Pleiotropic effects of vitamin D in chronic kidney disease

Role of Chronic Kidney Disease (CKD)-Mineral and Bone Disorder (MBD) in the Pathogenesis of Cardiovascular Disease in CKD

Cardiovascular disease (CVD) is the leading cause of death in patients with chronic kidney disease (CKD). Multiple factors account for the increased incidence of cardiovascular morbidity and mortality in patients with CKD. Traditional risk factors for atherosclerosis and arteriosclerosis, including age, hypertension, dyslipidemia, diabetes mellitus, and smoking, are also risk factors for CKD. Non-traditional risk factors specific for CKD are also involved in CVD pathogenesis in patients with CKD. Recently, CKD-mineral and bone disorder (CKD-MBD) has emerged as a key player in CVD pathogenesis in the context of CKD. CKD-MBD manifests as hypocalcemia and hyperphosphatemia in the later stages of CKD; however, it initially develops much earlier in disease course. The initial step in CKD-MBD involves decreased phosphate excretion in the urine, followed by increased circulating concentrations of fibroblast growth factor 23 (FGF23) and parathyroid hormone (PTH), which increase urinary phosphate excretion. Simultaneously, the serum calcitriol concentration decreases as a result of FGF23 elevation. Importantly, FGF23 and PTH cause left ventricular hypertrophy, arrhythmia, and cardiovascular calcification. More recently, calciprotein particles, which are nanoparticles composed of calcium, phosphate, and fetuin-A, among other components, have been reported to cause inflammation, cardiovascular calcification, and other clinically relevant outcomes. CKD-MBD has become one of the critical therapeutic targets for the prevention of cardiovascular events and is another link between cardiology and nephrology. In this review, we describe the role of CKD-MBD in the pathogenesis of cardiovascular disorders and present the current treatment strategies for CKD-MBD.

The Potential Influence of Uremic Toxins on the Homeostasis of Bones and Muscles in Chronic Kidney Disease

Patients with chronic kidney disease (CKD) often experience a high accumulation of protein-bound uremic toxins (PBUTs), specifically indoxyl sulfate (IS) and p-cresyl sulfate (pCS). In the early stages of CKD, the buildup of PBUTs inhibits bone and muscle function. As CKD progresses, elevated PBUT levels further hinder bone turnover and exacerbate muscle wasting. In the late stage of CKD, hyperparathyroidism worsens PBUT-induced muscle damage but can improve low bone turnover. PBUTs play a significant role in reducing both the quantity and quality of bone by affecting osteoblast and osteoclast lineage. IS, in particular, interferes with osteoblastogenesis by activating aryl hydrocarbon receptor (AhR) signaling, which reduces the expression of Runx2 and impedes osteoblast differentiation. High PBUT levels can also reduce calcitriol production, increase the expression of Wnt antagonists (SOST, DKK1), and decrease klotho expression, all of which contribute to low bone turnover disorders. Furthermore, PBUT accumulation leads to continuous muscle protein breakdown through the excessive production of reactive oxygen species (ROS) and inflammatory cytokines. Interactions between muscles and bones, mediated by various factors released from individual tissues, play a crucial role in the mutual modulation of bone and muscle in CKD. Exercise and nutritional therapy have the potential to yield favorable outcomes. Understanding the underlying mechanisms of bone and muscle loss in CKD can aid in developing new therapies for musculoskeletal diseases, particularly those related to bone loss and muscle wasting.

A Retrospective Study on Vitamin D Status and Its Association With Cardiometabolic Risk Factors Among Children With Chronic Kidney Disease at King Abdulaziz University Hospital

BACKGROUND

Vitamin D deficiency is a significant global health issue. It is prevalent in chronic kidney disease (CKD) patients, which is an important cause of death among children. Many studies have found a link between low vitamin D status in CKD patients and cardiovascular disease (CVD) risk factors. However, there are no data on this relationship in children with CKD in Saudi Arabia.

AIMS

We aimed to demonstrate this association among children with CKD admitted to the King Abdulaziz University Hospital (KAUH) in Jeddah, Saudi Arabia.

MATERIALS AND METHODS

Data were collected between June and August 2020 from a convenience sample of pediatric patients.

RESULTS

In total, 153 pediatric patients with CKD stages 2-5 were admitted to the KAUH between 2010 and 2019, and 67.3% had CKD stage 5. Approximately 4.6% and 10.5% of the participants were overweight or obese, respectively. Patients who fell into the lower 25-hydroxyvitamin D (25[OH]D) tertile were older, had higher body mass index (BMI) values, and had higher blood pressure than those in the upper two tertiles; however, these differences were not statistically significant. There was a significant inverse association of 25(OH)D levels with BMI, blood pressure, and serum creatinine levels.

CONCLUSIONS

The results of this retrospective study suggest that patients with CKD and lower vitamin D levels have a higher BMI and blood pressure and are therefore at higher risk of developing CVD. Future prospective studies with a larger sample size are needed to confirm these findings. Randomized clinical trials are also needed to investigate the effect of sufficient vitamin D status on reducing CVD in patients with CKD.

Serum vitamin D levels and acute kidney injury: a systemic review and meta-analysis

Numerous researches have evaluated the prevalence and clinical outcome of vitamin D deficiency in patients with chronic kidney disease (CKD) and end-stage renal disease (ESRD). But the quantitative vitamin D status in acute kidney injury (AKI) patients and its relationship with prognosis remains controversial. We conducted this systemic review and meta-analysis to assess the quantitative difference of vitamin D status, including serum 25(OH) D and 1,25(OH)2D levels, between AKI patients and non-AKI controls, and further explore whether vitamin D status can be clearly correlated with the mortality of AKI. Major databases, including PubMed, Web of Science and EBSCO, were searched until 1st September 2021. All published observational studies related to vitamin D and AKI According to predefined inclusion and exclusion criteria were extracted. Meta-analyses were performed using Review Manager 5.3.5. Four studies including five cohorts were included with a total of 413 patients. The serum 25(OH)D levels showed no statistically significant difference in AKI patients and non-AKI controls. On the other hand, the serum 1,25(OH)2D levels were significant lower in AKI patients than in non-AKI controls (MD =  - 17.79, 95% CI =  - 32.73 to - 2.85, P = 0.02). As for the relationship between serum vitamin D status and AKI patients' mortality, we were unable to give a consistent conclusion based on current limited and conflict study results. Our meta-analysis suggested that serum 1,25(OH)2D levels, rather than 25(OH)D, is significantly lower in AKI patients. The relationship between vitamin D status and clinical outcome of AKI remains controversial based on current evidence. Future comprehensive studies are required to confirm these relations and to elucidate potential mechanisms.

Effect of the administration of different forms of vitamin D on central blood pressure and aortic stiffness, and its implication in the reduction of albuminuria in chronic kidney disease

BACKGROUND AND OBJECTIVES

Vitamin D(vitD) participates in phospho-calcium metabolism and exerts multiple pleiotropic effects. There is tissue 1-α (OH)ase that converts 25-OH cholecalciferol (25 (OH) D) in calcitriol that exerts autocrine and paracrine effects. 25 (OH)D deficiency could limit these tissue effects of vitD. The administration of nutritional vitD and the activator of the vitD receptor, paricalcitol, may promote beneficial effects on vascular and renal function. The objective of this work was to study in subjects with chronic kidney disease (CKD) the effect that the administration of different forms of vitD has on arterial function and albuminuria, and the possible relationship between the modifications of these variables.

PATIENTS AND METHODS

We studied in 97 patients with CKD stages 3-4 the effect of the administration of cholecalciferol (group 2; n: 35) and paricalcitol (n: 31; group 3) on parameters derived from brachial blood pressure, aortic blood pressure and on aortic stiffness studied using carotid-femoral pulse velocity (Vp_c-f), and on albuminuria. A group of patients with stages 3-4 CKD who did not receive vitD therapy served as a control group (n: 31; group 1). All parameters were studied at baseline and after the follow-up period which was 7 ± 2 months.

RESULTS

In the baseline phase, no differences were observed between the groups in brachial systolic blood pressure (bSBP), central systolic blood pressure (SBP), brachial pulse pressure (bPP), and central pulse pressure (pCP) or in aortic stiffness that was increased in all groups with a baseline Vp_c-f value of 10.5 (9.2-12.1) m/sec. The baseline albuminuria value in the grouped patients was 229 (43-876) mg / g (median (interquartile range)), with no differences between the groups. Serum calcium and phosphorus increased significantly in those treated with cholecal-ciferol (native vitD) and paricalcitol (active vitD). Parathormone (PTH) values decreased in those treated with paricalcitol.bPP and cPP decreased in all groups treated with native and active vitD. No significant changes in bPP and cPP were observed in the control group. Vp_c-f did not change significantly in any of the groups, although the variation was quantitatively greater in group 3 (11.2±2 vs. 10.7±1.6 (P=.06)). No differences were observed in the changes in Vp_c-f between the groups when adjusted to the baseline values of estimated glomerular filtration rate (eGFR), albuminuria, PTH, vitD, brachial and central blood pressure parameters, and their changes with treatment.Those who received treatment with native and active vitD presented a significant decrease in albuminuria of 17% (group 2) and 21% (group 3) compared to a 16% increase in the untreated group (group 1) (P=.01). A decrease in albuminuria ≥30% was observed more frequently in the groups treated with some form of vitD (group 2: 23%; group 3: 45%) than in the control group (13%) (P=.03). The decrease in albuminuria observed in the groups treated with any of the forms of vitD did not vary when the baseline values of the biochemical parameters of phosphorus-calcium metabolism, those of arterial function (PPb, PPc, Vp_c-f) or its modifications were introduced as covariates. There was no significant correlation between changes in Vp_c-f and albuminuria. In logistic regression, changes in arterial function parameters were also not explanatory for the ≥30% decrease in albuminuria.

CONCLUSIONS

In patients with CKD stages 3-4, treated with RAS blockers and with residual albuminuria, the administration of or paricalcitol reduces brachial and aortic pulse pressures, and albuminuria. The decrease in albuminuria does not seem to be mediated, at least not decisively, by changes in central hemodynamics or aortic stiffness.

The Perspective of Vitamin D on suPAR-Related AKI in COVID-19

The coronavirus disease 2019 (COVID-19) pandemic has claimed the lives of millions of people around the world. Severe vitamin D deficiency can increase the risk of death in people with COVID-19. There is growing evidence that acute kidney injury (AKI) is common in COVID-19 patients and is associated with poorer clinical outcomes. The kidney effects of SARS-CoV-2 are directly mediated by angiotensin 2-converting enzyme (ACE2) receptors. AKI is also caused by indirect causes such as the hypercoagulable state and microvascular thrombosis. The increased release of soluble urokinase-type plasminogen activator receptor (suPAR) from immature myeloid cells reduces plasminogen activation by the competitive inhibition of urokinase-type plasminogen activator, which results in low plasmin levels and a fibrinolytic state in COVID-19. Frequent hypercoagulability in critically ill patients with COVID-19 may exacerbate the severity of thrombosis. Versican expression in proximal tubular cells leads to the proliferation of interstitial fibroblasts through the C3a and suPAR pathways. Vitamin D attenuates the local expression of podocyte uPAR and decreases elevated circulating suPAR levels caused by systemic inflammation. This decrease preserves the function and structure of the glomerular barrier, thereby maintaining renal function. The attenuated hyperinflammatory state reduces complement activation, resulting in lower serum C3a levels. Vitamin D can also protect against COVID-19 by modulating innate and adaptive immunity, increasing ACE2 expression, and inhibiting the renin-angiotensin-aldosterone system. We hypothesized that by reducing suPAR levels, appropriate vitamin D supplementation could prevent the progression and reduce the severity of AKI in COVID-19 patients, although the data available require further elucidation.

Relationship between serum 25-hydroxyvitamin D and target organ damage in children with essential hypertension

Researchers have shown that 25-hydroxyvitamin D (25[OH] D), a kind of active vitamin D in the human body, plays a role in cardiovascular disease (CVD). Low serum 25(OH) D levels have been found to be associated with elevated blood pressure (BP) in adults. However, measurement of 25(OH) D in hypertensive children has not been documented. The aim of this study was to investigate the relationship between 25(OH) D and target organ damage (TOD) in children with essential hypertension. We recruited a total of 346 children with essential hypertension and analyzed the correlation between serum 25(OH) D and TOD. Serum 25(OH) D concentration was significantly lower in the TOD than in the no-TOD group (t = 2.416, P = 0.016), as well as significantly lower in the two-organ damage than in the single-organ damage group (t = 3.140, P = 0.002). Pearson's correlation coefficient (PCC) indicated that serum 25(OH) D levels were negatively correlated with left ventricular mass index (LVMI; r = -0.110, P = 0.041) and albuminuria (r = -0.120, P = 0.026). Linear- regression analysis showed that 25(OH) D was a risk factor for left ventricular hypertrophy (LVH; β ± s.e. =-0.074 ± 0.036; 95% confidence interval [CI], - 0.145 to -0.003; P < 0.001) and renal damage (β ± s.e.= -0.018 ± 0.008; 95% CI, - 0.035 to -0.002; P = 0.004). In total, our data revealed that serum 25(OH) D was independently associated with hypertensive cardiac and renal damage, meaning that it was a risk factor for LVH and albuminuria in childhood hypertension.

Interplay between gut microbiota, bone health and vascular calcification in chronic kidney disease

Deregulations in gut microbiota may play a role in vascular and bone disease in chronic kidney disease (CKD). As glomerular filtration rate declines, the colon becomes more important as a site of excretion of urea and uric acid, and an increased bacterial proteolytic fermentation alters the gut microbial balance. A diet with limited amounts of fibre, as well as certain medications (eg phosphate binders, iron supplementation, antibiotics) further contribute to changes in gut microbiota composition among CKD patients. At the same time, both vascular calcification and bone disease are common in patients with advanced kidney disease. This narrative review describes emerging evidence on gut dysbiosis, vascular calcification, bone demineralization and their interrelationship termed the 'gut-bone-vascular axis' in progressive CKD. The role of diet, gut microbial metabolites (ie indoxyl sulphate, p-cresyl sulphate, trimethylamine N-oxide (TMAO) and short-chain fatty acids (SCFA)), vitamin K deficiency, inflammatory cytokines and their impact on both bone health and vascular calcification are discussed. This framework may open up novel preventive and therapeutic approaches targeting the microbiome in an attempt to improve cardiovascular and bone health in CKD.

Efficacy of high versus conventional dose of ergocalciferol supplementation on serum 25-hydroxyvitamin D and interleukin-6 levels among hemodialysis patients with vitamin D deficiency: A multicenter, randomized, controlled study

Long-term dialysis involves a chronic inflammatory state and produces a high prevalence of vitamin D deficiency. A clinical trial was conducted in hemodialysis with serum 25-hydroxyvitamin D (25[OH]D) level <30 ng/ml. The conventional-group (N = 35) and the high-dose group (N = 35) were treated with ergocalciferol according to the K/DOQI guidelines and double dosage of ergocalciferol from the recommendation for 8 weeks, respectively. The main outcomes were measured by serum 25[OH]D and interleukin-6 (IL-6). At the end of 8 weeks, a statistically significant greater increase was observed of mean serum 25[OH]D levels and a decrease of mean parathyroid hormone levels in the high-dose group compared with the conventional-dose group. The high dose group had the higher achievement of vitamin D sufficiency than the conventional-dose group (97.4% vs. 76.4%, p = 0.012). No significant difference was found in mean changes of serum IL-6 level in both groups, except subgroup patients with vitamin D deficiency or serum 25[OH]D <20 ng/ml, high dose treatment suppressed serum IL-6 level (-2.67 pg/ml [IQR -6.56 to -0.17], p = 0.039). No differences were observed between the two groups in adverse events. Oral high-dose ergocalciferol supplementation has achieved higher vitamin D sufficiency than standard dose in end stage renal disease patients on dialysis.

New progress in drugs treatment of diabetic kidney disease

Diabetic kidney disease (DKD) is not only one of the main complications of diabetes, but also the leading cause of the end-stage renal disease (ESRD). The occurrence and development of DKD have always been a serious clinical problem that leads to the increase of morbidity and mortality and the severe damage to the quality of life of human beings. Controlling blood glucose, blood pressure, blood lipids, and improving lifestyle can help slow the progress of DKD. In recent years, with the extensive research on the pathological mechanism and molecular mechanism of DKD, there are more and more new drugs based on this, such as new hypoglycemic drugs sodium-glucose cotransporter 2 (SGLT2) inhibitors, glucagon-like peptide-1 (GLP-1) inhibitors, and dipeptidyl peptidase-4 (DPP-4) inhibitors with good efficacy in clinical treatment. Besides, there are some newly developed drugs, including protein kinase C (PKC) inhibitors, advanced glycation end product (AGE) inhibitors, aldosterone receptor inhibitors, endothelin receptor (ETR) inhibitors, transforming growth factor-β (TGF-β) inhibitors, Rho kinase (ROCK) inhibitors and so on, which show positive effects in animal or clinical trials and bring hope for the treatment of DKD. In this review, we sort out the progress in the treatment of DKD in recent years, the research status of some emerging drugs, and the potential drugs for the treatment of DKD in the future, hoping to provide some directions for clinical treatment of DKD.

Risk factors for calciphylaxis in Chinese hemodialysis patients: a matched case-control study

Introduction

Calciphylaxis is a rare but potentially fatal disease commonly occurred in dialysis patients. Despite some previous studies on risk factors for calciphylaxis, there is still a lack of data from Chinese population.

Methods

The retrospective matched case–control study about calciphylaxis was performed in Zhongda Hospital affiliated to Southeast University. The case group involved 20 hemodialysis patients who were newly diagnosed with calciphylaxis from October 2017 to December 2018. The 40 noncalciphylaxis patients undergoing dialysis with the same age and duration of dialysis were randomly selected as controls.

Results

Most of calciphylaxis patients were male and elderly, while overweight people were more susceptible to the disease. Although incidence of secondary hyperparathyroidism was higher in calciphylaxis patients, the differences in duration of elevated serum intact parathyroid hormone (iPTH) and its highest value did not reach statistical significance compared with controls. No significant difference in warfarin therapy was discernible between two groups. The univariate regression analysis indicated that male, score of use of activated vitamin D and its analogues, corrected serum calcium level, serum phosphate, Ca × P product, iPTH, albumin, and alkaline phosphatase (ALP) level were significantly associated with calciphylaxis. Elevated levels of serum phosphate (OR 4.584, p = 0.027) and ALP (OR 1.179, p = 0.036), decreased level of serum albumin (OR 1.330, p = 0.013) were independent risk factors after multivariate analysis.

Conclusion

This is the first report of risk factors associated with calciphylaxis in China. Increased levels of serum phosphate and ALP, decreased level of serum albumin were vital high-risk factors for calciphylaxis in Chinese hemodialysis population.

Ferrotoxicity and Its Amelioration by Calcitriol in Cultured Renal Cells

Globally, acute kidney injury (AKI) is associated with significant mortality and an enormous economic burden. Whereas iron is essential for metabolically active renal cells, it has the potential to cause renal cytotoxicity by promoting Fenton chemistry-based oxidative stress involving lipid peroxidation. In addition, 1,25-dihydroxyvitamin D3 (calcitriol), the active form of vitamin D, is reported to have an antioxidative role. In this study, we intended to demonstrate the impact of vitamin D on iron-mediated oxidant stress and cytotoxicity of Vero cells exposed to iohexol, a low osmolar iodine-containing contrast media in vitro. Cultured Vero cells were pretreated with 1,25-dihydroxyvitamin D3 dissolved in absolute ethanol (0.05%, 2.0 mM) at a dose of 1 mM for 6 hours. Subsequently, iohexol was added at a concentration of 100 mg iodine per mL and incubated for 3 hours. Total cellular iron content was analysed by a flame atomic absorption spectrophotometer at 372 nm. Lipid peroxidation was determined by TBARS (thiobarbituric acid reactive species) assay. Antioxidants including total thiol content were assessed by Ellman’s method, catalase by colorimetric method, and superoxide dismutase (SOD) by nitroblue tetrazolium assay. The cells were stained with DAPI (4 ${}^{\prime }$ ,6-diamidino-2-phenylindole), and the cytotoxicity was evaluated by viability assay (MTT assay). The results indicated that iohexol exposure caused a significant increase of the total iron content in Vero cells. A concomitant increase of lipid peroxidation and decrease of total thiol protein levels, catalase, and superoxide dismutase activity were observed along with decreased cell viability in comparison with the controls. Furthermore, these changes were significantly reversed when the cells were pretreated with vitamin D prior to incubation with iohexol. Our findings of this in vitro model of iohexol-induced renotoxicity lend further support to the nephrotoxic potential of iron and underpin the possible clinical utility of vitamin D for the treatment and prevention of AKI.

Ferrotoxicity and Its Amelioration by Calcitriol in Cultured Renal Cells

Globally, acute kidney injury (AKI) is associated with significant mortality and an enormous economic burden. Whereas iron is essential for metabolically active renal cells, it has the potential to cause renal cytotoxicity by promoting Fenton chemistry-based oxidative stress involving lipid peroxidation. In addition, 1,25-dihydroxyvitamin D3 (calcitriol), the active form of vitamin D, is reported to have an antioxidative role. In this study, we intended to demonstrate the impact of vitamin D on iron-mediated oxidant stress and cytotoxicity of Vero cells exposed to iohexol, a low osmolar iodine-containing contrast media in vitro. Cultured Vero cells were pretreated with 1,25-dihydroxyvitamin D3 dissolved in absolute ethanol (0.05%, 2.0 mM) at a dose of 1 mM for 6 hours. Subsequently, iohexol was added at a concentration of 100 mg iodine per mL and incubated for 3 hours. Total cellular iron content was analysed by a flame atomic absorption spectrophotometer at 372 nm. Lipid peroxidation was determined by TBARS (thiobarbituric acid reactive species) assay. Antioxidants including total thiol content were assessed by Ellman's method, catalase by colorimetric method, and superoxide dismutase (SOD) by nitroblue tetrazolium assay. The cells were stained with DAPI (4',6-diamidino-2-phenylindole), and the cytotoxicity was evaluated by viability assay (MTT assay). The results indicated that iohexol exposure caused a significant increase of the total iron content in Vero cells. A concomitant increase of lipid peroxidation and decrease of total thiol protein levels, catalase, and superoxide dismutase activity were observed along with decreased cell viability in comparison with the controls. Furthermore, these changes were significantly reversed when the cells were pretreated with vitamin D prior to incubation with iohexol. Our findings of this in vitro model of iohexol-induced renotoxicity lend further support to the nephrotoxic potential of iron and underpin the possible clinical utility of vitamin D for the treatment and prevention of AKI.

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

BACKGROUND AND AIM

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

METHODS AND RESULTS

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

CONCLUSION

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

GOV REGISTRATION NUMBER

NCT03602430.

Cytokines, 25-OH vit D and disease activity in patients with juvenile-onset systemic lupus erythematosus

BACKGROUND

Juvenile onset systemic lupus erythematosus JO-SLE patients usually exhibit a more aggressive disease course compared to adult patients. Vitamin D deficiency is proposed to be associated with increased disease activity and flares of numerous autoimmune diseases like SLE, rheumatoid arthritis, and scleroderma.

OBJECTIVE

To evaluate the level of IL-17, IFN-γ, and 25-OH Vit D in JO-SLE patients versus healthy controls, and determine the correlation of those inflammatory mediators with SLE disease activity and damage scores. Furthermore, to analyze the relationship between 25-OH Vit D levels with the inflammatory cytokines (IFN-γ and IL-17) in JO-SLE patients.

PATIENTS AND METHODS

Fifty JO-SLE patients and 25 controls were included in this study. Clinical and laboratory data of patients at the time of the study were recorded. SLE disease activity and damage were assessed using the SLEDAI-2K disease score and SLICC damage index, respectively. Plasma 25-OH Vit D, IFN-γ, and IL-17 concentrations were determined using the human ELISA kit.

RESULTS

Plasma 25-OH Vit D levels (20 ng/mL) were significantly lower in JO-SLE patients compared to (31 ng/mL) controls (P = 0.014). Plasma levels of IFN-γ and IL-17 were significantly higher (163.5 and 25.5 pg./mL) in JO-SLE patients than (68.3 and 3 pg./mL) that of controls (P = 0.016 and P = 0.013). There was a significant negative correlation between 25-OH Vit D levels and SLEDAI-2K (R= -0.431) as well as IFN-γ (R= -0.471) plasma level (P = 0.022 and P = 0.027).

CONCLUSION

IFN-γ and IL-17 were significantly higher in JO-SLE patients, while 25-OH Vit D was significantly lower compared to controls. There was a negative correlation between 25-OH Vit D and each of SLEDAI-2K and IFN-γ.

Association between vitamin D levels and mortality in hemodialysis patients: a cohort study

Introduction: Low vitamin D levels are associated with mortality in hemodialysis (HD) patients; however, the serum vitamin D thresholds are unclear. This study aimed to identify the vitamin D level below which mortality increases in HD patients.Methods: A cohort of HD patients enrolled from January 2014 to January 2017 was evaluated. The variables were analyzed according to the season, namely, summer, winter, and annual average, mortality was the primary outcome. The patients were assigned to vitamin D quintiles, and multivariate Cox regression analysis adjusted for age, ethnicity, gender, body mass index (BMI), inhibitors of the renin-angiotensin system, statin, calcitriol, and antiplatelet drugs use, hemodialysis vintage, hypertension, diabetes mellitus, atherosclerotic disease, and C-reactive protein was performed.Results: There were studied 306 patients. Vitamin D levels of 18.0-23.6 ng/mL (hazard ratio [HR] = 4.30; 95% confidence interval [CI] 1.60-11.54, p = 0.004) and <18.0 ng/mL (HR = 3.83; 95% CI: 1.42-10.35, p = 0.008) in summer and vitamin D levels of 21.5-27.1 ng/mL (HR = 3.70; 95% CI: 1.50-9.11, p = 0.004) and ≤17.5 ng/mL (HR = 2.84; 95% CI: 1.13-7.13, p = 0.026) in winter were associated with mortality. The average annual values of vitamin D associated with all-cause mortality were <17.7 ng/dL (adjusted HR = 4.25, 95% CI: 1.57-11.48, p = 0.004), and between >17.7 ng/dL and ≤23.1 ng/dL (adjusted HR = 3.91, 95% CI: 1.47-10.42, p = 0.006).Conclusions: Annual average vitamin D levels <23.1 ng/mL were associated with higher all-cause mortality, regardless of the confounding variables evaluated.

Ferrotoxicity and its amelioration by endogenous vitamin D in experimental acute kidney injury

This work provides in-depth insights on catalytic iron-induced cytotoxicity and the resultant triggering of endogenous vitamin D synthesis in experimental acute kidney injury. Our results reveal significantly elevated levels of catalytic iron culminating in oxidant-mediated renal injury and a concomitant increase in 1,25-dihdyroxyvitamin D3 levels. Also, changes in other iron-related proteins including transferrin, ferritin, and hepcidin were observed both in the serum as well as in their mRNA expression. We consider all these findings vital since no connection between catalytic iron and vitamin D has been established so far. Furthermore, we believe that this work provides new and interesting results, with catalytic iron emerging as an important target in ameliorating renal cellular injury, possibly by timely administration of vitamin D. It also needs to be seen if these observations made in rats could be translated to humans by means of robust clinical trials.

Lipid status association with 25-hydroxy vitamin D: Cross sectional study of end stage renal disease patients

Background

Some observational studies indicate an association of 25-hydroxy vitamin D (25(OH)D) insufficiency and atherogenic cholesterol concentrations. The aim of this study was to investigate relationship between 25(OH)D concentrations and lipid parameters in end stage renal disease (ESRD) patients, separately for predialysis, hemodialysis and peritoneal dialysis patients.

Methods

We have adjusted 25(OH)D concentrations for seasonal variability with cosinor analysis, and performed all further analysis using these corrected 25(OH)D concentrations. Concentrations of 25(OH)D and the lipid parameters were determined in 214 ESRD patients and 50 control group participants. The analysis included the measurement of 25(OH)D by HPLC, apolipoprotein (Apo) AI, ApoB and Lp(a) by nephelometry, total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C) and triglyceride (TG) by spectrophotometry and manually calculated ApoB/ApoAI and LDL-C/HDL-C ratio.

Results

ESRD patients with adjusted 25(OH)D concentrations of 50 nmol/L had significantly higher TC (P = 0.005) and ApoAI (P = 0.049). Significantly higher HDLC (P = 0.011) and ApoAI (P = 0.020) were found in hemodialysis patients with the 25(OH)D concentrations of 50 nmol/L. The other analyzed lipid parameters differed significantly between predialysis, hemodialysis and peritoneal dialysis patients with 25(OH)D concentrations of < 50 nmol/L.

Conclusions

Our study indicate the significant relationship between 25(OH)D repletion and optimal concentrations of lipid parameters in ESRD patients. Further research is necessary to explain whether joint evaluation of vitamin D status and lipid abnormalities could improve cardiovascular outcome in ESRD patients.

Ferrotoxicity and its amelioration by endogenous vitamin D in experimental acute kidney injury

Acute kidney injury causes significant morbidity and mortality. This experimental animal study investigated the simultaneous impact of iron and vitamin D on acute kidney injury induced by iohexol, an iodinated, non-ionic monomeric radiocontrast agent in Wistar rats. Out of 36 healthy male Wistar rats, saline was injected into six control rats (group 1) and iohexol into the remaining 30 experimental rats (groups 2 to 6 comprising six rats each). Biochemical, renal histological changes, and gene expression of iron-regulating proteins and 1 α-hydroxylase were analyzed. Urinary neutrophil gelatinase-associated lipocalin (NGAL), serum creatinine, urine protein, serum and urine catalytic iron, 25-hydroxyvitamin D3, 1,25-dihydroxyvitamin D3, and tissue lipid peroxidation were assayed. Rats injected with iohexol showed elevated urinary NGAL (11.94 ± 6.79 ng/mL), serum creatinine (2.92 ± 0.91 mg/dL), and urinary protein levels (11.03 ± 9.68 mg/mg creatinine) together with histological evidence of tubular injury and iron accumulation. Gene expression of iron-regulating proteins and 1 α-hydroxylase was altered. Serum and urine catalytic iron levels were elevated (0.57 ± 0.17; 48.95 ± 29.13 µmol/L) compared to controls (0.49 ± 0.04; 20.7 ± 2.62 µmol/L, P < 0.001). Urine catalytic iron positively correlated with tissue peroxidation (r = 0.469, CI 0.122 to 0.667, P = 0.004) and urinary NGAL (r = 0.788, CI 0.620 to 0.887, P < 0.001). 25-hydroxyvitamin D3 (61.58 ± 9.60 ng/mL) and 1,25-dihydroxyvitamin D3 (50.44 ± 19.76 pg/mL) levels increased simultaneously. In a multivariate linear regression analysis, serum iron, urine catalytic iron, and tissue lipid peroxidation independently and positively predicted urinary NGAL, an acute kidney injury biomarker. This study highlights the nephrotoxic potential of catalytic iron besides demonstrating a concurrent induction of vitamin D endogenously for possible renoprotection in acute kidney injury.

Impact statement

This work provides in-depth insights on catalytic iron-induced cytotoxicity and the resultant triggering of endogenous vitamin D synthesis in experimental acute kidney injury. Our results reveal significantly elevated levels of catalytic iron culminating in oxidant-mediated renal injury and a concomitant increase in 1,25-dihdyroxyvitamin D3 levels. Also, changes in other iron-related proteins including transferrin, ferritin, and hepcidin were observed both in the serum as well as in their mRNA expression. We consider all these findings vital since no connection between catalytic iron and vitamin D has been established so far. Furthermore, we believe that this work provides new and interesting results, with catalytic iron emerging as an important target in ameliorating renal cellular injury, possibly by timely administration of vitamin D. It also needs to be seen if these observations made in rats could be translated to humans by means of robust clinical trials.

Antiproteinuria Effect of Calcitriol in Patients With Chronic Kidney Disease and Vitamin D Deficiency: A Randomized Controlled Study

OBJECTIVE

Vitamin D has been demonstrated to lessen proteinuria severity in chronic kidney disease (CKD). Compared with healthy populations, patients with CKD may have lower serum levels of 1,25-dihydroxy vitamin D (1,25-(OH)2 D) and 25-hydroxy vitamin D (25-(OH) D). We investigated the effect of  oral low-dose active vitamin D (calcitriol at 0.25 μg, 3 times weekly) on urinary protein excretion.

DESIGN AND METHODS

We conducted a nonblinded and non-placebo-controlled study. In total, 60 patients with CKD (average estimated glomerular filtration rate of >15 mL/min) who received a stable dose of angiotensin receptor blocker (ARB) or angiotensin-converting enzyme inhibitor (ACEI) were enrolled in this 24-week study. We randomly assigned these patients to the vitamin D group (oral calcitriol at 0.25 μg 3 times weekly with an ACEI or ARB) or the control group (ACEI or ARB). Change in the urine protein/creatinine ratio (uPCR) was the primary endpoint in this study.

RESULTS

The mean baseline uPCRs of the 2 groups were comparable (1.84 ± 0.83 g/g vs. 2.02 ± 0.97 g/g, control vs. vitamin D group; P = .46). After the 24-week treatment, the uPCRs were significantly lower than the baseline values in the vitamin D group (1.35 ± 0.64 g/g; P < .05) but not in the control group. The values of uPCR decreased significantly at 8, 16, and 24 weeks (P < .05 vs. baseline) in the vitamin D group. The values of uPCRs were significantly lower in the vitamin D group than in the control group at 8, 16, and 24 weeks (P < .05). A positive correlation was discovered between reduction in uPCRs at 24-week and baseline 25-(OH) D serum level in the vitamin D group (r = 0.738, P < .001).

CONCLUSION

Supplementary low-dose active vitamin D could reduce proteinuria in CKD patients with low serum 25-(OH) D levels.

A Review of the Potential Benefits of Increasing Vitamin D Status in Mongolian Adults through Food Fortification and Vitamin D Supplementation

Serum 25-hydroxyvitamin D (25(OH)D) concentrations are low in Mongolia, averaging 22 ng/mL in summer and only 8 ng/mL in winter. Mongolians have high incidence and/or prevalence of several diseases linked to low 25(OH)D concentrations, including ischemic heart disease, malignant neoplasms, cirrhosis of the liver, ischemic stroke, lower respiratory tract infections, preterm birth complications, and diabetes mellitus. Fortifying regularly consumed foods such as flour, milk, and edible oils with vitamin D₃ could raise 25(OH)D concentrations by about 10 ng/mL. However, to achieve 25(OH)D concentrations of 30–40 ng/mL in adults, vitamin D intakes of 1000 to 4000 IU/day would be required, making personal supplement use necessary. On the basis of prospective observational studies and clinical trials of disease incidence or known mortality rates and adverse pregnancy and birth outcomes, raising mean serum 25(OH)D concentrations to 40 ng/mL would likely reduce incidence and mortality rates for those and other diseases, reduce the rate of adverse pregnancy and birth outcomes, and increase mean life expectancy by one year or more.

The Emerging Role of Nutritional Vitamin D in Secondary Hyperparathyroidism in CKD

In chronic kidney disease (CKD), hyperphosphatemia induces fibroblast growth factor-23 (FGF-23) expression that disturbs renal 1,25-dihydroxy vitamin D (1,25D) synthesis; thereby increasing parathyroid hormone (PTH) production. FGF-23 acts on the parathyroid gland (PTG) to increase 1α-hydroxylase activity and results in increase intra-gland 1,25D production that attenuates PTH secretion efficiently if sufficient 25D are available. Interesting, calcimimetics can further increase PTG 1α-hydroxylase activity that emphasizes the demand for nutritional vitamin D (NVD) under high PTH status. In addition, the changes in hydroxylase enzyme activity highlight the greater parathyroid 25-hydroxyvitmain D (25D) requirement in secondary hyperparathyroidism (SHPT); the higher proportion of oxyphil cells as hyperplastic parathyroid progression; lower cytosolic vitamin D binding protein (DBP) content in the oxyphil cell; and calcitriol promote vitamin D degradation are all possible reasons supports nutritional vitamin D (NVD; e.g., Cholecalciferol) supplement is crucial in SHPT. Clinically, NVD can effectively restore serum 25D concentration and prevent the further increase in PTH level. Therefore, NVD might have the benefit of alleviating the development of SHPT in early CKD and further lowering PTH in moderate to severe SHPT in dialysis patients.

Impacts of Indoxyl Sulfate and p-Cresol Sulfate on Chronic Kidney Disease and Mitigating Effects of AST-120

Uremic toxins, such as indoxyl sulfate (IS) and p-cresol, or p-cresyl sulfate (PCS), are markedly accumulated in the organs of chronic kidney disease (CKD) patients. These toxins can induce inflammatory reactions and enhance oxidative stress, prompting glomerular sclerosis and interstitial fibrosis, to aggravate the decline of renal function. Consequently, uremic toxins play an important role in the worsening of renal and cardiovascular functions. Furthermore, they destroy the quantity and quality of bone. Oral sorbent AST-120 reduces serum levels of uremic toxins in CKD patients by adsorbing the precursors of IS and PCS generated by amino acid metabolism in the intestine. Accordingly, AST-120 decreases the serum IS levels and reduces the production of reactive oxygen species by endothelial cells, to impede the subsequent oxidative stress. This slows the progression of cardiovascular and renal diseases and improves bone metabolism in CKD patients. Although large-scale studies showed no obvious benefits from adding AST-120 to the standard therapy for CKD patients, subsequent sporadic studies may support its use. This article summarizes the mechanisms of the uremic toxins, IS, and PCS, and discusses the multiple effects of AST-120 in CKD patients.

Increase of endocan, a new marker for inflammation and endothelial dysfunction, in acute kidney injury

OBJECTIVE:

In this study, the clinical relevance of the levels of serum endocan and 25-hydroxyvitamin D [25(OH)D] was investigated in patients with acute kidney injury (AKI). Endocan or the endothelial cell-specific molecule 1 is a soluble proteoglycan secreted by vascular endothelial cells. It plays a significant role in immunity, inflammation, and endothelial function.

METHODS:

A total of 39 patients with AKI (19 females, 20 males) and 38 healthy individuals (18 females, 20 males) were included in the study. The levels of serum endocan, vitamin D, and other biochemical parameters were compared between the two groups.

RESULTS:

In the AKI group, the values of serum creatinine, endocan, parathormone, phosphorus, and uric acid were found to be higher, and the total protein, albumin, and calcium levels were lower compared to the control group. There was no difference between the two groups in terms of the serum vitamin D, magnesium, alkaline phosphatase, and gamma-glutamyl transferase.

CONCLUSION:

In patients with AKI, an increased endocan level is a significant marker of inflammation and endothelial injury. In addition, these patients experience vitamin D deficiency.

Effect of uremic toxin-indoxyl sulfate on the skeletal system

Chronic kidney disease-mineral bone disorders (CKD-MBD) exhibit abnormalities in the circulating mineral levels, vitamin D metabolism, and parathyroid function that contribute to the formation of a bone lesion. The uremic toxin, indoxyl sulfate (IS), accumulates in the blood in cases of renal failure and leads to bone loss. The bone and renal responses to the action of the parathyroid hormone (PTH) are progressively decreased in CKD in spite of increasing PTH levels, a condition commonly called PTH resistance. There is a high prevalence of low bone turnover or adynamic bone disease in the early stages of CKD. This could be due to the inhibition of bone turnover, such as in PTH resistance, reduced active vitamin D levels, diabetes, aluminum, and, increased IS. With an increase in IS, there is a decrease in the osteoblast Wnt/b-catenin signaling and increase in the expression of Wnt signaling inhibitors, such as sclerostin and Dickkopf-1 (DKK1). Thus, a majority of early CKD patients exhibit deterioration of bone quality owing to the action of IS, this scenario could be termed uremic osteoporosis. However, this mechanism is complicated and not fully understood. With progressive deterioration in the renal function, IS accumulates along with persistent PTH secretion, potentially leading to high-turnover bone disease because high serum PTH levels have the ability of overriding peripheral PTH resistance and other inhibitory factors of bone formation. Finally, it leads to deterioration in bone quantity with prominent bone resorption in end stage renal disease. Uremic toxins adsorbents may decelerate oxidative stress and improve bone health in CKD patients. This review article focuses on IS and bone loss in CKD patients.

Cholecalciferol Additively Reduces Serum Parathyroid Hormone Levels in Severe Secondary Hyperparathyroidism Treated with Calcitriol and Cinacalcet among Hemodialysis Patients

We evaluated the improvement of intact parathyroid hormone (iPTH) levels and bone parameters by supplementing nutritional vitamin D (cholecalciferol) to combined calcimimetic (cinacalcet) and active vitamin D analog (calcitriol) among severe secondary hyperparathyroidism (SHPT) hemodialysis (HD) patients. A randomized, controlled open-label study was undertaken in 60 HD patients with serum iPTH > 1000 pg/mL or persistently high iPTH ≥ 600 pg/mL even after >3 months of calcitriol (3 μg/week). The study group received oral cholecalciferol (5000 IU/ day) and the control group received a placebo. All patients received fixed dose cinacalcet (30 mg/day, orally) and calcitriol. Calcitriol was reduced if iPTH ≤ 300 pg/mL and cinacalcet was withdrawn if serum iPTH was persistently low (iPTH ≤ 300 pg/mL) for 4 weeks after the reduction of calcitriol. A significantly lower iPTH level was noted from the 20th week in the study group compared to the placebo group, and the target iPTH ≤ 300 pg/mL was achieved at the 24th week in the study group. Most patients achieved serum 25-(OH)D₃ ≥ 30 ng/mL in the study group. Nearly 40% of study patients gained >10% improvement in femoral neck (FN) bone mineral density (BMD). We conclude that cholecalciferol additively reduced serum iPTH levels, improved 25-(OH)D₃ levels and improved FN BMD when used together with cinacalcet/calcitriol in severe SHPT HD patients.

Chronic kidney disease and vitamin D metabolism in human bone marrow-derived MSCs

Vitamin D that is synthesized in the skin or is ingested undergoes sequential steps of metabolic activation via a cascade of cytochrome P450 enzymatic hydroxylations in the liver and kidney to produce 1α,25-dihydroxyvitamin D (1α,25(OH)2 D). There are many tissues that are able to synthesize 1α,25(OH)2 D, but the biological significance of extrarenal hydroxylases is unresolved. Human marrow-derived mesenchymal stem cells (marrow stromal cells, hMSCs) give rise to osteoblasts, and their differentiation is stimulated by 1α,25(OH)2 D. In addition to being targets of 1α,25(OH)2 D, hMSCs can synthesize it; on the basis of those observations, we further examined the local autocrine/paracrine role of vitamin D metabolism in osteoblast differentiation. Research with hMSCs from well-characterized subjects provides an innovative opportunity to evaluate the effects of clinical attributes on the regulation of hMSCs. Like the renal 1α-hydroxylase, the enzyme in hMSCs is constitutively decreased with age and chronic kidney disease (CKD); both are regulated by PTH1-34, insulin-like growth factor 1, calcium, 1α,25(OH)2 D, 25(OH)D, and fibroblast growth factor 23. CKD is associated with impaired renal biosynthesis of 1α,25(OH)2 D, low bone mass, and increased fracture risk. Studies with hMSCs from CKD patients or aged subjects indicate that circulating 25(OH)D may have an important role in osteoblast differentiation on vitamin D metabolism and action in hMSCs.

Vitamin-D concentrations, cardiovascular risk and events - a review of epidemiological evidence

Vitamin D has long been established as an elemental factor of bone physiology. Beyond mineral metabolism, the expression of the vitamin D receptor has been identified throughout the cardiovascular (CV) system. Experimental studies showed beneficial effects of vitamin D on heart and vessels, but vitamin D intoxication in animals also led to hypercalcemia and vascular calcification. Our knowledge has been extended by epidemiological studies that showed that 25-hydroxyvitamin D (25(OH)D) levels are inversely associated with an increased CV risk itself, but also with established CV risk factors, such as arterial hypertension, endothelial dysfunction and atherosclerosis. Conversely, randomized controlled trials could not document significant and consistent effects of vitamin D supplementation on CV risk or events. Potential explanations may lie in differences in reference ranges or the possibility that low vitamin D in CV disease is only an epiphenomenon. In the latter case, the key question is why low 25(OH)D levels are such a strong predictor of health. While we wait for new data, the current conclusion is that vitamin D is a strong risk marker for CV risk factors and for CV diseases itself.

Role of Vitamin D in Uremic Vascular Calcification

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

Electrolyte and Acid-Base Disorders in Chronic Kidney Disease and End-Stage Kidney Failure

The kidneys play a pivotal role in the regulation of electrolyte and acid-base balance. With progressive loss of kidney function, derangements in electrolytes and acid-base inevitably occur and contribute to poor patient outcomes. As chronic kidney disease (CKD) has become a worldwide epidemic, medical providers are increasingly confronted with such problems. Adequate diagnosis and treatment will minimize complications and can potentially be lifesaving. In this review, we discuss the current understanding of the disease process, clinical presentation, diagnosis and treatment strategies, integrating up-to-date knowledge in the field. Although electrolyte and acid-base derangements are significant causes of morbidity and mortality in CKD and end-stage renal disease patients, they can be effectively managed through a timely institution of combined preventive measures and pharmacological therapy. Exciting advances and several upcoming outcome trials will provide further information to guide treatment and improve patient outcomes.

Associations between dairy food consumption and chronic kidney disease in older adults

We aimed to assess the association between dairy product consumption and calcium intake with the prevalence and 10-year incidence of chronic kidney disease (CKD). 1185 participants aged ≥50 years at baseline were examined between 1992–4 and 2002–4. Dietary data were collected using a food frequency questionnaire, and servings of dairy food consumption were calculated. Baseline biochemistry including serum creatinine was measured. CKD was defined as Modification of Diet in Renal Disease Study estimated glomerular filtration rate <60 mL·min^−1.1.73 m⁻². Cross-sectional analysis showed that older adults in the highest quintile compared to the lowest quintile (reference group) of low/reduced fat dairy food consumption had reduced odds of CKD, multivariable-adjusted odds ratio, OR, 0.64 (95% confidence intervals, CI, 0.43–0.96). Increasing total intake of dietary calcium was associated with reduced odds of CKD (P-trend = 0.02); comparing highest versus lowest quintile: OR 0.62 (95% CI 0.42–0.92). Participants in the second versus first quintile of low/reduced fat dairy food consumption at baseline had 49% reduced risk of CKD 10 years later, OR 0.51 (95% CI 0.29–0.89). Higher consumption of low/reduced fat dairy foods was independently associated with lower risk of CKD. Additional population-based studies are warranted to confirm these findings.

Cholecalciferol Additively Reduces Serum Parathyroid Hormone and Increases Vitamin D and Cathelicidin Levels in Paricalcitol-Treated Secondary Hyperparathyroid Hemodialysis Patients

Background: Active Vitamin D analogues are used clinically for prevention and treatment of secondary hyperparathyroidism (SHPT) in hemodialysis (HD) patients. Nutritional vitamin D supplementation is used for additional local parathyroid (PTH) suppression, with lower incidence of hypercalcemia and hyperphosphatemia. This study evaluates the possible beneficial effects of combined vitamin D treatment (paricalcitol and cholecalciferol). Methods: Sixty HD patients with serum parathyroid hormone (iPTH) >300 pg/mL were enrolled. All patients administered 2 mcg/day of paricalcitol and were randomly allocated into control group (placebo) or study group (cholecalciferol) for 16 weeks. Serum 25(OH)D₃, iPTH and human cathelicidin (hCAP-18) were measured at baseline and during follow-up. Results: iPTH levels decreased in the study group appropriately and were more significantly decreased at 16 weeks. Study group had significantly increased 25(OH)D₃ levels. In addition, the study group had significantly increased serum hCAP-18 levels compared with control group. Correlation analysis showed a significant correlation between the percentage increase in serum hCAP-18 and 25(OH)D₃ levels. Conclusions: Cholecalciferol, in combination with paricalcitol, additively lowers the iPTH levels in a significant number of patients after 16 weeks of supplementation. A dose of 5000 IU/week of cholecalciferol could maintain serum 25(OH)D₃ levels above 30 ng/dL as early as 8 weeks after beginning supplementation. Doubling of serum cathelicidin levels were noted after 16 weeks of cholecalciferol supplementation in 40% of study patients.

Bone loss in chronic kidney disease: Quantity or quality?

Chronic kidney disease (CKD) patients experience bone loss and fracture because of a specific CKD-related systemic disorder known as CKD-mineral bone disorder (CKD-MBD). The bone turnover, mineralization, and volume (TMV) system describes the morphological bone lesions in renal osteodystrophy related to CKD-MBD. Bone turnover and bone volume are defined as high, normal, or low, and bone mineralization is classified as normal or abnormal. All types of bone histology related to TMV are responsible for both bone quantity and bone quality losses in CKD patients. This review focuses on current bone quantity and bone quality losses in CKD patients and finally discusses potential therapeutic measures.

Vitamin D and cardiovascular disease prevention

Vitamin D is a precursor of the steroid hormone calcitriol that is crucial for bone and mineral metabolism. Both the high prevalence of vitamin D deficiency in the general population and the identification of the vitamin D receptor in the heart and blood vessels raised interest in the potential cardiovascular effects of vitamin D. Experimental studies have demonstrated various cardiovascular protective actions of vitamin D, but vitamin D intoxication in animals is known to induce vascular calcification. In meta-analyses of epidemiological studies, vitamin D deficiency is associated with an increased cardiovascular risk. Findings from Mendelian randomization studies and randomized, controlled trials (RCTs) do not indicate significant effects of a general vitamin D supplementation on cardiovascular outcomes. Previous RCTs, however, were not adequately designed to address extraskeletal events, and did not focus on vitamin D-deficient individuals. Therefore, currently available evidence does not support cardiovascular benefits or harms of vitamin D supplementation with the commonly used doses, and whether vitamin D has cardiovascular effects in individuals with overt vitamin D deficiency remains to be evaluated. Here, we provide an update on clinical studies on vitamin D and cardiovascular risk, discuss ongoing vitamin D research, and consider the management of vitamin D deficiency from a cardiovascular health perspective.