Asymptomatic hyperuricemia following renal transplantation

Risk factors and management of hyperuricemia after renal transplantation

Hyperuricemia (HUA) is a common complication after renal transplantation. Currently, there is no uniform consensus on factors which increase the risk for and treatment of HUA in renal transplant recipients. The purpose of this review is to summarize current and proposed risk factors and strategies to manage HUA after renal transplantation in order to assist renal function protection and prolong graft survival time.

Prevalence of Musculoskeletal Manifestations in Adult Kidney Transplant's Recipients: A Systematic Review

Background and Objectives: The musculoskeletal (MSK) manifestations in the kidney transplant recipient (KTxR) could lead to decreased quality of life and increased morbidity and mortality. However, the prevalence of these MSK manifestations is still not well-recognized. This review aimed to investigate the prevalence and outcomes of MSK manifestations in KTxR in the last two decades. Materials and Methods: Research was performed in EBSCO, EMBASE, CINAHL, PubMed/MEDLINE, Cochrane, Google Scholar, PsycINFO, Scopus, Science Direct, and Web of Science electronic databases were searched during the years 2000–2020. Results: The PRISMA flow diagram revealed the search procedure and that 502 articles were retrieved from the initial search and a total of 26 articles were included for the final report in this review. Twelve studies reported bone loss, seven studies reported a bone pain syndrome (BPS) or cyclosporine-induced pain syndrome (CIPS), and seven studies reported hyperuricemia (HU) and gout. The prevalence of MSK manifestations in this review reported as follow: BPS/CIPS ranged from 0.82% to 20.7%, while bone loss ranged from 14% to 88%, and the prevalence of gout reported in three studies as 7.6%, 8.0%, and 22.37%, while HU ranged from 38% to 44.2%. Conclusions: The post-transplantation period is associated with profound MSK abnormalities of mineral metabolism and bone loss mainly caused by corticosteroid therapy, which confer an increased fracture risk. Cyclosporine (CyA) and tacrolimus were responsible for CIPS, while HU or gout was attributable to CyA. Late diagnosis or treatment of post-transplant bone disease is associated with lower quality of life among recipients

Association Between Dietary Intake and Serum Uric Acid Levels in Kidney Transplant Patients

OBJECTIVES

The aim of this study was to evaluate the association between dietary intake and uric acid (UA) levels in kidney transplant patients (KTPs).

METHODS

A cross-sectional study was performed with 113 KTPs. Dietary intake assessment was carried out thorough two 24-hour dietary recalls using the 5-step multiple pass method. We evaluated the intake of energy, carbohydrate, total protein, animal protein, vegetable protein, total fat, saturated fat, trans fat, monounsaturated fat, polyunsaturated fat, omega-3 and omega-6 fatty acids, cholesterol, total sugar, added sugars, total fiber, insoluble fiber, soluble fiber, alcohol, caffeine, fructose, glucose, lactose, sucrose, vitamin A, vitamin C, vitamin E, and calcium. The intake of several food groups (portions) was also evaluated. Hyperuricemia was classified as >7.0 and >6 mg/dL for men and women, respectively.

RESULTS

In odds ratio analyses, the individuals who ingested more vegetable protein (g/kg) and caffeine (mg) presented lower chance to have hyperuricemia. In linear regression, animal protein (g) intake was positively associated (β = 0.011, P = .048), while vegetable protein (g/kg) intake was inversely associated (β = -2.45, P = .047) with serum UA. However, after a multiple linear regression including vegetable and animal protein intakes together, only vegetable protein intake remained associated with UA. The intake of other nutrients and portions of food groups was not associated with UA. All the analyses were adjusted for sex, age, hypertension, body mass index, glomerular filtration rate, use of medicines, and caloric intake misreporting.

CONCLUSIONS

Vegetable protein and caffeine intakes were inversely associated with UA in KTPs.

Serum Uric Acid Is Positively Associated with Muscle Mass and Strength, but Not with Functional Capacity, in Kidney Transplant Patients

Background: Our aim was to associate serum uric acid (UA) with muscle mass, strength and functional capacity in kidney transplant patients (KTPs). Methods: A cross-sectional study was performed on 113 KTPs. The fat-free mass and total and appendicular muscle mass were estimated by performing a bioelectrical impedance analysis. The strength was evaluated using the handgrip strength test (HGS) and the five times sit to stand test (5STS). The functional capacity was evaluated using the 4 m walk test and the short physical performance battery (SPPB). Results: Linear regression showed that the UA levels were positively associated with the muscle mass, fat-free mass, appendicular muscle mass, muscle mass index and appendicular muscle mass index. The 5STS results (seconds) were inversely associated with the UA levels, showing that individuals with higher UA were more likely to have more strength. However, UA was not associated with the HGS, 4 m walk test and SPPB results. Conclusion: UA levels were positively associated with muscle mass and strength, but not with functional capacity, in KTPs.

Predictors of Hyperuricemia after Kidney Transplantation: Association with Graft Function

Background and objectives: In kidney transplant recipients (KTR), hyperuricemia (HU) is a commonly-observed phenomenon, due to calcineurin inhibitors and reduced kidney graft function. Factors predicting HU, and its association with graft function, remains equivocal. Materials and Methods: We conducted a retrospective longitudinal study to assess factors associated with HU in KTR, and to determine risk factors associated with graft function, measured as glomerular filtration rate (GFR). Moreover, GFR > 60 mL/min/1.73 m² was considered normal. HU was defined as a serum uric acid level of > 416 μmol/L (4.70 mg/dL) in men and >357 μmol/L (4.04 mg/dL) in women, or xanthine-oxidase inhibitor use. We built multiple logistic regression models to assess predictors of HU in KTR, as well as the association of demographic, clinical, and biochemical parameters of patients with normal GFR after a three-year follow-up. We investigated the effect modification of this association with HU. Results: There were 144 patients (mean age 46.6 ± 13.9), with 42.4% of them having HU. Predictors of HU in KTR were the presence of cystic diseases (OR = 9.68 (3.13; 29.9)), the use of diuretics (OR = 4.23 (1.51; 11.9)), and the male gender (OR = 2.45 (1.07; 5.56)). Being a younger age, of female gender, with a normal BMI, and the absence of diuretic medications increased the possibility of normal GFR. HU was the effect modifier of the association between demographic, clinical, and biochemical factors and a normal GFR. Conclusions: Factors associated with HU in KTR: Presence of cystic diseases, diuretic use, and male gender. HU was the effect modifier of the association of demographic, clinical, and biochemical factors to GFR.

Uric Acid and Arterial Stiffness

Hyperuricemia is usually associated with hypertension, diabetes mellitus, metabolic syndrome and chronic kidney disease. Accumulating data from epidemiological studies indicate an association of increased uric acid (UA) with cardiovascular diseases. Possible pathogenic mechanisms include enhancement of oxidative stress and systemic inflammation caused by hyperuricemia. Arterial stiffness may be one of the possible pathways between hyperuricemia and cardiovascular disease, but a clear relationship between increased UA and vascular alterations has not been confirmed. The review summarizes the epidemiological studies investigating the relationship between UA and arterial stiffness and highlights the results of interventional studies evaluating arterial stiffness parameters in patients treated with UA-lowering drugs.

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.

Risk of incident gout in kidney transplant recipients: A retrospective cohort study

AIM

Gout is a common complication in kidney transplant recipients. This study evaluated the association between kidney transplant recipients and the long-term risk of incident gout.

METHOD

For this age-matched and sex-matched retrospective cohort study, the Catastrophic Illness Certificate Database and the National Health Insurance Research Database were combined between 1997 and 2010. The study included 5917 patients with kidney transplants and 23 668 matched kidney transplant-free subjects. Hazard ratio (HR) for risk of incident gout was calculated using the Cox proportional hazards regression.

RESULTS

In this study, of the 5917 kidney transplant recipients, 521 (8.8%) had gout. The kidney transplant group had a higher risk of incident gout than those in the matched kidney transplant-free group (adjusted HR = 1.55, 95% confidence intervals [CI] = 1.36-1.77), particularly within 3 years following kidney transplant recipients (adjusted HR = 2.61, 95% CI = 2.13-3.20). We observed that at the >3 to 6 years and the >6 to 9 years follow-up, patients with kidney transplant did not have a significant association with risk of incident gout (adjusted HR = 0.92, P = 0.4806 and adjusted HR = 1.26, P = 0.1901, respectively).

CONCLUSION

These findings revealed that risk of incident gout increased within 3 years following kidney transplant recipients and the individual's long-term risk of incident gout between kidney transplant recipients and the general population remained similar.