Randomized controlled trial of cholecalciferol supplementation in chronic kidney disease patients with hypovitaminosis D

Alterations in regulators of the renal-bone axis, inflammation and iron status in older people with early renal impairment and the effect of vitamin D supplementation

CONTEXT

Chronic kidney disease (CKD) leads to alterations in fibroblast growth factor 23 (FGF23) and the renal-bone axis. This may be partly driven by altered inflammation and iron status. Vitamin D supplementation may reduce inflammation.

OBJECTIVE AND METHODS

Older adults with early CKD (estimated glomerular filtration rate (eGFR) 30-60 ml/min/1.73 m2; CKDG3a/b; n = 35) or normal renal function (eGFR >90 ml/min/1.73 m2; CKDG1; n = 35) received 12,000, 24,000 or 48,000 IU D3/month for 1 year. Markers of the renal-bone axis, inflammation and iron status were investigated pre- and post-supplementation. Predictors of c-terminal and intact FGF23 (cFGF23; iFGF23) were identified by univariate and multivariate regression.

RESULTS

Pre-supplementation, comparing CKDG3a/b to CKDG1, plasma cFGF23, iFGF23, PTH, sclerostin and TNFα were significantly higher and Klotho, 1,25-dihydroxyvitamin D and iron were lower. Post-supplementation, only cFGF23, 25(OH)D and IL6 differed between groups. The response to supplementation differed between eGFR groups. Only in the CKDG1 group, phosphate decreased, cFGF23, iFGF23 and procollagen type I N-propeptide increased. In the CKDG3a/b group, TNFα significantly decreased, and iron increased. Plasma 25(OH)D and IL10 increased, and carboxy-terminal collagen crosslinks decreased in both groups. In univariate models cFGF23 and iFGF23 were predicted by eGFR and regulators of calcium and phosphate metabolism at both time points; IL6 predicted cFGF23 (post-supplementation) and iFGF23 (pre-supplementation) in univariate models. Hepcidin predicted post-supplementation cFGF23 in multivariate models with eGFR.

CONCLUSION

Alterations in regulators of the renal-bone axis, inflammation and iron status were found in early CKD. The response to vitamin D3 supplementation differed between eGFR groups. Plasma IL6 predicted both cFGF23 and iFGF23 and hepcidin predicted cFGF23.

The Efficacy and Safety of High-Dose Cholecalciferol Therapy in Hemodialysis Patients

Vitamin D deficiency and insufficiency are highly prevalent in CKD, affecting over 80% of hemodialysis (HD) patients and requiring therapeutic intervention. Nephrological societies suggest the administration of cholecalciferol according to the guidelines for the general population. The aim of the observational study was to evaluate the efficacy and safety of the therapy with a high dose of cholecalciferol in HD patients with 25(OH)D deficiency and insufficiency to reach the target serum 25(OH)D level > 30 ng/mL. A total of 22 patients (16 M), with an average age of 72.5 ± 13.03 years and 25(OH)D concentration of 13.05 (9.00-17.90) ng/mL, were administered cholecalciferol at a therapeutic dose of 70,000 IU/week (20,000 IU + 20,000 IU + 30,000 IU, immediately after each dialysis session). All patients achieved the target value > 30 ng/mL, with a mean time of 2.86 ± 1.87 weeks. In the first week, the target level of 25(OH)D (100%) was reached by 2 patients (9.09%), in the second week by 15 patients (68.18%), in the fourth week by 18 patients (81.18%), and in the ninth week by all 22 patients (100%). A significant increase in 1,25(OH)2D levels was observed during the study. However, only 2 patients (9.09%) achieved a concentration of 1,25(OH)2D above 25 ng/mL-the lower limit of the reference range. The intact PTH concentrations remained unchanged during the observation period. No episodes of hypercalcemia were detected, and one new episode of hyperphosphatemia was observed. In conclusion, our study showed that the administration of a high-therapeutic dose of cholecalciferol allowed for a quick, effective, and safe leveling of 25(OH)D concentration in HD patients.

Effect of regulated vitamin D increase on vascular markers in patients with chronic kidney disease: A systematic review and meta-analysis of randomized controlled trials

AIM

The effect of increased vitamin D levels on vascular function in patients with chronic kidney disease (CKD) is controversial. This meta-analysis aimed to assess the effect of regulated vitamin D increase on vascular markers in patients with CKD.

DATA SYNTHESIS

We searched PubMed, Web of Science, Embase and ClinicalTrials.gov from database inception up until July 21, 2023. We included randomized controlled trials assessing the effects of using vitamin D and its analogues on vascular function in patients with CKD. Fixed-effects and random-effects model analyses were performed using weighted mean difference effects for each trial by heterogeneity (I2) assessment. Primary outcomes encompassed blood flow-mediated dilation (FMD)、pulse wave velocity (PWV) and augmentation index (AIx).

FINDINGS

From 1964 records we selected 12 trials, 5 (n = 331) on FMD, 8 (n = 626) on PWV and 4 (n = 393) on AIx. Vitamin D and VDRA supplementation failed to significantly improve FMD (WMD 1.68%; 95% CI -0.18 to 3.53; P = 0.08; I2 = 88%)、PWV (WMD -0.41 m/s; 95%CI -0.95 to 0.13; P = 0.14; I2 = 57%)and AIx (WMD -0.53%; 95%CI -1.69 to 0.63; P = 0.37; I2 = 0%). Subgroup analysis revealed that 2 μg paricalcitol significantly improved FMD (WMD 2.09%; 95%CI 1.28 to 2.90; P < 0.00001); I2 = 0%), as did cholecalciferol (WMD 5.49%; 95% CI 4.35 to 6.63; P < 0.00001).

CONCLUSION

Supplementation vitamin D and VDRA are associated with improved vascular function as measured by FMD, but not arterial stiffness as measured by PWV and AIx, tentatively suggesting that regulating the increase of vitamin D could not potentially reduce the incidence of cardiovascular disease.

Vitamin D supplementation in people with chronic kidney disease

Vitamin D supplements have long been advocated for people with chronic kidney disease based on data from observational studies among the general population and people with chronic kidney disease. These data consistently suggested that higher circulating concentrations of 25-hydroxyvitamin D are associated with improved fracture, cardiovascular, cancer, and mortality outcomes. In the past few years, large clinical trials have been conducted to assess the effects of vitamin D supplements on a range of clinically relevant outcomes. Most of these studies were performed in the general population, but they also enrolled people with chronic kidney disease. Virtually all of these trials were negative and contradicted the observational data. In this review, the key observational data and clinical trials are summarized, and potential explanations for the discrepancies between these studies are discussed.

The effects of vitamin D on all-cause mortality in different diseases: an evidence-map and umbrella review of 116 randomized controlled trials

Purpose

To conduct a solid evidence by synthesizing meta-analyses and updated RCTs about the effects of vitamin D on all-cause mortality in different health conditions.

Methods

Data sources: Pubmed, Embase, Web of Science, the Cochrane Library, Google Scholar from inception until 25th April, 2022. Study selection: English-language, meta-analyses and updated RCTs assessing the relationships between vitamin D and all-cause mortality. Data synthesis: Information of study characteristics, mortality, supplementation were extracted, estimating with fixed-effects model. A Measurement Tool to Assess Systematic Reviews, Grading of Recommendations Assessment, Development and Evaluation, and funnel plot was used to assess risk of bias. Main outcomes: All-cause mortality, cancer mortality, cardiovascular disease mortality.

Results

In total of 27 meta-analyses and 19 updated RCTs were selected, with a total of 116 RCTs and 149, 865 participants. Evidence confirms that vitamin D reduces respiratory cancer mortality (RR, 0.56 [95%CI, 0.33 to 0.96]). All-cause mortality is decreased in patients with COVID-19 (RR, 0.54[95%CI, 0.33 to 0.88]) and liver diseases (RR, 0.64 [95%CI, 0.50 to 0.81]), especially in liver cirrhosis (RR, 0.63 [95%CI, 0.50 to 0.81]). As for other health conditions, such as the general health, chronic kidney disease, critical illness, cardiovascular diseases, musculoskeletal diseases, sepsis, type 2 diabetes, no significant association was found between vitamin D and all-cause mortality.

Conclusions

Vitamin D may reduce respiratory cancer mortality in respiratory cancer patients and all-cause mortality in COVID-19 and liver disorders' patients. No benefits showed in all-cause mortality after vitamin D intervention among other health conditions. The hypothesis of reduced mortality with vitamin D still requires exploration.

Systematic review registration

https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=252921, identifier: CRD42021252921.

The clinical relevance of native vitamin D in pediatric kidney disease

Hypovitaminosis D has been reported to be common in chronic kidney disease (CKD) as well as in proteinuric disorders. We reviewed available evidence to assess clinically relevant effects of low vitamin D status and native vitamin D (NVD) therapy, in pediatric renal diseases. Online medical databases were searched for articles related to vitamin D status, associations of hypovitaminosis D and effects of NVD therapy in kidney disease. Hypovitaminosis D was associated with worse skeletal, cardiovascular, inflammatory, and renal survival outcomes in CKD. Low serum 25 hydroxy-vitamin D (25[OH]D) levels correlated positively with glomerular filtration rate and negatively with serum parathyroid (PTH) levels. However, to date, evidence of benefit of NVD supplementation is restricted mainly to improvements in serum PTH, and biochemical 25[OH]D targets form the basis of clinical practice recommendations for NVD therapy. In nephrotic syndrome (NS) relapse, studies indicate loss of 25[OH]D along with vitamin D binding protein in urine, and serum total 25[OH]D levels are low. Preliminary evidence indicates that free 25[OH]D may be a better guide to the biologically active fraction. NVD therapy in NS does not show consistent results in improving skeletal outcomes and hypercalciuria has been reported when total 25[OH]D levels were considered as indication for therapy. NVD formulations should be regularised, and therapy monitored adequately to avoid adverse effects.

Treatment of secondary hyperparathyroidism in non-dialysis CKD: an appraisal 2022s

The situation of secondary hyperparathyroidism (sHPT) in CKD patients not on dialysis (ND-CKD) is probably best characterised by the KDIGO CKD-MBD Update 2017 guideline 4.2.1 stating that the optimal PTH levels is not known in these stages. Furthermore, new caution became recommended with regard to the routine use of active vitamin D analogues in early CKD stages and moderate sHPT phenotypes, due to their potential risks for hypercalcaemia and hyperphosphataemia aggravation. Nevertheless, there is still a substantial clinical need to prevent the development of parathyroid gland autonomy with its associated consequences of bone and vascular damage including fracture risks and cardiovascular events. Therefore, we now attempt to review the current guideline-based and clinical practice management of sHPT in ND-CKD including their strengths and weaknesses, favouring individualised approaches respecting calcium and phosphate homeostasis. We further comment on extended-release calcifediol (ERC) as a new differential therapeutic option now also available in Europe, and on a potentially novel understanding of a required vitamin D saturation in more advanced CKD stages. There is no doubt, however, that knowledge gaps will remain in this issue unless powerful RCTs with hard and meaningful endpoints are performed.

The Comparative Effects of Different Types of Oral Vitamin Supplements on Arterial Stiffness: A Network Meta-Analysis

Arterial stiffness, a significant prognostic factor of cardiovascular disease, may be affected by dietary factors. Research on the effects of oral vitamin supplements on arterial stiffness and/or endothelial function has produced controversial results. Therefore, the aim of this network meta-analysis was to comparatively assess the effect of different types of oral vitamin supplements on arterial stiffness in the adult population. We searched the PubMed, Embase, Cochrane Library, and Web of Science databases for randomized controlled trials from their inception to 30 September 2021. A network meta-analysis using a frequentist perspective was conducted to assess the effects of different types of oral vitamin supplements on arterial stiffness, as determined by pulse wave velocity. In total, 22 studies were included, with a total of 1318 participants in the intervention group and 1115 participants in the placebo group. The included studies were listed in an ad hoc table describing direct and indirect comparisons of the different types of vitamins. Our findings showed that, in both pairwise comparison and frequentist network meta-analysis, the different types of oral vitamin supplements did not show statistically significant effects on arterial stiffness. However, when oral vitamin supplementation was longer than 12 weeks, vitamin D3 showed a significant reduction in arterial stiffness, compared with the placebo (ES: −0.15; 95% CI: −0.30, −0.00; −60.0% m/s) and vitamin D2 (ES: −0.25; 95% CI: −0.48, −0.02, −52.0% m/s). In summary, our study confirms that oral vitamin D3 supplementation for more than 12 weeks could be an effective approach to reduce arterial stiffness and could be considered a useful approach to improve vascular health in patients at high risk of cardiovascular disease.

Angiotensin Converting Enzyme Inhibitors May Increase While Active Vitamin D May Decrease the Risk of Severe Pneumonia in SARS-CoV-2 Infected Patients with Chronic Kidney Disease on Maintenance Hemodialysis

The group most at risk of death due to COVID-19 are patients on maintenance hemodialysis (HD). The study aims to describe the clinical course of the early phase of SARS-CoV-2 infection and find predictors of the development of COVID-19 severe pneumonia in this population. This is a case series of HD nonvaccinated patients with COVID-19 stratified into mild pneumonia and severe pneumonia group according to the chest computed tomography (CT) pneumonia total severity score (TSS) on admission. Epidemiological, demographic, clinical, and laboratory data were obtained from hospital records. 85 HD patients with a mean age of 69.74 (13.19) years and dialysis vintage of 38 (14-84) months were included. On admission, 29.14% of patients had no symptoms, 70.59% reported fatigue followed by fever-44.71%, shortness of breath-40.0%, and cough-30.59%. 20% of the patients had finger oxygen saturation less than 90%. In 28.81% of patients, pulmonary parenchyma was involved in at least 25%. The factors associated with severe pneumonia include fever, low oxygen saturation and arterial partial pressure of oxygen, increased C-reactive protein and ferritin serum levels, low blood count of lymphocytes as well as chronic treatment with angiotensin converting enzyme inhibitors; while the chronic active vitamin D treatment was associated with mild pneumonia. In conclusion, even though nearly one-third of the patients were completely asymptomatic, while the remaining usually reported only single symptoms, a large percentage of them had extensive inflammatory changes at diagnosis with SARS-CoV-2 infection. We identified potential predictors of severe pneumonia, which might help individualize pharmacological treatment and improve clinical outcomes.

Cholecalciferol Supplementation Attenuates Bone Loss in Incident Kidney Transplant Recipients: A Prespecified Secondary Endpoint Analysis of a Randomized Controlled Trial

Vitamin D deficiency, persistent hyperparathyroidism, and bone loss are common after kidney transplantation (KTx). However, limited evidence exists regarding the effects of cholecalciferol supplementation on parathyroid hormone (PTH) and bone loss after KTx. In this prespecified secondary endpoint analysis of a randomized controlled trial, we evaluated changes in PTH, bone metabolic markers, and bone mineral density (BMD). At 1 month post-transplant, we randomized 193 patients to an 11-month intervention with cholecalciferol (4000 IU/d) or placebo. The median baseline 25-hydroxyvitamin D (25[OH]D) level was 10 ng/mL and 44% of participants had osteopenia or osteoporosis. At the end of the study, the median 25(OH)D level was increased to 40 ng/mL in the cholecalciferol group and substantially unchanged in the placebo group. Compared with placebo, cholecalciferol significantly reduced whole PTH concentrations (between-group difference of -15%; 95% confidence interval [CI] -25 to -3), with greater treatment effects in subgroups with lower 25(OH)D, lower serum calcium, or higher estimated glomerular filtration rate (p_int  < 0.05). The percent change in lumbar spine (LS) BMD from before KTx to 12 months post-transplant was -0.2% (95% CI -1.4 to 0.9) in the cholecalciferol group and -1.9% (95% CI -3.0 to -0.8) in the placebo group, with a significant between-group difference (1.7%; 95% CI 0.1 to 3.3). The beneficial effect of cholecalciferol on LS BMD was prominent in patients with low bone mass p_int  < 0.05). Changes in serum calcium, phosphate, bone metabolic markers, and BMD at the distal radius were not different between groups. In mediation analyses, change in whole PTH levels explained 39% of treatment effects on BMD change. In conclusion, 4000 IU/d cholecalciferol significantly reduced PTH levels and attenuated LS BMD loss after KTx. This regimen has the potential to eliminate vitamin D deficiency and provides beneficial effects on bone health even under glucocorticoid treatment. © 2021 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Cholecalciferol vs. Small Doses of Alfacalcidol vs. Placebo in Chronic Kidney Disease Patients on Hemodialysis: A Randomized Parallel Group Study

Background

The ability of extrarenal tissues to convert 25(OH)D (calcidiol) into 1,25(OH)2D (calcitriol) and dependence of the conversion on substrate levels provide the rationale for supplementing vitamin D in dialysis patients who usually have severe depletion of both: 25(OH)D and 1,25(OH)2D. The primary aim of the study was to compare effects of small doses of cholecalciferol (12,000 IU/week) with frequently used in Europe, small doses of alfacalcidol (1.5 μg/week) or placebo, given for 12 weeks, on serum 1,25(OH)₂D in hemodialysis patients with 25(OH)D deficiency. Secondary outcomes were changes in serum calcium, phosphate, 25(OH)D, parathyroid hormone (PTH), fibroblast growth factor 23 (FGF23) and sclerostin during the treatment.

Methods

This was a prospective, randomized, partly double-blind (cholecalciferol vs. placebo) study. Out of 522 patients dialyzed in 5 centers in the Mazovian Province, 93 gave informed consent and met the inclusion criteria: any vitamin D metabolites and calcimimetics naïve; no history of liver or intestinal disease; serum 25(OH)D <20 ng/ml, iPTH <1,000 –>110 pg/ml, calcium <10.2, and phosphate <6.8 mg/dl. The subjects were stratified by serum iPTH, then randomized into 3 groups according to the treatment.

Results

To our knowledge, this is the first study comparing head-to-head these drugs in the hemodialysis population. There were no significant differences between the groups at baseline. 81 patients completed the study. Cholecalciferol normalized serum 25(OH)D, with a mean rise from 12.9 ± 6.7 to 31.3 ± 10.1 ng/ml (p < 0.0001). This was accompanied by a marked increase of 1,25(OH)₂D from 13.8 ± 9.3 to 25.1 ± 14.2 pmol/l (p < 0.0001). A rise in serum 1,25(OH)₂D was also observed in alfacalcidol treated patients, however much smaller (from 13.5 ± 10.1 to 18.5 ± 11.0 pmol/l; p = 0.02). Neither cholecalciferol nor alfacalcidol treatment resulted in significant changes in serum PTH and the remaining parameters.

Conclusions

In most patients, treatment with cholecalciferol in a 12,000 IU/week dose permits safe correction of 25(OH)D deficiency and is more effective than 1.5 μg/week dose of alfacalcidol in rising serum 1,25(OH)₂D. This, together with a lack of influence on circulating iPTH the usefulness of such small alfacalcidol doses in hemodialysis patients is debatable.

The effect of vitamin D supplementation on serum levels of fibroblast growth factor- 23: A systematic review and meta-analysis of randomized controlled trials

Previous studies of the effect of vtamin D on serum levels of fibroblast growth factor- 23 (FGF-23) have yeilded an inconsistent findings. This systematic review and meta-analysis of randomized controlled trials (RCTs) sought to investigate the effect of vitamin D supplementation on serum levels of FGF-23. PubMed, Scopus, ISI Web of Science, and the Cochrane Library were searched, from database inception to November 2020, for RCTs that evaluated the effects of native or active vitamin D supplementation on serum levels of FGF-23 in adults. Weighted mean difference (WMD) were calculated and random effects meta-analysis was used to estimate the overall effects. Twenty-seven trials were included in the meta-analysis. Supplementation with native vitamin D (23 studies, n = 2247 participants; weighted mean difference [WMD] = 0.5 pg/mL, 95 % CI: -0.52 to 1.51, P = 0.33; I² = 29.9 %), and active vitamin D (5 studies, n = 342 participants, WMD = 29.45 pg/mL, 95 % CI: -3.9 to 62.81, P = 0.08; I² = 99.3%) had no significant effects on serum FGF-23 concentration. In subgroup analyses, supplementation with ergocalciferol (3 studies, n = 205 participants; WMD = 18.27 pg/mL, 95 % CI: 5.36-31.17, P = 0.006), and daily dosing regimens (9 studies, n = 1374 participants; WMD = 0.41 pg/mL, 95 % CI: 0.22 to 0.59, P < 0.001) increased serum FGF-23 levels compared to control. Overall, our findings revealed no significan effect of vitamin D supplementation on serum FGF-23 concentration. However, further high quality, large-scale studies are needed to better elucidate this relationship.

Low serum 1,25(OH)2D3 in end-stage renal disease: is reduced 1α-hydroxylase the only problem?

Low serum 1,25-dihydroxyvitamin D (1,25(OH)2D) in end-stage renal disease (ESRD) is considered a consequence of elevated fibroblast growth factor 23 (FGF23) and concomitant reduced activity of renal 1α-hydroxylase (CYP27B1). Current ESRD treatment strategies to increase serum calcium and suppress secondary hyperparathyroidism involve supplementation with vitamin D analogues that circumvent 1α-hydroxylase. This overlooks the potential importance of 25-hydroxyvitamin D (25(OH)D) deficiency as a contributor to low serum 1,25(OH)2D. We investigated the effects of vitamin D (cholecalciferol) supplementation (40,000 IU for 12 weeks and maintenance dose of 20,000 IU fortnightly), on multiple serum vitamin D metabolites (25(OH)D, 1,25(OH)2D3 and 24,25(OH)2D3) in 55 haemodialysis patients. Baseline and 12 month data were compared using related-samples Wilcoxon signed rank test. All patients remained on active vitamin D analogues as part of routine ESRD care. 1,25(OH)2D3 levels were low at baseline (normal range: 60-120 pmol/L). Cholecalciferol supplementation normalised both serum 25(OH)D and 1,25(OH)2D3. Median serum 25(OH)D increased from 35.1 nmol/L (IQR: 23.0-47.5 nmol/L) to 119.9 nmol/L (IQR: 99.5-143.3 nmol/L) (P < 0.001). Median serum 1,25(OH)2D3 and 24,25(OH)2D3 increased from 48.3 pmol/L (IQR: 35.9-57.9 pmol/L) and 3.8 nmol/L (IQR: 2.3-6.0 nmol/L) to 96.2 pmol/L (IQR: 77.1-130.6 pmol/L) and 12.3 nmol/L (IQR: 9-16.4 nmol/L), respectively (P < 0.001). A non-significant reduction in daily active vitamin D analogue dose occurred, 0.94 µmcg at baseline to 0.77 µmcg at 12 months (P = 0.73). The ability to synthesise 1,25(OH)2D3 in ESRD is maintained but is substrate dependent, and serum 25(OH)D was a limiting factor at baseline. Therefore, 1,25(OH)2D3 deficiency in ESRD is partly a consequence of 25(OH)D deficiency, rather than solely due to reduced 1α-hydroxylase activity as suggested by current treatment strategies.

Impact of nutritional vitamin D supplementation on parathyroid hormone and 25-hydroxyvitamin D levels in non-dialysis chronic kidney disease: a meta-analysis

Background

Secondary hyperparathyroidism (SHPT) is a common and major complication in chronic kidney disease (CKD), reflecting the increase of parathyroid hormone (PTH) in response to reduced vitamin D signalling and hypocalcaemia. This meta-analysis evaluated the impact of nutritional vitamin D (NVD) (cholecalciferol or ergocalciferol) on SHPT-related biomarkers.

Methods

A systematic literature search was performed in PubMed to identify relevant randomized control trials to be included in the meta-analysis. Fixed- and random-effects models were used to pool study-level results. Effects were studied within NVD study arms and relative to control groups (placebo/no treatment); the former in order to identify the effect of actively altering biomarkers levels.

Results

Reductions in PTH from supplementation with NVD were small when observed within the NVD study arms (pooled reduction: 10.5 pg/mL) and larger when compared with placebo/no treatment (pooled reduction: 49.7 pg/mL). NVD supplementation increased levels of 25-hydroxyvitamin D [25(OH)D] in both analyses (increase within NVD study arm: 20.6 ng/mL, increase versus placebo/no treatment: 26.9 ng/mL). While small and statistically non-significant changes in phosphate and fibroblast growth factor 23 were observed, NVD supplementation caused calcium levels to increase when compared with placebo/no treatment (increase: 0.23 mg/dL).

Conclusions

Our results suggest that supplementation with NVD can be used to increase 25(OH)D to a certain extent, while the potential of NVD to actively reduce PTH in non-dialysis-CKD patients with SHPT is limited.

Current treatment options for secondary hyperparathyroidism in patients with stage 3 to 4 chronic kidney disease and vitamin D deficiency

Introduction: Secondary hyperparathyroidism (SHPT) represents a complication of chronic kidney disease (CKD). Vitamin D system is altered since early CKD, and vitamin D deficiency is an established trigger of SHPT. Although untreated SHPT may degenerate into tertiary hyperparathyroidism with detrimental consequences in advanced CKD, best treatments for counteracting SHPT from stage 3 CKD are still debated. Enthusiasm on prescription of vitamin D receptor activators (VDRA) in non-dialysis renal patients, has been mitigated by the risk of low bone turnover and positive calcium-phosphate balance. Nutritional vitamin D is now suggested as first-line therapy to treat SHPT with low 25(OH)D insufficiency. However, no high-grade evidence supports the best choice between ergocalciferol, cholecalciferol, and calcifediol (in its immediate or extended-release formulation).Areas covered: The review discusses available data on safety and efficacy of nutritional vitamin D, VDRA and nutritional therapy in replenishing 25(OH)D deficiency and counteracting SHPT in non-dialysis CKD patients.Expert opinion: Best treatment for low 25(OH)D and SHPT remains unknown, due to incomplete understanding of the best homeostatic, as mutable, adaptation of mineral metabolism to CKD progression. Nutritional vitamin D and nutritional therapy appear safest interventions, whenever contextualized with single-patient characteristics. VDRA should be restricted to uncontrolled SHPT by first-line therapy.

VITADIAL "Does correction of 25 OH-VITAmin D with cholecalciferol supplementation increase muscle strength in hemoDIALysis patients?": study protocol for a randomized controlled trial

BACKGROUND

Muscle strength decreases as kidney failure progresses. Low muscle strength affects more than 50% of hemodialysis patients and leads to daily life activities impairment. In the general population, numerous studies have linked low 25OH-vitamin D (25OHD) concentrations to the loss of the muscle strength and low physical performances. Data on native vitamin D and muscle function are scarce in the chronic kidney disease (CKD) population, but low 25OHD levels have been associated with poor muscle strength. We present in this article the protocol of an ongoing study named VITADIAL testing if cholecalciferol supplementation in hemodialysis patients with low 25OHD improves their muscle strength.

METHODS/DESIGN

VITADIAL is a prospective open randomized French multicenter study. All patients will have 25OHD levels ≤50nmol/L at randomization. One group will receive 100,000 UI cholecalciferol once a month during 6 months; the other group will receive no treatment during 6 months. In order to randomize patients with 25OHD ≤50nmol/L, supplemented patients will undergo a 3 months wash-out period renewable 3 times (maximum of 12 months wash-out) until 25OHD reaches a level ≤50nmol/L. The main objective of this study is to analyze if a 6-month period of oral cholecalciferol (i.e., native vitamin D) supplementation improves muscle strength of hemodialysis patients with low 25OHD vitamin D levels. Muscle strength will be assessed at 0, 3, and 6 months, by handgrip strength measured with a quantitative dynamometer. Secondary objectives are (1) to analyze 25OHD plasma levels after vitamin D wash-out and/or supplementation, as well as factors associated with 25OHD lowering speed during wash-out, and (2) to analyze if this supplementation improves patient's autonomy, reduces frailty risk, and improves quality of life. Fifty-four patients are needed in each group to meet our main objective.

DISCUSSION

In the general population, around 30 randomized studies analyzed the effects of vitamin D supplementation on muscle strength. These studies had very different designs, sizes, and studied population. Globally, these studies and the meta-analysis of studies favor a beneficial effect of vitamin D supplementation on muscle strength, but this effect is mainly found in the subgroup of aged patients and those with the lowest 25OHD concentrations at inclusion. We reported a positive independent association between 25OHD and handgrip strength in a population of 130 hemodialysis patients in a dose-dependent manner. In our cohort, a plateau effect was observed above 75 nmol/L. Only two randomized studies analyzed the effect of native vitamin D supplementation on muscle strength in hemodialysis patients, but unfortunately, these two studies were underpowered. VITADIAL is a trial specifically designed to assess whether cholecalciferol might benefit to hemodialysis patient's muscle strength.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04262934 . Registered on 10 February 2020 - Retrospectively registered.

Maintenance of Skeletal Muscle to Counteract Sarcopenia in Patients with Advanced Chronic Kidney Disease and Especially Those Undergoing Hemodialysis

Life extension in modern society has introduced new concepts regarding such disorders as frailty and sarcopenia, which has been recognized in various studies. At the same time, cutting-edge technology methods, e.g., renal replacement therapy for conditions such as hemodialysis (HD), have made it possible to protect patients from advanced lethal chronic kidney disease (CKD). Loss of muscle and fat mass, termed protein energy wasting (PEW), has been recognized as prognostic factor and, along with the increasing rate of HD introduction in elderly individuals in Japan, appropriate countermeasures are necessary. Although their origins differ, frailty, sarcopenia, and PEW share common components, among which skeletal muscle plays a central role in their etiologies. The nearest concept may be sarcopenia, for which diagnosis techniques have recently been reported. The focus of this review is on maintenance of skeletal muscle against aging and CKD/HD, based on muscle physiology and pathology. Clinically relevant and topical factors related to muscle wasting including sarcopenia, such as vitamin D, myostatin, insulin (related to diabetes), insulin-like growth factor I, mitochondria, and physical inactivity, are discussed. Findings presented thus far indicate that in addition to modulation of the aforementioned factors, exercise combined with nutritional supplementation may be a useful approach to overcome muscle wasting and sarcopenia in elderly patients undergoing HD treatments.

The effect of vitamin D supplementation on fibroblast growth factor-23 in patients with chronic kidney disease: A systematic review and meta-analysis

This is a meta-analysis of randomized controlled trials (RCTs) investigating the effects of oral vitamin D supplementation on serum fibroblast growth factor-23 (FGF23) concentrations in patients with chronic kidney disease (CKD). Manuscripts were extracted from PubMed/MEDLINE, Scopus, and ISI Web of Science through February 2020. Subgroup analyses, sensitivity analysis, and meta-regression assessments were performed. A total of eight clinical trials with nine treatment arms were included in the final analysis. The pooled results showed no significant changes in circulating FGF23 following vitamin D supplementation compared to the control group (Standardized mean difference (SMD): 0.24; 95% confidence intervals (CIs): -0.03 to 0.50, p > 0.05). Subgroup analyses found that studies which had participants with a body mass index (BMI) higher than 25 kg/m² , with an intervention duration shorter than 15 weeks, using phosphate binder medications, and trials that were on both patients with CKD undergoing hemodialysis and patients without hemodialysis treatment produced significant increases in FGF23 when concentration compared with the control group. This meta-analysis provides evidence that vitamin D supplementation does not have a significant effect on plasma FGF23 levels. However, further high-quality trials are required to identify the influence of oral vitamin D supplementation on FGF23 levels in patients with CKD.

Vitamin K and D Supplementation and Bone Health in Chronic Kidney Disease-Apart or Together?

Vitamin K (VK) and vitamin D (VD) deficiency/insufficiency is a common feature of chronic kidney disease (CKD), leading to impaired bone quality and a higher risk of fractures. CKD patients, with disturbances in VK and VD metabolism, do not have sufficient levels of these vitamins for maintaining normal bone formation and mineralization. So far, there has been no consensus on what serum VK and VD levels can be considered sufficient in this particular population. Moreover, there are no clear guidelines how supplementation of these vitamins should be carried out in the course of CKD. Based on the existing results of preclinical studies and clinical evidence, this review intends to discuss the effect of VK and VD on bone remodeling in CKD. Although the mechanisms of action and the effects of these vitamins on bone are distinct, we try to find evidence for synergy between them in relation to bone metabolism, to answer the question of whether combined supplementation of VK and VD will be more beneficial for bone health in the CKD population than administering each of these vitamins separately.

KDOQI Clinical Practice Guideline for Nutrition in CKD: 2020 Update

The National Kidney Foundation's Kidney Disease Outcomes Quality Initiative (KDOQI) has provided evidence-based guidelines for nutrition in kidney diseases since 1999. Since the publication of the first KDOQI nutrition guideline, there has been a great accumulation of new evidence regarding the management of nutritional aspects of kidney disease and sophistication in the guidelines process. The 2020 update to the KDOQI Clinical Practice Guideline for Nutrition in CKD was developed as a joint effort with the Academy of Nutrition and Dietetics (Academy). It provides comprehensive up-to-date information on the understanding and care of patients with chronic kidney disease (CKD), especially in terms of their metabolic and nutritional milieu for the practicing clinician and allied health care workers. The guideline was expanded to include not only patients with end-stage kidney disease or advanced CKD, but also patients with stages 1-5 CKD who are not receiving dialysis and patients with a functional kidney transplant. The updated guideline statements focus on 6 primary areas: nutritional assessment, medical nutrition therapy (MNT), dietary protein and energy intake, nutritional supplementation, micronutrients, and electrolytes. The guidelines primarily cover dietary management rather than all possible nutritional interventions. The evidence data and guideline statements were evaluated using Grading of Recommendations, Assessment, Development and Evaluation (GRADE) criteria. As applicable, each guideline statement is accompanied by rationale/background information, a detailed justification, monitoring and evaluation guidance, implementation considerations, special discussions, and recommendations for future research.

The impact of vitamin D supplementation on VDR gene expression and body composition in monozygotic twins: randomized controlled trial

Vitamin D supplementation is widely used. However, there is no consensus on the use and dosage of this supplement and the existing recommendations arise from studies based on the benefits that this nutrient can facilitate in bones. In addition, individual genetics can influence the response to supplementation, therefore, research involving monozygotic twins aims to reduce these differences in phenotypic responses. The objective of this randomised controlled study is to examine the effect of vitamin D supplementation on body composition and the expression of the vitamin D receptor (VDR) mRNA. An intervention was performed through supplementation with cholecalciferol at the concentration of 2000 IU in 90 healthy adult monozygotic twins (male or female pairs) for 2 months. The findings showed that serum vitamin D concentration increased by 65% and VDR gene expression sixty times (p = 0.001). Changes in body composition parameters were observed regarding body fat and lean mass. Our results indicate that an increase in serum vitamin D concentration may have potential therapeutic implications.

The effects of correction of vitamin D deficiency on arterial stiffness: A systematic review and updated meta-analysis of randomized controlled trials

It is unclear whether nutritional vitamin D supplementation in vitamin d-deficient persons improves arterial stiffness. To conduct a meta-analysis of the effects of the nutritional vitamin D therapy on arterial stiffness in adults with vitamin D deficiency, the Scopus, PUBMED, EMBASE, and Cochrane databases were searched for systematic reviews conducted up to October 5, 2018. Randomized clinical trials that compared nutritional vitamin D therapy with placebo in adults with vitamin D deficiency were eligible. Two reviewers independently evaluated eligibility of all retrieved studies based on titles and abstracts. Meta-analysis was performed using random effect or fixed effects model and inverse variance method was used to calculate the effect using standardized mean difference (SMD) and weighted mean difference. A leave-one-out method was used for sensitivity analysis. The main outcome was arterial stiffness, indicated by the carotid-femoral pulse wave velocity (PWV). We identified 237 records, of which 9 satisfied the inclusion criteria of the study. Our meta-analysis included relatively high-quality placebo-controlled randomized trials. In a random-effects model, nutritional vitamin D was associated with significant reductions in the pooled difference of PWV [(SMD: -0.29; 95 % CI: -0.51 to -0.06), p = 0.01; Cochran's Q test: chi² = 21.85; df = 9; p = 0.009; I² = 59 %; n = 909 from 9 studies]. All sensitivity analyses yielded similar results. Nutritional vitamin D supplementation significantly improved arterial stiffness (PWV) in several subgroups by correcting vitamin D deficiency, for a study duration of ≥4 months and a daily dose of vitamin D3 ≥ 2000 IU. The study indicated that the correction of vitamin D deficiency by nutritional vitamin D supplementation may improve arterial stiffness in vitamin d-deficient persons, especially by the correction of vitamin D deficiency with a daily dose of vitamin D3 ≥ 2000 IU. However, further studies are required to confirm this.

Pharmacologic Therapies for Aortic Stiffness in End-Stage Renal Disease: A Systematic Review and Meta-Analysis

Background:

Increased carotid-femoral pulse wave velocity (cf-PWV), a surrogate of increased aortic stiffness, is a risk factor for cardiovascular events and all-cause mortality in end-stage renal disease (ESRD). To minimize the deleterious effects of an increased aortic stiffness in ESRD patients, several interventions have been developed and cf-PWV has been used to monitor responses.

Objective:

The aim of this study was to determine the effects of pharmacologic interventions that target aortic stiffness on cf-PWV and systolic blood pressure (SBP) in adults with ESRD.

Study design:

This study implements a systematic review and meta-analysis.

Data sources:

MEDLINE, EMBASE, Cochrane Central, Health Technology Assessment, and EBM databases were searched.

Study eligibility, participants, and interventions:

Randomized and non-randomized studies involving adults (>18 years) with ESRD of any duration, receiving or not renal replacement therapy (hemodialysis, peritoneal dialysis) and exposed to a pharmacologic intervention whose effects were assessed by cf-PWV.

Methods:

Study screening, selection, data extraction, and quality assessments were performed by 2 independent reviewers. Narrative synthesis and quantitative data analysis summarized the review.

Results:

We included 1027 ESRD participants from 13 randomized and 5 non-randomized studies. Most pharmacologic interventions targeted bone mineral metabolism disorder or hypertension. Treatment with vitamin D analogues or cinacalcet did not decrease cf-PWV or SBP over placebo or matched controls (P > .05). Calcium-channel blockers (CCB) decreased cf-PWV and SBP compared with placebo or standard care (P < .05). Renin-angiotensin system inhibitors did not show any advantage over placebo in decreasing cf-PWV (P > .05).

Limitations:

Quality of evidence ranged from very low to moderate. Overall evidence was limited by the low number of studies, small sample sizes, and methodological inconsistencies.

Conclusions:

Pharmacologic interventions targeting aortic stiffness in ESRD have mixed effects on reducing cf-PWV, with some strategies suggesting potential benefit. The quality of evidence, however, is insufficient to draw definitive conclusions on their use to slow progression of aortic stiffness in ESRD. Further well-designed studies are needed to confirm these associations and their impact on cardiovascular outcomes in ESRD.

Registered in PROSPERO (CRD42016033463)

Effect of vitamin D supplementation on endothelial function - An updated systematic review with meta-analysis and meta-regression

BACKGROUND AND AIMS

Atherogenesis and endothelial dysfunction contribute to cardiovascular risk and vitamin D has been implemented in endothelial repair. This systematic review, meta-analysis and meta-regression aims to establish the effect of vitamin D supplementation on endothelial function.

METHODS AND RESULTS

To conduct the systematic review we searched the Cochrane Library of Controlled Trials, PubMed, ProQuest and EMBASE for randomized controlled trials that investigated the effects of vitamin D supplementation on flow-mediated dilation (FMD%), pulse wave velocity (PWV), and central augmentation index (AIx). Meta-analysis was based on a random effects model and inverse-variance methods to calculate either mean difference (MD) or standardized mean difference (SMD) as effects sizes. This was followed by meta-regression investigating the effect of baseline vitamin D concentrations, vitamin D dosing and study duration. Risk of bias was assessed using the JADAD scale and funnel plots. We identified 1056 studies of which 26 studies met inclusion criteria for quantitative analysis. Forty-two percent of the 2808 participants had either deficient or insufficient levels of vitamin D. FMD% (MD 1.17% (95% CI -0.20, 2.54), p = 0.095), PWV (SMD -0.09 m/s (95% CI -0.24, 0.07), p = 0.275) and AIx (SMD 0.05% (95% CI -0.1, 0.19), p = 0.52) showed no improvement with vitamin D supplementation. Sub-analysis and meta-regression revealed a tendency for AIx and FMD% to increase as weekly vitamin doses increased; no other significant relationships were identified.

CONCLUSIONS

Vitamin D supplementation showed no improvement in endothelial function. More evidence is required before recommendations for management of endothelial dysfunction can be made.

The role of vitamin D replacement therapy in serum FGF23 concentration in children with myelomeningocele compared with healthy children - a preliminary study

Background Fibroblast growth factor 23 (FGF23) is a recently discovered bone-derived regulator of vitamin D metabolism and phosphate homeostasis. It inhibits phosphate reabsorption and calcitriol production by the kidney. Myelomeningocele (MMC) remains the most severe form of neural tube defects involving serious locomotor disability, osteoporosis and pathologic fractures. We aimed to investigate the influence of vitamin D replacement therapy on serum FGF23 concentration in children with MMC and compare the results with healthy participants. Methods This prospective analysis was conducted on 16 children with MMC and 20 healthy children. Serum FGF23 levels were measured; for the studied group, before and after vitamin D replacement therapy with cholecalciferol (vitamin D3). The children's medical charts were analyzed to determine age, sex, anthropometric measurements, calcium and phosphate, cholecalciferol and renal function parameters. Results There were significant differences in vitamin D and FGF23 serum concentrations between the studied groups. The median vitamin D levels in the MMC group increased during replacement therapy (7 vs. 18.5 ng/mL, p = 0.29) in comparison to the median of 25.5 ng/mL in the control group. In MMC children we found a significant decrease in median serum FGF23 after vitamin D replacement therapy (from 42.1 to 0 RU/mL, p < 0.001). FGF23 correlated positively with albumin, serum and urine phosphate levels and negatively with alkaline phosphatase. Conclusions 1. Serum concentration of FGF-23 is increased in MMC children in comparison to a healthy control group. 2. Vitamin D replacement therapy decreases FGF23 concentrations in MMC children, although further studies are still warranted to gain detailed insight on the FGF23 in the MMC population. 3. Children with MMC present vitamin D deficiency. Nutrition supplemented with low doses of cholecalciferol (vitamin D3) (intakes reaching recommended daily allowances) was insufficient to correct 25(OH)-D level in that population of patients.

Effects of cholecalciferol supplementation on serum angiogenic biomarkers in breast cancer patients treated with tamoxifen: A controlled randomized clinical trial

OBJECTIVE

The aim of this study was to investigate the effects of cholecalciferol supplementation on serum levels of angiogenic parameters in patients with breast cancer (BC) who were treated with tamoxifen.

METHODS

This was a pilot-based, randomized, triple-blind, placebo-controlled clinical trial with 52 patients with BC randomly assigned to either an intervention group receiving weekly 50 000 IU cholecalciferol or a placebo group for 8 wk. At baseline and at end of study, serum levels of angiogenic growth factors such as vascular endothelial growth factor (VEGF)-A, angiopoietin (Ang)-2, hypoxia-inducible factor (Hif)-1, and high-sensitivity C-reactive protein were measured by enzyme-linked immunosorbent assay. Every 4 wk, a completed 3-d, 24-h dietary record and daily sunlight exposure checklist were collected and anthropometric variables were measured.

RESULTS

The ultimate number of participants in each arm was 22 for analyses. For premenopausal women, cholecalciferol supplementation resulted in a significant decrease in serum levels of Ang-2 and VEGF-A after 8 wk of treatment (P < 0.05). In the absence of vascular invasion, supplementation led to a significant decrease in Ang-2 levels compared with the placebo group (P < 0.05). Supplementation caused significant increases in Hif-1 in patients diagnosed with the infiltration of tumors into vascular or lymphatic vessels (P < 0.05).

CONCLUSION

Cholecalciferol supplementation achieved sufficient efficacy among patients with BC taking tamoxifen and could be effective in the reduction of angiogenic biomarkers particularly dependent on the infiltration status of the tumor to vessels. Further studies with larger subgroups should be investigated.

Nutritional vitamin D in CKD: Should we measure? Should we treat?

Vitamin Ddeficiency is frequently present in patients affected by chronic kidney disease (CKD). Experimental studies demonstrated that Vitamin D may play a role in the pathophysiology of diseases beyond mineral bone disorders in CKD (CKD-MBD). Unfortunately, the lack of large and interventional studies focused on the so called "non-classic" effects of 25(OH) Vitamin D supplementation in CKD patients, doesn't permit to conclude definitely about the beneficial effects of this supplementation in clinical practice. In conclusion, treatment of nutritional vitamin D deficiency in CKD may play a central role in both bone homeostasis and cardiovascular outcomes, but there is not clear evidence to support one formulation of nutritional vitamin D over another in CKD.

Effect of 9 months of vitamin D supplementation on arterial stiffness and blood pressure in Graves' disease: a randomized clinical trial

PURPOSE

Risk of cardiovascular disease (CVD) is increased in Graves' disease (GD). CVD is predicted by increased pulse wave velocity (PWV) and blood pressure (BP). GD and these risk factors are all associated with lower levels of vitamin D. We aimed to assess the effect of supplemental vitamin D on PWV and BP in GD.

METHODS

In a double-blinded trial, newly diagnosed GD patients were randomized to vitamin D3 70 µg/day (n = 44) or placebo (n = 42) as add-on to anti-thyroid medication. At baseline, 3 and 9 months PWV, BP and wave analysis were performed in office and 24 h setting. Between-group differences in change at 9 months were analyzed using linear mixed modelling. In subanalysis, effect of intervention in regard to baseline vitamin D insufficiency (25(OH)D < 50 nmol/L) was investigated. (The DAGMAR study, clinicaltrials.gov ID NCT02384668).

RESULTS

PWV was unaffected by intervention in main analysis. However in the subanalysis, comparing the response to intervention in the vitamin D insufficient (n = 28) and the vitamin D replete patients, supplemental vitamin D induced a significant decrease in office PWV of 1.2 (95% CI: -2.3; -0.1) m/s compared to placebo. Of notice, baseline PWV was non-significantly higher among the vitamin D insufficient as compared to the replete participants. In response to vitamin D, office central systolic BP (-3.9 (95% CI: -7.5; -0.3) and brachial mean BP (-3.3 (95% CI: -6.5; -0.3) declined whereas 24 h measurements were unaffected.

CONCLUSIONS

High-dose vitamin D supplementation did not affect PWV. We observed significant reduction in office but not 24 h BP. Subanalysis showed a clinically relevant PWV reduction among vitamin D insufficient participants, although regression towards the mean might contribute to findings. Further studies on supplemental vitamin D in GD should focus on patients with vitamin D insufficiency.

Effects of nutritional vitamin D supplementation on markers of bone and mineral metabolism in children with chronic kidney disease

Background

We investigated the effects of nutritional vitamin D supplementation on markers of bone and mineral metabolism, i.e. serum levels of fibroblast growth factor 23 (FGF23), Klotho, bone alkaline phosphatase (BAP) and sclerostin, in two cohorts with chronic kidney disease (CKD).

Methods

In all, 80 vitamin D-deficient children were selected: 40 with mild to moderate CKD from the ERGO study, a randomized trial of ergocalciferol supplementation [estimated glomerular filtration rate (eGFR) 55 mL/min/1.73 m2], and 40 with advanced CKD from the observational Cardiovascular Comorbidity in Children with Chronic Kidney Disease (4C) study (eGFR 24 mL/min/1.73 m2). In each study, vitamin D supplementation was started in 20 children and 20 matched children not receiving vitamin D served as controls. Measures were taken at baseline and after a median period of 8 months. Age- and gender-related standard deviation scores (SDSs) were calculated.

Results

Before vitamin D supplementation, children in the ERGO study had normal FGF23 (median 0.31 SDS) and BAP (-0.10 SDS) but decreased Klotho and sclerostin (-0.77 and -1.04 SDS, respectively), whereas 4C patients had increased FGF23 (3.87 SDS), BAP (0.78 SDS) and sclerostin (0.76 SDS) but normal Klotho (-0.27 SDS) levels. Vitamin D supplementation further increased FGF23 in 4C but not in ERGO patients. Serum Klotho and sclerostin normalized with vitamin D supplementation in ERGO but remained unchanged in 4C patients. BAP levels were unchanged in all patients. In the total cohort, significant effects of vitamin D supplementation were noted for Klotho at eGFR 40-70 mL/min/1.73 m2.

Conclusions

Vitamin D supplementation normalized Klotho and sclerostin in children with mild to moderate CKD but further increased FGF23 in advanced CKD.

Effect of Vitamin D Supplementation on Vascular Function and Inflammation in Patients with Chronic Kidney Disease: A Controversial Issue

Vitamin D deficiency is common in patients with CKD and is associated with vascular dysfunction and inflammation. In recent years, some randomized controlled trials have revealed the effect of vitamin D supplementation on vascular function and inflammation in CKD patients, but the results are inconsistent. Thus, in light of the controversy, we performed a systematic review and meta-analysis of the effect of vitamin D in patients with CKD. We searched the literature in multiple databases for clinical trials from the date of inception to December 2018. The standardized mean difference (SMD) effect size was pooled using fixed and random effects models. A total of 10 randomized controlled trials involving 579 patients were included in the meta-analysis; among these, 313 patients were treated with vitamin D, and the control group included 266 who received a placebo. This meta-analysis revealed no statistical significance in the levels of flow-mediated dilatation (SMD, 0.94; 95% CI, -0.33 to 2.21; P = 0.15); pulse wave velocity (SMD, -0.13; 95% CI, -0.38 to 0.13; P = 0.33); systolic BP (SMD, -0.04; 95% CI, -0.29 to 0.22; P = 0.77); diastolic BP (SMD, 0.01; 95% CI, -0.26 to 0.27; P = 0.97); and CRP (SMD, -0.09; 95% CI, -0.44 to 0.26; P = 0.61) between the vitamin D group and controls for patients with CKD. Short-term intervention with vitamin D was not associated with improvements in vascular function and inflammation, as measured by flow-mediated dilatation, pulse wave velocity, systolic BP, diastolic BP and CRP. This suggested that there is insufficient evidence to conclude the benefit of vitamin D supplementation on vascular function and inflammation in CKD patients.

Native Hypovitaminosis D in CKD Patients: From Experimental Evidence to Clinical Practice

Native hypovitaminosis D (n-hVITD) is frequently found from the early stages of chronic kidney disease (CKD) and its prevalence increases with CKD progression. Even if the implications of n-hVITD in chronic kidney disease-mineral bone disorder (CKD-MBD) have been extensively characterized in the literature, there is a lot of debate nowadays about the so called “unconventional effects” of native vitamin D (25(OH)VitD) supplementation in CKD patients. In this review, highlights of the dimension of the problem of n-hVITD in CKD stages 2–5 ND patients will be presented. In addition, it will focus on the “unconventional effects” of 25(OH)VitD supplementation, the clinical impact of n-hVITD and the most significant interventional studies regarding 25(OH)VitD supplementation in CKD stages 2–5 ND.

Benefit-risk balance of native vitamin D supplementation in chronic hemodialysis: what can we learn from the major clinical trials and international guidelines?

For some years, there has been a great renewal of interest in native vitamin D and its major involvement in osseous and non-osseous effects in the organism. Patients in chronic hemodialysis (CHD) constitute a specific population with different physiopathologic characteristics and needs, since morbidity and mortality are strongly correlated with vitamin D insufficiency. Vitamin D supplementation raises very pertinent questions for which we have only partial answers and we lack solid scientific proof to establish certain truths. Thus, we try through this mini-review to analyze the results of the main randomized clinical trials conducted during the last decade, and to discuss international guidelines concerning native vitamin D supplementation in CHD patients. Seven double-blind randomized clinical trials have evaluated native Vitamin D supplementation in CHD patients. These clinical trials began between 2007 and 2013 and studied relatively small samples of patients with an average of 50. All of these trials are important, but do not provide sufficient scientific proof concerning the advantages, consequences, and secondary effects of native vitamin D supplementation in CHD. None of the European, American, English, Asian, Australian, or Canadian recommendations have specified the targets, doses, duration, or the molecule of vitamin D supplementation in the patient on CHD. In 2017, the long-awaited KDIGO recommendations were published and despite the results of clinical trials conducted, the recommendations on native vitamin D supplementation in CHD were very imprecise and sparse, limited to suggesting correction of any state of vitamin D insufficiency or deficiency.

C-type natriuretic peptide attenuates renal osteodystrophy through inhibition of FGF-23/MAPK signaling

Renal osteodystrophy (ROD) occurs as early as chronic kidney disease (CKD) stage 2 and seems ubiquitous in almost all pediatric patients with CKD stage 5. Fibroblast growth factor (FGF)-23, a bone-derived endocrine regulator of phosphate homeostasis, is overexpressed in CKD and disturbs osteoblast differentiation and matrix mineralization. In contrast, C-type natriuretic peptide (CNP) acts as a potent positive regulator of bone growth. In the present study, we infused CNP into uremic rats and observed whether CNP could attenuate ROD through the inhibition of FGF-23 cascades. In uremic rats, CNP administration significantly alleviated renal dysfunction, calcium phosphate metabolic disorders, hypovitaminosis D, secondary hyperparathyroidism, the decrease in bone turnover markers and retarded bone pathological progression. More importantly, within FGF-23/mitogen-activated protein kinase (MAPK) signaling, the fibroblast growth factor receptor-1, Klotho and alternative (STAT-1/phospho-STAT-1) elements were upregulated by CNP, whereas FGF-23, RAF-1/phospho-RAF-1, and downstream (ERK/phospho-ERK and P38/phospho-P38) elements were paradoxically underexpressed in bone tissue. Therefore, CNP exerts a therapeutic effect on ROD through inhibition of FGF-23/MAPK signaling at the RAF-1 level.

The effects of vitamin D supplementation on endothelial activation among patients with metabolic syndrome and related disorders: a systematic review and meta-analysis of randomized controlled trials

Background and objective

The current systematic review and meta-analysis of randomized controlled trials (RCTs) was conducted to summarize the effect of vitamin D supplementation on endothelial activation among patients with metabolic syndrome and related disorders.

Methods

Cochrane library, Embase, PubMed, and Web of Science database were searched to identify related RCTs published before 30th April 2018. The heterogeneity among the included studies was assessed using Cochran’s Q test and I-square (I²) statistic. Data were pooled by using the random-effect model and standardized mean difference (SMD) was considered as summary effect size.

Results

Fourteen clinical trials that contained a total of 1253 participants were included in the current meta-analysis. Vitamin D supplementation significantly decreased von willebrand factor (vWF) (SMD -0.27; 95% CI, − 0.46, − 0.08; P = 0.006; I²:40.5%). However, we found no significant impact of vitamin D supplementation on intercellular adhesion molecule 1(ICAM-1) (SMD -1.96; 95% CI, − 4.02, 0.09; P = 0.06; I²:97.4%), vascular celladhesion molecule 1 (VCAM-1) (SMD -0.50; 95% CI, − 1.19, 0.19; P = 0.15; I²:91.2%), on E-selectin (SMD -0.04; 95% CI, − 0.36, 0.28; P = 0.81; I²:78.8%) and endothelin (SMD -0.49; 95% CI, − 1.18, 0.19; P = 0.15; I²:90.5%). The pooled data from trials of vitamin D supplementation with dosage of ≤4000 IU/day (− 0.37, 95% CI: -0.65, − 0.10, I²: 73.5%) significantly reduced vWF concentrations, while there was no effect of vitamin D supplementation on vWF concentrations among trials with the dosage of intervention > 4000 IU/day (− 0.17, 95% CI: -0.43, 0.10, I²: 0.0%). VWF concentrations significantly reduced in pooled data from trials with duration study ≤8 weeks (− 0.37, 95% CI: -0.67, − 0.07, I²: 60.6%), but there was no effect of vitamin D supplementation on vWF concentrations among trials with > 8 weeks (− 0.20, 95% CI: -0.45, 0.05, I²: 0.0%). While there was no effect of vitamin D supplementation on vWF concentrations among trials with total sample size of ≤60 patients (− 0.03, 95% CI: -0.42, 0.36, I²: 0.0%), vWF concentrations in trials with more than 60 patients decreased significantly (− 0.34, 95% CI: -0.56, − 0.12, I²: 60.9%).

Conclusions

Overall, the current meta-analysis demonstrated that vitamin D supplementation to patients with metabolic syndrome and related disorders resulted in an improvement in vWF, but did not affect ICAM-1, VCAM-1, E-selectin and endothelin levels.

Electronic supplementary material

The online version of this article (10.1186/s12986-018-0320-9) contains supplementary material, which is available to authorized users.

Effect of Vitamin D Supplementation on Markers of Vascular Function: A Systematic Review and Individual Participant Meta-Analysis

Background

Low 25‐hydroxyvitamin D levels are associated with an increased risk of cardiovascular events, but the effect of vitamin D supplementation on markers of vascular function associated with major adverse cardiovascular events is unclear.

Methods and Results

We conducted a systematic review and individual participant meta‐analysis to examine the effect of vitamin D supplementation on flow‐mediated dilatation of the brachial artery, pulse wave velocity, augmentation index, central blood pressure, microvascular function, and reactive hyperemia index. MEDLINE, CINAHL, EMBASE, Cochrane Central Register of Controlled Trials, and http://www.ClinicalTrials.gov were searched until the end of 2016 without language restrictions. Placebo‐controlled randomized trials of at least 4 weeks duration were included. Individual participant data were sought from investigators on included trials. Trial‐level meta‐analysis was performed using random‐effects models; individual participant meta‐analyses used a 2‐stage analytic strategy, examining effects in prespecified subgroups. 31 trials (2751 participants) were included; 29 trials (2641 participants) contributed data to trial‐level meta‐analysis, and 24 trials (2051 participants) contributed to individual‐participant analyses. Vitamin D3 daily dose equivalents ranged from 900 to 5000 IU; duration was 4 weeks to 12 months. Trial‐level meta‐analysis showed no significant effect of supplementation on macrovascular measures (flow‐mediated dilatation, 0.37% [95% confidence interval, −0.23 to 0.97]; carotid‐femoral pulse wave velocity, 0.00 m/s [95% confidence interval, −0.36 to 0.37]); similar results were obtained from individual participant data. Microvascular function showed a modest improvement in trial‐level data only. No consistent benefit was observed in subgroup analyses or between different vitamin D analogues.

Conclusions

Vitamin D supplementation had no significant effect on most markers of vascular function in this analysis.

Effects of vitamin D supplementation on FGF23: a randomized-controlled trial

Purpose

Fibroblast growth factor-23 (FGF23) is critical for phosphate homeostasis. Considering the high prevalence of vitamin D deficiency and the association of FGF23 with adverse outcomes, we investigated effects of vitamin D3 supplementation on FGF23 concentrations.

Methods

This is a post-hoc analysis of the Styrian Vitamin D Hypertension trial, a single-center, double-blind, randomized, placebo-controlled trial, conducted from 2011 to 2014 at the Medical University of Graz, Austria. Two hundred subjects with 25(OH)D concentrations < 30 ng/mL and arterial hypertension were randomized to receive either 2800 IU of vitamin D3 daily or placebo over 8 weeks. Primary outcome was the between-group difference in FGF23 levels at study end while adjusting for baseline values.

Results

Overall, 181 participants (mean ± standard deviation age, 60.1 ± 11.3; 48% women) with available c-term FGF23 concentrations were considered for the present analysis. Mean treatment duration was 54 ± 10 days in the vitamin D3 group and 54 ± 9 days in the placebo group. At baseline, FGF23 was significantly correlated with serum phosphate (r = 0.135; p = 0.002). Vitamin D3 supplementation had no significant effect on FGF23 in the entire cohort (mean treatment effect 0.374 pmol/L; 95% confidence interval − 0.024 to 0.772 pmol/L; p = 0.065), but increased FGF23 concentrations in subgroups with baseline 25(OH)D concentrations below 20 ng/mL (n = 70; mean treatment effect 0.973 pmol/L; 95% confidence interval − 0.032 to 1.979 pmol/L; p = 0.019) and 16 ng/mL (n = 40; mean treatment effect 0.593 pmol/L; 95% confidence interval 0.076 to 1.109; p = 0.022).

Conclusions

Vitamin D3 supplementation had no significant effect on FGF23 in the entire study cohort. We did, however, observe an increase of FGF23 concentrations in subgroups with low baseline 25(OH)D.

Efficacy of Nutritional Interventions on Inflammatory Markers in Haemodialysis Patients: A Systematic Review and Limited Meta-Analysis

Low-grade chronic inflammation is prevalent in patients undergoing haemodialysis (HD) treatment and is linked to the development of premature atherosclerosis and mortality. The non-pharmacological approach to treat inflammation in HD patients through nutritional intervention is well cited. We aimed to assess the efficacy of different nutritional interventions at improving inflammatory outcomes in HD patients, based on markers such as C-reactive protein (CRP), interleukin-6 (IL-6), and tumour necrosis factor-α (TNF-α). We searched PubMed, Cochrane Library, and Embase for randomized controlled trials (RCT) published before June 2017. Inclusion criteria included RCTs on adult patients on maintenance HD treatment with duration of nutritional interventions for a minimum 4 weeks. Risk of bias was assessed using the Jadad score. In total, 46 RCTs experimenting different nutritional interventions were included in the review and categorized into polyphenols rich foods, omega-3 fatty acids, antioxidants, vitamin D, fibres, and probiotics. Meta-analyses indicated significant reduction in CRP levels by omega-3 fatty acids (Random model effect: -0.667 mg/L, p < 0.001) and vitamin E (fixed model effect: -0.257 mg/L, p = 0.005). Evidence for other groups of nutritional interventions was inconclusive. In conclusion, our meta-analysis provided evidence that omega-3 fatty acids and vitamin E could improve inflammatory outcomes in HD patients.

The Effect of Vitamin D Supplementation on Bone Metabolic Markers in Chronic Kidney Disease

Use of active forms of vitamin D is advocated in patients with chronic kidney disease (CKD) for treatment of mineral bone disease because of the presumption that native forms of vitamin D would not undergo significant activation to calcitriol, the most active biological form of vitamin D. We present secondary analysis looking at bone turnover in subjects who completed the randomized, double blind, placebo-controlled trial investigating the effect of cholecalciferol supplementation on vascular function in nondiabetic CKD stage G3-G4 and vitamin D ≤20 ng/mL (Clinical Trials Registry of India: CTRI/2013/05/003648). Patients were randomized (1:1) to receive either two directly observed oral doses of 300,000 IU of cholecalciferol or matching placebo at baseline and 8 weeks. Of the 120 subjects enrolled, 58 in the cholecalciferol group and 59 in the placebo group completed the study. At 16 weeks, the serum 25(OH)D and 1,25(OH)₂ D levels increased in the cholecalciferol group but not in the placebo group (between-group difference in mean change: 23.40 ng/mL; 95% CI, 19.76 to 27.06; p < 0.001, and 14.98 pg/mL; 95% CI, 4.48 to 27.18; p = 0.007, respectively). Intact parathyroid hormone (iPTH) decreased in the cholecalciferol group (between-group difference in mean change -100.73 pg/mL (95% CI, -150.50 to -50.95; p < 0.001). Serum total and bone-specific alkaline phosphatase (SAP, BAP) and serum C-terminal cross-linked collagen type I telopeptides (CTX-1) were significantly reduced in cholecalciferol group (between group difference for change in mean: -20.25 U/L; 95% CI, -35.14 to -5.38 U/L; p = 0.008 for SAP; -12.54 U/L; 95% CI, -22.09 to -2.98 U/L; p = 0.013 for BAP; and -0.21 ng/mL; 95% CI, -0.38 to -0.05 ng/mL; p = 0.05 for CTX-1). Correlation analysis showed significant correlation of Δ25(OH)D with ΔiPTH (r = -0.409, p < 0.0001), Δ1,25(OH)₂ D (r = 0.305, p = 0.001), ΔSAP (r = -0.301, p = 0.002), ΔBAP (r = -0.264, p = 0.004), and ΔCTX-1 (r = -0.210, p = 0.0230). Cholecalciferol supplementation corrects vitamin D deficiency and is effective in lowering serum intact parathyroid hormone and bone turnover markers in early stages of CKD. © 2017 American Society for Bone and Mineral Research.

Is there a role or target value for nutritional vitamin D in chronic kidney disease?

Vitamin D is important for bone health in the general population but the value of vitamin D supplementation, and the role of 25-hydroxyvitamin D independently of 1,25-dihydroxyvitmain D, in individuals with chronic kidney disease (CKD), particularly in those who require dialysis, remains uncertain. Supplementation may improve some biochemical parameters, such as reducing PTH levels in patients to CKD-stage 4 who have vitamin D deficiency; but it remains to be established whether the role of nutritional vitamin D in maintaining bone health in the general population can be extrapolated to the CKD population. There is currently insufficient evidence to recommend conclusively that nutritional vitamin D supplementation should be prescribed to individuals with CKD who have 25-hydroxyvitamin D deficiency, either for skeletal or non-skeletal health outcomes.

Raising awareness on the therapeutic role of cholecalciferol in CKD: a multidisciplinary-based opinion

Vitamin D is recognized to play an essential role in health and disease. In kidney disease, vitamin D analogs have gained recognition for their involvement and potential therapeutic importance. Nephrologists are aware of the use of oral native vitamin D supplementation, however, uncertainty still exists with regard to the use of this treatment option in chronic kidney disease as well as clinical settings related to chronic kidney disease, where vitamin D supplementation may be an appropriate therapeutic choice. Two consecutive meetings were held in Florence in July and November 2016 comprising six experts in kidney disease (N = 3) and bone mineral metabolism (N = 3) to discuss a range of unresolved issues related to the use of cholecalciferol in chronic kidney disease. The panel focused on the following six key areas where issues relating to the use of oral vitamin D remain controversial: (1) vitamin D and parathyroid hormone levels in the general population, (2) cholecalciferol in chronic kidney disease, (3) vitamin D in cardiovascular disease, (4) vitamin D and renal bone disease, (5) vitamin D in rheumatological diseases affecting the kidney, (6) vitamin D and kidney transplantation.

Dose responses of vitamin D3 supplementation on arterial stiffness in overweight African Americans with vitamin D deficiency: A placebo controlled randomized trial

Background

Clinical trials are scant and equivocal on whether vitamin D can ameliorate arterial stiffness, particularly in populations at high risk for vitamin D deficiency and cardiovascular disease (CVD). This study determined the dose-response effects of vitamin D₃ supplementation on arterial stiffness in overweight African Americans with vitamin D deficiency.

Methods

Seventy overweight African Americans (aged 13–45 years) with serum 25-hydroxyvitamin D [25(OH)D] levels ≤ 20 ng/mL were randomized to monthly oral supplementation of 18,000 IU (~600 IU/day, n = 17), 60,000 IU (~2000 IU/day, n = 18), or 120,000 IU (~4000 IU/day, n = 18) of vitamin D₃ or placebo (n = 17) for 16-weeks. The arterial stiffness measurements, carotid-femoral pulse wave velocity (PWV) and carotid-radial PWV, were assessed by applanation tonometry at baseline and 16 weeks.

Results

Vitamin D₃ supplementation demonstrated a dose-response increase in serum 25(OH)D concentrations between groups (P<0.01). A significant downward linear trend was observed for carotid-femoral PWV (P<0.01), as the mean changes in carotid-femoral PWV across the four treatment groups were 0.13 m/s (95% CI: -0.24, 0.51 m/s) for placebo, 0.02 m/s (95% CI: -0.34, 0.38 m/s) for 600 IU/day group, -0.11 m/s (95% CI: -0.50, 0.27 m/s) for the 2,000 IU/day group, and -0.70 m/s (95% CI: -1.07, -0.32 m/s) for the 4,000 IU/day group. Findings were similar for carotid-radial PWV (P = 0.03), as the mean changes in carotid-radial PWV across the four treatment groups were 0.24 m/s (95% CI: -0.45, 0.92 m/s) for placebo, 0.09 m/s (95% CI: -0.54, 0.73 m/s) for 600 IU/day group, -0.57 m/s (95% CI: -1.20, 0.07 m/s) for the 2,000 IU/day group, and -0.61 m/s (95% CI: -1.25, 0.02 m/s) for the 4,000 IU/day group.

Conclusion

Arterial stiffness was improved by vitamin D₃ supplementation in a dose-response manner in overweight African Americans with vitamin D deficiency.

Con: Nutritional vitamin D replacement in chronic kidney disease and end-stage renal disease

Insufficiency of 25-hydroxyvitamin D [25(OH)D] is highly prevalent among patients with chronic kidney disease (CKD) or end-stage renal disease (ESRD) and is a critical component in the pathogenesis of secondary hyperparathyroidism. Accordingly, current National Kidney Foundation-Kidney Disease Outcomes Quality Initiative and Kidney Disease: Improving Global Outcomes guidelines recommend the correction of hypovitaminosis D through nutritional vitamin D replacement as a first-step therapeutic approach targeting secondary hyperparathyroidism. In this Polar Views debate, we summarize the existing evidence, aiming to defend the position that nutritional vitamin D replacement is not evidence-based and should not be applied to patients with CKD. This position is supported by the following: (i) our meta-analysis of randomized controlled trials shows that whereas nutritional vitamin D significantly increases serum 25(OH)D levels relative to placebo, there is no evidence either in predialysis CKD or in ESRD that parathyroid hormone (PTH) is lowered; (ii) on the other hand, in randomized head-to-head comparisons, nutritional vitamin D is shown to be inferior to activated vitamin D analogs in reducing PTH levels; (iii) nutritional vitamin D is reported to exert minimal to no beneficial actions in a series of surrogate risk factors, including aortic stiffness, left ventricular mass index (LVMI), epoetin utilization and immune function among others; and (iv) there is no evidence to support a benefit of nutritional vitamin D on survival and other 'hard' clinical outcomes. Whereas nutritional vitamin D replacement may restore 25(OH)D concentration to near normal, the real target of treating vitamin D insufficiency is to treat secondary hyperparathyroidism, which is untouched by nutritional vitamin D. Furthermore, the pleotropic benefits of nutritional vitamin D remain to be proven. Thus, there is little, if any, benefit of nutritional vitamin D replacement in CKD.

Randomized Controlled Trial for the Effect of Vitamin D Supplementation on Vascular Stiffness in CKD

BACKGROUND AND OBJECTIVES

Vitamin D is implicated in vascular health in CKD. This study compared placebo, calcifediol, and calcitriol treatment with changes in vascular stiffness, BP, proteinuria, mineral metabolism parameters, C-reactive protein, and fibroblast growth factor 23 in patients with stable CKD.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We conducted a double-blind, randomized controlled trial in out-patient CKD clinics in Vancouver, Canada, from February of 2011 to August of 2014, enrolling 119 patients with an eGFR of 15-45 ml/min per 1.73 m2. Change in pulse wave velocity (PWV) was measured after 6 months of treatment with a fixed dose of oral calcifediol (5000 IU 25-hydroxyvitamin D3), calcitriol (0.5 µg 1,25-dihydroxyvitamin D3), or placebo, thrice weekly.

RESULTS

Eighty-seven participants were evaluated. Mean age was 66 years, 71% were men, 40% were diabetic, and mean baseline PWV was 11.5 m/s (SD=3.9 m/s). After 6 months, the PWV decreased in the calcifediol group (mean change, -1.1; 95% confidence interval [95% CI], -2.2 to 0.1 m/s), remained unchanged in the calcitriol group (mean change, 0.2; 95% CI, -0.9 to 1.4 m/s), and increased in the placebo group (mean change, 1.1; 95% CI, -0.1 to 2.2 m/s). The overall P value for between-arm changes was 0.03. Absolute PWV change was significantly different between groups (P=0.04): the combined vitamin D treatment group saw decreased PWV (mean change, -0.4; 95% CI, -1.2 to 0.4 m/s) whereas the placebo group saw increased PWV (mean change, +1.1; 95% CI, -0.1 to 2.2 m/s). The treatment group demonstrated significantly decreased serum parathyroid hormone (mean difference, -0.5; 95% CI, -0.7 to -0.3 ln[pg/ml]; P<0.001) and increased calcium (mean difference, 0.4; 95% CI, -0.1 to 0.7 mg/dl; P=0.02). In observational analysis, participants in the highest 25-hydroxyvitamin D tertile at trial end had significant decreases in PWV (mean change, -1.0; 95% CI, -2.0 to 0.0 m/s) compared with the middle and lowest tertiles (P<0.01). Side effects were minor and rare.

CONCLUSIONS

Six months of supplemental vitamin D analogs at fixed doses may achieve a reduction of PWV in patients with advanced CKD. Because the treatment effect was attenuated when baseline PWV was included as a covariate, these findings should be replicated in larger populations and further studied.