Vitamin D receptor activators can protect against vascular calcification

Role of Nutrients in Pediatric Non-Dialysis Chronic Kidney Disease: From Pathogenesis to Correct Supplementation

Nutrition management is fundamental for children with chronic kidney disease (CKD). Fluid balance and low-protein and low-sodium diets are the more stressed fields from a nutritional point of view. At the same time, the role of micronutrients is often underestimated. Starting from the causes that could lead to potential micronutrient deficiencies in these patients, this review considers all micronutrients that could be administered in CKD to improve the prognosis of this disease.

Epimeric vitamin D and cardiovascular structure and function in advanced CKD and after kidney transplantation

BACKGROUND

25-hydroxyvitamin D can undergo C-3 epimerization to produce 3-epi-25(OH)D3. 3-epi-25(OH)D3 levels decline in chronic kidney disease (CKD), but its role in regulating the cardiovascular system is unknown. Herein, we examined the relationship between 3-epi-25(OH)D3, and cardiovascular functional and structural endpoints in patients with CKD.

METHODS

We examined n = 165 patients with advanced CKD from the Cardiopulmonary Exercise Testing in Renal Failure and After Kidney Transplantation (CAPER) study cohort, including those who underwent kidney transplant (KTR, n = 76) and waitlisted patients who did not (NTWC, n = 89). All patients underwent cardiopulmonary exercise testing and echocardiography at baseline, 2 months and 12 months. Serum 3-epi-25(OH)D3 was analyzed by liquid chromatography-tandem mass spectrometry.

RESULTS

Patients were stratified into quartiles of baseline 3-epi-25(OH)D3 (Q1: <0.4 ng/mL, n = 51; Q2: 0.4 ng/mL, n = 26; Q3: 0.5-0.7 ng/mL, n = 47; Q4: ≥0.8 ng/mL, n = 41). Patients in Q1 exhibited lower peak oxygen uptake [VO2Peak = 18.4 (16.2-20.8) mL/min/kg] compared with Q4 [20.8 (18.6-23.2) mL/min/kg; P = .009]. Linear mixed regression model showed that 3-epi-25(OH)D3 levels increased in KTR [from 0.47 (0.30) ng/mL to 0.90 (0.45) ng/mL] and declined in NTWC [from 0.61 (0.32) ng/mL to 0.45 (0.29) ng/mL; P < .001]. Serum 3-epi-25(OH)D3 was associated with VO2Peak longitudinally in both groups [KTR: β (standard error) = 2.53 (0.56), P < .001; NTWC: 2.73 (0.70), P < .001], but was not with left ventricular mass or arterial stiffness. Non-epimeric 25(OH)D3, 24,25(OH)2D3 and the 25(OH)D3:24,25(OH)2D3 ratio were not associated with any cardiovascular outcome (all P > .05).

CONCLUSIONS

Changes in 3-epi-25(OH)D3 levels may regulate cardiovascular functional capacity in patients with advanced CKD.

Effect of calcitriol treatment on arterial stiffness in people with type 2 diabetes and stage 3 chronic kidney disease

AIMS

Active vitamin D deficiency is associated with increased aortic-pulse wave velocity (Ao-PWV) in people with type 2 diabetes (T2DM) and chronic kidney disease (CKD). There are no randomised controlled trials investigating the effect of active vitamin D treatment on Ao-PWV in people with T2DM and CKD.

METHODS

A 48-week duration single-centre randomised double-blind parallel-group trial examined the impact of oral 1,25 dihydroxyvitamin D (calcitriol 0.25 mcg OD) as compared to placebo on a primary endpoint of Ao-PWV. People with T2DM and stable stage 3 CKD with intact parathyroid hormone (iPTH) level >30 pg/mL were eligible.

RESULTS

In total, 127 (70% male) people were randomised (calcitriol n = 64 or placebo n = 63). There was no change in Ao-PWV observed, mean ± standard deviation (SD), in the calcitriol group of 11.79 (±2.5) to 12.08 (3.0) m/s as compared to 10.90 (±2.4) to 11.39 (±2.6) m/s with placebo. The between-treatment group adjusted mean (95% confidence interval [(CI]] change was 0.23 (-0.58 to 1.05) m/s, P = .57. No effect of calcitriol was observed on central arterial pressures, albuminuria, serum calcium or phosphate levels. However, iPTH fell with calcitriol treatment (mean [95% CI] between-group difference of -27.8 (-42.3 to -13.2) pg/mL, P < .001.

CONCLUSION

In T2DM and stage 3 CKD, calcitriol as compared to placebo does not improve Ao-PWV or other markers of arterial stiffness. Our study does not provide evidence for the use of active vitamin D for improving arterial stiffness in T2DM with stage 3 CKD.

Vascular Calcification and the Gut and Blood Microbiome in Chronic Kidney Disease Patients on Peritoneal Dialysis: A Pilot Study

Vascular calcification (VC) is a frequent condition in chronic kidney disease (CKD) and a well-established risk factor for the development of cardiovascular disease (CVD). Gut dysbiosis may contribute to CVD and inflammation in CKD patients. Nonetheless, the role of gut and blood microbiomes in CKD-associated VC remains unknown. Therefore, this pilot study aimed to explore the link between gut and blood microbiomes and VC in CKD patients on peritoneal dialysis (CKD-PD). Our results showed relative changes in specific taxa between CKD-PD patients with and without VC, namely Coprobacter, Coprococcus 3, Lactobacillus, and Eubacterium eligens group in the gut, and Cutibacterium, Pajaroellobacter, Devosia, Hyphomicrobium, and Pelomonas in the blood. An association between VC and all-cause mortality risk in CKD-PD patients was also observed, and patients with higher mortality risk corroborate the changes of Eubacterium eligens in the gut and Devosia genus in the blood. Although we did not find differences in uremic toxins, intestinal translocation markers, and inflammatory parameters among CKD-PD patients with and without VC, soluble CD14 (sCD14), a nonspecific marker of monocyte activation, positively correlated with VC severity. Therefore, gut Eubacterium eligens group, blood Devosia, and circulating sCD14 should be further explored as biomarkers for VC, CVD, and mortality risk in CKD.

Vascular Calcification in Chronic Kidney Disease: Distinct Features of Pathogenesis and Clinical Implication

Vascular calcification (VC) is highly prevalent in patients with chronic kidney disease (CKD) and leads to increased cardiovascular morbidity and mortality. In patients with CKD, traditional factors do not fully explain the high prevalence of VC. This suggests that a CKD-specific pathobiology is involved in the development of VC and mounting evidence indicates that VC in CKD patients has distinct features of clinical presentation and that clinical implications are changed compared to those in the general population. In this review, we discuss the mechanism, diagnostic imaging modalities, clinical features and implications, and management of VC in patients with CKD.

Chronic kidney disease (CKD) is associated with a higher prevalence of vascular calcification (VC) and cardiovascular disease. VC in CKD patients showed different pathophysiological features from those of the general population. The pathogenesis of VC in CKD is a highly organized process, and prior studies have suggested that patients with CKD have their own specific contributors to the phenotypic change of vascular smooth muscle cells (VSMCs), including uremic toxins, CKD-mineral and bone disease (CKD-MBD), inflammation, and oxidative stress. For the diagnosis and monitoring of VC in CKD, several imaging modalities, including plain radiography, ultrasound, and computed tomography have been utilized. VC in CKD patients has distinct clinical features and implications. CKD patients revealed a more intense and more prevalent calcification on the intimal and medial layers, whereas intimal calcification is predominantly observed in the general population. While a higher VC score is clearly associated with a higher risk of all-cause mortality and cardiovascular events, a greater VC score in CKD patients does not fully reflect the burden of atherosclerosis, because they have more calcification at equal volumes of atheromatous plaques. The primary goal of VC treatment in CKD is the prevention of VC progression, and the main management is to control the biochemical components of CKD-MBD. Cinacalcet and non-calcium-containing phosphate binders are the mainstay of VC prevention in CKD-MBD management. VC in patients with CKD is an ongoing area of research and is expected to advance soon.

Oral Calcitriol Use, Vertebral Fractures, and Vitamin K in Hemodialysis Patients: A Cross-Sectional Study

Fractures and vascular calcifications (VCs) are common in patients with chronic kidney disease (CKD). They are related to abnormalities in vitamin D metabolism, calcium, phosphorus, parathyroid hormone, and fibroblast growth factor 23 (FGF23)/Klotho that occur with CKD. Impaired vitamin D metabolism and abnormal levels of calcium, phosphate, parathyroid hormone (PTH), and FGF23/Klotho drive bone and vascular changes in CKD. It is unclear if oral calcitriol safely mitigates fracture risk without increasing the burden of calcifications. Therefore, we investigated whether treatment with calcitriol affected the prevalence of fractures and VC progression in hemodialysis (HD) patients. This report is a secondary analysis of the Vitamin K Italian (VIKI) study, a cross-sectional study involving 387 HD patients. We assessed vitamin 25(OH)D, alkaline phosphatase, PTH, calcium, phosphate, osteocalcin or bone Gla protein, matrix Gla protein, and vitamin K levels. Vertebral fractures (VFs) and VCs were determined by spine radiograph. A reduction of >20% of vertebral body height was considered a VF. VCs were quantified by the length of calcific lesions along the arteries. The patients treated with oral calcitriol were 177 of 387 patients (45.7%). The prevalence of VF was lower in patients receiving oral calcitriol than in those untreated (48.6% versus 61.0%, p = 0.015), whereas the presence of aortic and iliac calcifications was similar (aortic: 81.9% versus 79.5%, respectively, p = 0.552; iliac: 52.0% and 59.5%, respectively, p = 0.167). In multivariable logistic regression analysis, oral calcitriol was associated with a 40.2% reduced odds of fracture (OR 0.598; 95% confidence interval [CI], 0.363-0.985; p = 0.043). In conclusion, we found a significant association between oral calcitriol and lower VF in HD patients without an increase in the burden of VC. Further prospective and interventional studies are needed to confirm these findings. © 2021 American Society for Bone and Mineral Research (ASBMR).

Clinical Approach to Vascular Calcification in Patients With Non-dialysis Dependent Chronic Kidney Disease: Mineral-Bone Disorder-Related Aspects

Chronic kidney disease (CKD) is associated with a very high morbimortality, mainly from cardiovascular origin, and CKD is currently considered in the high- or very high risk- cardiovascular risk category. CKD-mineral and bone disorders (CKD-MBDs), including vascular and/or valvular calcifications, are also associated with these poor outcomes. Vascular calcification (VC) is very prevalent (both intimal and medial), even in non-dialysis dependent patients, with a greater severity and more rapid progression. Simple X-ray based-scores such as Adragão's (AS) are useful prognostic tools and AS (even AS based on hand-X-ray only) may be superior to the classic Kauppila's score when evaluating non-dialysis CKD patients. Thus, in this mini-review, we briefly review CKD-MBD-related aspects of VC and its complex pathophysiology including the vast array of contributors and inhibitors. Furthermore, although VC is a surrogate marker and is not yet considered a treatment target, we consider that the presence of VC may be relevant in guiding therapeutic interventions, unless all patients are treated with the mindset of reducing the incidence or progression of VC with the currently available armamentarium. Avoiding phosphate loading, restricting calcium-based phosphate binders and high doses of vitamin D, and avoiding normalizing (within the normal limits for the assay) parathyroid hormone levels seem logical approaches. The availability of new drugs and future studies, including patients in early stages of CKD, may lead to significant improvements not only in patient risk stratification but also in attenuating the accelerated progression of VC in CKD.

Vitamin D: Not Just Bone Metabolism but a Key Player in Cardiovascular Diseases

Vitamin D is the first item of drug expenditure for the treatment of osteoporosis. Its deficiency is a condition that affects not only older individuals but also young people. Recently, the scientific community has focused its attention on the possible role of vitamin D in the development of several chronic diseases such as cardiovascular and metabolic diseases. This review aims to highlight the possible role of vitamin D in cardiovascular and metabolic diseases. In particular, here we examine (1) the role of vitamin D in diabetes mellitus, metabolic syndrome, and obesity, and its influence on insulin secretion; (2) its role in atherosclerosis, in which chronic vitamin D deficiency, lower than 20 ng/mL (50 nmol/L), has emerged among the new risk factors; (3) the role of vitamin D in essential hypertension, in which low plasma levels of vitamin D have been associated with both an increase in the prevalence of hypertension and diastolic hypertension; (4) the role of vitamin D in peripheral arteriopathies and aneurysmal pathology, reporting that patients with peripheral artery diseases had lower vitamin D values than non-suffering PAD controls; (5) the genetic and epigenetic role of vitamin D, highlighting its transcriptional regulation capacity; and (6) the role of vitamin D in cardiac remodeling and disease. Despite the many observational studies and meta-analyses supporting the critical role of vitamin D in cardiovascular physiopathology, clinical trials designed to evaluate the specific role of vitamin D in cardiovascular disease are scarce. The characterization of the importance of vitamin D as a marker of pathology should represent a future research challenge.

PTH suppression by calcitriol does not predict off-target actions in experimental CKD

Vitamin D receptor agonist (VDRA) therapy for PTH suppression is a mainstay for patients with severe CKD. Calcitriol (1,25‐(OH)₂D₃) is a former first‐line VDRA in CKD treatment. However, a consequence of its use in CKD is accelerated vascular calcification (VC). An experimental CKD model was used to determine whether altering the calcitriol delivery profile to obtain different PTH suppression levels could improve vascular health outcomes. High adenine diet (0.25%) was used to generate experimental CKD in rats. CKD rats were treated using different calcitriol dosing strategies: (a) 20 ng/kg SD (n = 8), (b) 80 ng/kg SD (n = 8), (c) 5 ng/kg QID (n = 9), or (d) 20 ng/kg QID (n = 9). Multiple targets of calcitriol were assessed which include arterial calcium and phosphate as well as circulating calcium, phosphate, PTH, FGF‐23, VWF, and vitamin D metabolome. PTH suppression occurred dose‐dependently after 1‐week calcitriol treatment (P < .01), but the suppressive effect was lost over time. Both VC and circulating FGF‐23 increased > 10× in all calcitriol‐treated rats (P < .05 and P < .001, respectively); similarly, circulating VWF increased at all time points (P < .05). Ad‐hoc analysis of CKD morbidities in treated rats indicated no differences in negative outcomes based on PTH suppression level (minimal‐, target‐, and over‐). Comparing different calcitriol dosing strategies revealed the following: (a) despite initial calcitriol‐influenced PTH suppression across all treatments, the ability to continually suppress PTH was markedly reduced by study conclusion and (b) PTH suppression level is not an adequate proxy for improvements in overall CKD morbidity. These findings show (a) a more holistic approach to evaluate CKD treatment efficacy aside from PTH suppression is needed and (b) that other VDRA therapies should be examined in CKD treatment.

Vitamin D Receptor (VDR) Gene Polymorphisms and Risk of Coronary Artery Disease (CAD): Systematic Review and Meta-analysis

Several studies have noted that vitamin D receptor (VDR) gene polymorphisms are involved in the susceptibility to Coronary artery disease (CAD). Nonetheless, the results have been inconclusive. Here, we performed the most up-to-date analysis of the association between VDR gene polymorphisms and risk of CAD. We conducted a comprehensive systematic search in the major electronic database, including Scopus and PubMed to look up for relevant studies evaluating the association between the VDR gene FokI (rs2228570), TaqI (rs731236), BsmI (rs1544410), and ApaI (rs7975232) polymorphisms and susceptibility to CAD published before December 2019. The level of association between VDR gene polymorphisms and susceptibility to CAD in the polled analysis was calculated by odds ratio (OR) and the corresponding 95% confidence interval (CI). We found 14 articles containing 20,398 cases and 9371 controls. The analysis revealed that all genetic models in the FokI SNP were associated with increased risk of CAD. Furthermore, for the ApaI SNP, except recessive model, all other genetic models significantly increased the risk of CAD in the overall analysis. In addition, it was divulged that both FokI and ApaI SNPs were involved in increasing the risk of CAD in Asians and Europeans in a number of models. FokI and ApaI polymorphisms may confer a susceptibility genetic risk factor for development of CAD, particularly in the Asian population.

Vascular calcification of chronic kidney disease: A brief review

Vascular calcification (VC) is highly prevalent among patients with chronic kidney disease (CKD). There is growing evidence that there is more underlying this condition than the histological presentation of atherosclerotic plaque and arteriosclerosis and that the risk of cardiovascular disease in the context of CKD might be explained by the presence of VC. While VC has been observed in the absence of overt abnormal mineral metabolism, this association is coupled to abnormal homeostasis of minerals in patients with CKD, due to hyperphosphatemia and hypercalcemia. Furthermore, recent studies have shown that the differentiation of vascular smooth muscle cells into an osteogenic phenotype is highly regulated by pro-calcifying and anti-calcifying factors. There are several imaging modalities currently used in clinical practice to evaluate the extent and severity of VC; each has different advantages and limitations. Although there is no universally accepted method for the treatment of VC, there is growing evidence of the beneficial effects of medical therapy for the condition. This study discusses the mechanism underlying VC, imaging modalities used for evaluation of the condition, and possible treatments.

An update on vascular calcification and potential therapeutics

Pathological calcification is a major cause of cardiovascular morbidities primarily in population with chronic kidney disease (CKD), end stage renal diseases (ERSD) and metabolic disorders. Investigators have accepted the fact that vascular calcification is not a passive process but a highly complex, cell mediated, active process in patients with cardiovascular disease (CVD) resulting from, metabolic insults of bone fragility, diabetes, hypertension, dyslipidemia and atherosclerosis. Over the years, studies have revealed various mechanisms of vascular calcification like induction of bone formation, apoptosis, alteration in Ca-P balance and loss of inhibition. Novel clinical studies targeting cellular mechanisms of calcification provide promising and potential avenues for drug development. The interventions include phosphate binders, sodium thiosulphate, vitamin K, calcimimetics, vitamin D, bisphosphonates, Myoinositol hexaphosphate (IP6), Denosumab and TNAP inhibitors. Concurrently investigators are also working towards reversing or curing pathological calcification. This review focuses on the relationship of vascular calcification to clinical diseases, regulators and factors causing calcification including genetics which have been identified. At present, there is lack of any significant preventive measures for calcifications and hence this review explores further possibilities for drug development and treatment modalities.

Impaired arterial vitamin D signaling occurs in the development of vascular calcification

Conflicting data exists as to whether vitamin D receptor agonists (VDRa) are protective of arterial calcification. Confounding this, is the inherent physiological differences between human and animal experimental models and our current fragmented understanding of arterial vitamin D metabolism, their alterations in disease states and responses to VDRa’s. Herein, the study aims to address these problems by leveraging frontiers in human arterial organ culture models. Human arteries were collected from a total of 24 patients (healthy controls, n = 12; end-stage CKD, n = 12). Cross-sectional and interventional studies were performed using arterial organ cultures treated with normal and calcifying (containing 5mmol/L CaCl₂ and 5mmol/L β-glycerophosphate) medium, ex vivo. To assess the role of VDRa therapy, arteries were treated with either calcitriol or paricalcitol. We found that human arteries express a functionally active vitamin D system, including the VDR, 1α-hydroxylase and 24-hydroxylase (24-OHase) components and these were dysregulated in CKD arteries. VDRa therapy increased VDR expression in healthy arteries (p<0.01) but not in CKD arteries. Arterial 1α-OHase (p<0.05) and 24-OHase mRNA and protein expression were modulated differentially in healthy and CKD arteries by VDRa therapy. VDRa exposure suppressed Runx2 and MMP-9 expression in CKD arteries, however only paricalcitol suppressed MMP-2. VDRa exposure did not modulate arterial calcification in all organ culture models. However, VDRa reduced expression of senescence associated β-galactosidase (SAβG) staining in human aortic-smooth muscle cells under calcifying conditions, in vitro. In conclusion, maladaptation of arterial vitamin D signaling components occurs in CKD. VDRa exposure can exert vasculo-protective effects and seems critical for the regulation of arterial health in CKD.

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

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

Mechanisms of Vascular Calcification in Kidney Disease

The increase in prevalence and severity of vascular calcification in chronic kidney disease is a result of complex interactions between changes in the vascular bed, mineral metabolites, and other uremic factors. Vascular calcification can occur in the intima and the media of arterial wall. Under permissive conditions, vascular smooth muscle cells (VSMCs) can transform to osteoblast-like phenotype. The membrane-bound vesicles released from transformed VSMCs and the apoptotic bodies derived from dying VSMCs serve as nucleating structures for calcium crystal formation. Alterations in the quality and the quantity of endogenous calcification inhibitors also give rise to an environment that potentiates calcification.

Vitamin D as A Protector of Arterial Health: Potential Role in Peripheral Arterial Disease Formation

Atherosclerotic occlusive diseases and aneurysms that affect large and medium-sized arteries outside the cardiac and cerebral circulation are collectively known as peripheral arterial disease (PAD). With a rise in the rate of aging population worldwide, the number of people diagnosed with PAD is rapidly increasing. The micronutrient vitamin D is an important steroid hormone that acts on many crucial cellular mechanisms. Experimental studies suggest that optimal levels of vitamin D have beneficial effects on the heart and blood vessels; however, high vitamin D concentrations have been implicated in promoting vascular calcification and arterial stiffness. Observations from various clinical studies shows that deficiency of vitamin D has been associated with a greater risk of PAD. Epidemiological studies have often reported an inverse relation between circulating vitamin D status measured in terms of 25-hydroxivitamin D [25(OH)D] levels and increased cardiovascular disease risk; however, randomized controlled trials did not show a consistent positive effect of vitamin D supplementation on cardiovascular disease risk or events. Even though PAD shares all the major risk factors with cardiovascular diseases, the effect of vitamin D deficiency in PAD is not clear. Current evidence suggests a strong role of vitamin D in promoting genomic and epigenomic changes. This review summarises the current literature that supports the notion that vitamin D deficiency may promote PAD formation. A better understanding of underlying pathological mechanisms will open up new therapeutic possibilities which is the main unmet need in PAD management. Furthermore, epigenetic evidence shows that a more holistic approach towards PAD prevention that incorporates a healthy lifestyle, adequate exercise and optimal nutrition may be more effective in protecting the genome and maintaining a healthy vasculature.

Evaluation of the association of Wnt signaling with coronary artery calcification in patients on dialysis with severe secondary hyperparathyroidism

BACKGROUND

Patients with end-stage renal disease have a higher risk of death from cardiovascular events, which can be mainly attributed to coronary artery calcification (CAC). Wnt signaling is involved in vascular development and may play a role in vascular calcification. This study aimed to evaluate CAC prevalence in patients on dialysis with severe secondary hyperparathyroidism (SHPT) and identify CAC risk factors.

METHODS

The study is a retrospective analysis of the severe hyperparathyroidism registration study that prospectively recruited patients on dialysis with severe SHPT who were candidates for parathyroidectomy, from October 2013 to May 2015. CAC and bone mineral density (BMD) were measured. Demographic and clinical data including calcium, phosphorus, alkaline phosphatase, intact parathyroid hormone, Dickkopf-related protein 1 (DKK1), and sclerostin levels were analyzed. CAC scores were reported in Agatston units (AU).

RESULTS

A total of 61 patients were included in this study. No CAC, mild CAC (<100 AU), moderate CAC (>100 AU), and severe CAC (>400 AU) were observed in 4.9%, 11.4%, 14.8%, and 68.9% of patients, respectively. DKK1 and sclerostin were not associated with CAC. In univariate analysis, CAC was significantly correlated with age, sex (male), total cholesterol, and intravenous pulse calcitriol (p<0.05). CAC was not inversely correlated with the BMD, T scores, or Z scores of the femoral neck (p>0.05). In multivariate analysis, the stepwise forward multiple linear regression revealed that CAC was associated with age, male sex and intravenous pulse calcitriol (p<0.05). Furthermore, serum sclerostin was positively correlated with the BMD of the femoral neck but negatively associated with intact parathyroid hormone (p<0.05). Serum sclerostin was significantly associated with severely low bone mass with Z-scores<-2.5 of the femoral neck, even when adjusted for serum intact parathyroid hormone, vitamin D status, dialysis pattern, sex, and DKK-1 (p<0.05).

CONCLUSIONS

The patients on dialysis with severe SHPT have a high prevalence of vascular calcification. Although the Wnt signaling pathway could play a role in hyperparathyroid bone disease, CAC may be mainly due to the treatment modality rather than the Wnt signaling pathway associated bone metabolism in patients on dialysis with severe SHPT.

Activation of vitamin D receptor attenuates high glucose-induced cellular injury partially dependent on CYP2J5 in murine renal tubule epithelial cell

AIMS

Vitamin D and its receptor, vitamin D receptor (VDR), have renoprotection effect against diabetic nephropathy (DN). But the exact mechanism has not been fully elucidated. Epoxyeicosatrienoic acids (EETs) are cytochrome P450 (CYP) epoxygenase-derived metabolites of arachidonic acid, protecting against diabetes and DN. Herein, we hypothesized that activation of VDR attenuated high glucose-induced cellular injury in renal tubular epithelial cells partially through up-regulating CYP2J5 expression.

MAIN METHODS

Streptozotocin (STZ) was injected to induce diabetic in wild type and Vdr^-/- mice. The effects of VDR knockout and an activator of VDR, paricalcitol, on the renal injury were detected. In vitro, a murine kidney proximal tubule epithelial cell line BU.MPT induced by high glucose were treated with or without paricalcitol (30 mM) for 12 h or 24 h.

KEY FINDINGS

The expression of CYP2J5 was significantly decreased both in wild type and Vdr^-/- diabetic mice induced by STZ. The STZ-induced kidney architecture damage and apoptosis rate in Vdr^-/- mice were more severe. In vitro, high glucose treatment strongly reduced the CYP2J5 expression and the synthesis of 14,15-EET in BU.MPT cells. Supplement of 14,15-EET significantly reduced the lactate dehydrogenase (LDH) release induced by high glucose in BU.MPT cells. Furthermore, treatment with paricalcitol attenuated cellular injury and restored the expression of CYP2J5 reduced by high glucose in BU.MPT cells.

SIGNIFICANCE

We conclude that activation of VDR attenuates high glucose-induced cellular injury partially dependent on CYP2J5 in murine renal tubule epithelial cells and paricalcitol may represent a potential therapy for DN.

Vitamin D-regulated osteocytic sclerostin and BMP2 modulate uremic extraskeletal calcification

We induced chronic kidney disease (CKD) with adenine in WT mice, mice with osteocyte-specific deletion of Cyp27b1, encoding the 25-hydroxyvitamin D 1(OH)ase [Oct-1(OH)ase-/-], and mice with global deletion of Cyp27b1 [global-1α(OH)ase-/-]; we then compared extraskeletal calcification. After adenine treatment, mice displayed increased blood urea nitrogen, decreased serum 1,25(OH)2D, and severe hyperparathyroidism. Skeletal expression of Cyp27b1 and of sclerostin and serum sclerostin all increased in WT mice but not in Oct-1α(OH)ase-/- mice or global-1α(OH)ase-/- mice. In contrast, skeletal expression of BMP2 and serum BMP2 rose in the Oct-1α(OH)ase-/- mice and in the global-1α(OH)ase-/- mice. Extraskeletal calcification occurred in muscle and blood vessels of mice with CKD and was highest in Oct-1α(OH)ase-/-mice. In vitro, recombinant sclerostin (100 ng/mL) significantly suppressed BMP2-induced osteoblastic transdifferentiation of vascular smooth muscle A7r5 cells and diminished BMP2-induced mineralization. Our study provides evidence that local osteocytic production of 1,25(OH)2D stimulates sclerostin and inhibits BMP2 production in murine CKD, thus mitigating osteoblastic transdifferentiation and mineralization of soft tissues. Increased osteocytic 1,25(OH)2D production, triggered by renal malfunction, may represent a "primary defensive response" to protect the organism from ectopic calcification by increasing sclerostin and suppressing BMP2 production.

Vitamin D and Atherosclerotic Cardiovascular Disease

CONTEXT

A large body of experimental and observational data has implicated vitamin D deficiency in the development of cardiovascular disease. However, evidence to support routine vitamin D supplementation to prevent or treat cardiovascular disease is lacking.

EVIDENCE ACQUISITION

A comprehensive literature review was performed using Pubmed and other literature search engines.

EVIDENCE SYNTHESIS

Mounting epidemiological evidence and data from Mendelian randomization studies support a link between vitamin D deficiency and adverse cardiovascular health outcomes, but randomized trial evidence to support vitamin D supplementation is sparse. Current public health guidelines restrict vitamin D intake recommendations to the maintenance of bone health and prevention of fractures. Two recently published large trials (VITAL and ViDA) that assessed the role of moderate-to-high dose vitamin D supplementation as primary prevention for cardiovascular outcomes in the general population had null results, and previous randomized trials have also been generally negative. These findings from general population cohorts that are largely replete in vitamin D may not be applicable to chronic kidney disease (CKD) populations, in which the use of active (1α-hydroxylated) vitamin D compounds is prevalent, or to other high-risk populations. Additionally, recent trials in the CKD population, and trials using vitamin D analogues have been limited.

CONCLUSIONS

Current randomized trials of vitamin D supplementation do not support benefits for cardiovascular health, but the evidence remains inconclusive. Additional randomized trials assessing larger numbers of participants with low baseline vitamin D levels, having longer follow-up periods, and testing higher vitamin D dosages, are needed to guide clinical practice.

Vitamin D and Calcimimetics in Cardiovascular Disease

Cardiovascular disease has earned its place as one of the leading noncommunicable diseases that has become a modern-day global epidemic. The increasing incidence and prevalence of chronic kidney disease (CKD) has added to this enormous burden, given that CKD is now recognized as an established risk factor for accelerated cardiovascular disease. In fact, cardiovascular disease remains the leading cause of death in the CKD population, with significant prognostic implications. Alterations in vitamin D levels as renal function declines has been linked invariably to the development of cardiovascular disease beyond a mere epiphenomenon, and has become an important focus in recent years in our search for new therapies. Another compound, cinacalcet, which belongs to the calcimimetic class of agents, also has taken center stage over the past few years as a potential cardiovasculoprotective agent. However, given limited well-designed randomized trials to inform us, our clinical practice for the management of cardiovascular disease in CKD has not been adequately refined. This article considers the biological mechanisms, regulation, and current experimental, clinical, and trial data available to help guide the therapeutic use of vitamin D and calcimimetics in the setting of CKD and cardiovascular disease.

Vitamin D and kidney disease

Calcium and phosphorus are essential minerals required for many critical biologic functions including cell signaling, energy metabolism, skeletal growth and integrity. Calcium and phosphate homeostasis are maintained primarily by regulation of epithelial calcium and phosphate cotransport in the kidney and intestine, processes that are tightly regulated by hormones including 1,25 dihydroxyvitamin D (1,25(OH)2D), fibroblast growth factor 23 (FGF23) and parathyroid hormone (PTH). In patients with chronic kidney disease (CKD), as renal function declines, disruption of feedback loops between these hormones have adverse consequences on several organ systems, including the skeleton, heart and vascular system. CKD-associated mineral and bone disorder (CKD-MBD) is defined as a systemic disorder of mineral and bone metabolism due to CKD manifested by abnormalities of calcium, phosphorus, PTH or vitamin D metabolism, abnormalities of bone turnover, mineralization and volume, and ectopic soft tissue calcification. Complications of CKD-MBD include vascular calcification, stroke, skeletal fracture and increased risk of death. Increased FGF23 and PTH concentrations, and 1,25(OH)2D deficiency contribute to the pathogenesis of CKD-MBD. Therefore, treatment of patients with CKD-MBD is focused on restoring the feedback loops to maintain normal calcium and phosphate balance to prevent skeletal and cardiovascular complications.

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.

Coronary artery calcification score and common iliac artery calcification score in non-dialysis CKD patients

AIM

Many studies have validated Agatston's coronary artery calcification score (CACS) for assessing vascular calcification (VC) in chronic kidney disease (CKD) patients. This study aimed to evaluate the CACS and common iliac artery calcification score (IACS) and to examine the variables related to each score.

METHODS

The subjects were 145 non-dialysis CKD patients. The CACS and IACS were determined using the same thoracicoabdominal multi-detector computed tomography. Multiple regression analyses were performed to assess the factors associated with the CACS or IACS. The associations between progression to renal replacement therapy (RRT) and the CACS or IACS were studied using Cox hazards models.

RESULTS

The subjects' median age, estimated glomerular filtration rate (eGFR), and follow-up period were 72 (62-78) years, 32 (18-50) mL/min/1.73m2 , and 864 (550-1425) days, respectively. Age, diabetes, the serum phosphate level, and the eGFR were found to be significant factors of the CACS [β (95% CI): 0.38 (0.02-0.04), P < 0.0001, 0.28 (0.19-0.50), P < 0.0001, 0.16 (0.03-0.45), P < 0.05 and -0.15 (-0.02-0.00), P < 0.05, respectively]. Age and diabetes were shown to be significant factors of the IACS [β (95% CI): 0.53 (0.04-0.06), P < 0.0001, and 0.18 (0.07-0.40), P < 0.01, respectively]. Progression to RRT occurred in 31 patients and was significantly associated with the CACS (hazard ratio: 1.01, P < 0.01), urinary protein level and eGFR, but not the IACS.

CONCLUSION

Chronic kidney disease related risk factors for VC, such as the eGFR and hyperphosphataemia, are significantly associated with a high CACS, but not a high IACS, and the CACS is a significant predictor of progression to RRT.

Public health relevance of drug-nutrition interactions

The public health relevance of drug–nutrition interactions is currently highly undervalued and overlooked. This is particularly the case for elderly persons where multi-morbidity and consequently polypharmacy is very common. Vitamins and other micronutrients have central functions in metabolism, and their interactions with drugs may result in clinically relevant physiological impairments but possibly also in positive effects. On 12 April 2016, the University Medical Center Groningen (The Netherlands), as part of its Healthy Ageing program, organized a workshop on the public health relevance of drug–nutrient interactions. In this meeting, experts in the field presented results from recent studies on interactions between pharmaceuticals and nutrients, and discussed the role of nutrition for elderly, focusing on those persons receiving pharmaceutical treatment. This paper summarizes the proceedings of the symposium and provides an outlook for future research needs and public health measures. Since food, pharma and health are closely interconnected domains, awareness is needed in the medical community about the potential relevance of drug–nutrition interactions. Experts and stakeholders should advocate for the integration of drug–nutrition evaluations in the drug development process. Strategies for the individual patients should be developed, by installing drug review protocols, screening for malnutrition and integrating this topic into the general medical advice.

Safety of Low-calcium Dialysate and its Effects on Coronary Artery Calcification in Patients Undergoing Maintenance Hemodialysis

To determine the safety of low-calcium-dialysate in patients undergoing maintenance hemodialysis (MHD) and its effects on coronary artery calcification (CAC) and analyze clinical risk factors for CAC. A total of 174 MHD patients were recruited and randomly divided into two groups: high-calcium dialysate (HCD, 1.5 mmol/L Ca²⁺) and low-calcium dialysate (LCD, 1.25 mmol/L Ca²⁺). Changes in CAC score (CACS) and cardiac function were evaluated using spiral computed tomography and echocardiography, respectively. Clinical and laboratory parameters were measured. Intra-dialysis adverse reactions were recorded and compared between the two groups. CACS was significantly lower in the LCD group than in the HCD group by the end of the study. Cardiac E/A_max was significantly higher in the LCD group than in the HCD group by the end of the study. There was no significant difference in the frequency of any intra-dialysis adverse reactions between the two groups during the study. LCD is helpful in maintaining cardiac diastolic function and postponing CAC progression. LCD does not increase intra-dialysis adverse reactions. Age may be the most important factor impacting CAC in MHD patients.

Therapeutic Interference With Vascular Calcification-Lessons From Klotho-Hypomorphic Mice and Beyond

Medial vascular calcification, a major pathophysiological process associated with cardiovascular disease and mortality, involves osteo-/chondrogenic transdifferentiation of vascular smooth muscle cells (VSMCs). In chronic kidney disease (CKD), osteo-/chondrogenic transdifferentiation of VSMCs and, thus, vascular calcification is mainly driven by hyperphosphatemia, resulting from impaired elimination of phosphate by the diseased kidneys. Hyperphosphatemia with subsequent vascular calcification is a hallmark of klotho-hypomorphic mice, which are characterized by rapid development of multiple age-related disorders and early death. In those animals, hyperphosphatemia results from unrestrained formation of 1,25(OH)₂D₃ with subsequent retention of calcium and phosphate. Analysis of klotho-hypomorphic mice and mice with vitamin D₃ overload uncovered several pathophysiological mechanisms participating in the orchestration of vascular calcification and several therapeutic opportunities to delay or even halt vascular calcification. The present brief review addresses the beneficial effects of bicarbonate, carbonic anhydrase inhibition, magnesium supplementation, mineralocorticoid receptor (MR) blockage, and ammonium salts. The case is made that bicarbonate is mainly effective by decreasing intestinal phosphate absorption, and that carbonic anhydrase inhibition leads to metabolic acidosis, which counteracts calcium-phosphate precipitation and VSMC transdifferentiation. Magnesium supplementation, MR blockage and ammonium salts are mainly effective by interference with osteo-/chondrogenic signaling in VSMCs. It should be pointed out that the, by far, most efficient substances are ammonium salts, which may virtually prevent vascular calcification. Future research will probably uncover further therapeutic options and, most importantly, reveal whether these observations in mice can be translated into treatment of patients suffering from vascular calcification, such as patients with CKD.

Etelcalcetide, A Novel Calcimimetic, Prevents Vascular Calcification in A Rat Model of Renal Insufficiency with Secondary Hyperparathyroidism

Etelcalcetide, a novel peptide agonist of the calcium-sensing receptor, prevents vascular calcification in a rat model of renal insufficiency with secondary hyperparathyroidism. Vascular calcification occurs frequently in patients with chronic kidney disease (CKD) and is a consequence of impaired mineral homeostasis and secondary hyperparathyroidism (SHPT). Etelcalcetide substantially lowers parathyroid hormone (PTH) and fibroblast growth factor-23 (FGF23) levels in SHPT patients on hemodialysis. This study compared the effects of etelcalcetide and paricalcitol on vascular calcification in rats with adenine-induced CKD and SHPT. Uremia and SHPT were induced in male Wistar rats fed a diet supplemented with 0.75% adenine for 4 weeks. Rats were injected with vehicle, etelcalcetide, or paricalcitol for 4 weeks from the beginning of adenine diet. Rats fed an adenine-free diet were included as nonuremic controls. Similar reductions in plasma PTH and parathyroid chief cell proliferation were observed in both etelcalcetide- and paricalcitol-treated rats. Serum calcium and phosphorus were significantly lower in etelcalcetide-treated uremic rats and was unchanged in paricalcitol-treated rats. Both serum FGF23 and aortic calcium content were significantly lower in etelcalcetide-treated uremic rats compared with either vehicle- or paricalcitol-treated uremic rats. The degree of aortic calcium content for etelcalcetide-treated rats was similar to that in nonuremic controls and corroborated findings of lack of histologic aortic mineralization in those groups. In conclusion, etelcalcetide and paricalcitol similarly attenuated progression of SHPT in an adenine rat model of CKD. However, etelcalcetide differentially prevented vascular calcification, at least in part, due to reductions in serum FGF23, calcium, and phosphorus levels.

High phosphate induces a pro-inflammatory response by vascular smooth muscle cells and modulation by vitamin D derivatives

In chronic kidney disease patients, high phosphate (HP) levels are associated with cardiovascular disease, the major cause of morbidity and mortality. Since serum phosphate has been independently correlated with inflammation, the present study aimed to investigate an independent direct effect of HP as a pro-inflammatory factor in VSMCs. A possible modulatory effect of vitamin D (VitD) was also investigated. The study was performed in an in vitro model of human aortic smooth muscle cells (HASMCs). Incubation of cells in an HP (3.3 mM) medium caused an increased expression of the pro-inflammatory mediators intercellular adhesion molecule 1 (ICAM-1), interleukins (ILs) IL-1β, IL-6, IL-8 and tumour necrosis factor α (TNF-α) (not corroborated at the protein levels for ICAM-1), as well as an increase in reactive oxygen/nitrogen species (ROS/RNS) production. This was accompanied by the activation of nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB) signalling as demonstrated by the increase in the nuclear translocation of nuclear factor κ-light-chain-enhancer of activated B cells protein 65 (p65-NF-κΒ) assessed by Western blotting and confocal microscopy. Since all these events were attenuated by an antioxidant pre-incubation with the radical scavenger Mn(III)tetrakis (4-benzoic acid) porphyrin (MnTBAP), it is suggested that the inflammatory response is upstream mediated by the ROS/RNS-induced activation of NF-κΒ. Addition of paricalcitol (PC) 3·10−8 M to cells in HP prevented the phosphate induced ROS/RNS increase, the activation of NF-κΒ and the cytokine up-regulation. A bimodal effect was observed, however, for different calcitriol (CTR) concentrations, 10−10 and 10−12 M attenuated but 10−8 M stimulated this phosphate induced pro-oxidative and pro-inflammatory response. Therefore, these findings provide novel mechanisms whereby HP may directly favour vascular dysfunctions and new insights into the protective effects exerted by VitD derivatives.

Effects of low calcium dialysate on the progression of coronary artery calcification in hemodialysis patients: An open-label 12-month randomized clinical trial

BACKGROUND

The association between the dialysate calcium level and coronary artery calcification (CAC) has not yet been evaluated in hemodialysis patients. The objective of this study was to determine whether lowering the dialysate calcium levels would decrease the progression of coronary artery calcification (CAC) compared to using standard calcium dialysate.

METHODS

We conducted an open-label randomized trial with parallel groups. The patients were randomly assigned to either 12-month treatment with low calcium dialysate (LCD; 1.25mmol/L, n=36) or standard calcium dialysate (SCD; 1.5mmol/L, n=40). The primary outcome was the change in the CAC scores assessed by 64-slice multidetector computed tomography after 12months.

RESULTS

During the treatment period, CAC scores increased in both groups, especially significant in LCD group (402.5±776.8, 580.5±1011.9, P=0.004). When we defined progressors as patients at second and third tertiles of CAC changes, progressor group had a higher proportion of LCD-treated patients than SCD-treated patients (P=0.0229). In multivariate analysis, LCD treatment is a significant risk factor for increase in CAC scores (odds ratio=5.720, 95% CI: 1.219-26.843, P=0.027).

CONCLUSIONS

Use of LCD may accelerate the progression of CAC in patients with chronic hemodialysis over a 12-month period.

TRIAL REGISTRATION

Clinical Research Information Service [Internet]; Osong (Chungcheongbuk-do): Korea Centers for Disease Control and Prevention, Ministry of Health and Welfare (Republic of Korea), 2010: KCT0000942. Available from: https://cris.nih.go.kr/cris/search/search_result_st01_kren.jsp?seq=3572&sLeft=2&type=my.

Comparison of the effects of novel vitamin D receptor analog VS-105 and paricalcitol on chronic kidney disease-mineral bone disorder in an experimental model of chronic kidney disease

When using vitamin D, the most important clinical problems are hypercalcemia, hyperphosphatemia, and vascular calcification. VS-105 is a novel vitamin D receptor (VDR) analog. In the present study, we compared the effects of VS-105 and paricalcitol on chronic kidney disease-mineral bone disorder (CKD-MBD) in a CKD rat model. We used male Sprague-Dawley (SD) rats and performed 5/6 nephrectomy at 8-9 weeks. At 10 weeks, the rats were classified into five groups and administered vehicle, low-dose paricalcitol (LP, 0.1μg/kg), high-dose paricalcitol (HP, 0.3μg/kg), low-dose VS-105 (LV, 0.2μg/kg), and high-dose VS-105 (HV, 0.6 μg/kg) three times a week for 10 weeks. There were no significant differences in blood pressure or renal function among the five groups. Alhough serum calcium levels were comparable between the LP and LV groups, they were higher in the HP group than in the HV group. Serum phosphate levels were higher in the paricalcitol-treated groups than in the VS-105-treated groups and paticularly higher in the HP group than in the other groups. The urinary excretion of phosphate was greater in the VS-105-treated groups than in the paricalcitol-treated groups. Serum parathyroid hormone (PTH) levels decreased and serum fibroblast growth factor-23 (FGF23) levels were elevated after administering paricalcitol and VS-105; however, serum FGF23 levels were remarkably elevated in the paricalcitol-treated groups. Further biochemical analyses revealed that the calcium content of the aorta was higher in the paricalcitol-treated groups than in the VS-105-treated group. VDR and Klotho expression in the kidney was significantly higher in the VS-105-treated groups than in the paricalcitol-treated groups although both agents increased these expressions. Our data suggest that VS-105 had a lesser effect on CKD-MBD than paricalcitol except in the case of serum PTH levels. The mechanism appears to be associated with the difference in VDR and Klotho expression.

The Strategy to Prevent and Regress the Vascular Calcification in Dialysis Patients

The high prevalence of arterial calcification in end-stage renal disease (ESRD) is far beyond the explanation by common cardiovascular risk factors such as aging, diabetes, hypertension, and dyslipidemia. The finding relies on the fact that vascular and valvular calcifications are predictors of cardiovascular diseases and mortality in persons with chronic renal failure. In addition to traditional cardiovascular risk factors such as diabetes mellitus and blood pressure control, other ESRD-related risks such as phosphate retention, excess calcium, and prolonged dialysis time also contribute to the development of vascular calcification. The strategies are to reverse "calcium paradox" and lower vascular calcification by decreasing procalcific factors including minimization of inflammation (through adequate dialysis and by avoiding malnutrition, intravenous labile iron, and positive calcium and phosphate balance), correction of high and low bone turnover, and restoration of anticalcification factor balance such as correction of vitamin D and K deficiency; parathyroid intervention is reserved for severe hyperparathyroidism. The role of bone antiresorption therapy such as bisphosphonates and denosumab in vascular calcification in high-bone-turnover disease remains unclear. The limited data on sodium thiosulfate are promising. However, if calcification is to be targeted, ensure that bone health is not compromised by the treatments.

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.

Crosstalk between Vitamins A, B12, D, K, C, and E Status and Arterial Stiffness

Arterial stiffness is associated with cardiovascular risk, morbidity, and mortality. The present paper reviews the main vitamins related to arterial stiffness and enabling destiffening, their mechanisms of action, providing a brief description of the latest studies in the area, and their implications for primary cardiovascular prevention, clinical practice, and therapy. Despite inconsistent evidence for destiffening induced by vitamin supplementation in several randomized clinical trials, positive results were obtained in specific populations. The main mechanisms are related to antiatherogenic effects, improvement of endothelial function (vitamins A, C, D, and E) and metabolic profile (vitamins A, B12, C, D, and K), inhibition of the renin-angiotensin-aldosterone system (vitamin D), anti-inflammatory (vitamins A, D, E, and K) and antioxidant effects (vitamins A, C, and E), decrease of homocysteine level (vitamin B12), and reversing calcification of arteries (vitamin K). Vitamins A, B12, C, D, E, and K status is important in evaluating cardiovascular risk, and vitamin supplementation may be an effective, individualized, and inexpensive destiffening therapy.

Absence of the Vitamin D Receptor Inhibits Atherosclerotic Plaque Calcification in Female Hypercholesterolemic Mice

Epidemiological and clinical data suggest adverse cardiovascular outcomes with respect to vitamin D deficiency. Here, we explored the effects of vitamin D in atherosclerotic plaque calcification in vivo by utilizing vitamin D receptor (Vdr)-deficient mice in an Apoe^-/- background. Animals were fed a high-fat diet (HFD) for either 12 or 18 weeks and then examined for atherosclerotic plaque development. In order to prevent calcium deficiency, Vdr^-/- and Apoe^-/- ;Vdr^-/- animals were fed a high-calcium rescue diet prior to initiation of the HFD feeding and supplemented with high-calcium water during HFD feeding. Although calcium supplementation improved bone mass in Vdr^-/- and Apoe^-/- ;Vdr^-/- mice, neither strain was fully rescued. Systemic inflammatory responses observed in the absence of VDR were exaggerated in Apoe^-/- mice. Whereas, hyperlipidemic profiles seen in Apoe^-/- mice were ameliorated in the absence of VDR. Micro-computed tomography (µCT) analysis revealed that six out of eight Apoe^-/- animals developed atherosclerotic plaque calcification following 12 weeks of HFD feeding and 100% of the mice developed plaque calcification after 18 weeks. In contrast, although atherosclerotic lesions were evident in Apoe^-/- ;Vdr^-/- mice at 12 and 18 weeks of HFD challenge, none of these animals developed plaque calcification at either time point. The active vitamin D hormone, 1,25(OH)₂ D₃ likely increased calcification in aortic smooth muscle cells perhaps by directly modulating expression of Alpl, Rankl, and Opg. Our data suggest that the absence of VDR inhibits atherosclerotic plaque calcification in hypercholesterolemic Apoe^-/- mice, providing additional insight into the role of vitamin D in atherosclerotic plaque calcification. J. Cell. Biochem. 118: 1050-1064, 2017. © 2016 Wiley Periodicals, Inc.

Vascular calcification: When should we interfere in chronic kidney disease patients and how?

Chronic kidney disease (CKD) patients are endangered with the highest mortality rate compared to other chronic diseases. Cardiovascular events account for up to 60% of the fatalities. Cardiovascular calcifications affect most of the CKD patients. Most of this calcification is related to disturbed renal phosphate handling. Fibroblast growth factor 23 and klotho deficiency were incriminated in the pathogenesis of vascular calcification through different mechanisms including their effects on endothelium and arterial wall smooth muscle cells. In addition, deficient klotho gene expression, a constant feature of CKD, promotes vascular pathology and shares in progression of the CKD. The role of gut in the etio-pathogenesis of systemic inflammation and vascular calcification is a newly discovered mechanism. This review will cover the medical history, prevalence, pathogenesis, clinical relevance, different tools used to diagnose, the ideal timing to prevent or to withhold the progression of vascular calcification and the different medications and medical procedures that can help to prolong the survival of CKD patients.

Cardiovascular calcifications in chronic kidney disease: Potential therapeutic implications

Cardiovascular (CV) calcification is a highly prevalent condition at all stages of chronic kidney disease (CKD) and is directly associated with increased CV and global morbidity and mortality. In the first part of this review, we have shown that CV calcifications represent an important part of the CKD-MBD complex and are a superior predictor of clinical outcomes in our patients. However, it is also necessary to demonstrate that CV calcification is a modifiable risk factor including the possibility of decreasing (or at least not aggravating) its progression with iatrogenic manoeuvres. Although, strictly speaking, only circumstantial evidence is available, it is known that certain drugs may modify the progression of CV calcifications, even though a direct causal link with improved survival has not been demonstrated. For example, non-calcium-based phosphate binders demonstrated the ability to attenuate the progression of CV calcification compared with the liberal use of calcium-based phosphate binders in several randomised clinical trials. Moreover, although only in experimental conditions, selective activators of the vitamin D receptor seem to have a wider therapeutic margin against CV calcification. Finally, calcimimetics seem to attenuate the progression of CV calcification in dialysis patients. While new therapeutic strategies are being developed (i.e. vitamin K, SNF472, etc.), we suggest that the evaluation of CV calcifications could be a diagnostic tool used by nephrologists to personalise their therapeutic decisions.

Predictors of abdominal aortic calcification progression in patients with chronic kidney disease without hemodialysis

BACKGROUND AND AIMS

Abdominal aortic calcification (AAC) is an important predictor of cardiovascular mortality in patients with chronic kidney disease (CKD). However, little is known regarding AAC progression in these patients. This study aimed to identify risk factors associated with AAC progression in patients with CKD without hemodialysis.

METHODS

We recruited 141 asymptomatic patients with CKD without hemodialysis [median estimated glomerular filtration rate (eGFR), 40.3 mL/min/1.73 m²] and evaluated the progression of the abdominal aortic calcification index (ACI) over 3 years. To identify risk factors contributing to the rate of ACI progression, the associations between baseline clinical characteristics and annual change in ACI for each CKD category were analyzed. The annual change of ACI (ΔACI/year) was calculated as follows: (second ACI - first ACI)/duration between the two evaluations.

RESULTS

Median ΔACI/year values significantly increased in advanced CKD stages (0.73%, 0.87%, and 2.24%/year for CKD stages G1-2, G3, and G4-5, respectively; p for trend = 0.041). The only independent risk factor for AAC progression in mild to moderate CKD (G1-3, eGFR ≥ 30 mL/min/1.73 m²) was pulse pressure level (β = 0.258, p = 0.012). In contrast, parathyroid hormone (PTH) level was significantly correlated with ΔACI/year (β = 0.426, p = 0.007) among patients with advanced CKD (G4-5, eGFR < 30 mL/min/1.73 m²).

CONCLUSIONS

This study suggests that the AAC progression rate was significantly accelerated in patients with advanced CKD. In addition, measuring PTH is useful to evaluate both bone turnover and AAC progression in patients with advanced CKD.

EFFECT OF ULTRASOUND-GUIDED DIRECT VITAMIN D INJECTIONS INTO PARATHYROID GLANDS ON LABORATORY MARKERS AND SURVIVAL OF PATIENTS WITH REFRACTORY SECONDARY HYPERPARATHYROIDISM

Aim. To evaluate the effect of local vitamin D injections into parathyroid glands on laboratory markers and survival in refractory hyperparathyroidism.

 Materials and methods. A comparison of the dynamics of secondary hyperparathyroidism laboratory markers and survival was performed in 37 patients with local vitamin D injections into the parathyroid glands under ultrasound guidance and in 62 patients with PTH higher than 600 pg/ml without reduction in PTH levels by more than 10% during 6 months, who continued to receive available conservative therapy. The mean duration of follow-up for groups was 40.5 and 33.2 months, respectively.

Results. In the local injection group (LIG) PTH level reduced by 347 ± 360 pg/ml (38%) during the first month after injection course, and by 214 ± 255 pg/ml (28%) between annual average levels before and after injection course, while in control group (CG) it rose by 84 ± 277 pg/ml (11%). In LIG phosphate level significantly reduced by 0.18 ± 0.24 mmol/l (9%) after injection course and annual average level did not change. In CG annual average phosphate level significantly rose by 0.15 ± 0.37 mmol/l (7%). Cumulative survival by Kaplan–Maier was significantly higher in LIG (p = 0.025). Differences in survival in univariate and multivariate Cox regression models were significantly associated only with the fact of local injections course (p =0.04 inboth models).

Conclusion. In current clinical practice the application of ultrasound-guided local vitamin D injections into parathyroid glands in patients with refractory hyperparathyroidism leads to a better control over laboratory markers and to significantly improved survival.

Why are kids with lupus at an increased risk of cardiovascular disease?

Juvenile-onset systemic lupus erythematosus (SLE) is an aggressive multisystem autoimmune disease. Despite improvements in outcomes for adult patients, children with SLE continue to have a lower life expectancy than adults with SLE, with more aggressive disease, a higher incidence of lupus nephritis and there is an emerging awareness of their increased risk of cardiovascular disease (CVD). In this review, we discuss the evidence for an increased risk of CVD in SLE, its pathogenesis, and the clinical approach to its management.

Vitamin D in patients with chronic kidney disease: a position statement of the Working Group "Trace Elements and Mineral Metabolism" of the Italian Society of Nephrology

In the late 1970s, calcitriol was introduced into clinical practice for the management of secondary renal hyperparathyroidism in chronic kidney disease (CKD). Since then, the use of calcifediol or other native forms of vitamin D was largely ignored until the publication of the 2009 Kidney Disease Improving Global Outcomes (KDIGO) recommendations. The guidelines suggested that measurement of circulating levels of 25(OH)D (calcifediol) and its supplementation were to be performed on the same basis as for the general population. This indication was based on the fact that the precursors of active vitamin D had provided to CKD patients considerable benefits in survival, mainly due to their pleiotropic effects on the cardiovascular system. However, despite the long-term use of various classes of vitamin D in CKD, a clear definition is still lacking concerning the most appropriate time for initiation of therapy, the best compound to prescribe (active metabolites or analogs), the proper dosage, and the most suitable duration of therapy. The aim of this position statement is to provide and critically appraise the current plentiful evidence on vitamin D in different clinical settings related to CKD, particularly focusing on outcomes, monitoring and treatment-associated risks. However, it should be taken in account that position statements are meant to provide guidance; therefore, they are not to be considered prescriptive for all patients and, importantly, they cannot replace the judgment of clinicians.

Ligand trap for the activin type IIA receptor protects against vascular disease and renal fibrosis in mice with chronic kidney disease

The causes of cardiovascular mortality associated with chronic kidney disease (CKD) are partly attributed to the CKD-mineral bone disorder (CKD-MBD). The causes of the early CKD-MBD are not well known. Our discovery of Wnt (portmanteau of wingless and int) inhibitors, especially Dickkopf 1, produced during renal repair as participating in the pathogenesis of the vascular and skeletal components of the CKD-MBD implied that additional pathogenic factors are critical. In the search for such factors, we studied the effects of activin receptor type IIA (ActRIIA) signaling by using a ligand trap for the receptor, RAP-011 (a soluble extracellular domain of ActRIIA fused to a murine IgG-Fc fragment). In a mouse model of CKD that stimulated atherosclerotic calcification, RAP-011 significantly increased aortic ActRIIA signaling assessed by the levels of phosphorylated Smad2/3. Furthermore, RAP-011 treatment significantly reversed CKD-induced vascular smooth muscle dedifferentiation as assessed by smooth muscle 22α levels, osteoblastic transition, and neointimal plaque calcification. In the diseased kidneys, RAP-011 significantly stimulated αklotho levels and it inhibited ActRIIA signaling and decreased renal fibrosis and proteinuria. RAP-011 treatment significantly decreased both renal and circulating Dickkopf 1 levels, showing that Wnt activation was downstream of ActRIIA. Thus, ActRIIA signaling in CKD contributes to the CKD-MBD and renal fibrosis. ActRIIA signaling may be a potential therapeutic target in CKD.

The role of bile acids in metabolic regulation

Bile acids (BA), long believed to only have lipid-digestive functions, have emerged as novel metabolic modulators. They have important endocrine effects through multiple cytoplasmic as well as nuclear receptors in various organs and tissues. BA affect multiple functions to control energy homeostasis, as well as glucose and lipid metabolism, predominantly by activating the nuclear farnesoid X receptor and the cytoplasmic G protein-coupled BA receptor TGR5 in a variety of tissues. However, BA also are aimed at many other cellular targets in a wide array of organs and cell compartments. Their role in the pathogenesis of diabetes, obesity and other 'diseases of civilization' becomes even more clear. They also interact with the gut microbiome, with important clinical implications, further extending the complexity of their biological functions. Therefore, it is not surprising that BA metabolism is substantially modulated by bariatric surgery, a phenomenon contributing favorably to the therapeutic effects of these surgical procedures. Based on these data, several therapeutic approaches to ameliorate obesity and diabetes have been proposed to affect the cellular targets of BA.

Reduction of Dialysate Calcium Level Reduces Progression of Coronary Artery Calcification and Improves Low Bone Turnover in Patients on Hemodialysis

Exposure to high Ca concentrations may influence the development of low-turnover bone disease and coronary artery calcification (CAC) in patients on hemodialysis (HD). In this randomized, controlled study, we investigated the effects of lowering dialysate Ca level on progression of CAC and histologic bone abnormalities in patients on HD. Patients on HD with intact parathyroid hormone levels ≤300 pg/ml receiving dialysate containing 1.75 or 1.50 mmol/L Ca (n=425) were randomized to the 1.25-mmol/L Ca (1.25 Ca; n=212) or the 1.75-mmol/L Ca (1.75 Ca; n=213) dialysate arm. Primary outcome was a change in CAC score measured by multislice computerized tomography; main secondary outcome was a change in bone histomorphometric parameters determined by analysis of bone biopsy specimens. CAC scores increased from 452±869 (mean±SD) in the 1.25 Ca group and 500±909 in the 1.75 Ca group (P=0.68) at baseline to 616±1086 and 803±1412, respectively, at 24 months (P=0.25). Progression rate was significantly lower in the 1.25 Ca group than in the 1.75 Ca group (P=0.03). The prevalence of histologically diagnosed low bone turnover decreased from 85.0% to 41.8% in the 1.25 Ca group (P=0.001) and did not change in the 1.75 Ca group. At 24 months, bone formation rate, trabecular thickness, and bone volume were higher in the 1.25 Ca group than in the 1.75 Ca group. Thus, lowering dialysate Ca levels slowed the progression of CAC and improved bone turnover in patients on HD with baseline intact parathyroid hormone levels ≤300 pg/ml.

Pre-treatment considerations in childhood hypertension due to chronic kidney disease

Hypertension (HTN) develops very early in childhood chronic kidney disease (CKD). It is linked with rapid progression of kidney disease, increased morbidity and mortality hence the imperative to start anti-hypertensive medication when blood pressure (BP) is persistently > 90^th percentile for age, gender, and height in non-dialyzing hypertensive children with CKD. HTN pathomechanism in CKD is multifactorial and complexly interwoven. The patient with CKD-associated HTN needs to be carefully evaluated for co-morbidities that frequently alter the course of the disease as successful treatment of HTN in CKD goes beyond life style modification and anti-hypertensive therapy alone. Chronic anaemia, volume overload, endothelial dysfunction, arterial media calcification, and metabolic derangements like secondary hyperparathyroidism, hyperphosphataemia, and calcitriol deficiency are a few co-morbidities that may cause or worsen HTN in CKD. It is important to know if the HTN is caused or made worse by the toxic effects of medications like erythropoietin, cyclosporine, tacrolimus, corticosteroids and non-steroidal anti-inflammatory drugs. Poor treatment response may be due to any of these co-morbidities and medications. A satisfactory hypertensive CKD outcome, therefore, depends very much on identifying and managing these co-morbid conditions and HTN promoting medications promptly and appropriately. This review attempts to point attention to factors that may affect successful treatment of the hypertensive CKD child and how to attain the desired therapeutic BP target.