High uric acid and low superoxide dismutase as possible predictors of all-cause and cardiovascular mortality in hemodialysis patients

Association between nutritional, inflammatory and oxidative status (NIOS) and risk of adverse outcomes in patients on haemodialysis (HD): the NIOS-HD prospective cohort study protocol

INTRODUCTION

The mortality of patients on chronic haemodialysis is 10-30 times greater than that of the general population and over 60% of these individuals die within the first 5 years of beginning haemodialysis. Although causes for excessive mortality in haemodialysis patients are not clearly defined, it seems that nutrition, inflammation and oxidative stress play key roles in this regard. Until now, no cohort study has focused on the association between nutritional, inflammatory or oxidative status and risk of complications and adverse outcomes in Iranian haemodialysis patients. Therefore, we sought to fill this gap and designed the Nutritional, Inflammatory, and Oxidative Status in Hemodialysis (NIOS-HD) prospective cohort study to determine the association of dietary factors, malnutrition, anthropometric indices, body composition, inflammation and oxidative stress with quality of life, dialysis access infections, hospitalisation, potential years of life lost and mortality in adults on maintenance haemodialysis in Isfahan, Iran.

METHODS AND ANALYSIS

The sample size of this cohort was estimated to be 300 participants. At baseline, demographic, medical and dialysis-related data of eligible patients will be recorded. In addition, participants will undergo anthropometric measurements, malnutrition assessment and body composition analysis. Also, their dietary intake and quality of life will be evaluated through interviewer-administered questionnaires. Moreover, their fasting blood samples will be collected and stored for biochemical assays including transthyretin, albumin, serum amyloid A, pentraxin-3, trimethylamine N-oxide, myeloperoxidase, paraoxonase-1 and superoxide dismutase. After baseline evaluation, patients will be followed up to 3 years to update exposure information (except biochemical assays) and measure adverse outcomes. Finally, collected data will be analysed using descriptive and inferential statistics.

ETHICS AND DISSEMINATION

The NIOS-HD is in agreement with the Declaration of Helsinki and has been approved by the Ethics Committee of Isfahan University of Medical Sciences (reference number: IR.MUI.

RESEARCH

REC.1399.605). Findings of this study will be published in academic journals.

The association between the serum uric acid to creatinine ratio and all-cause mortality in elderly hemodialysis patients

BACKGROUND

Elderly hemodialysis patients have a higher rate of mortality than nonelderly hemodialysis patients. Recent studies shown that the serum uric acid to creatinine ratio (SUA/Scr) was associated with all-cause mortality in general adults. The purpose of the present study was to investigate the association between the SUA/Scr and all-cause and cardiovascular disease mortality among elderly hemodialysis patients.

METHODS

A total of 222 patients (≥ 60 years) who received hemodialysis more than 8 h per week at Taizhou Second People's Hospital for at least 3 months were enrolled in the present study from January 2015 to December 2019. Clinical characteristics including age, sex and height et. al, were obtained from the hemodialysis database. The laboratory data, including albumin (ALB), total cholesterol (TC), serum uric acid (SUA), serum creatinine (Scr) and so on, were collected before hemodialysis and analyzed by automatic biochemical analyzer. Survival information was recorded during the follow-up period. Multiple Cox regression was carried out to analyze the association between SUA/Scr and all-cause mortality. The survival rate of each group was calculated by the Kaplan-Meier method, and the ratio of survival curves was analyzed by the log-rank test. The contribution of SUA/Scr for predicting all-cause mortality risk was evaluated by net reclassification improvement (NRI).

RESULTS

During the 19-month observation period, 78 patients died. Individuals in the nonsurviving group had significantly older ages (P < 0.001), body mass index (BMI) (P = 0.004), serum creatinine (P = 0.005) and prealbumin (P = 0.006) than surviving patients. After adjusting for age, sex, BMI, prealbumin, dialysis vintage, dialysis frequency, single-pool Kt/V (spKt/V), DM, hypertension and comorbidities, a higher ratio of SUA/Scr was independently associated with a higher risk of all-cause mortality (HR: 1.292; 95% CI: 1.013-1.648; P = 0.039). The predict value on all-cause mortality of SUA/Scr was superior to SUA (additive NRI = 0.214, P = 0.015) and Scr (additive NRI = 0.476, P < 0.001) among elderly hemodialysis patients.

CONCLUSION

The serum uric acid to creatinine ratio is strongly associated with all-cause mortality in elderly hemodialysis patients which is more predictive than SUA or Scr alone.

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

BACKGROUND

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

METHOD

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

RESULTS

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

CONCLUSIONS

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

Dysfunctional ABCG2 gene polymorphisms are associated with serum uric acid levels and all-cause mortality in hemodialysis patients

Dysfunctional variants of ATP-binding cassette transporter subfamily G member 2 (ABCG2), a urate transporter in the kidney and intestine, are the major causes of hyperuricemia and gout. A recent study found that ABCG2 is a major transporter of uremic toxins; however, few studies have investigated the relationship between ABCG2 gene polymorphisms and mortality. This prospective cohort study of 1214 hemodialysis patients investigated the association between serum uric acid levels and ABCG2 genotype and mortality. Genotyping of dysfunctional ABCG2 variants, Q126X (rs72552713) and Q141K (rs2231142), was performed using the patients’ DNA. During the study period, 220 patients died. Lower serum uric acid levels were associated with higher mortality (hazard ratio [HR] 1.89, 95% confidence interval [CI] 1.14–3.10, P ≤ 0.001). ABCG2 dysfunction, estimated by genetic variants, had a significant positive association with serum uric acid levels (full function: 7.4 ± 1.2 mg/dl, 3/4 function: 7.9 ± 1.3 mg/dl, 1/2 function: 8.2 ± 1.4 mg/dl, ≤ 1/4 function: 8.7 ± 1.3 mg/dl, P ≤ 0.001). This association remained significant on multiple regression analysis. The Cox proportional hazard analysis indicated that the ABCG2 ≤ 1/4 function type was significantly associated with higher mortality (HR 6.66, 95% CI 2.49 to 17.8, P ≤ 0.001) than the other function types. These results showed that ABCG2 plays a physiologically important role in uric acid excretion, and that ABCG2 dysfunction is a risk factor for mortality in hemodialysis patients.

Serum uric acid and cardiovascular mortality in chronic kidney disease: a meta-analysis

Background

Conflicting results have been reported from studies evaluating serum uric acid (SUA) levels as an independent risk factor for cardiovascular mortality in patients with chronic kidney disease (CKD).

Methods

We systematically searched MEDLINE, Web of Science, and bibliographies of retrieved articles to identify studies reporting on the association between SUA levels and cardiovascular mortality in patients with CKD. Random-effects models were used to calculate the pooled hazard ratios (HR) and corresponding 95% confidence intervals (CI).

Results

We included 11 studies with an overall sample of 27,081 patients with CKD in this meta-analysis. By meta-analysis, restricted to 7 studies (n = 11,050), patients with the highest SUA were associated with an increased risk of cardiovascular mortality (HR 1.47, 95% CI 1.11–1.96) compared with patients with the lowest SUA. There was no indication of publication bias or significant heterogeneity (I² = 40.4%; P = 0.109). Meta-analysis of 10 studies (n = 26,660) indicated that every 1 mg/dl increase in SUA levels increased a 12% risk in cardiovascular mortality (HR 1.12, 95% CI 1.02–1.24), with significant heterogeneity (I² = 79.2%, P < 0.001).

Conclusions

Higher SUA levels are associated with significantly increased risk of cardiovascular mortality in patients with CKD. More designed studies, especially randomized controlled trials, should be conducted to determine whether high SUA levels is a potentially modifiable risk factor for cardiovascular mortality in patients with CKD.

Electronic supplementary material

The online version of this article (10.1186/s12882-018-1143-7) contains supplementary material, which is available to authorized users.

Serum uric acid and mortality in chronic kidney disease: A systematic review and meta-analysis

BACKGROUND

Studies have shown inconsistent results about the association between serum uric acid levels and mortality in patients with chronic kidney disease (CKD).

METHODS

A systematic literature search in MEDLINE, Web of Science and bibliographies of retrieved articles was performed to identify studies investigating the association between serum uric acid and mortality in patients with CKD. Pooled hazard ratios (HR) and corresponding 95% confidence intervals (CIs) were calculated using random-effects models.

RESULTS

A total of 24 studies with 25,453 patients with CKD were included. By meta-analysis, patients with the highest serum uric acid level were associated with a significantly higher risk for mortality (14 studies; HR, 1.52; 95% CI, 1.33-1.73) compared with patients with the lowest serum uric acid level. For dose-response analysis, a linear relationship (8 studies; Pfor non-linearity=0.14) between serum uric acid levels and risk of mortality was found. Overall, an increase of 1mg/dl in serum uric acid level was associated with an 8% increased risk of mortality (21 studies; HR, 1.08; 95% CI, 1.04-1.11).

CONCLUSIONS

Elevated serum uric acid levels are significantly associated with risk of mortality in patients with CKD. Further randomized controlled trials should attempt to determine whether it improves survival to target serum uric acid in patients with CKD.

Serum uric acid predicts cardiovascular mortality in male peritoneal dialysis patients with diabetes

BACKGROUND AND AIMS

Serum uric acid may predict mortality in diabetic patients and dialysis patients. However, the relationship between serum uric acid and prognosis in diabetic peritoneal dialysis (PD) patients is unclear.

METHODS AND RESULTS

We conducted a cohort study of 1278 incident PD patients, (mean age 47.6 years), of which 328 (25.7%) had diabetes and 289 (22.6%) had diabetic nephropathy. During a median follow-up period of 30.7 months, 231 deaths occurred, of which 126 were ascribed to cardiovascular events. Mean serum uric acid was lower for diabetic patients than non-diabetic patients (6.8 ± 1.3 vs. 7.4 ± 1.4 mg/dL, respectively; P < 0.001). Cox regression models were adjusted for glycated hemoglobin, dialysis-related factors, traditional risk factors, and treatments. After adjustments, the highest sex-specific tertile of uric acid was associated with an increased risk of cardiovascular mortality (HR, 2.26; 95% CI, 1.14-4.48) compared to the lowest tertile in diabetic patients. Adjusted HRs per 1 mg/dL higher uric acid for all-cause and cardiovascular mortality were 1.09 (95% CI, 0.91-1.32) and 1.42 (95% CI, 1.13-1.79) for diabetic men and 1.06 (95% CI, 0.83-1.35) and 1.12 (95% CI, 0.78-1.61) for diabetic women, respectively. Elevated serum uric acid predicted a higher risk of all-cause and cardiovascular mortality in non-diabetic men but not in non-diabetic women.

CONCLUSIONS

Elevated serum uric acid is an independent predictor of cardiovascular mortality in diabetic male PD patients.

Hyperuricemia and chronic kidney disease: an enigma yet to be solved

The role of uric acid (UA) on the pathogenesis and progression of chronic kidney disease (CKD) remains controversial. Experimental and clinical studies indicate that UA is associated with several risk factors of CKD including diabetes, hypertension, oxidative stress, and inflammation and hyperuricemia could be considered as a common dominator linking CKD and cardiovascular disease. Notably, the impact of serum UA levels on the survival of CKD, dialysis patients, and renal transplant recipients is also a matter of debate, as there are conflicting results from clinical studies. At present, there is no definite data whether UA is causal, compensatory, coincidental or it is only an epiphenomenon in these patients. In this article, we attempt to review and elucidate the dark side of this old molecule in CKD and renal transplantation.

Association between allopurinol and mortality among Japanese hemodialysis patients: results from the DOPPS

Purpose

Allopurinol, for treating hyperuricemia, is associated with lower mortality among hyperuricemic patients without chronic kidney disease (CKD). Greater allopurinol utilization in hemodialysis (HD) in Japan versus other countries provides an opportunity for understanding allopurinol-related HD outcomes.

Methods

Data from 6,252 Japanese HD patients from phases 1–3 of the Dialysis Outcomes and Practice Patterns Study (1999–2008) at ~60 facilities per phase were analyzed. Mortality was compared for patients prescribed (25 %) versus not-prescribed allopurinol using Cox regression, overall, and in patient subgroups.

Results

Patients prescribed allopurinol were more likely to be younger, male, and non-diabetic, and had higher serum creatinine and lower (treated) serum uric acid levels (mean = 7.0 vs. 8.0 mg/dL, p < 0.001). The inverse association between allopurinol prescription and mortality in unadjusted analyses (HR 0.65, 95 % CI 0.52–0.81) was attenuated by covariate adjustment (HR 0.84, 0.66–1.06). In subgroup analyses, allopurinol was associated with lower mortality among patients with no history of cardiovascular disease (CVD) (HR 0.48, 0.28–0.83), but not among patients with CVD (HR 1.00, 0.76–1.32). A similar pattern was seen outside Japan and for cardiovascular (CV)-related mortality.

Conclusions

Allopurinol prescription was not significantly associated with case-mix-adjusted mortality in Japanese HD patients overall, but was associated with lower all-cause and CV-related mortality in the subgroup of patients with no prior CVD history. These findings in HD patients may be related to findings in non-dialysis CKD patients showing lower CV event rates and mortality, and improved endothelial function with allopurinol prescription. These results are useful for designing future trials of allopurinol use in HD patients.