Vitamin D receptor activation and left ventricular hypertrophy in advanced kidney disease

Vitamin D receptor gene polymorphism predicts left ventricular hypertrophy in maintenance hemodialysis

Background

To verify that the single nucleotide polymorphisms (SNP) of vitamin D receptor (VDR) may lead to genetic susceptibility to left ventricular hypertrophy (LVH), the present study was designed to study four SNPs of VDR associated with LVH in maintenance hemodialysis (MHD) patients of Han nationality.

Methods

120 MHD patients were recruited at Department of Nephrology, Zhongnan Hospital of Wuhan University to analyze the expression of genotype, allele and haplotype of Fok I, Bsm I, Apa I and Taq I in blood samples, and to explore their correlation with blood biochemical indexes and ventricular remodeling.

Results

The results showed that the risks of CVD included gender, dialysis time, heart rate, SBP, glycated hemoglobin, calcium, iPTH and CRP concentration. Moreover, LAD, LVDd, LVDs, IVST and LVMI in B allele of Bsm I increased significantly. Fok I, Apa I and Taq I polymorphisms have no significant difference between MHD with LVH and without LVH. Further study showed that VDR expression level decreased significantly in MHD patients with LVH, and the B allele was positively correlated with VDR Expression.

Conclusion

VDR Bsm I gene polymorphism may predict cardiovascular disease risk of MDH patients, and provided theoretical basis for early detection and prevention of cardiovascular complications.

Comparative Effects of Etelcalcetide and Maxacalcitol on Serum Calcification Propensity in Secondary Hyperparathyroidism: A Randomized Clinical Trial

BACKGROUND AND OBJECTIVES

Vitamin D receptor activators and calcimimetics (calcium-sensing receptor agonists) are two major options for medical treatment of secondary hyperparathyroidism. A higher serum calcification propensity (a shorter T₅₀ value) is a novel surrogate marker of calcification stress and mortality in patients with CKD. We tested a hypothesis that a calcimimetic agent etelcalcetide is more effective in increasing T₅₀ value than a vitamin D receptor activator maxacalcitol.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

A randomized, multicenter, open-label, blinded end point trial with active control was conducted in patients with secondary hyperparathyroidism undergoing hemodialysis in Japan. Patients were randomly assigned to receive intravenous etelcalcetide 5 mg thrice weekly (etelcalcetide group) or intravenous maxacalcitol 5 or 10 µg thrice weekly (maxacalcitol group). The primary, secondary, and tertiary outcomes were changes in T₅₀ value, handgrip strength, and score of the Dementia Assessment Sheet for Community-Based Integrated Care System from baseline to 12 months, respectively.

RESULTS

In total, 425 patients from 23 dialysis centers were screened for eligibility, 326 patients were randomized (etelcalcetide, n=167; control, n=159), and 321 were included in the intention-to-treat analysis (median age, 66 years; 113 women [35%]). The median (interquartile range) of T₅₀ value was changed from 116 minutes (interquartile range, 90-151) to 131 minutes (interquartile range, 102-176) in the maxacalcitol group, whereas it was changed from 123 minutes (interquartile range, 98-174) to 166 minutes (interquartile range, 127-218) in the etelcalcetide group. The increase in T₅₀ value was significantly greater in the etelcalcetide group (difference in change, 20 minutes; 95% confidence interval, 7 to 34 minutes; P=0.004). No significant between-group difference was found in the change in handgrip strength or in the Dementia Assessment Sheet for Community-Based Integrated Care System score.

CONCLUSIONS

Etelcalcetide was more effective in increasing T₅₀ value than maxacalcitol among patients on hemodialysis with secondary hyperparathyroidism. There was no difference in handgrip strength or cognition between the two drugs.

CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER

VICTORY; UMIN000030636 and jRCTs051180156.

The adaptive designs CONSORT extension (ACE) statement: a checklist with explanation and elaboration guideline for reporting randomised trials that use an adaptive design

Adaptive designs (ADs) allow pre-planned changes to an ongoing trial without compromising the validity of conclusions and it is essential to distinguish pre-planned from unplanned changes that may also occur. The reporting of ADs in randomised trials is inconsistent and needs improving. Incompletely reported AD randomised trials are difficult to reproduce and are hard to interpret and synthesise. This consequently hampers their ability to inform practice as well as future research and contributes to research waste. Better transparency and adequate reporting will enable the potential benefits of ADs to be realised.This extension to the Consolidated Standards Of Reporting Trials (CONSORT) 2010 statement was developed to enhance the reporting of randomised AD clinical trials. We developed an Adaptive designs CONSORT Extension (ACE) guideline through a two-stage Delphi process with input from multidisciplinary key stakeholders in clinical trials research in the public and private sectors from 21 countries, followed by a consensus meeting. Members of the CONSORT Group were involved during the development process.The paper presents the ACE checklists for AD randomised trial reports and abstracts, as well as an explanation with examples to aid the application of the guideline. The ACE checklist comprises seven new items, nine modified items, six unchanged items for which additional explanatory text clarifies further considerations for ADs, and 20 unchanged items not requiring further explanatory text. The ACE abstract checklist has one new item, one modified item, one unchanged item with additional explanatory text for ADs, and 15 unchanged items not requiring further explanatory text.The intention is to enhance transparency and improve reporting of AD randomised trials to improve the interpretability of their results and reproducibility of their methods, results and inference. We also hope indirectly to facilitate the much-needed knowledge transfer of innovative trial designs to maximise their potential benefits. In order to encourage its wide dissemination this article is freely accessible on the BMJ and Trials journal websites."To maximise the benefit to society, you need to not just do research but do it well" Douglas G Altman.

The Adaptive designs CONSORT Extension (ACE) statement: a checklist with explanation and elaboration guideline for reporting randomised trials that use an adaptive design

Adaptive designs (ADs) allow pre-planned changes to an ongoing trial without compromising the validity of conclusions and it is essential to distinguish pre-planned from unplanned changes that may also occur. The reporting of ADs in randomised trials is inconsistent and needs improving. Incompletely reported AD randomised trials are difficult to reproduce and are hard to interpret and synthesise. This consequently hampers their ability to inform practice as well as future research and contributes to research waste. Better transparency and adequate reporting will enable the potential benefits of ADs to be realised.This extension to the Consolidated Standards Of Reporting Trials (CONSORT) 2010 statement was developed to enhance the reporting of randomised AD clinical trials. We developed an Adaptive designs CONSORT Extension (ACE) guideline through a two-stage Delphi process with input from multidisciplinary key stakeholders in clinical trials research in the public and private sectors from 21 countries, followed by a consensus meeting. Members of the CONSORT Group were involved during the development process.The paper presents the ACE checklists for AD randomised trial reports and abstracts, as well as an explanation with examples to aid the application of the guideline. The ACE checklist comprises seven new items, nine modified items, six unchanged items for which additional explanatory text clarifies further considerations for ADs, and 20 unchanged items not requiring further explanatory text. The ACE abstract checklist has one new item, one modified item, one unchanged item with additional explanatory text for ADs, and 15 unchanged items not requiring further explanatory text.The intention is to enhance transparency and improve reporting of AD randomised trials to improve the interpretability of their results and reproducibility of their methods, results and inference. We also hope indirectly to facilitate the much-needed knowledge transfer of innovative trial designs to maximise their potential benefits.

Vitamin D Attenuates Loss of Endothelial Biomarker Expression in Cardio-Endothelial Cells

Vitamin D is associated with cardiovascular health through activating the vitamin D receptor that targets genes related to cardiovascular disease (CVD). The human cardiac microvascular endothelial cells (HCMECs) were used to develop mechanically and TGF-β1-induced fibrosis models, and the rat was used as the isoproterenol (ISO)-induced fibrosis model. The rats were injected with ISO for the first five days, followed by vitamin D injection for the consecutive three weeks before being sacrificed on the fourth week. Results showed that mechanical stretching reduced endothelial cell marker CD31 and VE-cadherin protein expressions, as well as increased α-smooth muscle actin (α-SMA) and fibronectin (FN). The transforming growth factor-β1 (TGF-β1) reduced CD31, and increased α-SMA and FN protein expression levels. Vitamin D presence led to higher protein expression of CD31, and lower protein expressions of α-SMA and FN compared to the control in the TGF-β1-induced fibrosis model. Additionally, protein expression of VE-cadherin was increased and fibroblast-specific protein-1 (FSP1) was decreased after vitamin D treatment in the ISO-induced fibrosis rat. In conclusion, vitamin D slightly inhibited fibrosis development in cell and animal models. Based on this study, the beneficial effect of vitamin D may be insignificant; however, further investigation of vitamin D’s effect in the long-term is required in the future.

Complement 7 Is Up-Regulated in Human Early Diabetic Kidney Disease

There is a temporal window from the time diabetes is diagnosed to the appearance of overt kidney disease during which time the disease progresses quietly without detection. Currently, there is no way to detect early diabetic nephropathy (EDN). Herein, we performed an unbiased assessment of gene-expression analysis of postmortem human kidneys to identify candidate genes that may contribute to EDN. We then studied one of the most promising differentially expressed genes in both kidney tissue and blood samples. Differential transcriptome analysis of EDN kidneys and matched nondiabetic controls showed alterations in five canonical pathways, and among them the complement pathway was the most significantly altered. One specific complement pathway gene, complement 7 (C7), was significantly elevated in EDN kidney. Real-time PCR confirmed more than a twofold increase of C7 expression in EDN kidneys compared with controls. Changes in C7 gene product level were confirmed by immunohistochemistry. C7 protein levels were elevated in proximal tubules of EDN kidneys. Serum C7 protein levels were also measured in EDN and control donors. C7 levels were significantly higher in EDN serum than control serum. This latter finding was independently confirmed in a second set of blood samples from a previously collected data set. Together, our data suggest that C7 is associated with EDN, and can be used as a molecular target for detection and/or treatment of EDN.

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.

Paricalcitol Attenuates Cardiac Fibrosis and Expression of Endothelial Cell Transition Markers in Isoproterenol-Induced Cardiomyopathic Rats

OBJECTIVES

Acute cardiomyopathy is a health problem worldwide. Few studies have shown an association between acute cardiomyopathy and low vitamin D status. Paricalcitol, a vitamin D receptor activator, clinically benefits patients with advanced kidney disease. The effect of paricalcitol supplement on cardiac remodeling in cardiomyopathic rats is unknown. This experimental study investigated the effect of paricalcitol in rats with cardiomyopathy induced by isoproterenol.

DESIGN

Prospective, randomized, controlled experimental study.

SETTING

Hospital-affiliated animal research institution.

SUBJECTS

Eight-week-old male Wistar-Kyoto rats.

INTERVENTIONS

Male Wistar-Kyoto rats were first injected intraperitoneally with isoproterenol to create a rat model of acute cardiomyopathy. Then paricalcitol was administered intraperitoneally to isoproterenol-injected rats at a dosage of 200 ng three times a week for 3 weeks. Relevant cardiomyopathy-related variables were measured regularly in three groups of rats, controls, isoproterenol, and isoproterenol plus paricalcitol. Rat hearts were obtained for evaluation of cardiac fibrosis using Masson trichrome staining and commercially available software, and evaluation of cell transition using immunofluorescence staining analysis.

MEASUREMENTS AND MAIN RESULTS

Isoproterenol infusions generated significant cardiac fibrosis (p < 0.001). Subsequent paricalcitol treatment attenuated the isoproterenol-induced cardiac fibrosis (p = 0.006). Fluorescence showed colocalization of endothelial and fibroblast cell markers (cluster differentiation 31 and α-smooth muscle actin, respectively) in the isoproterenol-treated hearts. Paricalcitol injections attenuated the isoproterenol-induced fluorescence intensity of two cell markers (p < 0.01).

CONCLUSIONS

Paricalcitol injections may ameliorate isoproterenol-induced cardiac fibrosis possibly through regulating cell transition.

The protective role of vitamin D on the heart and the kidney

For a long time, vitamin D was regarded as an essential component for the maintenance of appropriate calcium metabolism. Indeed, the calcium-related functions were broadly studied and validated in numerous clinical and epidemiologic studies. All of these vitamin D effects are mediated by a specific receptor. Remarkably, recent investigations show that the vitamin D receptor (VDR) also affects autoimmunity and by these means, the course of neoplasias and tissue inflammation. Moreover, the VDR regulates genes that affect cellular activity including cell differentiation and apoptosis and, by these means, angiogenesis. Actually, vitamin D deficiency has been associated with structural and functional cardiovascular changes that can be reversed by receptor stimulation. In this regard, some of the injurious effects of vitamin D deficiency such as myocardial hypertrophy and high blood pressure seem linked to increased renin-angiotensin activity. Interestingly, chronic renal disease, a condition often associated with greater cardiovascular risk, high blood pressure, myocardial hypertrophy and inappropriate stimulation of the renin angiotensin system, is also tied to inadequate vitamin D activity. In fact, studies in several animal models such as the rat ureteral obstruction model, the 5/6 nephrectomy model and others, clearly show that VDR stimulation prevents both structural and functional changes in the heart and the kidney. Clinical trials are needed to validate the vitamin D potential benefits in chronic kidney disease and its associated cardiovascular risk.

Vitamin D analogue therapy, cardiovascular risk and kidney function in people with Type 1 diabetes mellitus and diabetic nephropathy: a randomized trial

AIM

To evaluate the effects of therapy with the vitamin D analogue paricalcitol on markers of cardiovascular risk and kidney function in people with Type 1 diabetes mellitus and diabetic nephropathy.

METHODS

In a double-blind, randomized placebo-controlled, crossover trial, 48 participants on stable renin angiotensin aldosterone system blockade and diuretics were assigned, in random order, to 12 weeks of paricalcitol and 12 weeks of placebo therapy, separated by a 4-week washout period. Primary and secondary endpoints were changes in plasma N-terminal probrain natriuretic peptide and urinary albumin excretion rate obtained before and after each intervention. Glomerular filtration rates were estimated and measured ((51) Cr-EDTA plasma clearance glomerular filtration rate) after each intervention.

RESULTS

The mean (sd) age of the participants was 57 (9) years, the baseline geometric mean (95% CI) urinary albumin excretion rate was 148 (85-259) mg/24 h, the mean (sd) HbA1c was 70 (9) mmol/mol [8.6 (3)%], the mean (sd) estimated glomerular filtration rate was 47 (15) ml/min/1.73 m(2) and the mean (sd) 24-h blood pressure was 135 (17)/74 (10) mmHg. Compared with placebo therapy, vitamin D analogue therapy had no significant effect on plasma N-terminal probrain natriuretic peptide concentration (P = 0.6), urinary albumin excretion rate was reduced by 18% (P = 0.03 for comparison), estimated glomerular filtration rate was reduced by 5 ml/min/1.73 m(2) (P < 0.001) and measured glomerular filtration rate was reduced by 1.5 ml/min/1.73 m(2) (P = 0.2).

CONCLUSIONS

Paricalcitol therapy did not affect plasma N-terminal probrain natriuretic peptide concentration in people with Type 1 diabetes and diabetic nephropathy; however, the urinary albumin excretion rate was significantly lowered.

Reprint of: Vitamin D receptor activation and prevention of arterial ageing

In chronic kidney disease (CKD) patients, cardiovascular (CV) morbidity and mortality rate is higher than in the general population, because of frequently concomitant hypertension, peripheral vascular disease, heart failure, vascular calcification (VC), diabetes and mineral bone disease. Recently, another important factor associated to CV risk in CKD has been deeply investigated: vitamin D deficiency. Vitamin D Receptors (VDRs) are present in several systems and tissues and VDR activation is associated to positive effects, resulting in better blood pressure control and prevention of diabetic nephropathy. Unfortunately, the natural, non-selective vitamin D receptor activator (VDRA), calcitriol, is associated to higher serum calcium and phosphate levels, thus worsening CV risk in CKD. Recent data showed that the selective VDRA paricalcitol might have ameliorative CV effects. The potential positive impact of the use of paricalcitol on diabetic nephropathy, cardiac disease, hypertension, and VC may open new paths in the fight against CV disease in CKD patients.

Comparison of mineral metabolites as risk factors for adverse clinical outcomes in CKD

Patients with chronic kidney disease are at increased risk for progressing to end-stage renal disease, developing cardiovascular disease, and dying prematurely. Recent evidence has suggested that disordered mineral metabolism, which includes hyperphosphatemia, secondary hyperparathyroidism, vitamin D deficiency, and fibroblast growth factor 23 excess, may contribute to the high rates of adverse outcomes in this population. However, marked within-subject variability for some of these biochemical parameters exists, potentially detracting from the utility of certain metabolites as prognostic tools. This review summarizes the available data on the epidemiology of phosphate, parathyroid hormone, vitamin D, and fibroblast growth factor 23, and their relationships with adverse clinical outcomes in chronic kidney disease, compares the performance of each as a biomarker of risk and introduces recent insights into the pathophysiology behind some of the observed relationships.

Placental growth factor may predict increased left ventricular mass index in patients with mild to moderate chronic kidney disease--a prospective observational study

Background

Placental growth factor [PlGF) is a cardiovascular (CV) risk marker, which is related to left ventricle hypertrophy (LVH) in animal models. Currently there are no data available regarding the possible relationship of PlGF and the development of LVH or diastolic dysfunction in patients with chronic kidney disease (CKD) and the relationship of PlGF to other CV risk factors in CKD patients. The aim of our study was to determine the possible association of PlGF and several other CV risk markers to echocardiographic parameters in CKD population.

Methods

We prospectively examined selected laboratory (PlGF, fibroblast growth factor-23 -FGF23, vitamin D, parathyroid hormone, extracellular newly identified RAGE-binding protein - EN-RAGE, B-type natriuretic peptide - BNP) and echocardiographic parameters in 62 patients with CKD 2–4. Mean follow-up was 36 ±10 months. Laboratory and echocardiographic data were collected 2–3 times, at the shortest interval of 12 months apart. Multivariate regression analysis was used to detect independent correlations of variables.

Results

Increased left ventricular mass index (LVMI, g/m^2.7) was found in 29% patients with CKD 2–4, left ventricular (LV) diastolic dysfunction was detected in 74.1% patients (impaired LV relaxation in 43.5% patients and pseudonormal pattern in 30.6% patients). After 36 ± 10 months increased LVMI was found in 37.1% patients with CKD 2–4, LV diastolic dysfunction was detected in 75.8% patients (impaired LV relaxation in 43.5% patients and pseudonormal pattern in 32.3% patients). Following independent correlations were found: LVMI was related to PlGF, cholesterol, BNP, systolic blood pressure and serum creatinine. EN-RAGE correlated positively with left atrial diameter and inversely with E/A ratio. During the follow-up we found a significant increase in LVMI and left atrial diameter, whereas a significant decrease in LVEF was noted.

Conclusion

According to our data, PlGF is independently related to increased LV mass in CKD, whereas EN-RAGE is more likely related to diastolic dysfunction in this population.

FGF23 modifies the relationship between vitamin D and cardiac remodeling

BACKGROUND

There is growing evidence to support an important role for vitamin D and related hormones, parathyroid hormone and fibroblast growth factor 23 (FGF23), on cardiac remodeling in chronic kidney disease. Our objective was to determine the relationships between vitamin D and cardiac remodeling in chronic kidney disease and the effects of parathyroid hormone and FGF23 on these associations.

METHODS AND RESULTS

In 1431 participants from the Chronic Renal Insufficiency Cohort study, we measured 25-hydroxyvitamin D (25(OH)D), 1,25-dihydroxyvitamin D (1,25(OH)2D), FGF23, and parathyroid hormone and performed quantitative echocardiography. Using linear regression methods, we determined significant negative interactions between 25(OH)D and FGF23 on left ventricular (LV) mass (P=0.016), end-diastolic volume (P=0.029), and end-systolic volumes (P=0.021). In participants with an FGF23 level greater than the median of 123.5 RU/mL, each doubling of 25(OH)D was associated with a 2.5% (95% confidence interval, -4.8, -0.2) lower LV mass. This association was less pronounced with FGF23 levels less than the median (0.4%; 95% confidence interval, -1.9, 2.7). Conversely, in participants with deficient 25(OH)D levels <20 ng/mL, each doubling of FGF23 was associated with a 3.4% (95% confidence interval, 1.2, 5.6) greater LV mass compared with only a 1.6% (95% confidence interval, -0.2, 3.5) difference in participants with sufficient 25(OH)D. Similar findings were observed with 25(OH)D and volumes (P<0.05), and 1,25(OH)2D and LV mass and volumes (P<0.005). There was no effect modification by parathyroid hormone.

CONCLUSIONS

We identified significant interactions among 25(OH)D, 1,25(OH)2D, and FGF23 on cardiac remodeling. Increased LV mass and cavity dilatation were observed with low 25(OH)D and high FGF23. Our findings suggest that consideration of both hormones is crucial to understanding the role of either in cardiac remodeling, and may have important therapeutic implications.

Administered paricalcitol dose and survival in hemodialysis patients: a marginal structural model analysis

PURPOSE

Several observational studies have indicated that vitamin D receptor activators (VDRA), including paricalcitol, are associated with greater survival in maintenance hemodialysis (MHD) patients. However, patients with higher serum parathyroid hormone, a surrogate of higher death risk, are usually given higher VDRA doses, which can lead to confounding by indication and attenuate the expected survival advantage of high VDRA doses.

METHODS

We examined mortality-predictability of low (>1 but <10 µg/week) versus high (≥10 µg/week) dose of administered paricalcitol over time in a contemporary cohort of 15 442 MHD patients (age 64 ± 15 years, 55% men, 44% diabetes, 35% African-Americans) from all DaVita dialysis clinics across the USA (7/2001-6/2006 with survival follow-ups until 6/2007) using conventional Cox regression, propensity score (PS) matching, and marginal structural model (MSM) analyses.

RESULTS

In our conventional Cox models and PS matching models, low dose of paricalcitol was not associated with mortality either in baseline (hazard ratio (HR): 1.03, 95% confidence interval (CI): (0.97-1.09)) and (HR: 0.99, 95%CI:(0.86-1.14)) or time-dependent (HR: 1.04, 95%CI: (0.98-1.10)) and (HR: 1.12, 95%CI: (0.98-1.28)) models, respectively. In contrast, compared to high dose of paricalcitol, low dose was associated with a 26% higher risk of mortality (HR: 1.26, 95%CI: (1.19-1.35)) in MSM. The association between dose of paricalcitol and mortality was robust in almost all subgroups of patients using MSMs.

CONCLUSIONS

Higher dose of paricalcitol appears causally associated with greater survival in MHD patients. Randomized controlled trials need to verify the survival effect of paricalcitol dose in MHD patients are indicated.

[Vitamin D hormone system and diabetes mellitus: lessons from selective activators of vitamin D receptor and diabetes mellitus]

The vitamin D hormone system has significant skeletal and extra-skeletal effects. Vitamin D receptor occurs in different tissues, and several cells other than renal cells are able to locally produce active vitamin D, which is responsible for transcriptional control of hundreds of genes related to its pleiotropic effects. There is increasing evidence relating vitamin D to development and course of type 1 and 2 diabetes mellitus. Specifically, influence of vitamin D on the renin-angiotensin-aldosterone system, inflammatory response, and urinary albumin excretion could explain the relevant impact of vitamin D status on diabetic nephropathy. Selective vitamin D receptor activators are molecules able to reproduce agonistic or antagonistic effects of active vitamin D depending on the tissue or even on the cell type. Specifically, paricalcitol has a beneficial profile because of its potency to reduce parathyroid hormone, with lower effects on serum calcium or phosphate levels. Moreover, in patients with diabetes and renal disease, paricalcitol decreases microalbuminuria, hospitalization rates, and cardiovascular mortality. Therefore, these molecules represent an attractive new option to improve prognosis of renal disease in patients with diabetes.

Vitamin D receptor activation and prevention of arterial ageing

In chronic kidney disease (CKD) patients, cardiovascular (CV) morbidity and mortality rate is higher than in the general population, because of frequently concomitant hypertension, peripheral vascular disease, heart failure, vascular calcification (VC), diabetes and mineral bone disease. Recently, another important factor associated to CV risk in CKD has been deeply investigated: vitamin D deficiency. Vitamin D Receptors (VDRs) are present in several systems and tissues and VDR activation is associated to positive effects, resulting in better blood pressure control and prevention of diabetic nephropathy. Unfortunately, the natural, non-selective vitamin D receptor activator (VDRA), calcitriol, is associated to higher serum calcium and phosphate levels, thus worsening CV risk in CKD. Recent data showed that the selective VDRA paricalcitol might have ameliorative CV effects. The potential positive impact of the use of paricalcitol on diabetic nephropathy, cardiac disease, hypertension, and VC may open new paths in the fight against CV disease in CKD patients.

Vitamin D: roles in renal and cardiovascular protection

PURPOSE OF REVIEW

Great progress has been made in recent years in understanding the expanding roles of the vitamin D endocrine system beyond calcemic regulation, including pathophysiological actions in the kidney and the cardiovascular system. The purpose of this review is to update the recent advance regarding the effects of vitamin D and its analogs on the renal and cardiovascular system.

RECENT FINDINGS

Vitamin D deficiency is not only widely associated with chronic kidney disease and cardiovascular disease in humans, but may also accelerate the disease progression. Dysregulation of vitamin D metabolism caused by renal insufficiency contributes to the low vitamin D status. Preclinical and clinical studies have demonstrated impressive therapeutic outcome with low-calcemic vitamin D analogs in renal and cardiovascular disease. The mechanism underlying the renal and cardiovascular protection involves regulation of multiple signaling pathways by vitamin D including nuclear factor κB, Wnt/β-catenin and the renin-angiotensin system.

SUMMARY

The renal and cardiovascular protective activity of vitamin D revealed in recent studies has profound clinical implications. Nutritional correction of vitamin D deficiency and treatment with vitamin D analogs could be therapeutic options for renal and cardiovascular problems. New vitamin D analogs with better renal and cardiovascular therapeutic efficacy are highly desired. More randomized trials are needed to address these issues.

Vitamin D therapy in chronic kidney disease and end stage renal disease

Vitamin D has garnered much research and debate about supplementation in recent years, not only as it pertains to patients with kidney disease but also to those in the general population. This review discusses observational and available clinical trial evidence about the effects of both calcitriol and vitamin D analogs (active) and ergocalciferol and cholecalciferol (nutritional) vitamin D in patients with CKD and ESRD.

Optimal vitamin D, calcitriol, and vitamin D analog replacement in chronic kidney disease: to D or not to D: that is the question

PURPOSE OF REVIEW

Patients with chronic kidney disease (CKD) are often insufficient in 25(OH) vitamin D and are almost uniformly deficient in 1,25(OH)2 vitamin D, because of decreased renal hydroxylation resulting from hyperphosphatemia and elevated fibroblast growth factor-23 (FGF-23) levels. These same abnormalities lead to secondary hyperparathyroidism for which the administration of calcitriol or vitamin D analogs has been the mainstay of therapy for decades. This review summarizes new trials of vitamin D, calcitriol, and its analogs over the last 2 years.

RECENT FINDINGS

In addition to the endocrine effects of the vitamin D axis on bone and mineral metabolism, studies have demonstrated there is also extrarenal conversion of 25(OH) vitamin D to 1,25(OH)2 vitamin D in multiple cells leading to autocrine effects. This advance has led to the speculation that CKD patients may also need to be supplemented with ergocalciferol or cholecalciferol. Unfortunately, to date, the majority of interventional studies have focused on biochemical end points. There are no randomized controlled trials demonstrating that therapy with any formulation of vitamin D results in improved patient level outcomes.

SUMMARY

Despite the physiologic importance of vitamin D in health and disease, more research is required to determine which vitamin D derivative is required for optimal health in CKD patients.

The use of group sequential, information-based sample size re-estimation in the design of the PRIMO study of chronic kidney disease

BACKGROUND

Chronic kidney disease is associated with a marked increase in risk for left ventricular hypertrophy and cardiovascular mortality compared with the general population. Therapy with vitamin D receptor activators has been linked with reduced mortality in chronic kidney disease and an improvement in left ventricular hypertrophy in animal studies.

PURPOSE

PRIMO (Paricalcitol capsules benefits in Renal failure Induced cardia MOrbidity) is a multinational, multicenter randomized controlled trial to assess the effects of paricalcitol (a selective vitamin D receptor activator) on mild to moderate left ventricular hypertrophy in patients with chronic kidney disease.

METHODS

Subjects with mild-moderate chronic kidney disease are randomized to paricalcitol or placebo after confirming left ventricular hypertrophy using a cardiac echocardiogram. Cardiac magnetic resonance imaging is then used to assess left ventricular mass index at baseline, 24 and 48 weeks, which is the primary efficacy endpoint of the study. Because of limited prior data to estimate sample size, a maximum information group sequential design with sample size re-estimation is implemented to allow sample size adjustment based on the nuisance parameter estimated using the interim data. An interim efficacy analysis is planned at a pre-specified time point conditioned on the status of enrollment. The decision to increase sample size depends on the observed treatment effect. A repeated measures analysis model, using available data at Week 24 and 48 with a backup model of an ANCOVA analyzing change from baseline to the final nonmissing observation, are pre-specified to evaluate the treatment effect. Gamma-family of spending function is employed to control family-wise Type I error rate as stopping for success is planned in the interim efficacy analysis.

LIMITATIONS

If enrollment is slower than anticipated, the smaller sample size used in the interim efficacy analysis and the greater percent of missing week 48 data might decrease the parameter estimation accuracy, either for the nuisance parameter or for the treatment effect, which might in turn affect the interim decision-making.

CONCLUSIONS

The application of combining a group sequential design with a sample-size re-estimation in clinical trial design has the potential to improve efficiency and to increase the probability of trial success while ensuring integrity of the study.