vitamin-d-2 and Vascular-Calcification

The involvement of vitamin D deficiency in cardiovascular morbidity and mortality is attracting great interest. In patients with chronic kidney disease this association is stronger because vitamin D levels decrease as a result of renal progressive impairment. In chronic kidney disease secondary hyperparathyroidism commonly occurs in response to persistent hypocalcemia and hyperphosphatemia; moreover, parathyroid gland volume increases, vascular calcification is accelerated, and structural and functional modifications of the left ventricle are observed. These alterations entail both cardiac and renal involvement, resulting in cardio-renal syndrome. Recent studies concluded that vitamin D administration seems to have cardioprotective and renoprotective effects and improve peripheral vascular disease, vascular calcification, cardiac outcome, and blood pressure control. In clinical practice, therefore, the use of this hormone may play an important role in cardio-renal syndrome prevention.

Topics: Cardio-Renal Syndrome; Ergocalciferols; Humans; Hyperparathyroidism, Secondary; Hyperphosphatemia; Hypocalcemia; Kidney; Parathyroid Glands; Parathyroid Hormone; Receptors, Calcitriol; Renal Insufficiency, Chronic; Vascular Calcification; Vitamin D; Vitamin D Deficiency

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

Topics: Aging; Blood Pressure; Calcitriol; Calcium; Cardiovascular Diseases; Ergocalciferols; Humans; Hypertension; Kidney Failure, Chronic; Phosphates; Receptors, Calcitriol; 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.

Topics: Arteries; beta-Galactosidase; Calcitriol; Cells, Cultured; Core Binding Factor Alpha 1 Subunit; Cross-Sectional Studies; Ergocalciferols; Female; Humans; Male; Matrix Metalloproteinase 2; Matrix Metalloproteinase 9; Middle Aged; Myocytes, Smooth Muscle; Receptors, Calcitriol; Signal Transduction; Vascular Calcification; Vitamin D; Vitamin D3 24-Hydroxylase

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.

Topics: Animals; Disease Models, Animal; Ergocalciferols; Hyperparathyroidism, Secondary; Male; Peptides; Rats; Rats, Wistar; Renal Insufficiency; Vascular Calcification

Vascular calcification is a frequent complication of atherosclerosis, diabetes and chronic kidney disease. In the latter group of patients, calcification is commonly seen in tunica media where smooth muscle cells (SMC) undergo osteoblastic transformation. Risk factors such as elevated phosphorus levels and vitamin D3 analogues have been identified. In the light of earlier observations by our group and others, we sought to inhibit SMC calcification via induction of ferritin. Human aortic SMC were cultured using β-glycerophosphate with activated vitamin D3 , or inorganic phosphate with calcium, and induction of alkaline phosphatase (ALP) and osteocalcin as well as accumulation of calcium were used to monitor osteoblastic transformation. In addition, to examine the role of vitamin D3 analogues, plasma samples from patients on haemodialysis who had received calcitriol or paricalcitol were tested for their tendency to induce calcification of SMC. Addition of exogenous ferritin mitigates the transformation of SMC into osteoblast-like cells. Importantly, pharmacological induction of heavy chain ferritin by 3H-1,2-Dithiole-3-thione was able to inhibit the SMC transition into osteoblast-like cells and calcification of extracellular matrix. Plasma samples collected from patients after the administration of activated vitamin D3 caused significantly increased ALP activity in SMC compared to the samples drawn prior to activated vitamin D3 and here, again induction of ferritin diminished the osteoblastic transformation. Our data suggests that pharmacological induction of ferritin prevents osteoblastic transformation of SMC. Hence, utilization of such agents that will cause enhanced ferritin synthesis may have important clinical applications in prevention of vascular calcification.

Topics: Alkaline Phosphatase; Aorta; Calcitriol; Calcium; Cells, Cultured; Cholecalciferol; Ergocalciferols; Ferritins; Glycerophosphates; Humans; Muscle, Smooth, Vascular; Myocytes, Smooth Muscle; Osteoblasts; Osteocalcin; Phosphates; Thiones; Thiophenes; Vascular Calcification

The present study investigates the differential effect of two vitamin D receptor agonists, calcitriol and paricalcitol, on human aortic smooth muscle cells calcification in vitro. Human vascular smooth muscle cells were incubated in a high phosphate (HP) medium alone or supplemented with either calcitriol 10(-8)M (HP + CTR) or paricalcitol 3·10(-8) M (HP + PC). HP medium induced calcification, which was associated with the upregulation of mRNA expression of osteogenic factors such as bone morphogenetic protein 2 (BMP2), Runx2/Cbfa1, Msx2, and osteocalcin. In these cells, activation of Wnt/β-catenin signaling was evidenced by the translocation of β-catenin into the nucleus and the increase in the expression of direct target genes as cyclin D1, axin 2, and VCAN/versican. Addition of calcitriol to HP medium (HP + CTR) further increased calcification and also enhanced the expression of osteogenic factors together with a significant elevation of nuclear β-catenin levels and the expression of cyclin D1, axin 2, and VCAN. By contrast, the addition of paricalcitol (HP + PC) not only reduced calcification but also downregulated the expression of BMP2 and other osteoblastic phenotype markers as well as the levels of nuclear β-catenin and the expression of its target genes. The role of Wnt/β-catenin on phosphate- and calcitriol-induced calcification was further demonstrated by the inhibition of calcification after addition of Dickkopf-related protein 1 (DKK-1), a specific natural antagonist of the Wnt/β-catenin signaling pathway. In conclusion, the differential effect of calcitriol and paricalcitol on vascular calcification appears to be mediated by a distinct regulation of the BMP and Wnt/β-catenin signaling pathways.

Topics: Aorta; beta Catenin; Calcification, Physiologic; Calcitriol; Cell Line; Cells, Cultured; Ergocalciferols; Humans; Muscle, Smooth, Vascular; Myocytes, Smooth Muscle; Phosphates; Signal Transduction; Vascular Calcification; Wnt Proteins

Vascular calcification is common in chronic kidney disease, where cardiovascular mortality remains the leading cause of death. Patients with kidney disease are often prescribed vitamin D receptor agonists (VDRAs) that confer a survival benefit, but the underlying mechanisms remain unclear. Here we tested two VDRAs in a mouse chronic kidney disease model where dietary phosphate loading induced aortic medial calcification. Mice were given intraperitoneal calcitriol or paricalcitol three times per week for 3 weeks. These treatments were associated with half of the aortic calcification compared to no therapy, and there was no difference between the two agents. In the setting of a high-phosphate diet, serum parathyroid hormone and calcium levels were not significantly altered by treatment. VDRA therapy was associated with increased serum and urine klotho levels, increased phosphaturia, correction of hyperphosphatemia, and lowering of serum fibroblast growth factor-23. There was no effect on elastin remodeling or inflammation; however, the expression of the anticalcification factor, osteopontin, in aortic medial cells was increased. Paricalcitol upregulated osteopontin secretion from mouse vascular smooth muscle cells in culture. Thus, klotho and osteopontin were upregulated by VDRA therapy in chronic kidney disease, independent of changes in serum parathyroid hormone and calcium.

Topics: Animals; Aorta; Aortic Diseases; Calcitriol; Calcium; Cells, Cultured; Diet; Disease Models, Animal; Elastin; Ergocalciferols; Female; Fibroblast Growth Factor-23; Fibroblast Growth Factors; Glucuronidase; Injections, Intraperitoneal; Klotho Proteins; Mice; Mice, Inbred C57BL; Mice, Inbred DBA; Muscle, Smooth, Vascular; Myocytes, Smooth Muscle; Osteopontin; Parathyroid Hormone; Phosphates; Receptors, Calcitriol; Renal Insufficiency, Chronic; Time Factors; Up-Regulation; Vascular Calcification

Chronic kidney disease (CKD) is characterized by accelerated vascular calcification, which may in part be caused by deficiency of the anti-aging factor Klotho. Lau et al. demonstrate that administration of active vitamin D and its analog decreases aortic calcification in association with increases in two potent calcification inhibitors--the secreted form of Klotho and vascular osteopontin. These data might provide a new perspective on the association of active vitamin D with improved survival in patients with CKD.

Topics: Animals; Aorta; Aortic Diseases; Calcitriol; Diet; Ergocalciferols; Female; Glucuronidase; Klotho Proteins; Osteopontin; Phosphates; Receptors, Calcitriol; Renal Insufficiency, Chronic; Vascular Calcification