Low 25-hydroxyvitamin D levels and mortality in non-dialysis-dependent CKD

Association of serum 25-hydroxyvitamin D with cardiovascular and all-cause mortality in patients with chronic kidney disease: NHANES 2007‒2018 results

BACKGROUND

Vitamin D insufficiency is a prevalent issue in patients suffering from CKD. The purpose of this study was to determine whether serum 25(OH)D levels are associated with all-cause and cardiovascular mortality in patients with CKD.

METHODS

To examine the associations between 25(OH)D levels and cardiovascular mortality, this retrospective cohort study used the National Health and Nutrition Examination Survey (NHANES) and the National Death Index (NDI) 2007‒2018 database. A total of 2,668 eligible subjects were included in this study, with follow-up conducted until December 31, 2019. The associations were assessed using Cox proportional hazards regression, restricted cubic splines, Kaplan-Meier survival curves, and competing risks survival analysis. Furthermore, subgroup and sensitivity analyses were performed.

RESULTS

During a median follow-up of 72 months in a weighted population of 11,715,452 eligible participants, there were 665 deaths from any cause, including 196 cardiovascular-related deaths. After adjusting for covariates, lower levels of 25(OH)D were significantly associated with increased risks for both all-cause mortality (HR= 0.85, 95 % CI 0.77∼0.94) and cardiovascular mortality (SHR= 0.80, 95 % CI 0.67∼0.94). Consistent results were also observed when analyzing 25(OH)D as a categorical variable (quartile). Compared to group Q1, both group Q3 (HR = 0.71, 95 % CI 0.54‒0.93) and group Q4 (HR = 0.72, 95 % CI 0.55‒0.94) exhibited a significantly reduced mortality risk. Weighted restricted cubic splines revealed an inverse J-shaped linear association between levels of 25(OH) D and all-cause mortality ((PNonliner > 0.05). Subgroup analysis and sensitivity analysis yielded similar findings.

CONCLUSIONS

All-cause mortality and cardiovascular disease-related mortality were significantly increased by lower 25(OH)D levels, both as continuous and categorical variables. 25(OH)D has an inverse J-shaped linear association with all-cause and cardiovascular mortality.

L-shaped association of serum 25-hydroxyvitamin D with all-cause and cardiovascular mortality in older people with chronic kidney disease: results from the NHANES database prospective cohort study

BACKGROUND

This study was conducted to assess the association of serum 25-hydroxyvitamin D [25(OH)D] concentrations with all-cause and cardiovascular disease (CVD) mortality in older people with chronic kidney disease (CKD) in the United States.

METHODS

We identified 3230 CKD participants aged ≥ 60 years from the National Health and Nutrition Examination Survey (2001-2018). CKD was defined as an estimated glomerular filtration rate (eGFR) < 60 ml/min/1.73 m². Mortality outcomes were determined by linkage to National Death Index (NDI) records through December 31, 2019. Restricted cubic spline based on Cox regression models were utilized to elucidate the nonlinear relationship between serum 25(OH)D concentrations and mortality in patients with CKD.

RESULTS

During median 74 months of follow-up, 1615 all-cause death and 580 CVD death were recorded. We found an L-shaped association between serum 25(OH)D concentrations and all-cause and CVD mortality, reaching a plateau at 90 nmol/L. Accordingly, per one-unit increment in natural log-transformed 25(OH)D was associated with a 32% and 33% reduced risk of all-cause mortality (hazard ratio [HR] 0.68; 95%CI, 0.56 to 0.83) and CV mortality (HR 0.69; 95%CI, 0.49 to 0.97) in participants with serum 25(OH)D < 90 nmol/L, but no considerable difference was observed in participants with serum 25(OH)D ≥ 90 nmol/L. Compared with those in the deficiency group (< 50 nmol/L), insufficient (50 to < 75 nmol/L) and sufficient group (≥ 75 nmol/L) were significantly associated with lower all-cause mortality (HR,0.83; 95%CI, 0.71 to 0.97 and HR, 0.75; 95%CI, 0.64 to 0.89) and CV mortality (HR,0.87; 95%CI, 0.68 to 1.10 and HR, 0.77; 95%CI, 0.59 to < 1.0), respectively.

CONCLUSION

An L-shaped relationship between serum 25(OH)D levels with all-cause and CVD mortality was observed in elderly CKD patients in the United States. A 25(OH)D concentration of 90 nmol/L may be the target to reduce the risk of premature death.

Vitamin D and Diabetic Kidney Disease

Vitamin D is a hormone involved in many physiological processes. Its active form, 1,25(OH)₂D₃, modulates serum calcium-phosphate homeostasis and skeletal homeostasis. A growing body of evidence has demonstrated the renoprotective effects of vitamin D. Vitamin D modulates endothelial function, is associated with podocyte preservation, regulates the renin-angiotensin-aldosterone system, and has anti-inflammatory effects. Diabetic kidney disease (DKD) is a leading cause of end-stage kidney disease worldwide. There are numerous studies supporting vitamin D as a renoprotector, potentially delaying the onset of DKD. This review summarizes the findings of current research on vitamin D and its role in DKD.

Assessment of the Association of Vitamin D and the Risk of Tuberculosis among End-Stage Kidney Disease Population

We investigated the role of vitamin D in the risk of tuberculosis (TB) among patients with end-stage kidney disease (ESKD). The retrospective cohort was conducted with data of 20,985 patients with kidney disease and 20,985 controls without kidney disease (1:1 matching on age of cohort entry and sex) in the duration of 1997−2010 from the Taiwan National Health insurance database. Then, by a case−cohort study, among 20,985 kidney disease, 3194 ESKD patients were identified with matched 3194 non-ESKD patients. Multivariate analyses revealed a significant association between kidney disease and tuberculosis (adjusted incidence rate ratio (IRR) 1.57 (1.33−1.86)), and the risk increased after 3 years of follow-up the (adjusted IRR 3.79 (2.55−5.62)), but after more years of follow-up no significance was observed. We also found that ESKD increases the risk of tuberculosis (adjusted IRR 3.67 (2.27−5.93)). However, vitamin D usage was not related with the tuberculosis risk in ESKD patients (p > 0.1783). Our study showed increased risk of tuberculosis in kidney disease and ESKD patients, and vitamin D was not beneficial in ESKD.

Are Nutraceuticals Beneficial in Chronic Kidney Disease?

Chronic kidney disease (CKD) is a worldwide health problem in which prevalence is constantly rising. The pathophysiology of CKD is complicated and has not been fully resolved. However, elevated oxidative stress is considered to play a vital role in the development of this disease. CKD is also thought to be an inflammatory disorder in which uremic toxins participate in the development of the inflammatory milieu. A healthy, balanced diet supports the maintenance of a good health status as it helps to reduce the risk of the development of chronic diseases, including chronic kidney disease, diabetes mellitus, and hypertension. Numerous studies have demonstrated that functional molecules and nutrients, including fatty acids and fiber as well as nutraceuticals such as curcumin, steviol glycosides, and resveratrol not only exert beneficial effects on pro-inflammatory and anti-inflammatory pathways but also on gut mucosa. Nutraceuticals have attracted great interest recently due to their potential favorable physiological effects on the human body and their safety. This review presents some nutraceuticals in which consumption could exert a beneficial impact on the development and progression of renal disease as well cardiovascular disease.

Native vs. active vitamin D in children with chronic kidney disease: a cross-over study

BACKGROUND

The rationale for the prescription of vitamin D analogues in patients with chronic kidney disease (CKD) is still a matter of debate. We aimed to compare native vs. active forms of vitamin D on pre-dialysis children with CKD and evaluate effects on calcium (Ca), phosphorus (P), and parathyroid hormone (PTH).

METHODS

Thirty children with pre-dialysis CKD were enrolled in a prospective cross-over study. Patients were randomly classified into two groups. Group A received native cholecalciferol while group B received alfacalcidol for 3 months. After 1 month (washout period), patients were switched to receive the opposite form for another 3 months. Serum Ca, P, alkaline phosphatase (ALP), PTH, and 25(OH)D₃ were measured at study start (BL-1), end of first period (FU-1), before second period (BL-2), and after second period (FU-2).

RESULTS

There was significant increase in levels of 25(OH)D₃ after administration of either native or active vitamin D in the first period in both groups (p < 0.001 and < 0.001, respectively) and also in the second period for both groups (p = 0.02 and < 0.001, respectively). There was no significant difference between both groups regarding changes in serum Ca (1st period; p = 0.770 and 2nd period; p = 0.412), serum P (1st period; p = 0.835, 2nd period; p = 0.052), and serum PTH (1st period; p = 0.250, 2nd period; p = 0.539).

CONCLUSION

Alfacalcidol and native vitamin D3 were equally effective in decreasing PTH levels and increasing serum 25(OH)D₃ in pre-dialysis CKD patients. There was no significant difference between the two forms regarding changes in serum Ca or P. Graphical abstract.

Association Between Dyslipidemia and Serum Level of 25-Hydroxyvitamin-D in Early Chronic Kidney Disease, Not on Dialysis: An Observational Cross-Sectional Study from the Himalayan Country

Background

Patients with CKD have a higher prevalence of dyslipidemia and hypovitaminosis than the normal population. Recent studies in the general population have shown a potential link between 25(OH)D and dyslipidemia. However, such evidence in the early CKD population, especially in the Nepalese setting, is lacking. Thus, the present study aimed at investigating the status of 25(OH)D and dyslipidemia in the early CKD patients, and further to establish an association between 25(OH)D and lipid profile.

Patients and Methods

In this cross-sectional study, we analyzed 136 clinically stable non-dialyzed CKD patients. 25(OH)D and lipid profile were evaluated as a core variable, and their direction and magnitude of a relationship were evaluated.

Results

The estimated prevalence of dyslipidemia was 49.3%, and 63.2% population had a deficiency of 25(OH)D level. Compared with the patient with normal 25(OH)D level, the patient with deficient 25(OH)D level had a significantly higher level of LDL-c (P=0.04) and lower level of HDL-C (P=0.048). Serum 25(OH)D level was significantly lower in dyslipidemic patients than non-dyslipidemic patients (P=0.015). Regression analysis demonstrated a significant inverse relationship between serum 25(OH)D levels and LDL-c (β=−1.5; P=<0.001), and TC levels (β=−1.4;P=0.003), and the association remained unchanged with further adjustment for age, sex, HTN, DM, serum albumin and eGFR.

Conclusion

Our study unveiled a high rate of dyslipidemia and hypovitaminosis in a considerable number of early CKD patients. Low serum level of 25(OH)D was significantly correlated with a higher rate of dyslipidemia. These findings indicate some evidence for 25(OH)D level as a marker of dyslipidemia prediction, and that decrease in serum level of 25(OH)D is associated with increased serum level of LDL and TC; it could increase the risk of cardiovascular disease. Therefore, early recognition and timely management of hypovitaminosis and dyslipidemia is vital to prevent an inevitable cardiovascular event.

The use of activated vitamin D and risks of hospitalization for infection and amputation in incident hemodialysis patients in Taiwan: a nationwide population-based cohort study

BACKGROUND

Hemodialysis patients have a high risk of mortality. The most common causes of death are cardiovascular disease and infection. The potential hazard or benefit associated with vitamin D use and cardiovascular or infection outcome is poorly characterized.

METHODS

We conducted a retrospective observational cohort study by recruiting 52,757 patients older than 20 years from Taiwan National Health Insurance Research Database (NHIRD) who initiated maintenance hemodialysis between 2001 and 2009. Patients who were prescribed activated vitamin D before the 360th day from hemodialysis initiation were defined as vitamin D users. The primary outcome of interest includes occurrence of acute myocardial infarction (AMI), ischemic stroke, lower limb amputation, and hospitalization for infection, respectively, while death events are treated as competing events. We conducted competing risk analysis using subdistribution hazard regression model to estimate subdistribution hazard ratios (SHRs) in relation to various outcomes.

RESULTS

During the median follow-up of 1019 days, the vitamin D users had a lower crude mortality rate, lower incidences of AMI, ischemic stroke, amputation, and hospitalization for infection compared with non-users. Taking into consideration competing events of death, vitamin D users were associated with a lower hazard of lower limb amputation (SHR 0.84 [95% CI, 0.74-0.96]) and hospitalization for infection (SHR 0.90 [95% CI, 0.87-0.94]), but not AMI or ischemic stroke, after adjustment for potential confounders. Subgroup analyses and dose response evaluation both showed a consistent association of activated vitamin D treatment with decreased risk of amputation and infection.

CONCLUSION

The findings suggest that therapeutic activated vitamin D use in hemodialysis patients may be beneficial for decreasing infection events and amputation, of which the latter is a complication of peripheral vascular disease, rather than reducing major atherosclerotic cardiovascular events such as AMI or ischemic stroke.

Interactions between FGF23 and Genotype in Autosomal Dominant Polycystic Kidney Disease

BACKGROUND

Higher serum intact fibroblast growth factor 23 (iFGF23) was associated with disease progression in participants with autosomal dominant polycystic kidney disease (ADPKD) in the HALT-PKD Studies. PKD mutation is also an important determinant of progression. We hypothesized that serum levels of iFGF23 and vitamin D metabolites (1,25-dihydroxyvitamin D [1,25(OH)₂D] and 25-hydroxyvitamin D [25[OH]D]) differ according to ADPKD mutation and differentially predict clinical end points according to genotype (significant interaction between genotype and mineral metabolites).

METHODS

A total of 864 individuals with ADPKD who participated in the HALT-PKD Study A or B and had measurements of mineral metabolites (1,25[OH]₂D, 25[OH]D, iFGF23) were categorized by PKD mutation (PKD1 truncating, PKD1 nontruncating, PKD2, or no mutation detected [NMD]). The association of the interactions of genotype × iFGF23, genotype × 1,25(OH)2D, and genotype × 25(OH)D with (1) annualized change in eGFR; (2) mean annualized percentage change in height-corrected total kidney volume (Study A only); and (3) time to a composite of 50% reduction in eGFR, ESKD, or death were evaluated using linear regression and Cox proportional hazards regression.

RESULTS

Median (interquartile range) iFGF23 differed (PKD1 truncating, 55.8 [40.7-76.8]; PKD1 nontruncating, 49.9 [37.7-71.0]; PKD2, 49.0 [33.8-70.5]; NMD, 50.3 [39.7-67.4] pg/ml; P=0.03) and mean±SD 1,25(OH)₂D differed (PKD1 truncating, 32.8±12.8; PKD1 nontruncating, 33.4±12.5; PKD2, 34.1±13.1; NMD, 38.0±14.6 pg/ml; P=0.02) according to PKD genotype. There was a significant interaction between iFGF23 and genotype (P=0.02) for the composite end point in fully adjusted models, but no significant interaction between 1,25(OH)₂D or 25(OH)D and genotype for clinical end points.

CONCLUSIONS

ADPKD genotype interacts significantly with FGF23 to influence clinical end points. Whereas the worst outcomes were in individuals with a PKD1-truncating or -nontruncating mutation and the highest iFGF23 tertile, risk of the composite end point differed according to iFGF23 the most in the PKD1-nontruncating and PKD2 groups.

Ethnic minority disparities in progression and mortality of pre-dialysis chronic kidney disease: a systematic scoping review

Background

There are a growing number of studies on ethnic differences in progression and mortality for pre-dialysis chronic kidney disease (CKD), but this literature has yet to be synthesised, particularly for studies on mortality.

Methods

This scoping review synthesized existing literature on ethnic differences in progression and mortality for adults with pre-dialysis CKD, explored factors contributing to these differences, and identified gaps in the literature. A comprehensive search strategy using search terms for ethnicity and CKD was taken to identify potentially relevant studies. Nine databases were searched from 1992 to June 2017, with an updated search in February 2020.

Results

8059 articles were identified and screened. Fifty-five studies (2 systematic review, 7 non-systematic reviews, and 46 individual studies) were included in this review. Most were US studies and compared African-American/Afro-Caribbean and Caucasian populations, and fewer studies assessed outcomes for Hispanics and Asians. Most studies reported higher risk of CKD progression in Afro-Caribbean/African-Americans, Hispanics, and Asians, lower risk of mortality for Asians, and mixed findings on risk of mortality for Afro-Caribbean/African-Americans and Hispanics, compared to Caucasians. Biological factors such as hypertension, diabetes, and cardiovascular disease contributed to increased risk of progression for ethnic minorities but did not increase risk of mortality in these groups.

Conclusions

Higher rates of renal replacement therapy among ethnic minorities may be partly due to increased risk of progression and reduced mortality in these groups. The review identifies gaps in the literature and highlights a need for a more structured approach by researchers that would allow higher confidence in single studies and better harmonization of data across studies to advance our understanding of CKD progression and mortality.

Traditional and Non-traditional Clinical and Biochemical Risk Factors for Altered Kidney Function in Type II Diabetes mellitus Patients

Background:Exploring the risk factors associated with increased albumin excretion is necessary in patients with type 2 diabetes mellitus, due to the fact that such patients are exposed to an increased risk of progression to diabetic kidney disease and that non-traditional newly emerging factors could be corrected in order to reduce the progression rate. Material and methods:218 patients with type 2 diabetes mellitus were investigated regarding their urinary albumin/creatinine ratio. Clinical and laboratory data was collected from them, with biochemical investigations including serum uric acid and serum 25-hydroxi-vitamin D (25-OH-vitamin D) measurements. The prevalence of traditional and non-traditional risk factors for increased albumin excretion rate (albumin/creatinine ratio>30 mg/g), hyperuricemia and 25-OH-vitamin D deficiency, was determined after dividing patients into two groups, one with microalbuminuria and the other one with micro- or macroalbuminuria. Results:Of all patients, 104 (47.93%) had microalbuminuria, while 9.22% (20) presented macroalbuminuria. Poor glucose control (HbA1c .7%), female sex, hyperuricemia (uric acid .7 mg/dL), vitamin D deficiency (25-OH-vitamin D .50 nmol/L), hypertension (systolic hypertension or diastolic hypertension or hypertension treatment) and hypertriglyceridemia (triglycerides .150 mg/dL) had a statistically significant higher prevalence (p<0.05) in the 124 patients with microalbuminuria or macroalbuminuria compared to the 94 subjects wit normaoalbuminuria. Conclusion:Glucose control, hypertension and dyslipidemia are relevant traditional risk factors for an altered kidney function defined as urinary albumin/creatinine ratio >30 mg/g. However, hyperuricemia and 25-OH-vitamin D deficiency are long time ignored factors that could play an important role in the progression towards diabetic kidney disease.

Vitamin D Metabolic Ratio and Risks of Death and CKD Progression

Introduction

Assessment of impaired vitamin D metabolism is limited by lack of functional measures. CYP24A1-mediated vitamin D clearance, calculated as the ratio of serum 24,25-dihydroxyvitamin D3 to 25-hydroxyvitamin D3 (the vitamin D metabolic ratio, VDMR), is induced by 1,25-dihydroxyvitamin D and may assess tissue-level activity. We tested associations of the VDMR with risks of death and progression to end-stage renal disease (ESRD) in patients with chronic kidney disease (CKD).

Methods

We studied participants from the Chronic Renal Insufficiency Cohort (CRIC), which included a random subset of 1080 CRIC participants plus additional participants who experienced ESRD or died (case cohort study design). Serum 24,25-dihydroxyvitamin D3 and 25-hydroxyvitamin D3 was measured 1 year after enrollment. The primary outcomes included death and progression to ESRD. Using inverse probability weighting, we tested associations of VDMR (24,25[OH]₂D₃/25[OH]D₃) with risks of death and ESRD, adjusting for demographics, comorbidity, and kidney function (estimated glomerular filtration rate [eGFR] and urine protein-to-creatinine ratio [PCR]).

Results

There were a total of 708 ESRD events and 650 deaths events over mean (SD) follow-up periods of 4.9 (2.9) years and 6.5 (2.5) years, respectively. Lower VDMR was associated with increased risk of ESRD prior to adjusting for kidney function (hazard ratio [HR], 1.80 per 20 pg/ng lower VDMR; 95% confidence interval [CI], 1.56–2.08), but not with adjustment for kidney function (HR, 0.94 per 20 pg/ng; 95% CI, 0.81–1.10). Lower VDMR was associated with modestly increased mortality risk, including adjustment for kidney function (HR, 1.18 per 20 pg/ng; 95% CI, 1.02–1.36).

Conclusion

Lower VDMR, a measure of CYP24A1-mediated vitamin D clearance, was significantly associated with all-cause mortality but not with progression to ESRD in patients with CKD.

Role of Vitamin D Status in Diabetic Patients with Renal Disease

Diabetes mellitus (DM) poses a major public health problem worldwide, with ever-increasing incidence and prevalence in recent years. The Institute for Alternative Futures (IAF) expects that the total number of people with type 1 and type 2 DM in the United States will increase by 54%, from 19,629,000 to 54,913,000 people, between 2015 and 2030. Diabetic Nephropathy (DN) affects about one-third of patients with DM and currently ranks as the first cause of end-stage kidney disease in the Western world. The complexity of interactions of Vitamin D is directly related with progressive long-term changes implicated in the worsening of renal function. These changes result in a dysregulation of the vitamin D-dependent pathways. Various studies demonstrated a pivotal role of Vitamin D supplementation in regression of albuminuria and glomerulosclerosis, contrasting the increase of glomerular basement membrane thickening and podocyte effacement, with better renal and cardiovascular outcomes. The homeostasis and regulation of the nephron’s function are absolutely dependent from the cross-talk between endothelium and podocytes. Even if growing evidence proves that vitamin D may have antiproteinuric, anti-inflammatory and renoprotective effects in patients with DN, it is still worth investigating these aspects with both more in vitro studies and randomized controlled trials in larger patient series and with adequate follow-up to confirm the effects of long-term vitamin D analogue supplementation in DN and to evaluate the effectiveness of this therapy and the appropriate dosage.

Assessing the effect of oral activated vitamin D on overall survival in hemodialysis patients: a landmark analysis

BACKGROUND

Patients with end stage renal disease have a high all-cause and cardiovascular mortality. Secondary hyperparathyroidism and vitamin D deficiency are considered part of the mechanism for the excess mortality observed. We aimed to evaluate the relationship between vitamin D use and all-cause mortality.

METHODS

In this retrospective cohort study, we included all incident patients who started hemodialysis in Taiwan between 2001 and 2009. Patients were followed from landmark time, i.e., the 360th day from hemodialysis initiation, through the end of 2010 or death. We evaluated the association between activated vitamin D use or not before landmark time and all-cause mortality using conditional landmark analysis with Cox regression. We used group-based trajectory model to categorize high-dose versus average-dose users to evaluate dose-response relationships.

RESULTS

During the median follow-up of 1019 days from landmark time, vitamin D users had a lower crude mortality rate than non-users (8.98 versus 12.93 per 100 person-years). Compared with non-users, vitamin D users was associated with a lower risk of death in multivariate Cox model (HR 0.91 [95% CI, 0.87-0.95]) and after propensity score matching (HR 0.94 [95% CI, 0.90-0.98]). High-dose vitamin D users had a lower risk of death than conventional-dose users, HR 0.75 [95% CI, 0.63-0.89]. The association of vitamin D treatment with reduced mortality did not alter when we re-defined landmark time as the 180th day or repeated analyses in patients who underwent hemodialysis in the hospital setting.

CONCLUSIONS

Our findings supported the survival benefits of activated vitamin D among incident hemodialysis patients.

Native vitamin D in pre-dialysis chronic kidney disease

Chronic kidney disease patients have a high prevalence of vitamin D insufficiency/deficiency. Vitamin D deficiency has been associated with a variety of bone, metabolic and cardiovascular disorders. However, the role of native vitamin D supplementation (ergocalciferol, cholecalciferol or calcifediol) remains unclear in chronic kidney disease (CKD), particularly in the pre-dialytic phase. Several international guidelines have been developed on CKD-Mineral and Bone Disorder, but the optimal strategy for native vitamin D supplementation and its clinical benefit remains a subject of debate in the scientific community. This paper aims to review the available literature, including randomized clinical trials that evaluated the effects of native vitamin D supplementation on pre-dialysis CKD on biochemical and clinically relevant outcomes.

The association between serum vitamin D levels and renal tubular dysfunction in a general population exposed to cadmium in China

Cadmium exposure can cause renal tubular dysfunction. Recent studies show that vitamin D can play multiple roles in the body. However, the association between serum vitamin D levels and renal tubular dysfunction in a general population exposed to cadmium has not been clarified. We performed study to assess the effects of cadmium on serum 25(OH) D levels and the association between serum 25(OH) D levels and renal tubular dysfunction in a population environmentally exposed to cadmium. A total of 133 subjects living in control area and two cadmium polluted areas were included in the present study. Cadmium in urine (UCd) and blood (BCd), urinary β2Microglobulin (UBMG), urinary retinol binding protein (URBP) and serum 25 (OH) D were determined. Logistic regression was used to estimate the association between 25 (OH) D and prevalence of renal tubular dysfunction. No significant differences were observed in serum 25(OH) D levels among the four quartile of UCd and BCd after adjusting with cofounders. After adjusted with the confounders, the odds ratio (OR) of subjects with 25(OH) D ≥ 40 ng/ml were 0.20 (95%CI: 0.1–0.8) if UBMG was chosen as indicators of renal dysfunction and 0.28 (95%CI: 0.1–1.1) if URBP was chosen as indicators of renal dysfunction, compared with those with 25(OH) D < 30 ng/ml, respectively. Similar results were observed in those subjects living in cadmium polluted areas or with high level of UCd or BCd. Our data indicated that cadmium exposure did not affect serum 25(OH) D level and high 25 (OH) D levels were associated with a decreased risk of renal tubular dysfunction induced by cadmium.

Seasonal variations of U.S. mortality rates: Roles of solar ultraviolet-B doses, vitamin D, gene exp ression, and infections

Death rates in the U.S. show a pronounced seasonality. The broad seasonal variation shows about 25% higher death rates in winter than in summer with an additional few percent increase associated with the Christmas and New Year's holidays. A pronounced increase in death rates also starts in mid-September, shortly after the school year begins. The causes of death with large contributions to the observed seasonality include diseases of the circulatory system; the respiratory system; the digestive system; and endocrine, nutritional, and metabolic diseases. Researchers have identified several factors showing seasonal variation that could possibly explain the seasonal variations in mortality rate. These factors include seasonal variations in solar ultraviolet-B(UVB) doses and serum 25-hydroxyvitamin D [25(OH)D] concentrations, gene expression, ambient temperature and humidity, UVB effects on environmental pathogen load, environmental pollutants and allergens, and photoperiod (or length of day). The factors with the strongest support in this analysis are seasonal variations in solar UVB doses and 25(OH)D concentrations. In the U.S., population mean 25(OH)D concentrations range from 21ng/mL in March to 28ng/mL in August. Measures to ensure that all people had 25(OH)D concentrations >36ng/mL year round would probably reduce death rates significantly.

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

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

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

BACKGROUND AND OBJECTIVES

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

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

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

RESULTS

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

CONCLUSIONS

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

Effects of Vitamin D2 Supplementation on Vitamin D3 Metabolism in Health and CKD

BACKGROUND AND OBJECTIVES

Vitamin D supplements are prescribed to correct low circulating concentrations of 25-hydroxyvitamin D. In CKD, vitamin D metabolism is complicated by decreased conversion of 25-hydroxyvitamin D to 1,25-dihydroxyvitamin D by CYP27B1 and possibly decreased conversion of 25-hydroxyvitamin D to 24,25-dihydroxyvitamin D by CYP24A1. The aim of this study was to determine the effects of vitamin D2 supplementation on vitamin D metabolism in health and CKD.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We conducted a treatment-only intervention study of 25 individuals with CKD (eGFR<60 ml/min per 1.73 m2) and 44 individuals without CKD from three academic centers, all with screening 25-hydroxyvitamin D <30 ng/ml. Each participant was prescribed vitamin D2 (ergocalciferol) 50,000 IU orally twice weekly for 5 weeks. We tested whether changes in plasma concentrations of vitamin D metabolites and vitamin D metabolic ratios differed by CKD status. Plasma 1,25-dihydroxyvitamin D3-to-25-hydroxyvitamin D3 ratio and 24,25-dihydroxyvitamin D3-to-25-hydroxyvitamin D3 ratio were calculated as estimates of CYP27B1 and CYP24A1 function, respectively.

RESULTS

With treatment, plasma 25-hydroxyvitamin D2 and total 25-hydroxyvitamin D concentrations increased similarly for participants with and without CKD. For participants without CKD, 1,25-dihydroxyvitamin D2 increased (2.8±1.3-32.9±1.4 pg/ml), whereas 1,25-dihydroxyvitamin D3 decreased (45.6±1.9-14.6±1.9 pg/ml), resulting in no significant change in total 1,25-dihydroxyvitamin D; 1,25-dihydroxyvitamin D3-to-25-hydroxyvitamin D3 ratio decreased (3.0±0.2-1.7±0.2 pg/ng), and 24,25-dihydroxyvitamin D3-to-25-hydroxyvitamin D3 ratio increased (115.7±7.8-195.2±7.9 pg/ng). Individuals with CKD had lower baseline levels and smaller changes in magnitude for 1,25-dihydroxyvitamin D2 (2.1±1.6-24.4±1.6 pg/ml; P interaction =0.01), 1,25-dihydroxyvitamin D3-to-25-hydroxyvitamin D3 ratio (1.8±0.2-1.1±0.2 pg/ng; P interaction =0.05), and 24,25-dihydroxyvitamin D3-to-25-hydroxyvitamin D3 ratio (72.0±9.1-110.3±9.3 pg/ng; P interaction <0.001). Fibroblast growth factor-23 and parathyroid hormone were not significantly changed in either group.

CONCLUSIONS

Vitamin D2 supplementation decreases conversion of 25-hydroxyvitamin D3 to 1,25-dihydroxyvitamin D3 and induces vitamin D3 catabolism as evidenced by changes in D3 metabolites and vitamin D metabolic ratios. These effects occur without significant changes in fibroblast growth factor-23 or parathyroid hormone and are blunted in CKD.

PODCAST

This article contains a podcast at https://www.asn-online.org/media/podcast/CJASN/2017_08_02_CJASNPodcast_17_09.mp3.

Vitamin D status and all-cause mortality in patients with chronic kidney disease: A systematic review and dose-response meta-analysis

CONTEXT

Prevalence of vitamin D deficiency is high in patients with chronic kidney disease. Less attention has been paid to measurement and correction of serum level of 25(OH)D in these patients.

OBJECTIVE

We examined the association between different levels of serum 25(OH)D and risk of all-cause mortality in patients with chronic kidney disease.

DATA SOURCES

Systematic search were done using MedLine and EMBASE from inception up to November 2016. Reference lists of all relevant articles and reviews also were searched.

STUDY SELECTION

Prospective or retrospective cohort studies that reported risk estimates of all-cause mortality for three or more categories of serum 25(OH)D in patients with chronic kidney disease were selected. Studies that reported results as continuously also were included. Two independent investigators screened and selected the articles. Of 1281 identified studies, 13 prospective cohorts, two retrospective cohorts and one nested case-control study with 17053 patients and 7517 incident death were included.

DATA EXTRACTION

Two independent authors extracted data from included studies. Any discrepancies were resolved through consensus.

DATA SYNTHESIS

Reported risk estimates were combined using a random-effects model. Summary risk estimates of all-cause mortality were1.63 (95%CI: 1.32, 1.94) for severe deficiency (<10 ng/ml), 1.22 (95%CI: 1.09, 1.35) for mild deficiency (10-20 ng/ml) and 1.12 (95%CI: 1.06, 1.18) for insufficiency (20-30 ng/ml). Results were more evident in dialysis dependent patients. 10 ng/ml increment in serum 25(OH)D was associated with 21% reduction in the risk of overall mortality (RR: 0.79, 95%CI: 0.70, 0.87).Lower risk of all-cause mortality was observed at serum 25(OH)D about 25 to 30 ng/ml. Dialysis treatment was one of the sources of variation between studies.

CONCLUSIONS

Higher levels of serum 25(OH) D were associated with lower risk of all-cause mortality in patients with chronic kidney disease, but concerning serum levels more than 35 ng/mL we have no conclusive evidence.

Vitamin D deficiency is associated with increased risk of bacterial infections after kidney transplantation

BACKGROUND/AIMS

There may be an association between vitamin D levels and allograft outcomes in kidney transplant recipients (KTRs). However, few studies have been conducted to determine the association between vitamin D levels and post-transplant infections. This study investigated the impact of vitamin D deficiency on the risk of infection after kidney transplantation.

METHODS

We measured 25-hydroxyvitamin D (25(OH)D) levels prior to kidney transplantation. Vitamin D deficiency was defined as a serum 25(OH)D level < 20 ng/mL. We examined the incidence of various post-transplant infections during follow-up period. We used Cox proportional hazards regression analysis to determine factors associated with increased risk of post-transplant infections during the follow-up period.

RESULTS

A total of 164 KTRs were followed up for a mean of 24.8 ± 10.7 months. Among them, 135 patients (82.3%) had vitamin D deficiency. Patients with vitamin D deficiency had a significantly higher incidence of urinary tract infection (p = 0.027) and any bacterial infection (p = 0.010) compared to those without vitamin D deficiency. Vitamin D deficiency was not significantly associated with incidence of viral or fungal infections. Cox proportional hazards regression analysis revealed that vitamin D deficiency (hazard ratio, 11.07; 95% confidence interval, 1.46 to 84.03; p = 0.020) was independent risk factor for post-transplant bacterial infections.

CONCLUSIONS

Pre-transplant vitamin D deficiency was a significant risk factor for bacterial infections after kidney transplantation. Further studies are needed on possible benefits of vitamin D supplementation for preventing post-transplant bacterial infection.

Cholecalciferol v. ergocalciferol for 25-hydroxyvitamin D (25(OH)D) repletion in chronic kidney disease: a randomised clinical trial

Patients with chronic kidney disease (CKD) demonstrate complex mineral metabolism derangements and a high prevalence of vitamin D deficiency. However, the optimal method of 25-hydroxyvitamin D (25(OH)D) repletion is unknown, and trials analysing the comparative efficacy of cholecalciferol and ergocalciferol in this population are lacking. We conducted a randomised clinical trial of cholecalciferol 1250μg (50 000 IU) weekly v. ergocalciferol 1250μg (50 000 IU) weekly for 12 weeks in forty-four non-dialysis-dependent patients with stage 3-5 CKD. The primary outcome was change in total 25(OH)D from baseline to week 12 (immediately after therapy). Secondary analyses included the change in 1,25-dihydroxyvitamin D (1,25(OH)2D), parathyroid hormone (PTH), D2 and D3 sub-fractions of 25(OH)D and 1,25(OH)2D and total 25(OH)D from baseline to week 18 (6 weeks after therapy). Cholecalciferol therapy yielded a greater change in total 25(OH)D (45·0 (sd 16·5) ng/ml) v. ergocalciferol (30·7 (sd 15·3) ng/ml) from baseline to week 12 (P<0·01); this observation partially resulted from a substantial reduction in the 25(OH)D3 sub-fraction with ergocalciferol. However, following cessation of therapy, no statistical difference was observed for total 25(OH)D change from baseline to week 18 between cholecalciferol and ergocalciferol groups (22·4 (sd 12·7) v. 17·6 (sd 8·9) ng/ml, respectively; P=0·17). We observed no significant difference between these therapies with regard to changes in serum PTH or 1,25(OH)2D. Therapy with cholecalciferol, compared with ergocalciferol, is more effective at raising serum 25(OH)D in non-dialysis-dependent CKD patients while active therapy is ongoing. However, levels of 25(OH)D declined substantially in both arms following cessation of therapy, suggesting the need for maintenance therapy to sustain levels.

Vitamin D deficiency may predict a poorer outcome of IgA nephropathy

Background

Experimental studies showed that 25-hydroxy-vitamin D [25(OH)D] deficiency (defined as 25-hydroxy-vitamin D < 15 ng/ml) has been associated with CKD progression. Patients with IgA nephropathy have an exceptionally high rate of severe 25(OH)D deficiency; however, it is not known whether this deficiency is a risk factor for progression of IgA nephropathy. We conducted this study to investigate the relationship between the plasma level of 25(OH)D and certain clinical parameters and renal histologic lesions in the patients with IgA nephropathy, and to evaluate whether the 25(OH)D level could be a good prognostic marker for IgA nephropathy progression.

Methods

A total of 105 patients with biopsy-proven IgA nephropathy were enrolled between 2012 and 2015. The circulating concentration of 25(OH)D was determined using serum samples collected at the time of biopsy. The primary clinical endpoint was the decline of estimated glomerular filtration rate (eGFR; a 30 % or more decline compared to the baseline).

Results

Mean eGFR decreased and proteinuria worsened proportionally as circulating 25(OH)D decreased (P < 0.05). The 25(OH)D deficiency was correlated with a higher tubulointerstitial score by the Oxford classification (P = 0.008). The risk for reaching the primary endpoint was significantly higher in the patients with a 25(OH)D deficiency compared to those with a higher level of 25(OH)D (P = 0.001). As evaluated using the Cox proportional hazards model, 25(OH)D deficiency was found to be an independent risk factor for renal progression [HR 5.99, 95 % confidence intervals (CIs) 1.59–22.54, P = 0.008].

Conclusion

A 25(OH)D deficiency at baseline is significantly correlated with poorer clinical outcomes and more sever renal pathological features, and low levels of 25(OH)D at baseline were strongly associated with increased risk of renal progression in IgAN.

Electronic supplementary material

The online version of this article (doi:10.1186/s12882-016-0378-4) contains supplementary material, which is available to authorized users.

What is the optimal level of vitamin D in non-dialysis chronic kidney disease population?

AIM

To evaluate thresholds for serum 25(OH)D concentrations in relation to death, kidney progression and hospitalization in non-dialysis chronic kidney disease (CKD) population.

METHODS

Four hundred and seventy non-dialysis 3-5 stage CKD patients participating in OSERCE-2 study, a prospective, multicenter, cohort study, were prospectively evaluated and categorized into 3 groups according to 25(OH)D levels at enrollment (less than 20 ng/mL, between 20 and 29 ng/mL, and at or above 30 ng/mL), considering 25(OH)D between 20 and 29 ng/mL as reference group. Association between 25(OH)D levels and death (primary outcome), and time to first hospitalization and renal progression (secondary outcomes) over a 3-year follow-up, were assessed by Kaplan-Meier survival curves and Cox-proportional hazard models. To identify 25(OH)D levels at highest risk for outcomes, receiver operating characteristic (ROC) curves were performed.

RESULTS

Over 29 ± 12 mo of follow-up, 46 (10%) patients dead, 156 (33%) showed kidney progression, and 126 (27%) were hospitalized. After multivariate adjustment, 25(OH)D < 20 ng/mL was an independent predictor of all-cause mortality (HR = 2.33; 95%CI: 1.10-4.91; P = 0.027) and kidney progression (HR = 2.46; 95%CI: 1.63-3.71; P < 0.001), whereas the group with 25(OH)D at or above 30 ng/mL did not have a different hazard for outcomes from the reference group. Hospitalization outcomes were predicted by 25(OH) levels (HR = 0.98; 95%CI: 0.96-1.00; P = 0.027) in the unadjusted Cox proportional hazards model, but not after multivariate adjusting. ROC curves identified 25(OH)D levels at highest risk for death, kidney progression, and hospitalization, at 17.4 ng/mL [area under the curve (AUC) = 0.60; 95%CI: 0.52-0.69; P = 0.027], 18.6 ng/mL (AUC = 0.65; 95%CI: 0.60-0.71; P < 0.001), and 19.0 ng/mL (AUC = 0.56; 95%CI: 0.50-0.62; P = 0.048), respectively.

CONCLUSION

25(OH)D < 20 ng/mL was an independent predictor of death and progression in patients with stage 3-5 CKD, with no additional benefits when patients reached the levels at or above 30 ng/mL suggested as optimal by CKD guidelines.

Role of vitamin D in diabetes mellitus and chronic kidney disease

Approximately 30%-50% of people are recognized to have low levels of vitamin D, and insufficiency and deficiency of vitamin D are recognized as global health problems worldwide. Although the presence of hypovitamin D increases the risk of rickets and fractures, low vitamin D levels are also associated with hypertension, cancer, and cardiovascular disease. In addition, diabetes mellitus (DM) and chronic kidney disease (CKD) are also related to vitamin D levels. Vitamin D deficiency has been linked to onset and progression of DM. Although in patients with DM the relationship between vitamin D and insulin secretion, insulin resistance, and β-cell dysfunction are pointed out, evidence regarding vitamin D levels and DM is contradictory, and well controlled studies are needed. In addition, vitamin D influences the renin-angiotensin system, inflammation, and mineral bone disease, which may be associated with the cause and progression CKD. There is increasing evidence that vitamin D deficiency may be a risk factor for DM and CKD; however, it remains uncertain whether vitamin D deficiency also predisposes to death from DM and CKD. Although at this time, supplementation with vitamin D has not been shown to improve glycemic control or prevent incident DM, clinical trials with sufficient sample size, study periods, and optimal doses of vitamin D supplementation are still needed. This review focuses on the mechanism of vitamin D insufficiency and deficiency in DM or CKD, and discusses the current evidence regarding supplementation with vitamin D in patients with these diseases.

Race, Mineral Homeostasis and Mortality in Patients with End-Stage Renal Disease on Dialysis

BACKGROUND

Abnormalities in mineral homeostasis are ubiquitous in patients on dialysis, and influenced by race. In this study, we determine the race-specific relationship between mineral parameters and mortality in patients initiating hemodialysis.

METHODS

We measured the levels of fibroblast growth factor 23 (FGF23) and 25-hydroxyvitamin D (25 D) in 184 African American and 327 non-African American hemodialysis patients who enrolled between 1995 and 1998 in the Choices for Healthy Outcomes in Caring for ESRD Study. Serum calcium, phosphorus, parathyroid hormone (PTH) and total alkaline phosphatase levels were averaged from clinical measurements during the first 4.5 months of dialysis. We evaluated the associated prospective risk of mortality using multivariable Cox proportional hazards models stratified by race.

RESULTS

PTH and total alkaline phosphatase levels were higher, whereas calcium, phosphorus, FGF23 and 25 D levels were lower in African Americans compared to those of non-African Americans. Higher serum phosphorus and FGF23 levels were associated with greater mortality risk overall; however, phosphorus was only associated with risk among African Americans (HR 5.38, 95% CI 2.14-13.55 for quartile 4 vs. 1), but not among non-African Americans (p-interaction = 0.04). FGF23 was associated with mortality in both groups, but more strongly in African Americans (HR 3.91, 95% CI 1.74-8.82 for quartiles 4 vs. 1; p-interaction = 0.09). Serum calcium, PTH, and 25 D levels were not consistently associated with mortality. The lowest and highest quartiles of total alkaline phosphatase were associated with higher mortality risk, but this did not differ by race (p-interaction = 0.97).

CONCLUSIONS

Aberrant phosphorus homeostasis, reflected by higher phosphorus and FGF23, may be a risk factor for mortality in patients initiating hemodialysis, particularly among African Americans.

Effects of sun exposure and dietary vitamin D intake on serum 25-hydroxyvitamin D status in hemodialysis patients

BACKGROUND/OBJECTIVES

Vitamin D deficiency is common in hemodialysis patients. The aim of this study was to identify whether or not sun exposure and dietary vitamin D intake have effects on serum 25-hydroxyvitamin D (25(OH)D) status in hemodialysis (HD) patients. The objective was to identify the main determinants of serum vitamin D status in the study subjects.

SUBJECTS/METHODS

A cross-sectional study of 47 HD patients (19 males and 28 females) was performed. We assessed serum 25(OH)D and 1,25(OH)₂D levels between August and September 2012 and analyzed the prevalence of vitamin D deficiency in HD patients. To evaluate the determinants of serum 25(OH)D levels, we surveyed dietary vitamin D intake, degree of sun exposure, and outdoor activities. To compare biological variables, serum 25(OH)D was stratified as below 15 ng/ml or above 15 ng/ml.

RESULTS

Mean 25(OH)D and 1,25(OH)₂D levels were 13.5 ± 5.8 ng/ml and 20.6 ± 11.8 pg/ml, respectively. The proportions of serum 25(OH)D deficiency (< 15 ng/ml), insufficiency (15-< 30 ng/ml), and sufficiency (≥ 30 ng/ml) in subjects were 72.4%, 23.4%, and 4.3%, respectively. Prevalence of vitamin D deficiency in female patients was 78.6%, whereas that in males was 63.2% (P = 0.046). Vitamin D intake and sun exposure time were not significantly different between the two stratified serum 25(OH)D levels. Dietary intake of vitamin D did not contribute to increased serum 25(OH)D levels in HD patients. The main effective factors affecting serum 25(OH)D status were found to be the sun exposure and active outdoor exercise.

CONCLUSIONS

Hypovitaminosis D is common in HD patients and is higher in females than in males. Sun exposure is the most important determinant of serum 25(OH)D status in HD patients.

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

BACKGROUND/AIMS

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

METHODS

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

RESULTS

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

CONCLUSION

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

A randomized control trial to assess the impact of vitamin D supplementation compared to placebo on vascular stiffness in chronic kidney disease patients

BACKGROUND

Vitamin D deficiency is associated with cardiovascular (CV) risk in multiple populations, including those with chronic kidney disease (CKD). The active form of the hormone (1,25 OH2D3) binds to receptors in multiple organs. CKD patients are deficient in both 25 Vitamin D and 1,25 OH2D3. Clinical trial data demonstrating the benefits of vitamin D formulations are limited, and fail to show significant benefits on CV outcomes, and have compared different compounds, in various populations, and focused on a variety of outcomes. A understanding of the mechanism by which different vitamin D compounds confer CV protection in CKD is important for the design of future studies.

METHODS/DESIGN

This 3 arm randomized prospective double-blinded placebo-controlled study examining the impact of calcitriol (1,25 OH2D3) and 25-hydroxyvitamin D3 supplementation compared to placebo on vascular stiffness, as measured by pulse wave velocity (PWV). Patients are enrolled from 2 tertiary care institutions if they meet inclusion criteria (stable estimated glomerular filtration rate (eGFR) between 15-45ml/min, <±5ml/min change in previous 6 months), on stable doses of renin-angiotensin aldosterone system blockade. For those already receiving vitamin D therapies, a 3 month washout period before randomization is mandatory. Treatment duration is 6 months; medications are given thrice weekly in fixed doses. The primary outcome measure is Vascular stiffness, measured non-invasively by pulse wave velocity (PWV). Other measurements include BP, kidney function and serial blood levels of biomarkers. The primary analysis will compare any vitamin D therapy versus placebo for the primary outcome defined as the change of PWV from baseline to 6 months. Analysis of covariance will be used to detect differences between vitamin D preparations in the magnitude of reduction in PWV.

DISCUSSION

This study is novel in that we are using a robust study design in CKD patients (not on dialysis) comparing placebo to different forms of vitamin D supplementation in fixed doses, irrespective of baseline values. We hope to demonstrate the biological mechanistic effect of vitamin D supplementation on vascular function in order for this information to be used in designing larger randomized controlled trials.

TRIAL REGISTRATION

Current Controlled Trials NCT01247311. Date of Registration: November 12, 2010.

Incidence of Vitamin D Insufficiency in Coastal South-Eastern US Patient Population With Cardiovascular Disease

Background

Vitamin D insufficiency is increasingly gaining prominence as an associated cardiovascular disease (CVD) risk factor, often thought to be an issue in colder climates and higher altitudes. The intent of this study was to ascertain vitamin D levels in the southern Alabama gulf-coast region that has a high number of sunny days along with an annual average elevated UV ray index.

Methods

An observational retrospective study of 204 patients with established CVD treated at the University of South Alabama’s Heart Center from January 2007 through January 2013 was undertaken. One-way ANOVA analyses were performed to determine any significant difference in the mean 25-hydroxyvitamin D (25(OH)D) serum based on gender and also based on race/ethnicity. Further, odds ratio (OR) was computed to ascertain if there was a relationship between vitamin D insufficiency and elevated body mass index (BMI).

Results

Out of 204 patients, 53.4% (n = 109) were found to have vitamin D insufficiency (25(OH)D = 20.1 ng/mL), while 46.6% (n = 95) were within the normal range (25(OH)D = 37.8 ng/mL). The mean 25(OH)D of the entire group was 28.3, indicating a general trend of vitamin D insufficiency for patients treated at the cardiology clinics.

Conclusion

This study established the prevalence of vitamin D insufficiency in the hot and high UV ray index climate of the coastal south-eastern United States. Also, it revealed the relationship of increased BMI with low 25(OH)D serum level. More extensive studies should be conducted in similar climates to further assess vitamin D insufficiency.

Associations between serum-intact parathyroid hormone, serum 25-hydroxyvitamin D, oral vitamin D analogs and metabolic syndrome in peritoneal dialysis patients: a multi-center cross-sectional study

INTRODUCTION

Although previous studies have suggested associations between serum intact parathyroid hormone (iPTH), 25-hydroxyvitamin D (25(OH)D) and metabolic syndrome (MS) in the general population, these associations are still uncharacterized in peritoneal dialysis (PD) patients.

METHODS

In total, 837 prevalent PD patients from 5 centers in China were enrolled between April 1, 2011 and November 1, 2011. The demographic data, biochemical parameters and medical records were collected, except for serum 25(OH)D which was measured in 347 of 837 patients. The definition of MS was modified from National Cholesterol Education Program Third Adult Treatment Panel (NCEP-ATPIII).

RESULTS

55.4% of 837 patients were found to have MS. The median concentration of iPTH, 25(OH)D and doses of oral vitamin D analogs for participants with MS was significantly lower than those without MS. The iPTH, 25(OH)D values and doses of vitamin D analogs were all associated with one or more components of MS. After multivariate adjustment, low serum iPTH values and oral vitamin D analogs, rather than serum 25(OH)D, were significantly associated with the presence of MS, abnormal fasting blood glucose (FBG) and high-density lipoprotein cholesterol (HDL-C). Compared to iPTH < 130 pg/mL, iPTH 130-585 pg/mL and > 585 pg/mL were associated with a lower risk of MS with adjusted odds ratio (OR) of 0.59 and 0.33, respectively. Taking vitamin D analogs was also associated with a lower risk of MS with adjusted OR of 0.55.

CONCLUSIONS

Serum iPTH and the use of active vitamin D supplements rather than serum 25(OH)D were independently associated with the presence of MS in patients on PD.

Immune, metabolic and epidemiological aspects of vitamin D in chronic kidney disease and transplant patients

Chronic kidney disease strongly impacts on mineral and bone metabolism. Despite numerous medications, the biological targets recommended by international guidelines are often unmet. Among the treatment armamentarium, native or nutritional vitamin D (25OHD3) has been rediscovered in the early 2000s, and its general and specific actions further studied. Effects on bone, immunity, infection prevention, muscle function and phosphocalcic metabolism have been reviewed. Assessment of nutritional vitamin D status showed very low serum 25OHD3 levels and increase in nutritional vitamin D prescription led to improvement in these levels. However, about 45% of adult CKD patients still have insufficient serum 25OHD3 levels. Epidemiological studies should be enforced to describe further the mineral and bone disease management in CKD.

Clinical detection, risk factors, and cardiovascular consequences of medial arterial calcification: a pattern of vascular injury associated with aberrant mineral metabolism

Patients with end-stage renal disease are characterized by extensive vascular calcification and high cardiovascular disease (CVD) risk. Calcification in end-stage renal disease patients represents at least two distinct pathologic processes. Calcification within the tunica intima frequently is associated with lipid-laden, flow-limiting atherosclerotic plaques. These appear as spotty areas of calcification interspersed with noncalcified arterial segments on plain radiography and generally are found near arterial branch points in medium-sized conduit arteries. In contrast, medial arterial calcification (MAC) involves deeper layers of the arterial wall; tends to affect the artery diffusely, appearing as a linear contiguous tram-track pattern of calcification on plain radiography; and often involves smaller muscular arteries such as the radial artery, intermammary arteries, and arteries in the ankle and foot. Both are related to CVD events, but potentially through different mechanisms. Atherosclerotic calcification may be marking the total burden of atherosclerosis, whereas MAC may lead to arterial stiffness and left ventricular hypertrophy. Existing data suggest that altered mineral metabolism may promote MAC, whereas heightened inflammation and oxidative stress contribute to atherosclerosis. Dysregulation of normal anticalcification factors and elastin degradation are common to both processes. Risk of vascular calcification also may be increased by the use of certain medications in the setting of chronic kidney disease. This review compares and contrasts known risk factors for MAC and atherosclerosis, describes existing and emerging technologies to distinguish between them, and reviews the existing literature linking each with CVD events in dialysis patients and in other settings.

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.

Vitamin D receptor activation and cardiovascular disease

Vitamin D has been recently associated with several renal, cardiovascular and inflammatory diseases, beyond mineral metabolism and bone health. This is due in part to widespread expression of vitamin D receptor (VDR) on tissues and cells such as heart, kidney, immune cells, brain and muscle. In chronic kidney disease (CKD) and other chronic disorders, vitamin D deficiency [serum 25(OH)D <20 ng/mL] is very common and is associated with adverse outcomes. Paricalcitol, a selective activator of VDR, has demonstrated in several experimental and clinical studies of diabetic and non-diabetic CKD a favourable profile compared to other VDR activators, alone or as add-on to standard therapy. These beneficial effects are mediated by different actions such as reduction of oxidative stress, inflammation, downregulation of cardiac and renal renin expression, downregulation of calcifying genes and direct vascular protective effects. Furthermore, paricalcitol beneficial effects may be independent of baseline serum parathyroid hormone (PTH), calcium and phosphate levels. These benefits should be confirmed in large and well-designed ongoing clinical trials.

Electronic health records: a new tool to combat chronic kidney disease?

Electronic health records (EHRs) were first developed in the 1960s as clinical information systems for document storage and retrieval. Adoption of EHRs has increased in the developed world and is increasing in developing countries. Studies have shown that quality of patient care is improved among health centers with EHRs. In this article, we review the structure and function of EHRs along with an examination of its potential application in CKD care and research. Well-designed patient registries using EHRs data allow for improved aggregation of patient data for quality improvement and to facilitate clinical research. Preliminary data from the United States and other countries have demonstrated that CKD care might improve with use of EHRs-based programs. We recently developed a CKD registry derived from EHRs data at our institution and complimented the registry with other patient details from the United States Renal Data System and the Social Security Death Index. This registry allows us to conduct a EHRs-based clinical trial that examines whether empowering patients with a personal health record or patient navigators improves CKD care, along with identifying participants for other clinical trials and conducting health services research. EHRs use have shown promising results in some settings, but not in others, perhaps attributed to the differences in EHRs adoption rates and varying functionality. Thus, future studies should explore the optimal methods of using EHRs to improve CKD care and research at the individual patient level, health system and population levels.

Association of low serum 25-hydroxyvitamin D levels and acute kidney injury in the critically ill

OBJECTIVE

Given the importance of inflammation in acute kidney injury and the relationship between vitamin D and inflammation, we sought to elucidate the effect of vitamin D on acute kidney injury. We hypothesized that deficiency in 25-hydroxyvitamin D prior to hospital admission would be associated with acute kidney injury in the critically ill.

DESIGN

Two-center observational study of patients treated in medical and surgical intensive care units.

SETTING

Two hundred nine medical and surgical intensive care beds in two teaching hospitals in Boston, Massachusetts.

PATIENTS

Two thousand seventy-five patients, aged ≥ 18 yrs, in whom serum 25-hydroxyvitamin D was measured prior to hospitalization between 1998 and 2009.

INTERVENTIONS

: None.

MEASUREMENTS AND MAIN RESULTS

The exposure of interest was preadmission serum 25-hydroxyvitamin D and categorized a priori as deficiency (25-hydroxyvitamin D <15 ng/mL), insufficiency (25-hydroxyvitamin D 15-30 ng/mL), or sufficiency (25-hydroxyvitamin D ≥ 30 ng/mL). The primary outcome was acute kidney injury defined as meeting Risk, Injury, Failure, Loss, and End-stage kidney disease (RIFLE) Injury or Failure criteria. Logistic regression examined the RIFLE criteria outcome. Adjusted odds ratios were estimated by multivariate logistic regression models. Preadmission 25-hydroxyvitamin D deficiency is predictive of acute kidney injury. Patients with 25-hydroxyvitamin D deficiency have an odds ratio for acute kidney injury of 1.73 (95% confidence interval 1.30-2.30; p < .0001) relative to patients with 25-hydroxyvitamin D sufficiency. 25-Hydroxyvitamin D deficiency remains a significant predictor of acute kidney injury following multivariable adjustment (adjusted odds ratio 1.50; 95% confidence interval 1.42-2.24; p < .0001). Patients with 25-hydroxyvitamin D insufficiency have an odds ratio for acute kidney injury of 1.49 (95% confidence interval 1.15-1.94; p = .003) and an adjusted odds ratio of 1.23 (95% confidence interval 1.12-1.72; p = .003) relative to patients with 25-hydroxyvitamin D sufficiency. In addition, preadmission 25-hydroxyvitamin D deficiency is predictive of mortality. Patients with 25-hydroxyvitamin D insufficiency have an odds ratio for 30-day mortality of 1.60 (95% confidence interval 1.18-2.17; p = .003) and an adjusted odds ratio of 1.61 (95% confidence interval 1.06-1.57; p = .004) relative to patients with 25-hydroxyvitamin D sufficiency.

CONCLUSION

Deficiency of 25-hydroxyvitamin D prior to hospital admission is a significant predictor of acute kidney injury and mortality in a critically ill patient population.

Mineral metabolism and outcomes in chronic kidney disease stage 2-4 patients

BACKGROUND

Marked hyperphosphatemia, hyperparathyroidism and 25-hydroxyvitamin D deficiency are associated with mortality in dialysis patients. Such data in chronic kidney disease stage 2-4 population are limited. It has been suggested that high-normal serum phosphate predicts worse renal and patient outcomes. The data regarding parathyroid hormone and outcomes in this population is limited. The present study examined mineral metabolism and its association with the development of end-stage renal disease and mortality in stage 2-4 chronic kidney disease patients.

METHODS

This is a prospective cohort study that included 466 non-dialysis chronic kidney disease stage 2-4 patients. Mineral parameters were obtained at the time of enrollment and the patients were followed prospectively for 25 (1-44) months or until they reached the endpoints of end-stage renal disease or mortality.

RESULTS

Hyperparathyroidism and 25-hydroxyvitamin D deficiency began to occur in the early stages of chronic kidney disease, whereas significant hyperphosphatemia only developed in the later stages. High-normal and mildly elevated serum phosphate (>4.2 mg/dL) predicted the composite outcome of end-stage renal disease or mortality after adjustments for cardiovascular risk factors, chronic kidney disease stage and other mineral parameters. Parathyroid hormone levels above the upper limit of normal (>65 pg/mL) predicted the future development of end-stage renal disease and the composite outcome of end-stage renal disease or mortality after adjustments. 25-hydroxyvitamin D deficiency (<15 ng/mL) was also associated with worse outcomes.

CONCLUSIONS

In chronic kidney disease, hyperparathyroidism developed prior to significant hyperphosphatemia confirming the presence phosphate retention early in the course of chronic kidney disease. High-normal serum phosphate and mildly elevated parathyroid hormone levels predicted worse renal and patient outcomes. This data emphasizes the need for early intervention in the care of chronic kidney disease stage 2-4 patients.

Ergocalciferol treatment and aspects of mineral homeostasis in patients with chronic kidney disease stage 4-5

BACKGROUND

Focus on non-classical effects and possible less side effects of treatment with nutritional vitamin D, raises the expectation of possible benefits from treating chronic kidney disease (CKD) patients with ergocalciferol (vitamin D2). Treatment with 1,25(OH)2 vitamin D (calcitriol) induces elevated fibroblast growth factor 23 (FGF23), while epidemiological studies have found positive effects of nutritional and 25(OH)vitamin D on mortality in CKD. Disturbed mineral homeostasis in CKD is correlated to adverse outcome and cardiovascular mortality. The objective was to examine the possible effects of treatment with high doses of ergocalciferol on parameters of mineral homeostasis in predialysis CKD patients.

METHODS

A total of 43 adult patients with CKD stage 4-5, not receiving vitamin D supplementation, were studied, and allocated by simple randomization to either an intervention (n = 26) or a control group (n = 17). The intervention group received ergocalciferol, 50.000 IU/week for 6 weeks. Plasma FGF23, creatinine, parathyroid hormone (PTH), phosphate and ionized calcium were obtained at baseline and after the 6 weeks.

RESULTS

The intervention group had a significant increase in 25(OH)D2 concentration from < 10 to 90 ± 4 nmol/L, while 1,25(OH)2D (62 ± 6 at baseline and 67 ± 6 pmol/L at 6 weeks) remained stable. No changes were seen in the circulating vitamin D concentrations in the control group. After the 6 weeks of treatment no significant changes were seen in concentration of creatinine, phosphate, ionized calcium, PTH and FGF23 remained stable.

CONCLUSION

No harmful effects of short-term treatment with high-dose ergocalciferol were observed on markers of mineral homeostasis and FGF23 in CKD patients stage 4-5.

The association of parathyroid hormone with ESRD and pre-ESRD mortality in the Kidney Early Evaluation Program

CONTEXT

Studies have suggested that PTH may influence mortality and progression of chronic kidney disease. However, the development of either event may influence the development of the other as a competing risk.

OBJECTIVE

The objective of the study was to examine the association of PTH with end-stage renal disease (ESRD) and pre-ESRD death using a competing risk survival model.

DESIGN, SETTING, AND PATIENTS

A total of 10,823 participants in the Kidney Early Evaluation Program with chronic kidney disease (estimated glomerular filtration rate < 60 ml/min per 1.73 m(2)) were examined from 2005 to 2010.

MAIN OUTCOME MEASURES

The association of PTH levels with ESRD and pre-ESRD mortality was ascertained by linking Kidney Early Evaluation Program data to the Social Security Administration Death Master File and the U.S. Renal Data System.

RESULTS

Among the cohort, the incidence of ESRD and pre-ESRD mortality was 6.4 and 20.1 events per 1000 person-years. Higher PTH levels were associated with increasing age, black race, lack of a high school education, cardiovascular disease, hypertension, and lower glomerular filtration rate. The incidence of ESRD and pre-ESRD mortality was lowest among participants in the second PTH quintile. After multivariate adjustment, as compared with the second quintile, the risk of pre-ESRD mortality was higher in the third [subhazard ratio (SHR) 1.52 (95% confidence interval 1.04-2.22)], fourth [SHR 1.73 (95% confidence interval 1.19-2.52)], and fifth [SHR 1.86 (1.28-2.52)] quintiles, respectively. Conversely, PTH was not associated with ESRD after multivariate adjustment. The association was not modified by diabetic status, gender, race, or glomerular filtration rate status.

CONCLUSIONS

Elevated PTH levels are associated with increased pre-ESRD mortality but not with ESRD.

Vitamin D supplementation in pre-dialysis chronic kidney disease: A systematic review

Vitamin D deficiency is associated with a variety of skeletal, cardiometabolic, and immunologic co-morbidities that are present in chronic kidney disease (CKD). We performed a systematic review to investigate the effects of vitamin D supplementation, in the form of ergocalciferol or cholecalciferol, on various health outcomes in early CKD. Seventeen clinical trials were identified, only two of which were randomized, placebo controlled trials. The majority of studies supplementing with > 2,000 IU/day of cholecalciferol achieved optimal vitamin D status, whereas studies supplementing with ergocalciferol were less consistent. Studies varied widely in their effects on lowering serum parathyroid hormone concentrations. Few studies investigated effects of vitamin D treatment on other clinical health indicators in early CKD. Rigorous studies are necessary to investigate optimal vitamin D dosing strategies in early CKD for the maintenance of adequate vitamin D status, management of secondary hyperparathyroidism and improvement of non-skeletal related clinical outcomes.