Effect of an oral dose of 25-hydroxyvitamin D3 on its blood levels in patients with the nephrotic syndrome

Vitamin D supplementation in children and young adults with persistent proteinuria secondary to glomerular disease

BACKGROUND

Vitamin D deficiency is common in glomerular disease. Supplementation may be ineffective due to ongoing urinary losses of vitamin D binding protein. We sought to determine if daily cholecalciferol supplementation would increase vitamin D concentrations in children with glomerular disease and persistent proteinuria, without adverse effects.

METHODS

Eighteen participants at least 5 years of age with primary glomerular disease and urine protein:creatinine ratio ≥ 0.5 were enrolled from four pediatric nephrology practices to receive cholecalciferol supplementation: 4,000 IU or 2,000 IU per day for serum 25 hydroxyvitamin vitamin D (25OHD) concentrations < 20 ng/mL and 20 ng/mL to < 30 ng/mL, respectively. Measures of vitamin D and mineral metabolism were obtained at baseline and weeks 6 and 12. Multivariable generalized estimating equation (GEE) regression estimated mean percent changes in serum 25OHD concentration.

RESULTS

Median baseline 25OHD was 12.8 ng/mL (IQR 9.3, 18.9) and increased to 27.8 ng/mL (20.5, 36.0) at week 6 (p < 0.001) without further significant increase at week 12. A total of 31% of participants had a level ≥ 30 ng/mL at week 12. Supplementation was stopped in two participants at week 6 for mildly elevated calcium and phosphorus, respectively, with subsequent declines in 25OHD of > 20 ng/mL. In the adjusted GEE model, 25OHD was 102% (95% CI: 64, 141) and 96% (95% CI: 51, 140) higher versus baseline at weeks 6 and 12, respectively (p < 0.001).

CONCLUSION

Cholecalciferol supplementation in vitamin D deficient children with glomerular disease and persistent proteinuria safely increases 25OHD concentration. Ideal dosing to fully replete 25OHD concentrations in this population remains unknown.

CLINICAL TRIAL

NCT01835639. A higher resolution version of the Graphical abstract is available as Supplementary information.

Role of vitamin D supplementation in the management of musculoskeletal diseases: update from an European Society of Clinical and Economical Aspects of Osteoporosis, Osteoarthritis and Musculoskeletal Diseases (ESCEO) working group

Vitamin D is a key component for optimal growth and for calcium-phosphate homeostasis. Skin photosynthesis is the main source of vitamin D. Limited sun exposure and insufficient dietary vitamin D supply justify vitamin D supplementation in certain age groups. In older adults, recommended doses for vitamin D supplementation vary between 200 and 2000 IU/day, to achieve a goal of circulating 25-hydroxyvitamin D (calcifediol) of at least 50 nmol/L. The target level depends on the population being supplemented, the assessed system, and the outcome. Several recent large randomized trials with oral vitamin D regimens varying between 2000 and 100,000 IU/month and mostly conducted in vitamin D-replete and healthy individuals have failed to detect any efficacy of these approaches for the prevention of fracture and falls. Considering the well-recognized major musculoskeletal disorders associated with severe vitamin D deficiency and taking into account a possible biphasic effects of vitamin D on fracture and fall risks, an European Society for Clinical and Economic Aspects of Osteoporosis, Osteoarthritis and Musculoskeletal Diseases (ESCEO) working group convened, carefully reviewed, and analyzed the meta-analyses of randomized controlled trials on the effects of vitamin D on fracture risk, falls or osteoarthritis, and came to the conclusion that 1000 IU daily should be recommended in patients at increased risk of vitamin D deficiency. The group also addressed the identification of patients possibly benefitting from a vitamin D loading dose to achieve early 25-hydroxyvitamin D therapeutic level or from calcifediol administration.

Effect of Oral Calcidiol Treatment on Its Serum Levels and Peritoneal Losses

Objectives

To evaluate calcidiol serum levels in a group of continuous ambulatory peritoneal dialysis (CAPO) patients and the effect of oral calcidiol treatment on serum levels and peritoneal losses.

Study design

Twenty patients (13 female, 7 male) were studied for 12 –60 months. Their ages ranged 22 72 years (mean 46±15). Serum calcidiol, total protein and urea were determined at baseline and after the administration per os of 0.133 mcg/day of calcidiol for 10 days. At the same time, calcidiol and total protein were measured in peritoneal effluent at baseline and at 5,10, and 40 days after starting this treatment.

Results

A significant and direct correlation between the calcidiol dialysis/plasma ratio and the peritoneal protein losses was found, both before and 40 days after calcidiol administration when calcidiol serum levels were the lowest. As calcidiol serum levels rose to the normal range in the course of the study, peritoneal losses of this metabolite increased slightly and correlated with calcidiol serum levels and urea mass transfer coefficient (MTC); the significant correlation between calcidiol serum levels and peritoneal protein losses disappeared.

Conclusions

When serum calcidiol levels are low, calcidiol peritoneal losses in patients on CAPO correlate with protein peritoneal losses. However, when serum calcidiollevels rise, the calcidiol peritoneal losses correlate with calcidiol serum levels and urea MTC, and not with protein peritoneal losses.

Modified-release calcifediol effectively controls secondary hyperparathyroidism associated with vitamin D insufficiency in chronic kidney disease

BACKGROUND/AIMS

Vitamin D insufficiency drives secondary hyperparathyroidism (SHPT) and is associated with increased cardiovascular mortality in patients with chronic kidney disease (CKD). SHPT is poorly addressed by current vitamin D repletion options. The present study evaluated a novel investigational vitamin D repletion therapy: a modified-release (MR) formulation of calcifediol designed to raise serum 25-hydroxyvitamin D in a gradual manner to minimize the induction of CYP24 and, thereby, improve the SHPT control.

METHODS

This randomized, double-blind, placebo-controlled trial evaluated MR calcifediol in CKD subjects (n = 78) with plasma intact parathyroid hormone (iPTH) >70 pg/ml and serum total 25-hydroxyvitamin D <30 ng/ml. Subjects received daily treatment for six weeks with oral MR calcifediol (30, 60 or 90 µg) or a placebo.

RESULTS

More than 90% of subjects treated with MR calcifediol achieved serum 25-hydroxyvitamin D levels ≥30 ng/ml versus 3% of subjects treated with placebo (p < 0.0001). Mean plasma iPTH decreased from baseline (140.3 pg/ml) by 20.9 ± 6.2% (SE), 32.8 ± 5.7 and 39.3 ± 4.3% in the 30, 60 and 90 µg dose groups, respectively, and increased 17.2 ± 7.8% in the pooled placebo group (p < 0.005). No clinically significant safety concerns arose during MR calcifediol treatment.

CONCLUSION

Oral MR calcifediol appears safe and highly effective in treating SHPT associated with vitamin D insufficiency in CKD.

Pharmacokinetics and pharmacodynamics of benazepril hydrochloride in patients with major proteinuria

We have investigated whether the pharmacokinetics and pharmacodynamics of the ACE inhibitor benazepril hydrochloride are altered with proteinuria by studying 8 patients with major proteinuria of different causes who were given a single dose of 10 mg p.o. The maximum plasma concentration of benazepril was found between 0.5 and 2 h after dosing (median 1 h). Its elimination was almost complete within 6 h. Peak plasma levels of benazeprilat, the active metabolite of benazepril, were observed between 1 and 6 h (median 2.5 h). The elimination of benazeprilat from plasma was biphasic, with mean initial and terminal half-lives of 3.0 and 17.3 h, respectively. On average, the pharmacokinetic parameters of benazepril and benazeprilat in the patients did not differ from those in a historical control group of healthy volunteers, but intersubject variability in the AUC and half-lives of benazeprilat was greater in the patients. Plasma ACE was completely inhibited from 1.5 to 6 h after dosing, and at 48 h the mean inhibition was still 42%. Plasma renin showed substantial intersubject variation. Mean supine blood pressure (systolic/diastolic) was reduced from baseline by a maximum of 18/13 mm Hg at 6 h. Proteinuria was diminished after benazepril in 7 patients. In conclusion, the results of this study suggest that proteinuria in the nephrotic range does not require a change in benazepril dosage.

Vitamin D metabolism in nephrotic rats

Vitamin D metabolites were measured in sera of normal, vitamin D deficient and nonazotemic nephrotic rats. The concentrations of all metabolites were reduced in nephrotic and vitamin D deficient animals although 1,25-dihydroxyvitamin D values remained relatively normal in the nephrotic group. Twenty-four hours after the intravenous injection of tritiated 25-hydroxycholecalciferol, approximately 34% of the injected radioactivity appeared in the urine of the nephrotic animals compared with 0.4% in the controls. In extracts from nephrotic sera subjected to high performance liquid chromatography, the percentage of radioactive counts comigrating with 1,25-dihydroxycholecalciferol and 24,25-dihydroxycholecalciferol was significantly increased. The various metabolites were present in urine in approximately the same ratios as in serum. Dynamic histomorphometry of tibial metaphyses showed no abnormality. Urinary losses of vitamin D metabolites constitute the major cause for low serum values in nephrotic rats. The apparent synthetic rates are not impaired.

Urinary and plasma vitamin D3 metabolites in the nephrotic syndrome

Using newly developed and established extraction, Lipidex-5000 chromatography, normal phase gradient HPLC, and ligand binding assay techniques we have directly measured plasma and urine levels of vitamin D3 and its metabolites in seven normal subjects and seven patients with nephrotic syndrome and normal renal function. Significant reductions in the plasma levels of vitamin D3, 24,25(OH)2D3, 25,26(OH)2D3, and 1,25(OH)2D3 were noted in all nephrotic patients. In conjunction with the plasma metabolite abnormalities, direct quantitative analysis of the urine in these patients revealed significant increases in nonconjugated 250HD3, 24,25(OH)2D3 and 1,25(OH)2D3. Significant correlations were noted between the plasma and/or urine metabolites and other mineral homeostatic parameters. The results indicate that the primary basis for the reductions in plasma vitamin D3 and its metabolites in the nephrotic syndrome is enhanced urinary excretion. The findings of normal serum ionized Ca and i-PTH levels in the patients with nephrosis suggest that reductions in bound and not free forms of vitamin D3 metabolites in plasma may occur in the initial stages of the nephrotic syndrome.