Lower risk for cardiovascular mortality in oral 1alpha-hydroxy vitamin D3 users in a haemodialysis population

Vitamin D and Clinical Outcomes in Dialysis

Most dialysis patients are vitamin D deficient, including deficiencies in both activated vitamin D (1, 25-dihydroxyvitamin D) and the less active 25-hydroxyvitamin D. These and other abnormalities associated with chronic kidney disease (CKD), if they remain untreated, lead to secondary hyperparathyroidism and bone changes, such as osteitis fibrosa cystica. Activated vitamin D has been proven to decrease parathyroid hormone (PTH) levels in dialysis patients and is currently used for this indication. There are multiple other potential "pleotrophic" effects associated with vitamin D therapy. These include associations with lower all-cause and cardiovascular mortality, lower rates of infections and improved glycemic indexes. Meta-analyses of multiple observational studies have shown activated vitamin D therapy to be associated with improved survival. Observational data also suggest fewer infections and better glucose control. There have been no randomized clinical trials powered to evaluate mortality or other clinical outcomes. Small trials of nutritional vitamin D (ergocalciferol and cholecalciferol) showed increases in 25-hydroxyvitamin D levels without hypercalcemia or hyperphosphatemia, even when given in addition to activated vitamin D therapy. While activated vitamin D therapy is associated with improved outcomes, it also leads to higher fibroblast growth factor 23 (FGF-23) levels, which may be detrimental in dialysis patients. Further research is needed to evaluate whether activated or nutritional vitamin D therapy are beneficial in dialysis patients for outcomes other than secondary hyperparathyroidism.

Associations among time-average mineral values, mortality and cardiovascular events in hemodialysis patients

Mineral and bone disease (CKD-MBD), disorders of mineral metabolism, is associated with mortality and cardiovascular disease in dialysis patients. However, the associations among time average mineral values (P, Ca and PTH) and clinical outcomes are not well investigated.

OBJECTIVES

This study examines the associations among mineral values and clinical outcomes from a single medical center.

METHODS

Adult patients who initiate hemodialysis in Taoyuan General Hospital from 2008 to 2013 were enrolled. We examined these associations using baseline and time-average model. The clinical outcomes included mortality, major adverse cardiovascular events (MACE) and cardiovascular events. We also examined the association between achieve K/DOQI guidelines' targets and clinical outcomes.

RESULTS

From a total of 284 hemodialysis patients, none of the baseline mineral values is associated with mortality and cardiovascular event, except hyperphosphatemia. Compared to patients achieved K/DOQI guidelines' targets, time average hyperphosphatemia is associated with MACE and first cardiovascular event [the adjusted hazard ratios (AHRs) are 6.343 and 3.278); whereas time average hypercalcemia is associated with MACE marginally (the AHR is 5.964). None of above clinical outcomes is related to hyperparathyroidism. The AHRs for mortality in those who only met PTH targets and none of the mineral value targets are 1.73 and 1.74, whereas the AHRs for cardiovascular events in those who met only Ca, only PTH, and none of the targets are 1.73, 1.81 and 2.54 (all ps < 0.05).

CONCLUSION

Time-average phosphate is associated with cardiovascular events after initiation of dialysis. Among mineral values, serum phosphate is still the strongest predictor for mortality and cardiovascular events.

Effect of active vitamin D on cardiovascular outcomes in predialysis chronic kidney diseases: A systematic review and meta-analysis

AIM

Vitamin D deficient patients present an increased risk of cardiovascular disease. We conducted this systematic review and meta-analysis to evaluate the effect of active vitamin D analogue on cardiovascular outcomes in predialysis chronic kidney disease.

METHODS

Pubmed, Embase, the Cochrane Library, CNKI, and article reference lists were searched for randomized controlled trials (RCTs) that compared active vitamin D analogues with placebo or no treatment for patients with predialysis chronic kidney disease. A meta-analysis was conducted using the standard methods consistent with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Reviewer Manager Software, ver. 5.2, was used.

RESULTS

Seven RCTs (five studies with paricalcitol and two studies with calcitriol, 731 patients) were included. Compared with control groups, active vitamin D reduced the incidence of cardiovascular events (RR, 0.27; 95% CI, 0.13-0.59), induced an increase in those with proteinuria reduction (RR, 1.9; 95% CI, 1.34-2.71), but did not alter left ventricular mass index and systolic function (MD, 0.42 g/m^2.7 ; 95% CI, -0.23-1.07 g/m^2.7 , P = 0.21 for left ventricular mass index and MD, -0.33; 95% CI, -0.74-0.07, P = 0.1 for left ventricular ejection fraction). Neither systolic blood pressure nor diastolic blood pressure was reduced by active vitamin D (MD, 0.3 mmHg; 95% CI, -4.95-5.56 mmHg; MD, -0.24 mmHg; 95% CI: -6.21-5.72 mmHg, respectively). Increased probability of hypercalcaemia after paricalcitol therapy was found (RR, 7.85; 95% CI, 2.92-21.10).

CONCLUSION

Active vitamin D reduced the incidence of cardiovascular events and induced a reduction in proteinuria, but its long-term effect on cardiac structure and function needed further confirmation. Increased probability of hypercalcaemia after paricalcitol therapy was found.

Vitamin D and Anaesthesia

Vitamin D is a vitamin not only associated with calcium-phosphorus metabolism but also affects many organ systems. Because of its effect on the immune system in recent years, it has attracted much attention. Vitamin D deficiency is a clinical condition that can be widely observed in the society. Thus, patients with vitamin D deficiency are often seen in anaesthesia practice. In the absence of vitamin D, prolongation of intensive care unit stay, increase in mortality and morbidity and also association of chronic diseases further increase the importance of vitamin D deficiency. The results obtained from studies have led to the question of whether poor surgical outcome is associated with vitamin D deficiency. We assessed the vitamin D deficiency and its negative consequences for the anaesthesiologist.

Efficacy of early treatment with calcimimetics in combination with reduced doses of vitamin d sterols in dialysis patients

Vitamin D is an important physiologic regulator of bone and mineral metabolism. In chronic kidney disease, reduced renal production of calcitriol contributes to secondary hyperparathyroidism (SHPT). Consequently, supplementation with vitamin D sterols is an important treatment for SHPT and its associated mineral and bone disorders. However, doses of vitamin D sterols required to suppress parathyroid hormone (PTH) secretion often promote hypercalcaemia and hyperphosphataemia. Therefore, there is a trade-off between reduced serum PTH and increased levels of serum calcium, phosphorus and calcium–phosphorus product. It has been suggested that treatment of SHPT with cinacalcet, a type II calcimimetic, with reduced doses of vitamin D sterols could enhance achievement of calcium and phosphorus treatment targets while maintaining goals for PTH. Recent clinical trials have evaluated this hypothesis and demonstrated that treatment with cinacalcet in combination with reduced doses of vitamin D sterols is an effective treatment for the management of SHPT.

Potent antiproliferative effects of 25-hydroxy-16-ene-23-yne-vitamin D₃ that resists the catalytic activity of both CYP27B1 and CYP24A1

The potency of 25-hydroxyvitamin D3 (25(OH)D3) is increased by several fold through its metabolism into 1α,25-dihydroxyvitamin D3 (1α,25(OH)2D3) by cytochrome P450 27B1 (CYP27B1). Thus, the pivotal role of 1α-hydroxylation in the activation of vitamin D compounds is well known. Here, we examined the metabolism of 25-hydroxy-16-ene-23-yne-vitamin D3 (25(OH)-16-ene-23-yne-D3), a synthetic analog of 25(OH)D3 in a cell-free system and demonstrated that 25(OH)-16-ene-23-yne-D3 is neither activated by CYP27B1 nor inactivated by cytochrome P450 24A1 (CYP24A1). These findings were also confirmed in immortalized normal human prostate epithelial cells (PZ-HPV-7) which are known to express both CYP27B1 and CYP24A1, indicating that the structural modifications featured in 25(OH)-16-ene-23-yne-D3 enable the analog to resist the actions of both CYP27B1 and CYP24A1. To provide intelligible structure-function information, we also performed molecular docking analysis between the analog and CYP27B1. Furthermore, 25(OH)-16-ene-23-yne-D3 was found to suppress the growth of PZ-HPV-7 cells with a potency equivalent to 1α,25(OH)2D3. The antiproliferative activity of 25(OH)-16-ene-23-yne-D3 was found to be vitamin D receptor (VDR)-dependent as it failed to inhibit the growth of mammary tumor cells derived from VDR-knockout mice. Furthermore, stable introduction of VDR into VDR-knockout cells restored the growth inhibition by 25(OH)-16-ene-23-yne-D3. Thus, we identified 25-hydroxy-16-ene-23-yne-vitamin D3 as a novel non-1α-hydroxylated vitamin D analog which is equipotent to 1α,25(OH)2D3 in its antiproliferative activity. We now propose that the low potency of the intrinsic VDR-mediated activities of 25(OH)D3 can be augmented to the level of 1α,25(OH)2D3 without its activation through 1α-hydroxylation by CYP27B1, but by simply preventing its inactivation by CYP24A1.

Vitamin D deficiency plays an important role in cardiac disease and affects patient outcome: Still a myth or a fact that needs exploration?

There is increasing evidence that a low vitamin D status may be an important and hitherto neglected factor of cardiovascular disease. This review is an overview of the current body of literature, and presents evidence of the mechanisms through which vitamin D deficiency affects the cardiovascular system in general and the heart in particular. Available data indicate that the majority of congestive heart failure patients have 25-hydroxyvitamin D deficiency. Furthermore, the low serum 25-hydroxyvitamin D level has a higher impact on hypertension, coronary artery disease an on the occurrence of relevant cardiac events. A serum 25-hydroxyvitamin D level below 75 nmol/l (30 ng/l) is generally regarded as vitamin D insufficiency in both adults and children, while a level below 50 nmol/l (20 ng/l) is considered deficiency. Levels below 50 nmol/l (20 ng/l) are linked independently to cardiovascular morbidity and mortality.

[Native vitamin D in dialysis patients]

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

Risk of heart failure among postmenopausal women: a secondary analysis of the randomized trial of vitamin D plus calcium of the women's health initiative

BACKGROUND

Vitamin D supplementation may be an inexpensive intervention to reduce heart failure (HF) incidence. However, there are insufficient data to support this hypothesis. This study evaluates whether vitamin D plus calcium (CaD) supplementation is associated with lower rates of HF in postmenopausal women and whether the effects differ between those at high versus low risk for HF.

METHODS AND RESULTS

Analyses were restricted to 35 983 (of original 36 282) women aged 50 to 79 years old in the Women's Health Initiative randomized trial of CaD supplementation who were randomized 1:1 in a double-blinded fashion to receive 1000 mg/d of calcium plus 400 IU/d of vitamin D3 or placebo. Overall, 744 adjudicated incident HF cases (intervention, 363; control, 381) occurred during a median follow-up of 7.1 (interquartile range, 1.6) years. CaD supplementation, compared with placebo, was not associated with reduced HF risk in the overall population, hazard ratio, 0.95; P=0.46. However, CaD supplementation had differential effects (P interaction=0.005) in subgroups stratified by baseline risk status of HF defined by the presence (high risk=17 449) or absence (low risk=18 534) of pre-existing HF precursors including coronary heart diseases, diabetes mellitus, or hypertension: 37% (hazard ratio, 0.63 [95% confidence interval, 0.46-0.87]) lower risk of HF in the low-risk versus hazard ratio, 1.06; P=0.51, in the high-risk subgroups.

CONCLUSIONS

CaD supplementation did not significantly reduce HF incidence in the overall cohort, however, it was beneficial among postmenopausal women without major HF precursors while of little value in high-risk subgroups. Additional studies are warranted to confirm these findings and investigate the underlying mechanism.

CLINICAL TRIAL REGISTRATION URL

http://www.clinicaltrials.gov. Unique identifier: NCT00000611.

Treatment of 25-OH vitamin D deficiency in older men with chronic kidney disease stages 3 and 4 is associated with reduction in cardiovascular events

Observational studies in healthy people suggest an inverse relationship between serum 25-hydroxyvitamin D (25OHD) levels and cardiovascular (CV) mortality. Treating vitamin D deficiency in patients with moderate chronic kidney disease (CKD) may reduce CV events in this high-risk population. Study data were abstracted from Harry S. Truman Memorial Veterans Hospital electronic medical record system. The medical records of all veterans who had CKD stages 3 and 4 and had 25OHD levels determined from April 2006 to September 2007 were reviewed. Patients with 25OHD deficiency, serum level <30 ng/mL, were included (N = 126, all men, mean age = 70 years). Successful 25OHD replacement was defined as prescription of ergocalciferol sufficient to increase serum 25OHD level by 25% from baseline within 6 months (treatment group, n = 90). Otherwise patients were considered as untreated controls (n = 36). The date when the 25OHD level was drawn was considered as the date of inclusion. All the patients were followed up from the date of inclusion until July 2009 to capture CV events prospectively. During mean follow-up of 27.2 months, 44% of the controls had CV events, whereas only 21% of the patients in the treatment group had CV events (P = 0.001). In multivariate logistic regression analysis, adjusting for CV disease predictors age, initial parathyroid hormone level, statin use, history of CV disease, and glomerular filtration rate, the estimated odds ratio for 25OHD replacement status was 0.37 (95% confidence interval: 0.14-1.0). Treatment of 25OHD deficiency with ergocalciferol in patients with moderate CKD is associated with significant reduction in CV events.

Aortic arch calcification predicts cardiovascular and all-cause mortality in maintenance hemodialysis patients

BACKGROUND/AIM

Vascular calcification is associated with cardiovascular risk in maintenance hemodialysis (MHD) patients. Previous reports have shown that simple assessment of aortic arch calcification (AoAC) using plain radiography is associated with cardiovascular mortality in the general population. We conducted a prospective study to investigate factors associated with the presence at baseline and progression of AoAC in MHD patients and examined its prognostic value in a short-term outcome.

METHODS

We prospectively evaluated chest X-rays in 301 asymptomatic MHD patients. The extent of AoAC was divided into three Grades (0, 1, 2+3). Demographic data including age, gender, dialysis vintage, co-morbidity and biochemical data were assessed and the patients were then followed for 3 years.

RESULTS

AoAC was observed in 126 patients (41.9%) as Grade 0, in 112 patients (37.2%) as Grade 1, and in 63 patients (20.9%) as Grade 2 and 3 at baseline. An increase in the severity of calcification was associated with older male patients who had lower serum albumin levels. During the follow-up period of 3 years, multivariate Cox proportional hazards analysis revealed that high-grade calcification was associated with cardiovascular and all-cause mortality. Patients with AoAC were associated with a worse outcome in survival analysis and the grade of AAC also influenced their survival. Moreover, all-cause death rates were significantly higher in the progression groups than in the non-progression groups.

CONCLUSIONS

The presence and progression of AoAC assessed by chest X-ray were independently associated with mortality in MHD patients. Regular follow-up by chest X-ray could be a simple and useful method to stratify mortality risk in MHD patients.

Use of vitamin D receptor activator, incident cardiovascular disease and death in a cohort of hemodialysis patients

The use of vitamin D receptor activators (VDRAs) is an independent predictor of a lower risk of death from cardiovascular disease (CVD) in patients with chronic kidney disease (CKD). We examined whether the use of VDRAs and other CKD-mineral bone disorder (MBD)-related factors are associated with incident CVD or death after CVD in hemodialysis patients. This is a historical cohort study of 37 690 prevalent hemodialysis patients without previous history of CVD at the end of 2004 extracted from a nationwide registry in Japan. The key exposure was the use of VDRAs, and the outcomes were incident CVD (myocardial infarction, cerebral infarction, cerebral hemorrhage, and sudden death) and death after CVD during the 1-year follow-up. VDRAs were used in 57% of the subjects at baseline. We identified 2433 patients with incident CVD and 397 deaths after the events. In multivariate logistic regression models, independent predictors of incident CVD were non-use of VDRA, higher intact PTH, non-use of calcium-based phosphate-binder, and non-use of non-calcium-based phosphate binder. Risk of death after CVD was not significantly associated with VDRA, whereas it was lower in those with lower corrected calcium, and the risk was higher in those with higher phosphate and in non-users of calcium-based phosphate binders. The use of VDRAs was associated with a lower risk of incident CVD but not with death after CVD in this large cohort of hemodialysis patients. The CKD-MBD-related predictors of poor outcomes are associated with the risk of incident CVD, the risk of death after CVD, or both.

Circulating levels of soluble receptor for advanced glycation end product are inversely associated with vascular calcification in patients on haemodialysis independent of S100A12 (EN-RAGE) levels

AIM

The receptor for advanced glycation end products (RAGE) has emerged as a central regulator of vascular inflammation and atherosclerosis. Soluble RAGE (sRAGE) has an anti-inflammatory effect by quenching ligands for RAGE. On the other hand, extracellular RAGE-binding protein S100A12 (EN-RAGE) shows a pro-inflammatory effect in a way, but may play pleiotropic roles related to inflammatory process. Therefore, we determined the levels of sRAGE and S100A12 in haemodialysis (HD) patients and evaluated their relationship with vascular calcification.

METHODS

We performed a cross-sectional study with 199 HD patients. Plain X-ray images of the lateral lumbar spine from all subjects were studied to calculate semiquantitative vascular calcification scores (VCS), as described by Kauppila. Commercially available enzyme linked immunosorbent assay (ELISA) kits were used to quantify the serum concentration of sRAGE and S100A12.

RESULTS

The patients were 57.1 ± 13.7 years of age; 54.3% were male, 49.2% were diabetic, and 36.2% had a history of cardiovascular disease. In a univariate analysis, serum sRAGE was negatively associated with VCS (log sRAGE, r=-0.208, P=0.003), whereas S100A12 showed a positive tendency (log S100A12, r=0.235, P=0.085). Even after adjustments for confounding risk factors, sRAGE was independently associated with VCS (β=-1.679, P=0.002).

CONCLUSION

This study demonstrated that the circulating sRAGE level was inversely associated with VCS in HD patients independent of the S100A12 level and the severity of systemic inflammation.

Novel metabolic biomarkers of cardiovascular disease

Coronary heart disease (CHD) accounts for one in every six deaths in US individuals. Great advances have been made in identifying important risk factors for CHD, such as hypertension, diabetes mellitus, smoking and hypercholesterolaemia, which have led to major developments in therapy. In particular, statins represent one of the greatest successes in the prevention of CHD. While these standard risk factors are important, an obvious opportunity exists to take advantage of ongoing scientific research to better risk-stratify individuals and to identify new treatment targets. In this Review, we summarize ongoing scientific research in a number of metabolic molecules or features, including lipoproteins, homocysteine, calcium metabolism and glycaemic markers. We evaluate the current state of the research and the strength of evidence supporting each emerging biomarker. We also discuss whether the associations with CHD are strong and consistent enough to improve current risk stratification metrics, and whether these markers enhance our understanding of the underlying biology of CHD and thus point towards new treatment options.

Active vitamin D and accelerated progression of aortic stiffness in hemodialysis patients: a longitudinal observational study

BACKGROUND

We hypothesized that high-dose active vitamin D therapy in the form of alphacalcidol (α-calcidol), used to treat secondary hyperparathyroidism in chronic kidney disease, could lead to vascular calcification and accelerated progression of aortic stiffness.

METHODS

We conducted an observational study in 85 patients on chronic hemodialysis, among which 70 were taking a weekly dose of α-calcidol of <2 µg and 15 were taking a weekly dose of ≥2 µg (pharmacological dose). Parathyroid hormone, 25-hydroxyvitamin D, fibroblast growth factor 23, and α-klotho were determined. Aortic stiffness was assessed by determination of carotid-femoral pulse wave velocity (cf-PWV) at baseline and after a mean follow-up of 1.2 years. A multivariable regression model was used to evaluate the impact of pharmacological dose of α-calcidol on the progression of aortic stiffness.

RESULTS

At baseline, clinical, biological, and hemodynamic parameters were similar. At follow-up, cf-PWV increased more in patients with pharmacological dose of α-calcidol (0.583±2.291 m/s vs. 1.948±1.475 m/s; P = 0.04). After adjustment for changes in mean blood pressure and duration of follow-up, pharmacological dose of α-calcidol was associated with a higher rate of progression of cf-PWV (0.969 m/s; 95% confidence interval = 0.111-1.827; P = 0.03), and this association persisted after further adjustments for parameters of mineral metabolism.

CONCLUSIONS

In this study, pharmacological dose of α-calcidol was associated with accelerated progression of aortic stiffness. This study suggest that the vascular safety of active vitamin D posology may need to be specifically addressed in the treatment of chronic kidney disease-related bone mineral disorder.

Vitamin D and chronic kidney disease

Chronic kidney disease (CKD) has been recognized as a significant global health problem because of the increased risk of total and cardiovascular morbidity and mortality. Vitamin D deficiency or insufficiency is common in patients with CKD, and serum levels of vitamin D appear to have an inverse correlation with kidney function. Growing evidence has indicated that vitamin D deficiency may contribute to deteriorating renal function, as well as increased morbidity and mortality in patients with CKD. Recent studies have suggested that treatment with active vitamin D or its analogues can ameliorate renal injury by reducing fibrosis, apoptosis, and inflammation in animal models; this treatment also decreases proteinuria and mortality in patients with CKD. These renoprotective effects of vitamin D treatment are far beyond its classical role in the maintenance of bone and mineral metabolism, in addition to its pleiotropic effects on extra-mineral metabolism. In this review, we discuss the altered metabolism of vitamin D in kidney disease, and the potential renoprotective mechanisms of vitamin D in experimental and clinical studies. In addition, issues regarding the effects of vitamin D treatment on clinical outcomes are discussed.

Vitamin D receptor signaling in renal and cardiovascular protection

The high prevalence of vitamin D deficiency in patients with chronic kidney disease is believed to be an important risk factor for the cardiorenal syndrome commonly seen in this patient population. African Americans suffer a disproportionally high incidence of renal and cardiovascular disease with poor disease outcome, which may be partly attributed to their low vitamin D status in part owing to low subcutaneous photoproduction of vitamin D. Mounting evidence from animal and clinical studies has shown beneficial effects of vitamin D therapy on the renal and cardiovascular systems, and the underlying renoprotective and cardioprotective mechanisms of vitamin D receptor (VDR)-mediated signaling are under intense investigation. In this article, our most recent understanding of the renal protective mechanism of the podocyte VDR signaling against diabetic nephropathy and the anti-atherosclerotic role of macrophage VDR signaling in the regulation of atherosclerosis is reviewed.

Vitamin D activates the Nrf2-Keap1 antioxidant pathway and ameliorates nephropathy in diabetic rats

BACKGROUND

Diabetic nephropathy is a major risk of end-stage kidney disease. Many complex factors relate to the progression of diabetic nephropathy. Using nonobese type 2 diabetes model rats, we confirmed that oxidative stress was a crucial factor. Because recent studies suggest that vitamin D could suppress oxidative stress, we explored whether the active vitamin D analog, maxacalcitol, could also attenuate oxidative stress and prevent the progression of diabetic nephropathy.

METHODS

Diabetic rats aged 20 weeks were divided into 3 groups and treated with insulin, maxacalcitol, and vehicle. At age 30 weeks, blood and urine analyses, renal histology, immunohistochemistry, real-time polymerase chain reaction, and western blot were performed.

RESULTS

Although maxacalcitol reduced albuminuria and mesangial matrix expansion, no significant differences were observed in blood pressure and creatinine clearance among the 3 treatment groups. Systemic and intrarenal oxidative stress was reduced by maxacalcitol therapy. Expressions of nuclear factor-κB and nicotinamide adenine dinucleotide phosphate oxidase in the kidney also decreased in the insulin-treated and maxacalcitol-treated groups but increased in the vehicle-alone group. In addition, the expression of nuclear factor erythroid 2-related factor 2 (Nrf2) decreased and Kelch-like erythroid cell-derived protein with CNC homology (ECH)-associated protein 1 (Keap1) increased in the vehicle-treated group; however, these expressions were restored in the maxacalcitol- and insulin-treated groups.

CONCLUSIONS

It is suggested that maxacalcitol attenuates the progression of diabetic nephropathy by suppression of oxidative stress and amelioration of the Nrf2-Keap1 pathway in nonobese type 2 diabetes without significant changes in blood pressure and glomerular filtration rate.

Vitamin D protects human endothelial cells from oxidative stress through the autophagic and survival pathways

CONTEXT

Recently, vitamin D (VitD) has been recognized as increasingly importance in many cellular functions of several tissues and organs other than bone. In particular, VitD showed important beneficial effects in the cardiovascular system. Although the relationship among VitD, endothelium, and cardiovascular disease is well established, little is known about the antioxidant effect of VitD.

OBJECTIVE

Our objective was to study the intracellular pathways activated by VitD in cultured human umbilical vein endothelial cells undergoing oxidative stress.

DESIGN

Nitric oxide production, cell viability, reactive oxygen species, the mitochondrial permeability transition pore, membrane potential, and caspase-3 activity were measured during oxidative stress induced by administration of 200 μM hydrogen peroxide for 20 minutes. Experiments were repeated in the presence of specific vitamin D receptor ligand ZK191784.

RESULTS

Pretreatment with VitD alone or in combination with ZK191784 is able to reduce the apoptosis-related gene expression, involving both intrinsic and extrinsic pathways. At the same time, it has been shown the activation of pro-autophagic beclin 1 and the phosphorylation of ERK1/2 and Akt, indicating a modulation between apoptosis and autophagy. Moreover, VitD alone or in combination with ZK191784 is able to prevent the loss of mitochondrial potential and the consequent cytochrome C release and caspase activation.

CONCLUSIONS

The present study shows that VitD may prevent endothelial cell death through modulation of the interplay between apoptosis and autophagy. This effect is obtained by inhibiting superoxide anion generation, maintaining mitochondria function and cell viability, activating survival kinases, and inducing NO production.

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

Background

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

Methods

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

Results

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

Conclusion

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

Trial registration

NCT01312714, Registration Date: March 9, 2011.

Aortic pulse wave velocity in haemodialysis patients is associated with the prescription of active vitamin D analogues

BACKGROUND

Cardiovascular disease remains the most common cause of death for haemodialysis patients. In addition to traditional cardiovascular risk factors, haemodialysis patients have additional risk factors, including vascular calcification. Pulse wave velocity (PWV) is a measurement of arterial stiffness, and we wished to determine whether PWV is affected by different factors in haemodialysis patients compared to the general population.

METHODS

Aortic PWV was measured in 303 adult patients attending for routine outpatient dialysis.

RESULTS

303 patients, 63.4% male, mean age 68.5 ± 15.8 years, 47.5% diabetic with a body mass index of 25.8 ± 5.3 kg/m(2), were studied. Systolic blood pressure (SBP) was 148.7 ± 28.6 mmHg and diastolic 80.4 ± 15.3 mmHg. Aortic PWV was 9.73 ± 2.08 m/s, and was correlated with SBP (β 0.015, F 5.29, p = 0.023), log serum parathyroid hormone (PTH) (β 1.58, F 13.85, p < 0.001) and prescription of alfacalcidol (β -1.11, F 6.81, p = 0.010). 197 patients had corresponding ECHO cardiograms, and in this cohort PWV was associated with SBP (β 0.017, F 7.49, p = 0.006), log serum parathyroid hormone (β 0.85, F 5.99, p < 0.015) and prescription of alfacalcidol (β -0.8, F 4.18, p = 0.042), left ventricular mass index (LVMI) (β 0.01, F 11.4, p = 0.001), and log serum triglycerides (β 1.43, F 4.79, p = 0.03).

CONCLUSIONS

We found that PWV, a measurement of arterial stiffness, was associated with both traditional cardiovascular risk factors, including SBP and LVMI, but also non-traditional risk factors such as prescription of active vitamin D analogues, suggesting a potential link between vascular calcification and arterial stiffness in haemodialysis patients.

Impact of new vitamin D data on future studies and treatment

PURPOSE OF REVIEW

This review evaluates recently published data on clinical effects of vitamin D supplementation, focusing on randomized, placebo-controlled trials and nontraditional actions on the cardiovascular and immune systems.

RECENT FINDINGS

Several randomized trials evaluating vitamin D therapy have recently emerged, in both the general population and in individuals with chronic kidney disease (CKD). In the former, measurable effects on cardiovascular risk factors have not been detected, with the possible exception of a modest reduction in blood pressure. Studies aimed at boosting immunity have demonstrated efficacy only in specific, high-risk populations. In CKD, the benefits of nutritional vitamin D appear largely limited to earlier stages of disease. Benefits of active vitamin D agents, outside of their known effects on mineral metabolism, have also thus far eluded detection. One possible exception that has accumulated supportive evidence is the link between active vitamin D analogs and decreased proteinuria. Large-scale clinical trials, now underway, will be critical to understanding of the potential benefits and hazards of vitamin D treatment.

SUMMARY

New trials evaluating the effects of vitamin D supplementation have failed to reveal any robust clinical benefits beyond its known actions on mineral and bone disease.

Inadequate awareness among chronic kidney disease patients regarding food and drinks containing artificially added phosphate

Hyperphosphatemia is an important determinant of morbidity and mortality in patients with chronic kidney disease (CKD). Patients with CKD are advised to consume a low phosphate diet and are often prescribed phosphate-lowering drug therapy. However, commercially processed food and drinks often contain phosphate compounds, but the phosphate level is not usually provided in the ingredient list, which makes it difficult for CKD patients to choose a correct diet. We conducted a survey of the awareness of food/beverages containing artificially added phosphate among CKD patients undergoing hemodialysis. The subjects were 153 patients (77 males and 76 females; average age 56±11 years) who were randomly selected from the Dialysis Center of Hirosaki City, Japan. The subjects were provided with a list of questions. The survey results showed that 93% of the subjects were aware of the presence of high sugar content in soda, whereas only 25% were aware of the presence of phosphate (phosphoric acid) in such drinks. Despite 78% of the subjects being aware of the detrimental effects of consumption of a high phosphate diet, 43% drank at least 1 to 5 cans of soda per week and about 17% consumed “fast food” once each week. We also assessed the immediate effects of high-phosphate containing carbonated soda consumption by determining urinary calcium, phosphate, protein and sugar contents in overnight fasted healthy volunteers (n = 55; average age 20.7±0.3 years old, 20 males and 35 females). Significantly higher urinary calcium (adjusted using urinary creatinine) excretion was found 2 h after consuming 350 ml of carbonated soda compared to the fasting baseline level (0.15±0.01 vs. 0.09±0.01, p = 0.001). Our survey results suggest that CKD patients undergoing hemodialysis are not adequately aware of the hidden source of phosphate in their diet, and emphasize the need for educational initiatives to raise awareness of this issue among CKD patients.

Increased active PTH(1-84) fraction as a predictor of poor mortality in male hemodialysis patients

We reported previously that serum parathyroid hormone [PTH(1-84)]/intact PTH[PTH(1-84) + PTH(7-84)] ratio provides the better marker for parathyroid function and bone turnover state than serum PTH level itself. The present study demonstrated that higher PTH(1-84)/intact PTH ratio, but not serum PTH(1-84) and intact PTH, predicted higher all-cause mortality in 177 male hemodialysis patients.

INTRODUCTION

We reported that PTH(1-84)/intact PTH ratio provides a clinically relevant marker for parathyroid function and the resultant bone turnover state. The purpose of our study was to investigate the association of PTH(1-84)/intact PTH ratio with all-cause mortality (ACM) in male hemodialysis patients.

METHODS

The study was performed for 70 months. Serum PTH in 177 male hemodialysis patients was measured with PTH(1-84)-specific whole PTH assay and intact PTH assay which cross-reacts with N-truncated PTH including PTH(7-84).

RESULTS

The patients (n = 177) were divided into higher and lower halves based on serum levels of PTH(1-84)/intact PTH ratio (cutoff value, 0.484), intact PTH (143.8 pg/mL), and PTH(1-84) (64.1 pg/mL). In Kaplan-Meier analysis, the higher group in whole PTH/intact PTH ratio had significantly higher ACM than the lower group (P = 0.020 by log-rank test), in contrast with the insignificant difference between the higher and lower groups in intact PTH and PTH(1-84). Multivariate Cox regression hazard analysis identified higher log [PTH(1-84)/intact PTH ratio], but not log intact PTH or log PTH(1-84) as a significant independent predictor [hazard ratio 14.428 (95% CI 2.486-83.728)] for ACM after adjustment for various factors including age, hemodialysis duration, presence/absence of diabetes mellitus, BMI, log C-reactive protein, serum albumin, calcium, and phosphate. The association existed between log [PTH(1-84)/intact PTH ratio] and ACM in those without vitamin D administration (n = 95).

CONCLUSION

Higher PTH(1-84)/intact PTH ratio, which provides a relevant marker for parathyroid function, may be a significant predictor of ACM in male hemodialysis patients.

Effects of switching from calcium carbonate to lanthanum carbonate on bone mineral metabolism in hemodialysis patients

Phosphate binders are useful for the treatment of hyperphosphatemia in hemodialysis (HD) patients. This study was performed to examine the effects of switching from calcium carbonate (CC) to lanthanum carbonate (LC) on bone mineral metabolism and inflammatory markers in HD patients. We conducted 29 stable HD patients receiving CC, which was replaced by LC and followed-up for 12 weeks. Patients underwent determinants of blood chemistries such as serum calcium (Ca), phosphorus, parathyroid hormone (PTH) and vitamin D status, and interleukin-6 (IL-6) mRNA levels in whole blood cells were evaluated by real-time PCR just before and after the treatment with LC. Corrected Ca [corrected] levels were significantly reduced, but serum phosphorus levels (P levels) were unchanged after LC treatment. Switching to LC increased whole-PTH, osteocalcin, 1,25(OH)(2) D(3) levels and 1,25(OH)(2) D(3)/25(OH)D(3) ratio. 1,25(OH)(2) D(3)/25(OH)D(3) ratio was negatively correlated with HD duration. Furthermore, whole blood cell IL-6 mRNA levels were significantly reduced by LC treatment. We provided that the switching from CC to LC improved Ca overload and ameliorated vitamin D and inflammatory status in HD patients. These observations suggest that LC may play a protective role for the progression of atherosclerosis and vascular calcification in these patients.

Vitamin D supplementation and mortality risk in chronic kidney disease: a meta-analysis of 20 observational studies

BACKGROUND

Vitamin D insufficiency correlates with mortality risk among patients with chronic kidney disease (CKD). The survival benefits of active vitamin D treatment have been assessed in patients with CKD not requiring dialysis and in patients with end stage renal disease (ESRD) requiring dialysis.

METHODS

MEDLINE, Embase, the Cochrance Library, and article reference lists were searched for relevant observational trials. The quality of the studies was evaluated using the Newcastle-Ottawa Scale (NOS) checklist. Pooled effects were calculated as hazard ratios (HR) using random-effects models.

RESULTS

Twenty studies (11 prospective cohorts, 6 historical cohorts and 3 retrospective cohorts) were included in the meta-analysis., Participants receiving vitamin D had lower mortality compared to those with no treatment (adjusted case mixed baseline model: HR, 0.74; 95% confidence interval [95% CI], 0.67-0.82; P <0.001; time-dependent Cox model: HR, 0.71; 95% CI, 0.57-0.89; P <0.001). Participants that received calcitriol (HR, 0.63; 95% CI, 0.50-0.79; P <0.001) and paricalcitol (HR, 0.43 95% CI, 0.29-0.63; P <0.001) had a lower cardiovascular mortality. Patients receiving paricalcitol had a survival advantage over those that received calcitriol (HR, 0.95; 95% CI, 0.91-0.99; P <0.001).

CONCLUSIONS

Vitamin D treatment was associated with decreased risk of all-cause and cardiovascular mortality in patients with CKD not requiring dialysis and patients with end stage renal disease (ESRD) requiring dialysis. There was a slight difference in survival depending on the type of vitamin D analogue. Well-designed randomized controlled trials are necessary to assess the survival benefits of vitamin D.

Impaired vitamin D metabolism in CKD

Vitamin D metabolism consists of both production and catabolism, which are enzymatically driven and highly regulated. Renal vitamin D metabolism requires filtration and tubular reabsorption of 25-hydroxyvitamin D and is regulated by parathyroid hormone, fibroblast growth factor-23, and 1,25-dihydroxyvitamin D. In chronic kidney disease, renal production of 1,25-dihydroxyvitamin D from 25-hydroxyvitamin D is reduced. In addition, pharmacokinetic studies and epidemiologic studies of 24,25-dihydroxyvitamin D, the most abundant product of 25-hydroxyvitamin D catabolism by CYP24A1, suggest that vitamin D catabolism also is reduced. New insights into the mechanisms and regulation of vitamin D metabolism may lead to novel approaches to assess and treat impaired vitamin D metabolism in chronic kidney disease.

Treatment with oral active vitamin D is associated with decreased risk of peritonitis and improved survival in patients on peritoneal dialysis

Peritonitis is a major complication of peritoneal dialysis (PD) being associated with hospitalization, catheter loss, technique failure, and increased mortality. Data on incidence rates and risk factors for peritonitis episodes vary between centers. In seven Austrian PD units clinical and laboratory data on each peritonitis episode were collected from all patients (n = 726) who performed PD between January 2000 and December 2009. The peritonitis incidence rate was 0.32 episodes/patient-year. In a multivariate analysis the risk of peritonitis was decreased by 57% in patients treated with oral active vitamin D (HR 0.43; 95% CI 0.28–0.64). Renal disease classified as “other or unknown” (HR 1.65; 95% CI 1.08–2.53) and serum albumin <3500 mg/dl (HR 1.49; 95% CI 1.04–2.15) were also associated with an increased risk of peritonitis. Albumin levels <3500 mg/dl (HR 1.89; 95% CI 1.13–3.17), age (HR 1.06 per year; 95% CI 1.03–1.09), and cardiomyopathy (HR 3.01; 95% CI 1.62–5.59) were associated with increased mortality, whereas treatment with oral active vitamin D was associated with a significantly lower risk of death (HR 0.46; 95% CI 0.27–0.81). In this retrospective multi-center study we identified several factors being related to increased risk of peritonitis in PD patients. Treatment with oral active vitamin D was identified as being independently associated with decreased risk of peritonitis, and decreased all-cause mortality in PD patients.

Oral paricalcitol reduces the prevalence of posttransplant hyperparathyroidism: results of an open label randomized trial

Postkidney transplant hyperparathyroidism is a significant problem. Vitamin D receptor agonists are known to suppress parathyroid hormone (PTH) secretion. We examined the effect of oral paricalcitol on posttransplant secondary hyperparathyroidism by conducting an open label randomized trial in which 100 incident kidney transplant recipients were randomized 1:1 to receive oral paricalcitol, 2 μg per day, for the first year posttransplant or no additional therapy. Serial measurements of serum PTH, calcium and bone alkaline phosphatase, 24-h urine calcium and bone density were performed. The primary endpoint was the frequency of hyperparathyroidism 1-year posttransplant. Eighty-seven patients completed the trial. One-year posttransplant, 29% of paricalcitol-treated subjects had hyperparathyroidism compared with 63% of untreated patients (p = 0.0005). Calcium supplementation was discontinued in two control and 15 treatment patients due to mild hypercalcemia or hypercalcuria. Paricalcitol was discontinued in four patients due to hypercalcuria/hypercalcemia and in one for preference. Two subjects required decreasing the dose of paricalcitol to 1 μg daily. Hypercalcemia was asymptomatic and reversible. Incidence of acute rejection, BK nephropathy and renal function at 1 year were similar between groups. Moderate renal allograft fibrosis was reduced in treated patients. Oral paricalcitol is effective in decreasing posttransplant hyperparathyroidism and may have beneficial effects on renal allograft histology.

PTH replacement therapy of hypoparathyroidism

Hypoparathyroidism is characterized by hypocalcemia with inappropriately low parathyroid hormone (PTH) levels. Bone turnover is abnormally low and bone mineral density (BMD) is typically increased. Plasma calcium levels can be normalized by treatment with calcium supplements and vitamin D analogs, but bone turnover remains low and patients complain of a reduced quality of life (QoL). During recent years, a number of studies have shown that PTH replacement therapy (PTH-RT) may maintain calcium levels within the normal range, while the need for calcium and vitamin D supplements is reduced. In the initial response to subcutaneous PTH injections once or twice daily, bone turnover is overstimulated. BMD increases in cancellous bone, but decreases in cortical bone due to an increased porosity. Microcomputed tomography scans and histomorphometric studies on bone biopsies have shown changes similar to the well-known bone anabolic effects of PTH treatment in osteoporosis rather than a normalization of bone remodeling balancing the anabolic and catabolic effects of PTH. Most recently, continuous PTH delivery by pump was shown to increase the levels of bone markers into the normal range (without overstimulation of bone turnover) and with a normalization of renal calcium excretion. As PTH has a short plasma half-life, these findings indicate that exposure to PTH once or twice daily is not sufficient to reestablish a calcium homeostasis and bone metabolism that resembles normal physiology. Further studies should assess the effects of continuous PTH exposure by pump delivery (or multiple daily injections) on BMD and bone histology, as well as the effects of PTH-RT on indices of QoL.

Comparison between calcitriol and calcitriol plus low-dose cinacalcet for the treatment of moderate to severe secondary hyperparathyroidism in chronic dialysis patients

Aim: Uremic hyperparathyroidism (UHPT) has been shown to contribute to the development and progression of chronic kidney disease—mineral bone disorder. UHPT is frequently observed in chronic dialysis patients, and patients with UHPT are associated with increased risk of all-cause and cardiovascular mortality. Cinacalcet is a novel agent that increases sensitivity to the calcium-sensing receptor and is approved for control of UHPT. Nevertheless, cinacalcet is costly and information regarding efficacy of low-dose cinacalcet on UHPT is limited. Methods: We conducted a retrospective study to evaluate treatment with either low-dose calcitriol combined with low-dose cinacalcet (25 mg) (d-Cinacalcet) or calcitriol alone (VitD) in dialysis patients with moderate to severe UHPT. A total of 81 dialysis patients were enrolled (40 subjects in d-Cinacalcet group and 41 subjects in VitD group). Demographic data including age, gender, duration on dialysis and biochemical data were reviewed and recorded. Results: At the end of the study, the intact parathyroid hormone (iPTH) levels of the d-Cinacalcet group declined significantly (from 1166.0 ± 469.3 pg/mL to 679.8 ± 421.6 pg/mL, p < 0.0001), while there was no significant change in the VitD group. Significant decrease of serum calcium (Ca: 9.9 ± 0.6 mg/dL vs. 9.6 ± 0.8 mg/dL, p = 0.002), phosphorus (P: 5.9 ± 1.3 mg/dL vs. 4.9 ± 0.9 mg/dL, p < 0.0001) and calcium phosphate product (Ca × P: 58.7 ± 15.0 mg²/dL² vs. 46.9 ± 8.9 mg²/dL², p < 0.0001) were observed in the d-Cinacalcet group. In addition, the subjects in the d-Cinacalcet group had a greater proportion to achieve Kidney Disease Outcomes Quality Initiative (KDOQI)-recommended biochemical targets than the subjects in the VitD group (Ca: 48% vs. 24%; P: 78% vs. 32%; Ca × P: 85% vs. 37%; iPTH: 15% vs. 0%). Conclusions: We conclude that combination therapy of low-dose cinacalcet and calcitriol is more effective than calcitriol alone as a treatment for moderate and severe UHPT in chronic dialysis patients. Furthermore, this therapy is associated with improvement in hyperphosphatemia and hypercalcemia.

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

BACKGROUND AND OBJECTIVES

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

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

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

RESULTS

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

CONCLUSIONS

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

Vitamin D treatment and mortality in chronic kidney disease: a systematic review and meta-analysis

BACKGROUND/AIMS

Hypovitaminosis D has been associated with an increased cardiovascular mortality in the general population and in patients with chronic kidney disease (CKD). Still, whether prescribing vitamin D reduces the risk of mortality in renal patients remains controversial.

METHODS

We searched PubMed, ClinicalTrials.gov and the Cochrane Library for long-term longitudinal studies comparing vitamin D compounds (25-hydroxyvitamin D, 1,25-dihydroxyvitamin D and synthetic derivatives) to placebo or no treatment in renal patients, and which evaluated mortality, to perform a meta-analysis. Data concerning study quality, population and effect size were extracted independently by two investigators using predefined forms.

RESULTS

Fourteen observational studies (194,932 patients) met all eligibility criteria. Most studies were performed in hemodialysis patients and all used calcitriol or synthetic analogues. In a random effects meta-analysis, receiving any vitamin D therapy significantly reduced the risk of all-cause mortality (relative risk 0.73, 95% CI 0.65-0.82). The relative risk of death was 0.72 (95% CI 0.65-0.80) after 3 years of therapy and 0.67 (95% CI 0.45-0.98) after 5 years. In meta-regression, the risk reduction was shown to be greater in patients with higher parathyroid hormone serum levels (p = 0.01). The risk of cardiovascular mortality was also significantly reduced in patients receiving any vitamin D derivative (relative risk 0.63, 95% CI 0.44-0.92).

CONCLUSION

Therapies with 1,25-dihydroxyvitamin D and analogues are associated with reduced mortality in CKD patients, and particularly in those suffering from secondary hyperparathyroidism. These results, based on observational evidence, are supportive of prescribing vitamin D therapies to CKD patients, while respecting good practice guidelines.

Role of vitamin d in cardiometabolic diseases

Vitamin D deficiency is a highly prevalent condition. Low vitamin D levels have long been associated with bone diseases, such as rickets in children and osteomalacia and osteoporosis in adults. However, it has become apparent in recent years that adequate vitamin D levels are also important for optimal functioning of many organs and tissues throughout the body, including the cardiovascular system. Evolving data indicate that vitamin D deficiency is associated with an increased risk of cardiovascular disease (CVD). Studies have shown that low vitamin D levels are associated with hypertension, diabetes, metabolic syndrome, left ventricular hypertrophy, and chronic vascular inflammation, all of which are risk factors for CVD. This paper reviews the definition and pathophysiology of vitamin D deficiency, clinical evidence linking vitamin D and CVD risk, diabetes and its complications, and metabolic syndrome.

Intravenous alfacalcidol once versus twice or thrice weekly in hemodialysis patients

Secondary hyperparathyroidism remains a serious problem in hemodialysis patients. The use of vitamin D analogs still constitutes a basis for its treatment. This study was carried out to evaluate the efficacy of intravenous administration of alfacalcidol once versus twice or thrice weekly in hemodialysis patients with secondary hyperparathyroidism. Twenty-nine end-stage renal disease patients maintained on hemodialysis for more than one year were included in this prospective study after signing the consent. These patients with secondary hyperparathyroidism had been on intravenous alfacalcidol twice or thrice per week and were followed up to 4 months (stage 1). Then they were shifted to intravenous alfacalcidol once weekly starting with the last total weekly intravenous dose for another 4 months (stage 2). The dose of alfacalcidol was adjusted according to intact parathyroid hormone, serum calcium and phosphorus levels, and calcium-phosphorus product. Intact parathyroid hormone, calcium, phosphorus, calcium-phosphorus product were measured monthly. Parathyroid ultrasound was done as a baseline and then repeated at the end of stage 1 and stage 2. The intact parathyroid hormone was reduced from 49.72 ± 2.72 pmol/L (mean ± standard error of the mean [SEM] during stage 1 to 42.13 ± 2.15 pmol/L during stage 2 (P = 0.005). Dose of alfacalcidol was reduced from 18.80 ± 1.15 µg/month (mean ± SEM) in stage 1 to 15.18 ± 1.27 µg/month in stage 2 (P = 0.008), and consequently the cost of alfacalcidol was reduced from 21.05 ± 1.25 US$/month (mean ± SEM) during stage 1 to 16.87 ± 1.40 US$/month during stage 2 (P = 0.008). Although the phosphorus level increased from 1.56 ± 0.36 mmol/L (mean ± SD) in stage 1 to 1.70 ± 0.46 mmol/ L in stage 2 (P = 0.003), and calcium-phosphorus product increased from 3.48 ± 0.82 mmol(2)/L(2) (mean ± SD) in stage 1 to 3.76 ± 1.00 mmol(2) /L(2) in stage 2 (P = 0.017), they remained in the target levels recommended by the Kidney Disease Outcomes Quality Initiative guidelines. No serious effects were observed during stage 1 and stage 2, respectively. Intravenous alfacalcidol once weekly is effective, safe and less costly in suppressing intact parathyroid hormone compared to twice or thrice weekly administration in chronic hemodialysis patients.

Fibroblast growth factor 23 inhibits extrarenal synthesis of 1,25-dihydroxyvitamin D in human monocytes

Vitamin D is a potent stimulator of monocyte innate immunity, and this effect is mediated via intracrine conversion of 25-hydroxyvitamin D (25OHD) to 1,25-dihydroxyvitamin D (1,25(OH)(2) D). In the kidney, synthesis of 1,25(OH)(2) D is suppressed by fibroblast growth factor 23 (FGF23), via transcriptional suppression of the vitamin D-activating enzyme 1α-hydroxylase (CYP27B1). We hypothesized that FGF23 also suppresses CYP27B1 in monocytes, with concomitant effects on intracrine responses to 1,25(OH)(2) D. Healthy donor peripheral blood mononuclear cell monocytes (PBMCm) and peritoneal dialysate monocyte (PDm) effluent from kidney disease patients were assessed at baseline to confirm the presence of mRNA for FGF23 receptors (FGFRs), with Klotho and FGFR1 being more strongly expressed than FGFR2/3/4 in both cell types. Immunohistochemistry showed coexpression of Klotho and FGFR1 in PBMCm and PDm, with this effect being enhanced following treatment with FGF23 in PBMCm but not PDm. Treatment with FGF23 activated mitogen-activated protein kinase (MAPK) and protein kinase B (Akt) pathways in PBMCm, demonstrating functional FGFR signaling in these cells. FGF23 treatment of PBMCm and PDm decreased expression of mRNA for CYP27B1. In PBMCm this was associated with downregulation of 25OHD to 1,25(OH)(2) D metabolism, and concomitant suppression of intracrine induced 24-hydroxylase (CYP24A1) and antibacterial cathelicidin (LL37). FGF23 suppression of CYP27B1 was particularly pronounced in PBMCm treated with interleukin-15 to stimulate synthesis of 1,25(OH)(2) D. These data indicate that FGF23 can inhibit extra-renal expression of CYP27B1 and subsequent intracrine responses to 1,25(OH)(2) D in two different human monocyte models. Elevated expression of FGF23 may therefore play a crucial role in defining immune responses to vitamin D and this, in turn, may be a key determinant of infection in patients with chronic kidney disease (CKD).

Meta-analysis: the efficacy and safety of paricalcitol for the treatment of secondary hyperparathyroidism and proteinuria in chronic kidney disease

Introduction. Previous studies have demonstrated the safety and efficacy of using Paricalcitol for the treatment of secondary hyperparathyroidism (SHPT) in patients on dialysis. The aim of the current meta-analysis was to assess the safety and efficacy of Paricalcitol for the management of SHPT in patients with chronic kidney disease (CKD) not yet on dialysis. A secondary aim was to determine if sufficient data was available to assess the effect of Paricalcitol for the management of proteinuria. Methods. A meta-analysis was conducted using the Cochrane Collaboration's RevMan 4.2 software. Results. Paricalcitol is effective in lowering PTH in patients with CKD not yet on dialysis and is also effective in lowering proteinuria in diabetic CKD patients. However, we uncovered a safety signal identifying an elevated calcium phosphate product and a trend towards the development of hypercalcemia. A phosphate elevation was not demonstrated because the target used in the clinical studies was a P > 5.5 mg/dl, a value appropriate for dialysis patients and not CKD patients. Conclusion. Although Paricalcitol is effective in lowering PTH, we advise caution in the use of any active Vitamin D analogues in patients with CKD because of the potential risk of exacerbating vascular calcification.

Relationship of BsmI polymorphism of vitamin D receptor gene with left ventricular hypertrophy and atherosclerosis in hemodialysis patients

BACKGROUND

Left ventricular hypertrophy (LVH) is a common manifestation of cardiovascular disease and has an important prognostic value in patients with end-stage renal disease (ESRD). Vitamin D receptor (VDR) has been intensively investigated, and one of these (BsmI) already has been associated with survival in the dialysis population.

OBJECTIVE

The aim of this study was to investigate the role of VDR polymorphism (BsmI) on the development of ventricular hypertrophy and atherosclerosis in hemodialysis patients. Subject and methods. The subjects were 80 patients with end-stage renal disease on maintenance hemodialysis, and 40 healthy controls. Clinical and laboratory parameters, including genetic variation in VDR gene (BsmI), were assessed. In addition, echocardiography and intima-media thickness were performed for all subjects.

RESULTS

There was no significant difference in the distribution of BsmI genotypes either in patients or in the control group. The frequency of the B allele of BsmI polymorphism (41.6%) in dialysis patients was similar to that of healthy control subjects (39.2%). Patients with BB genotype had significantly lower serum concentrations of 25-hydroxy vitamin D compared to both Bb and bb genotypes. The number of B alleles was positively correlated with left ventricular mass index (LVMI), but not with intima-media thickness.

CONCLUSION

These results suggest that the B alleles of the BsmI polymorphism could be considered as novel markers of altered vitamin D signaling in ESRD patients, and this alteration in BB genotype produces an increase in left ventricle mass.

Hypovitaminosis D and peripheral arterial disease: emerging link beyond cardiovascular risk factors

Vitamin D has received increasing interest for its beneficial effect on health. Beyond its conventional role in bone metabolism, emerging evidence suggests a possible link between low vitamin D levels and cardiovascular disease (CVD), including peripheral arterial disease (PAD), and cardiovascular risk factors. Vitamin D interacts either directly with the vascular tree or indirectly through its association with cardiovascular risk factors, but the exact mechanism remains controversial. This review outlines the association between hypovitaminosis D and PAD. Both entities are quite prevalent in the general population and, therefore, their potential association might have important clinical implications. Whether vitamin D deficiency represents a novel risk factor for PAD/CVD, and whether vitamin D supplementation would reduce the burden of CVD still remains to be answered. Until then, vitamin D intake is not recommended for PAD/CVD prevention. Outdoor physical activity, coupled with adequate but safe sun exposure, is a healthy lifestyle practice suggested for the prevention of both PAD and hypovitaminosis D.