25(OH)D deficiency has been associated with significantly worse physical performance in individuals with normal renal function. We examined the physical function, muscle strength and balance in age- and gender-matched 25 Stage 3 - 4 CKD patients and 47 Stage 5 CKD patients on peritoneal dialysis (PD) with vitamin D deficiency by objective methods and evaluated the effect of vitamin D replacement on physical performance tests: the "timed up and go" (TUG) test, gait velocity test, timed chair stand test, stair climb test, dynamic balance tests (TUG test, dynamic postural stability test), static balance test (functional reach test) and muscle strength in these two groups. At baseline 25(OH)D in the Stage 3 - 4 CKD patients and patients on PD were 6.9 ± 3.5 ng/ ml (17.2 ± 8.7 nmol/l) and 5.7 ± 3.3 ng/ml (14.2 ± 8.2 nmol/l), respectively (p > 0.05). Mean (± SD) 25(OH)D in Stage 3 - 4 CKD patients and those on PD were 52.0 ± 40.9 ng/ml (129.7 ± 102.2 nmol/l) and 41.9 ± 21, ng/ml (104,5 ± 52,6 nmol/l) respectively after vitamin D replacement (p > 0.05). When both Stage 3 - 4 CKD and dialysis patients became vitamin D-sufficient after vitamin D replacement, they took a significantly shorter time to complete the TUG test, gait velocity test, the timed chair stand test and stair climb test. Results of physical performance tests, static and dynamic balance tests and isometric strength tests improved in both groups after the treatment (p < 0.05). In conclusion, our results show that vitamin D supplementation improves muscle strength, functional ability and balance in both CKD and dialysis patients.

The aim of this study was to evaluate the prevalence of vitamin D deficiency in chronic renal failure (CRF) patients on peritoneal dialysis (PD) and to correlate the findings with various demographic and renal osteodystrophy markers. This cross-sectional, multicenter study was carried out in 273 PD patients with a mean age of 61.7 +/- 10.9 years and mean duration of PD 3.3 +/- 2.2 years. It included 123 female and 150 male patients from 20 centers in Greece and Turkey, countries that are on the same latitude, namely, 36-42 degrees north. We measured 25(OH)D3 and 1.25(OH)2D3 levels and some other clinical and laboratory indices of bone mineral metabolism. Of these 273 patients 92% (251 patients) had vitamin D deficiency i.e. serum 25(OH)D3 levels less than 15 ng/ml, 119 (43.6%) had severe vitamin D deficiency i.e., serum 25(OH)D3 levels, less than 5 ng/ml, 132 (48.4%) had moderate vitamin D deficiency i.e., serum 25(OH)D3 levels, 5-15 ng/ml, 12 (4.4%) vitamin D insufficiency i.e., serum 25(OH)D3 levels 15 - 30 ng/ml and only 10 (3.6%) had adequate vitamin D stores. We found no correlation between 25(OH)D3 levels and PTH, serum albumin, bone alkaline phosphatase, P, and Ca x P. In multiple regression analyses, the independent predictors of 25(OH)D3 were age, presence of diabetes (DM-CRF), levels of serum calcium and serum 1.25(OH)2D3. We found a high prevalence (92%) of vitamin D deficiency in these 273 PD patients, nearly one half of whom had severe vitamin D deficiency. Vitamin D deficiency is more common in DM-CRF patients than in non-DM-CRF patients. Our findings suggest that these patients should be considered for vitamin D supplementation.

Context. Despite the risk of aluminum (Al) toxicity in dialysis patients, little is known about its toxicokinetics (TK) in this population. A national contamination of dialysate solutions with Al provided the opportunity to study Al TK in peritoneal dialysis (PD) patients and to better understand the influence of covariates on its disposition. Methods. Al levels in serum and dialysate as well as other laboratory values were collected prospectively from 83 PD patients after correction of Al contamination. Population TK analyses were conducted with NONMEM VI using standard model discrimination criteria. Covariate analyses were also performed using stepwise forward regression followed by backward deletion. Results. After correction of Al exposure, serum levels declined in a biphasic manner, which was captured by the TK model. The TK of Al were best described by a 2-compartment model with linear elimination. Total creatinine clearance was a significant covariate for total clearance (CL). Mean parameter estimates for volume of central compartment (V1), CL, volume of peripheral compartment (V2), volume of distribution at steady-state (Vss), and intercompartmental clearance (Q) were 168 L, 8.99 L/day, 12 000 L, 12 168 L, and 4.93 L/day, respectively. Inter-individual variability for CL and V2 were 22.6 and 51.1%, respectively. Al distributional half-life was 8.5 days, while the terminal elimination half-life was 7.2 years. This model confirms that the large Vss reflects the widespread distribution of Al in bone, lungs, liver, and other tissues. Conclusion. This study describes the first population Al TK model in a large group of PD patients, which includes a covariate effect. The model confirms the extensive half-life and tissue distribution of Al in a dialysis-dependent population.