The role of nutritional vitamin D in chronic kidney disease-mineral and bone disorder in children and adults with chronic kidney disease, on dialysis, and after kidney transplantation-a European consensus statement

Vitamin D deficiency is common in patients with chronic kidney disease (CKD) and associates with poor outcomes. Current clinical practice guidelines recommend supplementation with nutritional vitamin D as for the general population. However, recent large-scale clinical trials in the general population failed to demonstrate a benefit of vitamin D supplementation on skeletal or non-skeletal outcomes, fueling a debate on the rationale for screening for and correcting vitamin D deficiency, both in non-CKD and CKD populations. In a collaboration between the European Renal Osteodystrophy initiative of the European Renal Association (ERA) and the European Society for Paediatric Nephrology (ESPN), an expert panel performed an extensive literature review and formulated clinical practice points on vitamin D supplementation in children and adults with CKD and after kidney transplantation. These were reviewed by a Delphi panel of members from relevant working groups of the ERA and ESPN. Key clinical practice points include recommendations to monitor for, and correct, vitamin D deficiency in children and adults with CKD and after kidney transplantation, targeting 25-hydroxyvitamin D levels >75 nmol/l (>30 ng/ml). Although vitamin D supplementation appears well-tolerated and safe, it is recommended to avoid mega-doses (≥100 000 IU) and very high levels of 25 hydroxyvitamin D (>150-200 nmol/l, or 60-80 ng/ml) to reduce the risk of toxicity. Future clinical trials should investigate the benefit of vitamin D supplementation on patient-relevant outcomes in the setting of vitamin D deficiency across different stages of CKD.

Associations of serum alkaline phosphatase level with all-cause and cardiovascular mortality in the general population

Background and aims

There are few population studies on the associations of serum alkaline phosphatase (AlkP) with all-cause and cardiovascular mortality. We aimed to investigate the relevancy of serum AlkP with all-cause and cardiovascular mortality in the general population.

Methods and results

Our research included 34,147 adults in the National Health and Nutrition Examination Survey (NHANES) from 1999 to 2014. Cox proportional hazards regression models were used to assess the associations of serum AlkP with all-cause and cardiovascular mortality. Mediation analysis was used to analyze mechanisms that might link serum AlkP to all-cause and cardiovascular mortality. After 139.7 ± 57.8 months of follow-up, 5413 participants experienced all-cause death and 1820 participants experienced cardiovascular death. Mortality rates per 1000 person-years from various diseases increased with increasing serum concentrations of AlkP, especially all-cause death, cerebrovascular disease and cardiovascular death. High serum AlkP level significantly increased all-cause and cardiovascular mortality. After multivariate adjustment, the highest AlkP group had the highest risk to experience all-cause (hazard ratio [HR] = 1.30, P < 0.001) and cardiovascular mortality (HR = 1.39, P < 0.001) than the lowest AlkP group. γ-glutamyl transpeptidase (GGT) (13.33% and 15.79%), followed by Vitamin D (8.33% and 7.14%) and C-reactive protein (CRP) (7.69% and 10.35%) were identified as possible major mediators.

Conclusion

Higher AlkP concentrations were associated with higher all-cause and cardiovascular mortality, largely related to mediated factors such as GGT, Vitamin D, and CRP. These findings suggest that lower serum AlkP level may reduce all-cause and cardiovascular mortality in general population.

The Association of Sleep Quality and Vitamin D Levels in Hemodialysis Patients

Background

To date, hemodialysis (HD) is the most common therapy for chronic kidney disease (CKD) patients. However, it causes different complications such as sleep disorders. Sleep regulation is connected to vitamin D; hence, its deficiency might influence the quality and duration of sleep. This study is aimed at evaluating the correlation of sleep quality and vitamin D levels in 80 HD patients.

Methods

This cross-sectional study was performed on 80 hemodialysis patients admitted to 29 Bahman hospitals in Tabriz, Iran. Before beginning of dialysis, serum 25 (OH) D levels were assessed among patients and the sleep patterns and sleep quality of patients were accurately calculated by the Pittsburgh sleep quality index (PSQI) standard questionnaire.

Results

Our results showed that 22 HD patients (27.5%) had severe sleep disorders. In addition, it was found that serum levels of vitamin D had significant correlation with sleep quality (r = −0.341, p = 0.002) in general, even after adjusting confounding factors such as calcium (Ca), phosphate (P), and parathyroid hormone (PTH) level. In poor sleepers (PSQI ≤ 5), a negative correlation was observed between the levels of vitamin D and PSQI score (r = −0.397, p = 0.004). PSQI scores in the normal range of PTH (r = −0.377, p = 0.006) and in >600 pg/ml of PTH (r = −0.675, p = 0.011) had a correlation with vitamin D levels. The level of vitamin D was the single independent predictor of sleep efficiency (β coefficient = −0.386, p = 0.001).

Conclusion

The present project reported that the positive effect of vitamin D is associated with sleep disorder in HD patients. In future studies, normal levels of Ca and P should be considered along with normal vitamin D levels among the included patients.

Case report: Osteomalacia due to bisphosphonate treatment in a patient on hemodialysis

Background

No publications have reported on osteomalacia in patients receiving intermittent cyclical therapy with etidronate (a bisphosphonate) and undergoing long-term hemodialysis (HD).

Case presentation

We report on a 46-year-old Japanese man admitted to our hospital for further examination of left forearm pain. Maintenance HD was started at age 24 years, and the man had been on HD since then. At age 38 years, surgical parathyroidectomy was performed for secondary hyperparathyroidism; iliac crest bone biopsy performed at the same time showed osteitis fibrosa. The active vitamin D₃ preparation calcitriol was started, and intermittent cyclical etidronate therapy was introduced 2 years later for osteoporosis. At age 45 years, the patient stopped taking calcitriol because of hypercalcemia but continued with etidronate. At age 46 years, a pseudofracture with a Looser zone occurred in the left ulna, and left femur bone biopsy revealed osteomalacia. Etidronate was discontinued, and calcitriol was restarted; open reduction and internal fixation with an angular stability plate were performed. Union of the bone was achieved 10 months after the operation. At age 49 years, a lumber bone biopsy confirmed improved bone morphometry.

Conclusions

We believe that intermittent cyclical etidronate therapy without administration of active vitamin D₃ during long-term HD might have induced osteomalacia, resulting in the ulna insufficiency fracture. Therefore, we propose that administration of active vitamin D₃ is essential to prevent osteomalacia in patients on long-term HD who are receiving bisphosphonates and have potential vitamin D₃ deficiency.

The impact of cholecalciferol on markers of vascular calcification in hemodialysis patients: A randomized placebo controlled study

BACKGROUND AND AIM

Vascular calcification is an independent risk factor for cardiovascular diseases and all-cause mortality in end stage renal disease, and particularly in hemodialysis patients. Vitamin D deficiency has been shown to be associated with vascular calcification among this category of patients. Cholecalciferol or vitamin D3; the native inactivated 25-hydroxy vitamin D [25(OH)D], has been proposed to have a good impact on vascular calcification and vitamin D deficiency. However, clinical data is still limited.

METHODS AND RESULTS

A prospective, randomized, placebo-controlled study was carried out to evaluate the effect of oral cholecalciferol on vascular calcification and 25(OH)D levels in hemodialysis patients. A total of sixty eligible hemodialysis patients were randomly assigned to either a treatment group (Oral 200.000IU Cholecalciferol per month) or a placebo group, for 3 months. Serum 25-hydroxy vitamin D (25(OH)D), fetuin-A, fibroblast growth factor (FGF-23), osteoprotegerin (OPG), calcium, phosphorus, their product (CaXP) and intact parathyroid hormone (iPTH) levels, were all assessed at baseline and at the end of the study. ClinicalTrials.gov registration number: NCT03602430. Cholecalciferol significantly increased serum levels of 25(OH)D and fetuin-A in the treatment group (p-value < 0.001), while no significant difference was observed in the placebo group. Cholecalciferol administration showed no effect on either FGF-23 or OPG. None of the treatment group patients experienced any adverse effects.

CONCLUSION

Cholecalciferol was shown to be an effective, tolerable, inexpensive pharmacotherapeutic option to overcome vitamin D deficiency, with a possible modulating effect on fetuin-A, among hemodialysis patients. CLINICALTRIALS.

GOV REGISTRATION NUMBER

NCT03602430.

A comparative analysis of the efficacy and safety of paricalcitol versus other vitamin D receptor activators in patients undergoing hemodialysis: A systematic review and meta-analysis of 15 randomized controlled trials

Paricalcitol, a new vitamin D receptor activator (VDRA), is reported to be more effective than other VDRAs in reducing calcium and phosphorus levels in patients undergoing hemodialysis. However, the efficacy and safety of paricalcitol remain controversial. This analysis compares paricalcitol with other VDRAs in patients undergoing hemodialysis. We searched the Cochrane Library, PubMed, EMBASE, Web of Science, and CNKI up to April 22, 2019. Standardized mean difference (SMD), risk ratio (RR) and 95% confidence interval (CI) values were estimated to compare the outcomes of the groups. Two reviewers extracted data and assessed trial quality independently. All statistical analyses were performed using the standard statistical procedures of RevMan 5.2 and Stata 12.0. Fifteen studies (N = 110,544) were included in this meta-analysis. Of these studies, 11 were randomized controlled trials (RCTs) and 4 were non-randomized studies of interventions (NRSIs). Patients receiving paricalcitol experienced better overall survival (OS) than patients receiving other VDRAs, with a pooled hazard ratio of 0.86 (95% CI 0.80–0.91; P < 0.00001). Intact parathyroid hormone (iPTH) levels were significantly reduced in the paricalcitol group compared to the group receiving other VDRAs, with a pooled SMD of -0.53 (95% CI -0.89– -0.16; P = 0.004). There was a significant increase in serum calcium levels from baseline in the paricalcitol group compared to the other VDRAs group when limiting the analysis to RCTs, with a pooled SMD of 2.14 (95% CI 0.90–3.38; P = 0.0007). Changes in serum calcium levels were significantly lower in the paricalcitol group when the analysis was limited to NRSIs, with a pooled SMD of -0.85 (95% CI -1.34–-0.35; P = 0.0008). The NSRI analysis also showed a significant reduction in serum phosphorus levels in the paricalcitol group, with a pooled SMD of -0.57 (95% CI -1.00–-0.13; P = 0.01). No significant differences were observed in the incidence of hypercalcemia, hyperphosphatemia, or adverse events. Generally, paricalcitol seems superior to other VDRAs in reducing mortality and iPTH levels in patients undergoing hemodialysis. However, the comparative effectiveness of paricalcitol in reducing serum calcium and phosphorus levels needs further exploration. No significant difference was found in the rate of adverse events.

Prognostic impact of alkaline phosphatase for in-hospital mortality in patients with acute coronary syndrome: a prospective cohort study in China

OBJECTIVES

Alkaline phosphatase (ALP) can promote vascular calcification, but the association between ALP and in-hospital mortality in patients with acute coronary syndrome (ACS) is not well defined.

DESIGN

A prospective cohort study.

SETTING AND PARTICIPANTS

A total of 6368 patients with ACS undergoing percutaneous coronary intervention (PCI) from 1 January 2010 to 31 December 2017 were analysed.

MAIN OUTCOME MEASURES

In-hospital mortality was used in this study.

RESULTS

ALP was analysed both as a continuous variable and according to three categories. After multivariable adjustment, in-hospital mortality was significantly higher in Tertile 3 group (ALP＞85 U/L) (OR: 2.399, 95% CI 1.080 to 5.333, p=0.032), compared with other two groups (Tertile 1: ＜66 U/L; Tertile 2: 66-85 U/L). When ALP was evaluated as a continuous variable, after multivariable adjustment, the ALP level was associated with an increased risk of in-hospital mortality (OR: 1.011, 95% CI 1.002 to 1.020, p=0.014). C-statistic of ALP for predicting in-hospital mortality was 0.630 (95% CI 0.618 to 0.642, p=0.001). The cut-off value was 72 U/L with a sensitivity of 0.764 and a specificity of 0.468. However, ALP could not significantly improve the prognostic performance of Global Registry of Acute Coronary Events (GRACE) score (GRACE score+ALP vs GRACE score: C-statistic: z=0.485, p=0.628; integrated discrimination improvement: 0.014, p=0.056; net reclassification improvement: 0.020, p=0.630).

CONCLUSIONS

In patients with ACS undergoing PCI, ALP was an independent predictor of in-hospital mortality. But it could not improve the prognostic performance of GRACE score.

Redox State of Human Serum Albumin and Inflammatory Biomarkers in Hemodialysis Patients with Secondary Hyperparathyroidism During Oral Calcitriol Supplementation for Vitamin D

Background:

Hemodialysis (HD) patients with secondary Hyperparathyroidism (s-HPT) are exposed to increased inflammation and oxidative stress. In HD patients, oxidized albumin is a reliable marker of oxidative stress and its clinical significance has been rarely studied.

Objective:

The objective of this study was to evaluate Cys34 Human Serum Albumin (HSA) as oxidative stress biomarker in HD patients with s-HPT and its relationship with inflammation on bone turnover markers during oral calcitriol supplementation for vitamin D.

Patients and Methods:

Fifteen stable hemodialysis patients with s-HPT (mean age 48.67±8.15, 11 males and 4 females) were used in the experiment to receive calcitriol treatment for 16 weeks (0.25mcg or 0.5 mcg once a day according to serum level of Ca and P for each). The changes in the serum biochemical parameters (Ca, P, ALP, and iPTH), inflammatory markers (CRP and IL-6 levels) and serum oxidative stress condition (SOD, IS and albumin ratio HNA/HMA) were evaluated before and at 8 and 16 weeks of calcitriol treatment. The correlations between those factors were studied.

Results:

All patients responded to oral calcitriol therapy, with a significant decrease in the serum iPTH. The results showed that calcitriol could effectively suppress iPTH secretion with a significant elevation of serum Ca and P but ALP remained unchanged during the study. It can also effectively reduce the inflammatory markers (CRP and IL-6), while increasing the oxidative markers (SOD and IS). Oxidative albumin ratio HNA/HMA showed a significant (p=0.001) reduction after 16 weeks of calcitriol treatment and the redox state of HSA showed a positive prediction for hyperparathyroidism and for inflammation.

Conclusion:

The redox state of HSA could be used as a predictor for monitoring hyperparathyroidism and inflammation during calcitriol treatment by retarding albumin oxidation in HD patients with secondary hyperparathyroidism.

Bacterial steroid hydroxylases: enzyme classes, their functions and comparison of their catalytic mechanisms

The steroid superfamily includes a wide range of compounds that are essential for living organisms of the animal and plant kingdoms. Structural modifications of steroids highly affect their biological activity. In this review, we focus on hydroxylation of steroids by bacterial hydroxylases, which take part in steroid catabolic pathways and play an important role in steroid degradation. We compare three distinct classes of metalloenzymes responsible for aerobic or anaerobic hydroxylation of steroids, namely: cytochrome P450, Rieske-type monooxygenase 3-ketosteroid 9α-hydroxylase, and molybdenum-containing steroid C25 dehydrogenases. We analyze the available literature data on reactivity, regioselectivity, and potential application of these enzymes in organic synthesis of hydroxysteroids. Moreover, we describe mechanistic hypotheses proposed for all three classes of enzymes along with experimental and theoretical evidences, which have provided grounds for their formulation. In case of the 3-ketosteroid 9α-hydroxylase, such a mechanistic hypothesis is formulated for the first time in the literature based on studies conducted for other Rieske monooxygenases. Finally, we provide comparative analysis of similarities and differences in the reaction mechanisms utilized by bacterial steroid hydroxylases.

Retinal capillary and arteriolar changes in patients with chronic kidney disease

RATIONALE

Premature cardiovascular disease is a leading cause of death in patients with chronic kidney disease (CKD). In animal models CKD has been shown to cause renal and extrarenal vascular remodeling and capillary rarefaction, but data in humans with CKD are sparse. Retinal arteriolar wall-to-lumen ratio (WLR) is an established marker of early end-organ damage and there is evidence that arteriolar and capillary changes in the retinal circulation mirror those in the general and in particular the cerebrovascular microcirculation.

OBJECTIVE

The aim of this study was to compare retinal capillary density and arteriolar structure between patients with CKD and healthy individuals.

METHODS

We compared 76 patients with CKD stage 3+ or proteinuria >500 mg/g creatinine in the presence of a normal GFR from the German Chronic Kidney Disease cohort to 53 healthy control subjects, who participated in clinical trials during 2007 and 2015 in our Clinical Research Center. Retinal vascular parameters were measured non-invasively in vivo by scanning laser Doppler Flowmetry (SLDF, Heidelberg Engineering, Germany). Capillary rarefaction was assessed by intercapillary distance.

RESULTS

Patients with CKD showed greater WLR (0.403 ± 0.11 vs 0.351 ± 0.11, p = 0.010) and greater wall thickness (WT) (15.1 ± 4.1 vs 13.5 ± 3.8, p = 0.026) compared to healthy individuals. Intercapillary distance (ICD) (22.4 ± 5.7 vs 20.2 ± 4.1, p = 0.008) was greater in the CKD group compared to the healthy control group. After adjustment for differences in clinical characteristics of the groups (age, gender, BMI, serum cholesterol) WLR (p = 0.046), WT (p = 0.025) and ICD (p = 0.003) remained significantly different between the two groups. There was a correlation between serum phosphate level and WLR in the CKD group (r = 0.288, p = 0.013).

CONCLUSION

Patients with moderately severe CKD show retinal signs of end-organ damage indicated by an increased wall-to-lumen ratio and capillary rarefaction.

Underrecognition and Underestimation of Disturbances in Calcium-Phosphate Balance in Kidney Transplant Recipients

Disturbances in mineral metabolism, namely chronic kidney disease-metabolic bone disease, became more profound with impairment of renal function. The aim of the study was to assess how often calcium, phosphate, alkaline phosphatase, and parathyroid hormone (PTH) were measured in kidney transplant recipients relative to hemodialyzed patients. In addition, prevalence of hypercalcemia defined as calcium concentration over 10.5 mg/dL was assessed.

PATIENTS AND METHODS

We studied 200 kidney allograft recipients and 100 hemodialyzed patients. Calcium, phosphate, alkaline phosphatase, 25-hydroxy vitamin D, and PTH were obtained from outpatient charts.

RESULTS

All the studied parameters were available in 100% of the hemodialyzed patients. In kidney allograft recipients, calcium and phosphate levels were available in 80%, alkaline phosphatase activity was available in 40%, PTH was available in less than 10%, and vitamin D was available in 1%. Hypercalcemia was present in 10% of hemodialyzed patients and in 5% of kidney allograft recipients. Vitamin D analogue was administered to 98% of hemodialyzed patients, whereas vitamin D was administered to 28% of kidney allograft recipients, particularly those with impaired kidney function. In conclusion, calcium and phosphate are seldom assessed on an outpatient basis in kidney allograft recipients, making the diagnosis and treatment of secondary hyperparathyroidism in this population difficult. Care of kidney transplant recipients could be substantially improved, particularly in regard to chronic kidney disease-metabolic bone disease, when regular check-ups for calcium-phosphate balance are implemented and proper treatment could be introduced to prevent further chronic kidney disease-metabolic bone disease.

25(OH)D3-enriched or fortified foods are more efficient at tackling inadequate vitamin D status than vitamin D3

The ability to synthesise sufficient vitamin D through sunlight in human subjects can be limited. Thus, diet has become an important contributor to vitamin D intake and status; however, there are only a few foods (e.g. egg yolk, oily fish) naturally rich in vitamin D. Therefore, vitamin D-enriched foods via supplementing the animals' diet with vitamin D or vitamin D fortification of foods have been proposed as strategies to increase vitamin D intake. Evidence that cholecalciferol (vitamin D3) and calcifediol (25(OH)D3) content of eggs, fish and milk increased in response to vitamin D3 supplementation of hens, fish or cows' diets was identified when vitamin D-enrichment studies were reviewed. However, evidence from supplementation studies with hens showed only dietary 25(OH)D3, not vitamin D3 supplementation, resulted in a pronounced increase of 25(OH)D3 in the eggs. Furthermore, evidence from randomised controlled trials indicated that a 25(OH)D3 oral supplement could be absorbed faster and more efficiently raise serum 25(OH)D concentration compared with vitamin D3 supplementation. Moreover, evidence showed the relative effectiveness of increasing vitamin D status using 25(OH)D3 varied between 3·13 and 7·14 times that of vitamin D3, probably due to the different characteristics of the investigated subjects or study design. Therefore, vitamin D-enrichment or fortified foods using 25(OH)D3 would appear to have advantages over vitamin D3. Further well-controlled studies are needed to assess the effects of 25(OH)D3 enriched or fortified foods in the general population and clinical patients.

Biochemical and structural characterization of CYP109A2, a vitamin D3 25-hydroxylase from Bacillus megaterium

Cytochrome P450 enzymes are increasingly investigated due to their potential application as biocatalysts with high regio- and/or stereo-selectivity and under mild conditions. Vitamin D₃ (VD₃ ) metabolites are of pharmaceutical importance and are applied for the treatment of VD₃ deficiency and other disorders. However, the chemical synthesis of VD₃ derivatives shows low specificity and low yields. In this study, cytochrome P450 CYP109A2 from Bacillus megaterium DSM319 was expressed, purified, and shown to oxidize VD₃ with high regio-selectivity. The in vitro conversion, using cytochrome P450 reductase (BmCPR) and ferredoxin (Fdx2) from the same strain, showed typical Michaelis-Menten reaction kinetics. A whole-cell system in B. megaterium overexpressing CYP109A2 reached 76 ± 5% conversion after 24 h and allowed to identify the main product by NMR analysis as 25-hydroxylated VD₃ . Product yield amounted to 54.9 mg·L^-1 ·day^-1 , rendering the established whole-cell system as a highly promising biocatalytic route for the production of this valuable metabolite. The crystal structure of substrate-free CYP109A2 was determined at 2.7 Å resolution, displaying an open conformation. Structural analysis predicts that CYP109A2 uses a highly similar set of residues for VD₃ binding as the related VD₃ hydroxylases CYP109E1 from B. megaterium and CYP107BR1 (Vdh) from Pseudonocardia autotrophica. However, the folds and sequences of the BC loops in these three P450s are highly divergent, leading to differences in the shape and apolar/polar surface distribution of their active site pockets, which may account for the observed differences in substrate specificity and the regio-selectivity of VD₃ hydroxylation.

DATABASE

The atomic coordinates and structure factors have been deposited in the Protein Data Bank with accession code 5OFQ (substrate-free CYP109A2).

ENZYMES

Cytochrome P450 monooxygenase CYP109A2, EC 1.14.14.1, UniProt ID: D5DF88, Ferredoxin, UniProt ID: D5DFQ0, cytochrome P450 reductase, EC 1.8.1.2, UniProt ID: D5DGX1.

Pharmacological Management of Secondary Hyperparathyroidism in Patients with Chronic Kidney Disease

Secondary hyperparathyroidism (SHPT) is a common complication of chronic kidney disease (CKD) and is part of the CKD-mineral bone disorder (CKD-MBD). SHPT is associated with increased risk of fracture and mortality; thus, SHPT control is recommended as kidney function declines. Effective SHPT management becomes more difficult once skeletal and cardiovascular adverse effects associated with severe SHPT have become established. However, interventional studies to lower parathyroid hormone (PTH) have so far shown inconsistent results in improving patient-centred outcomes such as mortality, cardiovascular events and fracture. Pharmacological treatment effect on PTH level is also inconsistent between pre-dialysis CKD and dialysis patients, which adds to the complexity of SHPT management. This review aims to give an overview on the pathophysiology, pharmacological and non-pharmacological treatment for SHPT in CKD including some of the limitations of current therapeutic options.

Role of Vitamin D in Uremic Vascular Calcification

The risk of cardiovascular death is 10 times higher in patients with CKD (chronic kidney disease) than in those without CKD. Vascular calcification, common in patients with CKD, is a predictor of cardiovascular mortality. Vitamin D deficiency, another complication of CKD, is associated with vascular calcification in patients with CKD. GFR decline, proteinuria, tubulointerstitial injury, and the therapeutic dose of active form vitamin D aggravate vitamin D deficiency and reduce its pleiotropic effect on the cardiovascular system. Vitamin D supplement for CKD patients provides a protective role in vascular calcification on the endothelium by (1) renin-angiotensin-aldosterone system inactivation, (2) alleviating insulin resistance, (3) reduction of cholesterol and inhibition of foam cell and cholesterol efflux in macrophages, and (4) modulating vascular regeneration. For the arterial calcification, vitamin D supplement provides adjunctive role in regressing proteinuria, reverse renal osteodystrophy, and restoring calcification inhibitors. Recently, adventitial progenitor cell has been linked to be involved in the vascular calcification. Vitamin D may provide a role in modulating adventitial progenitor cells. In summary, vitamin D supplement may provide an ancillary role for ameliorating uremic vascular calcification.

Characterization of cytochrome P450 CYP109E1 from Bacillus megaterium as a novel vitamin D3 hydroxylase

In this study the ability of CYP109E1 from Bacillus megaterium to metabolize vitamin D₃ (VD₃) was investigated. In an in vitro system using bovine adrenodoxin reductase (AdR) and adrenodoxin (Adx_4-108), VD₃ was converted by CYP109E1 into several products. Furthermore, a whole-cell system in B. megaterium MS941 was established. The new system showed a conversion of 95% after 24h. By NMR analysis it was found that CYP109E1 catalyzes hydroxylation of VD₃ at carbons C-24 and C-25, resulting in the formation of 24(S)-hydroxyvitamin D₃ (24S(OH)VD₃), 25-hydroxyvitamin D₃ (25(OH)VD₃) and 24S,25-dihydroxyvitamin D₃ (24S,25(OH)₂VD₃). Through time dependent whole-cell conversion of VD₃, we identified that the formation of 24S,25(OH)₂VD₃ by CYP109E1 is derived from VD₃ via the intermediate 24S(OH)VD₃. Moreover, using docking analysis and site-directed mutagenesis, we identified important active site residues capable of determining substrate specificity and regio-selectivity. HPLC analysis of the whole-cell conversion with the I85A-mutant revealed an increased selectivity towards 25-hydroxylation of VD₃ compared with the wild type activity, resulting in an approximately 2-fold increase of 25(OH)VD₃ production (45mgl^-1day^-1) compared to wild type (24.5mgl^-1day^-1).

An update on bone imaging and markers in chronic kidney disease

Bone disorders in chronic kidney disease (CKD) are associated with heightened risks of fractures, vascular calcification, poor quality of life and mortality compared to the general population. However, diagnosis and management of these disorders in CKD are complex and appreciably limited by current diagnostic modalities. Areas covered: Bone histomorphometry remains the gold standard for diagnosis but is not widely utilised and lacks feasibility as a monitoring tool. In practice, non-invasive imaging and biochemical markers are preferred to guide therapeutic decisions. Expert commentary: This review aims to summarize the risk factors for, and spectrum of bone disease in CKD, as well as appraise the clinical utility of dual energy X-ray densitometry, peripheral quantitative computed tomography, high-resolution peripheral quantitative computed tomography, and bone turnover markers.

Chronic Kidney Disease-Mineral Bone Disorder in the Elderly Peritoneal Dialysis Patient

PURPOSE

The purpose of this paper was to review the literature concerning the treatment of chronic kidney disease-mineral bone disorder (CKD-MBD) in the elderly peritoneal dialysis (PD) patient.

RESULTS

Chronic kidney disease-mineral bone disorder is a major problem in the elderly PD patient, with its associated increased fracture risk, vascular calcification, and accelerated mortality fracture risk. Peritoneal dialysis, however, bears a lower risk than hemodialysis (HD). The approach to CKD-MBD prophylaxis and treatment in the elderly PD patient is similar to other CKD patients, with some important differences. Avoidance of hypercalcemia, hyperphosphatemia, and hyperparathyroidism is important, as in other CKD groups, and is generally easier to attain. Calcium-free phosphate binders are recommended for normocalcemic and hypercalcemic patients. Normalization of vitamin D levels to > 75 nmol/L (> 30 pg/L) and low-dose active vitamin D therapy is recommended for all patients. Hyperparathryoidism is to be avoided by using active vitamin D and cinacalcet. Particular attention should be paid to treating protein malnutrition. Fracture prophylaxis (exercise, use of walkers, dwelling modifications) are important. Hypomagnesemia is common in PD and can be treated with magnesium supplements. Vitamin K deficiency is also common and has been identified as a cause of vascular calcification. Accordingly, warfarin treatment for this age group is problematic.

CONCLUSION

While treatment principles are similar to other dialysis patient groups, physicians should be aware of the special problems of the elderly group.

Evaluation of responses to vitamin D3 (cholecalciferol) in patients on dialysis: a systematic review and meta-analysis

Vitamin D plays a key role in mineral metabolism and its deficiency is often noted in patients on dialysis for end-stage renal disease (ESRD). We evaluated the efficacy and responses to vitamin D3 (cholecalciferol) in patients undergoing dialysis for ESRD. Randomized controlled trials or prospective studies comparing vitamin D3 supplementation to placebo in patients with ESRD on dialysis were searched from medical databases using the terms, 'Calcitriol/Cholecalciferol, vitamin D, chronic kidney disease, hemodialysis, serum calcium, parathyroid hormones (PTH), phosphorus, 25(OH)D, and 1,25(OH)2D'. The outcomes analyzed were serum calcium, PTH, phosphorus, 25(OH)D, and 1,25(OH) 2D levels. Of the 259 records identified, 9 studies with a total of 368 patients were chosen for the current meta-analysis. The number of patients, age, and gender distribution among the groups were comparable. Results reveal a greater increase in both 25(OH)D (Pooled difference in means=0.434, 95% CI 0.174 to 0.694, p=0.001) and 1,25(OH) 2D (Pooled difference in means=0.978, 95% CI 0.615 to 1.34, p<0.001) in the treatment arm, as compared to the placebo. There was no difference in the serum calcium or PTH among the two groups. However, patients in the treatment arm had a significant increase in phosphorus levels (Pooled difference in means=0.434, 95% CI 0.174 to 0.694, p=0.001). Vitamin D supplementation facilitated the maintenance of increased levels of 25(OH) D and 1,25(OH) 2D in patients undergoing dialysis for ESRD. This increase in vitamin D was not associated with hypercalcemia or significant changes in PTH levels.

Pleiotropic effects of vitamin D in chronic kidney disease

Low 25(OH)D levels are common in chronic kidney disease (CKD) patients and are implicated in all-cause mortality and morbidity risks. Furthermore, the progression of CKD is accompanied by a gradual decline in 25(OH)D production. Vitamin D deficiency in CKD causes skeletal disorders, such as osteoblast or osteoclast cell defects, bone turnover imbalance, and deterioration of bone quality, and nonskeletal disorders, such as metabolic syndrome, hypertension, immune dysfunction, hyperlipidemia, diabetes, and anemia. Extra-renal organs possess the enzymatic machinery for converting 25(OH)D to 1,25(OH)2D, which may play considerable biological roles beyond the traditional roles of vitamin D. Pharmacological 1,25(OH)2D dose causes hypercalcemia and hyperphosphatemia as well as adynamic bone disorder, which intensifies vascular calcification. Conversely, native vitamin D supplementation reduces the risk of hypercalcemia and hyperphosphatemia, which may play a role in managing bone and cardio-renal health and ultimately reducing mortality in CKD patients. Nevertheless, the combination of native vitamin D and active vitamin D can enhance therapy benefits of secondary hyperparathyroidism because of extra-renal 1α-hydroxylase activity in parathyroid gland. This article emphasizes the role of native vitamin D replacements in CKD, reviews vitamin D biology, and summarizes the present literature regarding native vitamin D replacement in the CKD population.

Molecular determinants for selective C25-hydroxylation of vitamins D2and D3by fungal peroxygenases

Regioselective hydroxylation of vitamin D byAgrocybe aegeritaandCoprinopsis cinereaperoxygenases was investigated in an experimental and computational study.

The effect of Vitamin D administration on treatment of anemia in end-stage renal disease patients with Vitamin D deficiency on hemodialysis: A placebo-controlled, double-blind clinical trial

Background:

Chronic kidney disease is a progressive and irreversible loss of renal function. Anemia is one of the main complications of end-stage renal disease (ESRD) which is linked closely with other complications of the disease. The primary therapy for anemia in these patients is erythropoietin (EPO). The goal of this study was to find the effect of Vitamin D administration in addition to the appropriate dose of EPO in ESRD patients with Vitamin D deficiency.

Materials and Methods:

This was a double-blind clinical trial on 64 ESRD patients undergoing hemodialysis in Amin and Noor Hospitals of Isfahan, Iran. The patients were divided into two groups of control and intervention. The intervention group was given Vitamin D supplements and the control group received placebo. The required dose of EPO to reach the target hemoglobin (Hb) was measured and statistically analyzed.

Results:

A total number of 32 females and 32 males were included in this study. All the patients in the treatment group were aged between 18 and 76 and the patients in the control group were aged between 21 and 76 years old. There was a significant statistical relationship between Vitamin D administration and the required dose of EPO in both groups (P = 0.013). However, there was no correlation between the concentration of Hb and serum Vitamin D levels.

Conclusion:

Based on the main finding of this study, the relationship between Vitamin D administration and required dose of EPO seems that the predicted dose of Vitamin D prescribing strategy in Kidney Disease Outcomes Quality Initiative guidelines is not adequate to achieve normal serum Vitamin D in ESRD patients.

The clinical use of vitamin D metabolites and their potential developments: a position statement from the European Society for Clinical and Economic Aspects of Osteoporosis and Osteoarthritis (ESCEO) and the International Osteoporosis Foundation (IOF)

Several compounds are produced along the complex pathways of vitamin D3 metabolism, and synthetic analogs have been generated to improve kinetics and/or vitamin D receptor activation. These metabolites display different chemical properties with respect to the parental or native vitamin D3, i.e., cholecalciferol, which has been, so far, the supplement most employed in the treatment of vitamin D inadequacy. Hydrophilic properties of vitamin D3 derivatives facilitate their intestinal absorption and their manageability in the case of intoxication because of the shorter half-life. Calcidiol is a more hydrophilic compound than parental vitamin D3. Active vitamin D analogs, capable of binding the vitamin D receptor evoking vitamin D-related biological effects, are mandatorily employed in hypoparathyroidism and kidney failure with impaired 1α-hydroxylation. They have been shown to increase BMD, supposedly ameliorating calcium absorption and/or directly affecting bone cells, although their use in these conditions is jeopardized by the development of hypercalciuria and mild hypercalcemia. Further studies are needed to assess their overall safety and effectiveness in the long-term and new intermittent regimens, especially when combined with the most effective antifracture agents.

Efficacy and safety of body weight-adapted oral cholecalciferol substitution in dialysis patients with vitamin D deficiency

Background

Vitamin D deficiency is highly prevalent in dialysis patients. Whether substitution of native vitamin D in these patients is beneficial is a matter of ongoing discussion, as is the optimal dosing schedule. The purpose of this study was to investigate the efficacy and safety of a body-weight adapted oral dosing regimen of cholecalciferol in dialysis patients.

Methods

In a prospective single-center study 56 prevalent dialysis patients with a baseline 25OHD₃ level <20 ng/mL received 100 IU of cholecalciferol per kg body weight once weekly orally for 26 weeks. 25OHD₃ was measured at baseline and at study end, iPTH every three months, serum calcium and phosphorous monthly. Concurrent medication including phosphate binders, calcitriol and cinacalcet and dialysate calcium concentration remained unchanged throughout the study.

Results

Baseline 25OHD₃ was 9.9 ± 4.1 ng/mL and increased to 26.1 ± 8.8 ng/mL (P = 0.01). Fourteen patients (27 %) achieved a level >30 ng/mL and all others above 20 ng/mL. Cinacalcet therapy was positively associated with the increase in 25OHD₃ (P = 0.024). The plasma iPTH level significantly decreased from median 362 pg/mL to 297 pg/mL (P = 0.01). This decline was more pronounced in patients with higher baseline iPTH levels (P < 0.01) and differed significantly dependent on concurrent calcitriol therapy. A significant iPTH decrease was observed in patients receiving calcitriol (P = 0.031). Serum calcium and phosphorous did not change significantly throughout the study period. Cholecalciferol substitution was well tolerated without adverse effects.

Conclusion

The dosing regimen of oral cholecalciferol supplementation with 100 IU per kg body weight per week for 26 weeks in dialysis patients with vitamin D deficiency causes a significant increase in 25OHD₃ close to the supposed target level of 30 ng/mL and a significant reduction in iPTH, without affecting serum calcium or phosphorous levels.

Nutritional vitamin D supplementation and health-related outcomes in hemodialysis patients: a protocol for a systematic review and meta-analysis

BACKGROUND

The prevalence of vitamin D deficiency in hemodialysis patients is high. While most hemodialysis patients are treated with activated vitamin D (1,25[OH]2D) to prevent renal osteodystrophy, clinical practices of the screening and treatment of 25(OH)2D deficiency are highly variable. It is unclear if nutritional vitamin D supplementation with D2 or D3 provides an additional clinical benefit beyond that provided by activated vitamin D treatment in this population.

METHODS/DESIGN

We will conduct a systematic review of nutritional vitamin D (D2/D3) supplementation and health-related outcomes in hemodialysis patients according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The primary objective is to assess the impact of nutritional vitamin D supplementation on clinical outcomes relevant in hemodialysis patients, such as mortality, cardiovascular events, infections, and fractures. Secondary outcomes will include anemia, hyperparathyroidism, medication use (erythrocyte-stimulating agents, activated vitamin D), and quality of life. We will search MEDLINE, Scopus, Web of Science, and ClinicalTrials.gov for randomized, controlled trials of nutritional vitamin D supplementation (ergocalciferol/D2 or cholecalciferol/D3) in chronic hemodialysis patients. The Cochrane Risk Assessment Tool will be used to assess the quality of eligible studies. We will perform meta-analyses using standard techniques for the outcomes listed above if pooling is deemed appropriate/sufficient. The results of this systematic review may highlight gaps in our knowledge of the relevance of nutritional vitamin D in end-stage renal disease, allowing for the informed design of clinical trials assessing the impact of nutritional vitamin D therapy in the hemodialysis population in the future.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42014013931.

Effect of cholecalciferol replacement on vascular calcification and left ventricular mass index in dialysis patients

OBJECTIVE

The aim of this study was to determine the effect of oral cholecalciferol treatment on vascular calcification, left ventricular mass index (LVMI) and other cardiac functions in dialysis patients.

DESIGN AND METHODS

A six-month course of oral cholecalciferol treatment was recommended to dialysis patients with vitamin D insufficiency. While 26 patients were given cholecalciferol treatment, 17 patients who could not tolerate to therapy received standard therapy. Initial biochemical parameters were measured, and they were measured again after 6 months of treatment. Echocardiographic measurements were also performed, and the vascular calcification score (VCS) was calculated at baseline and at the 6th month.

RESULTS

The cholecalciferol replacement group showed no significant change in LVMI and VCS values (p > 0.05). However, while LVMI was similar between groups at initial evaluation, it was lower in the cholecalciferol group at the 6th month when compared to the standard treatment group (141.8 ± 40.2 g/m(2) vs. 166.3 ± 31.4 g/m(2); p = 0.04). Likewise, left ventricular diastolic diameters (48.8 ± 5.1 mm vs. 47.5 ± 4.6 mm; p = 0.023) and left atrial diameters (41.2 ± 8.9 mm vs. 38.9 ± 8.1 mm; p = 0.006) decreased in the cholecalciferol group. Additionally, significant increases were observed in serum 25-hydroxyvitamin D (25(OH)D) and albumin levels, with a significant decrease in serum C-reactive protein levels.

CONCLUSION

A lesser increase in left ventricular mass and better diastolic functions was observed in dialysis patients after 6 months of cholecalciferol treatment.

[Native vitamin D in dialysis patients]

Chronic kidney disease is frequent and usually responsible of mineral and bone disorder. These abnormalities lead to increased morbidity and mortality. To become active, native vitamin D needs a first hydroxylation in the liver, and a second one in the kidney. Next to its action on bone metabolism, vitamin D also possesses pleiotropic actions on cardiovascular, immune and neurological systems as well as antineoplastic activities. End-stage renal disease (ESRD) is also associated with a decrease in vitamin D activity by mechanisms including the increase of plasma phosphate concentration, secretion of FGF-23 and decrease in 1α-hydroxylase activity. The prevalence of 25 hydroxy-vitamin D deficiency depends on the chosen cut-off value to define this lack. Currently it is well established that a patient has to be substituted when 25 hydroxy-vitamin D level is under 30 ng/mL. The use and monitoring of 1.25 hydroxy-vitamin D is still not recommended in routine practice. The goals of vitamin D treatment in case of ESRD are to substitute the deficiency and to prevent or treat hyperparathyroidism. Interest of native vitamin D in first intention is now well demonstrated. This review article describes the vitamin D metabolism and physiology and also the treatment for vitamin D deficiency in ESRD population.

Effect of cholecalciferol supplementation on inflammation and cellular alloimmunity in hemodialysis patients: data from a randomized controlled pilot trial

Background

Memory T-cells are mediators of transplant injury, and no therapy is known to prevent the development of cross-reactive memory alloimmunity. Activated vitamin D is immunomodulatory, and vitamin D deficiency, common in hemodialysis patients awaiting transplantation, is associated with a heightened alloimmune response. Thus, we tested the hypothesis that vitamin D₃ supplementation would prevent alloreactive T-cell memory formation in vitamin D-deficient hemodialysis patients.

Methods and Findings

We performed a 12-month single-center pilot randomized, controlled trial of 50,000 IU/week of cholecalciferol (D₃) versus no supplementation in 96 hemodialysis patients with serum 25(OH)D<25 ng/mL, measuring effects on serum 25(OH)D and phenotypic and functional properties of T-cells. Participants were randomized 2∶1 to active treatment versus control. D₃ supplementation increased serum 25(OH)D at 6 weeks (13.5 [11.2] ng/mL to 42.5 [18.5] ng/mL, p<0.001) and for the duration of the study. No episodes of sustained hypercalcemia occurred in either group. Results of IFNγ ELISPOT-based panel of reactive T-cell assays (PRT), quantifying alloreactive memory, demonstrated greater increases in the controls over 1 year compared to the treatment group (delta PRT in treatment 104.8+/−330.8 vs 252.9+/−431.3 in control), but these changes in PRT between groups did not reach statistical significance (p = 0.25).

Conclusions

D₃ supplements are safe, effective at treating vitamin D deficiency, and may prevent time-dependent increases in T-cell alloimmunity in hemodialysis patients, but their effects on alloimmunity need to be confirmed in larger studies. These findings support the routine supplementation of vitamin D-deficient transplant candidates on hemodialysis and highlight the need for large-scale prospective studies of vitamin D supplementation in transplant candidates and recipients.

Trial Registration

Clinicaltrials.gov NCT01175798

Vitamin D3 metabolite calcidiol primes human dendritic cells to promote the development of immunomodulatory IL-10-producing T cells

Vitamin D is recognized as a potent immunosuppressive drug. The suppressive effects of vitamin D are attributed to its physiologically active metabolite 1,25 dihydroxy vitamin D3 (calcitriol), which was shown, to prime dendritic cells (DCs) to promote the development of regulatory T (Treg) cells. Despite the potential benefit in treating autoimmune diseases, clinical application of calcitriol is hindered by deleterious side effects manifested by hypercalcemia and hypercalciuria. Conversely, the physiological precursors of calcitriol, vitamin D3 (cholecalciferol) and its first metabolite 25-hydroxy vitamin D3 (calcidiol) are widely applied in the clinic due to their low calcimic burden. However, the mechanisms by which cholecalciferol and calcidiol may modulate adaptive immunity remain elusive. This prompted us to unravel the immunosuppressive capacity of these precursors by assessing their influence on DC functions and the subsequent polarization of naïve CD4(+) T cells. In this study we show that, whereas cholecalciferol has insignificant effects on DC maturation and cytokine production, it only weakly primed DCs to induce suppressive T cells. However, like calcitriol, calcidiol not only exerted an inhibitory effect on DC maturation and cytokine production, and primed DCs to promote the development of suppressive IL-10-producing Treg cells. Strikingly, in contrast to the population of IL-10-producing Treg cells induced by calcitriol-primed DCs, the IL-10-producing Treg cells induced by calcidiol-primed DCs exhibited sustained IFN-γ production in face of their suppressive capacity. Experiments with the steroid synthesis inhibitor ketoconazole indicated that the immunomodulatory features of the precursors are dependent on their conversion into calcitriol. Collectively, calcidiol is a potent immune modulator, which may be more adequate than calcitriol for the treatment of chronic inflammatory diseases, since it is less hypercalcimic. This may be of particular interest for the treatment of allergic disease, where concurrent suppression and sustained IFN-γ production by Treg cells effectively counterbalance the Th2-dominated immune responses.

A randomized controlled trial of cholecalciferol supplementation in patients on maintenance hemodialysis

BACKGROUND

Vitamin D deficiency is common in Indian patients with chronic kidney disease (CKD) on maintenance hemodialysis (MHD), but optimal dose of cholecalciferol is unclear.

MATERIALS AND METHODS

A total of 45 consenting patients were randomized to intervention and control groups. In the intervention group, patients (n = 35) with serum 25-hydroxy vitamin D (25(OH)D) < 30 ng/mL (n = 33), received oral cholecalciferol 60,000 units/week for 6 weeks. The serum levels of 25(OH)D, calcium, phosphorus, albumin, and parathyroid hormone (PTH) were measured at 0, 6, and 12 weeks. In the control group (n = 10), these were estimated at 0 and 6 weeks.

RESULTS

In the intervention group, 25/35 patients completed the supplementation at 6 weeks and 20/35 were available at 12 weeks. The mean baseline level of 25(OH)D was 9.59 ± 7.59 ng/mL, and after 6 weeks 19.51 ± 4.27 ng/mL, mean increase being 9.99 ± 6.83 ng/mL, which was highly significant (P < 0.0001). After discontinuing supplementation at 6 weeks, serum 25(OH)D level dropped significantly from 6 to 12 weeks [-2.84 ± 6.25 ng/mL (P = 0.04)]. However, it was still significantly higher at 12 weeks (16.08 ± 8.27 ng/mL) as compared with the baseline. PTH and calcium did not change significantly with supplementation. The change in serum 25(OH)D level from baseline to 6 weeks in the intervention group was inversely related to baseline 25(OH)D levels and patient's weight. In the control group, change in 25(OH)D from baseline to 6 weeks was not significant.

CONCLUSION

Supplementation with cholecalciferol 60,000 unit/week for 6 weeks was insufficient to achieve optimal levels of 25(OH)D in Indian patients with CKD on MHD.

Circadian variation of mineral and bone parameters in end-stage renal disease

BACKGROUND

Mineral and bone parameters are actively managed in end-stage renal disease (ESRD). However, whether these undergo circadian variation is not known. We investigated the circadian variation of mineral and bone parameters in patients on long-term hemodialysis.

METHODS

Seventeen ESRD patients on long-term hemodialysis and eight volunteers without kidney disease were enrolled. Subjects had all medications that affect calcium-phosphate-parathyroid hormone balance (phosphate binders, vitamin D analogues, and calcimimetics) discontinued. Thereafter, for a period of 5 days, subjects consumed a diet controlled in calcium (1,200 mg per day) and phosphorus (1,000 mg per day) content. On the sixth day (a non-dialysis day for the ESRD patients), enrollees underwent twelve 2-h blood draws for phosphate, ionized calcium, parathyroid hormone (PTH), total 25-hydroxy vitamin D (25OHD), and fibroblast growth factor-23 (FGF-23).

RESULTS

In the ESRD patients plasma phosphate demonstrated significant circadian variation (P < 0.00001). The peak occurred around 3:30 am and nadir occurred around 11:00 am. Ionized calcium (P = 0.0036), PTH (P = 0.0004) and 25OHD (P = 0.009) also varied significantly during the circadian period; for ionized calcium peak and nadir occurred around 12:15 pm and 8:00 pm, parathyroid hormone 5:45 pm and 10:15 am, and 25OHD 9:45 am and 4:00 pm respectively. FGF-23 did not show a significant circadian variation. Only phosphate (P < 0.0001) and PTH (P = 0.00008) demonstrated circadian variation in the control group.

CONCLUSIONS

Blood concentrations of phosphate, calcium, PTH and 25-hydroxy vitamin D, exhibit a circadian variation in patients with ESRD. Knowledge of these phenomena is pertinent for the interpretation of clinical testing.

Biochemical parameters after cholecalciferol repletion in hemodialysis: results From the VitaDial randomized trial

BACKGROUND

The 2009 KDIGO (Kidney Disease: Improving Global Outcomes) chronic kidney disease-mineral and bone disorder clinical practice guideline suggests correcting 25-hydroxyvitamin D3 (25[OH]D) levels<30ng/mL in patients treated with maintenance hemodialysis, but does not provide a specific treatment protocol.

STUDY DESIGN

2-center, double-blind, randomized, 13-week, controlled trial followed by a 26-week open-label study.

SETTING & PARTICIPANTS

55 adult maintenance hemodialysis patients with 25(OH)D levels<30ng/mL were recruited from June 2008 through October 2009.

INTERVENTION

Cholecalciferol, 25,000IU, per week orally versus placebo for 13 weeks, then 26 weeks of individualized cholecalciferol prescription based on NKF-KDOQI (National Kidney Foundation-Kidney Disease Outcomes Quality Initiative) guidelines.

OUTCOMES

Primary end point was the percentage of patients with 25(OH)D levels≥30ng/mL at 13 weeks. Secondary outcomes included the percentage of patients with normal calcium, phosphorus, and intact parathyroid hormone (iPTH) blood levels. Safety measures included incidence of hypercalcemia and hypervitaminosis D.

MEASUREMENTS

Blood calcium and phosphate were measured weekly; iPTH, 25(OH)D, 1,25-dihydroxyvitamin D3 (1,25[OH]2D), and bone turnover markers, trimonthly; fetuin A and fibroblast growth factor 23 (FGF-23) serum levels and aortic calcification scores were determined at weeks 0 and 39.

RESULTS

The primary end point significantly increased in the treatment group compared with the placebo group (61.5% vs 7.4%; P<0.001), as well as 1,25(OH)2D levels (22.5 [IQR, 15-26] vs 11 [IQR, 10-15]pg/mL; P<0.001) and the proportion of patients achieving the target calcium level (76.9% vs 48.2%; P=0.03). Incidence of hypercalcemia and phosphate and iPTH levels were similar between groups. The second 26-week study phase did not significantly modify the prevalence of 25(OH)D level≥30ng/mL in patients issued from the placebo group.

LIMITATIONS

Small size of the study population.

CONCLUSIONS

Oral weekly administration of 25,000IU of cholecalciferol for 13 weeks is an effective, safe, inexpensive, and manageable way to increase 25(OH)D and 1,25(OH)2D levels in hemodialysis patients. Further evaluation of clinical end points is suggested.

Cardiovascular effects of cholecalciferol treatment in dialysis patients--a randomized controlled trial

BACKGROUND

Patients on chronic dialysis are at increased risk of vitamin D deficiency. In observational studies plasma 25-hydroxyvitamin D (p-25(OH) D) levels are inversely correlated with plasma BNP and adverse cardiovascular outcomes. Whether a causal relation exists has yet to be established. The aim of this study was to test the hypothesis that cholecalciferol supplementation improves cardiac function and reduces blood pressure (BP) and pulse wave velocity (PWV) in patients on chronic dialysis.

METHODS

In a randomized, placebo-controlled, double-blind study, we investigated the effect of 75 μg (3000 IU) cholecalciferol daily for 6 months, in patients on chronic dialysis. We performed two-dimensional echocardiography, with doppler and tissue-doppler imaging, 24-h ambulatory BP (24-h BP), PWV, augmentation index (AIx), central BP (cBP) and brain natriuretic peptide (BNP) measurements at baseline and after 6 months.

RESULTS

Sixty-four patients were allocated to the study. Fifty dialysis patients with a mean age of 68 years (range: 46-88) and baseline p-25(OH) D of 28 (20;53) nmol/l completed the trial. Cholecalciferol increased left ventricular (LV) volume, but had no impact on other parameters regarding LV structure or left atrial structure. LV systolic function, LV diastolic function, PWV, cBP, AIx and BNP were not changed in placebo or cholecalciferol group at follow-up. 24-h BP decreased significantly in placebo group and tended to decrease in cholecalciferol group without any difference between treatments.

CONCLUSION

Six months of cholecalciferol treatment in patients on chronic dialysis did not improve 24-h BP, arterial stiffness or cardiac function.

TRIAL REGISTRATION

NCT01312714, Registration Date: March 9, 2011.

Fragility fractures and osteoporosis in CKD: pathophysiology and diagnostic methods

Both chronic kidney disease (CKD) and osteoporosis are major public health problems associated with an aging population. Osteoporosis is characterized by reduced bone mineral density, while CKD results in qualitative changes in bone structure; both conditions increase the predisposition to fragility fractures. There is a significant coprevalence of osteoporotic fractures and CKD, particularly in the elderly population. Not only is the risk of fracture higher in the CKD population, but clinical outcomes are significantly worse, with substantial health care costs. Management of osteoporosis in the CKD population is particularly complex given the impact of renal osteodystrophy on bone quality and the limited safety and hard outcome data for current therapy in patients with severe CKD or on dialysis therapy. In this review, we discuss the pathophysiology of osteoporosis, the impact of CKD on bone strength, and the role of novel imaging techniques and biomarkers in predicting underlying renal osteodystrophy on bone histomorphometry in the context of CKD.

Osteomalacia induced by vitamin D deficiency in hemodialysis patients: the crucial role of vitamin D correction

Vitamin D deficiency/insufficiency is significantly prevalent in chronic kidney disease. Data in the literature are however scarce about the effects of this deficiency on bone metabolism in hemodialysis (HD) patients. Moreover, it is still debated whether low vitamin D levels should be normalized in HD patients. In this paper, we report two cases showing the deleterious consequences of vitamin D deficiency in HD patients which is characterised by hypophosphatemia, hypocalcemia and osteomalacia (OM) leading to bone fractures. As vitamin D repletion is an easy way to treat OM, this report underlines the importance of monitoring and correction of vitamin D deficiency in this population.

Oral postdialysis cholecalciferol supplementation in patients on maintenance hemodialysis: a dose-response approach

The aim of the present study was to evaluate the dose of postdialysis cholecalciferol needed to maintain the 25-hydroxyvitamin D [25(OH)D] levels in the optimal range of 75–150 nmol/L. Twenty-six patients who had low baseline 25(OH)D levels (mean 27.5 ± 14.9 nmol/L) were studied. The 25(OH)D levels were measured every 2 months for one year. During the first two months, all the patients received 2000 IU of cholecalciferol after each hemodialysis (=6000 IU/wk). Thereafter, the dose was individualized and adapted every 2 months by administering 1 to 6 cholecalciferol tablets (2000 IU each) per week (total weekly dose = 2000–12000 IU/wk). During cholecalciferol supplementation, the 25(OH)D concentrations rapidly increased from baseline to 140.1 ± 28.3 nmol/L at month 6 and 95.6 ± 20.9 nmol/L at month 12. At month twelve, 86% of the patients had 25(OH)D levels within the target range with a mean dose of 5917 ± 4106 IU/wk of cholecalciferol; however, the amount needed to maintain these levels varied widely from 0 (n = 2) to 12000 IU/wk (n = 5). In conclusion, postdialysis cholecalciferol prescription is quite effective in correcting vitamin D deficiency/insufficiency, but the amount of cholecalciferol needed to maintain the 25(OH)D levels within the optimal range over the long-term varies widely among patients and must be individualized.

Low Dietary Intake of Vitamin D and Vitamin D Deficiency in Hemodialysis Patients

BACKGROUND

The purpose of this study was to test the hypothesis that decreased dietary intake of Vitamin D contributes to Vitamin D deficiency in end-stage renal disease (ESRD) patients on hemodialysis (HD).

METHODS

We performed a cross-sectional study of 58 hemodialysis outpatients from two Mount Sinai Medical Center (MSMC)-affiliated outpatient HD units in New York City and 648 outpatients at MSMC with CKD stages I-IV. Serum 25(OH)D concentrations were measured from August 2010 to July of 2011 in recruited hemodialysis patients (n=58) and linked with results of dietary and lifestyle surveys. The Mount Sinai Data Warehouse (electronic medical record) was used to capture 25(OH) Vitamin D levels for outpatients with CKD stages I-IV who had Vitamin D testing during the same time period.

RESULTS

The prevalence of Vitamin D insufficiency/deficiency in the HD cohort was 96.6%. Mean (SD) and median (IQR) 25(OH)D concentrations were 15.65 (6.82) and 13.55 (10.15) ng/mL, respectively. Dietary surveys showed a median weekly Vitamin D intake of 1044 IU (IQR=808, vs. a recommended weekly allowance of 4200 IU) and specific avoidance of foods containing both Vitamin D and phosphorus. In contrast, mean and median 25(OH)D concentrations in patients with CKD stages I-IV were 25.66 (13.44) and 23.60 (15.48) ng/mL (p<0.001 vs. HD patients).

CONCLUSIONS

Vitamin D deficiency is more prevalent in HD patients than in pre-dialysis patients with CKD and is associated with decreased dietary intake of Vitamin D. Dialysis restrictions imposed to reduce dietary phosphorus intake likely contributes to the development of hypovitaminosis D in ESRD patients.

Calcidiol [25(OH)D3]: from diagnostic marker to therapeutical agent

OBJECTIVE

Osteoporosis is a skeletal disorder characterized by diminished bone strength, which results in an increased risk of fracture. Currently, osteoporosis is a public health priority due to the large number of individuals affected and the detrimental effect on quality of life. Primary osteoporosis, the most common form, usually results from age-related reduction in bone mineral strength. Over time, the individual's capacity to build bone is impaired, as the synthesis of vitamin D, the hormone responsible for calcium absorption, tends to decline. As serum calcium levels decrease, metabolic control serves to increase the removal of calcium from the skeleton to make up for the deficit. The synthesis of the 'hormone' vitamin D and its control therefore become central to intervention in involutional osteoporosis syndromes. In humans, plain vitamin D (cholecalciferol), also called parental or native vitamin D, is photosynthesized in the skin and then hydroxylated in the liver into the vitamin D analog calcidiol [25(OH)D3], which is hydroxylated again in the kidney into the vitamin D analog calcitriol [1,25(OH)2D3]. The advantage of administering vitamin D analogs is that the pro-drug calcidiol avoids the effect of declines in hepatic function, while calcitriol avoids the effect of declines in hepatic and kidney function. A strategy to enhance [25(OH)D3] levels to the optimal threshold of vitamin D is supplementation with the calcidiol metabolite itself. The goal of this paper is to review published studies on the efficacy of the calcidiol metabolite in increasing 25(OH)D3 serum levels and improving skeletal health parameters in humans.

METHODS

A library search of published papers in the area of use of calcidiol in humans from 1967 to 2013 was performed (key words: calcidiol, 25-hydroxy-vitamin D3, vitamin D supplementation, vitamin D metabolism, osteomalacia).

RESULTS AND CONCLUSION

The results of the survey made it possible to conclude that calcidiol is characterized by a number of features that make the compound ideal in conditions that require supplementation with a 25-hydroxylated metabolite.

Which vitamin D in CKD-MBD? The time of burning questions

Vitamin D is a common treatment against secondary hyperparathyroidism in renal patients. However, the rationale for the prescription of vitamin D sterols in chronic kidney disease (CKD) is rapidly increasing due to the coexistence of growing expectancies close to unsatisfactory evidences, such as (1) the lack of randomized controlled trials (RCTs) proving the superiority of any vitamin D sterol against placebo on patients centered outcomes, (2) the scanty clinical data on head to head comparisons between the multiple vitamin D sterols currently available, (3) the absence of RCTs confirming the crescent expectations on nutritional vitamin D pleiotropic effects even in CKD patients, (4) the promising effects of vitamin D receptors activators (VDRA) against proteinuria and myocardial hypertrophy in diabetic CKD cohorts, and (5) the conflicting data on the impact on mortality of VDRA versus calcimimetic centered regimens to control CKD-MBD. The present review arguments these issues focusing on the opened questions that nephrologists should consider dealing with the prescription of nutritional vitamin D or VDRA and with the choice of a VDRA versus a calcimimetic based regimen in CKD-MBD patients.

Prevalence of 25-OH vitamin D deficiency in a population of hemodialysis patients and efficacy of an oral ergocalciferol supplementation regimen

BACKGROUND/AIMS

Optimal dosing regimens for 25-OH vitamin D (VitD) deficiency are unknown in hemodialysis (HD) patients. Our aim was to evaluate the efficacy of prescribing ergocalciferol supplementation based on KDOQI guidelines for chronic kidney disease (CKD) stages III-IV in HD patients.

METHODS

We conducted a retrospective study of 96 urban, predominately African-American HD patients at a single-center dialysis unit with VitD insufficiency or deficiency treated with ergocalciferol. Patients were classified as either compliant or non-compliant with supplementation as determined by review of pharmacy records. The primary outcome was VitD levels 6 months after initiation of treatment and secondary outcomes were VitD levels at 11 months, bone/mineral and anemia parameters.

RESULTS

The population was predominately African-American (69%) and Hispanic (28%). There were 61 individuals in the compliant group and 35 individuals in the non-compliant group. The compliant group was older but otherwise similar in demographics and co-morbid conditions to the non-compliant group. After 6 months of treatment, the compliant group had a significant increase in VitD level (14.7 ± 6.0 to 28.7 ± 10.0 ng/ml, p < 0.0001) compared to the non-compliant group (14.7 ± 5.5 to 14.8 ± 7.1 ng/ml, p = 0.95). There were no differences in the incidence of hypercalcemia between the two groups. Except for a decrease in phosphorus in the compliant group (5.6 ± 1.6 to 4.9 ± 1.7 mg/dl, p = 0.004), there were no significant difference in bone/mineral or anemia parameters including dosing of darbepoetin.

CONCLUSION

An ergocalciferol-prescribing strategy using the KDOQI guidelines for stage III-IV kidney disease in HD patients with VitD deficiency or insufficiency is inadequate to achieve repletion or maintenance of normal VitD levels.

Alkaline Phosphatase, Serum Phosphate, and Incident Cardiovascular Disease and Total Mortality in Older Men

Objective—

We have examined the association between serum phosphate and alkaline phosphatase (ALP) with incident cardiovascular disease (CVD) outcomes and total mortality in older men.

Approach and Results—

A prospective study of 3381 men, aged 60 to 79 years, without a history of myocardial infarction or stroke followed up for an average 11 years during which there were 605 major CVD events (fatal coronary heart disease and nonfatal myocardial infarction, stroke, and CVD death) and 984 total deaths. ALP but not serum phosphate was associated with increased risk of coronary heart disease and overall CVD events which persisted after adjustment for CVD risk factors and markers of inflammation and after exclusion of men with chronic kidney disease (adjusted hazard ratio per SD, 1.19 [1.05, 1.34]; P =0.007 and 1.10 [1.01, 1.21]; P =0.04). In contrast, serum phosphate was only associated with increased CVD mortality owing to noncoronary heart disease or stroke causes (adjusted hazard ratio per SD, 1.35 [1.01, 1.83]; P =0.04). Both raised phosphate and ALP were associated with significantly increased total mortality after full adjustment and exclusion of men with chronic kidney disease.

Conclusions—

ALP but not serum phosphate is associated with coronary heart disease risk in elderly men. High levels of ALP and serum phosphate are both associated with increased total mortality.

Effects of cholecalciferol on functional, biochemical, vascular, and quality of life outcomes in hemodialysis patients

BACKGROUND AND OBJECTIVES

Observational studies suggest that calciferol supplementation may improve laboratory and patient-level outcomes of hemodialysis patients with reduced 25-hydroxyvitamin D [25(OH)D] levels. This randomized controlled trial examined effects of cholecalciferol supplementation in patients on hemodialysis.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Sixty patients with 25(OH)D levels ≤24 ng/ml (≤60 nmol/L) were randomized to receive 50,000 IU oral cholecalciferol or placebo, once weekly for 8 weeks and then monthly for 4 months. At baseline (autumn 2011) and 6 months, testing evaluated muscle strength, functional capacity, laboratory parameters, pulse wave velocity (PWV), and health-related quality of life (HRQOL) using the Kidney Disease Quality of Life-36 survey.

RESULTS

Patients were well matched by treatment allocation. Median age was 62 years (range, 20-86), 52% were women, 55% had a history of diabetes, and mean serum 25(OH)D was 17±5 ng/ml (43±13 nmol/L). Patients were assessed over 6 months by repeated-measures ANOVA. Patients allocated to cholecalciferol had significantly higher values of 25(OH)D (P<0.001), 1,25-dihydroxyvitamin D (P=0.04), and tartrate-resistant acid phosphatase-5b) (P=0.04) and a greater reduction in phosphorus values (P=0.03) than placebo-treated patients Values of serum calcium, intact parathyroid hormone, and episodes of hypercalcemia and hyperphosphatemia did not differ significantly between the groups. No significant differences were detected in muscle strength, functional capacity, PWV, or HRQOL.

CONCLUSIONS

In this randomized controlled trial, patients supplemented with cholecalciferol had higher 25(OH)D, 1,25-dihydroxyvitamin D, and tartrate-resistant acid phosphatase-5b levels, without increased calcium or phosphorus values. However, no effects were detected in muscle strength, functional capacity, PWV, or HRQOL.