The association between serum uric acid levels at 3 months after renal transplantation and the graft outcome in living donor renal transplantation. Transplant Proc. 2013;45:1548-1552. [PMID: 23726617 DOI: 10.1016/j.transproceed.2012.10.062]

Switching from allopurinol to febuxostat: efficacy and safety in the treatment of hyperuricemia in renal transplant recipients

The aim of this study was to evaluate the efficacy and tolerability of febuxostat in renal transplant recipients who were previously treated with allopurinol (the daily oral dose is 100 mg). A 6-month cohort study was conducted with 46 renal transplant recipients who had hyperuricemia. In 22 patients, treatment was changed from allopurinol to febuxostat (febuxostat was given at an oral dose of 20 mg once a day), and the other 24 patients continued the allopurinol treatment (the daily oral dose is 100 mg). The serum levels of uric acid (UA), creatinine, other biochemical parameters, estimated glomerular filtration rate (eGFR), and adverse events were measured at baseline as well as at 1, 3, and 6 months after the switch to febuxostat. Serum UA levels significantly decreased from 470.82 ± 34.37 to 378.77 ± 51.97 μmol/L in the febuxostat group, and decreased from 469.46 ± 33.47 to 428.21 ± 23.37 μmol/L in the allopurinol group. The eGFR increased from 75.55 to 85.23 mL/min in the febuxostat group, and decreased from 78.79 to 70.31 mL/min in the allopurinol group. In renal transplant recipients, febuxostat reduced the serum UA levels resulting in minor short-term improvement of renal function with no changes in the other biochemical parameters.

Association between post-transplant serum uric acid levels and kidney transplantation outcomes

Background

Serum uric acid (UA) level has been reported to be associated with chronic allograft nephropathy and graft failure in patients who undergo kidney transplantation (KT). However, the role of serum UA level in renal graft survival remains controversial.

Objective

This study aimed to investigate the effect of mean serum UA level during two different post-KT periods on long-term renal graft outcomes in a large population cohort in which living donor KT prevails.

Material and methods

A retrospective cohort study was performed using KT data prospectively collected at a single institution. Patients (n = 2,993) were divided into low-, normal-, and high-UA groups according to the mean serum UA level within the first year (1-YR) and 1–5 years (5-YR) after transplantation.

Results

In the 1-YR Cox proportional hazards analysis, the low- and high-UA groups had a significantly decreased and increased risk, respectively, for overall graft failure (OGF), death-censored graft failure (DCGF), and composite event (return to dialysis, retransplantation, death from graft dysfunction, and 40% decline in estimated glomerular filtration rate) compared with the normal-UA group. Similarly, in the 5-YR analysis, the low-UA group had a significantly reduced risk of DCGF compared with the normal-UA group, whereas the high-UA group had a significantly increased risk of all three graft outcomes. In a marginal structural model, hyperuricemia had a significant causal effect on worsening graft outcomes, with consideration of all confounding variables (OGF: hazard ratio [HR] 2.27, 95% confidence interval [CI] 1.33–3.78; DCGF: HR 2.38, 95% CI 1.09–4.9; composite event: HR 3.05, 95% CI 1.64–5.49).

Conclusions

A low-to-normal serum UA level within the first year and 1–5 years after KT is an independent factor for better renal allograft outcomes in the long-term follow-up period rather than high serum UA level.

Early onset hyperuricemia is a prognostic marker for kidney graft failure: Propensity score matching analysis in a Korean multicenter cohort

It remains inconclusive whether hyperuricemia is a true risk factor for kidney graft failure. In the current study, we investigated the association of hyperuricemia and graft outcome. We performed a multi-center cohort study that included 2620 kidney transplant recipients. The patients were classified as either normouricemic or hyperuricemic at 3 months after transplantation. Hyperuricemia was defined as a serum uric acid level ≥ 7.0 mg/dL in males or ≥ 6.0 mg/dL in females or based on the use of urate-lowering medications. The two groups were compared before and after propensity score matching. A total of 657 (25.1%) patients were classified as hyperuricemic. The proportion of hyperuricemic patients increased over time, reaching 44.2% of the total cohort at 5 years after transplantation. Estimated glomerular filtration rate and donor type were independently associated with hyperuricemia. Hyperuricemia was associated with graft loss according to multiple Cox regression analysis before propensity score matching (hazard ratio [HR] = 1.56, 95% confidence interval [CI] = 1.14-2.13, P = 0.005) as well as after matching (HR = 1.65, 95% CI = 1.13-2.42, p = 0.010). Cox regression models using time-varying hyperuricemia or marginal structural models adjusted with time-varying eGFR also demonstrated significant hazards of hyperuricemia for graft loss. Cardiovascular events and recipient survival were not associated with hyperuricemia. Overall, hyperuricemia, especially early onset after transplantation, showed an increased risk for graft failure. Further studies are warranted to determine whether lowering serum uric acid levels would be beneficial to graft survival.

Asymptomatic hyperuricemia following renal transplantation

Evidence is accumulating indicating a role for uric acid in the genesis and progression of kidney disease, and a few studies are beginning to show a possible beneficial effect of urate-lowering therapy. Whether this holds true for renal allograft recipients is not clear. In this short review evidence from epidemiological as well as intervention studies is summarized and discussed, with some practical considerations presented at the end.

Increased urine transforming growth factor β1 (TGF-β1) and serum uric acid are associated with an early decline of glomerular filtration rate in kidney transplant recipients

BACKGROUND

The renin-angiotensin system (RAS) and transforming growth factor β1 (TGF-β1) may play a role in the pathogenesis of fibrosis in kidney allografts. Experimental hyperuricemia shows activation of intrarenal RAS. However, the association between uric acid (UA), RAS, and TGF-β1 in allograft recipients has not been demonstrated. Therefore we investigated the association between serum UA levels, RAS, and TGF-β1 in kidney transplant recipients during the 1st year after transplantation.

METHODS

Sixty-two transplant recipients were included in the study. Serum UA level, plasma renin activity (PRA), and urine TGF-β1 concentration were studied at 3, 6, and 12 months after transplantation. Statistical correlation was demonstrated with the use of Spearman rank correlation coefficient. Receiver operating characteristic curve analysis and area under the curve were performed to assess the diagnostic performance to discriminate between estimated glomerular filtration rate (eGFR) <60 and ≥ 60 mL/min/1.73 m(2).

RESULTS

For all 62 patients, urine TGF-β1 and serum UA had a tendency to increase during the 1-year follow-up period, despite no statistically significant change in eGFR. We found that increased urine TGF-β1 was correlated with rising serum UA levels and a decrease of the eGFR (r = 0.27 [P = .01]; r = -0.38 [P = .0003]). In contrast, there was no significant change in PRA and it was not correlated with eGFR or TGF-β1 (r = -0.01; P = .93).

CONCLUSIONS

Increased urine TGF-β1 and serum UA level during the 1st year after transplantation correlated with a decline in eGFR. The evaluation of these parameters in the early post-transplantation period may identify patients at risk of allograft dysfunction.

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.

Uric acid and allograft loss from interstitial fibrosis/tubular atrophy: post hoc analysis from the angiotensin II blockade in chronic allograft nephropathy trial

BACKGROUND

Uric acid has been linked to the progression of native kidney disease. Studies evaluating its contribution to allograft function in kidney transplant recipients, among whom hyperuricemia is common, have yielded mixed results.

METHODS

We evaluated the association between baseline uric acid and the primary composite outcome of doubling of interstitium or ESRD from interstitial fibrosis and tubular atrophy (IF/TA) in the Angiotensin II Blockade for Chronic Allograft Nephropathy (ABCAN) Trial participants. Subjects underwent uric acid, iothalamte GFR, and urine albumin to creatinine (ACR) measurements annually for 5 years in addition to an allograft biopsy at baseline and 5 years.

RESULTS

Baseline uric acid was 5.57±1.48 mg/dL; male sex, higher BMI, diuretic use, and lower GFR were associated with higher uric acid, whereas older age, less than 3 HLA matches and having a female donor were associated with lower levels. In multivariate analysis adjusting for baseline GFR, uric acid was associated with doubling of interstitium or ESRD from IF/TA (OR 1.83, 95% CI, 1.06-3.17, P=0.03). Over time, a 1 mg/dL increase in time-varying uric acid was associated with a 2.39 mL/min lower final GFR (P<0.001) but not with the secondary outcome of creatinine doubling, ESRD, or death.

CONCLUSIONS

These data suggest that uric acid is associated with IF/TA and thus may be a viable target for intervention.

Uric acid has a J-shaped association with cardiovascular and all-cause mortality in kidney transplant recipients

The association between serum uric acid and kidney graft and recipient survival is uncertain. During 2000-2011, we measured serum uric acid at week 10 after transplantation. Of 2748 transplanted patients, 2200 (80.1%) attended this visit. After a median follow-up of 7.4 yr, 378 patients had died, 143 from a cardiovascular cause, and 185 patients lost their graft. The third quintile of uric acid levels (357-405 μM) had the lowest mortality risk and was used as reference group. In Cox proportional hazard models adjusting for graft and patient characteristics, the fifth quintile of uric acid levels (>474 μM) was independently associated with cardiovascular mortality (hazard ratio [HR] = 2.87 [1.55-5.32], p = 0.001) and all-cause mortality (HR = 1.57 [1.09-2.25], p = 0.02). Also, the lowest quintile of uric acid levels (<309 μM) showed a trend toward increased risk of cardiovascular mortality (HR = 1.79 [0.90-3.58], p = 0.10) and all-cause mortality (HR = 1.31 [0.89-1.93], p = 0.18). The increased risk at low uric acid levels was confined to diabetic recipients. Uric acid was not associated with death-censored graft loss. In conclusion, uric acid has a J-shaped association with cardiovascular and all-cause mortality in kidney transplant recipients.