR-slope and eGFR-AUC were 2.67 (95% CI 2.11-3.38), 8.34 (6.33-10.98), 19.08 (11.89-30.62), 13.08 (8.32-20.55) and 6.35 (4.96-8.13), respectively. Similar direction of the effects on the risk of developing ACS and mortality was observed. In the 2 × 2 risk matrices, patients with the highest quartile of eGFR-CV and concomitantly with the most severely declining quartiles of any other longitudinal eGFR change scale had the highest risk of all outcomes.

CONCLUSIONS

The dynamics of eGFR changes, both overall variability and longitudinal changes, over the first year following pre-ESRD program enrollment are crucial prognostic factors for the risk of progression to ESRD, ACS and deaths among patients with CKD. A risk matrix combining the first-year eGFR variability and longitudinal change scales following pre-ESRD enrollment is a novel approach for risk characterization in CKD care. Randomized trials in CKD may be required to ascertain comparable baseline eGFR dynamics.

Uric acid and inflammation in kidney disease

Asymptomatic hyperuricemia is frequently observed in patients with kidney disease. Although a substantial number of epidemiologic studies have suggested that an elevated uric acid level plays a causative role in the development and progression of kidney disease, whether hyperuricemia is simply a result of decreased renal excretion of uric acid or is a contributor to kidney disease remains a matter of debate. Over the last two decades, multiple experimental studies have expanded the knowledge of the biological effects of uric acid beyond its role in gout. In particular, uric acid induces immune system activation and alters the characteristics of resident kidney cells, such as tubular epithelial cells, endothelial cells, and vascular smooth muscle cells, toward a proinflammatory and profibrotic state. These findings have led to an increased awareness of uric acid as a potential and modifiable risk factor in kidney disease. Here, we discuss the effects of uric acid on the immune system and subsequently review the effects of uric acid on the kidneys mainly in the context of inflammation.

Incidence and risk factors of type 2 diabetes mellitus in individuals with different fasting plasma glucose levels

OBJECTIVE

Our aim was to examine the incidence and risk factors of type 2 diabetes mellitus (T2DM) among individuals with different fasting plasma glucose (FPG) levels.

METHODS

According to the first FPG value recorded between January 2006 and December 2017, individuals without T2DM (FPG <7 mmol/L) were divided into three groups: normal fasting glucose (NFG, FPG < 5.6 mmol/L), slightly impaired fasting glucose (IFG_low, 5.6 mmol/L ⩽ FPG < 6.1 mmol/L), and severely impaired fasting glucose (IFG_high, 6.1 mmol/L ⩽ FPG < 7.0 mmol/L). Physical examination results, blood biochemical indicators, and questionnaire survey data were collected and the T2DM incidence was examined during the follow-up period. A Cox regression model was used to analyze the T2DM risk factors in the three groups.

RESULTS

A total of 44,852 individuals (55.33% men) were included in our study. During the follow-up period (mean follow-up time: 3.73 ± 0.01 years), 2912 T2DM cases occurred. The T2DM incidence rate of the NFG, IFG_low, and IFG_high groups were 1.5%, 22.2%, and 43.8%, respectively (p < 0.05). In the NFG group, the risk factors for T2DM were older age, overweight, obesity, hypertension, hyperuricemia, and increased estimated glomerular filtration rate (eGFR); the protective factors were female sex and high high-density lipoprotein cholesterol (HDL-C). In the IFG_low group, the risk factors for T2DM were older age, overweight, obesity, hypertension, and high total cholesterol (TC); the protective factors were increased triglyceride, low-density lipoprotein cholesterol (LDL-C), and HDL-C. In the IFG_high group, the risk factors for T2DM were older age, obesity, high eGFR, and high TC; the protective factors were female sex, hyperuricemia, high LDL-C, and high HDL-C (all, p < 0.05).

CONCLUSIONS

The increased T2DM rates were associated with increased FPG. Risk factors for T2DM vary in the NFG, IFG_low, and IFG_high groups.

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.

First-4-week erythrocyte sedimentation rate variability predicts erythrocyte sedimentation rate trajectories and clinical course among patients with pyogenic vertebral osteomyelitis

BACKGROUND

The trajectory pattern of erythrocyte sedimentation rate (ESR) in patients with pyogenic vertebral osteomyelitis (PVO) and its clinical significance is unclear. We further evaluated whether the first-4-week ESR variability can predict the trajectory pattern, treatment duration and recurrence of PVO.

METHODS

The longitudinal ESR patterns of adults with PVO within the first 6 months were characterized through group-based trajectory modeling (GBTM). The ESR variability within the first 4 weeks was defined using the absolute difference (AD), coefficient of variation, percent change, and slope change. The first-4-week ESR variabilities were analyzed using ordinal logistic regression to predict the 6-month ESR trajectory and using logistic regression to predict treatment duration and recurrence likelihood. The discrimination and calibration of the prediction models were evaluated.

RESULTS

Three ESR trajectory patterns were identified though GBTM among patients with PVO: Group 1, initial moderate high ESR with fast response; Group 2, initial high ESR with fast response; Group 3, initial high ESR with slow response. Group 3 patients (initial high ESR with slow response) were older, received longer antibiotic treatment, and had more comorbidities and higher recurrence rates than patients in the other two groups. The initial ESR value and ESR - AD could predict the 6-month ESR trajectory. By incorporating the first-4-week ESR variabilities and the clinical features of patients, our models exhibited moderate discrimination performance to predict prolonged treatment (≥12 weeks; C statistic, 0.75; 95% confidence interval [CI], 0.70 to 0.81) and recurrence (C statistic, 0.69; 95% CI, 0.61 to 0.78).

CONCLUSIONS

The initial ESR value and first-4-week ESR variability are useful markers to predict the treatment duration and recurrence of PVO. Future studies should validate our findings in other populations.

Acute Kidney Injury in the Outpatient Setting Associates with Risk of End-Stage Renal Disease and Death in Patients with CKD

Current acute kidney injury (AKI) diagnostic criteria are restricted to the inpatient setting. We proposed a new AKI diagnostic algorithm for the outpatient setting and evaluate whether outpatient AKI (AKI_OPT) modifies the disease course among patients with chronic kidney disease (CKD) enrolled in the national predialysis registry. AKI_OPT was detected when a 50% increase in serum creatinine level or 35% decline in eGFR was observed in the 180-day period prior to enrollment in the predialysis care program. Outcomes were progression to end-stage renal disease (ESRD) and all-cause mortality. Association analyses were performed using multiple Cox regression and coarsened exact matching (CEM) analysis. Among 6,046 patients, 31.5% (1,905 patients) had developed AKI_OPT within the 180-day period before enrollment. The adjusted hazard ratios of the 1-year and overall risk of ESRD among patients with preceding AKI_OPT compared with those without AKI_OPT were 2.61 (95% CI: 2.15-3.18) and 1.97 (1.72-2.26), respectively. For 1-year and overall risk of all-cause mortality, patients with AKI_OPT had respectively a 141% (95% CI: 89-209%) and 84% (56-117%) higher risk than those without AKI_OPT. This statistical inference remained robust in CEM analysis. We also discovered a complete reversal in the eGFR slope before and after the AKI_OPT from -10.61 ± 0.32 to 0.25 ± 0.30 mL/min/1.73 m² per year; however, the loss of kidney function is not recovered. The new AKI_OPT diagnostic algorithm provides prognostic insight in patients with CKD.

AMPK alleviates high uric acid-induced Na+-K+-ATPase signaling impairment and cell injury in renal tubules

One of the mechanisms in hyperuricemia (HUA)-induced renal tubular injury is the impairment of Na⁺-K⁺-ATPase (NKA) signaling, which further triggers inflammation, autophagy, and mitochondrial dysfunction and leads to cell injury. Here, we used RNA sequencing to screen the most likely regulators of NKA signaling and found that the liver kinase B1(LKB1)/adenosine monophosphate (AMP)-activated protein kinase (AMPK)/ mammalian target of rapamycin (mTOR) pathway was the most abundantly enriched pathway in HUA. AMPK is a key regulator of cell energy metabolism; hence, we examined the effect of AMPK on HUA-induced dysregulation of NKA signaling and cell injury. We first detected AMPK activation in high uric acid (UA)-stimulated proximal tubular epithelial cells (PTECs). We further found that sustained treatment with the AMPK activator 5-aminoimidazole-4-carboxamide 1-β-d-ribofuranoside (AICAR), but not the AMPK inhibitor Compound C, significantly alleviated UA-induced reductions in NKA activity and NKA α1 subunit expression on the cell membrane by reducing NKA degradation in lysosomes; sustained AICAR treatment also significantly alleviated activation of the NKA downstream molecules Src and interleukin-1β (IL-1β) in PTECs. AICAR further alleviated high UA-induced apoptosis, autophagy, and mitochondrial dysfunction. Although AMPK activation by metformin did not reduce serum UA levels in hyperuricemic rats, it significantly alleviated HUA-induced renal tubular injury and NKA signaling impairment in vivo with effects similar to those of febuxostat. Our study suggests that AMPK activation may temporarily compensate for HUA-induced renal injury. Sustained AMPK activation could reduce lysosomal NKA degradation and maintain NKA function, thus alleviating NKA downstream inflammation and protecting tubular cells from high UA-induced renal tubular injury.

High serum levels of uric acid cause kidney tissue damage through cellular processes that have now been identified by researchers in China. Uric acid is a common component of urine, but causes damage if it is present in high levels in the blood (hyperuricemia). While investigating the mechanisms behind hyperuricemia, Zhibin Ye and co-workers at Fudan University in Shanghai recently showed that impairment of the Na⁺-K⁺-ATPase (NKA) signaling pathway, which regulates uric acid transportation through the kidneys, is a crucial feature of renal damage progression. The team have now shown that NKA is regulated by the AMP-activated protein kinase (AMPK) pathway, and that AMPK is enriched during the initial phases of hyperuricemia. Studies on rat models indicated that sustained AMPK activation restored NKA signaling, limiting damage from hyperuricemia.

Automation of the kidney function prediction and classification through ultrasound-based kidney imaging using deep learning

Prediction of kidney function and chronic kidney disease (CKD) through kidney ultrasound imaging has long been considered desirable in clinical practice because of its safety, convenience, and affordability. However, this highly desirable approach is beyond the capability of human vision. We developed a deep learning approach for automatically determining the estimated glomerular filtration rate (eGFR) and CKD status. We exploited the transfer learning technique, integrating the powerful ResNet model pretrained on an ImageNet dataset in our neural network architecture, to predict kidney function based on 4,505 kidney ultrasound images labeled using eGFRs derived from serum creatinine concentrations. To further extract the information from ultrasound images, we leveraged kidney length annotations to remove the peripheral region of the kidneys and applied various data augmentation schemes to produce additional data with variations. Bootstrap aggregation was also applied to avoid overfitting and improve the model's generalization. Moreover, the kidney function features obtained by our deep neural network were used to identify the CKD status defined by an eGFR of <60 ml/min/1.73 m2. A Pearson correlation coefficient of 0.741 indicated the strong relationship between artificial intelligence (AI)- and creatinine-based GFR estimations. Overall CKD status classification accuracy of our model was 85.6% -higher than that of experienced nephrologists (60.3%-80.1%). Our model is the first fundamental step toward realizing the potential of transforming kidney ultrasound imaging into an effective, real-time, distant screening tool. AI-GFR estimation offers the possibility of noninvasive assessment of kidney function, a key goal of AI-powered functional automation in clinical practice.

Longitudinal lipid trends and adverse outcomes in patients with CKD: a 13-year observational cohort study

Studies on the effects of longitudinal lipid trajectories on end-stage renal disease (ESRD) development and deaths among patients with chronic kidney disease (CKD) are limited. We conducted a registry-based prospective study using data from a 13-year multidisciplinary pre-ESRD care program. The final study population comprised 4,647 patients with CKD. Using group-based trajectory modeling, we dichotomized longitudinal trajectories of total cholesterol (T-CHO), triglyceride (TG), LDL cholesterol (LDL-C), and HDL cholesterol (HDL-C). Time to ESRD or death was analyzed using multiple Cox regression. At baseline, higher levels of T-CHO and LDL-C were associated with rapid progression to ESRD, whereas only HDL-C was positively associated with all-cause mortality [adjusted hazard ratio (HR), 1.20; 95% CI, 1.06-1.36; P-value, 0.005]. Compared with those with a normal T-CHO trajectory, the fully adjusted HR of patients with a high T-CHO trajectory for ESRD risk was 1.21 (P-value, 0.019). Subgroup analysis showed that a high TG trajectory was associated with a 49% increase in mortality risk in CKD patients without diabetes (P-value for interaction, 0.012). In contrast to what was observed based on baseline HDL-C, patients with a trajectory of frequent hypo-HDL cholesterolemia had higher risk of all-cause mortality (adjusted HR, 1.53; P-value, 0.014). Thus, only T-CHO, both at baseline and over the longitudinal course, demonstrated a significant potential risk of incident ESRD. The inconsistency in the observed directions of association between baseline levels and longitudinal trajectories of HDL-C warrants further research to unveil specific pathogenic mechanisms underlying the HDL-C metabolism in patients with CKD.

Association between post-transplant uric acid level and renal allograft fibrosis: Analysis using Banff pathologic scores from renal biopsies

Several experimental studies implicate uric acid in renal injury and fibrosis. The objective of this study was to examine the association between uric acid level and allograft fibrosis after kidney transplantation. 241 adult patients who underwent kidney transplantation between 2003 and 2014 were divided into three groups according to the sex specific tertiles of mean uric acid level within the first post-transplant year. The renal biopsies performed during 1 to 5 post-transplant year were analyzed to compare the degree of interstitial fibrosis and tubular atrophy (IF/TA). Mean interval between kidney transplantation and biopsy was similar between groups (23.7 ± 15.3 vs. 30.0 ± 18.6 vs. 27.5 ± 18.5 months, P = 0.072). The higher tertile uric acid level was, the more advanced grade of IF/TA was shown (P = 0.001). Multivariate analysis identified uric acid tertile was independent risk factor for severe IF/TA (odds ratio [95% confidence interval] was 3.16 [1.13-8.82] for tertile 2 and 3.70 [1.25-10.93] for tertile 3, versus tertile 1, respectively). Other independent factors were estimated glomerular filtration rate at 1year post-transplant (0.80 [CI 0.65-0.98]) and biopsy-proven rejection (2.34 [1.05-5.21]). Graft survival over 10 years was significantly lower in tertile 3 (P = 0.041). The results showed that higher uric acid level after kidney transplantation was associated with more severe IF/TA.