High-normal serum uric acid is associated with impaired glomerular filtration rate in nonproteinuric patients with type 1 diabetes

Efficacy of dotinurad in patients with severe renal dysfunction

BACKGROUND

Although hyperuricemia is associated with the progression of chronic kidney disease (CKD), a reduction in CKD progression by uric acid (UA)-lowering therapy has been controversial. Recently, dotinurad, a uricosuric drug with selective urate reabsorption inhibitory properties, has been developed. However, its efficacy in lowering serum UA levels and its effects on renal function in patients with severe renal dysfunction are unclear. Thus, this study aimed to determine the effects of dotinurad on renal function in patients with severe renal dysfunction.

METHODS

Data from 53 outpatients with hyperuricemia who newly received dotinurad between December 2020 and October 2022 were retrospectively analyzed. The mean baseline estimated glomerular filtration rate (eGFR) was 38.7 ± 17.0 mL/min/1.73 m2. The patients were divided into three groups based on their baseline eGFR: eGFR < 30 (n = 17), 30 ≤ eGFR < 45 (n = 17), and eGFR ≥ 45 (n = 19).

RESULTS

The mean follow-up period was 9.8 ± 4.5 (range, 3-21) months. Serum UA levels significantly decreased in all groups. Although eGFR did not significantly change in patients with 30 ≤ eGFR < 45 and eGFR ≥ 45 (P = 0.918 and P = 0.535, respectively), it improved significantly in patients with eGFR < 30 (P = 0.032). The proportion of patients with improved eGFR was significantly higher in patients with eGFR < 30 (P = 0.038) than in patients with 30 ≤ eGFR < 45 and eGFR ≥ 45. In the multivariate logistic regression analysis, baseline eGFR < 30 and achieving a serum UA level of ≤ 6.0 mg/dL were significantly associated with improved eGFR (P = 0.033 and P = 0.015, respectively).

CONCLUSIONS

Dotinurad may have UA-lowering effects and the potential to improve kidney function in patients with severe renal dysfunction.

Association of uric acid with the decline in estimated glomerular filtration rate in middle-aged and elderly populations: evidence based on the China Health and Retirement Longitudinal Study

OBJECTIVE

Whether uric acid (UA) has an effect on renal function remains controversial. We aimed to investigate the association between serum UA with the decline in estimated glomerular filtration rate (eGFR) in middle-aged and elderly populations in the China Health and Retirement Longitudinal Study (CHARLS).

DESIGN

Longitudinal cohort study.

SETTING

This was a second analysis of a public dataset (CHARLS).

PARTICIPANTS

In this study, 4538 middle-aged and elderly individuals were screened after removing individuals younger than 45 years old, with kidney disease, malignant tumour and missing values.

OUTCOME MEASURES

Blood tests were performed both in 2011 and 2015. Decline in eGFR was defined as an eGFR decrease of more than 25% or deterioration of the eGFR stage during the 4-year follow-up period. Logistic models corrected for multiple covariables were used to analyse the association of UA with the decline in eGFR.

RESULTS

The median (IQR) concentrations of serum UA grouped by quartiles were 3.1 (0.6), 3.9 (0.3), 4.6 (0.4) and 5.7 (1.0) mg/dL, respectively. After multivariable adjustment, the OR of the decline in eGFR was higher for quartile 2 (3.5-<4.2 mg/dL: OR 1.44; 95% CI 1.07 to 1.64; p<0.01), quartile 3 (4.2-<5.0 mg/dL: OR 1.72; 95% CI 1.36 to 2.18; p<0.001) and quartile 4 (≥5.0 mg/dL: OR 2.04; 95% CI 1.58 to 2.63; p<0.001) when compared with quartile 1 (<3.5 mg/dL), and the p value for the trend was <0.001.

CONCLUSIONS

Over a 4-year follow-up period, we found that elevated UA was associated with a decline in eGFR in the middle-aged and elderly individuals with normal renal function.

Could uric acid to high density lipoprotein-cholesterol ratio be considered as a marker of hemodialysis sufficiency?

Aim: Hemodialysis (HD) is one of the most widely utilized renal replacement therapies in individuals with end-stage chronic kidney disease (CKD). The purpose of this study was to compare the Uric acid to HDL cholesterol ratio (UHR) levels of well-treated HD patients to those of those who had inadequate HD therapy. Materials and Methods: Data on HD patients were acquired from patient files and the institution's database. A URR value of more than 70% designated the sufficient HD group, whereas less than 70% defined the insufficient HD group. Furthermore, laboratory data, such as the UHR of the study groups, were compared. Results: The UHRs for adequate and inadequate HD were 0.160±04 and 0.20±0.07, respectively. The UHR of patients with insufficient HD was substantially greater than that of the subjects with sufficient HD (p=0.004). Besides, UHR was substantially and positively connected with urea before HD (r=0.37, p=0.001), urea after HD (r=0.39, p=0.001), serum creatinine before HD (r=0.48, p0.001), serum creatinine after HD (r=0.45, p0.001), and negatively correlated with URR (r=-0.29, p=0.008), according to correlation analyses. In individuals with chronic renal disease, a UHR value higher than 0.16 exhibited 67% sensitivity and 57% specificity in detecting inadequate HD. Conclusion: We propose that UHR, in addition to URR, might be used to determine HS sufficiency in CKD patients undergoing HD therapy.

Total extract of Abelmoschus manihot L. alleviates uric acid-induced renal tubular epithelial injury via inhibition of caspase-8/caspase-3/NLRP3/GSDME signaling

Purpose: The incidence of uric acid (UA)-induced kidney injury is increasing owing to the high incidence of hyperuricemia in recent years. The flower of Abelmoschus manihot (Linneus) Medik is a traditional Chinese medicinal herb widely used in the treatment of some kidney diseases. In our previous study, we reported that the total extract of A. manihot L. flower (TEA) attenuated adriamycin-induced renal tubular cell injury. In this study, we aimed to evaluate the role of TEA in UA-induced tubular cell injury.

Methods: Normal rat proximal epithelial NRK-52E cells were incubated with UA to mimic hyperuricemia conditions. The role of TEA in the renal tubular cells was also assessed. The cellular morphology was observed using phase-contrast microscopy, and cell viability was analyzed using the Cell Counting kit-8. Living and dead cells were stained using a Calcein-AM/PI double stain kit. The release of lactate dehydrogenase (LDH) was analyzed by LDH cytotoxicity Assay Kit. The expression of target proteins was analyzed using western blot analysis.

Results: UA triggered NRK-52E cell injury, as evidenced by morphological changes, detachment of cells from the bottom, cell swelling, large bubbles blowing from cell membrane and loss of cell viability. UA increased release of LDH. UA induced the expression of p-ERK1/2 and the subsequent activation of caspase-8, caspase-3, and NLRP3 inflammasomes. Pyroptosis was elicited by UA after gasdermin E N-terminal (GSDME-NT) was cleaved from gasdermin E (GSDME). Z-DEVD-FMK, a caspase-3 inhibitor, suppressed the expression of both NLRP3 and GSDME-NT, but not that of caspase-8. INF39, an NLRP3 inhibitor, altered the expression of GSDME-NT expression, but not that caspase-3 and caspase-8. TEA alleviated UA-induced cell injury by suppressing ERK1/2/caspase-8/caspase-3/NLRP3/GSDME signaling.

Conclusion: GSDME-mediated pyroptosis was involved in UA-induced renal tubular cell injury. This is the first study to report that TEA protects renal tubular epithelial cells against UA by inhibiting the ERK/1/2/caspase-8/caspase-3/NLRP3/GSDME pathway.

Association of Uric Acid-Lowering Therapy With Incident Chronic Kidney Disease

IMPORTANCE

Uric acid is a waste metabolite produced from the breakdown of purines, and elevated serum uric acid levels are associated with higher risk of hypertension, cardiovascular disease, and mortality and progression of chronic kidney disease (CKD). Treatment of hyperuricemia in patients with preexisting CKD has not been shown to improve kidney outcomes, but the associations of uric acid-lowering therapies with the development of new-onset kidney disease in patients with estimated glomerular filtration rate (eGFR) within reference range and no albuminuria is unclear.

OBJECTIVE

To examine the association of initiating uric acid-lowering therapy with the incidence of CKD.

DESIGN, SETTING, AND PARTICIPANTS

This cohort study included patients with eGFR of 60 mL/min/1.73 m2 or greater and no albuminuria treated at US Department of Veterans Affairs health care facilities from 2004 to 2019. Clinical trial emulation methods, including propensity score weighting, were used to minimize confounding. Data were analyzed from 2020 to 2022.

EXPOSURE

Newly started uric acid-lowering therapy.

MAIN OUTCOMES AND MEASURES

The main outcomes were incidences of eGFR less than 60 mL/min/1.73 m2, new-onset albuminuria, and end-stage kidney disease.

RESULTS

A total of 269 651 patients were assessed (mean [SD] age, 57.4 [12.5] years; 252 171 [94%] men). Among these, 29 501 patients (10.9%) started uric acid-lowering therapy, and 240 150 patients (89.1%) did not. Baseline characteristics, including serum uric acid level, were similar among treated and untreated patients after propensity score weighting. In the overall cohort, uric acid-lowering therapy was associated with higher risk of both incident eGFR less than 60 mL/min/1.73 m2 (weighted subhazard ratio [SHR], 1.15 [95% CI, 1.10-1.20; P < .001) and incident albuminuria (SHR, 1.05 [95% CI, 1.01-1.09; P < .001) but was not associated with the risk of end-stage kidney disease (SHR, 0.96 [95% CI, 0.62-1.50]; P = .87). In subgroup analyses, the association of uric acid-lowering therapy with worse kidney outcomes was limited to patients with baseline serum uric acid levels of 8 mg/dL or less.

CONCLUSIONS AND RELEVANCE

These findings suggest that in patients with kidney function within reference range, uric acid-lowering therapy was not associated with beneficial kidney outcomes and may be associated with potential harm in patients with less severely elevated serum uric acid levels.

Early Trajectory of Estimated Glomerular Filtration Rate and Long-term Advanced Kidney and Cardiovascular Complications in Type 1 Diabetes

OBJECTIVE

Rapid loss of estimated glomerular filtration rate (eGFR) within its normal range has been proposed as a strong predictor of future kidney disease. We investigated this association of eGFR slope early in the course of type 1 diabetes with long-term incidence of kidney and cardiovascular complications.

RESEARCH DESIGN AND METHODS

The annual percentage change in eGFR (slope) was calculated during the Diabetes Control and Complications Trial (DCCT) for each of 1,441 participants over a mean of 6.5 years and dichotomized by the presence or absence of early rapid eGFR loss (slope ≤-3% per year) as the exposure of interest. Outcomes were incident reduced eGFR (eGFR <60 mL/min/1.73 m2), composite cardiovascular events, or major adverse cardiovascular events (MACE) during the subsequent 24 years post-DCCT closeout follow-up.

RESULTS

At DCCT closeout (the baseline for this analysis), diabetes duration was 12 ± 4.8 years, most participants (85.9%) had normoalbuminuria, mean eGFR was 117.0 ± 13.4 mL/min/1.73 m2, and 149 (10.4%) had experienced early rapid eGFR loss over the preceding trial phase. Over the 24-year subsequent follow-up, there were 187 reduced eGFR (6.3 per 1,000 person-years) and 113 MACE (3.6 per 1,000 person-years) events. Early rapid eGFR loss was associated with risk of reduced eGFR (hazard ratio [HR] 1.81, 95% CI 1.18-2.79, P = 0.0064), but not after adjustment for baseline eGFR level (HR 0.94, 95% CI 0.53-1.66, P = 0.84). There was no association with composite cardiovascular events or MACE.

CONCLUSIONS

In people with type 1 diabetes primarily with normal eGFR and normoalbuminuria, the preceding slope of eGFR confers no additional association with kidney or cardiovascular outcomes beyond knowledge of an individual's current level.

Xanthine oxidoreductase inhibitor topiroxostat ameliorates podocyte injury by inhibiting the reduction of nephrin and podoplanin

BACKGROUND

Topiroxostat, an inhibitor of xanthine oxidoreductase (XOR) was shown to reduce urinary albumin excretion of hyperuricemic patients with chronic kidney disease. However, its pharmacological mechanism is not well understood. In this study, we examined the effects of topiroxostat on glomerular podocytes. Podocyte is characterized by foot process and a unique cell-cell junction slit diaphragm functioning as a final barrier to prevent proteinuria.

METHODS

The effects of topiroxostat on the expressions of podocyte functional molecules were analysed in db/db mice, a diabetic nephropathy model, anti-nephrin antibody-induced rat podocyte injury model and cultured podocytes treated with adriamycin.

RESULTS

Topiroxostat treatment ameliorated albuminuria in db/db mice. The expression of desmin, a podocyte injury marker was increased, and nephrin and podocin, key molecules of slit diaphragm, and podoplanin, an essential molecule in maintaining foot process were downregulated in db/db mice. Topiroxostat treatment prevented the alterations in the expressions of these molecules in db/db mice. XOR activity in kidney was increased in rats with anti-nephrin antibody-induced podocyte injury. Topiroxostat treatment reduced XOR activity and restored the decreased expression of nephrin, podocin and podoplanin in the podocyte injury. Furthermore, topiroxostat enhanced the expression of podoplanin in injured human cultured podocytes.

CONCLUSIONS

Podocyte injury was evident in db/db mice. Topiroxostat ameliorated albuminuria in diabetic nephropathy model by preventing podocyte injury. Increase of XOR activity in kidney contributes to development of podocyte injury caused by stimulation to slit diaphragm. Topiroxostat has an effect to stabilize slit diaphragm and foot processes by inhibiting the reduction of nephrin, podocin and podoplanin.

Xanthine oxidoreductase inhibitor topiroxostat ameliorates podocyte injury by inhibiting the reduction of nephrin and podoplanin

BACKGROUND

Topiroxostat, an inhibitor of xanthine oxidoreductase (XOR) was shown to reduce urinary albumin excretion of hyperuricemic patients with chronic kidney disease. However, its pharmacological mechanism is not well understood. In this study, we examined the effects of topiroxostat on glomerular podocytes. Podocyte is characterized by foot process and a unique cell-cell junction slit diaphragm functioning as a final barrier to prevent proteinuria.

METHODS

The effects of topiroxostat on the expressions of podocyte functional molecules were analysed in db/db mice, a diabetic nephropathy model, anti-nephrin antibody-induced rat podocyte injury model and cultured podocytes treated with adriamycin.

RESULTS

Topiroxostat treatment ameliorated albuminuria in db/db mice. The expression of desmin, a podocyte injury marker was increased, and nephrin and podocin, key molecules of slit diaphragm, and podoplanin, an essential molecule in maintaining foot process were downregulated in db/db mice. Topiroxostat treatment prevented the alterations in the expressions of these molecules in db/db mice. XOR activity in kidney was increased in rats with anti-nephrin antibody-induced podocyte injury. Topiroxostat treatment reduced XOR activity and restored the decreased expression of nephrin, podocin and podoplanin in the podocyte injury. Furthermore, topiroxostat enhanced the expression of podoplanin in injured human cultured podocytes.

CONCLUSIONS

Podocyte injury was evident in db/db mice. Topiroxostat ameliorated albuminuria in diabetic nephropathy model by preventing podocyte injury. Increase of XOR activity in kidney contributes to development of podocyte injury caused by stimulation to slit diaphragm. Topiroxostat has an effect to stabilize slit diaphragm and foot processes by inhibiting the reduction of nephrin, podocin and podoplanin.

Creation of an adequate animal model of hyperuricemia (acute and chronic hyperuricemia); study of its reversibility and its maintenance

AIM

Hyperuricemia is defined by the European Rheumatology Society as a uric acid level greater than 6 mg/dl (60 mg/l or 360 μmol/l). Our goal was to evaluate the hypouricemic effect of nettle. For this reason, we have first of all try to create an hyperuricemic animal model which is very suitable because at the level of literature there is not an exact model, there are many models and our objective is to set an adequate model.

MATERIALS AND METHODS

An attempt has been made to test acute and chronic hyperuricemia by varying the duration and method of induction of potassium oxonate. Similarly, attempts have been made to induce chronic hyperuricemia through an animal and vegetable diet. The reversibility of hyperuricemia was tested with a maintenance protocol.

KEY FINDINGS

For the creation of the hyperuricemia model, it has been shown that acute hyperuricemia cannot be induced by short administration of potassium oxonate and persistent chronic hyperuricemia can be induced only after daily administration of oxonate of potassium by intraperitoneal injection for 15 days. Indeed, hyperuricemia was reversible after stopping the administration of potassium oxonate. The high-purine diet is also capable of inducing chronic hyperuricemia but to a less extent.

SIGNIFICANCE

After creating an adequate model of hyperuricemia while setting the dose of potassium oxonate, route of administration and duration. A maintenance protocol was followed which subsequently made it possible to deduce that the daily administration of potassium oxonate must be continued to maintain the hyperuricemia.

Renal effects of uric acid: hyperuricemia and hypouricemia

The prevalence of chronic kidney disease (CKD) is increasing worldwide. Although hyperuricemia has been associated with CKD in many studies, it remains controversial whether this is the cause or the result of decreased renal function. Recent observational studies of healthy populations and patients with CKD have reported that uric acid (UA) has an independent role in the development or progression of CKD. Experimental studies have shown several potential mechanisms by which hyperuricemia may cause or promote CKD. However, other reports have indicated an association between hypouricemia and CKD. This opposing effect is hypothesized to occur because UA is a major antioxidant in human plasma and is associated with oxidative stress. In this article, we discuss the potential association between UA imbalance and CKD and how they can be treated.

The dirty little secret of urate-lowering therapy: useless to stop chronic kidney disease progression and may increase mortality

Hyperuricaemia is frequent in chronic kidney disease (CKD). Observational studies have shown an association with adverse outcomes and acquired hyperuricaemia (meaning serum urate levels as low as 1.0 mg/dL) in animal models induces kidney injury. This evidence does not justify the widespread use of urate-lowering drugs for asymptomatic hyperuricaemia in CKD. However, promising results from small, open-label studies led some physicians to prescribe urate-lowering drugs to slow CKD progression. Two recent, large, placebo-controlled trials (CKD-FIX and PERL) showed no benefit from urate lowering with allopurinol on the primary endpoint of CKD progression, confirming prior negative results. Despite these negative findings, it was still argued that the study population could be optimized by enrolling younger non-proteinuric CKD patients with better preserved glomerular filtration rate (GFR). However, in these low-risk patients, GFR may be stable under placebo conditions. Additionally, the increased mortality trends already identified in gout trials of urate-lowering therapy were also observed in CKD-FIX and PERL, sending a strong safety signal: 21/449 (4.7%) and 10/444 (2.2%) patients died in the combined allopurinol and placebo groups, respectively [chi-squared P-value 0.048; relative risk 2.07 (95% CI 0.98–4.34); P = 0.06]. Given the absent evidence of benefit in multiple clinical trials and the potentially serious safety issues, the clear message should be that urate-lowering therapy should not be prescribed for the indication of slowing CKD progression. Additionally, regulatory agencies should urgently reassess the safety of chronic prescription of urate-lowering drugs for any indication.

Extreme hyperuricemia is a risk factor for infection-related deaths in incident dialysis patients: a multicenter prospective cohort study

Introduction

There are few studies on the association between serum uric acid (UA) level and mortality in incident dialysis patients. We aimed to clarify whether the serum UA level at dialysis initiation is associated with mortality during maintenance dialysis.

Methods

We enrolled 1486 incident dialysis patients who participated in a previous multicenter prospective cohort study in Japan. We classified the patients into the following five groups according to their serum UA levels at dialysis initiation: G1 with a serum UA level <6 mg/dL; G2, 6.0–8.0 mg/dL; G3, 8.0–10.0 mg/dL; G4, 10.0–12.0 mg/dL; and G5, ≥12.0 mg/dL. We created three models (Model 1: adjusted for age and sex, Model 2: adjusted for Model 1 + 12 variables, and Model 3: stepwise regression adjusted for Model 2 + 13 variables) and performed a multivariate Cox proportional hazard regression analysis to examine the association between the serum UA level and outcomes, including infection-related mortality.

Results

Hazard ratios (HRs) were calculated relative to the G2, because the all-cause mortality rate was the lowest in G2. For Models 1 and 2, the all-cause mortality rate was significantly higher in G5 than in G2 (HR: 1.63, 95% confidence interval [CI]: 1.14–2.33 and HR: 1.78, 95% CI: 1.19–2.68, respectively). For Models 1, 2, and 3, the infection-related mortality rate was significantly higher in G5 than in G2 (HR: 2.75, 95% CI: 1.37–5.54, HR: 3.09, 95% CI: 1.45–6.59, HR: 3.37, and 95% CI: 1.24–9.15, respectively).

Conclusions

Extreme hyperuricemia (serum UA level ≥12.0 mg/dL) at dialysis initiation is a risk factor for infection-related deaths.

Time-averaged serum uric acid and 10-year incident diabetic kidney disease: A prospective study from China

BACKGROUND

The association between serum uric acid (SUA) and the risk of diabetic kidney diseases (DKD) remains controversial. We aim to investigate the association between time-averaged SUA and long-term incident DKD among general population-based patients with diabetes.

METHODS

Altogether 1327 patients with diabetes and without kidney disease (estimated glomerular filtration rate [eGFR] ≥ 60 mL/min/1.73m² , and without proteinuria) were included. Incident DKD were defined by the occurrence of renal function decline (eGFR<60 mL/min/1.73m² ) and/or macroalbuminuria (urinary albumin-creatinine-ratio ≥ 30 mg/mM creatinine). The associations between baseline and time-averaged SUA and DKD were analyzed.

RESULTS

The mean age was 53.7 ± 8.0. During 10.2 ± 0.4 years' follow-up, 85 (6.4%) patients developed renal function decline and 101 (7.6%) patients developed macroalbuminuria. Compared to those with time-averaged SUA in the second quartile (207-240 μM/L for women, 233-272 μM/L for men), odds ratio (OR) for renal function decline was 1.92 (95% confidence interval [CI], 1.02 to 3.62; P = .04) among those with SUA in the top quartile (women≥285 μM/L; men≥324 μM/L); and OR for macroalbuminuria was 1.86 (95% CI 1.01 to 3.43; P = .05) among those with SUA in the bottom quartile (women ≤207 μM/L; men ≤233 μM/L)). No significant associations were observed between baseline SUA with incident DKD.

CONCLUSIONS

Long-term exposure to both high and low SUA level are associated with increased risk of incident DKD among patients with diabetes.

Uric acid is not associated with diabetic nephropathy and other complications in type 1 diabetes

BACKGROUND

To examine the association between plasma uric acid (UA) and the presence of diabetic complications including diabetic nephropathy and cardiovascular risk factors in patients with type 1 diabetes.

METHODS

This study, which is cross-sectional in design, included 676 Caucasian type 1 diabetes patients from the Steno Diabetes Center Copenhagen. Participants with UA within the three lowest sex-specific quartiles were compared with participants with levels in the highest quartile. Unadjusted and adjusted linear regression analyses were applied. Adjustment included sex, age, diabetes duration, body mass index, high-density lipoprotein cholesterol, smoking, haemoglobin A1c, 24-h pulse pressure, urinary albumin excretion rate (UAER), estimated glomerular filtration rate (eGFR) and treatment with renin-angiotensin-aldosterone system blockers.

RESULTS

Of the 676 patients, 372 (55%) were male, mean ± SD age was 55 ± 13 years and eGFR was 82 ± 26 mL/min/1.73 m2. The median UA was 0.30 (interquartile range 0.23-0.37) mmol/L. UA in the upper sex-specific quartile was associated with lower eGFR, higher UAER and carotid-femoral pulse wave velocity and lower 24 h and daytime diastolic blood pressure (BP) in unadjusted analyses (P < 0.001). Moreover, UA in the upper sex-specific quartile was associated with higher nighttime systolic BP and the presence of cardiovascular disease in unadjusted analyses (P ≤ 0.01), but significance was lost after adjustment (P ≥ 0.17). UA was higher across the retinopathy groups [nil (n = 142), simplex (n = 277), proliferative (n = 229) and blind (n = 19)] in unadjusted analyses (P < 0.0001), but not after adjustment (P = 0.12). Patients with an accelerated decline in eGFR (≥3 mL/min/year) had significantly higher UA at baseline (P = 0.006) compared with slow decliners (<3 mL/min/year), but significance was lost after adjustment (P = 0.10).

CONCLUSIONS

In type 1 diabetes patients, higher UA was associated with lower kidney function and other diabetic complications. The association between higher UA and lower eGFR and lower diastolic BP was independent of traditional risk factors.

Phosphatidylserine on microparticles and associated cells contributes to the hypercoagulable state in diabetic kidney disease

Background

Relatively little is known about the role of phosphatidylserine (PS) in procoagulant activity (PCA) in patients with diabetic kidney disease (DKD). This study was designed to evaluate whether exposed PS on microparticles (MPs) and MP-origin cells were involved in the hypercoagulability in DKD patients.

Methods

DKD patients (n = 90) were divided into three groups based on urinary albumin excretion rate, defined as normoalbuminuria (No-A) (<30 mg/24 h), microalbuminuria (Mi-A) (30-299 mg/24 h) or macroalbuminuria (Ma-A) (>300 mg/24 h), and compared with healthy controls (n = 30). Lactadherin was used to quantify PS exposure on MPs and their original cells. Healthy blood cells (BCs) and human umbilical vein endothelial cells (HUVECs) were treated with 25, 5 or 2.5 mmol/L glucose as well as 3-12 mg/dL uric acid and cells were evaluated by clotting time and purified coagulation complex assays. Fibrin production was determined by turbidity. PS exposure and fibrin strands were observed using confocal microscopy.

Results

Using flow cytometry, we found that PS+ MPs (derived from platelets, erythrocytes, HUVECs, neutrophils, monocytes and lymphocytes) and BCs were significantly higher in patients than in controls. Furthermore, the number of PS+ MPs and BCs in patients with Ma-A was significantly higher than in patients with No-A. Similarly, we observed markedly elevated PS exposure on HUVECs cultured with serum from patients with Ma-A versus serum from patients with Mi-A or normoalbuminuria. In addition, circulating PS+ MPs cooperated with PS+ cells, contributing to markedly shortened coagulation time and dramatically increased FXa/thrombin generation and fibrin formation in each DKD group. Confocal microscopy images demonstrated colocalization of fibrin with PS on HUVECs. Moreover, blockade of exposed PS on MPs and cells with lactadherin inhibited PCA by ∼80%. In vitro, BCs and endothelial cells exposed more PS in hypoglycemia or hyperglycemia. Interestingly, reconstitution experiments showed that hypoglycemia-treated cells could be further activated or injured when recovery is obtained reaching hyperglycemia. Moreover, uric acid induced PS exposure on cells (excluding platelets) at concentrations >6 mg/dL. Linear regression analysis showed that levels of PS+ BCs and microparticles were positively correlated with uric acid and proteinuria, but negatively correlated with glomerular filtration rate.

Conclusions

Our results suggest that PS+ MPs and MP-origin cells play procoagulant roles in patients with DKD. Blockade of PS could become a novel therapeutic modality for the prevention of thrombosis in these patients.

Xanthine Oxidase Inhibitor Febuxostat Exerts an Anti-Inflammatory Action and Protects against Diabetic Nephropathy Development in KK-Ay Obese Diabetic Mice

Hyperuricemia has been recognized as a risk factor for insulin resistance as well as one of the factors leading to diabetic kidney disease (DKD). Since DKD is the most common cause of end-stage renal disease, we investigated whether febuxostat, a xanthine oxidase (XO) inhibitor, exerts a protective effect against the development of DKD. We used KK-Ay mice, an established obese diabetic rodent model. Eight-week-old KK-Ay mice were provided drinking water with or without febuxostat (15 μg/mL) for 12 weeks and then subjected to experimentation. Urine albumin secretion and degrees of glomerular injury judged by microscopic observations were markedly higher in KK-Ay than in control lean mice. These elevations were significantly normalized by febuxostat treatment. On the other hand, body weights and high serum glucose concentrations and glycated albumin levels of KK-Ay mice were not affected by febuxostat treatment, despite glucose tolerance and insulin tolerance tests having revealed febuxostat significantly improved insulin sensitivity and glucose tolerance. Interestingly, the IL-1β, IL-6, MCP-1, and ICAM-1 mRNA levels, which were increased in KK-Ay mouse kidneys as compared with normal controls, were suppressed by febuxostat administration. These data indicate a protective effect of XO inhibitors against the development of DKD, and the underlying mechanism likely involves inflammation suppression which is independent of hyperglycemia amelioration.

Dietary Antioxidant Supplements and Uric Acid in Chronic Kidney Disease: A Review

Increased serum levels of uric acid have been associated with the onset and development of chronic kidney disease (CKD), cardiovascular disease, and mortality, through several molecular pathogenetic mechanisms, such as inflammation and oxidative stress. Oxidative stress is present even in the early stages of CKD, progresses parallelly with the deterioration of kidney function, and is even more exacerbated in end-stage renal disease patients undergoing maintenance hemodialysis. Although acting in the plasma as an antioxidant, once uric acid enters the intracellular environment; it behaves as a powerful pro-oxidant. Exogenous intake of antioxidants has been repeatedly shown to prevent inflammation, atherosclerosis and oxidative stress in CKD patients. Moreover, certain antioxidants have been proposed to exert uric acid-lowering properties. This review aims to present the available data regarding the effects of antioxidant supplements on both oxidative stress and uric acid serum levels, in a population particularly susceptible to oxidative damage such as CKD patients.

Associations of serum uric acid with total and cause-specific mortality: Findings from individuals and pooling prospective studies

BACKGROUND AND AIMS

There is considerable controversy regarding the link between serum uric acid (SUA) and mortality. We prospectively evaluated the association between SUA and risk of total and cause specific (coronary heart disease [CHD], cerebrovascular and cancer) mortality by using the National Health and Nutrition Examination Surveys (NHANES, 1999-2010). Furthermore, a systematic review and meta-analysis of cohort studies was performed to investigate pooled associations of SUA with all-cause and cause-specific mortality.

METHODS

Vital status through December 31, 2011 was ascertained. PubMed-Medline, SCOPUS, Web of Science and Google Scholar databases were searched (up to April 2018). Adjusted Cox proportional hazard regression models were used to determine the association between SUA and mortality. The DerSimonian-Laird method and generic inverse variance methods were used for quantitative data synthesis.

RESULTS

Overall, 21,025 individuals were included (mean age = 47.6 years, 48.7% men) and 3520 deaths occurred during the 144 months of follow-up. In adjusted models, individuals in the highest quartile of SUA had 10 and 8% greater risk of CHD and stroke mortality, whereas there was no link between SUA, all-cause and cancer mortality. The associations of CHD and stroke mortality with SUA were more pronounced in women and, among women, in those aged >50 years. Furthermore, all-cause mortality was positively and significantly related to SUA concentrations only in women. In the meta-analysis, SUA was shown to predict the risk of total (21%), CHD (24%) and stroke (29%) mortality. Furthermore, participants with a higher level of central adiposity had a greater risk of mortality from CHD and stroke for the same level of SUA.

CONCLUSIONS

Our results highlight the adverse impact of SUA on mortality, particularity in older (>50 years) women. The clinical implications of these findings remain to be established in future trials.

The association between serum uric acid to creatinine ratio and renal disease progression in type 2 diabetic patients in Chinese communities

AIMS

Serum uric acid (UA) increases in patients with kidney disease due to the impaired UA clearance. The present study sought to evaluate the association between UA/creatinine ratio (UA/Cr) and renal disease progression in patients with type 2 diabetes mellitus (T2DM) in Chinese communities.

METHODS

In the present retrospective longitudinal study, 3432 Chinese T2DM patients recruited from 11 community healthcare centers in Nanjing, China were included. Renal disease progression was defined as the occurrence of estimated glomerular filtration rate (eGFR) <15 mL/min/1.73 m² or doubling of baseline serum creatinine level. Cox regression analysis was used to estimate the association between UA/Cr and renal disease progression.

RESULTS

During a median follow-up of 30 months, 58 (1.70%) patients experienced progression of renal disease, which was more common among those with older ages, longer diabetes duration, and higher baseline eGFR. Multivariate analysis revealed that UA/Cr was an independent risk factor for renal disease progress (hazard ratio 1.364 [95% CI 1.131-1.646], P = 0.001) independently of age, sex, and other potential confounders.

CONCLUSIONS

UA/Cr might be a novel predictor of chronic kidney disease progression in T2DM patients.

Association between uric acid, renal haemodynamics and arterial stiffness over the natural history of type 1 diabetes

AIMS

To examine the relationship between normal plasma uric acid (PUA) levels, renal haemodynamic function, arterial stiffness and plasma renin and aldosterone over a wide range of type 1 diabetes (T1D) durations in adolescents, young adults and older adults.

MATERIALS AND METHODS

PUA, glomerular filtration rate (GFR), effective renal plasma flow (ERPF), vascular stiffness parameters (aortic augmentation index [AIx], carotid AIx, carotid femoral pulse wave velocity [cfPWV]), and plasma renin and aldosterone were measured during a euglycaemic clamp in people with T1D: 27 adolescents (mean ± SD age 16.8 ± 1.9 years), 52 young adults (mean ± SD age 25.6 ± 5.5 years) and 66 older adults (mean ± SD age 65.7 ± 7.5 years).

RESULTS

PUA was highest in patients with the longest T1D duration: 197 ± 44 μmol/L in adolescents versus 264 ± 82 μmol/L in older adults (P < 0.001). Higher PUA correlated with lower GFR only in older adults, even after correcting for age, glycated haemoglobin and sex (β = -2.12 ± 0.56; P = 0.0003), but not in adolescents or young adults. Higher PUA correlated with lower carotid AIx (β = -1.90, P = 0.02) in adolescents. In contrast, PUA correlated with higher cfPWV (P = 0.02) and higher plasma renin (P = 0.01) in older adults with T1D.

CONCLUSIONS

The relationship between higher PUA with lower GFR, increased arterial stiffness and renin angiotensin aldosterone system (RAAS) activation was observed only in older adults with longstanding T1D. T1D duration may modify the association between PUA, renal haemodynamic function and RAAS activation, leading to renal vasoconstriction and ischaemia. Further work must determine whether pharmacological PUA-lowering prevents or reverses injurious haemodynamic and neurohormonal sequelae of longstanding T1D, thereby improving clinical outcomes.

Evolving spectrum of diabetic nephropathy

Diabetes remains an important health issue as more patients with chronic and uncontrolled diabetes develop diabetic nephropathy (DN), which classically presents with proteinuria followed by a progressive decrease in renal function. However, an increasing proportion of DN patients have a decline in kidney function and vascular complications without proteinuria, known as non-proteinuric DN (NP-DN). Despite the increased incidence of NP-DN, few clinical or experimental studies have thoroughly investigated the pathophysiological mechanisms and targeted treatment for this form of DN. In this review, we will examine the differences between conventional DN and NP-DN and consider potential pathophysiological mechanisms, diagnostic markers, and treatment for both DN and NP-DN. The investigation of the pathophysiology of NP-DN should provide additional insight into the cardiovascular factors influencing renal function and disease and provide novel treatments for the vascular complications seen in diabetic patients.

The potential of N-glycosylation profiles as biomarkers for monitoring the progression of Type II diabetes mellitus towards diabetic kidney disease

Background

On a global scale, type II diabetes mellitus (T2DM) remain a major health problem and it is the driver for chronic kidney disease (CKD). Despite this association, we still do not have sufficient biomarkers to anticipate better outcomes. N-glycosylation profiles are robust biomarkers and can be used for early monitoring of the progression of T2DM towards CKD.

Methods

In this cross-sectional study, we recruited 241 T2DM patients from January to May 2016. Demographic and anthropometric data were collected, following which fasting blood samples were collected for clinical analyses. Renal function decline was determined by estimation of glomerular filtration rate (eGFR) and N-glycosylation profiles were analysed by Ultra-performance liquid chromatography (UPLC).

Results

The prevalence of undiagnosed CKD was 31.53%. Compared to men, women had a statistically significantly higher HbA1c (p = 0.031), TG (p = 0.015), HDL-c (p < 0.0001), creatinine (<0.0001), urea (p < 0.028) and uric acid (p < 0.0001). T2DM patients with undiagnosed CKD had higher serum creatinine (145.75 ± 50.83 vs 88.59 ± 19.46, p < 0.0001), higher uric acid (361.10 ± 115.37 vs 294.54 ± 97.75; p < 0.0001) and higher urea (5.17 ± 2.35 vs 3.58 ± 1.19; p < 0.0001). After performing logistic regression and adjusting for age, sex and BMI, three N-glycan peaks [OR (95%CI): (GP12 (0.05(0.01-0.54), p = 0.013)); GP16 (0.61(0.43-0.87), p = 0.006)); GP22 (0.60(0.39-0.92), p = 0.018)) were associated with renal function.

Conclusion

There was an increased prevalence of undiagnosed CKD among T2DM patients. This prevalence is the consequence of uncontrolled modifiable risk factors, which collectively may lead to end stage renal disease (ESRD). Although, the identified N-glycans could not adequately predict incident CKD, our investigation indicates the potential role of N-glycosylation in renal function and that their inclusion may improve risk stratification for CKD.

Association between circulating tumor necrosis factor-related biomarkers and estimated glomerular filtration rate in type 2 diabetes

Chronic inflammation plays a crucial role in the development/progression of diabetic kidney disease. The involvement of tumor necrosis factor (TNF)-related biomarkers [TNFα, progranulin (PGRN), TNF receptors (TNFR1 and TNFR2)] and uric acid (UA) in renal function decline was investigated in patients with type 2 diabetes (T2D). Serum TNF-related biomarkers and UA levels were measured in 594 Japanese patients with T2D and an eGFR ≥30 mL/min/1.73 m². Four TNF-related biomarkers and UA were negatively associated with estimated glomerular filtration rate (eGFR). In a logistic multivariate model, each TNF-related biomarker and UA was associated with lower eGFR (eGFR <60mL /min/1.73 m²) after adjustment for relevant covariates (basic model). Furthermore, UA and TNF-related biomarkers other than PGRN added a significant benefit for the risk factors of lower eGFR when measured together with a basic model (UA, ΔAUC, 0.049, p < 0.001; TNFα, ΔAUC, 0.022, p = 0.007; TNFR1, ΔAUC, 0.064, p < 0.001; TNFR2, ΔAUC, 0.052, p < 0.001) in receiver operating characteristic curve analysis. TNFR ligands were associated with lower eGFR, but the associations were not as strong as those with TNFRs or UA in patients with T2D and an eGFR ≥30 mL/min/1.73 m².

Serum uric acid to creatinine ratio correlates with β-cell function in type 2 diabetes

BACKGROUND

The correlation between serum uric acid (SUA) and β-cell function remains controversial. The present study aims to use a new index, renal function-normalized SUA, to observe its correlation with β-cell function in patients with type 2 diabetes (T2DM).

METHODS

A total of 713 patients with T2DM received standard 75-g oral glucose tolerance and insulin release test. Renal function-normalized SUA was calculated using SUA/creatinine and β-cell function was assessed by HOMA-B. Binary logistic regression analysis was used to estimate the association between SUA/creatinine and β-cell function.

RESULTS

There are positive correlations between SUA/creatinine and HOMA-B (r = 0.143, P < 0.001), as well as other indexes of β-cell function including modified β-cell function index (r = 0.104, P = 0.007), InsAUC30 (r = 0.100, P = 0.008), and InsAUC120 (r = 0.124, P = 0.001). SUA/creatinine also positively correlates with insulin resistance (HOMA-IR: r = 0.161, P < 0.001). Moreover, multivariate analysis revealed that SUA/creatinine was significantly associated with preserved β-cell function, independently of potential confounders including sex, BMI, and renal function.

CONCLUSIONS

SUA to creatinine ratio correlates with β-cell function in T2DM patients.

Circulating miRNA Profiles Associated With Hyperglycemia in Patients With Type 1 Diabetes

We investigated plasma microRNA (miRNA) profiles associated with variation of hyperglycemia, measured as hemoglobin A_1c (HbA_1c), in two panels of patients with type 1 diabetes (T1D). Using the HTG Molecular Diagnostics EdgeSeq platform, 2,083 miRNAs were measured in plasma from 71 patients included in a screening panel. Quantitative real-time PCR was used to measure the candidate miRNAs in plasma from 95 patients included in an independent replication panel. We found 10 miRNAs replicated in both panels and 4 with high statistical significance. The strongest positive correlations with HbA_1c were found with miR-125b-5p (r_s = 0.40, P = 6.0 × 10^-5) and miR-365a-3p (r_s = 0.35, P = 5.9 × 10^-4). The strongest negative correlations were found with miR-5190 (r_s = -0.30, P = 0.003) and miR-770-5p (r_s = -0.27, P = 0.008). Pathway analysis revealed that 50 Kyoto Encyclopedia of Genes and Genomes pathways were significantly enriched by genes targeted by these four miRNAs. The axon guidance signaling pathway was enriched (P < 1 × 10^-7) by genes targeted by all four miRNAs. In addition, three other pathways (Rap1 signaling, focal adhesion, and neurotrophin signaling) were also significantly enriched but with genes targeted by only by three of the identified miRNAs. In conclusion, our study identified four circulating miRNAs that were influenced by variation in hyperglycemia. Dysregulation of these miRNAs, which are associated with hyperglycemia in patients with T1D, may contribute to the development of diabetes complications. However, there are multitudes of possible mechanisms/pathways through which dysregulation of these miRNAs may impact risk of diabetes complications.

Association of serum uric acid with nephropathy in Iranian type 2 diabetic patients

Background

Diabetic nephropathy (DN) is the major cause of end-stage renal disease. Recent studies suggest that it is probable that uric acid is involved in the pathogenesis of diabetic nephropathy. This study aim was to investigate the association between serum uric acid and kidney function in Iranian patients with type 2 diabetes mellitus.

Methods

In this case-control study, a total of 201 diabetic patients with or without impaired kidney function (glomerular filtration rate/GFR < 60 and GFR ≥ 60) were selected. In both groups, serum fasting glucose (FBS), HbA1c, urea, creatinine, uric acid and lipid profile, urine albumin and GFR were measured and results were compared between the two groups. The results also categorized into three groups based on uric acid tertiles.

Results

Serum levels of uric acid, urea and creatinine as well as urine albumin/creatinine ratio (ACR) were significantly different between the two groups. GFR, creatinine and also urea were significantly different between uric acid tertiles (p < 0.05).

Conclusions

Serum uric acid is associated with decreased GFR as well as albuminuria and can be used as an indicator of DN.

Serum uric acid and renal function in patients with type 1 diabetes: a nationwide study in Brazil

BACKGROUND

Diabetes nephropathy is a microvascular complication associated with high morbidity and mortality in patients with type 1 diabetes, and its pathogenesis is not fully understood. Our aim was to evaluate the association between levels of serum uric acid and renal function assessed by glomerular filtration rate (GFR) and albuminuria in patients with type 1 diabetes.

METHODS

This is a multicenter, cross-sectional, observational study with 1686 patients, conducted between August 2011 and August 2014 in 14 public clinics from ten Brazilian cities. Renal function was estimated by CKD-EPI (adults) and by Schwartz (adolescents).

RESULTS

We analyzed 1686 patients, aged 30.1 ± 12.0, with 15.4 ± 9.3 years of duration of diabetes; 55.8% were female and 54.0% were Caucasians. Serum uric acid was related to renal function, with a mean of 4.8 ± 1.4 (in the normal renal function group) vs 5.2 ± 2.0 (GFR ≥ 60 ml/min and albuminuria) vs 6.5 ± 2.6 mg/dl (GFR < 60 ml/min). In the pooled group, multivariate analysis showed an inverse correlation between serum uric acid and GFR (r = - 0.316, p < 0.001) with a decrease of 4.11 ml/min in the GFR for every increase of 1 mg/dl in serum uric acid. Considering only patients with normal renal function (n = 1170), a decrease of 2.04 ml/min in the GFR for every increase of 1 mg/dl in Serum uric acid was noted using multivariate analysis.

CONCLUSIONS

Patients with higher levels of serum uric acid have worse renal function, independently of HbA1c or duration of diabetes, which persisted even in patients with normal renal function. Further prospective studies are necessary to establish if patients with higher serum uric acid may have an elevated risk for developing chronic kidney disease.

Does Altered Uric Acid Metabolism Contribute to Diabetic Kidney Disease Pathophysiology?

PURPOSE OF REVIEW

Multiple experimental and clinical studies have identified pathways by which uric acid may facilitate the development and progression of chronic kidney disease (CKD) in people with diabetes. However, it remains uncertain if the association of uric acid with CKD represents a pathogenic effect or merely reflects renal impairment.

RECENT FINDINGS

In contrast to many published reports, a recent Mendelian randomization study did not identify a causal link between uric acid and CKD in people with type 1 diabetes. Two recent multicenter randomized control trials, Preventing Early Renal Function Loss in Diabetes (PERL) and FEbuxostat versus placebo rAndomized controlled Trial regarding reduced renal function in patients with Hyperuricemia complicated by chRonic kidney disease stage 3 (FEATHER), were recently designed to assess if uric acid lowering slows progression of CKD. We review the evidence supporting a role for uric acid in the pathogenesis of CKD in people with diabetes and the putative benefits of uric acid lowering.

Hyperuricemia and metabolic syndrome in type 2 diabetes mellitus patients at Hawassa university comprehensive specialized hospital, South West Ethiopia

BACKGROUND

Metabolic syndrome is a cluster of the most dangerous heart attack risk factors such as diabetes and prediabetes, abdominal obesity, high cholesterol and high blood pressure. Hyperuricemia is a condition in which the serum uric acid concentration is greater than 5.5 mg per deciliter for child and greater than 7.2 and 6.0 mg per deciliters for male and female adults respectively.

METHODS

A cross-sectional study was conducted to determine the magnitude of hyperuricemia and associated factors among type 2 diabetes mellitus patients at Hawassa Comprehensive Specialized Hospital (HCSH) from February 28 to May 30 /2017. A random sampling technique was used to include 319 study subjects and a signed consent had been provided by each study subject before running any data collection. An interviewer administered structured questionnaire was used to collect socio-demographic and some clinically useful data. In addition to this, we reviewed the records of the study subjects to obtain other useful clinical data. Five milliliter blood specimen was collected from each study subjects after overnight fasting. A25TM Bio-System Random Access chemistry analyzer was used for blood sample analysis. All data were checked visually, coded and entered into epi-data version 3.4 and statistical analysis was performed using SPSS version 20.0 software. Bi-variate and multivariate logistic regressions were used to determine the association between explanatory and the outcome variables.

RESULTS

The prevalence of hyperuricemia and metabolic syndrome among type 2 diabetic patients in the study area were 33.8%(n = 106) and 70.1% (n = 220) respectively. Having age greater or equal to 45 years (AOR: 1.9, CI: 1.-3.2, P value =0.015) and having metabolic syndrome (AOR: 2.6, CI: 1.5-4.7, P value = 0.001) were the determinant variables for hyperuricemia among type 2 diabetic patients.

CONCLUSION

There was high prevalence of hyperuricemia among type 2 diabetic patients with high prevalence of metabolic syndrome. Therefore, regular health information about life style modification, early diagnosis and treatment for hyperuricemia and metabolic syndrome are essential to reduce hyperuricemia and metabolic syndrome in type 2 diabetic patients.

Association of Kidney Function and Waist Circumference with Uric Acid Levels in South Africans

BACKGROUND

Recent evidence that hyperuricemia is associated with incident chronic kidney disease (CKD) provides a potential therapeutic target for CKD that has not been explored in Africans. With hyperuricemia and gout increasing globally, we sought to determine their prevalence in South Africans with varying kidney function levels.

METHODS

This was a cross-sectional study of ambulatory adult patients presenting at a General Internal Medicine Outpatients Clinic between September 2012 and March 2014. Demographic, clinical, and laboratory data collected were analyzed using STATA11. Odds ratios (ORs) and 95% confidence intervals were determined using multivariable logistic regression with bootstrapping.

RESULTS

There were 225/261 (86.2%) black/Africans, 31/261 (11.9%) Indian South Africans, 3/261 (1.1%) Caucasians, and 2/261 (<1%) mixed ancestry South Africans. Mean age was 51.3 ± 14.5 years. Median (interquartile range) estimated glomerular filtration rate (eGFR) was 71 (38) mL/min/1.73 m² and 39.8% (104/261) of patients had CKD. Hyperuricemia prevalence was 43.7% (114/261) and increased from 16.7% in patients with eGFR ≥90 mL/min/1.73 m² to 74.2% with eGFR <30 mL/min/1.73 m² (P < 0.001). Gout prevalence was 5.4% (14/261), with equal distribution across eGFR categories (0.814). Factors independently associated with hyperuricemia were eGFR <90 [ORs 3.24 (1.15-9.14), 7.28 (2.26-23.49), and 7.88 (1.95-31.82) for eGFR 60-89.9, 30-60, and <30, respectively], albuminuria [2.32 (1.11-4.85)], and waist circumference [1.04 (1.01-1.06) per 1 cm increase]. In univariate and multivariable analysis, gout was positively associated with male gender and cardiovascular disease, while it was negatively associated with African ancestry, but none of these factors remained significant after bootstrapping; ORs 6.65 (0.64-69.24), 4.14 (0.61-28.07), and 0.18 (0.01-2.21), respectively.

CONCLUSION

Hyperuricemia prevalence was high, with CKD and waist circumference being the strongest predictors. Gout was uncommon in black Africans. With population data lacking, screening high-risk individuals may provide insight into the burden of hyperuricemia and gout in South Africa.

Asymptomatic hyperuricemia and chronic kidney disease: Narrative review of a treatment controversial

Today there is plausible evidence both on experimental and epidemiological basis, that hyperuricemia represents a risk factor for the development and progression of chronic kidney disease (CKD). Nevertheless, the role of serum uric acid lowering treatment in CKD is still a matter of serious controversy. Review of randomised controlled trials, suggests that there may be an improvement of renal function with allopurinol treatment in CKD stage 3-5. However, these studies have included a relatively limited number of participants and provide insufficient information on adverse events and on the incidence of the end stage renal disease. Therefore, before adequately powered randomised, placebo-controlled trials are completed we cannot recommend treating asymptomatic hyperuricemia in patients with CKD.

Renal and Vascular Effects of Uric Acid Lowering in Normouricemic Patients With Uncomplicated Type 1 Diabetes

Higher plasma uric acid (PUA) levels are associated with lower glomerular filtration rate (GFR) and higher blood pressure (BP) in patients with type 1 diabetes (T1D). Our aim was to determine the impact of PUA lowering on renal and vascular function in patients with uncomplicated T1D. T1D patients (n = 49) were studied under euglycemic and hyperglycemic conditions at baseline and after PUA lowering with febuxostat (FBX) for 8 weeks. Healthy control subjects were studied under normoglycemic conditions (n = 24). PUA, GFR (inulin), effective renal plasma flow (para-aminohippurate), BP, and hemodynamic responses to an infusion of angiotensin II (assessment of intrarenal renin-angiotensin-aldosterone system [RAAS]) were measured before and after FBX treatment. Arterial stiffness, flow-mediated dilation (FMD), nitroglycerin-mediated dilation (GMD), urinary nitric oxide (NO), and inflammatory markers were measured before and after FBX treatment. Gomez equations were used to estimate arteriolar afferent resistance, efferent resistance (R_E), and glomerular hydrostatic pressure (P_GLO). FBX had a modest systolic BP-lowering effect in T1D patients (112 ± 10 to 109 ± 9 mmHg, P = 0.049) without impacting arterial stiffness, FMD, GMD, or NO. FBX enhanced the filtration fraction response to hyperglycemia in T1D patients through larger increases in R_E, P_GLO, and interleukin-18 but without impacting the RAAS. FBX lowered systolic BP and modulated the renal R_E responses to hyperglycemia but without impacting the RAAS or NO levels, suggesting that PUA may augment other hemodynamic or inflammatory mechanisms that control the renal response to hyperglycemia at the efferent arteriole. Ongoing outcome trials will determine cardiorenal outcomes of PUA lowering in patients with T1D.

Correlation of retinal nerve fibre layer and macular thickness with serum uric acid among type 2 diabetes mellitus

Background

Uric acid is a final breakdown product of purine catabolism in humans. It’s a potent antioxidant and can also act as a pro-oxidant that induces oxidative stress on the vascular endothelial cells, thus mediating progression of diabetic related diseases. Various epidemiological and experimental evidence suggest that uric acid has a role in the etiology of type 2 diabetes mellitus. We conducted a cross-sectional study to evaluate the correlation of retinal nerve fibre layer (RNFL) and macular thickness with serum uric acid in type 2 diabetic patients.

Methods

A cross-sectional study was conducted in the Eye Clinic, Hospital Universiti Sains Malaysia, Kelantan between the period of August 2013 till July 2015 involving type 2 diabetes mellitus patients with no diabetic retinopathy and with non-proliferative diabetic retinopathy (NPDR). An evaluation for RNFL and macular thickness was measured using Spectralis Heidelberg optical coherence tomography. Six ml of venous blood was taken for the measurement of serum uric acid and glycosylated haemoglobin (HbA1_C).

Results

A total of 180 diabetic patients were recruited (90 patients with no diabetic retinopathy and 90 patients with NPDR) into the study. The mean level of serum uric acid for both the groups was within normal range and there was no significance difference between the two groups. Based on gender, both male and female gender showed significantly higher level of mean serum uric acid in no diabetic retinopathy group (p = 0.004 respectively). The mean serum uric acid was significantly higher in patient with HbA1_C < 6.5% (p < 0.031). Patients with NPDR have thicker RNFL and macular thickness compared to patients with no diabetic retinopathy. However, only the RNFL thickness of the temporal quadrant and the macular thickness of the superior outer, inferior outer and temporal outer subfields were statistically significant (p = 0.038, p = 0.004, 0.033 and <0.001 respectively). There was poor correlation between RNFL and macular thickness with serum uric acid in both the groups.

Conclusion

Serum uric acid showed a poor correlation with RNFL and macular thickness among type 2 diabetic patients.

Serum uric acid to creatinine ratio: A predictor of incident chronic kidney disease in type 2 diabetes mellitus patients with preserved kidney function

BACKGROUND

Serum uric acid has shown to be a predictor of renal disease progression in most but not all studies. This study aims to test whether renal function-normalized serum uric acid is superior to serum uric acid as the predictor of incident chronic kidney disease in type 2 diabetes mellitus patients.

METHODS

In this study, 1339 type 2 diabetes mellitus patients with estimated glomerular filtration rate ⩾60 mL/min/1.73 m² and normouricemia were included. Renal function-normalized serum uric acid was calculated using serum uric acid/creatinine. Cox regression analysis was used to estimate the association between serum uric acid, renal function-normalized serum uric acid and incident chronic kidney disease.

RESULTS

In total, 74 (5.53%) patients developed to chronic kidney disease 3 or greater during a median follow-up of 4 years, with older ages, longer diabetes duration and lower estimated glomerular filtration rate at baseline. The decline rate of estimated glomerular filtration rate was positively correlated with serum uric acid/creatinine ( r = 0.219, p < 0.001), but not serum uric acid ( r = 0.005, p = 0.858). Moreover, multivariate analysis revealed that serum uric acid was not an independent risk factor for incident chronic kidney disease ( p = 0.055), whereas serum uric acid to creatinine ratio was significantly associated with incident chronic kidney disease independently of potential confounders including baseline estimated glomerular filtration rate.

CONCLUSION

serum uric acid to creatinine ratio might be a better predictor of incident chronic kidney disease in type 2 diabetes mellitus patients.

Uric acid metabolism of kidney and intestine in a rat model of chronic kidney disease

Uric acid (UA) is a potential risk factor of the progression of chronic kidney disease (CKD). Recently, we reported that intestinal UA excretion might be enhanced via upregulation of the ATP-binding cassette transporter G2 (Abcg2) in a 5/6 nephrectomy (Nx) rat model. In the present study, we examined the mRNA and protein expressions of UA transporters, URAT1, GLUT9/URATv1, ABCG2 and NPT4 in the kidney and ileum in the same rat model. Additionally, we investigated the Abcg2 mRNA expression of ileum in hyperuricemic rat model by orally administering oxonic acid. Male Wistar rats were randomly assigned to three groups consisting of Nx group, oxonic acid-treated (Ox) group and sham-operated control group, and sacrificed at 8 weeks. Creatinine and UA were measured and the mRNA expressions of UA transporters in the kidney and intestine were evaluated by a real time PCR. UA transporters in the kidney sections were also examined by immunohistochemistry. Serum creatinine elevated in the Nx group whereas serum UA increased in the Ox group. Both the mRNA expression and the immunohistochemistry of the UA transporters were decreased in the Nx group, suggesting a marginal role in UA elevation in decreased kidney function. In contrast, the mRNA expression of Abcg2 in the ileum significantly increased in the Ox group. These results suggest that the upregulation of Abcg2 mRNA in the ileum triggered by an elevation of serum UA may play a compensatory role in increasing intestinal UA excretion.

Uricosuric targets of tranilast

Uric acid, generated from the metabolism of purines, has both proven and emerging roles in human disease. Serum uric acid in humans is determined by production and by the net balance of reabsorption and secretion in kidney and intestine. In the human kidney, epithelial reabsorption dominates over secretion, such that in normal subjects there is at least 90% net reabsorption of filtered urate resulting in a fractional excretion of <10%. Tranilast, an anti-inflammatory drug with pleiotropic effects, has a marked hypouricemic, uricosuric effect in humans. We report here that tranilast is a potent inhibitor of [¹⁴C]-urate transport mediated by the major reabsorptive urate transporters (URAT1, GLUT9, OAT4, and OAT10) in Xenopus oocytes; this provides an unequivocal molecular mechanism for the drug's uricosuric effect. Tranilast was found to inhibit urate transport mediated by URAT1 and GLUT9 in a fully reversible and noncompetitive (mixed) manner. In addition, tranilast inhibits the secretory urate transporters NPT1, OAT1, and OAT3 without affecting the secretory efflux pump ABCG2. Notably, while benzbromarone and probenecid inhibited urate as well as nicotinate transport, tranilast inhibited the urate transport function of URAT1, GLUT9, OAT4, OAT10, and NPT1, without significantly affecting nicotinate transport mediated by SMCT1 (IC ₅₀ ~1.1 mmol/L), SMCT2 (IC ₅₀ ~1.0 mmol/L), and URAT1 (IC ₅₀ ~178 μmol/L). In summary, tranilast causes uricosuria by inhibiting all the major reabsorptive urate transporters, selectively affecting urate over nicotinate transport. These data have implications for the treatment of hyperuricemia and gout, the pharmacology of tranilast, and the structure-function analysis of urate transport.

Increased plasma kidney injury molecule-1 suggests early progressive renal decline in non-proteinuric patients with type 1 diabetes

Progressively decreasing glomerular filtration rate (GFR), or renal decline, is seen in patients with type 1 diabetes (T1D) and normoalbuminuria or microalbuminuria. Here we examined the associations of kidney injury molecule-1 (KIM-1) in plasma and urine with the risk of renal decline and determine whether those associations are independent of markers of glomerular damage. The study group comprised patients with T1D from the 2nd Joslin Kidney Study of which 259 had normoalbuminuria and 203 had microalbuminuria. Serial measurements over 4 to 10 years of follow-up (median 8 years) of serum creatinine and cystatin C were used jointly to estimate eGFRcr-cys slopes and time of onset of CKD stage 3 or higher. Baseline urinary excretion of IgG2 and albumin were used as markers of glomerular damage, and urinary excretion of KIM-1 and its plasma concentration were used as markers of proximal tubular damage. All patients had normal renal function at baseline. During follow-up, renal decline (eGFRcr-cys loss 3.3% or more per year) developed in 96 patients and 62 progressed to CKD stage 3. For both outcomes, the risk rose with increasing baseline levels of plasma KIM-1. In multivariable models, elevated baseline plasma KIM-1 was strongly associated with risk of early progressive renal decline, regardless of baseline clinical characteristics, serum TNFR1 or markers of glomerular damage. Thus, damage to proximal tubules may play an independent role in the development of early progressive renal decline in non-proteinuric patients with T1D.

Association of serum uric acid levels with the risk of development or progression of albuminuria among Japanese patients with type 2 diabetes: a prospective cohort study [Diabetes Distress and Care Registry at Tenri (DDCRT 10)]

AIMS

To assess the prospective association between baseline serum uric acid level and subsequent risk of development or progression in albuminuria.

METHODS

Longitudinal data were obtained from 2518 patients with type 2 diabetes in the development cohort and registered in a Japanese diabetes registry. To assess the independent correlations between baseline serum uric acid quartiles and either the development or progression of diabetic nephropathy for 2 years, the Cox proportional hazards model was used and adjusted for potential confounders.

RESULTS

The mean patient age, body mass index, and glycated hemoglobin (HbA1c) level were 66.1 years, 24.6 kg/m(2), and 7.5 % (57.6 mmol/mol), respectively. The baseline serum uric acid levels, with mean values of 3.6, 4.9, 5.8, and 7.3 mg/dL from the first to fourth quartiles, were significantly associated with the urinary albumin/creatinine ratio at baseline (p < 0.001). Baseline uric acid levels were not significantly associated with the development of nephropathy, but they were with the progression of nephropathy. The multivariable-adjusted hazards ratios for the progression from microalbuminuria to macroalbuminuria were 2.17 [95 % confidence interval (CI) 1.15-4.08; p = 0.016], 3.04 (95 % CI 1.67-5.53; p < 0.001), and 3.56 (95 % CI 1.83-6.93; p < 0.0011) for the first, third, and fourth quartiles of serum uric acid levels, respectively, as compared to that for the second quartile. We did not observe significant association between uric acid levels and change in estimated glomerular filtration rate.

CONCLUSIONS

Low and high serum uric levels, independent of possible confounders, were associated with a subsequent risk of progression, not development, in albuminuria in type 2 diabetes patients. Therefore, serum uric acid levels may be useful for predicting the future risk of progression of microalbuminuria.

New Pathogenic Concepts and Therapeutic Approaches to Oxidative Stress in Chronic Kidney Disease

In chronic kidney disease inflammatory processes and stimulation of immune cells result in overproduction of free radicals. In combination with a reduced antioxidant capacity this causes oxidative stress. This review focuses on current pathogenic concepts of oxidative stress for the decline of kidney function and development of cardiovascular complications. We discuss the impact of mitochondrial alterations and dysfunction, a pathogenic role for hyperuricemia, and disturbances of vitamin D metabolism and signal transduction. Recent antioxidant therapy options including the use of vitamin D and pharmacologic therapies for hyperuricemia are discussed. Finally, we review some new therapy options in diabetic nephropathy including antidiabetic agents (noninsulin dependent), plant antioxidants, and food components as alternative antioxidant therapies.

Time to target uric acid to retard CKD progression

Uric acid (UA) remains a possible risk factor of chronic kidney disease (CKD) but its potential role should be elucidated given a fact that multidisciplinary treatments assure a sole strategy to inhibit the progression to end-stage renal disease (ESRD). In clinical setting, most observational studies showed that elevation of serum uric acid (SUA) independently predicts the incidence and the development of CKD. The meta-analysis showed that SUA-lowering therapy with allopurinol may retard the progression of CKD but did not reach conclusive results due to small-sized studies. Larger scale, randomized placebo-controlled trials to assess SUA-lowering therapy are needed. Our recent analysis by propensity score methods has shown that the threshold of SUA should be less than 6.5 mg/dL to abrogate ESRD. In animal models an increase in SUA by the administration of oxonic acid, uricase inhibitor, or nephrectomy can induce glomerular hypertension, arteriolosclerosis including afferent arteriolopathy and tubulointerstitial fibrosis. The ever-growing discoveries of urate transporters prompt us to learn UA metabolism in the kidney and intestine. One example is that the intestinal ABCG2 may play a compensatory role at face of decreased renal clearance of UA in nephrectomized rats, the trigger of which is not a uremic toxin but SUA itself. This review will summarize the recent knowledge on the relationship between SUA and the kidney and try to draw a conclusion when and how to treat asymptomatic hyperuricemia accompanied by CKD. Finally we will address a future perspective on UA study including a Mendelian randomization approach.

Clinical predictive factors in diabetic kidney disease progression

Diabetic kidney disease (DKD) represents a major component of the health burden associated with type 1 and type 2 diabetes. Recent advances have produced an explosion of ‘novel’ assay‐based risk markers for DKD, though clinical use remains restricted. Although many patients with progressive DKD follow a classical albuminuria‐based pathway, non‐albuminuric DKD progression is now well recognized. In general, the following clinical and biochemical characteristics have been associated with progressive DKD in both type 1 and type 2 diabetes: increased hemoglobin A1c, systolic blood pressure, albuminuria grade, early glomerular filtration rate decline, duration of diabetes, age (including pubertal onset) and serum uric acid; the presence of concomitant microvascular complications; and positive family history. The same is true in type 2 diabetes for male sex category, in patients following an albuminuric pathway to DKD, and also true for the presence of increased pulse wave velocity. The following baseline clinical characteristics have been proposed as risk factors for DKD progression, but with further research required to assess the nature of any relationship: dyslipidemia (including low‐density lipoprotein, total and high‐density lipoprotein cholesterol); elevated body mass index; smoking status; hyperfiltration; decreases in vitamin D, hemoglobin and uric acid excretion (all known consequences of advanced DKD); and patient test result visit‐to‐visit variability (hemoglobin A1c, blood pressure and high‐density lipoprotein cholesterol). The development of multifactorial ‘renal risk equations’ for type 2 diabetes has the potential to simplify the task of DKD prognostication; however, there are currently none for type 1 diabetes‐specific populations. Significant progress has been made in the prediction of DKD progression using readily available clinical data, though further work is required to elicit the role of several variables, and to consolidate data to facilitate clinical implementation.

Lower serum uric acid level predicts mortality in dialysis patients

We evaluated the impact of serum uric acid (SUA) on mortality in patients with chronic dialysis. A total of 4132 adult patients on dialysis were enrolled prospectively between August 2008 and September 2014. Among them, we included 1738 patients who maintained dialysis for at least 3 months and had available SUA in the database. We categorized the time averaged-SUA (TA-SUA) into 5 groups: <5.5, 5.5-6.4, 6.5-7.4, 7.5-8.4, and ≥8.5 mg/dL. Cox regression analysis was used to calculate the hazard ratio (HR) of all-cause mortality according to SUA group. The mean TA-SUA level was slightly higher in men than in women. Patients with lower TA-SUA level tended to have lower body mass index (BMI), phosphorus, serum albumin level, higher proportion of diabetes mellitus (DM), and higher proportion of malnourishment on the subjective global assessment (SGA). During a median follow-up of 43.9 months, 206 patients died. Patients with the highest SUA had a similar risk to the middle 3 TA-SUA groups, but the lowest TA-SUA group had a significantly elevated HR for mortality. The lowest TA-SUA group was significantly associated with increased all-cause mortality (adjusted HR, 1.720; 95% confidence interval, 1.007-2.937; P = 0.047) even after adjusting for demographic, comorbid, nutritional covariables, and medication use that could affect SUA levels. This association was prominent in patients with well nourishment on the SGA, a preserved serum albumin level, a higher BMI, and concomitant DM although these parameters had no significant interaction in the TA-SUA-mortality relationship except DM. In conclusion, a lower TA-SUA level <5.5 mg/dL predicted all-cause mortality in patients with chronic dialysis.

Pretransplant uric acid levels may be predictive for prognosis of renal transplant donors

BACKGROUND

The living kidney donor counseling prior to the operation may be helpful to learn how to properly care for the remaining single kidney for the rest of their lives. Worsening kidney function is associated with elevated serum uric acid (UA) levels. In this study, we compared the baseline laboratory findings of renal transplant donors with their follow-up laboratory values.

METHODS

The study consisted of 173 adult donors including 91 females and 82 males with a mean age of 46.82 ± 11.31 years. The follow-up clinical and laboratory examinations were performed on the third day at the end of the first and the sixth months of the surgery. According to donor's creatinine levels we constituted two groups: high creatinine and normal creatinine.

RESULTS

Patients within the high creatinine group had significantly higher mean serum UA levels when compared with the normal creatinine group. In multivariate analysis, among the other effective variables, UA level alone was found to be the most effective parameter predicting the post-transplant creatinine levels (p = 0.004, odds ratio: 12.4, 95% CI: 2.3-68.3) at sixth month post-transplantation. In the ROC analysis for the effects of UA, the following cutoff values were found: >6 mg/dL in men (sensitivity 81.3%, specificity 76.9%, positive predictive value 89.7%, negative predictive value 62.5%, accuracy 80%) and ≥5 mg/dL in women (sensitivity 72.2, specificity 74.4%, positive predictive value 89.7%, negative predictive value 62.5%, accuracy: 73.7%).

CONCLUSION

Pretransplant serum UA levels can give important clues regarding the renal functions of the donors during the postoperative period.

Management of Chronic Kidney Disease: The Relationship Between Serum Uric Acid and Development of Nephropathy

Chronic kidney disease (CKD) is increasingly recognized as a global health problem, and new and effective strategies are needed for the management of this condition. Recently, there has been renewed interest in the relationship between serum uric acid (SUA) levels and CKD, and several recent trials have demonstrated a possible link between SUA and the development and/or progression of CKD in patients with and without diabetes. The identification of key urate transporters such as urate transporter 1 and glucose transporter 9 has provided not only insights into the pathophysiology of hyperuricemia, but also possible links to other processes, such as glucose homeostasis. The renewed interest in the role of SUA in CKD has coincided with the development of sodium glucose co-transporter 2 inhibitors for the treatment of diabetes. In addition to improving glycemic control, these agents, acting via the kidneys in an insulin-independent manner, have also been shown to reduce SUA levels and potentially improve some measures of renal function. This review will discuss the role of uric acid in CKD treatment, and how SUA-lowering therapies may prevent or delay the progression of CKD.

FUNDING

Janssen Scientific Affairs.

Fructose and uric acid in diabetic nephropathy

Clinical studies have reported associations between serum uric acid levels and the development of diabetic nephropathy, but the underlying mechanisms remain elusive. There is evidence from animal studies that blocking uric acid production protects the kidney from tubulointerstitial injury, which may suggest a causal role for uric acid in the development of diabetic tubular injury. In turn, when fructose, which is endogenously produced in diabetes via the polyol pathway, is metabolised, uric acid is generated from a side-chain reaction driven by ATP depletion and purine nucleotide turnover. For this reason, uric acid derived from endogenous fructose could cause tubulointerstitial injury in diabetes. Accordingly, our research group recently demonstrated that blocking fructose metabolism in a diabetic mouse model mitigated the development of tubulointerstitial injury by lowering tubular uric acid production. In this review we discuss the relationship between uric acid and fructose as a novel mechanism for the development of diabetic tubular injury.

Defining, Treating, and Understanding Chronic Kidney Disease--A Complex Disorder

Chronic kidney disease (CKD) is prevalent in more than 20 million people in the United States. The majority of care provided to patients with this disease comes from primary care physicians, although it is often poorly understood. After an extensive literature review, it is clear that it can be difficult to classify and there are many barriers to care. Risk factors for both incident CKD and disease progression include hypertension, poor glycemic control, sociodemographic factors, acute kidney injury, metabolic acidosis, and possibly hyperuricemia and dietary factors. Treatment of patients with CKD should focus on mitigating risk factors, as well as common comorbidities such as cardiovascular disease, anemia, and bone mineral disease. Novel therapies such as pirfenidone, pentoxifylline, and endothelin-1 antagonists are being investigated with promising results.