Relationship between residual renal function and serum fibroblast growth factor 23 in patients on peritoneal dialysis

Diabetes mellitus modifies the association between chronic kidney disease-mineral and bone disorder biomarkers and aortic stiffness in peritoneal dialysis patients

This study aimed to investigate the relationship of four chronic kidney disease-mineral and bone disorder (CKD-MBD) biomarkers, including intact parathyroid hormone (PTH), fibroblast growth factor 23 (FGF23), soluble klotho, and fetuin-A, with aortic stiffness in peritoneal dialysis (PD) patients, comparing those with and without diabetes mellitus (DM). A total of 213 patients (mean age 58 ± 14 years; 81 (38.0%) patients with DM) were enrolled. Their aortic pulse wave velocity (PWV) was measured using pressure applanation tonometry, while serum intact PTH, FGF23, α-klotho, and fetuin-A levels were measured using enzyme-linked immunosorbent assay. Overall, patients with DM had higher aortic PWV than those without (9.9 ± 1.8 vs. 8.6 ± 1.4 m/s, p < 0.001). Among the four CKD-MBD biomarkers, FGF23 levels were significantly lower in DM group (462 [127-1790] vs. 1237 [251-3120] pg/mL, p = 0.028) and log-FGF23 independently predicted aortic PWV in DM group (β: 0.61, 95% confidence interval: 0.06-1.16, p = 0.029 in DM group; β: 0.10, 95% confidence interval: - 0.24-0.45, p = 0.546 in nonDM group; interaction p = 0.016). In conclusion, the association between FGF23 and aortic PWV was significantly modified by DM status in PD patients.

Residual Renal Phosphate Clearance in Patients Receiving Hemodialysis or Hemodiafiltration

OBJECTIVES

Substantial levels of residual renal clearance and urine output may occur in patients treated with hemodialysis or hemodiafiltration. However, the relationships among residual renal urea, creatinine, and phosphate clearances, respectively, and between clearances and urine volume have not been well described.

METHODS

We performed a prospective, cross-sectional study which enrolled hemodialysis and hemodiafiltration patients with a urine volume of >100 mL/day, in whom at least 2 residual renal clearances were obtained over a 6-month observation period. Urine was collected for 24 hours prior to the midweek treatment session and concentrations of urea, creatinine, and phosphate were measured.

RESULTS

Thirty-eight patients (24 men, 14 women) with a mean age of 70.4 ± 12.4 (SD) years were included in this analysis. All patients were dialyzed 3 times per week with mean treatment duration of 243 ± 7.89 minutes. Twenty patients were undergoing hemodiafiltration and 18 patients high-flux hemodialysis. In total, 102 dialysis sessions, of which 52 were hemodiafiltration, and urine collections were analyzed. Mean urine volume was 457 ± 254 mL per 24 hours. Residual renal clearance rates of urea (Kr Urea), creatinine (Kr Cr), and phosphate (Kr Phos) were 1.60 ± 0.979, 4.69 ± 3.79, and 1.98 ± 1.36 mL/minute, respectively. Mean ratios of Kr Cr/Kr Urea, Kr Phos/Kr Urea, and Kr Phos/Kr Cr were 2.83 ± 1.21, 1.23 ± 0.387, and 0.477 ± 0.185, respectively. There was a modest correlation between Kr Phos and daily urine volume (r = 0.605, P = .001).

CONCLUSIONS

In maintenance hemodialysis and hemodiafiltration patients, residual renal phosphate clearance is approximately 23% higher than residual renal urea clearance. Urine volume is a modestly accurate surrogate for estimating residual renal phosphate clearance, but only when urine volume is <300 mL/day.

Relationship between Residual Urine Output and Type of Dialysis with FGF23 Levels

Several studies investigated the role of fibroblast growth factor 23 (FGF23) in the regulation of renal phosphate excretion in chronic kidney disease (CKD). However, patients with residual urine output (UO) seem to control their serum phosphorus levels better. Our aim was to determine whether FGF23 levels are influenced by dialysis modality and UO. We performed a cross-sectional study in hemodialysis (HD) and peritoneal dialysis (PD) patients. The C-terminal FGF23 (cFGF23) levels were determined in plasma with a two-site enzyme-linked immunosorbent assay. The UO collection referred to an mL/day measurement. All p values were two-sided, and the statistical significance was set at p < 0.05. We enrolled 133 patients (58 HD, 75 PD, UO 70%). The median cFGF23 was significantly higher in HD vs. PD patients (p = 0.0017) and not significantly higher in patients without UO (p = 0.12). We found a negative correlation between cFGF23 and the UO volume (p = 0.0250), but the correlation was not significant when considering the type of dialysis treatment. Phosphorus (ß = 0.21677; p = 0.0007), type of dialysis (ß = −0.68392; p = 0.0003), and creatinine (ß = 0.08130; p = 0.0133) were significant and independent predictors of cFGF23 levels. In conclusion, cFGF23 was significantly higher in HD than in PD patients. We found a significant negative correlation between cFGF23 and the residual UO volume, but the correlation was not significant considering the type of dialysis. Our study reveals that dialysis modality is an independent predictor of FGF23 levels. In particular, PD is associated with lower FGF23 levels than HD.

Factors affecting the relationship between ionized and corrected calcium levels in peritoneal dialysis patients: a retrospective cross-sectional study

BACKGROUND

Chronic kidney disease-mineral and bone disorder (CKD-MBD) management in patients with end-stage renal disease is important owing to the risk of cardiovascular diseases. In clinical practice, we manage patients not by monitoring the levels of biologically active ionized calcium (iCa) but by monitoring total serum calcium or corrected calcium (cCa). We previously reported that iCa/cCa ratio was different between patients with hemodialysis and those with peritoneal dialysis (PD). In PD patients, several factors are expected to affect iCa/cCa ratio. Therefore, modifying the strategy to achieve better CKD-MBD management might be necessary; however, no reports have studied this to date. Therefore, we investigated the factors influencing iCa/cCa ratio in PD patients.

METHODS

This retrospective cross-sectional study examined background and laboratory data, including iCa, collected at routine outpatient visits. The patients were divided into the first, second, and third tertile of iCa/cCa ratio groups to compare patient background and laboratory data. Multiple regression analysis was used to investigate the factors influencing iCa/cCa ratio. We used multiple imputation to deal with missing covariate data.

RESULTS

In total, 169 PD patients were enrolled. In PD patients with lower iCa/cCa ratio, PD duration was longer and pH was higher. Urine volume and weekly renal Kt/V were lower in the patients with lower iCa/cCa ratio than in those with higher iCa/cCa ratio. iCa/cCa ratio and weekly renal Kt/V were directly correlated (r = 0.41, p < 0.01), and weekly renal Kt/V and pH were independent factors affecting iCa/cCa ratio (t = 2.86, p < 0.01 and t = - 5.42, p < 0.01, respectively).

CONCLUSIONS

iCa levels were lower in PD patients with lower residual renal function (RRF) even though their cCa levels were equal to those with maintained RRF, warranting caution in the assessment and management of CKD-MBD in PD patients.

Fibroblast growth factor-23 correlates with advanced disease conditions and predicts high risk of major adverse cardiac and cerebral events in end-stage renal disease patients undergoing continuous ambulatory peritoneal dialysis

BACKGROUND

This study aimed to investigate the correlation of serum fibroblast growth factor-23 (FGF-23) level with clinical indexes, in particular to explore the value of FGF-23 in predicting major adverse cardiac and cerebral event (MACCE) risk in end-stage renal disease (ESRD) patients undergoing continuous ambulatory peritoneal dialysis (CAPD).

METHODS

In 270 ESRD patients undergoing CAPD consecutively enrolled in this prospective cohort study, we collected serum samples and performed enzyme-linked immunosorbent assay to detect FGF-23 expression. MACCE-free survival was defined as the date from enrollment to the date of MACCE occurrence.

RESULTS

High levels of FGF-23 correlated with longer duration of dialysis (p = 0.002), elevated levels of calcium (p < 0.001), phosphorus (p = 0.037) and low density lipoprotein cholesterol (p = 0.027). MACCE occurrence rate was higher in the FGF-23 high-expression than low-expression group at 2 years (p = 0.028), 3 years (p = 0.001) and 4 years (p = 0.004). Kaplan-Meier curves revealed that MACCE-free survival was shorter in the FGF-23 high-expression than low-expression group (p = 0.004). Multivariate Cox's analysis showed that high FGF-23 expression (p = 0.011) as well as the duration of dialysis (p = 0.017), C-reactive protein (p = 0.011) and fasting blood glucose (p = 0.038) were independent predictive factors for reduced MACCE-free survival in ESRD patients undergoing CAPD.

CONCLUSION

High FGF-23 expression correlates with advanced disease conditions as well as increased MACCE risk, and is an independent factor predicting worse MACCE-free survival in ESRD patients undergoing CAPD.

Total Phosphate Elimination is Negatively Associated With Increased Serum Fibroblast Growth Factor 23 Levels in Patients who Undergo Peritoneal Dialysis

As fibroblast growth factor 23 (FGF23) has been shown to induce cardiovascular disease directly in patients with chronic kidney disease, identification of factors and treatments that can modulate serum FGF23 (sFGF23) level is clinically important. This retrospective longitudinal study investigated factors that modulate sFGF23 in 49 patients who underwent peritoneal dialysis (PD). sFGF23 ratio (sFGF23 at 18 months/baseline sFGF23) was used as an indicator of changes in sFGF23 level. Total phosphate elimination was the sum of both renal phosphate excretion and dialysate phosphate elimination. In multivariate analysis, log sFGF23 ratio was associated negatively with total phosphate elimination and the use of cinacalcet at baseline, and positively with the use of vitamin D receptor activators at baseline, even after adjusting for potential confounding factors. Our study indicates that maintaining phosphate elimination can prevent increased sFGF23_, thereby preventing cardiovascular events in patients who undergo PD.

Factors Associated with the Serum Myostatin Level in Patients Undergoing Peritoneal Dialysis: Potential Effects of Skeletal Muscle Mass and Vitamin D Receptor Activator Use

Myostatin is a member of the transforming growth factor-β family, which regulates synthesis and degradation of skeletal muscle proteins and is associated with the development of sarcopenia. It is up-regulated in the skeletal muscle of chronic kidney disease patients and is considered to be involved in the development of uremic sarcopenia. However, serum myostatin levels have rarely been determined, and the relationship between serum myostatin levels with clinical and metabolic factors remains unknown. This cross-sectional study investigated the association between serum myostatin level and clinical factors in 69 outpatients undergoing peritoneal dialysis. Serum myostatin level was determined by commercially available enzyme-linked immunosorbent assay (ELISA). Univariable and multivariable analysis were conducted to determine factors associated with serum myostatin levels. The factors included age, sex, diabetes mellitus, dialysis history, body mass index, residual kidney function, peritoneal dialysate volume, serum biochemistries, and the use of vitamin D receptor activators (VDRAs). Mean serum myostatin level was 7.59 ± 3.37 ng/mL. There was no association between serum myostatin level and residual kidney function. Serum myostatin levels were significantly and positively associated with lean body mass measured by the creatinine kinetic method and negatively associated with the use of VDRAs after adjustment for potential confounding factors. Our study indicated that serum myostatin levels are associated with skeletal muscle mass and are lower in patients treated with VDRAs. Further studies are necessary to determine the significance of measuring serum myostatin level in patients undergoing peritoneal dialysis.

The Association between Nutritional Markers and Biochemical Parameters and Residual Renal Function in Peritoneal Dialysis Patients

Residual renal function (RRF) is an important prognostic factor for peritoneal dialysis patients as it influences the quality of life and mortality. This study was conducted to explore the potential factors correlated with RRF. A cross-sectional study was conducted by recruiting 155 patients with residual GFR more than 1mL/min per 1.73m2 at the initiation of peritoneal dialysis. We collected the demographic characteristics, nutritional markers and biochemical parameters of all participants, and analyzed the correlation between these variables and residual GFR as well. The odds ratio of RRF loss associated with each of the nutritional markers and biochemical parameters were estimated by logistic regression model. The residual GFR was negatively correlated with serum phosphate (ORQ3 = 2.67, 95%CI: 1.03-6.92; ORQ4 = 3.45, 95%CI: 1.35-9.04), magnesium (ORQ4 = 3.77, 95%CI: 1.48-3.63), and creatinine (ORQ3 = 2.93, 95%CI: 1.09-7.88; ORQ4 = 8.64 95%CI: 2.79-26.78), while positively associated with normalized protein catabolic rate (ORQ3 = 0.24, 95%CI: 0.09-0.65; ORQ4 = 0.11, 95%CI: 0.03-0.35), 24 hours urine volume(ORQ1 = 22.87, 95%CI: 2.76-189.24; ORQ3 = 0.08, 95%CI: 0.02-0.28) and serum chlorine concentrations (ORQ1 = 5.34, 95%CI: 1.94-14.68; ORQ4 = 0.28, 95%CI: 0.09-0.85), respectively. Our study suggested that the nutritional markers and biochemical parameters, though not all, but at least in part were closely correlated with RRF in peritoneal dialysis patients.

Factors associated with serum soluble inhibitors of Wnt-β-catenin signaling (sclerostin and dickkopf-1) in patients undergoing peritoneal dialysis

AIM

Sclerostin and dickkopf-1 (Dkk-1) are soluble inhibitors of Wnt-β-catenin signaling and are involved in decreased bone formation and bone volume in patients with various bone diseases. The clinical characteristics of sclerostin and Dkk-1 and their impacts on mineral and bone metabolism remain undetermined in patients undergoing peritoneal dialysis (PD).

METHODS

This cross-sectional study investigated the association between serum sclerostin and Dkk-1 levels and mineral disorders in 74 outpatients under PD treatment. Levels of sclerostin and Dkk-1 in serum, urine, and peritoneal dialysate were determined using enzyme-linked immunosorbent assay kits. The associations between serum sclerostin and Dkk-1 levels and biochemical parameters were evaluated by linear regression analyses.

RESULTS

Median serum sclerostin and Dkk-1 levels were 138 pmol/L (range, 98.3-195.9 pmol/L) and 38.8 pmol/L (range, 28.5-47.1 pmol/L), respectively. Both sclerostin and Dkk-1 were excreted into urine and peritoneal dialysate. Multivariable linear regression analyses showed that serum sclerostin level was significantly associated with age, sex, parathyroid hormone level, and renal Kt/V. In contrast, serum Dkk-1 level was associated with platelet count and serum fibroblast growth factor 23 level but not with any of the bone metabolic markers.

CONCLUSION

Serum sclerostin was associated with serum intact parathyroid hormone, while Dkk-1 was associated with serum fibroblast growth factor 23 in patients undergoing PD. The utility of determining soluble Wnt-β-catenin inhibitors levels in patients undergoing PD requires further investigation.