Associations of fibroblast growth factor 23 with urate metabolism in patients with chronic kidney disease.

OBJECTIVE: In patients with preserved kidney function, a positive association of fibroblast growth factor 23 (FGF23) with serum uric acid (SUA) has been reported; however, the relationship in overall chronic kidney disease (CKD) patients has not been investigated. No report has examined the relationship between FGF23 and uric acid clearance (CUA). The aim of the present study was to determine whether FGF23 is independently associated with urate metabolism in patients with CKD stages 1-5. MATERIALS AND METHODS: In this cross-sectional study, 537 CKD patients were enrolled. SUA, CUA, FGF23, parathyroid hormone (PTH), and 1,25-dihydroxyvitamin D (1,25(OH)2D) were measured. Multivariable linear regression analysis was applied to determine independent factors associated with SUA or CUA. RESULTS: In all patients, both SUA and CUA were independently associated with male sex, use of diuretics, use of uric acid-lowering agents, estimated glomerular filtration rate, and log FGF23 (ß=0.29, P<0.01 for SUA; ß=-0.11, P<0.01 for CUA), but not with log PTH or log 1,25(OH)2D. Dyslipidemia and diabetes were also independent factors for SUA and CUA, respectively. In multivariable analyses by sex, log FGF23 was associated with SUA in both sexes (ß=0.32, P<0.01 in males vs. ß=0.20, P=0.02 in females). Conversely, log FGF23 was independently associated with CUA in males (ß=-0.15, P<0.01), but not in females (ß=-0.09, P=0.17). CONCLUSIONS: FGF23 was independently associated with urate metabolism in this population of CKD patients. FGF23 might also have a stronger association with urate metabolism in males compared with females.

Plasma B-type natriuretic peptide concentration is independently associated with kidney function decline in Japanese patients with chronic kidney disease.

BACKGROUND AND OBJECTIVE: The relationship between B-type natriuretic peptide (BNP) concentration and renal outcomes in patients with chronic kidney disease (CKD) remains unclear; therefore, it has not been determined whether BNP is related to renal outcomes, independent of cardiac parameters. This study was designed to clarify whether BNP concentration is associated with renal outcomes in CKD patients, independent of cardiac functional and structural alterations. METHODS: This prospective observational study included 372 consecutive patients with CKD. The renal endpoint was the composite of doubling of serum creatinine concentration and end-stage renal disease requiring dialysis. BNP concentrations were divided into quartiles. A Cox proportional hazards model was utilized to determine the risk factors for poor renal outcomes. RESULTS: During a median follow-up of 23.1 months, the renal endpoint was observed in 124 patients, including 14, 18, 37 and 55 patients in the first through fourth BNP quartiles, respectively. After adjustment for covariates, including cardiac parameters such as left atrial diameter, left ventricular mass index, left ventricular ejection fraction, and left ventricular hypertrophy, the hazard ratios (HRs) for renal outcomes became progressively higher for the second [HR, 1.50; 95% confidence interval (CI), 0.70-3.30), third (HR, 2.29; 95% CI, 1.11-4.91), and fourth (HR, 4.29; 95% CI, 2.05-9.39) BNP quartiles when compared with the lowest BNP quartile. CONCLUSION: Higher BNP levels were associated with adverse renal outcomes, independent of cardiac structure and function, suggesting that BNP may be a useful biomarker for exploring factors associated with kidney disease progression.

Association of serum total bilirubin with renal outcome in Japanese patients with stages 3-5 chronic kidney disease.

OBJECTIVE: Serum bilirubin has been reported to be associated with the progression of kidney disease in patients with diabetic nephropathy. Less is known, however, about the relationship between bilirubin and chronic kidney disease (CKD) of other etiologies. This study was designed to clarify whether serum total bilirubin concentration is associated with kidney disease progression in patients with CKD independent of etiology. MATERIALS AND METHODS: This prospective observational study enrolled 279 consecutive patients with stages 3-5 CKD. The renal endpoint was the composite of the doubling of serum creatinine or end-stage renal disease requiring dialysis. Patients were divided into three groups by their serum total bilirubin concentrations: ≤0.3 (lowest), 0.4-0.5 (middle), and ≥0.6 (highest) mg/dL. A Cox proportional hazards model was applied to determine the risk factors for poor renal outcome. RESULTS: The median follow-up period was 21months. One-hundred and three patients reached renal end points. After multivariable adjustment, a 0.1mg/dL increase in serum bilirubin was associated negatively with poor renal outcome (hazard ratio [HR], 0.73; 95% confidence interval [CI], 0.60-0.87). In addition, after adjustment for confounding factors, including traditional and nontraditional cardiovascular risk factors, the middle (HR 3.14, 95% CI 1.36-8.57) and lowest (HR 4.22, 95% CI 1.81-11.59) bilirubin groups had significantly higher HRs for renal outcome than the highest bilirubin group. CONCLUSIONS: Lower serum bilirubin concentration was independently associated with adverse renal outcomes, suggesting that the measurement of serum bilirubin is useful for predicting kidney disease progression in patients with moderate to severe CKD.